The rotating index on the airspeed indicator (that activates the fast/slow needle on the PFD) appears to stop at 250 knots. I’m pretty sure it will rotate all the way to the top of the airspeed scale on the actual instrument.

Currently, the fast/slow needle works very nicely below 10,000 feet where the aircraft is limited to flying no faster than 250 knots, but at Mach 0.80 cruise at higher altitudes, the IAS will normally be higher than 250.

15 minutes ago, JRBarrett said:

The rotating index on the airspeed indicator (that activates the fast/slow needle on the PFD) appears to stop at 250 knots. I’m pretty sure it will rotate all the way to the top of the airspeed scale on the actual instrument.

Currently, the fast/slow needle works very nicely below 10,000 feet where the aircraft is limited to flying no faster than 250 knots, but at Mach 0.80 cruise at higher altitudes, the IAS will normally be higher than 250.

I always thought this speed indexer was most useful at the lower speeds, such as during an approach where it helps to limit your scan requirements (don't need to check the airspeed indicator as much). The higher your speed, the smaller the percentage change represented by + or - 10 knots.

Al

Yes, I use it all the time in the sim during approach, and also during initial climb, to show when approaching the speed where slats need to be retracted.

But, it’s pretty useful in level cruise too, since power is controlled  manually. It will show any trend towards speed increasing or decreasing from the desired value with better visual resolution than looking at the pointer on the airspeed indicator.