Page 16 - August 2023

A starter generator installed on a King Air.
If you fly a King Air with -018 starter generators, you might want to check your logbooks to verify that both your starter generators are getting the drive spline lube at the required interval. Logic might dictate you look in your engine logs, but starter generators are an airframe item. Although attached to the engine, starter generators are engine accessories and the aircraft manufacturer (Beech) decides which accessories they want to use. Accordingly, all maintenance information regarding starter generators belongs in the airframe book. Maintenance on anything that came with the engine from the manufacturer (Pratt) belongs in the engine logbooks. Starter generators and tach generators are airframe items. Fuel controls and high-pressure fuel pumps are engine items. Unfortunately confusion abounds on this issue. It is not unusual to find airframe information in the engine logbooks and vice versa, so check all your logbooks to make sure you don’t miss anything.
Brushes
Both the -016 and the -018 starter generators are due for overhaul at 1,000 hours or when brush wear is down
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to minimum. Brushes should last 1,000 hours unless subjected to extreme use. A high volume of starts (as in high-cycle, low-time aircraft) will wear the brushes down faster.
There are those in the field who, if they found brushes worn-out before the 1,000-hour mark, would try to save money by changing the brushes only. In fact, there are some who subscribe to the idea of just changing the brushes until the unit fails completely. Changing just the brushes may be penny-wise, but is pound-foolish.
The problem with new brushes installed in the field is that the brushes won’t seat properly. New brushes have a straight edge but the armature is contoured. This makes the contact between the brushes and the armature very poor. Severe arcing at startup and at altitude is the result. Arcing burns up the armature and pits the new brushes. A vicious cycle ensues: the armature and the brushes degrade rapidly in their fight to obtain a better fit together. So the effort to save money by rebrushing the starter generator only serves to hasten the failure of both the brushes and the armature.
The brushes on your starter generators are checked at every phase inspection. Whenever I found brushes worn ›
AUGUST 2023