747 Speed Issues

[Seaton3310]

I'm in a 747 going transatlantic at 40k altitude with like half number of passengers and half fuel, yet I can't get above 260 knots. Anyone know why this might be? Gears and flaps up, not sure what else is going on but I should be able to hit at least 320 knots. Very frustrating.

Thank you.

[SteveFSX/P3D]

Not a jet guy but the IAS is not accurate at high altitude because of low air density or pressure going down the pitot tube ( I think )

You are looking for a Mach number somewhere at that altitude - or open the GPS and look at your ground speed.

[Drop]

Just F4 until your engines overheat!

[Drop]

Get a nice 650 IAS

[Duck]

Steve explained it pretty well. Indicated Air Speed (IAS) is what the pitot tube is directly telling your aircraft. If you would look at your True Air Speed (TAS,) then you'd see that quick speed you're actually going. Your ground speed can also tell you as well, but that can change due to winds. Hopefully that helped.

[Duck]

Steve Mak explained it quite well. At such altitudes, pilots go off of a mach speed rather then knots. Mach .78 is the average cruise, however a 747 can go up to mach .9. It's quite a fast jet, one of the fastest, faster then the 777 matter of fact.

[APUtech]

Originally posted by Seaton3310:

I'm in a 747 going transatlantic at 40k altitude with like half number of passengers and half fuel, yet I can't get above 260 knots. Anyone know why this might be? Gears and flaps up, not sure what else is going on but I should be able to hit at least 320 knots. Very frustrating.

Thank you.

Seaton3310, one thing that you can try is set your indicated airspeed in your auto-throttle to 280kts after passing 12,000 ft and lower your vertical speed to 1200 fpm after passing 18,000 ft (FL180). Once you pass FL200 (20,000) Switch your auto-throttle to Mach, using .66 mach as a baseline (or a bit higher) and gradually increase your mach setting until you get to your crusing altitude (FL400). By the time you reach your cruising altitude you should be around .82-.84 mach.

Once level, gradually increase your mach setting to as high as .88 mach; typically I cruise at .84 mach to keep my fuel flow (FF) around 6,000 gallons per engine per hour so that I can easily calculate how much fuel I'll need for a given flight, e.g., A 3-hour flight will use up at least 72,000 gallons, plus fuel used during climbout, plus at least 1 hour 45 minutes' fuel for reserve.

Adding those fuel usage factors together I calculate my estimated fuel needs to be around 25-27,000 gallons per hour, using the higher figure if a good portion of the climbout and cruise are in head or crosswind conditions.

There are other considerations to take note of (N1 and N2 speeds, etc) but flying the default or modified default 747 doesn't need to be that complicated. ;-)

Happy flying!

APUtech--die-hard 747 driver.

Edit: I do want to state that the suggestions that I've given above don't reflect "actual" by-the-book information on flying the Boeing 747 in FSX/FSX:SE, that they are basic guidelines which can make your flying experience a bit more informed. Too (laughing) the edit is to also repel trolls who love to jump on someone's post and try to pick it apart with their own "accurate" information and figures regarding a subject. ;-)

[Duck]

Originally posted by APUtech:

Originally posted by Seaton3310:

I'm in a 747 going transatlantic at 40k altitude with like half number of passengers and half fuel, yet I can't get above 260 knots. Anyone know why this might be? Gears and flaps up, not sure what else is going on but I should be able to hit at least 320 knots. Very frustrating.

Thank you.

Seaton3310, one thing that you can try is set your indicated airspeed in your auto-throttle to 280kts after passing 12,000 ft and lower your vertical speed to 1200 fpm after passing 18,000 ft (FL180). Once you pass FL200 (20,000) Switch your auto-throttle to Mach, using .66 mach as a baseline (or a bit higher) and gradually increase your mach setting until you get to your crusing altitude (FL400). By the time you reach your cruising altitude you should be around .82-.84 mach.

Once level, gradually increase your mach setting to as high as .88 mach; typically I cruise at .84 mach to keep my fuel flow (FF) around 6,000 gallons per engine per hour so that I can easily calculate how much fuel I'll need for a given flight, e.g., A 3-hour flight will use up at least 72,000 gallons, plus fuel used during climbout, plus at least 1 hour 45 minutes' fuel for reserve.

Adding those fuel usage factors together I calculate my estimated fuel needs to be around 25-27,000 gallons per hour, using the higher figure if a good portion of the climbout and cruise are in head or crosswind conditions.

There are other considerations to take note of (N1 and N2 speeds, etc) but flying the default or modified default 747 doesn't need to be that complicated. ;-)

Happy flying!

APUtech--die-hard 747 driver.

And my dear friend APUtech is quite experienced with Boeings.