Supersonic 747
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for what it's worth (and i'm not comparing the two machines) they pushed the a380 to M0.937 during the testing. and that's where they stopped.
i guess it took a lot of breakers being pulled out...
seb
i guess it took a lot of breakers being pulled out...
seb
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Regarding 747 (supersonic)
If you put a 747 into a fairly steep nose down attitude, you might be able to achieve a speed higher than mach .85 which is its cruise speed, but the wings and airframe were never designed to withstand those kinds of speeds. The airfoil is considered " subsonic" which means that it flies optimally below the speed of sound. I expect if you attempted to fly it beyond its specified design parameters, the wings would buffet violently, creating tremendous drag and possible structural deformation if it continued unabated. For an airplane to come close to the speed of sound (transonic) or beyond the speed of sound (supersonic) the airfoil must, among many other factors, have a high degree of sweep - like the Concorde. The airfoils currently on all modern jetliners, as remarkably advanced and efficient as they are, are simply not designed to deal with those kinds of speeds. They fly most efficiently between speeds of mach .74 and mach .85. Hope that helps you out!!!
---I would think think the failure mode would be flutter or divergence, as the 747 exhibited a Mdf of M 0.998 [flown by the OEM] so it does have a controllability at high Mach numbers.
as mentioned above the DC-8 was the first civilian airliner to go sonic [which is actually extends a little above Mach 1.000]. this was done in a high speed dive from 50000 ft. in {I believe ] 1953
The Boeing 727 also had an interesting excursion to Mach 1.?? after someone tried to emulate Ol' Tex
as mentioned above the DC-8 was the first civilian airliner to go sonic [which is actually extends a little above Mach 1.000]. this was done in a high speed dive from 50000 ft. in {I believe ] 1953
The Boeing 727 also had an interesting excursion to Mach 1.?? after someone tried to emulate Ol' Tex
Psychophysiological entity
I was just going to mention that. When they dumped the gear, the passing breeze modified the airframe. Just shows what one is up against when you try to get home early.
I flew past Geneva one day, and anouced to my pax that we had a ground speed greater than the speed of sound at our height. I wonder if there was one SOB that understood.
I flew past Geneva one day, and anouced to my pax that we had a ground speed greater than the speed of sound at our height. I wonder if there was one SOB that understood.
Thread Starter
18W, were you flying right-seat when you took that photo?
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Correct me if I am wrong, but in a normal cruise on the 747 doesn't the big hump at the front travel supersonically anyway? I believe the pronounced camber of the upper deck at that point results in the air above it travelling supersonically...
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The quoted Mdf of 0.998 for the 747 makes me smile.
First because it's only about 1 kt below Mach 1, secondly because an accuracy of 0.2% so close to Mach 1 is unlikely (think Machmeter and VSI "jump").
I would think they probably "hit" Mach 1 and a bit, but didn't want to write that in the final report
Oh, and to add another "airliner" to the Mach 1 club:
The RAF VC10s have the shorter fuselage of the early model VC10, but the more powerful engines of the later models.
It is told (but never confirmed officially AFAIK) that when empty and with most of the fuel burned off, they actually could reach and exceed Mach 1 in level flight at altitude......
Condor66,
I'm afraid you're barking up all the wrong trees.
- Jetliners are designed to withstand that sort of speed. The DC-8 supersonic dive was part of the flight test programme.
They are not designed to operate at that speed, because of the drag rise.
- There is no "tremendous buffet". We left that behind in the '50s.
- You don't need a Concorde-like sweep to reach and exceed Mach 1. The Sabre, the Hunter, the Mig-15 all had 30° to 35° sweep, and all were supersonic in a dive.
- You don't need a "supersonic" airfoil either to go supersonic. The aircraft cited above do not have "supersonic" airfoils, and neither does the DC-8.
First because it's only about 1 kt below Mach 1, secondly because an accuracy of 0.2% so close to Mach 1 is unlikely (think Machmeter and VSI "jump").
I would think they probably "hit" Mach 1 and a bit, but didn't want to write that in the final report
Oh, and to add another "airliner" to the Mach 1 club:
The RAF VC10s have the shorter fuselage of the early model VC10, but the more powerful engines of the later models.
It is told (but never confirmed officially AFAIK) that when empty and with most of the fuel burned off, they actually could reach and exceed Mach 1 in level flight at altitude......
Condor66,
I'm afraid you're barking up all the wrong trees.
- Jetliners are designed to withstand that sort of speed. The DC-8 supersonic dive was part of the flight test programme.
They are not designed to operate at that speed, because of the drag rise.
- There is no "tremendous buffet". We left that behind in the '50s.
- You don't need a Concorde-like sweep to reach and exceed Mach 1. The Sabre, the Hunter, the Mig-15 all had 30° to 35° sweep, and all were supersonic in a dive.
- You don't need a "supersonic" airfoil either to go supersonic. The aircraft cited above do not have "supersonic" airfoils, and neither does the DC-8.
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secondly because an accuracy of 0.2% so close to Mach 1 is unlikely
Melax, I think I know the incident you're speaking about???
a 727 departed controlled flight and entered a high speed upset, due to a TS encounter---but I don't know more--- i hope someone can enlighten us both further on the flight----in the same incident, I also believe and the had to wait until a much lower altitude to regain control due to high Mach or stab jamming??----sure seems people love to pull 'Chuck Yeagers' with the 727, however she's a tough one
jets can easily be pushed to their or past Vdf value while in a gentle climb at relatively low altitudes or---- way past Mmo to perhaps very close to Mdf at higher levels on thrust alone no dive needed!!!
Merry Christmas y Feliz Navidad, Happy Chanukah, Happy Kwanza---To all the wonderful contributers on Pprune---PA
a 727 departed controlled flight and entered a high speed upset, due to a TS encounter---but I don't know more--- i hope someone can enlighten us both further on the flight----in the same incident, I also believe and the had to wait until a much lower altitude to regain control due to high Mach or stab jamming??----sure seems people love to pull 'Chuck Yeagers' with the 727, however she's a tough one
jets can easily be pushed to their or past Vdf value while in a gentle climb at relatively low altitudes or---- way past Mmo to perhaps very close to Mdf at higher levels on thrust alone no dive needed!!!
Merry Christmas y Feliz Navidad, Happy Chanukah, Happy Kwanza---To all the wonderful contributers on Pprune---PA
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Mach .95 in a 744 a couple of years ago in mountain wave with the thrust levers at idle. Didn't cause any handling problems but the buffet noise above the flightdeck was rather alarming!
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Originally Posted by Condor66
For an airplane to come close to the speed of sound (transonic) or beyond the speed of sound (supersonic) the airfoil must, among many other factors, have a high degree of sweep
PBL
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The Pacific Southwest Airlines (PSA) BAe146 (reg: N350PS) achieved M1.2 before it broke up follwing a dive from 29 000ft to 13 000ft. This was the terrible hijacking in December 1987 when a disgruntled ex-employee shot both pilots and put the aircraft into a steep dive which killed all 44 people onboard.
