Speed limit?

Hey I’m on expert server flying a 787-8 from KSAN to KSFO. I always thought that the speed limit was 250 knots below 10,000 and 350 knots about 10,000. (Airspeed). Well that’s what I’ve always done and I don’t get violations for it. Well I was cruising at 20,000 and was at 349 knots to avoid the annoying warnings. I wanted to climb to 36,000 when I was over KLAX so I did. While climbing, I got a speed violation warning and my speed cruise control switched to Mach. It wanted me to stay under m.90 or 280 knots. Why did it randomly change my speed limit?

Because the higher you climb above 28,000 feet, the speed limit goes down.


It goes down due to thin air, I think.

No. It’s not an issue with the app.


Climbing to high levels in an airplane the IAS goes down and your Mach number goes up.

Initially you will fly speed in knots and you will see the Mach number going up, from the moment the AP speed control goes from IAS to Mach you have to follow Mach. When flying a fixed Mach number the higher you go the lower your IAS will be but depending on the wind your GS will increase normally.

Staying below the red barber pole for the overspeed all would be fine.


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