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Hi Bob,
I strongly suggest you mount your EC2 where it is easy to
get at. I mounted my "out of the way" forward and up under my instrument
panel thinking there would never be any need to remove it
{:>).
I have found that laying on my back with a spar
under my spine ,my shoulders bound by the fuselage side and my stick is getting
harder as I mature {:>). Tracy continues to upgrade and enhance
the EC2 (and probably will with the 20B version) so, you will likely removed it
for upgrades if nothing else. So far I have removed my (for various
reasons) probably half a dozen times.
Ed
----- Original Message -----
Sent: Wednesday, October 17, 2007 9:09
AM
Subject: [FlyRotary] Re: EC2 20B Injector
Power Circuits
So does this mean I shouldnt finish installing my EC2 cause I
may have to send it back to Tracy? Nows the time for me. I'm installing
now.
Bob Mears
Supermarine Spitfire
-----Original
Message-----
From: Joe Ewen <Jewen@comporium.net>
To: Rotary
motors in aircraft <flyrotary@lancaironline.net>
Sent:
Sun, 14 Oct 2007 10:28 pm
Subject: [FlyRotary] Re: EC2 20B Injector Power
Circuits
Hi Bob,
Don't know if you don't ask. A diode is a
device that allows current to flow only in one direction (DC circuit.)
Schottky is a particular diode construction. One desirable feature of a
Schottky is that it has a low forward voltage drop. All diodes have a
drop in voltage (like a small resistor.) In this case, the lower voltage
drop allows the injectors to continue firing slightly longer than other diode
types in the event of an alternator failure and lowering battery
voltage.
On the 20B, the injector control lines are wired
together, installing the diodes prevents the current / voltage from back
feeding between the primary and secondary circuits and the possible failure
modes I noted earlier. Application of diode(s) in this manner is
typically referred to as isolation diodes.
Since the EC2 controller internal jumps the 2
controller power feeds, I installed isolation diodes (Schottky) to prevent
similar problems between the 2 supply circuits.
You may also find diodes useful in
making annunciator press to test circuits. If you have 2
devices such as a transponder and a GPS that both need to share altitude
encoder inputs, isolation diodes would be used. Of course with any
avionics installations, follow the manufactures guidelines.
Joe
----- Original Message -----
Sent: Sunday, October 14, 2007 10:16
PM
Subject: [FlyRotary] Re: EC2 20B
Injector Power Circuits
Al
Hate
to continue to display my ignorance but what is a Schottky diodes.
When it comes to electronics I’m as dumb as a stump.
Bob
K
From: Rotary motors
in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of Al Gietzen
Sent: Sunday, October 14, 2007 5:42
PM
To: Rotary motors in aircraft
Subject: [FlyRotary]
Re: EC2 20B Injector Power Circuits
Joe;
You
are right. We discovered this crossfeed issue some time back. Is
applies only to the 20B version as the 13B has separate drivers for each
set. Install Schottky diodes in the circuits for each injector.
Tracy is aware of this, and has installed the diodes in his as
well.
Al
-----Original
Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
On Behalf Of Joe Ewen
Sent: Sunday, October 14, 2007 3:20
PM
To: Rotary motors in aircraft
Subject: [FlyRotary]
EC2 20B Injector Power Circuits
I have been
testing my wiring harness from the EC2. I found a behavior that I did
not expect. The manual drawing (EC2 manual) show a single injector
supply that splits at the Injector primary and secondary disable
switches. On my installation, I have 2 separate feeder circuits,
supply Primary comes from battery 1, and supply Secondary comes from
battery 2. I did this for redundancy. If I had a failure such as
a short to ground in either circuit, its related overload should trip, but
the other circuit should remain active.
While testing the
injector circuits, I noticed what I would term an abnormality. With
both injector disable switches in the enable position, I turned on the power
for the primary circuit (I have LED indicators on all circuits that
annunciate power present) and the secondary circuit also showed power
present even though the power switch for the secondary circuit was
off. The same is true when the secondary circuit is engaged and the
primary is off.
Initially this
led me to think I had miss wired something in the circuit. After
checking out the wiring, I found no issues. So I took a closer look at
the wiring diagram in the manual. It turns out the power was being
back feed through the injectors to the opposite circuit. On the 20B
version of the EC2, the injector control lines for each rotors injectors are
junctioned going into the EC2. For example the Rotor 1 Primary and
Secondary control lines are junctioned into a single input point at the
EC2.
I can see several
situations where this may lead to undesirable operation. For example,
if the Primary circuit had a hard short to ground, it would take out the
primary circuit's overload (CB or Fuse.) Since the primary and
secondary circuits are electrically connected on the control line, the other
circuit would also trip. Another situation that could occur is a
medium to high resistance short. Current would then flow uncontrolled
through the unaffected circuit's injector to the affected circuit's injector
then to the resistance short. This could keep both injectors on
100%. While this situation is unlikely, it seems
possible.
I
believe the 13B version uses separate control lines for each injector,
so this in not likely to be an issue on the 13B version.
It appears that
isolation diodes are needed to prevent these possible problems. Before
making any changes I have to look the circuit over more closely, as well as
a call to Tracy on the next service day. My question to the group,
especially anyone with a 20B, is am I looking at this
wrong?
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