Frequently asked questions

This list of frequently asked questions has been compiled by our technicians and troubleshooters from years of customer calls. It should help you troubleshoot issues you encounter.

If these answers don’t help, or your question isn’t in the list below, please call us to help you get your aircraft back in the air.

Many of the components listed below can be inspected, repaired, or overhauled at our facility keeping your costs and downtime to a minimum.

Magneto - FAQs

  • Bendix/Continental mags:

    -Any time the mag(s) are found outside the engine manufacturers limits: Inspect the condition of the contact points.

    -100-hour inspection: Inspection of old-style riveted impulse cams.

    -250-hour inspection: Impulse coupling assemblies on certain IO-540 series Lycoming engines.

    -500-hour inspection: Disassembly, inspection and relubrication of all components including the impulse coupling.

    -Overhaul: At engine overhaul, sudden stoppage, the expiry of 4 years in service, or the expiration of 5 years or 12 years (depending on Serial Number) from the date of last overhaul.

    Slick/Champion/LASAR mags:

    -100-hour inspection: Check of magneto to engine timing and condition of leads, wiring and pressurization system.

    -250-hour inspection: Impulse coupling assemblies on certain IO-540 series Lycoming engines.

    -Service Bulletin 2-19 requires certain mag serial numbers to have the impulse coupling

    inspected within 100 hours or before 400 hours TIS to inspect for rivet wear and damage.

    -500-hour inspection: Disassembly, inspection and relubrication of all components including the impulse coupling.

    -Overhaul: At engine overhaul, lightning strike, prop strike/sudden stoppage or immersion.

  • -The impulse spring on an impulse coupled mag may be broken, causing the timing to shift when rotating the crankshaft.

    -The points may be dirty or contaminated with oil causing higher resistance. The points should be replaced and the internal timing set.

  • -Check magneto to engine timing and adjust the mag timing if necessary. Large changes may be due to a broken impulse spring or worn points/unserviceable capacitor. See the following section for specific Slick/Champion instructions.

    -If the timing is ok, try leaning the engine slightly and checking the mag drop. If the mag drop decreases the engine may be running too rich and the fuel system may be the issue.

    -Rough mag drops may be indicative of worn/damaged spark plugs or mag/harness components.

    -Smooth mag drops may be indicative of improper engine/magneto timing or improper fuel flow.

  • -Normal engine operation causes wear on the contact points in the magneto. This can normally be fixed by changing the mag timing to the engine.

    -Champion has a Service Letter (SL4300/6300-74-20-001, readily available on Lycoming’s website in their Service Letter L264) that deals with timing drift. It requires tracking the timing drift in degrees during inspections. If the mag/engine timing changes more than 4 degrees since the last timing inspection then the mag must be disassembled and the internal timing adjusted. If the mag/engine timing changes more than 5 degrees cumulative since

  • -Magnetos produce an electric arc in operation. This can cause radio noise if it isn’t shielded properly by the magneto housing and harness leads or there is improper grounding between these components. Also harnesses that are old and brittle can arc internally.

    -Do not use noise suppressors on magnetos that have ‘flow through’ capacitors. They are only meant for the early style of Bendix/CMI mags that have the big P-lead connections (3/4” nut).

    Installing them on mags with ‘flow through’ capacitors (any mag with a 10-32 threaded stud for the p-lead connection or Bendix/CMI mags with the small (7/16”) knurled p-lead nut) can cause damage to the magneto capacitor and points.

  • -We recently became a Champion Aerospace Repair Station. This allows us to overhaul Slick/Champion mags according to the Champion requirement to replace all the components except the housings and rotor. 

    We are able to provide this quality of service for less than the price of a new Champion magneto. Our magnetos also have much better reliability than overhaul facilities that just time continue the internal components.

Fuel Injection - FAQs

  • -Nozzles must be flowed on a flow bench to measure their actual pressures and flows. 

    -Precision (Lycoming) recommends Hoppe's #9 Gun Cleaning solvent or MEK to clean nozzles. Continental recommends Stoddard Solvent PS-661. Soak them then clean and dry them. When tested, nozzles should spray a straight (approximately 1/16") stream of fuel with no dripping or alteration of the stream path. Never insert anything into the orifice to clean the nozzle. 

    -Nozzles can be field checked as a troubleshooting procedure for matched flows by removing the nozzles from the cylinders, installing them in the injector lines, putting small clean (about 6 oz.) containers under each nozzle, setting the engine controls for full throttle, full rich, and turning on the boost pump until the containers are half full. Set the containers on a level surface and compare the amount of fuel in them. A plugged or low flowing nozzle will have less fuel in the container compared to the other nozzles, while a nozzle that someone has tried cleaning by inserting wire, a drill or soaking in a solution that removes metal may have more fuel in the container. Be sure to properly install nozzles and lines with the correct lubricant/sealant and torque as per the manufacturer’s instructions.

    -Sometimes a tuned set of nozzles are used in Continental engines. The P/N will be different between cylinders, make sure the first digit of the nozzle dash number is the number of the cylinder it is installed in.

  • -Any change of a Continental fuel system component affects the calibration of the entire fuel system on the engine. This includes the fuel pump, throttle and control assembly, manifold valve, lines or nozzles. The latest revision of the Continental M-0 Standard Practice Maintenance Manual (previously S.I.D. 97-3) must be followed to set up fuel flows and pressures after any component change.

    -Also changes in ambient temperatures may affect fuel system calibration. The M-0 Manual recommends setting up the fuel system whenever there are changes in the operating environment of the engine (typically in the spring and fall). We have the necessary gauges and can perform the set-up procedures.

    -Usually a fuel pump on a turbocharged engine is vented to the air pressure in the induction system. A leaky fuel pump may introduce fuel to the induction system and cause the engine to run rich. Disconnect the line between the fuel pump and the induction system and if it contains fuel/residue then the pump is probably unserviceable.

  • -Generally a servo should be able to be adjusted within the range of the thumbwheel travel. Check for induction air leaks (including the primer system lines and fittings) or fuel leaks from a leaking primer system.

    -Measure the overall length of the mixture clevis assembly. Remove the spring and one of the clevis assembly pins then center the mixture thumbwheel with the assembly overall length reset to the previously measured length. Reinstall the spring, pin and new cotter pin then run the engine up to operating temperature and set the idle speed to the airframe manufacturer’s specifications and the mixture rise to 25-50 rpm.

  • -We recommend following the engine manufacturers overhaul period of 12 years from date of last overhaul. O-rings, seals, gaskets and diaphragms can dry out and cause fuel system issues.

  • -Precision's overhaul period is 12 years from date of last overhaul or at engine overhaul.

Starter - FAQs

  • -Lycoming: For older starters with "Bendix" style starter drives, spray them with a silicone lubricant every 50 hours to keep them from sticking in either the engaged or disengaged positions.

    - Continental: If you can hear the starter spin but the prop doesn’t then it’s likely the starter adapter is the culprit. We can overhaul or repair these units in house.

  • -The old O-200 ‘pull start’ starters used a cable and switch to engage the starter and turn it on from the cockpit. This cable needs to be periodically adjusted to engage the starter gear then engage the switch properly.

    -We found a great step by step voltage troubleshooting guide for most starter problems on the Sky-Tec website (it applies to most starter issues):

    https://skytec.aero/aircraft-starter-support/troubleshooting/

  • -At engine overhaul.

Carburetor - FAQs

  • -The idle mixture may be set too rich or lean. There should be 25-50 rpm rise at idle when the mixture control is moved from full rich to ICO over 2-3 seconds. Check for induction leaks as well as for primer system fuel leaks that might cause issues.

  • The accelerator pump linkage may need to be set to a different position. There are 3 holes in the lever that actuates the pump. Choose the one that increases or decreases the amount the pump is moved to control how much fuel is being delivered during acceleration.

  • -If a carburetor has been dropped or mishandled in shipping it can cause damage or misalignment of the float valve or even the float.

    -When checking the rigging of control cables with fuel in the carb fuel can be pumped into the induction system by the accelerator pump and drain down seeming to 'leak' from the engine. If the fuel stops 'leaking' after a few minutes this may be the cause.

    -Many times an aircraft primer system will leak after many years in service. Ensure the primer isn't the cause of the leak.

    -If airbox mounting hardware that is too long has been used it may puncture the float bowl. Remove the hardware to see if the fuel is coming from the threaded holes.

  • -A leaky primer system can cause fuel to be introduced while running causing a rich condition.

    -A leaky induction system or cracks in the primer system lines or fittings can cause a lean condition because air can be sucked in. This causes less air to be drawn through the carburetor which decreases the fuel introduced by the carburetor.

  • -The manufacturer recommends a 10-year overhaul period between overhauls. Also if the carb has been exposed to an engine/induction fire or any contamination (water/rust/dirt etc.) it should be overhauled.

Turbocharging - FAQs

  • -Turbochargers rely on higher air pressure on the induction and exhaust sides to keep the lower pressure oil in the center housing. If the oil drainage is slowed by coking, plugged gravity drain lines (in high mounted turbocharger applications) or a poorly operating scavenge pump (in low mounted turbocharger applications) the oil level can rise to the level of the turbine shaft and bearings and will leak out.

    -Damaged or leaking oil check valves in the turbo inlet and drain lines can allow oil to build up in the turbo. These check valves must be replaced at engine overhaul or whenever they leak.

    -High engine crankcase pressure (caused by a blocked breather or high piston blow-by) can slow the oil draining back into the crankcase as well.

  • -Many engines may overboost by about 2 inches Hg during the first takeoff of the day when the oil isn’t quite up to temperature in the controller/wastegate system.

    -When an engine's oil isn't warmed up to proper operating temperatures the thick oil cannot get through the restrictions in the controller and this causes the wastegate to stay closed longer, overboosting the engine. Allow your engine to come up to operating temperatures before going to higher power settings. Also allow for a 4-5 second interval for a smooth acceleration from idle to full power to allow the controller(s) to do their jobs.

  • -Inspect for induction and exhaust leaks or restrictions.

    -Inspect the turbocharger compressor wheel and turbine wheel for damage. When inspecting the turbine wheel (exhaust side) you can only see the trailing edges of the blades. You must use a flashlight and mirror or borescope to inspect the leading edges of the turbine blades.

    -Some turbocharger systems use manifold pressure lines routed to the controller(s). Ensure these lines aren't damaged.

    -If the system uses a Variable Absolute Pressure Controller (with a lever operated cam on top) make sure the linkage is set up correctly according to the manufacturer’s instructions. Most of these systems use a rod with a spring on it to actuate the controller. Make sure that when the throttle linkage is set with the air throttle lever touching the full throttle stop that the controller is at its high end stop with about .030" preload on the actuating rod spring (.030" between the link attached to the controller lever and the lock nut or jam nuts).

  • -At engine overhaul.


Alternator - FAQs

  • -Many times this is caused by worn brushes, but there are other factors. Many alternators have 500-hour inspection procedures to keep issues from getting to the failure point.

    -A loose/worn belt or loose/dirty wiring connections (including the engine ground strap).

    -On gear drive alternators the rubber filled drive gear may be slipping. Follow the engine manufacturer's 'slip test' torques to inspect the gear.

  • -Many alternator through bolts have recurring torque checks intervals. If these aren't done your alternator through bolts may become loose in operation and damage may occur.

    -10 hrs (one-time inspection) check through bolt torque and safeties.

    -50 hrs (one-time inspection) check through bolt torque and safeties.

    -100 hrs/annual (recurring) check through bolt torque and safeties.

    -500 hrs (recurring) remove and perform the 500-hour inspection procedures.

    -Engine overhaul and 12-year calendar life overhaul.

  • -The alternator has a rectifier assembly that converts the Alternating Current from the stator to Direct Current. If the rectifier or diodes are damaged the alternator produces an AC voltage. This voltage can be measured with an AC voltmeter between the positive and negative terminals of the alternator while the engine is running (make sure any noise suppressing capacitors are disconnected during this test and all precautions are taken to avoid personnel, engine or aircraft damage). An AC voltage of less than 1 volt is acceptable, anything more may cause radio noise.

  •  -At engine overhaul.

  • 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 married parts.

    Engine manufacturers typically provide instructions for engine break-in. Pro Aero Aviation provides copies of OEM break-in instructions with Lycoming and Continental engines.

  • “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 COMPLETE CLOSED THROTTLE DESCENTS. CLOSED THROTTLE OPERATION DURING DESCENTS WILL CAUSE RING FLUTTER WHICH CAN CAUSE DAMAGE TO THE CYLINDERS AND

    RINGS.”

  • “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.”

  • · Both Pro Aero Aviation and Aerosport power recommend the following manufacturers’ 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.