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Choosing a cruising altitude.

Pro Member Trainee
crossland99 Trainee

Okay, so most of the flight notes say "Cruise altitude would be determined by wind, weather and other factors...Optimum altitude is the altitude that gives the best fuel economy...a complete discussion is beyond the scope of this section."

Can any of you give a little more discussion? How should I choose a cruising altitude for a given flight. I've kind of been guessing.

5 Responses

Pro Member Chief Captain
CRJCapt Chief Captain

For propeller aircraft(unpressurized):

An altitude that will give aprox. 75% power with full throttle.

7,000-9,000 ft. MSL

Turboprops (low power types): FL180-FL220
Turboprops (High power types): FL180-FL280

Jets:

Depends on length of flight. Less than a hour- FL 220-260. Over 1 hour-FL 280-FL 410. Aircraft will be fastest at FL 280. This is because cruise is normally in Mach. The true airspeed of a given Mach number is related to temperature. The speed of sound travels slower at lower temperatures. .8 Mach is faster at FL 280 than FL350 because it's colder at FL 350. Above that you lose speed but save fuel and have greater range. The most efficient altitude for a jet is about FL330-340. Long range flight tend to fly higher. Normally westbound flights stay somewhat lower to stay out of the westerly winds(US). There are no hard and fast rules. Some of these figures are just my thoughts and some are what I've read. 🙂



Last edited by CRJCapt on Thu Mar 02, 2006 1:38 am, edited 1 time in total
Pro Member Chief Captain
Alex (Fire_Emblem_Master) Chief Captain

Usually just guesswork in Fs9. Depending on the distance, you would want a lower altitude for a short 15-30 minute flight, as far as I can tell, the wind isn't blowing in diff. directions depending on how high you are. Usually you would want to be nice and high to have a slower fuel burn rate though.

Hope it helps at least a tad 😎 😕

Don Wood Guest

First, there are regulations that each pilot must meet (at least in USA airspace). For VFR flights headed easterly (magnetic headings of 0 to 179 degrees), above 3,000 feet AGL and below 18,000 feet MSL, pilots must fly at odd thousands of feet plus 500 feet (3,500, 5,500, etc.). For westerly flights (magnetic headings 180 to 360 degrees), VFR pilots must fly at even thousands of feet plus 500 feet (4,500, 6,500, etc.).

IFR altitude assignments are made in the same mode but without adding the 500 feet. (3,000, 5,000, etc for easterly flights; 4,000, 6000, etc for westerly flights). Both VFR and IFR, altitudes must also take into account terrain clearance, minimum enroute altitudes, and controlled airspace altitudes. Above 18,000 feet MSL, all flights are IFR and there are different rules and wider spearations.

Within those limitations, pilots are free to choose an altitude while VFR and are free to request an enroute altitude on IFR flight plans. The selected altitude might take into account a pilot's or passenger's desire to flight-see (low altitudes selected), the planned duration of the flight, the characteristics of the particular a/c (does flying at higher altitudes provide economic benefit based on fuel consumption), headwinds or tailwinds, weather problems forecast enroute, and many other factors important to the pilot.

All other things being equal, winds are typically stronger at higher altitudes and most often are from the west. Therefore, if I was flying easterly, I'd usually cimb to higher altitudes to take advantage of tail winds and if I were flying westerly, I'd typically stay lower to avoid head winds.

Guest

upon making a new flightplan in FS via. GPS -
I always say - alright - if the flight is local - I fly via low-airways rules.

If its international I fly via high-airways rules.
Then I create the flight plan - and it will determain a cruising altitude for you.

Then I set the autopilot ALT to the height it gave me in the flight tracker, and thats it.

worked for me - no critisism from Flight Control 😀

Pro Member Chief Captain
Manuel Agustin Clausse (Agus0404) Chief Captain

RVSM Airspace

Standard ICAO Airspace

Track from
0° to 179°

Below 18,000 feet

Odd thousands
(3,000; 5,000; 7,000, etc.)

FL180 to FL290
Odd Flight Levels
(FL190; 210; 230, etc.)

Above FL290
Beginning at FL290
(FL290; 330; 370, etc.)

Track from
180° to 359°

Below 18,000 feet
Even thousands
(2,000; 4,000; 6,000, etc.)

FL180 to FL290
Even Flight Levels
(FL180; 200; 220, etc.)

Above FL290
Beginning at FL310
(FL310; 350; 390, etc.)

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