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An225
Topic Author
Posts: 273
Joined: Tue May 31, 2005 6:37 pm

Old Aircraft Maintenance

Sun Dec 18, 2011 8:32 am

Hello all,
I assume that this issue was probably discussed before but I hope that this thread will add something new...

I teach air transport management courses in Ben Gurion University, Israel, and the topic of maintaining old aircraft was discussed this week, and my students asked me how can old airliners and commercial GA aircraft are still in use. They gave me the example of the refurbished 1923 circa Fleet Model 1 entering service for scenic flights with Paradive. I replied that these aircraft need a tighter maintenance regime and spare parts are bought from strip-down airframes, and/or from companies holding the type certificate (not always the original manufacturer).

My students questions got me to further ponder on this issue.
Companies holding the type certificate are: REKOF for the Fokker line, Erickson for the S-64Skycrane, Viking Air for the DHC-6 Twin Otter, and Boeing for the MDD line. I assume that aircraft bone yards are also a very good source for major parts of old aircraft.

What interests me is the following:
1. What happens with rare aircraft? What would do a Fleet Model 1 mechanic when he needs parts for this rare aircraft
2. What happens with even common old airframes which needs gaskets, tubes, panels, etc.? or even special parts such as lavs, actuators, gauges, etc.?
3. What are the operators' choice and SOP when a part and/or assembly is completely dead/worn and they cannot overhaule it or find a similar part from their suppliers?
4. How does these operators do to satisfy the CAA's inspectors demands?
5. Who publish maintenance bulletin for very old aircraft?
6. Why is it still economical to use old DC-6's or even an old and rare Martin JRM Mars for commercial work?

Thanks,

An225
 
CanadianNorth
Posts: 3287
Joined: Sat Aug 24, 2002 11:41 am

RE: Old Aircraft Maintenance

Tue Dec 20, 2011 6:14 pm

Can't speak for most aircraft, but the HS-748s that I know and love are still quite well supported. BAe provides the updates, manuals, ADs, etc. and parts are available used from a variety of scrapped aircraft, and new parts are still widely available (at a price of course) from several companies.

Two notes people often forget... First many of the basic parts can be a generic part number used on multiple aircraft spanning several generations. For example several parts/seals/etc on the HS-748 are also used on other newer aircraft, such as the BAe ATP and the like. Another factor is who made the components... For example our Darts are a pretty ancient engine, but made by the same Rolls Royce who are still pumping out 777 engines, so we can still try them if we need something and can't find it anywhere. The landing gear is made by Dowty, which are still in business and making parts and manuals for their older designs. So it's not all about the manufacturer of the airframe, the component manufacturers are just as useful...
 
MD11Engineer
Posts: 13899
Joined: Sun Oct 26, 2003 5:25 am

RE: Old Aircraft Maintenance

Wed Dec 21, 2011 6:57 am

Quoting An225 (Thread starter):
1. What happens with rare aircraft? What would do a Fleet Model 1 mechanic when he needs parts for this rare aircraft
2. What happens with even common old airframes which needs gaskets, tubes, panels, etc.? or even special parts such as lavs, actuators, gauges, etc.?
3. What are the operators' choice and SOP when a part and/or assembly is completely dead/worn and they cannot overhaule it or find a similar part from their suppliers?
4. How does these operators do to satisfy the CAA's inspectors demands?
5. Who publish maintenance bulletin for very old aircraft?
6. Why is it still economical to use old DC-6's or even an old and rare Martin JRM Mars for commercial work?


I do a bit of historical aircraft restoration work on the side.
Standard parts (general hardware like nuts, bolts, seals etc.) for American aircraft made after the 1930s are usually pretty easy to source, since they usiually fullfill military standards, which are still in use today, even though the older standards might have been incorporated into newer standards.
E.g. most items of the old AN (Army-Navy) standard from the 1930s have beein incorporated into the MIL standard or later into the National Aerospace standard. You just need to go through the various specification sheets to see which part matches which.
With company standards it is a bit more difficult (E.g. BAC for Boeing standartised parts).
With aircraft from other countries it is a bit more difficult. E.g. at the moment I´m working on a Morane-Saulnier MS760 Paris jet from the 1950s. It is getting more and more difficult to find French aviation standard metric hardware.

Also, once an aircraft loses it´s manufacturer´s support (and there is no other company taking over), it gets banned from commercial service. E.g. Snecma withdrew it´s support for the Maboré engines used on the Fouga Magister and the Parisienne (a licence built version was used on the T-37 Tweety Bird). There are still companies around performing engine overhauls for this type, but since there is no manufacturer´s support anymore, aircraft equipped with those engines can only be flown as experimentals.
The same happened with the BAC 1-11, the Concorde, the AN-12, the AN-24 and other aircraft, basically grounding the fleets.
In some cases the aviation authorities issue special permits to still operate a historical aircraft commercially, e.g. Lufthansa´s Ju-52, but then the operator has to be able to prove that he can do all technical support himself. E.g. LH Technik has a design and parts manufacturing approval, so their engineers are allowed to design repairs and develop maintenance procedures, just like the original manufacturer, and they are allowed (and have the ability) to manufacture once off parts.

For some aircraft there still exist parts inventories with certain dealers, for some aircraft dating back to WW2.
But e.g. it becomes more and more difficult to find Rolls-Royce Merlin parts for Spitfires, Mustangs etc..
Rolls-Royce refuses to give the permission to another company to manufacture new Merlin parts because they are afraid of liability issues. So these warbirds are essentially running on spare parts manufactured and warehoused back in WW2.
The biggest problem are rubber parts, since they have a limited shelf life. E.g. the DeHavilland Vampyre´s nosewheel tyre is the same as the tailwheel of the Lancaster bomber and long not been manufactured anymore. Sure, some tyre company probably still has the mould in it´s store, but remanufacturing those old tyres is prohibitively expensive.
Last year we needed two main gear tyres for a Lockheed T-33. One manufacturer told us that he could make them, but we needed to buy at least 500 tyres to make it worthwhile.
As for manuals, for the T-33 I tried Lockheed without luck, but managed to borrow several boxes full of manuals from the German Luftwaffe Museum in Berlin (the Luftwaffe ooperated this aicraft type during the 1960s), which I than scanned onto a CD rom for use with my laptop.

The next problem is that each and every country used it´s own system in sorting manuals. While the American Technical Orders are quite similar to the commercial ATA 100 system and are still using the same setup, the French airforce system of the manuals of the MS 760 and the Fouga Magister is totally weird.

Jan
 
aviopic
Posts: 2423
Joined: Sat Mar 13, 2004 7:52 pm

RE: Old Aircraft Maintenance

Wed Dec 21, 2011 9:13 pm

Quoting An225 (Thread starter):
Companies holding the type certificate are: REKOF for the Fokker line

Rekkof does not have a type certificate for Fokker aircraft, Fokker does.
http://www.fokker.com/
 
chieft
Posts: 326
Joined: Thu Jun 16, 2005 11:35 pm

RE: Old Aircraft Maintenance

Thu Dec 22, 2011 5:20 pm

Quoting An225 (Thread starter):
1. What happens with rare aircraft? What would do a Fleet Model 1 mechanic when he needs parts for this rare aircraft
2. What happens with even common old airframes which needs gaskets, tubes, panels, etc.? or even special parts such as lavs, actuators, gauges, etc.?
3. What are the operators' choice and SOP when a part and/or assembly is completely dead/worn and they cannot overhaule it or find a similar part from their suppliers?
4. How does these operators do to satisfy the CAA's inspectors demands?
5. Who publish maintenance bulletin for very old aircraft?
6. Why is it still economical to use old DC-6's or even an old and rare Martin JRM Mars for commercial work?

Well, I try to give you some answeres and hope that fellow forum users will correct / add me:

1.) Mechanics of vintage / historic aircraft are well informed an know, where to get parts and who can help out. There are specialised dealers for such parts. Just an example this link: http://www.skysportengineering.co.uk/index.html

2) see 1)

3) If an operator cannot find acceptable parts, the aircraft is ripe for the museum...
4) You have to proof airworthiness as with any other aircraft; as far as I know, there are no exepmptions - which is OK in my humble opinion

5) CAA / JAA

6) It might be economical worth to operate vintage aircraft like a DC-6. Yes, you have the maintenance costs, but that is often cheaper than you think. The aircraft itself has about no capital costs (Possibly one reason why there are in the USA still so many DC-9s, some of them also still 40 years old) . Sometimes there is simply no matching replacement for vintage aircraft. Often you have a special operational environment in which only that vintage type canm operate. DC-3s i.e. have a so short T/O length, that is ideal for some special ops on short runways. Possibly the same with a DC-6 and other.

Hope this helps a little bit and would like to learn more about it too.
 
BUGYUL
Posts: 22
Joined: Sun Mar 25, 2012 8:25 pm

RE: Old Aircraft Maintenance

Sun Mar 25, 2012 10:25 pm

For over 25 years my company makes spare parts for various airplane models thru Boeing (both Douglas and Boeing 7-series models)
This is an ongoing issue with flight safety that how long is an airplane is designed for flying.
The brutal truth is no one knows because besides the parts which have a higher replacement requirement an alum skin and frame could last basically forever if maintained and checked for corrosion and cracks.
I can tell you that the oldest type of airplane we have made parts for are the Douglas DC-8 and the Boeing 707 they are designed in the late fifties,early sixties and yes they are still flying.
I can tell you that the landing gear requires the most frequent part checks and replacement because it takes a brutal punishment in each landing.

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