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Author Topic: [ok] Wrong takeoff roll data for 737NG  (Read 121 times)

Offline Andre

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[ok] Wrong takeoff roll data for 737NG
« on: August 31, 2016, 05:24:43 PM »
I just noticed the takeoff run at MTOW for the 737NG series seem way too low in the database. Wikipedia (not always the most reliable, but usually is) has it like this:

737-600 = 1,750 m
737-700 = 1,600 m
737-700ER = 2,100 m
737-800ER = 2,400 m
737-900 = Unknown, but most likely the same as 900ER
737-900ER = 3,000m

All numbers are at MTOW at sea level.

The -900 and -900ER versions are known to be absolute dogs regarding take-off length.. the long fuselage, low ground clearance and underpowered engines give it poor rotation angle, and make it a less than ideal aircraft for many routes, especially hot & high routes. The database currently have them at 1,800-1,900m which is way too short.

https://www.wikiwand.com/en/Boeing_737_Next_Generation

737 MAX numbers are still uncertain, but most likely around the same as NG or slightly better. Except the revised MAX 7 which will be an real powerhouse. It has 737-8 everything, just a shorter fuselage instead of a straight 737-700 upgrade. Somewhere around 737-400 size, just slightly less capacity.
« Last Edit: September 09, 2016, 10:41:00 AM by Sami »

Offline NovemberCharlie

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Re: Wrong takeoff roll data for 737NG
« Reply #1 on: September 06, 2016, 08:16:57 AM »
hi Andre,

I work as a flight dispatcher, mostly on 737s.
Our system does not work with required distances, but with weights.

Calculating performance for a B739 from GLA using the following data:
RWY 24 INTERSECTION D1 DRY, WIND: CLM, OAT: 15C, QNH: 1013
PACKS: OFF, A/I: OFF, FLAPS: 5, THRUST: FULL

Our program returned with a field length limited weight of 78885kg, a margin of only 2kg on our MTOW (paper derated), on the factored take off requirement.
This in turn means that EDI 24, from D1 is slightly above the minimum needed runway length for a 737-900.

This length is 2553m, however you need to keep in mind that our engines provide 26,000lbs of thrust and the highest rating for the -900 is 27,000lbs.

For reference a -800, rated 24,000lbs thrust with the same conditions gives: 75725kg FLLTOW
a -700, rated 22,000lbs thrust with the same conditions gives: 71958kg FLLTOW

TL;DR:
For the -900, with max thrust available the take off run should be below 2500m (though I think the AWS value of 1820m is a bit too low, at least for the 79tn variant)

cheers

Offline Sami

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Re: Wrong takeoff roll data for 737NG
« Reply #2 on: September 09, 2016, 10:33:18 AM »
Checked against Boeing's tables and unsurprisingly these Wiki numbers are wrong (some too low, some too high). Or perhaps not wrong but no idea on what they are based on.

737-600 at the lower MTOW variant (56tn) and basic engines (-7B18) can use as little as 1400m. The 65tn variant will the need all the way up to 2400m (!).

For 737-900 basic MTOW (74tn) I got about 2440m from the tables.

All are checked/updated though (in the limits what AWS runway model can do; so mainly for the basic variant).
« Last Edit: September 09, 2016, 10:38:28 AM by Sami »

 

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