From memory the FF's are not cleared for inverted spinning,
MikeeB,
Read the very interesting report in Baikonour's post:
For those interested,
here is a USAF document about spin tests they carried out on the Firefly.
Here's the relevant part:
Inverted Mode Discovery
The possibility of an inverted spin seemed remote, due to the reluctance of the aircraft to depart or spin from an inverted stall. We tried roll coupled entries, but could not generate sufficient roll rate to translate to a yaw rate. The only card left unturned was the effect of the elevator trim (remember that trim tab)--could it make a difference?
We found with the elevator trim set full nose up, the aircraft would spin inverted in either direction. This was accomplished from an inverted stall, with full forward stick and full pro-spin rudder held throughout the incipient stage (1 to 2 turns) and the developed spin. The full nose up setting of the trim tab allowed an extra bit of elevator control power when inverted. This in turn, kept the angle of attack high enough to allow a yaw rate to develop. And as we know, stall plus yaw equals spin.
Follow-On Tests
Naturally, Slingsby wanted to further investigate the inverted spin mode. Their follow-on testing completed before delivery verified the importance of the trim tab for inverted spins. Expanding from the QT&E sorties, they looked at both forward and aft CG, as well as heavy and light aircraft weights. In all cases, once the trim was set more than half nose up, the propensity for inverted spinning increased. The aircraft was more susceptible to inverted spins with right rudder, though it could spin both directions once the trim was set to full nose up (as we had done during QT&E). Slingsby also found the neutral recovery to be most effective for the inverted spin. In the end, Slingsby recommended the aircraft not be certified in this area and for inverted spins to remain a "prohibited" maneuver. In part, this decision was an economic one, as travelling the certification highway can be a long and expensive journey. And on-time delivery of the aircraft was paramount to both the USAF and the contractor.
This is a very interesting report and it merits reading completely. When I opened it, I had expected a typical, dull, factual USAF flight-test report. However, this is a very interesting, well-written paper, presumably presented at a conference. Does anyone have a reference?
I think the summary at the end of the paper is very telling:
Overall Assessment and Impact of Testing
On the USAF side, we were pleased with the Firefly's spin characteristics--how it spun when you wanted to and a when you weren't expecting it. The inverted spin potential seemed remote enough to eliminate most of the worry on part of the user. The T-3A had a no-nonsense, erect spin mode that would expose pilots to the spin environment in a safe and energy-efficient manner. As long as the pilot utilized rudder for primary anti-spin control, most mistakes during recovery could be tolerated.
I've never flown a T-67, but it seems to me, to be not a lot different from the Chipmunk - apply the correct recovery procedure and it will always come out of a spin.
As an aside, but relevant to robrob's comment about W&B of the T-3A, when I flew Chipmunks at UBAS is the 60s, there was never any discussion of gross weight or W&B. I presume the assumption was that even with ex-truckie middle-aged QFIs in the back seat, there was no issue.
