# Tag Info

67

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 is easier to ascend to greater heights. Commercial jets also carry more fuel which needs to be burned off to lighten the plane to go higher. It’s easier to ...

51

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. Everest at 29,029 feet (8848m) (twice). The only changes he made to the standard version were removing a few things like extra seats to reduce the weight, and of ...

41

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 experimentally verified by taking a barometer up to a mountain. This was first done in 1648 (and subject to hot debate regarding the nature of air) more than 250 years ...

34

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 emergency requiring immediate action, the pilot in command may deviate from any rule … to the extent required to meet that emergency. (FAR 91.3 (b)). So if you're ...

31

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 than 8,000 feet, the cabin descends to the cabin cruise altitude while the airplane is climbing. When the destination airport elevation is greater than 8,...

30

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 Everest, set in 1972 Reference: Wikipedia In 2005 Didier DelSalle famously touched down on the summit of Everest in an AS350 Squirrel Reference: Wikipedia. See ...

25

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 really do, you'll get a sunburn quite fast. I got a sun burn within an hour in an altitude of 3500m / 12000ft, though I was tanned due to two weeks at the beach. ...

25

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 Jets: According to this article the highest service ceiling for various business jets is at FL510, so none can reach FL600. Military Reconnaissance Aircraft: ...

24

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 for example at FL380 that will be 38000ft above the pressure level of 1013,25 hPa. This system assures that 2 aircraft which are 10 FL apart (e.g. FL370 and ...

22

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 air pressure on aircraft and engine performance was already known. Of course both civil and military aircraft were unpressurised before the start of jet-powered ...

22

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 high the overshooting tops can get is a balance of the positive buoyancy during parcel ascent against the negative buoyancy once it gets into the warming ...

22

As it stands, that 'border' between FL600 and above is undefined, and unregulated. There is no international agreement on the vertical limit of state sovereignty. Today, the need to settle this gap in the law is growing in importance. More and more states are developing their own domestic space launch capability. Few of these new space powers ...

20

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 cost bottled oxygen supplies specifically made for this situation. At 11,000ft it's unlikely lack of oxygen will make your mother really ill, a top of oxygen is ...

18

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 word "acute". Just having your Mom feeling a little light-headed is probably not going to hold up as a valid reason to divert lower in any faa action. And if ...

18

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". If you look at the flight envelope of the SR-71 below, it becomes clear that more altitude can be best bought with more speed. SR-71 flight envelope (picture ...

18

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 volume for range requirements, but it's mainly that you need the extra wing area to be able to fly that high with a reasonably efficient indicated airspeed at 50000 ...

15

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 aircraft are called 14 CFR 23.841 (General Aviation) and 14 CFR 25.841 (Commercial). Both paragraphs are pretty much identical and in summary say the following ...

14

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 dangerous to flight? Unknown. I know of no case where an aircraft has been hit by a Sprite.

14

Assuming maximum altitude for the highest blimp is 74,000 feet, and the rail to be angled at 15 degrees, it gives us a rail length of 285,000 feet. The HiSentinel stratospheric airship flew that high, and was able to carry only 36 kg. The steel rail/rope would weigh roughly 5.5 million kg. Based on steel density and a good sized rope, to withstand the ...

13

In general, no- except in emergencies or 'small' hurricanes. Commercial aircraft usually fly around bad weather (like hurricanes), not over it. Some of the hurricanes can reach upto 50,000+ ft height, making it all but impossible for most modern commercial aircraft to fly over them (except maybe you're flying a Concorde). Even for smaller storms, the ...

13

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 summarize some of the most important ones, starting with the planning that happens when planes are still at the ground at their departure airport, working our ...

12

No. The stagnation point temperature goes up with the square of true air speed. Temperature dissipation is proportional to true air speed and density. Lift is proportional to the square of airspeed and density. The lower wing loading of a glider (compared to the Shuttle, for example) means that all of the reentry will be slower, but that is not ...

12

That electric propulsion needs no oxygen is of little help for flying high. The composition of the atmosphere does not change too much with altitude, so it is the low atmospheric density which limits maximum altitude. We had this discussion before, and indeed solar-electric propulsion helped to reach record altitudes: The AeroVironment Helios set a record at ...

11

That's pretty much how space shuttles and other orbiting craft work. They are dropped from orbit, they do calculations to enter the atmosphere at a velocity and attitude that doesn't burn up the aircraft, then they glide to their landing airport. The entire journey is controlled, but unpowered flight. The flight surfaces are there to allow the pilots the ...

11

Your $v_\mathrm{ref}$ does not depend on density altitude since it is given in Indicated Airspeed, which already accounts for density effects. However, the True Airspeed and therefore also Groundspeed will be higher at a higher density altitude, resulting in more runway required to stop. The Flight Safety Foundation has a nice summary of factors influencing ...

10

The helicopter flies as long as the blades produce lift. Now,the lift is proportional to the density at a particular altitude. However, as altitude increases, the density goes down. Usually, the helicopter compensates for this by increasing the lift coefficient by increasing the blade pitch (as the blade rotational speed, and hence V is constant). However, ...

10

The higher takeoff speeds might exceed the speed rating of the usual tires. As a tire is rolling it deforms in two directions. As each section comes in contact with the runway it is pressed inward by the weight of the plane. After it leaves the runway surface the deformation is in the opposite direction from centrifugal force. This constant flexing is what ...

10

A door that is, say, 36" x 80" (0.9m x 2m), with a surface area of 2880 sq/in (1.8m2), at 8 psi (55kPa) max cabin pressure differential, which most airliners run at, will have roughly 12 tons (102kN) acting on the perimeter fittings trying to blow it out. Any other forces acting on it are microscopic in comparison. For non plug type doors that depend on ...

10

To combine the other two answers: Below the "transition altitude" (which is 18,000 feet in the US, 5,000 feet in Germany), the pilot has to pay attention to the current altimeter setting, and adjust it accordingly. However, they don't have to listen to ATIS/AWOS/etc., most controllers will give you the current altimeter setting when you check in with them, ...

9

The oxygen level at high altitude is the same as at sea level, namely 20.95%. What is lower is the oxygen pressure. To avoid flameout, pilots must avoid to throttle the engine down too much, so a minimum pressure in the combustors can be maintained. Designers can increase the altitude performance by building longer combustors. The speed of ignition is ...

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