The principle of “see and avoid” has been a necessity since the early days of aviation and it is still relevant in operations at uncontrolled airports. However, it has not prevented accidents involving airliners and it should not be relied upon to maintain safe separation iof airliners n controlled airspace.
A typical failure of the “see and avoid” principle occurred in 1956, when a TWA Lockheed Super Constellation and a United Airlines DC-7 collided at 21 000 ft above the Grand Canyon in Arizona, killing all 128 passengers and crew aboard the two aircraft. The Civil Aeronautics Board (CAB) accident investigation report, states:
“The present concept for separation of aircraft and avoidance of collision in VFR weather conditions, regardless of flight plan or clearance, depends on the flight crews' ability to visually provide separation between aircraft. Civil Air Regulations expressly place this responsibility on the pilots and the concept is commonly referred to as the "see and be seen" principle.
“The Board determines that the probable cause of this mid-air collision is that the pilots did not see each other in time to avoid the collision.”
Other examples of failure of "see and avoid" concerning airliners are the 1979 collision between a Pacific Southwest Boeing 727 and a Cessna 172 near San Diego (144 deaths) and the 1986 collision between an Aeromexico DC-9 and a Piper PA-28 in the Los Angeles Terminal Control Area (TCA) resulting in 82 deaths.
These accidents, in which the NTSB cited the failure of visual separation and “see and avoid” in controlled airspace, led to more stringent rules for General Aviation aircraft operating around major airports and the present classification of airspace in the USA.
Also in 1986, a collision occurred between a Twin Otter and a helicopter over the Grand Canyon National Park. In addition to the failure of “see and avoid” and relevant to the 2025 Washington DC accident, in the report the NTSB said:
“Also contributing to the accident was the modification and configuration of the routes of the rotary-wing operators resulting in their intersecting with the routes of Grand Canyon Airlines near Crystal Springs.”
Another risk factor which must be considered is the presence of military aircraft operating in airspace used by civilian airliners. The Aviation Safety Network database lists 58 midair collisions involving airliners with more than 3300 fatalities since 1954; 18 of these accidents involved a military aircraft.
We will now examine a possible reason why “see and avoid” failed in the case of the 2025 Washington DC accident:
At 20:46:01, when the CDA Local controller called PAT25 and advised them that a CRJ was at 1200 feet just south of the Woodrow Wilson Bridge, circling to runway 33, the helicopter was about 0.7 nm south of the (Arlington) Memorial Bridge and about to cross over the George Mason Memorial Bridge. At this point the helicopter was north of the airport and practically lined up with runway 01-19 so that the landing lights of any aircraft on approach to runway 01 would appear very bright. However, at this time, the CRJ had begun a slight turn to the right of the runway 01 centreline in order to initiate the circling visual approach to runway 33.
Behind the CRJ were two more airliners which the controller cleared to land on runway 01. To someone lined up with runway 01-19, the landing lights of these aircraft would appear brighter than those of an aircraft which was now pointing in another direction. According to the NTSB, the word “circling” was not recorded on the helicopter’s CVR; it is therefore possible that the crew of PAT25 misidentified the CRJ for the aircraft behind it and thereafter visually followed the path of this aircraft as it continued towards runway 01. As the helicopter continued flying south towards Hains Point, the aircraft lined up to land on runway 01 would appear on the right hand side of the helicopter, while the CRJ would be on its left. If the crew of the helicopter were wearing night vision goggles, these would restrict their field of vision, making it difficult to see the CRJ if they were looking to the right.
The above explanation underscores the difficulty (not to say the impossibility) of making a positive identification of another aircraft at night.
This tragic accident, which took the lives of 60 passengers and seven crew, dramatically demonstrates once again that “see and avoid” cannot be relied upon to maintain safe separation between airliners or between an airliner and a General Aviation or Military aircraft, even in daylight with good visibility.
In controlled airspace, the responsibility for maintaining safe separation between aircraft corresponds to the respective controller and should not be delegated to a pilot.
The next Blog discuses “visual separation” which in turn depends on the “see and avoid” principle
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