The International Cessna^® 170 Association

On an aborted take off we recently went through a wire fence (Farm type).
The engine was already throttled back and was switched off after striking the fence wire but did not stop as a result of the strike. The prop has two 1mm deep gouges on one blade and one on the other. As the prop was already overhauled in the past and was just in limits for a 170A we will replace it. We reran the engine to taxi the long way back to the hanger, it r5an fine. The question is what do you need to do to check the engine etc? Advice?....we prefer to fly safe!
*******
Bert

TCM says a mandatory engine tear-down inspection is Mandatory if the prop requires removal for repair. (If you have insurance, the only folks who'll save money by not complying with this Mandatory inspection will be the insurance company.)
The text of TCM SB96-11 follows, regarding Prop Strikes:


TELEDYNE CONTINENTAL ® AIRCRAFT ENGINE
SERVICE BULLETIN

SUBJECT: PROPELLER STRIKES AND HYDRAULIC LOCKS.
PURPOSE: PURPOSE: PART I: PROPELLER STRIKE INCIDENTS:
Provides definition of propeller strike and foreign object damage (FOD),
possible resulting damage that can occur from such incidents and
required inspections and corrective actions mandated by TCM to return
the engine to service.
PART II: HYDRAULIC LOCK:
Provides definition of hydraulic lock, the conditions that can lead to a
hydraulic lock event, how to prevent it, and the inspection and
corrective actions mandated by TCM to return the engine to service.
COMPLIANCE: PART I: Anytime a propeller strike incident occurs, perform the
inspections set forth in this Service Bulletin prior to further engine
operation.
PART II: As set forth in the instructions contained in PART II.
MODELS
AFFECTED: All Teledyne Continental Motors (TCM) engine models.
PART I - PROPELLER STRIKE INCIDENTS
A propeller strike is: (1) any incident, whether or not the engine is operating, that requires repair
to the propeller other than minor dressing of the blades as set forth in Part I, B of this Service
Bulletin or (2) any incident while the engine is operating in which the propeller makes contact
with any object that results in a loss of engine RPM. Propeller strikes against the ground or any
object, can cause engine and component damage even though the propeller may continue to
rotate. This damage can result in catastrophic engine failure.
A. PROPELLER STRIKE INSPECTIONS.
Following any propeller strike a complete engine disassembly and inspection is mandatory and
must be accomplished prior to further operation. Inspect all engine accessories in accordance
with the manufacturer's instructions. In addition to the engine component inspection
requirements set forth in the appropriate overhaul manual, pay particular attention to the
following areas while performing the specified non-destructive testing:
1. Crankshaft surfaces forward of the front main bearing journal. These surfaces must be free
of sludge, paint or any other substance that could mask reliable magnetic particle inspection
indications.
2. Forward crankcase bearing support and adjacent structure.
CATEGORY 3
SB96-11
FAA APPROVED
Supersedes M84-16
ISSUED REVISED PAGE NO REVISION
MO DAY YEAR MO DAY YEAR 2 of 4
09 10 96
TELEDYNE CONTINENTAL MOTORS
P.O. Box 90 MOBILE ALABAMA 36601
334-438-3411 SB96-11
NOTE ... In addition to any part that is damaged, TCM recommends for counterweight equipped
engines, replacement of all counterweight pins, bushings, end plates and snap rings regardless
of their condition.
B. MINOR FOREIGN OBJECT DAMAGE (FOD) INSPECTION.
For instances where the propeller is damaged by a small foreign object during operation, such
as a small stone, inspection and repair must be accomplished in accordance with the propeller
manufacturer's published instructions. Any time foreign object damage requires propeller
removal for repairs other than minor dressing of the blades, the incident is considered a
propeller strike and must be inspected as outlined in paragraph A above.
PART II - HYDRAULIC LOCK
WARNING
OVER PRIMING CAN CAUSE A FLOODED INTAKE RESULTING IN A
"HYDRAULIC LOCK" EVENT AND SUBSEQUENT ENGINE MALFUNCTION
OR FAILURE. IF YOU OVER PRIME, OR FLOOD YOUR ENGINE, MAKE
CERTAIN THAT ALL FUEL HAS DRAINED FROM THE INTAKE MANIFOLD
AND/OR CYLINDER PRIOR TO ATTEMPTING ENGINE STARTING.
WARNING
MODIFICATION OF OR DEVIATION FROM THE ORIGINAL INTAKE
MANIFOLD DESIGN MAY RESULT IN INSUFFICIENT DRAINAGE OF THE
INTAKE MANIFOLD, RESULTING IN AN INCREASED POTENTIAL FOR
HYDRAULIC LOCK. ALL INTAKE MANIFOLD DRAINS MUST BE PROPERLY
PLACED, AND OPERATIONAL.
A. GENERAL INFORMATION
Hydraulic lock is defined as a condition in which a volume of liquid, equal to or greater than the
clearance volume of the combustion chamber, is drawn into the cylinder during starting. This
liquid, being incompressible, restricts piston travel during the compression stroke. Damage only
occurs after the preceding cylinder or cylinders in the firing order have fired, thereby providing
the required force to drive the piston of the fluid filled cylinder through the compression stroke.
Most hydraulic lock events in horizontally opposed aircraft engines are due to fuel accumulation
in the induction system and/or cylinder assembly and usually occur in one of the forward
cylinders. Over priming prior to or during engine starting will allow fuel to accumulate in the
induction system or cylinder faster than the system drains can evacuate it. Other causes of
hydraulic lock can be attributed to:
1. Restricted or clogged induction system or cylinder drain(s).
2. Extended operation of the electric boost pump:
a. During failed engine start.
b. Following loss of power during ground operation.
ISSUED REVISED PAGE NO REVISION
MO DAY YEAR MO DAY YEAR 3 of 4
09 10 96
TELEDYNE CONTINENTAL MOTORS
P.O. Box 90 MOBILE ALABAMA 36601
334-438-3411 SB96-11
c. Following momentary engine shutdown.
d. During single engine operation for training purposes on twin engine aircraft.
3. Over priming and attempting engine start with the aircraft parked on an incline that negates
the effective operation of the drain system.
4. A failure to drain oil from cylinders that have been preserved.
Damage from a hydraulic lock can be extensive. Engine components such as connecting rods,
cylinder assemblies, pistons, piston pins, crankcase and crankshaft can be damaged due to the
extreme stress. Subsequent failure of these components can occur if the instructions set forth
in this service bulletin are not followed.
B. PRECAUTIONS PRIOR TO AND DURING STARTING
1. Owners, operators and maintenance personnel must become familiar with the type,
operation, total number and location(s) of the fuel drain(s). This information is provided in
the Aircraft Manufacturer's or STC holder's Maintenance and/or Flight Manual.
NOTE: Verify that the boost pump switch(es) are in the "OFF" position prior to turning the
master switch on.
Each time the engine is manually primed, or the electric boost pump is energized for fuel system
leak check or for priming before or during engine start, observe the following precautions:
a. Fuel priming must be accomplished in accordance with the instructions specified by the
Aircraft Manufacturer or STC holder and only with a properly functioning drain system.
b. Prime and start engine(s) while the aircraft is positioned on a level surface.
c. Prime only as long as required to achieve a stabilized fuel flow or pressure indication
and in no case exceed the Aircraft Manufacturer or STC holder's limitations.
d. If prolonged priming or inadvertent operation of the boost pump has occurred, verify
visually that fuel is running from the system drains. Starting must not be attempted until
all fuel has drained from the induction system.
e. If fuel draining is not noticed during priming, discontinue priming and remove, repair or
replace drain(s), associated hoses and hardware in accordance with the Aircraft
Manufacturer's instructions. Make certain that the system drains are functioning
properly and that fuel drains from the system prior to engaging the starter.
2. If the engine has been in storage and/or preserved, drain all preservative oil in accordance
with the latest revision of the TCM Service Bulletin concerning engine preservation prior to
engine operation.
C. SYSTEM DRAIN INSPECTION
At each scheduled maintenance interval, perform the following inspection to ensure that the
drain(s) function properly:
ISSUED REVISED PAGE NO REVISION
MO DAY YEAR MO DAY YEAR 4 of 4
09 10 96
TELEDYNE CONTINENTAL MOTORS
P.O. Box 90 MOBILE ALABAMA 36601
334-438-3411 SB96-11
WARNING
DO NOT ROTATE THE PROPELLER OR ALLOW ANY PERSONNEL TO
STAND IN THE AREA OF THE PROPELLER ARC WHILE PERFORMING THE
FOLLOWING INSPECTION.
1. Perform a normal engine start priming sequence in accordance with the Aircraft
Manufacturer or STC holder's instructions.
2. Observe the drain location(s) in the engine cowling and make certain that fuel drains from
each.
NOTE: On some installations, drains are located in the induction system where fuel draining
will not be observed during priming. In this case, the drain must be inspected as
necessary to determine that it is functioning properly.
3. Remove, clean or replace any drain that does not function properly.
D. INDICATIONS OF POSSIBLE HYDRAULIC LOCK
In the event the operator starts an over-primed/flooded engine, hydraulic lock may result.
Indications of hydraulic lock are difficult to detect since the engine will not normally exhibit any
unusual operation once the fuel-air mixture stabilizes. Therefore, the operator must be
cognizant of the fact that a hydraulic lock can occur anytime an attempt to start an overprimed/
flooded engine occurs. In the event that the operator starts an over-primed/flooded
engine or suspects a hydraulic lock has occurred, he must make certain that the inspection
procedures in Section E are followed.
E. INSPECTION PROCEDURES FOR SUSPECTED HYDRAULIC LOCK.
In the event of a suspected hydraulic lock, perform the following inspection:
1. Remove all cylinders and connecting rods in accordance with the applicable TCM Overhaul
Manual. Inspect the connecting rods in accordance with applicable TCM Overhaul Manual.
2. If all rods meet the criteria specified by TCM, reassemble the engine in accordance with the
overhaul manual.
3. If any connecting rod does not meet TCM acceptance criteria, remove and disassemble the
engine to allow inspection of the crankcase and crankshaft in accordance with the
applicable TCM Overhaul Manual. Replace any part that does not meet Overhaul Manual
inspection criteria. Replace each non-conforming connecting rod and its associated piston,
piston pin and cylinder assembly.
NOTE: Any parts that require replacement must be destroyed to prevent future installation.
4. Reassemble the engine in accordance with the applicable TCM Overhaul Manual and return
the aircraft to service.
AFFECTED
PUBLICATIONS: Insert a copy of this service bulletin into the appropriate section of all TCM
Maintenance and Operators Manuals.

Sounds like your prop is not bent and other than being at limits may be able to be fixed by dressing. If this would be the case then no tear down is necessary according to TCM.

This will be up to you and or your mechanic. It'll be your butt and your passengers flying behind this engine and maybe sometime down the road you'll sell the plane to someone else.

The only sure way to go is to tear down and inspect.

Just had to make the same call myself with a A-65 that the prop struck soft turf as it was coasting to a stop. Prop was so slightly bent that it was very difficult to detect. There was little to no damage to the edge of the prop.

A lot of knowledgeable people giving "FREE" advice said fix the prop and fly it. Insurance Co., after investigation said they'd pay for tear down cause of TCMs SB. Thats what I did and there was no damage. Everyone feels better. Insuance CO. is out $3500 and I'm out $1200 for unrelated engine repairs Insurance wouldn't pay for.

You'll notice that TCMs SB is dated 1996. Not sure if they had a written policy before this one. The SB is probably a "Cover Their Butt" SB.
(Just reread TCMs SB and they did have a message dated 1984)

Old timers will tell you in the old days with damage like mine and like yours sounds to be (going way out on a limb here), they'd have repaired or replace the prop and forgot about it.