TWIN COMANCHE C/R
DESCRIPTION
AIRPLANE AND SYSTEMS
ENGINE AND PROPELLER
The four cylinder Lycoming fuel injected engines are rated at 160 horsepower at 2700 RPM. The left
engine rotates clockwise and the right engine rotates counterclockwise. These engines are equipped with
geared starters, fuel injectors shielded ignition systems and special engines are available with optional Rajay
Turbochargers.
Engine mounts are of steel tube dynafocal mount construction. Engine cowls are cantilever structures
attached at the firewall, with side panels which are quickly removed by means of quick release fasteners.
The exhaust system is a cross-over type with exhaust gases directed overboard at the bottom of the
nacelles in the area of the cowl flaps. The cowl flaps are located on the bottom of the engine nacelles and
are manually operated by push-pull controls located in the cabin to the right of the power control
quadrant.
Oil coolers are mounted on the left rear baffle of each engine. Air passes through the oil coolers before
reaching the area of the cowl flaps.
The propellers are Hartzell, constant-speed, controllable, full-feathering units. These are controlled
entirely by use of the propeller control levers located in the center of the power control quadrant.
Feathering of the propellers is accomplished by moving the controls fully aft through the low RPM detent
into the feathering position. Feathering takes place in approximately six seconds. A propeller is unfeathered
by moving the prop control ahead and engaging-the starter.
THE OPTIONAL RAJAY TURBOCHARGER
The Rajay Turbocharger consists of a precisely balanced rotating shaft with a radial inflow turbine
wheel on one end and a centrifugal compressor impeller on the other. Normally wasted exhaust’gases drive.
the turbine which powers the impeller that supplies air under pressure to the engine air inlet. Since engine
horsepower is never used to drive the turbocharger, no additional mechanical load is imposed above those
of a naturally aspirated engine. Low altitude power and engine efficiency is thus provided at high altitudes
by converting exhaust gas energy to compressed air. Although true airspeeds increase, turbocharging does
not increase normal engine speeds, loads, or brake mean effective pressure limits.
The turbocharger bearings are lubricated with engine oil at a pressure of 30-50 psi at normal operating
temperatures. Pressure switches within the lubricant supply line will activate a red warning light if the
turbocharger oil pressure falls below 27-30 psi. If the light signal is received, the pilot should deactivate the
turbocharger.
The primary control in turbocharger operation is the degree of closure of the waste-gate valve. Boost
pressure is manually regulated by gradually turning the vernier control knobs to allow matching of manifold
pressure in both engines.
The induction system uses the normal throttle and fuel mixture controls that are used in non-turbo
operation. The air inlet box is designed to accommodate compressor discharge air without decreasing
normally aspirated take-off power. If the turbo compressor fails to deliver boost pressure, a check valve
door will open automatically as the engine reverts to normally aspirated operation. This function prevents a
prohibitive drop in throttling pressure and the corresponding loss of power that would occur if all the
engine air for normal operation were routed through the inoperative compressor.
Alternate air is available automatically if the inlet duct is obstructed during normally aspirated
operation.
AIRPLANE
AND SYSTEMS
ISSUED: Jung
1,197O
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