Is this pipe OK?
 

Got a WARM start the other day.....Skymaster pipe....I noticed the wrinkles on the left side of the pipe.....most are located where the accordian inner and outer sepearator is located (I know some of this is normal at the attachment between the inner and outer)....the worst "wrinkles" are located around the attachement point of the strap and behind the attachment point and the beginning of the outer pipe....not sure if it is normal for a bit of deformation at the strap attachemnt point, as I have previously mounted all my pipes without using the included straps......( my real concern is the wrinkling on the inner pipe just forward of the outer wall in pic #5).....some general pics of the outer color are also included for reference.....pipe has about 10-15 starts on it......there is a very tiny hole in the pipe where part of the accordian spacer is welded to the inner pipe.....u can see this hole just to the left of the seam in a few of the pics....it is the tiny white dot about 1" from the seam......might have been there from the start.....not sure about this...... opinions from those who have had/seen worse and what the result was....never seen a collapsed pipe or what is the beginning of it looks like and how fast it happens once it starts.....Thanks.....

RE: Is this pipe OK?
 

That is no good. Any more flights on that pipe is like time bomp clicking don't know when it will collapse.

RE: Is this pipe OK?
 

Time for a new one body.

RE: Is this pipe OK?
 

If you have any question what so ever replace it. You already have it out. Talk to Tam and get a new one. Best $180 you will spend. or was that $130 Tam? lol.

RE: Is this pipe OK?
 

OK ... who's got hold of Tam's keyboard and typing for him ? One 'bomp' and one missing indefinite article doesn't fool me. It this was really Tam, the above would be more like:


Tha pie no goooooo. An mo flyon nat pie sly thai bon glickink way. Dno went glapse. Daddy sel new wantew. ;)

If in doubt, replace the sucker (the pipe, not Tam). I still don't know for sure what caused the loss of my Super Bandit a while ago, but the best guess is a pipe collapse. So, if you don't want to turn $10k aircraft into a mess like this that probably had less than $250 worth of parts reusable/repairable, a couple of hundred bucks for a new pipe may be the best money you spend this year.

Gordon

RE: Is this pipe OK?
 

Ouch,

Yeah, it's toast. You were smart to check it out before putting it back in there! Give Gary Mueller at Jet Tech a call. He can build you a replacement to order with a fast turnaround and the best quality available for a straight pipe. Good luck!

RE: Is this pipe OK?
 

You should replace the pipe-Lookienogoody- Call Tam he fix you up good.
Gordon-DAMM sorry about the Bandit-didnt hear about that till now. Scotty

RE: Is this pipe OK?
 

a) Replacement cost of jet......$___XXXX.00
b) replacement cost of pipe.....$____200.00 (give or take..)
c) Difference = ......................$ __YYYY.00


Piece of mind equals the greater of b) or c) above $__________

:D

RE: Is this pipe OK?
 

Yeah, I already knew the answer before I posted......"an ounce of prevention....."

RE: Is this pipe OK?
 

In the current issue of RCJI Aug./Sept. 09, page 62, Olivier Nicolas addresses this very subject and mentions two lost jets because of collapsed pipes. He also replaced his with a Tam's.

RE: Is this pipe OK?
 

what actually is a pipe collapse (besides the obvious)......what causes it? Does the metal burn through, does it become annealed and too soft to maintain shape, never seen one.......

RE: Is this pipe OK?
 

You got one that is about half way there, how about this, restrict the back of that pipe then put a torch in the front 'till you see it get tosted, then give us the report or better yet show us a video of it happening.

RE: Is this pipe OK?
 

Hello Gordon,


was that the original pipe you used?


best regards,

Peterjan

RE: Is this pipe OK?
 

Hmm, 10-15 starts, and one warm start? How warm/hot was the start?

I'll be keeping an eye on my SM pipe for sure.

Anyone ever heard of titanium (jetcat) pipes collapsing?

RE: Is this pipe OK?
 

It was a while ago, so I don't recall whether I used the stock BVM pipe or had a replacement made.

What I do know is that PRIOR to the incident, I had an original Mk-1 Jetcat P160 in it, and it seized as those motors tended to do. As a result there was a short period of flames shooting out of the back of the motor before everything was bought under control. I'm not a pipe expert, so I took the input from some colleageus at the time, who told me the pipe seemed fine.

It was about 30 or so flights later that I lost the aircraft, so if this earlier incident was the trigger then that shows that your pipe doesn't have to be very obviously hurt from a hot-start / fire ; any slight weakening of the pipe's integrity may not be obvious immediately, and it my take a while for that to grow to the point of a fatal failure. Might be a good idea for a mag article / online feature, for some experts in the field to give us some pointers on how to watch our pipes and assess their continued health.

On the day we lost the Super Bandit, I forgot to take Powermax with me. We hunted around the local stores for some, but could find only pure Butane. A call to Bob Wilcox confimed the Butane should be OK, so we used it. On the starts that day (4 or 5 of them IIRC), there was a momentary deep rumble during each start-up, that went away after a couple of seconds. After scratching our heads a bit, we figured "it's only during the first few seconds when we are on gas rather than kero, so it's probably just a slight difference in the combustion of pure butane vs the regular mix.

In the second last flight, there was a momentary deep growl from the aircraft in the air, and my buddy who was flying the aircraft that day thought he had the onset of flutter so he immediately landed. Checked everything, and all hinges, pushrods, servo gear trains etc were checked and found to be fine. Flew it again, keeping it slower and closer to pay particular attention to noise, behaviour, etc. Part way through the flight, we again got a noise, and this time the pilot said "Now that I can hear it better, that sounds more like a compressor stall" and immediately chose to land it and do some more investigation. But, as he did his upwind turn to set up, he reported "&*** I don't have it", followed by "Actually, I've got everything but elevator" as he shut the motor down and we watched the subsequent creation of a 400+ ft debris field.

From examination of the debris, we could see that the elevator control surfaces, hinges etc were all fine. The servo wires to the elevators were toast. Might have been from one of the momentary two small post-crash fires that we saw at either end of the debirs field, but probably more likely that something went wrong with the pipe, and the wires got exposed to raw temps from the engine and caused the loss of elev control.

Odd thing about the pipe though .... the seams were still intact, there were no holes burned in the pipe walls, etc. The front end of the pipe has two straps attaching it to the bypass and those were still intact and attached to both the pipe and the bypass (though post-crash, the pipe was no longer over the end of the bypass despite still being bolted to it). So, where was the breach ? Best guess is that the pipe must have been able to distort enough to allow the bottom of the pipe to pull off the bypass (which is no easy feat when you see how far the pipe overlaps the bypass in a Super Bandit).

So, although I can not be 100% sure, a pipe collapse still seems the most likely of causes.

My point in typing all of the above up is to let you guys see the possible missed opportunities in preventing this problem. I could / should have gotten a PROFESSIONAL assessment of the pipe (or just have replaced it outright). Despite their best intentions, fellow enthusiasts who are not pipe experts, may not be the best judges of a pipe's condition, and the unusual noises that day (no, not Dave P's gaseous emissions - those aren't UNusual!) may have been warnings that a more someone else would have picked up on.

Gordon

RE: Is this pipe OK?
 

A collapse usually occurs post a hot start (or starts). The direct flame weakens the metal, this is usually evidenced by strong bluing/purple or worse yet wrinkeling. Going against what you would think the pipe fails due to negative pressure. The front part of the pipe is a negative pressure area due to the venturi effect of the exhaust stream, so the pipe looses integrity and collapses. Scotty

RE: Is this pipe OK?
 

When you guys say a warm/hot/wet start what exactly are you referring to? The gas combustion or kero? Sometimes I get short blue flames during the gas stage but Ive never seen anything more than that.

Would you say the majority of pipe failures are a result of a kero problem?

Ive seen some really intense flames (yellow/orange) that shoot 2 feet or so out of the pipe during the fuel ramp, Is that what is important to watch out for?

Pete

RE: Is this pipe OK?
 

Maybe a "hot start" is defined by the EGT exceeding a safe limit, Regardless of the reason?

RE: Is this pipe OK?
 

True but ONE hot start should not distroy a pipe if it is constucted properly and the hot start is put out quickly.

RE: Is this pipe OK?
 

Hey guys,

I pulled this pipe out of my TamJets F-16 earlier today. Its the older one with built up wing and ailerons. Anyhow, I ran a PST 600R in it for 5 flight, but had a few starts that failed to sustain at higher altitude. I just pulled everything out to prep it for a P-70. Aside from this, all my jets have run with an external turbine so I don't really have a reference point to compare to. Wadiathink, should I replace it?

Kelly

RE: Is this pipe OK?
 

Nope- That looks fine-normal,smooth generalized heat pattern. Scotty

RE: Is this pipe OK?
 

I had pipe in that condition in my A-4 with few fail start. It still running to now with hundred of flight. But the power of P-60 is less than P-70.
I would said is still good. But since you go for P-70. The diameter need to be bigger. Give me some money is better option for your sake.:D

RE: Is this pipe OK?
 

Scotty,
You are fire....good saleman had to write like me.[:@]

RE: Is this pipe OK?
 

Tam......GET OFF THE INTERNET AND FINISH MY PIPE!!!!!!!!!!! For the $100 I'm gonna pay you for it, I would have expeted it here overnight!!!!! :D :D :D
Ryan

RE: Is this pipe OK?
 

Now I like a guy that gets to the point!

Tam, I'll think about it... If I were aiming to fly this at Jets over Whidbey at the end of August (2 weeks from now...) what's your turnaround time?

Kelly