Mid-Air Collision

On December 7, 1997, following a pleasure flight in the area of Saint-Hubert, Quebec, a Cessna 150 (C150) joined the left-hand circuit downwind for Runway 29 at Mascouche Airport, Quebec, to come to a complete stop. At the same time, a Cessna 172 (C172), took off from Runway 29 to conduct touch-and-go landings on the runway following a left-hand circuit. The two aircraft collided in flight on the final leg for Runway 29 and crashed. There were two occupants on board each aircraft, and all four suffered fatal injuries. This synopsis is based on the Transportation Safety Board of Canada (TSB) Final Report A97Q0250.

The pilot of the C172 held a Class 3 Instructor Licence — Aeroplane Category. He had accumulated over 2500 hours’ flight time at the time of the occurrence. The instructor was to review exercises in the circuit before letting the student pilot make a solo flight. The student pilot had a little over 21 hours’ flight time. The pilot of the C150 had owned the aircraft since April 1997 and held a private licence. He had begun his training in September 1994 and had accumulated over 200 hours’ flight time. He had brought a passenger with him.

The weather was VFR and conditions favoured the use of Runway 29. Both aircraft had joined a left-hand circuit for Runway 29 at Mascouche. Another aircraft was preceding them, but it was on the ground, clear of the runway, by the time of the accident.

Data gathered from radar at the Montreal area control centre made it possible to reconstruct the following information:

1420:51 — The C150, arriving from the Saint-Hubert area, made a long detour northwards to approach Mascouche Airport on the upwind side of the circuit as the C172 took off from Runway 29.

1421:49 — When the C150 joined the left-hand downwind leg for Runway 29, it was preceded by another aircraft, which would have been first in the landing sequence. At that time, the C172 began its turn for the crosswind leg.

1423:11 — The C150 stretched its downwind leg while the aircraft ahead of it turned on the final leg. This aircraft would come to a complete stop. The C172 began the left-hand downwind leg for Runway 29.

1424:38 — The C150 was now established on the final leg about 5.8 NM from the end of the runway while the C172 was established on the base leg.

1425:17 — When the C172 turned on the final leg, it was four nautical miles from the end of the runway. The C150 was ahead of it but at a lower altitude. The approach speed of the C172 was higher than that of the C150.

1426:00 — The radar identified only one target and then none.

At the time of the occurrence, a camera in a police patrol car captured images of the collision showing that, shortly after the initial impact, the two aircraft adopted a high nose-up, almost vertical, attitude. The aircraft appeared to become entangled and then separated again just before hitting the ground. When they separated, there was insufficient altitude available for either aircraft to effect a recovery. Measurements taken from the videotape’s digitized images show that the aircraft were at an altitude of 450 ft AGL at the time of impact. The images confirm that the C172 was higher than the C150. The images also confirm that the C172’s landing light was on at the time of the mid-air collision while that of the C150 was off.

The use of the landing lights, both during the day and at night, greatly enhances the probability of the aircraft’s being seen. Transport Canada recommends that pilots use the landing light during the take-off and landing phases and when flying below 2000 ft within terminal areas or control zones. The landing light of the C172 was on, thereby increasing the possibility of its being identified by the C150 during certain phases of flight. This advantage, however, proved useless when the aircraft were on the final leg because the C172 was behind and above the C150.

The two aircraft crashed 2000 ft from the runway threshold. After the accident, the C150 had several laceration marks — caused by a propeller — on the top of the cabin; the aircraft’s structure was very damaged. The two aircraft used two-way VHF communication radios, which allowed them to communicate on the frequency employed by crews using Mascouche Airport. Mascouche Airport does not have a control tower or a two-way communication recording system.

Section 602.101 of the Canadian Aviation Regulations (CARs) specifies the procedures to join the circuit at an uncontrolled airport lying within a mandatory frequency (MF) area, and CAR 602.102 specifies the procedures for aircraft flying continuous circuits. The information gathered indicates that the crews established radio communication on entering the circuit, on the downwind leg and on the final leg, as prescribed in the regulations.

Crew attention is a determining factor in collision avoidance. Good scanning technique is required, as is looking outside the cockpit as often as possible. Close attention to radio communications helps form a mental image of the surrounding traffic and reduce the risks of collision.

Analysis — Although the C150’s pilot was arriving from the south, he had bypassed the airport in a long detour to the east in order to approach the airport on the north side and join the Runway 29 circuit. Thus, he followed the procedure for joining the circuit at an uncontrolled aerodrome in every respect, just as the pilot of the C172 was following the procedure for continuous circuits. Furthermore, the aircraft reported where they were supposed to.

The pilot of the C150 knew that another aircraft was ahead of him and probably decided to stretch out his downwind leg to give this aircraft time to touch down and clear the runway. The crew of the C172 did not stretch their downwind leg to follow the aircraft ahead. The crew may have confused the traffic that had just landed with the C150, still in the circuit, or perhaps they were not attentive to the communications that would have allowed them to know what aircraft were ahead.

The crew of each aircraft could have seen the other aircraft at several places in the circuit. The pilot of the C150 could have seen the C172 when he turned onto the base leg and after his turn onto the final leg. The pilot of the C172 could have seen the C150 while the C172 was on the downwind leg and during its descent on the base leg. Visual flight is limited by the ability to see and be seen. Several factors can alter a pilot's chances of seeing and being seen, such as the appearance of the aircraft, the environment, or a lack of attention or operation of the radios; any of these could explain the collision, but no single factor could be identified in the investigation. The lack of evasive action by either aircraft indicates that neither aircraft had noticed the other.

The TSB recently issued another final report on a nearly identical mid-air collision, Report A99P0056. On May 16, 1999, a Cessna 172, with one passenger on board, was conducting left-hand circuits to Runway 32 at 108 Mile Airport, B. C. Shortly after it turned onto final and descended toward the runway, the aircraft collided with a second Cessna 172, which was inbound to the airport from the south on an established straight-in approach to the same runway. The collision took place at about 300 ft AGL. Both aircraft were locked together by the collision and became uncontrollable. They descended at a steep angle and crashed about 2000 ft south of the approach end of the runway and about 500 ft east of the runway’s extended centerline.

A TSB review of mid-air collisions that occurred between August 1989 and August 1999 indicates that there were 17 accidents of this type in Canada during this 10-year period. Of these accidents, eight involved some form of formation flight. Of the remaining nine accidents, three occurred in practice training areas and six occurred in the vicinity of uncontrolled airports between aircraft that were not associated with each other.

Following a mid-air collision in 1995, the TSB recommended that Transport Canada (TC) ensure that aircraft are flown at reduced airspeeds, consistent with safe manoeuvring, in the vicinity of aerodromes where separation relies primarily on the see-and-avoid concept. The TSB further recommended that TC take both long- and short-term action to increase the ability of pilots to recognize in-flight collision geometry and optimize avoidance manoeuvring.

TC responded positively to both recommendations. In 1996, TC published four articles about collision avoidance in issue 2/96 of the Aviation Safety Letter. Additionally, TC has provided relevant information in the A.I.P. Canada and has produced and distributed a poster entitled "Uncontrolled Aerodrome VFR Circuit Procedures" to highlight and review applicable pilot reporting and communication requirements within MF and ATF areas. More recently, TC has published a series of manuals on human factors in aviation; developed a video on procedures to be used at uncontrolled aerodromes, titled A Simple Mistake; and amended the Flight Instructor Guide to provide more comprehensive training and education in related issues.

Recently, there have been three in-flight collisions in British Columbia involving a total of six aircraft and 12 people. All but three of the people involved died in the accidents. With the increasing concerns brought on by these accidents, NAV CANADA developed, and recently began conducting, pilot education sessions on air traffic procedures that are used at controlled and uncontrolled aerodromes. Both the TSB and TC have participated in these sessions to provide information on recent mid-air collisions and on the limitations of human recognition and response. This active program is expected to raise the awareness of operators, owners, and pilots of the importance of using all available equipment and procedures to reduce the risk of an in-flight collision.