Date: 21 Dec 97 02:32:44 From: email@example.com (Malcolm Weir) Organization: Little to None References: 1 2 3 4 5 Followups: 1
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On 10 Dec 97 04:05:02 , firstname.lastname@example.org (James Matthew Weber) caused to appear as if it was written: >>Were the rules for take-off different in the United States? I live under the >>former flight path the Concordes took upon approach to Dulles, and I can't >>recall them being any louder than another plane. I rarely saw them on >>takeoff, so I can't really compare. But, my question is did the Concorde >>follow different rules until it was off the coast to keep them quieter? >The short answer is yes. On takeoff in the USA, the afterburners are >shut off about 30 seconds into flight, and remain off until the >aircraft begins the runup to Mach 1, which occurs only after the >aricraft is out to sea. Dulles is a good way from the Atlantic Ocean, >so once burners are off, the aircraft flies about 20 minutes before >beginning the runup to Mach 1. Out of JFK, it usually takes a lot less >time to get clear of the mainland. >I believe out of Heathrow, they leave the burners on, and begin the >runup to Mach 1 as soon as they are clear of traffic, even it is is >over the UK. I believe ATC in the UK is pretty good about getting >them clear of the airport traffic in a hurry. This isn't correct. Takeoff at both JFK and LHR are essentially identical, with reheat on for 43 seconds after the start of the takeoff roll. The 'burners are then shut off until the aircraft has climbed to a suitable alititude (there's no point in wasting fuel with afterburners just to climb). Out of JFK, the runup to supersonic flight starts off Martha's Vineyard, at an altitude of approx. 30,000ft. This means that the aircraft climbs more-or-less directly to 30,000ft, then goes supersonic (and up to 53,000ft). Out of LHR, the runup starts over the Bristol Channel, which means that the aircraft flies level for a while before starting the run. In neither case does the aircraft go supersonic over land. For landing, the reverse is true (into LHR, supersonic flight ends over the Bristol Channel). HOWEVER, British ATC can employ special procedures ("recovering Concorde") to avoid having the thing lumber around London at subsonic speeds (which is unpleasant to the neighbours). I don't know how they handle BGI (Barbados), but the situation at Washington Dulles is very simple: they don't fly there... >I'd also point out the aircraft is a lot quieter on approach than on >takeoff. On approach, the aircraft is much lighter, and the burners >will always be off. This (quieter on approach) is true of any aircraft, in general. From personal experience, the *worst* noise Concorde generates is when it takes off from Runway 09L or 09R, and then does a U-turn over Teddington. But the evening 5PM approach is noticeably noisier (in London) than any other aircraft. Malc.