New 912 MML Airbox Temp. Check Procedure

PS – Don't mind the blue oil leaking out of the air filter element. The photos were taken some six months ago, after I worked out that I had over-oiled the filter and before I fixed it. I don't see the point in taking off the bottom cowl again just to get photos of the airbox looking nice and clean when these ones will do.

Hi Tim,

I’ve probably looked at over a thousand different Rotax installations in hundreds of different aircraft types, and I can honestly say I’ve never seen an intake and exhaust system quite like the one on the Sky Fox. It looks like someone took a page out of the Continental O-200 in a C150 and recreated it for a Rotax; it’s interesting!

With that said, the new requirement in the Rotax MML regarding the monitoring and testing of intake temperatures is going to be challenging, especially for those who do not have a Rotax airbox. Essentially, the only practical place for you to install the temperature probe is in your existing airbox, which would need to be modified to work.

I noticed you have a black tube connected between the two intake scat hoses (see attachment). Can you explain what the other end of this hose connects to? Does it connect to the intake manifold gauge?

There’s a reason I’m asking, as I might have an idea, but I need a bit more information first. Also, could you please take some photos of the top of your engine showing the carburetors and the intake crossover tube?

Thanks!

 Rotax-Owner

"Interesting" is one word for it. It's one of the earliest 912 powered types to achieve full type certification to JAR-VLA, so they didn't have a lot of precedents to work off when they were designing it, particularly being in Australia before the internet had really kicked off. I believe it's mostly from trying to fit it all into the cowling that they already had tooling for when they replaced the CA-21's Volkswagen conversion with the 912 in the CA-22/22A. Then they had to find somewhere else to put the exhausts and the oil tank when they stuck a nosewheel strut through the middle of everything with the CA-25N. Comparing the installation against the current 912 IM is good for a chuckle, but I assume that it did meet the requirements that were in effect in 1995 when the nosewheel installation achieved certification.

The hose you've circled is the carburettor vent line. The two 4mm hoses from the carbies join at a tee piece on the firewall and then a 1/4" hose runs down to the airbox. The vent line and its fitting on the airbox is mandated by an airworthiness directive (along with changes to the original carb. heat system and 165 main jets in the carbies) so any permanent modifications to that part would require applying for an AMOC from CASA.

Hi RO,

Please elaborate on the requirement to "Measure heat up of air intake." ??

Thanks😈