From: Josh Babcock <[EMAIL PROTECTED]> > I'm looking at the B-47 flight manual(s), and they have a correction > chart for altimeter error vs. altitude AGL with flaps down. Is this sort > of thing a common problem, or is it just some oddity with the Stratojet, > possibly due to static port location? It reads -40 ft at 0 AGL, correct > at 20, and then stabilizes at about +12 around 60 AGL. I I'm wondering > if I will have to concoct a special altimeter for this ac.
Aircraft have altimeter (and consequently also airspeed) errors due to: * Angle of attack * Slip and lack of coordination * Engine power (for forward mounted engine) * Ground effect (for low mounted port) * Flaps and configuration (non-forward port) * Attitude (for ports not colocated with pilot) Usually, the errors are small enough that pilots can ignore them. But for an aircraft rated for low non-ILS instrument approaches and potentially subject to emcon (i.e. no radar altimeter usage) it becomes non-optional to have accuracy of at least 20 ft. One way of looking at the error you describe is that the pilot believes he has 20% more altitude margin (when at the height of tree tops) and is just about to touch down when actually 15 ft in the air. The former may lead to loss of undercarriage against low building, the latter to a sudden 12 ft drop following a full stall landing. Both are things that cause severe embarrassment ... at best. It can easily be implemented as a lookup table that sits between the usual altimeter signal and the cockpit instrument if you desire. Perhaps even easier to do it programmatically as a little script. The biggest concern I have with it is not the FGFS implementation but the novice simulator pilots who will keep reporting bugs against your aircraft. Similar to the stream of complaints about compass turning error, the VSI error and the DG drift. So please do implement it, but then go and write a little message into the FAQ document. 8-) --- [This E-mail scanned for viruses by Declude Virus] _______________________________________________ Flightgear-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-devel
