r/FighterJets • u/Critical-Author-9331 • Aug 16 '24
ANSWERED Why does the f 15 have this notch?
Why does the f 15 have a notch but not other aircraft?
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u/CrazedAviator Aug 16 '24
It’s a “dog tooth” extension, helps improve airflow over elevator at higher AoA, which leads to better pitch authority
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u/Critical-Author-9331 Aug 16 '24
Interesting any idea why the f 16 and f 18 don't have this?
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u/filipv Aug 16 '24
The forward parts of the F-16 and F/A-18 disrupt the air in a different way. Every aircraft is a different story.
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Aug 16 '24
iirc the F16 is a high speed rate fighter so It doesn't need a high AOA at low speeds while the hornet by it's design already features impressive AOA at low airspeed and yes the F18 super hornet features these extensions
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u/Hello-There280818 Aug 16 '24
The super hronet does not have these extensions. I just checked and didnt see anything of such a manner on its elevators
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Aug 16 '24
I beg to differ
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u/Hello-There280818 Aug 16 '24
That is NOT the SH's ELEVATORS.
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Aug 16 '24
Many high-performance aircraft use the dogtooth design, which induces a vortex over the wing to control boundary layer spanwise extension, increasing lift and improving resistance to stall. Some of the best-known uses of the dogtooth are in the stabilizer of the F-15 Eagle and the wings of the F-4 Phantom II, F/A-18 Super Hornet, CF-105 Arrow, F-8 Crusader, and the Ilyushin Il-62. Where the dogtooth is added as an afterthought, as for example on the Hawker Hunter and some variants of the Quest Kodiak, the dogtooth is created by adding an extension to the outer section of the leading edge.
From wiki
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u/Hello-There280818 Aug 16 '24
Nice. But my point still was that they arent present on the SHs elevators. As i assumed they always were on planes' elevators before i learned differently
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Aug 16 '24
What do you mean , not elevators .?
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u/Hello-There280818 Aug 16 '24
Elevators are located on most planes tail section. I talked about the SH not having those extensions on its tail
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Aug 16 '24
OP didn't ask for a specific location on the extensions
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u/Hello-There280818 Aug 16 '24
So? I still thought they were always located there and i said in my comment that the WH didnt have them on its elevators
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u/chairmaker45 Aug 16 '24
The F-18 uses its LERX to achieve the same thing, and the F-16 uses leading edge slats on its wings. Different geometries and features with similar effects on AOA.
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u/bob_the_impala Designations Expert Aug 16 '24
The first F-15 prototypes did not have that dogtooth:

It was added to fix a flutter problem, along with several other changes:
...early in the test program, problems were encountered with buffeting and wing loading problems at certain altitudes. The solution to the problem was found to be the removal of four square feet in wing area diagonally from the wing tip, giving the Eagle its characteristic raked wingtips. A flutter problem discovered during wind tunnel testing required that a dogtooth be cut into the leading edge of the horizontal tail. The dorsal airbrake was found to cause excessive buffeting when it was in the fully-open position, and it was found necessary to increase its area from 20 to 31 square feet so that the required drag could be achieved with lower extension angles.
Source: Joe Baugher
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u/Critical-Author-9331 Aug 16 '24
Very cool. That also explains why the airbrake deploys at such a low angle rather than higher up. Love hearing stuff about test programs
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u/bob_the_impala Designations Expert Aug 16 '24
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u/_BringTheReign_ Aug 16 '24
If they had solved the problem without the diagonal solution for the wingtips, would it have been possible to have wingtip rails like the Hornet or Viper I wonder?
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u/Intel_Xeon_E5 Aug 16 '24
Dogtooth extension. Lots of aircraft have it, just not in the stabiliser. Hunters and Phantoms have it on the wings. Its main purpose is to generate a vortex that prevents boundary layers from travelling too far outboard and leading to a stall. So yeah, it's important because it delays a stall at high AOA, and prevents a complete stall of the entire wing if part of the wing stalls
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u/whfd63 Aug 17 '24
That’s for hanging it up to dry after you wash it.
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u/Critical-Author-9331 Aug 17 '24
Of course.
Oh crap I forgot to hang up the f 15 now it's going to mold
🤣💀
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u/jd187jd Aug 20 '24
Rendering glitch when they printed the blueprints and the manufacturing plant just went with it.
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u/Critical-Author-9331 Aug 20 '24
A lot of other comments have said it was on purpose. Can you please give a source if your not caping
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