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Flap Failure

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Flap Failure

Old 26th May 2004, 21:04
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Question Flap Failure

I was wondering recently, how many incidences of Flap Failure are normal in the space of a calendar month? Would 5 separate occurences on the same aircraft be considered excessive? How about 2 on successive sectors?
Trying to land a jet airliner flapless on a runway less than 1700m long must have a certain pucker factor...
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Old 26th May 2004, 21:25
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Who the hell wants to land FLAPLESS (maybe with max land weight?!) on a runway with less than 1700 meters?
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Old 26th May 2004, 21:31
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I believe the company policy is to carry only enough fuel for the primary alternate- the nearest 3000m runway would have been the third alternate.
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Old 27th May 2004, 00:43
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Thumbs up Please define failure.

Most certification authorities dictate that any failure of the flaps that would place the aircraft in jeopardy shall not occur more frequently than 1 10e9 or once in one billion hours and that is for the entire fleet of a given type of aircraft. Yes, five times on the same aircraft would be considered excessive to put it mildly and two times on the same day would put it off the chart from a safety point of view.

I can see the aircraft being released for revenue operations after the first failure was corrected but after that the aircraft should have been grounded.

What type of aircraft was it? Perchance was it an A-310?

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Old 27th May 2004, 01:45
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Canadair Regional Jet

I know a certain major airline in Canada that has experienced LOTS of flap failures on the CRJ. Doesn't happen so often now, but still happens.
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Old 27th May 2004, 11:14
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Not sure about 1x10e-9 Lu. Certification authorities (JAA and FAA) state that probability of catastrophic failure must not exceed 10e-9. Is a flap failure catastrophic? Most examples of catastrophic failure I have seen refer to total loss of thrust, total loss of hyd / elec power etc. which prevent the aircraft reaching a suitable aerodrome. Though I stand to be corrected
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Old 27th May 2004, 11:22
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I would have thought one failure per career would be sufficient for any one!
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Old 27th May 2004, 11:28
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For the enlightenment of all, this is what Mr Boeing has to say about it ( from the FlightCrew Training Manual ):
All Flaps Up Landing

The probability of both leading and trailing edge devices failing to extend is remote. If a flaps up landing situation were to be encountered in service, the pilot should consider the following techniques. Training to this condition should be limited to the flight simulator.

After selecting a suitable landing airfield and prior to beginning the approach, consider reduction of airplane gross weight (burn off fuel) to reduce touchdown speed.

Fly a wide pattern to allow for the increased turning radius required for the higher maneuvering speed. Establish final approximately 10 miles from the runway. This allows time to extend the gear and decelerate to the target speed while in level flight and complete all required checklists. Maintain no slower than flaps up maneuvering speed until established on final. Maneuver with normal bank angles until on final.

Final Approach

Use an ILS glidepath if available. Do not reduce the airspeed to the final approach speed until aligned with the final approach. Prior to intercepting descent profile, decrease airspeed to command speed and maintain this speed until the landing is assured.

The normal rate of descent on final is approximately 900 fpm due to the higher ground speed. Final approach body attitude is approximately 1 - 2 higher than a flaps 30 approach. Do not make a flat approach (shallow glidepath angle) or aim for the threshold of the runway. Plan touchdown at the 1,000 foot point.

Use manual control of thrust levers. Due to automatic speed protection, autothrottle use may result in higher than desired speed on final. Engines will be at low idle speed due to no flap extension. When engines are near idle RPM, time required for engines to accelerate is longer than normal.

Note: Use of the autopilot during approach phase is acceptable. Do not autoland. Speedbrakes are not recommended for airspeed reduction below 800 feet. If landing is anticipated beyond the normal touch down zone, go around.


Fly the airplane onto the runway at the recommended touchdown point. Flare only enough to achieve acceptable reduction in the rate of descent. Do not allow the airplane to float. Floating just above the runway surface to deplete additional speed wastes available runway and increases the possibility of a tail strike. Do not risk touchdown beyond the normal touchdown zone in an effort to achieve a smooth landing.

Slight forward pressure on the control column may be required to achieve touchdown at the desired point and to lower the nosewheel to the runway. After lowering the nosewheel to the runway, hold forward control column pressure and expeditiously accomplish the landing roll procedure. Full reverse thrust is required for a longer period of time.

Use of autobrakes is recommended. Autobrake setting should be consistent with runway length. (See Autobrakes Landing distance in the Performance Inflight section of the QRH). Use manual braking if deceleration is not suitable for the desired stopping distance.

Immediate initiation of reverse thrust at main gear touchdown (reverse thrust is more effective at high speeds) and full reverse thrust allows the autobrake system to reduce brake pressure to the minimum level. Less than maximum reverse thrust increases brake energy requirements and may result in excessive brake temperatures.
The following gives some ideas of the 'Flaps-Up' landing distances required:

Boeing QRH B737-700 - Landing weight 55,000Kg requires Vref(Flap40)+55Kt and a landing reference distance of:
  • Dry runway - 1155m ( 3754' )
  • Wet runway - 1565m ( 5086' ) where braking action = good
Boeing QRH B737-300 - Landing weight of 48,000Kg requires Vref(Flap40)+55Kt and a landing reference distance of:
  • Dry runway - 1215m ( 3950' )
  • Wet runway - 1563m ( 5080' ) where braking action = good
Nb. The above figures are actual ( unfactored ) distances and include the distance from 50' HAT ( 305m of air distance ) and the use of max manual braking and maximum reverse-thrust.

So, subject to certain provisos, if the only(?) problem is that all the flaps are 'Up' then, if the a/c in question was a B737 (300/700), you could indeed land and stop it within 1700m.

That said, I personally would be looking for the longest into-wind runway I could find as well as looking to see if I could maybe get the leading or trailing edges to deploy ( e.g. blip the 'AltFlap' switch to deploy the leading edges, albeit without asym protection ).
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Old 27th May 2004, 11:38
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A flap retraction failure could be a lot more critical than an extension one.
Happened to a colleague during a Go-around on an ILS approach.
The diversion fuel didn't then mean anything so he was stuck over an airport with minima precluding a normal approach...
One of these days when one earns one's salary.
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