www.generalaviationmaintenance.ie

Component Maintenance - Magnetos - Scope of Work

Slick and Kelly Aerospace Magnetos .

ARC Renewals

As Authorised Independent Airworthiness Review Staff, we can carry out an Airworthiness Review for the purposes of the issue of an ARC once we are doing it in the context of a 100 hr/Annual Inspection on the aircraft (non-commercial under 2,730kg MTOW). The Airworthiness Review (AR) process involves:

Review of the Aircraft Maintenance Programme (AMP). (This involves examining the existing AMP to see if anything has changed - e.g. any alterations to pilot owners in group ownership situations, the adequacy of the AMP - e.g. to see if any unscheduled maintenance tasks/events are as a result of DAH recommendations which have been left out of the AMP).
Checking that all applicable Airworthiness Directives have been complied with and that such compliance is recorded in the logbooks.
Checking Life Limited Components
Physical survey of the aircraft
Checking that Type Certificate Data Sheet, Supplemental Type Certificate(s) are in order and the latest revision of the Flight Manual is onboard.

We document the Airworthiness Review and keep the record on file. We issue EASA Form 15c and send a copy by registered post to the IAA (the IAA fee for the ARC is €120 but check the current IAA Fees Order to be sure).

Differential Compression tests

A differential compression test is usually part of the Annual/100hr inspection. This should be done when the engine is hot (preferably after a one hour flight). The results need to be treated with caution as this is a highly unreliable test. Low compression may be an indication of worn piston rings, poor valve seating etc but it needs to be followed up with a borescope inspection to obtain evidence to back up any diagnosis. Cylinder removal or a complete top overhaul should not be initiated on the basis of low compression alone.

Borescope Inspections

Borescope inspections of the engine can reveal problems and impending failures. Poor differential compression test results should always be followed up with a borescope inspection. See photos below of an exhaust valve in a Lycoming O235 L2C engine which show the quality of image and detail which can be seen. The borescope allows us to spot asymmetric heating/colour patterns caused by exhaust gas leakage. Valve guide wear can also be spotted. Scoring or scuffing on cylinder walls indicates broken or improperly gapped piston rings. Pitting corrosion on cylinder walls will indicate corrosion due to moisture and low utilisation. If exhaust gases are leaking around an exhaust valve, the valve can be rehabilitated by lapping in situ without the need to remove the cylinder (which should only be done as a last resort). This may prevent an in-flight engine failure and expensive repair.

A satisfactory borescope inspection provides reassurance that the engine is in good health. It is also usually an essential step in providing an engine TBO extension.

For anyone availing of SAVVY Aviation's excellent consultancy/engine monitoring packages, we can capture the borescope images in accordance with Savvy's recommended protocol (11 images per cylinder) and supply them to the aircraft owner on a USB memory stick for the owner to upload them to the Savvy site themselves.