The U.S. Air Force has urged its pilots stationed at RAF Lakenheath to keep their cockpit windows clean in order to avoid collisions with British aircraft.
The warning comes after F-15s based out of southeastern England were involved in 19 near-misses with U.K. aircraft over the past five years, according to a report from the U.K. Airprox Board, obtained by the BBC. The board is responsible for British airspace safety.
Some of the incidents may have occurred because smaller civilian aircraft are not equipped with transponders, which would emit signals that could reliably be picked up by an F-15’s radar.
A reference sheet used by American pilots stationed at RAF Lakenheath instructs them to ensure their windscreens are clean and to “scan, scan and scan,” as a part of their in-flight actions.
“The next time you fly, consciously note how much time you spend looking outside the cockpit,” the reference sheet reads. “Compensate for the blind spots due to aircraft design and flight attitude by moving the head and maneuvering the aircraft.”
During an April incident, two F-15s narrowly avoided a British civilian glider after the American pilot identified the civilian by eyesight, rather than relying on radar.
“The fast-jet banked sharply and steeply right, pulled hard and rolled inverted,” according to the civilian account of the incident contained within an Airprox Board report. “There was no need for the glider pilot to take avoiding action because of the aggressive action taken by the fast-jet.”
The British Glider Association commended the F-15 pilot’s vigilance during the incident, according to the BBC.
The civilian pilot assessed the risk of collision as “high,” while the F-15 formation’s lead pilot assessed it as “low,” according to the report.
“The lead pilot had spotted the glider in good time, and had called it to his wingman so that he too avoided it,” the Airprox Board report states. “In doing so, the [U.S. Air Forces in Europe] advisor noted that the manoeuvre taken by the wingman sounded dramatic, but was in fact standard practice at low-level.”
The near-misses haven’t been isolated to smaller civilian planes, however.
A more serious incident occurred in January, when two F-15s nearly collided with a Royal Air Force Voyager tanker aircraft.
The BBC reported the near-miss occurred at about 16,000 feet and roughly 10 miles off the coast of north Norfolk, after the Voyager had refueled two RAF Typhoons.
The aircraft were within 50 meters of one another at one point, according to the RAF pilot, who said “light turbulence was experienced as the Voyager flew through the F-15 jetwash,” according to the Airprox report of the incident.
“The Voyager pilot opined that it should not be underestimated how close this incident was to being what could have been a catastrophic mid-air collision,” the report reads.
In that incident, the Airprox Board determined “there had been a serious risk of collision where luck had played a major part.”