View Full Version : Boeing 737NG, CAT 3A or B?

27th Feb 2009, 15:15
Hi, just wondering if the 737NG is CAT3A or CAT3B.


27th Feb 2009, 15:17
3a! bloop bloop

27th Feb 2009, 18:25

but it is quite a disadvantage regarding the A320 family which is cat3B.

ford cortina
27th Feb 2009, 18:29
Marlbro_2002, please explain....
I have no problem with 3A:ok:

27th Feb 2009, 18:34
Actually they can be CATIIIb, you just have to pay for it.

27th Feb 2009, 18:36
Should I assume you knew the answer before you posed the question?

'Quite a disadvantage'? Probably for most pilots, absolutely no difference in a career in terms of diversions! I wouldn't worry about it! The difference is so small, and unlikely to be ever an advantage or disadvantage! Just Cat 3 is all that matters! It's only a certification thing anyway.

27th Feb 2009, 19:08
As Rainboe said the difference is not really all that big. But of course it is there, 50ft DH vs 0 and 200m RVR vs 75 or 125 single engine.

If you order the fail operational version of the NG it brings quite a bit of improvement (in my opinion) with it. You can do single engine autoland and automatic go-arounds, using flaps 30 instead of flaps 15.

And to be honest, it is quite interesting to see the automatic make an absolutely nice and smooth approach with crosswinds up to 25kts, decrab during the flare and keep the rollout exactly on the centerline.

Hank the F/C
27th Feb 2009, 19:25
Hey Denti, from what year did the 737 have "fail operational " I have only flown the fail passive and is this common because I have never heard about it on the 737:confused:

27th Feb 2009, 19:41
The last 747-200s I flew, had the full Cat.IIIb equipment.
But NO 747s were ever certificated for it. They were Cat.IIIa airplanes.
As far as certification was concerned...
Sometimes in the late 1990s, our airline stopped doing any Cat.IIIa.
They found Cat.II minimums to be quite sufficient for our operations.
Something along the lines "is it necessary" to have full Cat.IIIa capability...?
To fly (statistics) 3 or 4 approaches per year into MXP...? - It was NOT...
We kept operating merely with Cat.II until their recent final retirement.
Yes, we (at times) operated the full Cat.IIIb to see if it still "worked".
That is including the ARC (Automatic Rollout Control) = which is Cat.IIIb.
Such capability was maintained, until the last days.
Quoting a (now retired) chief pilot "if you ever need all that - use it..."
After all, we knew it worked last week on that plane.
Guess what...? I have no problems with such philosophy.
But then I am retired too. Cat.IIIc rocking chair if you care to know.
Happy contrails

27th Feb 2009, 20:33
I think the FCCs support fail operational and the additional required rudder channel since 2001. We receive our NGs with fail operational since 2006 though.

Hank the F/C
27th Feb 2009, 21:00
As I said I never heard about fail operational but I think itīs great to hear that the 737 finaly reached the 20th century:} I flew the MD80 before and that bastard had it 30 years ago, pitty though they have it as an option because the cheap operators in Europe wonīt spend the money on a feature that all other aircraft have:{

27th Feb 2009, 21:30
As far as i know easyjet ordered its -700s with that feature but abandoned its use because of increased maintenance and training costs. And the secondary airline in germany ordered 85 NGs to be delivered between 2006 and 2014 with that option (and all the other nice stuff like vertical situation display, IAN, GBAS capability etc). Dunno if any other european airline ordered it so far.

Hank the F/C
27th Feb 2009, 21:58
Canīt tell you but I donīt think that Oīleary will pay for anything but two wings and two engines:} But anyway a question, will you get the nose up trim at 300 ft with dual ch. and can you make an aut. G/A with single ch. if you have the fail operational option:confused:

27th Feb 2009, 22:34
Yes, and yes. Well, you still get the nose up trim and you can do CAT IIIa approaches and automatic go-arounds with one engine out. However, the rudder kicks out during the GA at 400ft AGL or when you select another roll mode (LNAV is usually automaticly selected at 400') so you have to be aware of that or you will get a huge yaw all of a sudden :)

28th Feb 2009, 01:29
Just a short note to remind those that might have forgotten, or never knew...

The 'ole Lockheed TriStar was absolutely the first wide-body to have full CATIIIB capability and certification, right from the factory, circa 1972
According to a recently retired DAL system chief pilot, who has flown 'em all, only the B777 comes close in smoothness of operation.
Especially, touchdown and roll out guideance.

Back to normal programming.:}

Broomstick Flier
28th Feb 2009, 13:56
Hi 411A,

Sorry for the thread drift, but ever thought in writing a book about your experiences with Lockheed's finest? :ok:


28th Feb 2009, 14:22
When easyJet ordered its NG's they were only 3A. After we'd received about about 17 NG's (up to JT), Mr Boeing introduced the roll-out channel which gave them 3B capability. As Boeing is not able to retrofit this mod on the earlier NG's, we operate all our NG's to CAT3A. As the flight deck is pretty much identical, it is not safe to have your crews operating both versions as the actions required in case of an engine failure on approach are fundamentally different. i.e 3A go-around/3B land.

28th Feb 2009, 15:08
Is Cat 3B really worth it ?

I understand that maintenance costs for 3B as opposed to 3A are much greater. For the amount of time per year that the RVR is less than 200m, the costs/benefit analysis doesn't stack up.

I also recall the day when one of my (now defunct) company's aircraft sneaked into LIN when the RVR was 75m. Cockpit crew all very pleased with themselves until they realised that they were now stuck there as they needed 125m RVR to get out again.......................... and it didn't reach this level until the following day :rolleyes:

1st Mar 2009, 03:29
Hi 411A,

Sorry for the thread drift, but ever thought in writing a book about your experiences with Lockheed's finest?


I second that! :ok:

I always find great knowledge and humor in his posts.

Unlike certain others:yuk:

Leo :8

1st Mar 2009, 07:50
If you pay for ir you shall get it.
I have flown a 737-800NG with fail operational automatics for upto 3B.Also flown the 737-900ER with dual HUD which took us all the way down to a single engine Cat 3C autoland.
So to say that the 737 didn't do fail operational ILS approaches would be incorrect.
Just Fyi....

2nd Mar 2009, 23:39
You mean that just by having a HUD installed you are able to perform CAT 3B?


3rd Mar 2009, 02:04
The MD-80 was Cat IIIa; Fail Operational rudder is the key to IIIb. I remember engineering at McDouglas wanting Fail Op Squared for the rudder, whatever that is, for IIIb.

Didn't the 737ng get the Collins Triplex Autoland system like the other Boeings when they went to IIIb? Up to that point, they had dual Honeywell Fright Guidance system, same as MD-80.


3rd Mar 2009, 17:11
As you are probably aware,Cat 3B requires yaw control or lateral tracking of the localiser.As you are probably also aware that the single most difficult part of zero zero vis(3C) landings is the taxying.Thats where the HUD comes in as a very important tool.
We don't have automatic taxying as yet....!!

3rd Mar 2009, 19:16
Well hopefully that time will never come, or how could we pilots get lost?

I know that it requires lateral tracking. My surprise was when it was mentioned that with a HUD, it would automatically become CAT3B.
I know that for some aircraft it is basically like that.
For example, the Saab 2000 is able for CAT 3 hand-flown with a HUD installed.
And even that is CAT 3A.

Regarding CAT 3B operations, I fly the A330 and we use 75m rvr and no dh as minimums. The same thing is valid for our A320 fleet.
If we use it? Yes we do, but operationally, I've never encountered such conditions for real. In my opinion, CAT 3A is enough.


3rd Mar 2009, 21:51
The other half of HUD is low vis takeoffs, like 150' RVR, IIRC.

The Alaska Airlines 727 fleet were Cat IIIa with the Flight Dynamics HUD way back when. Augmenting Cat IIIa autoland with HUD can get you IIIb.


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