"Matt Barrow" wrote in message
...
"Dudley Henriques" wrote in message
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The combination of a Merlin V1650-7 and a Hamilton or Aero Products
propeller at between 35 and 45 inches and between 2700 and 3000 RPM have
a sound so distinctive that many who have heard it never forget it.

Dudley, you just answered a question I've been wondering about for nearly
40 years.

I've always knew about that distinctive Merlin sounds, but there's a
secondary sound (that prop) that together makes the "Mustang Sound" like
nothing else on earth.

You could fly 1000 airplanes with 1 P51 included in the mix somewhere
directly over my head with me blind folded and I'd pick out the 51 in a
nano-second :-)

Most of the actual sound the ear picks up from an airplane is caused by the
prop. In the case of the Mustang, with a Hamilton Standard propeller, you
have a prop with an 11 foot 2 inch diameter. Naturally a prop this size has
a tip speed problem so in a stock Merlin its geared down to a .491:1 through
a reduction gear to the engine RPM. At 3000 RPM , the prop is actually
rotating at 1473RPM. Its mostly the sound the prop makes as it works the air
coupled with the exhaust tuning through the tubes that gives the 51 its
distinctive sound. There's also a contribution through the radiator that
adds just a "touch" to the mix.
My conception has always been that its a moaning sound; sort of like a low
pitched moaning wail.
Dudley