B737 Vref ICE

[VH-ELP]

I'm hoping this question hasn't already been covered at length, but does anyone know the reason/s that the B737 QRH calls for Vref ICE (+10kts) to be applied when landing flaps 15 i.e B hydraulic failure, 1 inop landing etc.

I can understand why you would want to use Vref Ice generally, but cannot understand why it is only applied to the Flap 15 approach speed and not flaps up or 40.

Kind regards.

[Hudson]

VH-ELP. I wondered the same thing and contacted a friend at Boeing, Seattle. The reason given why Vref Ice is applied to the NG and not to the Classics is that they have different wings. The Vref Ice policy was because when Boeing was doing initial flight testing, they put artificial ice on the wings. The FMC automatically compensates for the change in performance for the ice at flaps 30 and 40, but was not sufficient to compensate for flap 15, so an extra 10 knots has to be added for performance, and to keep the Ref speed out of the amber band.

The problem with the ice was not the wings but the empennage.
Sorry if that all sounds a bit vague but that's how the info came back to me.