Re: Relative Engine Power

Date:         15 Apr 97 03:22:43 
From: (H Andrew Chuang)
Organization: Concentric Internet Services
References:   1
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In article <airliners.1997.910@ohare.Chicago.COM> john r. ( wrote:
> Can anyone give me some approximate guidelines to compare jet engine
> thrust and rotating shaft power.

power = force x velocity

Thus, 1 lb thrust @ 375 mph (or 550 ft/sec) is equivalent to 1 shp.

> We were recently looking over The Queen Mary at Long Beach and in the
> engine room it said that the four turbines produced about 260,000 horse
> power between them. About as much as a modern Jumbo I said but was
> greeted with disbelief.
> Was I that far out ?

Well, pardon my ignorance.  How fast can (or could) the Queen Mary
travel?  40 kts perhaps?  If so, then the equivalent thrust at cruise
will be:

260,000 * 375 / (40 * 1.15) ~ 2,200,000 lbf

The total thrust of a B747 with four PW4056 engines is 224,000 lbf.
Nevertheless, I do not think the thrust comparsion of two objects
moving at very different speeds is meaningful.