I'm cruising at an altitude of Flight Level 310 and a speed of 290 knots given by the fms this can't be right as the speed should be 400+ knots.Any help thanks.Ive looked on plane finder via app for ipod touch and seen md-11's cruising at a speed of 450 knots.

 

Please Help!

 

Thanks

You know that you see IAS instead of TAS on your speedtape?

IAS = Only true at sea level at 15°C and 1013 hPa, however this is the speed by which the airplaine gets "damaged" if overspeeded

TAS = Real speed against sorrounding air. Higher than IAS.

 

You fly wiht IAS but you move with TAS and you have a GS.

 

IAS..Indicated Air Speed

TAS..True Air Speed

GS..Groundspeed

If you were flying at 400 knots at FL310, I think you'd fly her apart...

Thanks a lot pal your a hero,your help has made an incredible advance with my flying the pmdg md11,fast response.Here's a picture of what i mean.

Ehh.... It's kinda hard to open a picture on your computer...

Anyway, just wanted to add to Jonathan's response:

The way an aircraft measures speed is via the pitot tube. It is a tube that points forward outside the aircraft. If you go faster the internal pressure increases. This makes the airspeed needle show a higher speed. Since the aircraft flies at high altitude the pressure is lower. This means that the Indicated speed is lower than what it actually is.

 

This one of the absolute basic instruments in aviation. If you are interested in flying I suggest you look up these instruments because all planes use them and understanding them makes your flying experience much more interesting.

 

Wikipedia will help you a lot:

http://en.wikipedia....t-static_system

http://en.wikipedia....speed_indicator

 

Hope this helps

Manfred

You could fly the tutorial flight. You would learn a lot about what is expected to happen. You can then look up teh manuals for anything you still don't understand.

Thanks a lot pal your a hero,your help has made an incredible advance with my flying the pmdg md11,fast response.Here's a picture of what i mean.

 

Getting snippy with people around here is a good way to not get help. His answer might not explain why exactly you're having this "problem," but being snippy back isn't going to get him to help you any further.

 

What you're seeing is not a problem. What you're seeing has been explained above, slightly, but let me explain further:

 

When people quote speeds, ranges and maximum altitudes, they're generic numbers. First, those "max" speeds are calculated as True Airspeed, which is not what you see on the panel. On the panel, you see Indicated Air Speed. So, what you're seeing as the "max airspeed" on an aircraft data table (on Airliners.net or Wikipedia or otherwise) is not what you'll see when flying the bird. Second, your max alt issue is probably caused by you being too heavy. The aircraft's max alt is determined both by the length of the flight segment (distance between departure and destination), and the weight of the aircraft. Heavier aircraft must fly lower to achieve better performance. The reason is that it would require too much thrust to operate at the higher altitudes, thus consuming more fuel. In the more extreme cases, there's just not enough thrust to keep you up there.

 

General rule of thumb:

Aviation is never always anything.

 

If you see a quoted max airspeed, that's not always true as it's different with different weights, temps, loads and altitudes.

If you see a quoted range, that's not always true as it's different with different weights, temps, loads, altitudes and wind speeds.

...and so on.

 

Everyone assumes aviation is very formulaic, and it's very not.

 

Hopefully that answers your questions.

Thanks a lot pal your a hero,your help has made an incredible advance with my flying the pmdg md11,fast response.Here's a picture of what i mean.

 

If you're looking for performance information on you're ipod, you're hardly in a position to get cheeky around people who know more than you think you do. I know everybody has to start somewhere in FS, but perhaps you've bitten off more than you can chew?

 

I typically wouldn't mind helping you, but you need an attitude adjustment, and perhaps an English class.

 

Paul

I'm not trying to get rude,i was only saying thanks for the help as i'm new to the pmdg md11 recently purchasing it last week.

Do you mean the term used by myself (Thanks alot pal) is on the otherhand rude if so i didn't mean it that way.

Do you mean the term used by myself (Thanks alot pal) is on the otherhand rude if so i didn't mean it that way.

 

That was my assumption, but if that was not your intention, I'm sorry for making that assumption.

I'm not trying to get rude,i was only saying thanks for the help as i'm new to the pmdg md11 recently purchasing it last week.

Do you mean the term used by myself (Thanks alot pal) is on the otherhand rude if so i didn't mean it that way.

 

If you didn't mean it the way I read it, then I apologize. Sometimes the internet can be a poor place to convey emotions.

 

Paul

Quick rule of thumb here....if you are flying above F210-F240, forget about indicated airspeed....the only way to standardise progress through the air mass is with reference to speed of sound(which also varies according to altitude, pressure, etc).

 

So if you are on the ground, an indicated airspeed of 200knots will mean something totally different than at F300...look at groundspeed....the speed at which your aeroplane moves in relation to the ground....200 knots indicated airspeed at sea level will be around 200 nautical miles per hour over the ground (200 knots groundspeed)....at F300....200knots indicated airspeed will be nowhere near 200 nm per hour over the ground....why?? the air density for starters....air is a lot thinner the higher you go. Indicated airspeed is NOT a measure of your speed....it is a measure of parcels of air by your pitot tube....ie, it measures how much pressure the air is exerting on the tube....the higher you go, the less pressure...but it doesnt necessarily mean you are going slower, but you are higher up so 1nm on the ground is more than 1nm at F300....

 

So in other words, if you are higher up, use a standard method to judge your speed....MACH is a calibrated measure of your aeroplane in relation to speed of sound...an MD-11 will cruise happily at around M.82 or 82% of the speed of sound.

Thanks everyone for your help :) I know have a much more knowable mind about the speed situations in an aircraft when cruising at different levels of altitude.

 

Many Thanks

Howard