New engine sends shock waves through auto industry

[CDK]

Originally Posted by Jeremy Harris

Very true. I can recall really worrying about fuel burn whilst sat on the ground at ground idle waiting for people to get on board during quick turnarounds - turbo prop engines used to burn darn near as much fuel just turning and burning on the ground as they did during normal cruise flight.

You exaggerate things Jeremy.
Jets need a lot of rpm to keep the fire going, but at 50% throttle they do not stall at ground level. I guess the actual consumption is even lower than 50% at that setting.
But it rules out any vehicle application where piston engines are in use now.

[Jeremy Harris]

Originally Posted by CDK

You exaggerate things Jeremy.
Jets need a lot of rpm to keep the fire going, but at 50% throttle they do not stall at ground level. I guess the actual consumption is even lower than 50% at that setting.
But it rules out any vehicle application where piston engines are in use now.

I didn't mention anything about stalling (which doesn't happen, anyway, with this type of engine, if you ignore compressor surge that can occur under extreme conditions and is effectively an internal stall) just that the SFC was high when running at ground idle. The civil chaps don't do this for long, as they're not supposed to load people or gear on and off with the engines running, but we used to do it from time to time on trials work and I can assure you that the fuel burn was high enough to cause concern when stuck on the ground for half an hour or so between sorties. With the power levers at idle the props were automatically at zero pitch, so the power demand was low; the problem was simply one of the engines being horribly inefficient when running fairly cool and at ground level. Mind you, these were old technology compared to modern fuel efficient engines, which undoubtedly exacerbated the effect. The worst offender I can recall was the old Astazou 16D, we used to joke that it burnt more fuel on the ground than it did in the air. This was pretty clear to people outside too, from all the incompletely burnt fuel being chucked out the back.