Weight & Balance for the Piper PA-23 Aztec

Control System and Surfaces 14 Fuel System Electrical System Finish Instrument Panel. Radio Equipment . Seats Baggage Compartments. Cabin Features Heating and Ventilating System 680501 15 11992 22 22 23 23 23 25 25 26 26 96 26 • 26 THE PIPER AZTEC "D" SECTION II SECTION II DESIGN INFORMATION ENGINE AND PROPELLER The Lycoming 10-540-C4B5 engines in the Aztec are rated at 250 HP at 2575 RPM. These engines have a compression ratio of 8.5:1 and use 91/96 minimum octane aviation fuel. Both engines on the Aztec are equipped with a geared starter, alternator, vacuum pump, fuel injectors, two magnetos, shielded ignition system, diaphragm fuel pump, propeller governor and an oil thermostat. The left engine is equipped with a hydraulic pump. Engine mounts are of steel tubing construction and incorporate vibration absorbing Lord mounts. Engine cowls are cantilever structures, attached at the firewall. Side panels are quickly removable by means of quick release fasteners. The nose section is split for quick removal. The exhaust system is a crossover type with exhaust gases directed outboard at the the bottom of the nacelles in the area of the cowl flaps. The cowl flaps, located on the bottom of the engine nacelles provide additional cooling for ground operation or high temperature conditions. Manual push-pull controls for the cowl flaps are located on the fuel control panel. An efficient aluminum oil cooler is mounted on a rear baffle of each engine. Engine oil drainage is accomplished with quick oil drain valves located on the inboard rear corner of the engine crankcases. The "Compact" Hartzell HC-E2YK-2RB, HC-E2YR-2RB, HC-E2 YK-2RBS, or HC-E2YR-2RBS propellers are constant speed, full feathering units which represent new concepts in basic design. They are low in weight with simplicity of design and ruggedly constructed. The propellers with designations ending in "S" contain springs, to safeguard against an overspeed due to loss of the air charge. This spring 701015 6 SECTION II THE PIPER AZTEC "D" produces sufficient force to control propeller rpm, within normal operating range, provided airspeed is reduced and power is applied slowly. The propellers are controlled by the levers in the center of th control quadrant. Feathering of the propellers, which takes approximately three to ten seconds, is accomplished by moving the controls fully aft through the low RPM detent into the feathering position. A propeller is unfeathered by moving the prop control ahead and engaging the starter. (See Section III, for complete feathering and unfeathering instructions.) FUEL INJECTION The Bendix RSA-5 Type Fuel Injection System installed in the Aztec is based on the principle of measuring airflow and using the airflow signals to operate a servo valve. The accu- rately regulated fuel pressure established by the servo valve, when applied across a fuel control (jetting system), makes fuel flow proportional to airflow. Fuel pressure regulation, by means of a servo valve, neces sitates only a minimum fuel pressure drop through the entire. metering system. This makes it possible to maintain metering pressure above vapor forming conditions, and at the same time does not require a high inlet fuel pressure. An inherent feature of the Servo System is self-purging, which eliminates any possi- bility of vapor lock and the associated problem of difficult starting. The Airflow Sensing System, which is incorporated in the Servo Regulator, consists of the throttle body containing the throttle valve and venturi. The differential pressure between the entrance and the throat of the venturi is a measurement of air entering the engine. These pressures are applied to an air diaphragm in the Servo Regulator to create a force across the diaphragm. A change in power will change the airflow to the en- gine which in turn will change the force across the air diaphragm in the Servo Regulator. The air diaphragm in the Servo Regulator converts the 7 701015