Celsius display of temperature has always existed in Aircraft cockpits with no Fahrenheit in sight except on the small single engine planes by Cessna and Piper. The stupidity of the situation prior to 1996 (if memory serves) is that pilots in the US used Celsius in the air and Fahrenheit on the ground.
Mike Payne On 05/09/2011, at 08:37 , Kilopascal wrote: > Could this be part of the reason that the US METAR adopted the Celsius scale > and abandoned Fahrenheit? It appears from your description that the Celsius > scale is important for the determination of altitude. If the Fahrenheit > scale were used, then conversions would be required and the possibility of > error could result. > > Did you know that the resistance of a wire can be determined via a formula if > the present temperature is known, the reference resistance is known and the > reference temperature is known (usually 20°C)? If I know the resistance of a > wire at 20°C, I can calculate the resistance of the same wire at 90°C. > > http://www.allaboutcircuits.com/vol_1/chpt_12/6.html > > The formula only works if either kelvins or degrees Celsius is used. For some > reason the coefficient of resistance only exists in degrees Celsius > (=kelvin), but not Fahrenheit. I don't know if someone ever tried to make > the formula work and failed, but to this day it has never been done. > > > [USMA:51074] Re: planes collide > > Michael Payne > Sun, 04 Sep 2011 16:36:01 -0700 > > I agree, but the International Standard Atmosphere is used every day in the > aviation world. We even have a readout in the cockpit of the ISA temperature > which is Celsius plus or minus the difference from Standard. It gives SAT, > TAT > and ISA. Because of the speed thru the air, the probe and leading edges heat > up > which gives Total Air Temperature. In Concorde this was around +90-100C, TAT > was a limiting factor on speed. The SAT is the real outside air temperature > (Static Air Temp), ISA generally varies between +20C to -20C at altitude > based > solely on what the temperature would be if it were a standard ISA day at that > altitude. All of this is based solely on ISA temperature lapse rate and > altitude. > > Plus every airspeed indicator, altimeter, vertical rate indicator, etc, has > to > be calibrated using ISA tables. Aircraft performance is based and changes, > depending on whether it's hotter or colder than standard temperature and > altitude. The takeoff run in say Aspen (2400 m altitude) is considerable > longer > because of the elevation, ISA standard temp -1C. If the temperature in Aspen > is > 27C as it is today, that's ISA plus 28C for takeoff, performance suffers and > pilots need tables to figure out how much runway and performance the airplane > will have if one engine quits at an inopportune time. All of this data is > based > on the ISA. > > Mike Payne > > > On 04/09/2011, at 17:13 , John M. Steele wrote: > > > The SI Brochure seems to distinguish (in nomenclature) between the > > "standard > > pressure" which I agree is 1 bar or 100 kPa, and the "standard atmosphere" > > which is Resolution 4 of 10th CGPM as 101.325 kPa. That decision has never > > been abrogated. It specifically says is is for general use, thus is not > > limited to thermometry or altimetry, although certainly important there. > > > > --- On Sun, 9/4/11, Michael Payne <[email protected]> wrote: > > > > From: Michael Payne <[email protected]> > > Subject: [USMA:51069] Re: planes collide > > To: "U.S. Metric Association" <[email protected]> > > Cc: "U.S. Metric Association" <[email protected]> > > Date: Sunday, September 4, 2011, 4:26 PM > > > > In 1999, the International Union of Pure and Applied Chemistry (IUPAC) said > > that for the purposes of specifying the properties of substances, “the > > standard pressure” should be defined as precisely 100 kPa (≈750.01 torr) or > > 29.53 inHg rather than the 101.325 kPa value of “one standard atmosphere” > > (From Wikipedia). > > > > I think we're talking about 2 different things here, the Standard > > Atmosphere > > and the International Standard Atmosphere. I know the latter is purely a > > set > > of units set up to calibrate and test things worldwide to the same > > standard. > > 15C, 1 Atmosphere of 1013,25 hPa. It's heavily used in the aerospace > > industry > > for calibration and performance. Everyone has to be on the same page for > > these two items. > > > > A bit more research is needed. > > > > Mike Payne > > > > > > On 04/09/2011, at 07:39 , John M. Steele wrote: > > > >> One (standard) atmosphere is 101.325 kPa. However, properties for many > >> chemicals are specified at 1 bar (100 kPa) rather than 1 atm. There is > >> also > >> a 'technical atmosphere" 98.0665 kPa (based on kilogram-force), which is > >> now > >> deprecated and rarely used.. > >> > >> --- On Sun, 9/4/11, Michael Payne <[email protected]> wrote: > >> > >> From: Michael Payne <[email protected]> > >> Subject: [USMA:51064] Re: planes collide > >> To: "U.S. Metric Association" <[email protected]> > >> Date: Sunday, September 4, 2011, 6:58 AM > >> > >> I believe one atmosphere is still 100 kPa, the 1013,25 comes from the > >> International Standard Atmosphere. > >> > >> Commonly referred to as the ISA it's what manufacturers use to calibrate > >> instruments and what aircraft makers use to calibrate the performance of > >> aircraft. In the aviation world we constantly refer to the temperature > >> being > >> below or above ISA, the lapse rate is fixed under ISA as 1.98 C up to > >> 36090 > >> (11000 m) where it's supposed to be constant. Obviously in the real world > >> it > >> changes which has an affect on performance. > >> > >> Mike Payne > >> > >> On 03/09/2011, at 13:57 , G. Stanley Doore wrote: > >> > >>> The 1013.25 mbar (101.325 kPa) pressure for altimeter settings is NOT > >>> "arbitrary" as Kilopascal & Wiki write. The standard altimeter setting > >>> for > >>> worldwide altimeter settings was determined from the mean surface > >>> pressure > >>> level. > >>> Stan Doore > >>> On Sep 3, 2011 11:36 AM, "Michael Payne" <[email protected]> wrote: > >> > > >
