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If you are experiencing control problems with your constant speed propeller, you should consider the possibility that the source of the problem may not be the propeller or governor.
Lycoming and Continental engines incorporate provisions in the front main bearing journal area designed to transfer oil to and from the prop governor and back and forth through the crankshaft to the prop. Lycoming engines transfer this oil through an annulus in the front main bearing, while Continental engines typically utilize a transfer collar between the front main bearings.
Lycoming published Service Instruction No. 1462A Propeller Oil Control Leak Test Procedure (With Propeller Installed on Engine) It is prescribed:
Whenever sluggish propeller action is reported.
Whenever the engine does not hold RPM during cruise, climb or descent.
Whenever the engine is going into feather during landing roll out with reduced throttle setting.
Service Instruction 1462A describes an air pressure check (differential pressure) designed to show the condition of governor oil passages, front main bearing clearance and positioning of the governor circuit oil plug. While Continental does not have a published procedure to test the integrity oil passages, transfer collar or governor circuit oil plug a similar differential pressure check can be a useful troubleshooting tool. A well fitted Continental transfer collar will generally exhibit a differential pressure of 78-80/80 until residual oil is displaced allowing air to escape.
Loss of engine oil pressure can also lead to a shortage of oil available to the governor. This condition will also exhibit similar symptoms. If you are experiencing loss of prop control, it is important to check engine oil screens and filters to confirm that the engine is not sustaining a failure and producing metal.
Many mechanics find the adjustment of Continental Fuel Injections systems to be a mysterious and daunting task.
This does not have to be the case. With the correct tools and set-up information, it can be relatively easy to achieve Smooth, Safe engine operation.
Correct fuel injection system adjustment is critical to safe efficient engine operation.
Effective throttle response, control of cylinder head temperatures, exhaust gas temperatures, and ultimately power output of the engine are all tied directly to a properly adjusted fuel injection system.
Detailed procedures and Specifications for fuel system adjustment are found in Continental Maintenance Manual M-0. Extensive tables are provided which detail pressure and flow parameters for individual engine models. Please ensure that you are using a current copy of this manual.
M-0 provides detailed schematics of various types of fuel systems which detail hose routing and test gauge attachment. Detailed drawings are provided which show various fuel system components and where adjustments are made. In most cases, the drawings will indicate which direction to turn the adjuster.
Continental recommends the use of a “Porta-Test” unit, or calibrated gauges for confirmation and calibration of fuel system pressures. If calibrated gauges are used, M-0 specifies the range and increment of the gauges to be used. These adjustments must be precise and require the use of precision gauges.
Continental fuel injection systems generally incorporate high pressure (full power) and low pressure (idle) adjustments. It is important to understand that adjustment of one parameter can (and usually does) affect the other. Adjustment of the fuel injection system usually requires small adjustments of both the high and low pressures until both parameters meet the specifications.
Lycoming recently released Service Bulletin SB 632 (Identification of Connecting Rods with Non-Conforming Small End Bushings).
The bulletin includes a list of affected engines that were built or repaired at the factory, as well as a list of parts with ship dates from the factory.
Aero Recip has conducted a thorough review of our stock of engines and parts. We have never stocked or sold any engines that are listed in the service bulletin. Likewise, we have not purchased any of the affected stock of Connecting Rod Bushings or Connecting Rod Assemblies listed in Table 2 of the service bulletin.
If you have any further questions or concerns, please call 1-800-561-5544 or email me at firstname.lastname@example.org
Engine break-in is a very important phase in the life of your engine. Successful break-in will help to provide you with an engine which uses minimal oil and achieves optimal performance. While it may seem counter-intuitive, engine break-in is actually a period of controlled wear between mating parts.
Engine manufacturers typically provide instructions for engine break-in. Aero Recip provides copies of OEM break-in instructions with Lycoming and Continental engines. For Pratt and Whitney engines, Aero Recip provides enhanced break-in instructions based on our years of experience along with the OEM guidance.
Let’s look at some highlights of these various instructions:
LYCOMING – SERVICE INSTRUCTION 1427C
“The purpose for this engine break-in procedure is for the correct piston ring seating and stable oil consumption on a top overhauled engine or a newly overhauled engine that is installed in the aircraft.”
“At cruise altitude, decrease power to approximately 75% and continue flight for 2 hours. For the second hour, do power settings alternating between 65% and 75% power as per the applicable POH.”
“For correct piston ring seating, in a top overhauled or a newly overhauled engine, operate the aircraft at 65% to 75% cruise power until oil consumption is stable.”
“For a normally aspirated (non-turbocharged) engine, it will be necessary to operate at cruise power at lower altitudes. Density altitude in excess of 8,000 feet (2438 m) will prevent the engine from reaching sufficient cruise power for an acceptable break-in; 5000 feet (1524 m) is recommended.”
“DO NOT DO CLOSED THROTTLE DESCENTS. CLOSED THROTTLE OPERATION DURING DESCENTS WILL CAUSE RING FLUTTER WHICH CAN CAUSE DAMAGE TO THE CYLINDERS AND RINGS.”
CONTINENTAL – MAINTENANCE MANUAL M-0
“The recommended break-in period for Continental Motors engines is 25 hours.”
“At Cruise Altitude: Maintain level flight cruise at 75% power with best power or richer mixture for the first hour of operation.”
“Best power mixture is 100º – 150ºF (38º-66ºC) rich of peak exhaust gas temperature.”
“For the second and subsequent hours of flight, alternate cruise power settings between 65% and 75% power with appropriate best power mixture settings.”
“Avoid long descents at high engine RPM to prevent undesirable engine cooling. If power must be reduced for long periods, adjust the propeller to minimum governing RPM to obtain desired performance levels. If outside temperature is extremely cold, it may be desirable to increase drag to maintain engine power without gaining excess airspeed. Do not permit cylinder head temperature to drop below 300ºF (149ºC).”
“Avoid long descents at cruise power RPM with manifold pressure below 18 in. Hg.”
Pratt & Whitney does not have extensive instructions relating to engine break-in, they state:
“lean mixture cruising (high manifold pressure) and over-speeding should be avoided in this period, except in cases of emergency.”
“Higher than normal cylinder temperatures may be evident for the first several hours of operation until rings are properly seated, and particular care should be taken to ensure that specified temperature and manifold pressure limits are not exceeded.”
“Service experience indicates that straight mineral oils are preferred for engine test, and the first 25 – 50 hours of operation, to provide quicker piston ring break-in plus internal sealing or coating on oil wetted surfaces.”
WHILE AERO RECIP RECOMMENDS FOLLOWING MANUFACTURER’S, INSTRUCTIONS REGARDING OILS APPROVED FOR ENGINE BREAK-IN, WE DO NOT RECOMMEND THE USE OF SEMI-SYNTHETIC OILS, AS THE SYNTHETIC COMPONENT OF THE OIL CAN HAMPER THE BREAK-IN PROCESS.
IT IS IMPORTANT TO REMEMBER THAT MOST ASHLESS DISPERSANT OILS ARE IN FACT MINERAL BASED OILS AND ARE SATISFACTORY FOR ENGINE BREAK-IN.
TYPICALLY, TURBOCHARGED ENGINES REQUIRE ASHLESS DISPERSANT OIL FOR BREAK-IN AND THROUGHOUT THEIR LIFE.
IT IS VERY IMPORTANT TO REMEMBER TO PRE-OIL YOUR ENGINE THOROUGHLY PRIOR TO INITIAL GROUND RUNS AND FLIGHT TESTING.
WHILE AERO RECIP DOES NOT WANT YOU TO ABUSE YOUR NEWLY OVERHAULED ENGINE, WE JOKINGLY TELL CUSTOMERS TO “FLY IT LIKE THEY STOLE IT” AND DON’T BABY THEIR ENGINES.
Aircraft:DHC-2 Beaver with Pratt & Whitney R-985 engine
Excessive oil leak from the engine’s magneto drives, and has abnormal pressure in the oil tank
On a busy June weekend, the operator’s PRM is unable to determine why the magneto drives are leaking. All engine instruments and performance are normal. Customer and pilot safety being the priority, the aircraft is grounded until the reason for of the leak and pressurized oil tank is confirmed and repaired.
After attempting unsuccessfully to contact another engine shop, the PRM contacts Aero Recip on its 24-7 AOG line. Aero Recip answers immediately and connects the PRM with Aero Recip Technical Advisor, Wayne Cathers.
After careful analysis of the situation, Wayne directs the operator’s PRM to check for a cork in the rear case. “We pulled the fuel pump and drive off and reached in behind to find the port – that allows the oil out – blocked by the generator drive cork seal.A cork is located. It had become lodged in the rear case drain port, impeding oil flow, causing the rear case to fill with oil.”
The OEM installed generator is commonly replaced with an alternator. In these cases, the alternator drive spline can push the cork seal out of the bottom of the accessory drive gear, which causes the cork to fall into the rear case, potentially migrating to the outlet drain port.“We converted the generator to an alternator drive on the R-985 a year earlier,” the PRM explains, “which pushed out the cork.After about 300 hours the cork became lodged in the drain hole and oil built up in the rear case.”
On confirming the cause of the leak, according to the PRM, “Wayne’s instructions really helped.After removing the cork, we reinstalled the fuel pump and drive, tested the engine and returned the aircraft to service.“We’re definitely happy with AeroRecip’s knowledge and support. It meant we could sleep at night knowing everything was running smoothly again.”
Running and engine “lean of peak” is a hot topic among owners and pilots of piston engine aircraft operating in the industry today. Rising fuel costs make it look like an attractive option for reducing operating costs, and in some cases extending the fuel range of an aircraft to eliminate the need for a fuel stop on route to your destination.
The facts prove that under the correct conditions, engines can be run lean of peak successfully with good results. The real question is whether or not the correct conditions exist to successfully run lean of peak.
We feel that the most important requirements for running an engine lean of peak are:
Balanced Fuel and Airflows to Each Cylinder!
Pilot knowledge is the single most important aspect of successfully operating lean of peak. A knowledgeable pilot is better equipped to make an informed decision based on conditions at hand and engine instrumentation. A knowledgeable pilot is also able to react appropriately to information gleaned from engine instrumentation.
Adequate engine monitoring instrumentation is also crucial to provide the pilot with enough information to make correct fuel mixture adjustments. An engine monitoring system is required which provides EGT readings for all cylinders, CHT readings for all cylinders and actual (as opposed to calculated from pressure) fuel flow readings.
Not every engine is created equal and not all engines are capable of running lean of peak. Uneven fuel and airflows to individual cylinders can result in one or more cylinders running excessively hot while others are in the correct temperature range. Leaning an engine such as this until all cylinder temperatures are comfortable lean of peak may result in an engine that stumbles, or runs rough. Balanced fuel and airflows are essential to provide EGT and CHT readings, which are close together throughout the operating temperature range for the engine. This will allow the fuel mixture to be leaned to the desired EGT lean of peak without damaging individual cylinders, and providing smooth engine operation.
Finally, it is very important for an engine to be well maintained and in good condition for it to be expected to operate safely lean of peak. Obstructed fuel injection nozzles, intake leaks, or ignition problems could have disastrous results when attempting to run lean of peak.
TIME OF COMPLIANCE: Any time an engine is expected to sit idle for extended periods
Approved inhibiting oil
A “Flyaway” Inhibiting Oil is recommended to be used for aircraft engines expected to sit idle for extended periods. Any MIL-C-6529C Type II “flyaway” oil is approved for use. For example, Phillips 66 Antirust oil SAE 20W50 is an approved inhibiting oil. Operational hours should not exceed 10 hours total.
Recommended inhibiting procedure by Aero Recip (Canada) Ltd.
At the end of the flying season or any time the aircraft is to sit idle for extended periods, drain all existing oil from the oil tank and engine oil sumps. Service all oil screens and filters. Install new Antirust Oil to the proper level. If the aircraft has sat for some time, carry out the normal pre-oil and then go flying. The aircraft should be fl own for at least sixty (60) minutes at normal operating temperatures or if desired for the next couple of flights. Further recommended preservation instructions can be found in the Pratt & Whitney Maintenance Manual, Continental Service Bulletin M99-1, or Lycoming Service Letter L180B.
Before aircraft is released to service
Before returning the aircraft to service, it is advisable to carry out the proper pre-oiling procedure before starting the engine. This is necessary to force all air from the internal oil passages and to ensure proper lubrication of all bearing surfaces and other moving parts. The aircraft may be fl own with the inhibiting oil for one or two flights but then the oil must be drained and replenished with Phillips 66 X/C Aviation Oil or any approved engine oil.
Does your engine have low oil pressure and/or high oil temperature? Low oil pressure and high oil temperature quite often go “hand in hand”. Before removing the engine check the oil screen or oil filter for metal. Check the oil pressure with a calibrated oil pressure gauge. Replace the oil temperature gauge with a calibrated gauge and replace the oil temperature sending unit with a new one or one of known condition. It is not uncommon for gauges to go out of calibration. As an AMO we are required to calibrate our gauges on a regular basis to ensure accuracy and we would assume that the aircraft gauges are also calibrated on a regular basis.
Remove the oil pressure relief valve and inspect the plunger or ball and the seat. If there is a plunger installed check the movement on the shaft. Sometimes a small piece of carbon will become lodged on the seat and cause low oil pressure. The piece of carbon or other contaminate will usually disappear when removing the oil pressure relief valve assembly from the engine.
If you have high oil temperature determine the cause. Is the engine making metal? What is the condition of the baffles? Are the intercylinder baffles fitting snug against the cylinders? Are the intercylinder baffles worn and/or cracked? What is the condition of the baffle seals? The baffle seals should face into the direction of the air fl ow and be in full contact with the engine cowl in static position. If the seals do not touch the cowls with the engine in static position they will not touch the cowls in flight. To check the seals put a light up the cowl flaps. If you can see light around the seals when looking through the bug eyes then the seals need replacing.
We have observed over the years that intercylinder baffles and the perimeter baffles are much neglected accessories. These items are commonly found to be worn, missing, bent and cracked which may result in one or more cylinders operating at unusually high temperatures. Good examples of unserviceable baffles can be found in Teledyne Continental Motors Service Bulletin SID97-2 (latest revision). The baffling installed on the engine of today is the result of considerable study. Special wrap around baffles now guide the cooling air completely around the cylinder heads and barrels. On a pressure air-cooled system it is important to understand that to control the airflow from the propeller and ram air there has to be a pressure differential inside the cowling. Peripheral baffles with rubber seals are installed on the engine to provide this pressure differential. On most installations this pressure differential is around 4 to 6 inches of water pressure. Heat related problems have become more prevalent with the fleet of aircraft getting older and more power upgrades being made. Therefore, it is very important to make sure the baffles are maintained properly.
Both radial and opposed engines must have the proper running clearance between the valve stem and the rocker arm. Most opposed engines have hydraulic lifters therefore the correct push rod length must be selected to maintain the proper running clearance. At overhaul, the correct push rod length is installed for each cylinder. When a cylinder is changed in the field, the replacement cylinder may have a different valve seat depth or valve seat width than the cylinder removed therefore it may be necessary to change the push rod in order to get the correct clearance. It is very important to collapse the hydraulic lifters by bleeding all the oil out, then check the clearance and select the proper push rod by part number. Before setting the valves, be sure that the proper torque and tightening sequence was used during the cylinder installation.
Pratt and Whitney R985, R1340 and R1830 radial engines are the same principle but have solid lifters therefore have an adjusting screw and lock nut on the rocker arm. Different push rod lengths are also required on these engines only the push rod length is adjusted by adding or removing different thickness washers from under the push rod socket. This procedure is also done during overhaul to obtain the correct valve clearances. If the rods are the correct length, the adjusting screw should also be within limits, no less than 2 threads and no more than 5 threads showing on the end of the adjusting screw after the lock nut has been tightened.
CAUTION There is a removal and inspection procedure and a special tool is required for installing a push rod socket. The installation of the push rod socket without the correct interference fi t can cause damage to the push rod and socket. In some instances the socket has come off. An improperly installed socket causes the rocker arm valve adjustment screw to be out of limits or worse yet, allowing the jam nut on the adjusting screw to come loose and pound a hole in the rocker cover. After adjusting the valve clearance to the proper limits, make sure you have at least 10 thou clearance between the valve spring outer washer and the rocker arm even though you have clearance between the valve stem and the rocker adjustment screw. We have seen evidence where the rocker arm comes in contact with the valve spring washer putting pressure to one side of the valve and valve keepers causing the keepers and valve stem to wear until the valve and valve guide fails. When this happens, the valve breaks loose and pounds a hole in the piston and usually exits through the cylinder head. This also causes damage to the link rod as well as filling the engine with metal. Radial engines will quit in flight as a result of a broken push rod, rocker arm or a loose or broken adjustment screw. If this occurs in any one cylinder, the valves won’t open, especially the exhaust valve. The combustion fi res back through the intake into the supercharger, disturbing the fuel distribution to the rest of the cylinders. Any pilot that has had this experience will tell you that it is almost impossible to keep the engine running. By close inspections and working to the proper manuals and table of limits this type of failure can be avoided.
From time to time engines arrive at Aero Recip looking like they have been involved in an incident when in fact they were just damaged from improper mounting when shipped by a commercial carrier or brought to our facility by the owner. Engines that are shipped on a pallet or an old tire often encounter some sort of damage ranging from bent or broken oil and fuel lines, broken magneto flanges and carburetor bodies to dented oil sumps (particularly on Continental engines). If you are building a crate to transport the engine, make sure that the support brackets are strong enough to support the weight of the engine. Remember that depending on the model, the engines weigh between 300 to 1200 lbs and the bouncing of the engine in a truck (particularly a commercial carrier) will bend or break a flimsy mount.
If you are shipping via a commercial carrier make sure that the engine has a solid cover. Commercial carriers haul as much freight as possible in each trailer and have been known to pile heavy freight on top of an uncovered engine resulting in damage. If you do not have a crate, call us at 1-800-561-5544. We will be glad to ship you one of our engine containers. The additional freight cost to ship an empty container to you is cheap when compared to the replacement of a magneto body or oil sump.
Prior to packing an engine for shipment, drain the oil and fuel (hazardous) and use suitable covers over all fuel and oil fittings as well as any other openings on the engine accessories. This prevents foreign objects from entering the engine. These objects can go undetected on repairs when the engine is not completely dismantled. Be sure to include all the accessories and parts necessary to run the engine, don’t leave half of it on the workbench and remember that the engine log book is considered part of the engine, make sure it’s included.
Protect your engine, it’s an expensive investment.