c5load From United States of America, joined Sep 2008, 917 posts, RR: 0 Posted (3 years 1 month 2 weeks 11 hours ago) and read 9569 times:
Watching "United 93" the other day (RIP), it showed the 757 cockpit going inverted, so I can only assume that to be true. Were the passengers just simply unable to recover in time or once a plane like that goes inverted, is it impossible to recover no matter how much time they have?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
stratosphere From United States of America, joined Sep 2007, 1614 posts, RR: 4 Reply 1, posted (3 years 1 month 2 weeks 11 hours ago) and read 9558 times:
Tex Johnston Boeing chief test pilot for the 707 did a barrel roll in a 707 in a demo flight over Lake Washington
ual747 From , joined Dec 1969, posts, RR: Reply 2, posted (3 years 1 month 2 weeks 11 hours ago) and read 9549 times:
Anything can fly inverted for a certain amount of time, given enough propulsion. In fact, anything can fly as long as there is enough energy propelling it forward and up.
But to answer your question:
Yes, it can, but structurally it would begin to fail, along with all of the fuel lines/hydraulic lines which rely on gravity for some functions.
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 3, posted (3 years 1 month 2 weeks 10 hours ago) and read 9467 times:
Recovery is certainly possible given enough altitude and assuming the aircraft does not exceed structural limits. UA93 was either too close to the ground and/or going too fast to recover, or the pax simply didn't have the skillset required.
"Simple" inverted flight (just flying along upside down) should be fine structurally, but as mentioned gravity dependent systems like fuel and possibly lubrication would mean the engines would eventually stop. Also, negative g limits are lower than positive g limits, so the risk of structural failure is higher.
Tex Johnston did a barrel roll, meaning the aircraft was in a one g condition the whole time. In essence, the aircraft did not
"know" that it was inverted.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
chrisjw From United States of America, joined Jan 2009, 114 posts, RR: 0 Reply 4, posted (3 years 1 month 1 week 6 days 15 hours ago) and read 8975 times:
I thought I read on here that the 777 went inverted during it's certification flight testing when it was doing stalls. I may be wrong though.
alaska737 From United States of America, joined Feb 2006, 1056 posts, RR: 6 Reply 5, posted (3 years 1 month 1 week 6 days 13 hours ago) and read 8850 times:
Debbie Rihn Harvey flew a Southwest 737 inverted, I have no idea how long, but I did see the picture.
747400sp From United States of America, joined Aug 2003, 3301 posts, RR: 2 Reply 7, posted (3 years 4 weeks 1 day 11 hours ago) and read 7635 times:
I believe a Fed EX DC10 30 flew inverted when the second officer tried to kill him self and the crew. The Captain had to fly the DC10 like a fighter jet to blow the second officer plot.
RoseFlyer From United States of America, joined Feb 2004, 8754 posts, RR: 52 Reply 8, posted (3 years 4 weeks 1 day 9 hours ago) and read 7593 times:
Quoting ual747 (Reply 2): Anything can fly inverted for a certain amount of time, given enough propulsion. In fact, anything can fly as long as there is enough energy propelling it forward and up.
If a modern jet (with the exception of the 787) flies inverted, the hydraulic system will fail rather quickly since it is a pressurized gravity system that uses air pressure to supply hydraulic fluid. When inverted, the hydraulic pumps will cavitate and fail within minutes.
Depending on fuel quantity, fuel may fail since gravity is required.
The last system to fail will be engines and IDG/APU as they use a scavenge system for oil that does require gravity.
Military aircraft have additional scavenge pumps and different reservoir pressurization so that they will not fail when inverted. Fuel systems use a different type of fuel pump as well.
If you have never designed an airplane part before, let the real designers do the work!
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 10, posted (3 years 4 weeks 9 hours ago) and read 7107 times:
Quoting 747400sp (Reply 7): I believe a Fed EX DC10 30 flew inverted when the second officer tried to kill him self and the crew. The Captain had to fly the DC10 like a fighter jet to blow the second officer plot.
Zkpilot From New Zealand, joined Mar 2006, 4739 posts, RR: 10 Reply 11, posted (3 years 3 weeks 6 days 23 hours ago) and read 6992 times:
Quoting HAWK21M (Reply 10): Quoting 747400sp (Reply 7):
I believe a Fed EX DC10 30 flew inverted when the second officer tried to kill him self and the crew. The Captain had to fly the DC10 like a fighter jet to blow the second officer plot.
Whats this story about?.
regds
MEL.
An engineer who had been stood down managed to jumpseat on that flight. He had weapons with him (I think hammer/axe) that he used to hit the FO then the Capt. The Capt then made some abrupt control manuevers that sent the engineer flying out of the flight deck where the FO and I think at one stage the Capt also struggled with him. They eventually managed to land the plane and have police arrest the Engineer.
The whole incident is on 'Air Crash Investigation' (Nat Geo).
Ok this link explains it better: http://en.wikipedia.org/wiki/FedEx_Flight_705
Season 3 Episode 4
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 12, posted (3 years 3 weeks 6 days 20 hours ago) and read 6893 times:
When aircraft fly inverted they do so with a very high angle of attack (AOA) so the wing can create lift.
Since airlines have very little elevator movement in the down direction (aircraft nose down) I don't think you could get the AOA high enough to allow the wing to create the required lift.
flybaurLAX From United States of America, joined Oct 2008, 634 posts, RR: 0 Reply 13, posted (3 years 3 weeks 6 days 19 hours ago) and read 6875 times:
Quoting 474218 (Reply 12): Since airlines have very little elevator movement in the down direction (aircraft nose down) I don't think you could get the AOA high enough to allow the wing to create the required lift.
A 737-700 will fly upside down, but it will lose altitude pretty fast, and unless you drop the gear the airspeed will increase pretty quickly.
Mastropiero From Spain, joined Dec 2005, 121 posts, RR: 0 Reply 14, posted (3 years 3 weeks 6 days 19 hours ago) and read 6863 times:
Quoting flybaurLAX (Reply 13): Since airlines have very little elevator movement in the down direction (aircraft nose down) I don't think you could get the AOA high enough to allow the wing to create the required lift.
I don´t think I agree. The only way to increase AOA, as far as I know, is elevator up. Air doesn´t care whether you´re flying through it upside down or not, it will work the same way. The only difference is that when you´re flying normal, lift goes against gravity, whereas upside down lift goes towards it, hence you would lose altitude...... I hope I got my facts right, I am a complete "aficionado", so be kind to me if I´m wrong....
Mastropiero From Spain, joined Dec 2005, 121 posts, RR: 0 Reply 16, posted (3 years 3 weeks 6 days 18 hours ago) and read 6841 times:
Quoting 474218 (Reply 15): If your upside down, down becomes up and up becomes down.
Lol, yeah, I got the basics of that one figured out. However, in order to increase the AOA, you still need to pull back on your stick/yoke, thus commanding "elevator up".
I assume you are thinking that in order to increase the AOA you have to point the nose towards the sky?? That´s the only sense I make out of your sentence:
Quoting 474218 (Reply 12): Since airlines have very little elevator movement in the down direction (aircraft nose down)
I repeat, air doesn´t know whether you are upside down or not. It will meet the wings in the same way, and it will behave the same way. It doesn´t matter if "up becomes down" or not.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 17, posted (3 years 3 weeks 6 days 18 hours ago) and read 6829 times:
Quoting Mastropiero (Reply 16): Lol, yeah, I got the basics of that one figured out. However, in order to increase the AOA, you still need to pull back on your stick/yoke, thus commanding "elevator up".
I assume you are thinking that in order to increase the AOA you have to point the nose towards the sky?? That´s the only sense I make out of your sentence:
Yes you have to increase the AOA to fly inverted, point the nose to the sky and when you are inverted you increase the AOA by pushing the column/stick forward.
MD11Engineer From Germany, joined Oct 2003, 13343 posts, RR: 64 Reply 18, posted (3 years 3 weeks 6 days 18 hours ago) and read 6821 times:
Quoting RoseFlyer (Reply 8): If a modern jet (with the exception of the 787) flies inverted, the hydraulic system will fail rather quickly since it is a pressurized gravity system that uses air pressure to supply hydraulic fluid. When inverted, the hydraulic pumps will cavitate and fail within minutes.
Possibly not on Douglas aircraft, since they use a hydraulic reservoir design pressurized by hydraulic pressure itself through a bootstrap piston system. There is no (or should be no) air in the reservoir. On Boeings and Airbi I concur.
HaveBlue From United States of America, joined Jan 2004, 2069 posts, RR: 1 Reply 19, posted (3 years 3 weeks 6 days 11 hours ago) and read 6716 times:
Quoting c5load (Thread starter): Were the passengers just simply unable to recover in time or once a plane like that goes inverted, is it impossible to recover no matter how much time they have?
The way I remember it is that when the terrorists realized the passengers were about to breach the door the lead terrorists said to put it down. They knew they were about to get overrun and decided to suicide it into the ground instead of fighting with and possibly losing against the passengers. That's the way I remember it but I may be wrong.
So anotherwords in my version the terrorists intentionally flew it into the ground as they were aware the passengers had overtaken the bad guys in the back and were trying like hell to get into the cockpit.
soon7x7 From United States of America, joined May 2006, 2802 posts, RR: 14 Reply 20, posted (3 years 3 weeks 6 days 9 hours ago) and read 6682 times:
I can't see an intentional sustained inverted flight possible as the fuel scavenge pumps are located at the bottom of the tanks which would now be on the top...fuel starvation would result...in addition the angle of attack would be so radical, the wing design (critical wings) could not sustain it...I would also be concerned about angle of attack where the engine nacelles are concerned...it might cause compressor stalls...
Flight 93 was an inverted dive as many aircraft out of control have a tendancy to roll onto their backs...
Test Johnstons roll is about as close as I imagine you could get...even a 747 could execute that maneuver but sustained?...I don't think so...
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 21, posted (3 years 3 weeks 6 days 9 hours ago) and read 6668 times:
Tex Johnston performed a barrel roll. This means that the aircraft is experiencing more or less 1 g towards the "floor" all the way through, even when upside down. So fuel pumps and lubrication work as normal.
As soon 7x7 says this is not the same as sustained inverted flight.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
CPH-R From Denmark, joined May 2001, 5746 posts, RR: 4 Reply 22, posted (3 years 3 weeks 6 days ago) and read 6602 times:
The hhead of QI did a barrel roll with an empty ATR over SGD a couple of years ago. A spotter caught it on camera and all hell broke lose, courtesy of the tabloids: http://jp.dk/uknews/article1699863.ece
3MilesToWRO From Poland, joined Mar 2006, 266 posts, RR: 0 Reply 23, posted (3 years 3 weeks 5 days 22 hours ago) and read 6559 times:
Quoting Mastropiero (Reply 16):
Lol, yeah, I got the basics of that one figured out. However, in order to increase the AOA, you still need to pull back on your stick/yoke, thus commanding "elevator up".
No. As long as we talk about stable flight upside down you all the time must have leading edge higher than trailing edge. And "higher" is related to Earth surface, not to aircraft floor. Which means that flying inverted you must reverse the trim. The tail must pull down to Earth, so in inverted flight it must be commanded what normally would be named "nose down".
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 24, posted (3 years 3 weeks 5 days 21 hours ago) and read 6538 times:
Quoting MD11Engineer (Reply 18): Possibly not on Douglas aircraft, since they use a hydraulic reservoir design pressurized by hydraulic pressure itself through a bootstrap piston system. There is no (or should be no) air in the reservoir. On Boeings and Airbi I concur.
Boeing has switched to bootstrap hydraulics for 787.
Tom.
25 Mastropiero: Thanks, I understand it now. I got somehow confused..... this leads to another question. Assuming, for a moment, that you can indeed command enough "
26 Zkpilot: negative.... your subsequent comment is more like it. You have to push forward (what would normally be down) when inverted to have a higher AoA...ie
27 vikkyvik: Not to nitpick ( ), but when you're talking about AOA, then you're talking about an angle relative to the freestream flow, not the Earth.
28 tdscanuck: Yes. The slope of the Cl vs. AoA curve is almost completely independent of the exact airfoil (assuming a clean wing here)...it's always going to be a
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