PART IV-HANDLING
is investigated with care until pilots are aware of the
high speed characteristics.
(b) Clean aircraft or with RP's
At high altitudes the first sign of compressibility is given
by a slight lateral rocking at about 0.78M. At this speed
there is generally slight airframe buffet and the ailerons
are very sensitive. Compressibility effects are, however,
not marked, but as speed is further increased porpoising
commences reaching a maximum at 0.84M giving con-
siderable stick force as the nose rises. Below 20,000 ft.
the symptoms are similar but occur at slightly lower
mach numbers and are less marked. When flying with
RP's the high mach number characteristics are similar,
but become apparent at lower speeds. At high indicated
airspeeds the controls become noticeably heavier, and the
aircraft must be trimmed into the dive.
(c) With drop tanks or bombs
The onset of compressibility is denoted by lateral un-
steadiness at about 0.74M and may be accompanied by
rudder buffet. As speed is further increased a general
airframe buffet becomes apparent. When 1,000 lb.
bombs are carried there is a noticeable aileron buffet and
increased lateral rocking. Porpoising commences at
about 0.76M. Lateral rocking and aileron buffeting is
also encountered at indicated airspeeds in excess of 360
knots when aiming 1,000 lb. bombs.
(d) Recovery
Recovery is effected by extending the airbrakes and
throttling back. Use of airbrakes at high mach numbers
or airspeeds produces a sudden nose-up change of trim
and an increase in general airframe buffet. When drop
tanks are carried the airbrakes are not to be extended
above 0.70M.
CIRCUIT PROCEDURE AND LANDING
73. Circuit procedure
(a) Join the circuit with sufficient fuel for a landing and
possible overshoot, i.e. approx. 450 lb. Select the correct
V.H.F. frequency and unmute. Airspeed should be54
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