SB653 - Continental Motors

SB653 - Continental Motors
TELEDYNE CONTINENTAL
®
AIRCRAFT ENGINE
CATEGORY 3
SB653
SERVICE BULLETIN
Compliance Will Enhance Safety
FAA APPROVED
SUBJECT:
HOT MAGNETO TEST
PURPOSE:
To provide test procedure to ensure the integrity of the magneto grounding circuit.
EQUIPMENT
AFFECTED:
All ignition systems utilizing TCM or Bendix magnetos and/or ignition switches on
all aircraft types.
GENERAL INFORMATION:
Magneto ignition systems must be tested in the following manner to ensure magnetos are grounded
after engine shutdown in order to avoid engine ignition from movement of the propeller.
DETAILED INSTRUCTIONS:
1. Prior to engine shut-down, and prior to performing any maintenance on the engine, perform the
Magneto RPM drop-off Test as detailed in the Pilot’s Operating Handbook (Normally found under
Preflight Engine Run-Up Procedures).
2. If no RPM drop is noted when a magneto is individually selected, either the magneto selected is
timed far in advance of the magneto, or a discontinuity exists between the other magneto
primary circuit and airframe ground. Either condition must be remedied before further flight and
before moving the propeller by hand.
3. Stop the engine using normal procedures as detailed in the Pilot’s Operating Handbook.
WARNING
THE ENGINE MAY INADVERTENTLY EXPERIENCE IGNITION OR START-UP
ANY TIME THE PROPELLER IS MOVED. INJURY, DEATH OR DAMAGE TO
PROPERTY MAY RESULT.
4. If there is evidence of discontinuity in the magneto grounding circuit, inspect circuit connections
for cleanliness and tightness, inspect wire and fed-through capacitors (whether mounted inside
or outside the magneto) for continuity, and inspect switch (es) for correct electrical operation.
Repair or replace malfunctioning parts as necessary as specified in the appropriate service
manual.
NOTE . . . Do not use an ohmmeter or continuity tester to troubleshoot the magneto grounding
circuit with the magneto connected, as false continuity to ground will be read through the points or
coil primary windings. Instead, position the magneto shaft so that the points are open, and use a
magneto timing light to troubleshoot the magneto grounding circuit with the magneto connected.
ISSUED
MO
DAY
05
23
REVISED
YEAR
95
MO
DAY
YEAR
TELEDYNE
CONTINENTAL MOTORS
P.O. Box 90 Mobile AL 36601
334-438-3411
PAGE NO REVISION
1 of 1
SB653
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