After/Back Fire Causing Loose Exhaust?????

vontresc

vontresc

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vonSegelGoober
OK, here is the situation. The other day I get a call from one of the club pilots, saying that the Archer is running pretty rough. I go to check it the next day, and yes it sounds weird and runs rough. A check of the engine monitor shows nothing super wrong, but I notice that 2/4 EGTs are lower than 1/3. So I uncowl the plane, and check the intakes/exhaust, and lo and beholed NONE of the 4 nuts on the 2/4 exhaust flanges were there.

So we've found the issue. The damn exhaust isn't attached. We had just gotten some work done on that side (new exhaust shroud $$$). I assumed that the show had ****ed up (not the first time unfortunately), so I was half expecting them to be sorry we'll get this fixed. This is where I have some REAL questions, as their explanation was that we likely had after fire issues, and that caused the gaskets to be compromised leading to the nuts getting loose. They claimed that they had properly torqued the bolts and the MX supervisor says he saw them do it. I just have NEVER heard of a failure like this.

Is this something that happens? I just think that an after fire powerful enough to blow through a pair of metal gaskets would be pretty violent and noticeable. None of the pilots said they had any backfires.

Peter
 
I could see it happening, but not with blow pruff metal gaskets.
I doubt it was because of back fire.
Something is not adding up.
That's all I got right now.
 
Someone forgot the nuts, or left them loose and vibration shook them off. The mechanic got distracted or just wasn't paying attention. The Dirty Dozen factors in aircraft maintenance errors:

1731708579243.png

In this case, Distraction is a strong possibility. Cellphones should not be allowed on the shop floor. They are horrible distractors.
 
I've had a couple idiot moments where I turned off the mags during run-up, and instinctively turned them back on without thinking, followed by a loud bang in the exhaust. Never found an exhaust nut loose or missing, or a blown exhaust gasket.
Someone forgot to tighten them, and now they're trying to blow smoke up your exhaust.
 
I'm guessing that once the subpoena hits the mailbox all the insisting that it was done correctly and witnessed will be a thing of the past. Losing a nut or even a couple might be *cough* explained away but this sounds like someone got distracted and didn't finish the job ... :dunno:
 
vontresc said:
OK, here is the situation. The other day I get a call from one of the club pilots, saying that the Archer is running pretty rough. I go to check it the next day, and yes it sounds weird and runs rough. A check of the engine monitor shows nothing super wrong, but I notice that 2/4 EGTs are lower than 1/3. So I uncowl the plane, and check the intakes/exhaust, and lo and beholed NONE of the 4 nuts on the 2/4 exhaust flanges were there.

So we've found the issue. The damn exhaust isn't attached. We had just gotten some work done on that side (new exhaust shroud $$$). I assumed that the show had ****ed up (not the first time unfortunately), so I was half expecting them to be sorry we'll get this fixed. This is where I have some REAL questions, as their explanation was that we likely had after fire issues, and that caused the gaskets to be compromised leading to the nuts getting loose. They claimed that they had properly torqued the bolts and the MX supervisor says he saw them do it. I just have NEVER heard of a failure like this.

Is this something that happens? I just think that an after fire powerful enough to blow through a pair of metal gaskets would be pretty violent and noticeable. None of the pilots said they had any backfires.

Peter
Click to expand...
While you can't prove the shop was responsible, you should at least tell the MX supervisor you're disappointed that's the best story he could come up with, using a suitably condescending tone and expression of incredulity.
 
Hey @vontresc! Haven't seen you here in a while! Welcome back.

IMO, it sounds like their usual shoddy work. "I saw them do it" yeah right.

For those not acquainted, this is the same shop that charged up a battery and then left the master on afterwards...

Another series with them: Nose gear was shimmying at certain speeds. They serviced the shimmy dampener and said it was good. Still shimmying. They replaced the nose tire and said it was good. Still shimmying. I believe there may have been a third repair... But then @vontresc looked at it and found that one of the two mounting bolts for the nose gear was completely missing! So they replaced it, and... A week or two later it was missing again, despite loctite being specified in the maintenance manual.

And this is a Part 145 certified shop.
 
If split type lock washers were used and they cracked there would be no

torque on the nuts. Not so with star washers.

Was the shop asked to perform the 2 tasks or were they asked to

diagnose the shimmy?
 
4(!) nuts loosened up at the same time? Not likely user error. Occam's razor says most likely cause is improperly torqued exhaust manifold nuts.

I had something similar happen to me on an XC about 10 hours after a cylinder replacement. One nut on the exhaust manifold for the replaced cylinder departed somewhere over PA. The other nut was still holding fast. Gasket was fine. One nut later and the cheapest labor charge I have ever had on an airplane and I was back on my way. Stuff happens, especially in sloppy shops. This was the last straw for me. (On prior occasions, I found various tools and rags in the engine compartment after maintenance, and on one occasion an unacceptable signoff on the condition of the spinner backplate nearly caused an accident.)
 
Magman said:
Was the shop asked to perform the 2 tasks or were they asked to diagnose the shimmy?
Click to expand...
Diagnose the shimmy.

Unfortunately, the MO of this place is to pay as little as they can, so they tend to hire people straight out of A&P school and pay them crap. Inevitably, this means that they leave for greener pastures fairly quickly once they have some experience, and thus you're always working with newbies. As far as management, if you stick around, whoever is next in line seems to automatically become the shop manager. They've gotten lucky and had some good ones, but they've also had some absolutely terrible ones.
 
AV8R_87 said:
I've had a couple idiot moments where I turned off the mags during run-up, and instinctively turned them back on without thinking, followed by a loud bang in the exhaust. Never found an exhaust nut loose or missing, or a blown exhaust gasket.
Someone forgot to tighten them, and now they're trying to blow smoke up your exhaust.
Click to expand...
This ^^
 
AV8R_87 said:
I've had a couple idiot moments where I turned off the mags during run-up, and instinctively turned them back on without thinking, followed by a loud bang in the exhaust. Never found an exhaust nut loose or missing, or a blown exhaust gasket.
Someone forgot to tighten them, and now they're trying to blow smoke up your exhaust.
Click to expand...
As Rod Machado refers to it: his student's click-click-click-BANG mag check.
 
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