Sunday, May 17, 2009

The Sky is Failing


If you read this blog very often you've heard me caution pilots about being overly reliant on any single method of navigation, like GPS. Since the GPS was declared fully operational in 1995, pilots, sailors, hikers, drivers, cell phone users, and the military all have become accustomed to the convenience provided by this no-cost system (okay, you have to buy the GPS receiver). Even the next generation air traffic control system NexGen, which the FAA has been furiously flogging as the panacea for everything from air traffic delays to tooth decay, relies heavily on GPS. But those plans might need to change.

A recently released GAO report entitled Global Positioning System: Significant Challenges in Sustaining and Upgrading Widely Used Capabilities has many wondering about the stability and sustainability of our constellation of GPS satellites, whether or not the Air Force can improve and "replenish" the system in time, and what our daily lives on the ground, at sea, and in the air might look like if GPS became unavailable or degraded.

The GAO's 61 page report is interesting reading, especially when compared to the glowing claims made by the FAA about the progress that's been made enhancing GPS availability and growing the number of RNAV procedures for aircraft. And if you are wondering if GPS is an aging system in need of repair or a robust system that continues to be expanded and enhanced, the truth probably lies somewhere in between.

One key questions that needs to be addressed is this: What is the useful service life of a GPS satellite? A solid answer is hard to come by, but one thing of which we can be certain of is that satellites have worn out in the past and more will wear out in the future. Of the current constellation of 31 GPS satellites, thirteen entered service between 1990 and 1997, twelve entered service between 1997 and 2004, and the remaining six satellites were launched between 2004 and 2009. That means about a third of the GPS satellites are between 12 and 19 years old; a sobering thought.

One of many problems that aging GPS satellites can experience involves clock errors. Since GPS receiver's position is calculated based on signals from several satellites, knowing the time each of the signals was sent and the time it was received is crucial. Each GPS satellite has four clocks that are periodically refreshed from the master station on the ground and each satellite will broadcast an estimate of time offset of the onboard atomic clock from the GPS system time. Since GPS signals travel at the speed of light, even minute errors in clock settings or offset estimates can result in large positional errors for GPS receivers. According to the GNSS Evolutionary Architecture Study released in February of 2008:
... large clock runoffs were experienced on SV22 [space vehicle #22] on July 28, 2001; SV27 on May 26, 2003; SV35 on June 11, 2003, and SV23 on January 1, 2004. These events generated range measurement errors of 1000 meters or more . The pseudorange error on SV22 on July 28, 2001, was reported to be 200,000m by some users and 300,000m by others.

Other problems that can afflict aging GPS satellite's include the failure of positioning components, propulsion systems, and a degradation of the power supplied by each satellite's solar array. The GAO report points out that the Air Force can often switch to a satellite's back-up system. And they can manage the power problem to an extent by powering down satellites when they are not needed or by shutting down power to "secondary payload" systems. These sorts of measures may extend the service life of older satellites, but it's clear that nothing lasts forever. New replacement satellites must be planned for and launched on schedule.

This leads to the GAO's main concern with the US Air Force's poor track record of creating and launching new satellites on schedule and within budget. Not only has the track record in Phase IIF been poor, the schedule for Phase IIIA actually compresses the lead time to produce and launch satellites. Without going into all the details of feature creep, government contractor inefficiencies, and the like, the bottom line is that the Air Force may not succeed and we GPS users may have to do with fewer satellites. Here's the GAO's estimate of how many satellites we may have to do with, or without. If they are right, the probability of having 24 functioning GPS satellites between 2010 and 2012 hovers around 85%.


The FAA's enhancement plans for GPS follows several phases and the FAA's aggressive creation of RNAV approaches with LPV minima in Phase II has been nothing short of astounding. Only a few years ago I was writing about LPV approaches from a strictly theoretical standpoint and now they outnumber ILS approaches. We are now in Phase III and a few of the stated goals are to :
  • Provide LPV approaches with 200' DA (most are currently 250 feet)
  • Transition support and enhancement of WAAS to the FAA
  • And prepare for an increase in predicted solar activity
The FAA appears to be doing a good job and enhancements to the WAAS ground components have significantly expanded WAAS RNP 0.3 availability.




And LPV coverage has been extended significantly, too.



Increasing GPS receiver accuracy using the Space-Based Augmentation System (WAAS) is obviously on track. People who study such things predict that there will be an increase in solar ionospheric disturbances beginning somewhere around 2022 and lasting for some number of years. Solar activity has reduced WAAS availability in the past and it's reasonable to expect it will happen again. Some have suggested that LORAN could be a back-up system, but for aviation that idea seems dead on arrival: There are few functioning LORAN units out there and no new units that I know of currently being manufactured for aviation use. The FAA has decommissioned many NDBs and they plan to decommission more (basically not fix the ones that fail). They'd also like to do away with most VOR stations. For better or worse, we seem to have put all our navigational eggs into the GPS space basket.

And the future could be very interesting indeed.

Wednesday, May 13, 2009

The Wrong Stuff

Tuesday's NTSB hearing on the crash of Colgan Air flight 3407 is getting a lot of coverage and for a balanced technical assessment, I recommend you read a post by Sam. Sam is currently an RJ captain for a regional airline and a former Dash 8 first officer. I've never flown for a regional passenger airline and I have no flight time in the Dash 8, but I did a stint flying cargo under part 135. I have some experience with the duty time regulations, the economic stress that regional pilots face, and the effect this has on a pilot's performance. My conclusion is that pilots, the airlines, the government, and the flying public are all complicit in the current state of affairs at the regional airlines. I'll warn you in advance that I'm going to say things that you might find controversial, so suck it up! This is the blogosphere and we don't always have to walk lockstep or hold hands and sing Kumbaya.

Pilots who attempt to earn a living flying are addicts, myself included. Okay, maybe our obsession with flying is more a psychological dependency than addiction, but consider the parallels. No matter how bad the working conditions, how low the pay, how miserable the management, how poorly maintained the aircraft, how isolated the lifestyle, pilots will do almost anything for the opportunity to fly. For some of us, the rush starts once the cabin door is closed. For others, it's when the engines start. Even if you are a jaded veteran with thousands of hours, you're not immune to the feeling of the wheels leaving the runway. Once airborne, the troubles fade away and for those many minutes or hours, you're flying again.

Perhaps flying hooks up our brains with a supply of dopamine, but whatever the mechanism it sure drives pilots to make some kooky choices. These talented, intelligent, and highly-skilled professionals seem to blithely accept low pay, early mornings, late nights, long duty days, bad weather, working on holidays, isolation from family and friends, and even AIDS - Aviation-Induced Divorce Syndrome. It's obvious that denial (or at least compartmentalization) is a crucial skill for professional pilots. It's no secret that many pilots will practically fly for free and, in the process, subsidize their airline's operation. And their employers know it.

Management at regional airlines are trying make a profit in a business with lot of variable costs (like fuel) and uncertainties (like weather delays). Where better to start than by keeping wages low? Low wages were the primary reason I quit flying freight. Sure there were the stresses and risks with single-pilot operations, having to fly through bad weather rather than fly on top of it, and the long hours. Then I came to realize that I could earn at least twice as much as a freelance flight instructor than I could as a part 135 pilot, even if I hung on and racked up several years of seniority. And yet I still miss it! You see, pilots love what they do so much that they have a really hard time being objective about what might be wrong in their work environment.

The pilots who fly for regional airlines, especially the low-seniority first officers, are under some serious stress. Stress is a huge risk factor in aviation safety because it narrows the perceptual field and reduces a pilot's ability to perform. Fatigue, which often goes hand-in-hand with stress, increases reaction time and impairs decision making. I've read how the young woman first officer on Colgan Flight 3407 earned so little that she lived with her parents, sometimes held a second job, and commuted across the country to her flying job. She often slept on the crew lounge sofa, I'm assuming because she couldn't afford or didn't want a hotel room. Part of the legendary mystique of being a professional pilot is paying your dues, though once you've slept on a crew couch a few times the allure wears off pretty quickly.

Pilot's are generally goal-oriented and have a predisposition to a perform no matter what. If you call in sick or fatigued, it seems there's always another motivated pilot (addict) just waiting to take your place, maybe even your job. Yet the replacement pilot might be just as fatigued and stressed as you. How much stress and fatigue you're willing to endure depends on your age, your goals in life, and how badly you need your flying fix. Airline management knows all of this and they use it to their advantage.

As convenient as it would be to lay all of the responsibility at the feet of the regional airline management, let's not forget the role of the flying public. People want, no they expect to be able to fly to most any part of the country as cheaply as possible. They don't want to be troubled with knowledge of how the aviation sausage is made, they just want a low price. People will pay $35 to get a package shipped overnight all the while complaining mightily about the airfare involved in shipping their own carcass across the country in air conditioned, pressurized comfort. And many passengers seem to still believe that pilots work just a few days a week, earn upwards of $100,000 a year, and live a country club lifestyle. The fact is that most regional pilots are living hand-to-mouth and don't even get a cost-of-living adjustment for expensive pilot bases like Boston or San Francisco. Low airfares certainly don't help their cause. Greater public awareness of the poor wages earned by regional pilots and cabin crews could be one of the few good things to come from this accident.

The federal government's role is their continued failure to adequately address the twin safety issues of stress and fatigue. Well not all of the government: The NTSB has been pushing for years for an overhaul of the federal duty time regulations for flight and cabin crew members while the FAA and the airline industry have fiercely resisted change. As it stands, flight crews can be on duty for 16 hours or more each day and the 8 hours of rest they must get every 24 hours often does not take into account the time it takes to get to the hotel, eat, and take care of personal affairs. Consider the research conducted at Boston's Harvard Medical School which showed that being awake for 24 hours was equivalent to a blood alcohol level of 0.10% . Getting 5 hours of sleep per night for a week had the same effect. The press has a field day when crew members are found to be drunk on the job, as well they should. By and large, fatigue seems to be tacitly ignored.

Given their work environment, it's hard to expect pilots to be objective about the stress and fatigue they face. Airlines are trying to make a profit in a very difficult business with strong price pressure, so when it comes to fatigue they probably don't ask and pilots probably won't tell. The government has dropped the ball with regard to ensuring reasonable duty limits and reasonable rest time. The press may have found a convenient scapegoat in the form of the flight's low-time captain and the allegedly incomplete simulator training he received. Sure it's difficult to identify all the causal factors that led to a fiery crash on that snowy night, but low wages, stress and fatigue must be examined as contributing factors to this accident and the crew's ineffective performance. Or we could just continue to deny there's a problem ...

Monday, May 11, 2009

Don't Call Me at the Old Number

Never seen the 1950's Jimmy Stewart movie Harvey? Well you probably won't understand what the title of this post is referring to. Stewart plays Elwood P. Doud, a nice guy in every respect except for the fact that he has a friend - a 6 foot tall invisible rabbit named Harvey - which no one else can see. Several times in the film he hands his business card to someone, after crossing out something on it, and explaining he has a new phone number.

Many non-towered airports share the same common traffic advisory frequency and though this is an antiquated system, it mostly works. Where the system starts to break down is when the skies get crowded, like on weekends and holidays. The few CTAF frequencies there are get busy because many non-towered airports share one of two common CTAF frequencies - 122.8 or 122.7. Some new frequencies are beginning to be assigned, but the way pilots determine whether or not a radio call they just heard might affect them is the convention of prefacing all CTAF announcements with the name of the airport. So far so, so good.

Some of the airports within a 100 mile or so radius of the San Francisco Bay Area that share the frequency 122.8 include Halfmoon Bay, Sonoma Skypark, Ocean Ridge, Cloverdale, Rio Vista, Watts Woodland, Colusa County, Kingdon, Rancho Murietta, Westover, Oakdale, Turlock, Tracy, Los Banos, and Wattsonville. Many of these airports are infrequently used, but many are quite busy with training aircraft. It's not uncommon to hear pilots at other airports more than 50 miles away. I often hear jet traffic inbound to Truckee making CTAF announcements while high over the Sierra Mountains and wonder how far their transmissions might be heard. You don't have to be at a high altitude for your signal to carry. I remember making a CTAF call inbound to Visalia at 2000 feet and having someone in Byron (140 nm away) say "Hey John, is that you?"

When the frequencies get crowded, it can be hard to get a word in edgewise and when two aircraft try to transmit at the same time, you get a loud squeal and nobody hears anything. Radio communication, see-and-avoid procedures, and luck are what keep aircraft from hitting one another at these small airports. For their part the FAA has begun to assign new CTAF frequencies to many non-towered airports as a way to reduce congestion on the freqencies and this a great idea. In fact, Rio Vista just got a new frequency on March 1 of this year.

RIU 02/167 O88 COM CTAF/UNICOM 122.725 VICE 122.8 WEF 0903010800


Translate this NOTAM and you'll understand that the old CTAF frequency of 122.8 has been replaced with the frequency 122.725. Then you will hopefully mark up your VFR sectional and A/FD with the new frequency. Since Rio Vista is frequented by many of the part 141 training school aircraft in the area, this new frequency should help a lot. The problem is this NOTAM and the new frequency assignment seem to have been lost on about 50% of the pilots using the Rio Vista Airport. Either they have not gotten a pre-flight briefing since March 1 or they aren't reading the NOTAMs carefully.

I'm not instructing as much since last October, but I've still been to Rio Vista a dozen times since March and each time at least one aircraft is still using the old frequency. And why not? The current San Francisco VFR sectional still lists the frequency as 122.8 as do all the relevant Jeppesen VFR+GPS charts. Heck, even the latest Airport Facility Directory and all the latest NACO approach charts still list the CTAF as 122.8. Why this is I can only guess.

The next San Francisco VFR sectional is due out at the end of August of this year and perhaps the FAA's charting division wants to harmonize the release of that sectional with an updated A/FD and terminal procedures. A great idea to someone sitting at a desk, but not such a great idea for someone flying an aircraft into Rio Vista. I haven't noticed if the airport information signs on the Rio Vista airport actually reference the new frequency or not. I even emailed the folks at Airnav, but they said they don't update their online information until the FAA makes the changes, presumably to the A/FD. So even Airnav still lists the old, wrong frequency. What's a pilot or instructor to do?

My current, preferred procedure at Rio Vista is to tune the #1 radio to 122.725 and use that as the CTAF. Okay, so I'm a boy scout, but heck there's a NOTAM. I don't want to be called on the carpet for not complying with 14 CFR 91.103, but I don't have a death wish either. I tune the #2 radio to 122.8 (the old frequency) and monitor it, too. If I hear someone on the old frequency, I quickly transmit a courtesy explanation of the new frequency in use - if I can get a word in edgewise. Sometimes the old frequency is so busy with calls from other airports that listening to two frequencies becomes a distraction in and of itself. So this new frequency assignment was supposed to reduce radio conflicts and make things safer, but it has actually made things less safe.

One simple solution would have been to wait until a few days before the new San Francisco VFR sectional was to be published and then release the NOTAM. Now that the cat is out of the bag, at least the next versions of the A/FD and the terminal procedures should be updated. For completeness, another solution would be to release a NOTAM retracting the previous NOTAM. Yeah, that sounds about right for the FAA ...

My suggestion for pilots who want to avoid missing these important, but obscure NOTAMs is to get an online briefing from DUATS or DUAT and then use your browser's search feature to locate all the instances of the airport identifiers for places where you plan to operate. DUAT lets you request your briefing output as plain English, which also helps.



This yields:

RIU 02/167 O88 COMMUNICATIONS CTAF/UNICOM 122.725 INSTEAD/VERSUS 122.8 WITH EFFECT FROM OR EFFECTIVE FROM 0903010800


FltPlan has a nice way of formatting relevant NOTAMs for a particular airport that makes them stand out.



The sad fact is that there really is no substitute for wading through all the darn NOTAMs. For more information that you could ever possibly want on NOTAMs, read this. And even if it's a beautiful VFR day, get a briefing, read those NOTAMs, and keep your eyes peeled.

And don't call me at the old number.

Wednesday, May 06, 2009

Play Well With Others

I sometimes receive suggestions from readers about topics they'd like to see covered, which was the genesis for this post. If you have a suggestion, you can always email me at freightxdogxtalesxatxgmailzcom - just remove the Xs and replace the Z with a ".".

The FAA (and many instructors) do a good job of explaining what a complicated airspace system we have in the US, but we could do a better job of explaining why different classes of airspace exist. Pilots may be able to identify airspace classes on a chart, correctly describe the altitudes and lateral dimensions, and belch out the visibility and cloud clearance requirements by rote, but an understanding level of knowledge is more elusive. My concern today is simply Class E and G airspace, how VFR and IFR traffic can coexist at non-towered airports, how to make clear position reports whether you are VFR or IFR, and a common sense approach to resolving conflicts.

Why Class E?

All pilots need to remember that Class E airspace defines an area that may be shared by aircraft operating under instrument flight rules (IFR) and aircraft operating under visual flight rules (VFR) without an air traffic controller providing separation. What separates these aircraft is the see-and-avoid concept.

Class E airspace will surround non-towered airports with one or more instrument approach procedures and rural heliports that support emergency medical flight operations. Class E can also exist at airports that don't have continuous control tower operations: The airspace around the airport is Class D when the tower is open, but reverts to either Class E, Class G, or a combination of the two when the tower is closed. The best way to know is to check the Airport/Facility Directory entry for that airport.

IFR aircraft can operate in Class E in instrument meteorological conditions (IMC), in visual meteorological conditions (VMC), or they may be passing in and out of the clouds, so 14 CFR 91.155 requires pilots under VFR to comply with specific flight visibility and cloud clearance requirements. This helps ensure that VFR and IFR aircraft have a fighting chance to see and avoid one another since ATC isn't there to play referee and point out traffic.

Class E Depiction

Class E airspace is explicitly depicted in a variety of ways on VFR charts, but it can also be implied. A dotted magenta line encloses areas of Class E airspace starting at the surface and extending up to 18,000 feet. Surface Class E is usually defined around an airport where the FAA definitely doesn't want scud-running VFR aircraft who might pose a hazard to aircraft on an instrument approach.

The magenta vignette encloses areas where Class E starts at 700 feet above ground level (AGL) up to 18,000 feet. It is also found around non-towered airports that have instrument approach procedures or EMS heliports. The shape of the magenta vignette roughly describes the instrument approach final approach course, the missed approach segment, and/or the instrument departure path for that airport. Beneath the 700 foot floor of Class E airspace is Class G, or uncontrolled airspace.



I'm leaving out some of the other ways Class E airspace is depicted and remember that Class G (or uncontrolled) airspace exists underneath the magenta vignette. Adjacent to the magenta dotted line or vignette depiction, Class G exists from the surface up to 1200 feet above ground level and above 1200 feet, Class E up to 18,000 feet is implied. During the daytime, Class G has much laxer requirements for VFR visibility and cloud clearance than Class E and this will figure into the discussion a bit later.

Two Cars in Kansas

Let's get back to IFR and VFR traffic sharing the same airspace. Let's say you are a VFR pilot inbound to Ukiah, California from the Southeast. You were receiving flight following from Oakland Center when, about 12 miles out Oakland Center tells you "radar service terminated, squawk VFR, frequency change approved." You've already listened to the surface weather and know there is a 3,000 foot broken ceiling with 5 miles visibility in haze. The winds are 310 at 12 knots and runway 33 appears to be indicated. The sky is clear in your current location, so you begin a VFR descent to get under the cloud layer ahead. Next, you change frequencies and make your first announcement on the common traffic advisory frequency (CTAF):

Ukiah traffic, Mooney 123, 10 miles Southeast, 4000 feet and descending, planning right traffic runway 33, Ukiah.

Unbeknownst to you, there is a freight aircraft that is also inbound to Ukiah from the Northwest, operating under Part 135, and on an instrument flight plan. A bit later, Oakland Center clears the freight aircraft for an instrument approach and ends with:

Boxhauler 333, radar service terminated, change to advisory frequency approved, report cancellation of IFR on this frequency or with flight service, traffic is a VFR Mooney inbound from the Southeast, good day.

Since you've changed frequency, you don't hear that exchange. You've maneuvered your Mooney under the overcast, you have 5 miles visibility and are 500' below the clouds when you hear:

Ukiah traffic, Boxhauler 333, 8 miles Northwest, 3500, localizer 15 approach, Ukiah.


Get the Flick

You need to quickly assemble a mental picture of your situation: The freight aircraft is inbound to the same airport from the opposite direction, they may still be in the clouds, and they're planning to land on the runway opposite the one you have chosen. They just changed to the common traffic frequency so they did not hear your initial CTAF announcement. What's more, they probably have a faster groundspeed than you. Who has right-of-way? What should you say? How do you work out the opposite runway conflict?

The regulations (14 CFR 91.113) say that whoever gets to the airport first and it at a lower altitude in a position to land has the right of way. What's more that aircraft can land on any runway they want because all runways are active. This is why I recommend avoiding the commonly used phrase "the active" at non-towered airports - all the runways are potentially active.

Some pilots mights say Ukiah is an "uncontrolled airport," but that's a misnomer. It's certainly not in uncontrolled airspace since Class E extends all the way to the surface. More importantly, there is control at all non-towered airports. It's called self-control on the part of the pilots operating there, whether they are VFR or IFR. The keys to working out traffic pattern conflicts are clear communication, common sense, and courteous cooperation.

Where you At?

Clear communication using accepted phraseology is a good first step. Instrument-rated pilots, you can mention the instrument approach you are flying, but it won't be of any use to non-instrument-rated pilots or to pilots who are unfamiliar with the approaches to the airport. Reporting your position using approach fix names is just as meaningless. So whether VFR or IFR, keep it simple:
  • The airport name
  • Your aircraft model and tail number (or company and flight number)
  • Distance and cardinal direction from the airport
  • Your intentions.
Remember there could also be aircraft operating at a non-towered airport that don't have a radio or there could be an aircraft with a radio that has failed, so keep your eyes peeled for other traffic and expect the unexpected.

Speak Up

When you hear another aircraft make a CTAF announcement and realize there's potential conflict, that's your cue to say something. In our scenario, after you hear the freight aircraft make their announcement, you might say:

Ukiah traffic, Mooney 123 is 4 miles Southeast at 2500, planning right traffic, runway 33, looking for Boxhauler, Ukiah.

You can ask other aircraft if they are still in the clouds, what their ground speed is, or anything else that will provide you with the verbal equivalent of TCAS. If the other aircraft is still in IMC, you could ask them to say their intentions.
Ukiah traffic, Mooney 123, 3 mile forty-five, right traffic 33, the field is VFR, winds favoring runway 33, Boxhauler, say intentions, Ukiah.


Share Your Toys

Pilots at non-towered operations should have the same goal that air traffic controllers have: The safe and orderly flow of traffic. If another aircraft is faster and it's safe to do so, let them go first. Fly a wide downwind, slow down, or maneuver to give them time to land and clear the runway.

Instrument pilots, remember that you don't own the sky just because you are on an instrument flight plan or flying a practice approach. And remember too that not everyone understands instrument procedures and terms.

On the flips side, I've flown a lot of practice approaches with instrument students into non-towered airport and I can sympathize. When I hear someone inbound on an approach and they say they would like to circle in a non-VFR manner or do a straight-in approach, I try to accommodate their request if I can do so safely. Widening my traffic pattern or slowing down might cost me, what, two or three minutes of my time?

VFR pilots remember that you need to be at least 500 feet beneath the clouds in Class E airspace. Practicing touch-and-goes at a non-towered airport when the ceiling is low is risky business: Don't do it. Flying a non-standard 690 foot AGL traffic pattern so that you are just outside of Class E, technically VFR, and legal is also a poor choice.

Safe operations at non-towered airports depend on good radio technique, assembling a mental picture of what is happening, and being cooperative. Adhering to the rules also helps, but rules can't cover every eventuality. There's no replacement for courtesy and common sense. Being sharp and on-the-ball helps, too.

Sunday, May 03, 2009

Broken Circle

On January 3, 2009 at 1710 mountain standard time (MST) a Learjet 45, N279AJ, sustained substantial damage when attempting to land during a snowstorm at Telluride Regional Airport (KTEX), Telluride, CO. The airplane was owned by LJ279, LLC, Missoula, MT and operated by Aero Jet Services, Scottsdale, AZ. The CFR 49 Part 91 positioning flight was conducted using instrument flight rules and had departed Scottsdale Airport (KSDL), Scottsdale, AZ at 1503 MST. The pilot occupying the left seat was not injured and the pilot occupying the right seat received minor injuries. Both pilots were able to exit the airplane unassisted.

The circle-to-land maneuver is one of the more risky activities that you may do under instrument flight rules, second only to the contact approach. Many freight operators manage these risks by prohibiting their pilots from executing circle-to-land maneuvers at night and most part 121 operators prohibit circling approaches altogether. To understand why a circling approach is potentially more dangerous than a straight-in approach, you need to understand why these minima exist and the challenges that pilots face when executing the circle-to-land maneuver.

Examine the Circular File
One of several situations that require a circle-to-land maneuver is when an approach procedure's final approach course is more than 30˚ out of alignment with any runway at the airport (15˚ for GPS approaches). In these cases, no straight-in approach minima will be published, the approach name will use a letter (starting from the beginning of the alphabet) instead of a specific runway, and the pilot must adhere to the circling minima. This approach into Hanford, California has a final approach segment that is at a right angle to both runways, so you may have no choice but to enter a modified traffic pattern and circle to land on either runway 32 or 14. If you acquire the necessary visual references early enough, nothing in the regulations prevents you from maneuvering early for a straight-in landing.



The NDB or GPS-A approach to Lakeport terminates at the NDB (which has been out of service for almost as long as I can remember) and the pilot must fly visually to the airport, provided they have the necessary visibility and high enough cloud ceiling. It is important to realize that if you begin flying a visual segment like this, then lose visual references and decide to execute the missed approach, it's likely you won't have the normal 40:1 obstruction clearance that you would if you began the missed approach at the missed approach point. Anytime you elect to fly the missed approach, you best climb like a striped monkey (i.e. at your aircraft's best rate of climb) until you reach a safe altitude.



Many pilots don't know or never learned that circling minima will also be provided when the descent gradient from the final approach fix to the runway threshold exceeds 400 feet per nautical mile, even when the final approach course is aligned with the runway. The reason is simple: You may arrive at the missed approach point, visually acquire the runway, yet be too hight to execute a landing using normal maneuvers. This is exactly what happened to the accident flight crew.

One of my favorite examples is the Gillespie LOC-D approach. The localizer is aligned with the runway, but no straight-in minima are published due to terrain and obstructions.


Finally, circling minima are often published in addition to straight-in minima. The circling minima, which are usually higher, allow the pilot to descend on the approach and, once they have the necessary visual references and are at or above the circling minima, maneuver to land on a different runway. This can be advantageous if the surface winds are favoring a different runway for which there is no instrument approach.

The Telluride LOC/DME RWY 9 approach has both straight-in and circling minima, but unlike most approaches, the straight-in minima and the circling minima are the same. I don't know if this is the approach that the accident flight crew was flying, but it likely was because the localizer offers the lowest minima of any of the approaches into that airport.



Manage the Risks
NACO instrument approach charts provide an inset map that shows the airport runway layout, relevant obstructions, and the final approach course relative to the runways. If you are using Jepp charts, you'll need to have the airport diagram out and at the ready, but that diagram won't show the approach course relative to the runways.

On reason the circle-to-land maneuver is more risky is that the pilot must transition from flying on instruments to flying by visual references and then begin maneuvering in a modified traffic pattern fashion. Throw in poor visibility, high surface winds, or night conditions and you've got yourself a real handful. Often the circling MDA is lower than the normal VFR traffic pattern and the obstruction clearance while circling in the protected area is a mere 300 feet, which means it can be really easy to run into something. The size of protected area for circling depends on the aircraft's approach speed, and generally speaking, the larger the aircraft, the faster the approach speed.
  • Category A is for aircraft flying at 90 knots or less
  • B: 91 - 120 knots
  • C: 121 to-140 knots
  • D: 141 - 166 knots
  • E: 167 knots and above

The diagram shows an idealized runway environment. Many instrument approaches contain a notice that the circling is not allowed in certain areas around the airport, due to obstructions. And some approaches specify that circling is not authorized at night. The Telluride approach is a good example of both. But of greater interest is that the approach speed of a Lear 45 may have required category C minima, which are not authorized on this approach.

In a statement provided by the Pilot-In-Command (PIC), upon arrival to KTEX the weather was reported to be below minimums; the crew elected to hold over the Cones VOR and wait to see if weather conditions would improve. The crew was given instructions, by air traffic control, to hold as published and to expect further clearance (EFC) at 1630. When the weather improved to a visibility of 4 miles and a ceiling of 2300 feet, the PIC requested a descent and approach to KTEX. At approximately 4 miles from the airport, the pilot acquired the airport environment but was not in position to land, so he called for a missed approach back to Cones VOR.

If your destination airport is reporting conditions below minima, you are not prohibited under part 91 from attempting the approach. The accident aircraft was reportedly being repositioned under part 91, but the crew elected to adhere to part 135 and 121 requirements of not beginning the approach unless landing minima were being reported at the surface. They even waited until the weather improved to considerably better than the circling minima and they had a plan B, too. But things went South from there.

The pilot then requested a second attempt to land stating that "if we did not land, we would like to be sequenced to into KMTJ" Montrose Regional Airport Montrose, CO, their alternate airport. On the second approach, both crew members stated that they had acquired the runway environment; however, they were still too high for a visual approach. The crew elected to do a 360-degree, right, descending turn, in order to get in a better position for landing. On completion of the turn, they again affirmed the runway environment and that they were aligned with the extended centerline of the runway. The airplane touched down and after full thrust reversers were deployed, the nose gear collapsed. The airplane began to slide in snow and came to a stop about mid-field, in an upright position.


Let the Circle Be Unbroken
The preliminary accident reports stated that the accident aircraft actually failed to touch down on the runway, which is curious given that the localizer appears fairly well aligned with the runway centerline. Did the crew become distracted or disoriented by the poor visibility and blowing snow?

An on-scene investigation was conducted by a Federal Aviation Administration (FAA) inspector. The initial examination of the area indicated that the airplane had touched down about 20-feet to the right, of the runway. Additionally, the airplane's wings were torn from the fuselage and the tail section had separated just aft of the engines, during the contact with the ground.
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Weather reported at KTEX 10 minutes prior to the accident was winds 260 degrees at 8 knots, visibility of 3 miles, scattered clouds at 400 feet, broken clouds at 2300 feet, temperature of 6 degrees Celsius, dew point of 6 degrees Celsius, and altimeter setting 29.85 inches of mercury.

Should you need to fly a circling approach, turn up the sensitivity on your spidey senses and consider some techniques that may prevent you from becoming an accident statistic.

If the surface winds are not aligned with the straight-in runway, you probably have a tailwind on the approach. Monitor your groundspeed carefully and consider configuring gear and flaps as necessary to control your groundspeed. Be prepared for a faster than normal speed when you break out and acquire visual references.

Slowing down will also aid you in the circling maneuver since a slower speed will give you a higher rate of turn and a smaller radius of turn with a shallower bank angle.

If the surface winds are high and you'll need to circle, you may want to go to your alternate. Even if the ceiling and visibility are above circling minima, high winds may just ruin your day.

Should you lose visual references while circling, don't kid yourself; it's time to get out of Dodge. Begin climbing, remaining in the protected circling area if necessary, and execute the missed approach ASAP.

Use the VASI and PAPI. If you stay on or above the glide path and within 10˚ of the centerline, you'll be guaranteed obstruction clearance within 4 miles of the threshold.

If ATC gives you advance notice of a need to circle, it will sound something like this:

Barnburner 123 is two miles from Mooselips, fly heading 230, maintain 3000 until established, cleared for the ILS 25, circle runway 7.

When landing at a towered airport, expect the controller to give you a cardinal direction to turn, such as:

Barnburner 123, at minimums, circle south, enter left traffic, runway 9.

Here is an illustration of various ways that a circling maneuver might be conducted, but keep in mind any circling restrictions at your particular destination.

If you have to fly the missed approach once, you may well be better off going to your alternate rather than risking a second approach. The risks of attempting multiple approaches to the same airport are subtle, but very real.

Circle-to-land maneuvers must be demonstrated on an instrument rating practical test and on an instrument proficiency check, so instrument-rated GA pilots should be familiar and proficient with the maneuver. But if the need arises for you to circle-to-land on a real-world instrument approach, be aware that you're doing something that entails more risk than a straight-in approach and landing. Like the accident flight crew, you may be better off executing Plan B and going to your alternate.