A320: "Thrust Idle"

[vilas]

SpeedFreak

in the end fly the descent that makes you the happiest,
Is this your company SOP on descent? Also in your 6 monthly route check do you descend the same way as you mentioned?

[clark y]

Cobravila, in my experience the Idle performance factor on the status page (as per WhyBeFlier's post) is an important part as to wether the descent profile is accurate. The company I fly for has IAE powered A320s and A321s. In the past on a managed descent the A320s were always slow and the A321s were good. The idle factor was changed across both types. the result was the A320s good and the A321s always ended up way too fast. The company fixed the A321s idle factor and they began reasonably good.
Another issue I find is that on the A320 is that when you modify the descent speed on the performance page (before descent starts), if you you use 280kts, it flies the managed descent at a reasonable 280kts. If you try it with 320kts, the managed profile will usually end up requiring a speed of 340kts.

[Sue Ridgepipe]

The idle segment assumes a given managed speed flown with idle thrust plus a small amount of thrust. This gives some flexibility to keep the aircraft on the descent path if engine anti-ice is used or if winds vary. This explains THR DES on the FMA.

The thing is, it can still say THR IDLE on the FMA and have 45% N1, it doesn't always show THR DES as the FCTM suggests. In fact now that I think about it, I don't think I've ever seen THR DES displayed on the FMA.
So THR IDLE on the FMA is not necessarily idle thrust, you need to look at the EWD to see what's going on.

[dkz]

THR DES is a 330/340 thing, there is no THR DES a/thr mode on the 320 ...

[Sue Ridgepipe]

Thanks for clarifying that dkz I thought that might be the case, it's just a bit confusing when the A320 FCTM has a couple of references to THR DES in it.