While researching the Cirrus SR22 fatal accident at Arbor Vitae, WI, the tracklog has some odd ground speeds:
00:04 45.75 -89.73 163 5500 descending Minneapolis Center
00:05 45.80 -89.73 163 5100 descending Minneapolis Center
00:06 45.85 -89.74 169 4300 descending Minneapolis Center
00:07 45.81 -89.75 24 3900 descending Minneapolis Center
00:08 45.79 -89.71 56 3300 descending Minneapolis Center
00:09 45.82 -89.72 42 3200 descending Minneapolis Center
00:10 45.86 -89.73 78 3200 level Minneapolis Center
00:11 45.89 -89.73 108 2600 descending Minneapolis Center
00:12 45.92 -89.74 108 2100 descending Minneapolis Center
00:13 45.95 -89.74 108 2100 level Minneapolis Center
Any explanations for why ground speed would change from 169 to 24 to 56 to 42 to 78 to 108 over a 5 minute period? Vso for an SR22 is 59 knots, so something seems pretty odd.
I think the key here is *ground *speed. I don’t know what the winds were but it is possible that the ground speed was 24 knots if there was a strong enough wind.
Ground speeds as seen by ATC radar can be off by quite a bit when an aircraft is turning, especially at lower levels where the airspeed is lower as in a landing or holding pattern. Does this correspond with the turns he made south of ARV?
I have seen this on procedure turns where Flight Aware will update over the final approach fix (FAF) and after the course reversal, the next update will be just before or after the FAF yielding an extraordinary low ground speed time.
Don’t know if this applies to this flight, but what you say above I would suspect is the most plausible explanation.
I seriously doubt that one will find a 145 knot change in windspeed between 3000 and 4000 feet MSL
