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Guest Peter Bowcut

Real-World question about 747 speed intervene mode

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Guest Peter Bowcut

On the following video linked below this paragraph, the 747 Captain initiates speed intervene mode shortly after takeoff. LNAV and VNAV are engaged, as well as the center autopilot. Note the aircraft is still well below 10,000 ft (and hence the standard 250kt 'speed limit') when the Captain announces "speed intervene" and dials the MCP speed window to 342 knots. Question: is speed intervene mode on the real -400 only 'armed' below 10,000 ft when VNAV is engaged? On the PMDG 747 speed intervene below 10,000 ft will accelerate the aircraft to the MCP commanded speed. I've also watched the same procedure below 10,000 ft on the ITVV Virgin Airways 747 video, and was just wondering what the deal is. I'm guessing both of these aircrews aren't busting ATC speed limits. :) Thanks for any info! Here is the video:http://video.google.com/videoplay?docid=41...7+cockpit&hl=en

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Although you cant hear it on the RT he must have been cleared "no atc speed control" and so Capt Don Grange selects his econ climb speed once the flaps are up. A very common and standard practice.The speed intervene is available at any altitude.CheersJon

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Guest B1900 Mech

I think transition altitude over there is around 7000?

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>>I think transition altitude over there is around 7000?<


Jeff

Commercial | Instrument | Multi-Engine Land

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The 250 knots under 10' does not apply to heavy 747s. It is normal to proceed to whatever climb speed is desired well below 10'..Best,Randy J. Smith<<>>


Randy J Smith

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>>The 250 knots under 10' does not apply to heavy 747s. It is>normal to proceed to whatever climb speed is desired well>below 10'..>I am afraid you MUST obtain ATC clearance for that, I mean "heavies can go beyond 250Kt" is not an automatic rule.Jose Luis.


signed: José Luis

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>>>>The 250 knots under 10' does not apply to heavy 747s. It is>>normal to proceed to whatever climb speed is desired well>>below 10'..>>>>I am afraid you MUST obtain ATC clearance for that, I mean>"heavies can go beyond 250Kt" is not an automatic rule.>>Jose Luis.If one's V2 speed is 160 knots (V2+100=260) then one will already be flying faster than the airport restriction. No ATC required. Now, it is true they need to be cleared to go faster for climb but 250 knots never comes before safety..Best,Randy J. Smith<<>>


Randy J Smith

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"Now, it is true they need to be cleared to go faster for climb but 250 knots never comes before safety.."Is keeping flaps deployed unsafe below 10,000'?Q>

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>Is keeping flaps deployed unsafe below 10,000'?>No it is not. It's just noisy and can ruin a climb profile or use quite some more fuel on slow climbing aircraft. But yeah since it is not safety relevant you need to ask ATC for highspeed. At least in my part of the world. Regards,Markus


Markus Burkhard

 

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On most of the DVDs I've watched.. the speed relief is cleared prior to departure.. if you listen to the brief on the Virgin Atlantic DVD you'll hear Alan say they're cleared above the 250 knots to 275 or something.. and this won't be a problem with ATC..The 250 knot cap.. is not a concrete rule that is inflexible.. but like all air traffic rules.. you can only break them with express permission from ATC itself.. Vatsim.. is a bit annoying in this regard as a lot of controllers enforce the 250 knot rule a bit too rigidly.. and I always request higher only to be denied.."Departure.. BA288 is heavy request relief on the speed restriction.. ""No.. BA288 maintain 250 knots"In reality they would accomodate you unless other traffic positions prohibit it.. Radar Contact simulates this well.. as you leave the ground and begin your climb.. you can request relief on the speed restriction.. and generally you're cleared to 280knots.. same with approaches.. if ATC request you to reduce to 230.. and your flap 1 speed is 232 or something.. you might request 235 knots.. so you can keep a clean configuration while you're in the queue..Craig


Craig Read, EGLL

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"But yeah since it is not safety relevant you need to ask ATC for highspeed. At least in my part of the world."Thanks, Marcus.Whilst I respect the opinion of airchair critics and DVD experts also, sometimes it's good to hear the opinion of a real pilot :-PWe fully understand that policy varies from region to region (and in some cases airport to airport)... At least the folks here can rest in peace knowing that their aircraft won't disintegrate if they come across a "totally unreasonable" ATC controller (who has nothing better to do than uphold the laws of the land/air in his region).Cheers.Q>

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