Mosquito Airframe Life

[daveymac82c]

Hi everyone,

I was checkin' out the message board on www.mossie.org (cool site) and came across a discussion that mentioned the notion that the De Havilland Mosquito's airframe was only designed to last 500 hrs, but if taken care of could last longer. This might explain why there aren't any flying today.

I'm interested to know if it's true that the Mossie was designed with an airframe life expectancy limited to 500hrs. Oh, and thinking about that, many hours did the average warplane rack up during their careers between '39-'45? I'm wondering if 500 hrs is more than enough time to live a full life in war-time.

Cheers,

David

[RMAllnutt]

Most military aircraft back then weren't expected to last more than that in combat... it wasn't just mosquitoes. The thing about mosquitos that is of concern most is delamination of the plywood. If you can prevent that from happening, you are ok (ie... keep it out of too much moisture, but not too little either, and keep it from getting too hot). Wood, unlike metal, doesn't have a fatigue index, so theoretically, you could keep flying them for ever, provided the glues held out.

Cheers,
Richard

PS. Modern glues being used in today's reconstructions are far superior to their WWII counterparts.

[P51Mstg]

Well, on TV one night I heard them say that the Lancaster was expected to have a combat life of only 8 Hours on average. Germans made the jets because they could build a jet engine (service life 25 hours before scrapped) in a fraction of the 2000 man hours it took to build the Benz engine for the 109. In the last couple of FW190 series, the 20mm cannons didn't come out of the wings and were built in. So how long did you think they expected them to last?

Galvanic corrosion caused by dissimilar metals being put together caused Spits to rot over the years (which is why all the rivets get replaced) and the same thing on Japanese planes. So nobody expected them to last too long.

On guns, SKS and AK47 barrels are gone in 2000 rounds. In Iraq, there was some flack over buying the Iraqi Police NEW AK-47s when there were so many used ones around. At $75 each on the open market, its not worth looking at and inspecting each one to see if they were still serviceable. A T-72 tank has a tube life of 250 rounds or so, US tanks last 5000 rounds.

One day my son asked why there weren't many P51Bs left? I explained, that by the time the B's got there, they were basically worn out. The same for most of the D's at the end of the war. When the Swedes got them, they were pretty much gone. Most of the bomber would never have made it home to be scrapped here, but they could quickly move a lot of troops back home (10 at a time or so). The armor (tanks) got a lot of fixing done on them, but they were way too heavy to bring back home.

Simply put (as we all know) at the end of the war there was so much stuff it wasn't funny. My old DI SGT Hakes told me that when he went into the Army in the mid 60's there was still warehouses full of WWII leftover personal equipment. WWII 1911 45 pistols were used until the mid 80s and they still used Greaseguns (M3A1 submachineguns) in US tanks in Iraq war #1.

Pretty incredible stuff if you ask me.

Mark H

[daveymac82c]

Hey Richard,

Thanks for the reply! Before posting this thread I never really considered the expected life span of airplanes being used for combat. Looking back at WWII we can see how that technology was improving very rapidly and with each new technology or improvement older airplanes were getting outdated. So I suppose a long lasting airframe was not the main interest of designers.

Wasn't there a German fighter jet that was designed to be built by relatively unskilled workers and could be built very quickly? I figure it's construction was not intended to last very long either. The Heinkel He 162 or something like that, right? I can imagine those were not designed as anything more than a last effort by the German forces. Regardless, a very cool looking airplane if I am right with what I think it looks like.

On the topic of Mosquitos though, I can't wait for Bob Jenns to get his flying. I don't know when that'll be but I'm going to try and drop by his hangar to see his progress over the next couple of weeks.

Cheers,

David

[muddyboots]

.50 cal bullets stamped 1943 were also still being fired in DSI. How do I know? I have a couple of casings on my desk that I picked up after a test fire in Saudi Arabia...

Some stuff had a wear out date...and some didn't

[daveymac82c]

Pardon my ignorance, but what's DSI?

Cheers,

David

[RickH]

Desert Storm I

[JDK]

The Mosquito lifespan thing is very interesting, but here's a LOT of myths out there. I'll try and come back with some chapter & verse next week, when I've got my notes from a recent conversation with a Tech Curator restoring one.

Ironically the original Casien glue was better than the syntetic type they used later in the war, apparently, with certain provisos - like applying it properly, not letting it get wet or hot (tropical no-no) and stoping it being eaten, being organic, it was bug-tasty...

Galvanic corrosion caused by dissimilar metals being put together caused Spits to rot over the years (which is why all the rivets get replaced) and the same thing on Japanese planes. So nobody expected them to last too long.

I understood it was just that magnesium rivets weren't expected to last 50 years. Certainly my understanding is the sheet metal might be OK metallurgically, but the rivets can just go to dust in your hand.

One day my son asked why there weren't many P51Bs left? I explained, that by the time the B's got there, they were basically worn out. The same for most of the D's at the end of the war. When the Swedes got them, they were pretty much gone.

That's certainly part of the story, but being replaced by newer and 'better' machinery was also part of it. That's why there's relatively more 1945 service aircraft around than there is 1939 -41 stuff. The early/pre-war stuff had to avoid being used up, replaced or modified.

[Bill Greenwood]

As for Spitfire rivets, if you keep them painted and protected from moisture I think they last indefinitley. Any bare metal rust or corrodes if not protected from moisture and especially salt and chemicals. My plane is 62 years old and we just replaced most of the rivets a few years ago. The original ones are not pure magnesium, they are an alloy containing magnesium, probably because it is lighter for the same strength than steel. We used the original type. I am not a metalurgist, not even a real A&P, but I have never read any factory data that a Spit was only built to last a few years, and I doubt if that was true.

[muddyboots]

Pardon my ignorance, but what's DSI?

Cheers,

David

Sorry Dave. DS I work better? Desert Storm I

[Bruce]

The Mosquito didnt have a design life as such. Remember the effects of fatigue were not well known until another de Havilland product, the Comet 1 started to fall out of the sky.

In the UK, thats why Chipmunks, Provosts, Vampires and so on are being grounded - as they reach the end of their fatigue life. Spitfires, Hurricanes and so on never had one specified, so they will keep getting rebuilt.

When they did the major on Mosquito RR299 back in 1992, the question was asked by the guy responsible for it. The answer came back, 'How do you life a tree?'

In short, the reason that there are so few Mossies surviving and none flying, is that the wooden airframe degrades quite quickly if left outside for more than a few months. The fuselage will swiftly become unrepairable after 18-24 months outside with no maintenance, in a less than benign climate such as we have in the UK!

Cheers for now


Bruce

[Mark V]

The Mosquito lifespan thing is very interesting, but there's a LOT of myths out there.

There are - I think the majority arise out of a combination of hindsight (we know now how long the average Lancaster airframe survived in WWII operational use for example) and the post-war introduction of airframe life in response to the discovery of fatigue failure. As Bruce says the latter simply was not considered and even if the aircraft designer, engineer or factory worker was aware of the former, I doubt that it particularly influenced what they were doing.

[Jiggersfromsphilly]

The Battleship Wisconsin fired shells that were from 1938 during DS1.

[Jeff Hunt]

Here is a photo of Bob Jens's Mosquito as of 18October2007.





Jeff

[daveymac82c]

Thanks for posting that picture of Bob's plane. I hope to be seeing it in person soon. I just have to coordinate it.

-David