Two altimeters
Cut & Paste Intellectual
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Mr FD
Respectfully suggest a quick peak at PANS-OPS Doc 8168 -OPS/611 or for easy reading JAR-OPS 1 - Minima Specification - say for Cat 1 Mins and review PEC (Position Error Correction) For really snoozy reading - pressure instruments ...... installation errors....static tubes....alignment......zzzzzzzzzzzzz.
Gen in POH for A/C type. Stick to NDB approaches until fully satisfied on this matter
Respectfully suggest a quick peak at PANS-OPS Doc 8168 -OPS/611 or for easy reading JAR-OPS 1 - Minima Specification - say for Cat 1 Mins and review PEC (Position Error Correction) For really snoozy reading - pressure instruments ...... installation errors....static tubes....alignment......zzzzzzzzzzzzz.
Gen in POH for A/C type. Stick to NDB approaches until fully satisfied on this matter
There most definitely is position error for altimeters. Oz requires (used to require?) PEC to be applied to precision approach DA. If PEC tables not available for the a/c then a minimum of 50' to be added to DA.
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Then there's altimeter temperature error proportional to ISA deviation. Corrections mandatory when a/d at or below freezing. Then chuck in a super low QNH 945 - makes yer wonder how the whole show keeps chugging along
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UL730 - that, of course, is what QNE is for.
If your altimeter won't set 945, you set 1013 and request QNE from ATC. Say they report 'QNE 1314ft'. Then you pretend the aerodrome is at 1314ft, adding the heights on the IAP to this to give altitudes to check on finals.
Personally I like Q codes. There are several lists on the web and I'm sure there'll be a thread around somewhere. One you still hear very regularly is QSY, of course.
Tim
If your altimeter won't set 945, you set 1013 and request QNE from ATC. Say they report 'QNE 1314ft'. Then you pretend the aerodrome is at 1314ft, adding the heights on the IAP to this to give altitudes to check on finals.
Personally I like Q codes. There are several lists on the web and I'm sure there'll be a thread around somewhere. One you still hear very regularly is QSY, of course.
Tim
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Having learnt to fly gliders in the UK, the norm was to set QFE and leave it - a gap in basic training which never really covered x/c flying. I generally flew on QFE as this is what I was used to. This was most useful at the top of a winch launch in guiding me to how long I had to find a thermal.
Flying x/c, I noted the offset above or below for both QNE and QNH - I still used QFE for the reason above. The rest of the time, I then generally ignored it except for avoiding airspace. The only other key information I wanted was in calculating a final glide - always to the starting field, so QFE is best - pressure is generally stable when a thermal x/c can be flown. I do this to double check the electrics that base the final glide on GPS altitude - no idea what this is based on, but as long as I calibrate by giving field elevation of start field, I seem to get reliable results.
Having moved to Oz, I now am basically forced to use QNH - I can't set QFE on any altimiter I have used here yet as the field is too high (2200') - not a problem in the UK - highest field I flew from was about 1000', but it is here and is in the US. This is probably the main reason for the difference.
As to having 2 altimiters, for the UK, I would set 1 to QNH and 1 to 1013 and leave them.
In Oz, if my understanding is correct, both would have to be set to QNH until transition at 10,000', when 1013 has to be set.
Flying x/c, I noted the offset above or below for both QNE and QNH - I still used QFE for the reason above. The rest of the time, I then generally ignored it except for avoiding airspace. The only other key information I wanted was in calculating a final glide - always to the starting field, so QFE is best - pressure is generally stable when a thermal x/c can be flown. I do this to double check the electrics that base the final glide on GPS altitude - no idea what this is based on, but as long as I calibrate by giving field elevation of start field, I seem to get reliable results.
Having moved to Oz, I now am basically forced to use QNH - I can't set QFE on any altimiter I have used here yet as the field is too high (2200') - not a problem in the UK - highest field I flew from was about 1000', but it is here and is in the US. This is probably the main reason for the difference.
As to having 2 altimiters, for the UK, I would set 1 to QNH and 1 to 1013 and leave them.
In Oz, if my understanding is correct, both would have to be set to QNH until transition at 10,000', when 1013 has to be set.
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Back to Cusco's question - if the transponder gets its info from an altimeter on your panel, that altimeter will have the word ENCODING printed on the dial (well, all the ones I've flown did).
I was a radio amateur from a tender age, forced to use morse cos I wuz too poor to buy a microphone and build a modulator, and I think Q codes are wonderful .
QNE is worrying - it means "field elevation shown with 1013 set" (sometimes called pressure altitude), but I often read postings from people who think it's the Q code for "set 1013" rather than QNH or QFE.
Like many, I was brought up to use QFE for takeoff and landing and QNH for everything else. IFR training in the USA soon cured me. QNH on both, and cross-check. Or 1013 on both, ditto. Close to trans alt/level and I'll have one of each. Each to his own, I suppose.
I was a radio amateur from a tender age, forced to use morse cos I wuz too poor to buy a microphone and build a modulator, and I think Q codes are wonderful .
QNE is worrying - it means "field elevation shown with 1013 set" (sometimes called pressure altitude), but I often read postings from people who think it's the Q code for "set 1013" rather than QNH or QFE.
Like many, I was brought up to use QFE for takeoff and landing and QNH for everything else. IFR training in the USA soon cured me. QNH on both, and cross-check. Or 1013 on both, ditto. Close to trans alt/level and I'll have one of each. Each to his own, I suppose.
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With the rare delights of 2 altimeters, I revert to the KISS keep it simple stupid approach.
In short, I always keep both altimeters on the same setting be that QFE, QNH, 1013 etc. It allows me the joy of crosschecking at appropriate times, particularly during approaches.
Furthermore, you can only fly with reference to one so why add confusion by having them all on different settings. Using different altimeters just adds complication to the instrument scan, whereas it makes more sense to use a primary and backup method.
IMHO of course,
Obs cop
In short, I always keep both altimeters on the same setting be that QFE, QNH, 1013 etc. It allows me the joy of crosschecking at appropriate times, particularly during approaches.
Furthermore, you can only fly with reference to one so why add confusion by having them all on different settings. Using different altimeters just adds complication to the instrument scan, whereas it makes more sense to use a primary and backup method.
IMHO of course,
Obs cop
- and then try to remember what it is I've decided 
Cut & Paste Intellectual
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There is a delightfully coloured pink AIC issued by those clever chaps at AIS that discusses instrument pressure settings in conditions of abnormally low atmospheric pressure settings.
When these conditions prevail, perceived wisdom is, unless you have an altimeter suitably adorned with a setting range that accommodates a QNH below 950 and IMC is likely to be encountered, which is prob 90, given the instability in the atmosphere at these barometric levels – take off should not be made.
If VMC prevail for the whole flight – set system to lowest possible setting and chug along with alacrity.
Instrument let downs in UK on QNE, in IMC because the altimeters can’t read the correct QNH might at best induce a cosy chat with insurers over tea and biscuits. At worst – a more profound meeting with those cheerful chaps at the Coroner’s Court who constantly complain about unnecessary workload.
When these conditions prevail, perceived wisdom is, unless you have an altimeter suitably adorned with a setting range that accommodates a QNH below 950 and IMC is likely to be encountered, which is prob 90, given the instability in the atmosphere at these barometric levels – take off should not be made.
If VMC prevail for the whole flight – set system to lowest possible setting and chug along with alacrity.
Instrument let downs in UK on QNE, in IMC because the altimeters can’t read the correct QNH might at best induce a cosy chat with insurers over tea and biscuits. At worst – a more profound meeting with those cheerful chaps at the Coroner’s Court who constantly complain about unnecessary workload.
