The IFR High Dive

Richard shares his IFR insight and gives his own interpretation on why the “loss of control” accident type is so prevalent.

From the NTSB: “The controller asked the pilot if he had weather radar on board, and he reported he did and it gave him weather every five minutes.

“At 0930, the controller reported to the pilot that the ‘lightest weather’ was ‘about a one nine five heading for seven miles and then it looks like you will be able to get back to Richmond.’

“At 0933, the controller informed the pilot, ‘looks like direct Richmond will work out for you now, and … should be exiting all of that weather I am receiving in about two miles.’ The pilot responded, ‘yes sir, that’s, uh, pretty much what we are looking at.’

“At 0935 the pilot reported, ‘echo mike is turning direct Richmond.’ He additionally reported to the controller that there was ‘a lot of lightning’ in the area; however, the turbulence was light.

“At 0936 the pilot reported, ‘echo mike, we just, uh, we got a problem. Looks like we just lost … we lost attitude.’

“The controller responded, ‘okay, uh, five echo mike, roger I’m showing you northbound right now and, uh, do whatever you need to, ah, the weather is off to your, uh, right from about your twelve o’clock back through your six o’clock on the right side and it’s about four miles east of you.’

“No further transmissions were received from the pilot.”

The Twin Comanche hit hard, likely out of control. The above is from the NTSB preliminary report. The final report with a probable cause will be a while coming, but will likely include the phrase “loss of control” and the word “thunderstorm.”

Business jets and airliners have few accidents. Of the ones that they do have, a loss of control or en route accident is rare indeed. In general aviation, en route losses of control, as in the accident just related, are common occurrences. Sure, the jets fly above much of the en route weather, but the fact that we might fly in a few more clouds is no explanation for anything other than the fact that we do a lousy job of flying in those clouds.

In total, accidents involving IFR flights, where the accident sequence begins with the airplane on an IFR flight plan and flying in instrument meteorological conditions, account for about 25 percent of the fatal accidents in certified airplanes in the contiguous 48 states. Almost half of those accidents involved a loss of control when flying in terminal and en route airspace in the most recent three-year period. That does not include a few cases where the pilot lost control inside the final approach fix on an approach.

Why is the loss of control so prevalent as an accident type?

At the risk of sounding like a broken record, because I have said this many times before, a lot of this can be laid squarely on the training and proficiency work that is done in general aviation. En route weather strategy and cloud flying is not generally taught and, until and unless a proposed change in the FARs is enacted, there has been no requirement that we do en route flying to stay legally current. The emphasis on repetitive approaches and holding patterns is badly misplaced.

Even though we fly down in more clouds than the jets do, not a whole lot of time is flown IFR in instrument meteoro-logical conditions. I fly on an IFR flight plan all of the time and have been doing so for many years. Yet less than 10 percent of my hours are “real” IFR, or that flown in clouds. Other pilots report similar percentages. As pointed out before, 25 percent of the serious wrecks in 10 percent of the flying outlines a high risk area.

Further, when studying this subject, a lot of accidents fall into the “approach” category, which suggests a pilot coming to grief while sniffing for asphalt. That’s not the way it works in real life. For it to be a real approach event, it would have to take place relatively near the airport. A lot of so-called approach accidents occur well away from the airport and involve a loss of control.

The actual low approach, where the risk does indeed increase the closer you get to the ground, starts at the final approach fix, inbound.

One thing needs to be added about approaches before addressing the en route problem. With WAAS, we get vertical guidance on GPS approaches. Will that make it safer? Apparently not. More serious accidents occur while pilots are negotiating ILS than non-precision approaches. I don’t know of any definitive information on the number of each type approach flown by general aviation airplanes, but I’d bet we fly a lot more non-precision approaches and will continue to do so until most users have WAAS and thus vertical guidance. Apparently the quality of the flying counts for a lot more than does the type approach.

When there is a terminal/en route loss of control, there is often a distraction. That distraction is often turbulence as found around thunderstorms as well as in frontal zones and areas of wind shear. Just a moderate amount of turbulence can make cloud flying a nightmare in a light airplane. Certainly what seems like reasonable bumpiness in clear air feels like it is magnified many times when we are flying in clouds. Flying in turbulence under a hood is not a very good simulation of what goes on in clouds, either. Just rain drumming on the windshield can be a major distraction.

Even though more weather radar information is available on the ground as well as in the cockpit, the number of thunderstorm-related en route accidents appears to be increasing.

The pilot in the accident related at the beginning of this story apparently had some form of weather in the cockpit. The pilot said that he had it and that it gave him information every five minutes. That’s the general update rate on Nexrad from most of the weather services, so that is apparently what he had.

From the discussion, it sounds like this pilot was avoiding the areas of heavier rain. But that is not all it takes. There can be turbulence, really bad turbulence, around thunderstorms and in any clouds associated with thunderstorms, whether or not rain is falling.

The pilot said he lost “attitude.” He might have meant “altitude” but, whatever, the airplane got away from him and turbulence was the likely reason for this.

Using Nexrad information for close storm avoidance is not a good idea. It’s a strategic tool and should be used to avoid, not penetrate, areas of weather. If it is not used strategically, the NTSB folks are going to find an ever-increasing number of handheld Nexrad receivers in the wreckage of airplanes that are lost en route.

I remember the day this accident happened. It was an active day and visually the clouds in the area where he was flying would have appeared fearful. I say that only to emphasize the fact that if it looks mean to the eye it probably is mean, regardless of what a Nexrad picture might show. Best look at stuff like that from a distance.

High-performance singles and light twins stand out in the IFR/IMC accidents, with, I think, proportionally more singles on the list. There are a few engine-failure wrecks, in singles and twins, but these are a drop in the bucket.

One equipment item that these piston airplanes have in common is an autopilot. From the types involved, virtually all have this item of equipment.

For the person flying single-pilot IFR, an autopilot is an absolute necessity. However, if a pilot does not understand everything about the autopilot, it might cause trouble for the pilot when the going gets rough.

Many autopilots have disconnect parameters. Turbulence could cause these parameters to be exceeded. In that case, the autopilot would simply shut down and the pilot would have to hand-fly or, at least, reset the autopilot. These parameters are in the autopilot supplement in the pilot’s operating handbook, and knowing all about them is important for each autopilot in each airplane that you fly. Pay special attention to any parameter that could be exceeded in turbulence.

Then there are some general autopilot features you need to understand if the device is to help you maintain control of the airplane in turbulence.

If the turbulence is convective, that means there are up- and downdrafts. That also means that if the altitude (or vertical speed) hold is engaged, the airspeed will reflect the effects of the vertical currents. The aggressive use of power may or may not allow the airspeed to be kept within limits. If the airspeed strays far away from maneuvering speed, that is definitely not good. Also, in a downdraft (or in ice or near the ceiling of the airplane), the autopilot can fly into a stall.

On a rate-based autopilot, all the device knows is rate of change. It doesn’t know anything about attitude. Thus the pitch function of such autopilots is counterproductive if convection is present. Turn the pitch function off? Unfortunately, that is not possible with some popular autopilots, so if operating in turbulence with up- and downdrafts, the whole autopilot might have to be turned off and the airplane hand flown. To me that is double jeopardy and the separation of pitch and roll should be enabled on any autopilot that is to be used in clouds.

One more thing about rate-based autopilots. In roll, in turbulence, they might cause the airplane to wallow about. That’s because they can’t instantly react to the rolling motion in turbulence. A rate of turn has to develop to call the autopilot to action. I have found, with my rate-based S-Tec autopilot, that it is best to use the wings-level mode, not the heading or nav mode, in turbulence. That way the autopilot concentrates on getting the wings back to level, not on chasing a selected heading or nav track. It thus flies a bit more smoothly.

When the air gets really rough, wings-level is the challenge, too. When control of an airplane is lost, it’s almost always roll control that is lost first. When that progresses far enough, into a steep enough bank, then pitch control becomes unavailable until the wings are brought back toward level. It is that steep bank and subsequent loss of pitch control that results in a spiral dive and those 15,000-feet-per-minute plunges to earth that are found in some accident reports.

An attitude-based autopilot does better in turbulence. The best thing is to let it fly, not on altitude or vertical speed hold, and let the airplane ride with the currents in a level pitch attitude. Air traffic controllers are usually helpful in assigning block altitudes to allow the airplane to ride up and down. If the autopilot has an airspeed hold, as the new Garmin does, maneuvering speed might be selected. I have not flown one of these autopilots in any serious level of turbulence, though, so I would reserve judgment on that.

If a light airplane is flown into the most serious turbulence of a thunderstorm, neither a real pilot nor an autopilot can likely keep it under control. The swirls in the air caused by the updrafts and downdrafts rubbing together might engulf the airplane and cause rolling and pitching moments that exceed the available control authority. That is scary to contemplate and underlines the best way of dealing with thunderstorm turbulence: abstinence.

Thunderstorms are obvious. Stay well away. When it comes to other turbulent clouds, it is best to minimize the time that you spend in them. For example, if a front is located pretty well along your course line, offset the flight by a hundred miles to get some of the flight away from the frontal zone. Certainly the way to get through a front with the least bumps is to fly through it at a right angle.

Frontal turbulence outside of thunderstorms or building cumulus is related to wind shear. This can be enthusiastic turbulence, with the most pronounced found as fronts are occluding. That is definitely something to stay away from.

Wind shear turbulence lacks the up- and downdrafts of convective turbulence, but it can be just as pesky and, when encountered while cloud flying, can be a handful in any airplane, especially in a light airplane. It can be real wham-bam stuff and is what beats the jets up while cruising near jet cores or streaks, where strong winds aloft are surrounded by wind that isn’t so strong.

There are plenty of other factors that lead to a loss of control but none compare with turbulence. Ice can be the distraction that leads to a loss of control and there the loss might come in the form of an original departure from controlled flight in a stall. That could evolve into a high speed event or, in some cases, airplanes just come spinning out of the clouds.

Instrumentation problems have long been a factor, whether because of a problem with systems, such as vacuum or electric, or with the instruments themselves. After any such failure the pilot’s ability to keep the wings level with what is left is the determinant of success.

There are also loss of control events where there is no identified reason for the occurrence. Spatial disorientation might be the culprit, or the pilot might have become impaired or dozed off.

Whatever the cause, we get back to the basics in looking for a cure. Some pilots take upset training, and any training is productive. All pilots, in the course of getting an instrument rating, perform recoveries from unusual attitudes. These techniques might help a pilot snatch control back at the beginning of an event, especially if the landing gear is extended and the throttle closed, but I doubt that they would do much good after a pilot has fully lost control of an airplane.

To fully lose control, a pilot has to become thoroughly discombobulated, confused and lost in space. To say that such a pilot can reach back and find what it would take to get out of that fix is a stretch. Pilots just don’t fly so poorly that they screw everything up and then suddenly become so smart that, with a burst of brilliance and fancy footwork, it all gets put back together.

So, the moral to the story is that staying in control is what keeps your name out of the paper. And the first and foremost element of staying in control is the ability to keep the wings of that puppy level, or close to it, no matter what. Simple, isn’t it?


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