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SV: SV: Birds vs. Jets

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
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. 

Tommy Tyrberg

-----Ursprungligt meddelande-----
Från: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] För Richard
W. Travsky
Skickat: den 23 mars 2009 16:53
Till: dinosaur@usc.edu
Ämne: Re: SV: Birds vs. Jets

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
> (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...

> -----Ursprungligt meddelande-----
> Från: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] För Mark
> Hallett
> Skickat: den 20 mars 2009 21:28
> Going back to a related issue-- medium-large birds getting sucked into
> jet engine intakes-- would it not be possible to design an
> convex metal grid covering the intake that could deflect bird
> and yet withstand the force of the  engine's suction and not obstruct
> it? Sort of like a steam locomotive's "cow catcher". --Mark