Sunday, December 31, 2006

In the Blink of an Eye

The week between Christmas and New Year's Eve was set to be a slow one. The week started out with poor weather and the few instructional flights I had scheduled on Tuesday were cancelled. Wednesday, the clouds cleared but the winds were blowing strong - gusts exceeding 40 knots were recorded at several major airports. Aloft, things were even crazier with pilot reports from airliners clocking 45 to 50 knot winds as low as 3000 feet.

Thursdays saw the winds decrease a bit and I did two flights: One in the morning with an instructor candidate and the other an evening flight with an instrument candidate. The winds were still blowing that morning and climbing out toward the Central Valley we ran into a couple of downdrafts where climb power and Vx (best angle of climb speed) showed a 200 foot-per-minute descent. Landings at a local non-towered airport were also interesting with a 40 degree quartering headwind at 18 knots gusting to 35 knots. Eights-on-plyons (a ground reference maneuver) were pretty interesting given the strong winds. I demonstrated one crosswind landing for my instructor candidate. As I began the roundout over the runway and removed the crab angle, I found I had nearly full left rudder applied and significant right aileron. I was prepared to go around if things got worse, but it turned out to be one the best landings I've made in a while. It reminded me of what a old instructor said to me when I was first learning to handle really strong crosswind landings: "I enjoy a good crosswind during landing - it gives me something to do."

When nightfall arrived, the wind speed had dropped significantly and the city lights around the Bay Area were twinkling in the cold, crystalline air. This flight would be Running the Gauntlet: An ILS approach, followed by one turn in a hold over a VOR, followed by a VOR alpha approach to a different airport based on the same VOR, a circle to land at the non-towered airport, culminating in a DME arc off a different VOR to intercept the intermediate approach course for an RNAV approach. My instrument candidate got his plane stabilized on the ILS and was waiting for glideslope intercept, his eyes hidden from view under his foggles.

Two miles outside the marker, in a flash, I saw the brief outlines of a flock of geese come straight over the nose and disappear over the top of the aircraft. I instinctively reached for the controls, but never really touched them. The event was over in a flash and I didn't hear the dreaded sound of an impact, so I took a deep breath and we continued on. The pilot asked me if something was the matter and I told him what I had seen. Why geese were flying at 1400 feet above ground level at night was a mystery to me, but I told the tower of our close encounter and I assume he made entered a PIREP for us. Had those geese been any lower, they would have come through the windshield and that would have been B A D.

Back on the ground, I inspected the plane with my flashlight while the owner re-fueled. I couldn't find any sign of impact or damage until I inspected the propeller. The prop was intact and undamaged, too, but on just one tip there was a smear of blood. I remembered seeing some feather or dust or something for an instant as the geese went over us. One of them must have just grazed the tip of the prop.

I'm amazed at how quickly the months, weeks and days of the 2006 have gone by. A quick review of my records shows I recommended 10 candidates for check rides in 2006: two private pilot, three commercial multiengine, two commercial single engine, one instrument, and two initial flight instructors. All but one passed on the first try. No bad considering I spent the first half of the year teaching part time while I worked full time as a freight dog. And it's sad, but I see that my income from flight instructing for 6 months was 10% more than the annual salary I had a freight dog. While no one is in aviation to make a fortune, I find it sad that professional pilots are so poorly compensated.

So as 2006 draws to a close, I'd like to wish all of you a safe and prosperous New Year.

Friday, December 22, 2006

Tiny Thread

Tuesday morning came early because of a charter flight I agreed to accept only the night before. A recently-soloed student pilot I was to fly with that morning agreed to fly on his own. As for my afternoon instructional flight, the proposed charter schedule was to have me back in the Bay Area by 1pm. I had to be at a nearby airport (read 45 minute drive) by 6:15am, get the aircraft to a Central Valley airport by 7am, and fly three passengers to the southern end of the San Joaquin Valley. As I contemplated this at 5am over my morning espresso, everything seemed to be planned to perfection. And that had me worried.

I arrived at the plane, preflighted it and found it hadn't been fueled in advance. The first, tiny bare thread had appeared, but I resolved to take this in stride. Arrived in the Central Valley with 15 minutes to spare, but the jet center ramp crew was already busy re-fueling two other aircraft and there would be a delay before they could get to us. "Don't pull on that thread!" I said to myself.

The temperatures were near freezing and as the plane sat on the ramp, water began to condense on the airframe. For this aircraft there is an Airworthiness Directive that requires a tactile touch inspection for frost in these conditions, so I borrowed the ramp crew's ladder, did the inspection, and found no frost. Finally the plane was refueled, the passengers were boarded and briefed, and I began the engine start sequence.

Turning on the avionics masters, everything appeared normal at first. Then a loud alert tone sounded and stayed on. I was baffled at first, trying to figure out what was beeping at me. No annunciators, radar altimeter was set properly ... there it is, the autopilot is showing a electric pitch trim failure. Now, how to stop the damned noise? I resolved to turn off avionics bus 1, which powers the autopilot (among other things), then turn it back on. This is the classic software engineer troubleshooting approach (or is it the cave man approach?) - start over and see if it does it again. The tone and the pitch trim failure annunciation return, so I pull the circuit breaker for the autopilot and all is quite again. Guess I'll be hand-flying the whole way. "That bare thread seems to have gotten a bit longer ..."

Finally underway, 25 minutes later than scheduled, the plane glides above the haze of an inversion layer, toward a marvelous golden sunrise. I've programmed a direct course on the GPS and the bleed air heat is finally taking the chill off the cabin temperature. At cruise altitude, I trim the plane, making allowances for a small fuel imbalance. Then I turn off the seatbelt and no-smoking signs, sit back, and enjoy the view with the thumb and fingers of my left hand gently holding the yoke.

If you have to hand-fly a plane, you couldn't ask for better flying weather. With a fingertip grip, I only need to gently push or tug on the yoke to keep the plane pointed southward. It's always amazing to me that only a few grams of pressure is required to keep the plane straight and level. I'm treating my passengers to a super-smooth flight. I turn around briefly and see them in the club seating area, talking, apparently oblivious to my efforts. "Do everything right and no one remembers, make one mistake and no one forgets." I assume they are irritated that we got a late start, then decide to just enjoy the scenery. "Perhaps that little bit of thread hanging is nothing to worry about."

As we arrive in the pattern for the non-towered field, I see that one of my passengers has come forward and he looks worried. "We don't want to land at the airport in town!" I assure him that we are not landing at the wrong airport and ask him to please be seated for landing. He looks skeptical, but goes back to his seat. I clear the power lines just south of the threshold, then grease the big bird on the runway, and taxi to the ramp. After chocking the wheels, I lower the stairway and my passengers scurry away for their meeting. Before they do, we exchange cell phone numbers, just in case, and they promise to return by noon or 12:30. I have an uneasy feeling and begin thinking about that tiny thread ...

The nearby FBO has a small comfortable lounge and there's wireless internet. Sweet! More importantly, the staff is friendly and unassuming. There's a cat sleeping on the sofa, which I find oddly comforting and homey. I check my email, then decide to contact my afternoon student and ask if we can push his lesson back an hour. He's agreeable and I'm a little more at ease with the schedule. So I sit back and delve into the Barry Maitland mystery novel I'm reading.

Around 11:30am, I decide to get the plane unlocked and ready to go. Soon it's 11:45. Then noon. Then 12:30. I consider calling my passengers, but decide it will only annoy them. I resign myself to being the hired help and I call my afternoon student to explain my predicament. He agrees to reschedule for another day and it's clear that the original schedule has now completely unraveled. There's nothing I can do and, after all, I did predict this might happen. So I climb into the cockpit and soon I'm lost again in the mystery I'm reading, having forgotten about the mystery of why my passengers are late. At 1:40pm, my passengers arrive, offer a half-hearted apology for being late, which I accept as graciously as I can, being a professional and all that. By 1:50pm we're climbing northward.

I drop my passengers off and I'm back at the aircraft's home airport by 3:30pm. By the time the plane is back in the hangar and I'm on my way, it's 4pm and the pre-holiday traffic back into the Bay Area has ratcheted up to it's usual, insane level. Threading my VW through the maze of traffic, I feel like a tiny ant inside a giant ant hill. I arrive home just as the sun has set on the shortest day of the year. I'm back home and the best laid plans that came unraveled are behind me.

Monday, December 18, 2006

The Whole Bloggin' World!

Here's a link to a Bay Area newspaper article on local blogs. Check it out. It even includes a reference to Aviation Mentor. Aw, shucks ...

Sunday, December 17, 2006

Sponging off Others

I don't often fly with pilots more experienced than myself. When I do, I go into sponge mode, carefully observing everything the pilot does and how they handle the aircraft. I may make notes afterward on what I learned. I'm often in sponge mode anytime a pilot of any ability is flying the aircraft since being a careful observer is what allows an instructor to offer constructive feedback. It also provides the opportunity to learn something you hadn't considered before. I guess I've spent the better part of my life being a sponge and learning by observing.

Though I gave up training long ago, I was a dedicated aikidoka for nearly 10 years and that was were I became aware of beginner's mind: Releasing concepts of authority and rank in order to increase your awareness and enhance your learning. At one dojo where I trained, there was one class held each week where all participants, regardless of rank, wore a white belt. Those were often the most interesting training experiences in aikido.

From the age of about 8 years onward, I was busy learning to play music, another sort of monkey see, monkey do process where you spend a lot of time observing, then mimicking behavior. And before that, I was engrossed in the primary learning process that all of us use as infants and children. To learn language and discover how the world operates, children first experience and then mimic. As we grow older and more experienced, many of us have a tendency to lose the skill to quietly observe and then mimic behavior. We can become set in our ways. We may even think we've seen it all. It doesn't have to be that way

Maybe what gets in the way is insecurity about our own identity, our concept of ourselves, our ego. After all, we live in a culture that has a high regard for the individual, at times it seems to the exclusion of almost everything else. Americans seem particularly obsessed with 1) youth, 2) fame, and 3) monetary wealth. In the face of these pressures, it takes a great deal of courage to admit you don't know something. If you make it to that point, you then must find a competent teacher, turn down the volume on your own ego, and begin trying to be a sponge. You have to give yourself over to the teacher, to trust them. Of course there's a balance to be between openness and preserving one's own identity. To borrow another saying from Eastern philosophy: A person must make themselves into the right kind of vessel - open in the right ways and closed in the right ways.

If you are a teacher who is responsible for creating a structured learning experience for students, you can't be so much of a sponge that you give up your leadership role. As a flight instructor, I still strive to recognize that there are many different ways to fly an airplane. One of the most exciting things a teacher can is experience is having a student who claims to have discovered a different technique and who can make a convincing argument for their approach. What I find convincing is a rational, considered set of reasons for doing something a certain way, backed up by practical evidence that the technique is effective, safe, doesn't violate any regulations, and isn't against the aircraft manufacturer's operating limitations. Explanations I do not find compelling include "Because I'm lazy," or "I heard someone else say it that way on the radio," or "Well, it's on the checklist."

Innovation is one of the things that made America successful. Stodginess, egoism, and fear of the unknown are antithetical to innovation and are pitfalls that all teachers and students (perhaps all of us) must avoid. So are sloth and an unwillingness to consider something new. Whether you are a student pilot, a flight instructor, a gardener, or a dentist, consider spending a few moments each week being a sponge. No matter what your endeavor is in life, beginner's mind might be your gateway to learning something new.

Monday, December 11, 2006

What You Don't Know ...

The weather this past weekend was pretty much as forecast - rainy with strong southerly winds. Three separate weather systems actually rolled through. The first system was fairly benign and just added moisture to a relatively dry atmosphere. The added moisture content allowed the second system to be a bit more vigorous. The last system that hit on Sunday was the coldest and strongest so far.

I had two multiengine instructional flights to teach on Saturday. Most of the stuff we'd planned to do was VFR maneuvering at 5000' and above. It was clear this was going to be hard to do with the ceilings were varying between 4000 and 6000 feet. So for the first lesson, we decided to go with plan B and do an IFR flight to Stockton for a couple of ILS approaches with a simulated engine failure. I had checked the NEXRAD images 10 minutes or so before departure. During the flight, we were in and out of the clouds at 5000'. The ride got particularly rough and rainy near Mt. Diablo. I found myself wishing I had on-board radar like I used to have in the Caravan. The trip back was equally rough and on two occasions we flew through solid rain showers and even picked up a trace of rime ice.

For the second flight multi-engine flight, we resolved to stay in the pattern at Oakland. It was clear the second weather system was approaching, we just didn't know how fast it was moving. With the exception of an occasional bizjet departure or arrival, we had Oakland's runway 9L traffic pattern to ourselves. The surface wind was the main reason there weren't many other aircraft - 140˚ to 150˚, 14 knots and gusting into the upper twenty knot range. The landings were challenging and we both enjoyed the challenge of doing short field landings and simulated single-engine landings with the strong crosswind. Just as we finished, rain began pelting the East Bay.

Back on terra firma that night, I found myself wondering if I could justify the cost of acquiring a hand-held GPS receiver with XM weather capability to the Minister of Finance (aka my lovely wife). I've written before about the limitations of on-board radar and XM-provided NEXRAD images, but when the weather is crappy you need all the information you can get. Since on-board radar isn't available, the best I can do right now is check the weather prior to departure, make some educated and conservative guesses about the weather conditions, and talk to flight watch once I'm airborne if things look worse than I expected. So having XM-provided NEXRAD images in flight would be much more desirable than my current situation. The $2000 plus price tag for a Garmin 396 or 496 would be a big hit on our finances and consequently a tough sell.

So I was interested to learn that Bushnell, a company I've always associated with things like scopes for hunting rifles, has announced a hand-held GPS with WAAS and XM weather capability that is set to list for about $500 when it is released sometime in February of 2007. Sure, there are other XM weather solutions for aviation (pricey PDAs, tablet PCs) and the Bushnell ONIX400CR presumably doesn't know anything about aviation waypoints, VORs, and such. But for the relatively low price, who cares? I've yet to see this unit, but it could be a reasonably-priced alternative to having a pricey Garmin unit. Since most of the aircraft I fly already have panel-mounted, IFR-certified GPS, I would use a unit like this solely for NEXRAD and satellite images.

I'm looking forward to learning more about the ONIX400CR in the coming weeks, Maybe it will come to market in time for Valentine's Day?

Friday, December 08, 2006

Dreams of Flight

Last week, I'm set to do the first flight with a CFI candidate who has been referred to me. After a notice of disapproval, he's been stalled for a couple of weeks. The Thanksgiving holiday didn't help matters, nor did a week of bad weather we had in late October. He's anxious to make some headway and anyone who's earned more than two certificates or ratings knows how many things can get in the way of a check ride. I'm sitting in the left seat, alternating between being a student pilot or an FAA inspector, as he calls Ground and asks to taxi to the longer of the two runways. It occurs to me to suggest the shorter runway is closer, but I keep my mouth shut. After an uneventful run-up, he begins teaching a soft field takeoff. His technique is very good, we're off the runway, accelerating in ground effect, then pitching up to climb, his hand is poised to remove the flaps when ... the engine sputters and quits!

After the requisite one second of astonishment, I see the palm of my left hand is pushing firmly on the yoke forward while stating the obvious "We're landing!" As the aircraft pitches forward, the engine roars to life, back from the dead. He starts to climb, or has the restoration of power simply caused the nose to pitch up? I'm no longer astonished and quickly reach forward and pull the throttle, repeating emphatically "We're landing." We touch down on the remaining runway and roll to the very end. I'm glad I kept my mouth shut and we didn't take the shorter runway - we could have ended up in the trees. Instead, no one is hurt, the plane isn't damaged, and we taxi back to parking, happy to let a mechanic sort this one out.

Monday starts with me like an expectant father. I'm always like this when I have recommended a pilot for a practical test. The check ride is scheduled to start at noon and though it's my day off, I find myself looking at my watch around 1pm. "Hmm ... no call from the DPE so all the endorsements and paperwork must have been acceptable." 3pm arrives and I wonder if the oral portion of the test is complete: "They must be in the air by now ..." 4:30pm rolls around and I'm walking my dog: "Sundown is not far off, I'll give my student a call" But it rolls over to voicemail immediately. At 5pm, my cell rings. She passed, had the usual adventure with this particular DPE, and seems astounded that the check ride is over. "Oh, he said to tell you that you did a good job." Hey, I wasn't the one flying the plane on the check ride ... Congrats Elise!

Tuesday sees a second flight with the same CFI candidate, this time in a different plane. It goes well and I suggest he call the FSDO to schedule the re-check. A few phone calls and the re-check is set for tomorrow morning! Who says the FAA doesn't offer good service on check rides? We spend several hours going through the aircraft logbooks, identifying all the airworthiness directives that affect the plane. I know the inspector won't like some of the entries in the aircraft logbooks. I try talking to the mechanic about re-doing them. I'm unsuccessful and leave with the feeling that the mechanic was just about to punch me in the mouth. "Pick you battles" I tell myself. We fill out the form 8710 and I make the requisite endorsement. "Am I ready?" he asks. "I wouldn't endorse you if you weren't." Then I jump into my car, hop on the freeway at 5pm to drive to meet another CFI to sign him off for his CFI-I knowledge test. Traffic is heavy so I call him, suggest we meet at Peet's so I can grab a mocha and a snack - a really late lunch. Next comes a night flight with an instrument candidate that both of us wish had gone better. Then it's back home for dinner and an hour to unwind before bed.

Wednesday morning starts early with a meeting with the FAA inspector to chat about my CFI candidate before his re-check. I do my best to smooth things with regard to the aircraft logbooks, and then I'm off to do an instructional flight to Truckee that had been postponed several times due to uncooperative winds aloft. This day we have very calm winds aloft, clear skies, and mild temperatures. Skimming over the Sierra Nevada, just south of Interstate 80, we cross over the Blue Canyon airport, coated with snow. Heading to the ridge that separates us from the Truckee airport, I wait for my pilot to start his descent. He starts a bit late, but with some coaching from yours truly he's able to get down and slow down. He does a great landing. On the return trip, the climb performance of this plane at 8000 to 10,500 feet is quite good - 600 to 700 feet per minute. Of course the OAT is only 5˚ C. The visibility is excellent. I glance to the north and I can see Mt. Shasta in the distance. We arrive back to find that my CFI candidate has passed the oral portion, but the inspector doesn't like the aircraft logs and has given a letter of discontinuance. This is supremely frustrating because the mechanic, if he had just changed the entries as requested, could have prevented this whole mess. My CFI candidate wants to fly again, and the only time I have is tonight ... after I complete another checkout flight in the DiamondStar. Three flights later and another 6 plus hour instructional flying day is done.

My first lesson on Thursday starts later, so I can sleep a bit later. I meet a student pilot who just completed his pre-solo phase check with another instructor. He had protested that he didn't feel ready, but the phase check went very well and I arrive this morning with a trick up my sleeve - a sticker on which I've printed his solo endorsements. We take off, go to the practice area, do some maneuvers, the head back for touch and goes as a warm-up. After two good landings, I suggest that we make the next one a full-stop, I'll get out, and he can see how the plane flies without the 180 pound windbag onboard. He agrees, I endorse his logbook and medical certificate, and after three trips around the patch, he's one of the newest student pilots in the country. I'm always amazed at the feeling of giving someone their wings, which is essentially the authority bestowed on flight instructors. Congrats Bill!

Next, I'm back on the road to meet a new commercial multi-engine student at a different airport. After much paperwork and some discussion about single-engine aerodynamics and procedures, we're off for his first flight. He does well and flies smoothly - something I wish I saw more often in pilots I instruct. He's having a blast and it fun to see him having such a good time.

I gobble down a snack, then meet my instrument student for his second flight of the week. This flight goes much, much better and I observe that he flies that way on the next flight, I'll sign him off for the check ride. During the flight, I see a light on Mt. Diablo that I've not seen before - two red flashes, then a white flash. I ask ATC if they know what it is an get an unenthusiastic "what light?" Another pilot on frequency tells me it's an old navigation beacon that was decommissioned. The beacon, a remnant of the kind that used to define the Federal Airway System, is turned on for just one night each year as a memorial for the December 7, 1941 attack on Pearl Harbor.

Friday is another early start with the commercial multi student and the weather forecast calls for rain to move into Northern California. The winds have picked up and the Bay Area airports are already on the southeast plan. We head to the northeast for maneuvers high above Travis Air Force Base with high clouds streaming in from the frontal system that is approaching. Travis Approach gives us traffic advisories but the frequency is eerily quite. We're able to get a practice GPS approach into Concord, even though they have traffic departing the opposite direction. The Concord tower controller is even friendly and cheerful - I usually find them to be uniformly cross and irritable, probably the result of less than ideal working conditions. Back at Oakland, the winds at the surface are light and variable. Above 800' AGL, things are rockin' and rollin'. We do a few touch and goes, but it's clear my student is worn out. Due to the weather, this was a short day allowing me an afternoon nap before I go to the gym.

Three lessons scheduled for tomorrow, but it's not clear the weather will cooperate.

Monday, December 04, 2006

Flying in the (Alphabet) Soup

NOTE: For a more up-to-date discussion, see Understanding RNAV Approaches.

NDBs are being phased out, GPS manufacturers are claiming that soon everyone will fly precision approaches to airports with virtually no specialized equipment on the ground, GPS approaches with vertical guidance are being created at an impressive rate, Garmin has finally certified the long-anticipated WAAS upgrade for their popular 430/530 GPS receivers, and the FAA says in the Instrument Rating Practical Test Standards that a GPS approach with vertical guidance is still considered a non-precision approach.

Yes, the aviation world has gone crazy.

If you need more evidence, look at this approach chart and you'll see three different approach minima: LPV, LNAV/VNAV, and LNAV. To understand which minima apply to the aircraft you are flying, you'll have to jump into the alphabet soup. First, here's my take on the history of RNAV which I think is relatively accurate.

Back in the late 1970's and early 80's, RNAV units (think "aRea NAVigation) like this King KNS-80 were the coolest thing since sliced bread because they allowed a pilot to create waypoints (colorfully referred to at the time as "phantom stations") based on DME distances (called Rho) and VOR radials (called Theta). And no one seemed to mind much that using these units often required a lot of button pushing and knob twisting. And as reliable and affordable Rho-theta navigational systems became available, the FAA began developing approach procedures for these units called RNAV approaches.

In large, expensive aircraft, multi-sensor Flight Management Systems (FMS) became widespread. These FMS utilized a variety of ground-based navigation aids, combined with inertial reference units, to provide seamless and accurate navigation.

When IFR-certified GPS units came along and the FAA began creating GPS approaches, they were worried about reliability. So they created GPS approaches that overlaid existing VOR or NDB approaches and required the pilot to have the other navigational equipment on board and to monitor that equipment during a GPS approach. Gradually the FAA became convinced that GPS was maybe pretty good, they no longer required the pilot to monitor the other navigation systems, and they even created (gasp!) stand-alone GPS approaches where GPS was the primary means of navigation.

I won't even go into LORAN, a land-based radio navigation system that seemed to fall out of favor for air navigation quicker than you can say "decommissioned NDB." And as FMS and IFR-certified GPS units became widespread, the FAA decided that it needed a broader category that would contain Rho-theta systems, FMS, and GPS. Rather than come up with a new term, the existing term RNAV was redefined to include them all.

To accommodate both FMS and GPS-equipped aircraft, approaches started being created with titles like RNAV (GPS) RWY 31. In some cases, there was more than one version of an RNAV (GPS) approach to the same runway and the title had to have a suffix added like Z or Y added to the end to get around the limitation in many FMS databases that precluded more than one approach having the same name.

ICAO standards began to be formed for Required Navigational Performance (RNP) to describe the accuracy required of air navigational systems for different phases of flight. Recently, RNP approaches have been created for specially authorized aircraft and flight crews that combine curved approach and departure paths with reduced obstruction clearance that some might call spine-tingling. And in classic, confusing fashion, the term RNP, initially developed to describe the accuracy of navigational systems, was appropriated as an approach classification, too.

The nice thing about standards is that there are so many of them.

So where are we today? RNAV includes any IFR-certified GPS, multi-sensor FMS (many include GPS in the array of navigational sensors), or approved Rho/Theta unit (like the now ancient KNS-80). I won't go into which equipment suffix you add to your aircraft because that depends or whether or not your aircraft meets the new Reduced Vertical Separation Minima standards. We now have RNP approaches (requiring special aircraft and aircrew training and certification), RNAV (GPS) approaches that can be flown with an IFR-certified GPS or the appropriate FMS, standalone GPS approaches, GPS overlay approaches (with titles like VOR or GPS A), and all the standard VOR, ILS, LOC and NDB approaches. Eventually, all standalone GPS approaches with names like GPS RWY XX will be renamed RNAV (GPS) RWY XX. So now that it's established, at least for now, what RNAV means, take a look at the different minima on RNAV (GPS) approaches.

For aircraft with older IFR GPS units certificated under TSO C129A1 (not WAAS-enabled), you're stuck with LNAV - lateral navigation - minima. This means you'll fly a non-precision approach with a Minimum Descent Altitude (MDA) and a visibility restriction. In the U.S., visibility ultimately determines whether or not you can legally descend below the MDA and land. If you have a GPS certificated under TSO C145A or C146A (WAAS-enabled), you can use the LNAV, LNAV/VNAV, or the LPV minima. In case you're wondering, LPV (according to the Aeronautical Information Manual's glossary of terms) stands for "Localizer Precision with Vertical guidance." There is also the acronym APV - which seems to be a broader category - Approach with Vertical Guidance. Interestingly, the FAA's Instrument Procedures Handbook says that LPV is not an acronym - our tax dollars at work! Anyway, the topic at hand is knowing which set of minima to use.

Since I have yet to fly an aircraft with a GPS unit certified under TSO C145A or C146A (aka WAAS-enabled), I have been reading the new manual for the Garmin 530W (WAAS-enabled) and it contains some enlightening details. Using the 530W, you load the KSLE RNAV (GPS) approach just as you would any other GPS approach, specifying the Initial Approach Fix you wish to use to transition to the approach or the Vectors-to-Final option if ATC is guiding you to the intermediate approach course.

Two miles from the Final Approach Fix (LOTKE), the CDI sensitivity will begin to change from TERMINAL mode (full scale CDI deflection representing 1.0 nautical miles) to an angular course width of 2˚ or the width specified for the approach. Sixty seconds from LOTKE, the receiver will check the Horizontal Arm Limit (HAL) and Vertical Arm Limit (VAL) to determine if there is sufficient GPS course integrity to perform the LPV approach. If there is sufficient integrity, you'll see the TERM annunciation in the lower left of the 530's display change to LPV and that, along with a glide slope indication on your CDI or HSI, is your cue to use LPV minima. You should intercept the LPV glideslope just as you would an ILS glideslope and descend to the Decision Height shown on the chart before landing or executing the missed approach procedure.

If there isn't enough course integrity to provide an LPV approach (did you check GPS NOTAMs prior to takeoff?), the annunciation will change to LNAV and you'll see a message "Approach downgraded - use the LNAV minima." The Garmin manual refers to an LPV approach as a "precision approach" in spite of the fact the FAA currently still considers an LPV approach to be a non-precision approach. And if the course integrity isn't sufficient for an LNAV approach, you'll see a message telling you to abort the approach, the annunciation will change to TERM sensitivity, and you should climb, fly to the Missed Approach Point, and then execute the missed approach procedure.

Since you might not know which set of approach minima will apply to your approach, how do you request the approach? The FAA's Instrument Procedures Handbook says that if the approach has a title like "OAK RNAV (GPS) RWY 27R", you should tell ATC "request the Oakland RNAV 27 Right approach." Yet when I've done this, the NORCAL controllers seem a bit confused and ultimately clear me for the "Oakland GPS 27 Right approach." The bottom line is that as far as ATC is concerned, you are flying an RNAV approach. It's up to you to fly the appropriate minima.

While it strikes me as an odd design choice to have a GPS receiver that doesn't know which type of approach you will be flying until 60 seconds before the final approach fix, I like the fact that this emphasizes something many pilots fail to grasp: GPS is not infallible. An unwelcome increase in workload for GA single-pilot IFR comes from having to brief more than one set of approach minima, depending on the GPS receiver's performance. Crossing the FAF is not the right time to throw the pilot a curve, but there's more, unfortunately. Here's a quote from the Garmin GNS530W Pilot Guide and Reference:
GPS approaches with vertical guidance may be either LNAV/VNAV or LNAV approaches with advisory vertical guidance. LNAV-only approaches with advisory guidance only have LNAV minima listed on the bottom of the approach plate. The glidepath is typically denoted by a light dashed line on the vertical profile (Jeppesen only) with an associated glidepath angle (usually in the 3.00˚ range). These approaches are indicated with "LNAV/+V".

For approaches with LNAV/VNAV minimums, those will be controlling. For LNAV approaches with advisory vertical guidance, the LNAV minimums will be controlling. Approaches confirmed as "LNAV/VNAV" approaches in the Jeppesen NavData are indicated with an "L/VNAV" annunciation. At the time of this publication, not all of the LNAV/VNAV approaches have been identified as such in the Jeppesen NavData, therefore some LNAV/VNAV approaches may still be identified with "LNAV/+V" annunciation.

You can download newer versions of the Garmin 430 and 530 PC simulators that have updated databases (spring of 2006), but they don't appear to let you experiment with any of the LPV or LNAV/VNAV behavior. Oh, and on my PC the simulator constantly displays a message that the GPS processor needs servicing.

If you've waded through all this mess, let me offer my last observations. Designing instrument approach and departure procedures has become increasingly complicated. While new technology promises to make instrument flying safer, it's not clear to me that this is actually happening. A pilot's job in the cockpit has become a morass of details and minutiae. Many of the systems pilots are being forced to use seem to have been designed by people who like puzzles and who are probably not pilots themselves. So if you are an instrument-rated GA pilot who flies single-pilot IFR, your work could end up being more complicated than ever. The more things change, the more they stay the same, I guess.