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I heard that acrobatic flight, Russians, Americans use qfe but is it always the case? Also why doesn't everyone use it? Isn't qfe field pressure better than qnh local pressure... Does a pilot ever use qfe or field pressure in big airplanes like airbus or boing . I know pilots can input local pressure or standard pressure std = 1013.25 hpa ...but can they input qfe ? or not all airplanes have qfe?

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  • $\begingroup$ reminder to put answers, however partial, in the answer field. $\endgroup$
    – Federico
    Jun 18, 2022 at 4:57

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Also why doesn't everyone use it? Isn't qfe field pressure better than qnh local pressure...

Advantage of QFE is that it will read 0 on the field (and therefore approximately height in the pattern), so the pilot does not have to think about the runway elevation.

However a big disadvantage is that it is specific to the airfield. So when you have multiple airports near each other, you'd have aircraft flying around with different QFE settings. Which makes it work poorly for the other two purposes altitude is needed for: separation of aircraft from each other and separation from terrain. Plus it increases the risk of problems because pilot forgot to change the value.

With QNH everybody in the area will be using the same value, so everybody can be confident two aircraft reporting different altitude do indeed have different altitude. And there is one minimum safe altitude that applies to aircraft departing from and arriving to all the airports in the vicinity. The price is that the pilot has to remember the pattern and landing altitudes for that particular airport. It is a small price compared to all the risks of using QFE.

acrobatic flight

This is a notable exception. Aerobatic aircraft doing the aerobatic routine only flies in a tight show box where all other traffic is excluded, and the pilot has a lot of altitude values where he needs to initiate the various figures so he is high enough not to hit the ground and low enough that the spectators see him well. So there is makes sense to set the altimeter to read 0 at the ground, i.e. QFE, so he does not have to make any adjustments dependent on the location where he's performing.

I know pilots can input local pressure or standard pressure std = 1013.25 hpa ...but can they input qfe ? or not all airplanes have qfe?

QFE is entered the same way the QNH is entered. It is, however, possible that for high altitude airport the QFE is lower than the lowest value the altimeter will accept.

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In the U.S., the use of QFE (altimeter setting that displays height above field elevation) instead of, or in addition to, QNH (altimeter setting that displays height above mean sea level) would be a decision made by the operator (e.g. airline company, corporate operation, individual pilot, etc.) and not by a regulatory requirement.

Years ago Eastern Airlines used to set both QFE and QNH (using different cockpit altimeters) when descending into a terminal area prior to landing. I think there were also some other carriers with the same or similar Standard Operating Procedure (SOP).

I'm not aware of any operator currently using (simultaneously) both QFE and QNH.

I believe that the potential for confusion or inadvertent misinterpretation (viewing different indicated altitudes from different altimeters in the same cockpit) and the wide use and availability of radar/radio altimeters may have reduced the use and value of this SOP.

Also, ATC assigned altitudes (for aircraft separation purposes) are referenced to QNH or QNE (altitude/flight level associated with an altimeter setting of 29.92 in. Hg/1013 hPa), published altitudes on sectional charts depicting Class B, C and D airspace vertical boundaries are referenced to QNH (in the U.S.), and most (not all) other published and procedural altitudes are referenced to QNH or QNE. So using QFE as your only altimeter source would not be appropriate for most normal flight operations.

QFE can be calculated using the current QNH and the field elevation/Touch Down Zone Elevation of the airport of landing.

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I learned PPL and IFR in the USA. QFE was briefly mentioned in training but everything else at all times was QNH. ATC always reported in QNH as did inflight and online weather services (I have seen a handful of METARS give QFE in remarks). Sectional/visual and IFR charts give all altitudes in MSL so QNH is preferred (one can calculate AGL of obstructions, mountains, etc).

On IFR approaches knowing QFE may be helpful if equipped with multiple altimeters since you often look at height above touchdown zone/runway.

I have read Russia used to use QFE (and Lat/Long coordinates) but had changed recently to QNH or offers it. A few countries like China use altitude in meters, other report airport winds in meters per second, some use flight levels at 1013 hpa etc. In USA we use degrees C instead of F for aviation yet nautical miles and feet.

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  • $\begingroup$ Flightlevels are per Definition always measured to 1013 hPa. What’s your point? $\endgroup$
    – pcfreakxx
    Jun 19, 2022 at 21:40
  • $\begingroup$ They measure all altitudes in flight level instead of regular QNH $\endgroup$
    – BobJohnson
    Jun 20, 2022 at 2:37
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    $\begingroup$ I never heard of that before, which countries are you referring to? I know places with TA as low as 2500ft or 3000ft, but I can’t believe it’s legal to use FL at every level. $\endgroup$
    – pcfreakxx
    Jun 20, 2022 at 6:27
  • $\begingroup$ @BobJohnson Incorrect. QNE is only used above the Transition Level. The TL in some countries may be lower than you’re used to, but it is never zero. $\endgroup$
    – StephenS
    Jun 21, 2022 at 20:06

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