Getting too technical for me.
My friend that flies one says it has a three blade prop. A THREE BLADE PROP! On
one of the biggest PT6es available! He says it gives him more speed than a 4 or
5 blade, but isn't more noisy.
----- Original Message -----
From: "ChrisB" <ftog@xxxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Saturday, August 31, 2019 4:03:11 AM
Subject: Re: [OM] IMB: TBM 850 at the Airport
Perhaps the tip exceeds a local Mach value rather than the actual speed of
sound, Bill.
Chris
C M I Barker | Gamlingay
> On 30 Aug 2019, at 06:52, Bill Pearce <billpearce@xxxxxxxxxx> wrote:
>
> 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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