SB533C Recommended Action for sudden Engine Stoppage, Propeller_Rotor Strike or Loss of Propeller_Rotor Blade or Ti (1).

Recommended Action for Sudden Engine Stoppage, Propeller/Rotor Strike or Loss of Propeller/Rotor Blade or Tip

All Lycoming reciprocating aircraft engines


Applies to all Lycoming aircraft engines (not just direct drive engines); added checklist specific for Lycoming geared engines; updated checklist which applies to all other Lycoming aircraft engines, added check for connecting rod squareness to the checklists.

NOTICE: Incomplete review of all the information in this document can cause errors. Read the entire Service Bulletin to make sure you have a complete understanding of the requirements.

This Service Bulletin identifies propeller/rotor damage conditions and gives corrective action recommendations for aircraft engines that have had propeller /rotor damage as well as any of the following:

  • Separation of the propeller/rotor blade from the hub
  • Loss of a propeller or rotor blade tip
  • Sudden stoppage

A propeller strike includes:

  • Any incident, whether or not the engine is operating, where repair of the propeller is necessary
  • Any incident during engine operation where the propeller has impact on a solid object. This incident includes propeller strikes against the ground. Although the propeller can continue to turn, damage to the engine can occur, possibly with progression to engine failure
  • Sudden RPM drop on impact to water, tall grass, or similar yielding medium where propeller damage does not usually occur

A propeller strike can occur at taxi speeds and during touch-and-go operations with propeller tip ground contact. In addition, propeller strikes also include situations where an aircraft is stationary and a landing gear collapse occurs causing one or more blades to be bent, or where a hangar door (or other object) hits the propeller blade. These instances are cases of sudden engine stoppage because of potentially severe side loading on the crankshaft propeller flange, front bearing, and seal.

Circumstances of a propeller strike cannot always be used as predictors for the extent of engine damage or its future reliability. There can be varying degrees of damage to an engine and propeller from a propeller strike. The initial damage can be hidden but could become progressively worse with time and wear.

Given these possibilities and the fact that there is no identified clear, quantifiable threshold limit or gradient standard to reliably measure the extent of damage to an engine, Lycoming Engines can only recommend BEFORE FURTHER FLIGHT, that you complete the tasks in the sequential order shown in the applicable “Inspection Checklist After a Propeller Strike” included in this Service Bulletin as the corrective action for a propeller strike. One checklist applies specifically to Lycoming geared engines (GO-435, GO480, GSO-480, IGO-480, IGO-540, IGSO-540, and TIGO-541) while the other checklist is for all other Lycoming aircraft engines. Make a copy of the checklist that applies to your engine model, complete it and keep it as a service record. Record all results and any corrective action taken in compliance as per the revision of this Service Bulletin in the engine logbook.


Connecting Rod Parallelism and Squareness Gage

A. Verify that the bearing cap is assembled correctly and is tightened securely.

B. Insert the tapered sleeves (Figure 2) of the Connecting Rod Parallelism and Squareness Gage in the bearing holes in the connecting rod.

C. Pull arbors through the sleeves.

D. Put the gage arm on the arbor.

E. Turn the adjusting screw on the gage arm until it just contacts the arbor.

F. Lock the adjusting screw with the wing nut.

G. Make sure the adjusting screw just contacts the arbor.

H. Remove the gage arm and place it on the other end of the arbor.

I. Measure the distance between arbors.

For exact parallelism or alignment, the distances measured on both sides are to be the same. Record the measurement.

J. Remove the gage arm (Figure 2).

K. Keep the sleeves and arbors in place.


L. Put the parallel blocks (Figure 3) of the Connecting Rod Parallelism and Squareness Gage on the surface plate.

M. Put the ends of the arbors on the parallel blocks.

N. For the squareness or twist check, measure clearance at the four check points in Figure 3 where the arbors rest on the parallel blocks using a feeler gage. Record the measurement.

O. Compare the clearance between each arbor and the parallel blocks against the values in the latest revision of the Service Table of Limits – SSP-1776. If out of tolerance, replace the connecting rods and examine the crankshaft to make sure the crankshaft is not damaged.