Fatal Mid-Air Collision at Watsonville Municipal, CA

The Final Approach

At about 2:55 p.m. on August 18, 2022, two small airplanes were converging on the same runway at Watsonville Municipal Airport in California.

One was a Cessna 152, registration N49931, a single-engine aircraft being flown in the airport traffic pattern. The other was a Cessna 340A, N740WJ, a twin-engine airplane approaching the airport from the east.

The weather was not the obvious problem. Visibility was about 10 miles, conditions were visual, and there was no storm obscuring the runway. Watsonville was a non-towered airport, meaning there was no operating control tower assigning landing sequence or providing conventional separation. Pilots were expected to communicate their positions and maintain visual separation themselves. (FAA Safety)

Both pilots were making radio calls.

Both pilots knew other traffic was nearby.

And yet, in the final seconds, the two aircraft occupied the same piece of sky.

The Cessna 152 was turning toward final for Runway 20. The Cessna 340A was making a straight-in approach to the same runway. The pilots eventually became aware of one another, but the available separation had already collapsed.

The 152 pilot announced a go-around.

Seconds later, the airplanes collided at roughly 150 feet above the ground. (Accidents App)

All three people aboard the two airplanes were killed.

The accident became a particularly important case study because the aircraft were functioning normally, the weather was good, the pilots were communicating, and the collision occurred in an environment where both pilots were supposed to be looking for conflicting traffic.

Two Different Approaches to the Same Runway

The Cessna 152 had been conducting repeated takeoffs and landings in the traffic pattern at Watsonville.

According to the NTSB investigation, the pilot had been making position reports for most of the previous traffic-pattern legs. The Cessna 340 pilot, meanwhile, was receiving flight-following services before approaching Watsonville and then transitioned to the airport's CTAF environment.

The twin-engine aircraft initially reported its position about 10 miles east of the airport at approximately 4,500 feet and announced that it would make a straight-in approach to Runway 20.

The 152 then reported downwind.

The Cessna 340 subsequently reported three miles from Runway 20 on the straight-in approach.

Then the Cessna 152 reported turning left base.

At that point, the two flight paths were converging.

The radio calls created a record of the developing conflict, but neither pilot had yet established the visual separation necessary to guarantee that the aircraft would remain clear of one another. (Accidents App)

The Cessna 340 pilot later reported that he was one mile from the airport and was looking for the traffic on the left base.

The Cessna 152 pilot saw him.

But what he saw was not a comfortably separated aircraft on a predictable final approach.

The twin Cessna was closing rapidly.

The 152 pilot announced that he was going around because the other airplane was coming toward him quickly.

Speed Became a Critical Factor

The NTSB's reconstruction using ADS-B data revealed an important detail.

The Cessna 340 maintained a groundspeed of approximately 180 knots throughout its approach until the collision.

That is extremely fast for an airplane that is approaching a runway to land.

The investigation found that the Cessna 340's landing gear and wing flaps were still retracted when the wreckage was examined. Those findings were consistent with the aircraft not yet being configured for landing when the collision occurred. (FAA Safety)

The speed mattered because it reduced the time available for the pilots to detect, interpret and avoid the conflicting aircraft.

At 180 knots, an airplane covers three nautical miles in approximately one minute.

That means the difference between a traffic conflict being merely noticeable and becoming immediately dangerous can be measured in seconds.

The Cessna 152 was slower and was operating within the normal traffic pattern. The Cessna 340 was approaching from outside the pattern at substantially higher speed.

The result was a rapidly changing geometry.

A pilot looking for another aircraft does not simply need to see it. The pilot has to determine its direction, speed, altitude and projected flight path, then decide whether the aircraft will remain clear.

When the conflicting aircraft is moving much faster than expected, the visual picture can change very quickly.

The Collision

Witnesses described seeing the Cessna 340 moving unusually quickly during the approach.

One witness observed the Cessna 152 turning onto final and heard its pilot announce the go-around.

The witness then saw the Cessna 340 maneuver and its wing strike the Cessna 152.

The collision occurred at approximately 150 feet above ground level.

The Cessna 152 fell onto airport property. Its left wing separated and portions of the aircraft were scattered away from the main wreckage.

The Cessna 340 continued into the airport environment and eventually crashed into a hangar area, where a post-impact fire occurred. (Accidents App)

Contemporary reporting initially described the event simply as two aircraft colliding while attempting to land. The Associated Press reported that the airport did not have a control tower and that two people were aboard the twin-engine Cessna while the Cessna 152 carried only its pilot. (News Channel 3-12)

The later investigation provided the much more detailed picture.

No Mechanical Failure

Investigators examined both aircraft.

They found no evidence of a mechanical malfunction that would have prevented normal operation.

That is significant because neither airplane was forced into the collision by an engine failure, control-system malfunction or structural problem.

The accident developed through the interaction of flight paths, speed, traffic awareness and visual avoidance.

The NTSB also examined toxicology results from both pilots. Low levels of substances were detected, but the Board did not consider the findings causal to the accident. (FAA Safety)

The central problem remained the failure of the Cessna 340 pilot to see and avoid the Cessna 152.

NTSB Probable Cause

The National Transportation Safety Board determined:

— National Transportation Safety Board, WPR22FA309. (Bureau of Aircraft Accidents Archives)

That wording is important.

The NTSB did not determine that the accident was caused by a communications failure. The pilots were communicating.

And it did not identify a mechanical failure.

The critical failure was visual traffic avoidance.

The Non-Towered Airport Problem

Watsonville illustrates a fundamental difference between towered and non-towered airport operations.

At a towered airport, controllers normally sequence arriving aircraft and issue landing clearances.

At a non-towered airport, the system depends much more heavily on pilots creating a shared traffic picture through standardized radio calls, predictable patterns and visual scanning.

The FAA encourages pilots to use standard traffic patterns and emphasizes that the pilot in command remains responsible for collision avoidance. (Accidents App)

That does not mean radio calls are unnecessary.

Quite the opposite.

Radio calls create situational awareness.

But a radio transmission is not the same thing as separation.

A pilot can report a position accurately and still create an unexpected conflict through speed, geometry or approach choice.

And a pilot can believe another airplane has seen him when it has not.

Accident Facts

The NTSB docket contains CTAF recordings, ADS-B data from both airplanes, witness statements, aircraft examinations and medical information, making the accident unusually well documented for an ATC-focused reconstruction. (NTSB Data)

The Broader Safety Lesson

The Watsonville collision is a reminder that good weather can create a false sense of security.

There was no catastrophic mechanical failure.

There was no loss of radio communication.

There were simply two airplanes, one runway and insufficient separation during the last seconds of the approach.

The most important lesson is therefore not simply to make radio calls.

It is to build a complete traffic picture and continuously verify that picture visually.

Straight-in approaches can be efficient, but they must never disrupt the flow of traffic already operating in the pattern. Speed must be managed so that pilots have enough time to identify conflicting traffic and react.

At Watsonville, the final warning came from the smaller airplane's pilot.

He saw the danger.

He attempted to go around.

But at roughly 150 feet above the ground, with a much faster airplane closing from behind, there was no longer enough margin.

Three people died because two perfectly flyable airplanes arrived at the same point in space at nearly the same time.

That is the essence of the see-and-avoid problem: the aircraft do not need to fail for the system to fail.

Sources

• Original ATC recording