Four stroke engine maintenance

	From left to right:  Fellow Xtreme owner Wayne Campbell and Ken Armstrong study Bing carb starting circuit. Also shown, James Mohns foreground, David King, Tony Gagliano and Gerry Kinsey during classroom session.
	Ken Armstrong runs up his Xtreme while Director of Maintenance, Rob Seaton, shows Tony Gagliano vacuum system for balancing carbs.
	Rotax engine cut aways
	Rotax engine cut aways
	Rotax engine cut aways
	Course graduation photo with instructors

As an aircraft owner and professional pilot who often flies Rotax four-stroke engines, I have been subject to inconveniences due to the significant shortage of AME and A&P mechanics who are qualified on these engines across North America.

Since Rotax is approaching five million engines in service and will soon introduce their six cylinder series in the 200-300 hp range to OEM customers who are desirous of these engines, it is a prudent engine shop that qualifies their staff on these popular powerplants.  But few do. 

Although I forecast this trend in ignorance will end as these organizations smarten up and the proliferation of these popular powerplants continues; nonetheless getting knowledgeable service on these engines can lead to problems. 

Thus, I invested a week of my time to learn the tips, tricks and requirements of these engines while acquiring the maintenance and tear down manuals for the series to aid my AME of choice when it comes to working on my machine.

Essentially, the 900 series Rotax are so beefy, they are inherently trouble free. However, like any engine, there are normal servicing procedures that need to be completed on a scheduled basis to ensure the engine is set up to produce the maximum power in a minimal vibration environment. Unfortunately, too many operators ignore these inspections and the same is true of engineers who are selected to maintain them.

While I am not a qualified AME, I have worked with my engineering counterparts on many of the 400 planes and helicopters I have flown and can readily observe these relatively new engines are the wave of the future. 

Moreover, they are very different to maintain and troubleshoot when compared to the Lycomings, Continentals, Franklins and other engines that formed our fleets of yesteryear.  

These Rotax’s have to be different with their modern day ignition systems and gearboxes that multiply propeller thrust while reducing fuel flow and pollution. The market demands these advances and sales numbers confirm this observation.

Many mechanics look at these horizontally opposed flat engines and reckon they look like the old technology aircraft engines, so they must be similar to work on. They aren’t!   For instance, did you know that applying the choke at any throttle setting beyond idle will lean the mixture on the Rotax series? 

Did you know these four strokes feature essentially trouble free, redundant CDI ignition and dry sump lubrication systems and there is no pump to return crankcase oil to the reservoir? (Oil is returned courtesy of crankage pressure – simple but efficient as there are no reliability or maintenance issues....).

The engineer looking for magnetos to time or overhaul is going to be stumped. For that matter, the CDI system requires little attention. The Rotax’s dual altitude-compensating carbs on the popular 900 series Rotax engines require not only mechanical linkage tuning, but also pneumatic tuning with simple equipment on a regular basis to ensure they are working together. It’s not difficult to accomplish – just mandatory. 

Failure to balance them correctly can lead to a host of additional engine problems related to vibration. Additionally, there are gearbox friction tests that should be accomplished at regular intervals and cleaning requirements for operators who use high lead fuels such as 100LL. 

Accumulation of lead in the gearbox from 100LL fuel can cause internal gearbox clutch sticking with the result the setting should be checked regularly. Incidentally, this clutch is a brilliant idea as it protects your engine from damage that would typically be caused by a propeller/ground strike and provides additional operational benefits. 

MAINTENANCE TRAINING

I have just completed the basic and heavy maintenance courses at the Vernon, B.C. facility and after a decade of Rotax operations professionally and privately, my eyes have been opened. 

Over the five days of training I have participated in taking every portion of these engines and gearboxes apart, set them up and ran trouble shooting checks.

Why has a professional pilot found it necessary to learn about these engines? Well, a host of reasons, not the least of which is to protect my investment in a Diamond Katana Xtreme motorglider by understanding the engine systems that keep me aloft and enabling me to work with an engineer in case I encounter problems. 

I’m not the only one. Half the attendees were owner/operators and the rest were technicians with growing shops or fleets of Rotax powered aircraft to maintain.

Engineers, who like me, used to think these engines were flimsy and wouldn’t make it in the market place require an attitude adjustment. There was a time years ago when my COPA articles were critical of these engines and their support. The companies listened and those times are past and the issues resolved. 

Now, the challenge is getting Aircraft Maintenance Organizations (AMO’s) to train their mechanics on these popular engines.

Av Serve Owner/Operator, James Mohns (AMO53-03) of Carp Airport, Ontario listened to the message and has become a guru on the broad spectrum of Rotax engines. He is running a thriving business and continues to attend training courses to increase his knowledge – which is most impressive. (Phone 613-839-0395, av_serv@yahoo.ca).

Owner/operators are quickly learning it is unwise to take their Rotax engine business to organizations that have not been trained to service their powerplants. Giles Mercier of Eden Flight Ontario also attended with Braulio, one of his technical staff, to obtain the necessary data to maintain his fleet of training aircraft. 

Other mechanics attending the four stroke Maintenance and Troubleshooting course and then the Heavy Maintenance course included representatives from fleet operators such as: American Blimp Corporation and General Atomics as well as several kit builders and Rotax operators.

Seeking knowledgeable maintenance personnel is especially important in the case of the four stroke engines where most maintenance issues have been the result of improper operator or maintenance facility procedures.  

Rotech’s maintenance/overhaul facility in Vernon sees the use of incorrect lubricants, sealant, materials, installation, torque values and a host of other problems as a result of faulty servicing. Initially, the engine design took the knocks, but the truth is becoming increasingly clear as faulty maintenance almost always raises its ugly head during teardowns. 

In fact, the engine is so strong, TBO’s are steadily increasing with operator experience and product enhancements and it is not uncommon for some schools and operators to run these engines on condition to 3,600 hours before considering overhaul (normal recommend TBO is currently 1,200 for turbocharged versions and 1,500 hours for normally aspirated).

The light weight of these engines, reliability and their fuel miserly operation in a time of rising oil prices will make them increasingly popular with aviators – especially when the higher horsepower engines begin to enter the market late this year. 

Shops that have been reticent to send their technicians to the Vernon Rotax facility for training will lose potential customers to shops who have invested in their future by taking advantage of skill expansion. 

Additionally, the customer who visits an approved shop for his Rotax engine maintenance may also be in the market for airframe, avionics or other services. 

Can your shop afford not to provide Rotax service?

For more information about my experience with Rotax engines or training, you can contact the author at aviator-horizon@telus.net

To contact the Rotax training folks, visit their website at www.rotech.ca or call 250-260-6299

Kenneth Armstrong has flown more than 400 fixed and rotary wing aircraft over 15,000 flight hours and has been published in more than 60 aviations magazines worldwide. He won the Canadian Aviation Safety Award in 1996 for his flying and editorial contributions and advises he is not associated with Rotax or Rotech in any way – other than as a customer.