Our Featherweight Flywheel is the lightest ring gear support assembly available for Lycoming 360, 540, and 720 engines and their variants.  Due to our vast experience with Magnesium, a material that is well-known for its exceptional strength to weight ratio, coupled with our use of the latest CAD/FEA modeling software and in-depth engine testing, we are able to manufacture a starter ring gear support that is strong enough to handle severe conditions, while being extremely lightweight.

 Our 149 tooth Featherweight Flywheel weighs just 3.1 pounds (1.4kg). 

 The most common Lycoming ring gear supports weigh between 6.5 - 7.0 pounds.

That means our Featherweight Flywheels typically drop more than 3 pounds from the nose of the aircraft.

In addition to reducing static weight at typically the most beneficial area to the aircraft, a lightweight flywheel increases the rate of engine acceleration, most importantly when recovering from aerobatic maneuvers and other instances requiring quick application of the throttle. The weight reduction of our flywheel also helps to offset the weight gain associated with upgrading to a constant speed propeller or when adding a starter/electrical system to an aircraft.

While it may seem like a simple item, significant development and testing has gone into creating a very lightweight assembly that can stand up to the high loads created during starting.  Additional loads created by high dynamic compression engines and brutal peak loads caused by backfires during starting have been designed for and tested.

Because some electronic ignition systems use the ring gear support to mount crankshaft position sensing equipment, we have designed our assembly to work with most types.  Our flywheel can be used with these systems:

• LightSpeed Engineering Mini-Sensor system or rear Hall-Effect Module
  
• Emag (Pmag) 114 or 200 series
  

Our lightest Featherweight Flywheels are designed to be used with the popular rear-mounted lightweight alternators that are available from B&C (SD-8 & SD-20) and PlanePower (FS1-14B).  At a slight weight penalty, we also offer a direct-replacement for the standard Lycoming ring gear support (pictured below).  This assembly includes the standard 9-3/4" alternator belt pulley for use with a front/case mounted alternator.

 After installing the appropriate hardened-steel ring gear, we dynamically balance our flywheel assemblies to tighter tolerances than the factory ring gear support.  A proper dynamic balance has many benefits, from increased cycle efficiency to greater durability at higher RPM levels.  Our Hofmann electronic balancing machine allows us to balance components with an accuracy of 0.1 gram-millimeters (=0.000139 ounce-inches).  We also provide documentation on the dynamic balancing results for each flywheel assembly that we manufacture.

But while you can be assured that our flywheel is properly balanced, upon installation you should not assume that you can simply transfer weights from previous prop balancing unless you know the complete history of your old ring gear support assembly.  Just because the old flywheel appears to be balanced, it can be significantly out-of-balance if the ring gear has been replaced, flywheel has been damaged/repaired, etc.  A good dynamic prop balance is a worthwhile investment.

For easy ignition timing setup and adjustments of both standard magnetos and electronic ignition systems, the ring gear support has major timing marks that are machined into the outer ring at 0°(TDC Compression - Cyl.1), and 20°, 25°, 30°, 35°, and 40°BTDC.  We also machine minor marks at each degree increment between 20° and 40°.  These marks are meant to align with the crankcase split, for sighting down the top of the case.  Or for the highest degree of accuracy, we recommend installing a pointer plate to the front of the engine.

 Flywheel Pricing:

 Lycoming O/IO/AEIO - 360/370/375/390:

 Lycoming O/IO/AEIO - 540/580:

 Replacement Ring Gears for Featherweight Flywheels:

Standard Lycoming Ring Gear Support Assembly Weights:

(Total weight varies with options, ring gear type, and balancing)