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B737MAX LAND 2/3

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B737MAX LAND 2/3

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Old 8th Sep 2018, 19:15
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B737MAX LAND 2/3

Hello guys and gals,

I am trying to obtain an understanding of the logic behind the annunciation of either LAND 3 or LAND 2 on the Autopilot status display during a dual channel approach. More specifically, which items the aircraft monitors itself and would, if inoperative, render a downgrade from LAND 3 to LAND 2.

The FCOM does not cover this.

The AFM has the following list of items required to be operative with LAND 3/2 displayed.

Fail-Operational
The autopilot system has been shown to meet the applicable airworthiness performance and integrity criteria established by CS AWO Subparts 1 and 3 for an automatic landing system with the following functions operative and LAND 3 annunciated:
Two engine operation at flaps 30 or 40
Autoland status annunciation on both Displays
Autothrottle at the start of final approach
Approach Minima Display for each Pilot or no minima for no DH operation
Windshield Wipers for each Pilot
Flight Mode Annunciator for each Pilot
Normal flight controls
Anti-skid brake system

Fail-Passive
The autopilot system has been shown to meet the applicable airworthiness performance and integrity criteria established by CS-AWO Subparts 1 and 3 for an automatic landing system with the following functions operative and LAND 2 annunciated:
One engine operation at flaps 30 or two engine operation at flaps 30 or 40
Autoland status annunciation on both Displays
Approach Minima Display for each Pilot
Windshield Wipers for each Pilot
Flight Mode Annunciator for each Pilot
Normal flight controls

The autopilot is of course not monitoring all these items requiring the flight crew to assess the status of the aircraft prior to approach.
My question is really; What is the autopilot/AFDS monitoring that would cause it to downgrade itself from LAND 3 to LAND 2 (or NO AUTOLAND for that matter).

Hope that all makes sense.

Last edited by _Viking_; 9th Sep 2018 at 09:44. Reason: more detailed wording
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Old 9th Sep 2018, 09:18
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What you have to realise is that the fail operational capability on the NG and MAX is a bit of a Frankenstein job (and a minor miracle that this was approved by the authorities) - two FCCs with two IRSs and two MMRs magically provide triplex redundancy. Reasons for a downgrade to LAND 2 may be that your ISFD is inop, that is the third attitude source for an autoland in this installation - also, if the rudder servo fails to respond to FCC commands during the self test the airplane won't be LAND 3 capable. The items you mentioned are supposed to be checked by the pilots, they are of course not all monitored - the airplane will even happily land on a single autopilot, not that Boeing would want you to try that LAND 2 simply means that you've downgraded to a fail-passive autoland like on any bog standard 737 since the classics, not terribly restrictive if you don't need the last 50 feet of minimums.
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Old 9th Sep 2018, 18:47
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LAND 3 with 2 autopilots?
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Old 10th Sep 2018, 06:35
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Originally Posted by oceancrosser View Post
LAND 3 with 2 autopilots?
Add it to the laundry list of things that managed to get passed by the FAA with this type certificate.
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Old 10th Sep 2018, 06:45
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A VW Kombi retrofitted with a V8 engine and an Atari as one trainer used to remark...
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Old 13th Sep 2018, 17:51
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Originally Posted by STBYRUD View Post
the airplane will even happily land on a single autopilot, not that Boeing would want you to try that.
As a matter of interest have you actually tried this?

I've encountered a lot of people who make this claim, but when asked, offer "I tried it in the sim" as evidence.

Given that a 737 auto land is pretty agricultural at the best of times, and that simulation of things outside the certification envelope has no need to be accurate, I am not hugely optimistic!
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Old 13th Sep 2018, 18:52
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LAND 3 with 2 autopilots?
Who would have guessed, I wouldn't!
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Old 14th Sep 2018, 08:00
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Originally Posted by Capt Pit Bull View Post
Given that a 737 auto land is pretty agricultural at the best of times, and that simulation of things outside the certification envelope has no need to be accurate, I am not hugely optimistic!
I have to say that the autoland in the fail operational 737NGs was actually very nice indeed, and even better, in my view, than what the A320 manages. Not at all the same performance than the fail passive ones. But then, no idea how the MAX manages. Did they make the fail operational autoflight system standard with the MAX? Or is it still a customer option?
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Old 14th Sep 2018, 11:19
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Originally Posted by Denti View Post
Did they make the fail operational autoflight system standard with the MAX? Or is it still a customer option?
It's still an option. The Max's in the company I'm flying for are not equipped with it, whereas nearly the whole NG fleet is. I believe the cost of the option + maintenance is way higher than the cost of having to divert in the very very rare case you actually need Cat3B.
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Old 19th Sep 2018, 06:49
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Originally Posted by Capt Pit Bull View Post
As a matter of interest have you actually tried this?

I've encountered a lot of people who make this claim, but when asked, offer "I tried it in the sim" as evidence.

Given that a 737 auto land is pretty agricultural at the best of times, and that simulation of things outside the certification envelope has no need to be accurate, I am not hugely optimistic!
I have done this in a 737-200, of all things. As a brand new F/O, flying with a very experienced Captain who explained the function then demo'd it in VMC. It worked great - for a single data point In my ignorance, I assumed this was all cool, and have subsequently gotten a better appreciation of the potential risks he took, but I still appreciate the demo.

Note that this is all to the best of my recollection. I'm pretty sure it was a single channel 'autoland' (yes, I know that's not really a 'thing'!) - I remember the briefing he gave me on the fact that the aircraft would do it, even though it wasn't something that jumped out at you from the FCOM.

The Captain in question has since passed away, but in our neck of the woods he was widely respected. For reference, he commanded the B747 that overflew the stadium during the 1995 rugby world cup, also depicted in the movie Invictus
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