During operation, periodic instrumental inspection of the technical condition of electric starters, generators, electric pumps, electromechanisms, contactors, and other elements of starting systems is carried out in the laboratory. In some cases, these objects can be checked directly on the aircraft by creating real load conditions for them.
Electrical parameters can be measured with devices connected via adapters in the cut of their power cables. It is this method that is easiest for checking ignition starting coils, whose main parameters are the current value in the primary circuit under corresponding load of the secondary circuit and the electrical resistance of insulation of current-carrying parts.
However, for objects such as electric starters and electric pumps, it is insufficient to check only their electrical parameters (current consumption, electrical resistance of insulation) during periodic inspection. To assess their condition, it is important to know the state of the commutator-brush assemblies, and for electric starters, also the state of the soldering of the armature winding to the commutator segment lugs. Since a thorough inspection of these assemblies on the aircraft is practically impossible, periodic inspection of electric starters and pumps must be carried out in the laboratory.
The most sensitive to changes during operation are program devices and relay amplifiers. They are usually placed in a single housing, forming so-called starting panels or engine start automation boxes. The main parameters of starting panels are their static characteristics:
- accuracy (in time) of issuing sequential commands and execution of the entire program by the start time automatic device or the external characteristic of the tachogenerator (sensitive element of the programming device) – for systems where the start program is executed depending on the rotational speed of the aircraft engine turbine shaft;
- value of pickup and dropout voltage of command relays, intermediate relays, and contactors; for some relays and contactors, also the value of contact pressure, force of operating springs;
- value of electrical resistance of insulation of individual electrical circuits.
Testing of starting panels is carried out on special test benches that allow assessing the operability of individual panel elements and performing checks of technical parameters of the program device, relays, and contactors. The equipment set of such a bench usually includes:
- a voltage-adjustable DC power source or a potentiometer that allows changing the circuit supply voltage from 0 to 30 V when measuring the pickup and dropout voltage of relays, contactors, and during other checks;
- an electric stopwatch for determining the time elapsed from the moment the system is turned on until the closure (opening) of a particular control circuit by the command device;
- electrical measuring instruments and light indicators for closure (opening) of individual command passage circuits;
- load devices;
- switching apparatus for controlling the activation of the test object and individual measuring circuits of the bench.
All these elements are connected by common electrical circuits.
PR