A380 cruise altitude record

[Porrohman]

ONE GREEN AND HOPING asked;

just how high can today's jets sustain cruise in commercial conditions.

Here are some examples that I found from various sources including Boeing's web site;

Boeing 367-80 = 43,000ft
Boeing 707-120 = 42,000ft
Boeing 707-320B = 36,000ft
Boeing 707-338C = 39,000ft
Boeing 727 = 40,000ft
Boeing 737-100/200 = 35,000ft
Boeing 737 200adv/300/400/500 = 37,000ft
Boeing 737-600/700/800/900 = 41,000ft
Boeing 747 = 45,000ft
Boeing 757 = 42,000ft
Boeing 767 = 39,000ft (except 767-300ER which is 43,100ft and 767-400 which is 43,300ft)
Boeing 777 = 43,000ft

VC10 Type 1101/1151/1154 = 38,000ft
VC10 Type 1102/1103 = 43,000ft (greater wing area than Type 1101)

Comet 1 = 42,000ft
Comet 4 = 40,000ft
Comet 4B = 38,000ft
Comet 4C = 39,000ft

Convair 880 = 40,000ft

L1011 = 42,000ft

DC10 = 42,000ft
DC9 = 37,000ft
MD80 = 40,000ft

A310 = 40,000ft
A340 = 39,000ft
A318/319/320/321 = 39,000ft
A330 = 39,000ft (max ceiling = 41,000ft)
A380 = 43,000ft

If you're interested in any others, search the internet for "[aircraft name]" + "service ceiling".

Some airliners run out of lift/power or create too much drag at high altitude (due to higher AoA because of thinner air), some have pressurisation limits (e.g. 737-100/200), some are limited by the closing gap between Mmo and stall speed and some might be limited by other factors. All of these are then affected by the aircraft's weight at any particular time during a flight, air density and temperature, cruise speed and other factors.

I suspect that the 747's ceiling is highest because its wing was optimised for a higher mach number than any of the other aircraft I've listed. This will allow the safe margin between Mmo and stall speed to be maintained until a higher altitude.

Comparing the Comet 4, 4B and 4C illustrates how wing size and all-up weight can affect the service ceiling of an aircraft. The engines on all three versions produced the same thrust. The Comet 4B was designed for European routes whereas the Comet 4 was optimised for long range routes. The Comet 4B was therefore given a shorter, lighter wing than the Comet 4, and a longer fuselage that could carry more passengers. Even though the Comet 4B's MTOW was less than the Comet 4, and the engines had the same thrust, it couldn't cruise as high as the 4 because of the shorter wing span. Nevertheless the 4B was a better compromise for the shorter routes it flew. The long range 4C had same wing span and MTOW as the Comet 4 but had the lengthened fuselage of the 4B. As a result, the 4C's service ceiling was less than the 4 but more than the 4B.

After a heavy take-off, most aircraft, especially long range ones, won't be able to climb straight to their service ceiling. As fuel is burned off, the optimum cruise altitude will increase and, subject to ATC permissions, the aircraft will climb in a series of steps. A very long wingspan and decent power to weight ratio tend to allow higher altitudes to be reached sooner, hence the reason why the A380 and A330 tend to perform quite well in this area compared to, say, the 747-200.

I'm not sure how binding service ceilings are on operators. I remember flying in an Eastern Provincial Airways 737-200adv and reaching 41,000ft on a flight between Halifax and Toronto. We had been cruising at 37,000ft (which is the official service ceiling for this variant) when we encountered a region of massive cumulonimbus clouds. We weaved our way between the tops for a while, which was a lot of fun, but we couldn't easily fly around all of them. The pilot announced that we were going to try to climb over the tops. A while later he said we'd reached 41,000ft but the tops ahead were still higher than us. He warned us that it was about to get very bumpy as there was a build-up we couldn't avoid. He wasn't joking! The aircraft was only about one third full which will certainly have helped with reaching that altitude. As far as I know, the service ceiling on the 737-200adv is limited by the cabin pressurisation so presumably the risk of taking it to 41,000ft was more to do with the effect of the thinner air on the passengers rather than other limitations of the aircraft. I'm not sure how close the Mmo and stall speed on a 737-200adv are at that altitude but the margin between the two will be less than at 37,000ft. I had the impression that our AoA was higher at 41,000ft which it probably was due to the thinner air. I suspect that 41,000ft wasn't a very efficient altitude for a 737-200adv to fly at as higher AoA = more drag = more power = higher fuel consumption. When we'd passed the worst of the CuNims we descended (presumably back to 37,000ft but the pilot didn't say).