inches or hPa

[blueloo]

Most or many Jepp charts show transition with a note - set hPa or inches. When not advised or if you can't find the little bit of print, and you are given both inches/hPa on the ATIS what do you set? For example Narita.... (Unless someone can find a reference for Narita.....)

Schools of thought;
1) Difference between inches and hPa negligible so why start a thread on it.
2) if you have inches, use them as they are more accurate...
3) some glaringly obvious statement or reference I have forgotten about....

[Flight Detent]

....4) If the place isn't/hasn't been of/from American origin, use hPa.

Cheers...FD...

[Pontius]

Japan national procedures and, therefore, Narita units of measurement:

Altimeter setting......Inches of Mercury (Hectopascals on request).

In truth though, Narita ATIS does give both but ATC will use inches unless you ask specifically for mb.

[blueloo]

FD - that crossed my mind too.

Thanks Pontius

[safetypee]

The ICAO standard is hPa; ICAO Annex 5 - Units of Measurement to be Used in Air and Ground Operations (page 7). Those countries who have signed up to ICAO should use hPa, or if not, state the alternative to be used in their airspace by exemption in the appropriate ICAO Annex.

With the complexities of modern world operations where there appears to be increasing opportunity for confusion and error, perhaps in hindsight those countries who deviate from the ICAO standard should consider the effect of their different standard on human performance.

[411A]

The simple fact is...those countries who choose to divate from ICAO, do so for very good reasons, and this is delineated in Jepp pages accordingly.

In addition, as Japanese ATC was originally set up using US FAA procedures, it is therefore entirely reasonable to expect same when flying there.

Especially appreciated is the constant transition layer, versus the hodge-podge application in Europe.

Yes, I know, some pilots can't understand the ATC folks in Japan...my advice, try harder....as their English is quite likely better than your Japanese language skills.

[Pontius]

The ICAO standard is hPa; ICAO Annex 5 - Units of Measurement to be Used in Air and Ground Operations (page 7). Those countries who have signed up to ICAO should use hPa, or if not, state the alternative to be used in their airspace by exemption in the appropriate ICAO Annex.

Japan has, hence my writing:

Japan national procedures

[Flight Detent]

Yeah Safetypee...

I thought that right up to the time I was advised Hpa in French at CDG.

Cheers...FD...

[safetypee]

411A, perhaps an example of the ‘very good reasons’ might help the discussion.
Are these reasons still applicable in Japan or other ‘deviant’ countries; or are the risks of human error in current operations greater than those of altimetry when using modern systems?

[Pontius]

Safetypee,

I think you're making a mountain out of a molehill here. It's really not rocket science; if you're flying a machine with round dials then set either mbs or inches in the altimeter windows that say inches or mbs (they're located next to each other, so they're not difficult to find). If you're flying a machine with a TV, press the button that says 'inches/mbs' and behold the scale change on the screen and adjust accordingly.

Human factors apply to many aspects of altimitery but setting inches or mbs doesn't. If one can't put the right numbers, e.g 29.92 versus 1013 on the correct dial of the altimeter then serving fries should be one's career and not flying aircraft.

[411A]

411A, perhaps an example of the ‘very good reasons’ might help the discussion.

OK, here is one for your good self to consider....numbers.

Let us consider the United States of America.
In the USA, there are located thousands more aircraft than the rest of the world, combined.
I'm not just talking airliners, I'm considering all aircraft, airline, general aviation and military.
Here, we use inches of mercury for setting the pressure altimeter.
Always have, always will.

If pilots flying to the USA can not learn to use the inches instead of HP's, when both scales are normally indicated on their pressure altimeter, these pilots need to be sent back for re-training.

The tail does not wag the dog.

[Flash2001]

Hecto, deka etc. were moribund until aviation and meteorology revived them (or at least hecto). Good scientific practice is to use the prefix in steps of 3 orders of magnitude; pascals, kilopascals, megapascals and so on.

After an excellent landing you can use the airplane again!

[safetypee]

Pontius, I think that you over simplify the problem (or that I over state it). However, having investigated several incidents of mixed up altimeter settings, I believe that the potential for error requires a high level of attention, which IMHO parts of the industry fail to provide.
I may be over sensitive to the issue, but having made the hPa/in mistake once (IMC), I think that the subject is worthy of discussion. [QNH 998 (mb) given by an American ATC unit based in a “European” ATC environment resulted in 29.98 in being set. Expectation bias, bad habit (clipping ‘in’ setting to three digits), fatigue, unfamiliar location – Keflavík Iceland.]

411A, sorry, but I don’t see your points as good reasons for deviating from an international standard. These might reflect a macho, individualistic, national culture, but they, and the use of inches, will not remove the opportunity for error when flying outside of the US.
I don’t expect any change, but at least the opportunity for error should be acknowledged and robust defences provided rather than throw the ‘bad apples’ out of the basket (blame and train; the old way of looking at human error).

With respect to the thread, a suitable error defence might be to avoid publishing the option of hPA/inches on the Jepp chart, thus removing the confusion raised by the original question. Better still provide a reminder on the chart that the altimeter setting is ‘inches’.

[Gargleblaster]

Drifting off topic here, but I was in the US earlier this summer, and for fun tried to figure out what the percentage of salt was in a can of soda. It contains X fl.oz. It has Y mg. of salt. Thats Z % of the recommended daily allowance. I gave up.

IMHO the USA is a bit challenging on units in general.

Did you know that one US mile is 5280 feet and one US gallon is 148.94684081 US liquid ounces ?

Doesn't make sense where I come from :-)

Online Conversion - Volume Conversion

[411A]

411A, sorry, but I don’t see your points as good reasons for deviating from an international standard.

Makes no difference.
We (in the USA) do, that's all that matters.
Full stop.

You might try working on the Russians and the Chinese, as regards metres.
An uphill fight, to be sure.

One idea springs to mind.
Co-operate, or step aside.

IF you fly internationally (as I have for the last 35+ years), you 'go with the flow'.
To do otherwise is like trying to pi** into a hurricane.
IE: prepare for wet boots.


Sorry, I'm sure you mean well, but these are the facts, like it, or not.

[Flash2001]

GB

1 US (liquid) gallon is 128 US fluid ounces by definition.

Anyone who mixes systems (mg/oz, g/mile) etc. should be shot with a ball of his own excrement.

After an excellent landing you can use the airplane again!

[Chippie Chappie]

As 411A says, the Americans will and that's all that matters. However, I still feel sorry for the the families of the two USAF F-15 pilots who ploughed into the side of a hill in Northern UK because they mistook millibars for inches.

Back to the original question. Go with what the controller tells you. If they say inches, use inches. If they say millibars, use millibars. If they say QFE rather than QNH (Check with the USAF Thunderbird pilot who got them mixed up) use QFE. If you're not sure, clarify with the controller.

Cheers,

Chips

[Boingboingdriver]

in the UK any altimeter setting below 1000 millibars (ie 999) miliibars MUST be stated after the Number ie taxi blah blah QNH 1000 or QNH is 999 millibars..thats to avoid people normally using HPA settings to avoid setting 29 .99HPA rather than 999Mb.

[Pontius]

Safetypee,

I think the industry does pay attention to the issues but it still requires a bit of thought, without the gobbledegook of 'Human Factors', blah , blah, blah. You have to use your brain a little and that's what pilots are paid for. The industry has made it very easy to set the correct numbers in the correct dials and the ergonomic designers have made it pretty well child-proof. The industry even ensures there's somebody else sitting alongside you to double-check it. Writing a thesis on the woes of a non-existent problem sounds like a typical management response, when really they should spend less time in the office and more time on the line. In a Big British airline there are two particular names that spring to mind whenever this sort of discussion comes up. They are both managers and write more drivel about human factors, decision making, etc etc than anyone else in the civilised world. They make a huge thing out of occurences that the rest of us don't think about, the 'how to make a decision' process really blows my mind. They even had flow diagrams for it . For goodness sake, make a decision. End of discussion. Anyway, these two particular names are so well known for their 'errors' on the line that they really don't deserve the title of 'pilot'. As the saying goes, 'If you can't do, teach'. This very topic smacks of that and it seems you're trying to mitigate your lack of preparation by 'blaming' it on everything being wrong with the industry and, since you made a mistake, everybody else should have to be inundated with more rambling nonsense from phsyco nuts that write a lot but say nothing.

An unfamiliar airfield. Sorry mate but (a)Keflavik is an absolute non-event as far as taxing airfields are concerned and (b)if it was unfamiliar why had you not prepared yourself beforehand and read that they use inches instead of mbs? Again, no rocket science here. You were unprepared and that is not a reason for a human factors investigation into altimetry procedures.

Whenever I, and I'm sure 99.9% of the airline world, go to an airport I don't have just one occasion of setting the QNH. I've seen it on the metar at the briefing. I've listened to the ATIS or got it from ACARS. I've listened to 'Approach' and I've listened to 'Tower', so your one incorrect hearing should have rung alarm bells in your head. I hardly think a QNH that should have been 1015 and ends up as 998 qualifies as 'expectation bias'; it's nothing like what you should have been expecting!

Overall, I would say you were just being dull that day. Yes, that qualifies as a human factor but it's a personal one for you and we're not going to learn and neither is the industry going to need to tighten it's procedures because you missed so many occasions to 'trap' the error (I thought I'd put one of today's favourite phrases in just to let you know I have listened to the lectures). It sucks to be told you were wrong and none of us like it, but to blame the rest of the world for your mistake and try to palm it off on 'human factors' design and implementation of altimeter settings smacks of somebody who should apply for a management job at a well-known British airline.

And, oh my god, I've just thought of another thing that will probably cause me to crash and it's certainly worth investigating immediatley; the Yanks say 'altimeter setting' and not 'QNH' Just think what problems THAT could cause........(none for me but, no doubt, a worthless HF exercise would say otherwise).

[18-Wheeler]

All these difference standards are daft, and certainly have killed people in the past and more to come in the future.
The sooner the entire world goes to full metric the better.