Recreational Flyer

November/December 2001

 

"THREE INVERTED"

by Bill Tee

"No! This is not an aerobatic team but a totally new three-cylinder diesel engine designed specifically for aircraft use. This revolutionary power plant is the product of the fertile mind of an Australian private pilot, Mark Wilksch, now residing in the UK.

Mark began his technical career in Adelaide, Australia in 1979 by becom­ing involved in racing car develop­ment and preparation. Subsequently Mark became involved in aviation while doing engineering work for the Royal Australian Air Force.

Upon moving to the UK in 1990 Mark became involved in formula-1 racing car engineering and develop­ment and also did some contract work for BMW in Munich, Germany.

In January 1992 Mark filled the position of chief engineer for the Ford Motor Company on advanced gasoline fuel injected engines and subsequently moved to Cosworth Engineering in July 1992. He became involved in research into a replacement for the Continental 0-200 for the Continental Motor Company in the USA.

In 1994 Mark began his company, Wilksch Airmotive Ltd. He "SAW THE FUTURE AND IT WAS DIESEL!"

On 21 November 1997 the proof-of-concept two-cylinder 80 HP two-stroke inverted turbo diesel took successfully to the air in a Piper J3 Cub.

The success of this event prompted Mark to proceed with the develop­ment and production of his present offering, a turbo-charged, liquid-cooled inverted engine producing 120 HP at 2600 direct-drive RPM. What else is in the future? How about a 4 cylinder engine of 160 HP and even a 5 cylinder of 200 HP all based on the same modu­lar design.

"Why a diesel?" you may ask. Have you witnessed the present day diffi­culty of obtaining high octane avgas? Have you heard the protests of the petroleum companies of the world complaining of the nuisance of produc­ing avgas at all, since they produce so little of it compared to their other prod­ucts? Are you also aware that in many parts of the world avgas is virtually unknown? Diesel fuel and Jet A or at least one or the other of these fuels are available wherever mechanized trans­port is available. Also, other fuels such as heating oil and environmen­tally friendly vegetation products can be used in such a suitably developed compression-ignition engine.

When you consider the functioning of an aircraft piston engine, is not the new light-weight diesel engine the log­ical choice? An aircraft engine runs for long periods of time at a constant RPM. Instant acceleration is not a crit­ical item. An aircraft engine requires maximum torque and horse power at relatively low RPMs, preferably with­out gearing. This is where the diesel engine really shines. Also the elimi­nation of an electrical ignition system, except glow plugs for cold-weather starting, increases reliability. This is one less system to go wrong an4 there is no ignition noise to bother you on your radio[s].

On 31 December 1999 the great day arrived when the WAM 120 engine took to the air for its first flight in a new Europa, and it was successful! Since this great day other airframe manufac­turers have climbed on board and now names such as Pelican of Canada and DynAero of France are associated with the WAM 120. Other airframe instal­lations under development are for the Jodel 1050 and D 11, the LongEz [remote radiator], the RV9 and the com­pany's test bed for 2002, Thorp T-211. At the time of this writing two of the WAM 120 engines have been ordered for North America. One in the USA and another in Burlington Ontario Canada and are due for delivery before the end of this year. I am eagerly looking for­ward to the first flight of the first diesel powered Europa in Canada.

Weight, the age old bugaboo of the diesel engine does not appear to be an issue in the case of the WAM-CITEC engine. Weight with radiator, starter, turbo intercooler and 12 volt alterna­tor is around the 100kg mark. Six liters of oil, four liters of coolant, four Lord mounts, propeller and exhaust silencer are additional. The weight has been kept under control by the use of a high strength aluminum - magnesium - sili­con light alloy. The light weight and smoothness of the WAM 120 are partly due to the fact that the engine produces one power stroke per cylinder per rev­olution.

While running, the air is forced by the turbo charger into the cylinders by means of annular porting around the pressed-in cylinder sleeves. A super­charger is used for charging the cyl­inders at starter cranking RPM's for start-up. Thereafter, the turbo takes over to provide excellent hot and high performance and the supercharger is just along for the ride. This forced-air charge pushes the exhaust out of the cylinder through two exhaust poppet valves per head. These are driven by a 'single underhead camshaft' that runs and lives in the wet oil sump of this engine. No lack of lubrication here!

One problem that has always bugged the inverted engine [or cylin­der] is oil leaking into the combustion chamber. Sufficient amounts can cause a hydraulic lock that usually severely damages the engine if not discovered before starting it. Mark has addressed this problem by designing the very sturdy pistons [20 to I compression ratio] to not permit any oil to seep by them. Instead of running down the cyl­inder walls into the combustion cham­ber the oil fills the piston, at least partly.

Mark reports that he has never seen a piston more than half full. To prevent the oil from seeping by the wrist pin, he has eliminated the part. Instead of a wrist pin the piston is attached to the connecting rod by means of a ball joint. This ball joint allows the piston to rotate while the engine is running thus eliminating the wear pattern that we see on normal piston/cylinder com­binations. Mark has assured us that the piston does indeed rotate while the engine is running.

The steel crankshaft of the WAMI2O is a thing of beauty with its dual SAE 1/ ARP-502 propeller flange, and generous radii at the cheeks of its lengthy large-diameter main and con­necting-rod journals. Crankshaft prob­lems with this unit should indeed be a rarity!

The high pressure liquid cooling system of this engine allows closer piston clearances for greater efficiency and reduced mechanical noise. I can attest that having seen and heard the prototype 3 cylinder engine run on a dynamometer this is a quiet, smooth engine. Near turbine-like is a term that comes to mind! Smoothness is guaran­teed by the built in gear driven balance shaft. There was not the rattling, clank­ing and shaking one experiences with the popular air cooled aero engines that we are all used to.

What is the next step for Wilksch Airmotive? While I was enjoying a brief visit with Mark Wilksch [he is a man who knows the value of time and respects it] he showed me the raw casting for a new injector pump designed to handle Jet A fuel. Because jet fuel has lesser qualities than diesel fuel, this injector pump will be lubricated by engine oil to provide it a long and trou­ble free life. Such are the concerns of Wilksch Airmotive!

What are the immediate advan­tages on running an aero diesel engine? How about cheaper fuel for a start, and less of it [around 3 1/3 gallons per hour @65 % power]! There should be greater reliability and reduced maintenance due to elimination of electrical ignition. There is no mixture or carbu­retor heat control [no carburetor = no carburetor icing]. One should experi­ence constant power to a higher alti­tude via turbo charging. There would be a greater choice of fuels. One would enjoy the smoothness and quietness of modern technology. With liquid cool­ing, comes the potential for ade­quate cabin heater similar to the one in your car - a very important item during Canadian winters. Finally, no more shock cooling on a sudden reduc­tion of power.

In its tractor configuration there is no need to build your own cooling system. The engine comes complete with the radiator mounted on the engine and hooked up. It is ready to run with the addition of fluid [pushers will probably need the radiator relocated].

Is the diesel engine the way of the immediate future for low horsepower engines? I believe that it is. I feel that we are quite distant from a small cheap economical turbine power plant for small private aircraft. I am convinced that the small turbine engine will never approach the piston engine's specific fuel consumption, at least in the life time of most of us.

Although the WAM 120 is not the only aero diesel engine being devel­oped I believe that it is probably the closest to production and delivery to customers. "