Hi,

 

I would like someone to help me understand the meaning and the tabel of VREF15,30 and 40 and how a probate calculation of a landing distance and VREF should be done

 

I have tried this formula http://www.b737.org.uk/vspeedcalc2.htm and using page 760 in the FCOM1 (737-800 Flaps 30 Dry Runway)

 

For cross check i have used TOPCAT and todc.sas.dk/todc.index.htm (LN-RRH SAS 737-800 VREF+5)

 

Airport EKCH

RWY 22L

TEMP+10C

QNH 1013

WIND 0/0

Landing Weight 60.000kg

FLAPS 30

 

A/C=ON

Antiice=OFF

Landing mode= Manual

 

From SAS i get VREF+5 146 and MAX MANUAL 1010M , AUTOBRAKE 2=2234m

From TOPCAT i get VREF+5 147 and Landing Distance (Actual) 923m Manual landing

 

 

I don´t understand how you get to the VREF speed . I calculate like this (might be wrong i know :-) thats why i want some help)

 

VREF30(40tons)x3-1knots=119 .Then half the amount up to 60 tons(our landing weight) frome 40 (20-10)

 

Then 10+40=50x3-1=149knots ???

 

PS!

What would the landing distance be if you use FCOM1 Page 760 ? the same as TOPCAT and SAS??

 

Thanks for helping me out here :-)

 

Michael Moe

Michael,

 

Forget the Vspeed calculator on the web page you referenced. VREF speeds are provided directly in the FCOM (as well as other places). See page 710 of the NGX FCOM Vol 1. VREF for 60,000 kg at flaps 30 is 142 knots. As shown by TOPCAT, VREF + 5 = 147 knots. It's not surprising that TOPCAT matches the FCOM value since TOPCAT uses Boeing documentation for its results.

 

Don Stimson

I can tell you how to do it with TOPCAT: hit Compute.

Thanks, again had overlook that page

 

Michael Moe