C-47 - indefinite airframe life?

[RJM]

I'm helping (as little as possible) my son put together a report on an influential manmade artefact for his history class. The 'Important Historical Artefact' he has chosen is the C47/DC3.

A very interesting topic, but one important statement has to be verified. Is it correct to say that provided its systems are maintained, the 'indefinite life' of the over-engineered airframe will allow the aircraft to fly virtually for ever?

Amazing if true, but neither he nor I have been able to substantiate the claim.

Can anyone help, in relation to either military or civil versions?

Thanks on my 14 y o's behalf.

[Onan the Clumsy]

Perhaps in engineering terms, I really couldn't say, but there may be other factors that render the thesis unimportant. Feul availability comes to mind as one.

...or even fuel :ugh:

[Baskitt Kase]

...provided its systems are maintained, the 'indefinite life' of the over-engineered airframe will allow the aircraft to fly virtually for ever? That's technically true of every aircraft! Any ac fully maintained could have fatigued components replaced with new ones, allowing the ac to continue flying safely. It is possible to replicate and replace any ac component (apart from the original crew!). Now, whether it is finacially vaible to do so is another story, when you reach the point of lathing individual items to order etc, the cost of the maintenance will outweigh the value of the ac.

[con-pilot]

Well one thing that the good old DC-3 has going for it is that it is not a pressurized aircraft that alone will greatly reduce metal fatigue.

But then at what point is an old airplane is considered original? I know for a fact that a B-52 has been overhauled and modified so many times that the only original piece on the airframe is the co-pilot’s left rudder peddle. That includes the skin.

[Taffer]

Reminds me of the episode of 'Only Fools and Horses', where Trigger gets an award for services to the council, using the same brush for 20 years.

"This old broom's had 17 new heads and 14 new handles in its time".

[RJM]

Thanks all, esp Onan for his incisive analysis. The lad's read the above, and will modify his grand claim somewhat.

[albatross]

Most DC-3s I have delt with are pretty much original airframes except for crash repairs.
As far as I know the only structural AD of any note is the wing attach angles inspection/replace outboard of the engines.
I assume someone with much more knowledge than I will wade in with TRUTH.

[Fourfans]

There certainly are a lot of DC-3's flying around still in their original threads. The KISS principle is not a bad one when producing aircraft to last. (T-33 is another good example)

Fourfans

[Safeware]

Con pilot:

I know for a fact that a B-52 has been overhauled and modified so many times that the only original piece on the airframe is the co-pilot’s left rudder peddle. That includes the skin.

I find that v hard to believe - without some serious dismantling, there are some components of an airframe structure that you just ain't going to take apart and replace. Maybe a complete new mission system or such like, but the only way I could see your claim working would be to take the rudder pedal out of an A model and transfer it and the airframe number and history to a later model. All based on the fatigue life of a rudder pedal, yeah :rolleyes:

The nearest I can think of the RAF coming to this was when the 2 F3s collided at night doing NVG over the north sea, one ditched, one got back but was sooooo bent. The plan was RTW to take the front third off, inspect for damage at the join and if ok put an F2 nose back on. Question arose that if successful, what number would it come back with, consensus was that of the 'original' F3 because the airframe number should stay with the centre section.

Never heard if it got any further.

Anyone know?

sw

[Doctor Cruces]

Used to work for an airline that flew DC3's.

Your lad might be interested to know the the airframe was so strong that the Zero Fuel Weight was the same as the Max Take Off Weight.

Doc C

[con-pilot]

No that’s a true story Safeware. There was a story in the local newspaper about this, I figured that the newspaper got it facts wrong, as usual, and check into this story. It was confirmed by the base information officer at Tinker AFB.

[MrBernoulli]

I used to fly DC3s and C47s, a little over 20 years ago, and I distinctly recall the engineers talking about it's lack of airframe fatigue life.

I assumed that it meant there was no recording of sortie profile against airborne time (as you would with an RAF aircraft). Consequently there was no FI (fatigue index) number constantly counting down to the day when the aircraft would be scrapped - like I recall in the Jet Provost and Victor ...... to name but a couple.

The only reason a Dak would not fly until the ends of time would be a lack of normal maintenance. Sure, they used to inspect the darker recesses of the airframe at fairly regular intervals but that has become general practise. Solid as a solid thing, they were!

[enginesuck]

Main spars do not last forever - cant be replaced so ---- no is the answer.

[Bert Stiles]

Errr - The DC-3 doesn't have a mainspar - could that be the point ?..

B.S.

[Samuel]

Actually ES, the DC3/C47 doesn't have a main spar, everything is just bolted together and, given the technical support for fuel and engines, could be around in another fifty years.

In 1976 the RNZAF bought 10 ex-RAF Andovers, and some of the Daks they replaced were sold to the South African Air Force, which re-engined them with a turbo-prop and renamed them Dackletons. They are still flying, the Andover has long gone!

[Bert Stiles]

No Military Mods - so this hasn't been shifted to History + Nostaglia.

BS.

[Onan the Clumsy]

Thanks all, esp Onan for his incisive analysis. Yes sorry about that. What I was trying to suggest was an alternative answer to your son's problem, namely that the question of airframe life (which may or may not be answerabe) might, at some future time, become secondary to some other question such as fuel availability, part availability, legislation etc and therefore irrelevant.

I was trying to give him something to let him show the teacher that he'd thought about the original question in more dimensions than originally required.




...ok, I was just being a smart alec, but that doesn't stop it from being a possible answer.

[Iron City]

For civil aircraft these days there is generally a service life on the airframe that is included in the type certification, so many hours or so many cycles (takeoffs and (hopefully) a matching number of landings).

In the olden days when DC-3s and Beech 18s and such were designed most aircraft crashed or were otherwise not useful in a lot shorter time than the airframe would fatigue at, so the type certification did not have a service life limit, meaning you are legal to fly it forever unless you see cracks, fatigue, etc. This can be a particular problem in commercial operation (anything for hire or remuneration) because the aircaft must be inspected every 100 hours. The Beech 18 is a very good case study in what happens when the aircraft lasts a lot longer than intended.

DC-3s were originally type certified as a modification to the DC-2, I think, and then C-47s/R4Ds were built by the billions that were sort of copies but not exactly. You can look at the Type Certificate Data Sheet for the DC-3A, C various C-47/R4D and other mil produced aircraft on the FAA web site at www.airweb.faa.gov. There is a U.S. practice of type certifying an aircraft that was originally built for the military on the basis of a bunch of them being flown by the military and they seem to be okay and nobody has found a big problem with them (called military equivilancy). The military does the same and makes type certification under Part 25 of the FAR a criteria for buying aircraft derived from civil ones (for example all the various King Air variants like UC-12, T-44, etc) All the Goodyear blimps were civil type certificated using military equivilancy because there was no civil type certification criteria or standard. In the case of the C-47/R4D there were a boat load of them available for nothing after WW II and it seemed reasonable to allow them to be used in air commerce so long as they got a good inspection to ssure airworthiness and were modified to a more or less civil standard. This is what was done, and a number of "DC-3s" that you see are really C-47/R4Ds that had this happen. During WWII there were also olive drab painted very military looking aircraft that were really DC-3s that had been bought up. The last DC-3 I was in, N-34, is in reality an R4D and still has the Douglas makers plate with dates, serial numbers and all right where it should be in the cockpit.

[ImageGear]

Followed them into FACT a few times, (Not as exciting as flaring shortly after a Shacklebomber has rotated tho')

With 5 bladed turbo props, flir, etc this has got to be among the most modded

http://www.jetphotos.net/viewphoto.php?id=135081

Imagegear

[RJM]

Thanks again all. My son said he presented his work with the statement that 'many experts believe...' about the airframe fatigue life, then mentioned some of the many factors you guys brought up. PPRuNe should share in the copyright!

He got an excellent mark for his work, btw, so thanks again.