Milt
30th May 2014, 05:14
AIRBUS A320 FLAP SEGMENT FLUTTER
The inboard ends of the main flap segments develop non divergent flutter when flaps are fully extended and at all speeds down to about 50 Kts.
There could be serious consequences if a structural failure occurs although there may be sufficient aileron to control the roll.
What does an experienced experimental test pilot do when he moves from the pilots seat to one as passenger? This TP on my first flight in an A320 became alarmed during the push back from the gate when the sounds of a furiously barking dog reverberated. Close observation soon revealed that the abnormal sound was that of an electrically driven hydraulic pump topping up a hydraulic system. Other pax showed alarm and there were no reassurances from the crew. How can Airbus Industries get away with the abnormal barking dogs sounds at a critical time for those making their first flight in an A320?
This TP then settled down to determine the smoothness of aircraft handling by the operating pilot. The post WW11 hangover of wheel brake misuse is gradully making way for smooth feathering of brake application and release. Experience of this usually means that smooth brake use results in smooth manual handling in flight during those rare times when pilots are flying without the automatics.
Back to the flap fluttering problem. I first became aware of the flap flutter on a flight when I was seated such that I could readily see the source of a significant fuselage vibration as full flap was deployed. The inboard end of the main flap segments overhang their tracks by about 3/4 feet. It is this overhang which, at its end, flutters with an amplitude and frequency equivalent to the maximum rate that I can shake my oustretched hand. Eventually fatigue will do its thing and something will fail, hopefully failsafe.
Following my second experience of the flap flutter I managed to cause the aircraft Captain some concern when he appreciated that my comments were TP based. He stated that the fuselage vibration could not be felt up front nor through the side stick controller. Captain Howard stated his intention to report the problem to the engineers.
I am now very much aware of my own shortcomings in assumtions of the past that the rear ends of aircraft undertaking flight tests would most likely look after themselves. But what flight testers would bother to install accelerometers and other instrumentation on flaps. Perhaps Airbus Industries are aware of the problem and can provide some reassurances as to continued structural integrity.
The inboard ends of the main flap segments develop non divergent flutter when flaps are fully extended and at all speeds down to about 50 Kts.
There could be serious consequences if a structural failure occurs although there may be sufficient aileron to control the roll.
What does an experienced experimental test pilot do when he moves from the pilots seat to one as passenger? This TP on my first flight in an A320 became alarmed during the push back from the gate when the sounds of a furiously barking dog reverberated. Close observation soon revealed that the abnormal sound was that of an electrically driven hydraulic pump topping up a hydraulic system. Other pax showed alarm and there were no reassurances from the crew. How can Airbus Industries get away with the abnormal barking dogs sounds at a critical time for those making their first flight in an A320?
This TP then settled down to determine the smoothness of aircraft handling by the operating pilot. The post WW11 hangover of wheel brake misuse is gradully making way for smooth feathering of brake application and release. Experience of this usually means that smooth brake use results in smooth manual handling in flight during those rare times when pilots are flying without the automatics.
Back to the flap fluttering problem. I first became aware of the flap flutter on a flight when I was seated such that I could readily see the source of a significant fuselage vibration as full flap was deployed. The inboard end of the main flap segments overhang their tracks by about 3/4 feet. It is this overhang which, at its end, flutters with an amplitude and frequency equivalent to the maximum rate that I can shake my oustretched hand. Eventually fatigue will do its thing and something will fail, hopefully failsafe.
Following my second experience of the flap flutter I managed to cause the aircraft Captain some concern when he appreciated that my comments were TP based. He stated that the fuselage vibration could not be felt up front nor through the side stick controller. Captain Howard stated his intention to report the problem to the engineers.
I am now very much aware of my own shortcomings in assumtions of the past that the rear ends of aircraft undertaking flight tests would most likely look after themselves. But what flight testers would bother to install accelerometers and other instrumentation on flaps. Perhaps Airbus Industries are aware of the problem and can provide some reassurances as to continued structural integrity.