# Silly Jet Plane Question - F104

Disclaimer: I know diddly squat about aircraft

A cow-orker, sitting at my desk as I type, has, in all seriousness, suggested that the F-104 fighter jet was retired from service because “It’s so fast it shoots itself down.” It would seem this would be at least a physical improbability if not impossibility. “Yeah, it accelerates faster than the bullets accelerate.”

Now, my tenuous grasp of physics would suggest that the velocity of the bullet in flight (V[sub]Bullet[/sub]) would be equal, at least at first, to the velocity of the jet (V[sub]Jet[/sub]) plus the normal muzzle velocity of bullet at a standstill. Now, the bullet will slow down because of wind resistance, gravity, whatnot. But it should also describe a parabolic arc towards the earth.

This sounds a lot like a joke by Mad Magazine in their Star Wars issue. What’s the Straight Dope?

There was another thread on the F104 earlier this month:

In regards to the cow orker, that seems like a silly statement. But what do I know about physics, I was an English major.

Well…without making any judgement about your coworker’s theory, I guess it’s at least possible for a jet to shoot itself down. The projectiles/bullets stop accelerating once they leave the cannon/gun and begin to decelerate. The airplane, of course, can continue to accelerate. So I * guess it’s possible to fire some rounds straight ahead and in an upward trajectory and then accelerate so fast that by the time you intersect with them, you are moving at a very high relative velocity.

But it pretty much looks like the reasons that the F-104 was retired included it being an unforgiving and unsafe aircraft, and not fitting the requirements of the Air Force at the time.

Thanks, interesting stuff at the link. He mentioned the F-104 initially as it’s part as a “chase vehicle” in Space Shuttle launches. When pressed a bit he says some guy (at NASA?) told him this but allows maybe the guy was “full of it”, but that he’s just taking what someone in an authority position says. From the linked thread it would seem the F-104 was retired since a) it’s initial mission was never useful and b) it didn’t adapt well to other missions.

I am interested to see if my assumptions regards the physics of shooting oneself down are correct.

I’ve heard the same said about the F-8 Crusader but just a sea story AFAIK. The physics just don’t work out for this ever being a problem in normal flight operations though I did find an unsupported claim that such an event happened at a gunnery range where a plane fired during climb only to be later hit by those same bullets on the downward trajectory.

The F-104 wasn’t the fastest fighter that fired guns so why did we never hear of this being an issue with the F-4 Phantom II which was even faster? It is normal for there to be limits to the safe flight envelope for weapons so even if this was true, and it isn’t, they would just include it in the operations manual rather than retiring it from service. The F-104 was retired because it became obsolete. It had great speed for its time but due to the tiny size of the fuselage there wasn’t much room for an engine and the pilot let alone fuel.

Ridiculous. There is no way an F-104, or any other airplane powered by anything short of antimatter, can accelerate fast enough to “run into” a fired bullet in straight and level flight. Even if it could, the pilot would be rendered senseless by the g-forces. If you drop the assumption of straight and level flight, an F-104 – and any other airplane armed with a gun – could conceivably collide with its own bullets, although whether the relative velocity could be high enough to cause damage is debatable.

Besides, F-104s carried missiles (some models didn’t have a gun at all). If the gun were causing problems, they’d just scrap the gun, not the whole plane. Or they’d just instruct the pilots not to hit the afterburner right after squeezing off some rounds.

If memory serves, there has been one incident of a fighter shooting itself down. I don’t believe it was a 104, though. The cannon shells decelerated enough that the jet caught up to them and essentially ran through the stream of bullets at several hundred miles an hour relative speed. I’ll look for a cite.

Here we are:

Cite

Oddly enough, my cite searching first turned up a different incident involving an F-104 which “shot itself down” in a different way - during testing a 20mm shell exploded while being fired, and the shell fragments got sucked into the engine. The pilot had to make a dead-stick landing, which I imagine is no mean feat in a Starfighter.

I’ve also heard of an incident where an F-14 suffered a malfunction when it launched a Phoenix missile that basically resulted in one of the missile’s fins slicing open the bottom of the plane because it didn’t drop clear of the plane before igniting the engine. Not quite the same thing as running into it’s own bullets though.

I’ve also heard of an incident (I don’t remember the specifics, could have been one of the aforementioned incidents) where a fighter fired it’s guns in a climb, then nosed over and hit the afterburner, and managed, through some fluke of physics, to catch up with the bullets as they fell back towards the Earth.

I think the F-11 incident is BS because it only has a top speed of 750mp. I did find a cite for that happening due to defective ammunition which tumbled in the air and ended up fodding the engine.

http://www.cincinnati.com/freetime/strange/011000_strange.html

I didn’t mean BS on you but on the cite’s description. The pilot’s name was the same in both our references so it was probably the same event and I would not call it a plane shooting itself down.

The F-104 basically went out of service in the US Air Force when it became obsolete for its designed role of high speed interceptor. It remained in service in other air forces and was further developed as a high speed attack aircraft, as the small size and small wing made it an excellent low-level flyer at high speeds.

It also acquired a bad reputation as a widow-maker, especially with the German Luftwaffe, although this was mostly due to the F-104 being a very “hot” airplane requiring better-than-average piloting skills to get the best out of it. A hot plane at low level and high speed doesn’t give much room for error, and the notoriously bad Luftwaffe maintenance during this period didn’t help any.

A bit of airplane trivia: The F-104A, designed for high altitude flight, had the pilot’s ejection seat firing downwards through the bottom of the fuselage. When the role changed to low-level flight (and better ejection seats allowed safe 0/0 ejection with the plane still on the ground) this was changed so that the seat ejected upwards in standard fashion.

I’ve heard, anecdotally, that the forward cannon on the A-10 kicks so hard that, if fired for more than a few seconds, it can slow the plane’s forward momentum enough to stall. This is akin to ‘shooting itself down’.

This has come up here before, and apparently it’s a myth. Here’s some threads on this topic:

The A-10 is a badass plane, nonetheless.

At the ‘Nightmare’ Ranges in Korea in 63-64, the F-105’s were always reminded by the FC’s and / or Range controller to not descend below trajectory as they started their runs.

Make of that what you will.