View Full Version : High Elevation Operations

12th Jan 2002, 08:11
I would like to hear from anyone who knows about certification requirements to operate aircraft at airports above 10,000 feet.Anything I have flown has a max TO or Landing limit of 10,000.(not that its a problem in Australia!)I gather there are airports in South America at higher elevations.Surely a One Engine Inoperative TO would be impossible in many aircraft types.What rules govern these operations?

12th Jan 2002, 18:26
Well, I have been in and out of La Paz (Bolivia) a
few times. Elevation 13,300 feet.
Severly weight restricted and VERY long runway.
Airplane needs a "High altitude switch" to keep the masks from coming down when ya climb the cabin.

I guess the airlines write the procedures and training programs, then the FAA and local authorities approve or disapprove..

13th Jan 2002, 10:00
Since the performance charts come from the manufacturer, I believe that the manufacturer has to sign off on any high altitude waivers. I do know that is the case in most business jets. My employer conducts opertations in Central and South America and I have gotten performance charts from the manufacturer for very high altitude operations. Part of the package is a waiver for operations above the altitude limits for Takeoffs and Landings.

13th Jan 2002, 10:28
What type of airplanes, what altitudes and what type of operations?

Light piston or turbin twin: non commercial use, you risk your own neck.

Part 25 certified airplane: aircraft limitations such as max altitude for take off and landing, OAT limitations, and Engine starting limitations. Minimum runway lenghts. The highest approved altitude I have seen approved for take off and landing 14000 feet.

Part 25 certified airplane with commercial use (airline type). Same as above with additional limitions variable on each operator.

When you get up as high as La poz, you have to start thinking about your personal well-being. Hypoxia will set in !

13th Jan 2002, 11:10
Thanks for the replies from all.My thoughts concerned TO and Landing at La Paz in particular.Most of my experience has been in Saab 340's flying in Australia and I wondered if they were operated in high elevation environments given that they would not be able to climb on one.Is it jet operations only for RPT at La Paz?

13th Jan 2002, 17:46
We fly B-757s into La-Paz.
Required to wear the mask on approach and landing.
Also when programming the 'puters and for t/o.

Some other company flies B-727 into La Paz.

Seen some old piston twins rotting away in the grass next to the airport. DC-4s and 6s meh thinks.

13th Jan 2002, 18:53
I posted this some time ago but it's a helluva story. From 'Splash of Colors', by John Nance. Required reading before thinking about La Paz.

There is one more problem with high-altitude airports—the need of the human body for oxygen. At about 13,000 feet, for one not used to living in such rarefied air, a slight degree of hypoxia (reduced awareness and judgment resulting from too little oxygen to the brain) usually occurs after about thirty minutes. Braniff’s pilots were required to breathe 100 percent oxygen from thirty minutes prior to departure from La Paz, regardless of how they felt. The reason centers around the fact that different people will be affected in different ways, but without the use of on-board oxygen a pilot can become sufficiently hypoxic (and be sufficiently unaware of it) to make significant mistakes reading his charts and checking them. One night in 1974, that is precisely what occurred.

The 220,000-pound Braniff DC-8 (at its maximum weight for this altitude), bound for Lima under a canopy of stars in the most crystal-clear night sky imaginable, rolled onto the first section of the runway with the flaps properly set at 12 degrees and advanced power. The captain, copilot, and flight engineer had been on the ground about an hour and didn’t feel they needed to breathe any oxygen before departure. They were feeling fine and sharp and had been here many times before.

A small piece of paper called a data card and containing the numbers for the takeoff rested on the center pedestal in front of the throttles, over one of the radio control heads—the place the crews normally kept it. As the speed built up and the airspeed indicator on the captain’s panel came off the peg, he glanced down and re-checked his V1 and rotation speeds, which the copilot was to call out when reached. As it indicated on the data card, at 122 knots of airspeed (over 145 knots of ground speed) the copilot called “Ro-tate,” and the captain pulled back on the yoke.

The aircraft felt much heavier than usual; the response to the pull on the yoke was minimal, but finally he managed to get it into about an 8-degree nose-high attitude. And there it stayed. They had used up over 9,000 feet of runway, and the red lights marking the end of the 13,000-foot strip of concrete were coming up fast—at over 165 miles per hour. The DC-8 was still rolling along on its main wheels, nose reared up into the air at an 8-degree angle, airspeed indicator now hovering just above 120 knots, and not accelerating. The captain pulled harder, bringing the nose up a bit farther. Still the red lights grew brighter—and the main wheels stayed on the ground. The heartbeats of all three men quickened slightly, but at such a tense moment, the problems at hand are han-dled quickly but routinely. There is no time for panic, even if that were the normal response of a seasoned airline pilot to a rapidly deteriorating situation—which it is not.

There was now less than 1,000 feet of runway left. The nose was as high as 9 degrees, the indicated airspeed still around 120, and the main wheels were still on the ground. Nothing but blackness seemed to exist to the west of the two red marker lights—nothing but the blackness of the altiplano, fortunately flat as a West Texas pasture between the end of the concrete and the shores of Lake Titicaca 10 miles to the west.

Just as the red lights disappeared from view, the captain did the only thing there was left to do—he pulled hard on the yoke and “yanked” the nose of the giant airliner as high as he could without contacting the tail skid.

As the last vestige of concrete passed beneath the wheels, they had gained a couple of feet of altitude, enough to clear the red lights at the end—but no more. The aircraft was now airborne in “ground effect,” a cushion of air compressed by the huge mass of metal screaming across it and tenuously holding it above the surface. At the captain’s command “Gear Up,” the copilot reached up with his left hand and raised the gear handle. The huge gear doors on the main gear opened, increasing the drag momentarily and canceling any acceleration as they hung suspended over— nothing. There was nothing visible in front of them in the blackness.

The gear thudded into place on the uplocks and the doors closed at last. The captain was holding as high a deck angle as he dared, watching the airspeed finally, slowly, begin to increase, watching the vertical velocity indicator (rate of climb) and keeping it slightly positive, and watching the radio altimeter (an extremely precise in-strument that gives the altitude of the aircraft above the surface with accuracy better than plus or minus 2 feet) showing first almost nothing, then 10 feet—moving ever so slowly upward.

The 220,000-pound machine full of people and baggage and fuel was now screaming along barely off the ground over the flat Bolivian terrain, barely clearing unseen fences and small rises in the land-scape, caught in a position in which the deck angle was so high, and the resulting drag so great, that even the thrust of all four engines at maximum power was barely able to keep the airspeed from drop-ping. The aircraft was leaving a wake of dust and dirt behind it as it skimmed over the ground.

Finally it began to accelerate and gain 20—then 30—then 40 feet. The captain relaxed his back pressure ever so slightly and let the nose drop a tiny bit, which lowered the drag coefficient and made the thrust of the straining turbojet engines greater than the overall drag—and at that moment he knew they would make it.

As the climb-out finally became normal and the DC-8 passed through 2,000 feet above the surface with flaps retracted, the effect of the adrenaline began to overpower the slight hypoxia that had influenced them, and with limbs beginning to shake slightly (and an oblivious load of passengers who never suspected a thing was wrong, never suspected they had almost been in the middle of a monstrous aircraft accident), they yanked out the books and re-calculated the speeds.

There it was. For the weight and the temperature, 140 knots was VR. They had horsed it off 18 knots early, and nearly, well……. The prospect of what would have become of their craft settling down in the dirt on the other side of those lights at 165 miles per hour was too frightening to go into. All three of them knew that if the captain had been too abrupt—dropped one ounce of back pressure after they had lifted off or increased it any—they would be on the ground right now. But his skill deserved mixed accolades—he had checked the airspeeds without oxygen back at the ramp, too. All that skill, all that experience had canceled out a simple but potentially fatal mis-take. At Lima the craft would have stagnated a bit on speed, then gone right on with the takeoff. At La Paz, the margins were so thin, there was little room for error—the error they had made.

Killer Shark
14th Jan 2002, 08:53
Aircraft performance is not usually the problem, as extrapolation rules for higher-than-tested altitudes are well established. The limited takeoff weights are generally a good indication of the poor capabaility at these altitudes.

Really, the tricky bit is testing and certifying systems, particularly the ECS and powerplants. The certifying authority for the aircraft type is responsible for giving the aircraft its ticket to actually operate from high elevations, and then the local authorities may also have their own say in operations on particular routes.

Generally, the manufacturer must test at the desired elevation, or close to it, to demonstrate succesful operation. In addition, a fair amount of analysis is required to back up the case. Then, demonstrations from the actual airports are the done thing.

Take Airbus and Boeing for instance. To operate from Bangda, Tibet (approx 14200ft), both companies had to actually go there and demonstrate to the customer that it all works, and this was on top of the certification effort.

As was pointed out, masks dropping, along with trouble opening doors, engine operability, engine margins, actual ability to set power, demonstrated capability to fly unusual procedures without increased pilot workload etc have to be convincing to authorities and customers alike.

It's not a 5 minute job!

Killer Shark
14th Jan 2002, 09:00
...and I forgot to add, the rules to be followed are generally not to be found in FARs, JARs etc, but are agreed upon following negotiation with certifying and local authorities.

Plenty of guidance material exists outside of the rules (Advisory Circulars, AMJs, Authority policy documents etc), but careful negotiation is required to understand their many different interpretations.

For example, engines must be tested for capability to achieve thrust used for performance (engine temperature limits, powersetting stability etc) within 3000ft of the certifying altitude, according to AC 25-7 and many policy documents, but if you intend to fly from La Paz, expect the authorities to expect you to test/demonstrate there!

14th Jan 2002, 11:31
Great posts. Only thing I can add is that if it isnt climbing , ignore the profile, level off and get the flaps up. Be very careful. You may not be getting the correct temps. or weights of cargo , etc. Also, ... I really dont like flying into any South American high altitude airports at night. Listen to these posts mate !!!!!!

14th Jan 2002, 19:46
Polzin, Having been there and some airports in your neck of the woods, I am in concurance with your statement. That is no place to play at night if you haven't been there before.

But don't get too comfortable there though.

Willit Run
16th Jan 2002, 05:11
The A-300 is certified to 14,000 ft for TO.
Not sure I'd want to take off at a really high place with only 2 motors though, but folks do all the time I guess, so its what you feel comfortable with.
Polzin doesn't like south america cause he can't say "Fajita" very well!