The Schweizer 300CB

One operator shares a few basic maintenance tips


Chris Cooper says, “After two years of early retirement I knew it wasn’t for me, so I decided to get back to my aviation roots by opening a helicopter flight school.” He began by consulting with operators of small reciprocating engine helicopters around the country and ultimately chose to use the Schweizer as his primary trainer.

Since opening Hummingbird Helicopters of Minnesota in 2002, his company has operated as many as five helicopters and gained approximately 12,500 flight hours of experience in the Schweizer 300s and Robinson R-22 and R-44 helicopters. Cooper uses these small helicopters primarily for flight training, air rides, photo flights, deer survey, and just about any other use he can find for them.

Cooper says, “I’m a Vietnam era helicopter maintenance test pilot and even though I do not have an A&P certificate, I’ve always maintained a close involvement with aircraft maintenance. I’ve learned the importance of paying very close attention to detail when maintaining a helicopter.” He goes on to share a few lessons learned relating to maintaining the Schweizer 300CB helicopter.

Lubrication
Bill Halpin, director of maintenance for Hummingbird Helicopters, shares, “Grease is cheap and helicopter components are expensive. As you know not all grease is the same, so don’t make assumptions about lubricating using the same type of grease.”

Cooper and Halpin went on to discuss some of the lubrication practices that have been implemented for their Schweizer 300CB. The first stop was the lubrication chart in the Handbook of Maintenance Instructions (HMI) for the 300CB. It’s easy to see that numerous types of lubricants are required and that many areas of the helicopter have different lubrication intervals. Cooper provides the example of the belt drive assembly on the 300CB which consists of a lower drive pulley, an upper drive pulley, and an idler pulley all having different lubricating requirements.

Halpin explains that it’s important to understand the basic concept of purge lubrication; which means to pump new grease into a grease fitting or grease nipple (commonly referred to as a Zerk fitting after the inventor Oscar Zerk in 1929) until all the old grease has been visibly displaced. The HMI requires certain points on the 300CB be greased every 25 flight hours of operation.

Cooper says, “We’ve learned that lubricating certain areas at 10 flight hour intervals is a much better practice for our type of operation. As an example the three main rotor pitch bearings, the flapping hinge bearings, the upper and lower swash plate scissors links, the main rotor droop stop, and the main rotor swash plate bearing sleeve all get purge lubricated at every 10 flight hours on our Schweizer.”

They also caution helicopter maintainers to be mindful of the operating environment. There may be multiple types of grease approved for one application. Make sure you use the best type of grease for the climate you operate in.

An example of this is the Anderol 786 grease which the HMI states is used when the temperatures are 17.8 C or 0 F and above. Cooper shares, “Here in the cold climates we routinely operate in temperatures below 0 F. We’ve learned that an approved alternative Syn-Tec 3913G1 holds up better in these cold weather operations.”

Another tip regarding operating environments is to always purge lubrication after operating the helicopter in the rain, or in dusty or dirty conditions. The HMI for the 300CB speaks to lubricating the rotor head bearings after operating in the rain.

Purge lubrication also requires a detailed cleaning when completed. You need to remove the excess grease that was displaced during the lubrication task. The rotating areas of the helicopter will sling a certain amount of grease, so removing all excess after the purge will provide a cleaner area.

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