Stan that is exactly how i am feeling currently and I have not even sat in a helicycle with its rotors turning yet. I am now almost convinced that my turbine exploded due to the faulty fuel control (or motor) which can be confirmed in this guys VERY informative and factual articles on his website below. He makes a few statements out of one of his articles below which should prove that my repaired fuel control (motor) probably was the main factor that my turbine oversped and exploded, BUT there could also have been a potentiator that was fully open during startup along with the faulty motor on the fuel control??;
"Solar T-62T-32 ECU Pro's and Con's
Many experimental aircraft, especially rotorcraft, utilise the Solar T-62T-32 engine as their
primary power plant. The engine itself can be considered robust and reliable, yet there's
the inconvenience that its fuel control unit (FCU) isn't equipped with a mechanical
(flyweight) governor but requires an electronic governing system.
Well, here are my two (euro...)cents of information regarding ECU operation and possible
malfunction.
1. A severe overspeed (or failure of a single channel engine RPM pickup) is the most
severe malfunction a pilot may encounter. Either way, an improper, or uncertain RPM
reading to the ECU is always a clear indication for a shutdown of the engine. If the engine,
for any reason, actually overspeeds, the result of an uncontained disintegration of the
rotating assembly of a turbine engine is always more dangerous than a forced
autorotation.
If the engine RPM signal to the ECU (in case of an electronically controlled engine like the
Solar T-62T-32) is interrupted, there's no way to control RPM or keep the engine from
overspeeding. In this situation, forget about manually controlling the engine if there isn't a
mechanical (flyweight) backup device (which isn't standard on the SOALRs that we love
so much -- for good reasone I have to say).
2. If you are worried about the main fuel shutoff valve of the Solar T32-T62 engine, forget
it. The main fuel valve is one of the safest devices of this engine's fuel control unit. If you
want to worry, then rather think about the flexible wires inside the torque motor that
connect its (mobile) armature to the external socket. Even though these wires are of
reasonably high quality (meaning very thin individual strands), the insulation may solidify
and cause damage to the strands. Every time I get my hands on a Solar T62-T32, one of
the first things I do is replacing the flexible wires inside the torque motor with high quality
measurement equipment wires of approximately the same cross-section. Also, when
converting a T62 to experimental aviation usage, always replace the original wiring loom, if
possible also use new connectors!
3. I agree that solely an electronic contol of the engine RPM is only second best, but if
done properly, it's pretty good anyway. In the specific case of the Solar T-62T-32, it is
mandatory to check the return spring of the torque motor for condition and especially
corrosion during EVERY pre-flight check. As long as this spring is intact as well as the
torque motor itself (including the wires), the system is a very safe and reliable,
configuration.
4. Electrical supply to the ECU / Governor. This is the single weak point (in standard
installations) that can cause the engine to fail. Especially, since usually the electrical
supply is shared among many devices on a typical helicopter. There's a considerable
amount of wiring involved and then there's the question to put a fuse into the ECU supply
or not. All this may fail, wires may fray and cause shorts and so on. Yet, there's a simple
way to solve this problem, and that's adding a backup battery only for the ECU, located in
close proximity of the ECU. Since the current consumption of the ECU and engine, once
running, is reasonably low (about 2 amps), this backup battery wouldn't need to be big and
heavy. Use decouplig diodes and you should be fine.
5. In order to control engine RPM, you need to record engine RPM and nothing else. In
case of a single shaft engine, compressor delivery pressure will vary considerably during
load changes, even if the engine is running at the same speed all the time. Also, it
depends on atmospheric conditions. So any other input to the ECU than RPM is an
improper replacement. Of course, manual control may be an option for an experienced
pilot. But if he'll react fast enough in case of an ECU failure to prevent the engine from
flaming out is another question.
So im my opinion the clue from all this is quite simple: Do the installation as accurate as
possible, double-check everything. Make sure you use the proper tools and techniques
when doing electrical installations. Add an electrical back-up power supply system to the
engine control circuitry. Adjust the hydromechanical fuel control unit properly. Do a proper
pre-flight check before each start that includes testing the engine back-up systems and a
visual inspection of the torque motor return spring. And then, probably the most important
single thing: Practice autorotations so you know how your machine will behave in case of
an engine failure!