See and Avoid

I knew the pilot of the Piper Cheyenne turboprop that January 24 collided with a Cessna 172 near Denver. Midair collision — it’s a terrifying prospect. Running into another airplane, followed by an uncontrollable descent to the earth, may be the greatest fear among general aviation pilots. Certainly this particular collision was tragic for the five who died aboard the two airplanes, and their families, as well as those injured or who suffered damage to their homes on the ground. But it’s also a reminder for the rest of us.

Although the threat is terrifying, there are things we can do to avoid midair collisions. In his book See and Avoid (Times Journal Publishing Company, Oklahoma City, OK 1988), aerobatics instructor Fred G. DeLacerda tells us how we can quantify the threat of a midair collision, and more importantly, how we can lessen our chances of that most terrifying encounter.

DeLacerda says that the “typical” midair collision follows this pattern:

  • They usually take placed in daylight hours, between April and October.
  • Skies are usually clear and visibility unrestricted at the time of the collision.
  • Most often the airplanes are not on flight plans, and not talking to Air Traffic Control.
  • Midairs usually happen at a slow speed and within 3000 feet of the ground, with a faster airplane overtaking a slower one — more than one-third (35%) of the time the faster airplane comes directly from behind. The airplanes approach head-on only five percent of the time.
  • 75% of all midairs happen within five miles of an airport.
  • Half of the pilots involved have over 1000 total flying hours; of those with fewer than 1000 total time, “pilots with fewer than 100 hours are the most frequently involved.
  • Midair collisions are almost universally fatal.

Inexperience among low-time pilots and complacency among those with more than 1000 hours, combined with excellent weather at the very beginning or the very end of a flight, seem to be the collective culprit. What can we do about it?

Seeing other air traffic in time to evaluate the threat of collision, and to maneuver to avoid impact as required, demands we consider:

  • Restrictions to visibility: Ever see airplanes taxiing with foil-type cabin shades or, in older types, rear-cabin curtains drawn? Many airplane designs have poor enough visibility as it is. Remove all cabin shades and open all curtains before flight to give yourself the best chance of seeing other airplanes.
  • Window cleanliness: Bugs or bird-dropping smears or just plain old windows may hide airplanes until it’s too late. If the windscreen is scratched or crazed enough so can’t see out, the airplane isn’t really airworthy.
  • Your own eyes: Wear glasses if you need them — don’t let pride lead to a collision. If you have trouble seeing at night, don’t fly at night.
  • Your passengers: Every passenger is a useful set of eyes. Unless it will scare them silly, take advantage of what help they can provide.

INSIDER’S TIP: I know one pilot who flies with a pocketful of $1 bills. He tells his passengers (usually his children) he’ll give $1 to whoever sees another airplane and points it out. If he (the pilot) sees another airplane first, though, he’ll take $2 from every passenger. He says it can be a lively traffic avoidance game — and airplanes never go unseen for long!

  • Air Traffic Control: Of course, ATC is a great help to you in avoiding collisions. But don’t delegate traffic avoidance entirely to ATC — both the Cheyenne and the 172 that collided near Denver had requested flight following. You’re still responsible to see and avoid.
  • Airport traffic patterns: Don’t shortcut the “45 degree entry/downwind/base/final” pattern at non-towered airports. It’s designed to make you predictable, and therefore avoidable, to other pilots.
  • Radio calls: Likewise, use your radio as suggested in the Aeronautical Information Manual. But again, never assume no one’s there just because you hear nothing on the radio.
  • Technology: There are now traffic avoidance devices trickling down into general aviation cockpits. They have limitations, too, and they may not all detect all airplanes. You’ll still have to see and avoid the traffic close in — but at least these devices tell you where to look!

DeLacerda’s research states that it takes one-tenth of a second for the average pilot to see an airplane at the distance of four miles, and for that information to transmit to the pilot’s brain. About a second lapses while the pilot’s brain recognizes that object as an airplane — it takes five more seconds to determine if there’s a danger of collision…

INSIDER’S TIP: An airplane on a collision path will have no relative movement. The way the human eye is “assembled,” it’s more prone to be sensitive to movement in peripheral vision. An object that is not moving is harder to detect since there’s no relative motion to “catch the eye.

…Next the typical pilot requires four seconds to make a decision about an evasive maneuver, and close to half a second to command his/her muscles to make a control input. The lag time between the pilot commanding a course or altitude change is from one to two seconds.

According to DeLacerda, in the end, it would take you a minimum of 11.5 to 12.5 seconds to see and avoid an airplane on a collision course.

WHAT IT MEANS: Two 100-knot airplanes closing nearly head-on must be at least 0.6 miles at the point of first recognition to allow enough time for an evasive maneuver to be successfully executed. A 180-knot (at low altitude) turboprop pilot coming up from the six o’clock position on a 90-knot trainer has to visually acquire the slower plane at least 0.3 miles out to barely miss the other airplane. Coming head-on, someone in that turboprop-and-trainer conflict must see the other from at nearly a full mile out to predict and avoid the collision.

The recent Denver collision was somewhat atypical of DeLacerda’s “typical” midair, in that both airplanes were participating in ATC “Flight Following” services, and the collision took place after sunset. But in many ways the elements were just as DeLacerda describes. Conventional wisdom is that most midair collisions occur near uncontrolled airports. At the time Dr. DeLacerda wrote his book that may have been the case, but by my observation, more and more midair collisions seem to be reported while at least one of the pilots was under the protection of Air Traffic Control. The Waukegan Field, Illinois, collision of a few years ago that killed popular Chicago radio personality Bob Collins and a Mooney Cadet / Piper Lance accident last year over Fairfield, New Jersey, suggest to me that too many midairs are taking place while the pilots are “talking” to controllers.

IMPORTANT: All ATC traffic advisories (even under IFR) are given on a time-available basis only; if a pilot is flying in visual meteorological conditions he/she is expected (by the controllers) to see and avoid other airplanes without ATC assistance. The Air Traffic Control system is designed to keep IFR airplanes from running into other IFR airplanes when in instrument meteorological conditions. When in visual conditions, even on an instrument clearance or in Class B airspace, the expectation is that the pilots will detect and maneuver around other airplanes.

BOTTOM LINE: The Denver Post wisely called this most recent midair collision “a tragedy, not a trend.” AOPA reports that the annual rate of midair collisions in the U.S. — an average of 24 in the late ’80s when DeLacerda’s work was published — is now down to seven a year. Don’t let that improvement, good weather, lots of logged flying time, or ATC contact lull you into a false sense of comfort. Work to actively see and avoid other airplanes.