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jay907uk

Problems with take off

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Hi,When I take off and have LNAV/VNAV selected the aircraft pitches up to high and climbs about 5000-6000 fpm does anybody have any idea how I can stop this from happeneing without having to have V/S selected all the time as it doesn't comply with the SID departure and reaches the altidue to quick,I have set my speed to V2+10 on MCP and it passes that and just climbs then will slow down eventually.ThanksJason Thompson

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>Hi,>>When I take off and have LNAV/VNAV selected the aircraft>pitches up to high and climbs about 5000-6000 fpm does anybody>have any idea how I can stop this from happeneing Best first guess - you might me too light and using max TO thrust.If this is the case - use thrust derate.

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Hi Adam,I usually use the TO-1 and climb 1 or the TO-2 and climb 2 RgdsJason Thompson

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When you say LNAV and VNAV are selected, I am guessing you mean those modes are armed. Look on your PFD screen at the top (The FMA or Flight Mode Annunciator) they should appear in white. I'll go through this step-by-step, with my apologies if I'm covering areas you already know about...Prior to starting the takeoff run, you should have these modes ARMED(as outlined above), the autopilot OFF and the flight directors ON. You also need to have set the correct takeoff trim, the FMC will give you this value on the 777 I think? It does on most Boeings.The autopilot won't rotate the aircraft for you. It is your responsibility to rotate the aircraft at the appropriate speed, then with the aircraft climbing, match your climbout angle to the flight director bars on the PFD. This is where the takeoff trim setting becomes important. If you've set the take off trim correctly then you should be able to establish the initial climbout angle with your controls, reduce the back pressure and the aircraft should hold ROUGHLY the right angle, you will probably have to make minor adjustments but it should be close.LNAV and VNAV modes only become active (green) after takeoff, LNAV at 50ft, VNAV at 400ft. Even THEN you still won't have engaged the autopilot so the only thing that will happen is the Flight Director bars will show YOU what to do. You're still in charge of the handling at this point. Keep those FD bars centred!So, use the elevator trim to remove any remaining pressure you have to hold on the joystick/yoke. Then engage the autopilot, this will be somewhere between 500-2500 feet, depending on how quickly you get the aircraft trimmed and stable in the climb. Never engage the autopilot before you've trimmed the aircraft, bad things can happen.From there the autopilot is in charge of the aircraft's pitch (VNAV) and roll (LNAV).Assuming you haven't been doing it this way, try it out and let us know how it all behaves. If you HAVE been doing this, what are your fuel/pax/cargo loadings like?

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That's good, now, assuming you use VNAV for climb, you mention having the MCP speed set to V2+10, is the MCP window blank during climb out ? IOW, do you let VNAV manage the speed ? As soon as you cross the acceleration height VNAV will pitch down to accelerate and the consequently, the climb rate will decrease. Does this happen ?Adam

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Not that it will solve your problem but the MCP should be set to V2. The flight director then demands V2+10.

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