IMHO the market has spoken towards minimum cost while delivering the required mission capability 
Homebuilts mostly can’t fly overt IFR so why buy certified gear?
If there were uncertified GPSs which contain the GPS approaches in the database so one could fly them all including LPV and homebuilts could fly IFR openly then everyone would buy them.
It’s probably not in Garmin’s interest to sell such products.
LeSving wrote:
What is the point of exceeding the TSO? What does that even mean?
Before i bought my MGL iEFIS several years ago, i was able to meet the South African designer and talked to him about avionics, that was a bit of an eye opener for me. The point about exceeding TSO was that the FAA TSO regs written for design and production of avionics in some cases were specific down to specific chips and components that needed to be installed, along with higher cost, lower accuracy, and higher power consumption that one would be forced to use. The example he showed me was a “FAA certified GPS” unit that is compatible to and plugs into the MGL system. This standalone GPS unit was in an anodised aluminium box, was several times larger in size than the MGL equivalent, was less accurate and took longer to acquire satellites. I forget the actual numbers, but lets say for example the TSO specified an accuracy of say 15m, the TSO GPS unit could _not_be more accurate than that or it didn’t meet TSO, (This was still before WAAS procedures became widely adopted), but that the MGL units would be accurate down to 3m for instance.
So they had written the software for their EFIS system with user selectable options on which GPS to use as the primary, which GPS for the secondary, and whether to use one or the other as a default in case of a discrepancy between both, it was set up something like that, best of both worlds. But also, you did not have to buy a certified TSO GPS unit for the system to operate, it would run fine on the MGL unit only, because dead reckoning is still legal for IFR enroute navigation, so let you conscience be your guide i guess.
“I think the biggest issues we face with GA avionics is…”
Peter are you saying that Garmin GTN/G1000 type products (for example) have “crap” design, quality and reliability? I would say quite the contrary and would argue that it is actually quite surprising that we have these high quality products available given that the size of the market is so small and companies such as Garmin have much bigger markets to focus on (see Sennheiser thread).
There will always be room to build a technically superior product but building a company or operation that is sustainable and can support the product long term is hard part. Which is why if I was building an IFR experimental I would just buy a GTN and be done with it. Anything else would only provide marginal benefits that are unlikely to offset all sorts of other hassle.
There is a lot of good stuff out there. For example the 1990s King boxes (which I have) were mostly really good.
Today, the G500/G1000 seems to be good. The jury is very much out on the Avidyne IFD boxes whose “delivered QA level” is very poor (most have to go back).
I don’t think the market is as small as many believe. Garmin has sold some fantastic number of 430 and 530 boxes (6 figures?). If you can kill the competition (or buy it and run down most of their product line, as Garmin did with Apollo) and run the cash cows for 10-15 years, you can do really well. The gross margins are massive – a GNS430 costs about $200 in parts and direct labour.
I think Sennheiser packed up because Bose has been eating everybody’s lunch at the top end, probably with some patents.
tomjnx wrote:
I don’t know the N reg experimental IFR market. But the EASA reg VFR experimentals I’ve seen pretty much all used non-TSO instruments. So yes, the market has spoken. Against TSO.
If you had read this, this discussion would have been simpler There is no requirement for any equipment in a homebuilt to be certified, and this includes any and all IFR avionics. The problem is the airspace requirements. The airspace codes requires IFR equipment to meet the TSO, and this is regardless if the aircraft or equipment is certified or not. This means you have to show that the IFR equipment meets the performance requirements of the TSO, and the easiest and cheapest and most effective way to do that is to install equipment built under a TSO authorization = certified equipment.
Peter wrote:
Homebuilts mostly can’t fly overt IFR so why buy certified gear?
They certainly can, but not in the UK apparently. But nobody cares about the UK anyway because there is not even an experimental category there. Experimentals does not exist in the UK.
Gafunflier wrote:
But also, you did not have to buy a certified TSO GPS unit for the system to operate, it would run fine on the MGL unit only, because dead reckoning is still legal for IFR enroute navigation, so let you conscience be your guide i guess.
I’m installing MGL EFIS and MGL radio and digital circuit breakers on my Onex. However, the transponder has to meet the TSO (or some EASA this or that), so it has to be certified. I have no practical experience with IFR, but in Norwegian airspace the requirements for IFR is RNAV 5 above FL100. Below, there is no requirements at all except for approaches. Redundancy is a requirement, I think?, at least you have to be able to somehow know your position if your main instrument fails, but that could be handled also by radar (again, I think?). So in principle I would be able to fly IFR, at least en-route, with my MGL EFIS. The only question left is why?
Gafunflier wrote:
I forget the actual numbers, but lets say for example the TSO specified an accuracy of say 15m, the TSO GPS unit could _not_be more accurate than that or it didn’t meet TSO
Given the meaning of the term “accuracy”, I find that impossible.
Peter,
and other ones with too expensive a/c’s to maintain!
From Coss Aviation, Cape Town you can order custom made RV’s and probably for delivery next year. They have production line for these and 10 years experience. Think about to fly it home!
www.cossaviation.co.za
Well, the USA used to dilute civilian GPS receiver accuracy on purpose some years ago when GPS was introduced, it was called “selective availability”. Their reasoning was so that GPS could not be used by enemies with as much precision as it could by their own military. It was only once selective availability was dropped in May 2000 that authorities could start working with GPS for approaches (together with WAAS) and implement narrower corridors for GPS based enroute navigation.
Gafunflier wrote:
Well, the USA used to dilute civilian GPS receiver accuracy on purpose some years ago when GPS was introduced, it was called “selective availability”. Their reasoning was so that GPS could not be used by enemies with as much precision as it could by their own military. It was only once selective availability was dropped in May 2000 that authorities could start working with GPS for approaches (together with WAAS) and implement narrower corridors for GPS based enroute navigation.
I know all about that, but that’s something different entirely! We’re talking about the receiver being required to have an accuracy of 15m (or some other number) but not less. I can’t see how that can possibly be engineered unless the receiver is designed to randomly give slightly incorrect positions on purpose.
Airborne_Again wrote:
I know all about that, but that’s something different entirely! We’re talking about the receiver being required to have an accuracy of 15m (or some other number) but not less. I can’t see how that can possibly be engineered unless the receiver is designed to randomly give slightly incorrect positions on purpose.
Maybe getting more accuracy is down to the filter rate / number of calculations per second and other variables the newer generation chips can do better than older generation ones in order to pinpoint a position with more accuracy than older chips. Who knows. But the point being the newer chips still have to be designed to the exact spec of the older chips to meet the TSO, which means you repeat the same result, less accuracy compared to newer chips.
Does one need that extra accuracy, perhaps when using a taxi chart overlay at an airport with multiple connecting intersections in low visibility
I think we’ve beaten this subject to death now, onwards and upwards
