B737 Vref Ice

[framer]

Hi Folks,
I understand that with selection of wing anti-ice (and TAI) that the min maneuvre speed tape and the stick shaker logic are adjusted to account for icing (ie they´re raised). Also that the FMC computed Vref is not adjusted and therefore you have to add 10 kts to Vref 15 in order to get Vref Ice.
What I don´t understand is why this is only applied to flap 15 landings and not to flap 30 and 40.
Can anyone enlighten me?
Kind Regards, Framer

[Tee Emm]

Suggest you contact Boeing Flight Training as they are usually happy to reply with the reasoning.

[captplaystation]

Think it is something to do with flap 15 "normally" being a SE landing setting (obviously other non-engine related non-normals too) but can't remember exactly why this resulted in the increment.

[de facto]

VREF ICE is used when the NnC directs to flaps 15 landing to increase maneuvring margins during Go Around .
Flaps 15 in NNc are normally used when flight controls are an issue (stabiliser/elevator and flaps/slats not in proper position..).
Thats the way i read it.

[B737900er]

De Factor your also forgot engine inop :ok:

[framer]

VREF ICE is used when the NnC directs to flaps 15 landing to increase maneuvring margins during Go Around
I'm not quite so clear on it. Once the Wing ANti Ice has been used, or the TAI is being used, the stick shaker speed is raised, and the min manouevre speed is raised, but the FMC ref speeds are not. With that in mind I think that Vref ICE is just as much to do with the approach as it is with the go-around. I'm happy to be proven wrong though.
Also, I still don't know why it doesn't need to be added to Flap 30 and 40 landings.
Thanks for your input so far, appreciated.

[Pub User]

Once the Wing ANti Ice has been used, or the TAI is being used, the stick shaker speed is raised, and the min manouevre speed is raised, but the FMC ref speeds are not.

You've partially answered your own question there. With a Flap 15 approach the margin between minimum manouevre speed and Vref is quite small, and is made even smaller by use of TAI or WAI, thus the addition of 10kts to the Vref. With a F30 or F40 approach, the margin is sufficiently large not to require any additional 'buffer'.

The go-around manouevre margin is another thing, and is taken care of by the following instruction (cut from the QRH):

Maintain VREF 15 + 5 knots or VREF ICE + 5 knots minimum on final approach to assure sufficient maneuver margin and speed for go-around.