To the B 737 experts

[gearpins]

The B 737 ng in our fleet do not have CAT III B capability.
Would like to know what kind of mod has been incorporated to achieve this capability since the Autopilot has no control over rudder / rudder trim.
And the requirement to be able to auto land / rollout even in a single engine situation is a requirement for CAT III B.
Appreciate all responses as my experience in this fleet is limited.
Cheers:confused:

[RRTrentSymphony]

As a pilot flying a modified CATIIIB capable (but not allowed in some countries for us as we didn't certify it in all the countries we fly to yet) 737-800, there is quite a costly process in my opinion and here are some of the modifications made:

Replaced our backup instruments with digital ISFD and all the rewiring required for the ISFD (it provides 3rd source of data for autoland).

Installed the collins EDFCS-730 autopilot system on our first overhaul after delivery from previous customer.

There was an extra C/R (clear/recall) button on the usually blanked button slots beneath the ENG, SYS buttons near the autobrake selector. Functions as a clear/recall for text on the engine display like on the 777, quite cool.

Installed the collins 2274-COL-AC1-07 software package on our FMCs.

Installed GLU-925 GPS landing system (not sure if this is required, not a tech)

Installed APN-241K real-time terrain tracking radar (for mountain approaches in unmapped areas), probably not a requirement in most airline's operating conditions, but is needed for our mountain operations

Custom HUD installed, probably also not required but we are damn lucky to get one (two acutally-one of the 6 dual HUD 737s in the world) in out jets after a negotiation on lowered salaries (to pay for these systems)

New autopilot rudder servo and rudder channel in the autopilot (comes with the collins package)

And a few more, probably autoland unrelated mods, I'll go have a talk with the tech next time I'm on the line.

Also, you need CFM56-7B27E engines for single engine CATIIIB autoland, unless you are landing with the landing weight below 60,000kg since you have to use flaps 30 for autoland, therefore go-around at flaps 15. At max landing weight with the -7B27E engine and bleeds off landing, the -800 would yield only a 1.2% go around gradient so you may be more limited in weight at some airports and conditions if using CATIIIB single engine autoland with lower thrust engines. Short field package for 737NG can help improve the go-around gradient slightly due to less slats deployed but most airports without mountains around shouldn't be a problem. Our 737NG's don't go near max weights at those critical places so we didn't get the short field package.

Some airports may not be CATIIIB certified, especially the rural airports that some NG's fly into as they don't have CATIIIB lighting on their runways & taxiways (most of them), but since we don't usually fly passengers and operate on a special license, the runway lighting issue is not a problem in some countries for us.

[Denti]

Think i answered yesterday on your question but that thread got deleted somehow. Anyway, we fly the fail operational variant of the NG (both 700 and 800) since around 2005, CAT IIIb down to no DH/75m RVR and CAT IIIa to 50ft DH and 125m RVR in the first segment, 75m for the rest of the relevant distance.

Required for the CAT IIIb operation is the Rockwell Collins Enhanced Digital Autoflight System which does have a rudder channel. Of course rudder servos are needed to utilise that. The Collins MCP which includes the autothrottle computer and FCC is needed as well, however as far as i know that is standard equipment since a certain line number. And of course the ISFD is needed as a third attitude source since the 737 only has two IRSs. It is still a dual autopilot installation, not a three channel one.

During dual channel operation the rudder will be used by the autoflight system below 1500ft AGL (to be more precise after the successfull confidence test) and will stop working during G/A whenever a new lateral mode is selected, either automatically or manually. Especially during OEI operation better be prepared or there will be a violent yaw when that happens.

We use the 26k variant of the CFM-56BE on the 800s and 22k on the 700. On the 700 we do not have any problems at all and can use any weight up to max take off weight for landing and go-around with quite a margin, on the 800 we have to check performance for everything above 65t. However we do have the short field performance kit installed on our 800s which helps quite a bit.

Interesting to read above that apparently some pilots pay for their work equipment out of their own pockets, wonder when they start asking you to bring your own 737 to work. That is something neither me or my colleagues would be willing to do, either the company needs it than they have to buy it themselves, or they dont, in which case it is their decision if they buy it or not. Quite contrary, if the equipment gets more complex and allows operation into situations that were not possible without it, it is a clear reason for higher pay.

[Sciolistes]

Custom HUD installed, probably also not required but we are damn lucky to get one (two acutally-one of the 6 dual HUD 737s in the world) in out jets after a negotiation on lowered salaries (to pay for these systems)
:eek:

We use the HGS system for manual CAT3A approach and landing. So I'm told, this is significantly cheaper than getting the autopilot certified.

[Capt. Inop]

Many of our B737NG's are CAT3b due to the newer autopilots and the activated rudder channel.
Not all, since lots of them were ment to delivery for other companies.

[gearpins]

Thank you folks for all the responses especially RRTrentSymphony and Denti.
Yep the previous thread disappeared for some strange reason.
with the rudder channel installed i can begin to understand how it works.
Find the FCOM very limited in info.
thanks once again
cheers:)