"I fly a C172 but have lots of time in faster airplanes. I got into the habit of flying IFR approaches at higher airspeeds, so I still do that. When do you suggest pulling the power to slow to below VFE (maximum flap extension speed) in order to add flaps?"- Cary A.
“A couple of considerations apply here. First, to use Category A minimums you should be flying the approach at less than 90 knots.
Ideally you want to set and maintain this speed before descending on the glide slope. A stabilized approach always works out better.
My experience has shown that most light airplanes including higher performance singles – Money 231, C182, C210, etc. – can fly the approach at about 90 knots with approach flaps set. If you want to fly faster it is your choice, then you should use Category B minimums, however.
Regarding your C172, it probably will fly the approach effectively with no flaps at approximately 85-90 knots.
Decision Altitude on an ILS is reached about ½ mile from the runway threshold at about 200 feet (or maybe a little more). If at flap speed, this allows for progressive application of flaps for a full flap landing.
On a non-precision approach, MDA may be reached some distance from the runway. At approximately 400 to 700 feet AGL, it’s not a good idea to reduce power below that required to maintain VFE of about 85 knots for your airplane. When the runway is in sight and you are sure you are in a position to land, begin deploying the flaps and start your descent while reducing power. This is especially important in the case of a circle to land approach.
The control of airspeed relative to VFE is the secret. Excessive speed and the inability to deploy the flaps creates an overrun exposure for you. If you are landing at an airport with higher speed jet traffic, it is a good idea to let ATC know your intended speed on the approach so that they can provide proper spacing.”
Watch this Instrument Approach scenario video.