Pavlin From , joined Dec 1969, posts, RR: Posted (9 years 6 months 1 week 4 days 19 hours ago) and read 20520 times:
We all know that we can't convert directly beetwen one another. But unwritten rule is that 1 lb of thrust equals 2 HP. But there is a big difference when you compare A340 and An-22. They have almost same MTOW 250.000 kg (An-22 has less speed), but the A340-200 has 4 30000 lb thrust engines. AN-22 has 4 15000 HP engines. So the A340-200 would have around 240000 HP versus only 60000HP for An-22 at very similar performance. So why the big difference?
Rsbj From United States of America, joined Jan 2006, 153 posts, RR: 0
Reply 3, posted (9 years 6 months 1 week 3 days 20 hours ago) and read 20445 times:
I've heard the conversion is around 3 to 5 : 1. 2:1 may be accurate at zero airspeed.
Prop decay factors into the equation too. At 0 knots, the ratio would be less than at cruise speed because a prop loses power as speed increases. Turbofans do too, but not as much; though I do not know the percentage differance.