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flybynight
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777 cruising altitude

Wed Jul 12, 2017 8:54 pm

Looking at flights on Flightradar 24, it seems that 777's consistently fly around 35,000 feet (point of reference is Seattle area, so several hours into long trans-Pacific or trans-Atlantic flights) while A330/340/380 seems to be closer to 40,000.
I know that 777's are capable of flying as high as the comparable 330 or 340, but is 35,000 a sweet spot for the 777?
Heia Norge!
 
eraugrad02
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Re: 777 cruising altitude

Wed Jul 12, 2017 11:07 pm

It's usually initially because of fuel weight once an amount of fuel is burned of, they ask for higher. And also its not always a better ride the higher you are.
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ikolkyo
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Re: 777 cruising altitude

Wed Jul 12, 2017 11:22 pm

Heavy A330s and A340s are most definitely the same way.
 
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glen
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Re: 777 cruising altitude

Thu Jul 13, 2017 12:35 am

ikolkyo wrote:
Heavy A330s and A340s are most definitely the same way.


That's about right for the A330. A A340 at MTOW won't go aboove FL330; optimum is even lower.
"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
 
crownvic
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Re: 777 cruising altitude

Thu Jul 13, 2017 3:43 am

I just checked mid-Pacific transpacs on FR24, and nearly every 773 is over 40K in cruise.
 
horsepowerchef
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Re: 777 cruising altitude

Thu Jul 13, 2017 4:33 am

77W's tend to cruise lower than the non-stretched 777's due to their increased wing loading.
 
OYVKH
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Re: 777 cruising altitude

Thu Jul 13, 2017 7:05 pm

Can't say anything about the 77W...On the A330 though, which DK operates with 405 pax, they go straight up to FL410 easily on a 2-3h flight, and FL400 for a 4h flight approx. This is assuming a ''standard'' landing weight of 170t.
FL410 is achievable at 180t, and FL400 and 190t. MTOW departures (233t) are normally going straight up to FL350/360 (optimum might sometimes be lower of course).

Regards,

OY-VKH
 
mmo
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Re: 777 cruising altitude

Thu Jul 13, 2017 8:00 pm

The 777W at MTOW (775,000LBS) will be able to go to 320 depending on the OAT. However, generally 300/310 (depending on direction) is where you will go due to the temp deviation. towards the alter stages of the flight 390-410 are no problem but depending on winds it might be better to stay where you are.
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SCAT15F
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Re: 777 cruising altitude

Fri Jul 14, 2017 4:36 am

horsepowerchef wrote:
77W's tend to cruise lower than the non-stretched 777's due to their increased wing loading.


That's no joke. The 77W at ~165 lbs/sq ft has just about the highest wing loading of any aircraft flying. No wonder it needs two 115k engines.

By comparison the A3510 and A388 are in the 130's, and the 747SP was as low as 115 lbs/sq ft. at max takeoff weight.
 
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Francoflier
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Re: 777 cruising altitude

Fri Jul 14, 2017 4:56 am

It depends what version of the 777 you're talking about.

A heavy -200A model will happily operate in the high 30s - low 40s straight off the bat.
A heavy -300A will be happier in the mid 30s
A heavy -300ER will barely make the low 30s...

The thing is, they all essentially share the same wing. The 77W/77L/77F have a slightly extended wing, but not enough to reduce the wing loading significantly as they are quite a lot heavier than the 'small wing' models.

Basically, at the 2 extreme of the scale you'll find the light -200A, which has more than enough wing and is engine-limited, and at the other end you have the heavy -300ER, which has to make do with a wing a size too small, but compensates with massive amounts of power, and is thus wing-limited.

And then there's everything in between: -300A, -200ER, -200LR, -200F...
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flybynight
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Re: 777 cruising altitude

Fri Jul 14, 2017 7:11 pm

crownvic wrote:
I just checked mid-Pacific transpacs on FR24, and nearly every 773 is over 40K in cruise.



Really? I look all the time and most 777's (such as UA's, AA, ANA's etc) seem to seldom cruise over 35,000. I know the 777 is capable of altitudes of 43,000 ( I have personally been on one at 42,000 over Oregon), but I find it weird that an A330 or B787 flying similar routes seem to be constantly 2,000 - 4,000 feet higher.
Heia Norge!
 
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flybynight
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Re: 777 cruising altitude

Fri Jul 14, 2017 7:12 pm

Francoflier wrote:
It depends what version of the 777 you're talking about.

A heavy -200A model will happily operate in the high 30s - low 40s straight off the bat.
A heavy -300A will be happier in the mid 30s
A heavy -300ER will barely make the low 30s...

The thing is, they all essentially share the same wing. The 77W/77L/77F have a slightly extended wing, but not enough to reduce the wing loading significantly as they are quite a lot heavier than the 'small wing' models.

Basically, at the 2 extreme of the scale you'll find the light -200A, which has more than enough wing and is engine-limited, and at the other end you have the heavy -300ER, which has to make do with a wing a size too small, but compensates with massive amounts of power, and is thus wing-limited.

And then there's everything in between: -300A, -200ER, -200LR, -200F...


Thanks...this is what I was looking for!! Good answer.
Heia Norge!
 
Andre3K
Posts: 73
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Re: 777 cruising altitude

Sat Jul 15, 2017 2:58 am

flybynight wrote:
Francoflier wrote:
It depends what version of the 777 you're talking about.

A heavy -200A model will happily operate in the high 30s - low 40s straight off the bat.
A heavy -300A will be happier in the mid 30s
A heavy -300ER will barely make the low 30s...

The thing is, they all essentially share the same wing. The 77W/77L/77F have a slightly extended wing, but not enough to reduce the wing loading significantly as they are quite a lot heavier than the 'small wing' models.

Basically, at the 2 extreme of the scale you'll find the light -200A, which has more than enough wing and is engine-limited, and at the other end you have the heavy -300ER, which has to make do with a wing a size too small, but compensates with massive amounts of power, and is thus wing-limited.

And then there's everything in between: -300A, -200ER, -200LR, -200F...


Thanks...this is what I was looking for!! Good answer.


The only thing that really matters is that there were/are plenty of PAYING AIRLINES and CUSTOMERS who don't really care how high the cruise is, so long as it's profitable and fairly inexpensive.

Now if I could choose a cruise height, it would be cool to see the curvature of the earth somewhere up in the 50's.
 
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Starlionblue
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Re: 777 cruising altitude

Sat Jul 15, 2017 4:03 am

Andre3K wrote:
flybynight wrote:
Francoflier wrote:
It depends what version of the 777 you're talking about.

A heavy -200A model will happily operate in the high 30s - low 40s straight off the bat.
A heavy -300A will be happier in the mid 30s
A heavy -300ER will barely make the low 30s...

The thing is, they all essentially share the same wing. The 77W/77L/77F have a slightly extended wing, but not enough to reduce the wing loading significantly as they are quite a lot heavier than the 'small wing' models.

Basically, at the 2 extreme of the scale you'll find the light -200A, which has more than enough wing and is engine-limited, and at the other end you have the heavy -300ER, which has to make do with a wing a size too small, but compensates with massive amounts of power, and is thus wing-limited.

And then there's everything in between: -300A, -200ER, -200LR, -200F...


Thanks...this is what I was looking for!! Good answer.


The only thing that really matters is that there were/are plenty of PAYING AIRLINES and CUSTOMERS who don't really care how high the cruise is, so long as it's profitable and fairly inexpensive.

Now if I could choose a cruise height, it would be cool to see the curvature of the earth somewhere up in the 50's.


Absolutely right. However, there are economic advantages to a higher cruise altitude, for example less traffic and thus more likely to get direct routings and optimal altitudes, less weather avoidance and so on.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Andre3K
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Re: 777 cruising altitude

Sat Jul 15, 2017 6:08 pm

Starlionblue wrote:
Andre3K wrote:
flybynight wrote:

Thanks...this is what I was looking for!! Good answer.


The only thing that really matters is that there were/are plenty of PAYING AIRLINES and CUSTOMERS who don't really care how high the cruise is, so long as it's profitable and fairly inexpensive.

Now if I could choose a cruise height, it would be cool to see the curvature of the earth somewhere up in the 50's.


Absolutely right. However, there are economic advantages to a higher cruise altitude, for example less traffic and thus more likely to get direct routings and optimal altitudes, less weather avoidance and so on.



Yes of course. But isn't there also a penalty for climbing higher (longer high power setting to reach higher alt)? I know that might be offset somewhat by a longer decent at low power but it seems to me like cruising as high as possible just because you can get there wouldn't be the most economical. Obviously the FMC would advise against going higher than optimum but as far as I know it can't stop you from exceeding the recommended optimum.
 
Chaostheory
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Re: 777 cruising altitude

Sat Jul 15, 2017 10:51 pm

Andre3K wrote:
Yes of course. But isn't there also a penalty for climbing higher (longer high power setting to reach higher alt)? I know that might be offset somewhat by a longer decent at low power but it seems to me like cruising as high as possible just because you can get there wouldn't be the most economical. Obviously the FMC would advise against going higher than optimum but as far as I know it can't stop you from exceeding the recommended optimum.


Beyond a point, the overall trip efficiency afforded by higher altitude cruise offsets the cost (time and fuel) to get there.

Also, any pilot worth his salt wouldn't go above optimum cruise unless there was little choice. The performance margins, for both wings and engines, are wafer thin at cruise altitudes which is why you (should) respect them and don't degrade them any further.
 
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Starlionblue
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Re: 777 cruising altitude

Sat Jul 15, 2017 11:58 pm

Chaostheory wrote:
Andre3K wrote:
Yes of course. But isn't there also a penalty for climbing higher (longer high power setting to reach higher alt)? I know that might be offset somewhat by a longer decent at low power but it seems to me like cruising as high as possible just because you can get there wouldn't be the most economical. Obviously the FMC would advise against going higher than optimum but as far as I know it can't stop you from exceeding the recommended optimum.


Beyond a point, the overall trip efficiency afforded by higher altitude cruise offsets the cost (time and fuel) to get there.

Also, any pilot worth his salt wouldn't go above optimum cruise unless there was little choice. The performance margins, for both wings and engines, are wafer thin at cruise altitudes which is why you (should) respect them and don't degrade them any further.


Difference between optimum and maximum altitudes. In the Airbus, we will often go above "optimum" altitude if we believed we could get an altitude from ATC now but not later. "Claiming the high ground" if you will. However, going above the "rec max" altitude we would not do due to the performance limits mentioned.


Also if we climb higher we have longer high power setting in the climb but also longer idle in the descent. Either way it doesn't take that long a trip for the extra climb to often be worth it. Depends on weight.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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Re: 777 cruising altitude

Sun Jul 16, 2017 5:00 am

Boeing aircraft have optimum, maximum and recommended altitudes, in addition to the good
reasons Sblue has mentioned there are other occasions it will 'pay' to go higher than optimum,
for example to take advantage of a significant tailwind, in thus case recommended may well be
higher than optimum altitude but not the same as maximum.


You'd need to have a pretty good reason to go to max altitude however, not much margin between
low and high speed buffet there, if you allow the aircraft to decelerate at that level you will probably not have
adequate thrust to recover and have to descend to get your speed back.


An example where it might be worthwhile would be a situation where you'd be held to an inefficient low cruising
level for an entire Atlantic crossing because of other traffic unless you can accept going to 'max' prior to joining
the track system, in this case you'd redeem the lost efficiency 'down track' as you become lighter.


Only worth considering with pilot reports of smooth air at this max altitude, otherwise, don't even consider it.
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Chaostheory
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Re: 777 cruising altitude

Sun Jul 16, 2017 9:03 am

Max Q wrote:
Boeing aircraft have optimum, maximum and recommended altitudes, in addition to the good
reasons Sblue has mentioned there are other occasions it will 'pay' to go higher than optimum,
for example to take advantage of a significant tailwind, in thus case recommended may well be
higher than optimum altitude but not the same as maximum.


You'd need to have a pretty good reason to go to max altitude however, not much margin between
low and high speed buffet there, if you allow the aircraft to decelerate at that level you will probably not have
adequate thrust to recover and have to descend to get your speed back.


An example where it might be worthwhile would be a situation where you'd be held to an inefficient low cruising
level for an entire Atlantic crossing because of other traffic unless you can accept going to 'max' prior to joining
the track system, in this case you'd redeem the lost efficiency 'down track' as you become lighter.


Only worth considering with pilot reports of smooth air at this max altitude, otherwise, don't even consider it.


Absolutely. I don't disagree with you and I shouldn't have been as vague in my initial post. However, I think far too many crews aren't aware of how little performance they have available up there and how quickly it can diminish, especially above ISA temperatures. There have been more than a handful of "Oops" moments with crews getting into low/high speed buffet or over controlling even when below opt cruise.
 
Max Q
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Re: 777 cruising altitude

Mon Jul 17, 2017 3:41 am

Chaostheory wrote:
Max Q wrote:
Boeing aircraft have optimum, maximum and recommended altitudes, in addition to the good
reasons Sblue has mentioned there are other occasions it will 'pay' to go higher than optimum,
for example to take advantage of a significant tailwind, in thus case recommended may well be
higher than optimum altitude but not the same as maximum.


You'd need to have a pretty good reason to go to max altitude however, not much margin between
low and high speed buffet there, if you allow the aircraft to decelerate at that level you will probably not have
adequate thrust to recover and have to descend to get your speed back.


An example where it might be worthwhile would be a situation where you'd be held to an inefficient low cruising
level for an entire Atlantic crossing because of other traffic unless you can accept going to 'max' prior to joining
the track system, in this case you'd redeem the lost efficiency 'down track' as you become lighter.


Only worth considering with pilot reports of smooth air at this max altitude, otherwise, don't even consider it.


Absolutely. I don't disagree with you and I shouldn't have been as vague in my initial post. However, I think far too many crews aren't aware of how little performance they have available up there and how quickly it can diminish, especially above ISA temperatures. There have been more than a handful of "Oops" moments with crews getting into low/high speed buffet or over controlling even when below opt cruise.



Yes, completely agree with those points, if you do go to max altitude it should be with great care and on the rare occasions
i've done it i'll tend towards keeping the speed on the higher side, easy to slow down if you're too fast but next to impossible
to accelerate if you get slow.
The best contribution to safety is a competent Pilot.

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