F-16 Inlet Question

KJ_Lesnick

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The F-16 inlet is a mixed-compression (at least two-shocks in the duct) inlet right?

KJ_Lesnick
 

FalconPilot

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I don't remember from my aero classes...but I did fly the F16...and always understood it to be a "simple" inlet...all subsonic flow inside the inlet. Isn't the plate above the inlet to create the shock so that all flow is subsonic?
MMO is 2.05, 800KCAS at low altitudes.
Also - there are two inlets...SI (small inlet) and BI (big inlet). The latter added 6 inches to each side of the "smile" and was for the increased mass flow needed for the GE engines (F110-100/129/134). I flew GEs with both SI and BI - and it was amazing the thrust increase just from the extra air.
 

Trident

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Yes, a simple pitot inlet as far as I know.
 

KJ_Lesnick

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Kind of odd that they managed to make a pitot-inlet work effectively at high-speed. From what I was told the F-16 had great acceleration at high-supersonic speeds,

KJ
 

overscan (PaulMM)

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KJ_Lesnick said:
Kind of odd that they managed to make a pitot-inlet work effectively at high-speed. From what I was told the F-16 had great acceleration at high-supersonic speeds,

KJ

Transonic and low supersonic, yes. Mach 2, not so much.
 

KJ_Lesnick

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You know, looking at that duct, it looks like it has a notable convergent divergent shape to it. Could be wrong here but that generally looks like it wouldn't be subsonic from the entry to the exit.

DSCN0778.jpg


Could be wrong though


KJ Lesnick
Let's hope I don't get a heart-attack :p
 

KJ_Lesnick

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Dammit, the image didn't post...

How do I post an image on this site?
 

KJ_Lesnick

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This was the picture I wanted to post
 

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flateric

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F-16 inlet (both 'old' "small mouth" Normal Shock Inlet (NSI) and 'new' "big mouth" Modular Common Inlet Duct (MCID)) are Normal Shock Inlets. http://www.habu2.net/vipers/viperblocks/
It's convergent divergent diffuser inlet actually.
I'm attaching some pics that can make situation more clear.
 

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KJ_Lesnick

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flateric said:
F-16 inlet (both 'old' "small mouth" Normal Shock Inlet (NSI) and 'new' "big mouth" Modular Common Inlet Duct (MCID)) are Normal Shock Inlets. http://www.habu2.net/vipers/viperblocks/
It's convergent divergent diffuser inlet actually.
I'm attaching some pics that can make situation more clear.

I'm actually more confused!

The second picture appears to show multiple shock-waves, and the 4th picture shows clearly "Oblique Shock" which is a shockwave that slows flow from a supersonic to a lower, but still supersonic speed... not a normal shock which slows you down from a supersonic to a subsonic speed...

While I'm at it, I might as well ask some other questions
-What's that thin rod-like thing in the inlet duct (standing vertical in the middle of the duct)?
-What's the ECS-inlet?
-In the third image on the underside of the fuselage ahead of the intake are several markers (HRF3/F14, HRF2/F1, HRF1/F13)


KJ_Lesnick
 

Trident

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KJ_Lesnick said:
The second picture appears to show multiple shock-waves, and the 4th picture shows clearly "Oblique Shock" which is a shockwave that slows flow from a supersonic to a lower, but still supersonic speed... not a normal shock which slows you down from a supersonic to a subsonic speed...

True. Those pictures you mention probably apply only to the J-79 powered F-16-79 as indicated by the file name. That inlet seems to be slightly different to the standard Falcon intake, looks like it used an oblique shock followed by a curved isentropic compression ramp to slow the air to subsonic speeds before entering the divergent duct section of the standard F-16 inlet. I'm not sure whether the latter has a convergent section at all.

KJ_Lesnick said:
-What's the ECS-inlet?

Environmental Control System?
 

r16

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ı don't have anything to say but I do remember that the J-79 engined aircraft "had the shocks" , can't truly translate it from the idea in my mind in Turkish , but the rest of the F-16s had simple inlets .
 

Sundog

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The F-16's inlet is a pitot inlet and the bar in the middle, based on what I've been told, is a heater for anti-icing.
 

flateric

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"...a thin, centerline, airfoil-shaped tension strut member
inside the cowl, which minimizes cowl deflections under load and allows a lighter
and less costly structural design. Flow quality is not affected by the strut."

YF-16 INLET DESIGN AND PERFORMANCE
J. E. Hawkins
Senior Propulsion Engineer
General D'ynamics' Fort Worth Division
Fort Worth, Texas

AIAA 74-1062
 

ouroboros

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And now for something completely different...
 

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dannydale

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Mach 2 in an F-16? That's impressive; I thought it topped out around M1.6. That inlet design looks dead sexah, too.
 

Sundog

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"...a thin, centerline, airfoil-shaped tension strut member
inside the cowl, which minimizes cowl deflections under load and allows a lighter
and less costly structural design. Flow quality is not affected by the strut."

Thanks, I had wondered about that, but didn't have any evidence for it.
 

KJ_Lesnick

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If the F-16's inlet was highly limited in speed, where did all that stuff I heard awhile back online about the F-16 accelerating particularly well at supersonic speed (something a typical pitot-type inlet wouldn't be able to do very well) come from? ???


Kendra Lesnick
 

RAP

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M2.2 inlet design for F-16. May be similar to what was installed on the F16/79.
 

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gtg947h

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KJ_Lesnick said:
If the F-16's inlet was highly limited in speed, where did all that stuff I heard awhile back online about the F-16 accelerating particularly well at supersonic speed (something a typical pitot-type inlet wouldn't be able to do very well) come from? ???


Kendra Lesnick

It wasn't a pitot inlet, really. There is a compression ramp (which also serves as a boundary layer splitter), but it was fixed at one setting (probably optimized for M1-1.2 or so, I'd guess). Getting good higher supersonic performance means you'll want a variable inlet ramp.
 

sferrin

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KJ_Lesnick said:
Getting good higher supersonic performance means you'll want a variable inlet ramp.

Neither the XF8U-3 nor F-22 have a variable inlet ramp and have no problem with Mach 2+ speeds. There is more than one way to skin a cat.
 
Last edited:

Richard N

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F-16 VARIABLE RAMP-INLET Conformal IIIA
 

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TomcatViP

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You have all the ambiant air, more or less in stagnation, activated by the pressure difference caused by the engine, rushing toward the inlet from all the volume of air surrounding the airplane. Hence, a lot of that air flow impinge the inlet cowl at a high angle of attack. Hence the vortex cores all around its lip.
 

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F-2 inlet with a block 50 inlet. The F-2 nose drops and it had to be redesigned, supposedly optimized for the F110-IHI-129.
 

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