Spinning and T67s

[EGBKFLYER]

Have read the previous posts on spinning T67s, which has answered most of my questions except one. I guess this is a general question anyway:

The Firefly is known to take a while to recover from a fully developed spin - why is this?

I'm surmising rotational inertia (high aspect and therefore larger distance from the centre of rotation?), relative lack of rudder authority to stop the yaw quickly?

Would be interested in your thoughts.

[DB6]

Correction: the Firefly is rumoured to take a while to recover. It doesn't - if the correct recovery actions are taken it recovers immediately (within 2 turns) every time. I have spun Fireflies (T67M 260s) hundreds of times and never once had a problem with recovery, even after a 23-turn spin. Recovery will be delayed if the stick is moved forward before rotation stops having applied opposite rudder, as a high-rotational spin may develop, but I believe this is no different to e.g the Bulldog.

[Send Clowns]

Have to agree with DB6 in every particular. I have spun Fireflies, 'dogs, Grobs and Cessna 152s, and almost did an HR200/120, dozens of times in the T67 and it was no harder to recover than any (apart from the 152). Never went more than about 5 turns though; 23 is perhaps a little excessive! The only spin I don't like the 152's in fact - at least the T67 is stable and relatively comfortable in the developed rotations.

[fireflybob]

Agree - never had a problem with spin recovery in T67 as long as correct recovery technique used.

It would be a good idea to find an experienced instructor who has been through the CFS training and is familiar with the T67 to show you high rotational spin and what to do etc.

History repeats itself - my dad instructed on Miles Magisters during the war and they got a (unjustified) reputation for problems recovering from a spin. He always told me that so long as you applied and maintained the correct recovery action there was never any problem!

[BEagle]

I've only ever spun the T67A, but that was fine. You had to be very careful with aerobatic weight though - and no more than the precisely calculated fuel state depending on crew weight was ever acceptable. Spin entry and recovery seemed entirely benign.

The Bulldog was normally OK, but on occasion they could be a bit slow to recover from a normal spin. I'm convinced that was probably because the fuel was out of imbalance limits... You were supposed to ensure that there was no more than a 3(?) gallon imbalance and students were encouraged to make sufficient checks to ensure they stayed inside this limit. Trouble was, the gauges were utter cr@p and weren't really good enough for the task. So your carefully balanced fuel could, in fact, be outside limits without you knowing it - and that certainly made a difference to spinning! One QFI castigated his student for poor spin recovery technique - this surprised me as he was normally pretty good. I flew the same a/c a couple of days later; we flew with 'both' selected and the ball firmaly in the middle, but the gauges showed one side coming down quicker than the other.... We didn't touch anything, but landed and had the contents checked during the refuel - both sides took the same amount, so they must have been equal in the first place. Made a note in the 'spinning' student's record that the delayed recovery was probably due to a/c unserviceability and NOT his fault!

Why are light a/c fuel gauges such utter rubbish?

[DB6]

Returning to the first post (and I'm on dodgy ground here without resorting to textbooks) although the Firefly has a high aspect ratio, so you might think the rotational momentum would be higher, this also has the effect of slowing the spin which would reduce it ( think ice-skater's arms). Different Fireflies have different fuel tank arrangements - the M's have fuel in the wings and the A, B, C etc. in the fuselage - which affect the nature of the spin ( flatter/steeper etc.) but not as far as I know the recovery except, as BEagle mentions, in the case of fuel imbalance.
The rudder effectiveness question is not really valid as the Firefly has a very effective rudder - the M260s have a ventral rudder extension to compensate for the longer nose - however what can happen in the case of incorrect recovery is that if the stick is moved forward before rudder is applied the down elevator will shield more of the rudder from the incident airflow thus delaying the recovery. The POH mentions moving the stick back then forward again in extreme cases but I've never known that to be necessary. In addition the nose with it's heavy engine will be lower and thus nearer to the spin axis, increasing the rotation rate - think skater's arms again. The main problem is that high rotational spins can result in very high rates of descent, around 6-8000 fpm in the Firefly although I was told of Bulldogs achieving 12,000 fpm during CFS trials, which seriously limits your thinking time.
Oh, and all of my Firefly spinning was done with the parachute option :ok: .

[Send Clowns]

There was a story in "I Learnt About Flying From That" concerning a Cessna 152 of all aircraft in a spin with imbalanced fuel. The (very experienced) instructor had to reset pro-spin controls and snap in full anti-spin control to finally recover - in by far the easiest aircraft to recover I have ever spun! Can affect all, and at least in aircraft with selectable fuel tanks there is some encouragement to fuel-balance awareness.

[gemini76]

SEND CLOWNS.........fuel imbalance.

Almost embarrassed to admit this..............
On our fleet we have a C152 with straight wingtips, and this aircraft is ideal for pattering a spin. With no power and full pro spin to the left at 60 knots will enter slowly allowing plenty of time to patter, identify direction of spin with T/C etc, before settling into the classic 152 spin.
However, one nice sunny day with a low houred post PPL who had never, but wanted to spin we did just that. After the usual expletives from the LH seat for the first demo, student wished to continue. After 5 recoveries, I felt that the student had got the hang of it, and so I followed him through at the 6th attempt. Entry was correct with full pro spin controls held ,at the correct speed, again to the left. The aircraft pointed staright down to terra firma with NO rotation, and increasing speed rapidly. After a quick glance rearwards to make sure we hadn't lost the rudder, I recovered from the ensuing dive.
Not convinced that there was no structural damage, a very careful flight back to the field!!
Freda check.......Fuel...left indicating empty, right indicating full!!!
Dread to think what may have happened if I'd tried one to the right!! Lesson learned....................

[hugh flung_dung]

DB6, you said:
Recovery will be delayed if the stick is moved forward before rotation stops having applied opposite rudder, as a high-rotational spin may develop,.
I haven't spun the M260 but have spun rather a lot in Bulldog, T67A and others.... I assume you meant to say "if the stick is moved forward before having applied full opposite rudder"(?)
I'd hate anyone to get the wrong idea about spin recovery.

And now an embarrassing confession:\
At the end of an aeros course I was demonstrating spin mishandling in the Bulldog (from FL100, with chutes) and, after a few HROT turns, applied standard recovery (stick back again, full opposite rudder, pause, stick progressively......) nothing happened - or, more accurately, nothing changed because the HROT spin continued but even faster. The clue came when I realised that the harder I pushed the stick forward the faster we went round. After a considerable number of turns (but still above safety height) the brain woke up and I realised that the rudder wasn't FULL. Back to the start again and it stopped in a couple of turns.
Post flight analysis .... brand new and VERY soft shoes (thrown in the bin that night).

[DB6]

Hugh, correctamundo, although I have sped up spins in the 260 by moving the stick forwards without pausing after applying opposite rudder as well.