AeroDesignWorks HORNET-III User manual
HORNET-III manual
Firmware v3.0
AeroDesignWorks GmbH
Wankelstr. 57
D-50996 Köln
Germany
27th April 2022
Contents
1 Introduction 2
1.1 Hardwareinformation....................................... 2
1.2 Liability and limited warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Components and connecting 4
2.1 Groundsupportunit........................................ 4
2.2 I/Oboard ............................................. 4
2.3 Fuelsystem ............................................ 5
2.4 Powersupply ........................................... 5
2.5 GPSmodule............................................ 6
2.6 Telemetrymodule......................................... 6
3 Engine operation overview 7
3.1 Engineoperationmodes ..................................... 7
3.2 Differences in operating behaviour between HORNET-III and HORNET-III-ClubSport . . . . . 7
4 Using the Ground Support Unit (GSU) 9
4.1 Poweronmessages ........................................ 9
4.2 Statusscreens........................................... 10
4.3 Enginestatuses .......................................... 11
4.4 Terminationstatuses ....................................... 12
4.5 Mainmenu ............................................ 12
4.5.1 Runtimesettings..................................... 12
4.5.2 Useradjustments..................................... 12
4.5.3 Systemandperiphery................................... 13
4.5.4 GPSandairspeedvalue ................................. 14
4.5.5 Testfunctions....................................... 15
4.5.6 Expertmenu ....................................... 15
4.6 Necessary settings before starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5 Engine operation details 17
5.1 RadioControl(RC)........................................ 17
5.2 Throttlepositions ......................................... 17
5.2.1 Definedpositions..................................... 17
5.2.2 Starting, running and stopping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.2.3 Throttlecurve....................................... 17
5.3 Autostart ............................................. 18
5.4 Autocalibration.......................................... 19
5.5 Automaticmode.......................................... 19
5.6 Fail-safemode .......................................... 19
5.7 Cool-downmode ......................................... 19
5.8 Auxiliarychannel......................................... 20
5.8.1 Using the auxiliary channel to replace the RC’s trimming . . . . . . . . . . . . . . . . 20
5.8.2 Smokervalve....................................... 20
6 Contact and support 21
7 Changelog 21
8 Acknowledgements 21
1
1 Introduction
The HORNET-III is an engine control unit (ECU) for model jet turbines, originally developed and produced
by ProJET electronic components GmbH, Fuchsmühl, Germany. Its home builder version (still distributed by
ProJET) can be used for engines of a wide range of manufacturers. All HORNET-III variants have the following
features in common:
• ECU settings accessible via Ground Support Unit (GSU).
• Engine can be started using standard fuel or an auxiliary gas.
• Controls an analogue (brushed) fuel pump.
• RPM sensor can be optic or magnetic (Hall).
• Dynamic throttle response depending on the temperature and RPM sensor signals.
• Fail-safe mode in case run time errors (e.g. one or both sensors fail and other errors).
• Support for connecting to a GPS module.
• Support for a smoker valve.
• Communication with XBee modules for saving telemetry data.
After acquiring the BF Turbines product line in 2017, AeroDesignWorks GmbH purchased the HORNET-
III firmware source code together with a license to use, modify and redistribute the firmware in 2018. The goal
was to be able to make modifications for the BF range of engines. AeroDesignWorks and ProJET continue
to work together on the hardware, but starting in 2021, AeroDesignWorks distributes their HORNET-III ECUs
with a new firmware starting at version v3.0.
• All HORNET-III ECUs sold by AeroDesignWorks only work with our own range of model jet engines.
• As they are configured for a fuel start, we no longer provide information on using an auxiliary gas.
• The firmware version v3.0 brought some changes that affect the end user and hence a long overdue update
to the manual.
ProJET developed a HORNET-III capable of powering and controlling brushless fuel pumps called HORNET-
III-BLC (Brushless Controller), which uses different hardware and cannot be used with analogue fuel pumps.
There are some notable differences, which will be mentioned in the manual where appropriate.
1.1 Hardware information
The HORNET-III is powered by an Atmel Atmega2560 processor, which has 256 KB of program memory and
4 KB of EEPROM to persistently store settings. The EEPROM has an unlimited amount of read cycles and a
limited but large (100,000+) amount of write cycles per byte.
• The maximum supported battery voltage is 12.8Vfor continuous operation.
• The receiver input supports 5 cells with a maximum voltage of 7.5Vand a minimum pulse amplitude of
2.7V.
• The fuel pump can be supplied with a current of 10Afor continuous operation, with peaks of 20Afor up
to 0.2s.
• The starter can be supplied with a current of 10Afor continuous operation, with peaks of 20Afor up to
0.2s.
• The glow plug can be supplied with a current of 10Afor continuous operation, with peaks of 20Afor up
to 0.2ms.
• The fuel valves can be supplied with a current of 0.25Afor continuous operation, with peaks of 0.5Afor
up to 1s.
2
SECTION 1.
1.2 Liability and limited warranty
By using this product, you agree to hold AeroDesignWorks GmbH free from any form of liability for damage
or injury, direct or indirect, resulting from using this product. As AeroDesignWorks GmbH cannot supervise
the proper installation and operation of the jet engine, the electronic components and the radio controller, the
end user is responsible for all of this.
The product comes with a 24 month limited warranty from the date of purchase. It applies only to defects
(material or operational) present at the time of purchase. It does NOT apply to improper handling, normal wear,
overloading or damage due to use of incompatible accessories.
3
SECTION 2. Components and connecting
2 Components and connecting
For operating a model jet engine, the following components need to be connected to the HORNET-III:
1. A Ground Support Unit (GSU).
2. An I/O board (with LED and buzzer).
3. RPM and temperature sensors together with an amplifier.
4. A fuel pump.
HORNET-III: Analogue pump, e.g. the AeroDesignWorks B100F and B140F ship with HP-Tech
ZP30725F pumps, while the B300F ships with an HP-Tech ZP48031 pump.
HORNET-III-ClubSport: Brushless pump, e.g. the AeroDesignWorks B140F ClubSport ships with
an HP-Tech BZP21L40 pump.
5. A battery for power supply.
All new AeroDesignWorks model jet engines ship with these accessories except for the battery. How these
components are connected is shown in Figure 1a.
Note that there are two fuel valves for the two fuel lines labeled KEROSENE and IGNITION on the engine.
These valves and their fuel lines refered to as main and ignition in this manual.
2.1 Ground support unit
The usage of the GSU is covered in Section 4.
2.2 I/O board
The I/O board can (and should be) placed between the GSU and the HORNET-III. It can be kept in the model
will use the LED and the speaker for feedback.
LED
1. Green: Engine is off.
2. Orange: Engine is in standby mode and ready to accept the starter signal from the RC.
3. Red: Engine is running in automatic mode.
Speaker
1. Short beeps: ECU starting.
2. Long beep: Engine is starting.
3. Sequence of short beeps: Error message: Low battery voltage, temperature sensor failure or glow plug
failure
When the engine is off, the button can be pressed to operate the fuel pump (e.g. if there is a lot of air in the
fuel lines).
WARNING
Be careful not to flood the engine with fuel!
4
SECTION 2. Components and connecting
Anschlussschema Kraftstoffstart
Hoppertank
Filzpendel /
felt pendulum
Pumpe/
fuel pump
Kraftstoffventil/
Kerosene valve
Ignitionventil/
ignition valve
Y Festo
Akku / battery
i/o-Platine /
i/o-board
Filter
Messingpendel /
brazen pendulum
Haupttank /
main tank
Ignitionventil/
igniotion valve
Kraftstoffventil/
Kerosene valve
Pumpe/
fuel pump Akku /
battery
Hochstrom zur
Turbine / High
current to the
turbine
Datenverbindung
zur Turbine /
Data connection
to turbine
Verbindung zur
Fernbedienung /
Remote control
connection
Verbindung zu
I/O Platine und
GSU/ Connection
to I/O board and
GSU
GSU
ECU
Tankentlüftung /
Tank ventilation
Hochstrom / H igh current
Datenkabel / data
Datenkabel / data
Fernbedienung /
remote control
(a) Connection scheme.
(b) ECU connectors.
Figure 1: Connecting the HORNET-III.
2.3 Fuel system
The overall reliability of the jet engine system depends on a well-made fuel system. New AeroDesignWorks
model jet engines ship with high quality components (fuel pump and valves, connectors, . . . ). If you need to
make adjustments or exchange components, some suggestions are:
• Use a high quality fuel pump like the ones shipped with the corresponding AeroDesignWorks jet engines.
• Use fuel valves of high quality.
• Use a hopper tank with felt pendulum in front of the main fuel tank(s).
• Do not use fuel filters directly before the fuel pump.
• Use a fuel feed line with the largest possible diameter.
2.4 Power supply
Since all components (like glow plug, starter, valves, fuel pump) are supplied by a single battery, its capacity
should be sufficiently high (≥2500mAh).
5
SECTION 2. Components and connecting
WARNING
Carefully monitor the battery voltage, especially during and after the first few flights, as a low battery
voltage can be fatal e.g. to maintaining a sufficient fuel flow.
Disconnect the battery from the ECU if it is not operated for several days.
2.5 GPS module
A GPS module can be connected to the corresponding outlet on the ECU. It does not need to be configured
via GSU. The GPS data is available in the corresponding menu (see Section 4.5.4) or can be transmitted by a
telemetry module.
2.6 Telemetry module
A telemetry module can be connected. It is placed between ECU and I/O board and usually comes with an
integrated battery. It needs to be configured via GSU in the corresponding menu (see Section 4.5.3).
6
SECTION 3. Engine operation overview
3 Engine operation overview
This is summary of how the ECU controls various stages during the engine operation to better understand the
following section about using the GSU (Section 4). The details about how the ECU controls the engine and the
various settings can be found in 5.
3.1 Engine operation modes
The ECU define several modes of engine operation, which can be controlled by the RC (see Section 5.2).
1. Off: The engine is off. Settings can be adjusted via GSU (see Section 4). The engine can then be put
into standby mode using the RC. In standby mode, the ECU accepts a starter signal from the RC and
commences the autostart sequence.
2. Autostart: The engine goes from standby mode to operation mode and idle RPM by performing several
steps like pre-heating, switching on the burner, fuel ignition and finally increasing the RPM (see Section
5.3).
When using an analogue (brushed) pump, there is also a phase called auto calibration (see Section
5.4), which is needed to determine some characteristic voltages for specific fuel flows and RPM. This is
due to brushed pumps slightly differing in their operation characteristic.
A HORNET-III-ClubSport with brushless pump does not need the auto calibration because all brush-
less pumps of the same model have the same operation characteristic (with only negligible differences).
3. Automatic: The engine is running. The ECU responds to the RC’s throttle position, which can govern
thrust or RPM or any linear combination between these two characteristic curves (see Section 5.2). It
automatically adapts the fuel flow to match the user’s input, depending on the RPM and temperature
sensors and monitoring both signals to ensure a safe operation of the engine (see Section 5.5). Telemetry
is transmitted (if using a telemetry module). It is possible to turn off the engine and going into cool-down
mode.
4. Fail-safe: If the ECU recieves errors from the RC during the Automatic phase (e.g. no signal or signal
errors), it switches to fail-safe mode if it is configured (see Section 5.6). After a user-defined delay,
fail-safe mode is activated for up to 10sand the ECU assumes a prescribed throttle position.
5. Cool-down: After the ECU shuts down the engine, the starter will hold the start RPM for several seconds
to allow the engine to cool down. The ECU automatically switches to off afterwards.
3.2 Differences in operating behaviour between HORNET-III and HORNET-III-ClubSport
As mentioned in the introduction, the ProJET HORNET-III and HORNET-III-BLC use different hardware,
but the same firmware (as of writing, the firmare version is 2.8). Most notably, they use the same code for
controlling the pump’s behaviour and require auto calibration (see Section 5.4).
To better leverage the brushless pump’s quicker response and the fact that different pumps of the same model
have the same operating behaviour (pump voltage and flow at a specific pressure) up to negligible differences,
AeroDesignWorks modified the firmware of the HORNET-III-ClubSport. This new firmware is designated v3.0.
The AeroDesignWorks HORNET-III-ClubSport uses a priori knowledge of the pump’s characteristic curves
and also employs a PI controller for controlling the fuel flow to match the user’s throttle input (and thus RPM).
The result is a much more responsive feel of the jet engine. A comparison of measurement data can be
found in Figure 2. This was done with the same engine by only changing the ECU and fuel pump between
measurements.
•nrpm: The normalised RPM, where 0 corresponds to idle and 1,000 to full RPM (in the case of the
B140F 130,000).
•Controller signal: This corresponds to the normalised throttle position, where 0 corresponds to idle and
1,000 to full throttle.
7
SECTION 3. Engine operation overview
Figure 2: Comparison of measurement data: B140F with HORNET-III vs. B140F ClubSport with HORNET-
III-ClubSport.
•Pump pressure: This is plotted to visualise how quickly the pump reacts.
As the engine has to slow down the acceleration towards maximum RPM to prevent overshoots, we meas-
ured the time from the controller signal assuming its maximum value to the engine reaching 98% of the max-
imum RPM (note the vertical green lines in Figure 2). With this definition of the acceleration phase, the
HORNET-III-controlled engine took 3.1s, while the HORNET-III-ClubSport-controlled engine took 2.1s. The
pump pressure curve is not as smooth as for the HORNET-III-controlled engine, as the pump reacts more
quickly and the PI-controller is more aggressive.
8
SECTION 4. Using the Ground Support Unit (GSU)
4 Using the Ground Support Unit (GSU)
The GSU is a small terminal with an LCD with two lines and 16 characters each and four buttons (up ↑↑, down
↓↓, escape ✘and enter ✓).
Figure 3: An AeroDesignWorks GSU.
WARNING
Do not permanently install the GSU in the aircraft model, as the LCD might have a negative impact on
the RC’s range!
Regardless, the GSU can be used to change ECU parameters while the engine is running.
• The menu can be navigated up (↑↑) and down (↓↓), sub menus can be entered (✓) and left (✘).
• Values can be adjusted up (↑↑), down (↓↓), saved (✓) or discarded (✘). Changes to values are written to the
EEPROM automatically upon saving them.
• When the engine is in standby mode, the start sequence can be initiated by simultaneously pressing up
(↑↑) and escape (✘). This might be needed if one HORNET-III is used to simultaneously control more than
one engine.
• The expert menu can be unlocked by simultaneously pressing and holding up (↑↑) and down (↓↓), see
Section 4.5.6.
4.1 Power on messages
After starting the ECU, some messages will be displayed on the GSU. The startup procedure will also produce
some messages.
1. ECU and firmware version, e.g
HORNET-III CS E
V3.0 2021-10-22
In this example, a HORNET-III-ClubSport is used and its expert mode is unlocked, signified by the last
character Eon the first line.
2. The engine that was connected last, e.g.
005 AEROD.WORKS
B140F
The three digit number is the model ID of the engine.
9
SECTION 4. Using the Ground Support Unit (GSU)
These messages will be repeated if the GSU is removed and reconnect, or if it is connected after the initial
startup procedure. The following messages are printed by startup routines and will not be displayed again if the
GSU is reconnected.
3. Connection to GPS module: The ECU will try three times before giving up
CONNECT TO GPS
TRY 2/3 FOUND.
or CONNECT TO GPS
NO GPS MODULE
4. Connection to XBee module: This ECU will only try to connect to an XBee module if it was configured
during an earlier start. In this case, the GSU will display
INITIALISE XBEE
OK
or INITIALISE XBEE
FAILED
if the previously configured module was not found.
5. Connection to engine:
CONNECTING TO
ENGINE... :000
The last three digit number is the number of failed connection attempts. If you see something other than
000, there might be a problem with one of the cables. When the connection is successful, the GSU will
display e.g.
CONNECTED TO
#4711 TYPE: 005
In this example, the successfully connected to an engine with serial number 4711 of type 005
6. Result of RPM check:
RPM CHECK
OK
or RPM CHECK
FAILED
This checks the full throttle RPM currently set against the maximum value and limits the full throttle rpm
if an inconsistency is detected.
4.2 Status screens
The HORNET-III will by default display its first of six status screens. The default behaviour is that up (↑↑) and
(↓↓) switch between the screens, enter (✓) opens the main menu (see Section 4.5) and escape (✘) returns to the
first status screen.
1. Standard status screen.
TEMP. THR./rRPM
STATUS PvVOLT
e.g. 20◦C 0.0/-OFF
OFF Pv0.00
where TEMP. is the measured exhaust temperature, THR. is the throttle position, rRPM is the relative RPM
(in %), STATUS is the engine status (see Section 4.3) and PvVOLT is the fuel pump voltage in V. If there
the throttle signal is outside the limits stored by learning the RC timing (see 4.5.2) the message -FAIL is
displayed instead of the relative RPM.
2. Last run termination status.
LAST RUN
RUN_STATUS
where RUN_STATUS is a run termination status (see Section 4.4).
10
SECTION 4. Using the Ground Support Unit (GSU)
3. Last run minimum and maximum values. On this screen, enter (✓) cycles between the different values:
Pump voltage
Temperature
RPM
Fail-safe information, e.g.
FS_COUNT: 0x
FS-TIME: 0s
In this example, the fail-safe program was never invoked, so the total time spent in the fail-safe program
is 0s.
4. Battery status. Shows the battery voltage and a visual indicator. The values used for determining the
battery status can be configured in the main menu (see Section 4.5).
5. Fuel status. Shows the fuel level with a visual indicator.
WARNING
There is no way to accurately measure the fuel level, so it is calculated from some predefined
values (e.g. fuel flow at idle speed, fuel flow at full speed) and some user supplied values (the fuel
tank size).
These values can be configured in the main menu (see Section 4.5).
4.3 Engine statuses
Table 1 contains all engine statuses the GSU can display. Most statuses are related to the various stages of
the autostart process (see Section 5.3) and are given in the order they are displayed during a successful startup
procedure.
Status Description
OFF Engine is is off, can be switched to standby by moving the throttle first to neutral
and then to full (see Section 5.2.2).
STANDBY Engine is ready to receive the start sequence: Move the throttle from full position to
off position. If the throttle is then set to full position within three seconds, the ECU
will initiate the autostart sequence (see Section 5.2.2).
PROP IGNIT Engine ignition using auxiliary gas. Not relevant for AeroDesignWorks engines.
BURNER ON Burner is on for the engine start using fuel.
FUELIGNIT Ignition sequence for engine start using fuel.
FUELHEAT After fuel ignition, the engine will heat up using constant RPM and pump voltage.
RAMP DELAY The starter will increase its RPM, but the fuel flow will be kept constant.
RAMP UP The engine will increase its RPM to idle speed by increasing the pump voltage and
thus the fuel flow.
AUTO Engine is operating in automatic mode.
SLOWDOWN Engine is turning off, waiting for RPM to go to 0.
COOLDOWN Engine is turned off, cooling down with constant RPM from the starter after reach-
ing 0 RPM briefly.
Table 1: Engine statuses displayed on the GSU.
As engines using an analogue (brushed) fuel pump need an additional auto calibration phase, they have
additional engine statuses (see Table 2).
11
SECTION 4. Using the Ground Support Unit (GSU)
Status Description
WAIT ACC Waiting for the acceleration to stop (nearing STEADY).
STEADY Waiting for the RPM to stabilise (at idle or calibration speed).
CAL IDLE The ECU tries to find the correct pump voltage for idle RPM.
CALIBRATE The engine accelerates to calibration RPM and waits for the RPM to stabilise.
GO IDLE The engine drops back to idle RPM.
PVOLT DELAY Pump voltage increase was too high during auto calibration, delaying further accel-
eration.
TEMP DELAY Exhaust temperature increase was too high during auto calibration, delaying further
acceleration.
Table 2: Additional engine statuses for engine setups with analogue (brushed) pumps displayed on the GSU.
4.4 Termination statuses
Table 4 contains all statuses with which a run can be terminated that are not related to the auto calibration (see
Section 5.4) needed only when using an analogue (brushed) fuel pump, which are found in Table 3 (also see
Section 5.4).
Status Description
CALIBRATION FAIL-
URE
The RPM during auto calibration was more than 5,000 RPM off target.
FLAMEOUT DURING
CALIBRATION
Exhaust temperature went below 250 ◦C which indicates a flameout.
FELL BELOW MIN.
CAL. RPM
The RPM dropped below the acceptable limit during calibration.
MAX. CAL. VOLT.
EXCEEDED
The maximum fuel pump voltage allowed was exceeded without reaching the re-
quired RPM.
CALCULATED MAX.
PUMPVOLT. EXCEED
The calculated voltage needed for maximum RPM exceeds the maximum voltage
(see Section 5.4).
CAL. PLAUSI FAIL
dV MIN-CAL <0.2V
The voltage difference between idle and calibration speed is less than 0.2V, which
indicates an error during calibration.
CAL. PLAUSI FAIL
dV CAL-MAX <0.6V
The voltage difference between calibration and maximum speed is less than 0.6V,
which indicates an error during calibration.
Table 3: Run termination statuses related to the auto calibration displayed on the GSU.
If an error is encountered during auto calibration, the engine will go to status SLOWDOWN and power down.
4.5 Main menu
The main menu is accessed from the status screen by pressing the enter (✓) button on the GSU. It has five
regular sub menus and the expert menu, which is locked by default because it exposes many parameters which
are outside the scope of normal user adjustments should only be changed by a qualified person (see Section
4.5.6).
4.5.1 Run time settings
This sub menu contains settings that affect the engine at run time, see Table 5.
4.5.2 User adjustments
This menu contains adjustments the user needs to make at least once, and some of them at the beginning of
each session (e.g. the ambient temperature), see Table 6.
12
SECTION 4. Using the Ground Support Unit (GSU)
Status Description
WITHOUT ERRORS No error was encountered during the last run.
FAILURE THROTTLE
PULSE
The RC’s throttle pulse failed, possibly bad signal reception or loss.
RPM SENSOR
FAILURE
Failure of the RPM sensor, either no signal or errors detected.
TEMP SENSOR
FAILURE
The temperature sensor reported implausible values and might be malfunctioning.
EXCEEDED MAXIMUM
RPM
The engine went over its hard maximum RPM limit, possibly due to a configuration
error or faulty RPM sensor.
FELL BELOW
MINIMUM RPM
The engine went below its hard minimum RPM limit, possibly due to a configura-
tion error or faulty RPM sensor.
MAXIMUM TEMP
EXCEEDED
The exhaust temperature exceeded 800 ◦C for an extended period of time.
FLAMEOUT DURING
RUN
The temperature fell below 200 ◦C, indicating a flameout.
FLAMEOUT DURING
FUEL HEAT
The temperature fell below 200 ◦C, indicating a flameout. Might be due to an
interrupted fuel supply (e.g. air bubbles).
FLAMEOUT DURING
RAMP UP
The temperature fell below 200 ◦C, indicating a flameout. Might be due to an
interrupted fuel supply (e.g. air bubbles).
RPM < 2,000 DUR-
ING FUEL HEAT
The engine could not reach the required RPM. May be due to a broken starter or a
jammed engine.
RPM < 5,000 DUR-
ING RAMP UP
The engine could not reach the required RPM. May be due to a broken starter or a
jammed engine.
BATTERY VOLTAGE
TOO LOW
The battery voltage fell below the limit set by the user in the main menu (see Section
4.5).
FUEL PUMP FAILURE The fuel pump exceeded the maximum voltage allowed by the ECU, most likely
because it could not meet the fuel flow required for the RPM requested by the user.
This indicates a blocked fuel line or pump.
FAIL SAFE TIMEOUT The ECU remained in fail-safe mode longer than the user allowed to classify as a
successful run (see Section 5.6).
Table 4: Run termination statuses displayed on the GSU.
Learning RC Timings
The three throttle positions (see Section 5.2) and the RC switch function (if any) must be set.
1. THRO. LO/TRIM LO: The off position. Move both throttle and trimming to minimum.
2. TRIM TO MAXIMUM: The neutral position. Keep throttle at minimum and move the trimming to max-
imum.
3. THROTTLE MAXIMUM: The full position. Move throttle to maximum and keep the trimming to maximum.
4. SET SWITCH LO: The switch’s off position.
5. SET SWITCH HI: The switch’s on position.
6. Sanity check for the throttle positions and the RC switch positions (if any) as they must be distinguishable.
If the check fails,the RC functions are disabled to avoid starting the engine with malfunctioning controls.
4.5.3 System and periphery
This sub menu settings for the system and periphery devices (see Table 7).
13
SECTION 4. Using the Ground Support Unit (GSU)
Menu item Description
1.1 RPM FULL THR. The full throttle RPM. Can be set lower than the default value, e.g. to limit
the resulting thrust and / or fuel consumption.
1.2 RPM IDLE Can be lowered slightly or increased from the default setting, e.g. in extreme
ambient conditions.
1.3 ACC/DEC DYNAMIC Can be set to FAST,MEDIUM (default) or SLOW to adjust the engine’s respons-
iveness to the throttle position.
1.4 THROTTLE CURVE The throttle position can govern the RPM, the thrust, or a convex combina-
tion of the Two, Here, the fraction of the nonlinear part corresponding to the
thrust can be set. 0% means the throttle position governs the RPM, 100% that
it approximately governs the thrust. A combination of the two (20% - 70%)
is recommended for better control at both low and high RPM (see Section
5.2.3).
1.5 PUMP VOLTAGE
START
Adjusts the fuel pump voltage during startup. If it is set too low, the autostart
program may fail due to a fuel shortage. If it is set too high, excess fuel might
extinguish the combustor or even produce an open flame in or after the thrust
nozzle!
1.6 FAILSAFE PROGRAM Adjust the FAILSAFE DELAY,FAILSAFE TIMEOUT and FAILSAFE
THROTTLE (see Section 5.6).
Table 5: Entries in the RUNTIME SETTINGS menu.
Menu item Description
2.1 LEARN RC TIMING The RC timings must be learned, see Section 4.5.2.
2.2 SET AMBIENT TEM-
PERATURE
The ambient temperature should be set at the beginning of each session as
functions and safety checks depend on it.
2.3 BATTERY VOLTAGES Set the voltage at which the battery is considered empty or full here. This is
important for the battery warning.
2.4 FUEL CONSUMPTION Set the fuel flow at fuel pump voltages 1Vand 2Vand the fuel tank size here.
2.5 RC SWITCH FUNC-
TIONS
The RC switch can be set to NO FUNCTION,ON/OFF SWITCH (to replace the
trimming, see Section 5.8.1) or SMOKER VALVE (see Section 5.8.2) here.
Table 6: Entries in the USER ADJUSTMENTS menu
Menu item Description
3.1 LANGUAGE Switch between English and German (Deutsch).
3.2 ENGINE STATISTICS Show engine statistics using up (↑↑) and down (↓↓) keys, such as the connected
engine type, firmware version, total run time, serial number, manufacturing
week and year and the total number of revolutions.
3.3 TELEMETRY MODULE Here the telemetry sampling rate can be set between 0/s(off) and 10/sand
a com channel between 1 and 9 can be chosen.
3.4 RESET TO DEFAULTS The ECU can be reset to factory defaults, overwriting all user adjustments.
Table 7: Entries in the SYSTEM AND PERIPHERY menu
4.5.4 GPS and airspeed value
In this sub menu, data from the GPS module (if any) can be displayed by using the up (↑↑) and down (↓↓) keys
on seven screens. Enter (✓) has no function in this sub menu, and escape (✘) returns to the main menu.
1. LA, LO: Latitude and longitude.
2. U, C: UTC time and GPS fix status (NOK for not OK,OK for a valid GPS position, 3D for a valid 3D GPS
position) in the first line, current movement direction in degrees and number of satellites in use (should
be about seven in most circumstances).
14
SECTION 4. Using the Ground Support Unit (GSU)
3. GPS V, GPS ALT: Current GPS ground speed in km
hand altitude in m.
4. DISTANCE R, X, Y: Travelled ground distance, travelled distance longitudinal, travelled distance latit-
udinal.
5. G MAX R, G MAX V: Maximum ground distance from the take off point in mand maximum ground speed
in m
s.
6. G MAX ALT, G MIN ALT: Maximum and minimum altitude in m.
7. IAS, MAX IAS: Indicated airspeed and maximum indicated airspeed in km
h.
Keep in mind that ground speed and air speed can differ significantly.
4.5.5 Test functions
This menu gives access to various test functions to manually operate connected devices (fuel pump, valves) or
to query sensors (RPM, temperature, RC), see Table 8).
Menu item Description
5.1 FUEL PUMP Pressing enter (✓) enters a sub menu where the fuel pump’s voltage can be
adjusted using the up (↑↑) and down (↓↓) keys. Pressing enter (✓) then starts
the fuel pump and escape (✘) aborts. This program can only be used when
the engine is off.
5.2 GLOW OUTPUT Pressing enter (✓) enters a sub menu where the glow plug’s voltage can be
adjusted using the up (↑↑) and down (↓↓) keys. Pressing enter (✓) then turns on
the glow plug and escape (✘) aborts. This program can only be used when
the engine is off.
5.3 IGNIT. FUEL Pressing enter (✓) switches the valve from OFF to ON and vice-versa.
5.4 FUEL VALVE Pressing enter (✓) switches the valve from OFF to ON and vice-versa.
5.5 SMOKE VALVE Pressing enter (✓) switches the valve from OFF to ON and vice-versa.
5.6 RC TMNG. THR Shows the RC signal for the throttle position.
5.7 RPM SENSOR Shows the RPM sensor’s signal.
5.8 TEMP SENSOR Shows the temperature sensor’s signal.
5.9 STARTER TEST Pressing enter (✓) once enables setting the starter’s voltage using the up (↑↑)
and down (↓↓) keys. Pressing enter (✓) again switches the starter to on. Press-
ing escape (✘) aborts and / or switches the starter to off.
Table 8: Entries in the TEST FUNCTIONS menu
WARNING
Fire hazard! Be careful not to flood the engine with fuel using the fuel pump test (5.1).
4.5.6 Expert menu
The expert menu is locked by default. Its unlocking can be triggered by pressing and holding the up (↑↑) and
down (↓↓) keys and the releasing them simultaneously. A four digit number is the unlock challenge. The expert
menu is unlocked if the user enter the correct input for the unlock challenge by using the up (↑↑) and down (↓↓)
keys. Enter (✓) confirms the unlock code, while escape (✘) returns to the main menu without completing the
unlocking process.
CODE : 8144
INPUT: 127
15
SECTION 4. Using the Ground Support Unit (GSU)
WARNING
The expert menu has access to parameters outside the scope of normal use of the ECU. These values
should only be adjusted by qualified personnel! Therefor, the expert menu is not explicitly documented
here. If you feel that you need to change settings that are not accessible through the normal menus,
4.6 Necessary settings before starting
At the start of each session (i.e. before the engine’s first start of the day), the GSU should be used to set the
ambient temperature (Section 4.5.2) as several safety catches and functions depend on a correct temperature.
As the RC timings are stored persistently, it is not strictly necessary to learn the RC timings again if nothing
has changed in the hardware. Nevertheless, many users do this before their first flight of the day.
16
SECTION 5. Engine operation details
5 Engine operation details
5.1 Radio Control (RC)
Only one channel is needed for the RC’s throttle signal. With the throttle channel, the engine can be started,
controlled and shut down. The additional channel available (labeled AUX on the housing, see Figure 1a) can be
used by connecting an auxiliary input patch cable (1-to-1) and can be configured either for digital trimming or
a smoker valve (see Section 5.8).
The throttle channel’s timings must be learned using the GSU (see Section 4.5.2), while the auxiliary
channel does not need this as it can only have the states ON and OFF.
5.2 Throttle positions
The ECU recognises three throttle positions.
5.2.1 Defined positions
1. Off: Both throttle and trimming are set to minimum. Engine is off.
2. Neutral: Throttle set to minimum and trimming is set to maximum. Corresponds to idle RPM.
3. Full: Both throttle and trimming are set to maximum. Corresponds to maximum RPM and thrust.
If the RC uses digital trimming, the additional auxiliary channel (see Section 5.8) can be configured in the
corresponding menu via GSU (see 4.5.2).
5.2.2 Starting, running and stopping
1. Off to Standby: When the engine is in off mode, move the throttle first to neutral and then to full
position. This will put the engine into standby mode.
2. Start: When the engine is in standby mode, move the throttle from full position to off position. If the
throttle is then set to full position within three seconds, the ECU will initiate the autostart sequence.
3. Running: After successfully completing the autostart sequence, the ECU puts the engine in automatic
mode. In this mode, a throttle position between neutral and full controls the engine’s RPM and thrust.
4. Stop: When the engine is running, it can be stopped by moving the throttle to the off position. The ECU
will shut down the fuel pump and run the cool-down sequence before switching the engine to off mode.
5.2.3 Throttle curve
The throttle position on the RC will command a certain engine RPM. The neutral setting will always correspond
to idle RPM, while the full setting will always correspond to the maximum RPM. Between these two settings, it
is a matter of personal preference and control whether the throttle position should command the engine’s RPM,
the thrust, or a convex combination of the two functions describing this.
There is an approximately cubic relation between thrust and RPM: F≈a·(RPM)3with a∈R>0. This
means that
• If the throttle position commands the RPM, the thrust near full RPM becomes hard to control, as e.g.
90% RPM correspond to 72.9% thrust (see Figure 4b, the line corresponding to c1=0). If an analogue
controller is used, this means that almost 30% of the thrust is governed by only 10% of the lever stroke!
• If the throttle position command the thrust, the RPM near idle become hard to control for the same
reasons, as 10% of the thrust already correspond to ≈46.4% of the full RPM (see Figure 4a, the line
corresponding to c1=1).
17
SECTION 5. Engine operation details
For these reasons, it is very useful to use a convex combination of these relationships as the throttle curve
to avoid the RPM or thrust to react too sensitively to the throttle position at either end of the range.
Assuming the throttle position is mapped to [0,1]such that off corresponds to 0 and full corresponds to 1,
we get the target relative RPM function as
r:[0,1]→[0,1],r(s) = (1−c1)s+c13
√s.(1)
As our throttle position will only be between idle and off, we need the linear mapping
τ:[0,1]−>[0,1],τ(t):=at +b,(2)
with b:=RPMidle
RPM f ull ,a:= (1+b)−1.
Now we can get the true RPM as a function of the relative throttle position t∈[0,1], where 0 corresponds
to neutral and 1 corresponds to full
R:[0,1]→[0,1],R(t) = RPMidle +r◦τ(t)(RPM f ull −RPMidle).(3)
This way, R(0) = RPMidle,R(1) = RPM f ull and Ris a convex combination of a linear function and a root
function in between.
(a) Relative rpm over relative throttle for differ-
ent values of c1.
(b) Relative thrust over relative throttle for dif-
ferent values of c1.
These convex combinations (the grey and black lines corresponding to c1=0.3 and c1=0.7 in Figures 4a,
4b) result in throttle curves that are easier to control at both low and high RPM.
5.3 Autostart
The autostart sequence can be triggered when the engine is in standby mode. The sequence is as follows (with
statuses as given on the GSU, also see Table 1).
1. BURNER ON: The glow plug is switched on for 8s. The starter slowly increases the engine’s RPM.
2. FUEL IGNIT: Modulation of the starter fuel valve and starting of the fuel pump. Upon successful fuel
ignition (exhaust temperature exceeds 150 ◦C), transition to FUEL HEAT.
3. FUEL HEAT: Transition from ignition to main line fuel supply. The burner is still supplied with fuel while
the main fuel line valve is opened. The starter’s voltage (and thus the RPM) is increased slowly.
4. RAMP UP: The engine’s RPM is increased by increasing the main fuel line’s flow rate. The starter and
burner are switched off at the configured RPM, respectively.
After the completion of the autostart sequence, the engine is running at idle RPM. If a HORNET-III with
analogue (brushed) pump is used, the ECU will then execute the auto calibration (Section 5.4). If a HORNET-
III-ClubSport is used, the engine will be in automatic mode (see Section 5.5) and ready to go!
18
SECTION 5. Engine operation details
5.4 Auto calibration
A HORNET-III with analogue (brushed) pump needs to perform this step for a sufficiently precise guess of the
pump’s voltage for full RPM for a correct throttle response until the correct voltage is known.
The reason for this is that the brushed pump’s characteristic curves are not entirely consistent and may differ
between between devices of the same model, or even due to different ambient conditions. Brushless pumps do
not have these inconsistencies up to negligible differences and do not require auto calibration.
The auto calibration sequence consists of the following steps.
1. Starting at idle RPM, the engine accelerates to the calibration RPM.
2. After reaching the calibration RPM, the ECU waits for the RPM, fuel flow and pump voltage to stabilise.
3. The engine then drops back to idle RPM.
4. Now that the pump voltage is known for idle and calibration RPM, an educated guess for the correct
pump voltage for full RPM can be made.
After completing the auto calibration, the engine will be in automatic mode (see Section 5.5).
5.5 Automatic mode
This is the standard mode of engine operation and will display as AUTO on the GSU. If a HORNET-III with
analogue (brushed) fuel pump is used, the engine will run in mode AUTO* (automatic, pump voltage for full
RPM not yet known) until reaching full RPM once.
• The RPM between idle and full RPM is controlled by the user’s input.
• This is achieved by an RPM and temperature dependent fuel flow.
• Telemetry data is transmitted if a telemetry module is connected and configured.
• Temperature and RPM are monitored by the ECU, as are the battery voltage, the RC signal and the fuel
pump voltage.
• In case the RC signal is lost or outside acceptable ranges, the ECU will switch to failsafe mode (Section
5.6).
5.6 Fail-safe mode
If the RC signal is lost, the ECU will switch to fail-safe mode, which can be configured in the corresponding
menu via GSU (see Section 4.5.1). By default, the fail-safe mode is off, meaning the engine will shut down if
the RC signal is lost.
•FAILSAFE DELAY: The time (in s) the ECU will operate normally if the RC signal is lost before switching
to fail-safe mode. Setting this to 0 will deactivate the fail-safe mode.
•FAILSAFE TIMEOUT: The time (in s) the ECU is allowed to operate in fail-safe mode. After this time, the
engine will shut down by stopping the fuel pump. The default is 0, meaning instant shutdown.
•FAILSAFE THROTTLE: The throttle position the ECU assumes in fail-safe mode. Default is 0, so the
engine will go to idle speed.
If the fail-safe program was activated and for how long it ran during the last engine run can be found on a
status screen via GSU (see Section 4.2).
5.7 Cool-down mode
After the engine came to a standstill after turning off, the starter will cool the engine until the measured tem-
perature is below the corresponding threshold.
19
Table of contents
