[klem]

Guys I have been fortunate to get a reply from a current Hurricane MkI display pilot. He asks to remain anonymous but gives me the following:

"I have the privilege of flying and displaying Hurricane Mk1, [serial deleted]. It will not surprise you to know that in deference to it's age and historical importance we do not fly the aircraft as aggressively as it would have been flown during combat. Particularly, we avoid negative g so I am not well placed to answer your question specifically. However, I can give you some clues.

First, I can tell you that it does not require negative g to make the engine suffer from a shortage of fuel supply; a significant reduction of g down to, say, 0.3g can be enough to make the engine misfire. This can be experienced towards the top of a wing-over but I would estimate that the reduction in g needs to be maintained for 2 seconds or more before there are any effects. Undoubtedly, if the reduction in g was greater (to less than zero g) and particularly if the bunt was abrupt then the effect could be instantaneous. I have never, though, experienced any misfiring in turbulence; albeit, were the turbulence severe enough to produce g spikes to less than zero g, I would not rule out the possibility of the odd cough from the engine. Of interest to you I am sure is that on recovery from an episode of fuel starvation the engine recovers through a short period of over-richness shown by, I would estimate, up to a second of black, sooty exhaust before normal combustion is resumed.

Good luck with your simulation."

It's not a complete profile of the problem but it gives some useful check points for whatever 1C come up with so I hope they will use the information for that purpose.

I suppose the thing the Merlin flyers want to know is that the effect isn't overmodelled to an unrealistic and irritating degree in level flight or modest pushovers into what might be called 'normal' descents.

What the Axis flyers want to know is that an aggressive pushover in combat will have the Melin cutting out and preserving their escape maneouvre.

The truth will lie somewhere in the middle but is probably not too critical if the two situations are preserved.

I think what the report tells us is that for modest maneouvres there is little if any effect and for sustained reduced G of perhaps 0.3G there is something like a 2 second delay or more before it occurs, perhaps due to the carburettor trying to keep up on the knife-edge of the problem. Recovery seems to be in the order of a second once positive G is restored.

A question remains, for an aggressive pushover causing that level of negative G that first causes virtually instantaneous fuel cutoff at the carburettor inlet, exactly how fast would the fuel cutoff at the carburettor inlet occur and how quickly would the carburettor fuel be used up and the engine be affected? If 1C were able to decide on a G figure for a near instantaneous cutout they would I suppose still be left looking at the 'curve' for intermediate values and times.

Hope this has helped.