April 9, 201115 yr If the left side radio altimeter is malfunctioning in a landing configuration, will the autothrottle go to retard mode, even if the plane altitude is few hundreds feet AGL ?Benjamin
April 9, 201115 yr If the left side radio altimeter is malfunctioning in a landing configuration, will the autothrottle go to retard mode, even if the plane altitude is few hundreds feet AGL ?BenjaminYou mean similar to the Turkish crash at EHAM? Rónán O Cadhain.
April 9, 201115 yr Author You mean similar to the Turkish crash at EHAM?Yes, absolutelyI don't think Boeing changed the system behavior yet.Also another question : Do you have on modern airliner "any brand" some cross-feed check between radio altimeter and EGPWS database ?Benjamin
April 9, 201115 yr Yes, absolutelyI don't think Boeing changed the system behavior yet.Also another question : Do you have on modern airliner "any brand" some cross-feed check between radio altimeter and EGPWS database ?BenjaminNo, EGPWS just uses stored data and the radio alt only displays your height above ground directly beneath you and not the surrounding terrain... Rónán O Cadhain.
April 9, 201115 yr Author No, EGPWS just uses stored data and the radio alt only displays your height above ground directly beneath you and not the surrounding terrain...That astonishing that you don't have this cross-feed parameters safety !If I understand it well (please correct me if I'm wrong :(), you have the :- EGPWS, that take his position from a mix of IRS-GPS, and use it on a geographical database, so it shows the AGL + the terrain surrounding the aircraft and its danger- Pressure altimeter, with correct barometric setting display the actual MSL- Radar altimeter, where you can read your actual AGLFor exemple, if you set an incorrect barometric setting, the system "should" tell you, since it can compare informations from EGPWS and Radar altimeter VS EGPWS.Another one, if your radar altimeter is buggy, the system "should" notice you, by comparing it to the EGPWS and pressure altimeter.If 1 of those 3 instruments are in disagreement you shouldn't be able to perform some task, like autoland or autothrottle retard. And most importantly, you should be warned.Benjamin
April 12, 201115 yr Well, the Boeing system is still based on the crew maintaining awareness as to what their aircraft is doing. The Turkish crew failed miserably at this. However, on the NG, the Captain/FO altimeters are set independently, and there are comparator warnings if the altimeters come out of sync.However, to answer your question as to why there is no comparator between the EGPWS, RALT and BALT, it has to do with the fact that the radar altimeter is affected by things such as buildings and other associated stuff on the ground. As only obstacles that are hazards to flight are included in the EGPWS database, so it would be constantly throwing a fit while flying over populated areas. Joe Sherrill
April 12, 201115 yr Well, the Boeing system is still based on the crew maintaining awareness as to what their aircraft is doing. The Turkish crew failed miserably at this.Well said! Ryan Syferd (KSEA)
April 12, 201115 yr Author However, to answer your question as to why there is no comparator between the EGPWS, RALT and BALT, it has to do with the fact that the radar altimeter is affected by things such as buildings and other associated stuff on the ground. As only obstacles that are hazards to flight are included in the EGPWS database, so it would be constantly throwing a fit while flying over populated areas.Perfect answer ! thanks.Ben
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