Inflight Breakup of a New Zealand Van’s RV-7
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Join Date: Nov 2015
Location: Paisley, Florida USA
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Rudder use seems to be a lost art these days. I've encountered quite a few pilots who seem to fly with their feet firmly planted on the cockpit floor.
Cheers,
Grog
Cheers,
Grog
Join Date: Jan 2008
Location: UK
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Genghis your points are very well made as usual and we have to respect your engineering and flying credentials. In the airline world backed up by manufacturers advice we always teach in a nose low recovery scenario to roll the wings level prior to pitching. The thrust issue is semi optional dependant on aircraft type etc. I don’t know of any instructors who teach differently. However to reinforce that everyday is a school day I was asked to describe rolling g in my FI renewal last year. To my eternal shame I was not even aware of such a thing after 47 years flying, mainly airliners. The examiner, bless him, took the opportunity to educate rather than berate my lack of knowledge.
Coming to this new, as my friend DAR asked if I'd take a look. What a dreadful report.
Firstly the repeated obsession with whether the passenger was flying or not? Why is this even relevant? Experienced pilots let pax fly all the time - and with an ATPL(H) this pilot was very experienced with nearly 400hrs FW and over 4000hrs RW. It also says that he was known seldom to relinquish control anyhow. He is the captain , and should be more than capable of handling the manoeuvers in question, or recovering if his pax got into them. So why is this even being mentioned?
Secondly the conclusion of rudder flutter is far from conclusive to me in the report. The rudder was still attached to the fin, and one wing had come off. So torsional divergence failure of the wing, and/or overload due to incorrect application of rudder above Va are both in the frame. These aren't discussed. I'm not saying it couldn't have been flutter - I am saying that the investigators seem to have been a bit eager to shoot for a single explanation.
That said, that the aeroplane failed structurally in flight is clearly the case. Which brings me to another major omission in this report - any investigation of the handling characteristics and whether they (pitch stability, spiral stability being things I'd be looking at) have characteristics likely to cause inadvertent overspeed. Is there anything in this aeroplane that makes it hard to recover from a spiral dive? Is there a tendency over Vne to lock into a dive? They really should have had a test pilot looking at a similar aeroplane.
Here's another point not discussed in the report. The *correct* recovery from a spiral dive is power-roll-pitch IN THAT ORDER. I have certainly as an instructor seen a lot of pilots incorrectly applying pitch and roll together, which as an engineer I know creates a high potential for airframe overstress and breakup of the nature that happened here. Is this being adequately taught to FW PPLs? - I have some doubts, and the report missed the opportunity to ask that.
Also not mentioned in the report, is the possibility of mis-diagnosis of a spiral dive as a spin, and incorrect application of spin recovery actions to recover from the spiral dive. That would be totally consistent with the evidence presented.
Also the statement that "Flight at any airspeed over Vne, however, exposes the aircraft to the possibility of flutter." misses that flutter can be experienced in a maladjusted aeroplane below Vne. I've seen it test flying a couple of aeroplanes, even in level flight, with incorrect adjustments in the elevator and pitch trimmer circuits, one was certainly heading for an in-flight breakup if I'd not known what I was doing.
I do like the recommendation for verbal overspeed warnings in light GA EFIS. At the same time, most light aeroplanes provide loads of warnings (pitch attitude, wind noise, the ASI itself) of overspeed, which isn't mentioned in the report.
Not a happy read, on multiple levels.
G
Firstly the repeated obsession with whether the passenger was flying or not? Why is this even relevant? Experienced pilots let pax fly all the time - and with an ATPL(H) this pilot was very experienced with nearly 400hrs FW and over 4000hrs RW. It also says that he was known seldom to relinquish control anyhow. He is the captain , and should be more than capable of handling the manoeuvers in question, or recovering if his pax got into them. So why is this even being mentioned?
Secondly the conclusion of rudder flutter is far from conclusive to me in the report. The rudder was still attached to the fin, and one wing had come off. So torsional divergence failure of the wing, and/or overload due to incorrect application of rudder above Va are both in the frame. These aren't discussed. I'm not saying it couldn't have been flutter - I am saying that the investigators seem to have been a bit eager to shoot for a single explanation.
That said, that the aeroplane failed structurally in flight is clearly the case. Which brings me to another major omission in this report - any investigation of the handling characteristics and whether they (pitch stability, spiral stability being things I'd be looking at) have characteristics likely to cause inadvertent overspeed. Is there anything in this aeroplane that makes it hard to recover from a spiral dive? Is there a tendency over Vne to lock into a dive? They really should have had a test pilot looking at a similar aeroplane.
Here's another point not discussed in the report. The *correct* recovery from a spiral dive is power-roll-pitch IN THAT ORDER. I have certainly as an instructor seen a lot of pilots incorrectly applying pitch and roll together, which as an engineer I know creates a high potential for airframe overstress and breakup of the nature that happened here. Is this being adequately taught to FW PPLs? - I have some doubts, and the report missed the opportunity to ask that.
Also not mentioned in the report, is the possibility of mis-diagnosis of a spiral dive as a spin, and incorrect application of spin recovery actions to recover from the spiral dive. That would be totally consistent with the evidence presented.
Also the statement that "Flight at any airspeed over Vne, however, exposes the aircraft to the possibility of flutter." misses that flutter can be experienced in a maladjusted aeroplane below Vne. I've seen it test flying a couple of aeroplanes, even in level flight, with incorrect adjustments in the elevator and pitch trimmer circuits, one was certainly heading for an in-flight breakup if I'd not known what I was doing.
I do like the recommendation for verbal overspeed warnings in light GA EFIS. At the same time, most light aeroplanes provide loads of warnings (pitch attitude, wind noise, the ASI itself) of overspeed, which isn't mentioned in the report.
Not a happy read, on multiple levels.
G
It has the trifecta of bad things in an aerobatic aeroplane
1) It is quite slippery and will gain speed very quickly on a downline
2) It has light elevator forces and so it is easy to pull a lot of Gee especially in the event of a panic pull
3) It has a surprisingly poor roll rate. Rolling to erect from the inverted or even wings level from a high bank angle takes a long time which is problematic if the airplane is well nose down and accelerating like mad
In addition the forward opening canopy is not jetsonable and so there is no way to abandon the aircraft with a parachute descent if it breaks up or is unrecoverable
The other challenge is of course how the aircraft was built. Even minor lapses by the builder can be catastrophic under high loads. The Canadian crash mentioned in the report was precipitated by the weight of too much paint on the rudder which unbalanced it and left it more predisposed to flutter.
I advised all my students to take a basic aerobatic course. Some did not really like aerobatics and did not pursue aerobatic flying after learning the first basic aerobatic , but all reported that they were much more confident they could control and recover the aircraft no matter what orientation it was in
RV Aerobatics
I fellow I know once asked me to do some basic aerobatic training in his RV7. I refused as I consider this aircraft completely unsuited for any aerobatic or near aerobatic maneuvering except in the hands of an experienced aerobatic pilot.
It has the trifecta of bad things in an aerobatic aeroplane
1) It is quite slippery and will gain speed very quickly on a downline
2) It has light elevator forces and so it is easy to pull a lot of Gee especially in the event of a panic pull
3) It has a surprisingly poor roll rate. Rolling to erect from the inverted or even wings level from a high bank angle takes a long time which is problematic if the airplane is well nose down and accelerating like mad
In addition the forward opening canopy is not jetsonable and so there is no way to abandon the aircraft with a parachute descent if it breaks up or is unrecoverable
The other challenge is of course how the aircraft was built. Even minor lapses by the builder can be catastrophic under high loads. The Canadian crash mentioned in the report was precipitated by the weight of too much paint on the rudder which unbalanced it and left it more predisposed to flutter.
It has the trifecta of bad things in an aerobatic aeroplane
1) It is quite slippery and will gain speed very quickly on a downline
2) It has light elevator forces and so it is easy to pull a lot of Gee especially in the event of a panic pull
3) It has a surprisingly poor roll rate. Rolling to erect from the inverted or even wings level from a high bank angle takes a long time which is problematic if the airplane is well nose down and accelerating like mad
In addition the forward opening canopy is not jetsonable and so there is no way to abandon the aircraft with a parachute descent if it breaks up or is unrecoverable
The other challenge is of course how the aircraft was built. Even minor lapses by the builder can be catastrophic under high loads. The Canadian crash mentioned in the report was precipitated by the weight of too much paint on the rudder which unbalanced it and left it more predisposed to flutter.
Point 1). Agreed, especially with the coarse fixed pitch propellor usually attached, but the installation of a constant speed propeller greatly aids in controlling excessive speed.
Point 2). Yup! Be very careful, Fly with 2 fingers (& don’t get scared!
)Point 3). Every RV-7/7A (4+) I’ve flown had a roll rate at Va of at least 120 degrees per second, which in my mind is sufficiently rapid for recovery from an unwanted attitude. I would MUCH rather be in an RV whilst nose low and inverted than a Citabria or a Cessna Aerobat! Having also taught aerobatics in gliders (Blanik L-13 to DG-1000), I find this aircraft similar in rewarding an appreciation for when to roll, and when to push (& when to take over!). The only real criticism I have in the roll characteristics is the vibration that shows at large aileron deflections at cruise speeds and higher, (which isn’t all that bad of a thing when above Va).
Point 3A). A canopy jettison lever is standard (IIRC), if not, it certainly is available - at least 3 of the planes I’ve flown were equipped with one - a T handle in the upper centre of the panel. Besides it’s obvious advantage in emergency egressing, a lot of people install it as it is very handy to completely remove the canopy when working on the radios & instruments.
Point 3B). Totally agree. While I have also refused to fly certain certified airframes, I flat out tell prospective homebuilt aerobats on first contact that I will not fly any amateur-builts until I have conducted a thorough inspection of their particular aircraft. I will not do acro in amateur-built glassfibre airframes simply because I am not knowledgeable enough to do a meaningful inspection of the structure.
Regards,
Jamesel
