brent@poseidon.UUCP (Brent P. Callaghan) (12/16/85)
>> Now for the key question: do you call your lawyer when a 747 flies >> overhead? Do you KNOW? > >There is at least one case on record in which a small jet's crew were >thoroughly alarmed for a moment because their radar altimeter suddenly >showed a much lower altitude than the barometric altimeter. Then suddenly >things were back to normal. Then they realized there was a 747 a few >thousand feet underneath, slowly pulling ahead of them... I guess this is getting the discussion a bit off the point, but it reminded me of the testimony of an Air New Zealand DC10 captain at the inquiry into the Mount Erebus disaster in 1980: He was giving evidence regarding the accuracy of the "AINS" (Area Inertial Navigation System). Air New Zealand has a 5,000 mile route to Honolulu. At the same time, two DC10's would depart Auckland and Honolulu on reciprocal courses. Several hours out over the Pacific the aircraft would pass each other at different altitudes. The crew on the high aircraft could see the low aircraft pass on their radar altimeter ! -- Made in New Zealand --> Brent Callaghan AT&T Information Systems, Lincroft, NJ {ihnp4|mtuxo|pegasus}!poseidon!brent (201) 576-3475
dsi@unccvax.UUCP (Dataspan Inc) (12/18/85)
> >> Now for the key question: do you call your lawyer when a 747 flies > >> overhead? Do you KNOW? Is it necessary? Back in the dark ages (when satellite antennas cost $2000 and there was no such thing as a 120 degree LNA) we were installing a satellite system on Interstate-85 in Charlotte, NC. This earth station turns out to be right at the end of R/W 5-23 at Douglas Field. I don't know what the horizontal distance is exactly to the end of 23 but the aircraft on approach are sufficiently low enough to see small mechanical parts. They are the usual short-haul stuff (727/737/DC-9/BAC 1-11) flying over (directly) and cause no problems for TASO Grade 1 downlinking of television. However, you can see the effects of the radar altimeter for about 5 sec after flyby...at the output of the LNA. It was not visible at the first IF and has caused our client no problems. In the transmit case, I don't know if the high EIRP (typically 5000 w) would cause the aircraft any problems, or for that matter, the occupants inside. However, I believe (and am going to check the dreaded cookie company rules and regulations) that you would have no standing if you were stupid enough to put your earth station at the end of a runway, or, for that matter, between the outer marker and the runway and 10000 feet on either side. Outside the controlled area (I'm not a pilot, and know very little from doing numerous broadcast applications) the "footprint" of a 747 wouldn't affect anything... If you can afford an uplink, you can afford a consulting engineer whose job is to plan for contingencies like this. The Commission common carrier bureau is a whole 'nother world from Mass Media, and they can be picky to the point of trivia. Has a 747-flyby actually screwed up someone's uplink? David Anthony Chief Development Engineer DataSpan, Inc.