Near Collision Between Cessna 404 and Eurocopter EC 135T2 in Stuttgart Control Zone

Casualties unknown • Kontrollzone Stuttgart, DE

A serious flight disturbance occurred in the Stuttgart control zone when a Cessna 404 and an EC 135T2 helicopter approached within 0.1 NM and 100 feet of each other.

What happened

On July 9, 2007, at 13:41 local time, a serious flight disturbance occurred within the Stuttgart control zone (Class D airspace). The incident involved a Cessna 4/04 performing a commercial IFR departure toward Girona, Spain, and an Eurocopter EC 135T2 helicopter crossing the control zone under VFR conditions.

The Cessna 404 departed Stuttgart Runway 25 and was subsequently handed over from Stuttgart Tower to Langen Radar. During the climb, the Cessna crew requested a deviation from their assigned departure route to fly directly toward Olben. While the radar controller instructed the crew to wait, the aircraft continued its climb.

Throughout the sequence, air traffic controllers provided multiple traffic advisories. The helicopter crew received a TCAS Traffic Advisory (TA) approximately 23 seconds before the encounter. Although the helicopter crew eventually sighted the Cessna, the two aircraft reached a horizontal separation of only 0.1 NM with a vertical separation of 100 ft. The Cessna crew reported having to execute a decisive turn to avoid a collision.

The investigation

The BFU investigation examined the communication between the two different air traffic control units (Stuttgart Tower and Langen Radar) and the various radio frequencies in use. The investigation reviewed radar recordings, radio transcripts, and the operational procedures regarding the handoff of IFR traffic. The investigators also analyzed the visual sightings and the use of onboard collision avoidance technology (TCAS) by the helicopter crew.

Findings

  • The incident was driven by the presence of mixed VFR and IFR traffic within the same controlled airspace.
  • The two aircraft were being managed by different air traffic control centers on different radio frequencies.
  • Misjudgments and false expectations by both the air traffic controllers and the flight crews contributed to the close approach.
  • The Stuttgart Tower controller expected the Cessna to turn left based on its assigned route, assuming a slight correction by the helicopter would suffice.
  • The Langen Radar controller assumed the helicopter crew had long since spotted the Cessna and would perform independent separation.
  • The Cessna crew, believing the helicopter crew had seen them via radar confirmation, expected the helicopter to maneuver away.
  • The helicopter crew was unaware that the Cessna was operating under IFR rules, and they had not been informed of this status.

Probable cause

The close approach was caused by the complexities of managing mixed VFR and IFR traffic across different control sectors, compounded by erroneous expectations from both controllers and flight crews regarding the other aircraft's intentions and visibility.

Frequently asked questions

What happened in the 2007-07-09 1) Cessna Aircraft Company C404 accident near Kontrollzone Stuttgart, DE?

A serious flight disturbance occurred in the Stuttgart control zone when a Cessna 404 and an EC 135T2 helicopter approached within 0.1 NM and 100 feet of each other.

What aircraft was involved and where did it happen?

The accident on 2007-07-09 involved a 1) Cessna Aircraft Company C404, at Kontrollzone Stuttgart, DE.

What was the probable cause of the accident?

The close approach was caused by the complexities of managing mixed VFR and IFR traffic across different control sectors, compounded by erroneous expectations from both controllers and flight crews regarding the other aircraft's intentions and visibility.

Loading the flight search…