Mailing List flyrotary@lancaironline.net Message #62289
From: Steven W. Boese <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: What do you think may be happening?
Date: Fri, 15 Jan 2016 21:09:45 +0000
To: Rotary motors in aircraft <flyrotary@lancaironline.net>


Bill, 

I've embedded some comments below:


I am a little confused as to what may be going on with my EC-2. 
I recently had an incident where the engine went very lean just after take off and during the climb out to pattern altitude. The power to the secondary injectors may have been lost causing the engine to go lean above staging threshold MAP.  I didn’t do any troubleshooting.  I just set the mixture control to as rich as possible and continued in the pattern to land.  Depending on the size of the primary injectors, setting the mixture richer would at least partially compensate for the loss of the secondary injectors. 
On the ground, I could find no problems with fuel, either tank, fuel pressure, etc.  I would have expected the mixture to go somewhat rich when the MAP went below the staging threshold if the mixture control had been left in the richer position.
 
I decided to follow Steve’s procedure below.  After doing this procedure, the engine ran smoothly from idle to 22 inches on the ground.  I put it into mode 9 and let it change a few spots on the MAP.  Almost all the MAP table was still set at zero.  The there may have been no power to the secondary injectors during this procedure so the mixture would have correct above the staging threshold MAP within the flow capacity of the primary injectors as a result of the tuning.

At this point the controller is set to maintain a reasonable mixture using just the primary injectors.  I taxied out to fly and during the takeoff run, at about 29 inches and 7100 rpm, the engine went very rich, 10:1. This is what would happen if the power to the secondary injectors was restored at the time the engine went rich.  I adjusted the mixture knob during the takeoff run to about 9-9:30 o’clock.  This compensated for using all 4 injectors now.  At about 200 feet of altitude, the mixture suddenly went to about 17:1.  This is what would happen if the secondary injector power was lost again.  I moved the mixture knob to about 3 o’clock, but it really didn’t help much.  At the high MAP, the primary injectors alone may have not been able to supply enough fuel so trying to make the mixture richer with the manual control would have been ineffective. When I got to pattern altitude and pulled the power back, the mixture seemed to stabilize at around 13 or so.  When the MAP was decreased below the staging threshold MAP, the controller would have been using just the primary injectors which it had been tuned to do correctly.  I made the landing and back to the hangar with no incident. Most likely all at MAP below the staging threshold MAP.
 
On the ground again I checked the MAP and the table was at zero at all the places the engine had been operating during the climb out.  No corruption of the MAP table had occurred.


The comments are just a guess as to what may have been going on, but they seem to fit your observations.  It would seem to me that the problem would more likely be in the power path to the secondary injectors rather than a problem with the cold start function.  The cold start function would affect the both the primary and secondary injector operation.


Steve Boese




From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Bill Bradburry <flyrotary@lancaironline.net>
Sent: Friday, January 15, 2016 11:27 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: What do you think may be happening?
 

Steve,

 

I suppose that would be the secondary injector disable switch.  That would explain the engine going lean, I am not certain how the engine going rich would play in unless the problem somehow involved the cold start function.  That could be somehow possible since the same switch would be involved in both functions.   I will check that circuit out and see if I can find a bad connection or switch.

 

Bill

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