Friday, April 24, 2015

Kludge + Indirection = Confusion

Perhaps it was living through The Great Depression that inspired my grandfather to concoct one of his favorite sayings: Patch by patch is neighborly, but patch upon patch is beggarly. And "patch upon patch" certainly comes to mind when considering how the FAA disseminates charts and makes changes to important data. Two examples come to mind: enhanced circling minima and the new cold temperature-restricted airports. 

Wagons in a Circle

Consider approach categories and standard circling approach maneuvering radii. First, pilots have to memorize the airspeeds associated with Categories A, B, C, D and E. This isn't a big deal since most of GA flyers use aircraft that fall in category B - approach speeds within 91 and 120 knots indicated airspeed. Where do you find the definitions for approach categories? Why in the front matter of the terminal procedures, of course! There are two problems with this arrangement:

  1. Many pilots now use electronic flight bags, they aren't carrying paper version of the terminal procedures, and locating the front matter to reference this tabular data is not trivial.
  2. Even if you are still using paper charts, imagine the workload required to flip through your binder to locate that data, while flying single-pilot.

New circling minima on some instrument approaches were announced a few years ago and the motivation seemed both sound and simple: A given indicated airspeed results in a higher true airspeed as altitude increases, that leads to larger radius of turn, and so the existing circling minima were not adequate for ensuring required obstacle clearance while circling at some high-altitude airports. The FAA's solution was a classic engineer's solution: A complicated set of gradually increasing radii based on airport elevation that was simply too involved to commit to memory. One proposed implementation, described in the minutes from the Aeronautical Charting Forum minutes, would have been put the actual circling radii right there on the approach chart! Imagine that: An excellent idea that, unfortunately, was abandoned.

There is actually plenty of room to put both the airspeeds and radii right there on the plate. Why not?

The final implementation was a classic FAA kludge: Look at the approach chart, notice the  C , refer the terminal procedures front matter to locate the chart to determine how close you need to be to the runway environment while circling-to-land based on an approach category that you've memorized. Luckily, there's a simple solution: Look at approach chart, find the circling minima for your aircraft category, note the minimum visibility on the chart, and stay within that distance from the runway environment while circling. Geez! Circling approaches are hazardous enough. Come on Aeronav, toss us a bone here!

From Hot to Cold ...

While teaching an instrument student recently, I needed to locate a representative chart to illustrate the  C  symbol and expanded circling minima. That's when I noticed something new: A white snowflake symbol on a black background and a temperature. This symbol is not defined in any of the FAA's Aeronautical Chart User's Guides (at least I couldn't find it).

Persevere and you find this NOTAM: Cold Temperature Restricted Airports which explains that if the altimeter in your aircraft does not correct for cold temperature and you're flying into one of the 272 cold temperature restricted airports, you'll need to apply a cold temperature correction on one or more segments of the approach procedure in order to have adequate obstruction clearance. Here the FAA has outdone themselves because you need 3 pieces of disparate information:

  1. The instrument approach chart
  2. ICAO Cold Temperature Error Table (found in the AIM, section 7-2-3)
  3. A copy of the aforementioned NOTAM

Then, near as I can tell, the corrections are actually quite simple ...

  1. Get the surface weather for Truckee
  2. Look up Truckee in the NOTAM to determine which segment(s) of the approach need to be corrected based on the currently reported temperature
  3. Subtract the altitude(s) from the field elevation to determine height above airport (HAA)
  4. Locate the HAA in the top row of the ICAO Cold Temperature Error Table
  5. Find the reported temperature in the left column
  6. Locate the correction (you'll probably have to do a 4-way interpolation if the altitude and temperature fall between the values in the chart)
  7. Add the correction to the affected altitudes on the chart
  8. Round up to the nearest 100 feet
  9. Fly those indicated altitudes instead of the altitudes charted
There are some definite advantages to flying glass panel aircraft, because Garmin tells me that if you fly a G1000 aircraft, then the air data computer will automatically compensate for cold temperatures.

The FAA certainly faces ongoing challenges because when they have to make a change to charted information, they have a large base of "customers" and a lot of existing charts. Still, there's got to be a better way to get information critical to flight into the hands of pilots.

And don't get me started on ADS-B!

Thursday, February 05, 2015

Flying in the Raw

A pilot pointed out recently how a G1000-equipped aircraft with a current navigation database did not have an approach into the airport he happened to be visiting: Pearson Field in Vancouver, Washington (KVUO). There's only one approach into Pearson, so why would the G1000 not know about it? Had an error been made when the database was created? It's been a while since I've written about a particular G1000 behavioral oddities, so now consider the oddity of an approach procedure missing from the G1000 database. If you fly into Pearson regularly you may already be familiar with the reason, but even if you are familiar with this situation it nevertheless points out an important skill that instrument pilots need to acquire and practice: Flying raw data.


A voicemail left with the Jeppesen navdata folks eventually led to a return phone call and explanation: Yes, the KVUO LDA-A approach is not contained in the G1000 database (or presumably in any other GPS receiver's database) because this is the only case in the US where a localizer installed at one airport (KPDX) for an ILS is used to implement an LDA approach at another, nearby airport (KVUO).


The approaches even have two approach fixes in common: BUXOM and TRAYL. Unfortunately, the programming language used to code approaches for the GPS database and executed by GPS receivers, ARINC 424, does not allow a localizer established for an ILS at one airport to also be used for an approach at another airport. So Jeppesen chose not to include the KVUO LDA-A in the navigation database, even though the LDA approach is the only instrument approach into Pearson. This means users of the G1000, and presumably other GPS receivers, may want to know how to set-up and fly an approach the old-school way.

Raw Data

Tune NAV1 to the localizer manually, verify the Morse code ID is correct, and ensure the front course is set on the HSI (or CDI #1 for non-G1000 installations). Tune NAV2 to the Battle Ground VOR, verify the Morse code is correct, and set bearing pointer #2 (or CDI #2) to use NAV2. When you've joined the localizer, use the tail of the bearing pointer (or adjust CDI #2) so you'll know when you've passed the BTG radials that define the step-down fixes on the approach. If this sounds awkward, you are probably a Child of the Magenta Line who needs more exposure to the way instrument flying was done for decades.

The Instrument Rating Practical Test Standards requires applicants to demonstrate the ability to fly an approach without reference to the primary attitude and heading instrument. Perhaps applicants should also be required to demonstrate flying an approach without using the GPS. Selecting an approach with the G1000 does much of the work for you, sets the primary navigation frequency, sets the navigation course, and may prevent you from acquiring understanding and correlative levels of knowledge with regard to radio navigation.

A Little Less Old School

Now if you fly into Pearson on a regular basis, there's another way to prepare for this approach, though the set-up work is best done on the ground or during low workload while in flight. You can manually create a flight plan that defines the sequence of fixes that make up the approach, which is similar to what you'd see if the LDA approach was defined in the GPS's aviation database and you selected the approach. I'm going to illustrate using screen shots from Garmin's GTN Trainer app for the iPad, but the process is essentially the same in a G1000 or most any other GPS receiver.

You're still going to fly the localizer and you'll need to tune it manually, verify the Morse code, and verify the front course of 103˚ is set on the HSI (or CDI, if so equipped). In your GPS flight plan, add the fixes BUXOM and TRAYL. ZEZJI and QEHBY are not included in the GPS database (Hey Jeppesen, toss us a bone here!), but you can enter them as user-defined waypoints. Simply insert a fix named ZEZJI, your GPS will say that no such fix exists, and give you the option of creating a user-defined waypoint. Accept that option and define ZEZJI on the 283˚ radial and 4.7 miles out from IVDG localizer. Then repeat the process for QEHBY on the 283˚ radial and 2.9 miles out.

Create user waypoint? Yes, please!

Rho-theta using IVDG localizer

Enter theta (radial is opposite of front course), then rho (distance) on the next screen (not shown)

If you want, you can define these waypoints by entering the latitude and longitude for ZEZJI and QEHBY, but more numbers and user input steps are more complicated and error prone. Lastly, insert the BTG VOR into the flight plan since that's where you'll be headed if you end up flying the missed approach segment and you should see something like this.

In both options remember that you'll be flying the localizer, not the magenta line. In option #2, you have the luxury the GPS flight plan sequencing appropriately so you'll know where you are on the profile view of the chart. You can even combine both options and use the cross-radials and the GPS to verify your position.

If you're old enough to remember VOR/DME RNAV approaches, which seem to have all been replaced with RNAV (GPS) approaches, you'll recall it was standard procedure to enter each approach fix in a VOR/DME RNAV approach as a VOR radial and distance into a unit like the Bendix-King KNS-80. I'm getting all misty just thinking about it ...

The venerable KNS-80 VOR/DME RNAV receiver


Now you may be asking yourself "Is it legal to define your own flight plan for an approach?" I'm not a lawyer, but let's use the tried and true method of testing an argument by prefacing it with "Your honor" and see how it sounds.

Your honor, since IFR-certified GPS is a legal substitute for DME, and since I defined the ZEZJI and GEHBY correctly using rho-theta from the IVDG localizer, and since I was flying the localizer, I believe my procedure to be both legal and safe.

This argument sounds pretty good to me, but the first option (flying the localizer and displaying the cross-radials) seems easier from the get-go and involves less head-down time: There are times when flying raw data is less distracting than trying to bend the G1000 to your will, provided you're one of those increasingly rare pilots who actually knows how to fly raw data.

Saturday, January 31, 2015

January 2015 Photos

Sonoma County

Cross DAWNA 13,000

Montecito Sunset

Reversionary mode practice

North SF and San Pablo Bays

Quiet New Year's Day at SMO

West LA view from KSMO

ABBAS (another beautiful Bay Area sunset)