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Ignition
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CHAPTER 74
IGNITION
1. General
This Chapter tells you about the ignition system for the engine. It gives you the general data about the ignition system. It gives you the trouble-shooting data for the ignition system and it tells you how to remove/install the ignition switch.
For more data on the components of the ignition system refer to the Lycoming Maintenance Manual, the LASAR Operating Manual and the equipment manufacturers' manuals.
Note: Equipment which is certified for installation in the DA 40 is listed in Section 6.5 of the Airplane Flight Manual. Such equipment may be installed in accordance with the Airplane Maintenance Manual.
Any equipment which is not listed in Section 6.5 of the Airplane Flight Manual is called "Additional Equipment". The installation of Additional Equipment is a modification which must be handled in accordance with national regulations or a Service Bulletin.
2. Description
The DA 40 has dual ignition. The SlickSTART magneto booster system is standard equipment, the limited-authority-spark-advance-regulator (LASAR) system is optional. Two Slick magnetos supply the high voltage electrical impulses to the spark plugs. An ignition switch in the cockpit controls the magnetos and screened cables connect the magnetos to the spark-plugs. Two spark-plugs in each cylinder give ignition. The engine ignition firing order is 1-3-2-4.
A. SlickSTART Booster System
The SlickSTART booster receives power only when the starter is engaged. Therefore this system only affects the engine start-up process.
B. LASAR System
During engine start-up, the LASAR system sets the ignition timing to 0° before top-dead-center (BTDC) and boosts the power of the electrical impulse to the spark-plugs. As the engine RPM increases to 275 RPM the LASAR system advances the engine ignition timing according to the engine personality map (EPM). When the engine RPM increases to 700 RPM the LASAR system reduces the power of the electrical impulses to their usual value.
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INSTRUMENT PANEL FIREWALL ENGINE COMPARTMENT
Figure 1: Engine Ignition Schematic Diagram
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Ignition
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The LASAR system is an automatic system. If the ignition switch is set to the BOTH position or the START position, then the LASAR system is switched on. If the LASAR system fails or the ignition switch is set to any position other than BOTH or START, then the magnetos will operate in back-up mode. In back-up mode the timing of the magnetos is fixed at 25° BTDC. A white ignition status light (IGN or IGNITION) on the annunciator panel tells the pilot when the LASAR system is in back-up mode.
3. Ignition System Components
Figures 1 shows the schematic diagram of the ignition system. The ignition system has these components:
A. Ignition Switch
The ignition switch is at the lower face of the instrument panel, on the left half. You operate the ignition switch with a key. The ignition switch has these positions:
) OFF Both magnetos grounded, LASAR system (if installed) in back-up mode.
) R Right magneto live, left magneto grounded, LASAR system (if installed) in back-up mode.
) L Left magneto live, right magneto grounded, LASAR system (if installed) in back-up mode.
) BOTH Both magnetos live, LASAR system (if installed) in automatic mode if the engine is running. LASAR system in back-up mode if the engine is not running.
) START Both magnetos live, LASAR system (if installed) in automatic mode and starter relay ON.
You cannot repair the ignition switch.
B. Ignition Switch Cables
Cables connect the ignition switch to the SlickSTART booster control unit or LASAR control unit. The control unit has special electrical cables which connect to the left magneto and connect to the right magneto.
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