953 nut 67,469 #1 Posted Monday at 11:05 AM July 27, 1949, the world’s first jet-propelled airliner, the British De Havilland Comet, makes its maiden test-flight in England. The jet engine would ultimately revolutionize the airline industry, shrinking air travel time in half by enabling planes to climb faster and fly higher. 3 4 Share this post Link to post Share on other sites
8ntruck 9,063 #2 Posted Monday at 12:02 PM The Comet was a lesson in the failure analysis class I took in college. Several of them fell out of the sky. Turns out that fatigue cracks in the fuselage were the cause. Seems the stress concentrations caused by the small radii in the corners of the passenger windows provided places for the cracks to start, while cabin pressurization and flight stresses caused them to grow. This lesson is why passenger windows in airliners are that odd shape that is a combination of a square and a circle today. 2 3 Share this post Link to post Share on other sites
Sparky-(Admin) 25,946 #3 Posted Monday at 02:09 PM 2 hours ago, 8ntruck said: The Comet was a lesson in the failure analysis class I took in college. Several of them fell out of the sky. Turns out that fatigue cracks in the fuselage were the cause. Seems the stress concentrations caused by the small radii in the corners of the passenger windows provided places for the cracks to start, while cabin pressurization and flight stresses caused them to grow. This lesson is why passenger windows in airliners are that odd shape that is a combination of a square and a circle today. Didnt know that…I’ll be looking at the window on my next flight a bit more closely! 3 1 Share this post Link to post Share on other sites
SylvanLakeWH 31,758 #4 Posted Monday at 02:19 PM 2 hours ago, 8ntruck said: odd shape that is a combination of a square and a circle Ahh... that's why 's are designed that way... to address the incredible forces brought to bear on the frame due to speed and g-forces... 5 Share this post Link to post Share on other sites
ri702bill 12,502 #5 Posted Monday at 09:06 PM Yup - you get a WH airborne, the re-entry & landing can be sketchy at best!! 3 Share this post Link to post Share on other sites
Beap52 2,389 #6 Posted Monday at 10:14 PM I always check for cracks when flying. Now I'll start checking radii of windows as well! 1 Share this post Link to post Share on other sites
rmaynard 17,433 #7 Posted Monday at 11:07 PM And this is why you drill a hole at the end of a crack in metal to keep the crack from growing. 3 1 Share this post Link to post Share on other sites
SylvanLakeWH 31,758 #8 Posted yesterday at 01:20 AM 2 hours ago, rmaynard said: And this is why you drill a hole at the end of a crack in metal to keep the crack from growing. I wonder why the airlines don't just do this? Works great on a ... 1 2 Share this post Link to post Share on other sites
Beap52 2,389 #9 Posted yesterday at 01:33 AM 12 minutes ago, SylvanLakeWH said: I wonder why the airlines don't just do this? Works great on a ... Maybe I'll start flying with my cordless drill and a 1/8" drill bit 3 Share this post Link to post Share on other sites
8ntruck 9,063 #10 Posted 8 hours ago 20 hours ago, rmaynard said: And this is why you drill a hole at the end of a crack in metal to keep the crack from growing. 18 hours ago, SylvanLakeWH said: I wonder why the airlines don't just do this? Works great on a ... Airlines have done this. I was on a Convair 580 turbo prop twin for a short flight, probably in the 1990's. Had a wing seat, and was idly looking out the windows when I saw 2 'rivets' on the wing that were not lined up with any of the other rivets. On a closer look, I noticed a crack running between them, probably about 2" long. This will bring up the subjects of critical crack length and minimum detectable crack lengths in fatigue theory. 1 Share this post Link to post Share on other sites
SylvanLakeWH 31,758 #11 Posted 8 hours ago 1 minute ago, 8ntruck said: I noticed a crack running between them, probably about 2" long. No duct tape? Share this post Link to post Share on other sites
8ntruck 9,063 #12 Posted 8 hours ago (edited) 10 minutes ago, SylvanLakeWH said: No duct tape? Nope, they had drilled the stopper holes. That was on Northwest Airlines. I bet you've had a flight or two on that airline. Edited 8 hours ago by 8ntruck Share this post Link to post Share on other sites
wh500special 2,435 #13 Posted 1 hour ago (edited) 7 hours ago, 8ntruck said: This will bring up the subjects of critical crack length and minimum detectable crack lengths in fatigue theory. I was thinking the same thing! My Materials Science prof was a kook, but I loved him and his classes. He used to carry around a three ring binder of newspaper clippings of engineering disasters and material failures that he could refer to at a moment’s notice to prove a point or make a morbid joke. I wish I could remember his quote about why aluminum is such a great material for airplanes, but it had something to do with having a critical crack length long enough for a hungover inspector to see after a weekend in Vegas. Or something to that effect. The giggles ripped through the classroom at the speed of sound…(Rimshot) I also had him for colloids and surface chemistry. Somehow, also laugh riots… Steve Edited 1 hour ago by wh500special Share this post Link to post Share on other sites
