Am I dense, or where does it go?

Tjhe time difference between Washington and London is 6 hrs
So if the VS21 takes of at London at 11.30 local (thats 0530 washington) it arrives at 14.40 Washington
Flight time 9 hrs 40 min
Coming back it takes off Washington 19.00 ( 01.00 london)
Lands at 07.05
Flight time 7h 5min

Why does it take 2 1/2hrs longer going than coming back?

Its 8h:10m going and 7h:05m comming back, due to jet stream winds.

Hi Silverfox

The flying time calculations in the example you've used are wrong - should've been: out 9hr 10min, in 6hr 5min. Anyway, that's beside the point - actually the time difference for Washington is GMT -5 (non-DST) & GMT -4 (DST), so they're currently 5 hours behind us.

So,
VS021: Dep LHR @ 1130hrs BST (0630hrs EDT)
Arr IAD @ 1440hrs EDT = 8hrs 10mins flying time
VS022: Dep IAD @ 1900hrs EDT (0000hrs BST)
Arr LHR @ 0705hrs BST = 7hrs 5mins flying time

The 1hr 5mins difference coming Eastbound is due to the favourable jet stream coming home

HTH

Cheers

Michael

Hi,

Sorry if this is basic, but it's bound to be the next question.

If an Aircraft travels through the air at a given speed (airspeed) and the air is still then this is also the speed across the surface of the earth (ground speed)

But if the air is moving (wind) then the groundspeed is increased or decreased depending on which direction the air is moving.

e.g.

The jet stream (wind) across the North Atlantic travels from East to west. So aircraft flying from Londonv -> USA are flying into the wind (headwind). This means that while at a particular airspeed their goundspeed is reduced. so LGW to MCO is 9h 30mins.

Aircraft flying from the USA to London are flying with the wind (tailwind) so the air they are flying through is moving in the same direction that they are. So for the same given airspeed that have an increased groundspeed. Hence MCO - LGW 7h 15mins approx.

Dispatchers monitor the weather very closely and plan routes to avoid the jetstream as much as possible on the way to USA and take maximum advantage of it on the return.

Why? Passenger satisfaction? No. Fuel Economy.

Hope this helps.

Neil.

If i had realised that the time difference was 5hrs instead of 6!!, then i wouldnt have asked the question.I knew the jetstream had some effect but i wasnt going to accept a 3hr discrepency (with the 6hr time zone) with it being 5hrs it brings it down nicely to what i thought, and regards the jetstream last time i went the airspeed going was more than the groundspeed and v/v on the return.
thanks to all who pointed out my very basic error and took the time to explain