Ultimate Ground Speed Check: Tales from the Dreamliner

"ttyymmnn" (ttyymmnn) 02/19/2019 at 15:16 • Filed to: wingspan, Planelopnik

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Aided by a 230 mph tailwind, Virgin Atlantic Flight 8, Boeing 787 service from Los Angeles to London, was clocked with a groundspeed of 801 mph 35,000 feet over Pennsylvania, breaking the previous record of 776 mph. Not surprisingly, the Dreamliner arrived at its destination 48 minutes early.

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WilliamsSW > ttyymmnn 02/19/2019 at 15:26

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Meanwhile a westbound A340 is moving backwards...

shop-teacher > ttyymmnn 02/19/2019 at 15:30

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I assume they then sat on the tarmac for an hour or so before getting a gate then, right?

Thomas Donohue > ttyymmnn 02/19/2019 at 15:30

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Flights from NY to Chicago/Seattle/etc must have been miserable going against the ‘streak’.

OPPOsaurus WRX > ttyymmnn 02/19/2019 at 15:31

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so would that produce a sonic boom?

ttyymmnn > shop-teacher 02/19/2019 at 15:32

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That’s actually entirely possible, if their arrival gate was occupied. 

ttyymmnn > Thomas Donohue 02/19/2019 at 15:33

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I don’t know much about that sort of thing, but it’s possible they could have flown beneath it.

For Sweden > ttyymmnn 02/19/2019 at 15:34

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This is how fast I want to leave Pennsylvania.

ttyymmnn > OPPOsaurus WRX 02/19/2019 at 15:35

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No. The WaPo article discusses that a bit, and I’m not an engineer. But my understanding is that while this speed is measured over the ground (ground speed), Mach is a measurement of airspeed, which is the speed of the aircraft relative to the air around it. Since they were being pushed by the wind, they were moving with it. It’s like that old joke about how you can walk faster than an airplane by walking forward in the aisle while the airplane is flying. You are going the speed of the airplane plus the speed of your walking.

HammerheadFistpunch > OPPOsaurus WRX 02/19/2019 at 15:35

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I wouldn’t think so since their airspeed never exceed Mach 1

ttyymmnn > For Sweden 02/19/2019 at 15:35

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Fly right over the potholes.

ITA97, now with more Jag @ opposite-lock.com > OPPOsaurus WRX 02/19/2019 at 15:40

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No. Their airspeed would’ve been far lower. The were moving along in a 230mph stream of air, and their ground speed was their airspeed through that 230mph tailwind plus the tailwind itself.  They were never moving through the air at anything approaching mach 1.

WilliamsSW > ttyymmnn 02/19/2019 at 15:47

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They would avoid that - they would fly higher/lower or a different route (likely the latter, the transition between the jet and slower moving air is probably pretty damn turbulent).

ttyymmnn > WilliamsSW 02/19/2019 at 15:51

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Can those jet stream speeds be monitored in real time? Or would they rely on reports from airliners in the stream?

davesaddiction @ opposite-lock.com > ttyymmnn 02/19/2019 at 15:52

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And... on Jalopnik 15 minutes later...

WilliamsSW > ttyymmnn 02/19/2019 at 15:54

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They’re forecasted - see below.  Not sure how well they’re accurately measured in real time, but they would use any and all data, including ride reports, to assess them.

https://www.wunderground.com/maps/wind/jet-stream

ttyymmnn > davesaddiction @ opposite-lock.com 02/19/2019 at 15:57

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Not surprising. They at least put more effort into rewriting somebody else’s article than I did. I did get the Flight Aware data myself.

Wrong Wheel Drive (41%) > Thomas Donohue 02/19/2019 at 16:03

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I had family come in last week for vacation from NY to LA. The turbulent weather led to a required fuel stop in Vegas along the way for the nonstop flight. Also was super bumpy due to the lower altitude they had to fly at during the latter half of the journey. 

Thomas Donohue > ttyymmnn 02/19/2019 at 16:07

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They usually change the route a bit, but you still can’t avoid the headwinds.  It will be longer/slower....in this case 20-30 minutes longer flight time going west.

Thomas Donohue > WilliamsSW 02/19/2019 at 16:10

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Per the article, y esterdays 231 mph reading was from a weather balloon launched on Long Island.

WilliamsSW > Thomas Donohue 02/19/2019 at 16:39

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Right - and they try to map it out, but it’s not an exact science.

Rusty Vandura - www.tinyurl.com/keepoppo > OPPOsaurus WRX 02/19/2019 at 16:51

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Think of one of those long “escalator” walkways in the airport that when you walk at your normal speed, but you move twice as fast relative to the ground you’re walking past. So it is with the aircraft and the tailwind; relative to the air that the aircraft is flying through, the ship is moving less than the speed of sound. But relative to the ground , the plane is moving very fast. I don’t know what the speed of sound is, but if there were no tailwind, 801 mph might break the sound barrier. And tear off the 787s wings...

Rusty Vandura - www.tinyurl.com/keepoppo > WilliamsSW 02/19/2019 at 16:55

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Though entirely unrelated, your remark makes me think of the tail guns in the B-52 that they removed because the bullets didn’t go far enough without running out of energy to be effective to warrant having them on board.

MattHurting > For Sweden 02/19/2019 at 17:31

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Exactly why there are Steelers fans everywhere; they grew up there and got the hell out of there ASAP.

WilliamsSW > shop-teacher 02/19/2019 at 17:41

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That, or they spent 45 minutes holding over Heathrow.

I’ve been on flights that crossed the Atlantic 30-45 minutes ahead of schedule, and landed 20 minutes *late* after holding there.  

ttyymmnn > Rusty Vandura - www.tinyurl.com/keepoppo 02/19/2019 at 18:29

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The speed of sound varies with altitude, temperature, and a few other factors. 

Highlander-Datsuns are Forever > ttyymmnn 02/19/2019 at 20:46

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Pv=mrt 

ttyymmnn > Highlander-Datsuns are Forever 02/19/2019 at 21:00

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philsphan09 > ttyymmnn 02/19/2019 at 22:48

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I was on a flight from Milwaukee to Philly today and we hit 690, which I thought was crazy fast for one of those small regional jets.  

ttyymmnn > philsphan09 02/19/2019 at 22:49

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That was almost certainly ground speed. What was the airline and flight number?

philsphan09 > ttyymmnn 02/19/2019 at 22:53

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Definitely was ground speed.  AA4902

ttyymmnn > philsphan09 02/19/2019 at 23:33

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Y’all were bookin . You hit 686 (highest speed shown on the FlightAware data) at 32,000 ft soon after starting descent. The jet stream is still hauling ass in that part of the country. (Click the wind map to embiggen)

ttyymmnn > philsphan09 02/19/2019 at 23:33

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Y’all were booking . You hit 686 (highest speed shown on the FlightAware data) at 32,000 ft soon after starting descent. The jet stream is still hauling ass in that part of the country.

philsphan09 > ttyymmnn 02/20/2019 at 05:59

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The pilot was like “yeah the flight today is going to be very quick”