Congratulations @Peter many hours of safe flying in the future!
Aerofab at Thruxton did a major avionics upgrade on a TB20 so it may be worth comparing notes.
I’m very confident the biggest change (and “wow, this feels like a new airplane” effect) would come from a digital autopilot. Dual G5 + GFC500. Instead of dual large IFD screens I’d go for a less expensive GPS175 or GNC355A and flightstream-pair it with an iPad (big screen and practically “free” from a cost point).
Snoopy wrote:
I’m very confident the biggest change (and “wow, this feels like a new airplane” effect) would come from a digital autopilot. Dual G5 + GFC500. Instead of dual large IFD screens I’d go for a less expensive GPS175 or GNC355A and flightstream-pair it with an iPad (big screen and practically “free” from a cost point).
I think I can guess Peter’s reply but KFC225 already is a digital, attitude based autopilot and not the same as say KAP140 which looks almost identical but is rate based and not as good.
A limitation of the current setup is no GPS Steering function, it will only fly the track on the CDI – so on a windy day it may struggle a little to hold a perfect localiser on an RNP approach but otherwise it’s a really good and accurate autopilot. It even flies a surprisingly accurate glide slope using the VS function. ILS approaches are very accurate.
That said, I haven’t flown with a GFC500 so I can’t say how much better it might be in the TB20, though a friend has one in a TL Sting and it’s been described as “all over the place” but obviously this is down to the type of plane and not the AP itself.
IMO the weak point is the KI256 artificial horizon – it’s a temperamental POS in my opinion and I do not trust it.
Perhaps the main benefit would be the much smaller and more reliable Garmin servos. I guess the “Level” button is worth having too.
I would never install a GFC500; it is one of these and it is amazing that probably 99% of people who install it don’t know that. The GFC600 is OK in this respect but a) no TB STC and b) any "GFC needs a G5 so the 2 x SN3500 would need to be ripped out, and then you are looking at a mother of an avionics job.
Yes the KI256 is a weak link but there are solutions which can be implemented as an isolated standalone job.
Peter wrote:
I would never install a GFC500; it is one of these and it is amazing that probably 99% of people who install it don’t know that.
Not sure they care! :) If the GPS has failed you’d have to use heading and VSI to follow the FAT. And it is even funnier at EGKA where you have only RNP approaches. :)
Peter wrote:
b) any "GFC needs a G5 so the 2 x SN3500 would need to be ripped out, and then you are looking at a mother of an avionics job.
If you install an extra G5 somewhere in the corner, you don’t care, right? I don’t remember it saying that the G5 has to be in the primary field of vision. :)
But on a serious note, I think if the KFC225 fails some time after you’ve installed GTN, then the choice is between: buying another KFC225 or using the same amount of money to buy GFC500 + G5 and get the Continous Descend (VNAV feature that works on GFC) and FL CH as in climb/descend at constant IAS.
I bet you the G5 does have to be in primary field of view.
The KFC225 system is
)It is quite manageable really… and it flies very well. It does have ARINC429 roll steering input but it’s better to use analog because, with a good system config, you can fly ILS or LPV and it sees no difference; it sees both as ILS (AFAIK this is possible only via a SN3500 with the roll steering option). Various previous threads on this aspect.
Constant IAS is not specially better than the PIT mode.
It does have ARINC429 roll steering input
So it’s KLN that does not provide GPSS? is that hardware module missing? or software?
I did read about in MooneySpace that the new KLN90 does it but older KLN89 does not, so they get G5 to do it
Peter
Avionics installations are getting less onerous as the kit improves, my feeling is the kit in your aircraft is good enough to continue with just the GPS being upgraded to WAAS to get you full precision approach capability.
Just putting in 2x G5’s to drive a Garmin autopilot gives very little advantage over what you have presently installed.
To go to the next level you would need to ditch all the mechanical stuff and go G500txi and present all the aircraft gauges on the screen along with the Garmin autopilot………….. it would look good and be reliable but give you very little extra in terms of mission capability and cost a fortune.
What might be worth considering if you go for a GTN760/650 is a datalink for weather.
It does have ARINC429 roll steering input So it’s KLN that does not provide GPSS? is that hardware module missing? or software? I did read about in MooneySpace that the older KLN90 does it but KLN89 does not, so they get G5 to do it
I have a KLN90B with SN3500 I have turn anticipation no real GPSS with ARINC from KLN90B coupled to CENTURY 41 through sandel. Flies LNAV beautiful with GA mode in case of missed.
The SN3500 can do GPSS software enabled with a WAAS unit. WAAS I believe has a an extended path and terminator data set which can be translated in enhanced GPSS steering signals
The KLN94 outputs GPS data at 1Hz, and the roll steering converter makers (both DAC and Sandel) claim that this is too slow to deliver usable analog roll steering. They want 5Hz. I am 100% sure this is BS; they are just too lazy to do even the most basic curve fitting to the data. GA avionics is just short of any talent; the Apollo people left in 1972. I have already built, just for fun, a converter from KLN94 (or any GPS) to WAAS-grade ARINC429 position data, and could easily produce a heading-bug-emulating roll steering converter the same way.
Avionics installs are easier today because almost every job is Garmin and Garmin and you just follow the IM diagrams, and everything else is either not connected or has been ripped out
A&C – exactly my view. Just cancelled a long flight today and entirely due to aircraft performance (ceiling).
The KLN boxes will be dead one day so one will need to change then. Probably in a few years’ time.
