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Wing drop at stall

Old 18th Aug 2019, 17:00
  #41 (permalink)  
 
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Originally Posted by Genghis the Engineer View Post
I've spun a Hunter inverted. Enter at 30,000ft, 4 turns, recover, pull out from the dive - bottoms at about 15,000ft. Concentrated the mind on height loss - but as it's a swept wing jet massing around 10 tonnes, not all that representative of light GA typically massing about a tonne, with a propeller and a straight wing.

G
As a general observation an inverted spin will not happen in your typical GA trainer. The closest I have come was a botched immelman entry in a C 150 Aerobat. It ran out of steam near the top of the half loop and the student had let quite a bit of yaw develop. I did not say anything because I wanted to see what the student would do when we departed controlled flight. When the airplane stalled it initially flipped over in the start of an inverted spin but then flipped back over to an erect spin which almost immediately developed into a spiral dive. The student sat frozen at the controls doing nothing with a rather humorous gobsmacked expression while all this was happening until I yelled at him," Analyse and Recover !" at which point he did an acceptable spiral dive recovery

The bottom line from my POV. Any discussion of inverted spins have no relevance to the topic of stall/spin in ab initio training

As a general observation I would suggest failing to teach control of yaw and then failing to demand students control yaw in all phases of flight is a weakness in flight training. Unfortunately modern trainers, especially the C 172 will let students get away with feet on the floor flying. One result of this is effective control of yaw when the aircraft stalls and during the subsequent recovery. If yaw is controlled it is impossible for the aircraft to spin so failure to control yaw is not good.......
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Old 18th Aug 2019, 17:15
  #42 (permalink)  
 
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The bottom line from my POV. Any discussion of inverted spins have no relevance to the topic of stall/spin in ab initio training
Oh I'd discuss it, somewhere around 2-5 minutes on the ground, then get on with something much more immediate and relevant.

G
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Old 19th Aug 2019, 16:33
  #43 (permalink)  
 
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Smile

Probably got more out of the foregoing posts than I have on many an FI/FE Seminar(s)!!
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Old 19th Aug 2019, 23:45
  #44 (permalink)  
 
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As a general observation an inverted spin will not happen in your typical GA trainer
maybe not but you then go on to quote the aerobat in a cocked up aerobatic manoeuvre, and many aerobatic aircraft (maybe not so much the aerobat) WILL get into an inverted spin from a botched manoeuvre, the most likely I have found (and how it happened to me) is going for a vertical roll into a stall turn, stick goes forward to keep vertical and you the put rudder in possibly against aileron and off you go.
You then say this should not be discussed in ab initio, unfortunately there are pilots that will try aeros without proper training, these are the ones most likely to mess it up and at least if it is discussed then they have some idea how to recover - also it is not a bad thing if they then go on to aeros to already know the principle, after all it is not that hard to teach - opposite rudder, stick progressively back OR forward until the spin stops! (Obviously just concentrating here on how little change you need to make rather than going through full spin recovery detail)
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Old 20th Aug 2019, 10:15
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One of the few good things that have come out of EASA is the introduction of the Aerobatic rating. This at the least reminds pilots that they are not qualified to perform aerobatics until they are properly trained and assessed.

There is only so much you can do within the PPL syllabus before you overload it and possibly put people off flying. When I learnt to fly spinning was mandatory and many left flying because they would not accept the impending spin training or suffered an intolerable reaction to it. The current stalling syllabus is sufficient in its current form when it is completed fully. Sadly this is not always the case. As with some other parts of the syllabus stall training it is not completed, as detailed, but is only carried out sufficient to meet the requirements of the skill test.
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Old 23rd Aug 2019, 04:31
  #46 (permalink)  
 
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Foxmoth

I stand by my contention that the common trainers such as the C 152/C172 or Pa 28 series can’t enter an inverted spin as the significant wing dihedral makes them naturally unstable inverted so that they will transition into an erect spin on their own during the spin entry.

In the case of the C152 aerobat, my experience has been that even in full into yaw aileron and full power would not generate a stable inverted spin

The message for an initio student should not be how to deal with a botched hammerhead, it should be on the importance of reducing AOA to get the wing flying again and control of yaw to prevent a departure from controlled flight
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Old 23rd Aug 2019, 21:32
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BPF, to be honest even a sustained erect spin is difficult to achieve in these aircraft, and I would certainly agree the emphasis should be on reducing AoA to get the aircraft flying, where I would disagree is your statement
Any discussion of inverted spins have no relevance to the topic of stall/spin in ab initio training
, this certainly should not be discussed with all students as it will confuse, but anyone that has the interest and capability of understanding it should not be blocked from something that will expand their knowledge and understanding of stall/spin.
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Old 23rd Aug 2019, 22:23
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Fox. Think you have the order wrong there. Unstall the wings first, then full opposite rudder unless the POH says otherwise.
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Old 23rd Aug 2019, 23:08
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Originally Posted by rarelyathome View Post
Fox. Think you have the order wrong there. Unstall the wings first, then full opposite rudder unless the POH says otherwise.
Negative.

The "Standard Spin Recovery" used as the start point for flight testing is found in AC23-8 and is opposite rudder, then stick forward. Whilst many aeroplanes may have variations from that, SSR is invariably the baseline.

G

Last edited by Genghis the Engineer; 24th Aug 2019 at 08:39.
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Old 24th Aug 2019, 04:03
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Thanks G - it was late Apologies Fox

Last edited by rarelyathome; 24th Aug 2019 at 07:11.
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Old 24th Aug 2019, 10:11
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Forgive a little thread drift. I just chanced upon a video of a float plane crashing on take-off due to a wing drop stall.

https://abcnews.go.com/WNT/video/vid...g-off-65157413

I realize that I have seen several videos showing similar crash on take-off, they seem to result from loss of power on take-off, but then no evidence of any attempt to lower the nose and deal with the issue. That float plane for example seemed to maintain a high AoA until it fell from the sky with one wing down. It looks like he had an entire lake to put it back down on but he didn't. If my interpretation is right, any thoughts on why this happens ? Does the pilot just freeze ? Or is there actually no time/authority to get the nose down at a critical point?

Last edited by double_barrel; 24th Aug 2019 at 11:05.
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Old 25th Aug 2019, 01:50
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DB

Normal float plane takeoffs have the airplane becoming airborne at minimum flying speed so the drill is to become airborne and then accelerate in ground effect until climb speed is reached and then climb away. Float planes are more vulnerable to clumsy handling right at and after liftoff so you do see more stall accidents in this area compared to land planes. Gusty winds exacerbate the issue and require good skills to manage safely
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Old 25th Aug 2019, 01:59
  #53 (permalink)  
 
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Originally Posted by Genghis the Engineer View Post

The "Standard Spin Recovery" used as the start point for flight testing is found in AC23-8 and is opposite rudder, then stick forward. Whilst many aeroplanes may have variations from that, SSR is invariably the baseline.

G
When I am teaching aerobatics we do quite a bit of spinning. One of the things I watch for are students who relax the back pressure prior to first stopping the yaw with the rudder as this can create a very interesting ride

In the ab initio context I demonstrate one spin as a way to show the consequences of not recognizing and avoiding the stall and if the airplane does inadvertently stall; not controlling yaw. The spin recovery is required if the airplane is actually spinning which on all common trainers, requires at least half a turn if not more. Recognition and avoidance of the stall should be the primary focus of ab initio training and instilling the instinctive reaction of froward stick full power and rudder to control yaw at the first sign of the aircraft stalling.
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Old 25th Aug 2019, 21:48
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A very experienced test pilot, who became a flying instructor, referred to this in my hearing as "conducting the orchestra" - where pilots, instead of holding the controls firmly and initially in the pro-spin / initial condition, kept moving the stick around, and often didn't keep the rudder on the stop either. As you say, it creates interesting and inconsistent recoveries.

I agree that correct actions in the early incipient stage of the spin are not the same as those from a developed spin. Historically that basically was throttle closed/controls centralised. Interestingly, I explored that during some refresher aerobatic training last year, and the very experienced ex-military aerobatic instructor teaching me insisted that in his opinion whilst that worked consistently, he preferred the UPRT drill of unload in pitch / roll wings parallel with the horizon / pitch to level flight attitude.

So, what else could we do? We went and set up some deliberate gross mishandling upsets, and tried the two different recoveries with identical entries.

The result? Both worked first time every time, but his preferred UPRT approach gave us consistently about half the height loss. I am a convert!

G
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Old 26th Aug 2019, 09:05
  #55 (permalink)  
 
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Genghis

Please detail the the full recovery from the spin that your instructor was teaching. To my knowledge the EASA UPRT is a course but doesn't specify technique.
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Old 26th Aug 2019, 09:31
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The full recovery from the spin was exactly as the POH (in this case for a T67M260), the UPRT - which we also used for an undefined early incipient spin (by undefined I mean from a manoeuver not a standard spin entry, and so with spin direction not yet defined) was as I've said above.

G
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Old 26th Aug 2019, 10:42
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I'm still unclear Genghis what it is you are saying. I've attached the T67 Mark 11 spin recovery section albeit this aircraft has the less powerful 150/160 hp engine than the aircraft that you flew. I don't know if the recovery is different.

An issue for understanding for me could be the use of the word "incipient". In aerobatics the term covers the first 3-4 rotations or until the spin stabilizes. In the PPL syllabus the term applies to "wing drop" before rotation begins. There is a very important difference in the recovery technique between these two situations.
Attached Files
File Type: pdf
T67 Mark 11 spin recovery.pdf (310.8 KB, 14 views)
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Old 26th Aug 2019, 11:03
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Now there's an argument I had with the late, great Darrol Stinton a few times. What is incipient?

Darrol used to reckon it was about the first 6 turns, and instrumented data I've been through from flight tests tends to agree with him - but the convention I am using here is that it is the phase between initial loss of control and the spin mode (e.g. erect to the left) becoming clear to the pilot.

G
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Old 26th Aug 2019, 14:43
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Originally Posted by Genghis the Engineer View Post
What is incipient?
Equally, RAF Central Flying School now have quite a nice definition that works with my own students for defining incipient vs full spinning: an incipient spin is one that does not require a full spin recovery technique, while a full spin is one that does not recover using an incipient recovery technique. There is of course the caveat of individual aircraft having their own optimum recovery techniques - cf the farce of the Robin 2160 when first brought into the UK - but as an overall rule it works well. DS of course explored the various modes rather more thoroughly than most of us might in day to day flying, with more understanding of how differing flight path may affect the spin modes!
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Old 26th Aug 2019, 16:05
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The robin 2160 gives pretty much the expected 'standard stall recovery' technique within it's POH. An interesting quote directly from it's manual: “Only one action is important – keep the rudder fully in opposite direction!”.

Following an interesting discussion with a number of aerobatic competition pilots I was surprised to hear that recovery from the incipient spin (most common during a short display) was primarily stick forward, I had to try this and found flying the R2160 that indeed by doing this you could recover well onto a very precise and predetermined heading. But what of using such a technique when recovering from a fully developed spin. I also tried this climbing to a safe height. I kept the spin to 6 rotations and then pushed the stick forward: it could have been set in concrete, it was immovable. I then applied maximum opposite rudder and was then, quite quickly, able to recover using the recommended POH spin recovery technique.

The R2160 manual also states that after 3 rotations the engine may stop but, this is not of concern because the engine will recover power quickly following recovery. The CAA did not like this so put in the restriction of a maximum of two turns. The engine stops very rarely but if it It does the POH is proved correct.
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