AdamSmith Posted March 13, 2016 Share Posted March 13, 2016 If you are a nervous flyer who worries about turbulence snapping off the wing, have a look at this video... http://www.businessinsider.com/the-wings-of-this-airbus-plane-can-bend-way-more-than-you-thought-possible-2016-3 ...it shows an Airbus fuselage being tested in production (actually in late stage of design verification). They strap down the body, then flex the wing up and down through a range of 17 feet -- way more than the little wiggles you ever see out the window in flight. MsAnn 1 Quote Link to comment Share on other sites More sharing options...
Members BigK Posted March 13, 2016 Members Share Posted March 13, 2016 Pretty amazing Quote Link to comment Share on other sites More sharing options...
Members RA1 Posted March 13, 2016 Members Share Posted March 13, 2016 The B787 was tested to 150% of design limit which was a wing flex of 25 feet. If it ain't Boeing, I aint going. However, somewhere these is a video showing how much the 707 wing flexed to include actually "losing" engine due to same. Wing and aircraft survived regardless. Best regards, RA1 AdamSmith 1 Quote Link to comment Share on other sites More sharing options...
AdamSmith Posted March 13, 2016 Author Share Posted March 13, 2016 The B787 was tested to 150% of design limit which was a wing flex of 25 feet. If it ain't Boeing, I aint going. However, somewhere these is a video showing how much the 707 wing flexed to include actually "losing" engine due to same. Wing and aircraft survived regardless. Best regards, RA1 Here is video of the 777 wing being tested to destruction, and failing at 154% of design limit. https://www.youtube.com/watch?v=Ai2HmvAXcU0 I first saw this on a business visit to the Paris headquarters of Dassault Systemes, a Dassault Aviation spinoff that makes the software used by Boeing (and Airbus) to design their aircraft. They were showing it to me to make the point that their structural analysis software, used in designing the structure, accurately predicted the wing failure modes to within a whisker of where it actually did fail in this physical test. MsAnn 1 Quote Link to comment Share on other sites More sharing options...
AdamSmith Posted March 13, 2016 Author Share Posted March 13, 2016 Aha! And here is the 787 test: Quote Link to comment Share on other sites More sharing options...
Members MsGuy Posted March 13, 2016 Members Share Posted March 13, 2016 That's all well and good but I suspect that if I were to look out my window and see the wings flapping away at anywhere near design limits, I wouldn't be able to finish my drink for the stench of poop wafting out of the pilot's cabin. MsAnn and AdamSmith 2 Quote Link to comment Share on other sites More sharing options...
AdamSmith Posted March 13, 2016 Author Share Posted March 13, 2016 That's all well and good but I suspect that if I were to look out my window and see the wings flapping away at anywhere near design limits, I wouldn't be able to finish my drink for the stench of poop wafting out of the pilot's cabin. And what thread would be complete without... Quote Link to comment Share on other sites More sharing options...
AdamSmith Posted March 13, 2016 Author Share Posted March 13, 2016 P.S. RA1 can correct if I'm wrong, but I believe it IS possible to tear the wings off by putting the aircraft into a powered dive. I think this can create aerodynamic stresses beyond the structural failure point. Quote Link to comment Share on other sites More sharing options...
Members MsGuy Posted March 13, 2016 Members Share Posted March 13, 2016 I'm no engineer, AS, but I would think that the point of maximum stress would occur when you tried to pull out of the dive. You know, when the wings are trying to change direction but the fuselage is doing its damnedest to continue on course. Quote Link to comment Share on other sites More sharing options...
AdamSmith Posted March 13, 2016 Author Share Posted March 13, 2016 I'm no engineer, AS, but I would think that the point of maximum stress would occur when you tried to pull out of the dive. You know, when the wings are trying to change direction but the fuselage is doing its damnedest to continue on course. Well, you made me look it up. Googling just now reveals that when a plane reaches its certified "Vne" ("never-exceed speed"), the least added stress such as a slight bump of turbulence is enough to push the airframe past its structural limits. So in a sense you're right, but it need not be a maneuver or motion remotely as severe as what you depicted. Quote Link to comment Share on other sites More sharing options...
Members RA1 Posted March 14, 2016 Members Share Posted March 14, 2016 Many aircraft have exceeded Vne without harm. However, whenever this happens the pilot becomes a test pilot. Virtually everything that happens after exceeding this speed is theoretical (even though one might live to talk about one's own experience doing so). You might be interested to know that the MU-2 (Mitsubishi turbo-prop) was often flown at well over Vne in descents when cargo pilots late at night were headed for the barn (in a hurry to get home). I have heard tell of 350 KIAS (knots indicated airspeed) which is 55 knots over Vne. Various models of the Lear Jet have had what many called a "go fast" switch which interrupted the software designed to alert the pilot of over speed as well as counter act it if continued. Earlier Part 23 aircraft were certified to withstand 35 feet per second vertical gusts and later Part 23 50 feet per second. I have often thought that pilots who came to grief during an encounter with a thunderstorm did so by "giving up" and over stressing the airframe or wings at some point. However, a strong enough storm will do it regardless. Best regards, RA1 OneFinger and AdamSmith 2 Quote Link to comment Share on other sites More sharing options...
AdamSmith Posted March 15, 2016 Author Share Posted March 15, 2016 I'm no engineer, AS, but I would think that the point of maximum stress would occur when you tried to pull out of the dive. You know, when the wings are trying to change direction but the fuselage is doing its damnedest to continue on course. "The dive speed is the absolute maximum speed above which the aircraft must not fly. Typically, to achieve this speed, the aircraft must enter a dive (steep descent), as the engines cannot produce sufficient thrust to overcome aerodynamic drag in level flight. At the dive speed, excessive aircraft vibrations develop which put the aircraft structural integrity at stake." http://theflyingengineer.com/tag/overspeed/ Quote Link to comment Share on other sites More sharing options...
Members RA1 Posted March 15, 2016 Members Share Posted March 15, 2016 Dive speed. Not a normal US term in this sense but again, a theoretical number. The quoted text is about the A320 and does not necessarily apply to any other aircraft. You might be interested in looking up the Airbus "chainsaw" which was an early aircraft used to demonstrate such as the "normal law" which through software precluded the aircraft from exceeding various parameters. Either no one knows for sure or no one is willing to admit that possibly the test pilot or demo pilot disabled part of the normal law (because the aircraft was making unusual maneuvers near the ground when the normal law would assume an imminent landing) and managed to plow through trees at the end of a runway thus earning a perhaps undeserved nickname. Many aircraft will exceed the speed of sound in level flight or the max "approved" speed, although most are not airliners. I once listened to a senior Boeing captain complain about his FO (First Officer) who left the autopilot in Mach hold during a descent. Using indicated airspeed to using indicated Mach occurs in the mid-20,000 foot range. If the TAS (True Air Speed) at altitude is say 0.80 Mach, one can easily calculate that near sea level that same air speed will be about 480 knots indicated. Just a tad over the MMO (Max operating speed) of say 325 knots indicated. Best regards, RA1 AdamSmith 1 Quote Link to comment Share on other sites More sharing options...
