Trutrak, ILS and GPSS

[Deelee]

Hi folks, I almost hijacked the G5/GNC 255/TruTrak integration thread, but I think my question is different enough, so here goes:

I have a Trutrak Vizion, an Aspen EFD 1000 Pro and a Garmin 430w. The 430w is connected to to the Aspen and also the TT. The TT has a switch that lets you toggle taking input from the 430w or the Aspen. The Aspen will only send HDG to the TT. For GPSS, it needs to be coupled to the 430w. As far as I know, flipping that switch to connect TT to either Aspen or 430 does nothing to the connection between the 430w and the Aspen.

Confusing enough? Now here is my question:
I know the Trutrak will not follow green-needle guidance - it won't shoot an ILS approach basically. But here is the question - and this is a hypothetical, what-if, non-legally binding question - If I have an ILS approach loaded in the 430w and get vectored to the final approach course (let's say I have the leg active between the IAF and an initial fix on the appraoch), I flip the CDI to VLOC so the Aspen is showing green needles and the localizer/GS information, if I flip the switch to connect the Trutrak to the 430w and put it in GPSS mode.... will the Trutrak follow the magenta line on the 430w that represents the ILS approach? I know I won't get vertical guidance, but will the TT follow that line in GPSS mode? So that (again, hypothetically) the TT could follow the localizer (really following the GPS magenta line) with pilot monitoring the green lateral diamond on the Aspen? And, hypothetically, the pilot could put the TT in vertical speed mode and command a -500 fpm descent to put the aircraft on glideslope and then fine tune based on the Aspen glideslope green diamond (maybe using power or a bit of trim?)?

Again, all hypothetical and I can't fly today to try this out in VMC... But it seems like the coupling of the 430w to the Aspen in VLOC mode is separate from the coupling of the 430w to Trutrak in GPSS mode... and maybe this would work? Hypothetically?

(and no, the answer isn't to get a GFC500 or STEC that can shoot ILS approaches.... my AMUs are spent)

Thanks!

 

[Jesse Saint]

The TruTrak will follow whatever GPS flight plan is on the 430W regardless of the GPS/VLOC position.

 

[nrimmer]

Seems possible. I can set my Aera 660, which is tied to my G5s and TT, direct to a VOR (or LOC), center the OBS needle and it simulates tracking the VOR and keeps the magenta line centered. Legality in IMC is another question, but it does work.

 

[Deelee]

Thanks all! This is helpful.

Obviously I would never do this... especially on a checkride... and I have been hand-flying the ILS/LOC approaches once LOC intercept. But...

Is it legal to leave the autopilot engaged following the GPS flight plan/track, but have the CDI switched to VLOC for raw data which would be driving the HSI and green diamonds on the Aspen? I think the reg says something like - for a LOC/ILS/VOR approach, you have to be using raw radio nav data to drive your CDI/HSI/nav instruments...

But is it illegal to have the autopilot flying the GPS track while you monitor the green needles that are being fed data from the radio nav sources per the regs?

 

[nrimmer]

The simple answer (and maybe correct, maybe not) is no. That’s what my instructor and I agreed on during instrument training - under instrument rules we did not use the VFR GPS to drive an autopilot that is actively manipulating the controls. However as with many laws and rules/regs, you really need to dig into the exact text to see what it says. Often the answer is not as black and white as people commonly believe.

 

[Deelee]

Ah ok yes, the Area660 is not an IFR-capable GPS. The 430w WAAS panel mount GPS is IFR-capable... wonder if that makes any difference. Again, as long ast the AP can manipulate the controls off GPSS signal while the nav instruments (HSI and GS) are being fed from the 430w nav radio. Pilot is monitoring the raw data on the HSI/GS.

Guess a similar question would be is it legal to leave the AP in HDG mode while pilot is monitoring the raw radio data... and if that is legal, would it not be legal for the AP to fly the plane based on any source (including GPS) as long as pilot is only using the raw radio nav (LOC/GS) data to monitor to ensure aircraft is on LOC and GS?

All hypothetical and now I am just curious in terms of the legality of this.

 

[CRQFlier]

I think the TT has the same limitation as the trio - cant be used below 500' agl (or 700?). So I think you can follow magenta until then, but you're responsible for following the needles throughout the approach.

Sent from my SM-G960U1 using Tapatalk

 

[David Megginson]

Hi folks, I almost hijacked the G5/GNC 255/TruTrak integration thread, but I think my question is different enough, so here goes:

I have a Trutrak Vizion, an Aspen EFD 1000 Pro and a Garmin 430w. The 430w is connected to to the Aspen and also the TT. The TT has a switch that lets you toggle taking input from the 430w or the Aspen. The Aspen will only send HDG to the TT. For GPSS, it needs to be coupled to the 430w. As far as I know, flipping that switch to connect TT to either Aspen or 430 does nothing to the connection between the 430w and the Aspen.

Confusing enough? Now here is my question:
I know the Trutrak will not follow green-needle guidance - it won't shoot an ILS approach basically. But here is the question - and this is a hypothetical, what-if, non-legally binding question - If I have an ILS approach loaded in the 430w and get vectored to the final approach course (let's say I have the leg active between the IAF and an initial fix on the appraoch), I flip the CDI to VLOC so the Aspen is showing green needles and the localizer/GS information, if I flip the switch to connect the Trutrak to the 430w and put it in GPSS mode.... will the Trutrak follow the magenta line on the 430w that represents the ILS approach? I know I won't get vertical guidance, but will the TT follow that line in GPSS mode? So that (again, hypothetically) the TT could follow the localizer (really following the GPS magenta line) with pilot monitoring the green lateral diamond on the Aspen? And, hypothetically, the pilot could put the TT in vertical speed mode and command a -500 fpm descent to put the aircraft on glideslope and then fine tune based on the Aspen glideslope green diamond (maybe using power or a bit of trim?)?

Again, all hypothetical and I can't fly today to try this out in VMC... But it seems like the coupling of the 430w to the Aspen in VLOC mode is separate from the coupling of the 430w to Trutrak in GPSS mode... and maybe this would work? Hypothetically?

(and no, the answer isn't to get a GFC500 or STEC that can shoot ILS approaches.... my AMUs are spent)

Thanks!

We're not allowed to take GPS navigation input for an ILS approach past the FAF with any autopilot. Since the TT isn't certified for coupled approaches anyway (even above 700 ft AGL), your best bet would be to choose heading mode (if it's available with the the TT hooked up to an Aspen) or track mode, and keep the CDI centred that way, with small adjustments.

 

[nrimmer]

We're not allowed to take GPS navigation input for an ILS approach past the FAF with any autopilot. Since the TT isn't certified for coupled approaches anyway (even above 700 ft AGL), your best bet would be to choose heading mode (if it's available with the the TT hooked up to an Aspen) or track mode, and keep the CDI centred that way, with small adjustments.

According to the TruTrak manual it flies coupled approaches (the placard limits it to 700’ AGL). See attached...

 

[Peter Anderson]

I know this is the experimental world, but with my GRT HS pfd, it can drive my TT vision with vertical guidance. If I load an ils from my gtn, the pfd will order the tru tack to fly the needles. It’s pretty slick. I can also toggle the gtn or the GRT pfd to control the trutrack.


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[AlphaMike]

I know this is the experimental world, but with my GRT HS pfd, it can drive my TT vision with vertical guidance. If I load an ils from my gtn, the pfd will order the tru tack to fly the needles. It’s pretty slick. I can also toggle the gtn or the GRT pfd to control the trutrack.


Sent from my iPhone using Tapatalk Pro

That’s exactly why my next bird will be an experimental!

 

[David Megginson]

According to the TruTrak manual it flies coupled approaches (the placard limits it to 700’ AGL). See attached...

Yes, but the AFMS also says that they're not authorised for IFR use (because TT and later B-K never worked to get the certification). It will also couple only for RNAV approaches (including LPV), not ILS, unless it's getting that info through the E5 or similar (not sure if that's possible).

 

[David Megginson]

That’s exactly why my next bird will be an experimental!

I'm pretty sure that even experimental aircraft aren't supposed to couple to the advisory GPS guidance for an ILS approach once inside the FAF. That's an IFR reg, not a question of certification. If you're coupled, you have to be following the LOC and GS signal — pilots forgetting to switch their GPS CDI to VLOC before the FAF of a ILS (if the switch doesn't happen automatically) is an easy way to flunk an instrument proficiency check, and the examiner doesn't care whether your plane is certified or experimental.

 

[AlphaMike]

I'm pretty sure that even experimental aircraft aren't supposed to couple to the advisory GPS guidance for an ILS approach once inside the FAF. That's an IFR reg, not a question of certification. If you're coupled, you have to be following the LOC and GS signal — pilots forgetting to switch their GPS CDI to VLOC before the FAF of a ILS (if the switch doesn't happen automatically) is an easy way to flunk an instrument proficiency check, and the examiner doesn't care whether your plane is certified or experimental.

I’m not talking about that. Just the options that are available for experimental aircraft vs certified. I could have worded it better, I’ll probably always have a certified aircraft but I plan at some point to get an experimental as a “fun” second aircraft. So much cheaper and way less hoops to jump through.

 

[David Megginson]

I’m not talking about that. Just the options that are available for experimental aircraft vs certified. I could have worded it better, I’ll probably always have a certified aircraft but I plan at some point to get an experimental as a “fun” second aircraft. So much cheaper and way less hoops to jump through.

Sounds fun. And yes, you definitely would be legal to fly RNAV approaches, including LPV, coupled with the TT in an experimental aircraft — the whole idea (as you already know) is that you're self-certifying the safety of the equipment, relieving the FAA of its usual responsibility to protect your passengers (hence the big placard for them to read on the panel of an experimental aircraft).