IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
72-20
March 2020
Page 145
IO-390-D Series Engine Maintenance Manual
Crankshaft Inspection Checklist for IO-390-D Series Engines (Cont.)
Item
Comments
Findings/
Corrective Action
Done
Criteria for Crankshaft Gear Replacement
Lycoming Engines no longer approves rework or repair of an unacceptable crankshaft gear.
Replace the crankshaft gear with a serviceable crankshaft gear if any of the following are found
during the crankshaft gear identification and inspection.
•
If the pilot flange diameter is less than 2.125 in. (53.975 mm) or is not in compliance with
dimensions shown in Figure 29
•
If the crankshaft gear does not have the larger scallops as shown in Figure 28 (the larger
scallops enable the shim check)
•
Damaged counterbore face of the crankshaft gear
•
If the crankshaft gear has a hole or slot and there are any nicks or dents on the hole or slot
•
Nicks or deformities on the slot and teeth of the crankshaft gear
•
Pitting or wear
•
Crankshaft gear that fails magnetic particle inspection
•
Clearance between the mating surfaces of the crankshaft gear and crankshaft counterbore
(There must not be any clearance when the crankshaft gear is installed.)
Crankshaft Counterbore Inspection
CAUTION
DO NOT TRY TO REPAIR THE CRANKSHAFT COUNTERBORE
THREADS IN THE FIELD. IF THIS TYPE OF REPAIR IS NECESSARY, IT
IS RECOMMENDED THE CRANKSHAFT BE SENT TO THE FACTORY
(THROUGH AN AUTHORIZED LYCOMING DISTRIBUTOR) WITH
PAPERWORK THAT IDENTIFIES THE NECESSARY REPAIR.
NOTICE:
Prior to inspection, the crankshaft counterbore must be clean, dry, and free of debris.
Refer to the “Crankshaft Counterbore Cleaning” procedure in Chapter 05-30.
Make sure the threads in the
counterbored end of the
crankshaft are intact and not
galled, stripped, or damaged.
If the threads are galled, stripped
or damaged, it is recommended
the crankshaft be sent to
Lycoming Engines (through an
authorized Lycoming distributor)
with paperwork that identifies the
type of damage. Do not try to
repair the threads in the field.
Measure the Inside Diameter
(ID) of the crankshaft
counterbore at the rear of the
crankshaft to make sure there is a
correct fit between the ID of the
crankshaft and the Outside
Diameter (OD) of the crankshaft
gear pilot flange. The crankshaft
counterbore diameter at the rear
of the crankshaft must not be
more than 2.126 in. (54.000 mm)
when measured at any location.
If the diameter is oversized,
replace the crankshaft.
Lycoming Engines no longer
approves rework or repair of an
unacceptable crankshaft
counterbore diameter.
