Auto retract failure

[Bill Tugnett]

On our last two flights, when the ignition was switched OFF the auto retract failed & the engine had to be retracted manually.

Replicating the sequence on the ground, the ECU flashed "BRAKE? .. BRAKE? ..", an audible pulse tone sounded & automatic engine retraction did not occur.

Ref  FM  7.3.31 Cancel this warning by pushing the Menu button, then automatic retraction will proceed (otherwise manual retraction & manual prop brake is required). The reason for this failure is " ... the requirements for starting the automatic retraction process have not been met"

And the requirements are: 

1)  "... engine rpm >2000 & >2000rpm for at least 10s"  &

2)  "... the limit switch for the extended position is closed"

I'm certain condition 1) was met. Unsure re Condition 2) as the extended limit switch is mounted on the spindle drive & appears to be a magnetic reed type? When fully extended, the "extended" LED is illuminated, suggesting the switch is closed.

I'd appreciate advice / suggestions on how to check this. The Wiring Diagram (MM #10) lacks detail. Thanks,  Bill   (VH-FIG)

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[Mark Zivley]

Bill,

It's possible that you have an issue with one of the prop position sensors.  I don't remember the specific messages, but this sounds similar to an issue I had last year.  I adjusted the sensors a little bit closer to the prop mounting hub where the metal target is located and the problem went away.

Depending on the proximity sensor your glider ended up with, it may require being in a fairly dark hangar to see the LED lights on the sensors to see if they are detecting the target.  If not, small adjustments and don't tighten too much or you can break the sensors...

You can also do a dry run as follows:

Extend the engine with the ignition switch, wait a few seconds after fully extended and then turn the ignition OFF.   Rotate the prop backwards so that the target is before both sensors.  Then push the menu button to acknowledge the "Brake" message.  Gently pull the prop forward so the target approaches the first sensor.  When it reaches the first sensor, the brake should grab and hold for 3 seconds.  Then it starts to pulse.   You can keep some light forward rotation pressure on the prop at this point.  When the second sensor is reached, it will start the auto retract.

You can stop the retract with the mast up switch.

If this process doesn't work, then it's probably a sensor adjustment or failed sensor.

Mark

[bucc...@gmail.com]

We had the same trouble.  Fault was with the position sensor.  The wires are very fine and with the constant vibrations they fail.  We have several replacements on standby because the failure is quite common.  :(

[Bill Tugnett]

Thanks for the suggestions. Problem still not resolved entirely, but I think it's the positioning of the sensors that's causing the problem. I can see the lit LED's & adjust it in the hangar & have the retraction work perfectly, however in the air the prop occasionally flicks past the vertical, requiring a second attempt. I'll keep at it. Rgds, Bill

[bucc...@gmail.com]

It important to periodically clean the cam wheel for the braking mechanism.  Use brake cleaner to degrease the surface of the braking cam wheel.  Oil from the exhaust builds up on this surface making the mechanism less effective.

[CPT Drive]

Hi Bill. Not sure if what I had was the same, but this is what I did.

First check if the position sensors are amber when in a dark hangar when the propellor is in the 9 o'clock and 3 o'clock position. (I did on a previous occasion have to replace prop sensor 1). 

If both have an amber glow, move the prop to the vertical and both amber lights on the end of the sensors should go out.

If not, clean the end of the sensors and the pads on the propellor hub, move the propellor again to the vertical after cleaning and hopefully they with go out.

I think it is the rubber residue coming off the v-belts that makes this area dirty.

If that gets the lights to go off, THEN go to the engine controller and push the menu button when it displays "Brake?"  The brake servo should come to life. Move the propellor slowly by hand to the vertical (if not already). The auto pulse braking should be going and once the prop is vertical, the spindle drive will automatically lower the pylon.

Kind regards,

Angus Tapper

Glide Queenstown

New Zealand