cruise altitude
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cruise altitude
hi everybody;
this is my first message to this forum...it looks like a wide range participated forum that I felt myself in a heaven
so first of all best wishes for everyone...
my question;
I am speaking for airliners;
I need to know that is there a rule of thumb about to select the best cruise altitude due to the range...
For ex., for normal condition (all factors are average; weight, weather, time, etc); we have a range about 1000 km, do we need to climb to 37000 ft (or lets say around 33000 ft)...or what would your answer for 500 km. is there a min range to think to climb to 33000 ft?
I have limited data, associated with a B757, and according to that data, the airliner needs to fly 125 nm (231 km) to reach the 37000 ft and another 130 nm (240 km) to descent from that altitude; so the sum is about 470 km. I will base my research on this data and I try to figure out how many additional range would make the flilght economic for flying at this altitude...
other words; can we speak about a start point of range to be able to use the high cruise altitude ?
sorry about the long message but I hope it is sufficiently understandable
Enis
this is my first message to this forum...it looks like a wide range participated forum that I felt myself in a heaven
so first of all best wishes for everyone...my question;
I am speaking for airliners;
I need to know that is there a rule of thumb about to select the best cruise altitude due to the range...
For ex., for normal condition (all factors are average; weight, weather, time, etc); we have a range about 1000 km, do we need to climb to 37000 ft (or lets say around 33000 ft)...or what would your answer for 500 km. is there a min range to think to climb to 33000 ft?
I have limited data, associated with a B757, and according to that data, the airliner needs to fly 125 nm (231 km) to reach the 37000 ft and another 130 nm (240 km) to descent from that altitude; so the sum is about 470 km. I will base my research on this data and I try to figure out how many additional range would make the flilght economic for flying at this altitude...
other words; can we speak about a start point of range to be able to use the high cruise altitude ?
sorry about the long message but I hope it is sufficiently understandable
Enis
Join Date: Jun 2005
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Hola Enis -
xxx
Many factors to consider as to FL level selection. All planes different.
And for same airplane types, how heavy are they...?
Climb/distance to TOC cruise FL depends mostly on their weight/payload.
xxx
With a heavy 747, the best I could hope was some FL280 initially.
And might take some 150 NM to get there.
With the 727 - medium payload, short distance, 120 NM might be ok.
And FL 310/330 was fine.
xxx
The only "somewhat" general rule is point of descent.
With all types of jet airliners I flew... 3 times the FL for distance to start descent.
As example - FL 350 = 105 NM for descent. Correct some for winds aloft.
Using the above data, you could derive an approximate FL selection.
xxx
Happy contrails
xxx
Many factors to consider as to FL level selection. All planes different.
And for same airplane types, how heavy are they...?
Climb/distance to TOC cruise FL depends mostly on their weight/payload.
xxx
With a heavy 747, the best I could hope was some FL280 initially.
And might take some 150 NM to get there.
With the 727 - medium payload, short distance, 120 NM might be ok.
And FL 310/330 was fine.
xxx
The only "somewhat" general rule is point of descent.
With all types of jet airliners I flew... 3 times the FL for distance to start descent.
As example - FL 350 = 105 NM for descent. Correct some for winds aloft.
Using the above data, you could derive an approximate FL selection.
xxx
Happy contrails
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ex902,
Welcome to PPRuNe!
Your Flight Planning data should provide you with the information that you need, but a "quick and dirty" cruise level is approximately 1000 feet for each 10 miles of distance, up to the optimum level.
For Example, if you are planning a 310 nm flight, 31000 feet would be a good "rough" level to begin examining wind gradient etc. to refine it further.
That works pretty well in ISA+15 environments for aircraft in the B757 league, but beware, all aircraft are different!!!!!
Regards and Welcome,
Old Smokey
Welcome to PPRuNe!
Your Flight Planning data should provide you with the information that you need, but a "quick and dirty" cruise level is approximately 1000 feet for each 10 miles of distance, up to the optimum level.
For Example, if you are planning a 310 nm flight, 31000 feet would be a good "rough" level to begin examining wind gradient etc. to refine it further.
That works pretty well in ISA+15 environments for aircraft in the B757 league, but beware, all aircraft are different!!!!!
Regards and Welcome,
Old Smokey
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A short-range operator in the Far East once ran some sums from the performance book - and quickly concluded that least fuel burn resulted by climbing until they intersected the descent profile.
I managed to convince them this was not a good idea - mostly because of shock cooling, dropping from MCL (high EGT) down to idle midway on every flight. They relented and included a short 5 or 10 min. cruise segment.
I managed to convince them this was not a good idea - mostly because of shock cooling, dropping from MCL (high EGT) down to idle midway on every flight. They relented and included a short 5 or 10 min. cruise segment.
