Aerospire MultiGov

Reviewer: Rob Turnbull
Review Date: 14th November 2007
Supplier Aerospire.com
Manufacturer: Aerospire LLC
Unit Cost: $110

Introduction

My thanks go to Bob Li of Aerospire for supplying the MultiGov for review.

This review will be performed using the Trex 600n Pro and a Spektrum DX7 transmitter.

The MultiGov is a combined governor and limiter in one unit. You can set the MultiGov up to be either a governor or a limiter in any of it's 3 speed settings, independent of each other. For example, Speed 1 might be set as a governor, while Speed 2 and 3 might be set as limiters.

In limiter mode, it is more aggressive during an underspeed condition whereas the full governor mode is meant more for smooth flight. That said, both will work well for most styles of flying.

It also offers a vareity of programming features that allow the unit to be tweaked to perform just how you want, as we will see.

The package includes the governor itself in an anti-static bag, the programming interface and a bag containing an hall effects sensor, a few carbon mounting brackets, pull tie (zip tie) and heatshrink tubing to build the mounted sensor with. Two magnets were also included, which will be fitted to the fan.

Here's a few shots of the package and its contents.

  • What comes in the bagWhat comes in the bag
  • The programming unitThe programming unit
  • Multigov in an anti-static bagMultigov in an anti-static bag
  • Hall effect sensor, mounts, magnets and fixingsHall effect sensor, mounts, magnets and fixings

The programming unit

The programming unit incorporates a nice bright screen which displays all the settings as you go through them in large letters. There are also four push buttons grouped in pairs at the bottom of the units left and right corners. The left pair of buttons give you access to the basic menu when you hold one button down for 3 seconds, or access to the advanced menu if you hold them both down for 3 seconds. The right pair of buttons are used to change the value displayed on the screen when programming.

The cable will only plug into the unit one way around, due to the shape of the plug and socket. This is the same on the governor unit too.

Fitting the unit to the helicopter

The first job that needs to be done is to build and mount the hall effect sensor to the heli. Bob has written a very clear article on his website showing exactly how to do this on the Align Trex600 Nitro, as has been used for this review. The only thing I did differently to Bob's described method was to fit the sensor bracket mounting bolts through the frame with the nuts on the outside.

With the sensor mounted to the helicopter, the MultiGov unit also needs to be mounted to the helicopter. The sticky foam pad that MultiGov comes fitted to is incredibly sticky - there's no possible way (that I can see) that this thing will shake or vibrate loose in flight! As I'm a big fan of using velcro (or hook and loop) pads and straps to attach things to my heli, I stuck a velcro pad to the underside of the Multigov anti-vibration pad and mounted it to the helicopter on the front of the nose piece.

  • Sensor fitted to the Trex 600nSensor fitted to the Trex 600n
  • MultiGov unit mounted to helicopterMultiGov unit mounted to helicopter

Wiring it up

The wiring is clearly marked on the unit, and also in the instructions, so wiring up the MultiGov unit should not be a problem. Ensure that the signal wire of all the four wires are fitted nearest the centre of the unit. There is a blue flashing LED in the middle (when the unit is powered up), called the heart - if all the signal wires are closest to that, it's installed correctly.

The top left set of pins takes the sensor input.

The bottom left set of pins is where the throttle servo should be connected.

The top right set of pins takes the throttle channel input from the receiver.

The bottom right set of pins takes the auxilliary channel input from the receiver. This enables you to flick a transmitted switch to change to a different "Speed" setup.

  • The four groups of pins, and the heart in the middleThe four groups of pins, and the heart in the middle

Basic configuration

I use the Spektrum DX7 transmitter, so I decided that I would do a standard setup and just use two speed settings (of the 3 available to me using this governor/limiter). These would be assigned to the Aux2 switch. Once again, Bob Li has an article on his website which covers how you can program the DX7 (and other popular Futaba and JR transmitters) to use the IdleUp switch to change between the speed settings. I'm quite happy using two speed settings, so I will cover how I've set it up on the Aux2 switch of my DX7 here.

The first thing you need to do is plug in the programming interface and then turn the helicopter on. While the programming screen is displaying the welcome message, you should press and hold either the Prev or Next button on the unit (bottom left buttons) in order to enter the configuration menu.

When you have timed it right, there will be a 3 second countdown until the configuration menu is entered. if you release the button before the countdown is complete, you don't enter the menu - simple.

The first screen you see once you are in the configuration menu is the firmware revision number the unit is currently running. At the time of writing this article, version 2.0 is the current firmware revision.

  • The firmware revision screenThe firmware revision screen

Pressing the Next menu button, bottom left of the programming unit, will take you to the Speed1 setting. This is where you decide what headspeed you want to run, and whether to use Full Governor mode or Overspeed Limiter mode. These two modes are described in the manual which can be downloaded from the Aerospire website.

I fly 3D and following Bob's advice, I will be doing all of my 3D flying in Overspeed Limiter mode, as the Multigov has been designed to be more aggressive, and therefore better suited to 3D flight, in this mode.

At this stage, I have set up the Multigov unit to work on the Aux2 switch, which allows me to setup two Speeds on the governor.

I set Speed1 at 1950 RPM in Full Governor Mode.

Toggle between Full Governor and Overspeed Limiter modes by pressing the +Value and -Value buttons at the same time.

  • Setting Speed 1Setting Speed 1
  • The Aux2 switch is up for Speed1The Aux2 switch is up for Speed1

Because I'm using a 2 position switch, I don't get the option of setting Speed2, so the unit skips that in the display and jumps straight to Speed3.

I set Speed3 at 2150 RPM in Overspeed Limiter Mode.

  • Setting Speed 3Setting Speed 3
  • The Aux2 switch is down for Speed3The Aux2 switch is down for Speed3

The next screen is where you enter the gear ratio for the helicopter you're flying. In my case, the unit was being installed on the Trex 600n, which has an 8.5:1 gear ratio. Using the +Value and -Value buttons on the bottom right of the programming unit allows you to specify the correct value.

  • Setting the main gear ratioSetting the main gear ratio

After the gear ratio screen you have the Sensor screen which shows you if the sensor is picking up on the magnet or not. When the sensor is not over the magnet, the display will show Sensor 0 and when the sensor is over the magnet, the reading will be close to, or at, 100. I've had 99, and 100 displayed in my time with the unit.

  • Sensor test - away from the magnetSensor test - away from the magnet
  • Sensor test - over the magnetSensor test - over the magnet

Next, the Idle throttle position and High throttle positions are calibrated in the unit.

With the programming unit displaying Set Idle, move the throttle stick to the low position (Idle) and press the +Value button. The displayed value is stored in the unit as the Idle throttle servo position and the display now shows Set High. Move the throttle stick to the High throttle stick position and press the +Value button. The displayed value is stored in the unit as the High throttle servo position.

  • Setting the Idle throttle servo valueSetting the Idle throttle servo value
  • Setting the Idle throttle servo value (low stick)Setting the Idle throttle servo value (low stick)
  • Setting the High throttle servo valueSetting the High throttle servo value
  • Setting the High throttle servo value (high stick)Setting the High throttle servo value (high stick)

The unit then displays Test Idle and the throttle servo moves to the Idle position you just calibrated. Pressing the +Value button will show Test High on the screen and the throttle servo will move to the High position previously calibrated.

Continuing to press the +Value button will cycle between Test Idle and Test High, while the servo will move to the current Test position.

  • Test IdleTest Idle
  • Throttle servo moves to the Idle positionThrottle servo moves to the Idle position
  • Test HighTest High
  • Throttle servo moves to the fully open positionThrottle servo moves to the fully open position

The next screen is the Governor test screen. Once the unit is calibrated, you can use the throttle stick to see where the governor unit will actually kick in, and ensure it stays in, by moving the stick from fully down to fully up. The screen should display Gov. Test -> Off until you reach approximately 1/4 stick, from then on, it should read Gov. Test -> On.

  • Governor test mode - offGovernor test mode - off
  • Governor test mode - off at lowstickGovernor test mode - off at lowstick
  • Governor test mode - onGovernor test mode - on
  • Governor test mode - on at approx 1/4 stickGovernor test mode - on at approx 1/4 stick
  • Governor test mode - onGovernor test mode - still on
  • Governor test mode - still on at full stickGovernor test mode - still on at full stick

The final setting in the basic configuration menu is the Low Throttle Percent setting, which sets the lowest governed throttle point based on the low and high points previously set in the basic config (Set Idle and Set High). Generally, you probably won't need to change this number, but if you have overspeeding issues, lowering this number can help. For underspeeding issues, raising this number can help.

  • Set the low throttle percent pointSet the low throttle percent point

That's it for the settings in the basic configuration menu, the last two screens will show the copyright notice, and then an instruction to power off to exit the configuration mode. No need to worry about saving data, it saves it as you go along.

  • Copyright noticeCopyright notice
  • Power off to exitPower off to exit

Advanced configuration

If the default settings are simply not quite doing the business for you, and it can happen, although my experience so far has been very good with the default settings, then you might want to venture into the advanced configuration menu options. The few settings that I have tweaked in here are the Base Gain setting which I tweaked up to 65, which I believe is actually set as the default value on the shipping units now, and the Overspeed aggressiveness value (OvSpdAgres) which was lowered to reduce and slightly better manage the overspeeding when unloading the head in manoeuvres such as fast descents. Both of these tweaks came on the recommendation from Bob, so perhaps these will simply be in as defaults now.

The most important options for fine tuning are BaseGain and OvSpdAgres. Increasing the BaseGain value will increase the aggressiveness in holding RPM and will reduce overspeeding if you are experiencing it.  The downside is that having it too high can cause motor hunting.  If you actually like a little overspeeding, for a little more 3D recovery power, you might adjust to somewhere in between the default value and the point at which it starts hunting. It only needs changing from its default value for real fine tuning.
 
The OvSpdAgres setting only applies to the limiter mode. It manages the speed at which the throttle servo is moved during an underspeed condition, but setting it too fast can cause overspeeding. It's a trade-off, and again, the default setting is very good.

I also reduced the value entered in the Startup Speed setting from the default of 10, to 8. A higher value results in a quicker startup, and I felt this slightly slower speed would be safer still. The startup speed is used to determine how fast the engine should come back up to full speed from an aborted throttle hold situation. i.e. If you are performing an auto-rotation and things are looking bad, you can flick out of heading hold and the governor will bring the power back up in a controlled manner - the speed of which is determined by this setting.

Here's a quick run-down of the advanced menu screens in the order they will appear as you scroll through them using the Next menu button. Please see the manual for an explanation of which setting affects what part of the governor response.

  • Adaptive modeAdaptive mode
  • Base gainBase gain
  • Gain aggressivenessGain aggressiveness
  • Adaptive mode aggressivnessAdaptive mode aggressivness
  • Overspeed Throttle Curve LimitOverspeed Throttle Curve Limit
  • Overspeed aggressivenessOverspeed aggressiveness
  • Hovering rotor speed thresholdHovering rotor speed threshold
  • Startup speedStartup speed
  • FeedforwardFeedforward
  • Copyright noticeCopyright notice

Flight testing

As per the manual, my throttle curve in IdleUp 2 is set to 100 - 80 - 100 in a V curve formation. The governor doesn't require a flat line throttle in order to work effectively in Overspeed mode, which is what I have used in pretty much all of my flights so far. Further testing to switch between Overspeed Limiter mode and Full Governor mode will follow in due course.

The spool up procedure is as normal through to half stick, which is zero degrees of pitch on my Trex600n setup for 3D. From then on, I flick into IdleUp 2, and the Full governor stage kicks in, although my routine is to flick into Idleup 2 and then straight away flick to Overspeed Limiter mode to get the headspeed up to 2150. The transition to 2150 headspeed from the 1950 of Full Governor mode takes around 4 to 5 seconds, it depends how long it is left at the Full Governor stage. I like the steady increase in speed.

The performance of this governor in flight feels very good. The headspeed appears to be pretty consistent through a flight, and it picks back up very quickly after being loaded up in heavy pitch/cyclic manoeuvres.

The most impressive thing for me is the overspeed limiting of this unit. No matter how great a governor may claim to be at overspeed limiting, it will always be battling against the fact that the engine actually has to overspeed in the first place before a governor can do anything about it. The Multigov overspeed limiting works extremely well as far as my flight testing has determined, managing to reduce the amount of overspeeding that I was used to seeing when using the RevMax - the RevMax was ok at overspeed limiting, the Multigov is better.

Data logged flight

Using the following set of manoeuvres, I have datalogged a flight to record the headspeed across the flight. I would expect to see dips in the headspeed as the rotor disc is loaded up, and overspeed as the rotor disc is unloaded through the manoeuvres. I would hope to see these moments of over and underspeed minimised by the governor doing it's best to compensate where necessary.

Each manoeuvre is followed by a 10 second delay so that the manoeuvres can be easily identified on the graph.

The manoeuvres were performed in the following order.

  1. Full pitch climb out for approximately 10 seconds
  2. Tail slide
  3. Stationary flips (x10)
  4. Stationary rolls (x10)
  5. Four point tic tocs (x2)
  6. Tail left tic tocs (x10)
  7. Tail right tic tocs (x10)
  8. Large loop
  9. Slappers (x3)
  10. Forwards hurricane (x2)
  11. Backwards hurricane (x2)
  12. Climb out to a standard auto-rotation

As you can see, the graph shows the headspeed dropping off when it gets loaded up in a manoeuvre, and recovering back to the 2150 mark and staying there when unloading. The only real overspeeding times were in the tail slide (number 2) which is intentional, and in the slappers (number 9) which requires negative pitch to throw the heli towards the floor for half of the manoeuvre. If you take a broad look at this graph, you can see the general line across it at around the 2150 mark, which is good to see.

This next graph highlights the overspeed limiting of the Multigov unit - this is a close-up of the above graph starting during the hover period before manoeuvre 2 - the tail slide. I purposely overspeed the head in the tail slide to see what the governor does to correct it. The graph below shows a total time span of 15.12 seconds between 3.68 minutes and 3.92 minutes of the whole flight.

The text below the graph contained within the image shows the Interval, or total amount of data displayed on this graph, which is 0.252. Multiplying that by 60 (seconds) gives us 15.12 seconds in total. You can see the spike in overspeed at approximately 3.8 (minutes) and the limiter getting it under control at about 3.86 (minutes).

That works out to be approximately 2.6 seconds from the overspeed beginning to it being back under control. Notice that the overspeed begins it's downward turn in less than half that time, approximately 1.2 seconds.

Pros and Cons

Pros
Combined governor and limiter in one unit, choose your preference or use both in the same setup
Comes with good defaults pre-set
Easy to configure
Overspeed limiting is very good
Headpeed maintenance is very good
Smooth spool-up to desired governed headspeed
Slow startup speed for aborted autos is a great addition to the governor
Uses a standard hall effects sensor, so an existing sensor installation, from a Throttle Jockey for example, may be used
Only one programming unit required to program multiple governors
Cons
Requires the programming unit to use anything other than the default settings
Some of the advanced configuration options are a little confusing
Firmware is not updateable without sending the unit back to Aerospire

Conclusion

From the first flight I could tell that this was a step on from the governor I was previously using, the Throttle Jockey RevMax. The overspeed limiting seemed to be far quicker to settle the revs down than I had been previously used to.

The headspeed feels constant in flight, and the tachometer showed that the number I specified on the programming unit was being produced on the heli. The fact that you can be very specific about the headspeed you want to use is another bonus for the 3D flyer. Managing to hit the powerband for the engine being used, and to stay in that band as much as possible, is what any 3D flyer is after.

The unit is very versatile, having both governor and overspeed limiter modes, making it a great choice for any pilot.

I'm not suprised to see the data showing me what I had a feeling it would, having flown this governor for quite some time now. It is a very good unit and really feels like it is doing it's job well when flying.