Why do the RAF still use QFE?
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BV,
As I do not fly RAF Aircraft and have no idea what capability your altimeters have, and knowing the RAF is bound to have some policy, SOP, or Pilot Instructions re setting of Altimeters, perhaps you or some other RAF Pilot could answer that simple straight forward question.
It would be educational to have an explanation of how you determine when QFE settings will not be feasible and thus necessitate your use of QNH instead. That would also tell us what the limitations of the QFE method might be too.
Nothing sinister here, just somewhat curious how you go about your business as it is much different than the way most of us are experienced in doing.
As I do not fly RAF Aircraft and have no idea what capability your altimeters have, and knowing the RAF is bound to have some policy, SOP, or Pilot Instructions re setting of Altimeters, perhaps you or some other RAF Pilot could answer that simple straight forward question.
It would be educational to have an explanation of how you determine when QFE settings will not be feasible and thus necessitate your use of QNH instead. That would also tell us what the limitations of the QFE method might be too.
Nothing sinister here, just somewhat curious how you go about your business as it is much different than the way most of us are experienced in doing.
BB,
There's no need for any mathematics or conversion tables. It's a simple 2-step procedure:
1) If in a country where QFE is used at military airfields (e.g. UK), use QFE at military airfields.
2) If elsewhere, use QNH.
Personally, I would rather use QNH at all times in the UK as well. Having 2 ways of saying the same thing is great if you're writing a novel, but it goes against principles of standardisation and seamless interoperability that the world of aviation generally subscribes to. It's not difficult to switch from QFE to QNH when operating abroad, but then in my humble opinion it's not difficult to fly a circuit on QNH either. Certainly not difficult enough to bother maintaining a national difference in standards.
There's no need for any mathematics or conversion tables. It's a simple 2-step procedure:
1) If in a country where QFE is used at military airfields (e.g. UK), use QFE at military airfields.
2) If elsewhere, use QNH.
Personally, I would rather use QNH at all times in the UK as well. Having 2 ways of saying the same thing is great if you're writing a novel, but it goes against principles of standardisation and seamless interoperability that the world of aviation generally subscribes to. It's not difficult to switch from QFE to QNH when operating abroad, but then in my humble opinion it's not difficult to fly a circuit on QNH either. Certainly not difficult enough to bother maintaining a national difference in standards.
BB
I'll largely agree with the reply from Easy Street. As to why we use QFE, this has already been stated, but in short it often works better than QNH.
When sat in the back teaching visual circuits I want my stude to learn one set of figures, ie base your low-level, flapless, glide circuit or PFL critical points ALL on height above touchdown. It is easier. My terrain clearance is largely visual/procedural, ie the circuit patterns are based around the local geography. One set of figures are much easier to remember and work every time. Engine failure followed by a possible turnback or ejection, again just one set of figures to think about, especially in the heat of the moment. QNH would make this all somewhat more complex with no advantages.
Whenever I use my kitchen scales (not often!) I could make allowance for the weight of the bowl; I don't. I zero it with the bowl attached to get a new zero datum. I do the same when I check the tyre pressure on my car. 44psi or 3 bar works a treat, but it is actually an absolute pressure of 4 bar. Yes, we could make it harder and do a little extra maths, but why? Within the MATZ we are all on QFE.
Now send me to Luton in my wonder jet and I'll set QNH. All straightforward bar some additional number crunching so I can cross check my alt v dme as we trundle down the ILS (touchdown elevation + 300ft/nm). Approaching DA I hit TOGA and go around knowing I was about 200ft above the runway. In the preceding pattern I knew my vertical spacing from all the other traffic that I could hear on the same freq.
Off now to St Petersburg (okay, I'm now in the sim) and I'm probably back to QFE. Just as well as I also tell the altimeter to display in metres and not feet hence losing me the SA I have gained by operating in QFE.
Back home again, and if I'm lucky enough to be leading a formation display then again I want just one set of figures at each venue = QFE. Gate heights always the same, flypast heights also the same. Just can't afford to be descending to an incorrect altitude - even if it was a simple sum! Frees up some SA to use on other more important aspects of the display such as the wind! Even at a non-airfield based venue I'd like a display QFE if available.
There you go, QFE used when it is most beneficial, but QNH does also have its place.
I'll largely agree with the reply from Easy Street. As to why we use QFE, this has already been stated, but in short it often works better than QNH.
When sat in the back teaching visual circuits I want my stude to learn one set of figures, ie base your low-level, flapless, glide circuit or PFL critical points ALL on height above touchdown. It is easier. My terrain clearance is largely visual/procedural, ie the circuit patterns are based around the local geography. One set of figures are much easier to remember and work every time. Engine failure followed by a possible turnback or ejection, again just one set of figures to think about, especially in the heat of the moment. QNH would make this all somewhat more complex with no advantages.
Whenever I use my kitchen scales (not often!) I could make allowance for the weight of the bowl; I don't. I zero it with the bowl attached to get a new zero datum. I do the same when I check the tyre pressure on my car. 44psi or 3 bar works a treat, but it is actually an absolute pressure of 4 bar. Yes, we could make it harder and do a little extra maths, but why? Within the MATZ we are all on QFE.
Now send me to Luton in my wonder jet and I'll set QNH. All straightforward bar some additional number crunching so I can cross check my alt v dme as we trundle down the ILS (touchdown elevation + 300ft/nm). Approaching DA I hit TOGA and go around knowing I was about 200ft above the runway. In the preceding pattern I knew my vertical spacing from all the other traffic that I could hear on the same freq.
Off now to St Petersburg (okay, I'm now in the sim) and I'm probably back to QFE. Just as well as I also tell the altimeter to display in metres and not feet hence losing me the SA I have gained by operating in QFE.
Back home again, and if I'm lucky enough to be leading a formation display then again I want just one set of figures at each venue = QFE. Gate heights always the same, flypast heights also the same. Just can't afford to be descending to an incorrect altitude - even if it was a simple sum! Frees up some SA to use on other more important aspects of the display such as the wind! Even at a non-airfield based venue I'd like a display QFE if available.
There you go, QFE used when it is most beneficial, but QNH does also have its place.
Why do the RAF still use QFE?
BB.
Genuine apologies, I thought you were being facetious. Most of our altimeters will wind down to about 850 mb/hp so once you get up to airfields about 3000' amsl QFE becomes tricky. Hope that answers your question.
BV
Genuine apologies, I thought you were being facetious. Most of our altimeters will wind down to about 850 mb/hp so once you get up to airfields about 3000' amsl QFE becomes tricky. Hope that answers your question.
BV
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Ours cover a range of 28.0 to 31.0 Inches which is 3,000 feet as well.
A look at our map showing terrain elevations will show why we cannot use the QFE setting in a whole lot of the country.
A look at our map showing terrain elevations will show why we cannot use the QFE setting in a whole lot of the country.
Why do the RAF still use QFE?
Which is why I conceded several pages ago that QFE would not work in large parts of the USA.
Anyway I think this one has definitely run its course so I shall leave it there.
Toodle pip.
BV
Anyway I think this one has definitely run its course so I shall leave it there.
Toodle pip.
BV
HP
Not always true about the exclusive use of QFE in the MATZ. Prior to the change to QNH at BZN (OK not actually a MATZ but not a factor) the civvies were allowed to use QNH in the same pattern as the rest of us on QFE . I always wondered about the potential for problems with a 300 ft airfield and 500 separation and mixed settings. Now that BZN uses QNH one would be forgiven for thinking that the potential for mix up has gone. Unfortunately there are exceptions allowed -visiting FJs if memory serves.
Isn't the main point that QNH is the one system that covers all cases. What do the FJ mates set at Kandahar ? I do get the argument about students but do those at Shepard (spelling? ) in Texas have problems. IMHO the reversion to QFE (was it in the nineties) was a backward step.
Not always true about the exclusive use of QFE in the MATZ. Prior to the change to QNH at BZN (OK not actually a MATZ but not a factor) the civvies were allowed to use QNH in the same pattern as the rest of us on QFE . I always wondered about the potential for problems with a 300 ft airfield and 500 separation and mixed settings. Now that BZN uses QNH one would be forgiven for thinking that the potential for mix up has gone. Unfortunately there are exceptions allowed -visiting FJs if memory serves.
Isn't the main point that QNH is the one system that covers all cases. What do the FJ mates set at Kandahar ? I do get the argument about students but do those at Shepard (spelling? ) in Texas have problems. IMHO the reversion to QFE (was it in the nineties) was a backward step.
Vasco,
FJs at KAF use QNH. The FJ community isn't the driver for keeping QFE, although some seem to think it is (e.g. Brize offering QFE to FJs by default). I think the most ardent defenders of it are the instructional community, although as you correctly point out, if students everywhere else in the world can cope with QNH, one hopes that our potential future F35 and Typhoon pilots would also manage!
FJs at KAF use QNH. The FJ community isn't the driver for keeping QFE, although some seem to think it is (e.g. Brize offering QFE to FJs by default). I think the most ardent defenders of it are the instructional community, although as you correctly point out, if students everywhere else in the world can cope with QNH, one hopes that our potential future F35 and Typhoon pilots would also manage!
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That seems to be borne out by the posts here, easy. Of course it would be wrong to imply QFE doesn't or won't work. Indeed in the training scenario I can see the attraction. But throw in terrain or a trip overseas and it doesn't work. why have an SOP which has to be ditched as soon as things get interesting?
Back home again, and if I'm lucky enough to be leading a formation display then again I want just one set of figures at each venue = QFE.
Out of interest, what altimeter datum do non-RAF formation display teams use?
Out of interest, what altimeter datum do non-RAF formation display teams use?
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Easy Street,
Not sure how you come to the conclusion that the instructional community are the most ardent defenders of QFE. I've been instructing for 14 years and no-one has ever asked me for my opinion. That said, if they did, I'd find it difficult not to argue that having 0 on the alt when you are on the ground was a good thing - I'm not sure I'd be ardent about it, though. However, when you spend most of your LL time over the sea, the QFE/QNH debate is kind of meaningless.
Duncs
Not sure how you come to the conclusion that the instructional community are the most ardent defenders of QFE. I've been instructing for 14 years and no-one has ever asked me for my opinion. That said, if they did, I'd find it difficult not to argue that having 0 on the alt when you are on the ground was a good thing - I'm not sure I'd be ardent about it, though. However, when you spend most of your LL time over the sea, the QFE/QNH debate is kind of meaningless.
Duncs
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I'd find it difficult not to argue that having 0 on the alt when you are on the ground was a good thing - I'm not sure I'd be ardent about it, though.
As not all airfields are dead level flat and some can have marked differences in elevation then that "Zero Feet" indication might only be related to one very specific place on the Airfield (assuming no Altimeter Error).
Barometric Altimeter indications in reality are only "close guesses" as to where the aircraft is in relation to the ground.
Thus, when I hear the "0" number being thrown about I just have to wonder about the level of pedantry to which I am being confronted.
Just how accurate is that "0" indication in the best case.....or the worst case all things being considered in a rational reasonable way?
The FAA's advice re International Flying by US Pilots:
Altimetry
The U.S. and many other countries use inches of mercury to measure barometric pressure. Other countries use millibars (e.g., hectopascals or hPa). Some aircraft altimeters will display both; however, if only a single-display altimeter is available, it is necessary to have a conversion chart available.
The U.S. and other western countries use QNH altimeter procedures. Some countries (e.g., Russia) use QFE altimeter procedures. When operating under QFE altimetry, your altimeter will indicate zero when on a datum point somewhere on the airport surface, commonly a runway threshold. Complete understanding of the rules and procedures required to fly under QFE altimeter procedures is critical when operating in these countries. Some airports will supply QNH on request.
While the transition altitude/flight level in the U.S. is 18,000 feet (FL 180), it varies greatly elsewhere, and the flight levels may begin as low as 3,000 feet (FL 30). You may be assigned Flight Level six zero (FL 60), for example.
A few countries (e.g., China) use meters instead of feet. For altitude and speed, you will need conversion charts.
The U.S. and many other countries use inches of mercury to measure barometric pressure. Other countries use millibars (e.g., hectopascals or hPa). Some aircraft altimeters will display both; however, if only a single-display altimeter is available, it is necessary to have a conversion chart available.
The U.S. and other western countries use QNH altimeter procedures. Some countries (e.g., Russia) use QFE altimeter procedures. When operating under QFE altimetry, your altimeter will indicate zero when on a datum point somewhere on the airport surface, commonly a runway threshold. Complete understanding of the rules and procedures required to fly under QFE altimeter procedures is critical when operating in these countries. Some airports will supply QNH on request.
While the transition altitude/flight level in the U.S. is 18,000 feet (FL 180), it varies greatly elsewhere, and the flight levels may begin as low as 3,000 feet (FL 30). You may be assigned Flight Level six zero (FL 60), for example.
A few countries (e.g., China) use meters instead of feet. For altitude and speed, you will need conversion charts.
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Duncan, perhaps this was your point but throwing low level into the argument, over the sea or anywhere else is the reddest of herrings. Whether on QFE or QNH, nobody is, at least I hope they're not, using a baro alt to judge height above any given bit of terrain?
Last edited by ShotOne; 13th Jul 2014 at 16:24. Reason: Typo
The Thunderbirds have always flown with QNH (unsurprisingly, being American) but they used to 'think' in QFE. That was, until this accident. Now, they both use and 'think' QNH.
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One might just as well ask as to why the RAF stayed with "fighting area attacks" and using close formations with a "weaver" right into the Battle of Britain, that is until punishing loses forced them to follow the Luftwaffe with "pairs" and "finger fours", Frankly, the use of QFE and all the rest of the "Q code" should be a thing of the past, indeed I'm told that the pilot course I was on at FTS was the last one which had to learn the" Q code ". The military establishment is always resistant to change , One only has to read about the reception DH got from the "Blimps" at the top when they proposed the Mosquito, or Sir Frank Whittle received in his early turbine work, the RAF could have beaten the Germans with a jet into service easily had they been of more progressive outlook. This attitude is why the RAF still uses QFE, its nothing to do with any real advantage or disadvantage, if you wish to argue the point we can meet you at Puntzi Mountain, or any of a number of strips surrounded by big rocks, but I will be on QNH!
ShotOne.
Duncan D's reference to low flying is most certainly not a red herring. I'm sure the SOP for one particular (ex)user of the low flying system over the sea would be to set the baro alt to match the rad alt in S&L before using the baro as the master! Only way to do it at 100ft. Had a go myself in the Bucaneer sim long ago at Lossiemouth.
Not sure about the Nimrod, but I've used a similar technique when conducting low level trials (manoeuvring) over the sea. The rad alt is great for S&L but not much else!
BB
Agreed about airfields not being level, but QFE is invariably factored for the in-use touchdown zone. Not unusual at some fields to get a QFE change whenever the runway changed. Furthermore, most altimeters are accurate enough to read a pretty constant '0' at the threshold.
Don't however think we are using the altimeter 'approaching zero' to initiate the flare! It simply means that every airfield I fly visual circuits at I will be looking to fly downwind at 1000ft, halfway round finals at 650ft, roll wings level at 300ft over my 1 mile point. I may be a tad high or low, but it will there or thereabouts.
If you've not used QFE much then, like anything you are unfamiliar with, you'll be reluctant to change away from QNH. Trust me, having been using altimeters for over 30years in a wide a range of the aviation spectrum roles, QFE most certainly has it's place.
Duncan D's reference to low flying is most certainly not a red herring. I'm sure the SOP for one particular (ex)user of the low flying system over the sea would be to set the baro alt to match the rad alt in S&L before using the baro as the master! Only way to do it at 100ft. Had a go myself in the Bucaneer sim long ago at Lossiemouth.
Not sure about the Nimrod, but I've used a similar technique when conducting low level trials (manoeuvring) over the sea. The rad alt is great for S&L but not much else!
BB
As not all airfields are dead level flat and some can have marked differences in elevation then that "zero feet" indication might only be related to one very specific place
Don't however think we are using the altimeter 'approaching zero' to initiate the flare! It simply means that every airfield I fly visual circuits at I will be looking to fly downwind at 1000ft, halfway round finals at 650ft, roll wings level at 300ft over my 1 mile point. I may be a tad high or low, but it will there or thereabouts.
If you've not used QFE much then, like anything you are unfamiliar with, you'll be reluctant to change away from QNH. Trust me, having been using altimeters for over 30years in a wide a range of the aviation spectrum roles, QFE most certainly has it's place.
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I am sure it does.
Be that as it may, it does not eliminate any mental gymnastics while doing a Circuit or operating within the MATZ if there is any significant deviation in ground elevation or obstacles with some height.
As you point out, the QFE applies to the landing threshold of a particular Runway.
If one uses QNH, a quick glance as the posted MSA for the Approach or Runway in use gives one a fixed altitude at which safe flight is assured in the specified area to which it applies.
I would assume, while using a QFE setting, one has to make sure the selected height being flown is at or above the MSA for the area one is operating within.
Personally, I would find it much easier working off a single altitude reference but understand some are quite happy doing it differently as that is what they are used to doing.
Be that as it may, it does not eliminate any mental gymnastics while doing a Circuit or operating within the MATZ if there is any significant deviation in ground elevation or obstacles with some height.
As you point out, the QFE applies to the landing threshold of a particular Runway.
If one uses QNH, a quick glance as the posted MSA for the Approach or Runway in use gives one a fixed altitude at which safe flight is assured in the specified area to which it applies.
I would assume, while using a QFE setting, one has to make sure the selected height being flown is at or above the MSA for the area one is operating within.
Personally, I would find it much easier working off a single altitude reference but understand some are quite happy doing it differently as that is what they are used to doing.
ShotOne, Buccaneers would routinely fly at 420 kts at 100 ft asl with reference to the radalt. On accelerating to 550 (plus) knots, the baro alt would be matched to the radalt so that when entering a 4G turn with the radalt now unlocked, 100 ft asl could be monitored and called by the back-seater. In a glassy sea state, the baro alt, and the nav's monitoring of it, was absolutely vital to support accurate and safe height keeping in a high G turn.
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Simple answer would be because it's easier to look at your altimeter and see what height you actually are above the airfield on a low vis, critical approach, rather than to look at it and remember to correct for height above seal level.
DN
DN
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Not so, DN. On a low vis approach (decision height<200') all heights, call outs and minima are referenced to rad alt.
Very interesting, Darvan/Peacock, although in the context of this thread I stand by my "red herring" comment since such a unique self-generated alt setting is neither QFE nor QNH.
I'm intrigued that formation aerobatics has been thrown in as a reason for QFE. Although USAF's Thunderbirds use QNH, they had adopted the practice of giving their height checks and "gates" for various manoeuvres as heights agl rather than altitudes. This practice led to the spectacular (luckily non-fatal) crash described by easy st. and ceased thereafter. But great video on youtube!
Very interesting, Darvan/Peacock, although in the context of this thread I stand by my "red herring" comment since such a unique self-generated alt setting is neither QFE nor QNH.
I'm intrigued that formation aerobatics has been thrown in as a reason for QFE. Although USAF's Thunderbirds use QNH, they had adopted the practice of giving their height checks and "gates" for various manoeuvres as heights agl rather than altitudes. This practice led to the spectacular (luckily non-fatal) crash described by easy st. and ceased thereafter. But great video on youtube!