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Science USAF's F-15 Woes Continue to Unfold
Brandon Hill (Blog) - December 24, 2007 10:48 AM
Print E-mail del.icio.us 161 comment(s) - last by matriarch wolf.. on Feb 27 at 3:08 PM
Structural fatigue has been found in the "longerons" on eight grounded F-15s

It appears that the problems with F-15 are more than just skin deep. The aircraft, which has been in service for more than 30 years, continues to the hug the ground instead of protecting the skies over the United States.

A November 2 crash during a routine dogfighting maneuver in Missouri caused an F-15 to break apart in mid-air. The aircraft buckled and broke apart aft of the cockpit while performing an 8G dogfighting maneuver at 500 MPH.

"I heard a big rush of air, very loud, like a tornado ripping the roof off a house," said Maj. Stephen Stilwell. "It was like I was in a car and it's flipping down the road. I felt like the airplane was tumbling and I'm being slammed around, left, right, front and back."

Early analysis of Stilwell's crash and subsequent inspections of the grounded F-15s showed that cracks in the "longeron" main support beams aft of the cockpit were the cause of the crash. The Air Force discovered serious structural flaws of the longeron in eight aircraft.

"This is going to be a major problem, and it's going to be a difficult one to recover from," said retired Air Force Gen. Dick Hawley. "You could basically be without the nation's primary air superiority capability for an extended period of time, which puts us at risk."

"In my opinion, based on the engineering data we had, we should not be surprised that we're finding some failures in the major structural areas of the airplane," added retired Gen. Gregory S. Martin. "The question wasn't if they would fail, it was when those failures would occur."

The Air Force's F-15A, F-15B, F-15C and F-15D air superiority fighters routinely patrolled the skies over the United States before the intentional grounding -- that role is now filled by the smaller F-16 Fighting Falcon.

Some analysts in the aviation industry feel that the Air Force is possibly making a mountain out of a molehill in order to get its hands on additional F-22 Raptors at $132 million USD apiece. The Air Force is currently earmarked for 183 Raptors, but the problems with the F-15 could lead to additional purchases to fill the void left by F-15 airframes that are not structurally sound.

"I don't suspect that the Air Force is lying when it says it has discovered stress fractures in the longerons of the F-15s," said Center for Defense Information expert Winslow Wheeler. "But there's no big deal about that. Fix it."

There is currently no end in sight for F-15 groundings. More thorough investigations of the 442 airframes could last through January and there is no guarantee that the fighters would take to the sky shortly after the inspections are completed.

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By wwwebsurfer on 12/24/2007 11:08:29 AM , Rating: 3
While the F-15 has always been a superior fighter they say 'F-16' like it's not capable. What country has a fighter that has both the range to penetrate our skies and still pack a punch superior to the F-16? No one.

While I've got absolutely no problem shelling out for more Raptors - I agree that perhaps this problem is not as big as it seems.




RE: ....
By omnicronx on 12/24/2007 11:24:28 AM , Rating: 4
The F16 is an all purpose single engine multirole fighter, while it can do a little of everything, its not amazing at the f15's primary purpose, being a long range interceptor. The F15 is also a dual engine fighter, and can hit mach 2.5 at high altitude, something the f16 can not do.

I would also like to point out that the US has sold f16's or helped develop them in many other countries, as there are more than 4000 in service around the world today. So its not exactly like it's a trade secret and that they are vastly superior to everyone elses aircraft.


RE: ....
By lufoxe on 12/24/2007 11:33:50 AM , Rating: 4
it normally wouldn't an issue, but considering the F-16 has only a combat range of 340 (http://en.wikipedia.org/wiki/F-16_Fighting_Falcon) while the F-15 has a combat range of 1,222 (http://en.wikipedia.org/wiki/F-15) and the F-15 is deployed around the world, that's where it becomes a problem with the substitution.


RE: ....
By anthrax on 12/24/2007 11:37:18 AM , Rating: 4
The F15 is far superior to the F16 for its current role. These homeland security patrols aren't there to intercept russian bomber flying in from the north pole.

These partrols are designed to deter and foil 911 style attacks. Lets just say a airliner suddenly acts erraticall and deviates from the its flight plan. The immediate response isn't to blast the thing out of they sky with missles...

The first respone is the immediate dispatch of aircraft intercept and visually ID the plane. This is critical and time very short. A typical civlian airliner can travels at high subsonic peeds at mach 0.8... << The F15 superior performance will enable it to reach the suspect plane in less time, This gives homeland security & military leadership time to decide on how to deal with the threat. It also provides them with on scene information. It the plane really being hijacked or just has communication problems...etc .etc.

So how is the F15 technically superior to the F16 in the interceptor role ?

1. Superior engine thrust = faster acceleration, higher speed top speed.
2.) Superior fuel capacity = allows more liberal use of afterburners when intercepting targets. Allows greater distances to be covered at higher speeds.


RE: ....
By Amiga500 on 12/24/2007 11:46:35 AM , Rating: 4
At low and medium altitudes, the F-16 rules over the F-15.

At high altitudes, the F-15 is dominant.

Thats both maneuvering and acceleration.


RE: ....
By I800C0LLECT on 12/24/2007 12:01:16 PM , Rating: 1
So it's a good dog fighter...

We should let the foreign threat reach our door step before we're ready to hit back? That short range of the F16 could be paralleled to Germany and it's Messerschmidt through out the battles of Great Britain.

Imagine maintaining those capabilities and pooling them with several other advantages.

I don't think any of you realize what roles the F15 plays in our Air Force.


RE: ....
By rebturtle on 12/24/2007 1:36:00 PM , Rating: 3
quote:
We should let the foreign threat reach our door step before we're ready to hit back?


Do you really think anyone is going to get that close to our airspace without us noticing? Really, (Alaska notwithstanding) unless you have an unusual paranoia over Canada and Mexico, our coastlines could practically be covered by Piper Cubs. The carriers can track and intercept just about anything before it reaches our waters.

Not to say that we don't need the F15 or it's equivalent, but we're far from venerable without it.


RE: ....
By BladeVenom on 12/24/2007 3:15:57 PM , Rating: 5
Mexico already succeeded in invading the US. :)


RE: ....
By codeThug on 12/25/2007 12:51:24 AM , Rating: 3
While the rest of the country is being sold off to the Chinese and Arabs ala Citybank, Merrill Lynch, etc..


RE: ....
By Anonymous Freak on 12/24/2007 3:36:13 PM , Rating: 3
"The carriers" are not homeland defense. There are no groups of carriers stations along our coastlines. There *ARE* bases housing F-15s. I happen to live near the one that covers the Pacific coastline from Canada to California. I have seen F-15s take off in a hurry, in full afterburner, and go rocketing toward the coastline on more than one occasion. Once they even broke supersonic over the city (which is, 99% of the time, a strict no-no, implying it was a fast-moving incoming unidentified aircraft.)

Yes, the F-16 is a better "dogfighter". There is no real debate about that. But, as others have mentioned, the F-15 is a long-range interceptor. It can go fast, for long distances. The only other operational aircraft that matches its capabilities this way is the F-22.

Also, a couple notes about the F-15: It's official top speed is "Mach 2.5+", but the Air Force has documented that it can do Mach 3.2 in short bursts. Not that that speed is useful for much, since you would use so much fuel just REACHING that speed that you wouldn't have enough left to DO anything. The F-15 is also the only U.S. fighter that has more thrust than it weighs. This means that it can ACCELERATE straight up, like a rocket. One of the 'trick takeoffs' that the local F-15s used to do is go halfway down the runway at full military power, turn straight vertical, turn on the afterburners, and climb straight up to 30,000 feet+ before leveling off. It is VERY impressive to watch this. Although, again, it's not the most useful thing to do, since it is actually an INEFFICIENT way of gaining altitude, because you don't take advantage of the lift of the wings. But it does look impressive. :-p

The F-16 is a good aircraft, and definitely has its place. In some areas, it is even better than the F-15. (It can loiter at lower speeds than the F-15, so it is more useful as a close air support craft; although the A-10 is the perfect close support aircraft.) But for long-range interception, the F-15 can't be beat. (The F-14A was even superior to the F-15 in that role, but that's because that was its SOLE purpose in life. When they moved to the "SuperTomcat", it lost its edge over the F-15. Likewise, the F-15E "Strike Eagle" is not quite as good as the A-D models at long range interception, but is a much better ground-attack aircraft.)


RE: ....
By Cattman on 12/25/2007 2:52:27 AM , Rating: 2
Tons of planes can ACCELERATE going vertical including the F-16.


RE: ....
By 9nails on 12/25/2007 3:30:57 AM , Rating: 2
Not just accelerate, but to continue to accelerate as it climbs in altitude. Other aircraft cannot break through gravity's grip. They might be able to accelerate but will soon bleed off speed while in sustained vertical flight and cannot approach 30,000 feet from zero altitude like the F-15. Like they said, this isn't useful, but in a 3D dogfighting world this is just one more direction that an F-15 can run where other aircraft cannot follow. Simply put, the F-15 is a beast. In a large combat arena, the F-15 is always the aggressor. You need to coax an F-15 into a small combat zone to get the upper hand with a fancy fly-by-wire F-16. Otherwise the F-15 is a brute and has no problems reminding you why it's still America's first fighter when called to action.


RE: ....
By Motley on 12/25/2007 2:01:02 PM , Rating: 2
That isn't acceleration. "bleed off speed" is deceleration.


RE: ....
By Dasickninja on 12/25/2007 11:45:02 PM , Rating: 2
There is technically no such thing as deceleration. Only positive and negative acceleration.

Sorry for the pedantry.. that was pretty much beaten into us in Physics class. :)


RE: ....
By damncrackmonkey on 12/26/2007 2:42:28 AM , Rating: 2
quote:
The F-15 is also the only U.S. fighter that has more thrust than it weighs. This means that it can ACCELERATE straight up, like a rocket.


I would of thought VTOL's would be capable of vertical acceleration...


RE: ....
By 91TTZ on 12/26/2007 1:53:54 PM , Rating: 2
quote:
would of thought VTOL's would be capable of vertical acceleration...


None of our VTOL aircraft are fighters. The harrier would be the closest, but even that has an "A" designation (it's an attack aircraft, not a fighter)


RE: ....
By 91TTZ on 12/26/2007 1:51:59 PM , Rating: 2
quote:
Also, a couple notes about the F-15: It's official top speed is "Mach 2.5+", but the Air Force has documented that it can do Mach 3.2 in short bursts.


You're thinking of the Russian Mig-25, not the F-15. The F-15 can't go mach 3.2


RE: ....
By rcc on 12/26/2007 3:06:53 PM , Rating: 2
Most of the US fighters since the 70s have been capable of vertical acceleration. All it takes is a positive thrust to weight ratio. Obviously some do it better than others, and none do it when fully loaded for A/G. Since the early F15 models didn't have an air to ground capability, I suppose you could claim it was the only one that could with a "full" load.

Back in the 70s, one of the cool but useless stats was that the F15 could beat a Saturn V rocket from 0 to 50,000 feet. Of course after that it got it's doors blown off, but like all statistics if you can choose your filters you can pick your results.


RE: ....
By omnicronx on 12/24/07, Rating: -1