I think you are referring to an altimeter setting QFE that shows zero altitude on the airport. This used to be the case with British Airways (and the whole of the UK). BA or BOAC had a near miss in Nairobi (I think in the 70's) when they came out of the clouds at 6000 ft quite a distance from the airport thinking their altimeter would read zero . This may have been the impetus to change the procedure. Old altimeters could not set anything below about 950 hPa. Since then everyone but the Russians use QNH which shows airfield elevation on the ground with the equivalent sea level pressure at that airport. The way they do this is have an altimeter in the control tower set to airport elevation, this in turn will show the equivalent sea level pressure.
On 10/07/2013, at 17:52 , "Martin Vlietstra" <[email protected]> wrote: > Correction – ALL barometric altimeters in thousands of airplanes in the > United States. Altimeters in Europe show hPa (or mbar). > > Due to safety concerns, it will be very difficult to change, though I do see > one procedure: > > Air Traffic Control: Our airfield has altitude 85 metres and air pressure 995 > millibars > Pilot: [enters information onto his instruments which display “-10”.] > Acknowledge – I calculate your deviation to be negative 10 millibars from > expected pressure. > Air Traffic Control: Roger > This procedure is a completely new one that I thought of some years ago after > hearing that a Lufthansa 747 crashed in Nairobi when the pilot entered a > pressure of 938 mbar rather than 839 mbar. (Nairobi has a similar altitude to > Denver). The instrument would do the calculation and by returning what is > effectively a hash-sum, the pilot not only checks his input but gets worried > if the deviation is too far from zero. > > Any pilots like to comment? > > > From: [email protected] [mailto:[email protected]] On Behalf Of > m. f. moon > Sent: 10 July 2013 20:20 > To: U.S. Metric Association > Subject: [USMA:53060] Re: FAA must Metricate > > As one very simple example of the complexity and issues involved, consider > the simple and small Kollsman window on ALL barometric altimeters is > thousands of airplanes. These are and have been for many years in inches of > mercury. How do you deal with this in a clean and straightforward way? > > M moon > > > ------ Original Message ------ > Received: 11:29 AM PDT, 07/10/2013 > From: Michael Payne <[email protected]> > To: "U.S. Metric Association" <[email protected]> > Subject: [USMA:53059] Re: FAA must Metricate > > > With the prevalence of "glass" cockpits nowadays and the related software > it's just a case of pushing a button to display metres or feet on the > altimeters and altitude pre select window. All aircraft older than about 1996 > probably don't have this feature, note there are a lot of airlines still > using planes with "steam driven" (as the saying goes) gauges. But these tend > to be based in the 3rd world and some older US domestic airplanes like the > MD80-82 etc. I highly doubt there was any confusion between units on the > Asiana flight crash, it's just crew inattention. > > John Steel has all the information stated correctly. > > Mike Payne > > > On 10/07/2013, at 14:01 , "John M. Steele" <[email protected]> > wrote: > > > ALMOST world-wide feet. Russia, China and associates (CIS states, North > Korea, Mongolia) were using meters. > > Russia uses meters below transition level (where altimeters are adjusted for > local pressure) but has gone to feet for "flight levels" (no altimeter > adjustment, standard atmosphere is assumed) as part of introducing Reduced > Minimum Vertical Separation at and above 29000 ft . I'm not a pilot and I > can't adequately explain China but at least in RMVS space they assign a > flight level in meters, you have to convert on a government table and fly in > feet on a foot-graduated altimeter. (I don't know what they do below > transition altitude. I'm sure a pilot could explain it better. Almost all > commercial cruise is above 29000 feet and in RMVS space, where the reduced > separations have been introduced. > > In Russia, you have to change from feet to meters for landing (and reverse on > takeoff) but no change if you are overflying. I'm sure the switching > requires extra training. As a non-pilot, it seems risky, but I'm not sure > how much risk it introduces. Russia and China went in somewhat different > directions, each with their "associates" following, so there are two distinct > exception spaces in the world, plus rest-of-world feet. > > From: Paul Trusten <[email protected]> > To: U.S. Metric Association <[email protected]> > Cc: U.S. Metric Association <[email protected]> > Sent: Wednesday, July 10, 2013 1:36 PM > Subject: [USMA:53056] Re: FAA must Metricate > > Educate me, folks. I thought that feet were used worldwide in aviation > because of the perceived danger of changing over to metric in some kind of > terrifying interim. Do we in fact have both meters and feet being used in > flight? Talk about your Gimli-Mars tragedies-in-the-making! > > Paul Trusten, Reg. Pharmacist > Vice President > U.S. Metric Association, Inc. > Midland, Texas USA > http://www.metric.org/ > +1(432)528-7724 > [email protected] > > > On Jul 8, 2013, at 0:38, Bruce Arkwright Jr <[email protected]> wrote: > > > What if that poor tired Vietnamese pilot, forget he had hit the convert > > button, after crossing into our air space, but still read meters instead of > > feet as he approached the landing strip? Will FAA emit to that? At any rate > > its time for FAA to get on board! > > > > > > Bruce E. Arkwright, Jr > > Erie PA > > Linux and Metric User and Enforcer > > > > > > I will only invest in nukes that are 150 gigameters away. How much solar > > energy have you collected today? > > Id put my money on the sun and solar energy. What a source of power! I hope > > we don't have to wait till oil and coal run out before we tackle that. I > > wish I had a few more years left. -- Thomas Edison♽☯♑ > > > > > > > > > > >
