70 votes
Accepted

Why do private jets such as Gulfstream fly higher than other civilian jets?

There are several reasons and none of them really have to do with a private jet being more aerodynamic than a commercial jet. Private jets have better power to weight ratio than commercial jets so it ...
  • 656
54 votes

What prevents a small plane like a Cessna or Piper from flying as high as a jet?

We will take the case of an unsupercharged piston engine, as used in most small Cessnas and Pipers. All engines need the oxygen in air to burn their fuel. As an airplane climbs, the air thins out and ...
53 votes
Accepted

Do the Mt. Everest rescue helicopters have modified engines to operate at high altitudes?

No, the helicopters are standard production versions. The Eurocopter AS350 is a common model used for these operations. In 2005, Didier Delsalle landed a Eurocopter AS350 B3 on the summit of Mt. ...
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46 votes
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How is altitude reached by aircraft flying above the stratosphere measured?

They used inertial altitude on the X-15 for high altitude measurements. This works just like an IRS (Inertial Reference System), which was used on airliners of that era: you can get the position (...
  • 49.6k
42 votes

Does breathing 100% oxygen cause health issues?

When we discuss a mixture of gasses, it's often useful to compute the pressure of each component separately. This is called the "partial pressure" of that component. For instance, oxygen ...
41 votes
Accepted

How did aviation industry come to know about the drastic difference in air pressure in high altitude?

The entire reason why the Comet broke up in midair is because they pressurized the plane in the first place. It was known for a long time that air at high altitude was thinner. This can be ...
41 votes
Accepted

Could the SR-71 Blackbird be used for nearspace tourism?

Significant issues with the concept: the SR-71 lacks RCS, so you'd lose attitude control if you got significantly above normal operating height. I originally wrote that it doesn't handle in-flight ...
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36 votes
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Why are planes required to cruise at round flight levels only above 18000 ft of altitude?

In general, the minimum vertical distance two IFR aircraft can be (if they are not separated laterally) is 1,000 feet. This allows for inaccuracies, for example due to: altimeter error ...
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34 votes
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How should I deal with a passenger experiencing hypoxia over the Grand Canyon?

First, let's be crystal clear on something: A person experiencing symptoms of acute hypoxia is an emergency which requires immediate action to ensure the safety of that person. In an in-flight ...
  • 67.6k
33 votes
Accepted

How does an airliner deal with cabin altitude at an airport above 8000 ft?

Here is the text extracted from Boeing's 777 Flight Crew Operations Manual: In cabin altitude controller cruise mode, maximum cabin altitude is 8,000 feet. When the takeoff field elevation is higher ...
  • 39.3k
31 votes
Accepted

Why can't helicopters fly at high altitudes?

Don't believe everything you see in the movies. Doubly so if the movie originated in Hollywood. The world altitude record for a helicopter is 40,814ft (12440m), some 11,000 feet (3353m) higher then ...
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30 votes
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Are there any gliders that can fly over the Himalayas?

Do gliders (sailplanes) use ridge and wave lift in the Himalayas to go to extreme altitudes, possibly above Everest's peak? Yes, there are gliders touring Himalayan peaks over 8,000m, including ...
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29 votes
Accepted

Which aircraft can fly at FL600 or above?

Commercial Airliners: Both Concorde (service ceiling FL600) and the Tupolev Tu-144 (service ceiling FL660) could reach FL600. Most airliners have a service ceiling of around FL410 though. Business ...
27 votes
Accepted

What prevents a small plane like a Cessna or Piper from flying as high as a jet?

What limits a small plane to be able to fly at a much higher altitude? Money. Power and lift on an aeroplane both decrease with increasing altitude, as shown in the image above, from my paper copy ...
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27 votes
Accepted

What does the "High Alt Landing" guarded push button on the A320 exactly do?

The button raises the altitude at which the oxygen masks in the cabin automatically deploy. When landing at a high elevation airport, the masks might otherwise deploy during approach when the cabin ...
  • 49.6k
26 votes
Accepted

Are sun's UV rays more harmful on an airplane at high altitude?

Hmmm, opening the window at 30.000ft, where the air temperature is about -40°C/-40°F, air speed is extreme, you can't survive without oxygen, and you want to put your arm outside??? Well, if you ...
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24 votes

How do planes know what altitude they're cruising at?

Above Transition Altitude (e.g. this is 5000ft in Germany) the altitude is measured in flight levels (FL) - each FL equals 100ft and is measured above an artificial QNH of 1013,25 hPa. If you cruise ...
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22 votes

How did aviation industry come to know about the drastic difference in air pressure in high altitude?

Aside from mountaineering investigations, the service ceiling of WWII propeller-driven aircraft like the Spitfire was pushed up from about 34,000 feet to 45,000 feet, so the general effect of reduced ...
  • 2,995
22 votes
Accepted

Is there a ceiling on weather patterns?

Severe convection will have anvil tops at the tropopause and overshooting tops can penetrate much higher (severe thunderstorm warnings often use a value of 60,000 ft for threats to aircraft). How ...
  • 35k
22 votes

Could the SR-71 Blackbird be used for nearspace tourism?

I work and have worked with several SR-71 crew members. In the past, they have pointed out two principle impediments: Crew workload Cost Crew workload is shared between both crewmembers, and the ...
  • 17.5k
21 votes

Why do private jets such as Gulfstream fly higher than other civilian jets?

There are three main factors that let corporate jets with 50000+ ceilings get up that high. First and most importantly, they have very large wings. Partly this is because of the need for fuel ...
  • 111k
20 votes

How should I deal with a passenger experiencing hypoxia over the Grand Canyon?

You don't have to divert, in fact it may be a bad option depending on conditions (I would recommend you don't go if conditions will make diverting dicey though). You can treat the hypoxia with low ...
  • 50.9k
19 votes
Accepted

What are the limiting factors for high altitude planes (e.g: U2 or SR71) preventing them from going higher?

The limiting factor for subsonic aircraft, including the U-2, is well explained here. For supersonic aircraft this answer simply says the limit is "a combination of wing loading and maximum speed". ...
18 votes

How should I deal with a passenger experiencing hypoxia over the Grand Canyon?

The simple answer is to rent or buy a supplemental O2 system for Mom. Don't fake this one. As Voretaq7 said in the first answer, "A person experiencing symptoms of acute hypoxia" Focus on the ...
  • 10.2k
16 votes

Does breathing 100% oxygen cause health issues?

Yes... but not predictably, and (almost certainly) not seriously. If you're worried for yourself and you're not already dead and not doing any crazy maneuvers, it is vanishingly unlikely that you need ...
  • 457
15 votes

How does an airliner deal with cabin altitude at an airport above 8000 ft?

I am an aerospace engineer, who has worked on the design and certification of pressurized aircraft, so let me try and answer. The class of regulations that deals with the certification of pressurized ...
  • 159
15 votes

Could the SR-71 Blackbird be used for nearspace tourism?

Typical SR-71 missions proceeded as follows: Fill tanks on ground. Tanks leaking fuel like crazy, by design. Plane takes off, with fuel leaking everywhere. Plane gets to altitude, and flies very fast ...
  • 259
14 votes

Is there a ceiling on weather patterns?

No. Sprites, also known as upper atmosphere lightning, occur from 31 to 56 miles AGL. (source: Wikipedia) So weather phenomena routinely exceed your U2's altitude by a lot! Now are Sprites ...
  • 10.2k
14 votes
Accepted

How are aircraft separated at high altitude?

First of all, there is no such thing as a stall speed, but that is a topic of its own. The ATC system has numerous ways of dealing with keeping aircraft separated, even at high levels. Let me try to ...

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