jbmitt
Posts: 494
Joined: Fri Jan 18, 2002 3:59 am

Aerial Break-up Of An Aircraft

Sun Feb 24, 2002 6:13 pm

I just read an article, and it suggested, that of the two planes that crashed into the WTC. That one of them was flying so fast that it was in danger of breaking apart. What sort of speeds, would a plan de-sinegrate at? And any info on specific models?
 
Arsenal@LHR
Posts: 7510
Joined: Tue Mar 20, 2001 2:55 am

RE: Aerial Break-up Of An Aircraft

Sun Feb 24, 2002 11:16 pm

I'm no expert on structural engineering on planes, but exceeding the designated speed would break up any commercial airliner doing excessive speeds. Remember Egyptair flight 990, some people claimed it was flying at 700 mph went it crashed and that the fuselage broke in flight. UA 175 was doing 575 mph at 1000 feet, suprised it didn't break up.

Arsenal@LHR
In Arsene we trust!!
 
BWIrwy4
Posts: 877
Joined: Thu Nov 15, 2001 1:41 pm

RE: Aerial Break-up Of An Aircraft

Mon Feb 25, 2002 4:03 am

The PSA hijack/suicide in 1988 broke up after going supersonic
 
UPS763
Posts: 195
Joined: Wed Nov 14, 2001 7:00 am

RE: Aerial Break-up Of An Aircraft

Mon Feb 25, 2002 4:12 am

Not very clear on this subject, but could anyone shed light on the I believe it was China Airlines, a 747 SP that supposedly exceeded the sound barrier in a dive and recovered.

Thanks

Matt
 
airsicknessbag
Posts: 4626
Joined: Thu Aug 17, 2000 2:45 am

RE: Aerial Break-up Of An Aircraft

Mon Feb 25, 2002 10:33 pm

A Lufthansa 720 disintegrated in midair after doing a roll (!) in the early sixties.
Daniel
 
aerosol
Posts: 497
Joined: Mon Oct 23, 2000 10:31 pm

RE: Aerial Break-up Of An Aircraft

Mon Feb 25, 2002 10:45 pm

OT:
On pprune I read that the Lufthansa bird did not disintegrate, but had severe flap-damage. It was sad that the Lufthansapilot tried to copy a barrel roll which was performed in a test flight of a 707, but exceeded the max. g-force restrictions.
I would really like to see a video of a 707 doing a roll.
 
airsicknessbag
Posts: 4626
Joined: Thu Aug 17, 2000 2:45 am

RE: Aerial Break-up Of An Aircraft

Mon Feb 25, 2002 10:53 pm

Interesting. This is from the aviation-safety.net´s accident description: "A complete roll was flown, but while attempting a second roll, the plane went out of control in the inverted position. The Boeing became overstressed, disintegrated in flames." I wonder whether it was found out what happened.
Daniel
 
doug_or
Posts: 3127
Joined: Sat Mar 18, 2000 9:55 am

RE: Aerial Break-up Of An Aircraft

Mon Feb 25, 2002 11:09 pm

last reading from the black box on a COPA 737 that dove/spun out of control was in the 575 kts range. I would assume it broke up then if no more reading were recovered.
When in doubt, one B pump off
 
NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

RE: Aerial Break-up Of An Aircraft

Tue Feb 26, 2002 9:33 am

Ups763,
That 747 you mentioned had a problem (can't remember what exactly) that caused it to go into that dive, and you're right, it did go supersonic.
As I understand it, the 747 is certified to go supersonic to cover such an eventuality as will be the Sonic Cruiser.
Aircraft landed safely at SFO.
 
travatl
Posts: 1943
Joined: Sat Mar 03, 2001 4:57 pm

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 4:28 am

A Northwest Boeing 720 enroute from Miami to Chicago broke up over the Everglades in 1963 while attempting to recover from a turbulence induced dive. The aircraft's IAS exceeded 470 knots whiile in the 95 degree dive.

Travis
 
757man
Posts: 355
Joined: Sun Feb 11, 2001 6:59 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 4:38 am

I understand that the near legendary Vickers VC10 broke the sound barrier on more than one occasion - by pure accident. The RR Conways were supposed to be 'twitchy' to control and pilots used to take great care with them. However, some pilots who were new to the type didn't take as much care. None of these a/c were lost, but if you look at the wing design of them, you can probably see why they could go past the sound barrier.
 
crewchief32
Posts: 413
Joined: Wed Dec 20, 2000 3:16 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 4:57 am

Some airliners did not disintegarte in midair by excessive speed but due to mechanical failure, like the Braniff L-188 N9705C on Sept. 29th, 1959 or the NWA L-188 N121US on March 17th, 1960.

CC32
 
heavymetal
Posts: 4443
Joined: Fri May 08, 2015 3:37 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 5:01 am

Now I read it was estimated that UA 175 was doing just over normal cruise speed.....however, if I'm not mistaken, what might be normal at 35,000 feet is in fact much more perilous in the lowest altitudes. Is that not correct?
 
fanofjets
Posts: 1980
Joined: Thu Apr 13, 2000 2:26 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 5:17 am

To my knowledge, the only commercial airliner to exceed the sound barrier (except, of course, for the Concorde and Tu-144) was a DC-8-40 during a shallow dive. The flight with the RR Conway powered 'eight occurred in the early 1960s during a test flight; the plane was delivered to Canadian Pacific.

Click for large version
Click here for full size photo!

Photo © Bill ARMSTRONG



The issue is not so much speed as stress on the airframe encountered when the pilot tried to regain control of the plane. Two incidents come to mind: the China Airlines 747SP-09 and a 727-200 (I believe TWA); both aircraft sustained damage while coming out of a dive. Thankfully, both aircraft landed safely.

Click for large version
Click here for full size photo!

Photo © Peter Vercruijsse


The aeroplane has unveiled for us the true face of the earth. -Antoine de Saint-Exupery
 
NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 5:38 am

"however, if I'm not mistaken, what might be normal at 35,000 feet is in fact much more perilous in the lowest altitudes. Is that not correct?"

Yep,that's correct Heavymetal, partly due to the higher air density and therefore higher resistance at lower altitudes!  Smile

 
heavymetal
Posts: 4443
Joined: Fri May 08, 2015 3:37 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 5:44 am

thanks NZ!

(BTW your homeland looks amazing in the LOTR film)
 
NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 5:50 am

Oh Cool.....
I did a bit of work for that movie...most of it was shot around here but I haven't even seen it yet.
Son's seen it twice! Big grin
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: Aerial Break-up Of An Aircraft

Wed Feb 27, 2002 6:58 am

All airliners have different speed limits at different altitudes. In any case a hefty safety margin is built into these speed limits so they can handle severe turbulence without structural damage or extreme discomfort for the pax.

The morning of 9/11 must have been rather turbulence free. Therefore even an extreme violation of speed limits would hardly mean structural failure.

Approaching sonic speed is, however, an entirely different type of animal. No airliner - including the Concorde - would survive that in the dense air at low altitude.

If memory treats me well, then the Concorde limit is 340 kts. IAS at low altitude.

Regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs