A330-300 maximun airspeed limit serious bug

About one month ago I was received some violation for over speed when flying with A330-300. Problem was that in cruise flight on AP with speed 5kts close to max speed I have in one second about 10-15kts over speed. I try to slow down but was very slow reaction. But how it is possible? I was not sure, I spend some time on low grade than return to Grade 5.

Today I was made another flight with A330-300, I need to fast move this aircraft for about 1h flight so used low FL260 and fast speed to reach destination ASAP. And what happened? In cruise flight stabilized flight about 30 minutes from TO I heard alarm for over speed. My reaction was fast and I find the bug. Maximum airspeed was not stable in stable condition. So this is bug and must be repaired otherwise everybody can receive lots of violation.

What I find? After TO and climb to FL260 you can see max speed limit around 344kts. But randomly this maximum drops to about 339kts so if you select 340kts as your cruise speed you will receive lots of violation on long haul flights.

Because nobody understand this problem so one more time: This time was difference only 5kts, in my previous experience was 25-30kts change. Please understand that problem is not AP and/or winds, problem is that maximum speed limit changed for 30-60 seconds than moved back. All in stable cruise flight, no climb no descend. No altitude change. I am sorry I have no pictures from 25-30kts change because I was so shocked by this bug.

You’re kissing the speed tape, a little gust of wind and you’re over speeding and as a result you receive violations. Fly at a safe speed well below the speed tape, there is no need to fly so fast and push the aircrafts limit.


Autopilot is not precise. It does not keep your speed exactly on the speed set. It keeps it as close as possible. Winds, vertical speed and turbulence can easily change the speed.

I recommend you set your speed between 280kts - 310kts below FL300
And M0.80 - M0.84 above FL300

OK, so flight less 35kts for sure? Please read again my post.

This isnt a bug, as mentioned for the above reasons which I’m not going to repeat.

Your cruise speed is way too fast, a suggest the only bug here is a lack of knowledge in the aircraft you’re trying to fly.

A typical cruise speed for the A330 is M0.82, give or take 0.1. Your hour flight, remaining at FL260 and going as fast as you can is ridiculous. The higher you are, the quicker your ground speed is - in theory. You’re obviously basing this on favourable winds and what not. You should be planning your time limited fights based on information you know. I recommend anything around the 500nm Mark is a good hour flight.

Please, if you need help just ask for the information. I am open to a DM to discuss the A330 which is a favourite aircraft of mine, to discuss the above in more detail.


This has nothing to do with the problem.

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Never climb with more than 1500ft per min above 18000ft agl, I climbed with 2500 and was away for a couple of min and at that point it already stalled and I got 4 violations.

So I reread your post and you said that the speed tape went down as you climbed in altitude. This is not a bug and is normal and is basic science and common knowledge, in the higher altitudes your speed is based on Ground Speed (GS) not Airspeed, as you climb higher and higher the air is thinner and thinner.

This is not a bug, 345 knots for an airliner at a high altitude is way too fast and no wonder you received violations. 345 KIAS At FL260 is M.87, that is way too fast for the A330, no airliner on this planet goes that fast in cruise, slow down!

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How does it relate to this problem ??? I am in cruise stable flight, no climb.

Sorry, I am not stupid as you maybe think. I posted bug, not maximum speed change against flight levels.

So you think if you are in FL400, IAS for example 250kts and maximum at 260kts changed in seconds to 230kts all is absolutely ok? I think that not, sorry.

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If you wish to discuss this further, feel free to PM me.