Air-Minded: Whoa Nellie!

An F-15 pilot earned a tactical callsign yesterday.

Landing mishap: Oregon ANG F-15D Eagle in irrigation canal (photo credit: unknown)

Probably not, though. It’s true that tactical callsigns often originate in screwups, but usually not from serious ones, and whatever this was, it looks serious to me. I also understand the mishap pilot is an instructor at the Air Force’s F-15 schoolhouse, so he or she already had one, and tactical callsign changes are rare.

What we know: an F-15 landing at Kingsley Field near Klamath Falls, Oregon, ran off the runway yesterday afternoon and wound up in an irrigation canal. Although it was an F-15D model with two seats, the rear seat was unoccupied and the single pilot was able to walk away afterward with only minor injuries. A mishap investigation board has been convened.

Kingsley Field, aka Crater Lake/Klamath Regional Airport, is home to the Oregon Air National Guard’s 173rd Fighter Wing. One of the wing’s missions is to train pilots newly assigned to the F-15: currently the F-15C but in the near future the new F-15EX. Because of its training mission, the wing is equipped with a few F-15D two-seaters like the one that wound up in the ditch yesterday.

Anything else, at this point, is speculation, and we’re not supposed to comment until the facts are known. Well, the further I get from the long arm of the Air Force, the less I’m inclined to observe the pieties, so I’m just gonna jump in the speculation canal with both feet. Up to my neck.

The pilot was returning from a routine training mission and according to an early press release had declared an emergency prior to landing. The pilot, who remains unidentified, is said to be an instructor, which indicates he or she is highly experienced in the Eagle.

departure end
Google Map satellite view of runway 14 departure end and irrigation canal

There’s no official word on what manner of emergency the pilot experienced prior to landing, or why the pilot was unable to stop the aircraft on the runway. The runway in question is over 10,000 feet long, with another 700+ feet of overrun at the end. Minimum runway length for the F-15 (and for most other fighters operated by the Air Force) is 7,500 feet, and the majority of F-15 pilots have plenty of experience landing on those shorter strips. Ten thousand feet is a luxury, in fighter terms.

I suspect a combination of factors, not any one thing, led to yesterday’s mishap. If I’m correct, it’s a combination that never should have happened.

The F-15 has multiple hydraulic systems, and if one fails another will pick up the slack. There’s one system with no backup, though, and its failure can greatly complicate things when it comes to landing the airplane: the Utility A circuit. Utility A pressure is necessary to raise and lower the landing gear, also to operate nosewheel steering and wheel brakes. You need to put the gear down before landing, and once you’re on the ground you need brakes to help you slow to a stop (and nosewheel steering to keep you straight while you’re doing it).

Utility A failure, while rare, is a known malfunction, and many F-15 pilots have experienced it (I have, twice). The procedure is to declare an emergency and use the emergency handle to lower the gear (when you pull it the landing gear free-fall to the down position, where they’re held in position by over-center locks — which themselves sometimes fail). Once the gear is down you lower the tailhook in order to engage the approach end cable upon landing. When the hook snags the cable, you’ll come to an immediate stop. Should you miss the cable, a backup accumulator should provide enough emergency braking pressure to bring you to a stop on the runway (you’ll have to use differential brake pressure to stop in a straight line since you won’t have nosewheel steering). Should that fail — and it’s been known to happen — there’s another cable at the far end of the runway.

One thing that should never happen is that you find yourself rolling down the runway at speed with zero options remaining, helpless to stop. Hence the title of this post: Whoa Nellie!

Which is why I think an unfortunate (and unlikely) combination of factors put this jet and its pilot in the canal. Utility A failure is the one emergency I can think of that might result in being unable to stop — but only if other failures occur as well. Like for example the tailhook not lowering, or lowering with no pressure to hold it down so that it skips along the runway and misses both cables. And some sort of accumulator problem resulting in no emergency braking. Such a combination would have been unheard of in my day, but then again the F-15s I flew ranged in age from brand new to, at most, 15 years old. The jets they fly at Kingsley are well into their 40s, and failures of components and systems that never used to break are beginning to happen.

If you’re interested, you can read an earlier post of mine about F-15s, Utility A failure, and tailhook landings, which includes a photo of another Oregon ANG Eagle which, in May 2020, also suffered an unlikely combination of failures resulting in not only the tailhook missing the cable, accompanied by emergency braking and steering failure, but also the collapse of the right main landing gear and an excursion into the dirt alongside the runway. Apparently lightning can strike twice!

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