Safety Corner

VFR Into IMC

October 1, 1990

As long as there have been airplanes, people have flown them into lousy weather and crashed. The problem is not that this happens often — it doesn't, comparatively speaking. The problem is that it kills people in numbers way out of proportion to the relative infrequency of the event.

Between 1975 and 1986, accidents resulting from VFR flight into instrument meteorological conditions accounted for only 4 percent of all general aviation accidents but produced 19 percent of all fatalities. The good news is that, while the overall GA accident rate declined 37 percent over the 12-year period, the VFR-into-IMC accident rate declined 64 percent. The bad news is that 72 percent of the VFR-into-IMC accidents resulted in fatalities, compared to 17 percent of GA accidents overall.

Last year, the National Transportation Safety Board released a safety report titled "General Aviation Accidents Involving Visual Flight Rules Flight into Instrument Meteorological Conditions." The report presented a compilation of statistics from NTSB's Aviation Accident Data System. It analyzed 361 accidents that occurred between 1983 and early 1987 in which VFR flight into IMC was listed as the probable cause or a related factor; 276 of these were fatal accidents, with a total of 583 fatalities. Of the aircraft involved, 94 percent were airplanes; the rest were helicopters.

From the material tabulated in the safety study, NTSB created a profile of the pilots involved in the accidents:

  • 51 percent were between the ages of 40 and 59;
  • 71 percent held a private pilot certificate;
  • 952 percent had less than 500 total flight hours;
  • 46 percent had less than 100 hours in type;
  • 77 percent were not instrument rated;
  • 57 percent had less than 20 hours instrument time;
  • 55 percent received a weather briefing from a flight service station or the National Weather Service;
  • 80 percent had not filed a flight plan;
  • 83 percent were flying a single-engine airplane;
  • 62 percent were flying their own aircraft;
  • 75 percent were flying for personal reasons;
  • 62 percent were in the cruise phase of operation when the accident occurred;
  • 61 percent crashed in fog or ground fog; and
  • 75 percent were killed.

One more statistic has some pretty frightening implications: 72 percent of the accident aircraft were equipped for instrument flight.

The types of aircraft involved in VFR-into-IMC accidents were reflective of the most common types in the GA fleet: Beech Bonanzas, Cessna 100- and 200-series, and Piper PA-28- and -32-series airplanes appeared most frequently in the accident reports. The Bell JetRanger — the most common helicopter in the United States — was the type most frequently involved in (nine out of 22) helicopter VFR-into-IMC accidents.

(Helicopters were involved in 6 percent of the VFR-into-IMC accidents, while they accounted for only 2 percent of total GA accidents. Because helicopters characteristically operate closer to the ground than airplanes, because they can legally operate in lower weather minimums than airplanes, and because helicopter pilot work load — VFR as well as IFR — is so much higher than for airplanes, VFR flight into IMC poses a particularly high risk for helicopters.)

Okay, so we know who was flying and what they were flying. The next question is, What went wrong?

NTSB often assigns multiple probable causes and contributing factors to any one accident. For the 361 accidents reviewed here, 1,121 probable causes and 1,714 related factors were cited.

Of the probable causes, 97 percent were attributed to the flight crew, which included 361 pilots, eight copilots, and two dual students. Even considering the normal preponderance of "pilot error" findings in accident cases, this is a very high number indeed.

Of the flight-crew-related probable causes, 42 percent cited the manner in which weather information was obtained (or not obtained), assimilated, and used. For 40 percent of the accident pilots, there was no record of any briefing whatsoever. Unfortunately, it is impossible to determine at this remove how many might have been told "VFR not recommended" had they troubled to get a briefing. Not only is the failure to get a complete weather briefing foolish, it is illegal: FAR 91.103 reads, in part, "Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight. This information must include...for a flight under IFR or a flight not in the vicinity of an airport, weather reports and forecasts...... (emphases ours).

The pilots' handling of the aircraft was cited in 30 percent of the flight-crew-related probable causes. Without examining each case individually, it is impossible to say how many pilots became disoriented and lost control of the aircraft as opposed to encountering other aircraft- handling problems (botched precautionary or emergency landings, for example). The lesson here is that all pilots should be capable of operating an aircraft solely by reference to instruments at least to the extent that they would be able to initiate a 180 degree course reversal with no loss of altitude. Even the private pilot test standards ask for more than this.

Findings explicitly related to planning, judgment, and decision-making account for 14 percent of the flight-crew-related probable causes, though certainly some of the weather-information-related probable causes could be viewed in this context as well. In the real world, as opposed to the statistical world, any VFR-into-IMC encounter reflects on the pilot's planning, judgment, or decision-making; this reinforces the importance of teaching these skills during initial and recurrent training.

Surprisingly, only 3 percent of the flight-crew-related probable causes had to do with training or experience. This may reflect more on NTSB's methods of assigning causes than it does on the training of pilots who would continue VFR flight into IMC. On the other hand, increased pilot awareness of the hazards of VFR into IMC and improved training techniques might be partially responsible for the impressive decline in the VFR-into-IMC accident rate between 1975 and 1986. As judgment and decision-making training becomes more widespread, we can hope to see a continuing decline.

Seldom cited as a probable cause, environmental conditions accounted for 69 percent of the related factors. (Most of the remaining 31 percent of the related factors again involved the flight crews.) Half of the environmental factors involved weather conditions such as clouds, fog, or precipitation that may have reduced visibility or limited the airspace available for VFR flight.

Thirty-five percent of the VFR-into-IMC accidents occurred at night. Precipitation was reported in 47 percent of these cases (as opposed to 66 percent of the daylight accident cases). Unfortunately, while the statistics analyze restrictions to visibility (fog, haze, smoke, and/or blown dust or snow) for the accident base overall, they do not allow us to determine what visibility restrictions might have been present when the nighttime accidents occurred. This is important because visibility need not be severely limited to disorient a pilot at night. Any restriction to visibility at all, including darkness itself, can conceal the horizon (or accentuate a false horizon) and help to induce spatial disorientation and vertigo. Moreover, clouds and precipitation are simply harder to see and avoid at night; the loss of outside visual references can happen with extreme suddenness.

While preventing VFR-into-IMC accidents would not lower the overall accident rate by much, it would significantly improve general aviation's fatal accident rate. Besides, fatalities are not the only measure of human suffering: A scant 11 percent of the people involved in VFR-into-IMC accidents escaped alive and uninjured.

As is the case with most pilot-related accidents, VFR-into-IMC accidents are almost entirely preventable. How do we accomplish this?

First, flight instructors must ensure that students and flight review candidates fully understand the hazards of VFR flight into IMC. This must include the skills required to keep it from happening — the foremost of which is proficiency at acquiring, reading, and interpreting weather information. Particularly with the proliferation of self-briefing services, this requirement is becoming more crucial every day. Weather is a factor in 40 percent of all GA accidents and 25 percent of all fatal accidents, according to the AOPA Air Safety Foundation.

Hand in hand with this, pilots must develop the judgment required to respond appropriately to in-flight situations like deteriorating weather. Flight instructors must expand their own understanding and their teaching of judgment and decision-making skills. Not getting a weather briefing, launching into deteriorating conditions, and continuing VFR flight into IMC reflect nothing if not poor planning and judgment. To properly understand and teach these things, instructors must avail themselves of recurrent training where these subjects are explored.

Second, and just as important, flight instructors must ensure that students and flight review candidates become and remain proficient at handling an airplane while under the hood. The standards set by the FAA for the private pilot check ride — straight and level flight, straight constant- airspeed climbs and descents, and constant-rate turns to headings — should be regarded only as bare minimums. Recovery from unusual attitudes, particularly power-on spiral dives, should be emphasized. Mastery of advanced maneuvers, such as those outlined in the FAA's Instrument Flying Handbook (AC 61-27C), lessons 13 through 16, should be the goal of continuing proficiency training.

Third, pilots of every level of experience should take advantage of the recurrent training available to them through the annual or biennial flight review process. Sharpen existing skills, and learn new ones. There are few aviation endeavors as satisfying as being able to control an aircraft solely by reference to instruments. Look again at the profile and other statistics cited above and see how much of it applies to you and your flight operations. Remember that even ATPs flying instrument-equipped airplanes are not immune from VFR-into-IMC accidents.