High altitude ops
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High altitude ops
Hi folks,
I passed through Cuzco, Peru as a passenger on a LAN A319 last week and, given the airfield's high elevation (3,825 metres above sea level) I was kind of curious about a couple of aspects of the aircraft's operation (I saw the performance during two missed approaches). I was hoping someone on the forum could satisfy my curiosity;
1. Cabin altitude.
I dimly remember from my dispatch license training that cabin altitude is typically in the range from 6,000 to 7,000 ft. I also seem to remember that if cabin altitude rose over 10,000 ft the passenger oxygen masks would deploy. How do you get around this, landing at an airfield at 12,500 ft elevation? On an aircraft as complex as an A319 I can't imagine it's a simple as pulling the breaker? Performance aside, are there any other complications associated with configuring the aircraft to land that high?
2. Crew performance
Even after several days' acclimatising on the Andean highlands, I never really felt 100% fit at high altitude. How do the crew cope? Would the cockpit crew wear masks?
Thanks in advance for any light anyone can shed on these questions.
I passed through Cuzco, Peru as a passenger on a LAN A319 last week and, given the airfield's high elevation (3,825 metres above sea level) I was kind of curious about a couple of aspects of the aircraft's operation (I saw the performance during two missed approaches). I was hoping someone on the forum could satisfy my curiosity;
1. Cabin altitude.
I dimly remember from my dispatch license training that cabin altitude is typically in the range from 6,000 to 7,000 ft. I also seem to remember that if cabin altitude rose over 10,000 ft the passenger oxygen masks would deploy. How do you get around this, landing at an airfield at 12,500 ft elevation? On an aircraft as complex as an A319 I can't imagine it's a simple as pulling the breaker? Performance aside, are there any other complications associated with configuring the aircraft to land that high?
2. Crew performance
Even after several days' acclimatising on the Andean highlands, I never really felt 100% fit at high altitude. How do the crew cope? Would the cockpit crew wear masks?
Thanks in advance for any light anyone can shed on these questions.
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Usually the operator will have a separate and specific briefing for arrivals and departures into a high elevation airport (8,000' 14,500') including modified engine start procedures, an amended MEL, weather parameters, minimum rates of descent (given that the cabin altitude could climb on descent!!), and in some cases donning of oxygen masks for arrival. Depending on the topography the effectiveness of VHF radio communication as well instrument beacons could be compromised.
Dependant on aircraft type the airport elevation is programmed into the presurisation system via the overhead panel/FMC/FMS for high altitude mode before landing at that field. This will modify cabin flow rates and outflow valve operation in line with the airport's elevation and avoiding a cabin altitude warning (could activate above 8000'/8.6psi) and continued pressurisation of the cabin on landing (otherwise its difficult to open the doors for disembarkation/emergency evac).
The legal requirements for basing and operation at such fields are, I imagine, complex and vary from country to country, but some might include no of years of operation of operator, power system reliability of aircraft and maintenance to the equivalent of 120min ETOPS standards. For flight crew: age of commander, experience of the FO, pre-requisite ground & sim training (may include physiology observations and procedures to avoid dehydration) and no alcohol within upto 48 hours may form some of the stipulations for flight crew standards.
I am sure someone, who has more experience in this matter, will correct me if I am awry with some of the above general thoughts (I'm sure there are many more considerations) - hopefully it provides some initial food for thought though...
PP
Dependant on aircraft type the airport elevation is programmed into the presurisation system via the overhead panel/FMC/FMS for high altitude mode before landing at that field. This will modify cabin flow rates and outflow valve operation in line with the airport's elevation and avoiding a cabin altitude warning (could activate above 8000'/8.6psi) and continued pressurisation of the cabin on landing (otherwise its difficult to open the doors for disembarkation/emergency evac).
The legal requirements for basing and operation at such fields are, I imagine, complex and vary from country to country, but some might include no of years of operation of operator, power system reliability of aircraft and maintenance to the equivalent of 120min ETOPS standards. For flight crew: age of commander, experience of the FO, pre-requisite ground & sim training (may include physiology observations and procedures to avoid dehydration) and no alcohol within upto 48 hours may form some of the stipulations for flight crew standards.
I am sure someone, who has more experience in this matter, will correct me if I am awry with some of the above general thoughts (I'm sure there are many more considerations) - hopefully it provides some initial food for thought though...
PP
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.....avoiding a cabin altitude warning (could activate above 8000'/8.6psi) and continued pressurisation of the cabin on landing (otherwise its difficult to open the doors for disembarkation/emergency evac).
I'll take some English lessons for next time....
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Pilot Positive . . .
minimum rates of descent (given that the cabin altitude could climb on descent!!),
How long do you think it would take to "climb" the cabin from 6,000' to 13,500' at 500fpm? How about ...15min?
How long do you think it would take to raise the cabin from 6,000' to 13,500' at 750fpm? How about ...10min?
How long do you think it would take to descent from FL350 and to manoeuvre to land at 13,300'?
Hint: It would take you MORE than 15 minutes even if you were a test pilot.
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Fair point GlueBall, it was an observation about minimising the possible effects of high altitude acclimatisation more than an operational one - I.e. a ventured response to VS1711's original question concerning crew performance.
Your times assume a CPD without the benefits of level off and vectoring. The possible negative physiological impact would be the result of rapid increase in cabin altitude if on a CPD. Minimum ROD/minimum level off times could help to offset any of these, including hypoxia, by extending acclimatisation times without the use of oxygen.
The CAAC have been reviewing their requirements for the operations in to such fields - especially as they are looking to build/extend an increasing number of high altitude and very high altude airports such as YanJi, Bangda, and Linzhi and this aspect is being considered along with a number of other dynamics.
Glueball if you have any specific experiences in terms of very high altituide ops with operators you may have flown with then it would be good to hear them...
Your times assume a CPD without the benefits of level off and vectoring. The possible negative physiological impact would be the result of rapid increase in cabin altitude if on a CPD. Minimum ROD/minimum level off times could help to offset any of these, including hypoxia, by extending acclimatisation times without the use of oxygen.
The CAAC have been reviewing their requirements for the operations in to such fields - especially as they are looking to build/extend an increasing number of high altitude and very high altude airports such as YanJi, Bangda, and Linzhi and this aspect is being considered along with a number of other dynamics.
Glueball if you have any specific experiences in terms of very high altituide ops with operators you may have flown with then it would be good to hear them...
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Well yes, Captain Pilot Positive, I have travelled a great deal, including numerous departures many years ago into and out of LPB/SLLP "El Alto" aeropuerto at 13,313' where the cabin altitude would be raised to no higher than 13,500' prior to touchdown.
You can descent the airplane at 2000fpm and simultaneously climb the cabin at 750fpm from 6000' to 13,500' . . . .
Pressurized cabin altitude and airplane altitude are SEPARATE; it doesn't matter at what altitude the airplane is, or as you incorrectly fuse these altitudes, as would be the case in a non pressurized airframe . . ."Minimum ROD/minimum level off times could help to offset any of these, including hypoxia, by extending acclimatisation times without the use of oxygen."
You can be at any airplane altitude, descent the airplane at any rate and level off the airplane at any altitude and separately and manually control cabin altitude, cabin rate of climb, to be at [and to stay at] 7000' or at 13,313' at any time. There is no necessity to "level off" the airplane or to use "minimum [airplane] ROD" in order to acclimatize passengers, as passengers would have to acclimatize themselves to 13,313' airport elevation.
Ideally, the cabin is raised slowly so as to be at 13,500' [200' above airport elevation] when on final approach. Personally, I haven't seen any people at La Paz walking around with oxygen bottles.
You can descent the airplane at 2000fpm and simultaneously climb the cabin at 750fpm from 6000' to 13,500' . . . .
Pressurized cabin altitude and airplane altitude are SEPARATE; it doesn't matter at what altitude the airplane is, or as you incorrectly fuse these altitudes, as would be the case in a non pressurized airframe . . ."Minimum ROD/minimum level off times could help to offset any of these, including hypoxia, by extending acclimatisation times without the use of oxygen."
You can be at any airplane altitude, descent the airplane at any rate and level off the airplane at any altitude and separately and manually control cabin altitude, cabin rate of climb, to be at [and to stay at] 7000' or at 13,313' at any time. There is no necessity to "level off" the airplane or to use "minimum [airplane] ROD" in order to acclimatize passengers, as passengers would have to acclimatize themselves to 13,313' airport elevation.
Ideally, the cabin is raised slowly so as to be at 13,500' [200' above airport elevation] when on final approach. Personally, I haven't seen any people at La Paz walking around with oxygen bottles.
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Pressurized cabin altitude and airplane altitude are SEPARATE; it doesn't matter at what altitude the airplane is, or as you incorrectly fuse these altitudes, as would be the case in a non pressurized airframe
Perhaps you also meant to say that with non-pressurised cabins the cabin would descend in line with aircraft descent and there would be no cabin climb? Not sure how many brave souls out there would fly any form of passenger transport aircraft without some form of pressurisation and/or oxygen above some of the altitudes mentioned anyway! On the other hand....
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I wouldn't know the cabin pressure controllers of all aircraft, but I fly the B74 and when the auto pressurization controller goes on vacation, then the cabin is controlled MANUALLY; the 2 cabin outflow valves have back-up DC motors which are operated MANUALLY.
If ever or whenever as a passenger you fly into El Alto at 13,310' [AA operates B757] you won't see cabin oxygen masks drop from the ceiling, and you won't see people walking around with portable oxygen masks.
If ever or whenever as a passenger you fly into El Alto at 13,310' [AA operates B757] you won't see cabin oxygen masks drop from the ceiling, and you won't see people walking around with portable oxygen masks.
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you won't see cabin oxygen masks drop from the ceiling, and you won't see people walking around with portable oxygen masks.
What changes are there, if any, to your FTL when flying into high altitude airports? Do you have any experiences of crew performance degradation because of the high elevation of some of the fields you have flown from?
PP
Last edited by Pilot Positive; 5th May 2010 at 22:32.
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High Altitude Landing Pushbutton, among other things
There is a high altitude pushbutton on the ovhd panel. This makes the oxygen masks drop at 16000' instead of 14000, plus cancels the excess cabin altitude warning at 9550. I think you get it at a higher altitude, but I am not 100% sure, I stopped flying the 320 a few years ago. I think you also get the Cabin Altitude Ecam Advisory a little later. The use of this PB was under the supplementary techniques, and it was required for operations to airports at or above 9200'
Regarding training, we had a special airports operations ground school when joining the company, then you would finish your normal line training, which includes many sectors to this kind of airports. After that, we were all qualified to operate in and out of these airports.
About the special preparation, that was just up to the pilot. Normal regulations regarding alcohol and rest applied. Sometimes you could feel dizzy and tired, specially after the walk around, and then you could use your oxygen mask to recover during the short turn around. You could take off and land with the mask on, but I have never seen anybody doing it, and it was not a requirement, at least not when I was flying there.
To finish, I remember it was considered a special operation, but we used to go there many times per week, so I could say it was a special operation that was practiced very often (at least 6 times per week).
My comment is based on the experience I had from 2004 to 2006, so it might be a little different now. Anyway, I hope I cleared some of your doubts.
Regarding training, we had a special airports operations ground school when joining the company, then you would finish your normal line training, which includes many sectors to this kind of airports. After that, we were all qualified to operate in and out of these airports.
About the special preparation, that was just up to the pilot. Normal regulations regarding alcohol and rest applied. Sometimes you could feel dizzy and tired, specially after the walk around, and then you could use your oxygen mask to recover during the short turn around. You could take off and land with the mask on, but I have never seen anybody doing it, and it was not a requirement, at least not when I was flying there.
To finish, I remember it was considered a special operation, but we used to go there many times per week, so I could say it was a special operation that was practiced very often (at least 6 times per week).
My comment is based on the experience I had from 2004 to 2006, so it might be a little different now. Anyway, I hope I cleared some of your doubts.
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You land unpressurized.
Pilots wear O2 masks during arrival when cabin approaches 10,000' and from before engine start until cabin has descending below 10,000'(feels like it takes forever on departure
)
High ground speeds. Rotation is approx. 195 Kts
High alt switch to change altitudes for excessive cabin warning and for dropping O2 masks.
You walk slowly to deal with altitude issues.
Additional O2 bottles are available on the ground for passengers. Typically several get sick due to altitude adjustment issues. Never heard it being an issue for crew members(F/A's or pilots). Guess the the constant exposure to 5000'-7000'+ cabin cruise altitude helps.
Pilots wear O2 masks during arrival when cabin approaches 10,000' and from before engine start until cabin has descending below 10,000'(feels like it takes forever on departure
)High ground speeds. Rotation is approx. 195 Kts
High alt switch to change altitudes for excessive cabin warning and for dropping O2 masks.
You walk slowly to deal with altitude issues.
Additional O2 bottles are available on the ground for passengers. Typically several get sick due to altitude adjustment issues. Never heard it being an issue for crew members(F/A's or pilots). Guess the the constant exposure to 5000'-7000'+ cabin cruise altitude helps.
