Safety First Safety First Safety First, #22 July, 2016

The Airbus safety magazine July 2016

#22 Safety first Safety first Safety first, #22 July, 2016. Safety first is published by Airbus S.A.S. - 1, rond point The Airbus magazine contributing to the enhancement Maurice Bellonte - 31707 Blagnac Cedex/France. of the safety of aircraft operations by increasing knowledge Publisher and Editor: Yannick Malinge, and communication on safety related topics. Chief Product Safety Officer. Concept Design by Airbus Multi Media Support 20161577. Reference: GS 420.0045 Issue 22. Photos by Airbus, Lindner Fotografie, T. Denson, S. Ramadier, H. Goussé, P. Masclet, F. Lancelot, M. Lindner, P. Pigeyre. This brochure is printed on Stucco. This paper is produced in factories that are accredited EMAS and certified ISO 9001-14001, PEFC and FSC CoC. It is produced using pulp that has been whitened without either chlorine or acid. The paper is entirely recyclable and is Safety first is published by the Product Safety department. produced from trees grown in sustainable forest It is a source of specialist safety information for the use resources. of airlines who fly and maintain Airbus aircraft. It is also The printing inks use organic pigments or minerals. There is no use of basic dyes or distributed to other selected organizations and is available dangerous metals from the cadmium, lead, on tablets. mercury or hexavalent chromium group. Material for publication is obtained from multiple sources and includes selected information from the Airbus Flight Safety Confidential Reporting System, incident and accident investigation reports, system tests and flight tests. Material is also obtained from sources within the airline industry, studies and reports from government agencies and other aviation sources. © Airbus S.A.S. 2016 – All rights reserved. Proprietary documents. All articles in Safety first are presented for information By taking delivery of this Brochure only and are not intended to replace ICAO guidelines, (hereafter “Brochure”), you accept on behalf of your company to comply with the following standards or recommended practices, operator-mandated guidelines: requirements or technical orders. The contents do not No other intellectual property rights are granted supersede any requirements mand ated by the State of by the delivery of this Brochure than the right to read it, for the sole purpose of information. Registry of the Operator’s aircraft or supersede or amend This Brochure and its content shall any Airbus type-specific AFM, AMM, FCOM, MMEL not be modified and its illustrations documentation or any other approved documentation. and photos shall not be reproduced without prior written consent of Airbus. Articles may be reprinted without permission, except where This Brochure and the materials it contains shall not, in whole or in part, be sold, rented, or copyright source is indicated, but with acknowledgement licensed to any third party subject to payment. to Airbus. Where Airbus is not the author, the contents of This Brochure contains sensitive information the article do not necessarily reflect the views of Airbus, that is correct at the time of going to press. neither do they indicate Company policy. This information involves a number of factors that could change over time, effecting the true public representation. Airbus assumes no obligation Contributions, comment and feedback are welcome. Enquiries to update any information contained in this related to this publication should be addressed to: document or with respect to the information described herein. Airbus S.A.S. shall assume no liability for any damage in connection with the use of this Airbus Brochure and of the materials it contains, even if Airbus S.A.S. has been advised of the likelihood Product Safety department (GS) of such damages. 1, rond point Maurice Bellonte 31707 Blagnac Cedex - France Fax: +33(0)5 61 93 44 29

[email protected] Safety First #22 | July 2016 001 editorial

2015 is the safest year ever by number of fatal accidents: this is the positive achievement that we highlighted in our last Commercial Aviation Accidents Statistics brochure. But is this the signal that our long and complex journey with safety enhancement has reached an end? We believe that it is just the beginning of something new. YANNICK MALINGE There is no room for complacency in safety; instead good SVP & Chief results should force us to become even more creative and Product Safety Officer innovative. This ambition is what drove the introduction of our new collaborative project ‘Air Transport Safety: Destination 10x Together’. We are hopeful that this initiative will bring a new impetus to collaboration across our industry. It will first aim to form a diagnosis of safety at the Air Transport System level today, and then define together not only what the current and emerging safety threats and challenges are, but also opportunities to further reduce the accident rate.

In the frame of this project, a first survey was made during the last Flight Safety conference and it highlighted areas and safety threats that will need focus. Traffic and fleets growth implying increased congestion and recruiting & training needs, security and weather information were amongst the most cited.

We will continue to welcome your feedbacks and suggestions, and we will make sure these are heard and properly communicated to the benefit of all stakeholders across our industry.

Together, we must perpetuate our commitment to safety and strive to continue to improve collectively. The articles published in this new issue of our magazine have been written in this regard.

I hope that you will enjoy reading this new Safety first issue! NEWS

A statistical Analysis on Commercial Aviation Accidents: check the 2016 edition!

The new edition of our yearly brochure on commercial aviation accidents statistics is now available.

This statistical analysis examines the evolution of hull-loss and fatal accidents during revenue flights from 1958 to 2015. A particular focus is made on a breakdown of statistics by generations of aircraft and main accident cate- gories, namely Controlled Flight Into terrain (CFIT), Loss Of Control In-flight (LOC-I) and Runway Excursion (RE).

Visit our airbus.com website (keyword “safety”) or find it on our tablet application.

SAVE THE DATE NEWS

23rd FLIGHT SAFETY CONFERENCE – 2017

We are pleased to announce that the promotes flight safety across the fleets 23rd Flight Safety Conference will take of all our operators, we are unable to place in Santiago, Republic of Chile, accept requests to attend from outside from the 20th to the 23rd of March parties. 2017. A preliminary conference agenda will be announced in September and We welcome presentations from the formal invitations will be sent to our customers and encourage your our customers in January 2017 to participation as a speaker to share register. For any information regarding experiences and ideas and experience invitations, please contact Mrs. Nuria for improving aviation safety. Soler, email [email protected]. If you believe there is a topic that will The annual Airbus Flight Safety benefit other operators and/or Airbus, Conference has proven to be an and you are interested in being a excellent forum for the exchange speaker at this conference, please of information between Airbus and send a brief abstract and a bio or its customers. To ensure that we resume to [email protected] continue to have an open dialogue that 23rd Flight Safety Conference Santiago, Republic of Chile 20-23 March 2017

Safety First #22#18 | July 20162014 005

Safety first#22

PROCEDURES P06 Pitot Probe Performance Covered On the Ground P14 180° turns on runway Flight operations

Maintenance OPERATIONS

Engineering P22 Optimum use of weather radar Ground operations PROCEDURES Pitot Probe Performance Covered On the Ground

Pitot Probe Performance Covered On the Ground Pitot probes inlet obstruction will affect accuracy of the air data parameters calculated from its measurements such as the aircraft airspeed and Mach number. Pitot probes inlet obstruction on the ground can be caused by unexpected sources such as sand, dirt, dust or insect nesting activity. This is why it is important to think about when to install Pitot probe covers for an aircraft on the ground to protect its air data system performance.

BENOIT AYMERIC STÉPHANE DUQUESNE JACQUOT COTE Anemo/Inertial Systems Air Data and Inertial Accident/Incident Product Leader System Engineer Investigator Safety First #22 | July 2016 007

AN OBSTRUCTED PITOT PROBE MAY OCCUR IN LESS TIME THAN YOU THINK

In-service experience: impacts of a blocked Pitot The cause of the probe in a context of dispatch under MEL indicated airspeed In a recent incident, the captain of an reverted from normal to alternate law discrepancy was A330 rejected the take-off attempt and the autopilot became unavailable. after noticing an airspeed indication The crew performed an immediate due to a Pitot probe failure. Troubleshooting conducted in-flight turn-back. After the uneventful partially blocked in subsequently led to swap two of the Air landing, a detailed ground inspection less than two hours Data Inertial Reference Units (ADIRU) found conclusive evidence that the and the aircraft was dispatched with cause of the indicated airspeed by nesting wasps. ADIRU 2 inoperative as allowed by discrepancy was due to a Pitot probe the Minimum Equipment List (MEL). A partially blocked in less than two hours second take-off passed the critical V1 by nesting wasps. speed when an airspeed discrepancy was noticed again on the captain’s PFD. An investigation of another in-flight turn- The take-off had to be continued but back (from a non-Airbus aircraft type) at a wrong captain airspeed associated the same airport also showed that the with ADIRU 2 inoperative caused the inlet of the captain’s Pitot probe was A330’s auto-thrust and flight directors partly obstructed by material consistent to disengage, the flight controls mode with a mud-dauber wasp nest. Main reasons for Pitot obstruction: insects but not only… Insects can cause rejected take- issued by the Australian Civil Aviation off or in-flight turn-back events Safety Authority (CASA) following an The main and there are other potential investigation of an in-service occurrence. cause of airspeed sources of Pitot obstruction. But it is not only insect activity that can discrepancy below be the cause of Pitot blockage. Pitot “A mud dauber wasp can build a probe inlet obstruction by insect, dust, FL250 was Pitot significant nest capable of completely dirt or any materials (sand) is the main obstruction by blocking a Pitot probe, vent, or drain root cause of rejected take-off or in-flight in around 20 minutes” according turn-back events due to airspeed sand, dust, dirt to a recent airworthiness bulletin discrepancy below FL 250. or insects. PROCEDURES Pitot Probe Performance Covered On the Ground

(fig.1) Pitot probe simplified schematic (applicable for A320, A330 and A340 aircraft)

ADIRU1 ADIRU3 ADIRU2

Probe 1 Probe 3 Probe 2

Normal Display Reconfigurations

A PRECISION INSTRUMENT FOR MEASURING AIRSPEED

The Pitot probe consists of a tube pointing directly into the air flow(fig.2) and measuring the stagnation pressure called total pressure or Pitot pressure.

This total pressure information and the static pressure delivered by static ports on the fuselage are used to compute the indicated airspeed and Mach number provided by the ADIRU (fig.3).

Like any precision instrument, Pitot probes need to be protected on ground to provide correct airspeed and Mach number measurements in flight in order to fly the aircraft safely.

1 (fig.2) 2 Design principle of a Pitot 3 probe (applicable for A320, A330 and A340 aircraft) 3

1 Drain hole 2 Water trap 3 Heater cable wound around the pressure line 4 Total pressure line

5 Electrical connector 5

6 Pneumatic connector 6 (Quick disconnect) Safety First #22 | July 2016 009

Static port Static: P s Mach ADIRU Total pressure: P t Airspeed Pitot probe

(fig.3) PREVENTING PITOT PROBE Pitot probe principle OBSTRUCTION ON GROUND

Aircraft Maintenance Manual parking procedure

Parking procedures available in the devices, including Pitot probes (fig.4). Aircraft Maintenance Manual (AMM But many operators will not apply the section 10-11-00) will request that AMM parking procedure if the aircraft (fig.4) approved protective covers are installed only has a short turn-around time or Pitot probe locations on an Airbus on each of the air data probes or remains on the flight line. A330 or A340 aircraft

LEFT RIGHT

STATIC PORTS CAPT PITOT PROBE F/O PITOT STBY PITOT PROBE PROCEDURES Pitot Probe Performance Covered On the Ground

The proper protection for Pitot probes

Using the approved Pitot probe Airbus A310, A320, A330, and A340 covers (fig.5) is important as the aircraft families. Airbus A380 and covers for other manufacturer’s A350 aircraft have Multi-Function (fig.5) aircraft may not be the correct fit or Probes (MFP) and a standby Pitot Aircraft Pitot probe protective cover (applicable for A320, A330 and A340 aircraft) offer complete protection for the Pitot probe that use two different covers. probes of Airbus aircraft. The same Pitot probe and MFP covers are part Pitot probe cover can be used on of the flight kit for each aircraft.

When is Pitot probe too hot to handle on ground? Protective covers can be installed period of 15 minutes for the probe 30 minutes after engines shut down tip to cool to 70°C, it can take an as the probe heating is deactivated additional 15 minutes to reach when engines are turned off. After a ambient temperature.

AIRLINE ASSESSMENT – FROM OPERATIONAL BASES TO DESTINATION AIRPORTS

Is the Pitot probe protection a priority for ground handlers and maintenance teams?

With the recent finding from the example For example, check if a wildlife incident where a Pitot probe obstruction management plan is part of the occurred in less than two hours, it is airport’s hazard management important to know if Pitot probe protection strategy and what mitigations are is a priority in local airport ground in place to detect or manage insect handling or turn-around procedures. activity. Confirm how each airport will The aircraft operator should collaborate alert airlines or operators where there with the local airport authorities to assess is evidence that local conditions the risk of Pitot probes being blocked by may contribute to an increased sand, dust, dirt or insects activity at their risk of Pitot blockage to aircraft on operational base or destination airports. the ground. Safety First #22 | July 2016 011

Depending on the outcomes of this Airlines or operators should also Some airlines risk assessment, the operator should report any in-service incidents of Pitot consider implementing a specific policy probe obstruction to the local airport already have policies on the use of Pitot covers even for a authority and to Airbus. This will help in place for certain short turn-around time. Some airlines to determine root causes, prevent airports that require already have policies in place for certain further occurrences and track any airports that require Pitot covers to trends of obstructions of Pitot probes Pitot covers to be be used for all aircraft on the ground on ground. used for all aircraft regardless of turn-around times. on the ground regardless of turn- around times. AIRPORT PROACTIVE PREVENTION STRATEGIES

The airports can also implement alert aircraft operators and their ground preventive actions following an handlers to consider applying additional assessment of the locally occurring preventive measures to protect Pitot risks such as regularly inspecting for probes with the approved covers, even wasps or other insects at their sites. for short aircraft turn-around times. If It is important to continuously monitor there is a persisting problem, it may be and communicate with all airlines and necessary to issue a Notice to Airmen aircraft operators about any seasonal (NOTAM) making the pilots aware of (fig.6) increased insect activity, especially the risk (fig.6) and alert them to pay Example extract from NOTAM by wasps, and where there are local particular attention when checking their with item [3.] warning of mud wasp activity and the recommendation conditions causing accumulations of aircraft’s Pitot probes for any risk of to install Pitot tube covers - Courtesy sand, dirt or fine particle dust. This will obstruction. of Brisbane Airport Corporation PROCEDURES Pitot Probe Performance Covered On the Ground

ADDITIONAL AIRPORT MEASURES – UPPING THE ANTE

(fig.7) An example of where collaboration between Airlines Mud wasp awareness poster - and Airports can enhance the operational safety of Courtesy of Brisbane Airport Corporation aircraft

Like many other airports around the world, being located in a sub-tropical environment means Brisbane Airport (BNE) is ever vigilant about the presence of mud wasps on site. While the airport has always maintained a stringent monitoring and control regime for these pests, following an incident whereby a mud wasp nest blocked the air data instruments of an Airbus aircraft during a standard turn-around at Brisbane Airport, the Brisbane Airport Corporation (BAC) upped the ante by introducing additional measures to mitigate the ongoing risk of Pitot blockage on ground.

Airport to Airline Communication

BAC recommends the use of Pitot probe covers on aircraft at BNE to prevent possible obstructions from mud wasp activity. Results from pest inspections carried out by pest management professionals are emailed out (fig.8) weekly to all airlines and stakeholders. The notifications Array of 3D printed Pitot probes of various include the location and number of nests found and designs (A330, B737-400, B737-800, Dash-8, treated. Their “Watch out for the Mud Wasp” awareness B747 and E190) used for monitoring wasp activity and ecology study at Brisbane poster (fig.7) is a quick reference guide to the conditions airport. - Courtesy of Brisbane Airport to observe when the wasps are likely to be more active Corporation at BNE and details what information to report to the BAC wildlife coordinator via email or at the Brisbane Airport Wildlife Working Group.

Preventative pest control

BAC initiated a wasp ecology study consisting of an array of 3D printed Pitot probes of various designs (A330, B737-400, B737-800, Dash-8, B747 and E190), which are secured to sheets of metal to resemble the aircraft’s fuselage, and they are mounted in different parking positions around the airfield(fig.8) . Each location is inspected regularly for evidence of mud wasp activity and when there are nests found in any of the 3D printed Pitot tube arrays the contents are hatched and examined by an ecologist. Results from the study are expected in February 2017. This will help BAC achieve a better understanding of the species of mud wasp present at Brisbane, the impacts that they can have on aircraft operations and any further measures that can be taken to mitigate the risk. Safety First #22 | July 2016 013

FLIGHT CREW FOCUS ON PITOT PROBES

Additional safety barriers, embedded in Airbus Standard Operating Procedures (SOP), are available to flight crews in order to avoid taking- off with obstructed Pitot probes. SOP Exterior Walk Around (FCOM section PRO-NOR-SOP-05)

Always look at the Pitot probes probe and that the general condition carefully during the pre-flight exterior is good. This will give confidence that inspection and check that all of the the correct airspeed readouts will be covers are removed before flight. available on all of the instruments in Ensure there is no damage to the Pitot all flight phases. SOP Take-off (FCOM section PRO-NOR-SOP-12)

During the take-off phase, a partially which should be detected when cross or totally obstructed Pitot probe may checked with the other PFD. Standard lead to an underestimated, fluctuating Operating Procedures for Airbus aircraft or “flagged” airspeed information on require the flight crew to scan airspeeds the Primary Flight Display (PFD) or shown on the PFD throughout the take- standby instrument for the affected off and the Pilot Flying shall cross check Pitot probe. In this case, there is likely and confirm the airspeed indicated on to be an indicated airspeed discrepancy reaching 100 knots.

Pitot probe protection using the Airbus approved covers is the most effective way to prevent Pitot obstruction on ground. Airlines and operators should assess and monitor the risk of any obstruction to their aircraft’s Pitot probes at the airports where they are based or operating to. Airports can also play an active role by collaborating with their operators to manage airport hazards and communicate on any of the mitigations in place. Where there is an identified risk of Pitot obstruction due to sand, dirt, dust or insect nesting activity, the operator should consider applying a specific policy to use Pitot covers for aircraft on the ground regardless of turn-around times. Reporting any occurrences of Pitot probe obstruction to the local airport authorities and Airbus will help to monitor for adverse trends, put specific measures in place and communicate this information to the benefit of all airlines and operators. PROCEDURES 180° turns on runway

180° turns on runway Performing a 180° turn or U-turn on a runway may seem an ordinary maneuver compared to other phases of the flight. However, operational experience over the past 10 years shows that unintentionally leaving the runway while completing a U-turn can happen, even to experienced pilots, in any conditions, even on dry runway, on any aircraft type including the A320 family aircraft. A specific technique exists for such U-turns to avoid runway excursions.

STÉPHANE XAVIER BRIZAY JOLIVET Flight Operations Director Flight Safety Engineer Enhancement Safety First #22 | July 2016 015

U-TURNS ON RUNWAY: A SIGNIFICANT CONTRIBUTOR TO RUNWAY EXCURSIONS

Who would naturally think about U-turns load and defuel the aircraft when it on runways when referring to aviation has to be returned to the pavement, accidents? Although not intuitive, this not to mention the impact on airport relationship does exist. Indeed, operational operations with the potential closure of experience shows that a number of the runway and its associated safety runway excursions resulted from a failure implications. The airline involved is often to manage such a maneuver correctly. In put in an embarrassing position from a less than 10 years, more than 20 runway brand point of view due to the speed of excursions with some incidents leading modern visual communications. to an ICAO Annex 13 investigation have been reported to Airbus. The number of recent events may be growing due to a reporting bias, but Beyond the potential for significant the issue has now drawn attention aircraft damage or time for inspection from a safety vantage point. and repairs, the consequences of such events translate mainly into Thanks to the reported events, Airbus operational disturbance. They lead was able to analyze and understand to flight cancellation, the need to off- the conditions of occurrence. Lessons from in-service events

Some possible preconceived ideas are experience or the type of aircraft. Let’s dismissed by facts especially concerning review the 21 events reported to Airbus the runway contamination, the pilot’s over the past 10 years in figures:

Aircraft type A320 A330 A300/A310 A350 Total Runway state family family family

Contaminated 5 4 0 1 10

Dry 2 6 0 0 8

No information 0 1 2 0 3

Total 7 11 2 1 21 PROCEDURES 180° turns on runway

Any runway Beyond these two dimensions, a As for the pilot’s background, it turns thorough analysis of the events shows out that it was extremely variable excursion, as smooth that the runway surface quality is also an from one event to the other. In other as it may seem, important parameter. Indeed, a degraded words, a runway excursion when requires the aircraft or damaged runway surface may have performing a U-turn on a runway as much influence on the performance is not the preserve of the least to be checked prior of a U-turn as a contaminated runway. experienced pilots… to the next flight. Reporting: the most precious input to enhancing safety

In one surprising event, although As of today, the analysis of the events the crew had experienced a runway made available to Airbus through excursion, they realigned the aircraft reporting allowed us to dismiss possible To ensure the and took off. Damage on the gear preconceived ideas, such as: it only aircraft integrity for was observed at arrival. Even at occurs to the least experienced pilots low speed, a runway excursion can or only on contaminated runways or with the next flight, to damage the aircraft in a way that large aircraft. It also allows us to highlight allow safety lessons can affect the safety of the following the key points or parameters that need flights. Any runway excursion, as to be checked before initiating the turn to be learnt and smooth as it may seem, requires the and executing the maneuver, as well as to be able to take aircraft to be checked prior to the to emphasize the best technique and next flight in accordance with the tips to perform such turns safely. appropriate mitigation AMM guidelines. measures from Eventually, thanks to airlines reporting, analyzing all events Moreover, to ensure the aircraft integrity the technique available today in the for the next flight, to allow safety lessons FCOM is going to be revisited and of similar nature, all to be learnt and to be able to take improved as part of the FCTM. Key runway excursion appropriate mitigation measures from values relating to the recommended analyzing all events of similar nature, runway width will be kept in the FCOM. events need to be all runway excursion events need to These updates will be available by the reported. be reported. end of 2016. Safety First #22 | July 2016 017

TECHNIQUE AND TIPS TO PERFORM A SAFE U-TURN ON THE RUNWAY

The analysis of in-service events allowed As far as possible, a U-turn on the runway Performing a the technique for U-turns in the FCOM to needs to be prepared before arriving on be revisited. The philosophy of the new the runway. The preparation includes a safe U-turn on a revision will align with the existing content discussion on who will be PF and in which runway is not just a and emphasize the key steps of the direction should the turn be performed in technique for performing successful and accordance with the airline policy. matter of managing safe U-turns. The technique was initially the turn itself. It starts developed for U-turns on a runway, Performing a safe U-turn on a runway is before initiating the where there are standard markings at not just a matter of managing the turn the borders of the runway. itself. It starts before initiating the turn… turn…

Before initiating the turn

Initiating the turn in good conditions aspects beyond the ones mentioned relies on a number of complementary before.

Suitability of runway width with the conditions of the day Performing a safe U-turn on a runway used. Therefore, it may be necessary to The minimum requires anticipating the space required add some margins if these conditions are for the safe completion of the maneuver. not met (e.g. contaminated runway). required runway The minimum runway width for a given width to carry out aircraft type is provided in the FCOM. In summary, before considering a However, it is important to keep in mind U-turn on a runway, check that the a U-turn is based that this value is based on the following runway width is sufficient with respect on the following assumptions: the runway is dry, the to the minimum published in the FCOM assumptions: a dry runway surface quality is good and the possibly adjusted to the anticipated technique recommended by Airbus is conditions of the day. runway, a good runway surface and Consider the actual runway surface quality the application of the As previously mentioned, the state of surface. In other instances, pieces correct technique. the runway may require the margins of multiple layers of painted surface provided by the FCOM to be adapted. became detached over time, thus The maneuver is to be performed with generating depressions likely to retain the maximum available steering of the rain water even though the remainder of nose wheels and in such a configuration, the runway had already dried up. a poor surface may make the wheels slip and increase the turn radius. As a consequence, special care must be taken when the trajectory requires taxiing It is important to keep in mind that the aircraft over a painted surface. A good painted areas such as runway threshold friction coefficient experienced while still markings can be significantly more on the unpainted area is not necessarily slippery than the rest of the runway. representative of the one when on the Indeed, some investigations highlighted painted marks. The crew must be ready that the repainting of the white strips to reassess the situation if any unexpected tended to fill the runway’s textured skidding during the turn is experienced. PROCEDURES 180° turns on runway

Control the ground speed and adapt it to the conditions of the day

Remaining on the runway while In order to optimize the turn initiation point performing a U-turn requires control of and the distance required to complete the trajectory at all times. This involves the turn, it is recommended to adopt a before initiating the turn: divergence angle from the runway axis. The advisable divergence angle varies Stabilizing the trajectory depending on the aircraft type but it Stabilizing the initial trajectory before typically ranges between 15° and 25°. the turn is key in many respects. It allows for: As illustrated in Figure 1, increasing the - optimization of the point of initiation divergence angle leads to an increase of the turn in the turn radius. For example, adopt- - compliancy with the assumptions ing a divergence angle of 40° instead of used to determine the minimum the recommended 20° for an A330-300 runway width required, i.e. the leads to an increase of about 2 meters. maneuver is properly performed (initial Decreasing the divergence angle by too recommended divergence angle) large an amount would result in the main - reduction of the number of parameters landing gear possibly exiting the runway to be managed during the turn itself. at initiation of the turn.

Measure of Difference A330-300 necessary width compared Measure of Difference Divergence Nose Wheel with FCOM necessary width between 80 and angle Steering Angle recommended NWSA 80% (m) 95% NWSA (m) (NWSA) 95% (m) value of 20° (m) 10° 56.2 -0.17 65.6 9.4 Recommended 56.4 0 65.7 9.3 20° 40° 58.1 1.7 67.4 9.3

Stabilizing the ground speed As mentioned earlier, any degradation of The recommended ground speed for the the runway state either due to runway 180° maneuver should be between 5 and surface condition or contamination 10 kt on most aircraft. If the speed is not requires additional precautions and stabilized before the turn, larger thrust margins. In terms of speed, it is safer adjustments may be needed during to target the lower boundary of the the turn. However, these adjustments recommended speed window, namely can lead to an increase beyond the 5 kt, to perform a U-turn on a degraded recommended speed, and may be a runway. contributor to a runway excursion.

BEST PRACTICE

On A300/A310, A330/A340 and A350 families, on dry runways, the use of differential braking to stop one gear (Braked Pivot Turn technique) may induce stress on this gear and could have fatigue effects over time on the gear. Such a technique is therefore not recommended. However, on a wet or contaminated runway, the lower friction coefficient reduces the induced stresses and differential braking, whilst avoiding pivot braking, could help to manage the turn. This recommendation does not apply to A320 family and A380 aircraft, for which the Braked Pivot Turn technique is usually used without adverse effect on the gears. Safety First #22 | July 2016 019

(fig.1) α-10° Turn radius evolution as a function of the divergence angle α

The α NLG may leave The the MLG runway may leave α+20° the runway

Left MLG Optimum angle Turn radius close to exiting value (FCOM). increased. the runway.

Actual main gear path Actual nose gear path

Performing the turn

During the maneuver, the ground stop. To avoid stopping, applying some speed is a key parameter to manage: additional thrust may be necessary. the objective is to maintain a low (5 to However, gaining too much speed could 10 kt) but steady ground speed. If too increase the chances of the aircraft exiting much speed is lost, turning the aircraft the runway. Maintaining a continuous will become more difficult to manage and speed before and during the turn is it may eventually come to a complete therefore of paramount importance.

Initiating the turn

For field of view reasons, the turn is member on the right hand side is PF. recommended to be performed by the crew member sitting on the seat opposite The visual reference to initiate the turn to the direction of the U-turn. This means depends on the aircraft type. On most that to turn right, the flight crew member Airbus aircraft, the turn is to be initiated on the left hand side of the cockpit is PF; when the PF assesses that he/she is respectively to turn left, the flight crew physically directly over the runway edge. PROCEDURES 180° turns on runway

Once the PF reaches the appropriate progressively. This is why an aggressive initiation point, he/she needs to application of full nose wheel steering progressively use up to full tiller deflection should not be done. to turn the aircraft. The speed can be maintained by During this initial maneuver, due to the applying small amounts of asymmetric aircraft inertia the nose wheels are not thrust and keeping idle thrust on fully aligned with the aircraft trajectory. the engine on the inside of the turn. This misalignment reduces the grip of As explained before, maintaining a the nose wheels onto the runway and continuous speed is key and after any may lead the aircraft to skid if the nose adjustment to the thrust, the speed wheels are not turned smoothly and must be carefully monitored.

During the turn

As shown in Figure 1, if the divergence The role of the PM is at all times to angle affects the required turning monitor not only the aircraft trajectory distance, then the steering value is a but also the aircraft ground speed parameter even more significant. The and to call out any deviation. The minimum distance published in the PM can monitor the heading, the operation documentation considers ground speed indication as well as a full steering order throughout the the ETACS when available. Indeed, whole maneuver. by focusing on the outside, the PF cannot closely monitor these Throughout the turn, the PF is focused parameters and especially the on the dynamics of the maneuver. He/ aircraft ground speed to detect any she is looking outside in the direction excursion outside the recommended of the expected aircraft trajectory, and speed range; therefore, the role of the adjusting the aircraft speed accordingly. PM is essential.

Finishing the turn

In this phase of the turn, the main with the aircraft and therefore ready to challenge is to get the aircraft aligned initiate the take-off roll in good conditions. At any stage on the centre of the runway without before or during jeopardizing the remaining runway At any stage before or during the the maneuver, should length or the planned take-off distance maneuver, should any problem arise, available. stop and call the tower to get support any problem arise, from a tug. Keep in mind that it is most stop and call the When the aircraft is aligned with the preferable to call a tractor to finish the runway, the tiller is to be released maneuver, rather than to recover the tower to get support smoothly before stopping the aircraft to aircraft with a landing gear off of the from a tug. make sure that the nose wheel is aligned runway. Safety First #22 | July 2016 021

Performing a U-turn on a runway is not an insignificant maneuver. Safely performing it starts with good preparation and a precise initiation of the turn as well as implementing the technique properly at the right speed. Whether it has to be performed before taking-off or at the end of the flight, some key aspects are to be kept in mind: - Carefully check the minimum distance published in the operational manual versus the available runway width, keeping in mind that the minimum 180° turning distance published values correspond to a dry runway - Pay attention to the runway condition, both surface quality and contamination, as they may induce skid and may increase the turn width. Add reasonable margins accordingly - Adapt the speed to the runway condition (within the recommended speed range) - In case of a problem at any stage of the overall maneuver, stop the aircraft and call for support - Should the crew become aware that the aircraft has left the runway surface, even slightly, report the occurrence and inspect the aircraft before taking-off Some simple advice to avoid big problems! OPERATIONS Optimum use of weather radar

Optimum use of weather radar In recent years, there have been a number of flights where passengers or crew suffered injuries due to severe turbulence. In some other instances, the aircraft structure was substantially damaged following a hailstorm encounter. Clearly adverse weather can pose a threat to the safe and comfortable completion of a flight, thus it needs to be detected and avoided in a timely manner.

DAVID CHRISTIAN LAURENT MARCONNET NORDEN VIDAL Flight Operations Director Flight Surveillance Systems Support & Training Operations & Manager Standards Safety Training Policy Enhancement Safety First #22 | July 2016 023

The airborne weather radar system is an essential tool for pilots to assess the intensity of convective weather ahead of the aircraft. In this respect, it enables the strategic and tactical planning of a safe flight trajectory. Weather radar technology has evolved significantly in the last few years and a range of enhanced products is now available. If properly used, they permit pilots workload to be significantly reduced while substantially reducing encounters with adverse weather. This article offers an overview of the existing weather radar technologies, and provides information and tips on how to tune the system and correctly interpret the available displays.

WEATHER RADAR PRINCIPLE AND OPERATION

The weather radar system installed the crew to carefully optimize its Prevention on-board aircraft provides the pilot with use. This relies primarily on a good the necessary information to avoid - not meteorological knowledge of weather through anticipation penetrate - adverse weather. phenomena, along with a good is essential. To obtain the maximum benefit from understanding of the available radar the weather radar system requires functions. Flying in adverse weather: lessons learned

The aviation industry experience shows aircraft damage (fig.1). that although aircraft are equipped with These events have led us to wonder airborne weather radars, incursions why such encounters happen, and into very active convective cells still clearly show that prevention through occur, resulting in injuries or substantial anticipation is essential. (fig.1) Radome and windshield after hail encounter

Weather When it comes to understanding is the active monitoring of the overall radar is of help, why aircraft fitted with technologically meteorological situation by the crew, but the crew overall advanced weather radars can end in addition to the optimum use of the up flying in such unfavorable weather weather radar and correct understanding assessment patterns, we have to consider that getting of the information displayed. We must of the weather the best out of technology onboard is not forget that weather radar is of help, just a part of the answer. A key element but the crew overall assessment of the situation plays of adverse weather avoidance strategies weather situation plays the central role. the central role. OPERATIONS Optimum use of weather radar

HOW IS A CUMULONIMBUS, OFTEN CALLED “THUNDERSTORM”, STRUCTURED?

Three common threats to aircraft are turbulence (which Understanding how a cumulonimbus cloud is structured is caused when two masses of air collide at different and evolves is key in dodging the associated weather speeds), hail and windshear. All three of these are disturbances. by-products of thunderstorms. High concentration of Ice Crystals

FL 350 -40°C

23 000 ft -15°C

16 000 ft Freezing Level

WIND SHEAR TURBULENCE WIND SHEAR TURBULENCE DUST Super-cooled liquid droplet Ice crystals

Turbulence:

Turbulence associated with a cumulonimbus is not it is necessary to apply recommendations for weather limited to inside the cloud. Therefore, when flying in avoidance as summarized in this article. an area where cumulonimbus clouds have developed,

Hail:

The presence of hail within a Risk of encountering hail relative to cumulonimbus cloud position cumulonimbus varies with altitude and wind:

- Below FL 100, hail is equally likely to be encountered under the storm, in the cloud or around it (up to 2 NM).

- Between FL 100 and FL 200, approximately 60 percent of hail is encountered in the cumulonimbus and 40 percent is encountered outside the cloud, under the anvil.

- Above FL 200, hail is most likely to be encountered inside the cloud.

When hail is encountered outside driven upward within the cloud by is less risk of hail in humid air than the cloud, usually the threat of strong drafts. It then freezes and is in dry air. In fact, moisture in the air hail is greater downwind of the transformed into hail before being behaves as a heat conductor, and cumulonimbus because moisture is blown downwind. Paradoxically, there helps to melt the hail. Safety First #22 | July 2016 025

Weather radar principle

A knowledge of the radar principle tune this system and interpret the On the Airbus is paramount in order to accurately weather radar display correctly. fleet, all weather Reflectivity radars have full capability to allow Weather detection is based on the The weather radar echo returns vary reflectivity of water droplets(fig.2) . The in intensity as a function of the drop- wet turbulence weather echo appears on the Naviga- let size, composition and quantity. For detection. tion Display (ND) with a color scale that example, a water particle is five times goes from red (high reflectivity) to green more reflective than an ice particle of (low reflectivity). the same size.

High Re ectivity (fig.2) Wet Hail Weather radar principle

Good Re ectivity

Liquid Rain water

Wet Snow

Dry Hail

Dry Snow Low Re ectivity Fog Drizzle Low Re ectivity

Some weather radars are fitted of light rainfall, depicted in green in with a turbulence display mode. normal mode, is shown in magenta This function (the TURB function) is when there is high turbulence activity. based on the Doppler effect and is The TURB function is on most weather sensitive to precipitation movement. radars only active within a range of 40 Like the weather radar, the TURB NM (Doppler measurement capability) function needs a minimum amount of and should only be used in wet precipitation to be effective. An area turbulence. DID YOU

Weather radar operation KNOW Each type of weather radar has its own The flight crew uses four features to has an essential influence on the particularities. To get all the information on operate the radar: optimum tilt setting. the characteristics, limitations and opera- - Antenna tilt: this is the angle between - Gain control: this adjusts the tional recommendations of each weather the centre of the beam and the sensitivity of the receiver. radar model, the user guide of the radar horizon (fig.3). - Radar modes: weather (WX) or manufacturer needs to be studied. - Range control of the ND: this weather + turbulence (WX + T).

(fig.3) Definition of the TILT OPERATIONS Optimum use of weather radar

Weather radar limitations

Weather radar detection capability Reflectivity One of the weather radar limitations is winds produce large scale uplifts of that it indicates only the presence of dry air. The resulting weather cells have is not directly liquid water. The consequence is that much less reflectivity than mid-latitude proportional to a thunderstorm does not have the convective cells. However, turbulence same reflectivity over its altitude range in or above such clouds may have a the level of risk because the quantity of liquid water in higher intensity than indicated by the that may be the atmosphere decreases with the image on the weather radar display. encountered. altitude (fig.4). Yet, the convective On the other hand, air close to the cloud and associated threats may sea can be very humid. In this case, extend significantly above the upper thermal convection will produce clouds detection limit of the weather radar that are full of water: these clouds will (called ‘radar top’). This means that have a high reflectivity, but may not reflectivity is not directly proportional to necessarily be a high threat. the level of risk that may be encountered: a convective cloud may be dangerous, Consequently, limitations of weather even if the radar echo is weak. radars must be well understood and complemented by basic meteorological This is particularly true for equatorial knowledge of the crew and, where overland regions where converging possible, visual observation.

Turbulence Area Turbulent area, not detected Re ectivity by the weather radar Visible Top

Radar Top

0°C

(fig.4) Reflective image of a cumulonimbus

The weather radar detects: The weather radar does not detect:

- Rainfall - Ice crystals, dry hail * and snow - Wet hail and wet turbulence - Clear air turbulence - Windshear - Sandstorms (solid particles are almost transparent to the radar beam) - Lightning *

* The latest generations of weather radars offer hail and lightning prediction functions (see the following sections). Safety First #22 | July 2016 027

The beam attenuation phenomenon Another limitation of the weather radar and intensity of that weather may not be A black hole is called ‘shadowing’ or ‘attenuation’. accurately displayed to the pilot. What The weather radar display depends appears to be a thin or inexistent band behind a red area on signal returns: the more intense the of precipitation (fig.5) could in fact be on a weather radar precipitation, the less distance the radar the leading edge of a much larger area can see through. Therefore when the of precipitation. Secondly, any weather display should always radar echo is unable to make the two behind such strong shadowing cells be considered way trip through heavy precipitation, a will not be detected. This can result in as a zone that is ‘shadowing’ effect occurs. unexpected weather unfolding only after The result is twofold. First, the size, shape the cell has been circumnavigated. potentially very active and shadows weather further down the scanned path.

(fig.5) Attenuation caused by moderate to extreme precipitation

WEATHER RADAR TECHNOLOGY: THE DIFFERENT TYPES OF WEATHER RADAR

In cooperation with its suppliers, These continuous improvements have Airbus has continuously and pro- allowed the crew to be provided with actively supported weather radar optimized observation features and technology evolution over the years. weather threat assessment functions. NOTE Radars with manual controls Early generation of full manual Full manual control radars controlled radars without auto tilt are: Rockwell Collins WXR- Early generations of radars are not the expected weather on path and 701X family up to weather radar equipped with an automatic tilt the ND range selection. Then the pilot transceiver Part Number 622-5132- function; therefore the antenna tilt needs to analyze and understand the 624 and Honeywell RDR-4B family needs to be manually adjusted up individual radar slices of weather up to weather radar transceiver Part and down as the flight progresses displayed in order to get an overall Number 066-50008-0407. according to the aircraft’s altitude, picture. OPERATIONS Optimum use of weather radar

Autotilt radar (Honeywell RDR-4B family PN 066-50008-0409)

Honeywell introduced the first weather the EGPWS terrain database and radar featuring an automatic tilt automatically adjusts the antenna tilt computation named “Autotilt”. based on the aircraft position, altitude, When in Autotilt mode, the radar uses and the selected ND range (fig.6).

(fig.6) Honeywell Autotilt

Fully automatic radars Automatic The next generation of radars included - Offer independent pilot control and automatic functions, which: display selection. radars optimize - Scan airspace ahead of the aircraft weather detection with multiple beams These new radars optimize weather and decrease - Feature a three dimensional (3D) detection and decrease significantly buffer to store weather data the pilots’ workload necessary to significantly the - Automatically compute and adjust understand the complete picture of pilots’ workload. the antenna tilt the weather ahead.

A320 & A330 families: Multiscan radar (Rockwell Collins WXR-2100 family)

The WXR-2100 Multiscan weather antenna tilt settings. The image that is radar is part of this new generation displayed on the ND is the result of the of weather radars that offers an stored and combined information from automatic computation of tilt and gain each beam. control at all ranges, all altitudes and The radar automatically adjusts the gain all times (fig.7). and tilt based on various parameters This weather radar is designed to work in (aircraft altitude, geographical area, Multiscan automatic mode. Pilots select season, time of the day) to obtain only the desired range for the display the best weather display in each and the radar alternatively scans at two geographic region.

(fig.7) Rockwell Collins Multiscan Safety First #22 | July 2016 029

UpperUpper Beam Beam LowerLower Beam Beam

Upper Upper and lower Beam beams data merge Upper Upper and lower Beam beams data+ merge Ground Lower Clutter+ Suppression Beam Ground(GCS) Lower Clutter Suppression Beam (GCS)

A320 & A330 & A350 & A380 families: Honeywell RDR-4000

The Honeywell RDR-4000 model is part A380) to show the en route weather of the new generation of weather radars picture, as well as automatically scan including a 3D volumetric buffer. from the ground up to 60 000 feet to provide information targeted at various It can probe hundreds of miles ahead altitudes. The required display data (up to 320 NM on A320 & A330 families are then accessed from the 3D buffer and up to 640 NM on A350 and (fig.8 and 9).

(fig.8) Honeywell RDR-4000 control panel on A320 & A330 families OPERATIONS Optimum use of weather radar

(fig.9) Honeywell RDR-4000 control panel on A350 & A380

When it is activated in the automatic ‘OFF PATH’) depending on the flight mode, the radar RDR-4000 takes into profile. Weather conditions along the account a vertical trajectory envelope plane’s trajectory are displayed in solid (nominally +/- 4000 ft) along the vertical colors, while more distant vertical flight path of the aircraft based on the echoes are shown in striped pattern to flight path angle. It then defines if the help pilots determine whether weather weather echo is inside this envelope avoidance maneuver or rerouting is (relevant ‘ON PATH’) or not (secondary necessary (fig.10).

(fig.10) Honeywell RDR-4000 display Relevant ‘ON PATH’ weather displayed in solid colors

Secondary ‘OFF PATH’ weather displayed in striped pattern

The RDR-4000 can also be used in - the ND, for views along the vertical manual mode (elevation mode) as a flight path (in AUTO mode) or along tool for analyzing weather at user- the selected altitude (in ELEVN NOTE selected altitudes and thus, assess mode) or along the selected tilt angle the vertical expansion and structure (in TILT mode) These enhanced weather radars of convective clouds. are provided at Entry Into Service This system is available on the A380 - as well as on the Vertical Display for new programmes (A380, A350) and also on the A350 with an additional (VD) for views along the lateral flight and as a retrofit option for A320 and ‘weather ahead’ alerting function. On path (in AUTO mode) or along the A330 families. these aircraft, the weather displayed is selected azimuth (in AZIM mode) a computed image on: (fig.11). Safety First #22 | July 2016 031

(fig.11) Weather information displayed on the Vertical Display

Hail and lightning prediction: the new functions introduced by ‘step 2’ automatic radars

In continuity of RDR-4000 and AHEAD’) to alert the crew when the Multiscan WXR-2100, a new step of ND is not in weather mode development recently introduced: - Hazard functions offering: - Hail and lightning prediction • Lightning and hail prediction - Improved weather information. • Rain Echo Attenuation Compen- sation Technique (REACT): this Honeywell RDR-4000 (V2) function indicates areas where includes new features to improve the intensity of the radar echo has weather hazard assessment by been attenuated by intervening automatically providing the following weather. additional information (fig.12): • Extended turbulence detection - Weather alerting (‘WEATHER (up to 60 NM instead of 40).

(fig.12) Honeywell RDR-4000 V2 display

REACT

Lightning risk area Hail risk area 60 NM Turbulence OPERATIONS Optimum use of weather radar

Rockwell Collins Multiscan the corresponding threat based on WXR-2100 (V2) includes an automatic reflectivity characteristics(fig.13) . weather threat assessment (“Track This new radar also provides hazard While Scan” function). In continuity of functions, namely: the Multiscan, the aim of this version - Lightning and hail prediction is to provide not only a depiction of - Predictive OverFlight (this function the reflectivity of surrounding weather alerts the crew to growing cells cells, but also a threat assessment for that are potentially on the aircraft each cell detected. trajectory) Weather cells are first tracked and - Improved turbulence detection then, additional vertical scans are able to display an additional level of performed automatically to assess moderate turbulence.

(fig.13) Rockwell Collins Multiscan V2 threat Predictive OverFlight detection and analysis (convective phenomenon)

Two levels of turbulence (severe: plain magenta, moderate: magenta speckles)

Associated threats (area with hail and lightning probability)

NOTE

Honeywell RDR-4000 V2 and Rockwell Collins Multiscan WXR-2100 V2 weather radars were certified in July 2015 for A320 and A330/A340 families and are available as retrofit options. Safety First #22 | July 2016 033

Coming next… the future evolution of weather information

Airbus in cooperation with weather on aircraft. The next generation of radars suppliers, maintain their efforts weather radars is expected to benefit in designing and producing new from this research work and enable weather surveillance functions. Today, the detection of ice crystals to avoid at a research level, a strong focus is convective weather linked to ice placed on three main dimensions with crystal icing. the aim to improve pilots’ awareness of the weather ahead. 2. Weather display fusion to offer a single display of weather data 1. High Altitude Ice Crystal (HAIC) covering all weather threats. detection to avoid flying in ice The feasibility of collecting all “weather crystals areas. on board” information together with There are multiple threats attributed weather information collected by to ice crystals; for example, engine the radar (reflectivity, turbulence and vibrations, engine power loss, engine hazards) and merging them in a single damage or icing of air data probes. display is currently being studied. In fact, the formation of ice crystals at high altitude and their effect on 3. 3D weather analysis: automatic aircraft performance is recognized re-routing as an industry wide issue. Airbus in Work is also being carried out to allow the particular is leading the HAIC research automatic computation of an optimized project with several partners. This deviation route based on: the actual project aims to characterize and weather (weather on board and radar identify the environmental conditions data), the ongoing traffic and the stored of ice crystals, to improve aircraft flight plan. Such a function is expected operations through the development to facilitate pilot’s decision making and of appropriate detection and re-routing planning if needed. Additionally awareness technologies to be fitted it improves comfort. OPERATIONS Optimum use of weather radar

PUTTING THEORY INTO PRACTICE: HOW TO MAKE AN OPTIMUM USE OF THE AIRBORNE WEATHER RADAR

The weather radar is a tool for detecting, charts and online simulation) and during analyzing and avoiding adverse weather flight (update on weather information) and turbulence. As with any other - Adapted use of the weather radar, tool, adequate skills and the crew’s with the crew regularly assessing involvement are needed in order to use the range, gain and tilt, and making it efficiently. In fact, the management use of weather threat assessment of adverse weather still relies primarily functions when available in order to on the crew to actively monitor the display an optimum weather radar meteorological situation throughout the picture on the ND. flight, and make a full use of the available - Regular manual vertical and horizontal technology thanks to: scanning by the crew to increase - Awareness of weather radar capabilities situation awareness. and limitations, according to the - Correct understanding of the radar specificities outlined in the FCOM and image displayed. the manufacturer’s user guide. - Adequate strategic (mid-term) and - Preflight briefing (knowledge of the route tactical (short term) decision making climatology and weather forecast – for trajectory planning. How to optimally tune the weather radar and manage flights in convective weather? Flight planning: the importance of weather briefing and weather reports

Weather avoidance already starts in on both the weather briefing and their the briefing room before commencing knowledge of local climatology. Changing the flight, with a thorough assessment the flight route could be an option as well of en-route weather and decisions on as taking additional fuel for enhanced possible mitigation means. strategic and tactical options in flight. Before boarding, a weather briefing Once airborne, the weather radar should Once airborne, should reveal areas of predicted be used and tuned regularly in combination the weather radar significant weather activity. Equally, this with all available information, e.g. pre- should be used briefing should include the assessment of flight briefing, pilot’s knowledge and typical weather patterns in the area. For experience of the area’s typicality, reported and tuned regularly example in the tropics, cumulonimbus turbulence, updated weather reports… If in combination with intensity and development is greater at possible, the weather information should certain times of the day. The crew have be updated in flight regularly. Information all available weather the opportunity at this stage to plan a sought by ATC of turbulence encounters information. route to avoid active weather based are an additional means. INFORMATION

Safe operation in convective weather requires good theoretical knowledge of meteorology, particularly on the formation, development and characteristics of convective clouds in different regions of the world. This knowledge is usually provided in pilot licencing and operational training and is not covered by aircraft documentation (FCOM and FCTM). Safety First #22 | July 2016 035

Weather radar antenna tilt Effective management of the antenna The flight crew needs to periodically The automatic tilt along with an appropriate ND range scan: selection, are key tools to obtaining an - Vertically, using the antenna tilt function mode should be informative weather radar display on - Horizontally, using the range change. used as the default the ND. If available, the automatic mode mode, for detection The ND might not display cells at should be used as the default and initial evaluation aircraft flight level, only cells that are mode (unless mentioned differently of displayed weather. cut by the radar beam are shown in the FCOM), for detection and (fig.14). For this reason, the antenna initial evaluation of displayed Then, manual tilt needs to be adjusted up and down weather. Then, if adverse weather control should be regularly to scan weather ahead, is suspected (e.g. according to and it needs to be adjusted to the information gathered during the pre- used periodically ND range selection (except with the flight briefing), manual control should to analyze the most recent radar models where this be used regularly and actively to weather. adjustment is made automatically). analyze the weather ahead.

(fig.14) Display along radar beam

BEST PRACTICE

Even when the tilt is adjusted automatically, pilots are advised to reverse to the manual mode “MAN” regularly in order to scan the immediate weather ahead. This action allows the crew to assess the vertical structure and expansion of convective clouds.

Factors that can affect the relevancy of - The shape of thunderstorms the ND display and that should trigger - A pilot report from another aircraft in a tilt adjustment are: the vicinity. - A heading change In the case of a change in heading - An altitude change, or even a regular or altitude, leaving the antenna tilt on flight profile change (e.g. from climb auto may induce a risk of overlooking to cruise) weather or underestimating the OPERATIONS Optimum use of weather radar

severity of the weather. For example, convective cell because the tilt is at take-off or in climb, the tilt should be set incorrectly (too high in this case) set up if adverse weather is expected while in the auto-tilt mode. When the above the aircraft. Figure 15 is an antenna is tilted down, the ND shows example of radar overshooting a a much stronger activity. (fig.15) Weather radar display at different tilt settings

Overscanning

Correct storm display Presence of To analyze a convective cell, the flight then be used to scan the area verti- crew should use the tilt knob to obtain cally. Presence of yellow or green areas yellow or green areas a correct display and point the weather at high altitudes, above a red cell, may at high altitudes, radar beam to the most reflective part indicate a very turbulent area. of the cell. At high altitude, a thunder- above a red cell, storm may contain ice particles that In most cases in flight, the adequate may indicate a very have low reflectivity. If the tilt setting is antenna tilt setting shows some ground turbulent area. not adapted, the ND may display only returns at the top edge of the ND, which the upper (less reflective) part of the may be difficult to differentiate from convective cloud (overscanning). As genuine weather echoes. A change in a result, the flight crew may underes- antenna tilt rapidly changes the shape timate or not detect a thunderstorm. In and color of ground returns and eventually order to get accurate weather detec- causes them to disappear. This is not the tion, the weather radar antenna should case for weather echoes. Some weather also be pointed toward lower levels (i.e. radars are fitted with a Ground Clutter below freezing level), where water can Suppress (GCS) function. When turned still be found. If a red area is found at ON, it suppresses the ground return from a lower level, the antenna tilt should the display.

Display range management

To maintain a comprehensive situation therefore, the following ranges should be awareness, the flight crew needs to selected on the NDs: monitor both the short-distance and - Pilot Monitoring (PM) adjusts ranges to DID YOU long-distance weather. To this end, the plan the long-term weather avoidance KNOW crew should select different ranges on strategy (in cruise, typically 160 NM the Pilot Monitoring (PM) and Pilot Fly- and below). The FCTM provides useful guidance ing (PF) ND. - Pilot Flying (PF) adjusts ranges to moni- to correctly tune the weather radar in To avoid threatening convective weather, tor the severity of adverse weather, and accordance with the flight phase. the flight crew should make deviation decide on avoidance tactics (in cruise, decisions while still at least 40 NM away; typically 80 NM and below as required). Safety First #22 | July 2016 037

Course changes to avoid adverse seem safe when using a low range ND weather should be determined using display may reveal a blocked passage both displays. This prevents the “blind when observed at a higher range alley” effect: a course change that may (fig.16).

The crew should select different ranges on the Pilot Monitoring (PM) and Pilot Flying (PF) ND.

(fig.16) Blind alley effect

Gain adjustment

The sensitivity of the receiver may significant positive ISA deviations in a vary from one type of radar system to very humid atmosphere (typically the another. In the CAL (AUTO) position, Indian monsoon). In these cases, slowly the gain is in the optimum position to reducing the gain allows the detection detect standard convective clouds. of threatening areas: most red areas Manual settings are also available and slowly turn yellow, the yellow areas can be used to analyze weather. turn green and the green areas slowly disappear. The remaining red areas – At low altitudes, reducing the gain i.e. the red areas that are the last to turn might be justified for proper weather yellow, - are the most active parts of analysis. Due to increased humidity the cell and must be avoided (fig.17). at lower levels, convective cells are usually more reflective and the weather At high altitudes, water particles are radar display may have a tendency to frozen and clouds are less reflective. show a lot of red areas. This can also In this case, gain should be increased be the case at higher altitude with for threat evaluation purposes.

Gain decreased

(fig.17) Effect of gain reduction OPERATIONS Optimum use of weather radar

Turbulence and weather threats detection

Turbulence can be difficult to predict, the radar standard) (fig.18). Remem- but signs such as frequent and strong ber that the TURB function needs lightning and/or the specific shape of humidity; therefore clear air turbulence The TURB clouds (see the next section) can alert will not be displayed. function needs the crew to the likely presence of severe turbulence. If necessary and when In addition, the flight crew may be humidity; therefore available (according to the standard alerted by visual cues provided by the clear air turbulence of weather radar onboard), the TURB latest generations of weather radars function can additionally be used to that offer weather threat assessment will not be confirm the presence of wet turbulence functions, such as hail or lightning displayed. up to 40 NM (or 60 NM depending on predictions.

(fig.18) Turbulence detection (in magenta) Safety First #22 | July 2016 039

HOW TO CORRECTLY TUNE THE WEATHER RADAR AT A GLANCE

Study the weather radar’s specificities and limitations through Before flight the FCOM, FCTM and weather radar user guide.

Gather information about the Before forecasted weather and update and regularly during flight: weather during flight briefing, route climatology knowledge, reported turbulence…

Set the antenna tilt to auto as the default mode for detection and initial evaluation of weather, During flight and periodically use the manual modes to scan and analyze the weather situation.

In cruise the combination of the following ranges provides good weather awareness and allows to During flight avoid the “blind alley effect”: - 160 NM on the PM ND - 80 NM on the PF ND.

Use gain in AUTO/CAL mode by default, then regularly reduce During flight the gain for weather severity assessment.

Be attentive to the visual and oral cues provided by the weather During flight threat and hazard assessment functions (as installed). OPERATIONS Lithium batteries: safe to fly?

Weather radar data understanding: how to decide on an effective avoidance strategy?

Before any avoidance maneuver is to conduct an in-depth analysis of the initiated, the analysis the flight crew convective weather situation on-path makes of the weather radar display is and off-path and eventually, initiate essential. Doing so, the crew is able action if needed.

Correctly understanding the weather display is paramount

After the weather radar has been tuned conditions are too dangerous to fly in. correctly, the data displayed should be supplemented with the available weather Some ND displays contain specific charts, reports and the meteorological cues that should alert the flight crew. knowledge of the pilot. Altogether these Clouds shapes, in addition to colors, data enable the flight crew to get a should be observed carefully in order complete weather picture and establish to detect adverse weather conditions. an “area of threat”. This “area of threat” Closely spaced areas of different colors corresponds to the zone where the usually indicate highly turbulent zones flight crew estimates that the weather (fig.19).

(fig.19) Indication of a threat: closely spaced areas of different colors Some shapes are good indicators of changing shapes, whatever the form severe hail that also indicate strong they take, also indicate high weather vertical drafts (fig.20). Finally, fast activity.

Finger Hook (fig.20) Shapes indicative of adverse weather

U-Shape Scalloped Edges Safety First #22 | July 2016 041

Avoidance strategy Consider a The flight crew needs to remain vigilant been taken, flight crews need to bear in and active in using and tuning the mind the following advisory precautions minimum distance weather radar in order to be able to and limits before actually deciding the tra- of 40 NM from initiate an avoidance maneuver as early jectory of the avoidance maneuver. as possible. Indeed, weather radar a threatening information becomes more intense as If possible, it is preferable to perform convective cloud to the aircraft gets nearer the convective lateral avoidance instead of vertical initiate the avoidance weather zone, thus making avoidance avoidance. Indeed, vertical avoidance is decisions more difficult. For this reason, not always possible (particularly at high maneuver. crews should consider a minimum altitude) due to the reduction of buffet distance of 40 NM from the convective and performance margins. In addition, cloud to initiate the avoidance maneuver. some convective clouds may have a significant build-up speed, that extends Once the decision to deviate course has far above the radar visible top.

Lateral avoidance

• When possible, it is advisable to try (fig.21). An additional margin may be to avoid a storm by flying on the applied in case the convective clouds upwind side of a cumulonimbus. are very dynamic or have a significant Usually, there is less turbulence and build-up speed. hail upwind of a convective cloud. • If the aircraft trajectory goes • The “area of threat” identified by the between several convective clouds, flight crew (e.g. a cumulonimbus cloud) if possible maintain a margin of at should be cleared by a minimum of least 40 NM with the identified “area 20 NM laterally whenever possible of threat”.

Vertical avoidance

• Do not attempt to fly under a all indications (visual judgement, convective cloud, even when you weather radar, weather report, pilot’s can see through to the other side, report, etc) before they take the final due to possible severe turbulence, decision. windshear, microbursts and hail. If an aircraft must fly below a convective • If overflying a convective cloud cannot cloud (e.g. during approach), then the be avoided, apply a vertical margin of flight crew should take into account 5 000 feet (fig.21). OPERATIONS Optimum use of weather radar

5,000 feet 20 NM If possible, it is preferable to perform lateral avoidance instead of vertical avoidance.

(fig.21) Lateral and vertical circumvention margins

Practical example: typical scenario of severe weather avoidance strategy

Figure 22 shows a typical weather Route C: radar display indicating multiple areas of this route looks like a possible escape severe weather. What route would look route because it goes around most of like the preferable option? the storms by a wide safety margin. However, while doing so, the flight Route A: crew would need to keep a look at the this is the most direct route to destination cell to the left of this route, and see but it navigates right through the most whether it develops rapidly or not. In severe and active zone; therefore it is the addition, this route leads away from the path that carries the biggest risks and initial flight plan and therefore it could should not be an option. have operational implications such as fuel consumption or delays. Route B: this route could be tempting since it Route D: requires little deviation to the mainstream this route would be the preferable route and it looks like the most active option in terms of risks mitigation. red areas are avoided. Nevertheless, this trajectory leads downwind of the When faced with a situation where convective area, thus increasing the weather ahead reveals an extensive risk of encountering severe weather. storm system, several options are Additionally, the convective cells beneath always possible. Before the flight crew might be developing fast and upwards, makes a decision, it is prudent to ana- thus closing off the gap in between the red lyze weather carefully by scanning the zones. Before this option is considered, vertical expansion of the various cells, the flight crew would need to tilt the radar and if possible, consider deviation to antenna down to analyze weather and an alternate route. see what is below the apparent gap. Safety First #22 | July 2016 043

Route C

Route A Route B

Route D

(fig.22) Available options to avoiding weather

Regardless of how you locate a severe weather area – visual, by radar, or from a report – a key parameter to successful route planning and avoidance strategy is time. The weather radar, and enhanced models more particularly, can help you to analyze and understand distant weather accurately and evaluate weather scenarios from a distance. This system is a key tool to planning ahead to avoid last- minute decisions, and making a decision on circumnavigating a nasty convective cell with a comfortable safety margin. In addition to technology, you need to stay active in maintaining situation awareness throughout the flight. Regularly complement the radar images displayed by a manual vertical scan of surrounding cells, as well as gain and tilt adjustments as required. Last but not least, adhere to your knowledge of meteorology basics, local climatology and weather briefing to adopt the best course of actions, and navigate safely, effectively and comfortably to destination. ARTICLES PUBLISHED IN PREVIOUS ‘SAFETY FIRST’ ISSUES

Issue 21 Issue 20 Issue 19

January 2016 July 2015 January 2015

• Control your speed... in cruise • Control your speed... during climb • Tidy cockpit for safe flight • Lithium batteries: safe to fly? • Lateral runway excursions upon landing • Landing on contaminated runways • Wake vortices • Fuel monitoring on A320 Family aircraft • Understanding weight & balance • A320 Family Aircraft configuration • Hight-altitude manual flying • Wind shear: an invisible enemy to pilots?

Issue 18 Issue 17 Issue 16

July 2014 January 2014 July 2013

• Control your speed... at take-off • Airbus Brake Testing • Performance Based Navigation: • Safe operations with composite aircraft • Hard Landing, a Case Study for Crews RNP and RNP AR Approaches • Learning from the evidence and Maintenance Personnel • Atlantic Airways: Introduction • A320 Family cargo Containers/ pallets • Aircraft Protection during Washing and of RNP AR 0.1 Operations movement Painting • Flight Crews and De-Icing Personnel • Parts Departing from Aircraft (PDA) • Flight Data Analysis (FDA), a Predictive – Working together in Temporary Tool for Safety Management System Teamwork for safe Skies (SMS) • Low Speed Rejected Take-Off upon • Flying a Go-Around, Managing Energy Engine Failure • Late Changes before Departure

Issue 15 Issue 14 Issue 13

January 2013 July 2012 January 2012

• The Golden Rules for Pilots moving • Thrust Reverser Selection means • A320 Family / A330 Prevention and from PNF to PM Full-Stop Handling of Dual Bleed Loss • Airbus Crosswind Development and • Transient Loss of Communication due • The Fuel Penalty Factor Certification to Jammed Push-To-Talk A320 and • The Airbus TCAS Alert Prevention • The SMOKE/FUMES/AVNCS SMOKE A330/A340 Families (TCAP) Procedure • A380: Development of the Flight • A380: Development of the Flight • Post-Maintenance Foreign Objects Controls - Part 2 Controls - Part 1 Damage (FOD) Prevention • Preventing Fan Cowl Door Loss • Facing the Reality of everyday • Corrosion: • Do not forget that you are not alone in Maintenance Operations A Potential Safety Issue Maintenance Safety First #22 | July 2016 045

Issue 12 Issue 11 Issue 10

July 2011 January 2011 August 2010

• Airbus New Operational • What is Stall? How a Pilot Should • A380: Flutter Tests Landing Distances React in Front of a Stall Situation • Operational Landing Distances: • The Go Around Procedure • Minimum Control Speed Tests A New Standard for In-flight Landing • The Circling Approach on A380 Distance Assessment • VMU Tests on A380 • Radio Altimeter Erroneous Values • Go Around Handling • Automatic Landings • Automatic NAV Engagement at Go • A320: Landing Gear Downlock in Daily Operation Around • Situation Awareness and Decision Making

Issue 9 Issue 8 Issue 7

February 2010 July 2009 February 2009

• A320 Family: Evolution of Ground • The Runway Overrun Prevention • Airbus AP/FD TCAS Mode: A New Spoiler Logic System Step Towards Safety Improvement • Incorrect Pitch Trim Setting at Take-Off • The Take-Off Securing Function • Braking System Cross Connections • Technical Flight Familiarization • Computer Mixability: • Upset Recovery Training Aid, Revision 2 • Oxygen Safety An Important Function • Fuel Pumps Left in OFF Position • Fuel Spills During Refueling Operations • A320: Avoiding Dual Bleed Loss

Issue 6 Issue 5 Issue 4

July 2008 December 2007 June 2007

• A320: Runway Overrun • New CFIT Event During Non Precision • Operations Engineering Bulletin • FCTL Check after EFCS Reset on Ground Approach Reminder Function • A320: Possible Consequence of VMO/ • A320: Tail Strike at Take-Off? • Avoiding High Speed Rejected Take- MMO Exceedance • Unreliable Speed Offs Due to EGT Limit Exceedance • A320: Prevention of Tailstrikes • Compliance to Operational Procedures • Do you Know your ATC/TCAS Panel? • Low Fuel Situation Awareness • The Future Air Navigation • Managing Hailstorms • Rudder Pedal Jam System FANS B • Introducing the Maintenance Briefing • Why do Certain AMM Tasks Require Notes Equipment Resets? • A320: Dual hydraulic Loss • Slide/raft Improvement • Terrain Awareness and Warning Systems • Cabin Attendant Falling through the Operations Based on GPS Data Avionics Bay Access Panel in Cockpit

Issue 3 Issue 2 Issue 1

December 2006 September 2005 January 2005

• Dual Side Stick Inputs • Tailpipe or Engine Fire • Go Arounds in Addis-Ababa due to VOR • Trimmable Horizontal Stabilizer Damage • Managing Severe Turbulence Reception Problems • Pitot Probes Obstruction on Ground • Airbus Pilot Transition (ATP) • The Importance of the Pre-flight Flight • A340: Thrust Reverser Unlocked • Runway Excursions at Take-Off Control Check • Residual Cabin Pressure • A320: In-flight Thrust Reverser Deployment • Cabin Operations Briefing Notes • Airbus Flight Safety Manager Handbook • Hypoxia: An Invisible Enemy • Flight Operations Briefing Notes