# "Catastrophic Mechanical Failure" my ass. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [November 14, 2001, 8:14am UTC](https://boards.straightdope.com/t/catastrophic-mechanical-failure-my-ass/93289 "2001-11-14T08:14:34Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 15, 2001, 1:08pm UTC](https://boards.straightdope.com/t/catastrophic-mechanical-failure-my-ass/93289/21 "2001-11-15T13:08:08Z")
> [@](#): > > \*Originally posted by rsa \* > **Maybe because engines are _designed_ to detach under certain circumstances. Those huge engines are attached with 4 - 5 bolts the size of your pinky. They are designed to shear off if sufficient torque is applied. This is so that if an engine seizes, the gyroscopic torque doesn’t rip a section of the wing off.** This seems really odd, considering that I saw engineers from Boeing (who did not make the plane, I know) say that most all two-engined planes of this type could not fly anyhow with one engine, as the plane would be too unbalanced to possibly be controlled. If that was true, why would the engines be designed to shear off? And I’m not arguing that they are not designed to do so. I just wonder why bother, if the plane will crash anyhow? ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 15, 2001, 1:53pm UTC](https://boards.straightdope.com/t/catastrophic-mechanical-failure-my-ass/93289/22 "2001-11-15T13:53:46Z")
> [@](#): > > All I can say is that the explanation for TWA 800, the Swissair flight, and this one all seem…well, they set off my Suspicion Detector right away. I thought it had to be a bomb, too. But as I recall, the investigation found no evidence of one. It’s been a while since the news carried day-by-day coverage, but I remember hearing the experts explain the properties of metal that was subjected to a bomb blast and that they said they found no such properties in the wreckage. They also found no residue consistent with a bomb or any bomb parts. Some eyewitnesses say the aircraft just blew up, and other say they saw it hit with a missile (launched by the Navy). But eyewitnesses are notoriously unreliable. In the case of non-pilots seeing a crash, different people often see different things; and they are often unable to tell what an aircraft is doing. Beside that, if it wasn’t frayed wiring, then was it a bomb or was it a missile? People claim to have _seen_ a missile. But people have claimed to have seen Bigfoot too. The problem is that proving a negative is often difficult, especially when people get it in their heads that something other than “the official line” happened. In the case of TWA 800, there is no evidence of a bomb. There _is_ evidence that frayed wiring in a mostly empty fuel tank caused a spark that ignited the vapours. But once the public get it into their heads that there _was_ a bomb, then suddenly it’s a cover-up. And if it wasn’t the wiring, then is it a bomb, or a missile? There are believers in both camps. If the NTSB claims it was an electrical failure, then obviously the goverment is covering up the Truth. It becomes a Conspiracy Theory. There is no evidence that Apollo I or Apollo XIII were destroyed by bombs. They were both destroyed by frayed wiring. Or _were_ they? Maybe the Russians were trying to sabotage our attempts to fly to the moon? Given the lack of evidence that TWA 800 was brought down by a bomb, I’ll go with the official report that was published after many, many hours of investigation including metalurgical and chemical analysis. As for the recent crash, the evidence so far is pointing to some sort of structural failure. According to NPR yesterday, this same aircraft was involved in another incident of flying into wake turbulence or other turbulence a while ago in which passengers were injured. One would assume that it was inspected for damage. But damage could be missed. There are plenty of examples of things such as bridges, engine turbines or propellers that have had impurities invisible during inspection that cause catastrophic failures. Heck, the _Titanic_ seems now to have sunk because of substandard rivets. Two instances of wake turbulence on takeoff should _not_ have cause the Airbus to crash. Its structure _may_ have been weekened by the earlier encounter, but it _shouldn’t_ have been. Airplanes are designed with such things in mind. But as an engineer, you know that things don’t always happen as they should. Sometimes our best machines, even airplanes, break unexpectedly. Feces occurs. I’m not ruling out a bomb because the investigation has not been concluded; but so far the evidence points to a catastrophic structural failure, the cause of which has yet to be determined, not involving an explosive device. ---
**Author:** ![rsa](https://avatars.discourse-cdn.com/v4/letter/r/839c29/32.png) [@rsa](https://boards.straightdope.com/u/rsa)\ **Post date:** [November 15, 2001, 2:25pm UTC](https://boards.straightdope.com/t/catastrophic-mechanical-failure-my-ass/93289/23 "2001-11-15T14:25:00Z")
> [@](#): > > \*Originally posted by Anthracite \* > This seems really odd, considering that I saw engineers from Boeing (who did not make the plane, I know) say that most all two-engined planes of this type could not fly anyhow with one engine, as the plane would be too unbalanced to possibly be controlled The FAA requires that all passenger jets be certified to fly with the loss of an engine. Perhaps the Boeing engineers were referring to an engine separation during takeoff which is a pretty problematic situation. From this [Q&A on Airbus Engines](http://news.bbc.co.uk/hi/english/world/americas/newsid_1654000/1654124.stm): > [@](#): > > Q: Are they designed to come off in an emergency? > > A: Yes. Each engine is fitted with two “sacrificial” pins which are deliberately designed to break off cleanly so that an aircraft can lose an engine without the wing being damaged. > > Q: Can a plane fly if one engine falls off? > > A: Yes. Twin-engined aircraft are designed to be able to fly on one engine. Simulating a takeoff with only one engine is part of a pilot’s regular six-monthly flight training. However, there could be problems if the wing control surfaces, hydraulic systems or some other part of the aircraft was also damaged. [Previous page](https://boards.straightdope.com/t/catastrophic-mechanical-failure-my-ass/93289.md?page=1)