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Re: SV: SV: Birds vs. Jets



On Mon, 23 Mar 2009, Tommy Tyrberg wrote:
Those were solid cones. They were movable and were used to modify the
annular inlet geometry to match the speed since SR71 operated over a
very wide range of mach number. Incidentally the SR71 was very sensitive
to disturbances in the inlet flow and subject to violent engine stalls
"unstarts".

The 71 was the only one I could remember at the time. There's a MiG or two that use (used) cones.


However gridded inlets aren't intrinsically impossible. The F117 has
them to prevent radar from being reflected from the engine front. They
are aerodynamically inefficient, but that's the price you have to pay
for stealth.

-----Ursprungligt meddelande-----
Från: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] För Richard
W. Travsky
Skickat: den 23 mars 2009 16:53

On Sun, 22 Mar 2009, Tommy Tyrberg wrote:
It would have to be very robust, otherwise it would be much more
dangerous than the birds. Also it must not disturb the airstream
appreciably, jet engines being pretty sensitive to inlet turbulence.
Also consider how large it would have to be. You can pull a DC3
airframe
(minus wings and fins) through a modern jet-engine pod.
So, no it's not practical, though detachable grids have been used on
military aircraft to prevent accidents on ground.

You'd also have to consider the extra weight and effect on fuel economy.

Aerodynamically, the old SR71 had conical inlets, so thatmaspect of it
might pass ok...