Tolerating an un-airworthy aircraft. Wing drops at stall
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Be careful out there, I cringe when I hear stories like the one above!
Reminds me of an "alleged" event where the instructor and student conducted a claimed forty (40 ) turn spin from 10,000 ft in a Cessna 152 with a video camera recording the whole manoeuvre. The same aircraft was later well known for dropping the left wing very sharply at point of stall clean and with flap down. A maintenance inspection reportedly discovered a serious rigging discrepency. Question for the experts. Could the forces involved in numerous turns of a spin eventually lead to a rigging problem?
it's certified under a different and older certification so it's not obliged to meet new requirements. Archers have very benign stall characteristics in comparison to Warriors..but Never, ever spin an Archer but she really fights the stall both power on or power off even in turns
Same airframe just 20 hp difference, slightly heavier engine in the Archer which also has a higher MCTOW though I think some later Warriors have the same heavier MCTOW.
Like so:
With a steering nose wheel there is a lot more friction due to rods and springs and connectors.
The nose wheel may deflect a little during high power operations against spring tension but at idle it should be aligned especially with rudder pedals neutral.
There is no reason for the nose wheel to cause a wing drop in a power off stall.
Zero.
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I disagree.
These aircraft still need to meet their original design and certification requirements.
A consistent wing drop is a sign of a crooked or incorrectly repaired or incorrectly rigged aircraft.
That should not be tolerated.
Unfortunately we’re all guilty of being too eager to fly.
These aircraft still need to meet their original design and certification requirements.
A consistent wing drop is a sign of a crooked or incorrectly repaired or incorrectly rigged aircraft.
That should not be tolerated.
Unfortunately we’re all guilty of being too eager to fly.
Cessnas are much easier to rig by way of wing adjustment than Piper. They have a sort of cam mechanism that can adjust angle of incidence. As I understand it, wing rigging for the Pipers consist only in adjusting the wing flaps.
I once flew as an instructor in a Cherokee 6 that was horribly out of rig because of accident damage. The owner had bought it used and was not sophisticated enough to understand it until we flew as part of a 61.56 flight review. It was impossible to trim the ball center in that airplane.
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Correct, Cessna’s you adjust the rear wing bolt that is offset in a bushing, rotating the bushing alters the angle of attack of the wing. Pipers you adjust the flaps to correct it.
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Forgot to add, on the initial post, has it had the stall strips added, these were introduced to alleviate some of these issues, read the Service Bulletin below.
http://nctc.tk/PIPER/piper%20disc%20.../SB%20916B.pdf
http://nctc.tk/PIPER/piper%20disc%20.../SB%20916B.pdf
In all of the stalls I've done in the Warrior included a wing drop... nothing huge...I guess next chance, I will observe carefully but I have gotten the wing drop.
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Forgot to add, on the initial post, has it had the stall strips added, these were introduced to alleviate some of these issues, read the Service Bulletin below.
PURPOSE: Piper Aircraft Corporation has determined that additional PA-28-161 Aircraft (Warrior II) and PA-28-181 Aircraft (Archer II) not affected by Service Bulletin 916A, may exhibit an undesirable tendency to roll to the right just before and/or during stall high power and aft center-ofgravity loading conditions. If allowed to continue, this may result in roll attitudes up to 60°-90° of bank.
Just imagine the above description as a go-around from a bounce. Low speed, stall warning light or horn sounding, nose high attitude then WHACK the wing drops at 60-90 degrees angle. Even the Wirraway couldn't beat that..
Just thinking that perhaps in some cases it would be how far into the stall you fly...I go beyond buffeting and I completely ignore the stall warning buzzer... when I stall or teach the stall....I wanna see stall!...
There's an old aerobatic trick called a falling leaf in which you hold the plane into a stall and pick up the wing drop oscillations with rudder.
There's an old aerobatic trick called a falling leaf in which you hold the plane into a stall and pick up the wing drop oscillations with rudder.
Piper Warriors, Archers and Dakotas all appear to have benign stall characteristics during training, as the CG is near the forward limit. I would suggest a PA-28-151,161,181 or 236 would behave very differently at MTOW with the CG further aft. In fact, this would apply to most 4 seat training types.
Piper Warriors, Archers and Dakotas all appear to have benign stall characteristics during training, as the CG is near the forward limit. I would suggest a PA-28-151,161,181 or 236 would behave very differently at MTOW with the CG further aft. In fact, this would apply to most 4 seat training types.
Last edited by Pugilistic Animus; 26th Oct 2020 at 12:13.
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Just thinking that perhaps in some cases it would be how far into the stall you fly
One needs to be cognizant of the relevant requirements and what might have been done during the Type Certification program. Keep in mind that TC requirements vary over the years so a flick through the historical FARs and AC 23-8 revisions can be illuminating.
For instance, I recall a tale from a flight test short course, years ago, where the FT instructor related a tale from a USAF FT training program: the USAF student wanted to see what would happen should the particular aircraft (a well-known civil cabin class twin) be held into the stall. Now, the particular model, at TC, was only tested to stall onset as we were briefed at the time. The (very experienced) FT instructor, having seen it all before, let the student do the deed - result was the usual buffet, etc., followed by a rapid flick into an inverted spin.
Take away message: sometimes a bit of research is useful and, on occasion, this requires some discussion with the OEM FT folk to find out just what might have been done.
We really need to be a bit conservative out there in operating land .... especially should we not have all the details of the story ... PA, I suspect, is better informed than many. However, the many may, on occasion, allow their lesser knowledge overwhelm their caution.
One needs to be cognizant of the relevant requirements and what might have been done during the Type Certification program. Keep in mind that TC requirements vary over the years so a flick through the historical FARs and AC 23-8 revisions can be illuminating.
For instance, I recall a tale from a flight test short course, years ago, where the FT instructor related a tale from a USAF FT training program: the USAF student wanted to see what would happen should the particular aircraft (a well-known civil cabin class twin) be held into the stall. Now, the particular model, at TC, was only tested to stall onset as we were briefed at the time. The (very experienced) FT instructor, having seen it all before, let the student do the deed - result was the usual buffet, etc., followed by a rapid flick into an inverted spin.
Take away message: sometimes a bit of research is useful and, on occasion, this requires some discussion with the OEM FT folk to find out just what might have been done.
We really need to be a bit conservative out there in operating land .... especially should we not have all the details of the story ... PA, I suspect, is better informed than many. However, the many may, on occasion, allow their lesser knowledge overwhelm their caution.
I know of the fatal accident at the National Test Pilot School with the Derringer (it seems I need to get to 10 posts before I can provide a link) and somewhere there is a description of its stall behaviour which explains how it came to spin from which it didn't recover.
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Dave, I just relate the tale, as told by SR (who was the instructor TP being entertained), in Sydney when the folk came out around the early 90s. It was just a sideline anecdote so there was not much detail given but the basics of the story were that the stall was progressed and that the result was, as I recall the commentary, not unexpected, the aircraft being one which the school used routinely, as I recall. His story was that the original certification only looked at the initial stall indications with a prompt recovery. The student's exercise, however, quite obviously pushed the girl well into the stall regime. I presume that the approach to the stall would have been modest although I don't recall any specific comments on that point.
The point in my raising the tale for the newchums out there is that there be dragons and that part of the solution to the problem is knowledge .... You, of course, are at the other end of the hack, flick, zoom spectrum.
I'm happy to demonstrate either outcome to you in a Pitts.
I was quite happy to continue playing with gentle aeros after Aub ran us both through the aero endorsement down at Geelong so, pass on your kind offer - quite happy to go along for a sedate session of aeros, of course. As a sidenote, JSJ was the source of my "Chuck" nickname after a ride in the Chippie at RVAC in days now very long gone by.
This the one ? https://planecrashmap.com/plane/ca/N8602J/
The point in my raising the tale for the newchums out there is that there be dragons and that part of the solution to the problem is knowledge .... You, of course, are at the other end of the hack, flick, zoom spectrum.
I'm happy to demonstrate either outcome to you in a Pitts.
I was quite happy to continue playing with gentle aeros after Aub ran us both through the aero endorsement down at Geelong so, pass on your kind offer - quite happy to go along for a sedate session of aeros, of course. As a sidenote, JSJ was the source of my "Chuck" nickname after a ride in the Chippie at RVAC in days now very long gone by.
This the one ? https://planecrashmap.com/plane/ca/N8602J/
Yes, that's it. SR described it and his subsequent work when at Avalon some years ago.
Sean Roberts' excellent slideshow is available to download at flighttestsafety dot org/36-workshops/workshops?limit=4&start=16 look for “Taming the Stall/Departure Characteristics of the Derringer D-1 Aircraft”
Some info there is relevant to this thread. Especially the bit about "Adding power at the stall (FAA Training) can cause a departure and violates FAR certification criteria." The FAA has since amended their stall recovery procedure in Chapter 4 of the Airplane Flying Handbook and it seems that CASA is on track too with AC 61-16 and, hopefully, their future revised Flight Instructor Manual.
Sean Roberts' excellent slideshow is available to download at flighttestsafety dot org/36-workshops/workshops?limit=4&start=16 look for “Taming the Stall/Departure Characteristics of the Derringer D-1 Aircraft”
Some info there is relevant to this thread. Especially the bit about "Adding power at the stall (FAA Training) can cause a departure and violates FAR certification criteria." The FAA has since amended their stall recovery procedure in Chapter 4 of the Airplane Flying Handbook and it seems that CASA is on track too with AC 61-16 and, hopefully, their future revised Flight Instructor Manual.
An interesting thread and one, that with a couple of exceptions shows how largely ignorant of the certification standards for Normal category General Aviation (part 23) aircraft most Pruners are.
There was an emphatic statement made at one post about how certification stalling is conducted (Not You DJP) and the 1 kt/sec entry rate with wings level.
Very nice yes, but:
a) This is for the purpose of determination of stall speeds, from which other speeds are factored.
b) It is conducted within several more specific configurational conditions, such as Weight, CoG, power, trim setting and control deflection tolerances and rigging tolerances for primary and secondary control surfaces and for wing incidence, even control cable tensions.
c) Control inputs to arrest yaw are permitted At the point of stall (pitch attitude unable to be maintained by nose up input or minimum speed indicated) the control input is then held for a short additional period to ensure that speed is accurately assessed.
d) Other tests are conducted associated with stall handling with very different conditions associated for the purpose, different CoG, weights, power, turning flight and entry rates are used for the purposes of demonstrating compliance with this requirement, in order to establish the worst cases, for entry and recovery. These stalls are intended to reveal any potentially dangerous cases, and whilst the 15 degrees still applies, in general, it can be added to the 30 degrees of turn, and other cases allow much larger roll excursions when stalling from a turn in one direction, and rolling through level to the opposite wing down.
Bend a Lot, - No! you claim that normal variations of rigging will (or may) take any aircraft outside of its certified standards, not so, these are considered during testing with such conditions as listed above set to CRITICAL limits, which can be associated with either the entry or recovery phases.
John T – you are correct re SR and that story, two men died as a consequence of this type of demonstration when the schools aircraft spun in, - twins are subject to the same standards for stall speed determination, but NOT subject to the same standards for stall handling and asymmetries.
Hitch may be totally correct regarding his comments, AND the aircraft may well have been compliant and well maintained. But it is possible that it or others like it are not, as some aircraft are maintained to a budget and others to a standard. These two are not necessarily concordant.
The IP was making a good point about maintenance, my post is regarding the certification basis, and configuration and conditions applicable to these standards.
HD
There was an emphatic statement made at one post about how certification stalling is conducted (Not You DJP) and the 1 kt/sec entry rate with wings level.
Very nice yes, but:
a) This is for the purpose of determination of stall speeds, from which other speeds are factored.
b) It is conducted within several more specific configurational conditions, such as Weight, CoG, power, trim setting and control deflection tolerances and rigging tolerances for primary and secondary control surfaces and for wing incidence, even control cable tensions.
c) Control inputs to arrest yaw are permitted At the point of stall (pitch attitude unable to be maintained by nose up input or minimum speed indicated) the control input is then held for a short additional period to ensure that speed is accurately assessed.
d) Other tests are conducted associated with stall handling with very different conditions associated for the purpose, different CoG, weights, power, turning flight and entry rates are used for the purposes of demonstrating compliance with this requirement, in order to establish the worst cases, for entry and recovery. These stalls are intended to reveal any potentially dangerous cases, and whilst the 15 degrees still applies, in general, it can be added to the 30 degrees of turn, and other cases allow much larger roll excursions when stalling from a turn in one direction, and rolling through level to the opposite wing down.
Bend a Lot, - No! you claim that normal variations of rigging will (or may) take any aircraft outside of its certified standards, not so, these are considered during testing with such conditions as listed above set to CRITICAL limits, which can be associated with either the entry or recovery phases.
John T – you are correct re SR and that story, two men died as a consequence of this type of demonstration when the schools aircraft spun in, - twins are subject to the same standards for stall speed determination, but NOT subject to the same standards for stall handling and asymmetries.
Hitch may be totally correct regarding his comments, AND the aircraft may well have been compliant and well maintained. But it is possible that it or others like it are not, as some aircraft are maintained to a budget and others to a standard. These two are not necessarily concordant.
The IP was making a good point about maintenance, my post is regarding the certification basis, and configuration and conditions applicable to these standards.
HD
Moderator
For those folks who don't know the last two posters, I suggest that you heed their counsel well - both are longtime greybeards with a wealth of FT and certification background.
Sean Roberts' excellent slideshow
I'd forgotten Sean's presentation at Avalon - Dave's link is well-worth folks' time in having a look at the files. You might need to gloss over some of the graphs a tad but the basics are pretty clear from an educational perspective.
shows how largely ignorant of the certification standards for Normal category General Aviation (part 23) aircraft most Pruners are.
... and generally in the Industry. Dave and I have moved back into the theory training arena to some extent and, while our efforts represent only a drop in the training bucket, we do try to expose the newchums coming through to things a bit outside the MOS syllabus ... Things haven't changed much - I was actively involved in theory training back in the 70s/80s and the overall lack of knowledge and, worse, misinformation and OWTs, which then acquired the status of Gospel through the uncritical telling and retelling thereof, had to be experienced to be believed .. both then and now.
Sean Roberts' excellent slideshow
I'd forgotten Sean's presentation at Avalon - Dave's link is well-worth folks' time in having a look at the files. You might need to gloss over some of the graphs a tad but the basics are pretty clear from an educational perspective.
shows how largely ignorant of the certification standards for Normal category General Aviation (part 23) aircraft most Pruners are.
... and generally in the Industry. Dave and I have moved back into the theory training arena to some extent and, while our efforts represent only a drop in the training bucket, we do try to expose the newchums coming through to things a bit outside the MOS syllabus ... Things haven't changed much - I was actively involved in theory training back in the 70s/80s and the overall lack of knowledge and, worse, misinformation and OWTs, which then acquired the status of Gospel through the uncritical telling and retelling thereof, had to be experienced to be believed .. both then and now.
Chris Burns once said something like that to me. Next thing we were upside down in a non-aerobatic aircraft, then falling out of a barrel roll shortly after and he didn’t know where the throttle was in the aircraft (he was a demonstrating passenger).
Watch this!
Hold my beer!
Watch this!
Hold my beer!
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I have seen Piper aircraft that exhibit consistent wing drop for two reasons both of which are hard to see.
The first one was a Piper Seminole that the front wing attach spar bushing which is a press fit into the forward attach tab and that goes through 2 steel plates in the fuselage had been dislodged . The bushing is not clamped between the plates and can be dislodged from the fitting causing the leading edge to change angle of incidence by a couple degrees even with the main spar and rear fitting bolts correctly installed .You won't see it on less the aircraft is jacked up and you lift up the leading edge .The one my workmate found had cut about a third of the way through the bolt.the bushing can be seen by taking out the sidewalls in the cockpit forward of the seats .
The second cause is some one pushing on the Ailerons to move the aircraft which evan when you can't see the deformation by eye makes a difference that can't be rigged out. The only way to check is to swap in a known serviceable aileron and test fly.
This is specifically mentioned in the maintenance manuals.
The first one was a Piper Seminole that the front wing attach spar bushing which is a press fit into the forward attach tab and that goes through 2 steel plates in the fuselage had been dislodged . The bushing is not clamped between the plates and can be dislodged from the fitting causing the leading edge to change angle of incidence by a couple degrees even with the main spar and rear fitting bolts correctly installed .You won't see it on less the aircraft is jacked up and you lift up the leading edge .The one my workmate found had cut about a third of the way through the bolt.the bushing can be seen by taking out the sidewalls in the cockpit forward of the seats .
The second cause is some one pushing on the Ailerons to move the aircraft which evan when you can't see the deformation by eye makes a difference that can't be rigged out. The only way to check is to swap in a known serviceable aileron and test fly.
This is specifically mentioned in the maintenance manuals.