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Guide/Tutorial: Takeoff Performance in the 777

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Over the past few weeks (and months), there have been numerous threads and posts regarding calculating performance figures in the PMDG 777-200LR/F, especially takeoff figures including assumed temperatures and V-Speeds. In those threads that I participated in, I mentioned the use of numerous manuals, such as the FCOM and FPPM to gain some figures for take-off performance. This will be a guide on how to do so, particularly for the 777-300ER  fitted with GE90-115B’s.I would like to stress that while this is for the 300ER, assuming you have the appropriate manuals for the 200LR, the same method can be used. While I tried to use the FCOM as much as possible, some things are just not available in Volume 1 and therefore I was forced to use the FPPM.

 

First of all, before I start, I would like to make a note that is not how a real crew would calculate/obtain their takeoff performance. They would either use performance manuals created by the airline, which are airport and runway specific, or OPT software on the Boeing fitted EFB or on a small ‘e-laptop’ (10” screen netbook etc.).  You will see throughout the guide that a lot of rounding/conserving occurs, therefore there would be some discrepancies compared to if you used OPT software.

 

Some acronyms used throughout this guide are;

 

FPPM – Flight Planning and Performance Manual

FCOM – Flight Crew Operating Manual (and for the purposes of this guide, solely Volume 1)

OPT – Onboard Performance Tool

ATM – Assumed Temperature Method

V Speeds – V1, VR, V2

RW – Runway

TORA – Take Off Runway Available

ETOW – Estimated Take Off Weight

 

I would also like to add, that this is a very primitive way of gaining figures from the FPPM/FCOM. Really, if I was flying a real T7, and only had access to the FCOM or FPPM, and none of the tools I mentioned above, I would go through 5 different charts/tables which contain numerous considerations (Runway Slope, Obstacles, Tire Limits, Brake Energy Limits etc.). For the purpose of this exercise, I will only be using the figures from the Takeoff Field Limit chart and tables. For the purposes on a flight on FSX, this suffices fine IMO. In real life, the performance manuals provided by the airline take into consideration all these things, and therefore the time taken to come up with an assumed temperature and v-speed is considerably quicker than doing so through the FCOM and FPPM.

 

Now, lets get started!

 

First of all, the scenario that I will be using.Today, we are flying a 777-300ER, fitted with GE90-115B’s, out of Sydney (YSSY), with a planned departure of Runway 34L. RW34L, from intersection A6, has a TORA of 3900m (3962m to be exact). For weather purposes, we will assume there is a direct 10kt headwind (so METAR is reporting 335/10), and the runway condition is dry. Our company SOP’s call for a FLAP15 departure with a D-TO1 de-rate setting. The pressure altitude at Sydney is rounded to SLP (0ft).

Our ETOW today is 312450 KG’s(312.4T).

Now to calculate our figures;

 

Step 1: The first step to complete is to get our compensated TOW which will take into account the 10% decrease in available thrust due to our selection of a D-TO1 de-rate setting. To do that, we go the FPPM. We are working backwards with this table, as with most tables/graphs in the manual.

Now in the table, as you can see there is no exact match for our TOW (312.4t). With all these charts, you are taught to be conservative. So for our purposes, we are going to use the figures for a TOW of 314.7t.

 

D8lFs5D.jpg

 

So looking at the table above, you can see that with a TO1 de-rate setting, with a TOW of 312.4t (conserved up to 314.7t for planning purposes), the TOW that we should plan our figures for is now an amended 340t. This is due to the fact that we will have 10% less thrust available on the take-off roll.

 

N.B: If the airline dictates that D-TO2 is also available, there are similar charts in the FPPM which provide figures for 25% thrust decrease availability.

 

Step 2: It’s now time to find our corrected runway length to take into considering wind component and slope. Now as FSX’s runways aren’t sloped, I won’t be doing any calculations related to the slope. However, I will do so for wind component. The headwind component on RW34L is 10kts. The TORA from A6 sourced from ERSA is 3900m. We now can go to the FCOM and pull out the ‘Field Corrections’ chart.

 

zFcTsPI.jpg

 

We are once again going to be conservative and choose a shorter runway length then we actually have. In this case I have chosen 3800m. Going horizontally across from my runway length and vertically down from my headwind component, you can see that we arrive at a figure of 3950m. Due to the headwind component, we have virtually obtained another 150m of available takeoff runway.

 

Step 3: It’s now time to find our assumed temperature. For that we have 2 sources. We can either use nice, pretty and easy tables in the FCOM, or a nice graph that we can plot on from the FPPM. For the purposes of this tutorial, I will be using the tables from the FCOM (as most people don’t have access to the FPPM).

 

yHa0q4i.jpg

 

Once again, we start at our corrected runway length (which has been conserved back down to 3800m from 3950m), work horizontally across till we find our TOW (which has been conserved up to 341.6t from 340t), and go horizontally up to find our max OAT. Therefore today, our assumed temperature, with a D-TO1 rating will be 42°C.

 

Step 4: Time to get those important V-Speeds! Luckily, in the FPPM, we have a table to find our V-Speeds for D-TO1 take-off. Let’s pull out the V-Speed charts, for a dry runway with a D-TO1 rating.

 

Tj6ICYr.jpg

 

Now, since this chart is taking into considering the 10% thrust reduction, we DO NOT use our amended TOW which was calculated in Step 1. With our ETOW being 312.4t, I have rounded it up to 320t. Going horizontally across from 320t, and vertically down from Flaps 15, we arrive at our V-Speeds. V1 = 156, VR = 170 ad V2= 176. However, since we have a 10kt headwind, we must account for that such wind.

 

Therefore we must now pull out the ‘Wind V1 Adjustments’ table.

 

OzLrmEZ.jpg

 

Once again, going horizontally across from 320t, and vertically down from our headwind component of 10kt, a V1 correction of 1kt needs to be accounted for (Yeah, I know, not much!).

Therefore our takeoff performance looks something like this;

 

---------------------------------------------

YSSY 34L @ A6, 3960m TORA

D-T01, 42C

N1: 96.8%

 

V1: 157

VR: 170

V2: 176

----------------------------------------------

Step 6: Enter all the relevant data into the FMC. De-rate and assumed temperature is done through the THRUST LIM page, and the V-Speeds done through the TAKEOFF REF page.

 

KFtB49n.jpguULT28L.jpg

 

I hope this guide helps some of you when the T7 comes out, and helps you get some rough performance figures until either TOPCAT or another 3rd party developer (Aurasim etc.) is able to produce a 777 takeoff performance tool.

 

Any questions please ask away!

  • Upvote 22

Regards,
James White

 

Aerosoft (Airbus X Extended/Twin Otter Extended/PFPX) & Majestic Q400 Beta Team
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James,

  Very, very good post. It really will help me until TOPCAT releases some sorta update for the T7. However, PMDG never shipped the NGX with FPPM and so I assume we won't get one with the T7 either, do you know where I can get one?

Take Care


Ron Hamilton

 

"95% is half the truth, but most of it is lies, but if you read half of what is written, you'll be okay." __ Honey Boo Boo's Mom

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James,

 

  Very, very good post. It really will help me until TOPCAT releases some sorta update for the T7. However, PMDG never shipped the NGX with FPPM and so I assume we won't get one with the T7 either, do you know where I can get one?

 

Take Care

Hi Ron,

 

Yes, that was the problem that I was thinking about. Unfortunately I have no idea where the general public would be able to obtain one. It would be nice if PMDG could obtain a license to ship out the FPPM with the product aswell.


Regards,
James White

 

Aerosoft (Airbus X Extended/Twin Otter Extended/PFPX) & Majestic Q400 Beta Team
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It would be nice if PMDG could obtain a license to ship out the FPPM with the product aswell.

 

I think that information is Boeing's property and they wouldn't give PMDG permission to publish it.


Kenny Lee
"Keep climbing"
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I think that information is Boeing's property and they wouldn't give PMDG permission to publish it.

The operating manuals PMDG provided with the NGX are copies of the FCOM, which are too, Boeing's property.


Regards,
James White

 

Aerosoft (Airbus X Extended/Twin Otter Extended/PFPX) & Majestic Q400 Beta Team
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Tj6ICYr.jpg

 

Now, since this chart is taking into considering the 10% thrust reduction, we DO NOT use our amended TOW which was calculated in Step 1. With our ETOW being 312.4t, I have rounded it up to 320t. Going horizontally across from 320t, and vertically down from Flaps 15, we arrive at our V-Speeds. V1 = 156, VR = 170 ad V2= 176. However, since we have a 10kt headwind, we must account for that such wind.

 

Very good job, though I noticed this chart is showing the 'Wet Runway' heading, not the dry one as you mention.


Jorge Sanchez - KMIA
@iJorge511

Boeing777_Banner_Pilot.jpg

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Very good job, though I noticed this chart is showing the 'Wet Runway' heading, not the dry one as you mention.

Good spot... Next time I should try do it while I am not eating lunch :lol:

 

Unfortunately I can no longer edit my OP, however here is an ammended image.

 

QIr0A5c.jpg

 

My ammended speeds using the DRY tables are;

V1: 166

VR: 170

V2: 176


Regards,
James White

 

Aerosoft (Airbus X Extended/Twin Otter Extended/PFPX) & Majestic Q400 Beta Team
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What about obstacle limits? This is why runway specific charts are required.


Rob Prest

 

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What about obstacle limits? This is why runway specific charts are required.

 

I would also like to add, that this is a very primitive way of gaining figures from the FPPM/FCOM. Really, if I was flying a real T7, and only had access to the FCOM or FPPM, and none of the tools I mentioned above, I would go through 5 different charts/tables which contain numerous considerations (Runway Slope, Obstacles, Tire Limits, Brake Energy Limits etc.).

.....

 

Obstacles only limit the take-off weight. Unless there is a signifcant obstacle, which @ Sydney I assure you not there is not, MTOW is not penalised very much (and no, before anyone asks, centrepoint tower is not in the way :lol: ).

 

In any case, it is hard to find obstacle data with distance from brake release etc.


Regards,
James White

 

Aerosoft (Airbus X Extended/Twin Otter Extended/PFPX) & Majestic Q400 Beta Team
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This is a bit complicated for me. Can the 777 FMC computer be programmed  essentially like the 737 NGX without using tables, if one is not too concerned about saving a few bucks of fuel, and is willing to do a bit of "reasonable" guesswork (or to let the FMC do it...)?


Henri Arsenault

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Now what we need is a source for a complete set of these tables!  The PMDG NGX has many, but not all, of these and I fear the 777 may be similar.


Eric Szczesniak

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Great post, if only we had access to the FPPM book....

 

Just to clarify for anyone that is wondering, ERSA is the En Route Supplement Australia. This document is part of the AirServices Australia AIP and contains all relevant runway/communication/facilities/etc. information for the airports in Australia.


voz777_zpsa91dce79.jpg

 

"If you can't solve and equation with calculus, you're not using enough calculus" - A wise friend

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