Patent GB-560520-A (GB)
Title: Method and apparatus for detecting and neutralizing static charges on aircraft
IPC: B64D45/02
Filed: 1943-02-10
Abstract: 560,520. Protective arrangements. ANDRESEN, G. J. C. Feb. 10, 1943, No. 2244. [Class 38 (iv)] [Also in Groups XXXIII and XXXVI] Apparatus for neutralizing a static charge on an aircraft includes means for determining the sign of the charge with respect to the medium through which the aircraft is passing and means controlled by the detecting means for connecting the aircraft to means adapted to have a neutralizing effect thereon. Resistances 7, 8, 9 and the elements of a triode 3 form the arms of a bridge circuit having one junction point 32 connected to the body of the aircraft. Across the junction points 31, 33 is connected a battery 11 through a potentiometer 44, the negative pole of the battery being connected to the filament 34 of the triode 3. Across the junction points 30, 32 is connected a meter 12 shunted by a resistance 7a. The winding 13 of a polarized relay 14 is also connected across the points 30, 32. The grid 35 of the triode 3 is connected directly to the junction point 32. The plate 36 is connected to a metallic element 4 exposed to the field through which the aircraft is passing, being disposed, for example, in the propeller slip stream. The plate 36 is also connected to the point 32 through a resistance 5, a variable potentiometer resistance 5a and a battery 6 which maintains the plate 36 negative with respect to the grid 35. Normally the bridge is balanced, but a static charge alters the potential of the grid 35 and unbalances the bridge causing a current between the points 30, 32 in a direction dependent on the sign of the charge. The armature 37 of the relay 14 comprises two insulated conducting portions 38, 39, the latter of which is earthed. The portion 38 is connected to an insulated portion of the exhaust manifold 1 and engages contacts 40, 42 connected to the negative and positive poles of a battery 2. The portion 39 engages in one position a pair of contacts 41, C1, and in the other position a pair of contacts 42, C2. The contacts C1, C2 are connected to coils 20, 21 which operate a three-way valve 18 so as to connect a pump 19 with one of two tanks 15, 16. The tank 15 contains a liquid such as water which'when ionized by the exhaust produces ions which are predominantly negative, 'whilst the tank 16 contains liquid such as light oil which when ionized produces predominantly positive ions. One or other of these liquids is injected into the exhaust according to the' position of the armature 37. Assuming a static negative charge on the plane, the armature 37 moves to the right and connects the positive pole of the battery 2 to the plane and the negative pole to the insulated portion 1 of the exhaust manifold. The solenoid 20 is energized and connects the tank 15, containing water, to the pump 19 so that water is injected into the exhaust. The water vapour is ionized by the heat of the exhaust producing ions of a predominantly negative 'sign and is discharged with the exhaust. The battery and the ionized vapour therefore co-operate to neutralize the static charge on the plane.