V speeds calculations

Guest Discussion
1

Inspired by my upcoming Commercial checkride, I’ve been working on improving the precision of my flying. I’ve been having problems with float in my practice spot landings, and I think this is because I’m not modifying my final approach speed based on my actual operating weight. I believe the 77 kts recomendation for short field landing is at max gross. Since 77kts is 1.3 x Vs0, that suggests that landing single pilot with minimum VFR fuel reserves (2519 pounds in my plane) the Vref would be only 67kts. Using an appropriate figure when light has solved my float problem.

I’m working on a table of key Vspeeds for different weights. I’ve characterized the plane as min fuel, fuel to tabs, or full fuel, and single, dual or max gross. I’ve filled in all the figures I can from the POH or extrapolations. I’ve stuck this table into my checklists.

I’d appreciate it if anyone has comments on what I’ve got, or can figure out how to fill in the blanks I’ve left. I’m especially baffled by the BestGlide figures; I still don’t know why it doesn’t scale with Vs0 as in other planes. Anyway, the table I’m now using is quoted below:

CIRRUS SR22
Max Gross
Dual Full Fuel
Dual Fuel to Tabs
Dual min fuel
Single Pilot Full Fuel
Single Pilot Fuel:Tabs
Single Pilot VFR Day min fuel
Weight
3400
3145
2945
2735
2519
Vs0
59
57
55
53
51
Vr
73
71
70
69
68
Vy SL
101
97
94
91
87
Vy 10kft
95
91
88
85
82
Vx SL
78
Vx 10kft
82
Vx0 SL
91
Vx0 10kft
85
BestGlide
88
Vfinal
80
Vref
77
74
72
69
67
Va
133
128
124
119
114

-Curt

2

Though my aeronautical knowledge is too limited to say anything much on your work Curt, it looks good!
Has anyone done similar for SR20?

Cheers
Tony

3

I could email you the spreadsheet. Most of it operates just on the MAX GROSS figure and the POH V#'s entered in the first column. The exception is the Vr row, which is a formula that extrapolates based on the 3400# and 2900# numbers in the POH.

Usual caveats apply–the POH is the only source of #'s that you should use to fly your aircraft.

-Curt

4

I just looked at the SR20 POH and now I’m even more confused. The SR20 POH (online version) gives 95kias for 2900 pounds and 87kias for 2500 pounds. The SR20 makes sense given a V ~= sqrt(W) relationship. So you could use the same formulas I have for Va and Vs0 for Best Glide on the SR20. It just doesn’t work for the SR22. [:S]

That means the explanation William got from the FAA guy doesn’t cut it. The only aerodynamic difference I can think of is the vortex generators. Could they have this effect?

-Curt