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RodH
23rd Jun 2008, 01:00
Found this clip in Airbus' A380 news section.
Boy ! They sure have improved the flight envelope for the Emirates aircraft.

" Emirates Airlines is to receive its first Airbus A380 aircraft on July 28th as part of its new fleet of superjumbos.

Emirates is the largest customer for the A380 superjumbo as it has 58 of the aircraft currently on order with Airbus at a reported cost of $18.8 billion (9.4 billion).

The aircraft will travel from the Airbus facility in Hamburg to a delivery ceremony where the world will get the first look at its interior and facilities.

A380 aircraft can fly up to a 15,000 kilometres altitude, even at full load, thanks to its powerful Engine Alliance GP7200 engines. "
Rod H
:hmm::hmm::hmm::hmm::hmm:

A300Man
23rd Jun 2008, 02:54
Yes, keep discovering (outer space)!

I wonder if those showers and roulette tables will work at that altitude, Rod?

denabol
23rd Jun 2008, 03:19
Good one. But as a non pilot old time flyer, just how high can today's jets sustain cruise in commercial conditions. I remember the early Comet IVs out of Melbourne seemed to fly right on 40,000 feet most of the time perhaps because there was nothing else up there, and it did see 43,000 feet showing on the Qantas 747SPs on the Pacific flights, and more recently I saw 40,000 feet on an Emirates A345.

In fact I've seen 40,000 feet come up on most long range types at least once, but there seems to be some sort of a design or is it commercial barrier to going higher.

I never got to 60,000 feet on Concorde, but I did see it touch 59,000 feet on one flight and 58,000 on another but stay around 55,000 feet much of the time.

llondel
23rd Jun 2008, 06:25
Good one. But as a non pilot old time flyer, just how high can today's jets sustain cruise in commercial conditions.

This is a limitation of the engines used. When you've got a big turbofan, it tends to give up at around 40,000ft simply because the air that bypasses the engine core is thinner and has less propulsive effects so there's less power available as you go higher. When you have something that is a pure jet where all the air flows through the core, such as the Olympus in Concorde, and others found in some fighter aircraft, they'll keep going much higher.

Fatfish
23rd Jun 2008, 08:01
Wonder whats the thrust of those GE engines?

Tyres O'Flaherty
23rd Jun 2008, 08:13
About on the level of a saturn v stack by the sound of it :)

Fly380
23rd Jun 2008, 08:34
What about all those harmful rays.:eek:

MidgetBoy
23rd Jun 2008, 08:40
Good afternoon passengers, this is your chief flight attendant speaking. Please put your seatbelts back on as we begin to descend from our current altitude of 50 million feet down for landing in Dubai. The current temperature there is 35 degrees, but by the time we get there it'll probably be winter. You will be served dinner in a few minutes and then another 45 meals before we land.
Please choose Emirates again in the future.

navtopilot
23rd Jun 2008, 08:52
With a light load we climbed straight to FL450 KWI-CMB in a 747-400F

Coleman Myers
23rd Jun 2008, 09:35
Except you probably won't get the extra 45 meals out of Al Baker :rolleyes:

AMEandPPL
23rd Jun 2008, 10:18
A380 aircraft can fly up to a 15,000 kilometres altitude


ATC : " Emirates 1234, you are cleared for re-entry "


LOL

st7860
23rd Jun 2008, 14:51
Emirates 1234, ISS ahead, pls turn right heading 250 decend to 14,000 km"




(international space station)

Porrohman
24th Jun 2008, 03:08
denabol asked;

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

The higher you fly, the thinner the air gets and the closer the stall speed and the maximum mach number get to one another until the margin between the two becomes dangerously narrow.

Some aircraft will run out of lift and/or power or have other operational limitations before they get close to this point. If limits weren't set, some aircraft could be flown to a level where they would be literally flying a tightrope between Mmo and stall speed. An extreme example of this was the U2 spy plane. If the autopilot or an engine fails in such circumstances, the consequences can be quite challenging to cope with.

In 1985 a China Airlines 747SP suffered an engine failure whilst flying at FL410. The autopilot did its best to compensate for the reduced and assymetric thrust but the control inputs increased drag and, with reduced thrust available, the airspeed declined. The aircraft began to fly at an unusual attitude as the autopilot tried to maintain altitude and counteract the effects of the engine failure. After a couple of minutes, the pilot disconnected the autopilot, but he couldn't react fast enough to replace the large control inputs that had been being provided by the autopilot. The aircraft departed controlled flight and plunged 10,000ft in twenty seconds and a further 20,000ft in the next two minutes or so. By the time it recovered at about 10,000ft it had pulled up to 5G and suffered considerable damage. The aircraft landed safely at SFO and no-one was killed. The accident report blamed the pilots for not handling the engine failure correctly so the accident wasn't primarily caused by flying too high but it illustrates what can happen when problems aren't handled properly whilst cruising at high altitudes.

Manufacturers and regulators set a maximum permissable altitude (service ceiling) for each aircraft type. This is intended to give a safe margin between Mmo and stall speed at the service ceiling.

The service ceiling for an A380 is 43,000ft (13,115 metres). 747s can normally go to 43,000ft; 45,000ft is the max. Some biz jets can cruise much higher than this e.g. the service ceiling for a Gulfstream V is 51,000ft.

parabellum
24th Jun 2008, 11:50
And as an add on to all of the above one must also consider the amount of PAX Oxygen carried and how long it takes to get from, say, FL430 or higher, down to air good enough to breath in the event of an explosive decompression and be sure the oxygen doesn't run out too soon.

Coleman Myers
24th Jun 2008, 13:22
I think that would topple my gyro's - it must be pretty neat to see the curvature of the earth so clearly defined - but at that height the vertigo would probably sneak up on me !!!.

ONE GREEN AND HOPING
25th Jun 2008, 15:54
Good one. But as a non pilot old time flyer, just how high can today's jets sustain cruise in commercial conditions. I remember the early Comet IVs out of Melbourne seemed to fly right on 40,000 feet most of the time perhaps because there was nothing else up there, and it did see 43,000 feet showing on the Qantas 747SPs on the Pacific flights, and more recently I saw 40,000 feet on an Emirates A345.

____________________________________________________________ __
____________________________________________________________ __

I seem to recall when sitting either the UK CPL or maybe ATPL Flight Planning paper during the early 1960's that cruise-climb based on both the Comet and Britannia performance models was something that, at least in my case, took a certain amount of practice to get up to speed on. As with take-off performance, there were a few fold-out graphs and tables to be tackled. Some questions required working backwards from supplied weight and fuel figures at final cruise Flight level or similar. ( However we had smart Navigators to fly with, and who were specially good at sums. )

My point is that when the skys were generally less cluttered a continuous gradual climb from initial cruise altitude to final cruise altitude was allowed.
Both Turbo-props and pure jet aircraft had their particular periods of advantage in flight levels achievable into less busy skies, as of course Concorde did later on. I remember us still being able to cruise climb Britannias on North Atlantic and sub-Polar routes around 1966, or thereabouts. Pressure pattern navigation ( single heading/Zn formula to those who remember....... but don't ask me to explain ) was still in the Nav manual, but the only time I tried that was when our Chief Navigator cleared it with Shanwick and Gander in order to demonstrate to us that it worked.

I don't think our passengers were necessarily aware that we were creeping up in altitude for hours on end. I'm fairly sure Australian ATC let us do it at higher levels in the 707 days if there was nothing else around.

I suppose now there aren't that many available spaces in the sky for cruise climb, but I think we did it once before this person returned to shorthaul around 1999. Northern Europe to Japan ( 747-400 ) on a day when there was nothing between Northern Greenland and the Aleutians except us....well it passed the time.........

Maybe when oil hits $??? a barrel, cruise climb may once again be possible. Could save a bit of the precious fluid, as long as people can still afford to drive to the airport...........

HeathrowAirport
25th Jun 2008, 21:16
ATC : " Emirates 1234, you are cleared for re-entry "


LOL

More like Emirates 1234, your cleared for a slingshot around the moon.

ISS is only 340.5 km (183.86 nmi) up.

denabol
25th Jun 2008, 22:35
Thanks for the informative and very interesting replies to my question.

Since it began coming to Sydney I've flown their A380 each way to Singapore. Very 'soft' and quiet sort of jet, seemed to get off the deck in very little time and at a modest speed, but I followed the flight display at we were at 39,000 feet coming back from Changi straight off, and 38,000 feet leaving Sydney. Coming back we did also show 41,000 feet when breakfast came around while we were still somewhere south of Broken Hill. I understand that one of the big one's better habits is being able to avoid low level clutter at around 29,000 feet on heavy departures on older jets. I'm looking forward to seeing what their 787-9s do when they come on line since reading articles saying they would be used on comparatively shorter regional routes. Out of Canberra would be good but probably in my dreams, since I can get there maybe a bit easier than Sydney. Of course sub-orbital flight would be the real buzz. I'd love to see the earth from out there, but even if I could afford a joy flight in the thrill machine Virgin is offering passing the medical might be a problem. The silly old 'fart might die of a heart attack is probably what they'd say.

Porrohman
26th Jun 2008, 02:57
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).

mmeteesside
27th Jun 2008, 14:10
On a college trip last April we reached 41,000ft on an EZY 737 from Newcastle to Geneva. Pretty impressive seeing the curve of the Earth!

moleytt
27th Jun 2008, 16:55
On a Virgin A340 flight from LHR to Mumbai last year I woke up to see the flight tracking display read 42,000ft as we were passing over Northern Afghanistan. Great view :)

moleytt

st7860
27th Jun 2008, 16:56
maybe they went up to 42,000 feet for safety(in that area)

moleytt
27th Jun 2008, 17:05
Actually, on the return flight we were only at 37,000ft. I asked the Captain when he came into the cabin about the safety aspect of flying over Afghanistan and he reassured me that this altitude was beyond the range of ground to air missiles. So I just sat back and a few more glasses of wine :ok:

moleytt

Dirigible
27th Jun 2008, 19:21
The A340 has a max certified altitude of 41,100', (or 41,450' with mod 52536). The engines are quite capable of higher but the hull is not, due to the max differential pressure 8.85psi being a limitation.

Porrohman
29th Jun 2008, 11:49
Dirigible,

You sound quite knowledgeable regarding the A340. Do you know the altitude at which the Vmca for the A340 gets unacceptably close to the Mmo? What would the internal cabin altitude be at this height assuming that the pressure differential was maintained at 8.85psi?

Was the Virgin A340 flight breaking any rules by flying at FL420 or is the difference in the internal cabin altitude so small as to be irrelevant? Do the outside air temperature and the atmospheric air pressure affect the maximum permissable cruise altitude?

moleytt
30th Jun 2008, 23:38
Sounds like we were flying on the extremes :eek:

However, I'm sure Virgin and their Airbus trained crew would never go outside their designated flight envelope.

Moley

DILLIGAFF
1st Jul 2008, 22:13
I'm sure I read somewhere that the flight envelope of the U2R/TR1 at its maximum altitude was 4 knots. It said that if the pilot made a tight turn one wingtip would be stalling while the other would be overspeed.
D

Porrohman
3rd Jul 2008, 00:31
I'm sure I read somewhere that the flight envelope of the U2R/TR1 at its maximum altitude was 4 knots. It said that if the pilot made a tight turn one wingtip would be stalling while the other would be overspeed.

There are a couple of interesting mentions of this in Wikipedia;
High-aspect-ratio wings give the U-2 some glider (http://en.wikipedia.org/wiki/Glider)-like characteristics, with a lift-to-drag ratio (http://en.wikipedia.org/wiki/Lift-to-drag_ratio) estimated in the high 20s. To maintain their operational ceiling of 70,000 feet (21,336 m), the U-2A and U-2C models (no longer in service) must fly very near their maximum speed (http://en.wikipedia.org/wiki/Critical_mach). However, the aircraft's stall speed (http://en.wikipedia.org/wiki/Stall_speed) at that altitude is only ten knots (http://en.wikipedia.org/wiki/Knot_%28speed%29) (18 km/h) less than its maximum speed. This narrow window was referred to by the pilots as the "coffin corner (http://en.wikipedia.org/wiki/Coffin_corner_%28aviation%29)". For 90% of the time on a typical mission the U-2 was flying within only five knots above stall, which might cause a decrease in altitude likely to lead to detection, and additionally might overstress the lightly built airframe.[2] (http://en.wikipedia.org/wiki/Lockheed_U2#cite_note-I.26T-1)

Click on the "coffin corner" link (above) for more details.

My questions about Mmo and Vmca in my earlier posts were aimed at finding out where the "coffin corner" lies for commercial airliners such as the A340, A380, 747 etc. As the China Airlines 747 incident showed, airspeed can quickly drop towards Vmca in an engine out situation at high altitude with the autopilot is set to altitude hold mode.

The FAA Advisory Circular that is referenced at the bottom of the "Coffin Corner" article in Wikipedia gives a clearer explanation of the phenomenon and the associated dangers;


How wide is the safety margin between low-speed and high-speed buffet boundaries for an altitude and weight in a 30 bank? The answer may be easily determined by reference to the Cruise Maneuver/Buffet Limit Chart for a particular aircraft. For example, in a typical jet aircraft, the 1.0 G buffet-free margin at FL 350 is 135 Kts; at FL 450 this speed is reduced to a mere 26 Kts. Thus, the safety margin in airspeed spread diminishes rapidly as the aircraft climbs and leaves little room for safety in the event of an air turbulence encounter or accidental thunderstorm penetration.

Dirigible
3rd Jul 2008, 08:18
Vls, lowest selectable airspeed (not Vmca) on the A340 ensures a 0.3g buffet margin in cruise. The FMS will take all atmospheric conditions into account in selecting the highest attainable flight cruise level. This will be diplayed as Max flight level. A cruise flight level above this may be entered and accepted by the FMS, provided the margin is not reduced below 0.2g These are the defined max altitudes per the Flight Management Guidance Computer.

Certified Max altitude is different and defined as the lower of:
-maximum altitude at maximum cruise thrust in level flight, and
-maximum altitude at max climb thrust with 300 feet/minute vertical speed

The cabin altitude is limited to 7,350 ft for flights longer than 2.5 hrs. Two independent pneumatic safety valves prevent the cabin pressure from going too high (8.85 psi differential with external ambient pressure).

Hope that helps to clarify.

Guest 112233
5th Jul 2008, 10:01
My brother in law (Regular SLF) (not a pilot but a Scientist) once told me how on a B747 flight - Japan to SFO (It would have been a 200/400 Series ) JAL ? once went to FL500 to avoid Cu Nim activity over the pacific - Crew warned the passengers that they would climb. He remembes the Ozone smell in the Cabin -

Was he mistaken or could he be correct - sorry I don't have details of the Pax or Freight load or the actual date Etc. can the 742 or 744 reach these altitudes given load, OAT , local pressure / Turb / humidity conditions

CAT III NDB.
:hmm:

WHBM
5th Jul 2008, 14:21
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.
Alas an unwise thing to do. More than one aircraft has been lost in this way, most recently a Pulkovo Airlines Tupolev 154 flying over Ukraine which tried to climb over the storm, got into a narrow stall/buffet margin, then in the upset of the storm got into a stall. Being a high-tailed type an irrecoverable superstall followed. Moral. Don't go over storms, go around them.

ASN Aircraft accident Tupolev 154M RA-85185 Donetsk (http://aviation-safety.net/database/record.php?id=20060822-0)

Actually, on the return flight we were only at 37,000ft. I asked the Captain when he came into the cabin about the safety aspect of flying over Afghanistan and he reassured me that this altitude was beyond the range of ground to air missiles.Commercial aircraft are well beyond the range of any known missiles at cruising altitude. In the event of an engine failure which will cause the aircraft to need to descend to lower level there are special procedures which the crews are indoctrinated into.


once went to FL500 to avoid Cu Nim activity over the pacificMore likely to have been the FL450 (45,000 feet) service ceiling of the B747 (see above). Not only has it probably not got the engine performance to get up to 50,000, but it's hazardous (see my example above) and no professional crew would consider going outside the aircraft operating envelope for a moment.

Guest 112233
5th Jul 2008, 18:04
Thanks for the info.

Porrohman
5th Jul 2008, 19:05
Alas an unwise thing to do.


If the aircraft was getting too close to "coffin corner" and/or if there was severe turbulence in the tops we flew through then it was an unwise thing to do. I assume the aircrew would know how severe the turbulence would be via their weather radar and assesed the situation as safe? Can anyone tell me what the buffet margin is on a 737-200adv is at FL410? From what I've read on various web sites, the ceiling for the 737-200 was FL350 and the 737-200adv had a 2,000ft higher ceiling because of improved cabin pressurisation. Perhaps the service ceiling for these variants was more to do with cabin pressurisation than the capabilities of the engines & wing? I'm guessing that a temporary climb to FL410 with the pax and cabin crew strapped-in is unlikely to cause any cabin altitude difficulties for most occupants, but the margin between Mmo and Vmco will be narrower. I'm interested to know how narrow.

The 737-600/700/800/900 variants have ceiling of 41,000ft so perhaps taking a 737-200adv with a light payload to FL410 was more of a cabin altitude issue than a "coffin corner" risk?

TWApilot
8th Jul 2008, 06:42
The ceiling for a B767-200 and -300 is actually FL430.

In the States the FARs require one of the pilots to wear an oxygen mask constantly any time the airplane is above FL410. As a result, even though a lot of airplanes have an altitude capability of FL420 or FL430, you won't ever see a crew fly one that high -- no one wants to wear the oxygen mask the whole time you are up there. Not only would it be uncomfortable, but you would deplete the oxygen supply to the point where it would need to be serviced once the plane landed. That can be a pain, depending on where you are at.

Due to those reasons, the highest altitude you'll ever find me at is FL410.

jtr
8th Jul 2008, 10:10
Avoiding Cu Nimbs in the Pacific
My brother in law (Regular SLF) (not a pilot but a Scientist) once told me how on a B747 flight - Japan to SFO (It would have been a 200/400 Series ) JAL ? once went to FL500 to avoid Cu Nim activity over the pacific - Crew warned the passengers that they would climb. He remembes the Ozone smell in the Cabin -

Was he mistaken or could he be correct - sorry I don't have details of the Pax or Freight load or the actual date Etc. can the 742 or 744 reach these altitudes given load, OAT , local pressure / Turb / humidity conditions

CAT III NDB.


FL500, not likely considering

Max Op Alt 744 = 45,100
Cant be arsed working it out but Cab Max Diff of 9.2 (or is it 9.4) would mean either an overpressurisation or masks dropping (pax)
You would need to be ridiculously light (i.e. likely lighter than BEW) to get that high considering thrust limits.
You would probably run out of aerodynamic margin with MMO of 0.90 (0.92 depending on certification)


etc

chornedsnorkack
8th Jul 2008, 16:22
either an overpressurisation or masks dropping (pax)

IIRC, flying with cabin altitude above 8000 feet is forbidden, but it is at 10 000 feet that warning horn blows in cockpit and at 14 000 feet that masks drop in cabin. So, a plane could fly way above ceiling before masks drop.

TWApilot
8th Jul 2008, 17:07
I know that the airplanes must be built to maintain a cabin altitude of 8,000 ft or less, but... is that a European thing, that you can't fly with a cabin altitude above 8,000 ft? In the States we can fly passengers all day long with a cabin altitude of 10,000 ft. Many turboprop commuter aircraft with pressurization inoperative dispatch their flights unpressurized at 10,000 feet until the system can be repaired. I haven't even been dispatched in a jet with inop pressurization, but I have had it done in turboprops. The 757 MEL simply says that if operating unpressurized, aircraft altitude altitude must be 10,000 feet or less when carrying passengers.

I've not heard of any restriction preventing flight with a cabin above 8,000 feet. 10,000 feet is the only restriction I know of.

WHBM
8th Jul 2008, 17:17
I'd separately like to ask the experts how you handle the cabin pressure to arrive at La Paz airport, Bolivia, which is at an altitude of 13,600 feet. If you take off from sea level, say Miami, how is the cabin pressure handled.

Dirigible
8th Jul 2008, 18:20
On the Airbus, if a landing elevation is set (either manually or through the Flight Management Guidance System) that is higher than the cruise cabin altitude then the cabin altitude will increase to the higher of either the cabin altitude, or landing elevation-6000 feet.

The cabin altitude is limited to 7,350' on flights more than two and half hours or 8000' on shorter flights. In the La Paz example 13,600 feet, the cabin would be at either 7,600' feet (13,600'-6000')or 8,000' if a short flight. On descent the cabin altitude would then climb to achieve landing field pressure + 0.1 psi just prior to landing. 80 seconds after landing the outflow valves are controlled fully open to remove any residual pressure.

Incidentally,on the A330 and A340 max runway altitude for takeoff and landing is 12,500'.

singpilot
28th Aug 2008, 20:24
The time required to crash-dive, including recognition, recovery and implementation.

Regs say unpressurized breatheable atmosphere in specified time.

Time to emergency descend to 10000' or 14000' (depending on regulatory body) will sometimes restrict highest useable cruise altitude.

Also have a not-so-funny single pack fail at ETP LAX-HNL where cabin got so cold soft drink cans exploded, and the forward cabin and vestibule was standing room only.