Pax flat tyre thread continued briefly
Have tried to inform cabin crew on KLM flight AMS - CPH that one of the MLG tires was pre-flintstone standard (square), yep we were jumping in our seats during both TO and landing. Nada, ach, øv.
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Getting the "sads"
Splitpin, I was just emphasising that Milt Cottee would not have made a report had he not felt that what he saw was abnormal. As for an Engineer telling someone they were "dreaming", not the word I would use.
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Fairing Flutter Summary
Thanks to all for your posts. I did deliberately seek your posts by asking that question - What would you experts do next?
The answers and the airlines reponse clearly indicate a likely entrenched problem within the general engineering side of airline fleet maintenance, ie a belief that any aircraft type formally certified as airworthy can only reluctantly be seen to have any residual problems. I had hoped that the airline would have advised me that it was seeking confirmation of its preliminary determinations from the manufacturer in case the problem is one that has fallen through the cracks. Now it is my duty of care to take it out of the airline's hands seeking reassurances from both the local regulatory airworthiness authorities and the type manufacturer. I do accept that the problem may well have been previously determined by the certification authorities as satisfactory by means of a specific concession.
I contend that most Aeronautical Engineers will have some knowledge of the all too often diabolical effects of flutter (particularly of the divergent variety) on aircraft or their appendages. Nearly all will not have had practical experience. I further contend that there is little reason for a LAME to know much more than what the word means. Flutter prevention/analysis is a specialty within the Aerospace Engineering domain. Not so with the Experimental Test Pilot. We are all very apprehensive of flutter and any experimental TP will go to great lengths to ensure that the appropriate corners and margins of aircrafts' flight envelopes are approached with much care. We determine the safety margins of flight envelopes as a buffer against unintentional overshoots. Things, often called bonkers, are sometimes used to provide an impulse to excite those areas where flutter is presumed to lurk. I recently saw a high speed movie of an F-18 Hornet's wing approaching self destruct in one of those corners and the designs likely to enable the extension of the margin.
My own experience has been mostly involved with supervision of other TPs endangering themselves, the safety aspects involved and the review of flight tests. Many preliminary test results can be determined in a wind tunnel but there does not seem to be a substitute for flight testing. Most divergent flutters rapidly run away to failure/destruction.
I once flew in an RAF Hunter Mk7 two seater which suffered from what TP Bill Bedford conned me into thinking was rudder buzz when pulling about 3g at supersonic speeds. Its fluttering rudder resisted all our foot forces trying to stop the violence. After delivering 3 sonic bangs to a poor unsuspecting ship I called quits as I had some concern about the continuing integrity of the rear fuselage. The fix was a simple trim tab trailing edge strip rather than a change to rudder mass balance. Other approaches to the edges were no less fraught. Hence my sensitivity in this area.
As for general flap design problems. Flap design seems to be an aircraft designer's nightmare - a compromise between weight and stiffness and the penalties of having to use protrubing tracks/guides. When I was responsible for the RAAF's F-111s being delivered out of their Texas factory way back in the 70s I had to contend with the loss of several flap segments from two aircraft as they prepared to land at Sacramento in CA. A specialist team from the factory had to fit replacements and rerig the whole fleet to revised or correct specifications. Now one of you has told me of his experience with the flaps of another type where by out of adjustment or wear would sometimes allow the guide rollers travelling in the outboard auxiliary flap tracks to come out of the tracks resulting in excessive looseness and the odd loss of a flap segment. Ground inspections did not detect a fault as the rollers usually went back into the tracks during flap retraction.
Current knowledge, experience and wind tunnelling enables reasonably reliable predictions as to the liklihood of flutter anywhere close to an aircraft's flight envelopes.
Thanks to all for your posts. I did deliberately seek your posts by asking that question - What would you experts do next?
The answers and the airlines reponse clearly indicate a likely entrenched problem within the general engineering side of airline fleet maintenance, ie a belief that any aircraft type formally certified as airworthy can only reluctantly be seen to have any residual problems. I had hoped that the airline would have advised me that it was seeking confirmation of its preliminary determinations from the manufacturer in case the problem is one that has fallen through the cracks. Now it is my duty of care to take it out of the airline's hands seeking reassurances from both the local regulatory airworthiness authorities and the type manufacturer. I do accept that the problem may well have been previously determined by the certification authorities as satisfactory by means of a specific concession.
I contend that most Aeronautical Engineers will have some knowledge of the all too often diabolical effects of flutter (particularly of the divergent variety) on aircraft or their appendages. Nearly all will not have had practical experience. I further contend that there is little reason for a LAME to know much more than what the word means. Flutter prevention/analysis is a specialty within the Aerospace Engineering domain. Not so with the Experimental Test Pilot. We are all very apprehensive of flutter and any experimental TP will go to great lengths to ensure that the appropriate corners and margins of aircrafts' flight envelopes are approached with much care. We determine the safety margins of flight envelopes as a buffer against unintentional overshoots. Things, often called bonkers, are sometimes used to provide an impulse to excite those areas where flutter is presumed to lurk. I recently saw a high speed movie of an F-18 Hornet's wing approaching self destruct in one of those corners and the designs likely to enable the extension of the margin.
My own experience has been mostly involved with supervision of other TPs endangering themselves, the safety aspects involved and the review of flight tests. Many preliminary test results can be determined in a wind tunnel but there does not seem to be a substitute for flight testing. Most divergent flutters rapidly run away to failure/destruction.
I once flew in an RAF Hunter Mk7 two seater which suffered from what TP Bill Bedford conned me into thinking was rudder buzz when pulling about 3g at supersonic speeds. Its fluttering rudder resisted all our foot forces trying to stop the violence. After delivering 3 sonic bangs to a poor unsuspecting ship I called quits as I had some concern about the continuing integrity of the rear fuselage. The fix was a simple trim tab trailing edge strip rather than a change to rudder mass balance. Other approaches to the edges were no less fraught. Hence my sensitivity in this area.
As for general flap design problems. Flap design seems to be an aircraft designer's nightmare - a compromise between weight and stiffness and the penalties of having to use protrubing tracks/guides. When I was responsible for the RAAF's F-111s being delivered out of their Texas factory way back in the 70s I had to contend with the loss of several flap segments from two aircraft as they prepared to land at Sacramento in CA. A specialist team from the factory had to fit replacements and rerig the whole fleet to revised or correct specifications. Now one of you has told me of his experience with the flaps of another type where by out of adjustment or wear would sometimes allow the guide rollers travelling in the outboard auxiliary flap tracks to come out of the tracks resulting in excessive looseness and the odd loss of a flap segment. Ground inspections did not detect a fault as the rollers usually went back into the tracks during flap retraction.
Current knowledge, experience and wind tunnelling enables reasonably reliable predictions as to the liklihood of flutter anywhere close to an aircraft's flight envelopes.
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More on Probable Flutter
Reno P-51
If ever there was an almost perfect case of Divergent Flutter then the loss of control of the P-51 Mustang at Reno Nevada has almost certainly to be it.
That aircraft was extensively modified for high speed racing and was being operated way outside of its original manoeuvre envelope. The failure of the elevator trim tab is very evident in some very clear photos as is the resultant high g which must have come close to taking a wing off. Having flown the Mustang in combat and training with about 450 sorties I found it was generally nice to fly with good longitudinal stability except with an aft cg which occurred when the fuselage fuel tank behind the cockpit was more than about half full. With a full uselage tank it was a wrestle with it wanting to continuously pitch up or down.
The rudder has an anti trim tab to correct for low or negative horizontal stability.
Never did have any feel for the start of an elevator trim tab flutter but rarely did I fly it beyond its flight envelope.
It came as a surprise to me that the tail wheel extends to the down position under very high g. My last flight in a Mustang ended with - oops - no tail wheel.
It is my bet that Reno crash was a result of divergent flutter or overload of the elevator trim tab whilst the aircraft was being operated well outside of its manoeuvre boundaries.
Reno P-51
If ever there was an almost perfect case of Divergent Flutter then the loss of control of the P-51 Mustang at Reno Nevada has almost certainly to be it.
That aircraft was extensively modified for high speed racing and was being operated way outside of its original manoeuvre envelope. The failure of the elevator trim tab is very evident in some very clear photos as is the resultant high g which must have come close to taking a wing off. Having flown the Mustang in combat and training with about 450 sorties I found it was generally nice to fly with good longitudinal stability except with an aft cg which occurred when the fuselage fuel tank behind the cockpit was more than about half full. With a full uselage tank it was a wrestle with it wanting to continuously pitch up or down.
The rudder has an anti trim tab to correct for low or negative horizontal stability.
Never did have any feel for the start of an elevator trim tab flutter but rarely did I fly it beyond its flight envelope.
It came as a surprise to me that the tail wheel extends to the down position under very high g. My last flight in a Mustang ended with - oops - no tail wheel.
It is my bet that Reno crash was a result of divergent flutter or overload of the elevator trim tab whilst the aircraft was being operated well outside of its manoeuvre boundaries.
