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StrIA
24th Dec 2016, 11:03
Why it is not recommended to use FPV on takeoff or go around?
If you have answer, give me link.
Thanks.

Amadis of Gaul
24th Dec 2016, 17:49
Why would you want to use the bird for T/O or G/A? What would be the advantage of that?

dweeks
24th Dec 2016, 19:28
1) Because Airbus says not to.

2) More importantly, as a/c weight, altitude, temp, etc, can vary tremendously, you don't know that your aircraft will be able to actually sustain flight at the flight path angle you are pitching to. The bird is actual FPA, and what the airplane can fly on one takeoff may not be sustainable on another.

In contrast, an initial target pitch attitude of 15 degrees is considered sustainable, and then you tweak the pitch if need be to fly your desired target airspeed.

Kerosine
24th Dec 2016, 19:42
You might know this already strIA, if so skip to FCOM stuff at the bottom.

There are 2 modes for the FPV, with and without the Flight Path Director. Operationally we (my airline) do not fly with the FPV+director, so I'll assume for the moment we're talking about FPV alone.

For takeoff and go-around we are concerned primarily with the performance and obtaining the best angle of climb. In both EFATO and G/A cases we assume the power is fixed (at or close to maximum) and the attitude is the principle driver of airspeed and therefore performance. The FDs will give you an instantaneous, clear and accurate indication of required pitch to achieve the speed you require. The FPV on the other hand is not a command, it will show only your angle of climb (or descent!) thus removing an important pilot cue for pitch required. For this reason Airbus recommend against using it for takeoff.

That being said if you suffered an unexpected AP/FD failure it won't do any harm to have the FDs turned off and the FPV displayed.

PRO-SUP-31
There is inevitably some lag in-between the pilot's raising the nose to commence the go-around and the aircraft's responding by changing its trajectory. For the same reason the pilot does not use the FPV on take-off.

DSC-22-30-20
FD bars are automatically restored [G/A modes] at go-around engagement. If FPV/FPD was previously selected, it reverts to FD bars.

StrIA
25th Dec 2016, 02:55
Thank you very much. That is enough.

Bula
30th Dec 2016, 09:18
Indian carrier (I believe), crew targets 15 NU using the bone FD.

Let's just say this one was written in blood.

EZY Rider
30th Dec 2016, 10:38
Take off & go-around are considered dynamic manoeuvres.

From the FCTM:

"In dynamic manoeuvres, the "bird" is directly affected by the aircraft inertia and has a delayed reaction. As a result, the "bird" should not be used as a flight reference in dynamic manoeuvres.
The "bird" is the flying reference that should be used when flying a stabilized segment of trajectory, e.g. a non Precision Approach or visual circuit."

Hope that helps.

Escape Path
3rd Jan 2017, 02:58
The FPV shows aircraft trajectory with relation to the horizon. It is not vital (per se!) for the handling of the aircraft during takeoff or go around, particularly the performance of the aircraft, to know the trajectory of it as it's not a parameter that helps to manage the vital factors of aerodynamics (pitch and airspeed in this case), which the flight director does brilliantly.

Now, for approach on the other hand, it's quite useful to help to fly that common -3 path...

IFLY_INDIGO
3rd Jan 2017, 22:12
simply because I am not interested in knowing the trajectory precisely. All takeoffs have positive trajectory guaranteed.

I am interested in flying a pitch attitude that cares about V2+10 kts.

Iron Eagle
5th Jan 2017, 15:33
FCTM SI-020 THE FLIGHT PATH VECTOR