Autopilot FAQ

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Contents

Do I need an AP74 for the for the Dynon AP to work?

No. But the AP74's dedicated buttons and knob definitely makes the AP easier to use.

Is the HS34 functionality also included in the AP74?

Somewhat. Some of the front panel functionality - knobs and buttons, has been replaced (and improved upon) by the AP74. But the primary function of the HS34 - to allow you to connect your GPS and NAV radio to a Dynon EFIS for HSI and AP navigation sources, has not been replaced by the AP74.

Is the Dynon AP compatible with TruTrak's servos?

Electrically, no. Mechanically, yes. As TruTrak is the market leader, Dynon designed their servos to be mechanically similar for customers that would like to add a Dynon Autopilot to an aircraft that has previously had a TruTrak AP installed.

Dynon offers installation kits for a number of aircraft, as well as a generic kit - see the Dynon Online Store for details.

Because our servos are mechanically similar to TruTrak's, we may be able to provide an autopilot solution for your airplane if there is a TruTrak servo configuration that is known to work in your type of aircraft. However, PLEASE DO NOT CALL TruTrak for advice on servo configuration if you intend to install a Dynon AP. DO seek out fellow builders of your aircraft type for this type of configuration information. Feel free to post questions to our forum and post results and relevant information to the Servo Application Guide.

What airplanes can the Dynon Autopilot be used in?

SKYLEADER Aircraft (types 200 and 500) - See the link [1]

What happened to the AP76 Advanced AP Module?

Originally announced to be available in late 2008, the official status of the AP76 is now "Project On Hold".

Dynon VP and COO Nick Bogner provided an explanation in a discussion thread on Dynon's Online Forum.

What happened to the SV52 Servo?

The SV32 (30 inch-pounds torque) and SV42 (40 inch-pounds of torque) in their various configurations such as long-arm and capstan seem to meet the vast majority of aircraft configurations. To date, there hasn't been demonstrated demand for the SV52's 50 inch-pounds of torque.

How much power do the servos draw?

SV32

   Powered but disengaged: 0.1 amps
   Engaged and holding, 100% torque: 0.80 amps
   Engaged and moving, 100% torque: 1.33 amps

SV42

   Powered but disengaged: 0.1 amps
   Engaged and holding, 100% torque: 1.11 amps
   Engaged and moving, 100% torque: 2.03 amps

I'm building an RV and planning on using the new Dynon AP. Are both servos to be mounted in the fuselage or is the roll servo wing mounted?

Dynon's servo installation kits for the RV-7/8/9 are designed for mounting the roll servo in the right wing. If you wish to put it somewhere else, it will work, but Dynon's kits aren't designed for mounting the roll servo in other locations.

Dynon's RV-6 servo installation kit mounts the roll servo under the seat.

DSAB (Dynon Smart Avionics Bus) Wiring Questions

Can they be spliced in a star type config or must they be daisy chained? Is there any need for terminating resistors etc.?

Any wiring configuration is acceptable as long as all DSAB devices are electrically connected. So, star configuration would work, as would daisy chai configuration.

Perhaps the only consideration is which devices would get disconnected if a wire breaks in any particular place.

There is no need for terminating resistors.

How noise immune is the DSAB bus? Does it operate on a differential like two wire RS485 or is it just RS232 with your custom protocol on top?

DSAB is very robust and noise-resistant. DSAB is based on RS485 (now called EIA-485) based bus, with Dynon's DSAB protocol running on top of it.

Will long parallel runs of DSAB wires alongside power wires for the servo going to tolerate the noise generated by the servo?

That wiring configuration won't cause interference to DSAB.

Should the DSAB wires be shielded from the power wires?

It's not a requirement.

How is this additional (EFIS-to-servo) data flow on the DSAB bus going to affect the performance of interdisplay communications?

The DSAB protocol is very efficient - there's ample "bus time" for both, especially since DSAB was originally designed / specified to accommodate EFIS-to-servo communication.

I remember somewhere you mentioned that the servo will have an embedded processor, how will this thing handle lost data ect? Will the servo processor have smarts to report errors, torque, etc. to the EFIS for display and use for features like trim sensing etc?

Yes, the servo has an embedded processor. It's smart about lost data and has bidirectional communications so both it and the EFIS know if anything is up. For instance, it tells you if the servo is slipping from being overidden or not having enough torque foe the air loads.

Can we get some details on the user interface for the AP?

The AP adds very little to the screen. There is text in the lower left corner that tells you what mode it's in, such as: "AP: HDG ALT" or "AP: NAV OFF" Where the left one is the roll mode and the right one is the vertical mode. The lower right corner now has your heading and alt bug settings in text. This will be there for all customers in the next version, so it's not even technically an AP thing. The bugs are hollow when not being flown, and solid when being flown. That's it. Just like some companies can make a good AP with just a three digit numerical display, we don't need to show tons of stuff either. On or off, what mode. The only display of this info is on the PFD page. Without the AP74, you press menu buttons to turn it on and off or change modes. Bugs are changed like they are today. The AP will fly whatever is shown on the HSI when in NAV mode, but nothing is actually shown on the HSI page re: the AP. You give up nothing here. Approach sequencing and prearming will be features of the AP76, and have been announced with that product.

One question that has been created by a comment posted on another forum. What is Dynon's response to the fact that most people with APs and EFISes that use them in IMC have the ability to rely on the AP to help them in the event they lose the EFIS? Now with your system, the EFIS is the AP so if you lose it, your AP is also lost. Now I know that most people using a EFIS in IMC have dual EFIS's of which either could be configured to run the AP. How hard is it to do a DASB reconfig in the air and is it feasable to do this in the event of an AP controlling EFIS goes tipup while in IMC? Next question is that of the pitot data being lost. How much is this going to impact the EFIS's ability to control the AP?

We'd never suggest someone fly in IMC with only one EFIS, any brand. So you have two, right?

Think of it this way: One is your EFIS, one is your EFIS + AP. Lose the EFIS, you still have EFIS+AP. Lose the EFIS+AP, you still have EFIS. You basically have the same level of redundancy as you would have if you had alternatively configured with a single set of flight instruments backed up with an autopilot.

If you have a standalone AP and it dies, you have no AP. A Dynon equipped plane would be no different. Loss of one device in the plane can mean loss of AP, but that's true in any install.

We aren't able to answer the loss of pitot question yet, as the AP is still in development. We are aiming for a system that will still control the plane just fine with no pitot, but this is not a promise yet.

Remember though, loss of pitot can be a problem with any AP, since it may try and hold airspeed to prevent a stall. Of course, as airspeed bleeds off, it will keep pointing the nose down trying to get more airspeed. It's a tradeoff between stall prevention and pitot loss.

What about autotrim or trim sensing with the new AP

Trim control won't be a launch feature, but we've designed the system to be able to grow to possibly do this over time.

Trim sensing is something that we're taking a hard look at, but we don't have an announcement to make at this time on the availability of this feature.

The initial autopilot features - HDG, TRK, horizontal NAV, and ALT hold/change (either with or without an AP74) haven't required either to be able to fly the core airplanes we've been testing with (RVs).

What is the AP74 and why would I want one?

The AP-74 is totally optional. You hook the servos up to the EFIS via DSAB (2 wires). Once you hook up one or two servos, the EFIS starts displaying an "AP" menu, which lets you control the AP. This menu replaces the "BUGS" menu, and then BUGS are inside that menu.

You can literally hook one $750 servo to a D10A, D100, or D180 and get full roll or altitude control. Nothing else is needed, except maybe an install kit.

The AP74 gives you hard, external buttons for the AP functions. They also light up to provide mode status. These are the same functions that are inside the EFIS menu, but they're right there on the panel. The one thing that AP74 adds is the ability to pre-select what mode will be active when you engage the AP. So you can hit "NAV" before you hit "engage" and it will come on in NAV mode.

You also get a knob to set bugs, voice alerts, and auto-dimming with the AP74. The connector on the AP74 is a male D25. The pinout is the same as the HS34's main connector, but the only pins used are power, ground, DSAB, and audio.

Each servo has a wire on it for a disconnect button, so you still get a hard disconnect on your stick even without the AP74. This button can be used to disengage the AP, and can be used for control wheel steering, or you can hold it for a few seconds to engage the AP.

The AP74 will be available in both horizontal and vertical version when it starts shipping.

Which servo units are compatible with the Dynon AP?

You must use our servos. That's OK though, since they are cheaper, lighter, and smarter than all the other ones. They share the same mounting dimensions as TruTrak servos, which should make them easy to install.

Is altitude hold available?

If you install a pitch servo, you get altitude hold. You also get the ability to actually choose an altitude, not just fly the one you are already at.

What's the anticipated ship date for servos, AP unit, and/or software? How hard is the date?

The servos, AP74, and software will all be released at the same time. We're currently late summer. As always, no promises there.

I have a Garmin GNS 480 and intended to hook up a TruTrack Digiflight II VSGV. This would have allowed me to have the 480 fly me through a precision approach, execute the missed approach, take me to the missed approach point and hold - all while providing both lateral and vertical steering from the 480 to the autopilot. I have not installed the autopilot yet. Will your autopilot provide the same functionality, including the vertical steering on the approach?

Yes.

This will require the higher end control panel that won't be available until later this year. The AP76 Advanded Autopilot Module will cost $1500. You'll also need HS34 for ARINC-429 connectivity to the 480.

So ballpark, if you start with an EFIS-D10A, you'll be looking at:

EFIS-D10A + 2 servos + AP76 + HS34 = $5850. Installation kits will be slightly more, and of course you can outfit the EFIS with different options. We think a lot of people are going to choose this particular configuration though on the IFR side of things.

My TT supplies alt hold and Ascend/descent rate. Will your AP do the "up and downs" too?

We'll do one better- we'll fly to an actual altitude you ask for, not just vertical speed. So you can dial in 8,500' even if you are at 4,850' right now. We'll climb and descend to new altitudes at a rate you have set in the setup menu.

Buttons to actually set VS dynamically are a feature of the AP76 Advanced Autopilot Module.

In terms of wiring, how do you anticipate the the servos interface with EFIS? Connections to serial 1 or serial 2?

Neither. They're connected to the rest of the system via DSAB, which is a two wire per servo connection. You'll also need two wires for power/ground, and a 5th wire for disconnect.

Apart from the buttons to set the VS dynamically, what other features will the -76 have over the -74?

With the AP76 you also get:

The ability to fly fully coupled approaches. With the AP76 you can fly any glide slope or vertical guidance that shows up as on the HSI screen. The AP 74 only does altitude hold and change on the vertical axis. This feature alone puts it up against the highest end autopilots available from other folks. We'll have automatic approach sequencing so you can fly a heading and altitude until established on an ILS, for example.

You also get true pre-selects, meaning you can dial in a heading, track, altitude, etc before whacking the engage button. In contrast, the AP74 can pre-arm which mode will be active on engagement, but it always syncs your altitude and hdg/trk to what you're currently flying when you engage.

And, as you mentioned, you can dial in vertical speed on the fly with the AP76 as you'd find on other high end autopilots. The AP74 can fly to new altitudes, but always at a pre-set VS that you configure in a deeper setup menu.

You stated the last two buttons on the AP76 might change but what the heck is the function of the TRB and FD buttons as they exist on that picture?

"FD" is flight director. It lets you toggle it on and off easily.

"TRB" is turbulence. We'll need to complete more testing, but with a lot of autopilots, a gain that gives you really solid performance in smooth air really forces the airplane around a lot in turbulence as it tries to maintain a dead on heading or altitude. This button could adjust the gain of the autopilot for more comfortable performance in turbulence.

One of APs I looked at has a reciprocal heading capability. Sort of "if suddenly in the gloop hit a button - AP takes you on a rate 1 turn around and brings you out of the IMC". Seemed like a good idea to me though never been (or plan to consciously get ) in a spot where I'd need it. Would it be hard to add that form of feature and if not would you?

This is already in our product. There's a 180 turn button in the EFIS menu, and if you have the AP74 or AP76, holding the engage button for two seconds does a 180.

I already have a Dynon D100. What do I need to put the Autopilot working on my plane beside the two SV32 servos ? Does my actual 2007 D100 needs any update / retrofit ?

The servos plus a normal firmware update (that you do) that we'll release at the time of the autopilot release is all it takes. You an optionally add the AP74 for the dedicated controls, but it's not required.

On the wiring for the AP, the assumtion is that the AP disconnect goes to ground through a switch. Is this a correct assumption?

You want your disconnect switch to affect both servos' disconnect lines. This means you can wire both of them together in the back and send a single wire to the switch. The switch will connect the disconnect line to ground to disconnect the servo.