I typically read that CAT IIIB approaches must be flown by an autopilot to touchdown. Looking for a reference (regulatory bodies* in particular) to track the statement only leads to company SOPs.

In other words, with the runway in sight at or above the DH, is it written somewhere (excl. SOPs) that the pilot flying can/can't take manual control when the approach was started in CAT IIIB minima?

Full disclosure: I completely understand it's unwise and unsafe to even suggest hand flying an approach when that's the view:

enter image description here
RVR 200 m. (wikimedia.org)

* FAA, EASA, and ICAO, are acceptable (I couldn't find anything in ICAO Annex 6).


The ability to perform autoland approaches requires specific approvals. In the US, it is outlined in AC 120-28D Criteria for Approval of Category III Weather Minima for Takeoff, Landing, and Rollout. BTW, CAT I and CAT II approaches are covered by AC 120-29 Criteria for Approval of Category I and Category II Weather Minima for Approach.

The AC describes the necessary installed equipment, specific crew training requirements, and the need for operational procedures. Once approval is granted, the crew training and operational procedures become part of the airline Op Spec.

If any hand flying is allowed, it will be spelled out in the Op Spec. Since Op Specs do vary from airline to airline, it's not possible to state definitively what is or is not allowed.

That said, it is physically possible to manually take over and land the aircraft. If the crew has the runway in sight at 200 feet, it's really no different that a CAT I approach. At 50 feet on an autoland approach, the autopilot will be starting the flare and de-crab maneuver, so manual intervention at this point may or may not be allowable depending on the specific aircraft performance and the airline's operational philosophy.

  • $\begingroup$ I will check those documents, thanks! I also found 8900.1 CHG 225 and posted an answer. $\endgroup$ – ymb1 Sep 23 '18 at 18:05

I found 8900.1 CHG 225 (.pdf, Dec 2015) for the FAA, which says an aircraft must be flown automatically to touchdown for RVR <700 ft (200 m):

4-338 CAT III OPERATIONAL CONCEPTS. The weather and environmental conditions encountered in CAT III AWTAs severely restrict seeing-conditions. External visual reference is not acquired until the aircraft reaches a very low altitude. Typically, external visual references begin to become available below 100 feet. Even though external visual references are usually available before touchdown, the seeing-conditions are not sufficient for the pilot to consistently perform a safe, manual landing. Therefore, the aircraft must be controlled by instruments and special equipment throughout the approach, flare, and touchdown (deceleration for rotorcraft) in weather conditions as low as RVR 700 and through rollout to a safe taxi speed (air taxi or hover for rotorcraft) in weather conditions below RVR 700 (...)

Since CAT IIIA in the US is RVR >700 ft, it can be flown HUD to touchdown as @RalphJ has commented here, given that the carrier and equipment are authorized of course:

Cat IIIA approaches are routinely performed without an autopilot, for aircraft equipped with an approved HUD. — Ralph J

  • $\begingroup$ So why don't the rules allow for the possibility of using a sufficiently-advanced HUD to hand-fly a IIIB approach, should one be developed? $\endgroup$ – Sean May 19 at 0:44

A fail-operational autoland system would be able to continue the approach for any single failure below alert height (between 100 and 200ft RA for most aircraft). If autopilot would completely disconnect below alert height, it would mean that a multiple failure has occured.

This kind of scenario would be covered by company SOPs, however I doubt any sensible company would allow continuation of a Cat IIIb approach after complete autopilot failure. We are talking about hand flying an aircraft in RVR as low as 75m. Not the best idea.

  • $\begingroup$ I'm not asking about AP failure, rather the regulations for taking the controls after having the runway in sight (SOPs excluded). $\endgroup$ – ymb1 Sep 23 '18 at 16:12
  • $\begingroup$ With weather at Cat IIIb minima, you are likely to see the runway light(s) at around 10-20ft, which is during flare manuever. Why would a sane pilot try to disconnect autopilot and land manually? $\endgroup$ – RunawayPilot Sep 23 '18 at 16:13
  • $\begingroup$ Then it is not a Cat IIIb approach. See ICAO Annex 6, Part 1 reference: Category IIIB (CAT IIIB): a decision height lower than 15 m (50 ft) or no decision height and a runway visual range less than 175 m but not less than 50 m $\endgroup$ – RunawayPilot Sep 23 '18 at 16:18
  • $\begingroup$ When do you decide what minima you are going to use? It seems that if you're expecting and have briefed a IIIb approach, if you spot the runway before passing the IIIa minima it wouldn't be wise to suddenly change the approach type. $\endgroup$ – TomMcW Sep 23 '18 at 23:26

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