912 ULS Intake

Hi Darryl

No difference you can measure.  The statement was because Rotax did all the evaluations and block testing with the airbox for certification.  The airbox is useful in that it can be used for carb heat and also ties the carbs together for less individual bounce of the Bings on the intake sockets.  For overhaul authorised Rotax shops must use the airbox and a Rotax muffler with a calibrated propeller.  Any deviations in pressure altitude are to be corrected for matching power output.  

You can download the Type Certificate data from the Rotax or the EASA site. https://www.flyrotax.com/p/about-rotax/certificates

Note in the data that it refers to the Rotax parts catalogue and the dimensions with the airbox installed.  

Cheers

"The airbox is useful in that it can be used for carb heat and also ties the carbs together for less individual bounce of the Bings on the intake sockets."

For every gain there is most often a penalty:

Met a pilot/builder of a Europa. Early in the aircrafts life, the constant speed propeller, lost a blade. The resultant violent "vibration", almost caused the engine to leave the airframe. The engine stopped, seconds after the prop blade departed, preventing further damage. The pilot attributed the quick stop, that saved his life, down to not having an airbox - the individual carby's separating from the inlet manifolds, due to the violent engine movement. An experienced glider pilot, he made a good forced landing in a field. The aircraft required an extensive rebuild, from the cockpit forward. 

My Sonex/Rotax has an air box????