Keeping The Starter Engaged

The good news is that newer design starters don’t need any preventive maintenance. If the starter has permanent magnets, as do all lightweight starters, there’s no requirement or even recommendation for preventive maintenance. Rich Chaffee, general manager of Sky-Tec, put it bluntly, Just use it.

Bill Bainbridge, owner of B & C Specialties, the company that made the first lightweight aircraft starters, told us that his starters do not have permanent magnets, but do not need preventive maintenance.

If you have a heavyweight starter, it has brushes that wear and can break due to vibration. John Evans, who runs Aerotech of Louisville, a company that specializes in overhaul and repair of starters, told us that he recommends pulling a heavyweight starter every other annual and going through it to check on the condition of the components. He also recommends having the prop balanced on aircraft with heavyweight starters. Hes observed that doing so reduces vibration and improves their life.

Lycoming starters that use a Bendix drive to engage the engine flywheel have a frustrating tendency for the Bendix drive to not actually engage the flywheel, unless preventive maintenance is performed. The starter simply whirs while the prop remains stationary and the pilot steams. Its most common on airplanes that don’t fly regularly-allowing corrosion to develop on the steel shaft on which the Bendix drive moves, causing the drive to hang up. Those Bendix drives should be sprayed with dry silicon lubricant every 25 hours. It is also recommended that on those with brushes instead of permanent magnets, that the brushes be inspected every 100 hours.

When out in the boonies and a Bendix drive refuses to engage, shutting everything off, taking the key out of the ignition, getting out of the airplane and using something solid to tap on the cup around the drive has been known to free it.

Experienced pilots operating starters that sometimes have the Bendix drive hang up use a bush technique that takes advantage of the design of the drive to assure it will engage on the next start.
The Bendix drive is designed so that once it engages the engine flywheel, it will not disengage until the engine starts. Pilots who are concerned about the next start take an extra step after a normal post-flight shutdown: With the mixture at idle cutoff, they briefly-very briefly-hit the starter. The drive is normally nice and warm and will move freely because of the vibration of the just-concluded flight.
The Bendix will usually do its thing and engage the engine flywheel. Because the pilot only briefly activated the starter, the prop will barely move and the engine will not start. The starter is, however, now engaged to the engine flywheel and ready to turn the engine over when its time for the next flight.