Recently this column focused on the collision between a Cessna 172 and a Piper Cheyenne just west of the Denver Class B airspace (See and Avoid, Part 1). Five aboard the two airplanes died in the tragedy; six on the ground were hurt, and at least two homes were heavily damaged. Reader response to the article was high, and most either suggested or asked for more information about avoiding this most frightening albeit rare occurrence. Again, the goal is not to assess blame, but instead for all of us to learn from this unfortunate event, and perhaps change our way of doing things to make midair collisions even less likely.
The NTSB preliminary report of this collision is now available online. Read it and you’ll note the PA31 (flown by the man I knew) had an inoperative transponder, either broken or simply turned to something other than the Mode C, altitude-reporting position. The Cheyenne was therefore not reporting altitude, although ATC radar was painting his transponder target and the pilot was receiving Flight Following services. In that case the pilot should have (if he was aware of the transponder’s condition) advised ATC of any altitude changes, which might have helped the controller intercede and prevent the collision.
THERE JUST WASN’T TIME
There just wasn’t time the way this scenario played out, for only one of the pilots to act to avoid the collision. Only 2.5 minutes elapsed between the time the Cessna called for Flight Following and the moment the planes collided, nearly head-on. There was a 340-knot (over five miles a minute) closure rate. When ATC gave the Cheyenne the final traffic advisory (12 o’clock, one mile and, although the controller did not know it, at the same altitude) the pilots of either airplane had about 12 seconds’ maneuvering time to avoid either other. Important: The timeframe was exactly the “11.5 to 12.5 seconds” human factors expert Dr. Fred G. DeLacerda says is necessary to successfully see and avoid an airplane (from See and Avoid, Part 1). The low-light conditions and the lack of relative movement (while on a collision course) did not help; it seems the Cheyenne pilot had just begun an evasive maneuver (the reported sharp turn to the left) when the two hit…exactly as human factors research predicts an alert pilot would.
What more can we learn from this?
- When participating in flight following, advise ATC of any altitude changes — especially if they are not able to read your altitude. ATC was providing advisories to both pilots; knowing the Cheyenne was passing through the Skyhawk’s altitude might have made him/her more likely to have issued a suggested heading (or altitude) change to one or the other pilot.
- When advised of conflicting traffic, turn on strobes and landing lights. A flashing landing light (such as the Pulselight™ system, which automatically flashes on and off the landing light when the cockpit switch is in the “pulse” position) is far easier to see from a distance (all that flashing attracts the eye). Insider’s Tip: When in non-Pulselight™ airplanes I manually turn the landing light on and off a few times when I’ve been given a conflict alert close in.
- Keep the “big picture” in your head to prevent a collision. The Cessna pilot was not given a traffic alert, but might have noted that the Cheyenne was issued a traffic alert of a Cessna at 12 o’clock at his (the Cessna’s) altitude. If the pilot of the Cessna had detected he was the subject of a traffic call he might have been more vigilant, and able to pick out the Piper in time to maneuver… which may have averted the crash.
- We (as pilots and instructors) ought to review collision avoidance techniques, i.e., develop the strategy that, unless conditions specifically warrant otherwise, we should always maneuver to our right to avoid other traffic — keeping the other airplane to our left (the pilot’s side of the airplane) for greater visibility. If the Cessna pilot had been able to pick out the Cheyenne and had began his own “12 second” maneuver, and they had both turned the same direction (relative to their own flight paths), the two maneuvers may together have avoided catastrophe. This quintuple-fatality (and injurious to persons on the ground) would have become a “near miss.“
- When flying high-performance airplanes in low visibility at low altitude, throttle back to give yourself more time to see and avoid other traffic and obstacles — and others more time to find you and steer out of the way.
- If given a converging traffic alert within five miles, and you’re unable to visually identify the other airplane, make or ask for a shallow turn away from the target. Ask for an altitude change if you’re aware that you’re both at the same altitude (consider visibility and wing location — climb in a high-wing, descend in a low-wing). Don’t wait until you’re within a mile, when ATC radar does not provide the detail necessary to allow the controller to assist further.
- Don’t depend on ATC — “See and avoid” is the primary means of collision avoidance, even when under ATC guidance or control. Don’t assume ATC will protect you from all traffic; conflict alerts between even IFR airplanes are given on a “time available” basis. If you’re flying in visual meteorological conditions (VMC), ATC will expect you to maneuver visually around airplanes and obstacles, even if you’re flying a filed IFR flight plan.
BOTTOM LINE: Do everything you can to been “seen” — that includes turning on all the lights — whenever you’re given a traffic alert and keep the lights on as a general rule in congested airspace. To “avoid” an airplane you don’t see, communicate precisely with ATC — especially when traveling fast and / or when ATC has an incomplete picture of your altitude and / or intentions. And don’t forget to enjoy the view — sometimes what you see is more than pretty; sometimes, it can save your life.