Slow Takeoffs

[aerhead1 5]

First off, thank you PMDG for producing a beautiful aircraft. The 77W has been my favorite type now for the past few years. However, when I start a fully ultra long haul flight My takeoff roll has gone off the end of the runway more than once. For takeoff, I line up roll a few feet to make sure, then hit the autothrottle speed button to vr, which seems to come late. What am I doing wrong? Do I need to hold the brakes and spool up first?

[downscc 1,327]

Names on posts are required here, thanks.  Have you read the Tutorial discussion on how to execute a take-off?  The FMS takes runway lenght into account when calculating V1 so if your weights and configuration (including flaps) are set correctly then there should be no problem clearing the far end of the runway by at least 50 ft. Do not hold brakes and run up thrust, engage TO/GA after engines are stable at about 70% N1, it's all convered in the intro and tutorials.

[Stratox 22]

What route are you trying to fly? Whats are your weights and v speeds as calculated by the FMC?

[aerhead1 5]

My first attempt was Hong Kong to Chicago. I don't remember the weight cause the flight was yesterday.

[scandinavian13 5,192]

 

 

However, when I start a fully ultra long haul flight My takeoff roll has gone off the end of the runway more than once.

 

When you fly ultra long haul, you usually need to trade fuel for weight.

 

It's a pretty simple concept actually:

Pick up a piece of paper.  Now try to run.

Pick up a 50 pound weight.  Now try to run.

 

...which is easier?

 

Same thing for your plane.

 

Planes aren't built to take off of any runway with full fuel and/or passengers.  If you're full of fuel, you might have to hold back some passengers in order to get off of the runway, depending on the wind/temp/pressure, and runway length.

[pcubine 143]

However, when I start a fully ultra long haul flight My takeoff roll has gone off the end of the runway more than once.

Maybe you need to use TOPCAT too see if a takeoff for your gross weight is authorized.

[Chrjs 61]

Maybe you need to use TOPCAT too see if a takeoff for your gross weight is authorized.

Topcat does not provide data for the 300er yet, only for the lr/f which has different engines...

[Fabo 213]

 

 

The FMS takes runway lenght into account when calculating V1 so if your weights and configuration (including flaps) are set correctly then there should be no problem clearing the far end of the runway by at least 50 ft.

 

Does not, actually. The FMS will output balanced field values, will not check runway length (does it even have the info?). It is your job to check your corrected field length is limiting you to higher than your actual mass.

[pcubine 143]

Topcat does not provide data for the 300er yet, only for the lr/f which has different engines...

I believe the 777F can be used as a substitute until the 300ER is added to TOPCAT which maybe a loooooooooooog time.

[nathanpinard 0]

I'm no PDMG expert, but I have to ask the question: How long is the runway you are taking off from?

[downscc 1,327]

 

 

Does not, actually. The FMS will output balanced field values, will not check runway length (does it even have the info?). It is your job to check your corrected field length is limiting you to higher than your actual mass.

 

See FAR takeoff field length discussion FCTM pg 3.19; the FMC calculates the balanced V1 that incorporates TOGW and runway length. It displays the runway length on the TAKEOFF REF page, which it obtains from navadata file wpnavapt.txt and can be modified for intersection takeoff or extended overrun used for takeoff roll (FCOM 11.40.43).  After I get my chores done, I'll modify navdata to see what happens to V1 calc.

[FLEX1978 373]

I'm no PDMG expert, but I have to ask the question: How long is the runway you are taking off from?

 

He said his departure airport was Hong Kong (VHHH)   TORA is 3800 (M)

[Fabo 213]

 

 

ee FAR takeoff field length discussion FCTM pg 3.19; the FMC calculates the balanced V1 that incorporates TOGW and runway length.

 

Sorry, but it doesn't say that... I've checked rev.9 - which is included with the PMDG 777, and rev. 8 which I do have in electronic form.

 

It does say that FMC calculates balanced field V1, which is not dependent on actual runway length. Rather, minimal runway length is, assuming no clearway/stopway issues, same as balanced field length, which results from the same model as balanced V1.

 

Nowhere does it state in FCTM or FCOM at least as far as I have seen (revision and/or FMC software specific), that FMC considers actual length.

If you were confused by message "V SPEEDS UNAVAILABLE", this happens when something else goes wrong, namely, where minimum control speed (ground and air) is higher than maximum certified takeoff speeds, which happens typically in light aircraft without using derate on takeoff.

[kevinh 409]

First off, thank you PMDG for producing a beautiful aircraft. The 77W has been my favorite type now for the past few years. However, when I start a fully ultra long haul flight My takeoff roll has gone off the end of the runway more than once. For takeoff, I line up roll a few feet to make sure, then hit the autothrottle speed button to vr, which seems to come late. What am I doing wrong? Do I need to hold the brakes and spool up first?

What are you doing wrong? Using autothrottle speed mode for takeoff is the obvious problem. You need to use TOGA mode. See the manuals for the procedure. In the meantime try manually setting thrust levers to maximum and see how rapidly the 777 can accelerate.

[downscc 1,327]

 

 

It does say that FMC calculates balanced field V1, which is not dependent on actual runway length

 

Thank you Peter, for persistently pointing out my error. My misconception regarding V1 and application of the FAR (my real world experience is no larger than a C-414). Confirmed by setting up takeoff performance for the 77W at KIAH Ry 33R length 12001 ft then changing data to 6000 ft which is clearly too short for weight [FCOMv1 PD.30.3 MTOGW 378.7 kg (777.0 klbs) at 14C requires 4000 m (12,832 ft)] and the FMS is still providing the same V1 of 168 KIAS. Interesting. I need to pay more attention to FCOMv1. Thanks again.