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19

That is a QNH altimeter setting in inches of mercury, with the decimal omitted. So in the case given, that is a QNH of 30.11 inHg or about 1020 hPa.


14

Airline pilots generally get the QNH from the airport ATIS or similar. If they don't get it from there, ground control will give it before taxi. Above the transition level (11,000 feet (3,350 m) in Malaysia, 18,000 feet in the US), the altimeter is set to the standard pressure (29.92 inHg, 1013 hPa), also referred to as QNE. It doesn't take that long to ...


11

In the US, ATC simply broadcasts a notification on whatever frequency is needed. For the terminal environment, section 2-9-2 of the ATC orders says: Broadcast on all appropriate frequencies to advise aircraft of a change in the ATIS code/message. The phraseology is usually something like this: Attention all aircraft, Bowman information Kilo is now ...


10

It is used in aerobatic competition. It is much safer and easier to read AGL altitude directly from the altimeter than to attempt to do the arithmetic immediately prior to performing a maneuver. I normally fly out of a field at an elevation of 1000'. If I were to fly a contest in Colorado where field elevation is 8000' or higher, my altimeter will show an ...


9

Your question is quite not clear, you are challenging definitions and use of definitions, but you may start with a misunderstanding: QFE = pressure measured by an altimeter which is adjusted to ground level (it gives a height of 0 when the airplane is on the ground). Definitions To ensure clarity, QFE/QNH: are reference pressures, not altitudes are ...


8

There are actually multiple different answers depending on the specific type of altimeter system and what standard applies. The stand-alone altimeters in older aircraft and small GA aircraft (panel mounted "steam gauge") are certificated to SAE AS392C, Altimeter, Pressure Actuated Sensitive Type. The specified scale range is "at least 28.1 - 30.99 inches ...


8

The current QNH at an airport is included in METARs so you can grab it form there. There are a few online services to retrieve the METAR automatically, such as this one (using Vienna airport as an example). The latest METAR when I wrote this answer was: LOWW 281050Z 14010KT 9999 FEW040 SCT065 BKN300 04/M03 Q1012 NOSIG which shows a QNH of 1012. Note that ...


6

In metric: 1 milibar is approximately equal to 30 feet. This calculation is therefore also approximate but is good for airfield elevations to several hundred feet since we round to the nearest millibar. Divide the airfield altitude in feet by 30 to get the number of millibars above MSL. Add this to the QFE to get QNH or subtract it from QNH to get QFE. ...


5

In Canada at least, you are supposed to make the change between QNH (alt setting) and QNE (standard pressure) while in QNE airspace, whether climbing or descending; that is, right after passing the transition altitude while climbing, or just before passing transition altitude while descending. The variable overlap zone you describe resulting from the change ...


5

The QNH is the reference pressure of the aerodrome, not the aircraft. It is calculated such that an altimeter, which assumes ISA conditions otherwise, shows the correct altitude above mean sea level at the aerodrome: Airfield QNH is obtained by correcting a measured QFE to sea level using ISA regardless of the temperature structure of the atmosphere. As ...


5

That refers to an altimeter adjustment to compensate for local atmospheric variations in pressure. The reading given is what the atmospheric pressure would be on the field if it were at sea level in inches of Mercury (inHg). This is most often used in adjusting a sensitive barometric altimeter in an aircraft so that it reads an altitude which is within +/- ...


4

It is the barometric pressure at the airfield, in inches of mercury. It is to two decimals, so you got 30.11 inches of mercury. It is the same as QNH (which is the airfield pressure adjusted to sea level). From flightsim.com ... (it) is the barometric pressure, given in inches of mercury. If you look on a standard wall barometer, you'll see that it equates ...


4

Your question is a bit confusing since you seems to be already giving the definition for QNH and QFE. I'll just leave this example to see if it can clear things up for you: Let's say you are at an airfield which is at 500 feet above sea level. The ATIS tells you that the QNH is 1020hpa. While on the ground, if you set your altimeter to 1020hpa it will read ...


4

I've only done passing research on the matter before, so if anyone knows more please chime in. As far as I know the FAA uses NSRS (National Space Reference System), and the NSRS currently uses NOAA GEOID models, although this is expected to be changed in 2022. I'm not sure which regulation covers airport surveys, but you can reference AC 150/5300-18 (pdf). ...


3

This is related to why there is always a buffer of at least 1000ft between the Transition Altitude and the Transition Level. If you are at 4000ft and want to climb to FL070, then once you cross the TA at 5000ft, you set QNE and climb until your altimeter reads 7000. It does not matter whether the altimeter briefly changes to 4500 (or 5500) at the instant you ...


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

You can't just adjust the QNH setting to compensate. The temperature adjustment is not linear. The error increases with altitude, so when the altimeter is set for QNH the error at field level is zero. But it increases the higher you go. It's not just everything being X number of feet higher or lower. In your question you say "the aircraft's pressure ...


2

QNH and other airport information is communicated to incoming flights through ATIS. The only acknowledgement of this you will hear through ATC is aircraft first contacting the controller saying "with information Oscar" or similar, which means they have already heard the ATIS bulletin.


2

In the UK at least, QFE is used primarily by the military. There are still a number of airfields which are used by both the military and civilian flights (eg, RAF Northolt) and flying in there you will be given a QFE. As a civilian pilot, you are only likely to be given a QFE on joining to land at an airfield, and while in the circuit.


2

By either manually entering the indicated altitude, total air temperature, barometric pressure, etc., or feeding those variables via sensors connected to the GNSS unit, it is able to know the true airspeed, wind direction/speed and the head/tail wind components. Very useful for knowing the performance in-flight. Example interface for the Garmin GTN 650/750 ...


2

Indeed the US and the rest of the world handle this differently. In the US, if you are cleared to a flight level or altitude, you change the altimeter setting as you are about to cross the transition level (18,000 @ 29.92). [When] descending, even if cleared to an altitude at the time the cruising level is vacated, the altimeters will remain on standard ...


2

Yes the QNH value is based on the atmospheric pressure taken at the measurement site, then adjusted to represent that same atmospheric condition at seal level based on the normal expected pressure change between sea level and the measurement site, and at the standard temperature lapse rate. In other words, if the measurement site was 1000 ft above sea level ...


2

The pressure ranges for altimeters in the United States are set forth in a technical standing order. For example TSO-C10b in turn references SAE standard AS392C, which indicates the following performance parameters: Type I : range to 35,000 feet Type II: range to 50,000 feet Both adjustable from 28.1 to 30.99 inHg. These parameters have regulatory ...


1

Formula 33a (from the US Standard Atmosphere 1976 document you quote) gives you the pressure at a specific altitude in the U.S. Standard Atmosphere, and corresponds closely to airport/station level pressure in met reports (it corresponds exactly when the real atmosphere has the same characteristics as the Standard Atmosphere). An altimeter setting/QNH is ...


1

Because it is preferable to work with standard atmospheric data,(ISA international standard atmosphere where at mean sea level, the temperature is 15° and the pressure is 1013hPa) and because your navigation instruments will display your altitude with respect to a reference, on QNH setting, above the transition altitude the reference is MANDATORILY the ...


1

I just read about QNH and QFE so I thought I’d throw this out there to start the discussion. We don’t use QFE in the US but I think my logic is correct. From the FAA Instrument Procedures Handbook Barometric Pressure for Local Altimeter Setting (QNH) A local altimeter setting equivalent to the barometric pressure measured at an airport altimeter datum and ...


1

In the UK, General Aviation traffic typically uses QFE in the circuit, and regional QNH in the cruise. From Pooleys Air Navigation Manual: "It is very convenient for circuit operations if the altimeter can be set to indicate height above aerodrome level (aal). This means that a 1,000ft circuit at, for example, Leicester airfield (elevation 469 ft) can be ...


1

Where ICAO rules apply (e.g. most of the world), broadcasting a change in QNH to the entire frequency is not sufficient. The QNH is considered (for good reason) to be safety critical information, and so each aircrew most positively acknowledge that they have correctly received it. This means informing each aircraft on the frequency of the new QNH, and wait ...


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