V1 Reduction B737 contaminated

[Speedwinner]

Hello folks,

quick question:

When we do a takeoff on contaminated runway in our company, our working stations always reduces v1=Vmcg. My question is now: is this a requirement from JAA, is it because our company give this rule or arent there data values for adjusting the V1 on contaminated runways?

Any links hints tips?

Thanks!

SW

[ImbracableCrunk]

arent there data values for adjusting the V1 on contaminated runways?

Yes, there are.

I couldn't reproduce the table from the Flight Planning and Performance Manual, but here's the note at the bottom:

1. Obtain V1, VR and V2 for the actual weight using the Dry Runway Takeoff Speeds table.
2. If V1(MCG) limited, set V1 = V1(MCG). If not V1(MCG) limited, enter V1 Adjustment table with the actual weight to obtain V1
speed adjustment. If adjusted V1 is less than V1(MCG), set V1 = V1(MCG). V1 not to exceed VR.

[Sir George Cayley]

Bleeds on or off?

SGC

[safetypee]

For EU certificated aircraft, CS 25 AMC 1591 gives some guidance.
This indicates that V1 is used in the same way as for a wet runway, but where the stopping distance on a contaminated runway might be longer; this could require a lower V1. The lowest value being V1=Vmcg.

AMC 1591 6.2 Take-off on a Contaminated Runway
6.2.1 Except as modified by the effects of contaminant as derived below, performance assumptions remain unchanged from those used for a wet runway, in accordance with the agreed certification standard. These include accelerate-stop distance definition, time delays, take-off distance definition, engine failure accountability and stopping means other than by wheel brakes (but see paragraph 7.4.3).
6.2.2 Where airworthiness or operational standards permit operations on contaminated runways without engine failure accountability, or using a VSTOP and a VGO instead of a single V1, these performance assumptions may be retained. In this case, a simple method to derive a single V1 and associated data consistent with the performance assumptions of paragraph 6.2.1 must also be provided in the AFM.
(Where the AFM presents data using VSTOP and VGO, it must be stated in the AFM that use of this concept is acceptable only where operation under this standard is permitted. Para 8.3)
NOTE: VSTOP is the highest decision speed from which the aeroplane can stop within the accelerate-stop distance available. VGO is the lowest decision speed from which a continued take-off is possible within the take-off distance available.