tag:blogger.com,1999:blog-10000144.post2708389679349808924..comments2024-03-13T09:47:40.487+00:00Comments on Cockpit Conversation: Q.E.D.Aviatrixhttp://www.blogger.com/profile/13634111275860140084noreply@blogger.comBlogger19125tag:blogger.com,1999:blog-10000144.post-16612777824667711382009-03-07T22:40:00.000+00:002009-03-07T22:40:00.000+00:00As others have said, QFE is used in the UK quite a...As others have said, QFE is used in the UK quite a lot for military and GA traffic. However, I believe QNH is used more in busy transport airspace because you can have a common intecept altitude, a common SID climb altitude, etc. for separation between aircraft of different airports. Also, imagine the situational awareness of a pilot on a frequency with aircraft going to Luton, Heathrow, City each referring to different datums.<BR/><BR/>As far as Q codes go (in the UK):<BR/>-QDM is used quite a lot, and an aircraft may call up a tower with a VDF and request QDM, and he will get the bearing magnetic to the tower called!<BR/><BR/>-QSY is unofficial, but is often used as it is can be a 'neater' transmission.<BR/><BR/>http://en.wikipedia.org/wiki/Q_code#AviationAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-48691774874325276192009-03-05T05:38:00.000+00:002009-03-05T05:38:00.000+00:00I should have added that QNE is commonly referred ...I should have added that QNE is commonly referred to as the Q code for standard pressure, but that's not it's accurate definition.<BR/><BR/>S.Splendorhttps://www.blogger.com/profile/11010620882390615773noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-84156934334953889492009-03-05T05:35:00.000+00:002009-03-05T05:35:00.000+00:00I'm sorry to break the consensus but QNE isn't act...I'm sorry to break the consensus but QNE isn't actually the same as 1013/29.92 or standard pressure setting. It is the reading on your altimeter when you touch down with 1013 set, if that makes any sense. It is used when the QNH is outside an aircraft's altimeter sub-scale range.<BR/><BR/>Extreme example: QNH 1053, elevation 100ft. QNE would be -1020ft. (-40 x 28 = -1120 + 100)<BR/><BR/>A previous comment asks why QNH is used rather than QFE. I would venture the guess that terrain clearance is the answer - if QFE was used all hills/obstacle height figures would have to be in reference to the airfield in question - which would be rather unpractical and in my opinion confusing. QNH allows a single constant datum, and I never found it hard to remember field elevation.<BR/><BR/>S.Splendorhttps://www.blogger.com/profile/11010620882390615773noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-3841503186249449532009-03-04T16:41:00.000+00:002009-03-04T16:41:00.000+00:00Julien is right of course, the altimeter can alway...<I>Julien is right of course, the altimeter can always be set to the local QFE, no matter how high the altitude.</I><BR/><BR/>The part that Julien is right about is that it would have been clearer if I'd said "the altimeter can't be adjusted <I>for fields</I> that high" or "the Kollsman window numbers don't go that <I>low</I>." As Ed-Davies says, in the UK all the airfields are close enough to sea level that QFEs (I'll be able to remember "freaking exotic") are settable. But if I want to land at Leadville, in Colorado, I'd have to wind TEN INCHES off my altimeter to have it read zero on the ground. And that's not happening with the altimeter in any airplane I fly. I couldn't even set the QFE for Salt Lake City. QFE also assumes that there's someone on the ground to give you an altimeter setting. The QNH (hey, "home" it works) for a given airport is going to be fairly similar to that of an airfield ten or twenty miles away, and the adjustment when using a remote altimeter setting is printed right on the approach plate. But while the air pressure won't change too much over twenty miles, the terrain can. Does the pilot manually calculate a QFE at an uncontrolled airfield? If so, that calculation can't be any more difficult than the "airfield is at 2400' so circuit at 3400', turn final at 2900'" that North American pilots do.Aviatrixhttps://www.blogger.com/profile/13634111275860140084noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-71714600573864552009-03-04T16:32:00.000+00:002009-03-04T16:32:00.000+00:00About Schipol - I know nothing about 737 automatio...About Schipol - I know nothing about 737 automation or CAT-III approaches - but it does sound like the crew let automation and faulty radar altimeter pull the throttles to flight idle a bit early.<BR/><BR/>The investigation will continue, but early reports from Dutch authorities and the Boeing notice is <A HREF="http://www.pprune.org/rumours-news/363645-turkish-airliner-crashes-schiphol-54.html#post4764207" REL="nofollow">here</A>Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-17902859855688377812009-03-04T16:22:00.000+00:002009-03-04T16:22:00.000+00:00As an ex-RAF pilot it always puzzled me why anyone...As an ex-RAF pilot it always puzzled me why anyone would prefer to fly a circuit, or an approach to a runway, on anything but QFE. Knowing the real height above the airfield always struck me as being pretty important, particularly in bad weather. And Julien is right of course, the altimeter can always be set to the local QFE, no matter how high the altitude.<BR/><BR/>Given that a lot of places don't use QFE, there must be a good reason for it - ATC considerations at busy airports, I imagine. Even so, having the altimeter indicate height above sea level rather than the hard stuff you're about to land on is definitely an affront to logic.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-23983234685936789992009-03-04T15:47:00.000+00:002009-03-04T15:47:00.000+00:00A very timely subject, as the news today is report...A very timely subject, as the news today is reporting that the Turkish B737 crash in Amsterdam was most likely the result of a stall when the a/p responded to a faulty radar altimeter input. While that may have been the root cause of the crash (along with inattention to airspeed), it probably also made it survivable because the a/c hit nose high at very slow speed.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-65675596379891836952009-03-04T11:49:00.000+00:002009-03-04T11:49:00.000+00:00The QFE system is not very popular. I believe the ...<I>The QFE system is not very popular. I believe the British military uses it,...</I><BR/><BR/>And British civilians, at least in general aviation. QFE in the circuit (pattern), QNH when cross country; the tower gives you the pressures when you leave and rejoin. It comes of being a low level country with few, if any, airfields where you can't set QFE.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-83203469690664228832009-03-04T09:09:00.000+00:002009-03-04T09:09:00.000+00:00We used:Quantity From EarthQuantity Near H2OWe nev...We used:<BR/>Quantity From Earth<BR/>Quantity Near H2O<BR/><BR/>We never needed QNE.Louisehttps://www.blogger.com/profile/15614662014433797652noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-23124489126566787572009-03-04T07:20:00.000+00:002009-03-04T07:20:00.000+00:00And a bit if history is that the Q-codes were inve...And a bit if history is that the Q-codes were invented as a shorthand for use in Morse Code communications, originally in telegraphy and later in radio.<BR/><BR/>About the only surviving use today outside of limited use in aviation is in amateur radio, where QSL, QSB, QRN and QRM are all commonly used along with many others.AndyChttps://www.blogger.com/profile/10232582442528343282noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-85408026910350136372009-03-04T07:02:00.000+00:002009-03-04T07:02:00.000+00:00@anonymous: If you're climbning into cloud on a da...@anonymous: <BR/><BR/>If you're climbning into cloud on a dark night, discovering the problem at 2,000 feet is probably already too late.<BR/><BR/>Pitot measured speeds don't read accurately below a certain threshold. But it is one reason why the pilots do a verbal crosscheck at a defined speed during takeoff - typically at 80 knots.<BR/><BR/>That being said, there is a monitoring system on modern aircraft to detect discrepancies between the three sets of indicators. But figuring out which one to believe is often "the issue."<BR/><BR/>In the Aero Peru accident I was wondering why no one was looking at the radar altimeter as it should be completely independent of the air-sensing system. But it's always easier to figure this out from the comfort of an office chair.<BR/><BR/>And the only way to confirm that the pitot-static system is operating before flight would require moving air through it, which might be feasible? But if the system isn't taped over, or iced over or blocked by mud-wasp nests, it's incredibly reliable.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-64977909290129250352009-03-04T06:36:00.000+00:002009-03-04T06:36:00.000+00:00I was taught to remember ...qNE = Neighbors (are) ...I was taught to remember ...<BR/><BR/>qNE = Neighbors (are) Equivalent<BR/>qNH = Nautical Height<BR/>qFE = Freaking Exotic :)<BR/><BR/>And in the QNH world you have altitudes, QFE you have heights, and QNE you have, of course, flight levels.dpiercehttps://www.blogger.com/profile/03397601206317363858noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-13704993144625317362009-03-04T05:43:00.000+00:002009-03-04T05:43:00.000+00:00The way to keep all this straight is to think (cap...The way to keep all this straight is to think (capitalization for emphasis):<BR/><BR/>qFE: Field Elevation<BR/>qnH: Home<BR/>qnE: EnrouteUnknownhttps://www.blogger.com/profile/16788629696053744169noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-77823307095271896322009-03-04T05:13:00.000+00:002009-03-04T05:13:00.000+00:00Howdy!I just recently started following your writi...Howdy!<BR/><BR/>I just recently started following your writings, and I have to say I really appreciate your thoughts! I'm way further back just working on my instrument so its really amazing to read about the adventures of a pilot who is 'out there', so to speak.<BR/><BR/>Well, happy flying and thanks again for sharing.Johnsonhttps://www.blogger.com/profile/08981808634246802548noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-7578361835129647962009-03-04T04:23:00.000+00:002009-03-04T04:23:00.000+00:00So many losses from such a "simple" failure...Whic...<B>So many losses from such a "simple" failure...</B><BR/><BR/>Which begs the question: why hasn't more effort gone into designing avionics systems to test the reliability of air data sensors at the start of a flight?<BR/><BR/>I mean, it's not hugely difficult to implement an altitude crosscheck to take data from IRS, GPS, and radalt sources and throw up a warning flag if the plane has climbed 2000' from the runway but the measured static pressure hasn't changed.<BR/><BR/>Ditto testing pitots by checking that measured airspeed increases in proportion to measured wheel speed during the takeoff roll.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-530845424345841542009-03-04T04:06:00.000+00:002009-03-04T04:06:00.000+00:00Hi Aviatrix,When you sayEven if you could get the ...Hi Aviatrix,<BR/><BR/>When you say<BR/><BR/><I>Even if you could get the QFE, there are many airports in the US where you couldn't set it on an ordinary altimeter, because the numbers in the Kollsman window don't go that high.</I><BR/><BR/>did you mean to say "don't go that low"?<BR/><BR/>Apart from weird locations below sea level such as <A HREF="http://en.wikipedia.org/wiki/Furnace_Creek_Airport" REL="nofollow">Furnace Creek airport</A> in the US (-210 ft) or <A HREF="http://en.wikipedia.org/wiki/Schipol_airport" REL="nofollow">Schiphol airport</A> in the Netherlands (-11 ft), the QFE at a given place is always lower than the QNH. As far as I remember that's actually the only law in meteorology that does not have an exception: pressure goes down as altitude goes up.<BR/><BR/>One important point about flying "in the flight levels", i.e. with the altimeter set to 29.92, is that the purpose of maintaining a given altitude is primarily to ensure separation between airplanes, and not so much separation between airplanes and the ground.<BR/><BR/>Julien.Julienhttps://www.blogger.com/profile/00981068637782241298noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-64812774405831083642009-03-04T03:11:00.000+00:002009-03-04T03:11:00.000+00:00also:http://en.wikipedia.org/wiki/Birgenair_Flight...also:<BR/>http://en.wikipedia.org/wiki/Birgenair_Flight_301<BR/><BR/>http://en.wikipedia.org/wiki/AeroPeru_Flight_603<BR/><BR/>http://aviation-safety.net/database/record.php?id=19741201-1&lang=en<BR/><BR/>So many losses from such a "simple" failure...Aluwingshttps://www.blogger.com/profile/16518739658424324739noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-17987071167914821052009-03-04T02:33:00.000+00:002009-03-04T02:33:00.000+00:00Your 2nd paragraph reminds me about what happens w...Your 2nd paragraph reminds me about what happens when static ports are plugged. These ports are important for the altimeter, airspeed indicators, and vertical speed indicators. See <A HREF="http://aluwings.blogspot.com/2009/02/whos-flying-plane.html" REL="nofollow">aluwing's pt1 movie link from 2:18 onward</A> for the consequences of no such basic instrumentation at night ... in IMC.<BR/>The clip begins with calling a Duchess an Cirrus SR20, but it gets better @ 2:18.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-66865930368761177412009-03-04T00:16:00.000+00:002009-03-04T00:16:00.000+00:00QNEQNEAnonymousnoreply@blogger.com