Section 16.11–16.13

Installation, Ground Operation & Storage

Engine mounts and cowling, the run-up mag check, shock cooling, ground-running care and preservation.

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Main ideas

The engine is carried on mounts that absorb vibration and carry thrust and torque into the airframe, behind a firewall, inside a cowling with baffles that direct cooling air; flexible lines and connections allow for movement.
Ground operation follows a set procedure: start, warm-up until oil temperature/pressure are healthy, run-up to check each magneto (the dead-cut/RPM-drop 'mag check') and cycle the propeller, then monitor temperatures and pressures — avoiding prolonged ground running, which overheats an air-cooled engine.
The magneto (dead-cut) check confirms both ignition systems and their plugs work, that the RPM drop on each mag is within limits and roughly equal, and that the switch grounds the mags correctly.
'Shock cooling' — a rapid power reduction that cools the cylinders too quickly (e.g. a fast descent at low power) — can crack cylinders and is avoided by gradual power changes.
Storage and preservation protect an inactive engine: inhibiting oil, dehydrator (desiccant) plugs, sealed intakes/exhausts and periodic turning; CORROSION (from moisture and inactivity, attacking cylinder walls and the camshaft) is the chief enemy — the engine must be de-preserved before flight.
⚠ Exam trap: the run-up mag check verifies each magneto/plug set and that the switch grounds the mags; the main threat to a STORED piston engine is internal CORROSION from inactivity/moisture — hence inhibiting oil and desiccant plugs.

Solved examples

During the run-up the RPM drop on the left magneto is far larger than on the right (and near the limit). What does an excessive single-mag RPM drop suggest?
A large RPM drop on one magneto means that ignition system is not firing all its plugs properly — commonly a fouled or dead spark plug, a faulty HT lead, or a magneto timing/internal fault on that side. Because dual ignition also aids combustion, running on the weak mag is rougher and slower; the fault must be investigated before flight.

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