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Altimeter setting


Hippo

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1 hour ago, Yurgon said:

It would help if you chose your words carefully. QNE is either a pressure setting or an altitude. It can't be both. It's either measured in inHg or in feet.

It can be both, just like how distance can be expressed in seconds or meters, but is typically expressed as meters.

QNE is typically expressed as a pressure setting, e.g. inches of mercury, but it also represents a pressure altitude.

I think you are not understanding what pressure altitude is.

1 hour ago, Yurgon said:

There's no need to explain the relation between altitudes, air pressure differences and so on. I think everyone here understands that. The question is not "What is QNE and how do we use it?", the question is "How is QNE defined?". Or to be more precise, the question is "With 2 different definitions for QNE, which one is correct?"

Both definitions are correct, you are not understanding what they have written.

1 hour ago, Yurgon said:

All that is fine. The underlying problem remains that one definition says "QNE is the pressure setting of 29.92 inHg" and another definition says "QNE is a runway threshold pressure altitude when the altimeter is set to 29.92 inHg". Which, once again, means that there are conflicting definitions where it is either a pressure setting (in inHg) or an altitude (in feet, at a specific place, at a specific time).

If you set your altimeter to 29.92 inHg it will indicate an altitude that is equal to the runway threshold pressure altitude. Both definitions are correct, the former one is just written in more layman's terms.

-> Set your altimeter to 29.92 a.k.a. QNE a.k.a. standard pressure -> look at your altitude while parked on the runway threshold -> this is the field's pressure altitude

-> Set your altimeter to QNH per ATIS/METAR -> look at your altitude while parked on the runway threshold -> this is the field's altitude


Edited by MARLAN_

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2 hours ago, Yurgon said:

Glad we were able to reach this distinction. 😉

I thank you for your explanations and your attempt to help me understand.

It would help if you chose your words carefully. QNE is either a pressure setting or an altitude. It can't be both. It's either measured in inHg or in feet.

There's no need to explain the relation between altitudes, air pressure differences and so on. I think everyone here understands that. The question is not "What is QNE and how do we use it?", the question is "How is QNE defined?". Or to be more precise, the question is "With 2 different definitions for QNE, which one is correct?"

Yeah, seems to me as well that someone is just using wrong terminology there.

All that is fine. The underlying problem remains that one definition says "QNE is the pressure setting of 29.92 inHg" and another definition says "QNE is a runway threshold pressure altitude when the altimeter is set to 29.92 inHg". Which, once again, means that there are conflicting definitions where it is either a pressure setting (in inHg) or an altitude (in feet, at a specific place, at a specific time).

You just repeated one of these definitions while ignoring the fact that another one exists. I want to thank you for the great explanations. But we're no closer to solving the underlying problem here, which as far as I'm concerned was addressed in the meantime.

QNE is the altimeter setting value equal to the ISA sea level pressure and will cause an altimeter to display pressure altitude. This is practically a setting of 29.92(3) inches mercury (equivalent: 760mm Hg, 1013mb, 101.3kPa, 1 atm).

No other definition of QNE exists. QNE is not an altitude of any kind and has nothing to do with runways or runway thresholds. Any claim to that effect is incorrect.

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3 hours ago, MARLAN_ said:

It can be both, just like how distance can be expressed in seconds or meters, but is typically expressed as meters.

Oh. Uh. Okay. Remind me not to take you seriously for the next couple of kilometers. One inch soon you'll understand.

3 hours ago, MARLAN_ said:

I think you are not understanding what pressure altitude is.

And I think you don't understand the definition of the word definition. We should probably leave it at that for the distance being.

1 hour ago, Frederf said:

QNE is the altimeter setting value equal to the ISA sea level pressure and will cause an altimeter to display pressure altitude. This is practically a setting of 29.92(3) inches mercury (equivalent: 760mm Hg, 1013mb, 101.3kPa, 1 atm).

No other definition of QNE exists. QNE is not an altitude of any kind and has nothing to do with runways or runway thresholds. Any claim to that effect is incorrect.

It would sure be simpler if we could just define a definition away.

The fact of the matter remains, another definition exists, it has been written down, there are multiple sources, it has been quoted and linked in this very thread.

Any authoritative source in favor of one definition or the other would be most welcome.

On a side note, it's actually quite funny how just about anyone in this discussion promotes another definition. 😉

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Using runway thresholds to explain QNE is certainly a simplification as it is more accurately defined as pressure altitude, but there are certainly definitions that use runway thresholds as part of it, and it's not wrong, because when you're on the runway, with QNE set, your altimeter will display pressure altitude. I think explaining it that way helps understanding.

I do totally agree though that it's more accurately defined as pressure altitude.

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5 minutes ago, Yurgon said:

Oh. Uh. Okay. Remind me not to take you seriously for the next couple of kilometers. One inch soon you'll understand.

Huh? My comment clearly went over your head.

5 minutes ago, Yurgon said:

Any authoritative source in favor of one definition or the other would be most welcome.

See: FAA-H-8083-25B, it's defined about 5 times in there as myself and Frederf are explaining to you.

This topic is becoming pointless.


Edited by MARLAN_

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Historically radiotelephony has used Q-codes, including QNE, to make a complex question and answer exchange. QNE under this frankly antiquated usage based on non-ICAO/FAA definitions the passed info is indeed an altimeter indication. You have to look through some radiotelephony documents to get this. The official question and official answer encoded by QNE (remember this is Morse encoding) is:

Question

What indication will my altimeter give on landing at
... (
place) at ... hours, my sub-scale being set to
1013.2 millibars (29.92 inches)?

Answer

On landing at ... (place) at ... hours, with your sub
scale being set to 1013.2 millibars (29.92 inches), your
altimeter will indicate ... (
figures and units).

In this radiotelephony exchange when doing pressure altitude landing operations, which no one does, then QNE is indeed a pressure altitude along with a reminder what the pressure setting to reference is. I have never heard of this nonsense before but it's legit. The controller/airport would calculate what pressure altitude their aerodrome/runway numbers/runway threshold is and relay that info. It's from QFE operations where QFE setting is impossible because it's off the settable scale. I'm guessing this only applies in places that routinely use QFE referenced altimeters (UK, Russia) and sometimes the QFE setting is off the altimeter scale so they need a backup plan.

QNE as defined in any modern FAA/ICAO document is the ISA standard sea level pressure. You should automatically assume that any reference to QNE is about the pressure, not an altitude. This will serve you well in 99.9% of situations. If for some reason you're under Morse-based R/T doing QFE ops and the QFE setting is impossible to set so you have to reference pressure altitude for approach and landing purposes, yes QNE is asking and replying an altimeter indication.

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1 hour ago, MARLAN_ said:

See: FAA-H-8083-25B, it's defined about 5 times in there as myself and Frederf are explaining to you.

This one? My PDF reader doesn't find the term "QNE" at all in that PDF document.

6 minutes ago, Frederf said:

I have never heard of this nonsense before but it's legit.

I never said it made sense, only that someone once defined it this way. 😉

It would really help if the FAA or any other authority had an official definition, and if that included any prior definitions and marked them as deprecated, so that there would be a source that anyone could easily refer to. But even the ITU (International Telecommunication Union) doesn't have such a central register, or at least I couldn't find one, although it would seem plausible that this would be the one authoritative agency regarding this matter (Q-codes in general, not just QNE).

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The -23B part of the PHOA doesn't have it, but the -16B part does pages 2-44/2-45 and glossary https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/instrument_procedures_handbook/media/faa-h-8083-16b.pdf. Here are some some other FAA docs:

J.O. 7340.2L Contractions https://www.faa.gov/documentLibrary/media/Order/7340.2L_CNT_Bsc_w_Chg_1_2_dtd_7_14_22.pdf has QNH, QFE not QNE

Pilot/Controller Glossary https://www.faa.gov/air_traffic/publications/media/pcg_10-12-17.pdf has all three

The FAR AIM has one reference to QFE but not QNH and QNE except in the P/CG which is sometimes published attached

J.O 7110.65 has some references but clicking on QNE/QNH links back to the P/CG

Here, go nuts: https://www.faa.gov/search/?q=QNE&startAt=0#content

 

Q-codes are a messy historical phenomenon. FAA nor ICAO can authoritatively override beyond their institutions. All they can do is indicate which parts they adopt officially and how those adoptions are interpreted. Extraneous factoids are beyond their control. If you want to be lawyer proof you have to trace all info back to your favorite authority.

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40 minutes ago, Yurgon said:

This one? My PDF reader doesn't find the term "QNE" at all in that PDF document.

It would really help if the FAA or any other authority had an official definition

It's literally in the document if you read it, it isn't labelled QNE, look at pressure altitude as I've explained multiple times.

54 minutes ago, Frederf said:

Historically radiotelephony has used Q-codes, including QNE, to make a complex question and answer exchange. QNE under this frankly antiquated usage based on non-ICAO/FAA definitions the passed info is indeed an altimeter indication. You have to look through some radiotelephony documents to get this. The official question and official answer encoded by QNE (remember this is Morse encoding) is:

Question

What indication will my altimeter give on landing at
... (
place) at ... hours, my sub-scale being set to
1013.2 millibars (29.92 inches)?

Answer

On landing at ... (place) at ... hours, with your sub
scale being set to 1013.2 millibars (29.92 inches), your
altimeter will indicate ... (
figures and units).

In this radiotelephony exchange when doing pressure altitude landing operations, which no one does, then QNE is indeed a pressure altitude along with a reminder what the pressure setting to reference is. I have never heard of this nonsense before but it's legit. The controller/airport would calculate what pressure altitude their aerodrome/runway numbers/runway threshold is and relay that info. It's from QFE operations where QFE setting is impossible because it's off the settable scale. I'm guessing this only applies in places that routinely use QFE referenced altimeters (UK, Russia) and sometimes the QFE setting is off the altimeter scale so they need a backup plan.

QNE as defined in any modern FAA/ICAO document is the ISA standard sea level pressure. You should automatically assume that any reference to QNE is about the pressure, not an altitude. This will serve you well in 99.9% of situations. If for some reason you're under Morse-based R/T doing QFE ops and the QFE setting is impossible to set so you have to reference pressure altitude for approach and landing purposes, yes QNE is asking and replying an altimeter indication.

The FAA handbook also explains the relation with pressure altitude & standard pressure (QNE). Just because you haven't heard it doesn't make it nonsense. As you said, UK/Russia may use this more often, and the definition exists. (This is aside from the fact it is still a mathematical equivalency as well which applies globally)

I have never said referring to QNE as the pressure altitude is common place, I've said multiple times its not, but you guys keep saying as some sort of fact that it is straight up not an altitude, and I am just saying it absolutely is an altitude (pressure altitude), that altitude changes based on local conditions. It isn't just some antiquated radio system either, it is also a mathematical equivalency as previously mentioned. That pressure altitude when at the field is well, the pressure altitude at the field (duh), so it's not wrong to define QNE as the pressure altitude at the runway threshold (but certainly not the common use of QNE which is a pressure setting, e.g. 29.92/1013.25/etc.)

I'm done replying here before this gets any worse. Frederf you obviously understand the topic, just getting a touch stuck on common usage vs. definition. I only brought up pressure altitude and its relation in the first place because Yurgon seems to think the definitions are in conflict (they aren't). Yurgon, you're so confidently wrong you really ought to just read up on pressure altitude instead of constantly trying to insult me, looks really silly when you're so off the mark with your understanding of this topic. The fact you think multiple official definitions are in conflict should tell you something (read the handbook).

image.png

(P.S. 29.92 (Pressure Altitude) = 29.92 (QNE) to clear that up. I didn't think I would need to say 29.92 = 29.92 but here we are)


Edited by MARLAN_

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8 hours ago, MARLAN_ said:

It's literally in the document if you read it, it isn't labelled QNE, look at pressure altitude as I've explained multiple times.

Okay, let's make it really simple.

Please define QNE, and provide a source for that definition.

Just to be clear, I'm not asking you to explain what it is, or what it's used for. I'm not asking you to explain how it correlates with other things. I'm not asking you to explain the relation between QNE and other things, or how one can be calculated or derived from the other, or how they depend on one another. I'm asking you to provide the definition for the term QNE, as you understand it. That shouldn't be too hard.


Edited by Yurgon
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vor 10 Stunden schrieb Frederf:

Historically radiotelephony has used Q-codes, including QNE, to make a complex question and answer exchange. QNE under this frankly antiquated usage based on non-ICAO/FAA definitions the passed info is indeed an altimeter indication. You have to look through some radiotelephony documents to get this. The official question and official answer encoded by QNE (remember this is Morse encoding) is:

Question

What indication will my altimeter give on landing at
... (
place) at ... hours, my sub-scale being set to
1013.2 millibars (29.92 inches)?

Answer

On landing at ... (place) at ... hours, with your sub
scale being set to 1013.2 millibars (29.92 inches), your
altimeter will indicate ... (
figures and units).

In this radiotelephony exchange when doing pressure altitude landing operations, which no one does, then QNE is indeed a pressure altitude along with a reminder what the pressure setting to reference is. I have never heard of this nonsense before but it's legit. The controller/airport would calculate what pressure altitude their aerodrome/runway numbers/runway threshold is and relay that info. It's from QFE operations where QFE setting is impossible because it's off the settable scale. I'm guessing this only applies in places that routinely use QFE referenced altimeters (UK, Russia) and sometimes the QFE setting is off the altimeter scale so they need a backup plan.

QNE as defined in any modern FAA/ICAO document is the ISA standard sea level pressure. You should automatically assume that any reference to QNE is about the pressure, not an altitude. This will serve you well in 99.9% of situations. If for some reason you're under Morse-based R/T doing QFE ops and the QFE setting is impossible to set so you have to reference pressure altitude for approach and landing purposes, yes QNE is asking and replying an altimeter indication.

That's basically the whole explanation. 

A Q-Code can't be a "value"... The answer to the question defined as the Q-Code is a value. In case of QNE the answer is a number in feet that reads on the station's altimeter when set to ISA (the pressure altitude of the location).

In case of QFE it is the current pressure setting in hPa or InHG when the altimeter of the ground station reads the elevation of the station, or the runway threshold (a pressure).

Shagrat

 

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vor 39 Minuten schrieb Yurgon:

Okay, let's make it really simple.

Please define QNE, and provide a source for that definition.

Just to be clear, I'm not asking you to explain what it is, or what it's used for. I'm not asking you to explain how it correlates with other things. I'm not asking you to explain the relation between QNE and other things, or how one can be calculated or derived from the other, or how they depend on one another. I'm asking you to provide the definition for the term QNE, as you understand it. That shouldn't be too hard.

 

Q-Codes are defined as short codes to convey complex requests or information in a 3 letter morse code. The definition is it is either a question/request, or the answer to the question/request. If you morse the code it is followed by a question mark in morse code to indicate the request. The recipient answers with the same Q-Code and the appropriate info. In this case a number representing feet in reference to standard pressure setting. 

Shagrat

 

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Guys...here is a quote from the german wikipedia page. I leave it to you to put that into google translate.

Spoileralert: pretty much all of you are right...but still that discussion is pointless.

 

QNE ist kein von der Internationalen Zivilluftfahrtorganisation ICAO für den Gebrauch in der Luftfahrt definierter Q-Code[3]. Es gibt allerdings nationale Luftfahrtbehörden oder Wetterdienste (z. B. Deutscher Wetterdienst), die diesen festlegen, wie z. B. die Zivilluftfahrtbehörde des Vereinigten Königreichs (CAA) im Radiotelephony Manual von 2016[4]. Jedoch weichen diese nationalen bzw. nur für Teilgebiete der Luftfahrt geltenden Definitionen teils voneinander ab.

In Deutschland findet dieser Q-Code im Luftfahrthandbuch[5] jedoch keine Erwähnung. Die Verwendung des (im Allgemeinen inoffiziellen) Codes QNE ist somit aufgrund einer fehlenden globalen Definition und dem Vorhandensein von lokalen, mitunter verschiedenen Festlegungen problematisch.

Der Begriff QNE bezeichnet in deutschsprachigen Ländern die Druckhöhe über der Druckfläche 1013,25 hPa (Einstellung erfolgt auf der Druckskala des Höhenmessers oberhalb der Transition Altitude).

 

I mean this is a forum....you can discuss whatever you like, but this has left the realm of what a pilot really cares about.

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vor 21 Stunden schrieb Yurgon:
Am 25.7.2022 um 19:34 schrieb Frederf:

Re: "Standard QNH". That's not the correct term.

Yeah, seems to me as well that someone is just using wrong terminology there.

It is just an operational thing. The term QNE is never used in the Cockpit, at least I´ve never herd it nor is it one of the SOP´s. It´s also not a common thing in the US. 
In the cockpit you would call out 
PF: "QNH standard set, passing FL130......now"

PM:"QNH standard set and cross checked". 

 

In the end everyone is talking from the same thing, however terminology varies between operators, Countys and regulations. No point in discussing who is right and wrong, because we are all right and wrong at the same time. That´s probably Schrödingers Q setting then. 

 


Edited by Spock14
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  • 4 weeks later...
On 6/4/2022 at 12:35 PM, Hippo said:

Wouldn't it be more likely for a regional QNH to be used rather than standard?  Can anyone confirm what standard USN F-18 procedure for this is?

Massive shout-out to Jell-O, host of the Fighter Pilot Podcast! It put this question to him and he answered it in the Q&A section of episode 149.

The question was if US Navy jets operating from the carrier would transition to the standard pressure setting, and Jell-O's answer was very straightforward:

He'd just set the altimeter to show 60 feet prior to take-off, because that's the height of the carrier deck, and leave it at that pressure setting for the rest of the flight.

Only when coming in to land in Case 2 or Case 3, they'd get the altimeter setting from the carrier; once below 5,000 feet they'd set the HUD to show radar altitude, and the exact QNH wouldn't matter any more. In Case 1, it sounds like he never changed the altimeter at all.

He also said when doing 2v2 dogfights at higher altitudes in the middle of the ocean, he doesn't remember setting 29.92.

However, his guest Flounder said he indeed remembers setting 29.92 when going above 18,000 feet, and that when flying in-theater he would set the local pressure for that area.

So I suppose over the oceans it doesn't matter all that much, but in DCS we're probably not doing it wrong if we're transitioning to standard pressure setting in US Navy jets above 18,000 feet. I also assume that there's going to be a controlling agency, or specific airspaces, to ensure separation between military and civilian aircraft.

And finally I assume that things would be different when operating under civilian ATC control and that, in that case, local flying procedures take precedence.

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  • 6 months later...

Could someone JUST please explain simply and concretly what and how to set altitudes on coldstart with F/A-18C, to get my autodropped bombs not to fall 500m short. Information also about effect / meaning /reading and setting the "standby attitude meter ("SAI") (just the meaning of it for the plane itself, and does it effect somehow to something else to the meter it self. (on cold start, why not while flying itself. Does THAT effect somewhere else than the attitude meter itself? "Uncage by turning the knob". Turning it to "where"? Does it take its place automatically or what am I actually doing by turning the knob and uncaging it? Let it "float"? There reads also in knob it self  "pull to cage", but dont understand how that works, or more precisle how i should "uncage the stndby attitude meter" #24 on checklist, and whats the meaning of that.)  Thank You. And ps. Sry for complicated question. My English is not so good, so I have to "go around" some grammar 😄 "some" ;D


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Your altimeter should already be pre-set for MSL on cold start.

The SAI is just a backup attitude indicator, the INS provides the primary attitude reference data for the computers.

You can also press Sensor Control Switch forward to enable air-to-ground ranging (AGR on the HUD) for the radar.

There's also a small bug regarding the GPS correction for the INS (primarily affects CCIP indication, but might affect AUTO releases as well). Change POS/AINS on the HSI to POS/GPS and see if it's any better.

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