The following Cranfield University website appears to have a large number of technical reports related to the De Havilland Comet … RE: de Havilland Comet Design changes Compositepro (Chemical) 13 Feb 22 16:18 I am willing to be wrong on the above prognosis but I think there is substantially more to Comet redesign than stop making cracks during manufacturing.
#De havilland comet crack#
In summary, given the structures sensitivity to crack initiation and given that cracks would have appeared with usage, I doubt if preventing cracks from appearing during manufacturing would have gone enough in the way to make it airworthy again.Īnother pointer in that direction is a 707 marketing video released during that time which demonstrated slow crack growth when fuselage was penetrated by steel harpoons and I don't know if the Comet could have demonstrated that (slow propagation) given how sensitive it's to crack initiation itself. Itself cause, I think one way or the other, a crack would have appeared with increased usage either due to manufacturing defects or otherwise. So, on the Comet, I think it's the fast and unarrested propagation that was the problem rather than the apperance of the crack All you can do is to ensure that when one starts, you have designs in place to slow them down until the inspections pick them. I thought you can almost reliably never stop a crack from initiating. RE: de Havilland Comet Design changes crackman (Aerospace) 10 Feb 22 majority of efforts aren't to stop propagation, it's to never start one to begin with and to detect any that have started." Not to say high stresses were not significant, which they obviously were, but if you include at least 4 or more stopped drilled cracks in the same area, the stresses would be even higher.Īnyway, the comet is a great case study and still has some valuable information for learning. Also, Dr Paul Withey has presented several papers on this topic and confirmed the presence of damage in the original panel at the ADF cutouts. If you search online, I presented a paper at AAS 2017 which shows the stop drilled cracks and also presented some of it at ASIP 2021, you might be able to find the papers online. The punch drilling operation induced damage in the holed thru "ripping" of the material.
#De havilland comet full#
Note the subsequent full scale fatigue test by RAE did not replicate the failures at the ADF cutouts in the crown of the fuselage but instead showed failures at the cabin windows and the test article did not have any stopped drilled cracks. It is discussed in the public hearings but was written off as standard practice. The stopped drill cracks where a result of the punch drilling opertion dehavilland employed on the early produced aircraft. Beware, it is quite large (over 1000 pages) and expensive to obtain a copy.īy the way, little advertised fact is that the structure recovered from the accident aircraft had stopped drilled cracks in numerous areas around the adf cutouts. There are also RAE papers showing the stress investigations around cutouts.Īs for other significant sources, you could always contact The Hub at farnborough and get a copy of the full original accident investigation as I did many years ago.
If you want to see the changes, you can look at the comet 4 or nimrod structural ipc and srm and compare to the comet 1. RE: de Havilland Comet Design changes berkshire (Aeronautics) 10 Feb 22 16:39 Any pointers in that direction would be great! I will also welcome less than ideal answers ☺️. While a lot seems to written about what led to the accident, I couldn't find much by the way of specific design changes that were incorporated to make it airworthy again. An ideal answer would be one which compares the old and new design almost side by side. Adding stiffners around windows to allowing stress away from the cutoutsīut I was hoping for some definitive answers rather than guessing.
Changing some of the cutout profiles to reduce the Kts.Ĥ. Better materials in terms of crack resistance/growth (fracture toughness?)ģ.
Reduction of general stress levels by making the skins thickerĢ. Possible amends I could think of (based on my limited knowledge) were:ġ. What I am interested however is the specific changes that were made to the design to make it airworthy again.
Testing only the fwd fuse and effect of end restraints Overloading the fatigue specimen before the fatigue test itselfģ. Underestimation of stresses at the cornersĢ. I have read the investigation report which spoke of:ġ. I am trying to learn the specific design related issues with the de Havilland Comet.
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