Sudden overspeed during cruise

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1

Hi there,

In the last couple of weeks I experienced some sudden overspeed warnings while cruising at
M0.84. The first time I had to throttle all the way to idle in order to return to the desired speed. Today it happened on a flight from EHAM to SMJP, as my tablet is always close by I heard the overspeed warning of Infinite Flight and the speed had spiked and this time returned to the normal M0.84 by itself.

Is this a known issue or does it only happen to me?

The device I’m using is the Samsung Tab S7 Plus running on android 13 and the latest security patch.

Kind regards,
Eric Welling

2

If you are in active climb below flight level 280 then your speed will not be automatically decreased as the speed limit decreases.

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3

Hi, what aircraft were you flying and at what altitude?

For example, testing the a321 just now, I am over the speed limit at m0.84 no matter what cruise altitude I try.

If you’re flying an aircraft where m0.84 is just a bit under the max speed, a sudden change in winds can push you over the limit.

4
  1. M.084 is a tad to fast for A320 series, i reccomend 0.79-0.82 in my opinion
  2. did you input a desired speed into AP and it automatically set it to M0.84 instead?
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5

The op didn’t say what aircraft. What aircraft is the question.

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6

oh i saw a glimpse of your reply saying a320 and i put a320 lol

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7

lol what? .78 is standard. .82 is absolute maximum.

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8

oh ok, thats just what i use

9

It happens only on the B777-300 ER for me. Altitude is above 37000 feet and the airspeed is around 240kts at those altitudes. The wind never is an issue when the spiking of the airspeed by at least 20kts occur. It is Infinite Flight that suddenly increase the speed, the speed setting in the autopilot stays at M0.84.

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10

Hm ok that is strange as M.04 is the regukar cruising speed. I will brb and test this out for myself.

11

I think the wind makes you overspeed.

12

No, it is not the wind. The wind increase your ground speed but not the airspeed as far as I know, it is always around 240kts at those altitudes. When it happened yesterday, flying west, I had a mild wind head on.

13

A sudden increase in headwind will cause the airspeed to rapidly increase momentarily (potentially over the speed limit) until the airplane has time to slow down again. I have had this happen to me before. My best guess is that sometimes the live weather does not smoothly blend together, and you get a large spike in headwind thus airspeed when moving between regions.

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14

Wind change increases or decreases your airspeed first of all!

15

After things settle down your IAS returns to normal, but during the transition to settling down is where you can overspeed:

So, it’s good to have a bit of a safety margin to allow for any such sudden wind shifts.

(note that an abrupt change in temperature will also cause an immediate change in airspeed, until the autothrottle responds to return to the new normal: the IAS you set, but interpreted in terms of the new temp)

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16

the ERJ 190 has a max speed of 319kts which is just below its over speed of 320kts

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