What aircraft was involved and where did it happen?

The accident on 2021-10-18 involved a Panavia Aircraft PA-200 (Tornado), at TRA Lauter (ED-R205), DE.

What was the probable cause of the accident?

The near mid-air collision was caused by the military aircraft descending below the established minimum altitude and the air traffic controllers' failure to provide adequate separation between the training maneuvers and the transiting civilian aircraft.

Near Mid-Air Collision in German Training Airspace

A military Tornado and a civilian Cirrus SR 22 experienced a close approach in the Lauter training airspace due to altitude restriction errors and inadequate separation.

What happened

On October 18, 2021, a near mid-air collision occurred within the Temporary Reserved Airspace (TRA) Lauter (ED-R205). The incident involved two PA-200 (Tornado) aircraft performing Basic Fighter Manoeuvres (BFM) and a civilian SR 22 flying an IFR route from Antwerp to Lugano. The closest distance between the aircraft was determined to be approximately 0.4 NM horizontally and 200 ft vertically.

The military formation was conducting air combat tactics involving high-intensity vertical maneuvers. During the maneuvers, the Control and Reporting Center (CRC) had previously increased the minimum usable flight level (floor) from FL 100 to FL 110. However, the pilot of the PA-200 did not fully internalize this new restriction, continuing the exercise under the assumption that FL 100 was still the floor. Meanwhile, the SR 22 was transiting the airspace at FL 100.

As the PA-200 descended, it breached the FL 110 limit. The Weapon Systems Officer (WSO) in the military aircraft noted the floor was being reached and called "Terminate," but the pilot did not immediately react to the instruction. The pilot of the SR 22 reported seeing a military aircraft maneuvering across his flight path but was unable to take evasive action in time.

The investigation

The BFU examined the actions of the flight crews, the air traffic controllers at the CRC, and the coordination between Langen Radar and the CRC. The investigation looked into the communication regarding the new flight level floor and the use of the "Terminate" versus "Knock it off" terminology. The investigation also reviewed the influence of the Aircraft Controller Assistant (ACA) on the decision-making process of the active controller and the procedures for allowing civilian traffic through active military training airspace.

Findings

The pilot of the PA-200 failed to maintain the required minimum altitude of FL 110.
The WSO used the term "Terminate" instead of "Knock it off"; the latter is the correct term for a flight safety hazard and likely would have prompted a faster reaction from the pilot.
The CRC controller failed to ensure sufficient separation between the military maneuvers and the civilian traffic, specifically by not implementing a lateral separation plan.
An experienced Aircraft Controller Assistant (ACA) improperly influenced the active controller's decision to keep the floor at FL 110 rather than raising it to FL 120.
The CRC allowed the SR 22 to transit the training airspace without seeking prior coordination or consent from the military users.
The PA-200 crew did not perform an "Alpha-Check" to verify that all parties were using the same reference point for traffic information.
The primary cause was that the involved crews recognized the impending collision risk too late to prevent the dangerous approach.