Mandatory ALERT Service Bulletin: Inspection and Replacement of Oil Spray Nozzle for ROTAX® Engine Types 912 i, 915 i, and 916 i (Series) SB-912 i-016 / SB-915 i-016 SB-916 i-006

Nathan Holderbein wrote:

Sorry, I'm not exactly answer your question directly...but I have thought that it may not necessarily need to be assembled as shown in the diagram. Would an elbow between the special tool and meter, maybe a small length of tube, throw the flow off so much as to invalidate the test? This would reduce the necessary space for the whole setup.

We're looking for a flow greater than 4(1.05), so an acceptable reading even with some theoretical loss of flow from an elbow and some tube would be an acceptable result, right? 

If it fails but is right on the bubble, you would take whatever steps to re-test in the straight configuration?

I would think what you are suggesting would be valid.  I could see putting the regulator, gauge, shutoff, and flow meter on one side of a 2 foot flex hose, then the 3D printed toold on the other end would result in a good reading, as long as no air leaks.

I'm curious if anyone has info on the Loctite products that are specified for the nozzle and the mounting screw. They seem backwards to me when you look up the intended applications of 603 and 243. 243 is for threads, 603 is for mating cylindrical parts. Rotax specs 603 on the threads and 243 on the nozzle.

I'm not saying that it's behind any of these failures, but it's curious coincidence in light of the explanation they give for blockage.

If you have concerns about the condition of the stator and your engine falls within the serial number range listed in both the non-certified and certified Service Bulletins, WE recommend you perform the pressure test of the sprayer nozzle, regardless of how many hours your engine has (even if it’s over 200 hours). it’s always wise to err on the side of caution “When in doubt, test it out.”

In addition to the pressure test, you can also perform a resistance test on Generators A and B as described in the Service Bulletin. However, it’s important to note that this test alone does not provide a complete inspection, especially if your sprayer nozzle fails the pressure test. A critical part of the inspection process is the physical inspection of the stator, as outlined on page 13, Section 3.5.3, Step #7. This step requires checking for discoloration, signs of overheating, or any issues with resistance values. The Service Bulletin clearly states: “If the stator shows signs of discoloration or overheating and/or the resistance values are outside of the nominal range, the stator assembly is unserviceable and must be replaced.”

If you want to go above and beyond the initial pressure test, you can perform both the pressure test (if it passes) and check the resistance values of both Generators A and B as described on page 13, Section 3.5.3, Step #6. While this step is not mandatory, if it provides you with peace of mind, it’s certainly a precautionary measure you can take.

We are still working on obtaining the 3D print file needed to create the tool, as well as compiling a list of the other required testing items (pressure regulator, flow meter, and shut-off valve) Additionally, we’re identifying reliable and “inexpensive” sources where these tools can be purchased. We understand this is a high-priority item for ROTAX owners, and we are committed to providing an update as soon as possible.

Thank you, having the 3D file would be very helpful, looking forward to the release!

Nathan Holderbein wrote:

For those that seem to be in the clear based on time but are still a little concerned, could there be anything to glean about the stator condition by performing the resistance test in the SB? Do we know if there is a gradual degradation of the stator as it approaches failure?

The typical failure is a melting of the insulating varnish on the stator windings, which then goes to ground or shorts across the coil winding.  In theory this could be somewhat progressive as the insulation degrades, but a simple ohm meter typically won’t pick this up until the winding is grounded. It may be possible with a megger tester that would apply a higher voltage to test the windings, but without knowing what voltage setting is safe for the windings that may do more harm than good.

One simple test that may be useful is to use an inductive type amp meter and look for a balance across all three phase wires that run from the stator to the regulator (yellow wires).  You have to test each lead separately with the engine running and electrical loads turned on.  If one wire is carrying a significantly different load, that may indicate that phase is failing.  When I lost my first regulator I did this amp test on each of the stator leads and one was carrying 50% less current than the other two.  I suspected a problem but could not prove it with the ohm tests. The stator failed completely a couple of flight hours later.