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Nautical Air Miles (NAM)

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NoPax

NoPax NoMore
Joined
May 25, 2005
Posts
362
A few months ago, while studying towards my ATP written, there was a couple of flight planning questions relating to Nautical Air Miles.

Recently, I got to fly in a CJ1, from Austin to Dallas, and we climbed to FL220. The pilot wanted to climb higher - maybe FL280, and new to the whole jet experience, I didn't say anything (& we didn't get higher).

Its about 165NM, and I seem to recall the NAM chart for the 737 recommending a lower altitude (?).

What exactly are Nautical Air Miles, and how could a pilot flying Part 91 use this to their advantage - ie how can I explain that FL280 would be a waste of time?

Thanks
 
NAM is Nautical Ground Miles corrected for wind.

Example, 1 hour flight, ground distance 400NGM, headwind component 50kt = 450NAM

What you are thinking of is optimum altitude for short flights. For the B737 there is a short cruise table that gives you an optimum altitude for that gives you at least 1 minute at cruise level.

FL 280 may be a waste in a 737, but i might be closer to optimum for a light jet, you'd have to go into the performance manuals to get the exact answer for that aircraft.

Hope that answers your question
 
Stby One said:
NAM is Nautical Ground Miles corrected for wind.

Example, 1 hour flight, ground distance 400NGM, headwind component 50kt = 450NAM

Thanks.

I'll have to do a little digging in the manuals to find the optimum altitude for short cruise flights.

Now I just have to learn what all the buttons do!
 
Nautical air miles or often called ESAD (equal still air distance) is the NGM (nm ground miles) corrected for wind.

formula for NAM is;

NAM = NGM * (avg TAS/avg GS)

AUS-DAL = 200 nm (NGM)

TAS = 400 kts
Wind = 30kts headwind -
GS = 370 kts

NAM = 216 nm
 
FlyDouglasJets said:
Higher is not always better, if it decreases your Groundspeed substantially, due to a strong jetcore headwind.

Yes, and that concept compltely escapes some of the pilots. There have been far too many times that I have planned a flight at say 340 and at the first position report they say they're at 410......... The fact that you can go that high does not necessarrily mean you're gonna burn less gas. Just fly the damn flight plan already....
Whew, sorry
 
FlightOpsAB said:
Yes, and that concept compltely escapes some of the pilots. There have been far too many times that I have planned a flight at say 340 and at the first position report they say they're at 410......... The fact that you can go that high does not necessarrily mean you're gonna burn less gas. Just fly the dang flight plan already....
Whew, sorry

True dat, and niether is going great-circle direct the most efficient path from A-B. "Ahh....my FMC planned arrival fuel is showing less than :30 minutes, after I took that giant 1000nm direct routing about 2hrs ago". Where should I land?

You can't train stupid.

The Dude
 
FlyDouglasJets said:
niether is going great-circle direct the most efficient path from A-B. "Ahh....my FMC planned arrival fuel is showing less than :30 minutes, after I took that giant 1000nm direct routing about 2hrs ago".

OK, I think I'm missing something. I thought the shortest distance between two points was direct.

If you are talking about jet-stream winds, then I can see that, or am I missing something else?
 
NoPax said:
OK, I think I'm missing something. I thought the shortest distance between two points was direct.

If you are talking about jet-stream winds, then I can see that, or am I missing something else?

You got it, a direct might be a good idea some of the time, but def not ALL the time. Jetstream, tropopause, etc. Of course the change in fuel burn might not be all that great, but it adds up.
 

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