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vonmar

WindShear & aircraft radar?

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Today an AA flight could not depart for KDFW because the aircrafts radar was not working and KDFW had storms.I was told the aircrafts radar must be working before departure.So, is this an individual airlines (AAL) rule or a KDFW rule for landing aircraft when storms are in the area?If the aircrafts radar failed enroute to KDFW would it have to go to an alternate airport?On windshear. Is it like from ground based doppler radar at the airport or does the aircraft have sensors for it (warning) or could it be built into the aircrafts own radar?

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>Today an AA flight could not depart for KDFW because the>aircrafts radar was not working and KDFW had storms.Sounds sensible.>I was told the aircrafts radar must be working before>departure.When an aircraft has a defect the pilots consult (what we refer to as) the MEL (Minimum Equipment List). This (usually heavyweight) document tells us what equipment we can dispatch without and any caveats/operational or technical procedures we must follow.>So, is this an individual airlines (AAL) rule or a KDFW rule>for landing aircraft when storms are in the area?My guess (and I reiterate this is my guess) is that the aircraft MEL said something like "You can dispatch without the weather radar working providing no CB/Thunderstorm activity is forecast along your route". It was ... so they couldn't. It's an aircraft limitation, as specified by the manufacturer.If airlines could say when their aircraft could go they would always say "go" and airports don't give a monkeys whether or not planes go anywhere so I doubt they get consulted.>If the aircrafts radar failed enroute to KDFW would it have to>go to an alternate airport?The pilots would have to sort it out the best they could. Going to the alternate would certainly be an option they considered, although if the alternate (or indeed the route to the alternate) has thunderstorms then it wouldn't help. If it were by day then the crew could simply see and avoid the worst of it, although that depends on the severity of the storms and how far apart they all are. Embedded CB's can be a kicker too so they would be very cautious of that approach.>On windshear. Is it like from ground based doppler radar at>the airport or does the aircraft have sensors for it (warning)>or could it be built into the aircrafts own radar?I know the US have much better windshear prediction systems than we do in Europe (mainly because there is so much more of it there), the only system we have is something on board the aircraft detecting abrupt speed changes. It's not very good though. Some of our newer aircraft have a PWS (Predictive Windshear System) built into the weather radar. I've not flown it much and it's never predicted any ... but then again we've never had a great deal so it's difficult for me to pass judgement on how good it is.Hope this helps,Ian

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Ian,Thanks for the great reply here.Much appreciated!

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On a related issue:Middle Seat: Crossing the Atlantic with a dead engineWednesday, March 02, 2005By Scott McCartney, The Wall Street Journalhttp://www.post-gazette.com/pg/05061/465083.stmQuoteStuart Matthews, president of the Flight Safety Foundation, a nonprofit aviation-safety group, says he's been on a 747 that had to shut down an engine while cruising, and it continued on to its destination rather than diverting to the nearest airport. "Lots of aircraft fly across the Atlantic with fewer than three engines," he said.UnQuoteIf Mr Matthews had been faily quoted and his comments presented in context and fairly: then, decideing to continue on to one's scheduled destination airport rather than diverting, is a decision in which several factors are involved e.g. it might well be totally sensible to continue on to the scheduled airport after an engine failure if the failure is not reasonably deemed particularly serious and there are other posative factors such as e.g. the presence of airports en-route to the scheduled destination airport to which the aircraft can divert if the situation of the aircraft should un-expectedy detoriate, since the Atlantic being a large ocean is not particularly endowed with airports as opposed to for example the Eastern Seaboard of the USA, the idea of overflying the Atlantic after an engine failure is nothing short of bonkers. As for the comment, that two engined aircraft fly the Atlantic, the issue with the 747 is that as it is a four engined aircraft, [ it is designed for normal operation with four fully functioning engines and a two engined aircraft is designed for normal operations with two fully functioning engines ], to fly a four engined aircraft with three engines across an ocean in normal passenger service as a matter of choice, is quite simply an abuse of how such an aircraft should be operated. With three engines, in operation on a four engined aircraft this will incur the penalty of asymetric thrust, with greater fuel consumption and reduced altitude capability. Furthermore one would presume that none of the flight crew were licensed aircraft mechanical engineers and thus their ability to ascertain exactly what was the severity of the problem with the engine would be limited by that issue, and even if one of the crew was so licensed, it would be impossible to inspect the aircraft whilst in flight. As for the issue of dumping fuel, QuoteTurning around a plane and landing it immediately can be an expensive proposition. First, there is the cost of dumping tons of expensive jet fuel (planes have difficulty landing with full tanks), and the likely additional cost of putting up the passengers in hotels. In addition, under last month's new EU rules on passenger compensation, British Airways would have also had to pay travelers 210,600 euros, or about $280,000 -- 600 euros apiece -- if they got to London's Heathrow Airport more than five hours late.UnQuoteWhy could the aircraft not have flown to New York, in which case I would presume that there would have been no need to dump fuel and there the passengers could have been transfered to another aircraft.Best and Warm RegardsAdrian Wainer

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