War Weary - Time Expired Aircraft
 

I was reading American Eagles Vol. 4 last night and the book makes reference to 'WW' marked P-51's. At some flight hour count, these 'war weary' aircraft were pulled out of combat and transfered to operational training units. Does anyone know what the hour count was for P-47's and P-51's?

I got the impression from the book that regardless of an aircraft's structural condition, individual aircraft were pulled of the line on a strict flight hour count.

Does anyone have details on this fascinating aspect of combat logistics?


Thanks!


Bronc

Re: War Weary - Time Expired Aircraft
 

Very interesting question! I always count on US type airplanes as machines with very durable structure (even to some level resistant to combat punishment), engines was also strong so I would also like to know what assembly section was reason for this 'hour counting'

Cheers :)

Re: War Weary - Time Expired Aircraft
 

I believe most US "War Weary" aircraft were sent to secondary units due to newer sub-types being available. Not so much an airframe/hours issue.

Re: War Weary - Time Expired Aircraft
 

If it was still in good condition there'd be no reason to label it as "Weary". All aircraft have fixed structural lives, and the more they are used the nearer they approach failure. Nowadays this is closely monitored by the Fatigue Index, but before this came into use coarser methods of judgement were used. I don't know what methods were used by the USAAF or Luftwaffe, but some measure of total flying hours will have been involved. Even before reaching this limit, and accentuated by pulling high g, they can suffer structural warping. On a lower level, panels get bashed so that they don't fit as well as they used to. Gaps and steps appear. Skins get dented. This increases the drag. It becomes clear that this particular airframe is slower than its squadron mates. It doesn't accelerate as well, it doesn't climb as well, it doesn't turn as well, perhaps it's (comparatively) a bit of a pig to fly. OK for use in training, or for hack flying, but you don't want to take it into combat.

Re: War Weary - Time Expired Aircraft
 

If it was still in good condition there'd be no reason to label it as "Weary". A mint condition P-51A would be labelled "Weary" when P-51B, C, D's became available and relegated to secondary units, it wouldn't matter how many airframe hours it had. Weary can also mean outdated.

All aircraft have fixed structural lives, and the more they are used the nearer they approach failure. Nowadays this is closely monitored by the Fatigue Index, but before this came into use coarser methods of judgement were used. I don't know what methods were used by the USAAF or Luftwaffe, but some measure of total flying hours will have been involved. Even before reaching this limit, and accentuated by pulling high g, they can suffer structural warping. They didn't come close to racking up enough hours to approach airframe failure. Accidents or combat damage were the main problem. Structual warping would send an airplane to overhual or scrap.
If you take the B-17 Nine-O-Nine with 140 missions, average each mission at 10 hours long, that's only 1400 hours. Granted this is a lot of hours of combat time, but only a small dent in structural airframe time. Unpressurized, probably never exceedind 2G's, it could have flown for years. Most fighters only had a few hundred hours on them when retired, if not lost to accidents, combat damage, or replaced with new equipment.

On a lower level, panels get bashed so that they don't fit as well as they used to. Gaps and steps appear. Skins get dented. This increases the drag. This miniscule amount of drag would be just about impossible to measure let alone detect.

It becomes clear that this particular airframe is slower than its squadron mates. It doesn't accelerate as well, it doesn't climb as well, it doesn't turn as well, perhaps it's (comparatively) a bit of a pig to fly.
The amount of damage needed to cause a measurable amount of drag to affect acceleration, climb, turning, etc., would render the airframe useless.

Re: War Weary - Time Expired Aircraft
 

Here are quotes from American Eagles 4 - P-51 Mustang Units of the 8th Air Force on page 56.

"Mustangs being in short supply, the [OTU] was the recipient of cast-offs from operational units."

"...and the WW (War-Weary, which indicated that the aircraft was time-expired and therefore unfit for further combat)..."

I understand the cast-off process and agree with all the comments above. It's the "time-expired" comment that I was wondering about.

Bronc

Re: War Weary - Time Expired Aircraft
 

Only in the last couple of days I was sent some information regarding 9 P-47s from the 56th FG being declared War Weary. Six of which are dated between 30th Jan and 15th Feb 1945.
Total AirFrame Time ranges from 324.15hrs to 684.15hrs.

Nige
http://56thfightergroup.co.uk/

Re: War Weary - Time Expired Aircraft
 

Just my two cents worth based on 40 years of operating aircraft: the decrease in performance due to heavy usage is very easily noticeable if you pay attention. This could result from loss of engine power, or the airframe changes that Graham mentioned. These all can occur long before required overhaul intervals or fatigue lives are reached. Every operation I have been with that had multiple aircraft always had "good" ones and "bad" ones.

I've spent the last few years going through RCAF records for my web site, and I regularly find references to individual aircraft being "dogs", with poor performance or undesirable handling qualities. These were often aircraft that had been repaired, and were officially "airworthy" but unpopular with the crews.

I suspect that if your life depended on getting the last few knots or last g out of an airframe you would be very aware of these changes.

Re: War Weary - Time Expired Aircraft
 

In reply to Revi16, I do not know what precise meaning the USAAF attached to "War Weary". It may be just as you say, but that does not mean that airframes, particularly in this case fighters, do not become weary, in the more recognised sense of tired and worn. They did and do.
If you wish to argue that US aircraft would show this less because they were built to higher structural limits than those of other nations, this is probably true. However, it is not true that the problem did not exist.

A few hundred hours, for WW2 fighters pulling multiple g on a fairly regular basis, is a significant part of their life.

Drag increases from distorted panels, increased steps and gaps, and even rough paint, ARE noticeable. Just polishing an aircraft makes it go faster. Each increment may be small but they all add up. I spent some years in a design office working on jet fighters, and this is one of the messages most difficult to get across when discussing build standards. "But it is only a tiny amount..." like "It is only a small weight increase." "Just a little bit pregnant." (No, I didn't hear that one.) But there is another request tomorrow, and tomorrow, and tomorrow... We are talking about steps and gaps and distortion of the order of tens of thousands of an inch. They not only add individually small drags but affect the smooth flow over larger areas. This sort of damage occurs at a lower level than major distortions that would indeed result in scrap or at least rework. It results in higher landing speeds and hence more stress applied to the airframe in that way. They result in more drag in the cruise and hence lower range.

Reading of WW2 literature will show many examples of older aircraft being passed down from senior pilots to juniors, because older airframes being considered slower and less agile. Not just because a later model became available. In their biographies, pilots complain about being posted to training units, not least because the aircraft are old and tired. There are extreme cases such as Malta. The Russians complained (in particular) about those of the Hurricanes and Spitfires sent to them that were reworked examples that had already served tours of duty on the Western Front.

In the later years of WW2, the US did benefit from a seemingly endless supply of new aircraft that meant they could withdraw used machines that still had considerable life remaining. This no doubt reduced the exposure of US pilots to any genuinely worn machines. That doesn't mean they couldn't and didn't exist.

Re: War Weary - Time Expired Aircraft
 

The war-weary 'WW' marked P-51's depicted in the book "look" worn out. There is no doubt about that. They just have that look.

And some of the operational ones don't look much better. The P-47 book (Vol. 3) has pictures of some very worn out, but operational, Razorbacks.

I think this thread touches on a fact most of us often ignore: that combat aircraft on both sides were weapons of war not unlike like tanks. Both looked and performed "factory fresh" for a very, very, short period of time.

Who was the Eastern Front Luftwaffe Expert that stress-wrinkled the skin of both wings on his first mission, and over revved the engine (and crash landed) on his second?

Bronc