Ed
wrote:
Its a real airplane now
{:>)!!. You know you are going to have to take some time at some
point to give us all a rundown on your first 40 hours. I suspect that
due to the lack of messages from you to the contrary that it must have been
mostly smooth going.
Some of the usual
delays getting going. Some surprises on weight and balance; delays
waiting for workable insurance quote; delays waiting for test pilot since the
insurance company wouldn’t cover me in my plane, etc. Other than that, I
guess three main issues:
The most time
consuming, and on-going, issue has been with the EC2. I realize that the
unit works well on Tracy’s and similar
installations, but it did not accommodate my combination of composite
airplane, 3-rotor engine, and my electrical system design. After lots of
checking and changes, some of which helped, but didn’t solve the problem; we
finally added additional filtering on the circuit board; and that problem went
away.
In the process we
identified some additional issues arising from the way in which the 2-rotor
version was adapted to the 3-rotor. This has been resolved by adding
Schottky diodes in the circuits to the injectors to prevent partial pulses
going to the set of injectors turned off by staging, or by the disable
switches.
There are two
remaining issues. Controller “A” works fine on the ground, but the mixture
gets progressively leaner as altitude is increased. By 6000 ft it runs out of
manual adjustment, and it has to be switched to controller “B”, which works
just fine. Both controllers read the MAP from the same line via a ‘T’.
Very mysterious. We are replacing the pressure sensor on A on the
outside chance that will solve the problem, even though the measured output
from the A and B sensors are the same when the unit is powered up (out of the
plane) at different altitudes (measured at 1400’ and 5300’).
The other is that
there is something strange about the timing. At low power things appear
fine; switching off leading ignition has more effect than switching off
trailing, as expected. At operating power levels, however; switching off
leading has almost no noticeable effect; whereas switching off trailing drops
the rpm by 400+ rpm – which suggests that the timing is very late. Yet
advancing the timing via mode 8 does not make any improvement. What is
wrong with this picture? It is possible that the added filters caused a
delay in the timing, although analysis suggests the effect would be
small. Why doesn’t advancing the timing improve the power? Is there a
timing change to one set of coils associated with disabling the other?
We are removing the filtering capacitors from the ignition circuits as a test
to see what the effect is.
Tracy has been
cooperative and as helpful as can be expected throughout this process, but we
are at opposite ends of the country (FL and CA). Fortunately my son is
expert in this field, and has been great help; although he is in CO, still far
away.
Other than that the
things that come to mind are that I needed to make some small adjustments on
the incidence angles of the wings and the canard; and the marginally high oil
temps that I have mentioned here recently. As soon as the EC2 is back
in, I expect to due some measurements and tests to remedy that
issue.
Have a happy
4th!!
Al
P.S. I’ve attached
a photo of my plane taken at a recent local air show. It’s amazing how
much attention an unusual airplane with an unusual engine attracts; at even a
small air show.