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Wear And Tear

Sat Feb 05, 2000 12:18 pm

Here's a question for all you A&P's out there. I'll use a 737 in this example.
At my airline, the engines on the B737 are started in the order #1 and #2. After the flight reaches the destination, #1 is left running until the ground power is hooked up. My question:Do the #1 engines on our 737's experience greater wear and tear than their #2 counterparts. I would think this to be marginally true since #1 runs several minutes more/day than #2. Any thoughts?
 
Buff
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RE: Wear And Tear

Sat Feb 05, 2000 12:39 pm

Sorry to jump in ahead of Buzz, Jim or any of the other eminently qualified AME's, but I believe as long as the engine cycles, i.e. starts and shutdowns are the same, then additional wear of which you speak is inconsequential. I'll leave the rest of the technospeak to the experts...

Best Regards,

Buff
 
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RE: Wear And Tear

Sat Feb 05, 2000 2:24 pm

I don't know. At "my" carrier,737's are lit off #2 first then #1. If the APU is on MEL,then #1 is left running till 400Hz is plugged in. A lot of times,an engine will be changed on condition (failed boroscope inspection,performance,damage),and therefore each engine has a "life' of it's own. Just because a plane was delivered new,doesn't necessarily mean both engines will hit their TBO's at the same time,because of other issues over an engines lifespan. It still goes by hours on the wing,not by actual running time. I often suspect myself though,that certain items that get used on the ground will tend to be changed more often. Like,say,running the same fuel boost pumps for the APU (I always try to crossfeed off the other tank while I have a plane under "my possesion" while I'm working on it to mitigate extra wear and tear on the usual APU feed boost pump--a bit obsessive huh?). Actually though,I don't really see much correlation twixt components changed and their ostensibly greater..or less use.
 
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Bruce
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Engines

Sat Feb 05, 2000 3:28 pm

This thread brings a question to mind...kind of related. An engine has to be changed or overhauled when it reaches XXX hours. When the plane lands, and is expected to have a quick turnaround as usual, and the crew discovers that it has reached that number of hours, do they just say "ok, this one's grounded for repairs" and the hell with the pax who have to wait for.....what? another jet? different flight?

Or, do they "schedule" this downtime ahead of time?

And, when they have to overhaul an engine do they actually change out the complete unit or just take it apart and how long does that take?
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
CX Flyboy
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RE: Engines

Sat Feb 05, 2000 3:59 pm

It wouls be a very badly run airline that suddenly realised during a turn-around that they had time expired engines! These things are planned in advance, and an engine can be changed in less than an hour at HAECO in HKG (And probably most other places too). The new engine goes on and the planes is dispatched again after checks. Meanwhile (In HKG) the engine makes its way across to the other side of HKG for a lenthy overhaul at a dedicated engine centre.

Having said that, I saw a Turkmenistan 757 parked at Manchester (UK) are ages. I was told that the engines had been taken for an overhaul and that there were no spares, so the aircraft sat engineless for a number of weeks before the engines were retured and the aircraft left. I am not sure how true this is. It sounds very strange. Perhaps some of the MAN guys out there can tell me more if they remember it. EZ-A012 I think it was.
 
Buff
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RE: Wear And Tear

Sat Feb 05, 2000 4:37 pm

An hour may be a little TOO generous! But routine engine changes can be very quick indeed depending on the experience of the maintenance department. An Air Transat A330 just finished sitting on the ramp in CYYC for over a week needing an engine change. The new engine had to be delivered by an AN-124.

As CX flyboy stated, a routine engine change will be known well in advance by a progressive maintenance department and will be a "non-event" in the life of the airline.

Best Regards,

Buff
 
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RE: Wear And Tear

Sun Feb 06, 2000 1:35 am

Bruce: You're kidding,right? Time changes for components that are time changed (as opposed to condition) are all monitored continuously by a hoarde of people in the maintenence department who do just that. In many,if not most cases time controlled maintainence is sheduled hundreds of hours in advance and often to co-incide with concurrent down time (for other reasons). CX Flyboy: An hour for an engine R&R? Wow! Even a BAE146 engine change (the easiest one going) takes 4 or 5 hours. Don't forget that after an engine is pulled,the whole A/C side pylon/firewall/engine interface is inspected and corrective action must be performed on items found. It also depends on how complete an engine is. Many times an engine will come bare,and the T/R or nose cowl will have to be swapped over from the old one---very time consuming. Is the work being perfomed inside,or out in the weather? Having partaken in a few hundred engine changes over the years,I'll cite a few good estimates for "without a hitch" engine R&R's. DC9/80,727,737-200 can probably be done in about 8 hours. 737-300 and up: about 12. 757 (RR) and 767 about 16 hours. Leak checks,run up/trim/or ops checks,and a mountain of paperwork add some time as well. It should also be noted that the mechanic signing off the engine change (or any other time controlled item) will also enter this (the part,serial #,position) into the companies computer system so that it too can be monitored.
 
CX Flyboy
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RE: Wear And Tear

Sun Feb 06, 2000 1:52 am

I could well have been wrong. I just fly em I don't fix em! I read somewhere about an Evergreen 747 that had come to Hong Kong and the crew had left the aircraft with HAECO and went off to the office. When they came back in a little over an hour, they asked the engineers how long it would take them to replace it. The guys were doing the finishing touches and said that's it, the new engine is on.

Now, I'm not in a position to say how true this was, but it's what I read. Perhaps exaggerated for effect, but if it wasn't fast, it wouldn't have been mentionned in the article I read.

It's good to get feedback from someone that really knows though!
 
aca320
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RE: Wear And Tear

Sun Feb 06, 2000 2:25 am

While I really can't comment on the 47 having done the 9 and the bus it takes about 2 to 3 hrs depending on possible setbacks stuck bolts seized clamps ext. of course the newer the model of a/c the quicker the change with the 9 you have to go and do a trim run which can take an hour or two espicially when your in ywg in jan and its -49 on the ramp (no I'm not kidding) whereas on the bus a 20 min run usually suffices hope that answers your question.