A320: CAT IIIB without FDs
 

Can anyone provide reference (regulatory, manufacturer, but not from specific airline docs such as MEL) showing that CAT IIIB approaches are/are not permitted with both FDs inoperative.

So far I checked, AFM, FCOM, MMEL, Getting to grips..., my guess is nothing prevents you to conduct such approaches without FDs.

If anyone has JAR-AWO in pdf, would appreciate to see it.

Check QRH 5.04. Top line of the table

hth

yeah...and?

It says AP/FD...2 AP ENGAGED. So far, does not answer my question ;)

purely as an FYI and not directly related, some A/C e.g. 747-400 - will ONLY do FD off approaches below 1,500' (if your outfit is too tight to tick all the option boxes)

Latest revision to QRH - TR 608-1.

So no, you don't need FDs. Hope that answers your question.

Brilliant Gary!
Just got to check this TR out.

shortfuel, the TR 608-1 reports also :for these reason, as stated by BRAKES HOT, you can find the solution directly on an updated QRH page 5.4. The term "FD" has been removed remaining "AP" only, so FD is not considered required in any approach.

Spotted it! Thanks!
It wasn't placed properly (at all) and I couldn't guess that it was an actual TR on our paper copy on board.
I was wondering why AI referred only to AP's in AP/FD required equipment section.
It's now crystal clear!
Funny enough, our A330 MEL does not permit for CAT IIIB without FD's (clearly written) while our A320 MEL has no provision for that dispatch case...:ugh:

It apparently varies by operator. Where I used to fly the A320/319 2 FDs are required for Cat II and II. The way our 757/767s are set up though the FDs did not work when set up for an autoland which is required for Cat II or III.

Rick - you say you 'used to fly' the A320/321. The TR which I quoted is new, and applies to all Airbus A320 family aircraft - it may be that your old company has since applied it.

There is nothing to stop a company from continuing to apply a more restrictive MEL, of course, but the MEL is a company document, not a technical specification from the manufacturer. A320 aircraft do not need FDs to do CAT 2/3 autolands.

“It apparently varies by operator.” (#9)
More likely that the system design / certification / manufacturer's intent specifies the use / display of the FD.
E.g. there is little point in displaying a lower reliability 'duplex’ FD system when flying with a highly reliable ‘triplex’ autopilot.
By not showing the FD, this removes any possible confusion / clutter during the approach and forces the crew to focus on the raw ILS display for monitoring the accuracy / progression of the flight path.

I can see some of the logic in the argument for no FD's, however I believe that problems with raw data with the FD's on can easily be taught and emphasized in training...eg loc drift etc...why downgrade your aircraft?

“ … problems with raw data with the FD's on can easily be taught and emphasized in training …” (#12)
One of the problems with assumptions (as above) is that they can be wrong considering the range of human behaviours and situations which might be encountered in operations, e.g. FD fixation.
IIRC there was a regional jet fatal accident in France due over focus on the FD during the approach.
Where a high integrity auto pilot is being used, switching off the FD does not downgrade the aircraft, it still has the same capability. Furthermore it could be argued that the less complicated monitoring scan pattern – focussing on the important parameters, adds safety capability to the operation as there is less opportunity for error.

Sorry if this is a stupid question,as I have never flown with the FDs off, except during visual manouvering with the AP off.

In flt with the AP engaged, switching the FD's off will not cause any mode reversions and you can fly all the way to Cat III with them off. Is that correct?

Yup, Correct.


(FWIW, I also found it strange on the 757, when it removed the F/Ds during the approach!)

Have there been instances on modern aircraft whereby the FD's have proven to be a problem on the low vis approaches? Or is the recent relaxation of the FD requirement strickly for MEL purposes to allow dispatch?