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Kayro
Topic Author
Posts: 3
Joined: Sat Nov 07, 2020 10:36 am

### Can a B777LR take off at MTOW from a wet 2,7km rwy?

Hello

Emirates pre covid was flying from Fort Lauderdale to Dubai with a B777-200LR. Their longest runway is 2743m.
Currently they are flying from Miami to Dubai with a B777-300ER in ca. 14 hours.

My guess is now:
the OEW of a B777-200LR is about 155 tonnes?
(I read somewhere Emirates' planes are always very
heavy because of their heavy first and business class).

Plus food, pax and cargo let's say 45 tonnes = 200t
What is the average fuel flow for a LR for a 14hours flight? 8 tonnes? Plus reserve they would need about 120t of fuel.
Let's assume, TOW would be around 320t. If you look at Boeing's chart, a LR with GE90-115BL engines would need 2,5km at 30°Celsius, zero winds.

Does this chart mean TOGA thrust? And do pilots rotate at 2,5km or are they already airborne at 50 feet or something?

How much more runway would be necessary, if it was raining?
Can they take off with MTOW at 347t from a wet 2,7km runway, with only 320t or what would be the limit in this case?

mxaxai
Posts: 2713
Joined: Sat Jun 18, 2016 7:29 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Takeoff runway length requirements are calculated with the assumption that one engine fails. So the runway must be long enough to either stop within the remaining distance or continue the takeoff with only one engine. Stopping is usually possible only up to a certain speed, called V1. If there's wind or if the runway is wet or icy, that must be accounted for.

A normal takeoff should be much higher than 50 ft at the runway end. You would expect to get airborne at around 1/2 to 3/4 of the runway length, give or take. FLL's runway would enable takeoffs up to ~335t in calm and dry weather, according to the chart. This chart assumes TOGA thrust.

Note that the pilots use a different chart that's customized to their specific aircraft configuration and regulations (or rather, they run the numbers through a computer). If the runway is longer than necessary, which is often the case, they can choose less thrust to reduce noise and engine wear and tear.

CosmicCruiser
Posts: 2518
Joined: Tue Feb 22, 2005 3:01 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Is the runway grooved?

Aaron747
Posts: 15685
Joined: Thu Aug 07, 2003 2:07 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

CosmicCruiser wrote:
Is the runway grooved?

Indeed it is:

Runway 10L/28R
Dimensions: 9000 x 150 ft. / 2743 x 46 m
Surface: asphalt/concrete/grooved, in excellent condition
Weight bearing capacity:
PCN 95 /R/B/W/T
Single wheel: 100.0, ST 175
Double wheel: 200.0
Double tandem: 468.0
Dual double tandem: 800.0

http://www.airnav.com/airport/kfll

zeke
Posts: 16320
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Kayro wrote:
Hello

Emirates pre covid was flying from Fort Lauderdale to Dubai with a B777-200LR. Their longest runway is 2743m.
Currently they are flying from Miami to Dubai with a B777-300ER in ca. 14 hours.

My guess is now:
the OEW of a B777-200LR is about 155 tonnes?
(I read somewhere Emirates' planes are always very
heavy because of their heavy first and business class).

Plus food, pax and cargo let's say 45 tonnes = 200t
What is the average fuel flow for a LR for a 14hours flight? 8 tonnes? Plus reserve they would need about 120t of fuel.
Let's assume, TOW would be around 320t. If you look at Boeing's chart, a LR with GE90-115BL engines would need 2,5km at 30°Celsius, zero winds.

Does this chart mean TOGA thrust? And do pilots rotate at 2,5km or are they already airborne at 50 feet or something?

How much more runway would be necessary, if it was raining?
Can they take off with MTOW at 347t from a wet 2,7km runway, with only 320t or what would be the limit in this case?

Trip fuel would probably be around 100 tonnes, with around 110 tonnes in total required with contingency and reserves. The weights you are using are reasonable.

I think the aircraft should be fine on a 9000 ft at those weights, essentially it’s a sea level, that being said that chart is just for runway performance, takeoff performance includes the runway performance and obstacles after liftoff which can be controlling. That is the difference between using that chart, and the real FLL.

I think it wouldn’t need TOGA, pilots rotate the aircraft when the rotation speed is reached, not when a specific distance is passed on the runway.

The authoritative answer would have to come from someone with access to the obstacle database and performance program for FLL.

Woodreau
Posts: 2128
Joined: Mon Sep 24, 2001 6:44 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

If the runway is grooved it’s considered to be a dry runway even when raining. At least that’s how it is at the three airlines I’ve worked at.

CRJockey
Posts: 354
Joined: Mon Feb 10, 2020 11:54 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Woodreau wrote:
If the runway is grooved it’s considered to be a dry runway even when raining. At least that’s how it is at the three airlines I’ve worked at.

Interesting. We handle it differently as we simply say: does the runway look wet, calculate wet. Does it say wet on the ATIS, calculate wet.

The calculation tool (not OEM, but airline specific) then takes the groove into account which more or less produces „dry“ performance regarding distances.

zeke
Posts: 16320
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Woodreau wrote:
If the runway is grooved it’s considered to be a dry runway even when raining. At least that’s how it is at the three airlines I’ve worked at.

That isn’t the way the FAA sees it.

Tartarus
Posts: 40
Joined: Tue Jul 12, 2016 9:36 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

zeke wrote:
The authoritative answer would have to come from someone with access to the obstacle database and performance program for FLL.

KFLL
B77L
Wind calm
30'C
29.92/1013
Alt CG
APU-to-Packs
TOGA

10L:
Dry...307,704 kgs
Wet...304,383 kgs

28R:
Dry...320,537 kgs
Wet...316,859 kgs

zeke
Posts: 16320
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Thank you, that tells me there is something in the takeoff splay

Starlionblue
Posts: 20760
Joined: Fri Feb 27, 2004 9:54 pm

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

It's weird that 10L would be more limiting. The terrain is flat as a pancake. Looking at Google Maps, the airport charts, and the VFR chart I can't see any notable obstacles in that direction. It's just a highway, some low light industrial buildings, a waterway, and then the ocean. Street view from the road beyond the runway end shows a whole lot of nothing. There is a 580ft minimum altitude a few miles out but it's the same in both directions.

EDIT: Found it. Container port. But it's pretty far off to the south of the extended centerline. I guess not far enough.

Airport Charts: http://www.airnav.com/airport/fll

VFR Chart: https://skyvector.com/?ll=26.0715864445 ... 301&zoom=1

GalaxyFlyer
Posts: 8078
Joined: Fri Jan 01, 2016 4:44 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Lauderdale used to have a rail line off the end of the easterly runway. Weight manual had a penalty if there was a train on the track, so container port might be an improvement.

e38
Posts: 879
Joined: Sun May 04, 2008 10:09 pm

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

Kayro (Topic author)

Kayro wrote:
And do pilots rotate at 2,5km or are they already airborne at 50 feet or something?

I'm not sure I quite understand what you are asking, but pilots do not rotate at a specific distance down the runway. Instead, rotation is initiated at Vr.

As you know, takeoff data is predicated on losing an engine. Should it occur prior to V1, the takeoff is rejected; after V1, the takeoff is continued. In the event of the loss of an engine at V1, for the takeoff data to be valid, the aircraft must cross the departure end of the runway at least 35 feet above DER. If all engines are operating, this will of course, be higher. From what I can determine from the chart you posted, the Takeoff Field Length depicted on the left side of the chart represents the amount of runway required to accelerate to V1, then either bring the aircraft to a stop on the runway in the event of a rejected takeoff or achieve an altitude of 35 feet if the takeoff is continued.

e38

TropicalSky
Posts: 579
Joined: Fri May 05, 2017 1:37 pm

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

rail line is still there and operational

GalaxyFlyer wrote:
Lauderdale used to have a rail line off the end of the easterly runway. Weight manual had a penalty if there was a train on the track, so container port might be an improvement.

AirKevin
Posts: 813
Joined: Wed Apr 26, 2017 2:18 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

GalaxyFlyer wrote:
Lauderdale used to have a rail line off the end of the easterly runway. Weight manual had a penalty if there was a train on the track, so container port might be an improvement.

So how did they determine if there was a train on the tracks.

GalaxyFlyer
Posts: 8078
Joined: Fri Jan 01, 2016 4:44 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

You looked down the runway, pretty simple but not infallible. Generally the data assumed a train. Many a late afternoon B727, load reduced by three occupants termed infants, temp was 1 or 2c below the current temp and 5 knots of HW in the calculation. Usually it cooked enough not delay things, pretty predictable. The effect of a couple of infants being on board, much less so.

GalaxyFlyer
Posts: 8078
Joined: Fri Jan 01, 2016 4:44 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

TropicalSky wrote:
rail line is still there and operational

GalaxyFlyer wrote:
Lauderdale used to have a rail line off the end of the easterly runway. Weight manual had a penalty if there was a train on the track, so container port might be an improvement.

Yes, but much improved, below runway surface now.

AirKevin
Posts: 813
Joined: Wed Apr 26, 2017 2:18 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

GalaxyFlyer wrote:
You looked down the runway, pretty simple but not infallible. Generally the data assumed a train.

I was about to say, if you had the data for without a train, and you look down the runway and there is one, then you're screwed unless you wait for the train to go away. But I guess if the data always assumes a train is there, then that's a different story.

GalaxyFlyer
Posts: 8078
Joined: Fri Jan 01, 2016 4:44 am

### Re: Can a B777LR take off at MTOW from a wet 2,7km rwy?

It wasn’t a huge penalty, maybe 500-1000 pounds, but every take-off on a warm day in KFLL was at the limits in a 727-200 with D9 engines.

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