Peter Duniho writes:

Flaps enhance lift at the expense of drag. On a small airplane, large
complex flaps would not produce a significant enough reduction in drag
during cruise flight to justify the cost, complexity, and weight.

However, the larger and faster the airplane, the more there can be
accomplished by reducing drag significantly during cruise, especially
compared to the airfoil required to land such planes safely and within the
runways available to them (generally no longer than a couple of miles or
so).

You could land a 747 without flaps, but you'd use a LOT more pavement (maybe
double?), runway length that just isn't available. On the other hand, you
could design a 747 with an airfoil that allowed for shorter landings, but
cruise speed would suffer. The airplane is large enough and fast enough
that the extra expense and weight of flaps more than makes up for its cost
during cruise, while still allowing for reasonable landing performance.

Thanks. That makes sense.

Hopefully this one example has answered the general question of "why do
large airplanes have features not found on small airplanes?" You could
spend months asking that same question, using different features, and the
answer would always be the same: economics and usefulness.

You're saying that there really isn't any technical, aerodynamic
reason why a large aircraft would require extensive flaps while a
small aircraft would not? That is, the advantages and disadvantages
from a flying standpoint are the same in both cases?

I know there are economic considerations, but since small private
planes seem to handle quite differently from large planes I was
wondering if there are fundamental differences in the aerodynamics
that might be related to scale (physical dimensions). That is, would
a giant version of a small plane, three times as big but with
identical proportions and size-to-weight ratio, fly in the same way?

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