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Dynon Skyview HDX got an FAA STC

achimha wrote:

This whole story about what an involved process it is to adjust autopilot parameters to an airframe is BS. I’ve flown with a Piper S-TEC transplanted into a Cessna without adjustments and it performed equally bad as in the Piper but not worse.

LOL

The elephant is the circulation
ENVA ENOP ENMO, Norway

This whole story about what an involved process it is to adjust autopilot parameters to an airframe is BS

I don’t agree; take a flight in an SR20 with an STEC, a “suitably loaded” Seneca with one, etc…

Control systems theory is however a well developed science, since around WW2. The procedures for characterising the system behaviour are well known. With planes one needs to have decent margins because they don’t behave in simple ways, and the behaviour is very different for small-signal v. large-signal disturbances.

Administrator
Shoreham EGKA, United Kingdom

I have witnessed somebody adjusting an S-TEC for a completely different airplane in flight by slightly changing a few pots. It was a trivial process and even before it was “working”. And yes, this was for very different planes like in your SR20 vs Seneca.

I’d be more willing to accept the justification of the process if the market wasn’t dominated by substandard APs that perform very poorly. All the certification rules do is protect the business of companies that got lots of STCs under highly dubious circumstances and prevent others from brining in modern products to more than a handful of airframes.

All these autopilot parameters depends on the airframe and the location of servos on the controls (cables/pushrods).

So from my perspective (I was one of the first Europa owner to install a Dynon autopilot system), the time consuming item is to choose the servo brackets location, develop the brackets (will typically be reused between airframes with similar control mechanisms/servo location) and install these.

Fly the plane to tune up settings is a matter of 2 flights: one in calm air and one in turbulent air. As an installer, If you really understand how the different parameters are working together, it becomes pretty simple to tune these up for a specific airframe. And Dynon has access to their own autopilot expert and has extensive experience supporting customers with plenty of different airframes (see all the different experimentals around the world).

So when a company has such wide expertise on plenty of different airframes, has already the basics for many airframes (standard brackets for RVs) and many willing customers, it can only go fast to have a long list of airframes added to the STC.

Belgium

Not if you want some decent margins, together with a not too sub optimal transient performance. You can make anything “work” if you are happy to compromise.

Fly behind a kfc225 if you want to see a properly optimised control loop…

Administrator
Shoreham EGKA, United Kingdom

Here is the procedure for the MGL autopilot (and servos). Starting at page 12.

The elephant is the circulation
ENVA ENOP ENMO, Norway

Peter wrote:

Fly behind a kfc225 if you want to see a properly optimised control loop…

How do you know that Dynon installs such as ploucanco’s perform worse than your KFC225?

Is there such a thing as small vs large signal disturbance on a digital autopilot / platform?

I would be very worried if a certified airframe doesn’t behave in simple ways.

Is there such a thing as small vs large signal disturbance on a digital autopilot / platform?

Yes of course.

I would be very worried if a certified airframe doesn’t behave in simple ways.

I can’t help you there… aerodynamics is not simple.

How do you know that Dynon installs such as ploucanco’s perform worse than your KFC225?

I don’t; I am saying that sorting out the control loop parameters for all corners of the envelope (speed and loading, etc) is not as easy as is made up – unless you are happy with STEC-type performance e.g. snaking in even slight turbulence (the case even on a Cirrus with a 55X), etc. I also fully accept that most pilots will not notice a crappy performing autopilot Especially given the market it addressed (or had been addressed to date i.e. homebuilts intended for VFR only). I am not saying the Dynon is crap (since I have not flown behind one) but if the control loop calibration is as simple as is claimed it will be very sub-optimal. Especially as some of the types in the historical marketplace have marginal stability anyway, and control forces bordering on non-monotonic.

From post #16, MGL autopilot manual, this text

makes it clear what a bodge this is. The last para especially is a laugh…

I also noticed this

Are there no slipping clutches?

It does however appear to have IAS input, which is good.

Administrator
Shoreham EGKA, United Kingdom

From my perspective, this is a major news that will have major impact on how high end avionics will be deployed in the future in GA:
From http://www.dynonavionics.com/certified/

Dynon (Skyview HDX) received STC approval for many models of the Cessna 172 in March 2018. The initial Approved Model List (AML) is for Cessna 172F, 172G, 172H, 172I, 172K, 172L, 172M, 172N, 172P, 172Q, 172R, and 172S models. Approval does not restrict the operational use of the aircraft, and allows for flight in both IFR and VFR. Dynon will be seeking additional approvals for both single and twin-engine aircraft in the coming months.

Pricing for the certified/PMA versions of approved Dynon products will be the same as existing experimental/light sport customers. The STC for Cessna 172 aircraft is priced at $2,000.

The first installations will be available in Q2 2018 through US Sport Aircraft + Thrust Flight in Texas, Merrill Field Instruments in Alaska, and a Dynon-affiliated facility in the Pacific Northwest.

So now you have the opportunity to land your old Cessna lands in the 21 century!

Belgium
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