Cruising .89

I am flying a 787 - 9 from Abu Dhabi to Tokyo right now. Because I am time restraint I am cruising at .89 Mach. According to specifications from Boeing the Dreamliner can handle this in a realistic scenario. my only fear is if I leave the auto pilot on for an extended amount of time I could get a tailwind and bump above .90 over and over again and pile up violations. Is this a possibility, should I be scared?

M.089 is on the brink to overspeeding. I would strongly suggest NOT using it.

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Maybe next time, fly a shorter route 😬 ?

In the meantime, maybe slow down to 0.87-0.88, or you could take the risk (highly discouraged).

You are the pilot, so obviously the decision is yours.

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Do you think .88 is safe?

Do you mind telling me what the current winds are like? And your current location, please.

Just to let you know, the typical cruise speed for the 787 is about M.084 - M.086, why do you need to take it to the limits?

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I have a wind coming diagonally from behind me around 38 knots. I am flying over Pakistan right now

I looked up all the limit information, I’m within its limits but I have an obligation tomorrow at 9 so i want to land before it

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Yeah, as you enter India and then China, the tailwinds pick up, according to windy.com. I wouldn’t risk it if I were you.

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Ok i will go to.88. Thank you

I’d also like to point out that cruising faster uses more fuel than normal cruise speed.

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Thank you, I also took that into consideration but I bought enough Reserve fuel

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I decieded to go back to .86, its more realistic and less dangerous

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Mach number is a function of how fast air moves over the wing, so a headwind or tailwind won’t change your mach number. Like others have said, don’t cruise so fast. You only lose a few minutes by going faster anyways.

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Was about to say that, wind doesn’t affect mach number in any way.

In this case my advise probably isn’t the one to listen too, but I would regularly go up to the aircrafts published limit, and never had any problems 🤷🏻‍♂️

Not that you should though… 😂

Didn’t IF change the speed limit for violations down to M0.87?

But couldn’t it push my plane faster meaning that I would be above .90? Like basic physics

The autopilot will maintain the airspeed which is what it would give you violations for, now depending on winds your ground speed may fluctuate dramatically, but your airspeed and Mach speed should all be relatively stable…

It could push you faster, but that will change ground speed not mach number.