Thursday, April 30, 2009

iPhone EFB

Shortly after recently reviewing iPhone aviation apps, I learned of another cool app called SkyCharts that lets you view VFR sectionals, Airport/Facility Directory information, and Terminal Procedures (STARs, SIDs, and approaches) on your iPhone. If that sounds boring or similar to other apps, bear with me because at US$9.99, SkyCharts offers some surprisingly useful and powerful features.

The iPhone's screen is admittedly small and any images it displays are going to be of limited use - especially if your eyes are over 50 years of age! You wouldn't want to do something crazy like not carry paper versions of your charts and rely on your iPhone, would you? Still, the iPhone could be considered an Off-The-Shelf device that, on the surface at least, would meet the requirements of a class 1 Electronic Flight Bag per Advisory Circular 91-78. But there's the problem of the iPhone also being a cellphone ...

When you first launch SkyCharts, you'll see a splash screen for a few seconds, then the app asks permission to use your current location. Many iPhone apps do this, so I just said yes. The app also asks permission to do an initial update and warns you it could take awhile. For me, the update process took less than a couple of minutes, but I was connected to my WiFi network at home. I've not tried doing the update with 3G or Edge connectivity.

Please ensure all electronic devices ...

You'll also see a disclaimer message that you must acknowledge and this bears some in-depth consideration.

Some people may be routinely using their cellphones while airborne in GA aircraft, but it's not legal. The FAA may not care, as long as you are VFR or have determined that the phone will not interfere with your IFR 14 CFR 91 operation, but the FCC does care. The regulation, 47 CFR 22.295, is pretty clear: It doesn't just say that you can't make any calls, it says that cellphones have to be turned off.

While it is possible to put an iPhone into airplane mode, which turns off the cellphone component, airplane mode also turns off the GPS receiver. It would be nice if Apple would provide a way to turn the phone and Bluetooth off, but leave the GPS alive. We can but hope ...

Assuming the iPhone could allow the phone component to be switched off and the GPS receiver to remain active, this brings up the question of whether or not an iPhone's GPS receiver can be used while airborne. My research (and personal experience) indicates that using a non-aviation handheld GPS receiver on board an airliner is not a problem. Every time I have asked, I've been told it's fine once the cabin crew announces it is permissible to use approved electronic devices. Some people claim the TSA doesn't allow handheld GPS units on airliners, but I've never seen this substantiated by any regulation or rule.

Here's a video of SkyCharts in action (not posted by me). Apparently this iPhone is not in airplane mode as it shows the aircraft's approximate position, georeferenced on the moving map. I'm told that jail-breaking an iPhone may allow you to have airplane mode with the GPS still active.

Where you at?

With the iPhone in airplane mode, SkyCharts still allows you to drag and zoom the chart using the usual iPhone gestures. And by double-tapping on an airport, you can access the A/FD entry or the terminal procedures for that airport. Assuming you initially launch SkyCharts with the iPhone's airplane mode turned off (GPS active), the app will cache the appropriate VFR sectional for your current location along with the related A/FD entires and terminal procedures.

Here's a portion of the San Francisco VFR Sectional showing the greater Sacramento Metropolitan area in landscape view. Sectional charts can be viewed in portrait or landscape view, but the A/FD and terminal procedures can currently only be viewed in portrait mode. I tried double-tapping on KSAC while in landscape view and I just got a pop-up telling me the latitude and longitude. In portrait view, double-tapping showed all the A/FD and TPP data available for KSAC.

The D-> button on the lower left side of the chart view allows you to switch your view to a particular airport. Given the ambiguity in the US between VOR and airport IDs, I'd like to see SkyCharts support 4-character ICAO-style airport identifiers, but that's nitpicking. After entering the 3-character identifier for Telluride, Colorado, I got my choice of displaying the sectional chart, the A/FD (this option includes terminal procedures) or simply calling the airport's ASOS.

Cache Me if You Can

If you want to cache more charts, press the Information icon on the lower right side of the chart view. You can select any of the VFR sectionals for the continental US (support for Hawaii and Alaska are slated for a future release). Given the amount of data for each sectional, caching is best done while connected to a WiFi network rather than over a 3G or Edge connection.

Once you have cached the data you want, SkyCharts is still quite useful in the air with airplane mode turned on. Sure, you lose the georeferenced position on the chart, but you have easy, fingertip access to a lot of data.

Airport data has been available in Avidyne and Garmin panel mount units for some time, but that data has some serious limits. I've always been amazed that simple, important stuff just isn't there, like the traffic pattern altitude, whether the runways are left or right pattern, and details on noise abatement procedures. This is where SkyCharts provides a big advantage: You have the A/FD entry for any airport in your area (or in the continental US) at your fingertips.

The developer of SkyCharts has a lot of updates planned and support seems to be very responsive. I'd like to see support for displaying A/FD entries in landscape mode, which would make them much more readable and useful. I'd also like to see support for low-altitude en route IFR charts, but I hope that future releases remain true to the app's name. It's really about charts and adding too many extraneous features could actually make this cool app a little less appealing, to me at least.

I found SkyCharts to be useful and certainly worth the price. Heck, it's fun to just sit in a comfy chair with your iPhone on a rainy day, scroll around the US, daydream about future trips, or just call up approach charts for far-flung airports. Check it out!

Friday, April 24, 2009

Your Pal George

Research into human multi-tasking, especially an often-cited study by Carnegie Mellon University, has shown that there are significant neurological costs associated with switching between multiple tasks, something that happens a lot in single-pilot instrument flying. For example, when subjects in the CMU study were told to imagine rotating an object while listening to complex sentences, their performance on both tasks dropped significantly. Guess that helps explain why pilots flying single-pilot IFR miss so many radio calls from ATC and why long periods of hand-flying can be so tiring. Trying to multi-task does not make us stupid per se, but it does reduce our performance.

Most newer GA aircraft are equipped with autopilots and this is a good trend. I can't think of one instrument instructor I've spoken to who doesn't believe a functioning autopilot to be a critical safety factor in single-pilot flying. Effective use of an autopilot might not make you a smarter, but it can improve your performance, reduce fatigue, and keep you from doing something stupid.

It's common for me to encounter pilots who have never been trained in the use of autopilots and lack system-level knowledge. Some pilots may even have been taught, or they subscribe to the notion, that using the autopilot is cheating. I believe that autopilot knowledge is important, so even student pilots who train with me in autopilot-equipped aircraft must to demonstrate competence in using George (a common monicker for the autopilot). Of course they also need to demonstrate stick-and-rudder hand-flying skills, too.

Consider the recent events in Florida where a low-time private pilot had to take control of a King Air B200 after the pilot became incapacitated and then died. One of the first issues facing the pilot was how to wrest control of the aircraft from the autopilot. You never know when an understanding of autopilot flying could come in handy!

Before George can be your buddy, you must understand him and a good way to start is to read the documentation for your particular aircraft. A/P information is usually found in your aircraft's Approved Flight Manual in the Supplements section. Since this section is toward the back of the AFM, pilots seem to never get to reading this important stuff. Once you've found the supplement, you'll see that it follows the same GAMA format that is used in most AFM - Limitations, Emergency Procedures, Normal Procedures, System Description, Performance, and so on. Reading the supplement can help you avoid these common A/P mistakes.
  • Failing to know or respect the A/P limitations
  • Lack of system-level knowledge
  • Not understanding the modes of operation
  • Trial-and-error button pushing
  • Failing to recognize undesired or uncommanded mode changes
Know George's Limits

The Limitations section of the autopilot supplement usually contains the following limits. Your autopilot may list other limits, too.
  • Minimum altitude for engaging after takeoff
  • Minimum and maximum airspeeds with the A/P engaged
  • Maximum flap configuration with the A/P engaged
  • Minimum altitude for flying precision and non-precision approaches
  • A/P use in airframe icing conditions
I frequently encounter pilots who don't know or respect the altitude limitations for their autopilot. These altitude limitation are based, in part, on the maximum predicted altitude loss that could occur should the autopilot malfunction. Knowing these numbers are critical and could save you should your autopilot malfunction at the end of an instrument approach down to minima.

Trust, but Verify

Most manufacturer's documentation will state that the A/P may not be used in flight unless it was first tested on the ground prior to flight. Don't confuse this preflight functional test with the system self-test that many units will perform when they are powered on or that you initiate by pressing a TEST button. Many manufacturers' checklists don't include the numerous steps for the autopilot functional test in their normal checklist, so use the procedure found in the supplement.

The preflight test usually includes engaging the autopilot, verifying resistance on the pitch and roll axes, engaging the heading and navigation functions and verifying that the roll inputs are correct. The last step is to disengage George, so you may as well test the A/P prior to verifying the flight controls are free and correct. The actual test procedure varies by model of autopilot, so always use the manufacturer's procedure for your particular unit. For convenience, some pilots create their own aircraft checklist that includes the manufacturer's A/P preflight test.

If the autopilot fails the pre-flight test, don't use it in flight! What's more, you should disable the autopilot (usually by pulling and wire-wrapping the circuit breaker), placard the autopilot as inoperative, and make a maintenance log entry per 14 CFR 91.213. You should also consider the added risk of a single-pilot IFR flight with an inoperative autopilot. A long flight in IMC without an autopilot may entail risks you're not willing to take.

Ain't Misbehavin'

To use an A/P effectively, you must understand what equipment provides pitch and roll inputs to your particular autopilot. For example, the King KAP140, popular in Cessna aircraft, receives roll input from an electrically-driven turn coordinator. Two-axis KAP 140 autopilots sense changes in pitch with an accelerometer and through static pressure changes via a dedicated pitot system. The autopilot/flight director in the Caravans I used to fly receive pitch and roll inputs from a special attitude indicator (called an attitude deviation indicator) that was often vacuum-driven. Once you understand how your A/P senses pitch and roll, you'll be better prepared to know when George is sick and not to be trusted.

If George malfunctions, and malfunctions are quite possible, you'll need to know all the ways to disengage him. A disconnect button (often red in color) is usually provided on the left yoke and many A/Ps will provide an aural alarm when the autopilot disengages. Pilots not used to autopilots often mistake the disconnect button for the communication radio's push-to-talk button. Some A/P systems (like the KAP 140) will disconnect if the pilot uses the electric trim switch. Pulling the A/P circuit breaker may be your last resort if George is being disagreeable and won't disengage in the normal fashion. Again, let the manufacturer's documentation for your particular autopilot be your guide.

The State You're In

Autopilots usually have a variety modes of operation for roll and pitch control. Lateral (roll) modes include simply holding the wings level, following the heading bug on the HSI or heading indicator, or intercepting and tracking a navigation source.

Vertical (pitch) modes are provided in two-axis A/Ps and include maintaining altitude, climbing or descending at a particular rate or airspeed, and tracking a vertical navigation source (ILS glideslope or GPS glidepath or vertical path). Some A/Ps will allow you to specify an altitude to capture when climbing or descending. You may also be able to specify the vertical speed (feet per minute) or airspeed (in knots) you want the autopilot to maintain in the climb or descent. Light GA aircraft A/Ps don't (yet) control engine power, so you'll need to manage the throttle yourself.

The adage "Garbage in, garbage out" applies to autopilots: You can command George to enter a climb or a descent that may exceed the capabilities of your aircraft or cause you to enter a stall. Remember that while George may be controlling the plane, you are pilot in command. Never let George take you in any direction or into any flight condition you don't want to go.

Most autopilots will display the current lateral and vertical modes as well as any modes that are armed. For example, many autopilots allow you to engage heading mode, set the heading bug to an intercept for a VOR or GPS course, and then arm NAV (navigation) mode. As the selected navigation course comes alive, the A/P will switch to NAV mode and track the desired navigational course (VOR, localizer, or GPS).

Many autopilots (but not all) will not only track a localizer course, they will also descend on a glideslope for an ILS. The recommended procedure for engaging this approach mode is usually to start out in NAV mode, with the A/P tracking the localizer. Command the A/P to descend to the published glideslope intercept altitude at the appropriate time and capture that altitude. Then arm the approach mode and you should see an indication that the glideslope is armed. As the glideslope is intercepted from below, the autopilot will pitch down to track the glideslope. You'll need to manage the power and be ready to disconnect the A/P at or slightly before the decision height.

It's critical that you read the display before you start impulsively pushing buttons. This is by far the most common error I see pilots make. Trial and error is not a productive activity to be engaged in during a high-workload phase of flight close to the ground and it usually belies a lack of understanding of basic autopilot functions and modes.

The KAP 140 display, for example, shows the selected modes in the top half of the A/P display and any modes that are armed are shown in the lower half of the display. Here's the KAP 140 set to maintain altitude (ALT), track the heading bug (HDG), and intercept the current navigation course (NAV ARM).

The G1000 with the GFC 700 autopilot displays its mode information right above the attitude indicator on the primary flight display. Here's the GFC 700 set to intercept the a localizer and descend to 3,300 feet. The active modes are displayed in green and the armed modes in white. The lateral navigation, shown on the left side, is heading mode (HDG shown in green) with the NAV mode armed to capture the localizer (shown as LOC in white). The center field shows the A/P is active (AP in green). The vertical navigation mode is vertical speed (VS shown in green) with a 300 foot per minute descent rate to capture the selected altitude of 3,300 feet (shown as ALTS in white).

Here's the GFC 700 tracking the localizer and the glideslope.

Given all the possible combinations of autopilot modes, I recommend pilots receive training and then do some VFR practice before relying on the autopilot in instrument conditions. You'll need to regularly practice your autopilot skills to stay sharp, but you need to maintain your hand-flying skills, too. A G1000 simulator or PC-based trainer are great ways to accomplish autopilot training.

Letting George Help

Pilots often complain that using the autopilot isn't real flying, but it's really just another type of flying. To maintain proficiency, you'll need to practice both hand-flying and autopilot flying regularly. Successful A/P use depends on good systems management and a good manager knows when to delegate. You shouldn't hesitate to let George fly the plane during high-workload phases of flight, such as:
  • Flying in complex airspace with lots of traffic
  • Flying a complex departure procedure
  • While evaluating XM weather displays or radar returns
  • While copying a complicated clearance or holding instruction
  • While briefing an instrument approach or STAR (Standard Terminal ARrival)
  • When being vectored to an approach
  • Flying an approach close to minima
  • Flying an approach when you are fatigued
  • Flying the missed approach (above the minimum altitude for A/P engagement)
  • While performing an abnormal or emergency check list
It's a Wrap

Newer autopilots have brought the flight director concept to light GA aircraft. The flight director (FD) displays command bars on the attitude indicator providing visual clues to the flight control inputs you need to make. It can be harder to recognize that something is wrong when the FD alone is being used because you're busy flying the plane and following the command bars - remember that study on multi-tasking and performance? So do your best to divide your attention and make sure the pitch and roll suggestions made by the FD are what you intended. If they aren't, it's best to disengage the FD, hand-fly, and re-engage the FD or AP when you've figured out what was set incorrectly.

If you fly an autopilot-equipped aircraft, become proficient with it's operation. Read the manual, get some instruction, and be sure to practice both hand-flying and managing the autopilot. And remember that being proficient in autopilot management isn't cheating, it's often the smart thing to do.

Saturday, April 18, 2009

Understanding RNAV approaches

While perusing the searches people use to find my blog, I often notice that many are looking for information on RNAV approaches. My earlier posts on this topic were done using examples from a PC simulator when LPV approaches were first becoming available. Now that the number of LPV approaches outnumber the ILS approaches available and I've flown hundreds of different RNAV approaches, it's clearly time to revisit this complex and popular topic. So here's practical information on RNAV approach design, naming conventions, the different approach minima that you might encounter, the types of vertical guidance that may be offered, how ATC will get you established on the approach, and some pre-flight planning considerations.

*** Note: After reading this, you may want to check out a more recent post on Radius-to-Fix legs >>>

Tomaeto, Tomahto

RNAV stands for aRea NAVigation and encompasses a variety of aircraft equipment described in U.S Terminal and En Route Area Navigation (RNAV) Operations. Appropriately certified GPS units are considered RNAV as are many Flight Management Systems. Older VOR/DME RNAV units are also consider RNAV units, but in a much more limited way. In simplest terms, an IFR-certified GPS unit is most often the straw that stirs the RNAV drink for most GA aircraft.

For RNAV-equipped aircraft, it's easy for a pilot to navigate directly to a VOR, NDB, intersection, or approach waypoint. That's why RNAV approaches are often designed with a Terminal Arrival Area or TAA (not to be confused with a Technically-Advanced Aircraft). The TAA is a T-, Y- or L-shaped arrangement of Initial Approach waypoints designed to simplify the interaction between ATC and the pilot. A good, detailed description can be found in the Aeronautical Information Manual section 5-4-5(d).

What's in a Name?

Any approach title items contained in parenthesis are omitted when referring to the approach, so both the pilot and ATC would refer to the approach shown below as the "RNAV Runway 12 approach" - GPS is left out because it appears in parenthesis. A stand-alone GPS approach, like the Rio Vista GPS RWY 25 approach would be called a GPS approach. Confusing? Yeah, but supposedly all GPS approaches are eventually going to be renamed to RNAV approaches, it will just take some time.

If you desire an RNAV approach, think like a controller and include your approach request when you check in. Controllers usually appreciate this as it is unambiguous and it saves time.
Santa Barbara approach, Barnburner 123, 7000, request Santa Maria RNAV 12, direct WINCH, with information Foxtrot.
Some RNAV approaches contain "RNP" in parenthesis, which stands for Required Navigational Performance. These SAAAR (Special Aircraft & Aircrew Authorization Required) approaches are not available to us mere mortals.

Some RNAV approaches contain the letter Z or Y and the reason is simple: FMS databases can't handle two approaches to the same runway using the same navigational system, so the letters Z or Y are added to prevent ambiguity. Some kludge, eh? The deal is this: RNAV Z approaches usually provide lower approach minima (typically LPV) than RNAV Y (typically LNAV and LNAV/VNAV) approaches, but sometimes the opposite is true. More on approach minima later.

So what approaches can you fly with an old VOR/DME RNAV unit like the venerable King KNS80? The only RNAV approaches you can fly with these units are the ones named
"VOR/DME RNAV ..." There are 60 to 70 of these approaches in the US, like the UKI VOR/DME RNAV or GPS-B approach. Someone could write a master's thesis on the details behind the naming of that approach!

Cleared Direct ...

A controller will typically clear you to the nearest IAF and then provide an approach clearance. The pilot loads the RNAV approach with the IAF transition specified by the controller, activates the approach, and then follows the guidance to each of the waypoints in the sequence that make up the approach. Consider the Santa Maria RNAV (GPS) RWY 12 approach.

There are three IAFs: OVMAF, WINCH, and LILWU. ATC will usually clear you to the IAF nearest to your position. If you are approaching from the Southeast, "direct WINCH" would be a safe bet and you'd need to fly the HILO (hold in-lieu of a procedure turn) to reverse course. The transitions from OVMAF and LILWU all say "No PT" and you should not fly the HILO without ATC's permission (see 14 CFR 91.175(j) Limitation on Procedure Turns).

Many pilots I've spoken to are confused by TAAs that have a 90 degree turn from the Initial Approach segment to the Intermediate Approach segment. Relax because GPS units provide turn anticipation and the TAA waypoints are fly-by waypoints (you're not required fly right over them). The GPS knows your ground speed, actual track, and the number of degrees of turn required, so just pay attention to your GPS, start the turn when it tells you to turn, and you should end up right on intermediate approach course.

*** Edited 4/22/09, based on NTC comments ***
What about the Vectors-To-Final option for loading an approach? Use it with caution because ATC is restricted from clearing you direct to any waypoint inside the Intermediate Fix (IF) or vectoring you any closer than 3 miles from the FAF on an RNAV approach. Not that this hasn't stopped some controllers from doing otherwise. Vectors-To-Final will only display the the FAF and MAP and I'm not sure why Garmin units even provide you this option for RNAV approaches. I guess it could be useful in an emergency, but not in normal operations.

Many GPS units also contain VOR receivers so ensure that your HSI or CDI is displaying the GPS course. Otherwise you might get confused when the course doesn't come alive and ATC starts asking you what the heck you are doing.

When to Descend?

The Santa Maria RNAV (GPS) RWY 12 approach depicts the Minimum Safe Altitude in sectors based on the waypoints WINCH and LIWLU, but many RNAV approaches have a conventional MSA depiction. Nice of the FAA to keep it simple, eh? You reference the MSA altitudes like the one depicted on the Santa Maria approach once you're cleared for the approach without any altitude restriction from ATC.

Let's say you're approaching from the Northwest and Santa Barbara approach clears you direct WINCH. You load the approach with WINCH as the transition and activate the approach. Your GPS may then ask you if you want to load the hold and you say ... wait for it ... NO!

Your GPS says the desired track to WINCH is 142 degrees and ATC clears you for the approach. You are at 7000 feet and 9 miles from WINCH, so you can descend to 5500 feet. Once you are within 6 miles of WINCH, you can descend to 3300 feet. Passing WINCH, follow the altitudes listed on the profile view of the approach chart. Simple, once you understand the conventions.

The "How Low?" Lowdown

RNAV approach charts may have as many as four different types of approach minima (ceiling and visibility) and this is probably the thing than confuses most pilots who are new to RNAV approaches. The possible minima are labeled:
  • LNAV - lateral navigation only, no descent guidance
  • LNAV/VNAV - lateral navigation with advisory descent guidance
  • LPV - Localizer Performance with Vertical guidance
  • CIRCLING - when straight-in minima are not published or circling is desired.
If your GPS is non-WAAS (TSO C129), then life is pretty simple: You only get LNAV minima and you fly the approach like any other non-precision approach, descending as indicated on the profile view of the approach chart. A good practice is to perform a RAIM check on a TSO C129 unit prior to departure and again prior to reaching the IAF.

If you have a WAAS GPS unit (TSO C145 or 146) you can skip the RAIM check, but you should check for WAAS outage NOTAMs for your destination as part of your preflight briefing. With a WAAS unit, the approach chart minima you will use will depend on the course sensitivity the GPS unit displays when your are flying the approach, a few miles outside the FAF. This course sensitivity depends on the WAAS signal integrity and may vary from day to day and hour to hour.

When you activate the approach, your WAAS unit will probably display TERM sensitivity - a full-scale deflection of the course needle (left or right) represents a 1 mile displacement (left or right) from the desired track.

Somewhere before the FAF, usually at the last intermediate fix before the FAF, the sensitivity will change to either LNAV, LNAV+V, L/VNAV, or LPV. (Some approaches list GLS minima as N/A, but this is just a placeholder, it will be replaced eventually with LPV.)

LNAV+V, L/VNAV, or LPV course sensitivities all offer basically a 0.3 mile full-scale deviation and they also provide vertical guidance, but there are crucial differences between the type of vertical guidance provided.

Anytime vertical guidance is provided, be aware that the glidepath may be provided all the way to the surface. Therefore the pilot must ensure they (or the autopilot) do not descend below the MDA or DA appropriate for the course sensitivity displayed by their GPS unless the appropriate visual references described in 14 CFR 91.175 are present.

Advisory Guidance

LNAV+V provides only advisory guidance and this is considered a non-precision approach: You need to ensure you do not descend below any step-down altitude listed on the approach chart's profile view. You may see LNAV+V on some RNAV approach charts that only have LNAV minima, but you may also see it on an RNAV approach where the required signal integrity for LPV is unavailable. RNAV approaches with only circling minima and with an approach course that is more than 30 degrees out of alignment with any runway will not display advisory guidance. The advisory vertical guidance should be a constant glide angle required to get you to MDA a bit before the missed approach point. If you are an adherent to the "dive and drive" style of non-precision approach flying (I am not, by the way), then you can ignore the advisory guidance all together and fly a less-than-stabilized approach.


This sensitivity is Garmin's way of telling you that this is an Approach with Vertical Guidance (APV): If you follow the glidepath and the lateral guidance to the Decision Altitude, you won't hit anything. I suspect Garmin chose L/VNAV because 1) they didn't have enough characters available to display LNAV/VNAV and 2) they wanted it to be distinguishable from LNAV/+V. Find that confusing? You're not alone!

L/VNAV vertical guidance is provided all the way to the surface. Therefore the pilot must ensure they (or the autopilot) do not descend below the DA unless the appropriate visual references described in 14 CFR 91.175 are present.


This sensitivity is also to a Decision Altitude and is considered an Approach with Vertical Guidance (APV). The LPV approach provides lateral and vertical guidance similar to an ILS, but usually to a DA no lower than 250 HAT and no less than 1/2 mile visibility.

LPV sensitivity will be annunciated at the last fix before the final approach fix. On the Oakland RNAV (GPS) RWY 27L, this is also where the glidepath will begin being displayed on most GPS units. Interestingly, glidepath intercept is depicted on this chart's profile view at the FAF. For an ILS, the makes sense because of the physical construction and limitations of the ILS. RNAV glidepaths don't have these limitations, so I don't see any risk in following the LPV glidepath as soon as it appears. Just verify your altitudes at each waypoint.

Glidepath to Where?

Pilots have asked me if the glidepath provided for L/VNAV or LPV approaches, like an ILS glideslope, would take them to the touchdown zone. I'm not certain, but my understanding is that the glidepath (or glideslope) for CAT I approaches takes the aircraft to a Threshold Crossing Height (TCH). Look at any RNAV approach chart that provides LNAV/VNAV or LPV minima and you should find that a glideslope angle and TCH are listed, just as you'd find for an ILS.

In order to Serve you Better

If you see an error message saying that the GPS is unusable while flying an RNAV approach and still outside the FAF, you need to execute the missed approach. If this happens inside the FAF, the regulations say you can continue the approach. The only way I'd continue is if I already had the required visual references or some sort of emergency.

When planning to fly an RNAV Z approach, you'd best have the RNAV Y version of the approach handy, too. If the required WAAS signal integrity is not available, your GPS may inform you that the approach has been downgraded and that you should use the LNAV minima - those minima won't be shown on your RNAV Y approach chart, but on the RNAV Z approach chart. Nice curveball, huh?

Absence Makes the Pilot Go Missed

You loaded and activated the approach correctly, you identified the correct minima to use, you got to the MDA or DA and you don't see the required visual references. It's time for the missed approach and all IFR-certified GPS units (except older GNS480) will suspend waypoint sequencing at the MAP. You'll need to press a button (and perhaps set a new desired track on your CDI) to start navigating on the missed approach segment. For most Garmin units, you press the OBS button or softkey. For many King units, you press the Direct button.

Too Complex?

Many a pilot has complained to me that RNAV approaches are just too complex. I agree. I think the approach designers and the RNAV avionics designers have created their own treehouse with some pretty complex rules, dependencies, and exceptions. The pilot guides for these products try to describe these operational subtleties, but this is some complex @#%& for single-pilot IFR.

If you've made it this far, congratulations: It's a rare instrument pilot who can stomach this much minutiae. If there's something I forgot to cover, email me or post a comment. And lastly, this post took a fair amount of time to craft. If you found it useful, please click on the donate button on the upper right corner of this page. The amount you donate is up to you, but every little bit helps.

Thursday, April 16, 2009

Quick Look: G1000 PC Trainer V9.03

Here's a quick review of Garmin's new G1000 PC trainer Cessna Nav III version 9.03 with Synthetic , albeit a bit later than promised. I ordered this software over a week ago, but Garmin sent me the old version. After sleuthing around on the Garmin website, I uncovered a support phone number and explained the problem. The correct version was on the way, but that would take a few more days. So a friend loaned me his CD (he got the correct version on the first try) and I installed it on both my PC and my MacBook under VMWare Fusion. Both installations are running Windows XP. The next day, my CD arrived.

The G1000 PC trainer can be launched in one of two ways: As a single window (either MFD or PFD) or in a dual-screen mode. This new version seems to launch more quickly on both my PC and under latest version of VMWare Fusion. One change in version 9.03 is that reversionary mode seems to be automatically selected in the single-screen mode. I checked the pull-down menu and reversionary mode was not selected, so I tried cycling it on and off. No change. This was not the behavior in the previous version of the PC trainer.

So I exited the application and launched the dual-screen version. Since my PC has two graphics cards and two monitors, I positioned the PDF on one screen and the MFD on the other. Powering on the PFD, it looks the same as earlier version for the first few seconds. Then the SV kicks in. Here's I've positioned the aircraft just south of Mount Diablo, near SALAD intersection.

Below, notice the autopilot is activated which displays the magenta command bars and the yellow airplane symbol. With SV, an additional green Flight Path Marker is displayed at ground speeds above 30 knots as is a white horizon line. The FPM depicts the approximate projected path of the aircraft, accounting for wind speed and direction. Point the FPM where you want to go and the plane will go there, within the limits of the aircraft and the laws of physics. In this shot, I've pointed the FPM at the radio tower on top of Mt. Diablo. The FPM seemed pretty accurate and I got terrain warnings as I got closer to the tower, but you gotta admit the PFD display is getting pretty crowded. And we haven't even added pathways to the mix.

In classic Garmin fashion, the SV options are buried - you access then by pressing the PFD softkey on the PFD (hey, it's their terminology, not mine!). Next press the SV softkey and you'll see four options: SYN TERR - toggle SV on and off, PATHWAY - toggles on the 3D perspective of desired route, HRZN HDG - toggles the display of heading along the horizon, APTSIGNS - toggles airport marker. Here's a shot that shows the heading displayed along the white horizon line and the airport sign for Livermore (KLVK).

The pathway display is most helpful on departure, arrival, and approach, but one huge drawback is climbs and descents (except on a glideslope or glidepath) are not depicted, at all.

Granted, my processor has a clock speed 1.8Ghz and 2.0Ghz is recommended for dual-screen mode with two monitors, but the PFD exhibited some weird behavior. The heading would abruptly shift left about 15 degrees and back every 5 seconds or so. After a few cycles of this behavior, the autopilot would disengage. The good news is that I didn't see this problem in the single-screen version (though I was restricted to reversionary mode). Another problem in dual-screen mode was that to pause the application, I needed to select this from the pull-down menu on the MFD - most of the time. The behavior wasn't completely repeatable, so I suspect this is a bug.

One thing I forgot to mention is that you can now enter the baro min (minimum descent altitude or decision height) when you load an approach. You can still access baro min through the timer softkey (which always struck me as odd), but this new approach loading scheme is a much more logical approach. I hope this gets added to no-SV G1000 systems as an software update.

Too bad that Garmin doesn't provide a more efficient way to acquire and upgrade this product, but it's not a bad deal for US$24.95 (plus shipping). And Garmin deserves high marks for making this sort of product available since it gives people a low-cost way to practice using the product without burning any gas. I don't think the two G1000 C172 owners I know will be springing for the US$10,000 upgrade, so this simulator is a relatively inexpensive way to learn about the latest developments. Check it out!

Monday, April 13, 2009

Caution: Bird Activity

Bird strikes became newsworthy recently with the dramatic ditching of US Airways Flight 1549 in January of this year after multiple bird strikes caused both engines to fail. Now the FAA wants to keep the raw data on bird strikes "confidential" (read "secret"). The justification being offered seems tenuous, at best. Here are some quotes from the Notice of Proposed Rulemaking, which the public may comment on until April 20, 2009.
The Agency is concerned that there is a serious potential that information related to bird strikes will not be submitted because of fear that the disclosure of raw data could unfairly cast unfounded aspersions on the submitter.

When it comes to safety issues, knowledge is power, except apparently when that knowledge might scare airline passengers away from particular airports or airlines.
The complexity of the information warrants care with its interpretation; releasing this information without benefit of proper analysis would not only produce an inaccurate perception of the individual airports and airlines but also inaccurate and inappropriate comparisons between airports/airlines.

Apparently our public servants think it's okay to make public some scary data, but other sorts of sorts of scary data must be kept secret; the sort of scary data that might adversely affect commerce. If third parties, including the news media, want to access the raw data to provide their own analysis, I think that's a good thing. The FAA seems to be saying that they, and they alone, know how to interpret raw data which I find unbelievably arrogant. Considering the agency's past performance on a variety of issues (aircraft safety inspections, management of air traffic control, etc.), two things are clear: They think they know best and they have the ability to screw up an anvil.

Whatever you think, you have until April 20 to comment by fax (202–493–2251), or by mail at:

U.S. Department of Transportation
Docket Operations M–30
West Building Ground Floor
Room W12–140
1200 New Jersey Avenue, SE.
Washington, DC 20590

You can also comment on-line, though I found it to be a bit complicated. Go to this link and search for docket number FAA-2009-0245.

On the next screen, locate and click on the rules link.

On the next screen, click on the comments link and post your feelings about this proposed rule.

Here's some interpreted data on strikes that has been published to date. According to Wildlife Strikes to Civil Aircraft in the United States 1990–2007, the threat of wildlife strikes to aircraft are on the rise due to three factors. First, many wildlife populations have increased and/or have adapted to living in urban areas. Next, there are more aircraft flying - passenger aircraft operations have increased dramatically since 1980. Lastly, more airlines are flying two-engine aircraft as opposed to three or four engine aircraft and fewer engines means less redundancy and less safety.

If you think your odds of hitting a bird or other animal are low, think again. In the 18-year period between 1990 and 2007, over 82,000 animal strikes were reported. Birds accounted for over 97 percent of the encounters, terrestrial mammals for about 2 percent, bats for 0.3 percent, and reptiles for 0.1 percent. Just over half of reported bird strikes occurred between July and October and if you think birds don't fly in the dark, 38 percent of strikes occurred at night. 60 percent of bird strikes occurred at 100 feet above ground or less, 73 percent occurred at 500 feet or less, and 92 percent occurred at or below 3,000 feet. The record altitude for a bird strike? 32,500 feet. 60 percent of the strikes occurred during landing or approach to landing. 37 percent occurred during takeoff and climb-out.

58 percent of terrestrial mammal strikes occurred between July and November. 33 percent of deer strikes occurred between October and November. 64 percent of the terrestrial mammal strikes occurred at night and 89 percent occurred during the takeoff or landing phase.

Now that didn't hurt, did it?

I've had three bird strikes and countless near misses. The first, and most dramatic bird strike happened during a daytime instructional flight at about 400 feet above ground, right after takeoff. The bird was a turkey vulture that I estimate weighed 15 to 18 pounds. The bird hit the leading edge of the right wing, just outboard of the wing strut. The sound of impact was quite loud. I took control of the aircraft, verified all the primary flight controls were functioning, and we returned for landing. After landing we found a three foot portion of the leading edge was significantly deformed, though I didn't notice any change in flight handling or performance after the strike. Our encounter was fairly lucky, for us anyway. Had the turkey vulture struck the windshield, the results would have been much worse. Here's an eagle that collided with a Schweizer helicopter, hitting a passenger in the chest and causing a fractured shoulder.

On several occasions I ferried Caravans to maintenance under a ferry permit after they had been damaged by bird strikes. The Caravan driver's old joke is that if you're going to hit a bird, try to hit a duck or a goose such that you skewer it on one of the two massive pitot masts. That way you can turn the pitot heat on and cook the bird on your way in and have something to eat after you land. Of course, this is just a joke.

If my bird encounters have taught me anything it is to take immediate evasive action anytime I see birds that pose a threat. There is a lot of folklore about how birds can or may get out of your way, when they may dive and when they may climb. Some of this may or may not be true, so the best advice I can offer is don't just sit there and passively expect the birds to get out of your way. If you see birds before or during takeoff, wait or abort the takeoff until the area clears. At a towered airport, tell the tower or ground controller if birds are an issue. Many airports have bird hazing protocols and ground crews may be dispatched to scare the birds away. If you see birds during approach to landing, remember you can always go around. Again, tell the tower about what you've seen since that information can help other pilots who may be following you. Sometimes, like at night, you may not see the birds until it is too late to take any action and you have to hope for the best.

As for terrestrial mammals, I've had my share of near misses with deer, coyotes, foxes, skunks, and stray dogs. Just like birds, you need to take action if you see an animal on or near the runway where you are departing or landing. If you can see the animal, don't assume it will get out of or stay out of your way. When in doubt, aborting a takeoff or executing a go-around is the prudent thing to do.

If you do collide with a bird, remember to report the event after you have safely landed. You can now report these encounters using this on-line form. It's actually a heck of a lot easier to report a bird strike than it is to comment on Notices of Proposed Rulemaking. If you hit a bird and the remains are accessible to you, follow the instructions on the site for sending the remains to the Smithsonian for identification. I've never submitted bird remains. In the case of the turkey vulture collision, the bird fell somewhere into a slough and was "unavailable for comment."

Wednesday, April 08, 2009

Must Have Apps

Note: For an up-to-date review of iPhone and iPad apps, click here.

I've had an iPhone for about 7 months now and it has definitely proven to be one of the most worthwhile devices I've ever purchased. In addition to the built-in features like email, calendar, contacts and web browsing, I love the ability to extend the device's usefulness with third-part applications. I wrote last year about switching to LogTen on my iPhone and on my Mac for logging all my flight times. I have to say this app is a must have, especially for Mac users.

I've found some other useful iPhone apps and here they are, in no particular order.

Filing Flight Plans

While DUAT provides a mobile device version of their web site, I don't find it much easier to use than the regular, non-mobile web site version. For a friendly, easy-to-read flight plan interface, nothing beats FltPlan. Access it using the web browser of your choice on your regular computer and create a user id at no charge. When you access FltPlan on your iPhone using Safari, login and you can get a quick and concise weather briefing (which meets the requirements of 14 CFR 91.103). You can file IFR flight plans very quickly and easily well as get access to radar summary and weather depiction charts, NEXRAD for an airport or a route, winds aloft, PIREPs and more. I don't have many suggestions for improving this site. The content has obviously been very well thought out, though the layout sometimes seems a bit crude.

Airport Directory Information

And another tip of the hat is in order to the folks at FltPlan for creating the free FltDeck Airport/FBO Info Guide app. I sure wish I'd had this on last summer's ferry flight since it provides lots of information on all airports in the continental US as well as Canada, Mexico, and the Caribbean. An important point to mention is that this is a stand-alone app: Once you install it, you don't need a network or 3G connection to access airport information and that means you can look up information while in flight with your phone in airplane mode.

Weight & Balance

Weight and balance spreadsheets have proven useful to me for years and I usually create one for each aircraft that I fly. I even created one years ago for the Caravan and it really simplified my life by letting me let the ramp crew know quickly and accurately how much cargo my plane could take that day. Wanting to weight & balance on the iPhone seemed like an obvious idea and Spreadsheet lets you do this easily. Create a weight and balance spreadsheet in Excel (I assume OpenOffice would work, too), then save a copy in XML format. You can use Spreadsheet's built-in file transfer feature to move the XML spreadsheet to your iPhone and you're in business baby! The original price has increased slightly since I bought it to $7.99, but it's worth it.

Surface Weather and TAFs

There are a lot of aviation weather iPhone apps out there and while ForeFlight is probably the best in breed, it's a little expensive for my current budget. I've tried a few of the cheaper apps, but for my money Aero Weather provides a lot of bang for little bucks - it's free! You create a list of favorite airports and you get a simple, concise, easy-to-read list of those airports. If you want to see the TAF for an airport, you can get that, too. And you have the option of raw or decoded formats. Remember this data does not meet all the requirements of a weather briefing for the purposes of 14 CFR 91.103, but it can give you a good overview of the weather situation in your area.

Another low-cost weather app is AirWx which only costs US$6.99. Like Aero Weather, AirWx lets you create a list of favorite airports, access METARS and TAFS, but it adds features like an E6B calculator and the ability to access weather charts, AF/D entries, and terminal procedures for many airports. It's not exactly what I'd call user-friendly and the E6B, while functional, is a bit cumbersome, but the price is reasonable.

E6B Calculator

While AirWx provides a usable E6B, PilotWizz does a bit better job. The price is either free or a low US$9.99 if you decide to buy the Pro version. It even has a holding pattern feature, though I think it's more useful as a teaching/learning tool than for actual use in flight.


I also use a few non-aviation apps (most of them free) that I can recommend, including:

Skype - internet telephony meets iPhone
Google Earth
Pandora - music
Shazam - music
iBart - for Bay-Area Rapid Transit train schedules
TouchType - for email and Twitter (once I'm ready to stream my consciousness)
Wikipanion - for reconciling bets and disagreements on facts, history ...
Tides - so I can walk my dogs near SF Bay without Taz disappearing into the mud flats!

Any aviation apps you use that I haven't mentioned? Please chime in, but be forewarned that spam and inappropriate comments will be sent to /dev/null.