How do the airliners climb to cruise FL?

[Meflyplane4you]

Just curious, if a 767-300ER took off at MGTOW and had a final altitude of FL350, would the 767 have to level off at a lower altitude to burn a little fuel before being "capable" of reaching FL350? Is this what the airliners do? If not, what kind of climb rate do they usually use once they get up to those higher altitudes? I am under the impression that they "cruise climb" near their cruise speed. Thanks guys!
Nick.
COMM ASMEL-I, AGI, IGI.

[pvalexl]

I think I have the answer. On a recent flight I took to Honolulu, Hawaii aboard a 767-400ER. What happened was the pilot climbed to FL270, and held there for say...500nm. Then the pilot climbed to the final altitude at FL330. Aparently, he was burning off some fuel in order to have the power to make it to a higher altitude. The same thing happened on the way back. I know this stuff because I had all the info on my PTV aboard the plane. You may want to verify this with a 767 pilot, but I think I am correct.

[Silverblade]

Airliners don't climb at a specific rate, they climb at a combination of power setting and indicated airpseed;

And yes, depending on the distance of the trip and final cruise altitude, they climb in one or two steps to burn off enough fuel to safely operate at the higher altitudes.

Silverblade

http://www.flightsim.com/dcforum/Use...cd439d9f5d.jpg

[Trev]

They also climb to altitude the most economic way (costs) as worked out by the FMC from the info. for that flight that has been put into it, weights etc.

Trevor


http://www.flightsim.com/dcforum/Use...2435af4702.gif

[Toomba]

Which is why Flt Plans have a hard time working when you just can't get to your Cruise Alt fast enough to satisfy ATC in FS2k2.

[Meflyplane4you]

Thanks a lot for your replies fella's! If anybody else has anything to add, feel free!
Nick.

[Magdrop]

As mentioned above the FMC is the key to selecting cruising levels.

Ideal economic cruising level will be based on weight, outside air temperature and direction of flight. As weight reduces a higher level will be needed for the most economic cruising level.

In airspace that is subject to 2000 vertical separation, available levels are 310, 330, 350 etc. 310, 350 and 390 are westbound levels (tracks between 180 and 359 degrees) and 290,330 and 370 are eastbound. Oceanic tracks tend to work to different rules, and in Europe and on the North Atlantic 1000 foot vertical separation is now used.

A heavy 767 might make 330 from take off, but would need to burn a lot of fuel before it was light enough to climb to the next available level of 370.

In flight the "CRUISE" page of the FMC will show the optimum level, and it up to the crew to negotiate with ATC to achieve this level.

In the instance you mention where the initial level was 270 it would be likely that the level was restricted by other traffic, rather than weight etc.

En-route climbs, called STEP climbs, are usually performed at a good rate of climb between levels. The only commercial a/c that regularly use cruise climb, i.e. gently drift upwards at cruising speed as weight reduces are Concordes.

The limit to cruising height is not so much based on the maximum height that the a/c can achieve, but is based more on having an sufficient gap between limiting mach number and stalling speed to cope with turbulent air.

[pvalexl]

I think that we weren't at FL270 due to restricted traffic, considering we were in the middle of the pacific. However, we did later climb to Fl330. (My guess after we had burned enough fuel)

[Vike]

[font size="1" color="#FF0000"]LAST EDITED ON Apr-19-02 AT 06:17PM (EDT)[/font][p]I'm no expert but I doubt that a modern jet like a 767 would have to level off below 30,000 to burn fuel before climbing to fl330. I think its more likely that the flight plan was restricted to that altitude and even if the skies would appear deserted, theres' any number of reasons why this would be the casem including weather, military traffic etc.

[pvalexl]

you would be surprised at how bulky a 767 is with a full tank.