I know a guy here that is a test pilot on the Beech AT-6, and has a PhD in aero
engineering, who says no prop tip ever goes supersonic. But hes kind of a
blustery loudmouth who thinks he know everything, so I'm thinking his PhD is
from ITT Tech..
----- Original Message -----
From: "Jim Nichols" <jhnichols@xxxxxxxxxxxxx>
To: olympus@xxxxxxxxxxxxxxxxx
Sent: Friday, August 30, 2019 12:24:56 AM
Subject: Re: [OM] IMB: TBM 850 at the Airport
Mike,
A lot of research has gone into optimizing propeller design. One
problem has been dealing with tip speed. If the tip speed goes
supersonic, much of your energy goes into noise and tip losses. Hence,
as horsepower goes up, the prop can't just get larger in diameter. They
try to hold the diameter small enough to avoid the tip losses while
increasing the ability to absorb horsepower by optimizing the number and
shape of the blades.
If you have ever heard a WWII North American AT-6 or Navy SN-J at an
airshow, you probably have an idea of the sound of a propeller going
supersonic.
Jim Nichols
Tullahoma, TN USA
On 8/29/2019 6:48 PM, Mike Gordon via olympus wrote:
> Fuel burn related to all those blades on the prop? I am no engineer but would
> seem efficiency would be down with each blade turning in the wake of the
> previous.
> Probably a myriad of other variables that would not even know to think about
> but the number of blades strikes the lay person as unusual.
>
> Mike
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