Simviation Forums

I recently started flying on VATSIM. ATC advised that a Boeing 777 will cruise nicely at 540 at FL320.  I dialed the 540 into my speed selector and pressed the Speed Hold Button. At FL320, the aircraft held at around 350 and never made it to the 540 as selected on the Speed Hold Button and as suggested by aTC. BTW, ATC never advised that I was going to slow even though my Airspeed showed 350. What am I missing here??

thanks

Speedbird_1961

540 seems awfully fast, especially since  the airspeed indicator is represented in knots, rather than mph.  This would mean that ATC advised you to go 621 mph.

As for your aircraft limitations, I don't know enough about F$ aircraft models to know what the problem is, but I would suspect that they've been designed to put somewhat of a limit on the speed you can fly, so as to not rip the airframe  to shreds.

Go to your SETTINGS in SF and see if your have Indicated  airspeed or Actual airspeed checked.

540 sounds like a groundspeed in MPH, about mach .8.  Look at your GPS to see what the groundspeed is in Knots and multiply that by .85 for MPH.

540 sounds like a groundspeed in MPH, about mach .8.

Could be, but why would ATC be giving him ANYTHING in mph, let alone groundspeed?

I can't imagine WHY they would tell him to go 540 but groundspeed is the only rate that makes any sense.  The MS manual says cruise speed is 555 mph/ mach .84, and the MS manual always overrates performance.

He can only get up to 350 KIAS because the engines are maxed out.  He should get an overspeed warning and an overstress crash long before he gets to 350 - unless he has this turned off.

Whats the difference between, indicated airspeed and actual airspeed?

It's one of those things you learn once and forget.

Indicated airspeed is how fast your ac thinks it's going.  This is important for stall speeds and such.

Actual airspeed is how fast your ac is really going.  This is important for calculating flying times.

Both of these vary with winds and air density (temp and altitude), so there's gound speed, which is pretty much self explanatory.

Since I've grossly oversimplified this, here's a boring scientific explanation http://stoenworks.com/Tutorials/Underst ... speed.html

Whats the difference between, indicated airspeed and actual airspeed?

I suck at explaining but okay

Yes. Good explination.

In FS, as the real world, the higher your altitude is, the harder it is for the aircraft to obtain "cruise" speed, due to the thinner air. You can probably make and hold 540 kts at FL200, but when you climb to, say, FL300, your speed will drop off

Atmospheric Physics 101.

thanks for all the help. This has sparked some interest I see.  Yes, I was rather surprised that the ATC recommended an airspeed of 540 since I had never flown past 350 or so, and usually cruise at around 250. On my flightplan which I filed I indicated an airspeed of 250 and ATC suggested that I increase it to 540. Me being a NEWBIE at VATSIM, I did as was suggested. I fly with "realism" set to "hard." The aircraft did not overstress, nor was there an "overspeed" warning, and I was truely surprised to see that with 540 dialed in, the aircraft "held" nicely at about 350. Im not sure, but 350 wouldnt cause "overstress".  I have checked the cfg file on the Boeing 777-200ER and it indicated a max speed of 482.0 Knots True (KTAS).

thanks

Speedbird_1961

This is all cobblers anyway.

No one works in miles per hour

No one even works in knots at that altitude in a heavy

At FL 320 a 777 will cruise happily at mach 0.85 and if pushed will attain a max of about 0.9

No one knows or cares what that is in mph - it varies according to temp and pressure - but if you look at your GPS for example you will see what your true groundspeed is in knots

Flying heavies is different to flying lights. Let's say you switch to mach at say 10000ft  you'll find you're around 0.3/4 mach from memory. You will overspeed at a very low mach reading at low altitudes. You ramp up your mach as you climb ... .45 , .5, .6...... until you reach your cruising speed at alt - 0.85 mach.

It pays to read the manuals from time to time - POSKY include some great flight manuals with their aircraft - trouble is people are too busy flying to read them and then wonder why they don't do things right  ;D

That told ya!

Roger