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Using Flaps

Generally speaking, your landings should be stabilized approaches terminating with wheels touching the ground in a nose-high attitude at the slowest possible forward speed.  If there is one sentence in this entire article that one was the most important.  Maybe its worth reading again.

Generally speaking, your landings should be stabilized approaches terminating with wheels touching the ground in a nose-high attitude at the slowest possible forward speed. With that said, full flaps are used and set while as you finished turning final.  Every airline captain knows the importance of using full flaps on landing, and as a ritual, so should you.

There are always exceptions to the rule.  When you chose to use less than full-flaps its usually because the situation calls for a higher than normal approach speed.  A higher than normal approach speed increases risk for a variety of reasons including longer runway length required and controllability concerns. Valid reasons to use less than full flaps include:

1. Practicing partial-flap and no-flaps landings.  Should you even attempt this?  Certainly. What happens if your electric flaps fail?  What if they are jammed shut?  Flaps reduce stalling speed, so remember to use a higher than normal approach speed when practicing partial and no-flaps landings.
2. Gusty conditions and wind shear: these conditions suggest a higher margin between normal approach speed and stall speed.  Remember the rule of gust: increase the approach speed by half of the gust factor.  For example, gusting 10 knots above published winds means add 5 knots to your approach speed.
3. Strong crosswinds: i.e. 40-100% of max demonstrated crosswind component.  Not only will controllability be increased on the approach, control surfaces on the empennage will not be appreciably affected when using partial flaps with strong cross wind components.
4. Icing considerations:  particularly when you are at high risk of tail stalls or increasing that margin between approach speed and stalling speed.  See the Articles section for more information on icing considerations.
5. Slips to landing:  In some aircraft slips with full flaps is to be avoided.  The reason for this is the disturbed airflow from the wings washing the horizontal stabilizer.  This disturbs the downward lift of the horizontal stabilizer and can cause a tail stall.  This is typical in high wing aircraft at greater than 30 degrees of flaps.

Some folks believe that a strong headwind directly down the runway might be a reason to use less than full flaps.  Remember your goal is to land at the slowest possible forward speed.  Strong headwinds reduce ground speed not indicated airspeed.  Remember that your landing profile is based on indicated airspeed, not true airspeed or ground speed.  If you have gusty, headwinds, then see bullet #2 above.

Other folks believe that high density altitude conditions require less than full flaps. In these circumstances you are probably going to use more runway.  Using partial flaps increases approach speed which will cause you to use even more runway.  Remember that your landing profile is based on indicated airspeed, not true airspeed or ground speed.

One Final Point.  Check your POH.  Particularly read the notes on flap usage, crosswind landings, icing, and performance data on landing distance.

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