B737NG Autoland?

[Alex Whittingham]

Can anyone tell me, is the B737NG authorised for CAT IIIB operations? If so, how does it get round the requirement for three independent autolpilot channels, does it have a third 'comparison' channel?

[Butter side-up]

My understanding is that it is so authorised. It does in fact have three channels - but only two of them can be accessed via the MCP.

[Track]

Never heard of a 737 being capable of CAT IIIB ops. What do you mean three channels? To my knowledge it has only two AP's and subsequent channels, both accessible through MCP. This makes the system fail passive, so only IIIA.. .. .greetz. .----------------. .Track

[Butter side-up]

I am not 737 rated - so I was just expressing my understanding based on what I had read - look forward to reading the answer from an expert.

[lost soul]

I think we need an input from an eJ pilot here- I understand that later this year all their new -700's will be Cat 3B??

[Track]

I fly both 737-300 and -7/800. The 737 AFS compromises two FCC computers (so 2 channels) controlled by one MCP panel (on wich there are two AP switches, A and B). This makes the system fail passive(one AP failure means no autoland). The 737 is capable of CAT IIIA autolands without coupled rollout, i.e. the pilot disconnects the AP shortly after touchdown and performs a manual rollout. For CAT IIIB you need a fail operational system(3 AP's). One other option is to have a head up display installed, in this case you can fly manual to CAT IIIA minima.

[SeaOfClouds]

Track is right that the 737NG is not capable of Cat IIIB operation but Boeing is working on it right now and hope to get it certified by Fall this year.. .. .----------. .An engineer who knows how planes fly but doesn't know how to fly a plane <img border="0" title="" alt="[Smile]" src="smile.gif" />

[fullyfine]

In the BBJ manuals there is mention that - once approved - cat 3B will be allowed using the HUD rather than a third 'George'. The HUD also giving the necessary roll out guidance.. .. .Onwards and Upwards.

[Mike Southcott]

It was mentioned during my last OPC that at some stage later this year all our new 737-700's would be Cat.IIIB.. .Apparently the requirement for a third autopilot is being circumvented by improving/amending authority over the rudder to assist in the roll-out.. .Sorry I can't be more specific but it wasn't really the time to go into it. I'll see if I can get some more info.

[Phoenix_X]

Close to what's been said, I understand that the CAT3b -700s will be equipped with a third channel (with rudder authority) not accessible through the MCP.

[moleslayer]

One or two posts refer to,quote: "only two autopilots,fail passive,so Cat3A only". .. .Not sure about that one being correct,I believe (prepare to be shot down by Airbus pilots)the A320 series only have 2AP's,but 3ADC/IRU,so Cat3B.. .. .I think it's probably the centerline guidance,(among other things)that give it the 3B capability.. . . . <small>[ 27 March 2002, 15:36: Message edited by: moleslayer ]</small>

[Carnage Matey!]

Correct moleslayer. In fact the A320s we operate can autoland and roll out down to Cat2. Even with an engine out.

[moleslayer]

I believe some authorities even allow 3A autolands with engine out <img border="0" title="" alt="[Wink]" src="wink.gif" />

[avioniker]

Just to throw in my two cents
Boeing was unwilling to certify the current Honeywell autopilot for whatever political/financial reasons. Starting very soon a Collins Autopilot will be the installed unit and it will be certified for Cat III operations.
Now if American can only work out the bugs with their HUD...:confused:

[greyfox]

Currently the B737NG is CATIIIa only (Fail passive) as it only has 2 autopilots , however Boeing are considering a mod state for the existing NG's and will probably include it as standard on the 900X to have a 3rd A/P to enable CATIIIb.

[kriskross]

Hi all,

Sounds to me as if my understanding of the latest situation with regard to Cat 111B on the 737NG may help here.

At present, yes the NG is Cat 111A only, as I understand it with or without the HUD, maybe some of my American Airlines friends can enlighten us on this ( another subject!!), but EZY will have Cat 111B capability on the 700 with effect from this winter. Don't get excited EZY, this will probably not mean we are flying 111B this winter, as we have to establish procedures, currently in hand, and get crews trained and approved. An Alaskan Airlines 900, I believe, is currently flying with the mods incorporated, but EZY's aircraft will be the first 700.

The layout will be similar to the A320 series, with 2 A/Ps only, monitored through the MMR and FMC, and incorporates a new standby instrument display, whether this is strictly required for the Cat 111B I do not know, but I believe it is part of the required package.

There has of course got to be a channel through to the rudder for rollout, but the take off minima are not reduced, at least under our current regulations, which means we may be able to land but not take off again!!!

[Phoenix_X]

Rather that than take off and not land again :D

[kriskross]

Totally agree!!!!!!

[BusBoy]

Moleslayer

quite right
A320 has 2 Aps
can be operated to Cat IIIB (75m No DH)