Steve,
The wideband may be picking up a small fuel imbalance
between the two rotors. Or is could be perfectly normal for all widebands to
jump around. I would expect an increase in EGT’s with a gradual partial
blockage. A high EGT alarm would give some indication. I would also
expect a steady but higher than normal temp with a build in restruction. But
with a sudden blockage at high power? The answer may not be of any value since
only a pressure sensor would tell the pilot to stop trouble shooting.
Bobby
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Steven W. Boese
Sent: Sunday, March 20, 2011 8:20
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Forced
Landing.
Bobby,
I have not done any testing with a
wideband O2 sensor. Unless the engine were operating right on a threshold
of a large untuned injector pulse width change (staging is the only thing that
comes to mind), it seems unlikely that the variation in O2 sensor would be
associated with injector delay.
Within the limits that were tested, the
EGT increased with increased exhaust back pressure due to partial
blockage. The mixture was somewhat rich and no change in O2 sensor was
seen. Lean mixtures were not investigated at that time.
Steve
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bobby J. Hughes
Sent: Sunday, March 20, 2011 7:46
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Forced
Landing.
Steve,
Thanks for the offer. Actually I think it
would be great if you could conduct a test. I had thought about a block off
plate that could be pulled into place with a long wire. This would allow
a high power test run with a sudden blockage. It’s the only way I can
come up with to create a not so dramatic reinactment. Your test stand would be
a better platform then the airplane. The engine was popping and shaking when
the failure occurred. As best I can remember my wideband O2 was off the scale
lean but I’m not certain. Speaking of wideband O2’s. My wideband
has always jumping around a few 10ths or more. My EM3 get’s a narrowband
output from the wideband. The EM3’s mixture bar appears stable. Could the
wideband be seeing a injector bounce associated with the injector delay? As an
example when leaned for cruise, say 13.2 it’s often switching rapidally
between 13.1 and 13.3. At this point the engine seems reasonable smooth. The
larger the bounce the less smooth the engine becomes. Have you done any of your
testing with a wideband?
Bobby