Originally Posted by
nkt2000
You guys are starting to worry me. I have done almost all of my training in C172s and have had my license since September last year. My instructor always told me that approach speed was 65 knots and 60 knots for short field landing. Two other instructors I have since done checkouts with also concurred with 65 knots for normal landing approach. So how come this is too fast all of a sudden?
If it is too fast, where does the old addage "65, stay alive" originate from.
The POH (172P) gives a range of speeds for final approach:- 60 to 70 KIAS with 30 degrees of flap. 65 is simply the middle of this range. These speeds are at max weight of 2400lbs, but the POH does say "may be used at any lesser weight".
It is possible to calculate lower approach speeds for lower weights. The approach speed is usually around 1.3 X the stalling speed in the landing configuration. This stalling speed will itself vary with weight, using the formula : Vs new = Vs old x the square root of (new weight/old weight). Hence the stalling speed at 2200 lbs will be 0.97 x the 2400 lb stall speed in the POH. You could apply the same calculation to approach speed. You need to take some care though, since the airspeed indicator becomes less accurate at very low speeds due to position error.