A320 NEO Open Climb Thrust Logic

[vilas]

Originally Posted by CW247

That's very helpful. I'm on a mission now to discover how many pilots know this. It's not in the FCTM.

don't waste your time No pilot knows this. It's not their fault it's not written in any document published by Airbus. As I said before this was disclosed to investigators of Sochi accident of Armavia air line flight 967. I study accidents/incidents so came across it.You can download the report from aviation safety website and you will find it there.

[CW247]

OK, I'll make it my mission to get Airbus to put it in the FCTM then

[321XLR]

Originally Posted by vilas

Scagrams is right. Perhaps it is a translation from Russian. What I quoted wasn't my guess work. It was data provided by Airbus in a fatal accident inquiry. So there's no question of its authenticity. In simpler language it means initiation of OP CLB is through SPEED, VS mode and real characteristic of OP CLB starts from 95% of CLB N1 i.e. when thrust almost reaches CLB. Design philosophy. In a go around irrespective of lateral mode TRK/HDG or Nav the SRS changes only to OP CLB. Why? Design philosophy.

Originally Posted by vilas

Now that you know the design of the mode one could prioritise between climb and speed reduction. If climb has priority then wait till climb N1 is set then reduce speed that will climb also pitch it up to reduce speed. Want to reduce speed then do it simultaneously with pulling climb.

villas can you provide a "operational real world" scenario and walk us thru this ? Would a pilot watch N1, then pull selected speed?

isn't Airbus philosophy is "use the automation" ? In theory, open climb ignores constraints and "climbs unrestricted." Period, the end. Managed Climb, obeys contraints to include altitude and speed. Period, the end.

Is it basically safe to say that (this is why we go to recurrent....consider this a short refresh...) :

THR CLIMB/THR IDLE - "THR"-XXX in the FMA = FIXED THRUST. Speed controlled via PITCH

SPEED or MACH in the FMA = VARIABLE THRUST. Speed controlled by THRUST / POWER.

Example-1: Tracking the ILS on the glideslope, SPEED should be in FMA, as it should. You cannot have large pitch variations and track the glideslope. You are also slowing to VAPP.
Example-2: Level flight at FL350. MACH in FMA. Again, to maintain Mach number or Cost Index or whatever cruise speed, you cannot be changing pitch while in level flight.

Again

THR-xxx = FIXED THRUST
SPEED or MACH = VARIABLE THRUST

Correct ?

[vilas]

Originally Posted by 321XLR

villas can you provide a "operational real world" scenario and walk us thru this ? Would a pilot watch N1, then pull selected speed?

isn't Airbus philosophy is "use the automation" ? In theory, open climb ignores constraints and "climbs unrestricted." Period, the end. Managed Climb, obeys contraints to include altitude and speed. Period, the end.

Is it basically safe to say that (this is why we go to recurrent....consider this a short refresh...) :

THR CLIMB/THR IDLE - "THR"-XXX in the FMA = FIXED THRUST. Speed controlled via PITCH

SPEED or MACH in the FMA = VARIABLE THRUST. Speed controlled by THRUST / POWER.

Example-1: Tracking the ILS on the glideslope, SPEED should be in FMA, as it should. You cannot have large pitch variations and track the glideslope. You are also slowing to VAPP.
Example-2: Level flight at FL350. MACH in FMA. Again, to maintain Mach number or Cost Index or whatever cruise speed, you cannot be changing pitch while in level flight.

Again

THR-xxx = FIXED THRUST
SPEED or MACH = VARIABLE THRUST

Correct ?

After pulling climb wait for aircraft to pitch up before pulling speed. There is another situation when FMA shows THR IDLE but it's higher than idle. It's when starting descent from TOD if there is repressurisation segment then it will use higher than idle thrust till it get into correct depressurisation profile. Basically what you say is correct.

[CVividasku]

So, has anyone tried to reproduce this behavior ?

Let's start from FL110, 300kt. Reduce speed to 250 kt. N1 diminishes, airspeed drops.
Pull ALT. If I followed correctly, we are in speed VS mode. So the airplane should keep low N1 until speed is established, while pulling up (which will only accelerate the speed reduction).
And we should notice a long period of time during which the airplane is in THR CLB OP CLB with low N1... Interesting.

The same should go if speed was reduced immediately after pulling alt.

Does the same go for the opposite, increase speed just before engaging open des ?