Does the SR22B come standard with the GPSS function on the 430"s? I would be interested reading any current experience with same.

I can’t comment on experience with it yet, but GPSS does come with the SR22B. It is not part of the GNS430, but is integral to the STec 55x.

The earlier STec’s had a separate unit which contained the switching for the GPSS. My understanding is that the switching is now built into the STec panel unit.


I like the GPSS on my SR22B and use it a lot. The biggest advantage is for flying multiple legs with different headings, like a flight plan, or a GPS approach. As you probably know, without GPSS, when an autopilot has to turn, it will overshoot the new heading and have to buttonhook back to pick up the correct track. With GPSS, the GPS will anticipate the turn based on your ground speed and the heading change, and begin the turn early so it can roll out on the correct heading. I’ve flown practice GPS approaches at 170 knots with the autopilot and it worked flawlessly. The alternative is to set the heading bug, switch the autopilot to HDG mode, crank the bug around until you’re on course, then re-engage NAV mode. It’s much easier to just sit back and watch GPSS do it automagically.

Engaging GPSS is easy. Just press the “NAV” button on the autopilot twice. The “GPSS” indicator on the autopilot panel will turn on.

GPSS will also fly perfect DME arcs without having to twist the OBS. You can set the Sandel to autoslew, so it will change to the new heading automatically.

I believe Garmin could also have programmed the GNS 430 to fly procedure turns and holding patterns with GPSS, but for some reason, they chose not to.

I generally use GPSS when I’m in cruise with the autopilot on. It works well, although for some reason it flies about 1,000 feet to the right of the course line. Everything else works so well that I’m not inclined to try to fix this minor flaw.


Here’s a view from an SR20 owner who has had GPSS added to my STEC 55. [By the way, although it isn’t part of the GNS430, it does use the GPS data from the top Garmin.]

I really enjoy my GPSS. It makes the tracking of my route flawless, and it makes me much less forgetful (not that I ever missed a waypoint… nyaaah… not MOI!) I think it’s one of those “little luxuries” that is hard to explain – but I believe that once you fly with it, you’ll love it forever.


GPSS also takes the HSI completely out of the autopilot picture–you can twist the course needle all day long and the autopilot doesn’t care (it’s not paying attention.)

About the only mildly useful side effect of this that I’ve come up with is for doing the mandatory 30 day VOR check (the only time I ever actually tune in VORs.) With GPSS, you can switch the 430 to VLOC mode and twist the course pointer around to check your #1 VOR receiver against the #2, and the autopilot will keep flying the GPS course.

Actually, this side effect isn’t even that useful; with the Sandel EHSI you can display the VOR radials from the two receivers at the bottom of the screen by selecting them as the RMI sources, and that’s independent of the course needle anyhow.


Sure is, if you’re flying on an IFR flight plan.

I have GPSS on my SR20, and I love it. By bypassing the HSI, which has been problem prone on the SR20, the autopilot will still work with the HSI kaput. Also, the GPSS is much better at accurately tracking on the flight plan.

That is a pilot check, not shop. Must be done AND LOGGED within previous 30 days. It is a favorite ramp check bust.

91.171 VOR equipment check for IFR operations.
(a) No person may operate a civil aircraft under IFR using the VOR system of radio navigation unless the VOR equipment of that aircraft -
(1) Is maintained, checked, and inspected under an approved procedure; or
(2) Has been operationally checked within the preceding 30 days, and was found to be within the limits of the permissible indicated bearing error set forth in paragraph (b) or © of this section.
(b) Except as provided in paragraph © of this section, each person conducting a VOR check under paragraph (a)(2) of this section shall -
(1) Use, at the airport of intended departure, an FAA-operated or approved test signal or a test signal radiated by a certificated and appropriately rated radio repair station or, outside the United States, a test signal operated or approved by an appropriate authority to check the VOR equipment (the maximum permissible indicated bearing error is ±4°); or
(2) Use, at the airport of intended departure, a point on the airport surface designated as a VOR system checkpoint by the Administrator, or, outside the United States, by an appropriate authority (the maximum permissible bearing error is ±4°);
(3) If neither a test signal nor a designated checkpoint on the surface is available, use an airborne checkpoint designated by the Administrator or, outside the United States, by an appropriate authority (the maximum permissible bearing error is ±6°); or
(4) If no check signal or point is available, while in flight -
(i) Select a VOR radial that lies along the centerline of an established VOR airway;
(ii) Select a prominent ground point along the selected radial preferably more than 20 nautical miles from the VOR ground facility and maneuver the aircraft directly over the point at a reasonably low altitude; and
(iii) Note the VOR bearing indicated by the receiver when over the ground point (the maximum permissible variation between the published radial and the indicated bearing is 6°).
© If dual system VOR (units independent of each other except for the antenna) is installed in the aircraft, the person checking the equipment may check one system against the other in place of the check procedures specified in paragraph (b) of this section. Both systems shall be tuned to the same VOR ground facility and note the indicated bearings to that station. The maximum permissible variation between the two indicated bearings is 4°.
(d) Each person making the VOR operational check, as specified in paragraph (b) or © of this section, shall enter the date, place, bearing error, and sign the aircraft log or other record. In addition, if a test signal radiated by a repair station, as specified in paragraph (b)(1) of this section, is used, an entry must be made in the aircraft log or other record by the repair station certificate holder or the certificate holder’s representative certifying to the bearing transmitted by the repair station for the check and the date of transmission.

The VOR check is indeed mandatory for IFR ops if VOR equipment is used. Here’s a suggestion to minimize any ramp check problems. Note that paragraph d of the regulation states that you need to log the check in the aircraft log “OR OTHER RECORD” (caps are mine). Since there is no need to keep the record in the aircraft why not log it in a totally separate place (like the comment section of your pilot’s logbook that also need not be carried with you in the aircraft).
If you’re ramp checked tell the inspector that you would be happy to send him the documents requested and, before you do, make sure they’re up to date.
Never, but never, give the inspector anything that isn’t required to be on board at the time of the check. Remember, he can’t require you to produce something on the spot that you’re not required to carry with you.
Jerry Seckler

Thanks Gordon,
I recently obatained my private for VFR… I didn’t need this regulation yet…but will learn all about it in round 2!

That is correct. However, I feel that the required 30 day check makes a lot of sense and I do them and log them religiously in my aircraft in their own little notebook pad.

Another note re ramp check. You do not have to allow the inspectior to board the aircraft. If you are in a hurry simply tell the inspector that and show your license and medical (show - do not surrender!) and you should be allowed to go. And we’re all in a hurry when we fly, right?

Always good advice with one caveat: If you have the info (logs, etc.) in the aircraft, think twice about not providing it. If the inspector sees it (& he may look through the plane), you are majorly busted for refusing to provide it.

While you may be able to convince him that you didn’t know that you had it in the airplane as you usually keep it elsewhere, that is not an argument which I would like to advance.

IMHO, it is always a good idea to keep the logs separate from the aircraft. My two main reasons are i) if the aircraft is stolen it is more difficult to sell without them and it is also certainly less lucrative for the thief. ii) If anything were to happen to the plane, the logbooks are safer elsewhere.


I’m reading posts about GPSS and implications that the Garmin 430 does not have it. I have a Garmin 430 in a 1976 Skylane working with the original autopilot. It anticipates turns. If there is an enroute dog leg it does not fly over the waypoint before turning. It makes a smooth turn without overshooting the outbound radial.
How is GPSS different than that?

I don’t advocate not doing the checks. In fact I do a check on EVERY flight. Now I do them with the bearing pointers on the Sandel and compare 1 and 2. I must confess however that I sometimes forget to log the check. My post was simply a comment about how to avoid problems that were alluded to regarding VOR checks and ramp checks.
I also think though that as a practical matter the checks still allow an unacceptable level of error. Assume that your #2 VOR reads 5 degrees low and the #1 reads 9 degrees low and you’re using the “1 vs 2” check method. They are within 4 degrees of each other and yet the error on the #1 (that I assume is the primary) is unacceptable. I think that if you’re flying IFR you will be in radar contact most of the time and a far more accurate check might be to ask the controller when you think you’re on an airway centerline if you really are. Do it along a long airway segment when you’re about 40-50 miles form the VOR in order to maximize your error. If he says no, check with the avionics shop. I understand that the controller check doesn’t fulfill the legal requirements but it is probably more reliable.
Jerry Seckler

“No person may operate a civil aircraft under IFR using the VOR system of radio navigation unless the VOR equipment of that aircraft -”

So, if ramp checked, then you answer “I wasn’t using VOR navigation, I was using my certified IFR GPS Receiver”

Don’t need VOR check if you’re not using VOR, if I read it correctly.

Paul SR22 #250

Except for the…

AIM 1-1-21-e-1(b) Aircraft using GPS navigation equipment under IFR must be equipped with an approved and operational alternate means of navigation appropriate to the flight. Active monitoring of alternative navigation equipment is not required if the GPS receiver uses RAIM for integrity monitoring. Active monitoring of an alternate means of navigation is required when the RAIM capability of the GPS equipment is lost.

So unless you put in an ADF, you still need to have an operational VOR for any IFR flightplan. You would also need it to list an alternate with less than VFR minimums.


So, if ramp checked, then you answer “I wasn’t using VOR navigation, I was using my certified IFR GPS Receiver”

That might be hard to do if you just landed on an ILS, LOC, or VOR only approach.

Phil, as I recall the GNS 430 does actively monitor the RAIM. In fact, I have had an occasional RAIM flag pop up from time to time, which indicate that the monitoring is going on all the time.

Yes, I think that is correct, but that only means that you don’t have to tune and monitor the VOR while you have RAIM integrity. You would still need a legal VOR navigation system, and if RAIM is not available, you would then need to tune in and use the VOR for enroute nav and approach. If RAIM fails after the FAF and the rwy is not visible for a VFR final approach, then you have to execute the published missed using the VOR to the hold. At least, that is how I read it.


In the first production run of the SR20s they installed an STEC 55 autopilot (optional) as opposed to the newer model which has the 55x with built-in GPSS. The Garmin 430s always output the GPSS digital signal (ARINC 429 digital data) however the older STEC 55 could not utilize that data.

It is a shortcoming in the STEC not the Garmin which can be addressed by adding an $800 GPSS module to the autopilot.

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