Rotax 503 UL DCDI 50HP

by Michael A. Anderson

Rotax 503 UL DCDI 50HP


  • 2-stroke engine specially developed for recreational aircraft
  • 2 cylinders, cooled by fan
  • Piston ported intake
  • Dual capacitor discharge Ignition (DCDI)
  • Dual Bing carburetors
  • Mikuni pulse driven diaphragm fuel pump
  • Recoil or electric starter
  • Available with various exhaust system configurations
  • Operates on automotive fuel with a minimum of 87 octane rating (Canadian standards) and super 2-stroke oil of API-TC classification, automatically provided by oil injection, or premixed with a 50:1 ratio
  • Challenger owners, we make the installation of oil injection possible!
  • Time Between Overhauls (TBO): 300 hours


Maximum power 49.6HP / 37.0kW
@6500 RPM
Maximum torque 41.3ft-lb / 56NM
@6000 RPM
Maximum RPM 6800 RPM

Combustion chambers

Bore 2.84″ / 72.0mm
Stroke 2.40″ / 61.0mm
Displacement / 496.7cm³
Compression ratio Theoretical: 10.8
Effective: 6.2


Engine with carburetors 73.2lbs / 33.2Kg
Exhaust system 11.2lbs / 5.1Kg
Air filter 1.1lbs / 0.5Kg
No gearbox, no electric starter 85.5lbs / 38.8Kg
B gearbox,
no electric starter
95.4lbs / 43.3Kg
B gearbox,
electric starter
106.2lbs / 48.2Kg
C gearbox,
no electric starter
103.1lbs / 46.8Kg
C gearbox,
electric starter
113.9lbs / 51.7Kg
E gearbox 110.2lbs / 50.0Kg


Information sheet 503info.pdf / 375Kb / Adobe Acrobat format
Performance graphs 503perf.pdf / 20Kb / Adobe Acrobat format
Technical drawings 503draw.pdf / 146Kb / Adobe Acrobat format
Service documentation