John F,
Interesting. The problems with ascertaining spin direction that you had in the AV-8B and I had in the Tornado probably have the same cause and occurred after a short but very rapid departure. However, what I saw after the Alpha Jet flat spin fitted the dictionary definition of nystagmus and I think was caused by a prolonged high yaw rate. The question is whether nystagmus is caused by prolonged rotation or sudden rapid rotation. Also, did you have any "flicking" sensation of the visual scene? I will try to dig a little deeper on this.
BEagle,
The fuel asymmetry effect that you saw in the Bulldog is one that could (and did!) occur in the Hunter also. We span the Hunter T7 with two 100 g drop tanks on the inboard underwing pylons. These were ungauged tanks, and the internal fuel was split into left and right groups, each with its own gauge. One day I was acting as safety pilot in telemetry and the sortie was planned to start with a normal, erect spin. This spin mode was normally moderately oscillatory about all axes but the first spin was the smoothest, steadiest spin that I had ever seen a Hunter perform! I was not too concerned as the recovery was reasonably normal and the precise nature of the spin in the Hunter was somewhat unpredictable. I, and the tutor in the cockpit, thought that it would be interesting to see what happened next. The second spin was a normal entry with full outspin aileron applied after one and a half turns (to demonstrate the pro spin, stabilising effect of outspin aileron upon the spin of a swept wing aircraft). This one was even more smooth and had an even higher rotation rate! After the normal 4 turns the recovery controls (full opposite rudder and stick progressively forward) were applied correctly. The stick soon reached the forward stop and the controls were held in the recovery position for a considerable time before the spin finally stopped. We decided to stop spinning at that point and try to work out the cause of this atypical behaviour. The internal fuel gauges were still indicating full (i.e. there was still some fuel in the underwing tanks) but I started to suspect a lateral fuel asymmetry. Soon, one internal tank gauge started to reduce, but it had decreased by 300 lbs before the other gauge started to drop. In other words, there had been a 300 lb asymmetry in the underwing tanks. The fuel was then balanced by selective booster pump switching and the sortie continued with all subsequent spins being normal.
So, what could we have done to mitigate the lack of fuel gauging? Firstly, there must have been a refuelling error (as there was no sign of a leak). The fuel put in plus fuel remaining should have equalled 4850 lbs (which was signed for in the F700); we never bottomed this one out! Secondly, in air-to-ground days with the Hunter there was an SOP that once at a safe height after take-off you deselected the aileron hydro-booster and trimmed the ailerons in manual (via a trim tab) such that if you had a reversion to manual at low level, it was laterally in trim. (Note that the powered ailerons had a separate spring feel bias for trimming with the hydro-booster on). This manual aileron check would probably have shown the asymmetry but the pilot on this sortie was not a A-G Hunter man and this SOP was not widespread at Boscombe by this time.
Out of interest, The Tucano spin is relatively insensitive to lateral fuel asymmetry at the 100 kg maximum (which is the maximum for flight overall).
OVERTALK,
Did this airframe have the same flick roll characteristics in both directions? When we span the Hunter inverted we always retorqued the underwing tanks after flight as they did become a little loose sometimes.