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Stuck_in_an_ATR
10th Oct 2012, 17:33
Hi! I am a 'Bus driver and know next to nothing on the 737, but I was asked for some help with CAT II ops. I'd like to get some info on the following:

- are single autopilot CAT II approaches allowed on the 737?
- if yes, are they practiced by any operators?
- what is the minimum a/p disengagement height in case of 1CH and how does it affect the DH for CAT II? (both for the -400 and the -800)
- can CAT II approach be performed without a/p on the 737? (heard this was an option with F/O flying the app manually and Capt taking over at DH). Is this allowed in EASA land?

c100driver
10th Oct 2012, 19:20
For B737CL in our operation.
Single channel AP limited to Cat1
Minimum Altitude for AP 50' unless dual channel auto land (AFM limit)
Autopilot required for ops below Cat1
Not all B737CL have AFM approval for Cat3a operations

Don't have any info on B737NG's

B737-pilot
11th Oct 2012, 07:31
We were alllowed to do single channel CAT 2 approach in the classics because the A/P can remain engaged till 50 ft AGL . (JAA) Acording OPS 1 you have to keep the A/P engaged till 80% of the minima => 100 RA X .8 = 80 ft where you had to disconnect and perform a manual landing if you have visual reference. Boeing introduced new limitations for CAA registered aircraft that in my opinion make no sense, but that's other story.

Regarding NG , MUH (minimum use height) of the A/P single channel is 158 ft => NO single channel CAT 2 approach allowed.

Hobo
11th Oct 2012, 07:37
Not sure about 400/800 but the classic would do a single channel autoland. Very useful in a dire emergency, eg uncontrollable engine fire and low vis.

BOAC
11th Oct 2012, 08:20
We were alllowed to do single channel CAT 2 approach in the classics because the A/P can remain engaged till 50 ft AGL - you sure of that? There must have been a significant amendment to the Boeing limits!

It used to be 140 ATE for Classic and 50 for NG.

Stuck_in_an_ATR
11th Oct 2012, 12:45
It used to be 140 ATE for Classic and 50 for NG.

That's basically what I'm asking for. I haven't seen the AFM of the plane concerned, but I was told that the min. A/P disengagement height is somewhere around 140', yet 1CH CAT II approaches are approved. Trying to figure out how it is supposed to work.

Can any of the 737-400 Jocks check their AFM and tell me the minimum disengagement height?

BOAC
11th Oct 2012, 15:11
Stuck - it can get complicated with a HUD - I'm not sure if any UK operators use one, however.

babisiliop
11th Oct 2012, 15:50
For Classic is 50f AGL for NG 158f

Denti
11th Oct 2012, 16:39
In my outfit the autopilot minimum use height for single channel operation of the NG has been defined as 160ft AGL, i guess its just the rounded up 158ft or slight differences within a fleet of several different variants. CAT II single channel operation is not allowed. However single engine autoland is approved, but that is still dual channel, although only fail passive instead of fail operational.