Starter Replacement: Consider Weight, Hot Starts

When its time to replace a starter, good choices abound. New starters have unprecedented reliability - so long as the pilot doesnt crank too long.Life Expectancy, Overhaul or Buy New? Buying New, Conclusion

Master switch-on. Mixture-rich. Fuel pump-on until pressure registers, then off. Ignition key-start.

Silence.

Fortunately that result is rare. Almost invariably, when we turn the ignition key to start or hit a starter button on a piston-engine airplane, the starter engages and the prop swings with vigor. Over the past 20 years, new technology has made aircraft starters remarkably reliable-the newer ones should last beyond the engines TBO, if not abused. So, when theres a big silence on hitting the start switch, the chances are that the problem is not with the starter itself. Nevertheless, the time does come when the starter slips its mortal coil and must either be replaced, rebuilt or overhauled.

Well talk about how to make your starter last, a little about troubleshooting problems and what options are available when it gives up the ghost.

 src=

Duty Cycle
The one thing a pilot absolutely needs to do to maximize starter life is to keep from overheating it-that means rigidly following the duty cycle limits.

The process of spinning a small, electric motor to turn over a larger piston engine means that heat is going to build up in the motor quickly. Each starter has a published duty cycle limit-the starter may be operated for a maximum number of seconds and then must cool for a minimum period of time. Tim Gauntt, Director of Product Support for Hartzell Engine Technologies, told us that the one way to almost certainly assure that you damage a starter is to operate it beyond the published duty cycle limits.

Hartzell and Sky-Tec duty cycle limitations call for no more than 10 seconds of turning the starter per attempt before letting it cool/rest. Thats it, 10 seconds. B & C Specialty allows 30 seconds, but then the starter must cool for two minutes.

For all Sky-Tec starters, the rest time after a 10-second start attempt is 20 seconds. The start/rest cycle can be repeated a maximum of six times.

For Hartzell Engineering Technology heavyweight and lightweight Magnaflite (formerly Kelly) starters, the rest time after each 10-second attempt must be 60 seconds. The cycle can occur three times before a 15-minute cooldown is required.

For Hartzells lightweight E-, X- and M-Drive (formerly Kelly) units, the cooldown/rest time is 20 seconds and the start/rest cycle may be repeated 20 times before a 10-minute cooldown is required.
We think those duty cycles are perfectly reasonable. If the engine doesnt start within those times, something is wrong with the engine that needs to be rectified.

Troubleshooting
If you turn the key or press the button and the prop doesnt start turning or only goes to the next compression stroke and stops, dont assume the starter is the problem. Most likely its an electrical system problem. Rich Chaffee of Sky-Tec told us unequivocally that the first step of troubleshooting a starter problem is to pick up a voltmeter. That was echoed by Tim Gauntt of Hartzell. The websites for Hartzell and Sky-Tec have clear guidelines for troubleshooting starter issues-just follow them. Our compliments to both companies for websites that provide a great deal of information in a user-friendly manner. We, unfortunately, cant say the same about B & Cs website due to its lack of info.

Kickback
Aircraft starters were not designed to be forced backward. If the engine kicks back during a start, theres a good chance the starter will be damaged.

Kickback is caused by mistiming of the engines starting system or a problem with the mags that allows a mag that shouldnt be firing to do so during the start. If a cylinder fires before TDC it will develop from 20 to 50 HP backward against the 2-HP starter motor. The starter loses. Kickback can even break teeth on the ring gear of a Lycoming engine.

There is nothing in a pilots starting technique that can cause kickback except for cranking the engine with the mags on BOTH when the POH calls for cranking on one mag-such as on many American Champion aircraft.

Newer starters are designed to break internal components so that no teeth are broken on the ring gear-its cheaper to replace a starter. Hartzell and Sky-Tec offer models of their starters that are protected against kickback.

Starter warranties generally do not cover damage due to kickback. The only one we did find that did so was on Hartzells E-Drive series.

Life Expectancy
In the real world of hot starts, renters grinding the starters of 172s until the battery goes flat and less-than-perfect ignition systems, we got all sorts of responses to the question of starter life. Scott Ward of T & W Electrical Service, a company that has been overhauling starters for decades, told us that they routinely get heavyweight starters that have lasted 800-1000 hours, depending on how hard the airplane starts.

Derek DeRuiter of Northwoods Aviation in Cadillac, Michigan, told us he typically gets from 1000-1500 hours out of a starter, and referred to a nearby Part 135 operator that primarily makes 15-minute flights from the mainland to an island in Lake Michigan as one who sees near the low end in starter life. However, we also got word that the newer lightweight and heavyweight starters will last more than 2000 hours.

Life Expectancy
In the real world of hot starts, renters grinding the starters of 172s until the battery goes flat and less-than-perfect ignition systems, we got all sorts of responses to the question of starter life. Scott Ward of T & W Electrical Service, a company that has been overhauling starters for decades, told us that they routinely get heavyweight starters that have lasted 800-1000 hours, depending on how hard the airplane starts.

Derek DeRuiter of Northwoods Aviation in Cadillac, Michigan, told us he typically gets from 1000-1500 hours out of a starter, and referred to a nearby Part 135 operator that primarily makes 15-minute flights from the mainland to an island in Lake Michigan as one who sees near the low end in starter life. However, we also got word that the newer lightweight and heavyweight starters will last more than 2000 hours.

 src=

Overhaul or Buy New?
Nevertheless, when your starter wears out, whats the better approach, overhaul or buy new?

From a dollars and cents perspective, overhauling (or rebuilding-the process is nearly the same, overhauls can be done in the field and rebuilds are performed by the manufacturer) is less expensive than buying new-figure half to two-thirds the price of a new starter of the same type. John Evans, head of Aerotech of Louisville put it pretty simply, If your starter has been working for the type of flying you do, you can save money by staying with what you have.

Almost all heavyweight starters can be overhauled at specialized shops. Many owners opt for exchanging their worn-out starter for another that has been overhauled or buying an overhauled starter from an overhaul shop or a supplier such as Aircraft Spruce. Depending on the type of starter, we were quoted prices from $200 to $500.

To the extent lightweight starters can be rebuilt-most can-it is through the manufacturer. Prices we saw were in the same range as heavyweight starter overhauls.

Warranties on overhauled/rebuilt starters vary-Hartzell offers six months or 250 hours, Aerotech warranties its overhauled starters for one year, Sky-Tec offers a two-year warranty on all of its starters, new or rebuilt and B & C provides a two-year or 200-hour warranty. Be aware that in order to get warranty credit, you must follow the terms of the warranty to the letter.

Buying New
The selection of new starters available is nothing short of impressive. Hartzell Engine Technologies acquired a number of the existing starter lines from such names as Delco, Prestolite and Kelly, has upgraded them and added a full line of lightweight, permanent magnet starters. If you have a piston-engine aircraft, Hartzell Engine Technologies makes a starter for it.

Sky-Tec has steadily expanded its line so that it makes high-torque lightweight starters for nearly every horizontally opposed, non-geared aircraft engine.

B & C Specialty Products makes lightweight starters for smaller piston engines, especially helicopters and is particularly popular with the airshow set using MT props where starting can be challenging due to lack of inertial mass of the flywheel and prop.

Technology has improved aircraft starters substantially in the last 20 years-much of it powered by a healthy competition between Hartzell Engine Technologies and Sky-Tec. Advanced clutches and solenoids for quick, clean engagement (the Bendix drive for Lycoming starters may become a thing of the past) and disengagement (the bane of starter adapters on Continental engines) mean that a new starter is likely to last through the life of the TBO of the engine on your airplane and well into the next one.

If weight is a consideration, heavyweight starters weigh in the 17-pound range. The newest lightweight starters are less than half that and, with high-torque motors, spin the engine much faster, making starting easier-especially hot starts.

Prices for new starters vary with the type of starter, but start as low as $359 and go up to over $700. We saw no TBOs for new starters. Sky-Tec recommends, not requires, rebuild at 2700 hours-according to GM Rich Chaffee, they should go longer.

Conclusion
If you decide to buy a new starter, our recommendation is to look at the websites for Hartzell Engine Technologies, Sky-Tec and B & C Specialty Products and then call them to talk about the airplane you have and the type of flying you do. They are not going to recommend an expensive, heavy-duty starter suitable for a flight school if you only put 100 hours a year on your airplane. Theyll also discuss weight and balance on your airplane-as choosing a heavyweight or lightweight starter may fix a c.g. problem.

In the scope of interviews with the manufacturers, we learned that each loves talking starters. Tim Gauntt of Hartzell and Rich Chaffee of Sky-Tec both commented that if they didnt get a call from an owner or a mechanic with starter questions during a day, they felt they were doing something wrong.