B737NG: High stage bleed valve & Cat3
 

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!

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

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).

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.

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?

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 ?

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?

Sure about that? In your airline maybe..