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National Advisory Committee for Aeronautics, Technical Notes - Characteristics of Two Sharp Nosed Airfoils Having Reduced Spinning Tendencies

According to Mr. L. D. Bell, of the Consolidated Air-
craft Corporation, certain undesirable spinning character—
istics of a commercial airplane were eliminated by the ad—
dition of a filler to the forward part of the wing to give
it a sharp leadingI. edge.. To ascertain what aer_ody_namic ef-
feet-s resnlt fromI such_ a change of" section, two airfoils
having sharp leadingI edges were tested in the variable—I"'
dens_ity wind tunnel. BotIh sections were de‘rived 'o'y modifyk
ing the Ghttfi 3981 The tests. whi.ch were made at a large'
value of the IReynolds Number, wer,e carried tIo very 1argeI'
angles of attack to provide data f.or applicIat ion to flighIt
.at angles of attack well bevond the stall.

The characteristics of the sharp—nosed. airfoils are.
compared with those of the normaIl Gott. 398 airfoil. IBoIth
of the sharp—nosed airfoils, which differ in the Iangle be—
tween the upper and lower surfaces at the leading edge,
have about the same characteristics. As compared with the
normal airfoil, the maximum lift is reduced by approximate—
ly 26 per cent, but the objectionable rapidly decreasing
lift with angle of attack beyond the stall is eliminated;
the profile drag of the section is slightly.reduced in the
range.of the lift coefficient between 0:2 and 0.85, butIat
higherIand lOwer lift coefficients the drag is increased”

According to Mr. L. D. Bell of the Consolidated Air—
craft Gorporation, certain undesirable spinning character—
istics of a commercial plane were eliminated by the ad—
dition of a filler to the forward part of the wing to give
it a. sharp leading edgeI the- modification having been first
suggested to him by the effects of a deposit of ice.’ Ace.
cordingly. Lt. Comdr. Diehl. through the Bureau of Aero-
nautics, Navy Department, requested the National Advisory
Committee for Aeronaut'ics tb'investigate, by tests in the
variable—density- wind tunnel, the characteristics of two
such modifications of the Gott. 598 airfoil. The tests
were made in November, 1931.? The re'sults are presented
in this note together with the results of a test of the
normal.

Attention is also called to another investigation of
the effects of nose shape, the results of which have re—
cently been published (reference 3). consisting of tests
in the variable-density wind' 'tunnel of nine symmetrical
airfoils-having different leading edge radii.