Yes…as a result of the Colgan, Air France, and other stall-related crashes, the “minimum altitude loss” language was removed from the ACS (the PTS at that time) about 12 years ago. Unfortunately it was ingrained for a lot of years before that, and it refuses to die.
It occurred to me while AFK that "with any full stall checks requiring factory involvement, ie. test pilots" could just as likely have been referring to production acceptance test pilots, who are (usually) similarly removed from the Yeager types but have detailed knowledge of the test criteria and procedures, including recovery as applicable.
FWIW: Yes. Have never seen or heard of a requirement for the Yeager type at the maintenance "field" level in my limited experiences. However, when going into the aircraft alteration weeds at the DER or DAR pilot levels have run across a couple who were of the former Yeager-ite clan.
Although it occurred decades ago, you might be thinking of ABX 827, a DC-8 that crashed during an attempted test of the stick shaker and pusher systems after extensive aircraft modernization mods. The jet stalled before activation of the warning systems, and incorrect pilot inputs caused a loss of control.
It's been a while and my recollection is of something different with more talk between the flight crew, so not sure if this is the one. Still, an interesting read.
We used to train to power-out with minimal altitude loss. After a steady stream of accidents, several already mentioned, that was changed. Now we handle stalls the same way we handle any upset. Push to ~.5g, which pushes you toward the center of the "envelope" (Vg diagram) which unloads the wing, improves control effectiveness and gives you bigger margins from buffet speeds.
That was N827AX in December of 1996. The aircraft had just finished conforming modifications to match the rest of their DC8 fleet. All three pilots were management pilots, two of them in the training department and the third was an assistant chief pilot. At that time, the old power-out technic was required on checkrides.
Full rudder authority is available to the pilots even when the yaw damper is engaged. We do not turn it off, even after an engine failure. It's job is to prevent dutch roll, not pilot rudder input.
So then, you ( @DOCHoliday and @nauga ) disagree with AI?
Not sure why you tagged me on this but I would defer to Hawker-specific command media on what to do with the yaw damper on Hawker aircraft. I have neither stalled nor flown a Hawker jet but have flown and stalled airplanes with yaw dampers (and pitch dampers and stab aug ad nauseum) that did not require that they be disengaged during *any* phase of normal flight. It's airplane-specific, not a general procedure. What's your point?
In my experience it would seem the yaw damper could work against the pilot's rudder inputs. For that reason, once the thing is turned on, it's pretty much a feet flat on the floor situation for the remainder of the flight until just before landing. So, I'm surprised you would agree with the other two, both of which are also highly experienced, opposite of my own take on the matter. But I'm open to learning about it.
On the other hand, I looked for some information from Google with these words: "hawker yaw damper limitations during stall maneuvers" and AI seems to agree with me (see above edit). So, you guys have the ball. Do you think stalling with the yaw damper engaged wouldn't have anything to do with these crashes?
I've never flown a Hawker. I've flown the DC8, DC9, CRJ, 757, 767, and 737. None of those required turning off the yaw damper for stalls in the sim. I'm never done a maintenance test flight that requires an approach to stall.
I have no idea what might or might not have had anything to do with these crashes, nor does anyone else here - but people like to defend their pet theories regardless of factual support. If Hawker manuals prohibit stalls with the yaw damper engaged then I wouldn't stall a Hawker with the yaw damper engaged. At this point based on information in this thread so far we do not know a) if the yaw damper was engaged, b) if the airplane was intentionally stalled, c) if stalls with the yaw damper engaged are prohibited in this airplane, or d) what other compounding factors were in play at the time.
I haven't read any "pet theories", have you?
I doubt if you're the only one who thinks that, in fact I'd bet it's unanimous
No, I'm only interested in what someone who's familiar with a Hawker has to say about it. The preliminary of the other Hawker crash mentioned the autopilot needing to be disengaged before stall-type maneuvers and I thought mention of the yaw damper was conspicuous by its absence. The corkscrew dive made me wonder if an engaged yaw damper could interfere with stall recovery, that's all, not "how it works".
I believe every 4 years the wing leading edges are removed for inspection, then reassembled, and the stall test performed in order to sign off the inspection. So I think you'll be hard pressed to find a flying Hawker without the test performed at least legally.
2 in not quite two years…so probably 40% of the fleet has had to do the stall test in that period. So well under 1/2%, and substantially less than that over the last decade. Tragic, but a smaller statistical blip than a lot of the accidents we talk about here.
I wouldn't say I have much familiarity with the Hawker but I do have an hour and change in it and a manual.
Thanks, I had seen that page on Juan Brown's slide discussing the Utah crash. Thing is, that seems to pertain to normal flying not to stall system calibration which would be in the maintenance manual. I've known at least two pilots who have wound up on their backs in Learjets of different models, one in a LR23 calibrating the AoA vanes and the other in a LR35 preparing for a type rating. The latter was on the jump seat observing. Both were very impressed and not in a good way.
It seems to refer to any time “When intentional stalls are carried out,” which would seem to me NOT to be normal flying.
It's in the "Normal Handling" section of the "Pilot's Operating Manual". To me, that implies the AC is fully compliant with certification standards. To me, stall calibration flights imply a conformity investigation as the status is unknown. YMMV.
Given that it lists control inputs to be taken if the stall characteristics are out of certification standards, my mileage does vary.
I see nothing very specific in the POH, like in which configurations it needs to be stall tested, etc. There's not a more detailed expanded description in the maintenance manual?
The tentative and rather poorly executed radio transmissions as the pilots requested a block altitude and positioning for the stall series (which may have been exacerbated by English language deficiencies) seemed to me an indication they may not have had experience in the process and were perhaps ill prepared to perform the task.
There is a test procedure in the maintenance manual, but nothing more on how to conduct stalls.
In my experiences with mx flights, the mx manual will establish the test parameters and test values but not instruct the pilot how to fly the aircraft which falls under the flight manual. And as noted in the Hawker AFM excerpt above it plainly states: "When intentional stalls are carried out, the following conditions apply:" So the pilots should have followed the AFM procedure and guidance while looking for the parameters and limits given in the mx manual test procedure. Another example would be when checking helicopter autorotation rotor speeds, while the mx manual requires the test it only gives the target rotor speed vs weight values but the RFM states how to perform the auto.
There are a few contract pilots that do travel specifically for this and similar tests and I believe the OEM also provides pilots on request. However, the decision to use them is up to the operator, mx shop, or the pilots themselves.
According to a pilot commenting on another forum who has experience doing these tests, the clean stall break is the worst, which is counter-intuitive to me. So, I would think stall warning calibration would start with more benign configurations and make any needed calibration adjustments before testing the clean configuration. However, neither the structural repair manual on Juan Brown's slide nor the POH on his other slide mentions that as a consideration. I would hope there is more specific documentation than what I've been able to see.
Interesting. Its my understanding that once the leading edges, etc. are reinstalled, a ground check is performed of the stall identification system per the mx manual. The test flight is to confirm the stall ID system activates properly prior to a stall. And if the stall system activates at the correct reference points, then the test is completed with no actual stall encountered.
Kinda looks like maybe some flying surfaces were shed on the way down.
Looking at this from the aviation safety professional perspective: A 98% success rate of any maneuver in aviation is horribly, unacceptably bad and merits a fleetwide grounding.
Well in that context, I would have stated that 99.999995% of the tests are completed without incident. Which is well below the overall average accident rate for this class aircraft.
We should’ve grounded checkrides a long time ago, I guess.
To a certain extent, a "pass" is anything that gets all the people safely on the ground.
Not sure how context changes the answer here?
In other words, it doesn’t matter what happens on the flight. Safety is defined by everyone getting safely on the ground at the end.
My reply was in reference to the stall test maintenance procedure and the general comments related to it. Not the flight safety of performing it. Hence the different numbers I provided. So yes, context is everything.
This.
