Model Forum / General / Models / July 2007

Considering its STOL capabilities, I suspect around 60 degrees.
The Cessna L-19/O-1 Bird Dog had 60.

I spent about 20 hours in a Beaver back in 1970 and I recall full
flaps looking like the wing was folded in half. I would be very
comfortable with 60 degrees for full flaps.

Enough to cause a crash if you didn't know what you were doing:
http://www.tsb.gc.ca/en/reports/air/2004/a04c0098/a04c0098.asp

"The DHC-2 Beaver aircraft flight manual contains the following
information about the use of full flap. Section 1.12.3 states that "FULL
FLAP is only required for emergency landing in very restricted areas."
Section 2.14.1 states that "Minimum run landings may be necessary under
extraordinary circumstances. Pilots familiar with the aircraft and
experienced in short landing technique may perform minimum run landings
by using full flap and reducing the airspeed on the final approach to
65-68 mph and maintaining that speed to the point of flare-out."

The short landing technique, as described in the aircraft flight manual,
requiring the use of full flap, increases aerodynamic drag significantly
and places the aircraft in a steep, nose-down attitude. The aircraft
buffets from the interaction of the flaps and airflow. Reportedly, the
pilot had received no training in short landing technique in previous
employment flying the Beaver, nor was there any record of such training
or experience. The pilot had flown only one training flight at Pickerel
Arm Camps, and that training did not include short landing technique.

Analysis

The most likely scenario, based on the damage to the aircraft and the
bank and impact angles, is that the aircraft experienced an aerodynamic
stall on final approach.

The size of the open-water area and the weather conditions at Fawcett
Lake would not have required the pilot to use a full-flap configuration,
which is specified for use only in an emergency landing in a restricted
area. However, the pilot selected FULL flap during the approach; the
reason for the selection could not be determined. While the pilot was
familiar with the aircraft type, training in this type of approach had
not been conducted recently, nor was there any information found to show
prior experience.

During an approach with full flap, a steeper-than-normal nose-down
attitude is required to maintain the required airspeed and, combined
with engine power, the approach path. Any shallowing of the approach
angle would bring the aircraft closer to the attitude that was normally
seen by the pilot during the final stages of an approach without full
flap. However, because of the drag at the full flap setting, there would
be a more rapid reduction in airspeed than on a normal approach, unless
significant engine power was added.

The full nose-down position of the elevator trim, consistent with the
aft C of G, indicates that the pilot may have been holding the elevator
in position with forward pressure on the control yoke to maintain the
desired approach path and airspeed. Any distraction could result in the
pilot relaxing the pressure on the control yoke and would result in a
shallowing of the approach angle. The heavy weight of the aircraft would
increase the stall speed. The pilot, without training in approach and
landing with full flap, may not have been aware of the nose-down pitch
attitude necessary to maintain the approach airspeed and the requirement
to maintain this pitch attitude until immediately prior to initiating
the landing flare. The additional buffet from the full flaps may also
have masked some of the aerodynamic stall characteristics. These factors
may have contributed to the pilot not recognizing the impending
aerodynamic stall. When the stall developed fully, the wing dropped
violently at an altitude that was insufficient for the pilot to recover
the aircraft."

Pat