Genscherist
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High Flight Levels

Tue Dec 04, 2018 5:04 pm

Hello!

When I set a Flightradar24-Filter to show me planes above 40000 ft only it's mostly A350s and B787s and a few Ryanair-Planes.

How come that other Aircrafts/Airlines usually don't fly that high though they could? Isn't it more economic to fly that high?

Thanks and best regards!
 
GalaxyFlyer
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Re: High Flight Levels

Tue Dec 04, 2018 6:03 pm

Cause they can’t, usually the wing won’t allow but some planes run out thrust at higher levels. The 777 typically starts around F290-310 on a long leg and ends around F379-390.
 
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trpmb6
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Re: High Flight Levels

Tue Dec 04, 2018 6:09 pm

All about the density altitude. At some point you just run out of air to chew on.
 
PSAatSAN4Ever
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Re: High Flight Levels

Tue Dec 04, 2018 6:11 pm

Someone correct me if this information is incorrect, but I thought I remember reading about United 93 that the hijackers took the plane up to 41,000 feet, something that was highly unusual but not out of the performance ability of the 757-200. I had thought 39,000 feet was the highest cruising altitude available until reading this. Was this unique to the 757?
 
GalaxyFlyer
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Re: High Flight Levels

Tue Dec 04, 2018 9:55 pm

F412 is the max, I believe, for most Boeings. The 747SP was F452.

GF
 
ChrisKen
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Re: High Flight Levels

Tue Dec 04, 2018 10:42 pm

it's not that today's aircraft can't fly that high it's just there was a change in the certification rules a few years back which mean aircraft now need to meet extended requirements at FL400 and above.
One of the reasons the A320 family are certified to 39,500ft and why aircraft that routinely flew higher now rarely do (eg 747/757/767)

Extra requirements would be more stringent requirements on the pressure hull and it's abilities to hold during leak scenarios and added O2 systems (pax & crew) for example.
Those extra requirements obviously don't justify the cost for many manufactuers and/or airlines.
 
geologyrocks
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Re: High Flight Levels

Tue Dec 04, 2018 10:49 pm

You’ll see 737-700’s up there as well.
 
GalaxyFlyer
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Re: High Flight Levels

Tue Dec 04, 2018 10:54 pm

I knew some big certification issues for F450 and another “jump” in the requirements for F510. Didn’t know that the standards changed for F400.

GF
 
77H
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Re: High Flight Levels

Tue Dec 04, 2018 11:00 pm

PSAatSAN4Ever wrote:
Someone correct me if this information is incorrect, but I thought I remember reading about United 93 that the hijackers took the plane up to 41,000 feet, something that was highly unusual but not out of the performance ability of the 757-200. I had thought 39,000 feet was the highest cruising altitude available until reading this. Was this unique to the 757?


I was on a UA 752 between HNL-LAX that was up at FL410. Highest FL I've been up to. The flight info screen on the seatback said it was -84 degrees F which I thought was wild.
I have also been at FL400 on a UA 77A between IAH-HNL.

77H
 
aklrno
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Re: High Flight Levels

Wed Dec 05, 2018 12:49 am

There is also a requirement that the aircraft be capable of descending to breathable air (10,000 feet?) in a certain amount of time in case of a depressurization event. Are there different maximum descent vertical speeds at play here?
 
GalaxyFlyer
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Re: High Flight Levels

Wed Dec 05, 2018 1:17 am

It has to descend so that the cabin is above F259 for no more than 2 minutes and never exceeds F400 after descent is initiated allowing for 17 seconds of reaction and the actions to begin the descent. Nominally, it’s about four minutes from macimum certified altitude to 10.000’. From F510, there’s some really high rates of descent and nose low position. On the order of 7-10,000 fpm.

GF
 
barney captain
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Re: High Flight Levels

Wed Dec 05, 2018 10:07 am

GalaxyFlyer wrote:
I knew some big certification issues for F450 and another “jump” in the requirements for F510. Didn’t know that the standards changed for F400.

GF


I've never heard of that either. We routinely go up to FL410 assuming we're light enough.
Southeast Of Disorder
 
stratclub
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Re: High Flight Levels

Wed Dec 05, 2018 4:30 pm

Good point. If an aircraft is near gross weight, it can't even reach it's certified altitude until it burns off some fuel.
 
buzzard302
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Re: High Flight Levels

Wed Dec 05, 2018 5:17 pm

I was on a Southwest 737-700 the other day. Full passenger load, we went straight to FL390. Not as high as you mention, but still up there.
 
barney captain
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Re: High Flight Levels

Wed Dec 05, 2018 5:24 pm

buzzard302 wrote:
I was on a Southwest 737-700 the other day. Full passenger load, we went straight to FL390. Not as high as you mention, but still up there.



Fuel is much more of a factor. Anything less than a 2 hour flight in a -700 and 390 is rarely an issue - even with full pax. The -800, not so much.
Southeast Of Disorder
 
GalaxyFlyer
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Re: High Flight Levels

Wed Dec 05, 2018 8:52 pm

stratclub wrote:
Good point. If an aircraft is near gross weight, it can't even reach it's certified altitude until it burns off some fuel.


Not some, a lot in most cases. A grossed out Global, certified to F510, started out at F390 or F400,depending on temperature. It’d climb to F430 about 4-5 hours later, F470 about another 5 hours and remain there for the last two hours. A light weight on a 2-3 hour leg could got to 450 in about 23 minutes. F490 or F510 in later builds (heavy interiors) never was an optimum level and involved cruising st about M.82) A C-5 with TF-39s would leave PHIK (PHNL on the civil side) typically at F260; climb entering Nadi to maybe F300 or 310 and finish under Brisbane Control climbing to F370/390. Above F350 depended on cabin leak rate, a lot had s hard time pressurizing up high. Certified ceiling isn’t often a limiting factor.
 
United857
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Re: High Flight Levels

Thu Dec 06, 2018 12:48 am

I believe a big part that allows the A350/787 to cruise so high are the automatic active variable camber flaps that allow the wing to modify its L/D ratio. Due to the lower air density at higher altitudes, indicated airspeed, which measures the quantity of air molecules flowing over the wing and thus the lift being produced, decreases for a constant mach speed, the unit of measurement for speed at high altitude. Therefore, an aircraft can only fly as high as its wings allow. On older aircraft with fixed flaps for cruise, aircraft had to compensate for the lower indicated airspeed at higher altitude by increasing pitch and thus the angle of attack of the wings. There is a limit to this, however, as eventually the wing will get to an angle of attack so high that it will start buffeting, and unless the plane is really light it could never achieve altitudes such as FL400.

With active variable camber flaps, however, the plane can increase the L/D ratio as indicated airspeed decreases at higher altitudes by extending the flaps a couple of degrees and take advantage of more direct routings due to the lack of traffic flying so high, shortening the flight time and therefore saving fuel (presumably the fuel savings from a shorter routing outweighs the additional fuel burn from potentially flying above the optimal altitude). The plane retract also retract those flaps when stuck at lower altitudes where the extra lift is not needed and doing so provides a decrease in drag.
 
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Starlionblue
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Re: High Flight Levels

Thu Dec 06, 2018 2:15 am

United857 wrote:
I believe a big part that allows the A350/787 to cruise so high are the automatic active variable camber flaps that allow the wing to modify its L/D ratio. Due to the lower air density at higher altitudes, indicated airspeed, which measures the quantity of air molecules flowing over the wing and thus the lift being produced, decreases for a constant mach speed, the unit of measurement for speed at high altitude. Therefore, an aircraft can only fly as high as its wings allow. On older aircraft with fixed flaps for cruise, aircraft had to compensate for the lower indicated airspeed at higher altitude by increasing pitch and thus the angle of attack of the wings. There is a limit to this, however, as eventually the wing will get to an angle of attack so high that it will start buffeting, and unless the plane is really light it could never achieve altitudes such as FL400.

With active variable camber flaps, however, the plane can increase the L/D ratio as indicated airspeed decreases at higher altitudes by extending the flaps a couple of degrees and take advantage of more direct routings due to the lack of traffic flying so high, shortening the flight time and therefore saving fuel (presumably the fuel savings from a shorter routing outweighs the additional fuel burn from potentially flying above the optimal altitude). The plane retract also retract those flaps when stuck at lower altitudes where the extra lift is not needed and doing so provides a decrease in drag.


AFAIK the flaps extending in cruise may have a bit to do with it, but that flap function on the A350 is mostly there to shift the centre of lift forward, which decreases fuel burn. The A330 achieves the same effect by moving fuel to the trim tank, which shifts the centre of gravity backwards.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Yikes!
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Re: High Flight Levels

Thu Dec 06, 2018 3:28 am

The 752 as well as the 763 was certified to FL420, where I had each at that Flight Level on occasion. It was a question of maximum differential keeping the cabin at 8,000.

Many corporate jets are now certified into the mid 50's. Concorde flew to FL620.

It's all a question of cabin altitude and what the airframe is capable of providing.
 
Max Q
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Re: High Flight Levels

Thu Dec 06, 2018 6:42 am

Yikes! wrote:
The 752 as well as the 763 was certified to FL420, where I had each at that Flight Level on occasion. It was a question of maximum differential keeping the cabin at 8,000.

Many corporate jets are now certified into the mid 50's. Concorde flew to FL620.

It's all a question of cabin altitude and what the airframe is capable of providing.




Our 757’s were certified to FL420 and 767’s to FL430

Been to 410 many times in both subtypes and to 430 once in a very light 767-200


Pretty sure all 747 models except the -8 were certified to FL450, I believe the -8 has a limit of FL430 as it could not descend fast enough from 450 in a decompression



Concorde’s certified maximum FL was 600
and it didn’t exceed this in regular service although in flight test it got as high as 68000 and as fast as Mach 2.2
The best contribution to safety is a competent Pilot.
 
GalaxyFlyer
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Re: High Flight Levels

Thu Dec 06, 2018 12:56 pm

F510 is the highest subsonic certification level—Gulfstream, Global, Citation X, several Learjet types, and I think one or two Falcon models. In my experience, fairly rare to go above 470; 490 felt okay in a Global but clearly stretching thins-Mach was down to .83 and turns brought the airspeed limits into view. F450 in a Global and you could do 30 degree banked turns without seeing the limit marks showing in the ASI.

GF
 
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longhauler
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Re: High Flight Levels

Thu Dec 06, 2018 1:44 pm

Where I fly, any flight above FL410 requires that one pilot must wear an oxygen mask. That alone keeps us no higher than 410. I only went up to 430 once (on oxygen) took pictures of the PFD then back down. ;)
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
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Starlionblue
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Re: High Flight Levels

Thu Dec 06, 2018 1:48 pm

longhauler wrote:
Where I fly, any flight above FL410 requires that one pilot must wear an oxygen mask. That alone keeps us no higher than 410. I only went up to 430 once (on oxygen) took pictures of the PFD then back down. ;)


Our manual says above FL300 requires a pilot to wear an oxygen mask when there is no other pilot on the flight deck...

Unless... The oxygen mask available is of the "quick-donning type". Which ours are.

Been to FL430. No mask. It's just like FL410 except... ahem... higher...
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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Re: High Flight Levels

Fri Dec 07, 2018 2:17 am

ALPA is working on a revision to the FAR that mandates one pilot be on
oxygen if the other leaves the flight deck above FL250


Their objective is to eliminate this requirement and retain the requirement for both pilots to wear masks above FL410
The best contribution to safety is a competent Pilot.
 
GalaxyFlyer
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Re: High Flight Levels

Fri Dec 07, 2018 2:46 pm

It’s only one pilot that needs to use O2 continuously above F410. FAR 91.211. The NBAA has been trying modify the F410 rule for several years—it’s frequently ignored, including the FAA’s own pilots from understanding working on the committee. The stats for depressurization in modern jets don’t support the requirement especially with realistic mitigation plans—chamber training, auto descent mode, sim training in use of EDM.

The hazard is O2 masks are designed for emergency use, not hours of wear, concerns on the drying aspect of hours of breathing dry O2, sanitary controls for multiple pilots using the same mask. The Global has a cruise mask that was like tying a rope around your head for two hours.

GF
 
vuelti24
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Re: High Flight Levels

Fri Dec 07, 2018 8:12 pm

Been FL410 on an AA 772 MIA-EZE
 
Max Q
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Re: High Flight Levels

Sat Dec 08, 2018 2:32 am

GalaxyFlyer wrote:
It’s only one pilot that needs to use O2 continuously above F410. FAR 91.211. The NBAA has been trying modify the F410 rule for several years—it’s frequently ignored, including the FAA’s own pilots from understanding working on the committee. The stats for depressurization in modern jets don’t support the requirement especially with realistic mitigation plans—chamber training, auto descent mode, sim training in use of EDM.

The hazard is O2 masks are designed for emergency use, not hours of wear, concerns on the drying aspect of hours of breathing dry O2, sanitary controls for multiple pilots using the same mask. The Global has a cruise mask that was like tying a rope around your head for two hours.

GF



I stand corrected, it is just one pilot that needs to be on O2 above 410


Many of these oxygen rules are ignored, I’ve always purged and cleaned out my mask with alcohol wipes thoroughly before every flight though, lots of pilots don’t


When you need it you don’t want a mouthful of dust and god knows what else
The best contribution to safety is a competent Pilot.
 
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ElroyJetson
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Re: High Flight Levels

Sat Dec 08, 2018 5:03 am

longhauler wrote:
Where I fly, any flight above FL410 requires that one pilot must wear an oxygen mask. That alone keeps us no higher than 410. I only went up to 430 once (on oxygen) took pictures of the PFD then back down. ;)



I remember being on a TWA 747 flight from JFK to LHR when I was a kid and the pilot saying we were at FL 45. I looked out the window and cloud deck over the Atlantic looked about 100 miles down. Never seen that since. The highest i recall on any flight since is FL 39 and that was on a 757.

I had no idea it is so restricted now days.
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747Whale
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Re: High Flight Levels

Sat Dec 08, 2018 5:59 am

PSAatSAN4Ever wrote:
Someone correct me if this information is incorrect, but I thought I remember reading about United 93 that the hijackers took the plane up to 41,000 feet, something that was highly unusual but not out of the performance ability of the 757-200. I had thought 39,000 feet was the highest cruising altitude available until reading this. Was this unique to the 757?


Selecting a cruise altitude is baed on several criteria; weight is chief among them. For a given weight and air temperature, there is an optimum altitude. To cruise above this altitude is to burn excess fuel; the airplane rapidly becomes less efficient with any excess altitude above optimum. It's more efficient to cruise below than above. Aircraft are often weight limited on long flights, and will "step climb," or increase altitude as fuel burns off, allowing a higher optimum altitude.

Winds aloft must also be considered. There is little point climbing 2,000' higher to achieve optimum, for example, when it might bean a 100 knot increase in headwind; in such a case it may be beneficial to alter flight path, take a longer route and fly lower at a less efficient altitude, and still come out ahead.

Passenger comfort is also a consideration, and altitude is often adjusted to the smoothest flight level available that is at or below optimum.
 
timh4000
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Re: High Flight Levels

Sat Dec 08, 2018 6:16 am

When I was stationed in Germany back in the mid 80's and would fly home on leave I always picked Pan Am. Always got the 747 and Back then it was just the captain's message about our flight. Initial climb would be to FL 32 and eventually to FL 41. That is the highest I have ever been. When my wife and I go to Florida I usually have the nav thing on and Typically the A320 we always fly on (jet blue) usually gets to about FL36.

In 2011 we took a direct flight from JFK to LAX on Virgin American. I didn't know what we were flying on, can't remember if the ticket had it on or not, she was holding them, We get to the gate and I see an A320 and I told her I don't think that one is ours, but it was. I didn't realize the A320 did cross the country. For the briefest moment I thought to myself this is really stretching it... but the logical brain kicked in and obviously they need min fuel safety requirements. Watching my favorite channel we maxed out at FL38.
 
GalaxyFlyer
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Re: High Flight Levels

Sat Dec 08, 2018 11:37 pm

ElroyJetson wrote:
longhauler wrote:
Where I fly, any flight above FL410 requires that one pilot must wear an oxygen mask. That alone keeps us no higher than 410. I only went up to 430 once (on oxygen) took pictures of the PFD then back down. ;)



I remember being on a TWA 747 flight from JFK to LHR when I was a kid and the pilot saying we were at FL 45. I looked out the window and cloud deck over the Atlantic looked about 100 miles down. Never seen that since. The highest i recall on any flight since is FL 39 and that was on a 757.

I had no idea it is so restricted now days.


There are no restrictions nowadays that weren’t there in those days—it’s all depends on aircraft certification and optimum range. FAR 91.211 hasn’t changed on oxygen use in 50 years.

GF
 
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cpd
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Re: High Flight Levels

Mon Dec 10, 2018 1:21 am

Max Q wrote:
Yikes! wrote:
The 752 as well as the 763 was certified to FL420, where I had each at that Flight Level on occasion. It was a question of maximum differential keeping the cabin at 8,000.

Many corporate jets are now certified into the mid 50's. Concorde flew to FL620.

It's all a question of cabin altitude and what the airframe is capable of providing.




Our 757’s were certified to FL420 and 767’s to FL430

Been to 410 many times in both subtypes and to 430 once in a very light 767-200


Pretty sure all 747 models except the -8 were certified to FL450, I believe the -8 has a limit of FL430 as it could not descend fast enough from 450 in a decompression



Concorde’s certified maximum FL was 600
and it didn’t exceed this in regular service although in flight test it got as high as 68000 and as fast as Mach 2.2


Believe F-WTSB went even higher than 68,000ft (according to the custodians of that plane), but none of them went any quicker than G-AXDN, despite attempts to beat it on a number of occasions (one time with G-BFKX if I remember right).

I've seen A380s go fairly high as well. And those United 747s used to always go very high from Sydney to Melbourne and back (those were the days).

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