PPRuNe Forums - View Single Post - Deliberately forced wing drop stalling in GFPT test
Old 13th Jul 2011, 00:47
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HarleyD
 
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I would not agree with that, the rate of stall/spin accidents below 1000 ft has not really changed significantly in the last 50 years. Still responsible for a lot of accidents, and unfortunately deaths as well.

"The Piper PA-38 Tomahawk, designed specifically for flight instruction, including easier demonstration of spins, was involved in 50 stall/spin accidents from 1982 through 1990, for a rate of 3.28 per 100 aircraft in the fleet. During the same period, the Cessna 150/152 had 259 stall/spin accidents, for a rate of 1.31 per 100 aircraft, and the Beech 77 suffered only four such accidents, for a rate of 1.64 per 100 aircraft."
The Reason for this was that even though the prototype/pre-production Tomahawk was in fact developed as a benign handling trainer, and certified as such, when placed into series production the Engineers at the manufacturing plant introduced several "productionization" mods which resulted in one of the most dangerous trainers ever built,. and which has a very high attrition rate in the world wide fleet. Some of the production mods inclded removing aerodynamic fixes incorporated to inprove its unpredictable stall/spin behavior and other structural mods related to the lightening of the wing by removing components (e.g some ribs) which reduced the torsional rigidity of the wing and allowed mainplane flexing during spinning.

Modern training aircraft have benign stalling characteristics and there are stringent rules on the amount of wing drop permitted in the certification process. These aircraft include the Cessna and Piper singles of a previous era.
I would not agree with that, the rate of stall/spin accidents below 1000 ft has not really changed significantly in the last 50 years. Still responsible for a lot of accidents, and unfortunately deaths as well
.
FAR 23 at the more recent amendment status and other similar certification standards require high stability, controllablity and maneuverability criteria, and importantly also mandate that in any recovery conventional inputs will enable prompt recovery. Even non-spinning certified aircraft must demonstrate prompt recovery when conventional recovery procedure is applied, even when loaded to gross weight, max aft C of G, full power and full flap (or partial flap, depending on the critical entry or recovery case) and this is with the control deflections set to the critical limit, and control cables rigged to minimum tensions. In this configuration recovery , after one full turn, must not exceed ONE ADDITIONAL TURN, when the recovery procedure is applied. so the aircraft must be capable of being sorted and recovered in one turn, so yes, design standards are very much higher these days.



I would suggest that whiilst 3000 ft seems over cautios altitude for ALL stalling, it does provide a level of comfort to the ab initio student, to whom this is very unfamiliar and stressful, as well as re-inforcing to more competent pilots that this is a maneuvre that is outside 'normal operating' procedures in general and should be treated respectfully, that it does also allow sufficient altitude for a stuffed up recovery, though a good instructor should recognize and prevent such a thing happening.

My understanding is that the Three thousand foot limitation allows for Two recovery mistakes on the way down.
No Student of mine would ever get the chance to make TWO stuff ups in a single recovery. Any stuff up is enough reason to take over, explain the situation, demonstrate the procedure again and the hand back for another go.

As an instructor I ecercise a degree of discretion regarding stalling practice altitudes, especially as the training level advances, CPL, Aeros, spinning

During Ag training stalling in a loaded aircraft is expected to be able to be demonstrated at 200' with a recovery by 100'. this is a highly incentivated training procedure, but certainly not for ab-initio or 'average' pilots.

HD
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