ua777222
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Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 4:49 am

Quick question about aircraft TTSN.

There is a 757, N757AG, that is now for sale with a VIP reconfiguration.

I was looking through the total time on the bird and it showed that both RR211-535-E4's with serial numbers that were in order, but with almost 4,000 hours difference between the two.

How does this occur? Were the engines leased out while it was in storage to two different operators?
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YWG
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 5:16 am

Quoting UA777222 (Thread starter):
How does this occur? Were the engines leased out while it was in storage to two different operators?

Maybe, but doubtful. Something could have happened to one of the engines earlier on and they might have had to do a swap. From there the engineers could have fixed the engine and just had it "laying around" waiting to be swapped out once an overhaul was due??
Contact Winnipeg center now on 134.4, good day.
 
411A
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 5:34 am

Quoting UA777222 (Thread starter):
How does this occur? Were the engines leased out while it was in storage to two different operators?

This does occur, occasionally, in my experience.
It is called revenue enhancement, and can occur with aircraft, owned by certain leasing companies, on a case by case basis.
 
ua777222
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 5:40 am

Does it adversely affect the value of the aircraft?
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411A
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 6:43 am

Quoting UA777222 (Reply 3):
Does it adversely affect the value of the aircraft?

According to some folks in the leasing companies I'm familiar with, not all that much...provided however that the hours/cycles are not excessive.

We had some FOD damage with one of our engines, and a replacement was leased for a short period, until the original engine was returned from a shop visit.
Standard procedure, in these cases.
 
ua777222
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 8:25 pm

Quoting 411A (Reply 4):
We had some FOD damage with one of our engines, and a replacement was leased for a short period, until the original engine was returned from a shop visit.
Standard procedure, in these cases.

Agreed. But we're talking over 33% difference.

Do some engines live out their lives as leased replacements?
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KELPkid
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 9:34 pm

Quoting UA777222 (Thread starter):
I was looking through the total time on the bird and it showed that both RR211-535-E4's with serial numbers that were in order, but with almost 4,000 hours difference between the two.

Lots of single engine taxi time?   Kidding, of course...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
411A
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 9:59 pm

Quoting ua777222 (Reply 5):
Do some engines live out their lives as leased replacements?

Oddly enough, in some cases, the answer is...yes.
 
Dalmd88
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RE: Aircraft Ttsn Discrepancy

Thu Apr 15, 2010 10:24 pm

Here is my take. Many lessors have it in the contract that the airplane will be returned to them with the same S/N engines. So one engine may stay on wing for a long time while the other is removed for a shop visit and then sits and then gets installed on another airframe or two. When the plane is due to be returned the engines meet up again.
 
bohica
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RE: Aircraft Ttsn Discrepancy

Fri Apr 16, 2010 12:15 am

Quoting DALMD88 (Reply 8):
Here is my take. Many lessors have it in the contract that the airplane will be returned to them with the same S/N engines.

   There are many other parts as well which have to be installed back onto the original airframe when it's returned to the lessors.
 
KELPkid
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RE: Aircraft Ttsn Discrepancy

Fri Apr 16, 2010 12:40 am

Quoting DALMD88 (Reply 8):
Many lessors have it in the contract that the airplane will be returned to them with the same S/N engines.

Why's that? I would think that engines get interchanged a lot in a fleet, and not only that, but might even change an operator or two when they get a complete teardown and rebuild...as a potential aircraft owner buying a used twin, I would only care that it has two engines of the right type, in good operating condition, that all recommended maintenance has been performed, and the engine itself is not in almost immediate need of an overhaul due to the hours accumulated.   

Of course, I don't think I've saved up nearly enough pennies to be buying a VIP 757 anytime soon, either  
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tdscanuck
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RE: Aircraft Ttsn Discrepancy

Fri Apr 16, 2010 4:41 am

Quoting ua777222 (Reply 5):
Agreed. But we're talking over 33% difference.

The fact that the two engines have adjacent serial numbers doesn't tell anything about their relative history once they left the factory. Engines almost never move around as paired sets...they could have been on totally different aircraft, or one in operation and one in storage, for huge chunks of their lives.

I've worked with a pair of engines that are adjacent serial numbers and have a factor of nearly 20 between their hours.

Quoting KELPkid (Reply 10):
Quoting DALMD88 (Reply 8):
Many lessors have it in the contract that the airplane will be returned to them with the same S/N engines.

Why's that?

It's a very easy way to achieve:

Quoting KELPkid (Reply 10):
as a potential aircraft owner buying a used twin, I would only care that it has two engines of the right type, in good operating condition, that all recommended maintenance has been performed, and the engine itself is not in almost immediate need of an overhaul due to the hours accumulated.

Leassors want this too. But it's relatively difficult to enshrine "good operating condition" and "not in almost immediate need of an overhaul" in a contract. Saying "I want those two S/N engines back" and stipulating that all recommended maintenance must be done (a normal clause) pretty much guarantees that you know the approximate state you'll get the engines back. It also ensure that the leassor has full maintenance history. As long as the airline has the leased engine, they need to keep the records, so the leassor knows that they'll have the full history. If they just said "two equivalent engines" they might get one that came to the airline from another source that didn't have full records, or whose records couldn't be verified. Then the leassor would be holding an engine whose pedigree they can't fully trace, which would impact value.

Tom.
 
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airportugal310
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RE: Aircraft Ttsn Discrepancy

Sat Apr 17, 2010 3:21 am

Quoting tdscanuck (Reply 11):
Leassors want this too. But it's relatively difficult to enshrine "good operating condition" and "not in almost immediate need of an overhaul" in a contract. Saying "I want those two S/N engines back" and stipulating that all recommended maintenance must be done (a normal clause) pretty much guarantees that you know the approximate state you'll get the engines back. It also ensure that the leassor has full maintenance history. As long as the airline has the leased engine, they need to keep the records, so the leassor knows that they'll have the full history. If they just said "two equivalent engines" they might get one that came to the airline from another source that didn't have full records, or whose records couldn't be verified. Then the leassor would be holding an engine whose pedigree they can't fully trace, which would impact value.

Very nice way to put it!

Do engines come with any kind of internal "hobbs" meter that shows hours on it?
I sell airplanes and airplane accessories
 
boeingfixer
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RE: Aircraft Ttsn Discrepancy

Sat Apr 17, 2010 4:05 am

Quoting Airportugal310 (Reply 12):
Do engines come with any kind of internal "hobbs" meter that shows hours on it?

No, they are calculated on installed flight time only which is taken from the journey log books. All engines are serialized and have hours tracked accordingly. When engine changes are required the flight hours are frozen on the changed engine until repairs are made. When the engine is reinstalled on an aircraft the total flight hours start again adding to the time at removal.

Cheers,

John
Cheers, John YYC
 
lotsamiles
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RE: Aircraft Ttsn Discrepancy

Sat Apr 17, 2010 10:31 pm

Quoting tdscanuck (Reply 11):
But it's relatively difficult to enshrine "good operating condition" and "not in almost immediate need of an overhaul" in a contract.

Lease contracts usually have requirements for the target time or cycles since the last overhaul/performance restoration of each engine at redelivery. Since each engine model has an interval between performance restorations that is fairly well understood (give or take geographical or utilization based differences), the amount of time remaining until the next restoration can be assumed from the hour or cycles since the last event.

Often there is a financial adjustment for each hour or cycle above or below the target value of performance life remaining (with a bare minimum) so that the operator has flexibility in planning shop visits prior to the end of the lease.

The same applies for the life limited parts in the engines, although for LLP's it is easier to quantify the life remaining since the parts are tracked to know exactly how many cycles are remaining at any given time.

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