Thursday, June 21, 2007

Keeping a Positive Attitude

The old joke goes:
Two atoms are walking together when one says
"I've lost one of my electrons!"
The other atom asks "Are you sure?"
"Yes, I'm positive ..."

Pilots flying technically advanced aircraft (those with glass panel instrument displays and other electrically-dependent things like FADEC) need to make sure all their electrons are in order. The G1000 database update problem I discussed previously was resolved and the sticking point turned out to be an improperly formatted SD card. Still, the experience points out an operating scenario (PFD and MFD databases out of synch and cross-fill disabled) that I suspect Garmin did not fully explore during their quality assurance process. If I ever again experience a situation where cross-fill is disabled in a G1000, the first thing I will do is cut the corpus callosum (enter reversionary mode), which seems to prevent much of the weird behavior I reported earlier.

With both the PFD and MFD databases updated and the G1000 in this new plane functioning properly, my next question was how could this 172 have a WAAS-enabled G1000 when there appear to be no manuals available on the Garmin web site for such a setup on a Cessna? It turns out that these manuals are available, they're just hard to find - go to Garmin's web site, pull-down the Support menu, select Manuals, then select Aviation, Integrated Avionics Systems , G1000: Cessna Nav III. The PDF manuals that refer to the WAAS G1000 all contain "System Software Version 0563.00 or later" in their titles.

Perusing these manuals showed that there were many new features. Some of the features involve the Garmin the GFC 700 AFCS (Automatic Flight Control System - an autopilot and flight director) which is not available on the C172, but is available on the C182, C206 and the Cessna Mustang. There are still a bunch of new features on the C172 WAAS G1000 like SafeTaxi™ and FliteCharts™. I'll cover those in another post.

Loading an RNAV approach with LPV minima looks like this. Note that the available RNAV minima appear next to the name of the approach. Sorry these photos are blurry and poorly framed, but I was flying so all of these were "Hail Mary" shots.

Here's the RNAV approach I loaded, which has LPV (Localizer Precision with Vertical guidance) minima:

When you have loaded and activated an RNAV approach, several indicators will appear that are new for the WAAS G1000. The Vertical Deviation indicator (a magenta V) appears at the top of the glideslope window to the left of the altitude tape. At the top of the altitude tape, the next RNAV altitude is displayed in magenta. On the vertical speed tape, to the right of the altitude tape, a Required Vertical Speed Indicator will appear. A Glidepath Indicator (a magenta V, turned on its side) will appear on the altitude tape.

On the WAAS G1000, the turn anticipation messages are prominently displayed on the top of the PFD - right in the pilot's primary field of view where they are hard to miss. Sweet!

Once you reach the FAF, the display changes to a conventional G1000 glideslope indication (note G at the top of the glideslope window and the regular magenta diamond-shaped glideslope indicator).

My first assumption was that the KAP 140 would capture and fly the RNAV glideslope if I intercepted the glideslope from below at VODSY (the FAF), just like you would for a regular ILS. The G1000 begins providing a Vertical Deviation indicator at JUPAP, well before the FAF. I had the KAP 140 in NAV and ALTitude hold mode, so I reasoned that pressing the APR (approach) button would capture the glideslope. Nope! I tried the same strategy just before VODSY when the "normal" glideslope indications appeared. Nada!

Perhaps there's some incompatibility between the WAAS G1000 and the KAP 140, but since they are two separate products from two separate companies with two separate manuals, it will take more research to find out why. Even if the KAP 140 can't fly an LPV approach with glideslope, you can fudge it by putting the autopilot in NAV mode and manually adjusting the VS (vertical speed) descent rate to stay on the glideslope.

I had the opportunity to fly an SR22 that had recently been upgraded to dual GNS 430W units (sorry, no photos). Actually, I was ferrying the plane back from a maintenance shop where the issue of a door that wouldn't close was addressed. Much to the chagrin of the owner and myself, we discovered upon arrival at the home airport that the doors were once again refusing to close without someone pushing on them from the outside, but that's another frustrating and sordid tale.

With some extra time on my hands on the flight back, plenty of fuel, and the owner's permission, I decided to fly the OAK RNAV 27L just to see how it would compare to the G1000 experience. This is where I discovered what a lot of other Cirrus pilots apparently already know - the Avidyne Entegra system doesn't play well with the new Garmin 430W. The Entegra primary flight display cannot currently display GPS alerts, such as the turn anticipation prompts. Selecting OBS mode on the GPS also doesn't work on the Entegra and gives an obscure RS232 data channel #4 message.

But what's really unfortunate is that the Entegra can't display an RNAV glideslope, such as LPV or LNAV/VNAV - the whole point of doing the upgrade in the first place. For their part, Avidyne is developing an Entegra upgrade to fix this problem and it should be available sometime this fall. To perform the upgrade, the Entegra will have to be removed from the aircraft and returned to Avidyne, then returned to the avionics shop or Cirrus service center. This means the aircraft owner will lose use of the aircraft a second time - once for the 430W upgrade and again for the Entegra upgrade. If I was a Cirrus owner (ha! me, own a plane!)who hasn't yet done the 430W upgrade, I'd wait until the Avidyne fix is available and do it all at once.

Cirrus owners who opted to upgrade to the 430W as soon as it became available are not getting all the utility they thought they'd get. It's not clear if Avidyne and Garmin didn't communicate the changes to the 430W or if Avidyne dropped the ball, but the aircraft owners and pilots are the ones suffering.

And the people at Cirrus who designed those swell doors that don't latch properly? Well I think they should be sent out to personally apologize to all the people they've inconvenienced. Or maybe they should just be locked their offices until they have designed a free retrofit - doors that will actually latch and stay closed.


Jason said...

Great post! I'm a number-junkie so learning details on those PFD screens is fun for me.

Are those problem SR22 doors on a newer aircraft or pre-G2?

milski said...

John, great post and extremely timely for me - my FBO got a new G1000 C172 about a week ago and I'm taking my CFII ride it in probably another week or two. I already have plenty of practice in a C182 but it was not WAAS enabled, so having the chance to see how things will work before going out in the airplane this weekend is really nice.
As a side note, what is the white cross indicator just under the heading bug window - in the first picture it's showing 1,3 and down and left arrow?

John said...


The SR22 I mentioned is a G2. An older SR20 I often fly has a style of doors that positively lock with a handle.


The "white cross" is one possible configuration for the wind indicator. The downward pointing arrow is the headwind component in knots and the horizontal arrow is the crosswind component in knots.

Good luck with the check ride!

John said...


For the 430W/530W (W) in combo with the KAP140 or KFC225, there is a two step procedure for getting the autopilot to track the GS. After passing the IF fix just prior to the FAF, the W generates a message "approach guidance available, Use PROC before A/P APR." You have to press the PROC button on the W, and move the cursor to choose “Enable A/P APR Outputs?” and press Enter. Then engage the autopilot by pressing the APR button. You won't get the message unless the W is configured properly to "Prompt for autopilot outputs". Some installers don't know this!

My guess is the G1000 works in a similar way and needs to be setup to generate the message.

john hawkins said...

as The ONE who advise the world on GPS mysteries, I suggest you take a look at
june 24th entry and give your opinion.
Has Garmin ever approached you to be a consultant? if not they ought to.
I too am a software type and know that interfaces designed by engineers are awful. But in the case of EFIS. I don't have any idea how to make them better. Do you?

John said...


I'll investigate the G1000 in a day or so to determine if it has a PROC->Enable A/P APR Outputs? option. I recall seeing a "approach guidance available" message, but didn't realize its significance.

John Hawkins,

I read the post and my only comment is I'd recommend against reprograming a GPS while flying a hold over a GPS waypoint UNLESS I had a way to fly that hold using the VOR receivers. In the example cited, the missed approach holding waypoint was in fact a VOR! Apparently it never occurred to the pilot (or the instructor never suggested) that it might be a good idea to tune the RST VOR on the 430's VOR receiver.

Many pilots I fly with get stuck in GPS mode and have a hard time changing gears and going back to VORs. Though it is more work, I recommend that the VOR receivers be tuned with something that could be helpful in the unlikely event the GPS goes Tango Uniform.

In a plane with dual 430 or 530 units with automatic crossfill enabled only from the TOP unit to the BOTTOM unit, I would consider loading and activating a new approach on the BOTTOM unit. This would leave the TOP unit undisturbed and let me continue to fly the hold using GPS alone. When given clearance to leave the hold and proceed to the next approach, I'd manually crossfill from the BOTTOM unit to the TOP unit. That's the only way I know to get ahead of the button pushing and knob twisting without shooting yourself in the foot.

As for my being a consultant to Garmin, I'm afraid they've created a user interface monster with the 430/530. Now they've propogated it to the G1000 and they have an installed base of equipment and customers who have no choice but to hold their noses and use the stuff. They've never approached me, they probably don't know I exist, and probably don't realize (or want to realize) how hard it can be to use their equipment in a single-pilot environment.

Could better a more effective interface be designed? Of course! But no one has asked me to design one ...

w said...

Hi John - I know this post is a few years old, but I'm curious if you ever got G1000+KAP140 to capture the GS for a GPS approach? Oddly, in Section 9 of Supplement 3 of the POH, it states "APR supplies vertical guidance only for ILS approaches, and then only when established on the localizer before glideslope intercept" but I'm told by countless many that it "works" for GPS approaches.

John Ewing said...


Yes! As of two years ago I witnessed a G1000 with a KAP 140 capture and fly an LPV approach glide path. The aircraft was (is) a DA42NG that had been converted from a DA42 TwinStar by the factory in London, Ontario.

The owner at the time opted to keep the KAP 140 instead of getting a GFC700 autopilot, which I think was a mistake. But I digress ...

So the KAP 140 and the G1000 can indeed play together on RNAV approaches with vertical guidance in APR mode, but it's up to the manufacturer to ensure that this happens.

It appears to me that Cessna's solution was to switch to the GFC700 autopilot and, unfortunately, leave the owner's of existing Cessna aircraft equipped with WAAS G1000 and the KAP 140 ... well, swinging in the breeze.