Aerotech F21

I've flown over a dozen F21s with no problems. I like having a single-use 24mm with that much punch. -- Richard "glad the F21s are flowing in the pipeline again" Hickok

Hmmm. Have you seen the thread "Magnelite & E&F motor failures"? There is a discussion of the same type CATO you describe in an F21-4.

Was it the 'new-style' or 'old style' cato-jet?

-- Joe Michel NAR 82797 L1

Last spring we flew a few and had a couple of them do the same thing.

Bill Eide DART-SD

Joe I don't think the F21 have had the single molded case upgrade like the advertized F20 29 mm. So in that light they must be your "old style jet".

The way you describe the F21's they must have a colorful past. Reminds me of Estes attempt at E motors with the BP E15's. I've only used them since spring to replace the E9 and mod. rockets.

Ken

This is actually a common failure mode for AT motors, although I've seen it more on BT motors (E30, F50, G80). When the case fractures, the propellant is actually snuffed by the sudden drop in pressure. It can, as others have noted, be caused by an overly-aggressive igniter, but even a standard copperhead can result in the same failure mode.

[Note: I'm not saying failures are common, just that of the failures I *have* seen, this is the most frequent.]

If you precision-weighed the propellant grain, I think you'd find that a small amount of it was consumed.

On bigger composite motors, such as 54mm, the same sort of 'snuff-out' failure can occur on a nozzle or rear closure failure. If it's a little way into the motor burn, there can be enough heat buildup that the fuel grain will actually reignite in a fraction of a second, and burn unconfined either inside the case or in mid-air if it happened to be ejected.

I have not seen one fail personally but there have been reports.

As always, important details are missing from the reports:

What was the igniter?

If it was "home-made" or "other than that supplied with the motor", was it so large that it could clog the nozzle on the way out? If so, that is your primary cause of failure.

-Fred Shecter NAR 20117

-- ""Remove "zorch" from address (2 places) to reply.

Usually that reignition is caused by a burning delay DESIGNED to not snuff out on pressure drop (by Korey Kline).

Jerry

Batch number is probably not as important for APCP as BP.

What probably IS critical is manufacturing location (ie Vegas, Ellis, Kosdon, Cedar City, Gary's closet). All using the same paperwork of course.

Just teasing, I've heard them called 'cato-jets' before. I thought Aerotech changed the case on that one, but I must have been thinking of the F-20

-- Joe Michel NAR 82797 L1

In order to be a "cato-jet", a motor has to exceed 10% failure rate.

Preferably by a margin.

I believe even errortech motors are safe from that.

Jerry

Dean F21-4w batch # on motor 001573 Ken

Kenneth Jarosch

1944 E. 4th. St. St. Paul , Mn. 55119-4006