Can strong jet stream push Boeing 777 supersonic?
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Originally Posted By: Cujet
Interestingly enough, it seems there are reports that the fastest corporate jets today have, in testing, slightly exceeded M1, at least in local area flow. Both the Cessna Citation X (10) and the Gulfstream G650 are said to have exceeded M1 in a dive. This was done for certification purposes. There were even reports of a G550 reaching M1.07 in a dive.
Not with me onboard, thanks...
Any time that you're over about 0.92 IMN, there will be local supersonic flow. The path around the fuselage, over wing roots, etc. will add to the relative motion of the air flowing over the airplane and those critical areas exceed Mach 1. That's why there is such a drag rise at roughly 0.92. Careful design, including a supercritical wing, can delay the onset of local supersonic flow, but it still will happen well below an overall speed of Mach 1.
Interestingly enough, it seems there are reports that the fastest corporate jets today have, in testing, slightly exceeded M1, at least in local area flow. Both the Cessna Citation X (10) and the Gulfstream G650 are said to have exceeded M1 in a dive. This was done for certification purposes. There were even reports of a G550 reaching M1.07 in a dive.
Not with me onboard, thanks...
Any time that you're over about 0.92 IMN, there will be local supersonic flow. The path around the fuselage, over wing roots, etc. will add to the relative motion of the air flowing over the airplane and those critical areas exceed Mach 1. That's why there is such a drag rise at roughly 0.92. Careful design, including a supercritical wing, can delay the onset of local supersonic flow, but it still will happen well below an overall speed of Mach 1.
Originally Posted By: Astro14
Originally Posted By: Cujet
Interestingly enough, it seems there are reports that the fastest corporate jets today have, in testing, slightly exceeded M1, at least in local area flow. Both the Cessna Citation X (10) and the Gulfstream G650 are said to have exceeded M1 in a dive. This was done for certification purposes. There were even reports of a G550 reaching M1.07 in a dive.
Not with me onboard, thanks...
Any time that you're over about 0.92 IMN, there will be local supersonic flow. The path around the fuselage, over wing roots, etc. will add to the relative motion of the air flowing over the airplane and those critical areas exceed Mach 1. That's why there is such a drag rise at roughly 0.92. Careful design, including a supercritical wing, can delay the onset of local supersonic flow, but it still will happen well below an overall speed of Mach 1.
That is quite true. In fact, even at lower speeds around M 0.87, we can occasionally see a shock wave form on top of the wing. It's most visible at sunrise and sunset.
I asked my Gulfstream G650 test pilot friend, and he mentioned that the G650 did indeed break the sound barrier in a dive. Including the sonic boom to ground observers.
The official report is as follows: In order to achieve the maximum speed of Mach 0.995, Gulfstream experimental test pilots Tom Horne and Gary Freeman along with flight test engineer Bill Osborne took Serial Number (S/N) 6001 into a dive, pitching the aircraft’s nose 16 to 18 degrees below the horizon. During the dive, flutter exciters introduced a range of vibration frequencies to the wing, tail and flight control surfaces to ensure the aircraft naturally dampened out the oscillations without further action from the pilots. Even under such extreme circumstances, the G650 performed flawlessly.
The sonic booms tells another story...
Originally Posted By: Cujet
Interestingly enough, it seems there are reports that the fastest corporate jets today have, in testing, slightly exceeded M1, at least in local area flow. Both the Cessna Citation X (10) and the Gulfstream G650 are said to have exceeded M1 in a dive. This was done for certification purposes. There were even reports of a G550 reaching M1.07 in a dive.
Not with me onboard, thanks...
Any time that you're over about 0.92 IMN, there will be local supersonic flow. The path around the fuselage, over wing roots, etc. will add to the relative motion of the air flowing over the airplane and those critical areas exceed Mach 1. That's why there is such a drag rise at roughly 0.92. Careful design, including a supercritical wing, can delay the onset of local supersonic flow, but it still will happen well below an overall speed of Mach 1.
That is quite true. In fact, even at lower speeds around M 0.87, we can occasionally see a shock wave form on top of the wing. It's most visible at sunrise and sunset.
I asked my Gulfstream G650 test pilot friend, and he mentioned that the G650 did indeed break the sound barrier in a dive. Including the sonic boom to ground observers.
The official report is as follows: In order to achieve the maximum speed of Mach 0.995, Gulfstream experimental test pilots Tom Horne and Gary Freeman along with flight test engineer Bill Osborne took Serial Number (S/N) 6001 into a dive, pitching the aircraft’s nose 16 to 18 degrees below the horizon. During the dive, flutter exciters introduced a range of vibration frequencies to the wing, tail and flight control surfaces to ensure the aircraft naturally dampened out the oscillations without further action from the pilots. Even under such extreme circumstances, the G650 performed flawlessly.
The sonic booms tells another story...
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What if the 777 had both engines near max RPM/power and a strong jet stream, can it create a sonic boom ?
Jet stream changes ground speed, not air speed.
Sonic boom happens when airspeed is above Mach 1.
At full thrust, the 777 can get close, but it won't go supersonic.
It's hard for people to visualize, but once the airplane is in the air, the ground doesn't really matter. I could be supersonic into a 600 KT headwind, and trucks on the highway would be going faster across the ground than I am.....
Sonic boom happens when airspeed is above Mach 1.
At full thrust, the 777 can get close, but it won't go supersonic.
It's hard for people to visualize, but once the airplane is in the air, the ground doesn't really matter. I could be supersonic into a 600 KT headwind, and trucks on the highway would be going faster across the ground than I am.....
Around here the low altitude winds can be strong enough that, if you pitch the nose up enough, and fly as close as you can to the edge of a stall, you won't have much forward groundspeed.
Might be possible to go backwards in one with a really low stall speed.
Might be possible to go backwards in one with a really low stall speed.
Probably the fastest 747 is Air Force One. It cannot go supersonic, but it can get very close, how close is classified. They want the next AF1 to also be a 747, that says something.
It is supposed to out climb and out accelerate a lot of planes, and I am sure it has some VERY impressive countermeasures. Of course he has some of the best pilots.
I watched Obama leave Joplin twice. Once at the airport and the takeoff roll was pretty short I thought. The other time at my house, about 3 miles from end of runway. The 747 was way higher in altitude than any other plane I have seen. Rolling coal and very noisy. As a side note, there was a black suburban parked at the end of my road and a healthy looking man in a suit with glasses was standing there. I do not think it would have been a good time to target practice.
Since you never give away secrets, the full emergency takeoff roll would probably be very short. The full emergency rate of climb would be pretty impressive too. I understand it can also dive at a very impressive rate.
None of this is scientific just my observations.
It is supposed to out climb and out accelerate a lot of planes, and I am sure it has some VERY impressive countermeasures. Of course he has some of the best pilots.
I watched Obama leave Joplin twice. Once at the airport and the takeoff roll was pretty short I thought. The other time at my house, about 3 miles from end of runway. The 747 was way higher in altitude than any other plane I have seen. Rolling coal and very noisy. As a side note, there was a black suburban parked at the end of my road and a healthy looking man in a suit with glasses was standing there. I do not think it would have been a good time to target practice.
Since you never give away secrets, the full emergency takeoff roll would probably be very short. The full emergency rate of climb would be pretty impressive too. I understand it can also dive at a very impressive rate.
None of this is scientific just my observations.
Originally Posted By: ragtoplvr
I watched Obama leave Joplin twice. Once at the airport and the takeoff roll was pretty short I thought. The other time at my house, about 3 miles from end of runway. The 747 was way higher in altitude than any other plane I have seen. Rolling coal and very noisy. As a side note, there was a black suburban parked at the end of my road and a healthy looking man in a suit with glasses was standing there. I do not think it would have been a good time to target practice.
Since you never give away secrets, the full emergency takeoff roll would probably be very short. The full emergency rate of climb would be pretty impressive too. I understand it can also dive at a very impressive rate.
Not having the weight of a few hundred passengers and their luggage on board probably does wonders for takeoff and climb performance.
I watched Obama leave Joplin twice. Once at the airport and the takeoff roll was pretty short I thought. The other time at my house, about 3 miles from end of runway. The 747 was way higher in altitude than any other plane I have seen. Rolling coal and very noisy. As a side note, there was a black suburban parked at the end of my road and a healthy looking man in a suit with glasses was standing there. I do not think it would have been a good time to target practice.
Since you never give away secrets, the full emergency takeoff roll would probably be very short. The full emergency rate of climb would be pretty impressive too. I understand it can also dive at a very impressive rate.
Not having the weight of a few hundred passengers and their luggage on board probably does wonders for takeoff and climb performance.
A 747 is a 747.
It can't do anything special just because it flies POTUS.
The engines are the same and the wing is the same.
These are the only two things that determine performance.
Any airline operator knows far more about 747 performance than does the Air Force.
Any airline operator has thousands of hours of operating experience with this aircraft for every hour the Air Force flies, and the same is true of the pilots.
It can't do anything special just because it flies POTUS.
The engines are the same and the wing is the same.
These are the only two things that determine performance.
Any airline operator knows far more about 747 performance than does the Air Force.
Any airline operator has thousands of hours of operating experience with this aircraft for every hour the Air Force flies, and the same is true of the pilots.
I thought AF One has radar jamming / warning receivers / chaff, etc... ?
Without hundreds of passengers and luggage any 747 will have an impressive climb rate, also its not carrying max fuel load since it flys short distances to dog and pony shows across the USA.
Without hundreds of passengers and luggage any 747 will have an impressive climb rate, also its not carrying max fuel load since it flys short distances to dog and pony shows across the USA.
Originally Posted By: Win
Around here the low altitude winds can be strong enough that, if you pitch the nose up enough, and fly as close as you can to the edge of a stall, you won't have much forward groundspeed.
Might be possible to go backwards in one with a really low stall speed.
Shortly after I started learning how to fly, I encountered a situation like the one you describe. It started getting pretty windy shortly after takeoff. As we were heading out to the training area I looked down and noticed our ground speed appeared to be pretty fast, at least compared to the 80kts ias. My instructor had me turn 180 degrees and pull the power; sure enough our ground speed dropped to zero. It was pretty fun! It took a while to make it back to the airport in that little 150.
Around here the low altitude winds can be strong enough that, if you pitch the nose up enough, and fly as close as you can to the edge of a stall, you won't have much forward groundspeed.
Might be possible to go backwards in one with a really low stall speed.
Shortly after I started learning how to fly, I encountered a situation like the one you describe. It started getting pretty windy shortly after takeoff. As we were heading out to the training area I looked down and noticed our ground speed appeared to be pretty fast, at least compared to the 80kts ias. My instructor had me turn 180 degrees and pull the power; sure enough our ground speed dropped to zero. It was pretty fun! It took a while to make it back to the airport in that little 150.
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