Walter M601 Start Control, Limiting and More

Harnessing the latest solid-state switching, digital processing and communication technologies, we provide to Walter M601 engine owners and operators an integrated start sequence controller, engine protection limiter, basic engine monitor and event recording system with other expansion options.

Easy Installation

We believe our system has many benefits over the alternative traditional method. No need to interconnect a host of small components such as relays, timers, interrupters and diodes using many wires to build-up a start-panel and then integrate that with Walter's engine limiting unit. Our system provides a straightforward, solid-state (no moving parts), one box, one connector solution at a cost less than the factory engine limiting unit alone.

Advanced Starting

While remaining compatible with the traditional Walter starting procedure, our system allows for advanced features due to its integrated nature. It has to measure key engine parameters (ITT, N1, N2, etc.) continuously to fulfill its engine protection limiter role, but these readings can also be employed towards more intelligent starting. If a parameter reading (ITT, voltage, etc.) is unfavorable for safe starting, our system's pre-start checks will be able to warn you beforehand. Even with the start under way, when only you can effectively abort the start, our system will indicate if it thinks you should.

Keeping Record

Every start and run (dry motoring) operation as well as every parameter exceed event is recorded in detail within the control unit. These "history" records can be downloaded by and displayed on a laptop computer for analysis. They are given in a time-graph format spanning the start, run or exceed event. Engine parameters (ITT, N1, N2, voltage, etc.) are plotted on the graph versus time. The controller even counts the total start cycles and flight hours, along with other useful information such as the maximum ITT and minimum voltage reached as well as the time-duration taken during your last start.

Three configurations to choose from

The system centers around the TSLM control unit, which provides all the standard functionality. But by adding a display (VR-3PD) to your panel, you'll gain additional digital primary engine indication plus a much improved user interface. By adding yet another fuel computer module (FAM), you'll be getting a fuel page to your display indicating fuel-flow, fuel remaining, fuel endurance and more, as well as advanced features where throttle quadrant lever and isolating valve switch positions are included in pre-start checking. The table below provides a summary of the three options and their features, which will be described in more detail thereafter.

Item	Unit(s)	Features
VR-M601-1	TSLM	Start sequence control, engine protection limiter, engine monitor, event recorder, run/motor sequence control, beta propeller limiting, pre-start checking, start abort annunciation, parameter exceeding annunciation, detailed time-graph recording, start cycle counting, flight hour counting, diagnostic testing, anti-flameout operation.
VR-M601-2	TSLM VR-3PD	All the above plus indication on the main page of inter-turbine temperature (ITT), gas generator speed (N1), propeller rpm (N2), engine torque, oil-pressure, bus voltage measured by TSLM. Indicates start cycles, flight hours, engine events, start max. ITT, start min. voltage, start duration on the information page.
VR-M601-3	TSLM VR-3PD FAM	All the above plus interfacing with a fuel-flow sensor, micro-switches on the fuel shut-off lever and power lever (ECL), and senses the isolating valve activation. Indicates on new fuel page (VR-3PD display), the fuel-flow rate, fuel remaining, fuel used, and fuel endurance. Allows setting of fuel remaining via display.

1) The Basic TSLM System

The most basic M601 start and limiting control solution we offer composes of a single TSLM. Below is the basic interfacing diagram to both the engine and the pilot.

M601 Engine Interface

For people familiar with the M601, the TSLM directly sense inter-turbine temperature (ITT), both N1 and N2 speed (tachgen) sensors, the propeller BETA (micro-switch) sensor as well as bus (battery) voltage. Sensing of additional engine torque and oil-pressure is possible but not required. The TSLM directly controls the low-voltage ignition and the electromagnetic (interrupter) valve controlling fuel supply to the torch igniters, the electromagnetic fuel-restriction (EHT) valve and the start-contactor to the starter/generator. All sensors, valves and exciters mentioned, except for the start-contactor and the two optional torque and oil-pressure sensors, are normally supplied with the M601 engine.

Operator Interface

There are three indicator lights on the basic panel:

1. The EHT light will activate whenever the EHT (fuel-reduction) valve is active - indicating that limiting is in progress.
2. The TSLM light will indicate different TSLM modes. This light will also blink a certain code to identify a specific error.
3. The EXEED light will activate during a start operation to advise the pilot to abort the start by pulling the fuel shut-off valve actuating lever (condition lever) back to the CLOSED position. The light will also activate after the start (eg. during flight) if one or more of the primary parameters (ITT, N1, N2, Torque) is exceeding.

There are also two panel mounted switches on the basic panel:

1. The START/RUN momentary switch will initiate either a START or a RUN operation only if the engine is not already running. If the engine is already running, the switch can activate and deactivate anti-flameout operation, which is an option described later.
2. The LIMIT enable On/Off switch is available to the operator only as a precaution should, at any time, an electrical circuit fault or TSLM failure inadvertently activate the EHT valve, resulting in some loss of engine power. The pilot will be able to compensate for (override) this problem by switching the LIMIT enable switch off, thereby de-energizing the EHT valve and restoring engine power.

Run Operation

When the START/RUN switch is depressed to RUN, the TSLM will turn on the starter-motor to spin the engine for a short duration to purge trapped fuel and vapours from the combustion chamber or to cool it down. Just remember that the shut-off valve lever (condition lever) must be in the closed position while doing the RUN.

Start Operation

When the START/RUN switch is depressed to START, the TSLM will initially perform some pre-start checks. If they all pass, the controller shall commence the start by turning on the starter-motor, ignition and interrupter fuel sequence to the torch igniters. From the time the engine lights-up (rapidly increasing ITT) the TSLM will control the EHT valve to limit both the absolute temperature as well as the rate of temperature rise during the start. When the engine nears idle speed (±60%), the TSLM will discontinue the starter-motor, ignition and the interrupter sequence to end the start. The TSLM start cycles counter will be incremented. Also remember that the EXCEED light will turn on at any time during the start if the TSLM senses a problem that it thinks would lead to the ITT exceeding.

Beta Operation

When the engine is running and the propeller BETA sensor signals BETA (reverse thrust) mode, the TSLM will activate the EHT valve as required to limit the propeller speed (N2).

Anti-Flameout Operation

When the engine is up-and-running and the START/RUN switch is pushed to the START position for one second, the TSLM will activate the torch igniter sequence and indicate this mode by activating the TSLM light. Anti-Flameout mode can lower the likelihood of turbine flameout during certain phases of a flight. This mode is deactivated when the START/RUN switch is pushed to the RUN position for one second.

Flight Operation

The TSLM enters flight mode when the gas generator speed (N1) exceeds 70%. While above this value, the total flight hours that the TSLM keeps track of will be counting. The TSLM will also activate the EXCEED light should any primary engine parameter (ITT, N1, N2, Torque) exceed its respective maximum value to prompt the pilot to reduce power.

Maintenance Operation

From time to time a Laptop PC and USB-to-Serial Converter may be connected to the TSLM, as depicted below, in order to perform maintenance operations on an installed system.

Maintenance operations allow you to confirm (troubleshoot) your installation, make adjustments and view both operational information and recorded events. All these tasks are done through the VR System Link software running on the laptop.

Verification of an installation is performed through diagnostic tests initiated from System Link. Diagnostics isolate and test a certain section (electrical circuit) of an installation to verify correct wiring for that section, as well as the operation of the sensor or device(s) the circuit leads to. These tests have been designed to reduce time spent on troubleshooting.

System Link also enables making adjustments to set-points, calibration values and other configuration settings, or just the viewing of operational information such as flight hours, start cycles, exceed counters, start max. ITT, start min. voltage, etc. Detailed graphs of recorded events such as start, run and exceedence graphs can be downloaded onto your laptop for examination and analysis.

2) Adding the VR Display

The system described so far can be expanded further by adding another component - the VR-3PD Display. The basic interfacing diagram would now include the VR-3PD as shown below.

The VR Display (3PD) is a standard 3.125" instrument which will enable the pilot to monitor the operation of the engine as well as the whole start control and limiting system. It connects to the TSLM via only 2 wires and beyond that only requires power and ground.

The Basics of the VR-3PD Display

1. Left-right selection switch
2. Name of current page
3. Page (or action) you'll get when selecting to the left
4. Page (or action) you'll get when selecting to the right
5. Parameter legend
6. Parameter value

The TSLM Page

The page is divided into 6 boxes each containing a parameter:

1. ITT - Inter-Turbine Temperature in degrees C
2. N1 - Turbine compressor speed in percentage
3. PROP - Propeller speed (N2) in RPM
4. TORQUE - Engine Torque in PSI
5. OIL-P - Oil-Pressure in PSI
6. VOLT - Bus / Battery Voltage

The Info Page

1. FLIGHT HOURS - Total hours the engine has been running above 70% N1
2. START CYCLES - Total start cycles counted
3. ENGINE EVENTS - Total amount of events recorded
4. START MAX ITT - The maximum ITT reached during the last start
5. START MIN VOLT - The minimum bus voltage reached during the last start
6. START DURATION - The time it took in seconds to reach idle during the last start

The Options Page

When viewing the OPTIONS page the user can access the menu by holding the selection switch to the right for more than 2 seconds. A cursor will appear to enable selecting a particular option.

1. Choosing PERFORM DIAGNOSTIC will let you select a diagnostic test
2. Choosing ADJUST BRIGHTNESS will let you adjust the brightness of the display
3. Choosing ADJUST CONTRAST will let you adjust the contrast of the display

Run Operation

During a run operation the word RUN will appear next to TSLM on the top-row. Also in the top-right of the screen STR will appear to indicate that the starter is active.

Start Operation

During a normal start operation the word START will appear next to TSLM on the top-row. Also in the top-right of the screen:

1. STR will appear to indicate that the starter is active.
2. IGN will appear to indicate that the ignition is active.
3. INT will appear to indicate that the interrupter is active.
4. LIM will appear and the ITT parameter legend will blink to indicate that the EHT (fuel restriction) valve is active to limit the ITT.
5. EXCEED will appear to indicate that the pilot should abort the start.

Beta Operation

During beta operation the word BETA will appear in the top-right of the screen. If the TSLM is limiting the propeller speed (N2), the word LIM will appear next to BETA on the top-row and the PROP parameter legend will blink.

Anti-Flameout Operation

During this operation AFO will appear next to TSLM on the top-row. Also in the top-right of the screen:

1. IGN will appear to indicate that the ignition is active.
2. INT will blink to indicate that the interrupter is being sequenced.

Parameter Exceeding

If a parameter is exceeding the word EXCEED will appear in the top-right of the screen and the relevant parameter legend (ITT in this case) will also blink.

3) Adding the FAM

The system described so far can be expanded further by adding another component - the FAM (Fuel and Auxiliary Module), which plugs directly into the back of the VR-3PD Display. The basic interfacing diagram would now also include the FAM as depicted below.

The FAM adds the following capabilities:

1. Fuel monitoring by way of fuel flow sensor
2. ISOL - emergency circuit for engine control (isolating valve) sensing
3. Throttle quadrant fuel shut-off valve (condition) lever in closed position (micro-switch) sensing
4. Throttle quadrant engine control lever (ECL) or power-lever in idle position (micro-switch) sensing

As shown above, the FAM enables the tracking of fuel consumption to calculate flow rate, fuel used, fuel remaining and fuel endurance. Also enabled are more advanced start control by the sensing of ISOL, condition lever shut-off and power lever idle inputs.

The Extra Fuel Page

A new page on the VR-3PD Display will fit between the TSLM and INFO pages, in order to show FUEL parameters to the pilot.

1. FLOW - Fuel flow rate in gallons or pounds per hour
2. REMAIN - Fuel remaining in gallons or pounds
3. USED - Fuel used in gallons or pounds
4. ENDURE - Fuel endurance in hours : minutes

Setting Fuel Remaining

New options are added to the OPTIONS page as illustrated to select:

1. FILL-UP FUEL REMAINING after your aircraft has been filled-up with fuel
2. ADJUST FUEL REMAINING to fine-tune the gallons or pounds of fuel remaining in your aircraft

Low Fuel Warning

The FAM provides for the setting of two low fuel warnings:

1. Should the Fuel Remaining value drop below a set-point, LOW FUEL will appear in the top-right of the FUEL page, while the REMAIN legend would be blinking
2. Should the Fuel Endurance value drop below a set-point, LOW FUEL will appear in the top-right of the FUEL page, while the ENDURE legend would be blinking

ISOL Functionality

The systems ability to detect (via the FAM) whether a pilot has selected the isolating valve (emergency FCU circuit) before issuing a start, can help prevent possible turbine damage resultant from unintentional selection thereof. This can be done simply by placing the start on hold and informing you whenever you issue a start with ISOL switch on, with the option thereafter to either proceed with the start or abort / cancel it completely through the VR display.

Condition Lever Functionality

The system can optionally detect (via the FAM) whenever the pilot has placed the fuel shut-off valve lever (condition lever) in the CLOSED position. This involves the mounting of a small micro-switch on the throttle quadrant condition lever assembly. The ability helps prevent damage that can result from incorrect placement of the lever in three circumstances. First, when you do a run, the system can warn you if the condition lever is not in the prescribed CLOSED position. Secondly, when doing a normal (ISOL off) start, the system can warn you if the lever is in the non-prescribed CLOSED position. Thirdly, when performing an emergency FCU circuit start (ISOL on), the system can warn you if this lever is not in the CLOSED position.

Engine Control Lever Functionality

The system can also detect (via the FAM) whether the pilot positions the engine control (power) lever in the IDLE position. This involves the mounting of a small micro-switch on the throttle quadrant power lever assembly. This ability can again warn the pilot if the power lever is not in the prescribed IDLE position when a start is issued.