In a Cessna 172 flying VFR on long final, when do I extend flaps to 10, 20, and 30 degrees?

Question

At the pilot-controlled airfield I use most frequently, we fly a standard rectangular pattern.

The normal-landing C172 flap sequence goes

1. Downwind: 10 degrees past the “abeam point” and airspeed in flap range
2. Base: 20 degrees
3. Final: 30 degrees when assured of making the runway

When making occasional landings at a nearby Class C airport, ATC sometimes puts me on vectors resulting in a long, straight-in final. In relation to such an approach, when do I extend flaps to 10, 20, and 30 degrees?

Answer 1

Here's what I do in a straight-in: fly it at cruise speed, and at 4 miles out, set power for final approach speed (you do know what that is, right? usually 15-17" or 15-1700RPM in a light aircraft; also, some engines need to be cooled more slowly than going straight from cruise power to approach power).

As the aircraft slows down, keep trimming the aircraft to stay on the VASI, and as you slow to Vfe for the different flap settings, bring those flaps in.

Full flaps should be in no lower than 500AGL for a stabilized approach.

You can adjust the 4 miles to suit your preferences and conditions (slow or faster, depending on skills, wind, and traffic).

"Full flaps when the runway is assured" is a rule of thumb. More important is to not make any configuration changes (flaps, trim, gear, speed brakes) below 500AGL in VFR.

If you learn how to do this, you will fit in with lots of different kinds of traffic, and you won't have the Baron on downwind have to fly 5 miles out because you're doing 60 on long final.

This skill is also worth learning because it you will have a mastery of the landing process and get you out of the slavish "do this, then do that, then do that" type of flying

Good approaches make good landings!

Answer 2

I visualise the standard lengths of the pattern and pretend I'm simply doing them in a straight line.

I'm sure you could figure out precise lengths or time intervals if you wanted to, but ultimately in a 172 in VFR you don't need to be exact - you just need to be fully configured and established by the usual point on final approach, as if you were completing a circuit.

The trap many people find with a straight-in approach is they leave everything too late - downwind checks, flap, etc. Make sure you allow enough room for about 15-30 seconds between flap extension, otherwise you'll find it difficult to maintain the approach angle.

As with everything, a good straight in approach takes practice!