Nautical Air Miles (NAM)

[FlyDouglasJets]

primary tools... the FMC fuel burn computation

The FMC fuel burn predictiong, if going DCT TO a fix 1000nm will use the following logic (at least the Honeywell units)

Predicted Groundspeed and thus segment time, and fuel burn will be based on the following;
current wind component, used for a decreasing mix up to 250~500nm ahead of the jet, and then a mix of that wind and the FMC wind for the next down-range FIX (which might be 900+nm in front of the jet).

The summary, the FMC fuel burn, especially during the WINTER, might lull one into a false sense, as this wind "mixing" may perhaps totally overlook (garbage in/out) a polar jetcore on the nose @ 150kts somewhere out near 500nm ahead.

The outcome ain't pretty, the predicted arrival fuel on the FMC may perhaps cause a new seat cushion post-arrival.

DD

 

[FlyDouglasJets]

Nopax- how about the tried and true formula for short-range flts (>300nm).
NAM * 100 = FLxxx

NAM = 200nm fly @ FL200
NAM = 150nm fly @FL150

 

[NoPax]

how about the tried and true formula for short-range flts (>300nm).
NAM * 100 = FLxxx

NAM = 200nm fly @ FL200
NAM = 150nm fly @FL150

I think you meant <300NM [less than], but ok that works too - and keeps him out of the 30s, clearing the way for your boys and girls.

 

[pilotyip]

nopax, the sextent was RNP-25. No one uses them anymore that I know of.

 

[Vector4fun]

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).

This may or may not be of interest to you, but AUS to DAL you'll likely always get AUS CWK2 NAVYS DUMPY2 DAL; and you'll never get higher than FL220, unless it's middle of the night. That's a Center restriction, and it's published on the CWK2 departure...

And since this is a dispatcher's forum, is it the dispatchers, or the pilots who never notice max altitudes on certain departure transitions, and thus constantly file FL290 and above on a transition that's clearly published for flights at or below 120? :erm:

 

[NoPax]

That's exactly what we got - AUS CWK2 NAVYS DUMPY2 DAL - and now I know why its called the 'Dumpy2' arrival.

Do you work in the AUS ATCT/AUS area?

 

[NoPax]

duplicate post

 

[Sctt@NJA]

No Pax, you may be better off not trying to advise the pilot of how high he should fly.

If I had someone along for a ride telling me I was flying too high or low for the trip I would consider that to be very annoying.

There are plenty of other factors that determine the best altitude and you really don't seem to be aware of any of them.

Let me ask you this... why do you think a 737 chart applies to any other airplane? If you had an airplane that climbs to fl 280 in 7 minutes at VMO and MMO how would it be a waste of time to go that high on a 165 mile leg?

I don't know anything about a CJ1 or the winds, ride, or route you were flying so I don't know if what the pilot was thinking was right, wrong or indifferent and frankly neither do you.

 

[NoPax]

No Pax, you may be better off not trying to advise the pilot of how high he should fly.

If I had someone along for a ride telling me I was flying too high or low for the trip I would consider that to be very annoying.

There are plenty of other factors that determine the best altitude and you really don't seem to be aware of any of them.

Let me ask you this... why do you think a 737 chart applies to any other airplane? If you had an airplane that climbs to fl 280 in 7 minutes at VMO and MMO how would it be a waste of time to go that high on a 165 mile leg?

I don't know anything about a CJ1 or the winds, ride, or route you were flying so I don't know if what the pilot was thinking was right, wrong or indifferent and frankly neither do you.

I don't think the 737 chart applies to other airplanes - I'm not dumb - I asked about Nautical Air Miles because I felt it was relevant to this situation, and felt I could learn something from dispatchers who deal with this every day, I'm glad I got a civil answer before you showed up.

Of course, flying a Commander everynight gives me no insight to flying a CJ1, and I'm also not stupid enough to spout off at a pilot, who was nice enough to let me ride along in the first place - I was just trying to gain some insight, you know learn something so I could maybe use it in the future.

The flight took 0.7. An educated guess that about 0.3 was taxi takeoff & climb and 0.2 was descent, arrival and taxi. That leaves a whole 12 minutes of cruise. My question was (which has already been answered), how could spending another 3 minutes climbing to a higher altitude, and taking that from cruise possibly shorten the flight, or use less gas - I wanted the arguments for and against it.

In fact we got the Dumpy2 arrival into DAL, that required crossing an intersection at 9000. The pilot had to slow the airplane below 250, and then struggled with an excessive rate of descent to get from FL220 to 9k - an obvious waste of energy, so higher would have been very uncomfortable (not that we had passengers anyway).

I see you too are spreading the NJA joy

 

[Sctt@NJA]

how I could explain this to a fairly low-time CJ1 pilot, when suggesting the altitude to fly at for shorter trips.

Sorry to rain on your parade, but I think its clear you wanted to show some CJ1 pilot that you know more than he does. I don't think you are here on a quest for aviation "truths", I think you are here for "ammo" to show this guy how smart you are.

Why else would you need to explain to him how high he should fly?

Also, Nautical Air Miles is just a way of measuring the effect of winds on how far an airplane needs to fly to get somewhere and has nothing to do with how high you should fly on short legs.