A320 Thrust modes
 

Hello everyone . I am not able to understand the various thrust modes in A320. According to me in climb and descend the mode should be speed mode because we climb or descend with constant speed but AFM says the thrusts is in power or thrust mode.
Can anyone please help me in understanding various modes of Thrust and open climb mode also.

When you climb or descend with constant thrust, the aircraft speed is controlled by adjusting the pitch.
if you fly with a constant VS or level, the aircraft speed is controlled by varying the thrust.

There are five fixed thrust modes. TOGA, FLEX, MCT, CLB & IDLE. When thrust is in one of these the speed is maintained by varying the pitch. In TOGA/FLEX it's in SRS which is also pitch mode. If you want precise ROC/ROD then the thrust will be in speed mode and it will vary to maintain speed.

When the thrust mode is SPEED, the thrust is controlling the speed.

If the pitch mode is V/S, the elevators are following the selected the rate of climb or descent.

Similarly, if the pitch mode is G/S, the elevators are following the GlideSlope.

If the pitch mode is ALT, the elevators are maintaining the selected altitude.

So, the only time that the elevators control the pitch to follow a selected/managed speed, is Open Climb/Descent, SRS, CLB, and DES (idle path), and in those cases the thrust will be in THR mode (climb or idle).

Well, in SRS thrust will be in TOGA or SOFT GA.

Or in climb detent also if you do a soft go around on an A320 with no soft GA function.:)

Soft or normal GA you need thrust levers first at TOGA to trigger SRS mode. They can be anywhere after that.

. . . and in fully manual mode, out of all detents, the Airbus thrust levers work just like any other thrust lever/throttle/loud-lever. One just has to be aware of what the autothrust was commanding prior to disconnect, and what it will command upon re-engagement, lest one be surprised. My informal "test" was, if one can go from fully automatic flight to fully manual and back to fully auto again without the passengers noticing, the pilot understands the autoflight/autothrust system.

Hi sourish,

To help with your understanding of the modes, it would help if we knew a bit about your experience.

Is this your first Turbine/Jet Rating?

Is this your first rating on something with a decent AutoPilot/Flight Director system?

The reason I ask is, in the bigger transport Jets, (EJet, 737, A320,777, A330 etc) the Thrust Modes and the Vertical modes are connected, unlike the training aircraft or even smaller Jets and TurboProps.

Lots of good advice already, but to really understand the Thrust Mode, you need to understand the Pitch Mode. Re Read the first 3 answers and they will provide you with the clues you need to get your head around this.

To use some "familiar" terms.

OP CLB or OP DES = SPEED ON ELEVATOR - Fixed THRUST setting and PITCH to control the speed.

OP CLB = CLB THRUST - and the speed is set via FMGC or FCU(selected) and is maintained by the Elevator pitching the aircraft

OP DES = IDLE THRUST - and the speed is set via FMGC or FCU(selected) and is maintained by the Elevator pitching the aircraft

SRS, V/S, CLB, DES, FPA, ALT, ALT*, ALT CRZ, ALT CST *, ALT CST, G/S*, G/S, FINAL APP and FD's OFF = SPEED ON THRUST - Fixed PITCH and THRUST to control Speed

(I think I got them all?)

In all these modes the aircraft pitches as directed, eg: 1500fpm and the thrust is adjusted to maintain the Speed set by the FMGC or manually via the FCU.

-EXCEPT-

CLB is basically the same as OP CLB = Max Thrust and Pitch for Speed but it will conform to ALTITUDE constraints so can shallow out the climb and reduce the thrust to maintain a speed.

DES is a 2.5º path at slightly more than IDLE thrust and will also conform to ALTITUDE constraints. DES also has the ability to go 20kts faster or slower to maintain the path and/or increase/decrease thrust as required to stay on the Path.

It is difficult to visualise, but have a search around on Youtube and you should be able to find some videos of the aircraft in action. It will make a lot more sense once you see it in action.

Good luck and have fun.

As a side note, the fact that the thrust levers don't move is immaterial, you get ALL your Thrust information from the FMA, ASI and N1 gauges. (I have flown 3 types of jets with movable thrust levers, and 1 without, you never set thrust from the position of the thrust lever in the quadrant in flight. eg: Power (N1) + ATT = Performance)

I find that quite often, people forget all about this thrust mode. It's the most versatile mode, as I can maintain a set speed, path or power setting in this mode.:)