F-135 engine space

All about the Pratt & Whitney F135 and the (cancelled) General Electric/Rolls-Royce F136
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eloise

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Unread post30 Jan 2017, 09:38

Why is the space between F-135 and F-35 airframe so much bigger than the space between F-110 and F-16 airframe?. Isn't that bad for stealth ?
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Corsair1963

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Unread post30 Jan 2017, 10:11

eloise wrote:Why is the space between F-135 and F-35 airframe so much bigger than the space between F-110 and F-16 airframe?. Isn't that bad for stealth ?
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I assume it helps to cool the exhaust of the P&W F135. Which, will decrease the IFR Signature of the F-35. Making it far harder to detect by IRST Systems.
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gideonic

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Unread post30 Jan 2017, 12:45

Garrya has a very nice blog post about it. Essentially it's for lowering the IR signature. Starting from "Internal Equipment Heating" and onwards:

https://basicsaboutaerodynamicsandavion ... -benefits/

Two pictures say more than a 1K words:
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johnwill

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Unread post30 Jan 2017, 16:56

Another function of the airflow is nacelle ventilation, to get rid of possible fuel leak fumes and reduce the temperature of surrounding structure and fuel tanks. F-16 has vent outlets at the bases of the vertical and horizontal tails. Nozzle and plume cooling was not required.
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eloise

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Unread post30 Jan 2017, 18:45

johnwill wrote:. F-16 has vent outlets at the bases of the vertical and horizontal tails.

Is the vent in red is this photo?
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Last edited by eloise on 30 Jan 2017, 20:21, edited 1 time in total.
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eloise

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Unread post30 Jan 2017, 18:48

gideonic wrote:Garrya has a very nice blog post about it. Essentially it's for lowering the IR signature. Starting from "Internal Equipment Heating" and onwards

Thanks you, i remember seeing that somewhere but can't recall exactly
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wrightwing

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Unread post30 Jan 2017, 21:22

eloise wrote:Why is the space between F-135 and F-35 airframe so much bigger than the space between F-110 and F-16 airframe?. Isn't that bad for stealth ?
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No
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SpudmanWP

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Unread post30 Jan 2017, 21:40

On an F135 related note... RC modelers have got the 3BSN working



Another guy has it tied into the flight controls and yes, the airframe is an F-22. Ignore that and just look that the nozzle gyrations during hover.

"The early bird gets the worm but the second mouse gets the cheese."
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johnwill

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Unread post30 Jan 2017, 22:07

eloise wrote:
johnwill wrote:. F-16 has vent outlets at the bases of the vertical and horizontal tails.

Is the vent in red is this photo?
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by

No. It is just under the tail at the forward end of the gap between the tail and fuselage. The horizontal tail vent is barely visible inboard of tbe speedbake.
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SpudmanWP

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Unread post30 Jan 2017, 22:38

johnwill wrote:No. It is just under the tail at the forward end of the gap between the tail and fuselage. The horizontal tail vent is barely visible inboard of tbe speedbake.


These?

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johnwill

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Unread post31 Jan 2017, 01:00

Yes. For ground operation, engine bleed air is blown through those openings to eject air from the engine cavity. You can barely see the ejector nozzles in the photo of the partially open speedbrake.
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SpudmanWP

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Unread post31 Jan 2017, 03:12

Here is a shot with better exposure

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"The early bird gets the worm but the second mouse gets the cheese."
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F16JOAT

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Unread post31 Jul 2017, 00:43

wrightwing wrote:
eloise wrote:Why is the space between F-135 and F-35 airframe so much bigger than the space between F-110 and F-16 airframe?. Isn't that bad for stealth ?
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No


The F16 needs to maintain an internal airflow of 22fps in order to have an effective nacelle ventilation system meaning that the fire propagation must also be controlled and tests showed that a wall of air flowing at 22fps is minimum. The nacelle vents are design along with the ejector system to help maintain this airflow on the ground but in the air the ejectors are off and the side nacelle scoops located under the wing help capture the airflow needed to achieve in flight requirements.

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