Canada’s Marsh Brothers Aviation (“Marsh Brothers”) has unveiled an innovative new bearing upgrade kit for the turbocharged engines on the Piper Aerostar aircraft.
Developed to boost bearing reliability and reduce replacement intervals, Marsh Brothers Aviation’s Aerostar Turbo Cross Shaft (TCS) Bearing Block Kit is the first upgrade solution to incorporate one of the company’s newest polymers, AeroTough HT (ATHT) – an engineered self-lubricating polymer developed specifically to withstand higher temperatures.
Incorporating all the key components required to replace the traditional turbo cross shaft bearings on the twin-engine, propeller-driven Piper Aerostar (formerly Ted Smith Aerostar) aircraft, the new kit has been demonstrated in extensive trials to provide a superior alternative to OEM parts.
The kit features the ATHT polymer bearing installed into an aluminum journal block (inboard/long and outboard/short) and also a high-strength stainless steel end shaft and upgraded OEM cross shaft, that screws into the main cross shaft across the engine. One TCS Kit is all that is needed for each engine, with no requirements for additional components, lubrication, or parts.
Replacing the original Inconel® superalloy bearings in the aircraft’s engine bay, the Marsh Brothers’ self-lubricating ATHT bearings – each measuring approximately ¾” diameter (19mm) – has a dramatic impact in reducing maintenance demands, said Nicholas Choo-Son, Director Business Development for Marsh Brothers Aviation.
“The original application required replacing the bearings every 150 flight hours. Marsh Brothers Aviation operates an Aerostar and previously we were typically changing out the bearings every year,” he said. “Since we developed the ATHT bearings, our company aircraft has flown three times the previous replacement interval and the materials are showing no sign of distress.”
Each aircraft requires four bearings – two for each engine. The cross shaft mechanism in the Aerostar is not easily accessible for replacing the bearings, so maintenance costs can be high. Marsh Brothers carried out some time studies working with installers, which established that it takes four to six hours to replace the bearings on one engine.
“So, we are talking about one-and-a-half to two days to replace all the bearings,” said Choo-Son. “There is a big cost factor involved in that.”
“Having the opportunity to fly the Marsh Brothers’ own Aerostar aircraft for three years while fitted with the ATHT bearings has been valuable in terms of building confidence along with the engineering analysis,” said Choo-Son. “The product development period stretches back five to six years, to the early stages of developing the ATHT polymer.”
Marsh Brothers has secured Transport Canada, FAA (Federal Aviation Administration) and EASA (European Union Aviation Safety Agency) approval for the Aerostar TCS Kit. The new product is configured to integrate with the upgraded cross shaft P/N 300035-527 with removable end shafts.
A high level of interest in the new TCS Kit is expected from pilots, owners, maintenance shops and Aerostar fleet operators. Four other Aerostar owners have already trialed the new product and become early adopters.
Jimmy Mullen of Mullens Aviation, who installed the new kit in his 1980 601P N601DJ Aerostar in July 2021, said: “These self-lubricating polymer bearings have saved time and money. The bearings last at least three times longer than the OEM metal bearings, significantly reducing aircraft lifecycle maintenance costs. The performance is excellent and they were very simple to install, taking far less time to replace.”
The new TCS Bearing Block Kit is Marsh Brothers Aviation’s first cross shaft application for an aircraft. Marsh Brothers is exploring other aircraft applications for this new engineered self-lubricating polymer material.
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A partnership between Marsh Brothers Aviation and DarkAero is generating considerable interest in the use of composite materials across the wider aviation industry. The collaboration between the companies, which started in 2018 with a chance meeting at an aviation event, is yielding results for Canada’s Marsh Brothers and the three-sibling start-up DarkAero with the development of the latter’s high-performance self-build aircraft kit.