Flight Directors on 737 and A320 different behaviour

[737Andi 6]

Hi,

I noticed that the flight director bars on the 737 are coupled to the speed knob on the mcp while the flight director bars of the A320 are not coupled to the speed knob of the FCU.
To make it clearer what I mean. If I change the speed to higher speeds in the 737 the FD bars are going down (nose poiting down to gain speed). In the A320 the same action is not moving the horizontal FD bar.

Hopefully my question is understandable.

Thank you!

Best regards Andi

[Chock 17,769]

Make sure you have both FDs on in the Airbus; with only one engaged, it affects the autothrottle mode.

[polosim 837]

30 minutes ago, 737Andi said:

737 are coupled to the speed knob on the mcp while the flight director bars of the A320 are not coupled to the speed

All depends which mode is active on Autoflight System. Speed mode  is related to LVL CHG on 737 and to Open CLB or Open DES on A320.

[jon b 2,041]

Don’t know Airbus they’re a complete mystery to me and often even the people who fly them, but on Boeings some APFDS modes use pitch for speed control, eg VNAV SPD.

However , If the autothrottle FMA is SPD then it’s the auto throttle that’s controlling speed.

[polosim 837]

13 minutes ago, jon b said:

Boeings some APFDS modes use pitch for speed control, eg VNAV SPD.

So many options, indeed.