A near-miss over Norfolk saw an RAF F-35 jet come within an estimated 300ft of a civilian helicopter.

The helicopter was flying over an area close to Roughton in north Norfolk, shortly after 4pm on Wednesday, February 24, when a formation of four jets all flew within 600ft.

The civilian pilot described the F-35s' actions as "inappropriate", as they had been flying straight and level for the previous 15 miles.

After being warned by Air Traffic Control that the military aircraft were close by, the helicopter dropped from 3,000 ft to 2,500ft.

In a report into the incident after a UK Airprox Board investigation, the helicopter pilot said the first RAF jet "passed ahead by about a mile", before the second passed directly overhead.

He also described the risk of collision as "high", but the lead F-35 pilot said it was "low".

Eastern Daily Press: A report into the near-miss showed that the F-35 jets were not fitted with a TCAS anti-collision system.A report into the near-miss showed that the F-35 jets were not fitted with a TCAS anti-collision system. (Image: UK Airprox Board)

The co-pilot's TCAS anti-collision system flagged up that one of the jets came within 500ft of a crash, but the Airprox Board report found that the F-35s were "not fitted" with the technology.

And military controllers at RAF Marham said they had to work with "degraded equipment".

A comment in the report said: "The Marham SATCO reports that the controller’s honest appraisal highlights the challenges faced by controllers and the propensity for cognitive error when managing complex situations, with sometimes degraded equipment.

"The Watchman radar is sensitive to interference and clutter, particularly during the kind of weather experienced that week."

The report concluded that safety manning and equipment was "partially effective" as "Marham radar was subject to high levels of clutter".

RAF HQ Air Command said: "The F-35 has many sensors that can pick up potential airborne conflicts, particularly in contested airspace.

"It was these sensors that were able to pick up the AW139, albeit late. However, it did allow [F-35 #2] to get visual, arrest their rate of descent and pass on the traffic to the trailing F-35s.

"All F35 operators were mandated to read this Airprox as a case study to help improve awareness of the importance of lookout as much as the continued need to follow good airmanship practice."

It also commended the helicopter crew for its "proactive actions to help reduce the risk of a collision".