A320 ND QUESTION
 

HERE IS THE SCENERIO
DUAL FD fault between 100 and v1， it is no doublt to lift the airplane
but after t/o it is allowed to nav by nd display, and fly the sid ？？？ it is legal？

If it’s a conventional SID you can continue. RNAV SID, you will have to request radar vector. You can continue the flight as long as you stay out of RVSM.

Why is it a ND question? And why should only FD fail by itself?

If it is a conventional SID - constructed using ground sited navigation beacons, then you can continue flying with autopilot using your raw data NAV instruments and HDG, (or TRACK in Airbus FBW). We used to fly SIDs out of Heathrow in unsophisticated aircraft using AP and HDG; referring to VOR radials in raw data. As far as I know it is still legal to fly like this - unless certain airports ban it?

One thing that might catch you out could be noise abatement, where less than accurate SID tracking might, in some cases incur a fine to your airline.

See FCOM PRO-SPO-51

If it’s a P-RNAV / RNAV 1 / RNP 1 departure, no:

REQUIRED RNAV 1(2) EQUIPMENT
The minimum navigation equipment required to enter RNAV1/RNAV2 airspace is:
‐ One FMGC
‐ One MCDU
‐ One GPS or one DME receiver to update the FM position
‐ Two IRS
‐ One FD in NAV mode
‐ Two NDs (the temporary display of ND information via the PFD/ND sw is permitted on PM side).


If it’s a conventional or RNAV overlay departure, yes:

REQUIRED RNAV 5 EQUIPMENT
The minimum navigation equipment required to enter RNAV 5 airspace is:
‐ One FMGC
‐ One MCDU
‐ One GPS or one DME receiver to update FM position
‐ Two NDs (the temporary display of ND information via the PFD/ND sw is permitted on PM side)
‐ One IRS.

Although you can do anything in an emergency, if you can justify it as the safe course of action.

thx a lot :ok:

it is a sim scenerio ,
same thing like dual fcu/fmgc fault， dual ac bus failure etc, instructor set them between 100 and v1
if you reject t.o, they would shout at you why you reject??? how do you know if you have enough rwy?/

You can do a no-FD take off, it is explained on the FCOM/FCTM

FCOM > Procedures > Normal Procedures > System Related Procedures > FMS > Take off > No Flight Director Takeoff

https://cimg4.ibsrv.net/gimg/pprune....bc6520fa2c.png
https://cimg5.ibsrv.net/gimg/pprune....128396dfdb.png
https://cimg6.ibsrv.net/gimg/pprune....7c41178bb2.png

If you have made the decision to reject and have started taking action to reject by the time you get to V1, then you have enough runway to stop.

I wouldn’t call a loss of both FDs, or even both FMGCs, an emergency. But seeing the current trend of automation dependency, I can see that it can easily develop into one.

Because above 100 kts you should only reject for serious malfunctions.

FCTM:
Above 100 kt, and below V1: Rejecting the takeoff at these speeds is a more serious matter, particularly on slippery runways. It could lead to a hazardous situation, if the speed is approaching V1. At these speeds, the Captain should be "go-minded" and very few situations should lead to the decision to reject the takeoff: 1.Fire warning, or severe damage 2.Sudden loss of engine thrust 3.Malfunctions or conditions that give unambiguous indications that the aircraft will not fly safely 4.Any red ECAM warning 5.Any amber ECAM caution listed below:
‐ F/CTL L(R) SIDESTICK FAULT ‐ ENG 1(2) FAIL ‐ ENG 1(2) REVERSER FAULT ‐ ENG 1(2) REVERSE UNLOCKED ‐ ENG 1(2) THR LEVER FAULT


A dual DC BUS failure affects the braking system, so you are limited to 1000psi. You might not be able to stop the aircraft within the ASDA.
If an ECAM is inhibited above 80 kts, it’s not recommended to reject at high speed for that failure.
(Although if you do reject, there’s no need for your instructor to shout at you.)

Surely there isn't even going to be an an obvious indication that both FDs have failed?

So, you're taking off from Innsbruck on a PRNAV SID, in IFR conditions. You lose both Flight Directors.

Do you:
1. Say to the other pilot - "Damn, we can't legally do a PRNAV SID without flight directors. I'm going to fly straight ahead until we can get vectors.", or
2. Say "It's an emergency, I'm going to follow the path on the Nav Display, and I don't care about the letter of the law." ?

Rotate at Vr and then ask for radar vectors due to navigation downgrade...... covers all scenarios then.

Another way of looking at it is when did you start the RNAV 1 op? Commencing the take off roll?

So when entering the RNAV 1 route you have the required equipment. During the RNAV 1 route only a nav system downgrade requires a notification to ATC. The A/P will happily follow the route from the FMGC.

What about the scenario where the radio is busy, and the SID involves an immediate turn?

Call for the AP ASAP so as to reduce workload. Fly runway heading, no matter what. Doing anything else would be illegal or against SOP.

Most SIDs I’ve flown with an immediate turn do so for a very good reason (terrain, traffic etc). I’d turn.