Originally Posted by
43Inches
Actually its to highlight that in addition to the MB and PARE techniques the A150 is still difficult to recover using POH technique and is unusual in this way.
In some spin modes it demands the correct application of the POH method. It is not difficult
Cessna especially emphasises even slight aileron deflection, leaving some power on, moving elevator before rudder, slow rather than brisk movement of the elevator.
There are other types which also demand, in some spin modes, correct application of the method in the POH. I had a scare in a Pitts S-2A (in the days before we knew about Beggs-Mueller) when it wouldn't recover from a spin after I'd delayed my normal control actions finishing a lomcevak. The S-2A in a power off spin to the right where outspin aileron is held to flatten the spin will not recover when aileron is neutralised using "normal spin recovery technique" according to the factory. They discovered this in 1980 and added an extra cockpit placard: "For flat spins use aileron with the spin for recovery". That placard hadn't long been in the aeroplane when I needed to know about it. I quickly considered what was going on and then fixed it.
Read Brian Lecomber's magazine article and his delayed spin recovery in an Extra 230. Read Dave Mond's article about his delayed spin recovery in a Pitts S-2B. Read the ATSB's accident report on VH-UPB for the Chipmunk spin saga 60+ years ago. Over the years I've had a number of spin instructors tell me about delayed recoveries in a Decathlon and I ask about their recovery technique - invariably I respond with "you were lucky that you didn't die" and refresh them on the correct recovery method amply described in the manuals.
Originally Posted by
43Inches
... should be careful about a number of factors, not the least weight and CG position ...
Inertia is related to those parameters but is a separate parameter. Cessna has noted "Distribution of the weight of the airplane can have a significant effect on spin behaviour. The addition of weight at any distance from the center of gravity of the airplane will increase its moment of inertia about two axes. This increased inertia independent of the center of gravity location or weight will tend to promote a less steep spin attitude and more sluggish recoveries." e.g. extra fuel will increase both roll and yaw moments of inertia. They are second moments (the moment arm squared) so there is a bigger change to the moments of inertia than CG for changes along the fuselage centre-line, even more so with tanks in the wing.
It is worth recalling this text from the FAA's Flight Instructor Bulletin #18: "The subject of airplane spinning is a complex one, which is often over-simplified during hangar-flying sessions. ….. This has resulted in some confusion and misunderstanding over the behaviour of airplanes in spinning flight, and it appears this lack of understanding may have contributed to some serious accidents. …" from 40+ years ago.