# Tag Info

46

There are quite a few airports near sea level since many larger cities are located near the sea. There are even some airports below sea level. Amsterdam Schiphol is somewhat famous for it (at least where I live), even though its official aerodrome elevation is only -11 ft or -3 m. According to Wikipedia's list of lowest airports, the lowest elevation airport ...

27

Short answer If you just wanted to know some places below sea level then there are plenty of related collections for places and airports and there is little interest to copy them here. But actually your question is not about such lists but whether an altimeter can show a negative altitude when used... while testing and working with avionics systems I have ...

26

Most modern airliners have L/Ds of 18 to 22:1 (sorry I couldn't find a direct reference). So from one nautical mile, 6076 ft, in the air you can glide around 18 to 22 nm in still air. Departure climb gradient at, say 4000 fpm, a typical both engines climb rate, which is about 40kt vertical speed, going 200 kts horizontally, is about 5:1. So you are climbing ...

25

The main limitation is that the receiver needs to have enough excess thrust available to be able to precisely maintain formation on the tanker. Near the service ceiling, you typically don't have a lot of excess thrust, so refueling happens somewhat lower than that. Since fighter generally have more excess thrust at a given altitude than a transport will, ...

21

First, the actual "impossible turn possible" altitude number is going to vary dramatically by factors such as hot, high, heavy, wind, how wind interacts with your departure path, and whatever the damage did to the airplane. This question was extensively examined on the very similar Airbus A320, after Chelsey "Sully" Sullenberger had a ...

19

From the NATO website describing the a330mrtt: The Airbus tankers will be able to refuel a wide range of aircraft such as NATO AWACS surveillance planes; F-35, F-16 and Rafale fighter aircraft; and C-17 transport planes. Refueling can be performed at an altitude up to 35,000 ft while cruising at speeds between 180 knots and 325 knots. The A330mrtt has a ...

13

There are several regions where you could (at least in theory) fly below sea level. For example, in the Dead Sea depression, that is the lowest stretch of land on the planet, reaching a maximum depth of roughly 400 meters below (geoid) mean sea level.

12

Airliner-type aircraft fly close to stall speed at cruise altitude as their maximum speed in terms of Mach (Mmo) and their stall speed are within 15-20 knots to each other. Tankers cannot fly any faster (excluding buddy tanking, which generally happens at much lower altitudes and in the vicinity of the carrier), so fighters are also constrained to fly close ...

8

Some of the answers have hinted at a bit of a problem in the question, but I think it's worth bringing it out a little more clearly: whose cruising altitude do you care about? When a KC-135Q is refueling an SR-71, it's flying what for it is high and fast--but for the SR-71 is fairly low and slow. When a (non-Q) KC-135 is refueling an A10, we get pretty much ...

6

Within the US, the recipe would be something along these lines: Eastbound Since FL 410 is an eastbound altitude Moderately short, 1-2 hours - not so short that climbing high isn't worth it, nor so long that the aircraft takes off so heavy with fuel that 410 can only happen as a step-climb An aircraft that can reach 410 For example, a 737 NG or Max or a ...

6

I can tell you my experience during my stay in Zaragoza Air Base in northeastern Spain, in 1998. After heavy maintenance work, the twin-seater was ready to fly. In order to check all work done, we did a parabolic flight in clean configuration (no loads under wings or fuselage). It was a flight test so we decided to push the limits a little and see the real ...

6

Generally when you run right at service ceiling you are near the edge of the operating envelope with little energy margin if things go off the rails, so you are in a relatively dangerous place (also, aerodynamic forces, and damping, are drastically reduced in the thin air, but the inertial mass is the same, which tends to exaggerate overcontrolling/overshoot ...

5

You need to correct your pressure altitude (FL85) for the barometer setting QNH first before you apply the temperature correction. I assume a 30ft / hPa offset here: $\textrm{barometric altitude} = \textrm{pressure altitude} + (\textrm{QNH} - 1013.25)\cdot 30 = 8500 -907.5 = 7592.5 \textrm{ft}$ Based on the pressure difference between sea level and your ...

5

For here in the US, I give you Furnace Creek Airport at an altitude of -210 feet. https://www.nps.gov/deva/planyourvisit/airports.htm The pattern altitude is +789 MSL but you'll be lower on final approach. Late goaround should make for some interesting instrument readings. I recall reading about a case where the avionics was coded for Furnace Creek being the ...

4

Frame challenge: when aircraft are operating below the transition altitude (which in the USA is 18,000' MSL), ATC radar scopes will correct the reported pressure altitude and display the proper MSL figure (rounded to the nearest 100'). If you are only dealing with a small number of flights, you may be able to submit a FOIA request to the FAA and get the ...

4

Using your examples: If the field elevation is 0 and the altimeter setting is 29.92 then both pressure altitude and indicated altitude will be 0. Remember, pressure altitude is the altitude displayed (indicated) on your altimeter when the altimeter is set to 29.92. If the temperature increases from 15C to 40C per your examples, and the altimeter setting for ...

4

Remember that the altimeter simply shows your "altitude" as a relative reference to the pressure at a known point. We generally use sea level, though it can also be set to reference ground level (again, at a known point). This is commonly used in the UK, known as the QFE, where the pilot will dial in the air pressure at an aerodrome. So in that ...

4

Per the description of BU-60-1 at JAXA it carried a suspended payload with several cameras and a GPS receiver to measure altitude. While the top of the balloon would indeed have been higher, the FAI rules linked by mins in a comment indicate that record altitude claims are read at the instrument, suggesting that the claimed altitude would be that measured at ...

3

Altimeters are "told" what the pressure is at MSL. They then apply a model of the pressure above that point to map to altitude. The model assumes standard temperature. The model becomes less correct as temperature deviates from standard. Because your scenario has the plane at a MSL field and the altimeter is set properly for MSL, the indicated ...

3

No, the true altitude can also be higher than the indicated altitude, if the temperature is higher than expected from the International Standard Atmosphere (ISA). This case is usually not as important as the opposite case because flying at higher true altitude does not create a risk due to terrain clearance. In a standard atmosphere, the indicated altitude ...

3

Airplanes are flown with respect to indicated airspeed; in terms of true airspeed, jets (and powerful turboprops) go faster and faster up to a point, and then they slow down a bit – that point is a crossover point: switching to an essentially constant Mach number. In a climb: As you wrote: the air density decreases, that means for a given IAS, the TAS ...

3

AFAIK there is no EASA regulations forcing a pilot to use one or the other. The default option is to use QNH, which shall be transmitted to all aircraft: (3) Except when it is known that the aircraft has already received the information in a directed transmission, an QNH altimeter setting shall be included in: (i) the descent clearance, when ...

3

Because Pressure altitude is a measure of the weight of the air above you. Temperature does not affect that. Heating the air just makes it expand. It still weighs the same.

3

The picture you have displayed is correct. But, your understanding of what it is saying is incorrect. The picture is explaining the reason your Indicated Altitude will change with temperature for the same True Altitude. And, your True Altitude will change with temperature (a potentially dangerous situation) for the same given Indicated Altitude. Your ...

3

The simple answer is, usually the altimeter setting does not change fast enough for it to be an issue. Near ground level, one-hundredth of an inch of mercury (00.01 inHg) corresponds to roughly ten feet of pressure altitude. Thus one inch of mercury corresponds to one thousand feet of altitude. (This rough rule of thumb can be seen by looking at a lowest-...

3

The commenters have a good point that the SOP documents you liked are for hobbyist simulation and are not necessarily faithful reproductions of real-world procedures. But even in the real world who owns which specific volume of the air at which specific altitudes is not necessarily correlated with the regulatory airspace class for a given volume of air at a ...

2

Below[1] shows the hypersonic breathing corridor. Without LOX or rocket assistance, the limit is around 140,000 feet (40 km) at around Mach 15. In 2004 NASA's X-43 achieved a record Mach 9.6 at 109,000 feet (nasa.gov), which if you compare below, is a good match for the aforementioned corridor. 1: Smart, Michael. "Scramjets." The Aeronautical ...

2

There are reasons why a Hornet would NOT go above its 50,000 feet service ceiling. Has it been done in testing? Probably. Has it happened accidentally? Probably. But there’s no reason to do so. Aircraft performance is pretty bad at the service ceiling, so BFM/ACM isn’t going to go well. Turn performance and speed will be very negatively impacted. Dropping ...

2

When you are at an airport and you set your altimeter to the setting received from AWOS, ATC, ATIS etc. your altimeter will read your current "true" altitude above mean sea level (msl). Generally what your altimeter is showing is assumed to be the airport's "airport elevation." The altitude displayed is usually very close to the published ...

2

"density decreases (the air expands) as temperature increases" – yes, when you add energy while keeping pressure constant. That is how a hot air balloon or a thermal works. If expansion is caused by reduced pressure, temperature decreases. What happens in the atmosphere is normally described as an isentropic process.

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