Initial System checkout
There are a couple of concepts you should keep in mind / understand before performing these tests. These concepts are very important to understanding how the tests work.
- Each ECU controls 1 set of spark plugs. Typically ECU # 1 controls the top spark plugs and ECU # 2 controls the bottom set. This does not change.
- When a single ECU is selected, the selected EWCU controls all 6 injectors. When “Both” ECUs are selected, ECU 1 controls injectors 1,2 & 3 and ECU controls injectors 4,5 & 6.
Before first engine start, there are a few things you should do to ensure the system is installed correctly.
- Confirm that the primary and secondary maps contain identical information except for the magnet position values.
- Ensure that the magnet position value for the primary and secondary ECUs are set to the values specified by SDS.
- Ensure that primary and secondary Hall sensors are connected to the corresponding ECU.
- Ensure all circuit breakers are “in”.
ECU Operation Test (Confirms ECUs are operating correctly and need only be done as part of initial system checkout. It should not be done as part of a pre-flight test.)
- Start engine and bring to idle RPM.
- Select ECU 1. Pull circuit breaker for ECU 2. Engine should continue operation with a 75-100 RPM drop.
- Reset circuit breaker for ECU 2.
- Select ECU 2. Pull circuit breaker for ECU 1. Engine should continue operation with a 75-100 RPM drop.
- Reset circuit breaker for ECU 1.
Notes: When ECU 1 or ECU 2 is selected only the selected ECU is controlling engine injectors operation along with a single coil pack. This results in a RPM drop.
If the ECU select switch is on the BOTH position, injectors 1-3 are controlled by ECU 1 and injectors 4-6 are controlled by ECU 2. Consequently, if either ECU circuit breaker is pulled, then engine will be running on only three injectors causing a very rough engine. This is not recommended.
Pre-flight Runup – Normal Operation
The tests below should be done before each flight as part of the normal run up process.
The runup process for the SDS system is similar to the process for a conventional dual magneto aircraft. Once oil temperature has reached 100F+ the following steps are suggested:
- Ensure both Coil Packs are on
- Ensure ECU select switch is on Both
- Throttle up to 2,100 rpm
Coil Pack Test (this is analogous to a magneto check)
- Switch Coil Pack 1 off. A 75-100 RPM drop should be noted.
- Switch Coil Pack 1 On.
- Switch Coil Pack 2 off. A 75-100 RPM drop should be noted.
- Switch Coil Pack 2 On.
ECU Injector Control Test (Confirms each ECU can control all 6 injectors)
- Select ECU 1. No change in engine rpm / operation should be noted.
- Select ECU 2. No change in engine rpm / operation should be noted.
Fuel Pump Operation Test
It is imperative that both fuel pumps are operating correctly for safe flight.
- Switch both fuel pumps on and note fuel pressure.
- Switch fuel pump # 1 off – there should be only a minimal change in pressure.
- Switch fuel pump # 1 on and number 2 off. Again, the fuel pressure drop should be minimal
- Cycle prop in accordance with prop manufacturer recommendations.
After completion of these tests, close throttle returning engine to idle RPM.
If any anomalous behavior is detected, the underlying issue(s) must be identified and corrected before flight.
Before Take Off Checks
- Ensure all circuit breakers are “in”. Abort take-off if any circuit breaker(s) have failed and resolve cause before further flight.
- Ensure ECU select switch is on “both”.
- Ensure Coil Packs 1 & 2 are both “on”.
- Ensure Fuel pumps 1 & 2 are both “on”.
- Ensure LOP (lean of peak) is “off”.
- Ensure mixture knob is set to desired position.
- Complete any other required pre-takeoff checks.