This section details generator maintenance intended as a five hour maintenance item that should be performed at or before every 5 hours of flight.

Performing routine checks on the fuel, air, and spark systems relative to EFI powered aircraft is recommended for maintaining the optimal performance expected from HA-EFI equipped UAS. This inspection should include a visual inspection of the fuel filter and fuel line integrity, the air filter cleanliness and integrity, and the spark plug integrity.

Fuel Filter and Fuel Line Integrity Inspection

Begin by removing the fuel line grommet located at the top of the fuel tank, and pull the fuel filter through the internal baffles. Inspect the wool filter making sure it is secure in its fuel line and check for debris or buildup that would otherwise obstruct the flow of fuel and remove it if possible. If removal of debris or buildup is not possible, replacement of the filter is recommended. Proceed to inspecting the fuel lines at both the fuel tank and generator and look for kinking, pulling, gouges, or possible thinning on any part of the line. If degradation or damage of any fuel line is suspected, replacement of the entire fuel line system is recommended.

Air Filter Inspection

Remove the air filter from the intake and throttle body of the generator. Inspect the air filter rubber interface to make sure it grasps the intake firmly and check the interior and exterior foam of the air filter for debris or buildup (which could consist of carbon deposits from exhaust, oil or gasoline spills, or environmental fallout) that could obstruct airflow and remove it if possible. If removal of debris or buildup is not possible, replacement of the air filter is recommended.

Spark Plug Inspection

If generator performance is in question, remove the spark plug boot, located at the bottom of the generator to reveal the spark plug. Using the included spark plug wrench, remove the spark plug and inspect the electrode. Look for degradation of the center electrode or side electrode, and any carbon deposits that may be present. If carbon deposits are present but minor in nature, carburetor cleaner or isopropyl alcohol may be used to remove deposits. For uncertainties, refer to the NGK manufacturer diagnostic chart.

NGK Spark Plug Diagnostic Chart

Normal Conditions

Normal (Unleaded Petrol): Standard wear patterns.
Normal (Lead Replacement Petrol): Typical appearance when using leaded fuel substitutes.

Symptoms, Causes, and Remedies

Symptom	Cause	Remedy
Hard starting; Misfiring; Black exhaust smoke	Carbon Fouled: Rich mixture; Retarded ignition; Low compression; Spark plug too cold.	Check float level, choke, ignition timing, air cleaner, and compression. Replace with correct heat range plug.
Hard starting; Misfiring; Grey/white exhaust smoke; Loss of oil	Oil Fouled: Worn rings or pistons; Leaking valve stem seals; Over-filled oil sump.	Replace worn components. Replace spark plug with correct heat range.
"Pinking" under acceleration; Engine run-on; Misfiring	Overheated: Lean mixture; Advanced ignition timing; Spark plug too hot.	Check for clogged jets, float level, and ignition timing. Replace with correct heat range plug.
Loss of power; Hard starting; Engine noise	Damaged: Foreign particles in cylinder; Broken or damaged valve.	Replace spark plugs. Remove foreign/damaged components.
Melted spark plug; Damaged piston crown; Cylinder head damage	Under Tightened: Spark plug incorrectly torqued or hand-tightened; Dirt in threads.	Tighten to correct torque. Replace damaged components and check compression.
Hard starting; Reduced fuel economy	Worn: Normal electrode wear (0.03mm/1000km); Fuel deposits.	Replace spark plug with correct heat range.

Visual Identification

Corona Stain: A reddish-brown stain above the metal shell insulator caused by oil particles adhering due to high voltage.

Effect: No deterioration to spark plug function.

Action: Change ONLY at recommended service intervals.

5 Hour Generator Maintenance