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G1000 upgraded to WAAS: LPV, KAP 140, and capturing vertical path

Hello,

Just as an intellectual game (just after PBN course), I looked into WAAS upgrade, for a non-WAAS G1000 C182.

As you may know, there is a SB released by Cessna, with a Modification Kit, to perform the upgrade. It costs several tens thousand of dollars – just mad. Maybe the parts will be less expensive some day, and upgrade will be more easily feasible.
The only good point is that upgrade is rather easy: just swap two GIA63 from the avionics bay for two GIA63W, and change the two COM/GPS antennas. Upgrade the software, and you’re done. Much easier than Peter’s next winter

My questions was about AP coupling.

Without WAAS, the KAP140 is able to couple in NAV mode with any NAV/GPS signal (lateral).
In APPR mode, it will follow an ILS, LOC and GLIDE (lateral and vertical).

After WAAS upgrade, you will be able to perform LPV approaches.
Here and there on internet, some people claim that the KAP140 will have horizontal and vertical coupling for LPV, as LPV generates the same kind of vertical signal as an ILS glide slope.

However, in a revision from the initial SB, Cessna states this:

The Honeywell KAP-140 autopilot, if installed and operational, will couple and track the lateral guidance provided by the SBAS navigational guidance. However, the vertical component of any GPS approach must be managed and flown by the pilot. The KAP-140 autopilot WILL NOT couple to GPS vertical guidance.

Would be interesting to read your opinion about this !

Last Edited by PetitCessnaVoyageur at 07 Oct 06:41

PetitCessnaVoyageur wrote:

The only good point is that upgrade is rather easy: just swap two GIA63 from the avionics bay for two GIA63W, and change the two COM/GPS antennas. Upgrade the software, and you’re done.

So how is the “tens of thousands of dollar” pricetag justified? Obviously the GIA63W units are not gonna be cheap but it appears to me that G1000 owners are completely over a barrel here as they have no choice if they want WAAS.

PetitCessnaVoyageur wrote:

The KAP-140 autopilot WILL NOT couple to GPS vertical guidance.

The question is why. The only way I can imagine this is via the G1000 software, that it inhibits the GS signal when in LPV mode to the AP. Or is there something within the KAP140 which prevents this? Will the G1000W provide vertical guidance to other AP’s like the S-Tec 55 or the KFC150/200/e.t.c?

LSZH, Switzerland

Cessna sells the whole WAAS modification kit for 35k$
This is a lot.

But when you look at the detail, there is not much into it.
As I said, the main stuff is 2×GIA63W and 2 WAAS COM/GPS antenna. You also have a supplemental antenna for XM, but… In Europe, it is useless, so you could eventually avoid this step.

So, the question resumes to: how one can get cheaper parts.

When I installed my TAS, it was the same thing.
Cessna sold an eye-watering expensive kit to install a KTA870.
I noted the needed parts, and started to look for second hand. In the end, I found a computer in UK (AppleHeli shop), and requested that the computer would be sent to Honeywell (USA) for inspection and to get a proper dual release FORM1/8130. I did the same for the directional antenna (certification in UK). Then the other parts from the MK list, I bought new.
In the end, we got all the needed parts for the MK, with all form 1 in due form, some parts being new, some refurbished.

The big advantage in my case is that all the cables for the KTA870 were already there, and we just had to follow the MK/SB instructions (around 10 hours of man power).
Installation was covered by the SB, so no minor or major mod to request.
And by sourcing the parts that way, the total cost was dramatically reduced.

Hence my position: a CAPS landed Cirrus would be the ideal donor for two GIA63W, the day I have the cash and motivation to do it

PS: I’ve already been offered a used GIA63W for $2500, so I guess it is not out of reach.
As I read somewhere Cirrus airframe are limited to 12000 hours, getting used parts is just question of time

Last Edited by PetitCessnaVoyageur at 07 Oct 11:52

Mooney_Driver wrote:

The question is why. The only way I can imagine this is via the G1000 software, that it inhibits the GS signal when in LPV mode to the AP. Or is there something within the KAP140 which prevents this? Will the G1000W provide vertical guidance to other AP’s like the S-Tec 55 or the KFC150/200/e.t.c?

I have no idea. I read some different stuff about that, so rather strange.

Mooney_Driver wrote:

So how is the “tens of thousands of dollar” pricetag justified?

See here. In short, a monopolist will try to set the price where the marginal revenue (NOT the price) reflects the marginal cost.

Mooney_Driver wrote:

it appears to me that G1000 owners are completely over a barrel here as they have no choice if they want WAAS

Yes. Please address your letter of protest to the competition commission, copying the aviation authorities.

Biggin Hill

Mooney_Driver wrote:

So how is the “tens of thousands of dollar” pricetag justified? Obviously the GIA63W units are not gonna be cheap but it appears to me that G1000 owners are completely over a barrel here as they have no choice if they want WAAS.

People selling things don’t have to justify the price. If it makes you feel better, Garmin are positively socialist compared with Rockwell Collins….

Last Edited by JasonC at 07 Oct 13:30
EGTK Oxford

Cobalt wrote:

Please address your letter of protest to the competition commission, copying the aviation authorities.

LOL, well, I can not really be a claimant as I thankfully do not have that problem.

LSZH, Switzerland

Mooney_Driver wrote:

The question is why. The only way I can imagine this is via the G1000 software, that it inhibits the GS signal when in LPV mode to the AP. Or is there something within the KAP140 which prevents this? Will the G1000W provide vertical guidance to other AP’s like the S-Tec 55 or the KFC150/200/e.t.c?

My guess is that to get FAA certification for vertical guidance, the KAP 140 and the KFC 225 autopilots had to implement what is known as “prompting”. This has to do with the way these autopilots handle navigation source mode switching. Unlike most autopilots, these autopilots will disconnect from approach or a navigation mode and enter roll mode anytime there is a switch between GPS and VOR/Localizer as the navigation source (or vice versa). So the normal sequence of simply faking the signals to make a GPS with vertical guidance (LPV, L/VNAV, or +V) look like an ILS does not work, because the switch goes from GPS to VOR/LOC as the source. The FAA would not support using these autopilots with vertical guidance, unless when the pilot selected approach mode, there was not a switch to roll mode. So on the GNS and GTN series GPS navigators, they are configured to select “Prompt” and a new discrete signal is added. Here is how it works with these navigators, at the point the FAF becomes the active fix and vertical navigation signals are asserted, the pilot gets a message instructing him to “Activate the autopilot outputs”. When this is done, the GPS signal is effectively switched to emulate an ILS localizer/GS. Only then is the pilot expected to press approach and since there isn’t a mode switch after this point, the fake ILS signals provide the vertical guidance. So the sequence on these autopilots goes something like this on a GNS530W. Message comes up, pilot presses PROC, enter, then approach. Autopilot couples and flies the LPV or … My guess is that this would involve a similar software update for the G1000/KAP 140 setup to work, and either Garmin or Cessna is unwilling to do it. Probably Cessna.

KUZA

I read apparently sane people swearing that the KAP140 coupled horizontally and vertically with LPV approaches.
Others stating it doesn’t work.
Cessna writing it will not work.
Maybe, there is specific setting one can modify as suggests NYCYankee ?

I think it involves hard wiring the ILS Energise wire

And maybe a few others.

AFAIK the autopilot doesn’t look for a GS until it has the LOC captured, and it won’t do that until you have pressed the APR button. So provided the LOC+GS signals are presented in valid forms at that point, it should “just work”. May not be legal… but if someone out there understands the signals (most installers don’t, but some do) it is no rocket science to work out how to connect it up. They are just analog signals (voltages), with some flags on separate wires.

Also, and it is a while ago since I looked at this, using the Sandel SN3500 EHSI and wiring the autopilot to its (analog) autopilot “FCS” outputs, gets around the problem and the autopilot cannot tell any difference between ILS and LPV. The EHSI fakes the source.

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