Abstract: A calibration device for a pitch change link (10) for a helicopter rotor grip where the link (10) includes a bearing (12) and includes a plurality of sequential reference numbers (22) equally spaced apart and concentrically disposed around the link (10). An indexing device (30) is mounted to the bearing (12) and is disposed adjacent to the plurality of sequential reference numbers (22) for locating one of the plurality of reference numbers (22) representing the length of the link (10). The indexing device (30) includes a window (40) which indexes one of the plurality of reference numbers (22) as the link (10) rotates.

Abstract: A method for detecting a crack in the main load bearing spar of a hilicopter rotor blade consists of attaching a capillary tube along an external surface of the spar and connecting the interior of the tube to a supply of colored liquid contained in a reservoir at a root end of the blade, whereby a crack in the spar causes a corresponding crack in the capillary tube resulting in visible leakage of the colored liquid.

Abstract: A propeller blade of fiber-reinforced plastic with a combined erosion, icing and lightning protection system has a metal shroud fitted to its leading edge, the shroud enclosing a cavity and accommodating a heating conductor at its interior. A ground line of the heating conductor is connected to ground and serves as a lightning conductor.

Abstract: An apparatus for detecting blade passing times includes a sensor for producing an input signal each time a blade passes the sensor. A zero crossing detector produces an output signal each time the input signal crosses a reference axis. A phase shifter shifts the phase of the input signal to produce a gating signal coinciding with the expected arrival time of the blade at the sensor. A gating device is responsive to the gating signal for conducting output signals which occur during the expected arrival time of the blade at the sensor.

Abstract: The pitch setting of a machine controllable pitch propeller is indicated with a high accuracy by comparing the positions of the portions within the vessel hull of a translating member fastened to the pitch change mechanism within the propeller hub and a non-translating member fastened adjacent one end to the hub and extending essentially free of axial load through the propeller shaft into the vessel hull.

Abstract: A measuring device (1, 12, 13, 14) is equipped with a blade angle indicator (1) indicating the blade angle adjustment of the rotor blades of a helicopter, a pressure altimeter (13) and an outside temperature probe (14). The measuring device (1, 12, 13, 14) is linked to a control device (4-6) which has a central processing unit (4) and a program memory (5). The memory (5) stores data processing instructions for determining density height from pressure height and outside temperature as well as data processing instructions corresponding to the helicopter operating instructions for determining the permissible maximum value of the blade angle from the density height. The control device (4-6) periodically determines the density height on the basis of the prevailing pressure height and outside temperature and the corresponding permissible maximum value of the blade angle.

Abstract: Apparatus for heating or cooling ambient air in the form of a temperature controlling propeller having a plurality of blades arranged around a rotatable hub, the blades carrying cells containing a heat retaining material. The cells are mounted in openings provided in the blades and retained therein. A thermometer may be mounted on the hub to monitor air temperature. The propeller is heated or chilled prior to mounting on a driven shaft. When the propeller is rotated by the shaft, it simultaneously circulates and heats or cools the surrounding air as desired.

Abstract: A main helicopter rotor on which a rotary tubular shaft supports, at its top end, an annular hub integral with the tubular shaft itself. The assembly consisting of the tubular shaft and the hub is closed off at the top by a bell connected in removable manner to the hub and enclosing an oscillating plate assembly supported on a fixed shaft extending inside the aforementioned tubular shaft. A rotary ring on the oscillating plate assembly is connected to blade pitch change levers via respective rocker arms connected in articulated manner to the aforementioned rotary ring via respective pins extending radially in relation to the aforementioned bell and accessible via respective radial holes formed through the same.

Abstract: A portable fan is provided with a remote control assembly to facilitate its use by handicapped persons. The switch on the fan is operated by a radio controlled receiver, and a hand held transmitter is designed to permit a user to select multiple fan speeds and direction of blade rotation. Additionally, the transmitter emits audible beeps so as to allow the use of the remote fan control by blind individuals.

Abstract: A multispeed ceiling fan having a plurality of blades, a speed-selecting switch and an a.c. split-phase induction motor. The motor has a rotor and at least one stator winding. The speed selecting switch is arranged to apply respectively different voltages or currents to the motor for each respective selected speed. At least one lamp is connected in parallel to either the main stator winding or in parallel to a phase-shifting capacitor in series with an auxiliary stator winding, as an indicator providing a visible indication of the selected speed for the motor. The at least one lamp may comprise a plurality of lamps, at least all but one being in series with a respective plurality of Zener diodes so that they become energized in sequence as the voltage across the respective lamps or across the lamps in series with the respective pluralities of diodes increases.

Abstract: A system for indicating cracks in a hollow aircraft blade, such as a helicopter blade. A system wherein a pressure differential is maintained within the blade with respect to the ambient atmosphere and including a pressure sensor for mounting on the blade in communication with the interior of the blade and having a member which moves in response to pressure changes within the blade, a beta radiation source mounted on the member and disposed for radiation transmission to a detector, a beta radiation detector for mounting on a nonrotating portion of the aircraft for receiving radiation from the source, and circuitry having the output of the detector as an input and providing an output which varies as a function of the position of the pressure sensor member for indicating the pressure condition within the blade. An improved beta radiation detector housing which substantially eliminates detector sensitivity to radar transmissions while maintaining sensitivity to nuclear radiation in the beta range.

Abstract: A remote parameter monitoring system utilizes a series of half-wave rectifier diodes in combination with a unique overlapping wiring arrangement to provide for location-specific detection of a parameter condition existing at a plurality of spaced locations. In one embodiment of the invention, the system is used for monitoring cracks in helicopter rotor blades and indicating to the crew in the cockpit both the fact of a cracked blade and the specific blade which is cracked. In such embodiment, the system includes a three-phase alternating current transformer whose primary windings are supplied by the helicopter's three-phase alternating current generators and whose secondary windings make up part of the wiring loops between the cockpit and the rotor blades. By controlling currents flowing in opposite directions in the wiring loops, the system allows for blade-specific crack detection of up to six rotor blades by means of only three wires between the rotor blade assembly and the cockpit area.

Abstract: A torque meter is provided for use in conjunction with a layshaft having a forward and rear end and which is rotatably mounted in a housing. The layshaft is axially movable with respect to the housing between a forward and a retracted position while a gearing arrangement in mesh with the layshaft urges the layshaft towards its forward position with a force proportional to the shaft torque. The torque meter comprises a body secured to the housing adjacent the front end of the layshaft which forms a chamber open to the front end of the layshaft while a piston is axially slidably mounted within the chamber. The chamber is pressurized with a fluid, such as oil, which urges the piston against the front end of the layshaft with a force proportional to the pressure so that the piston balances the layshaft against the axial force imposed by the engine. A fluid pressure gauge determines the pressure within the chamber which varies proportionately with the layshaft torque.

Abstract: An apparatus and method for indicating the rotational speed of a fan is disclosed. An electrical circuit is provided for selectively providing electrical power to a plurality of indicator lights mounted on the fan. The indicator lights are turned on and off in a coded sequence that indicates the speed at which the fan is rotating.

Abstract: Improved temperature detection system for use on film cooled turbine airfoils having a showerhead assembly with a series of parallel slots defined in the leading edge of an airfoil, each slot having a multiplicity of film flow ports exiting therefrom. A plurality of sensor assemblies are affixed to the airfoil showerhead and are couplable via electrodes to electronic sensing equipment for establishing the gas flow temperature.

Abstract: A rotor blade, for example for a rotary wing aircraft, has a wing section d a root section interconnected by a neck section surrounded by a blade angle adjustment sleeve which is stiff against torque moments for transmitting blade angle adjustment movements through the sleeve to the wing section. The trailing edge of the sleeve is provided with a gap which extends, at least partially, alongside the rear edge of the neck section for visually inspecting the neck section inside the sleeve even when the root section is connected to a rotor hub. A reflecting mirror may be used for inspecting all sides of the neck section through the gap.

Abstract: The blade angle of the blades is adjustable in a rotor for a rotary wing craft by a lever mechanism (13, 14 or 41, 42) secured to the radially inner end of an extension bushing (7; 7.1) or shaft (43). The extension bushing (7; 7.1) or shaft (43) is connected with its radially outer lever (15 or 44) to the blade root (2) or a blade root mounting (39, 50) of a rotor blade in an angular position adjustable manner for adjusting the tracking of the blades. The bushing (7; 7.1) or shaft (43) is adjustable in its angular position relative to the blade root (2) by adjustment screws cooperating with a free end of the lever (15 or 44) which reaches into a gap between two of such adjustment screws (16 or 45) cooperating with counter nuts (17 or 46). By adjusting the angular position of the bushing or shaft with the screws it is possible to assure a uniform tracking among all the blades of a multiblade rotor. Such uniform tracking is desirable if the blades of a rotor are to rotate in the same plane.

Abstract: The apparatus comprises one or more acoustical transducers associated with a particular interchangeable rotor blade for monitoring acoustic emissions emitted by the rotor blade under operating stress. The output of the transducers is connected to a computer associated with the particular aircraft. The transducer output signals are processed by the computer and filtered to allow real time stress return level readings so as to accumulate a count of critical acoustic emissions which are indicative of progressive irreversible structural fatigue or damage to the interchangeable rotor blade.

Abstract: An apparatus for adjusting the track of rotor blades through remote control, especially of a helicopter during flight. Each rotor blade has a two-part, lengthwise adjustable control rod with a servomotor which is associated with the supply unit for rotor blade control. A receiving/transmitting part is provided, and a control device (potentiometer) as well as a measuring device are installed in the control rod and are operatively connected with an operating station having an indicator or monitor. The receiving/transmitting part, and the energy source of the servomotor associated with the supply unit for rotor blade control, are integrated in the control rod and are combined with the servomotor to a structural unit and are accommodated in a common housing.

Abstract: A helicopter rotor blade to hub arm attachment configured to react centrifugal loads from the blade through a blade cuff, spindle, and elastomeric bearings utilizes a bolt in the bore of the spindle for secondary load path operation and a spindle integrity monitoring indicator to provide a visual showing of a deviation from the normal load path.

Abstract: A composite hub for a helicopter rotor, the hub having the form of a flat plate of laminated structure provided with a plurality of through holes each able to house an elastomeric coupling for connection of an associated blade, and a central layer of the said plate being constituted by a force distributor element in contact with each surface of which there is disposed at least one layer constituted by radial elements extending outwardly of an axis of rotation of the hub and an annular element disposed in contact with the free ends of the said radial elements; these latter being connected to the radial elements disposed on the other side of the distributor element by means of axial elements (25) defining part of the surface of the said aperture.

Abstract: A gas turbine engine control system is provided. In a preferred control system for use in combination with a helicopter, input signals respectively representative of power turbine speed error, power turbine shaft torque, and compressor shaft speed are employed. From these input signals, five intermediate signals are developed. One of the intermediate signals represents the main rotor speed error. Each of the five intermediate signals is provided with a separate predetermined gain and coupled to summation means. The predetermined gains are selected to be of values which reduce the effects of resonances provided by the main and tail rotors of the helicopter. The output of the summation means represents a control signal and may be employed to operate a fuel control valve.

Abstract: A friction connection is formed between an annular member such as a wheel, pulley or the like and a shaft by at least one annular wedge which clamps the annular member to the shaft by translating axial pressure from wedge-tightening screws into radial clamping forces. According to the invention, the annular member is provided with a groove centered on the axis of rotation and receiving an open measuring ring at least partly slidable in the groove, the relative spacing of the ends of which serves to indicate the radial clamping force.

Abstract: A helicopter rotor blade to hub arm attachment configured to react centrifugal loads from the blade through a blade cuff, spindle, and elastomeric bearings utilizes a pre-loaded bolt through the spindle for load sharing therewith and a spindle integrity monitoring indicator to provide a visual showing of a deviation from the normal load sharing proportion.

Abstract: The blades of a helicopter propeller are supervised by pressure-sensitive transducers operating a resonance circuit rotating therewith, for determining its frequency. The circuit includes a rotating secondary of a transformer, intermittently coupled to a stationary primary which is energized by a voltage having a frequency equal to the resonance frequency of the resonance circuit when there is no blade defect. An impedance senses the amplitude of these pulses which varies on detuning due to a blade defect. The pulses are processed to yield a warning. Scanning through a range of source frequencies permits identification of the defective blade. The circuit is supplemented for operational testing during flight as well as on the ground.

Abstract: An evaporator coil defrost control system for a refrigeration system comprising refrigerant compression means, a condenser coil, an evaporator coil, and an electric motor operated fan positioned adjacent to said evaporator coil and adapted, when energized, to blow air through said evaporator coil, said defrost control system comprising: strain sensing means connected to said fan blades and adapted to measure force applied to said fan and to produce a signal indicative of said measured force; controller means connected to said strain sensing means to receive the signal therefrom and having operative connections to said system, said controller being adapted to place said system in a defrost mode of operation upon said signal of said strain sensing means having a characteristic indicative of a significant frost build-up on said evaporator coil.

Abstract: A pulse generator is used to emit a pulse train of specific frequency while two pick-ups--one adjacent a circumferential array of control lugs on the rotor and the other adjacent the blades--emit start counting and stop counting pulses. The number of pulses generated by an external pulse generator are counted during the time interval for the passage of two lugs past a pick-up and the time interval for the passage of two adjacent blades past a pick-up for each revolution of the rotor. A quotient is then obtained from the two pulse numbers for each revolution and the difference between the maximum and minimum values of the quotients obtained during continued rotation is determined. If the difference exceeds a preset critical value, an activity signal is generated, for example to set off an alarm.

Abstract: A low-friction, axially extensible strut, automatically lockable in both tension and compression, for use as a secondary load path in helicopter main rotor force measurement systems.

Abstract: A finger tip actuated structural crack monitor operation wherein a conductive array is adhered to a structure which is susceptible to development of cracks upon fatigue. An interrogation module is mounted on the structure and is connected to the array with circuit means in the module to sense any momentary discontinuity in the array and to store a failure condition therein upon detection of such discontinuity. A readout means is manually operated to provide a human sensible indication of the existence of the failure condition.

Abstract: In a helicopter, torque display for a main rotor mast is mounted and connected to be driven from a power source at its base and connected to a main rotor at its tip. A reference member secured inside the main mast at the tip thereof depends freely and extends coaxially the length of the mast to a point adjacent the base thereof. A separate index is carried by the reference member adjacent to the base and by the main rotor mast adjacent to its base. A pick-off senses rotational movement of one index relative to the other and provides for actuation of a torque indicator for the pilot of the helicopter.

Abstract: A nondestructive method of applying and removing instrumentation on airfoils.

Abstract: In finishing the construction of a rotary wing, particularly helicopter rotor blade, the blade is weighed to determine the position of its static moment. The measured value is compared with a predetermined value and, if necessary, the static moment is adjusted by applying a high specific gravity filler material to the surface of the blade. The filler material has a specific gravity in a range of 6 to 10 p/cm.sup.3 and can be formed of a mixture of tungsten powder and epoxy resin. The weighing operation is performed on a three scale apparatus with one scale supporting the end of the blade attached to the rotor and the other two scales supporting the opposite end of the blade.

Abstract: A magnetic pickup for sensing the speed of a rotor disc having a nosepiece affixed to the disc containing one or more magnets. The magnets are contained within blind openings passing inwardly from the back of the nosepiece and arranged to position the magnets within an embossed section extending axially from the outer surface thereof. A stationary sensing probe is mounted adjacent to the embossed section which is capable of generating a voltage signal as the magnets are passed in close proximity with the sensing element.

Abstract: An aircraft forwardly propelled by a power plant including a pair of jet engines, is operated in a VTOL mode by powered rotation of a rotary wing mechanically rotoring the engines. When unloaded during fixed wing flight, the power plant is operated in an accelerating rocket mode preceding high speed ram jet operation. Radially extensible blades of the rotary wing vary the mechanical loading on the engines while adjustable chokes at the intake of each engine and in the outlet of a common after-burner for the engines, condition the power plant for its different operational modes.

Abstract: Rotary wing aircrafts include one or more rotors having a plurality of rotary blades. Each of the rotor blades has crack sensor in the form of an induction coil or conductive wire. The crack sensor is connected with a further induction coil to form a circuit of which inductance is changed when a crack is produced in the associated rotor blade. On a stationary part such as a stationary swash plate of the rotorcraft, there is provided a stationary induction coil which is brought into cyclical and electromagnetical co-operation with the further induction coil on the rotor as the rotor rotates. The stationary induction coil is connected with a load resistor and an oscillator in such a way that cracks in the rotor blades can be detected in the form of a voltage change at the load resistor.

Abstract: A variable length blade in telescopic form adapted to be used with similar blades to form a variable diameter rotor or propeller wherein the outer blade portion, at the will of the pilot, is caused to telescope with respect to the inner blade portion by jackscrew action and means are provided for limiting the extending and retracting movements of the blades and also for providing a continuing visual indication of the diameter of the rotor.

Abstract: Method and apparatus for continuously detecting cracks in aircraft blades while in flight. A hollow blade is sealed with a pressure differential, either above or below atmospheric. A reduction in the pressure differential such as results from cracks, is detected by a pressure sensor having a member which moves between a high pressure differential position and a low pressure differential position. A radiation source, typically a beta source, is carried on the member and moves from a shielded position to an unshielded position when the pressure differential drops. A radiation detector is mounted on a fixed portion of the aircraft and detects radiation from the source when the member moves to the unshielded position. The detector output may be used to operate a go-no go indicator providing a warning signal when the pressure differential falls below a predetermined value, or to operate an analog indicator providing an output varying as a function of the pressure differential.

Abstract: In an electrical system requiring an electrical interconnection between a rotating body and a relatively stationary body, a circuit provides a highly reliable electrical interconnection between the bodies through the use of multiple rotary electrical connection assemblies connected in parallel across the rotating interface during normal operation, and connected in series, from the relatively stationary body through one of the rotary electrical connection assemblies to the rotating body and returning to the stationary body through another one of the rotary electrical connection assemblies, for verification of the electrical continuity of the interconnection during a testing operation.