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enter image description here
Image source: fsnews.eu

I found this green arrow on the primary flight display (PFD) of a 777. What does it show? I'm assuming it's for showing acceleration and deceleration but I am not too sure. Is my assumption correct? Also, does it exist on other aircraft types?

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    $\begingroup$ Anyone else perplexed by the 30 knots and the bank? :D $\endgroup$
    – user14897
    May 14 at 15:58
  • $\begingroup$ @ymb1 According to the link you found, it's from a sim product, which is still in development. I guess they are just showing off what the PFD could display. $\endgroup$
    – Bianfable
    May 14 at 16:03

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The green arrow is the speed trend vector showing predicted airspeed in 10 seconds:

777 Airspeed Tape

2 Speed Trend Vector

Indicates predicted airspeed in ten seconds based on current acceleration or deceleration.

(Boeing 777 FCOMv2 10.10.4 - Flight Instruments, Displays - Controls and Indicators)

Other Boeing aircraft with a speed tape on the PFD (or ADI for early 757/767) have the same feature (I checked 737NG, 747-400, 747-8, 767 and 777 FCOMs). All have very similar descriptions, although the one for the 747-8 is more detailed:

Trend Indication

The tip of the arrow indicates predicted airspeed in ten seconds based on airspeed, inertial data, and winds. Rapidly changing wind speed or direction can affect predicted airspeed with no change to indicated airspeed.

Airbus aircraft also have a very similar feature, as already explained in this question: What scale is the speed trend line on a PFD's ASI?

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  • $\begingroup$ The Garmin G3X has an airspeed trend line too. $\endgroup$
    – tedder42
    May 15 at 6:13

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