The flight instructor reported that he and the pilot receiving instruction had completed a local instructional flight and were returning to the airport in Burlington, Mass.
While the Cirrus SR22 was about 1,700 foot mean sea level, the engine began running roughly and subsequently lost all power.
The pilot receiving instruction immediately handed over the flight controls to the flight instructor.
The flight instructor attempted to maneuver the airplane to a field for a forced landing, but realized that the airplane would not be able to reach the field, so the pilots activated the ballistic parachute system.
After the parachute deployed, the airplane touched down in an area of dense vegetation.
An examination of the engine revealed that the crankshaft had fractured at the No. 2 main journal and that the camshaft had fractured between the No. 2 and No. 3 main bearing supports.
The No. 2 main bearing had shifted, and fretting was present on the main bearing supports, consistent with a loss of clamping load on the crankcase, which resulted in movement of the No. 2 bearing and excessive loading on, and the ultimate failure of, the crankshaft.
The nuts securing the No. 5 cylinder to its two crankcase through bolts had less torque than that specified by the engine manufacturer’s installation guidance, and it is possible that the loss of clamping load on the crankcase was due to a loss of torque to the adjacent No. 5 cylinder crankcase through bolts.
According to maintenance records, the No. 5 cylinder had been removed and replaced about four months, or 27 flight hours, before the accident.
Although the logbook entry indicated that the through bolts were torqued “from each side to [the engine manufacturer’s] specifications,” it is likely that, while replacing the No. 5 cylinder, maintenance personnel did not properly torque the cylinder crankcase through bolts, which resulted in displacement of the No. 2 bearing and the catastrophic failure of the engine.
The NTSB determined the probable cause as a loss of clamping load of the No. 5 cylinder crankcase through bolts due to maintenance personnel’s failure to properly torque the through bolts during recent maintenance, which resulted in displacement of the No. 2 bearing and the subsequent catastrophic engine failure.
NTSB Identification: ERA14IA301
This June 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
There seems to be one common error in the torquing of fasteners, and that is, ” that for unknown reasons, people installing and torquing fasteners and lubing the fasteners before they torque them, This is a no no ! You never lube a torqued fastener. Oil is a very good loosenar, that is what it does best, If you lube a nut or bolt and then proceed to torque it, it will loose its torque as soon as you fire up the engine, and will continue to loosen until there is no torque left. The proper way to torque a fastener is to clean it very good in good clean solvent such as stoddard solvent or use a new fastener, clean it of any fist oil or preservative and use it without any lube at all, that way the fastener will remain torqued throughout its entirety. We have replaced dozens of cylinders in the shop and have not had any failures due to loosening fasteners. We also never lube nuts or bolts before torquing. This is in all your machinist handbooks..
Totally incorrect information. Aircraft cylinder through bolt nuts and base stud nuts require lube on the threads (as specified by the manufacturer) to achieve the proper clamping force and fastener pre load.
In the case of the Cirrus, were new nuts used on installation of the cylinder studs and through bolts. I don’t know what the procedure calls for, but it is a proven fact that reusing nuts will result in less clamping force even if the nuts are torqued to the correct value.
I was once part of a group where this was demonstrated using a load cell with a hole in the middle for a bolt to pass through. Each successive torqueing of the nut resulted in less and less clamping force. The object lesson was to never reuse nuts in critical applications.
Just like some owners wanting not to spend money on an annual inspections. But on the other hand would go out an purchase a Tesla to show off at the airport.
We have all seen mechanics the are mechanics and some that shouldn’t be. Possessing an A&P doesn’t not a mechanic make. Even some FBO’s are the same way. Bottom line is cash. Good work comes good pay.
I have been bending wrenches for over 45 years
FWIW,
Notwithstanding what may or may not hold up in a court of law regarding the accuracy of headlines, I would like to personally thank the people who put these articles out so people like me can read them, period.
PLEASE KEEP UP THE GREAT WORK
non atp flyer
Poor headline………… the NTSB has not given a definitive reason………. they stated it was likely… however that is not the same as….. “we have proved that this was the cause”………. it is circumstantial…….. a better headline………….. “suspected improper maintenance leads to deployment of the ballastic recovery chute system on an SR-22 Cirrus”.
Your headline would not stand in a court of law…………… and it does not help any pilot understand the rationale and significance of ensuring that maintenance procedures (from the OEM) are followed. 30 years ago an engine fell off a DC-10 coming out of Chicago…….. why? Because the maintenance folks took an un-approved shortcut in how they removed and replaced an engine…. a few flights later… the engine fell off and 150 people died.
Well, you are not quite accurate about the crash of AA191 in May of 1979. The engine falling off was only part of the reason. The pilot flying followed then current procedures to the letter and slowed to what he thought was Vmc. Unfortunately, when the engine departed the wing, hydraulic lines were severed, resulting in the slats retracting on that side of the wing and some flight controls loosing effectiveness. The increase in Vmc and the reduced control effectiveness doomed the plane. Even at the low altitude, if the pilots had known to increase their speed, they might have been able to fly out of the situation. In simulator trials, pilots who kept their current speed when the engine failed were able to maintain control and stay airborne.
No argument that improper maintenance procedures were the root cause, but FAA inspectors had witnessed the procedure on more than one occasion, and by not questioning anything, in truth gave tacit approval. Don’t know if FAA oversight was listed as a contributing factor.
Both incidents beg the question of how a pilot is supposed to know or check if a mechanic has used proper maintenance procedures. I am sure I would have no way of knowing if my mechanic had not torqued some bolts to the specified value.