Spin and Fuel Imbalance

[cthomas]

Hello everybody!

I'm new on this forum, so I apologize if I post on the wrong forum...

I'm wondering if there is a fuel imbalance limit to recover a spin on light aircrafts. I've heard that beyond 25% of imbalance between the right and left tank, a spin recovery is not certified. You may not be able to recover. Is it right? I've already check the EASA certification regulation CS23, but no luck. It's just written that the tests must be conducted with the maximum imbalance possible.

Any idea?

Thank you!

[sycamore]

ct, as you don`t provide further details,is this a new type of aircraft,or something that has been modified...?
In any case ,the aircraft /company/design staff should have all relevant details about A/B ratios, vertical wind-tunnel model tests,stalling test data, stressing ,pilot escape options.,requirement for anti-spin `chute,telemetry. The list is long,and especially so if you are doing this first time.Are you a certified Test Pilot...? Is the aircraft piston,t/prop or jet...?
When I taught student test pilots/engineers in a piston engine aircraft,I would stall the aircraft,then pull the nose up and stop the prop,then stall and spin.This way there were no prop induced effects,and spinning in either direction was generally the same.
Whilst the tests might require the `maximum` imbalance,it should be very cautiously approached,probably 5% increments,and the aircraft inspected each flight for signs of possible distress...Go very carefully.......

[Genghis the Engineer]

I'm not sure I can recall ever seeing any firm guidance and I've run several part 23 and smaller spin programmes.

I'm on the wrong continent to check my copy, but I wonder if there's anything in Darrol Stinton's "Flying Qualities and Flight Testing of the Aeroplane" ? DS did a lot of this sort of work over a lot of years, and that book contained much of his distilled wisdom. The other place worth looking would be FAA AC23-8.

G

[cthomas]

Thanks for your analysis. I've found a document written by Claude LELAIE about light aircrafts spin. It is said that every French light aircraft are certified with a maximum imbalance of 25% if wing fuel tank equipped. So, it may be only a French rule. As I'm flying a TB10, I've sent a request to SOCATA to get their flight test conditions. Do they have a regulation about that, or just a common way of doing that...
I'll keep you informed of their answer!

[sycamore]

Is there a Flight Test department in the DGAC,who should be able to help...?

[cthomas]

As I know, not. To be honest, the only way the DGAC would have to conduct flight tests would be prohibiting any aircraft to fly for safety measure. No flight, no spin, no problem
I'm still waiting for SOCATA answer.