Over-speed after take-off

[oscayala 0]

Frooglesim actually mentions this in his "Fully loaded part 2" video. It seems to be a known issue that after take off, because of the sheer siZe of the engines that when flying light, the aircraft isn't staying within the 250kts/10000ft restriction.

 

A quick fix that Froogle mentions in his video, and that I have been using myself, is on the FMC s VNAV page, add an extra restriction in of 230kts/8000ft. You will most likely break this new restriction, but you should stay below 250kts while under 10000ft.

 

Luke Cantrill

Fly UK - Cargo Operations

Thanks. Depending on what route I am flying, sometimes my first restriction in VNAV page is max, 185 knots until complete the first turn because high terrain in the vicinity, but the auto-throttle in not able to do it.

This sound to me like you're doing a light flight, low ZFW and/or little fuel in comparison to what this plane can really do.

 

I haven't had this problem, but all my flights have been over 13 hours with 600,000lbs+ GW with ZFW around 420,000lbs+... And even then she still has plenty power to almost shoot through speed restrictions.

Thanks a lot. I will try with heavy settings next time to compare. Those engines are very powerful.!!!

Derate your engines if light. I'm talking serious derates like TO-2 with a 65C assumed temp. These engines are incredibly powerful and it will do that in the real thing too - you can't pitch fast enough to stop the acceleration just after liftoff at full thrust without risking a tailstrike.

Thank you. I will increase the derate setting and try again.

I have mostly done "light" takeoffs so far and my speed after T/O stays within reasonable margins of the magenta speed.

 

Try setting your hardware throttles to "NEVER" (never override A/T) in the T7 options.

Thanks a lot Oliver. I will do it and check again.

Guys I think Ryan has pretty much covered it, at light weights you use full derated take off & climb power, combine with the highest assumed temperature you can get away with. Also consider using FLCH on departure, the aircraft will use pitch to maintain speed.

Thanks. Flight change is a good option

[XCLTM3 112]

I just tested this again.

 

1. I was previously using Assumed Temp take-offs (between 65 - 70) in any case.....that didn't help the situation.

 

2. I decided to try Oliver's (olli4740) suggestion regarding A/T Override -  set to NEVER.

 

3.  Departed YBBN on Short Fuel Load, and the bird stayed at V2 + 20 right after take-off. Excellent. (same flight & take-off cfg's as previously flown)

 

This worked a treat for me.

 

Thx olli!

 

Rgds,

[oscayala 0]

I appreciate all the comments and suggestions.

Doing the recommendations my 777 is taking off in a very accurate way now.

Thanks to everyone,

Oscayala

[Ed van de Vijver 2]

I don't think it's a bug or something. I noticed it to. Then I remembered the tutorial where it says to 'push your throttles fully forward' after THR REF annunciation. (page 0.00.63, second bullit). I noticed the next flight that the A/T is on HOLD on that instant, and I have A/T override set to 'only on Hold'. That means that, when a thrust setting of for example 92% (A/T from the FMC), full throttle overrides that setting, resulting in to much thrust and therefore overspeed.

In stead of full trottle your throttle setting after TO GA and THR REF is supposed to be matched with the programmed thrust. The small arrows on the N1 indicators have to align with the blue line of your physical trottles position.

Nobody seems to have read this line I posted in upper mentioned post:

 

Then I remembered the tutorial where it says to 'push your throttles fully forward' after THR REF annunciation. (page 0.00.63, second bullit).

 

That is simply not correct. I think some people will have their overspeed issues on take off because of that error in the tutorial.

[PikalaxALT 0]

Nobody seems to have read this line I posted in upper mentioned post:

 

Then I remembered the tutorial where it says to 'push your throttles fully forward' after THR REF annunciation. (page 0.00.63, second bullit).

 

That is simply not correct. I think some people will have their overspeed issues on take off because of that error in the tutorial.

 

Actually, that is correct.  If you don't do this and have A/T override enabled, the throttles will roll back.  By pushing the thrust levers forward, you are in essence authorizing takeoff thrust.  Alternatively, you can disable A/T override.

 

I will make these recommendations for underweight takeoffs:

 

1) Thrust derate and high assumed temperature (60-80 C when allowed; if runway is wet or contaminated, derate may be limited.  Do not allow more than 20 knots between V1 and VR.)

2) Steep climbout.  Use your pitch to manage your airspeed on takeoff and initial climb.

3) Fly the departure manually.  Raise the gear and flaps on schedule, and stabilize your airspeed at or below 250 knots before engaging autopilot.  If necessary, continue to fly manually until 10,000 feet (FL100).