To all, This is the reply from my nephew John, a former naval aviator as was his father Orv now retired after a long career with GE. John now sells Gulfstream airplanes. If any of you still have USMA 25645 on 2003-05-01 from Terry Simpson, that is the one I emailed to him.
Please notice that in the next to last sentence, John says "Going to metric would simplify a lot". I wish he had the time and inclination to jump on board for metric! Norm ----- Original Message ----- Sent: Wednesday, July 16, 2003 12:00 Subject: Re: Fw: [USMA:25645] RE: Atmospheric Pressure in Aviation > > Uncle Norm, > > Sorry I haven't responded to your email sooner. I haven't found there to > be too many problems with altimeter settings of late. Most altimeters in > current production corporate aircraft are part of an electronic flight > instrument package that allows you to choose the way you input the > barometric pressure. In fact, even older altimeters showed both versions on > millibars on the left and inches of mercury on the right. The real key > though, is how the pressure is read to the pilot by the controller. > Standard pressure of course is 29.92 inches of mercury, read by the > controller as Two niner niner two. Stardard millibars is about 1013. > Whenever a pilot is given a altimeter setting by a controller, it is > mandatory that he read it back. Since the range in inches of mercury > generally doesn't exceed 2 inches either way, a pilot should be able to > recognize if the number read to him is in inches or millibars. The example > in your email was certainly a legitimate case but the millibar reading > sould have specified the word millibars. Also, in this case, there was a > reference to the radar altitude which gives you the height above the > terrain in real terms and is not affected by the barometric pressure. > Plus, both pilots adjust their respective altimeters & cross check them for > accuracy and in this case there was a third pilot who could have checked it > as well. Like most incidents, situational awaremess is the key and there > is always a chance that a mistake will be made, no matter how we try to > simplify the system. Going to metric would simplify a lot. By the way, > our brochures always include metric units for aircraft weights, altitudes, > speeds, etc for customers in countries that are on the metric system. > > Hope things are well with everyone in Atlanta. > > John > > > John C. Scherrer > Sales Director, Key Accounts > Gulfstream Aerospace Corporation > 1616 Westgate Circle > Brentwood, TN 37027 > Office: 615-369-0855 > Fax: 615-369-0856 > Mobile: 615-943-1114 > >
