A380 cruise altitude record

[moleytt]

High over AFG

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]

maybe they went up to 42,000 feet for safety(in that area)

[moleytt]

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

moleytt

[Dirigible]

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]

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]

Flying high!

Sounds like we were flying on the extremes

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

Moley

[DILLIGAFF]

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]

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-like characteristics, with a 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. However, the aircraft's stall speed at that altitude is only ten knots (18 km/h) less than its maximum speed. This narrow window was referred to by the pilots as the "coffin corner". 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]

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]

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]

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.

[WHBM]

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

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 pacific

More 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]

Thanks for the info.

[Porrohman]

737-200adv @ FL410

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]

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]

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]

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]

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]

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]

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]

Something we have all forgotten.......

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.