V-Flyer

A thread on one of the FT forums eventually linked me to this thread today.

It seems that many airlines are 'slowing down' and saving fuel. While it can only be a good thing (in terms of cost saving/enviroment), I can't help but think that the numbers they're talking on another resource mean a transatlantic flight COULD increase by around half an hour if the carriers all adopt this method [:0]

So they slow planes down, save money on fuel and will probably still put up the Fuel Surchange.

If you slow down a plane, you fly at a lower altitude, which induces more drag, which requires more fuel, of which more is burned in any case because the journey is longer. There's a sweet spot of speed and altitude for modern high-bypass jet aircraft which can be tinkered (for example, new aircraft like the A340/380 and the 777/787 are not quite as fast as the 747 on average) but these are just at the margins.

Originally posted by frangipan
If you slow down a plane, you fly at a lower altitude

Depending on how much you slow down, that isn't exactly true. You can cruise at a slower speed and remain at a constant height using flight control inputs.

You hit the nail on the head by referencing it as a sweet spot. United purchased software that would calculate that sweet spot for them, and the savings are already adding up (I seem to recall $20 million a year being mentioned).

For anyone interested in the technical side, a full explanation can be found here
The first few slides show the trade-off between speed and maximum fuel efficiency.
The presentation is a few years old so the savings figures need to be adjusted up considerably.

This is a very interesting site for detailed aviation info.

Thanks for the link Bill, a very informative site. [y]

Originally posted by Bill S
The presentation is a few years old so the savings figures need to be adjusted up considerably.

Wow! $1 per gallon. I remember those days! [:D]

This was very interesting reading.

I reckon they must be. I was meeting someone off a flight at the weekend, I checked the flight status shortly after it took off, and it was showing departure as 15minutes early, but the ETA was already showing 20 minutes later than schedule (in simplistic terms already a 35minute longer flight) in the end it arrived 30 minutes later than scheduled.
Though I suppose it may have also been a stronger than usual jet stream.

Ah, THIS weekend, I know the issue if you're talking transatlantic (I was flying too). There was hardly any jetstream at all, so all Eastbound flights were taking considerably longer.

(Try 7:45 Eastbound from ORD [:0])


The good news being, I guess, all westbound flights saw the benefit [;)]

You can check where the Jetstream is heading by looking at This site . You can see the projected jet stream for the week.
At the moment the jetstream seems to benefit those travelling over Greenland etc towards the US.

Its a great site i use it all the time for the weather.