From: wisch@Apple.COM (Ed Wischmeyer)
Newsgroups: rec.aviation
Subject: C172 stalls in slips, airspeed changes, etc.
Date: 27 Jul 92 20:30:07 GMT
Organization: Apple Computer Inc., Cupertino, CA


Cessna 172 Flight Test Results

On Sunday, I went out and rented a Cessna 172 to investigate stalls out
of slips, climb with full flaps, etc. Due to the last minute decision to go,
and due to one too many house cleanings, I could not contact the two netters
who had expressed interest in going along. Sorry.

The aircraft was N4682G from West Valley Flying Club, and had a 40 degree
flap setting. Fuel at takeoff was about 3/4, with 200 pound of pilot up front.

Airspeed variations in slips:

With flaps up, at three different starting airspeeds, power off, I flew
straight, slip to the left, straight, slip to the right, and back to straight. The purpose was
to investigate airspeed variations in slips. Granted, it is quite possible to
go from glide to a nose high or nose low slip, so this is as much a measure of
pilot technique as anything else. However, the slips left and right were more
or less at the same pitch attitude, so the airspeed differences between left
and right slips are significant, although the differences between slipped and
straight may not be. The airspeeds in straight flight were recorded to show
any tendency to vary pitch attitude during the sequences. 62 KIAS was chosen
rather than 60 as it was full nose up trim.

All speeds KIAS
Straight  Left  Straight  Right  Straight  Right - Left
62         54    64        64     64           10
70         65    72        76     72           11
80         72    79        78     78           6

This clearly demonstrated a noticable decrease in indicated airspeed 
in a left slip with the single pitot source on the forward left fuselage, but
surprisingly, with the pitot source on the "downwind" side of the fuselage
in a right slip, there was comparatively little effect.

Stalls out of full slips:

Holding heading with the rudder, I banked the aircraft until running out of
rudder, and stalled it power off with this sideslip, with different flap
settings. All stalls were benign, with no tendency to wake up the sleeping,
and no tendency to go over the top. Generally, stalls were preceded by light
buffetting, and rolled off gently into the direction of bank.

       Left bank    Right bank
Flaps  KIAS Bank    KIAS Bank (degrees)
0       48   5       57   5
10      42   5       50   6
20      41   3       49   6
40      35   3       38   4

The ability to slip more to the right (ie, greater bank angle) was attributed
to P-factor giving addition effective left turning force. In other words, the
P-factor, even at idle, gave the same effect as left rudder. I'm not sure if
I believe this or not.

Rate of climb with full flaps:

Rather than do a careful timed climb, I just let things stabilize and then
read the vertical speed. At 2000 MSL, with airspeeds of 50, 55, and 60 KIAS,
I saw 400 ft/min at all speeds. At 4000 MSL, at 60 KIAS, I saw only 200 '/min, 
half of the rate at the lower altitude, and at 65 KIAS, 150 '/min.

Pilot proficiency and technique:

Pilot proficiency was good commercial/instructor level, but with little
or no recent time in the C-172 for a really accurate assessment. Pilot time
in Cessna 172 and 172RG, total, was about 400 to 500 hours. Instruments were
"as installed," with no special calibration. Each maneuver was done once,
with no practice or warmup. However, most bank angles in stalls should be
within one degree, and airspeeds should be accurate to about 2 KIAS.

Ed "test piloting is dull work" Wischmeyer
Newsgroups: rec.aviation