FAST Magazine 31- December 2003

FAST N°31 AIRBUS TECHNICAL DIGEST DECEMBER 2002 AIRBUS TECHNICAL DIGEST DECEMBER 2002 A340-500 Arctic flights 3 Capt. Michel Brandt Just happened… Coming soon… 8 Potable water purity 9 Christian Sparr Less maintenance, less costs 13 Christian Delmas PAGE 1 AirN@v: The Airbus solution for advanced 17 consultation of interactive E-documentation 31 FAST Jan Renette Index of previous articles 26 From the archives... 29 Polar flying Editor: Denis Dempster Customer Services 30 Art Director: Agnès Massol-Lacombe Around the clock… Around the world in association with Chandler Gooding London • Leeds • Toulouse Customer Services Marketing Tel: +33 5 61 93 39 29 Fax: +33 5 61 93 27 67 E-mail: [email protected] Printer Escourbiac FAST may be read on Internet http://www.airbus.com under Customer Services/Publications Airbus Customer Services © AIRBUS 2002. All rights reserved The articles herein may be reprinted without permission except where copyright source is indicated, but with acknowledgement to Airbus. Articles which may be subject to ongoing review must have their accuracy verified prior to reprint. The statements made herein do not constitute an offer. This issue of FAST has been printed on paper They are based on the assumptions shown and are expressed in good faith. produced without using chlorine, to reduce Where the supporting grounds for these statements are not shown, waste and help conserve natural resources. the Company will be pleased to explain the basis thereof. Every little helps! PAGE 2 FAST 31 FAST A340-500 ARCTIC FLIGHTS Customer Services A340-500 Arctic flights Two flights exceeding 10 hours each were required for Both flights were planned and operated by the Airbus the A340-500 fuel system certification and for the Flight Test Division: Toulouse-Keflavik and Keflavik- evaluation of the ADIRS performance. In addition, the Toulouse, each time via the North Pole. behaviour of the navigation system and the Electronic Instrument System (EIS) had to be checked in the polar This article recalls some aspects of the polar navigation area including flying over the North Pole itself. observed during these flights. PAGE 3 FAST 31 FAST Capt. Michel Brandt Airbus Test Pilot Flight Operations Support A340-500 ARCTIC FLIGHTS DIGRESSION ON On TRUE heading MAGNETIC HEADING We left Toulouse on 12 September Although the Flight Management 2002 with 12 people on board, maxi- and Guidance System (FMGS) Traditionally, the polar area was defined mum fuel uplift and full flight-test remained in GPS PRIMARY mode as an area of magnetic compass equipment, including ballast, which of navigation update all the time, uncertainty and the limit was sometimes gave a take-off-weight (TOW) of we were able to cross-check the set where the earth magnetic field is less 325,000kg. Our flight plan led us to FMGS navigation with the Auto- than 6 microtesla. Except for the standby Vigra VHF Omnidirectional Range matic Direction Finder (ADF) compass, modern aircraft no longer have (VOR) in Norway to intercept the sometimes at a very great distance, magnetic sensors “slaving” the gyro- Polar Track System (PTS) route up to 500 nautical miles (nm) from compass to the magnetic north. The “November”. This route follows the the Non-Directional Beacon (NDB). magnetic variation is extracted from meridian 10°E to the North Pole. However, the wave propagation tables in the Air Data/Inertial Reference may not be always as good, for System (ADIRS) and the Flight Although Magnetic Heading (MH) example, during periods of aurora Management System (FMS). These tables is available until 82°N at this long- borealis. give an accurate magnetic variation up to itude, we selected TRUE heading a latitude of 82° N, or 73° N in function reference as soon as we were estab- Flying in NAVigation autopilot of the longitude. Beyond this latitude lished on the PTS. With this selec- (NAV) mode, nothing significant TRUE reference must be used. tion, the indications on navigation happened until approaching the Consequently, the 6 microtesla limit has display (ND) (Figure 1 below) and North Pole. We observed the rela- no meaning for these navigation systems. Multipurpose Control and Display tive position of each Inertial We nevertheless observed during these Unit (MCDU) were in line with the Reference System (IRS) to antici- flights that the standby compass True Tracks (TT) given on our nav- pate the system behaviour while indication was coherent well above the igation charts. flying over the North Pole. charted 6 microtesla limit. PAGE 4 When passing 65°N latitude the DIGRESSION ON GRID TRACK FAST 31 FAST grid track (GT) appeared on the navigation display. When flying east to west or west to east at very high latitude on an orthodromic (great circle) route, the true track changes quite rapidly due to the convergence of the meridians. On older aircraft, the true heading was not directly available to the crew. “Old style” Horizontal Situation Indicators (HSI) were set in a so-called free gyro mode on the Grid North reference. The characteristic of the grid track is that it remains constant on an orthodromic route as indicated in the drawing below, right. With our modern navigation system, the grid track would not be mandatory, as the true track is always available and the navigation charts indicate the outbound GRID North Direction and inbound true tracks at each waypoint for cross- Geographic check. But the grid track Pole indication on the navigation display provides the crew with at least a convenient GT Figure 1 stable indication for navigation monitoring in this moving display TT environment. GT 0º TT L O N G GT - TT+Long. W TT Variable GT - TT-Long. E GT Constant Note: Where words are spelt in capital letters it refers (Valid for a polar stereographic projection) to their use as cockpit labels, messages and displays. A340-500 ARCTIC FLIGHTS Figure 2 Figure 3a Note: The TAXI CAMERA was selected “on” in flight so the flight test engineers could see the landscape from their station in the cabin. Figure 3b HEADING BEHAVIOUR The ECAM procedure cannot be At 20nm outbound from the North followed, as all heading indications Pole, everything was nominal and At about 20nm before the Pole the start to move very quickly and it was time for us to turn left to heading discrepancies on ND switching ATT HDG on IRS3 intercept “another” 180° course to became noticeable and finally trig- would not help. The autopilot the VOR of Thule (THT). gered, as expected, the HDG DIS- remained engaged in NAV mode CREPANCY Electronic Central- and the aircraft continued nicely Despite the magnetic variation of PAGE ised Aircraft Monitor (ECAM) straight ahead. 66°W at Thule, the VOR THT is 5 caution (Figure 2) and CHECK magnetically oriented (some VORs 31 FAST HDG on the ND and Primary Flight When flying exactly (with GPS in north Canada are oriented to the Display (PFD) (Figures 3a and 3b). accuracy) over the North Pole the geographic North). As we were fly- ND display swung over by one ing with TRUE reference, the VOR The heading discrepancy is due to hundred eighty degrees from a needle on ND in MAP mode or the fact that each IRS has a differ- True Heading (TH) close to 000° to ROSE NAV mode is automatically ent position relative to the Pole. a TH close to 180° (the drift was corrected with the magnetic varia- small). But very quickly all head- tion, so as to get a TRUE bearing. ings were again in agreement as Otherwise the needle would not shown on the flight test traces indicate the direction to THT. This given in Figure 4 (below), and the is marked by the magenta color of ECAM caution disappeared. the needle and the label CORR next Figure 4 HDG of each IRS plotted versus time in seconds. 359.00 The red line indicates the time of the flight over the 287.20 North Pole. Before reaching the 215.40 North Pole the heading calculated by each IRS was close to 360°/000°. 143.60 After passing the North Pole all headings 71.80 converged rapidly to approximately 180°." 0.00 0 20 40 60 80 100 120 Sec GMT START: 13:54:56 A340-500 ARCTIC FLIGHTS Figure 5 Leaving the oceanic airspace we deselected TRUE to revert to magnetic reference and continued to destination, arriving at Keflavik after 10 hours 45 minutes flight time, having enough fuel to return to Toulouse with more than the required reserves. The next day we left Keflavik for Toulouse and headed north east to join and follow the PTS route “Romeo” up to ROGSO, a waypoint located 230nm to the north of Thule. At this waypoint we turned right to the North Pole. On PTS “Romeo” we selected TRUE reference, as it is better for navigation monitoring; but this time, before crossing 82°N, we deselected TRUE to revert to magnetic reference in order to see how the ECAM will advise us to select the right heading reference. Ellesmere Island PAGE 6 FAST 31 FAST Flight test engineers at station Figure 6 to the VOR2 display as shown in After passing THT (Figure 6) the Figures 5 and 6. The indications of outbound true track to the 7440N the Digital Distance and Radio waypoint was 095°. On this leg the Magnetic Indicator (DDRMI) and true track changed significantly, the ND in ROSE VOR mode are not from 095° to 123° due to the con- corrected, as they would be on a vergence of the meridians, but the conventional aircraft. When we grid track remained conveniently were at 77nm to THT, the DDRMI constant and equal to 163°.

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