Rotax 912 UL DCDI 81HP

by Michael A. Anderson

Rotax 912 UL DCDI 81HP

  • 4-stroke engine specially developed for recreational aircraft. Also exists in certified versions: Rotax 912 A, Rotax 912 F.
  • 4 horizontally opposed cylinders, “boxer” configuration
  • Free air cooled cylinders, liquid cooled cylinder heads with integrated pump and expansion tank
  • Dry sump forced lubrication with integrated pump and separate oil tank
  • 8 valves, automatic adjustment by hydraulic valve tappet
  • Dual Capacitor Discharge Ignition (DCDI) with RFI noise suppression
  • Two Bing Constant Depression (CD) carburetors
  • Mechanically driven diaphragm fuel pump
  • Integrated electric starter
  • Integrated reduction gearbox, ratio of 2.27:1 or 2.43:1 with optional slipper clutch
  • Various liquid and oil radiators available
  • Many option available such as: Vacuum pump, external alternator, hydraulic propeller governor
  • Operates on automotive fuel with a minimum octane rating of 87 (Canadian standards)
  • Time Between Overhauls (TBO): 1500 hours*


Maximum Power
(5 minutes)
81HP / 59.6KW @ 5800 RPM
Maximum Power (sustained) 79HP / 58.9KW @ 5500 RPM
Maximum Torque 75.9ft-lb / 103NM @ 4800 RPM

Combustion Chambers

Bore 3.13″ / 79.5mm
Stroke 2.40″ / 61.0mm
Displacement / 1211.2cm³
Compression ratio 9.0:1


Engine with carburetors 121.2lbs / 55.0Kg
Exhaust System 8.8lbs / 4.0Kg
Air Filter 0.7lbs / 0.3Kg
Liquid Radiator 2.2lbs / 1.0Kg
Oil Radiator 1.1lbs / 0.5Kg
Regulator-Rectifier 0.2lbs / 0.1Kg
Installed Weight 134.2lbs / 60.9Kg
Weight/power ratio 1.66lbs/HP / 1.0Kg/KW


Information Sheet 912info.pdf / 429Kb / Adobe Acrobat format
Performance Graphs 912perf.pdf / 14Kb / Adobe Acrobat format
Technical Drawings 912draw.pdf / 438Kb / Adobe Acrobat format
Service Documentation