Start Your Engines: Solid-State Magneto Start Booster

The techniques and opinions on how to start aircraft engines are as varied as the airplanes, engines, and operators that encompass this topic.


The vibrator cannot boost impulse coupled magnetos and does not appreciably improve the voltage output of retard breaker magnetos. Typical starting voltage for an impulse coupled magneto application is only around 17kV at 1 spark per second (sps) at top dead center (TDC). However, with SlickSTART augmenting the primary output of the impulse coupled magneto, the output of the magneto is increased to nearly 23kV at 14 sps and continues to be delivered as long as the contact points are open, up to 60 degrees beyond TDC. Similarly, the output of a vibrator type ignition runs about 11kV at 11 sps while the SlickSTART-boosted magneto can produce nearly 23kV at 14 sps, effectively doubling the voltage and increasing the sparks per second available during start.

SlickSTART

The higher peak voltage and energy of the SlickSTART will initiate combustion of very lean or very rich mixtures and will fire plugs fouled by oil or fuel, whereas the same conditions may not be overcome by a standard impulse coupled or retard breaker magneto system. The longer duration of the SlickSTART spark event also allows more time for a combustible mixture to pass near the spark plug tip when a spark event occurs, further enhancing the SlickSTART’s capability to fire plugs during the most unforgiving of conditions.

Installation

Installation can be accomplished in about one hour and can be done with standard shop tools. Slick Service Letter SL2-96 provides complete installation documentation and includes the Supplemental Type Certificate. For certified aircraft, an FAA Form 337 will need to be completed after installation. Please note that the aircraft battery and ignition harness will need to be disconnected before installing SlickSTART and normal precautions must be taken when the P-lead is detached from the magneto, as accidental ignition is possible. Airframe manufacturer manuals may also be needed for additional wiring schematics.

There are several possible SlickSTART installations. The optimum mounting position is with the terminals facing down, on the engine side of the firewall. There are some applications, such as Mooney aircraft when an existing vibrator is being replaced, that require mounting in an inverted position with the terminals facing upward. The remaining installation procedures differ depending on the type of application.

When mounting on a firewall, locate a spot and drill two holes to match the bolt hole pattern. The unit is then attached with standard AN hardware. It may also be mounted on motor mount tubes, but there must be a ground path from the SlickSTART mounting base to airframe ground. If cushioned clamps are used, then a separate bonding strap must be installed from the base to airframe ground.

The simplest installation scenario is for impulse coupled magnetos. A wire connection from terminal 1 on the SlickSTART connects to the impulse coupled magneto’s capacitor terminal stud. Pin 2 and 3 are left unconnected in this installation. Voltage-In (VIN) is connected to the positive switched side of the starter solenoid. The ground terminal is connected to the ground point on the left magneto, or mag cover on Bendix magnetos.

Installation of SlickSTART and P-lead wires on magneto. Note how P-lead and SlickSTART boost wire are piggybacked and share the same terminal.

To install a SlickSTART as a replacement unit for the Bendix "Shower of Sparks" vibrator, first determine if the vibrator is a relay or non-relay type. A vibrator with a relay switches between primary and retard points while grounding the right magneto to prevent against kickback during engine start. The ignition switch controls these functions in a non-relay vibrator application. SlickSTART can be used with either application, but must be wired according to the specific installation instructions and wiring schemes detailed in Service Letter SL2-96.

Since the existing bolt hole pattern matches SlickSTART’s pattern, new holes will not have to be drilled and the SlickSTART can simply be bolted in place of the existing vibrator. Please note that this remove and replace installation does not apply to twin engine aircraft using a single vibrator. There is a subtle circuit difference between SlickSTART and vibrators. On twin engine applications using a single vibrator, SlickSTART will run continuously, so an individual SlickSTART is required for each engine.

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