FREQUENTLY ASKED QUESTIONS
CRITICAL SERVICE BULLETIN 99-3
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Q: What is the cause of the crankshaft fractures? A: TCM’s investigation has revealed that a small fracture in the crankshaft surface has occurred on a limited basis during crankshaft assembly.
Q: How can TCM assure me that after the crankshaft inspection, my engine will no longer be susceptible to this problem? A: The present inspection is designed to detect any surface fracture in the area known to have been fractured during crankshaft assembly. If the inspection does not detect a surface fracture in the affected area, a surface fracture should not occur in this area, unless a fracture is generated by other subsequent causes.
Q: What is the range of serial numbers of the affected engines? Is this range adequate enough to cover any possible problems and find all the affected crankshafts? A: Although the limited number of fractures are closely grouped around three dates in March, May and June, 1998, out of an abundance of caution, TCM is requiring inspection of all crankshafts manufactured in 1998. This should be sufficient to detect any other crankshafts that experience a problem.
Q: What is the factory doing differently that will guarantee the new crankshafts will not have the same problem? A: The factory has modified the procedure that was causing the problem. The problem with the crankshafts was an isolated one confined to a particular process and procedure. The factory will continue to stand behind its product.
Q: When can I safely fly my aircraft? A: As soon as the inspection is accomplished.
Q: If I had a field overhaul rather than a factory rebuilt engine and the crankshaft was replaced would I have a suspect engine? A: Any Crankshaft manufactured in 1998 is subject to the inspection, regardless of what engine it is installed in. Q: How is the inspection done? A: Two cylinders are removed to gain access to the crankshaft. Two connecting rods and the counterweights are also removed. The crankshaft is then visually inspected, inspected with an ultrasonic probe that can detect very small cracks.
Q: Who will do the work on the engine? A: The preparation for inspection by removing the cylinders and the replacement of the cylinders will be done by the FBO of your choice. TCM qualified personnel will perform the crankshaft inspection.
Q: Who will pay for this inspection? A: TCM will pay for the work as described in the Service Bulletin CSB 99-3.
Q: What happens if a problem is found with my engine? A: The engine will be removed and returned to TCM for crankshaft replacement. Following rebuild, the engine will be tested in the same manner as a new engine prior to return.
Q: Since this inspection requires removal of two cylinders; won’t this effect the ring seating and perhaps cause the engine to have low compression and burn oil? A: The procedure for cylinder removal in CSB 99-3 contains specific instructions to leave the piston and rings inside the cylinder bore and only pull the piston out far enough to remove the pin. This does not disturb the cylinder and ring interface and will not result in changes to cylinder operation.
Q: This inspection requires cylinder removal and throughbolt nuts to be removed. Shouldn’t the throughbolts be replaced and all throughbolts loosened and torqued in the right sequence. A: The removal of one or more cylinders in the field does not disturb the fit of the crankcase to the crankshaft as long as the correct torques are applied during the replacement. TCM CSB 99-3 provides instructions for the procedure along with the correct torque values to be used. Care must be taken to torque the throughbolts from both sides as is indicated in the instructions. The throughbolts are not removed from the case and do not need to be replaced. Q: Are these crankshafts VAR material or Air Melt? A: All crankshafts used by TCM are VAR materials. The cause of this issue is mechanical damage cracking the surface. The material has been checked and found to be correct and properly processed and is not a factor in this problem. |