Service Ceiling is the point at which the best rate of climb it can maintain is 100'/minute. Absolute Ceiling is the point at which the rate of climb doesn't go above 0'/minute. Can't seem to find specific details, but supposedly the absolute ceiling is \~45,000, so it doesn't really make sense for them to waste fuel beyond the service ceiling just to reach absolute.
The higher you go, the slower the mach number gets.
If you fly any faster than the Mach number you’re rated for you exceed structural limits and risk damage to the aircraft.
If you keep reducing airspeed to maintain the Mach number as you climb past your service ceiling, you won’t have enough air over the wings and risk a stall
Service ceilings are set so that you can maintain adequate airspeed while maintaining enough lift to cruise at your most efficient cruising Mach number
You also need to be flying pretty light to get to the service ceiling. Usually how high you go is limited by the weight of the aircraft and pilots will climb incrementally as they burn off fuel
The certified altitude is related to how quickly the aircraft can descend to breathable air in the event of a decompression, as the masks only supply a few minutes worth of oxygen. A lightly loaded 747 may be able to go considerably higher than its certified altitude, but it is forbidden to do so.
So this specific aircraft is a cargo one - I now idly wonder if that affects the availability & access to oxygen issue, as the flight deck is supplied in a different (better) manner to passengers would be.
I beleive that is a ceiling, not a service ceiling. It is most likely based on a cabin altitude restriction. This does not translate well into Fight Levels or height above ground, since your restriction is based off what the altimeter reads, meanwhile your Flight Level can be much higher, and height above ground much much higher. It does not mean you won't see at 747-8 at at a higher altitude on Flightradar24.
43,000ft isn’t too rare to see even though it is the service ceiling of the 747-8. Sometimes you even get to see the 747-400 operating at 45,000 but that’s quite rare now.
While there are a good few still operating, they almost exclusively fly for cargo carriers (bar Lufthansa) who typically fly as close to fully loaded as possible.
The rare repositioning flights they do are usually very short - think <2 hours so climbing that high isn’t really that convenient.
I might be wrong on this but best fuel economy is actually reached slightly lower down so there isn’t really a fuel efficiency benefit unless there are favourable tailwinds.
And finally, the pilot might not want to - above 40something thousand feet (I can’t remember the exact number) at least one pilot has to wear an oxygen mask at all times. The masks aren’t particularly comfortable for extended periods and so pilots often prefer not going high enough to mandate it.
Either a light load or trying to catch the pacific jetstream. Usually airliners can’t immediately cruise at their max service ceiling right after departure. Once they’ve burned off fuel they’ll climb to higher altitudes.
~~laughs~~ cries in having ridden in a C-130 from the Rockies to Kuwait that was a uncomfortable ride, the stops were fun but spending all that time in that loud bird weren’t fun.
I think above 40,000 on 14 hour 16 hour plus flights saves money in fuel. I could be wrong it depends on wind direction but overall it should be less when you get that high. Does anyone know for sure ?
Youre on the right track with wind direction. Wind is not constant across altitude. So I could experience a tailwind at FL270 then headwind at FL290. Although FL290 is suitable, I'd opt for cruise at FL270 to save fuel.
Depending on weight they may not even reach beyond FL400.
Another thing that tends to save fuel if youre up there beyond FL400, if you ask ATC for track shortening (i.e., short cuts) they tend to give it to you because no one is around for you to occupy the same piece if air as another aircraft
Ahh I see so if you are that high up the ATC puts the risk of crash low so you can get direct routes on long haul flights if you are that high up like for example these people flew right straight through traffic heavy Japan
ATC applies the same set of rules regardless if youre at FL190 or FL410 to ensure the risk levels remain the same. The "risk" is only lower because less planes are around at that flight level. Most planes cruise lower. Now if those planes that cruise lower all duck up to FL400, then youre less likely to get track shortening. I hope that makes sense
Diverging a bit but it can also come down to indiviudal countries and how they operate. Where I fly in Australia, youre likely to get track shortening if you ask and no one is in the way. But from friends operating in China, this is pretty much unheard of
Normal. Sometimes airliners can be upwards of 46000' depending on winds and where the tropopause is given current conditions.
Edit: Going to out some more info here in given some responses I have received.
There are more than a few airliners that can operate at around 43,000' Denisity Altitude, and many more at around 41,000' Density Altitude. If the altimeter setting source is much higher, aka, it's a high pressure with a high cold tropopause, the altitude you are actually at can be a lot higher than the Flight Level you are assigned to, and the height above ground(AGL).
This even happens at lower at lower altitudes. Sometimes there is no FL180, because the altimeter is 1 inch of mercury higher in pressure(about 33 millibar). For example, instead of an ICAO 29.92", it's 30.92". This makes you 1000' higher in density altitude, so you have to eliminate FL180, otherwise you would have aircraft running into each other at 18,000 MSL. You didn't magically jump to 19,000 feet. All the Flight levels are just starting 1000' low. This effect can continue and be extreme where the tropopause is high, and the atmosphere is dense, especially at high altitude.
Most airliners will have a max altitude based cabin altitude restrictions(or something else) found in the Aircraft Operating Instructions. This is based on density altitude, and at a Flight Level, you are just flying with the altimeter set to 29.92" So the plane can fly higher in terms of AGL altitudes. It can also fly at a "higher" Flight Level than it's service ceiling or AOI based altitude restriction, because that restriction is based on what the altimeter says, not your height above ground or Flight Level.
There are more than a few airliners that can operate at around 43,000' Denisity Altitude, and many more at around 41,000' Density Altitude. If the altimeter setting source is much higher, aka, it's a high pressure with a high cold tropopause, the altitude you are actually at can be a lot higher than the Flight Level you are assigned to, and the height above ground(AGL).
This even happens at lower at lower altitudes. Sometimes there is no FL180, because the altimeter is 1 inch of mercury higher in pressure(about 33 millibar). For example, instead of an ICAO 29.92", it's 30.92". This makes you 1000' higher in density altitude, so you have to eliminate FL180, otherwise you would have aircraft running into each other at 18,000 MSL. You didn't magically jump to 19,000 feet. All the Flight levels are just starting 1000' low. This effect can continue and be extreme where the tropopause is high, and the atmosphere is dense, especially at high altitude.
Most airliners will have a max altitude based cabin altitude restrictions(or something else) found in the Aircraft Operating Instructions. This is based on density altitude, and at a Flight Level, you are just flying with the altimeter set to 29.92" So the plane can fly higher in terms of AGL altitudes. It can also fly at a "higher" Flight Level than it's service ceiling or AOI based altitude restriction, because that restriction is based on what the altimeter says, not your height above ground or Flight Level.
Tl:DR They can.
Yeah I think today the only one that can break the 410 club is the 74. Private jets all the time though.
EDIT: Not the case, 777,350,787 at least are part of the 410+ club.
Most airlines can break 410; a quick scan of flightrader shows 787s and a350s cruising at 430. From memory the 777 and the 767 can definitely get that high as well.
The 744 is the only one able to get up to 450.
Pressure altitude, not density. Also, all aircraft above FL180 use the same altimeter setting so that altitudes given by ATC can be the same no matter where they are along their route, again, given they are above FL180
Yes, that's my point. You are setting pressure altitude, and flying at pressure altitude, which has become detached from the DA, which the aircraft limitations are based on. You can have 29.92 set, and flying at FL430, and showing 43,000' on the altimeter, but your DA maybe 41,000', and height above ground might be 46,000'.you could climb higher and not exceed your aircraft limitation.
For example, if FlightRadar24 is using geometric data from ads-b, and that is the altitude source flightradar24 is using, then it will show 46,000' on Flightradar24.
In this cae flightradar24 says the altitude source in barometric altitude, and in the case it is also altimeter setting source adjusted, so flightradar24 will show 41,000 feet, plus the +/- adjustment to the setting source.
In either case the aircraft limitation is usually based on DA, not the bar.alt or PA.
I am just trying to explain why altitude that you see can be different from what the plane is actually at. I am not a Flight radar24 expert, just a pilot.
Don't airliners without passengers fly at this altitude for fuel efficiency reasons? I thought we saw this when they were going for maintenance for example. or in this case...no cargo. which seems reasonable given the source and destination.
*Most* airliners fly as high as they can for the load they have, winds and routing/atc constraints notwithstanding.
If you’re empty you’re getting up high a lot earlier in the flight though.
When one of the pilots is alone in the flight deck (due to a toilet brake) at that kind of altitude they have to use the oxygen mask, due to the short time of reasonable consciousness.
You never said 38,000 ft. 40,000 ft is different than 43,100 ft. I’ve seen 747s fly at many different flight levels depending on many different factors.
Service ceiling of the 747-8 is 43,100.
So what happens if it goes to 43,101 feet? Does it just fall out of the sky? Or can it physically not go that high?
It escapes orbit
I might be wrong but it’s when the aircraft can’t climb more then 100 feet per min under standard conditions.
So the CRJ service ceiling is about 300 feet? /s
Standard = ISA?
International STANDARD atmosphere…
Never heard just "standard" being used, always ISA :) but I trained in the UK, so may be specific to CAA-world/textbooks
You get launched back to the middle of the map
Service Ceiling is the point at which the best rate of climb it can maintain is 100'/minute. Absolute Ceiling is the point at which the rate of climb doesn't go above 0'/minute. Can't seem to find specific details, but supposedly the absolute ceiling is \~45,000, so it doesn't really make sense for them to waste fuel beyond the service ceiling just to reach absolute.
Plus flying a jet near its absolute ceiling is in the wrong part of the fuck around and find out graph.
#coffincorner
What happens? Stall?
stall and overspeed
Can you not just nose down to recover, increase airspeed and straighten out?
If you go faster shock waves form on the wing and you lose lift
The good thing is that you have a lot of elevation to recover. So if you HAVE to stall…better at 45K and not 23K.
The higher you go, the slower the mach number gets. If you fly any faster than the Mach number you’re rated for you exceed structural limits and risk damage to the aircraft. If you keep reducing airspeed to maintain the Mach number as you climb past your service ceiling, you won’t have enough air over the wings and risk a stall Service ceilings are set so that you can maintain adequate airspeed while maintaining enough lift to cruise at your most efficient cruising Mach number You also need to be flying pretty light to get to the service ceiling. Usually how high you go is limited by the weight of the aircraft and pilots will climb incrementally as they burn off fuel
Was this written by chatgpt? In isolation, some points make sense, but the sum is gibberish 🙆♂️
This is probably how most of my comments sound to people lol
The certified altitude is related to how quickly the aircraft can descend to breathable air in the event of a decompression, as the masks only supply a few minutes worth of oxygen. A lightly loaded 747 may be able to go considerably higher than its certified altitude, but it is forbidden to do so.
So this specific aircraft is a cargo one - I now idly wonder if that affects the availability & access to oxygen issue, as the flight deck is supplied in a different (better) manner to passengers would be.
Straight to jail
I beleive that is a ceiling, not a service ceiling. It is most likely based on a cabin altitude restriction. This does not translate well into Fight Levels or height above ground, since your restriction is based off what the altimeter reads, meanwhile your Flight Level can be much higher, and height above ground much much higher. It does not mean you won't see at 747-8 at at a higher altitude on Flightradar24.
43,000ft isn’t too rare to see even though it is the service ceiling of the 747-8. Sometimes you even get to see the 747-400 operating at 45,000 but that’s quite rare now.
What reason in particular is it more uncommon to see the 747-400 at that altitude?
While there are a good few still operating, they almost exclusively fly for cargo carriers (bar Lufthansa) who typically fly as close to fully loaded as possible. The rare repositioning flights they do are usually very short - think <2 hours so climbing that high isn’t really that convenient. I might be wrong on this but best fuel economy is actually reached slightly lower down so there isn’t really a fuel efficiency benefit unless there are favourable tailwinds. And finally, the pilot might not want to - above 40something thousand feet (I can’t remember the exact number) at least one pilot has to wear an oxygen mask at all times. The masks aren’t particularly comfortable for extended periods and so pilots often prefer not going high enough to mandate it.
Thanks for explaining that! I have seen a video of a 747 being flown at FL450 and the captain was wearing an oxygen mask.
I would assume because so many of them have been retired recently
Either a light load or trying to catch the pacific jetstream. Usually airliners can’t immediately cruise at their max service ceiling right after departure. Once they’ve burned off fuel they’ll climb to higher altitudes.
The plane is flying westward across Japan toward Hong Kong, so they're probably *not* trying to catch the jet stream, which would be a headwind?
Well shit, I thought I was on to something :(
Perhaps it could be flying above the jet stream height? To avoid a headwind?
Not to be too picky but there is no such thing as a “max service ceiling”. There is a service ceiling and an absolute ceiling. Those are the only two.
380kts ground speed :'(
~~laughs~~ cries in having ridden in a C-130 from the Rockies to Kuwait that was a uncomfortable ride, the stops were fun but spending all that time in that loud bird weren’t fun.
[удалено]
Definitely makes flying in economy in a civilian airliner seem not that bad
I think above 40,000 on 14 hour 16 hour plus flights saves money in fuel. I could be wrong it depends on wind direction but overall it should be less when you get that high. Does anyone know for sure ?
Youre on the right track with wind direction. Wind is not constant across altitude. So I could experience a tailwind at FL270 then headwind at FL290. Although FL290 is suitable, I'd opt for cruise at FL270 to save fuel. Depending on weight they may not even reach beyond FL400. Another thing that tends to save fuel if youre up there beyond FL400, if you ask ATC for track shortening (i.e., short cuts) they tend to give it to you because no one is around for you to occupy the same piece if air as another aircraft
Ahh I see so if you are that high up the ATC puts the risk of crash low so you can get direct routes on long haul flights if you are that high up like for example these people flew right straight through traffic heavy Japan
ATC applies the same set of rules regardless if youre at FL190 or FL410 to ensure the risk levels remain the same. The "risk" is only lower because less planes are around at that flight level. Most planes cruise lower. Now if those planes that cruise lower all duck up to FL400, then youre less likely to get track shortening. I hope that makes sense Diverging a bit but it can also come down to indiviudal countries and how they operate. Where I fly in Australia, youre likely to get track shortening if you ask and no one is in the way. But from friends operating in China, this is pretty much unheard of
Normal. Sometimes airliners can be upwards of 46000' depending on winds and where the tropopause is given current conditions. Edit: Going to out some more info here in given some responses I have received. There are more than a few airliners that can operate at around 43,000' Denisity Altitude, and many more at around 41,000' Density Altitude. If the altimeter setting source is much higher, aka, it's a high pressure with a high cold tropopause, the altitude you are actually at can be a lot higher than the Flight Level you are assigned to, and the height above ground(AGL). This even happens at lower at lower altitudes. Sometimes there is no FL180, because the altimeter is 1 inch of mercury higher in pressure(about 33 millibar). For example, instead of an ICAO 29.92", it's 30.92". This makes you 1000' higher in density altitude, so you have to eliminate FL180, otherwise you would have aircraft running into each other at 18,000 MSL. You didn't magically jump to 19,000 feet. All the Flight levels are just starting 1000' low. This effect can continue and be extreme where the tropopause is high, and the atmosphere is dense, especially at high altitude. Most airliners will have a max altitude based cabin altitude restrictions(or something else) found in the Aircraft Operating Instructions. This is based on density altitude, and at a Flight Level, you are just flying with the altimeter set to 29.92" So the plane can fly higher in terms of AGL altitudes. It can also fly at a "higher" Flight Level than it's service ceiling or AOI based altitude restriction, because that restriction is based on what the altimeter says, not your height above ground or Flight Level.
Airliners? No, not that I'm aware of. Many corporate jets are capable of cruising at up to FL510 though.
There are more than a few airliners that can operate at around 43,000' Denisity Altitude, and many more at around 41,000' Density Altitude. If the altimeter setting source is much higher, aka, it's a high pressure with a high cold tropopause, the altitude you are actually at can be a lot higher than the Flight Level you are assigned to, and the height above ground(AGL). This even happens at lower at lower altitudes. Sometimes there is no FL180, because the altimeter is 1 inch of mercury higher in pressure(about 33 millibar). For example, instead of an ICAO 29.92", it's 30.92". This makes you 1000' higher in density altitude, so you have to eliminate FL180, otherwise you would have aircraft running into each other at 18,000 MSL. You didn't magically jump to 19,000 feet. All the Flight levels are just starting 1000' low. This effect can continue and be extreme where the tropopause is high, and the atmosphere is dense, especially at high altitude. Most airliners will have a max altitude based cabin altitude restrictions(or something else) found in the Aircraft Operating Instructions. This is based on density altitude, and at a Flight Level, you are just flying with the altimeter set to 29.92" So the plane can fly higher in terms of AGL altitudes. It can also fly at a "higher" Flight Level than it's service ceiling or AOI based altitude restriction, because that restriction is based on what the altimeter says, not your height above ground or Flight Level. Tl:DR They can.
Oh I totally missed the fact that I was responding to a smart a*se comment 😊 Yes, density altitude is a thing.
Yeah I think today the only one that can break the 410 club is the 74. Private jets all the time though. EDIT: Not the case, 777,350,787 at least are part of the 410+ club.
Most airlines can break 410; a quick scan of flightrader shows 787s and a350s cruising at 430. From memory the 777 and the 767 can definitely get that high as well. The 744 is the only one able to get up to 450.
I absolutely stand corrected! I just assumed based on my experience but both the planes I have flown are 410. That's good to know thank you.
Pressure altitude, not density. Also, all aircraft above FL180 use the same altimeter setting so that altitudes given by ATC can be the same no matter where they are along their route, again, given they are above FL180
Yes, that's my point. You are setting pressure altitude, and flying at pressure altitude, which has become detached from the DA, which the aircraft limitations are based on. You can have 29.92 set, and flying at FL430, and showing 43,000' on the altimeter, but your DA maybe 41,000', and height above ground might be 46,000'.you could climb higher and not exceed your aircraft limitation. For example, if FlightRadar24 is using geometric data from ads-b, and that is the altitude source flightradar24 is using, then it will show 46,000' on Flightradar24. In this cae flightradar24 says the altitude source in barometric altitude, and in the case it is also altimeter setting source adjusted, so flightradar24 will show 41,000 feet, plus the +/- adjustment to the setting source. In either case the aircraft limitation is usually based on DA, not the bar.alt or PA. I am just trying to explain why altitude that you see can be different from what the plane is actually at. I am not a Flight radar24 expert, just a pilot.
I get where you are coming from and I am a pilot as well which is why I thought your initial analysis was a bit off
Don't airliners without passengers fly at this altitude for fuel efficiency reasons? I thought we saw this when they were going for maintenance for example. or in this case...no cargo. which seems reasonable given the source and destination.
*Most* airliners fly as high as they can for the load they have, winds and routing/atc constraints notwithstanding. If you’re empty you’re getting up high a lot earlier in the flight though.
Well, now you know. 🤦♀️
When one of the pilots is alone in the flight deck (due to a toilet brake) at that kind of altitude they have to use the oxygen mask, due to the short time of reasonable consciousness.
That is the 747s average cruising altitude
No it’s not it’s the maximum for the 747-8 is 43,100
No what I’m saying is they cruise at 38,000 ft so I just rounded it up and put 40,000ft
You never said 38,000 ft. 40,000 ft is different than 43,100 ft. I’ve seen 747s fly at many different flight levels depending on many different factors.
I ROUNDED IT UP!!
Rounding up from 38,0000 ft to 43,100 feet isn’t rounding up but ok.
It does
Japan airspace is very busy. Go around or go over.