Did You Know...

[Doc Tinker]

A carrier ship's launching mechanism that helps planes to take off can throw your truck over a mile.

 

[KatDiesel]

The steam-powered catapults thrust a 48,000-pound aircraft 300 feet, from zero to 165 miles per hour in two seconds.

 

[joel]

Well, I'm not a physicist or mech e, but having taken over 300 catapult shots, launching a 56,000 pound jet from a dead stop to 160 mph in literally 2 seconds (I've timed it), I could believe that. Of course, that's assuming there's a part on our truck that wouldn't rip off when the cat fires... . THAT, I'd have a hard time believing!

 

[illflem]

Does the cat attach to the landing gear on a plane?

 

[KatDiesel]

Originally posted by illflem:
Does the cat attach to the landing gear on a plane?

On each plane's nose gear is a T-bar which locks into the catapult's shuttle which pulls the plane down the catapult.

 

[Sled Puller]

Has there ever been a plane that got stuck on the mechanism? What happened?

 

[joel]

MGM - I'm not sure if a launch bar has ever gotten stuck in the shuttle. The shuttle comes to a very abrupt stop at the end of the stroke. The XX,XXX thousand pound plane has the momentum advantage. There have been instances of the cat misfiring or not getting enough steam. Bottom line for us is: we have flying speed or we eject. Pretty cut and dry. On a rare occasion, the cat may be "cold" and stop early enough that the pilot can get out of the shuttle and stop on deck, but that's pretty rare.

 

[Doc Tinker]

For some reason, I'm under the impression that the bar that hooks the shuttle to the plane is designed to break off. Is that true?

Doc

 

[joel]

Doc -

Sort of, but not exactly. The launch bar doesn't break off. They put a "holdback fitting" into a piece on the back of the nose gear and that goes down into a notch on the deck, behind the shuttle. They are designed to break at a certain amount of pressure - 53,000# in our case. In fact, when we go onto the catapult and get hooked up, they acutally put pressure on the shuttle and we go to full power. That holdback fitting is what keeps us in place until the cat fires, breaking the holdback and shooting us off the deck. Newer planes use a magnetic device as a holdback. Not sure how, exactly... maybe it's mechanical, but there's no holdback piece. The fitting we use is a little white metal thing that looks like a dumbell. Part stays in the plane, part in the holdback bar that stays behind. I'll post a picture when I get home to my digital cam. Not sure I can get a whole one, but I have a half of one at home.

 

[RonaldLarson]

Yup, it's called a dog bone. It is an alloy specifically designed and heat treated for predictable breakaway pressure. It connects the airplane to the shuttle, and breaks when the plane's weight and the sudden stop of the shuttle exceed the pressure number. I had a customer who made them on equipment which I sold him many years ago.
Ron

 

[joel]

Actually, ron, it connects the plane to the deck of the carrier via a holdback bar and fitting on the BACK of the nose gear. When the cat fires, the holdback fitting breaks (for the non-magnetic ones) and the plane goes on it's merry way. Half of the holdback fitting stays with the plane, half with in the bar on the deck, which the cat crew tosses overboard. The holdback apparatus all stays and functions at the START of the stroke, not the end where the shuttle stops. I have some pictures of them, but since photopoint started charging, I'm working on setting up some new storage space for my pics. I'll post them later, once I get it activated.

Ok, here's the holdback pictures (it's kind of big - sorry about that). The pen is added for reference; it's a standard Bic pen.

#ad


This is the part that stays in the plane, not 2 halves of one holdback. If I can get a whole one from work today, I'll post another picture of it.

[This message has been edited by joel (edited 05-15-2001). ]