Pilot Operating Handbook
Cavalon
SECTION 3
EMERGENCY PROCEDURES
AutoGyro_POH_Cavalon 915iS Revision 1.0 – Issue Date 08.MAY.2019 3-6
3.9 Pitch oscillation recovery
There are generally two types of pitch oscillation: that caused by pilot over control (‘PIO,
Pilot Induced Oscillation’) and that caused by aerodynamic oscillation.
PIO is not generally found on two seat gyroplanes due their inherent stability. It is initiated
by the pilot over-controlling the stick. If a situation develops where a divergent aircraft
pitching oscillation is occurring in sympathy with fore-aft control stick inputs, firstly stop the
control input – do NOT try to control PIO with the stick.
For both situations, smoothly closing the throttle whilst maintaining a level flight attitude will
return the aircraft to a stable, slow speed condition very quickly, from which the pilot can
recover to normal flight.
Recovery from PIO or aerodynamic oscillation can result in height loss.
3.10 Vibration
A gyroplane is subject to a number of out of balance forces which will generate different
levels of vibration depending on the engine and rotor rpms, and on loading conditions.
Rotors are normally balanced two seated, so a reduction in occupant loading will naturally
change the rotor response.
1. Engine and propeller. Vibration in this area will change with engine rpm, and can
therefore be affected and isolated by the pilot. The propeller is normally balanced to less
than 0.1ips, meaning low vibration. Vibration will increase as the propeller gets dirty, and will
also increase if damaged. A sudden change in flight will indicate a fault has developed,
either through an impact (loose luggage, bird strike etc. passing through the propeller) or by
some mechanical failure. In the event the pilot should make a precautionary landing for
evaluation. Propeller damage may also be evident from a change in noise level.
Upon landing, carefully check the propeller for damage, loose bolts or evidence of
mechanical failure within the prop or engine. Especially check the engine to engine bearer
connections, and the engine bearer to airframe connections.
2. Rotor.
Rotors will vibrate in flight due to tracking errors (side to side stick shake), rotor CG
misalignment with the axis of the bearing in the flat plane (oscillatory stick shake), and also
in the vertical plane (two per rev shake). The amount of shake will not suddenly change in
flight or between flights unless there has been mechanical failure, external influence or rotor
strike.
Rotor vibration also depends on the rotor rotational speed, which in turn is dependent on
airspeed and aircraft loading.
Vibration will increase (and performance decrease dramatically) with dirt build up on the
rotor blades, so before any analysis make sure they are clean.
If there is a change in vibration in flight make a precautionary landing and investigate. If on
rotor startup, stop and investigate.
Check items:
Rotor impact with tail of aircraft.
Hanger damage e.g. twist or distortion of trailing edge.
Blade bent from ground handling.
If after a recent re-assembly of the rotor, that the blades and hubs are serial-number
matched, and that the shim washers are correctly matched to the hub bar and rotor tower.
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