Originally Posted by
Blip
Here's an excerp from our B737-800 manual. There are some days when you're simply not meant to fly.
SLUSH/STANDING WATER TAKEOFF - CFM56-7B26
GUIDANCE INFORMATION ONLY
(DO NOT TAKEOFF IF DEPTH EXCEEDS 13 mm)
To determine maximum takeoff weight and associated V1 (for a given runway) proceed as follows:-
(1) Find performance limit weight from specific takeoff table or generalised data and obtain
associated V1 for limit weight.
(2) Enter chart below with weight obtained in step 1, move vertically up to intercept the diagonal line
then move horizontally to the left to obtain contaminated runway weight limitation.
(3) Reduce V1 obtained in step 1, by V1 adjustment for contaminated depth from Table A below. Obtain
VR and V2 for actual takeoff weight from the same data source to obtain limit V1. Use adjusted V1 for takeoff unless adjusted V1 is greater than VR. If so set V1 equal to VR.
NOTE: If full V1 adjustment cannot be achieved (due min V constraints) then runway is too short.
Check Table B for a guide to minimum acceptable runway length for use with contaminated runways.
Thanks Blip.
I think we are on to a winner.
My Company OM makes no such statement, but the note stated above suggests to me that it would be correct to NOT schedule a take-off if contaminated V1 is less than Vmcg.
Therefore as you pointed out you need a longer runway, or an increase in takeoff weight (iINCREASING take-off weight DECREASES the V1 reduction of course, contrary to my earlier incorrect statement).
And yes, as KG correctly stands by his point, we should not be operating from contaminated runways, and should do so at our own risk... However, my point still stands that if a confusing element arises from our Company OM's then it should be addressed, irrespective of whether you would personally opt to use it.
Thanks, any further useful info would be much appreciated.
DTD.