Horsepower v thrust what's the ratio?

Question

Horsepower v thrust what's the ratio?

Answer 1

Power/ Thrust =

(Energy/ time) / Force =

(Force * distance/time)/Force =

distance/time.

Because

Thrust is a force.

Power = Energy / Time.

and

Energy = Force times distance.

Edit -- yeah, distance over time is speed.  Who would have guessed it?

Answer 2

In general, similar performance for aircraft with factor of 3 to 3.5 lb thrust per HP. For example, an ultralight with a 27HP engine had similar performance with an 81 lb thrust turbojet (except for noise and specific fuel consumption). Bede 5 has about 90HP or 300 and some lb thrust. In general, jet powered aircraft have slower acceleration and climb rate that prop planes with similar power to weight, but higher top speeds. Turbofans are light enough now that they put more power on jet aircraft to get better power to weight, improving takeoff and climb.

For high altitude (over 25,000 ft), and especially high speed, say over 400 mph, turbojets and turbofans are much better.

For slow speeds and low altitudes, prop planes better. I'm a big fan of reciprocating engines, but they have been little developed after 1945; in contrast turboprops, turbojets, and turbofans have been extensively developed and now dominate commercial markets, even though they have relatively high fuel consumption.

Technically, Power = force * velocity, so turbofans rate highly at speeds like 600 mph, where props can't go. Props loose efficiency and thrust at very high speeds, speeds of over 400 or 450 mph not feasible for normal prop driven aircraft. People who like turbines run these high speed calcs to prove that jets put out far more power than piston engines. You could also use the reverse argument, that the jet moving slowly on the runway is producing near zero useful power because velocity is near zero. The higher thrust at low speeds is why prop aircraft accelerate and climb better (for a given degree of streamlining and power to weight ratio).