Radio Altimeter Failure On 320

[420]

hey guys,got a question.

During the RA 1+2 failure... i have this doubt whether to leave the FD's on or off. because im thinking... "hey,are the FD's reliable during this failure?" i mean....i know its there and we can select it...but without the RA reading...would the FD's give reliable info?

just wondering and i cant seem to find the answer i want anywhere...


help.

[420]

oh and if there are already threads on this matter...apologies... please re-direct me. thanks

[Reel Marine]

Dual RA Failure is a tricky one, it doesnt tell you that you cant arm the approach mode thus you have to fly it like a localizer approach. Also its one of the failures that takes you from Normal Law to direct law upon gear down, so you have to know to use conf 3, ref plus 10 and add 20percent to your landing distance. Also your AP trips off so you have to hand fly it. The reccomended flying reference is the bird.

Hope this helps

[420]

yeap thats true and yes use of the bird is RECOMMENDED. but is the use of FD's any good or trustworthy. as u said,once the landing gears come down it reverts to direct law,meaning all prots lost.

so i feel,that with all the prots lost,the FD's are useless (BUT THEY ARE STILL THERE AND PPL USE THEM). so is it reliable????

i mean,ok for example,when the high speed prot kicks in,at around Vmo+16,the aircraft detects it and commands a pitch up motion to the aircraft hence reducing the speed. so you can practically see the FD bars command this pitch up motion as they move up.
so with the protections lost,i would assume that this so called FD commands are unavailable. and the pilot would then just follow the FD till kingdom come neglecting the basic scan. am i right in saying this?

also of course theres the thing about switching off the FD bars keeps the ATHR in speed mode....but i dont think that applies to this scenario regarding the RA's

[westinghouse]

hello,

on the 330's we have no issue abt removing the FD's in this faliure case. nor is it written anywhere.
the FD's can be used depending on the approach in use.
unlike the 320 direct law the 330 is much easier to handle.

chow.

[gearpins]

reliable alright

but a bloody pain to use on a loc app with your pm twiddling away on the v/s just so the fd can match the des angle. easier to fly ap off,conf-3 speed at vapp before you come up on glide fds off fly the glide sel gear and ask you pm to give some sexy callouts since auto calls are kaput.
...I think

[420]

of course its a pain to use v/s but even if we're on trkfpa the fd bars are still there.... so do we use them or not?? thats the question here....how reliable are they? and if they are where is it getting data inputs from. i just find it all too akward

[shortfuel]

"The final stages of the approach should be flown using raw data in
order to avoid possible excessive roll rates if LOC is still engaged. Indeed, as
the autopilot gains are no longer updated with the radio altitude signal, the
AP/FD behaviour may be unsatisfactory when approaching the ground."
FCTM
Hope you got your answer

[420]

FINALLY!!!!

makes perfect sense. thanks mate!~

[gearpins]

that did clear a few cobwebs thanks

[Bad to the bones]

If it help after dual Ra failure u r limited for non presition app only, an FD is not reliable for app, so FD must be off to avoid sending wrong data to ATHR.

[SIDSTAR]

The FDs are no use if you have to get the PNF to continuously programme them to show a sensible command. Hence Airbus recommends that they be switched off. Basic rule - leave them on if they are giving useful information but OFF if not. That's why they are switched off when you go visual on a non-precision approach but stay on in the visual portion of an ILS approach. On the ILS they are following an external reference which is still useful guidance.

With Dual Rad Alt failure you lose the autopilot due to loss of gain programming which reduces the autopilot sensitivity as you go down the "cone" towards the runway.

This failure is not well warned in FCOMs and can be a real pain if you are not aware of the implications - no AP, FD, APP mode and DIR Law, Conf 3 appr, +10 kts, +20% on landing distance. The big problem is that the ECAM only tells you about most of these when you put the gear down and you go into direct law. You need to know that when the ECAM tells you that you'll be in DIR LAW with gear down, you should look up FCOM 3 to prepare for the implications.

[loc22550]

Bad to the Bones, i think there is no reason why we should be limited to a Non precision App with dual RA fault...If you have an ILS and the glide slope information..use it .