Section 7 Pilot’s Operating Handbook
Description of Airplane and Systems EXTRA 500
To prevent extending of the landing gear during an intended
wheels-up landing without battery and generator power, the
directional valves are supplied with electrical power by an
additional circuit, which is fed by the hot bus when airborne. So
the landing gear is kept in the UP-position. On ground this
circuit is cut off by the landing gear safety (squat) switch. The
additional circuit is protected by the
GEAR-AUX-1 circuit
breaker located on the left side panel and the
GEAR-AUX-2
circuit breaker located on the DC power distribution box in the
engine compartment. The latter is not accessible for the pilot in
flight.
Hydraulic pressure is maintained throughout the flight while the
battery bus is powered. The system is equipped with a pressure
sensor, which will switch the pump on once the pressure drops.
In this case the hydraulic pump will automatically be switched
on. A nitrogen pressure accumulator reduces the frequency of
hydraulic pump action. The constant system pressure is needed
to safely hold the landing gear and doors in place. Consider that
landing gear will slowly extend when electrical and/or hydraulic
power is not available. This case will be indicated by the red
GEAR WARN warning light on the annunciator panel.
Illumination of the yellow HYDRAULIC PUMP caution light on
the annunciator panel indicates the activity of the hydraulic
pump. This light shall be used to monitor the pump cycles and
shall normally illuminate during landing gear operation and for
2 or 3 seconds after periods of several minutes of rest.
If the cycle deviates from this (longer pump action or shorter
periods of rest) the aircraft has to be brought to service as soon
as practical, because a leak in the hydraulic system must be
assumed. In the case the HYDRAULIC PUMP caution light
illuminates more than 1 minute permanently, or periods of rest
last only several seconds, the
HYDR circuit breaker has to be
pulled to prevent overheating of the pump motor.
In this case the landing gear will slowly extend which is
indicated by illuminating of the red GEAR WARN light on the
annunciator panel.
Airspeed has than to be reduced immediately to maximum
140 KIAS. Flight can be continued.
7-20 26. January 2011
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