Wind component

[Minuteman]

One interesting data point is "GSmini" on Airbii.

When the aircraft is following a Managed Approach Speed it will not let the groundspeed fall significantly below the value that was estimated when the performance numbers were set up in the FMS, which can be is done using the reported surface winds. If the aircraft encounters significantly higher winds on the approach, it will increase the airspeed in anticipation of a (possibly sudden) decrease in headwind as it descends to the threshold.

On days with relatively strong headwinds, the GSmini boundary can cause the actual airspeed go significantly higher than the planned approach speed.

 

[tgrayson]

it will not let the groundspeed fall significantly below the value

I'd heard that about the Airbus, but I asked at least one Airbus pilot about it and he had never heard of such a thing. It must only be on some models.

 

[HeyEng]

Not sure what tools other large airplanes have, but we have an alerting system where we load the landing winds and the INS figures the current winds. If the values differ by more than 15 knots, we get an alert, and we are required to increase the speed. Also, we increase our approach speed by the gust increment; eg 10G15, we increase our approach speed 5 knots, but only up to 10 knots total.

 

[minitour]

What difference does it make to the airplane what your groundspeed is?

None at all. But it may make a difference to you if you over-speed and blow out a tire or two.

-mini

 

[tgrayson]

None at all. But it may make a difference to you if you over-speed and blow out a tire or two.

Only a factor if you're landing with a tailwind.

 

[fish314]

Not sure what tools other large airplanes have, but we have an alerting system where we load the landing winds and the INS figures the current winds. If the values differ by more than 15 knots, we get an alert, and we are required to increase the speed. Also, we increase our approach speed by the gust increment; eg 10G15, we increase our approach speed 5 knots, but only up to 10 knots total.

When I flew KC-135's there was a similar procedure. We would calculate somthing called Minimum Groundspeed, which was the final approach speed minus the headwind component. It was mostly a factor for an anticipated performance decreasing wind shear, however. The idea was we would take our approach speed and subtract the headwind, and then compare that to get a predicted ground speed. If our actual groundspeed was less than that by 15 knots or more, we would increase our approach speed to equal the Vmin ground. That way if you went through the shear, after you lost the 15 knots, you would be back on speed. If instead the wind decreased gradually (no shear, in other words), flying Vmin ground the whole way down equated to a gradually slowing approach speed in terms of indicated.

But it had nothing to do with cross winds or gusty winds.