Safety U.S. AIR FORCE

Boeing B-17F-5-BO 41-24406 Under Control from its pylon, taking out the No. 4 en- Making sure your airplane is ready gine and some flight controls. The pilots definitely had their hands full; and yet for an approach and landing they were able to fly for 8 min., main- taining altitude and changing heading when they wanted. They began fuel BY JAMES ALBRIGHT [email protected] dumping almost immediately. But as they slowed the increasing angle of at- magine flying a B-17 deep into en- Aircraft icing? Asymmetric flaps? Hail tack (AOA) also increased drag, eventu- emy territory when a German ME- damage? Bird strike? Debris from an- ally overwhelming the thrust available 109 rams you, nearly slicing off your other aircraft on the runway? Or . . . until they ended up behind the power Ibomber’s tail. You’re still flying, still you get the idea. As a result of any such curve and outside their roll capability. proceeding, but will the airplane keep event, you may have doubts about the The crash that resulted killed the together as you finally limp back to base airworthiness of your aircraft. Should Boeing’s three crewmembers and a and then configure and slow for land- that occur, you may need to borrow a passenger in a jump seat, along with 39 ing? (Fortunately, for the crew who had page from military aviation: the control- people on the ground. to confront those circumstances on a lability check. Feb. 1, 1943, bombing mission, their Fly- ing Fortress lived up to its name and Consider the ‘Why?’ touched down safely.) Now fast forward and imagine your- There isn’t a lot written on self flying a business or commercial jet the subject of controllability when an Airbus A380 crosses your path checks. During my earliest just 1,000 ft. above. Countering the up- days in the U.S. Air Force, it set that follows takes every bit of your was a procedure we learned airmanship and physical strength to because many of the era’s return the airplane to straight and level aircraft were not as reliable flight. You suspect your aircraft may be as they could have been and bent. Well, as most readers know, you yet we did a lot of formation don’t have to imagine much, since that’s flying where the risk of a exactly what happened to the crew of a midair collision was always Bombardier Challenger 604 (D-AMSC) a consideration. So, we pi- on Jan. 8, 2017. lots talked about conduct- Or, what if your gives you an ing controllability checks aileron trim warning while you’re hap- and every now and then we pily crossing the ocean, and when you did them. But why would we disengage it, the airplane snaps into a need such a procedure these days when The estimated damage to Flight 1862 roll? This happened to a Challenger 604 aircraft are built so much better and (from the Netherlands accident report). (C-GKTO) on Nov. 18, 2017, while flying our maintenance programs are more from Europe to Canada. The aircraft likely to find problems before they bite The accident report says, “Because rolled rapidly until extreme force was us when airborne? of the marginal controllability a safe applied. After an emergency landing in Consider El Al Israel Airlines Flight landing became highly improbable, if Ireland, a significant amount of water 1862, a cargo that took off not virtually impossible.” That might be drained from the fuselage in an area from -Schiphol Interna- true. But there are a few things we can near control cables, so the operator sus- tional Airport (EHAM), Netherlands, on take away from this tragedy: (1) If the pected a water leak had caused a freez- Oct. 4, 1992. The aircraft was as heavy airplane is flying but continued flight is ing of the aileron trim mechanism. as it could have been under the condi- questionable, try to reduce gross weight Or, what about a lightning strike? tions when the No. 3 engine separated before reducing airspeed or increasing

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drag; (2) if faced with a loss of thrust hoc” troubleshooting and more apt to I asked Capt. Sullivan about the con- on one side, attempt to make turns into see just how controllable was their dam- trollability check and he was unequivo- the good engine(s) to improve roll-out aged aircraft. Maintenance procedures cal about its importance that day. “For capability; and (3) if you don’t have to have been improved to prevent another the QF72 accident, our electronic flight land immediately and controllability is case of the frozen MD-80 series stabi- controls were operating at an unknown in question, look for a sparsely popu- lizer jackscrew. But not all flight control level and I had serious concerns as to lated area where you can do a control- problems are mechanical in nature. their veracity and my level of control, lability check. On Oct. 7, 2008, Qantas Capt. Kevin especially close to the ground,” he said. Of course, this was a case where the Sullivan was flying an Airbus A330 that “Two uncommanded pitch-downs with problem was immediately recognizable came out of the factory with a computer no amplifying information from ECAM as a dire emergency where controllabil- design flaw that would only occur in a very [electronic centralized aircraft monitor] ity was at issue. But not all flight control rare set of circumstances. The design lim- meant we were in uncharted territory, problems present themselves so obvi- itation would only happen if a “data spike” so the control check confirmed op- ously. The case of Alaska Airlines Flight between an AOA transmitter and an air eration and appropriate control stick 261, for example, first appeared to be a data inertial reference unit (ADIRU) re- response, at altitude, prior to landing.” simple matter of troubleshooting to get peated itself in a 1.2-sec. window. The air- a failed system working again. craft series had logged 28 million flight Consider the ‘Why On Jan. 31, 2000, the crew of this Mc- hours without such an occurrence before Donnell Douglas MD-83 was faced with it happened to Flight 72. Not?’ and ‘How?’ what appeared to be a jammed stabilizer The electrical flight control system due to a faulty trim motor. In fact, the believed the aircraft was in a stall and If you have any doubt about your air- fault was a stabilizer jackscrew bare of over-speed condition simultaneously, craft’s airworthiness while in flight, lubrication that had ground many of the and pushed the nose over violently pressing on without taking steps to re- threads to its mating “acme” nut com- enough to throw a hundred passengers assure yourself might be an exercise in pletely off. The pilots worked with tech- and crewmembers in the cabin to the wishful thinking. Many Boeing manuals nicians on the ground to repeatedly try ceiling before hurling them back to the put it this way: “Troubleshooting beyond to break the jammed stabilizer free to floor again. The computers ignored Sul- checklist directed actions is rarely help- allow greater control for landing. When livan’s control inputs for a full 2 sec. be- ful and has caused further loss of sys- the stabilizer did break free, aerody- fore allowing him to return the aircraft tem function or failure. In some cases, namic loads caused it to dislocate from to straight and level flight. But then the accidents and incidents have resulted. the jackscrew and plunged the aircraft ADIRU did it again. The crew should consider additional into an uncontrollable dive into the Pa- The crew elected to divert to Royal actions beyond the checklist only when cific Ocean, killing all aboard. Australian Air Force Base Learmonth, completion of the published checklist We cannot fault the pilots for trying Western Australia (YPLM), all the while steps clearly results in an unacceptable everything in their power to trouble- unsure if their Airbus would continue to situation. In the case of airplane control- shoot and correct the flight control; allow them to control it over the wishes lability problems when a safe landing is CHRIS FINNEY a landing with a jammed stabilizer is of the computerized flight control sys- considered unlikely, airplane handling certainly a challenge. Few pilots have tem. Sullivan brought the airplane in evaluations with gear, flaps or speed had experience with controllability for a safe emergency landing after per- brakes extended may be appropriate. checks and guidance for the proce- forming a controllability check. Know- dure is rarely given by aircraft manu- ing the aircraft could be configured at a facturers. But we can speculate that safe altitude gave him the confidence to had these pilots known the procedure, attempt the landing from a controlled, they may have been less prone to “ad 3-deg. glidepath, fully configured.

Airbus A330-303, VH-QPA

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In the case of jammed flight controls, changes slowly until a damage assess- υ⁳After the damage assessment and han- do not attempt troubleshooting beyond ment and airplane handling evaluation dling characteristics are evaluated, the the actions directed in the NNC [Non- have been done and it is certain that lower crew should formulate a sequential plan Normal Checklist] unless the airplane airspeeds can be safely used. In addition, for the completion of the flight. If airplane cannot be safely landed with the existing limit bank angle to 15 deg. and avoid large performance is a concern, use of the alter- condition. Always comply with NNC ac- or rapid changes in engine thrust and air- nate flap or gear extension systems may tions to the extent possible.” speed that might adversely affect control- dictate that the check of airplane han- The best way to decide on a plan of lability. dling characteristics be done during the attack is to firmly grasp the desired re- υ⁳If possible, conduct the damage as- actual approach. Configuration changes sult: We are trying to get the airplane sessment and handling evaluation at an made by the alternate systems may not back on the ground in one piece. In order altitude that provides a safe margin for be reversible. to do that, we need to get the airplane recovery should flight path control be in- υ⁳The crew must exercise extreme cau- configured to as close to a normal state advertently compromised. tion on final approach with special em- as possible. υ⁳If structural damage is suspected, phasis on minimum safe speeds and υ⁳Will the landing gear come down in a attempt to assess the magnitude of the proper airplane configuration. If asym- landable condition? (Some aircraft land damage by direct visual observation from metrical thrust is being used for roll con- better gear up than with some combina- the flight deck and/or passenger cabin. trol or pitch authority is limited, plan to tions of main and nose gear. Finding out While only a small portion of the airplane leave thrust on until touchdown. early may give you a chance to try alter- is visible to the flight crew from the flight In addition, the flight manual for the nate methods or, if that fails, retracting deck, any visual observation data can be U.S. Air Force’s C-17A Globemaster III the gear to a more favorable combina- used to gain maximum knowledge of air- also provides several valuable tips on how tion.) plane configuration and status and can to do a controllability check:

C-17 on approach to Royal Air Force Brize Norton (EGVN)

MATT BIRCH υ⁳Will the flaps extend fully, and if not, be valuable in determining subsequent υ⁳Conduct the check at 5,000 to 10,000 ft. how far will they extend? If the flaps actions. AGL, if possible. move, will they move symmetrically? υ⁳If controllability is in question, con- υ⁳Monitor control stick and rudder pedal Finding out early may steer you to an- sider performing a check of the airplane position, as well as control surface move- other runway or affect the way you fly the handling characteristics. The purpose ment indicated on the MFD (multifunc- approach. of this check is to determine minimum tion display) CFG (configuration) format, υ⁳Will the airplane slow to normal ap- safe speeds and the appropriate config- to determine control authority remaining. proach and landing speeds without un- uration for landing. If flap damage has υ⁳The pilot must use prudent judgment in controllable roll, pitch or yaw? occurred, prior to accomplishing this making speed and configuration changes. Flying a controllability check at an al- check, consider the possible effects on υ⁳WARNING: If control authority de- titude low enough to simulate landing airplane control should an asymmetrical grades rapidly or required control input aerodynamic effects but high enough to condition occur if flap position is changed. approaches the limits of authority about provide a margin for recovery can be the Accomplish this check by slowly and me- any axis, with configuration change and/ key to answering these questions before thodically reducing speed and lowering or airspeed variation, immediately return doing it for real. Few aircraft manufactur- the flaps. to a configuration and speed at which ad- ers give their crews better insight to the υ⁳Lower the landing gear only if available equate control authority is known to exist. process than Boeing, which publishes the thrust allows. υ⁳As airspeed and configuration are following recommendations in its Boeing υ⁳If stick shaker or initial stall buffet are varied, be alert for aircraft buffet. Do not 737NG Flight Crew Training Manual: encountered at or before reaching the as- decrease speed below the minimum con- υ⁳Unless circumstances such as immi- sociated flap speed, or if a rapid increase figuration maneuvering speed. nent airplane breakup or loss of control in wheel deflection and full rudder de- υ⁳Factors such as turbulence and cross- dictate otherwise, the crew should take flection are necessary to maintain wings wind must be considered when deter- time to assess the effects of the damage level, increase speed to a safe level and mining a configuration and speed with and/or conditions before attempting to consider this speed to be the minimum adequate control margin best suited to land. approach speed for the established con- approach and landing. Apply estimated υ⁳Make configuration and airspeed figuration. crosswind controls required for landing

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to test effect on flight characteristics. are conducting a test, you should have in speed to decay about 1 or 2 kt. per sec- υ⁳Once the limiting configuration and mind what constitutes a failed test and ond, no higher. If at any point the air- minimum safe speed have been deter- how to extract yourself from that situa- craft begins to roll or buffet, discontinue mined, fly that speed plus 10 kt. during tion safely. For example, “If the aircraft the maneuver, taking note of the speed approach and landing. Refer to Abnor- rolls or exhibits a pitch change of more and configuration. mal Configuration Procedures, as ap- than 5 deg. during our slow extension (8) Once the aircraft reaches your propriate. of the speed brakes, we will stop the ex- target approach speed, accelerate and υ⁳WARNING: The speed must never tension, evaluate and retract the speed clean up to the extent necessary. You be decreased to the point at which full brakes.” might consider keeping the landing gear control deflection is required about any What follows are examples of adverse and some of the flaps extended, depend- axis since there may be no recovery behavior that might be worthy of aborting ing on the situation. capability beyond this point. This can a procedure: Plan your approach and landing: occur with no unusual stick or rudder υ⁳Unexpected aircraft roll, or a roll at a You should use the data obtained positions since EFCS is applying con- rate or direction unexpected with inten- from the controllability check to learn trols with no feedback to the pilots. tional movement of the ailerons. which flight control components can be υ⁳The approach speed must never be al- υ⁳Unexpected pitch changes. trusted and which will require an ad- lowed to decrease below the minimum υ⁳Adverse yaw (not produced by rudder justment to normal approach and land- safe maneuvering speed as determined inputs). ing procedures. If a higher than normal from this check. Routinely, fly minimum υ⁳Aircraft vibration or shuddering. approach speed is dictated by adverse safe speed plus 10 kt. as the target ap- υ⁳Flutter (a resonant vibration of a con- flying characteristics, be mindful of the proach speed. trol surface or its surrounding area). aircraft’s touchdown attitude (to pre- υ⁳Control jamming or sudden roughness vent a nose-first landing) and stopping Consider Developing to the controls. distances. Validate primary flight controls and Keep in mind that you should never Your Own Controllability pitot-static system: find yourself on approach at an airspeed Check (Just in Case) (1) Descend to 15,000 ft. (desired). lower than already demonstrated dur- (2) Slow to 250 KCAS. ing the controllability check and that I’ve taken these Boeing and C-17A pro- (3) Validate all airspeed indicators you should never find yourself needing cedures and added many from my Air and altimeters are in agreement. You full control deflection in any axis. If ei- Force functional check flight manuals to can check these against your GPS; the ther event occurs, you need to speed up. come up with my own generic controlla- altimeter will generally be within a few bility check. I’ve never had to use them hundred feet and the indicated (or cali- The Benefits of a “in the heat of battle” but if that day ever brated) speed should be about 20 or 30 kt. comes, I’ll be ready. higher than the ground speed corrected Controllability Check Brief crew duties, expectations, safe for wind. You can use this exercise to iden- attitude/AOAs and “knock it off” criteria: tify faulty instrumentation. In some cases, a controllability check (1) One pilot flies the aircraft while the (4) Select flight control synoptic pages. will only confirm that you have a per- other monitors aircraft status and makes (5) Each pilot should, in turn, exercise fectly flyable airplane and that will give note of performance. While pilots can one axis at a time. Start at neutral and you the confidence to approach and exchange duties (i.e., each pilot exercises look for any looseness. Using smooth and land using normal configurations and the flight controls), one pilot must always small inputs, exercise the control and look techniques. In other cases, however, be designated as the pilot flying. for any binding and other signs of abnor- the check will reveal you may need to (2) The expectation for each step of the mality. alter the configuration and fly at higher process must be verbalized prior to the Validate speed brakes, flaps, landing speeds. But there is at least one more step. For example, “We will now extend gear and low-speed flying characteristics: benefit: The time required to fly the con- the speed brakes slowly and smoothly; we (1) Look up approach speeds for each trollability check will force you to slow don’t want to see the aircraft roll on ex- possible flap setting, given the current down and be more deliberate about the tension or retraction and we want to see weight and altitude. steps to follow. the retraction completed to a clean wing.” (2) Descend to 10,000 ft. (desired). So, once again, imagine yourself fly- (3) Both pilots should have in mind (3) Slow to 250 KCAS. ing an aircraft where the ability to fly where the aircraft pitch, roll and yaw (4) Extend the speed brakes. Look for an approach to landing is in doubt. You should be for the maneuver to be at- symmetrical deployment and decelerate have sustained damage from hail, icing tempted. If the aircraft is equipped with to what should be close to a no-flap ma- or a foreign object. You may have had a flyable AOA instrument, pilots should neuvering speed. a mechanical, electrical or computer have in mind where the AOA should be. (5) Stow the speed brakes. The speed malfunction. For whatever reason, you With or without an AOA indicator, pi- brakes should stow symmetrically with- are no longer 100% sure about the air- lots should have knowledge of where the out any sign of floating. plane’s airworthiness. It seems to me pitch should be. For example, “We do not (6) Adjust the thrust to start a 500- that there is almost never anything to expect to see the nose pitch up or down fpm descent while holding your no-flap lose by doing a controllability check un- during speed brake extension. The AOA maneuvering speed. less you are on fire, running out of fuel, should remain steady.” (7) Extend each notch of flaps as the the weather coming down or there is (4) Both pilots should agree on results target speed permits, allowing the air- some other time constraint. And there that will cause an abort of the maneuver, craft to decelerate with the increased are times when doing a controllability the so-called “knock it off” call. Since you drag. Adjust the thrust to allow the check can be a lifesaver. BCA

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