1/8 Jet Stream Pushes NY-Heathrow Flights To Near-Supersonic Pace; Groundspeeds To 745 mph

[hatrack]

A jet stream roaring across the North Atlantic at more than 200 miles per hour early Thursday morning nearly succeeded in bringing back supersonic air travel for the New York to London route. Several flights from New York's John F. Kennedy International Airport made the trip from there to London's Heathrow Airport (from gate to gate) in about five hours and 20 minutes.

British Airways Flight 114, a Boeing 777-200 jet, took off from JFK at 10:50 p.m. ET, and landed at 9:06 a.m. local time, taking just five hours 16 minutes to make a trip that typically takes more than six hours.

At one point, according to Flight Aware, the jet was traveling at a groundspeed, which is the speed at which the plane is traveling relative to ground level, of 745 miles per hour. For comparison, the speed of sound at sea level is 761 miles per hour.



In other words, the 777 helped British Airways live up to its legacy of operating the Concorde aircraft on that route until 2003.

(The actual airspeed of the 777 was considerably lower, though, and the plane was traveling within normal design limits, below the speed of sound at altitude, according to Flight Aware data.)

EDIT

http://mashable.com/2015/01/08/jet-stream-new-york-london-flights/

[brooklynite]

1. Um, not quite

While the effective speed might have been close to supersonic (mach), the Concorde generally traveled LHR-JFK at mach 2 (at least it did when I flew it)

[Sanity Claws]

2. How well can a plane withstand such speed?

The SST was built to withstand Mach 1 and higher. The ordinary Boeing plane is not. Could such speed affect the physical integrity of the plane?

[Capt.Rocky300]

4. The aerodynamic forces on the aircraft remain the same for a given airspeed........

regardless of the groundspeed and that's what we're talking about here. There are exceptions such as wind shear but that's a not the case here.

[edhopper]

5. the jet stream

added 200 mph to plane. the relative speed to the air around it would be 200 mph less.

[petronius]

3. 'Speedbird' is right, in this case

Very cool, although they'll pay it back with interest on the return leg...

[muriel_volestrangler]

6. Looks dubious - that is also the scheduled time, and why "GMT (+1)" in the British winter?

I don't think stats from that site can be taken as accurate.

[discntnt_irny_srcsm]

7. Actually the scheduled arrival was 7:46AM...

...an hour and 20 minutes earlier. The flight was delayed leaving JFK by about the same time. Why this made the news I'm not sure as the same aircraft accomplished the same trip about a week earlier in 30 minutes less time. See the link.

http://flightaware.com/live/flight/BAW114/history/20150101/0230Z/KJFK/EGLL

[muriel_volestrangler]

8. The equivalent for this flight does show an instantaneous ground speed of 749 mph

http://uk.flightaware.com/live/flight/BAW114/history/20150108/0230Z/KJFK/EGLL/tracklog

when it's over Newfoundland. I suppose that's what is notable. Though I wonder how accurate that is - the one for the 1st Jan ends with it doing 155 mph on the ground after doing 55 mph to the west - ie while taxiing. That seems a bit swift for taxiing.

The 1st Jan one is, all in GMT, 0242 to 0822, takeoff to landing - 5hrs 40 min; 8th Jan 0350 to 0925 - 5 hrs 35 mins. But they will have to adjust speed to fit into a landing slot, so I suppose the overall flight time isn't that indicative of the tailwinds.

[discntnt_irny_srcsm]

9. I was looking at...

...http://uk.flightaware.com/live/flight/BAW114/history/20150101/0230Z/KJFK/EGLL
...which shows a flight time of 4:46 having flown 3,621 statue miles. Doing the math that's an average of 762 mph.

[muriel_volestrangler]

10. Ah - go to the 'Speed Filed: 477 kts (graph)' link from there

which goes to http://uk.flightaware.com/live/flight/BAW114/history/20150101/0230Z/KJFK/EGLL/tracklog

and that shows the flight, all in GMT, from 02:42 to 08:22 (it goes on to 08:25, but at 0 ft altitude). That would be 5 hours 40 minutes, from 21:42 EST to 08:22 GMT. Which would be 09:22 (GMT +1), I'd say - which is one reason I don't like them putting that '+1' in; I think they've taken an hour off the flight time.

That flight gets up to at least 679 mph ground speed (they have to approximate the mid-Atlantic positions, and don't give speeds there, but the estimates look believable).

[discntnt_irny_srcsm]

11. Given the speed of sound at that altitude...

...it's ground speed would make it transonic but IIRC mach is based on airspeed.

[muriel_volestrangler]

12. Yes, the mach number is relative to the air around the object

so it's airspeed.

[discntnt_irny_srcsm]

13. I take it you're air data literate and have a question

My memory isn't what it used to be. Do you know the relationship between say Ias, Cas, Tas... regarding ssec, OAT and such?

[muriel_volestrangler]

14. No, I don't know things like that

Mach number came up in engineering studies, as a dimensionless number. It's both the speed of the object relative to the local speed of sound, and relative to the movement of the fluid molecules (which is why it's important, because that affects how shockwaves form).

[discntnt_irny_srcsm]

15. thanks

I majored in Physics; fluid dynamics is a mixed memory.
A sad one remembering the class and a happy one knowing it's over.