A repair shop forwarded us a competitor’s set of FAA PMA starter generator bearings for further inspection and lab analysis. These bearings (for Goodrich/APC starter generators) were offered at a very affordable price. But we were curious, and asked ourselves: “How can these bearings that are the same size and somewhat similar in appearance be priced lower than the rest? More importantly, are they of the same design and material quality as those offered by Miraj and other industry leaders?” So we investigated, and below is a summary of our findings.

1. The PMA supplier of the affordable bearings in question was actually utilizing a $7 Chinese-made industrial bearing available from almost any indsutrialgrial/agricultural bearing distributor. They actually tried to rub off the name of the manufacturer from the seal itself, damaging it in the process. Conclusion: Why take the chance and install a $7 industrial bearing in your starter generator? Miraj supplies a precision US-made Abec 7 bearing for starter generator applications that is far safer and more durable. Never settle for a lesser product to save a few dollars — you always end up paying more in the long run.

2. The industrial bearings in question utilize only a low cost, Buna-N rubber seal rated for only 250 °F degrees. The PMA holder also utilized an industrial/consumer goods lubricant not used by any OEM or established industry aftermarket PMA holders. Conclusion: The use of an inferior seal and lubricant can lead to lubricant failure, overheating, and premature bearing failure. Why take a chance with your customer’s valuable equipment? Miraj supplies a bearing with Viton seals carrying a temperature rating of 550 °F degrees.

3. The PMA bearings utilized a ball piloted retainer/cage, which is not the type preferred by the OEMs and other industry leaders, Miraj included. This type of cage can lead to unacceptable levels of heat at high speeds, lubricant deterioration, and premature failure.