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Cheapest & Smallest Certified GPS for VNAV

wigglyamp wrote:

It’ll be interesting to see how EASA approach approval of the Dynon and Garmin attitude indicators that have recently received FAA STC approval without having specific equipment qualifications.

Maybe these are made according to applicable standards, but are not produced under a TSO Authorization? Similar to an experimental Lycoming. I guess stand alone attitude indicators are easier to certify than an EFIS also?

The elephant is the circulation
ENVA ENOP ENMO, Norway

For VFR non-certified aircraft, there are no specific equipment qualification requirements. However, in certified aircraft, electronic equipment including EFIS need to meet strict certification requirements. Software has to be compliant to DO-178B at level C or above depending on the aircraft weight category as stated in FAA AC23-1309-1C Complex electronic hardware must be complaint to DO-254. (EASA have adopted the same requirements).
The failure case for a particular type of equipment in a given airframe must be assessed using a failure modes and effects analysis and a fault tree is normally developed. In the case of an EFIS approved for primary attitude in IMC, failure cases such as total loss of attitude (EFIS and standby), or un-annunciated misleading EFIS attitude with good standby, must be shown to have a probability of failure better than 1E-7 (or even higher in heavier aircraft).
The equipment must meet environmental qualification per DO160 including vibration, temperature, emissions and RF susceptibility. Additional requirements also exist for compliance with HIRF and lightning – now addressed by EASA under AMC20-136 and 20-158.

It’ll be interesting to see how EASA approach approval of the Dynon and Garmin attitude indicators that have recently received FAA STC approval without having specific equipment qualifications.

Last Edited by wigglyamp at 14 Aug 18:41
Avionics geek.
Somewhere remote in Devon, UK.

Ok, so all we get so far is that we think it’s better than vacuum but worse than “certified IFR” however there is no measurable data or assessment protocol.

Shorrick_Mk2 wrote:

Is the software in a VFR box of a demonstrably lesser quality as in a IFR box?

Who knows? Considering it is enough with an old school vacuum driven horizon or two, I would think a new AHRS is much better in every single respect. But again, who knows? and that is probably the main issue. An instrument build and certified according to a TSO have fewer unknowns. Also, experimental stuff are updated regularly when bugs are found, improvements are made, but that could also create new bugs of course. What I mean, is the LAA should encourage people to get as much certified equipment as possible, include clever dissimilar redundancy etc, and otherwise do nothing, because IMO what they are doing now serves no one any good. How can LAA tell this stuff apart?

The elephant is the circulation
ENVA ENOP ENMO, Norway

Shorrick_Mk2 wrote:

Is the software in a VFR box of a demonstrably lesser quality as in a IFR box? If yes – please demonstrate or document the technical differences.

I admit I don’t know anything specifically about avionics programming, but I do know two things about software engineering in general which may be relevant:

- It costs a lot to certify software. It may be as good in the uncertified (VFR) box as in the certified (IFR) one, but you wouldn’t know.
- You can’t get good quality software by testing and debugging. It has to be designed in from the start.

ESKC (Uppsala/Sundbro), Sweden

Shorrick_Mk2 wrote:

Is the software in a VFR box of a demonstrably lesser quality as in a IFR box?

It’s not really the quality of the software as such, it’s the design assurance and the functionality. For IFR, the business logic tree has a lot more branches than for VFR.

LKBU (near Prague), Czech Republic

Perhaps my question was not clear. Is there a clear documented difference between a VFR EFIS and a IFR one? I know what the manual says – obviously if it is not certified it is not going to say IFR despite what is in the box.

Is the software in a VFR box of a demonstrably lesser quality as in a IFR box? If yes – please demonstrate or document the technical differences.

Shorrick_Mk2 wrote:

How does the design of an IFR EFIS vary from the design of a VFR EFIS?

Good question. But take a look at the manufacturers of experimental EFIS’es. They are all made for VFR, and the manuals clearly say so (with perhaps the exception of the G900X). Dynon means that for IFR, all equipment must be certified for instance (EAA does not mean that, but clearly states legal does not equal safe in this respect). My question is, why would you risk your life on alpha/beta quality software functioning 100% at all times, when there are other options that doesn’t even cost that much more (G500, Aspen systems etc). Even I, with my VFR only single seat Onex, have redundancy on the EFIS in case it should black out, or do something else strange, so I can shut it off and look at some other instruments. If I were to build myself an IFR travelling machine, for IMC, I would not put my life on the hands of alpha quality software. I would use true and trusted systems, certified systems like the G500 or Aspen or whatever else is available (high quality AHRS, autopilot and display technology). It is a bit strange the LAA advocate using these experimental systems for IFR IMC.

The elephant is the circulation
ENVA ENOP ENMO, Norway

How does the design of an IFR EFIS vary from the design of a VFR EFIS?

Peter wrote:

Whether the LAA approves I don’t know, and their IFR programme is something else to consider when buying avionics.

Considering there are new systems coming continuously, at least once every year from most manufacturers, and software updates much more often, I have a hard time understanding the rationale behind this “program”. By the time they finish “approving” a system, it will be obsolete or have major software updates in any case. The regulations here (EASA, FAA, but most importantly ICAO and airspace) are very simple; GPS units for IFR navigation have to be certified, transponder is mandatory and must be certified, radio is mandatory and must be certified. This leaves only display technology and gyro, which is 10% hardware and 90% untested and essentially alpha/beta quality software.

The EAA has a nice write up on this, and it’s is no different in Europe (except UK…) You can fly in IMC with a cheap EFIS, but why would you do that? Just about every single homebuilder who installs an EFIS for VFR, also installs some basic backup for alt and in ASI, just in case the big screen should malfunction. We do this even though a total black out is more of an unpleasant inconvenience than a life and death situation. For IFR in IMC, your life depend on that screen not malfunctioning, or the autopilot or the gyro. It makes no sense to me to cheap out on those things. From what I have seen on RVs, they either have old school certified IFR equipment, or they have certified GPS’es and G500s or some mix.

In essence the LAA is saying it is OK to use VFR equipment (experimental EFIS etc exclusively meant and designed for VFR) for “hard” IFR? Based on what experience? This seems to me to be a very odd thing to do.

The elephant is the circulation
ENVA ENOP ENMO, Norway
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