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SA 17yr old student crash

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SA 17yr old student crash

Old 14th Aug 2020, 02:52
  #21 (permalink)  
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The defect in the bushplane was reported to me by an authoritative source as being a manufacturing process control shortcoming. The result was that the airfoil of certain wings differed from the intended design due to "hand assembly", rather than jigged assembly to assure accuracy. Though not good, this problem could have been prevented from "getting out into the world" by more thorough production flight testing, including thorough stall testing.

I thoroughly stall test any plane I'm asked to fly, which has been modified, or is fresh out of maintenance. The forgoing was not the only surprise I've had over the years, just the most extreme example.
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Old 14th Aug 2020, 16:38
  #22 (permalink)  
 
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The "hand assembly" must have been grossly off to have affected the stall characteristics of the airplane ... unless the airplane wound up with a different airfoil section from one wing to the other. Could a rigging error, causing different angles of incidence from one wing to the other, have caused or exacerbated the vicious stall characteristics?

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Old 14th Aug 2020, 18:57
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unless the airplane wound up with a different airfoil section
That is what was explained to me after the construction processes for the planes were carefully evaluated by the authority. As I mentioned, two of the same model plane I flight tested, only a few serial numbers apart, had startlingly different stall characteristics.
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Old 14th Aug 2020, 19:11
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There's no way of adjusting the wing incidence on a PA28, unlike the Cessna off-set aft bushing. The maintenance manual method of lifting a heavy wing was to extend the flap pushrod by a couple of turns until it flew right!
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Old 16th Aug 2020, 14:55
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Not a flight instructor, but I have a suspicion.
Flying has two important aspects: the procedures and the physics. Not being very intimate with the second can kill you.
My suspicion is that regardless of flight time some pilots, while proficient at the procedures, do not have a good enough model of the physics of flight ingrained and present at all times.
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Old 16th Aug 2020, 15:09
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Originally Posted by jan99 View Post
Not a flight instructor, but I have a suspicion.
Flying has two important aspects: the procedures and the physics. Not being very intimate with the second can kill you.
My suspicion is that regardless of flight time some pilots, while proficient at the procedures, do not have a good enough model of the physics of flight ingrained and present at all times.
I call it "A Feel For The Airplane" which cannot be achieved without an appreciation of the physics of flight, as you so appropriately pointed out. Of course, I should substitute "aircraft" for "airplane" since it also applies to helicopters and lighter-than-air.

Cheers,
Grog
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Old 16th Aug 2020, 17:03
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I often find when training already licensed pilots to fly tailwheel aircraft for the first time, they lack an inherent feel for what the aircraft is telling them. They take some time to become pro-active rather than re-active to what the aeroplane is doing in a given manoeuvre.
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Old 17th Aug 2020, 09:59
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Could a rigging error, causing different angles of incidence from one wing to the other, have caused or exacerbated the vicious stall characteristics?

I once flew a Ceesna 152 from a flying school. At the time I was an instructor giving another instructor recurrent training as he had not flown for several months. I asked him to demonstrate a clean stall and recovery. He entered the stall smoothly and we were both taken completely by surprise when the aircraft dropped the left wing viciously to 60 degrees with the nose dropping to 30 degrees nose down. We lost 400 feet in the recovery. I had flown old military aircraft some with wing drop characteristics and was very experienced. But even then that Cessna 152 was one of the worst wing drop examples I had flown.

I took control and set up for another stall with full flap and 1500 RPM. Again,an equally sudden wing drop at the point of stall and by the time we recovered we had lost 600 ft and finished up 180 degrees from the original heading. There was no doubt the aircraft was un-airworthy and I reported the problem to the flying school as well as writing the defect in the aircraft maintenance document. The CFI stated he knew about the wing drop problem on that particular aircraft but was happy to accept the defect because he used it for PPL tests to test the students competency at recovering from a wing drop; this being a regulatory requirement for the PPL test.

Solo flying was not permitted by the flying school on that Cessna 152 because of the wing drop risk. The owner of the aircraft was a licenced aircraft mechanic who did his own maintenance. After I had recorded the wing drop defect in the maintenance document the owner signed off the aircraft as serviceable without rectification and it continued to be hired out.

Eventually action was taken by one disgruntled hirer to contact the Regulator as he was concerned the aircraft was being flown despite being demonstrably un-airworthy even though the maintenance document displayed a clean sheet devoid of defects. The Regulator sent an Examiner to test fly the aircraft. When the mechanic owner of the Cessna 152 realised a CAA Examiner had booked the aircraft for a test flight, he took the aircraft off line and re-rigged the wings before handing it over to the Examiner to test fly. The owner failed to tell the Examiner that he found the left wing to be grossly out of correct rigging and that he had now rectified the defect. The Examiner flew the aircraft testing the stall characteristics which by now were normal following the rectification by the owner. He reported to the Regulator that the Cessna 152 had no defects
Later, the disgruntled hirer who had experienced the severe wing drop was admonished by the Regulator and informed an Examiner would test him for his knowledge of recovery from a wing drop at the point of stall. The disgruntled hirer happened to be another experienced miliary pilot with thousands of flying hours and thus familiar with wing drop characteristics.

That Cessna 152 had been flown by many flying school instructors in the months before the first episode. While they were aware of its adverse stall characteristics through word of mouth, none would record the defect in the maintenance record for fear of job security. This is a common problem in general aviation operations. If any aircraft flown by students and instructors is found to have undesirable handling characteristics during stalling practice it becomes a flight safety issue. It becomes an airworthiness issue as well. Unless the pilot records the defect on the maintenance document as well as verbally to the operator, the next pilot to fly the aircraft could be in for an unpleasant surprise. There is also a moral obligation to report these sort of defects.

Last edited by Tee Emm; 17th Aug 2020 at 10:16.
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Old 17th Aug 2020, 10:34
  #29 (permalink)  

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Years ago, as a 17 year old student pilot on an RAF flying scholarship at Ipswich with Lonmet Aviation (that dates me a bit) I was allocated a 152 fresh out of major maintenance. I’d not flown it before and it was my last dual GH revision sortie prior to my final handling test, so it was a full profile, with the instructor there to hopefully sit on his hands and watch me trying my best.

As briefed, I did a standard stall entry from level flight. The aircraft markedly dropped its left wing, but it didn’t cause a major problem because I’d been taught how to deal with that.

We were also required to demonstrate and recover from a fully developed spin. I entered as per the previous stall and applied full left rudder at the buffet. The spin entry didn’t go like any other I’d seen. When it settled down, my instructor looked across at me and said “Have you noticed anything unusual”? “Yes”, said I, “We’re upside down”!

We were in an inverted spin and the prop then stopped.

My instructor asked what I was going to do to recover.....I replied that I’d better pull back rather than pushing forward on the yoke and he nodded! It recovered quite quickly as I remember and the engine restarted itself as we recovered from the descent.

I think the instructor was more shaken up by it than me, I knew no better I suppose. The aircraft was taken off line and it was found to have a difference in individual wing rigging when it had been put back together.
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Old 19th Aug 2020, 12:11
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Certification flight tests conducted by the manufacturer's test pilot include the maximum wing drop permitted by FAA rules is 15 degrees when conducting stall tests. This suggests that any flying school aircraft that exceeds this amount during practice stalls should be considered unairworthy until the defect is rectified.
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Old 19th Aug 2020, 17:07
  #31 (permalink)  
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Correct. When I fly certification test flights, or maintenance check flights, I will not sign off on a plane with a wing drop exceeding the certification standards. I would extend that any plane exhibiting too much wing drop should be rectified. To be honest, flying school airplanes are probably less the risk, as pilots intentionally stall them, so they're prepared to recover. It's the private airplanes, loaded up, and flown by pilots with little recent stall practice, which may bite worse when stalled.
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Old 19th Aug 2020, 18:33
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"the maximum wing drop permitted by FAA rules is 15 degrees when conducting stall tests."
Seeking information. How is the 15° test done? After a wing repair and recover, last year ourJodel had a wing drop on stall which I described as "acceptable". I'll be doing the 2020 LAA Permit test tomorrow if the weather allows. Is it with immediate remedial action, or after a pause?
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Old 19th Aug 2020, 19:03
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The actual wording of the requirement is:

(e) During the recovery part of the maneuver, it must be possible to prevent more than 15° of roll or yaw by the normal use of controls
So, if I can control the plane within that, I'm okay with it. If it's 20 degrees, and I have good control, I'm still okay with it. If it bites, and I feel that the control I have is not confident, even 15 degrees could seem questionable.

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Old 23rd Aug 2020, 09:58
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Pilot DAR. Question. Many years ago I was a QFI flying, among other types, RAAF Dakota aircraft. Practice stalls clean on the Dakota posed no problem. However in the approach configuration (full flap and approach power) in every case there was a sharp wing drop beyond 45 degrees and considerable altitude lost before full control was regained.

A former UK test pilot on PPRuNe made the point that if the stall was approached at one knot per second the wing should not have dropped unduly. While I recall we didn't reef the nose up to reach stall speed and the rate of speed decay was certainly faster than one knot per second nevertheless why would a savage wing drop occur with landing flap extended but not so in the clean configuration? Rate of speed decay was about the same clean or flap down but more than one knot per second.

The worst wing drop I ever experienced was not in a stall but at 200 ft after takeoff in a Dakota which was fitted with the usual rubber de-icing boots on the length of the wings. Just as the landing gear was retracting the starboard wing suddenly dropped without warning. Almost full aileron was required to level the wings along with some rudder. Weather was good with only light winds. A glance out of the pilots window revealed the deicing boot from the landing light out to the wing tip had split asunder and flapping everywhere. The loss of lift on that wing was marked.

The student in the left seat thought the starboard engine must have failed and tried to feather the propeller. Fortunately I was able to stop his hand as he reached for the feather button as engine instruments were normal.
I was concerned that using flaps for landing might produce more unexpected control difficulties so I elected to make a flapless landing As speed reduced during the flare and float the wing dropped and we touched down just as we ran out of aileron. An interesting experience.

Last edited by Judd; 23rd Aug 2020 at 10:16.
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Old 23rd Aug 2020, 12:48
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I have no experience flying the piston DC-3, but did a lot of stall testing on the turbine DC-3. Is was flying with the company training pilot right seat, so was accompanied by very competent supervision. That airplane had a nasty wing drop as the indication of the stall (usually a left wing drop). I accidentally did a half turn incipient spin twice during this testing. I know that the turbine DC-3 has different wingtips than the piston version, so there may be a difference there. The DC-3, and thus turbine DC-3 have an airframe designed and certified before refinement of stall handling characteristics as we know them now. I believe that DC-3's wings do not have a washout twist, so the whole wing can stall at once, rather than progressively root to tip - so warning is less, effects are more, it's just the way is is for some much older types. I found that this plane also had unusual pitch control forces as it approached the stall, it's just the way that plane is, though I would not certify a newer plane which handled that way. Happily, the DC-3 is not a type for which approach to stall should be common, and training is usually pretty good for their pilots. If GA trainers handled similarly, the landscape would be littered with wrecks!

A CAR 3 or Part 23 GA plane can be assumed to have compliant stall handling if correctly rigged. Pilots of airplanes other than those would be wise to seek advice or training relative to the type concerned. Most are probably still fine, but some antique types can be "different".
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Old 23rd Aug 2020, 13:07
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Correct - there's no wing washout on the DC3/C47 and the swept outer wing obviously affects the stall characteristics but the not-unknown dirty configuration 'bite' is strange.
There's an interesting 1937 NACA DC3 stall investigation video on Youtube that's worth watching.



Last edited by stevef; 23rd Aug 2020 at 23:04.
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Old 24th Aug 2020, 01:42
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Judd don't know about the RAAF but many civil operators had a requirement to only do wheelers, no three pointer attempts permitted, because of the stall roll off.
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Old 27th Aug 2020, 10:56
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After reading through this thread, my initial thoughts are to give up flying. As a future hirer, it seems from some of the thread answers, that any aircraft can have an incident which then impacts the standard stall recovery.

Thing is, we may never be imparted with the information as to which aircraft are affected.

Edited to say how sorry I feel for that young girl and her family. At 17, she should have had her whole life ahead of her

Last edited by white light; 27th Aug 2020 at 13:24.
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Old 27th Aug 2020, 13:24
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Originally Posted by white light View Post
After reading through this thread, my initial thoughts are to give up flying. As a future hirer, it seems from some of the thread answers, that any aircraft can have an incident which then impacts the standard stall recovery.

Thing is, we may never be imparted with the information as to which aircraft are affected.
This is why I am hesitant with a rental fleet of 30-40 year old aircraft.
Then again you should cover stalls during any sort of rental checkout and if you don’t like the behavior of that airplane you say so and rent another.
Apart from my little bit of fear mongering a stall is not something unexpected that just appears and jumps up to bite you in the behind.
During a normal flight profile you should never be close to a stall expect for about the last 5 inches before touch down.
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Old 27th Aug 2020, 20:10
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Apart from my little bit of fear mongering a stall is not something unexpected that just appears and jumps up to bite you in the behind.
During a normal flight profile you should never be close to a stall expect for about the last 5 inches before touch down.
Entirely agreed.

Yes, if in doubt, you should stall the plane during your checkout. If this request causes concern, there is a much bigger problem!

At altitude, practice stalls of a GA plane should not be concerning. Of course, having practiced at altitude, if you are uncomfortable with the characteristics observed during your practice at altitude, don't stall it at low altitude - then report it to someone! A correctly maintained, certified GA plane will stall very gently, and forgivingly. So, the variable is, has that plane been well maintained? If you doubt that, there are more reasons than just stall handling to cause you concern. Otherwise, it is up to you to be proficient in stall recovery technique, and thereafter, stall avoidance. If you're not comfortable, ask for a checkout, and practice stalls!
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