Where to Look
While you’re still in the clouds, the question of where to look has only one obvious answer — the flight instruments. But once you emerge into visual conditions, especially in the crummy visibility permitted by minimums on most approaches, you have to split your attention between the view outside and the critical information on the instruments.
When flying as a crew, we are all taught to divide the duties, with one pilot looking out the windshield and the other monitoring the instruments. Typically the pilot flying stays on the gauges until the pilot not flying, who has been looking out the windshield, spots the runway. At that point the roles can reverse, and the pilot flying looks up and continues visually to the runway while the pilot not flying assumes the instrument monitoring.
The reason it’s necessary to monitor the instruments during the visual portion of the approach is that the view through the windshield can be very misleading. In low visibility and flying close to the ground, it can be very difficult to judge rate of descent, and it’s easy to develop a higher than desired sink rate. A visual-approach slope guidance device at the runway is a huge help for staying on the glidepath, but many runways at general aviation airports don’t have such aids, so paying attention to vertical speed is important during the final approach.
Another reason to check the instruments frequently is that airspeed is virtually impossible to estimate by looking out of the windshield, and it’s easy to fly too fast or too slow on the way from the landing decision point to the runway. Airspeed management is made even more challenging because you probably had only approach flaps extended until seeing the runway. So now you have the configuration change of extending landing flaps and adjusting attitude to maintain an appropriate glidepath, both of which can require significant power changes to stay on target approach speed.
In a crew, the pilot monitoring the instruments pays careful attention to the airspeed, of course, and verbally tells the pilot flying of any trends away from Vref. He also monitors vertical speed to be sure that a dangerous sink rate doesn’t develop. If the approach is an ILS, the pilot watching the instruments monitors the localizer and glideslope all the way to the runway and alerts the pilot of any deviation.
It’s easy to see how a trained crew has a safety edge over the single pilot at the end of an approach, but the single pilot can compensate some by using a capable autopilot. The best way to fly an approach single-pilot is with the autopilot coupled. The autopilot becomes the “pilot flying,” and the human pilot is then freed up to divide his attention between the instruments and the view ahead.
You should leave the autopilot coupled until you have a solid view of the runway. On an ILS with everything stabilized, I am a little slow to uncouple the autopilot at DH and use a few more seconds to be certain I can see enough to land and that airspeed and sink rate are on target.
Flying a nonprecision approach is more complicated and involves more risk than flying the ILS does, but again, it pays to be slow to punch off the autopilot once you gain sight of the runway. A few seconds of time looking out the windshield and analyzing your position relative to the runway are well spent while the autopilot holds altitude and course. Often I will even disengage the altitude hold mode, but not the autopilot, and command the autopilot to begin a descent. This permits even more time to look out the windshield while still glancing at the instrument to be sure my speed and sink rate are OK.
Should You Circle?
The riskiest instrument approach of all ends with a circle to the runway instead of continuing straight in. Some circling approaches involve a complete traffic pattern to the other end of the runway, for example. Others may involve a final approach course that doesn’t line up with any runway, so you have to make some kind of base-to-final turn maneuver to line up after you acquire the airport visually.
The reason there is so much risk in a circling approach is that you are flying very close to the ground — typically 500 feet or maybe even less — in visibility as low as one mile, and those conditions really screw up our normal sensations of flying a traffic pattern. It’s easy to bank too steeply, or to lose track of airspeed as you look out the windshield at the runway through the murk, as the ground rushes past much closer than we are accustomed to seeing. You must not lose sight of the runway at any time, but you also need to carefully monitor altitude, airspeed and sink rate.
The risks in a circling approach in minimum weather conditions are so great that many operators don’t allow their pilots to fly them. And a circle in low visibility at night is about the highest risk maneuver I can think of in instrument flying.
I was based in Kansas City, Kansas, for Flying in the 1980s, and there is a pretty common winter and early-spring weather phenomenon in the Great Plains that creates very strong surface winds from the south with widespread low ceilings. At the time, New Century Airport had no approaches to the south, so we had to circle out of the ILS approach to Runway 36. Even with better than the one-mile visibility minimum, it was very uncomfortable to be flying downwind at 500 feet or a little less above the ground with a rip-roaring tailwind blowing during my turn to base, and then final, up toward Iowa. I flew the circle at near minimums only once in the dark and swore never again. And the terrain around that airport is very flat. Imagine a circling approach in hilly country and you can see why some pilots just won’t fly them.
One of the many benefits of GPS is that the need for circling approaches is vanishing at many airports, including at New Century, where there is a GPS approach now to Runway 18, so the need for a terrifying circle is gone. The same is true at thousands of other airports, and with luck, GPS will make a circling approach very rare. However, GPS can’t move hills or obstructions, so at some airports a straight-in approach won’t be possible to all runways even though GPS guidance is available.
The Essential Autopilot
If you must circle, the best way is, again, with split duties in a crew. One pilot looks out to maintain visual contact with the runway while the other monitors the instruments and calls out deviations in airspeed or altitude.
A good autopilot can be the other crew member for the single pilot in a circle. With the altitude hold and heading modes selected, the autopilot will not go below minimum altitude, and the pilot can rotate the heading bug to command the necessary turns. With the autopilot holding altitude and restricting bank angles, you can take quick glances at the airspeed to make sure it’s not trending up or down. In a real circle in low weather, I would leave the autopilot coupled until turning onto final, when you can begin the descent.
If you think I believe an autopilot is essential for safe single-pilot instrument flying, you’re right. And I’m in the good company of the FAA and major training providers such as FlightSafety and Simuflite. The FAA requires that a full-capability autopilot be operating for all single-pilot flights in jets — no autopilot, no legal flight without a copilot. And the training companies in conjunction with the FAA demand that pilots fully understand and use the autopilot for all critical portions of the training and for checking flights in the simulator. Of course, the autopilot will fail occasionally in the sim, but it must be used at other times in single-pilot flying.
If you don’t have a capable auto- pilot, you are at higher risk while flying instruments single-pilot. You can try to mitigate that risk by avoiding near-minimum weather conditions, but that doesn’t always work. The major issue is lack of accurate weather reporting at many general aviation airports. You may believe, based on available observations from other airports, that you are flying an approach with lots of margin only to find out that, when you descend to the minimum altitude, visibility conditions are worse than you expected.
The bottom line to completing an instrument approach safely is really no different than it is in other aspects of flying — it takes discipline. If you apply the preamble of FAR 91.175 and follow the requirements that you see the runway clearly and be in a position to make a normal approach and landing at all times during the visual portion, the risk is very small. If you instead opt for the zero margin for error that the approach minimums allow, you are going to be flying the most risky kind of scud running imaginable.