A320 OP CLB behaviour
 

Have you an FCOM reference for this ?

Recent convert to Airbus from Boeing here. It has it's oddities.

The autothrust is quite slow to react to changes, it probably targeted the lower speed first by reducing power and then realised you wanted to climb so it increased power. It's a 1980s design and can't keep up with even a modern smartphone. You would have been better off waiting until the aircraft was properly established in the climb before winding the speed back or managing it.

Nothing, it's the 5-year barrier. It happens, fuzzy logic.

There's no communication between the Ovespeed Protections and Autothrust. The system architecture is discussed in Safety First
Yes. Fifi can be very exciting sometimes!

Check Airman see below
 

Krismiler is correct, in this scenario it will target the speed first, even though the book says it will always give CLB Thrust in OP CLB.

If you just leave the speed were it is, the a/c will raise the nose at max 1G, and the thrust will come on as required to maintain the target speed. Once established in the climb, with CLB thrust set, the desired climb speed can be set.

Alternatively, if you need to start climbing asap, you can EXPEDITE (if fitted), and this will pitch to maintain Green Dot, therefore the thrust will increase sooner. I don't like this for a number of reasons:

The pitch is aggressive for Cabin Crew and pax, and the speed decays very quickly. If you go below your desired Climb speed, it can be a struggle to get the aircraft to pitch down to regain it while continuing the climb.

I have seen folks set a V/S initially too, and increase it as the thrust increases, before OP CLB, it works, but requires a lot more fiddling.

My preferred method, if down low, i.e. 5000ft to FL100 ish, i.e.: On a SID with speed canceled, and expecting a climb soon, keep a bit of a buffer to Vmax, say 15-20kts. (290 works well, and conforms with SID design parameters)

Then:
Set the cleared Altitude,
OP CLB
INCREASE the target speed by 5-10kts. (This will initiate a thrust increase, as the a/c has already pitched for the climb, and you will have CLB THR and OP CLB)
Set desired CLB speed target (I.e: Managed speed or en route climb speed)

It gives a smoother transition to the CLB Thrust, and CLB attitude, also a larger buffer to Vmax, if you hit some bumps.

(NOT TO BE USED IN THE HIGHER FLIGHT LEVELS)

There is many ways to achieve the same thing, but the Airbus works in mysterious ways, this is the way i have found to manage this problem.

Feel free to offer up other solutions.

Jeez man, all this hoopla about advanced avionics and elegant user-friendliness, and reading this it looks like I have to hack into the Pentagon to start a climb!

Hi Check Airman,
No. Unlike ALT* which is annunciated, the transition from ALT to CLB is annunciated immediately - but it can't be so.
There has to be a blend from AT controlling speed in ALT to Elevators controlling speed in CLM.
Your speed intervention was done during the transition phase whilst AT was still controlling speed.

Fun fact: at the same time the FMA will already tell you "climb thrust".
So in this case the FMA is obviously lying to you.
But only for a few seconds..

The following information was released by Airbus in Sochi crash investigation:
The logic of integration of the autopilot/flight director (AP/FD) pitch control and the
autothrust control
¬If AP/FD pitch mode controls a vertical trajectory (e.g. V/S, ALT), then AT controls speed.
¬If AP/FD pitch mode controls a speed (e.g. OP CLB), then AT controls thrust.
¬If no AP/FD pitch mode is engaged, then АТ controls speed.
Logic sequence of the OPEN CLB mode
¬for level change more than 1200 ft:
¬at OPEN CLB mode engagement by the pilot, V/S control with V/S target = +8000 ft/min (40 m/s) is applied for AP/FD, and SPEED/MACH mode is engaged for AT
¬when engine N1 reaches 95% N1CLB mode, AP/FD switches to SPEED/MACH control law, whereas AT switches to the THRUST mode
¬Throughout this time the FMA displays THR CLB for AT and OP CLB for AP/FD
The given scheme of engagement for the OPEN CLB mode ensures the uniformity of the aircraft response in all configurations and within the whole range of the flight altitudes and speeds.
¬For level change less than 1200 ft:
¬at OPEN CLB mode engagement by the pilot, V/S control with V/S target = + 1000 ft/min (5 m/s) is applied for AP/FD, and SPEED/MACH mode is engaged for AT
¬ Throughout this time FMA displays THR CLB for AT and OP CLB for AP/FD
In this case the climb is in fact performed in the vertical speed control mode.
***
It should also be noted that if the OPEN CLB mode is engaged less than 30 seconds after the aircraft level off function is activated, the autopilot is authorized to use the vertical acceleration at the maximum value of 0.3g, whereas usually it is only 0.15g.

how to complicate something so simple...select the altitude, pull the damn knob..after it starts to climb, select any speed change you desire...

Or more technically correct - wait until N1 reaches 95% as vllas posted #16

"when engine N1 reaches 95% N1CLB mode, AP/FD switches to SPEED/MACH
control law, whereas AT switches to the THRUST mode
¬Throughout this time the FMA displays THR CLB for AT and OP CLB for
AP/FD"