Noticed Something Interesting About the FBW A320

Discussion Hub Aircraft
1

So after removing my previous Experimental version of the FBW A320 mod to download World Update 4, I downloaded the latest version of the experimental A320 build. After doing so, I’ve noticed something interesting.

Before the update with my previous experimental build (the first with custom AP), when my power was set to idle, my engine ECAM display showed 19% when my throttles were set to idle. After removing that build and downloading the most recent build I’ve noticed now that at idle power, my engine ECAM display shows 24%. Now that big of a deal I’m sure it seems.

However, something else I noticed that is different between both builds is taxiing. Before the update, I needed just a slight bump of thrust to start moving and then I could return to idle (or very close to it - around 21-22%). This kept my taxi speed very manageable, around 20 knots. Now with the latest version, as soon as I release the parking brake, I begin gaining speed very rapidly.

When I looked at my engine ECAM display, I took noticed of the difference in idle thrust %. From this, I’ve concluded that is the direct result of why the taxiing is different now to where it begins rolling as soon as the brakes are released.

I know that the FBW A320 taxiing behavior has been mentioned in here many times in the past, but here’s my question:
I get that the FBW mod team is trying to replicate realistic taxiing behavior and continue making the mod as realistic as possible. However, in the real A320, is idle power around 19% or 24% like in the mod. This difference is exactly what is causing the “rolling as soon as the brake are released” issue everyone has been talking about. To me, it seems like the FBE team just coded it to where idle power is slightly more than before to create this effect, but it doesn’t seem correct. Again, you real life A320neo pilots out there, please let me know if this is correct behavior and flight modeling.

On a bit of side note, I’ve continued to study this behavior with the A320 taxiing and nearly every single video I’ve come across I notice that there is some slight increase in power to get the aircraft moving on the ground. Very rarely have I noticed it just quickly accelerate to 20-25 knots with no increase in thrust.

The behavior in the previous build (just before WU4) seemed to be more realistic in this sense and it actually made taxiing a bit easier. Now, not so much…

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What experimental build? I’m using the lastest Unstable Master Branch Build (with custom autopilot).
I’m seeing 19.7% at 600ft MSL and 15°C.

Just did a few patterns at very low weight (100000lbs) and at idle the A320 didn’t move at all on its own.

Had to increase to ~22% to get it moving and when returning thrust to idle, tha speed stayed at 6kts.

Experimented by setting thrust to 24% and even in this case it took the A320 40sec to reach 25kts.
Looks realistic to me.

3

I downloaded it yesterday evening. It’s experimental version fd5dcb5 if that’s what you’re referring to (with the custom autopilot).

As you mentioned, that’s how it was for me before the update and before deleting it. Idle was around 19% and if I kept it around 21%-22%, it would keep a constant speed while taxiing, around 20 knots.

I departed most recently from KPDX (Portland, OR) and at idle thrust (24% for me) I was taxiing at 25 knots pretty quickly.

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I’ve downloaded mine 5 days ago. I’ll going to check if there’s a newer version.
IRL you don’t have to add thrust in most cases to maintain the speed during taxiing and the A320 does accelerate if you are not too heavy.
You actually have to watch the brake temps to avoid a too high value when arriving at the runway for departure!

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I’m thinking you have the same version I previously did. Perhaps there was a new version that recently came out after World Update 4.

For my Portland flight, I was loaded at 75%, so relatively heavy.

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75% load of what? Fuel and passengers? What was the actual weight?
Did you taxi in both directions to make sure that there’s no slope?

edit: just installed the new version, again 19.7%. Throttle actually at 0% ?
At 150000lbs and 19.7% N1 the A320 kept 25kts when set. (Haven’t checked for slope.)

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Did you have any Anti-Ice on?

1 Like
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Yes, both engine and wing anti ice on.

9

Why? Wing anti-ice is never used during ground ops.

(At least) on the CEO you can’t even use wing anti-ice on ground.
If you select it, it’s only on for 30sec as a test cycle.

Wing and/or engine anti-ice will increase N1 to provide the required bleed air pressure.

Turn it off, problem solved.

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Oh wow, yeah that solved my problem. Interesting. I didn’t have that issue with the previous build I had installed. Must’ve fixed that.

So then when should anti-ice be turned on, especially if you’re taking off in low visibility/fog or icy conditions?

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Well, the increase of N1 with Anti-Ice is not an issue, it’s intended…

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You don’t turn wing anti-ice on for takeoff on most aircraft.
Some A320 procedures require you to turn on wing anti-ice when the severe ice detected message comes on.

On the A320 only the three outboard slats are heated anyway and the wing doesn’t even need to be deiced for takeoff :wink:
deicing the russian way.flv - YouTube

I never had to use wing anti-ice on the 767 in 10 years.

Engine anti-ice for takeoff is used in icing conditions.