Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Wmaker on April 01, 2010, 02:43:20 PM
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I've been caught off guard quite a few times with the failure of the left part of the lower wing in the Fokker D.VII in AH. The wing seems to fail during sustained loading right when the first signs of greyout are starting to show up on the edges of the screen. That G-loading for the AH's pilot is roughly at 5G mark when testing with a fighter equipped with a G-meter. I know that this method of determining the actual loading at the time of the failure isn't most accurate but it's all I have without a G-meter. It seems to be able to take peak loads that are somewhat higher than this, though.
I know that French, British and the Americans did extensive structural load testing for the D.VIIs after the war but unfortunately I haven't seen any of that data. However, here's something in the way of operational loading limits for the D.VII: http://www.rwebs.net/avhistory/bluemax/pndvii.html (http://www.rwebs.net/avhistory/bluemax/pndvii.html).
"Constructors' Notes and Instructions for Use, Fokker D.VII-65
NOTE: This publication has been reprinted by the Fighting Air
Command, the current owners and operators of the three Fokker
D.VII replica aircraft built by Rousseau Aviation for the film
The Blue Max. Some information contained in the original
publication and this reprint may not be correct for the aircraft
in their current configuration. Pilots should consult the F.A.C.
pilot's notes for these aircraft.
...
The Fokker D.VII-65 is a modern copy of the original D.VII. This
version suffixed 65, has been produced by Rousseau Aviation at
Ateliers Aeronautiques de la Cote d'Emeraude, Dinard Airport,
France.
The design has been undertaken on the basis of being a copy of
the genuine Fokker D.VII housed in the French Musee de l'Air at
Chalais Meudon, this example being one actually captured in
flying condition during 1918.
...
1.2. Limiting Accelerations based on Maximum Total Weight
Authorized of 2,310 lb / 1050 kgs for Utility Category
manoeuvres.
Maximum positive Plus 4.2
Maximum negative Minus 1.68"
I must admit, I was fairly surprised to see the maximum allowable G to be so low.
I just checked the weight in AH and it seems to be a bit on the high side for the wartime Fokker at 959kg. There are of course many different weights listed in different sources but normally the weight is listed at just under 900kg for the early production planes and bit over 900kg for the later aircraft. Anyway, about the G-loading. If we correct that 4.2G@1050kg for the 959kg we are at ~4.6G allowable and for the 900kg it's 4.9G. So the allowable "modern" G-limit is very close to the G-loading where a catastrophic failure occurs in AH. I know, it's hard to determine an accurate failure loading from all this but I think it's clear that it isn't a good engineering practice to determine allowable operating limit to be so close to a condition where a failure occurs?
As I just noticed the weight difference, I put something more concrete togerther on this thread later.
P.S Been having a lot of fun in the WWI arenas, thanks HTC!
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P.S Been having a lot of fun in the WWI arenas, thanks HTC!
No kidding? Really? Having fun eh? (http://bbs.hitechcreations.com/newscores/killsbyp.php?sortby=1&selectTour=WW1Tour1&pindex=107) And here I am jumping up and down getting all excited when I manage to see a single hit message in the text buffer.
:eek:
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Wmaker do you think the reproductions used stronger steel tubing that what was available in WW1? That could explain the difference.
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No kidding? Really? Having fun eh? (http://bbs.hitechcreations.com/newscores/killsbyp.php?sortby=1&selectTour=WW1Tour1&pindex=107) And here I am jumping up and down getting all excited when I manage to see a single hit message in the text buffer.
:eek:
Heh, I hope I can limit my flying time a bit more during the next tour. :) Darn you dealers for serving the addiction! :D
Wmaker do you think the reproductions used stronger steel tubing that what was available in WW1? That could explain the difference.
Well, the cantilever wings were all wooden construction with box spars. So if we were to assume that a failure would first occur in the wing itself (which by far is the most likely event) and not in its attachment points the steel tubings strenght is somewhat irrelevant. The outer struts themselves didn't really contribute much to the overall strenght of the structure.
Although, saying that the plane was "a copy of the genuine Fokker D.VII housed in the French Musee de l'Air" is maybe a bit misleading but it is still close. Some of the differences can be found from this article: http://thevintageaviator.co.nz/projects/fokker-dvii/build-story (http://thevintageaviator.co.nz/projects/fokker-dvii/build-story). Admittedly, there are some differences but it's the best analog I could find right now.
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I was wrong about the weight, my bad. Pyro has it correct. The weight I mentioned doesn't include the pilot but is a maximum allowable airframe weight without the pilot.