Saturday, May 26, 2007

GPS - SNAFU or FUBAR?

In case you haven't noticed, the specification and approval process for aviation RNAV/GPS navigation systems is a mess. Peruse the recent changes to the Aeronautical Information Manual section on GPS and RNP and you'll see what I mean. The main reason that things are a mess has to do with the fact that much of the certification process has been made transparent to the pilot.

By transparent I mean pilots must know some pretty detailed stuff about their GPS before they can use it under IFR. It used to be sufficient to 1) check the aircraft you were going to fly for an Approved Flight Manual supplement that stated the GPS receiver could be used under IFR, 2) verify the GPS database had not expired, and 3) perform a RAIM prediction. Contrast that with using a VOR receiver where the only regulatory requirement is that you perform and log a successful VOR check every 30 days. There is no operational test available to pilots to ensure proper glide slope receiver operation - I guess we're just supposed to accept that on faith. The bar has apparently been set much higher for GPS receivers and the databases they use.

Designing RNAV departure, arrival, and approach procedures that will keep pilots from running into stuff is a complicated business, which helps explain why the certification process for aviation GPS receivers is pretty darn complicated, too. But that complexity should be opaque as far as the pilot is concerned, the way it is for ILS, LOC, LDA, SDF, VOR, and NDB procedures. Instead of hiding the complexity for RNAV/GPS procedures, the FAA has published some of the GPS certification data in the AIM (cf. Table 1-1-5) and apparently they expect pilots to understand the various Technical Specification Orders (TSO) and Letters of Approval (LOA). Just what we pilots needed: More trivia, more acronyms, and more chances to break regulations without realizing it.

If you haven't already guessed why I'm grinding away on this topic, it's because AOPA (among others) recently realized that an update to AC 90-100A made in March of this year contains a bombshell - the only GPS receivers widely available for GA aircraft that are now approved for substitution for DME and ADF are the Garmin 400, 500, and G1000 series. Suddenly all the old Apollo units, the GNS 480, the Chelton Flight Systems units, and many of the King GPS units that thousands of pilots have been using as a substitution for DME and ADF are suddenly no longer approved for such uses. Oh, and these units can't be used to fly T-Routes either.

The affected GPS unit presumably still comply with the original TSO under which they were certificated, but they no longer comply with AC 90-100A. And let's not forget about all the Approved Flight Manual Supplements out there that say these GPS units are approved for these uses. One would assume that they are now incorrect. Talk about The large print giveth and the small print taketh away!

A reasonable person has to wonder "Why did it take until the end of May for this to become common knowledge?"

I've spent considerable time trying to parse AC 90-100A and AC 20-153 and the only thing that is crystal clear to me is that the FAA isn't making it easy for us pilots. Nor are the manufacturers of GPS receivers. It seems that the reason that the majority of GPS receivers certificated under TSO 129 have been rendered non-compliant is that the manufacturers do not have a Type 2 Letter of Approval (LOA) for the aviation databases that they generate for said GPS receivers. And if there is no Type 2 LOA, then the GPS receivers' use is restricted until such time as an LOA is granted by the FAA. For some GPS receivers, the LOA is pending while for others there are no plans to ever obtain an LOA, hence they will forever be limited.

The interesting thing here is that the FAA has recognized the importance of valid data for GPS receivers. I appreciate this as I had to point out to Garmin on at least one occasion that their database did not have all the initial approach fixes defined on a plate for an ILS approach to an airport in Northern California. Equally interesting is that a GPS that complies with the original requirements specified in the TSO years ago can still be rendered less useful after the fact by an advisory circular.

While you're contemplating that cascading chain of dominos, consider this spreadsheet which lists the compliance of virtually all GPS, RNAV, and FMS from Boeing to Rockwell. That spreadsheet was apparently created by someone at the FAA at the end of 2006.

So did the FAA not notify the manufacturers of the non-compliant hardware until a few weeks ago, even though they apparently knew this in December of 2006 and the updates to AC 90-100A were released in March of this year? For their parts, Garmin and Rockwell-Collins, posted their LOAs right around the time AC 90-100A was updated in March. But did the manufacturers notify their potential customers, customers who purchased their products, not to mention the pilots who don't own but use their equipment? I don't know the answers to these questions, but I wish I did.

With the push for ATC user fees, the FAA keeps talking about providing better service to their customers. Based on the state of FSS under Lockheed-Martin, this GPS fiasco, and the fact that virtually all Boeing, Airbus, Embraer, Dassualt, and Gulfstream equipment already seem to be in compliance with AC 90-100A, one has to wonder just who are these customers the FAA keeps talking about?

Thursday, May 17, 2007

Follow Your Nose

Paper or plastic? Low-fat, non-fat, decaf, half decaf? We face a dizzying array of choices in life. Some are mundane and some are annoying, like cellphone ring tones. Even aviation is not immune to the syndrome of too many choices. And one of the more interesting choices I see pilots make with moving map displays is North Up or Track up

Before I embark on my observations, let me say that I'm not one to claim there is only one right way to do things. When it comes to moving map displays, I personally prefer track-up. I find it to be more intuitive. When teaching pilotage, I also encourage student pilots to physically turn their terminal area chart or VFR sectional to orient the map so that it is pointed in the same direction as the aircraft. Of course all the printing on the charts is biased to north-up, but that doesn't bother me. After some cursory research on this topic, I found that my preferred way of doing business with maps (moving and otherwise) is often referred to as an ego-centered approach.

I have flown with several pilots who prefer a north-up orientation and I'd estimate that they account for about 25% of the pilot population I've encountered. Let me emphasize that this is just an estimate. An interesting observation about those who prefer north-up: To a person, I've found these pilots are down right flummoxed when they are confronted with a GPS with a moving map configured for track-up. One pilot, seeing me about to change a moving map configuration from north-up to track-up barked "Not track-up! That's wrong!" In contrast, most track-up pilots can tolerate a north-up representation, they just to prefer track up. I even know a pilot examiner who chastised a candidate who dared turn a map - "Always keep your map north-up!" was the examiner's retort. To my mind, north-up requires a mental transposition in order to visualize your trajectory.

The research I referred to earlier calls the north-up way of doing things a world-centered approach, though I think map- or chart-centered is more accurate. Imagine trying to read a book that is turned on it's side. It's possible, but not very easy to do without some practice. And remember that instrument approach charts are produced in a north-up orientation. I've seen more than one beginning instrument pilot become confused by this representation on this approach.



All usually goes well during the north-bound final approach segment, but they often become disoriented when flying the missed approach. I've theorized that this is because the final approach is essentially a track-up representation, while the missed approach hold entry is just the opposite. And more than once I've encouraged a pilot who was unsure about the hold entry to turn the plate upside down.

Then there are approaches with southbound final approach segments like this one, where the pilot has to do a translation in his or her head to visualize the track.




This led me to wonder if researching the NTSB accident statistics would yield any trends with regard to pilot disorientation while flying southbound approaches or approaches where the missed approach segment was 180˚ opposite the final approach course. After doing some tedious skimming of a few GA accident reports, the only conclusion I could come to was that experimental aircraft seem to make up the lion's share of reported fatal accidents.

Again, I'm not saying that those who prefer a north-up representation are evil. And if you prefer your charts with a twist of lemon, that's okay, too.

Tuesday, May 15, 2007

Catbird Seat

While transitioning through Class Charlie airspace, I heard an exchange between a pilot and a tower controller. I've never met the controller, but have talked to him countless times and always found him to be professional and courteous, especially to student pilots. The pilot asked "Is that Xxx?" and the controller answered "Yes, is that Yyy?" The pilot asked "How's it going?" and the controller replied "They're working us to death with overtime, so I'll be retiring in a few weeks."

Some of you may have noticed I added two new links to blogs that discuss FAA controllers' beefs with FAA management and manager behavior. I recommend you check out The Main Bang and FAA Follies. They are well-written and offer some compelling stories about our tax dollars at work. From what I read, the FAA management apparently is often successful in creating an inhospitable (and in some cases, downright hostile) work environment. New-hire controllers are paid so poorly during training that many just give up and many seasoned controllers are opting for retirement. The ATC system, contrary to what the FAA might be saying, appears to be seriously understaffed. Consider this one example if you need more proof.

As a pilot and instructor, I can appreciate how poor management of ATC staff can negatively affect controllers' attitudes toward their jobs and result in poorer service being provided. It seems to me the FAA needs to agree to a contract with controllers, improve staffing levels, and quit treating these professionals like a bunch of children. Read a bit of these two blogs and you'll probably have a new appreciation of what controllers are up against.

Tuesday, May 01, 2007

Here to Help

Before my recent trip to the East Coast, I decided to upgrade my PDF software. Normally I would have some trepidation about doing a software upgrade at a critical time (I was planning to take my laptop on the trip), but my experience with this software has been quite good. Imagine my surprise when, after upgrading (at cost that wasn't insignificant, I might add) any attempt to read a PDF file resulted in a crash of either the reader or my browser.

A somewhat circuitous review of their website uncovered a description of the exact problem I was seeing and a patch to download. I downloaded the patch, applied it as instructed, but the thing still crashed. I tried to call their customer support, but sat on hold for over 20 minutes before I decided I had to deal with this at a later time - I had to pack after all! So I did the reasonable thing and un-installed the upgrade, but something nefarious had occurred and the crash would still happen. Needless to say, this changed my workflow for reading and creating PDF files. I don't know about you, but I was surprised at how much I depend on PDF files.

Yesterday I got through to a very helpful support person, after listening to some funky Muzak for 20 minutes or so. He walked me through some potential fixes before I finally uncovered a misunderstanding I had with the patch process. Once that was behind me, everything worked as advertised. It was a fascinating example of two people, both with technical backgrounds, speaking the same language, but not really communicating.

The weather was great for an instrument training flight last night. We headed toward a towered airport; just over 50 miles away, to do an ILS and GPS approach. The Center controller was unwilling to give us a practice approach clearance, but provided flight following while my student tracked the approach. Since the controller wasn't going to say the things that would normally be said during a practice approach or an approach under IFR, I simulated the instructions the controller normally would give.
Piper 123, when able proceed direct COATI, descend and maintain 3000, expect the ILS 32 approach.
...
Piper 123 is 3 miles from COATI, cleared ILS runway 32 approach ...

As we arrived for a touch and go, the tower controller announced he was closed and we wished him a good night. We climbed straight out, checked in with Center and told them we wanted to go to the initial approach fix for a GPS approach, do a turn in the hold, and track it inbound under VFR conditions. He acknowledged with a sort of "Yes dear, maintain VFR ..."

About to enter the hold, we heard a regional airliner that had been cleared for an approach into the same airport we just departed announce they had a flap problem and that they were abandoning the approach. One of the pilots asked to fly north and climb to 5000 feet so they could run some checklists. What ensued was a series of miscues and miscommunications, mostly on the part of the controller.

The controller asked the airliner if they were declaring an emergency and when they said no, he instructed them to fly to the south. This involved nearly a 180-degree turn, which surprised me given the aircraft said they had a flap problem. My gut feeling was that this controller was not a pilot and didn't realize the possible implications his instructions could have on a flight with an abnormal flap condition. Next the controller asked if the airline wanted to be vectored back for the approach. Again one of the pilots said they needed some time to run their checklists and asked to climb to 7000 feet. The controller approved the climb but kept asking if they wanted vectors to try the approach again. The tone of voice of at least one of the pilots betrayed some stress and I was astounded the controller was bugging them when it seemed clear (to me at least) that they needed to be left alone to do some troubleshooting.

We reported procedure turn inbound and reminded the controller we wanted to track inbound on the GPS approach, adding that we could abandon our approach at any time if the airliner needed priority. The frequency then became quiet and my student got his first taste of flying a snowballing non-precision approach with a strong tailwind, the resulting high ground speed, and the high rate of descent required to get down in time. We were cleared to the advisory frequency, circled to the opposite runway, and did a touch and go with a stiff wind right down the runway.

Climbing out, we contacted Center for flight following and I could see the airliner's landing lights. It appeared they were again inbound toward the airport. I thought the Center controller would call us as traffic to the airliner or vice a versa, but he didn't. Instead, he cleared them for the same ILS we had just flown, but gave them a 4,500 foot crossing restriction at the initial approach fix. The approach chart lists a 3000-foot altitude at that fix. One of the airliner pilots began inquiring about the surface winds and an involved conversation ensued where the controller said they essentially didn't really know what the winds were. I thought about chiming in, saying that we had landed there 10 minutes ago and that the wind was straight down the runway, but I didn't want to further confuse the issue.

As we passed to the east of the airliner, I found myself thinking, "They're awfully high and if they can't use their flaps, there's no way they'll get down at a reasonable speed." Adding to the interest, the runway they were planning to use is just over 5000' long. Next the Center controller asked the airliner if they were established and one of the pilots said they were too high and asked for a left 360 to loose altitude and get reestablished. I could tell there was some tension in the airliner cockpit because both pilots would answer on the radio at different times. Shortly before we were handed off to the next sector, I heard the airline cancelling IFR, having finally arrived (safely, one would assume).

All in all, it was a good learning experience for my student and it sparked a discussion on ways to deal with controllers who don't seem to understand what a pilot is asking for. Controllers often don't realize that they can be a serious distraction when they begin asking pilots a bunch of questions that require the pilot to focus on the Controller instead of flying the plane. Ever see someone driving down a highway while trying to read a newspaper?

My other observations were that the airliner crew could have been more demanding in what they wanted from the controller. I also think they should have been clearer about needing some "quiet time," emphasizing that they would advise the controller when they were ready for the approach. When given the 4,500' crossing restriction, they could have asked for lower. But mostly I hope that controller gets a chance to jump seat on an airliner in the near future because there's a lot he's missing.