B737NG: High stage bleed valve & Cat3

[JeroenC]

Hi,

our MEL restricts our ops to Cat1 when the high stage bleed valve is INOP.
It mentions Boeing SR 1-292534973.
I don't see any relation?

Tnx for answers!

[mini-jumbo]

Can't see a link either. Our's doesn't prohibit CAT3 with a high stage valve inop.

[Westnest]

I couldn't made it. Maybe regarding that bad weather conditions, high pressure compress might be occur(280 kPa or more), where requiring a high stage bleed. But my theory is pure speculation, as we are able to CATIIIb in any kind of inoperation of bleed valves(not the 737 though).

[Denti]

Says about High Stage Valves (-300/-400/-500/-700/-800) that two are installed, one may be inoperative for dispatch:

(M) One may be inoperative locked closed provided a minimum of 60% N1 is maintained on associated engine during flight in icing conditions.

No restrictions on CAT III at all, neither IIIa nor IIIb.

[JeroenC]

Copy-and-paste:

9. High Stage Valves: C 2 1
(M)(O) One may be inoperative locked closed provided a minimum of 60% N1 is maintained on the associated engine during flight in icing conditions.
NOTE 1: Both high stage valves required to be operational for CAT3 operation (Ref: Boeing SR 1-292534973)

Nice he, all these different MELs for the same hardware?

[Jetpipe.]

The only connection is with icing conditions.. How are you going to keep >=60% on the throttles with a light a/c if doing a CAT IIIa Autoland? How often do you do a CAT III above 10° C ?

[JeroenC]

I see what you mean. But Cat3 are F40 mandatory. Only when you're very light you need < 60%. But indeed you cannot actively control thrust manually on Cat3, maybe that's the issue.

Strange that other operators don't have the restriction on Cat3 then?

Is there anywhere I can access these Boeing SRs?

[de facto]

I see what you mean. But Cat3 are F40 mandatory.
Sure about that? In your airline maybe..