Aircraft technical Basics: TM 1-412, Aircraft Propellers, 1941: VIII. Propeller Anti-Ice Equipment

SECTION VIII. PROPELLER ANTI-ICER EQUIPMENT

46. Performance.--a. The Eclipse pump (fig. 29) is designed to deliver a minimum of 4 quarts and a maximum of 10 quarts of anti-icer solution per hour to the propeller hub, pilot's windshield, or carburetor venturi, depending upon the particular installation. Each pump is designed for use in conjunction with two propellers. The pump motor is designed to operate on 12 volts, d. c., with a maximum current consumption of 2 amperes when operating at maximum capacity.

b. The Pesco pump (fig. 30) is used for the same purpose as the Eclipse pump. It is manufactured in two types; one operates on 12 volts, d. c., and delivers 50 cc. (minimum) to 170 cc. (maximum) per minute. The other operates on 24 volts, d. c., and delivers 60 cc. (minimum) to 175 cc. (maximum) per minute.

c. A control rheostat is designed for use in conjunction with both the Eclipse and Pesco type pumps as a means of remotely controlling the output of the pumps to the required value.

47. Description.-a. The Eclipse propeller anti-icer pump is an electrically driven dual diaphragm pump, suitable for operation from a 12-volt battery source, and designed to deliver a metered supply of alcohol-glycerine solution to a slinger ring located at the propeller hub. The dual pump consists of two fabric diaphragms actuated by a double cam driven by an electric motor through a worm reduction. Steel ball check valves are used in the inlet and outlet passages of the pump. All steel and bronze parts including valve springs are cadmium plated as protection against corrosion. The main pump body and lower housing are made from magnesium alloy, and the pump head is made from aluminum alloy. An oil reservoir in the pump base provides a self-containing automatic method of lubrication. Oil is distributed to all moving parts, with the exception of the motor bearings, by means of the underside of the pump diaphragms which are connected with the oil reservoir.

b. The Pesco propeller anti-icer pump is a combination of two small gear type pumps contained in a bronze housing and driven by a series wound direct current motor through a I0:1 reduction gear system. The purpose of the two sets of gears is to provide independent discharge from two different outlet ports for twin-engine installation.

e. A control rheostat suitable for mounting on the instrument panel is provided with each pump. The unit consists of a wire-wound variable resistance, assembled in a cast alloy housing. The shaft of the resister, which is rotated, extends through the front of the housing and is provided with a Bakelite knob to facilitate operation. A plate is mounted on the front of the housing and is suitably marked to indicate the proper direction of the knob to increase and decrease the output of the pump as desired.

48. Installation.-Before installing the propeller anti-icing pump, refer to the standard drawing for the airplane and the Air Corps Technical Orders pertaining to the type pump and the air-plane involved. The Eclipse type anti-icer pump should be primed when it is installed and whenever the tank runs dry. To prime with the electric motor running, back off the two inlet valve plugs approximately three turns. Leave pump running until all air is expelled from the system and a steady flow of liquid is obtained, then tighten the valve plugs. It is never necessary to prime the Pesco type pump. Figure 31 shows a typical installation.

49. Operation.-The operation of the propeller anti-icer pump is automatic upon operation of the control rheostat. When the control knob is turned all the way to the left, facing the knob, the circuit is open and the motor is inoperative. To place unit in operation, turn knob to the right to maximum output position for 30 seconds, then to the left until desired output is obtained. To increase output, turn knob to the right; to decrease output, turn to the left. The operating speed of each pump is varied in order to obtain the correct output.

50. Rubber-covered propeller spinners.-To prevent the building up of a heavy coating of ice on the front part of the propeller hub, a special de-icing spinner is attached to the front of the propeller. It is usually spun from aluminum. This insures a perfectly concentric and lightweight part. Inasmuch as it rotates with the propeller, it is manufactured as a balanced unit, and when possible after its installation, the propeller is rechecked for balance. A resilient covering of rubber is cemented to the outside of the spinner. When this rubber is coated with a special de-icer oil or castor oil, the surface adhesion is so lowered that centrifugal forces from the rotation are sufficient to fling off any particles as they form. After flight and during storage, the spinner is treated with a preservativ to retard the checking of the rubber.

FIGURE 29.-Anti-icer pump and controI (Eclipse).

FIGURE 30.-Anti-icer pump (Pesco) .

FIGURE 31.- Typical anti-icer installation (Pesco).