B-17's toughness

Discussion in 'Aviation' started by ralphwiggum, Apr 19, 2009.

  1. ralphwiggum

    ralphwiggum Member

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    Why was the B-17 able to take such thrashings from Luftwaffe flak and fighters and still fly? It seems to me that most other planes would never be able to take such punishment!! (Oddly my 2 all time favorites are the B-17 and FW 190!):rightfighter5:
     
  2. ccheese

    ccheese Member In Perpetuity
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    Probably because this airplane was designed and flown before computers.
    All of it's stress points were given a bit extra to CYA. Nowadays computers
    figure it all out so there is no extra. Of course, good old USA workmanship
    helped.

    Charles
     
  3. HoHun

    HoHun Active Member

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    Hi Ralph,

    Here is an older post I originally made in another thread, but as linking specific posts in multi-page thread is currently buggy, I'm repeating it here to spare you the search :)

    Regards,

    Henning (HoHun)

    ---Original-Post-Below------------------------------------

    Comparing the B-24 to the B-17, it really looks like the numbers show the B-24 to be the more survivable aircraft (by a narrow margin).

    I have got "B-17 Flying Fortress" by HP Willmott here with a breakdown of the 8th Air Force bomber units by type, sorties, tonnage on target and losses.

    Counting only the combat losses, I can compare the combat survivability of the B-17 and B-24. (I'm leaving out a few bomber groups operating both types as their successes and losses can't be identified by type.)

    The total 8th Air Force B-17/B-24 losses were 1.50 % per sortie.

    The B-17 losses were 1.64 % per sortie.

    The B-24 losses were 1.21 % per sortie.

    Surprise: The B-24 was the more survivable bomber!

    I initially assumed that the B-17's poorer performance could be attributed to its earlier arrival - many B-17s were lost when they tried to fly into the fangs of the Luftwaffe without fighter escort, after all.

    However, even when only taking into account bomb groups that arrived December 1943 (along with the Mustangs) or later, the B-17 still has the higher losses with B-17: 1.42 % vs. B-24: 1.11 %. The percentages mean that you're losing 4 B-17s where you'd have lost only 3 B-24s.

    (Since both aircraft carried virtually the same load per sortie, this doesn't change the picture either.)

    Highly interesting :)

    I just notice that the 492nd BG probably shouldn't be counted towards the totals as they had extremely heavy losses during "Carpetbagger" (agent dropping) night missions.

    The 801st / 492nd Bomb Group

    As they were a B-24 group, excluding them from the analysis (as they fly a completely different type of mission) would change the balance a bit further in favour of the B-24.


    Regards,

    Henning (HoHun)

    ---cut----------------

    100th BG (B-17): 8630 sorties, 177 lost in combat
    301st BG (B-17): 104 sorties, 1 lost in combat
    303rd BG (B-17): 10721 sorties, 165 lost in combat
    305th BG (B-17): 9231 sorties, 154 lost in combat
    306th BG (B-17): 9614 sorties, 171 lost in combat
    351st BG (B-17): 8600 sorties, 124 lost in combat
    379th BG (B-17): 10492 sorties, 141 lost in combat
    381st BG (B-17): 9035 sorties, 131 lost in combat
    384th BG (B-17): 9248 sorties, 159 lost in combat
    385th BG (B-17): 8264 sorties, 129 lost in combat
    390th BG (B-17): 8725 sorties, 144 lost in combat
    398th BG (B-17): 6419 sorties, 58 lost in combat
    401st BG (B-17): 7430 sorties, 95 lost in combat
    447th BG (B-17): 7605 sorties, 153 lost in combat
    452nd BG (B-17): 7279 sorties, 110 lost in combat
    457th BG (B-17): 7086 sorties, 83 lost in combat
    91st BG (B-17): 9591 sorties, 197 lost in combat
    92nd BG (B-17): 8633 sorties, 154 lost in combat
    94th BG (B-17): 8884 sorties, 153 lost in combat
    95th BG (B-17): 8903 sorties, 157 lost in combat
    96th BG (B-17): 8924 sorties, 189 lost in combat
    97th BG (B-17): 247 sorties, 4 lost in combat
    389th BG (B-24): 7579 sorties, 116 lost in combat
    392nd BG (B-24): 7060 sorties, 127 lost in combat
    445th BG (B-24): 7145 sorties, 108 lost in combat
    446th BG (B-24): 7259 sorties, 58 lost in combat
    448th BG (B-24): 9774 sorties, 101 lost in combat
    44th BG (B-24): 8009 sorties, 153 lost in combat
    453rd BG (B-24): 6655 sorties, 58 lost in combat
    458th BG (B-24): 5759 sorties, 47 lost in combat
    466th BG (B-24): 5762 sorties, 47 lost in combat
    467th BG (B-24): 5538 sorties, 29 lost in combat
    489th BG (B-24): 2998 sorties, 29 lost in combat
    491st BG (B-24): 5005 sorties, 47 lost in combat
    492nd BG (B-24): 1513 sorties, 51 lost in combat
    93rd BG (B-24): 8169 sorties, 100 lost in combat
     
  4. TheMustangRider

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    That's quite a surprise to me since I have read some accounts of bomber pilots that preffered the B-17 over the B-24 for being a more solid and rugged bomber. From what I have read a B-17 could fly with only one engine for a given period of time while a B-24 could not make home with two engines.
     
  5. HoHun

    HoHun Active Member

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    Hi Mustangrider,

    >That's quite a surprise to me since I have read some accounts of bomber pilots that preffered the B-17 over the B-24 for being a more solid and rugged bomber.

    As far as I can tell, the B-17 really had a reputation for ruggedness and the B-24 one for dangerous vulnerability. This reputation was not limited to the Allied side either, as the Luftwaffe fighter pilots seemed to think that the B-24 could be shot down more easily than the B-17.

    However, this reputation does not seem to be supported by the actual numbers, which is really food for thought.

    >From what I have read a B-17 could fly with only one engine for a given period of time while a B-24 could not make home with two engines.

    Hm, normally information of this kind would be found in the aircraft manuals, but I have a copy of a B-24D manual which only mentions engine failure on take-off (and failure of a single engine). I don't have a B-17 manual either. The B-29 manual I have certainly covers all kind of engine failure situations - if we could find something of that level of completeness, we'd probably know for sure :)

    I remember reading an article on the B-24 by Eric Brown, who conducted some flight-testing of the type for the RAF. It appears that if one experienced failure of a single engine when it was running at full power, one had to act very quickly to avoid large bank angles and loss of altitude from the resulting involuntary dive.

    Regards,

    Henning (HoHun)
     
  6. mkloby

    mkloby Active Member

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    There are so many variables that factor even into combat losses. Loss rates are also not equivalent to the ability to sustain damage.

    I would imagine that you would quickly need to pull power and feather feather the prop to reduce the drag. The degree of the emergency would depend on which engine was actually lost.
     
  7. HoHun

    HoHun Active Member

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    Hi Mkloby,

    >There are so many variables that factor even into combat losses.

    True, but we also have a very, very large data sample. There should not be any random bias for sure :)

    I also haven't been able to find any systematical bias in the data selection, but of course there might be something we haven't thought of yet.

    >Loss rates are also not equivalent to the ability to sustain damage.

    Good point, but do you see any difference between the B-17 and the B-24 with regard to the likelihood to receive damage?

    One thought we toyed around with in one or two older threads was that the B-24 was less likely to be hit due to differences in ceiling or speed. We didn't reach any useful conclusion though, if I remember correctly.

    Regards,

    Henning (HoHun)
     
  8. Waynos

    Waynos Active Member

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    There was a very good article (by which I mean entertaining, not accurate) published in Flight as early as 1939 in which, amongst a general appraisal of US types, the B-17 was dismissed as hopelessly obsolete and so vulnerable that it 'might be brought down by a single hit from aaircraft's machine gun'. But fear not Uncle Sam, apparently the DB-7 was so good that it almost came up to British standards! No, don't laugh, its rude. :)
     
  9. BombTaxi

    BombTaxi Active Member

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    Personally, I think the popular perception of the B-17 being tougher might well be down to the many pictures published of heavily damaged Forts that made it home. By contrast, one sees many pictures of B-24's dramatically 'folding up' after being hit in the wings, and few of heavily damaged ones that came home. I believe I am right in saying that the Davis wing was not particularly known for strength, and perhaps this and the sometimes dramatic nature of it's failure might have accounted for the perception among both US and German aircrew that the Liberator was easier to bring down?

    Waynos, I had to allow myself a moment of black humour over the press derision of the B-17. The USAAF also warned the RAF that the B-17C was not sufficiently armed to survive in daylight over Europe unescorted - advice which was ignored and tragically proved true during the type's short and disastrous career with 90 Squadron. In a further and final act of hubris, the USAAF then ignored it's own advice barely twelve months later and sent E and F variants out over Germany without full escoet - the consequences of which we all know...
     
  10. ToughOmbre

    ToughOmbre Active Member

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    My un-scientific observation with regard to the toughness of the Fort agrees with BT.

    I think we have all seen many pics of battle damaged B-17s and far fewer of damaged B-24s. And unless I'm mistaken, I do think the broad wing of the B-17 was stronger than Davis wing.

    Anyway, the pics from this site are incredible.....

    Battle-Damaged B-17 Flying Fortresses

    TO
     
  11. Flyboy2

    Flyboy2 Member

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    One factor that I'm aware of was the fact that alot of the B-17 was what you could call empty space. Take the wings for instance. The B-17 had huge wings which had lots of just air between the wing spars. Compared the the B-24 with its much smaller but higher lift wing, a wing hit to the B-17 may not damage as many critical structures, while a similar hit on the B-24 would have been catastrophic
     
  12. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    You've hit the nail on the head. Compare both aircraft from a top view.

    The Davis airfoil was efficient but was not designed to operate with a bunch of holes in it.
     
  13. MikeGazdik

    MikeGazdik Member

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    What about pure numbers of aircraft flown into harms way over Europe? I may be very wrong, but I think there were far more B-17's used over Europe as compared to B-24's. If that is correct, I think that would greatly affect thier statistical loss rate.

    The more you put over the continent, the more you are likely to lose.

    Plus the loss rate doesn't account for the ones that made it home, both B-17 and B-24. Which aircraft would you rather be in while making an emergency landing with flaps shout out, 1 or 2 engines out, and no landing gear or one main gear that wont lower? The guys that survive that landing are the ones who talk about how tough their airplanes were, and I think that is where the B-17 wins hands down!
     
  14. Watanbe

    Watanbe Member

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    I think you will find, I haven't got anything on hand to back this up, but the B24 was probably more numerous, if not, there certainly weren't far more B17's than B24's! Also the way Ho-Hun has calculated it shouldn't matter because it is loss rate per sortie!
     
  15. seesul

    seesul Active Member

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    During one speach to Willi Reschke I asked him on his opinion on B-24 and B-17.
    I was told B-24 was an easy-to-destroy target while B-17 was a hard nut.
    Willi got 20 4 engine bombers to his credit...
     
  16. Watanbe

    Watanbe Member

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    I'm willing to take that as an answer. I respect his opinion very highly!
     
  17. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Although the B-24 flew a bit faster and carried a larger bomb load, it was a quickly designed aircraft and had a lot of operatioal flaws through out its career, essentailly it was a flying truck. It leaked fuel in places, had a weak nose landing gear and also had a shimmy on the nose landing gear. Some pilots liked the aircraft when it was fully functional but I think most agreed that if it lost an engine or got some holes in the wing it was a sitting duck.
     
  18. MikeGazdik

    MikeGazdik Member

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    My main point was about the aircraft that did make it home. When an aircraft is shot down or blown out of the sky, its a loss.

    But the B-17's seem to have been able to limp home with much more severe damage than most any other bomber. Had they been less tough, thier loss rate would have been higher. If there were no B-17's at all, and all the U.S. had over Europe were B-24's, I think the loss per sortie would have been higher because the B-24 was more prone to failing to return after severe combat damage.

    I'm not good at developing statitistics, and I do respect those that can form them from the data they find. But I am a true believer that statistics can be made to show your point.

    Please don't interpret what I am saying as a dig at what Hohun has put up, that is some very well sorted out information without a doubt!
     
  19. HoHun

    HoHun Active Member

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    Hi Mike,

    >My main point was about the aircraft that did make it home. When an aircraft is shot down or blown out of the sky, its a loss.

    Your point about the ability to crash-land is a very important one - if aircraft that had to be written off as unrepairable after crash-landing in England are counted as losses, the loss count might in fact be misleading as a shot-up B-24 that vanishes into the North Sea would appear to be lost in the same manner as a shot up B-17 that grinds itself into scrap metal in a wheels-up landing on an English airfield. However, the B-24 crew would have vanished along with the aircraft, making the loss much more serious than that of the B-17, whose crew might have stepped out of the wreck without a scratch.

    >I'm not good at developing statitistics, and I do respect those that can form them from the data they find.

    Actually, you are very good at connecting the real-world chain of events with statistics, and you have found a possible systematical bias that might make the B-17 appear worse than it perhaps was :)

    We have been discussing this thread for the third time on this forum (after it had already been posted and discussed on another forum before), and in all these discussions no-one pointed out the results of a survivable crash in England until you came along!

    Very good out-of-the-box thinking here, you found the factor all of us had missed! :)

    This means that the conclusion that the B-24 is slightly more survivable than the B-17 can not be confidently drawn from the data I found, at least if we are concerned about the survival of the crew. We're going to have to find more detailed statistics that at least add the information whether an aircraft failed to return, or if it was written off after returning for a valid conclusion.

    We're back to square one, I'm afraid!

    Regards,

    Henning (HoHun)
     
  20. Colin1

    Colin1 Active Member

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