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Influence of Loading Condition on Piloting Technique for Spin Recovery for Pursuit Airplanes

SUMMARY

_Eeoent information as to the influence on spins and
spin recovery of the wing leading and load distribution
of present—day pursuit airplanes is discussed for the
guidance of pilots. It is pointed out that high wing
loadings and rearward center-of—gravity locations make
for more difficult spin recoveries. The high wing load-
ings also result in high rates of descent and large con-
trol forces for recovery. The pasition of the ailerons
may have a considerable effect on both the steady spin
and the recovery. The optimum position of the aileron
depends on the relative weight carried in the fuselage
and along the wings and may change with the expenditure
of load in flight. Unless conditions for a particular
airplane are completely understood, therefore, care
should be taken to maintain the ailerons neutral.

INTRODUCTION

Reference 1 gives an adequate discussion of general
piloting techniQue for recovery from spine and should
prove invaluable reading for all pilots who may have oc-
casioa to recover from spins. Since the publication of
reference 1, however. there have been changes in airplane
design as well_as increased experience in spinning, both
in flight and in the freemspinning wind tunnel. for mod»
ern pursuit or fighter airplanes. for example, the over-

_ all size and weight have greatly increased and, with the
installation of numerous wing gunc, the percentage of the
weight carried in the wings has aLeo increased. The pur-
pose of the preeent paper is to restate some of the points
made in reference 1 with a change of emphasis occasioned
by consideration of the high wing loadings and load dis-
tributions of preeentrday pursuit airplanes.
Only upright spins have been considered. as these
spins represent the type most commonly encountered. In
the spin tunnels. inverted spins appear to present little
difficulty as regards recovery characteristics. Diffi-
culties encountered in flight with inverted spins are be-
lieved largely attributable to the awkward position of
the pilot. the difficulty of applying full control deflec-
tions. and the confusion resulting from the inverted posi—
t on.

A good deal of the information summarised in the
present paper is based upon detailed discussions given
in references 1 to 5. Other papers of fundamental inter-
est with regard to spinning are references 6 and 7. '

EFFECT OF WING LOADING

One noteworthy recent design trend has been the in—
crease of the airplane weight supported by a given wing
area. A systematic investigation carried out in the spin
tunnel has indicated that as the wing loading is increased
the spins tend to become flatter. the rate of descent
higher, and the recovery slower. For the designer, the
layout of a tail giving satisfactory recoveries becomes
more difficult with these increased wing loadings.

For the pilot. even if the tail arrangement is ade—
quate. the higher wing loadinge'will be associated with a
higher rate of descent during the spin and a greater alti-
tude loss during recovery. Some'of the increase in the
rate of descent as compared with older designs is attribr
utable to the increased cleanness. For fully loaded pur—
suit airplanee, rates of descent of 200 miles per hour at
10,000 feet (equivalent to 18,000 ft/min or an indicated
airspeed of 170 mph) should not be unusual.. At this rate
the altitude less per turn is about 650 feet (6500 ft for
a 10-turn spin). With allowance for the entry and recov—
ery. deliberate spins should not be started at less than
15,000 feet. -

In connection with the suggested minimum spinning
altitude of 15,000 feet. it is of interest to note that
an increase in altitude increases the difference between
the densities of the airplane and the air and has much
the same effect on the spin as an increase in wing load-
ing. Recovery thus becomes increasingly difficult as the
altitude is increased,-