Approach Speed

Considerations on approach airspeed and configuration...

Approach flaps or not?

With Flaps Pros:

• Steepens approach without increasing airspeed
• Lower stall speed
• No configuration changes down to touchdown
• No big trim changes to touchdown

With Flaps Cons:

• Reduces max load factor to 3.3 (4.4 with flaps up) (though at approach speeds load factor is unlikely to be exceeded)
• Slower approach (may not have the option at busier airfield)
• Adds to Missed Approach workload (control forces and clean up chores)

Flaps Up Pros

• Approach speed can range from 78 to 110 (depending on circumstances) with power only change required for descent rate management
• Easier transition to Missed Approach
• Airplane can be configured for landing once MAP point is reached and field is in sight (drop full flaps) -- airplane will slow and still remain on glidepath

Flaps up Cons

• Transition from Approach phase to landing phase requires configuration change (flaps down, trim adjustment, airspeed adjustment)

There are four priorities on any approach: keep the stick(s) aligned, keep the airplane under control, be able to land at the end, or be able to go around if the runway environment is not visible.

Airspeed really shouldn't affect the first two (at least not the ~20 knot range we're considering). This the airspeed decision should be based the tradeoffs between landing safely and going around as safely. The problem with a missed is that it's usually somewhat a surprise, requires a significant PAC transition, and leads to more decisions and flying. The landing requires a transition from instruments to visual, and airspeed reduction.

So the question becomes: what is the optimum configuration that will require the least workload for either eventual outcome?

Though our preference and expectation is landing, we have to temper that with the possibility of a missed -- as much as we fly an approach to land, we have to fly every approach as if it may result in a missed.

My option in the Bonanza are gear down and 0, 15, or 30 degrees flap. If I fly the approach with no flaps, then I need to drop two notches of flaps sometime after establishing the runway and do the required trimming. 15 degrees reduces this by one.

I don't think full flaps is a good option for approach as it requires too much power to maintain the relatively shallow glideslope.

So, what I'll do is go up to altitude and try with and without, and then go fly some ILS approaches and see what PAC is required for each as well as what the missed entails.

The other airspeed consideration is timing -- the charts give us the exact time to the MAP given 60, 90 and 120 KIAS. The closer I can be to 90 kts GS the better.