914 Overboost

Hi Shaun

If you have correct readings and the prop setting has been input as per BUDS then your prop is not good.  The prop has to load the engine to control the engine, there is no speed control on RPM other than the pitch.  

If you are additionally not getting a red lamp flashing at overspeed then you have a serious problem.  Exceeding 40 inch HG should give you a solid red lamp.

Don't fly it tell you can fix your warning lamps. Download the log file and send it to someone who can read it.

Cheers

I did not set the prop pitch with BUDS, is there a document/guidance for doing that?

I was fixated on the RPM gage so I haven't checked if the warning light comes on, I will watch for that, the lights do self test normally when powered.

Rotax Wizard wrote:

Hi Shaun

If you have correct readings and the prop setting has been input as per BUDS then your prop is not good.  The prop has to load the engine to control the engine, there is no speed control on RPM other than the pitch.  

If you are additionally not getting a red lamp flashing at overspeed then you have a serious problem.  Exceeding 40 inch HG should give you a solid red lamp.

Don't fly it tell you can fix your warning lamps. Download the log file and send it to someone who can read it.

Cheers

RW, can you explain what you mean when you say "the prop setting has been input as per BUDS" ?

Thanks.

In a 914 installation you must set the "0" throttle position of the TCU after you have completed the installation and get it running.  The wide open throttle or 115% value also have to be set.  This is to tell the TCU the values of the throttle potentiometer (found on the 2/4 carb throttle shaft) The Prop has to control the RPM to hold the engine at or slightly below 5800 RPM.  In the event of a runaway engine, say broken throttle for example, the Prop pitch has to control RPM.  The settings as per the manual are relative to the TCU and throttle.  Given that the loading for WOT is by prop pitch.  

The TCU has 2 lamps if wired as per the manual.  One should be orange, this is for sensor failure or anomily of the sensors.  The other is red, in the event of an overspeed it will flash red.  In the event of overboost it will be solid, both cases can lead to serious engine failure. 

Hope that is better, it is good to review the reference material in the maintenance manual heavy and the installation manual.  Sorry if I was confusing. 

Cheers

Ah yep I did calibrate the throttle position and installed the 2 lights.