Near Miss Between Two Cessna Aircraft Near Marl-Polsum

Incident Overview and Aircraft Details On 9 August 2020, a serious incident occurred near Marl-Polsum involving two Cessna aircraft. The first aircraft was a Cessna 208B, a single-engine turboprop high-wing aircraft used for parachute drops, manufactured in 1993 with serial number 208B0358. It was operated by a German company and equipped with a PowerFLARM collision warning system and a V3+ display. The second aircraft was a Cessna 172P, a single-engine piston high-wing aircraft manufactured in 1981 with serial number 74204, privately operated and not equipped with a collision warning device. Both aircraft had transponders that were switched on. ## Flight Progression and Approach The Cessna 208B was on a descent to Marl-Loemühle aerodrome after dropping 18 parachutists at flight level 140. At 16:37, the pilot received clearance from Langen Radar to descend to the west with QNH 1016. At 16:38, he was given own navigation, and at 16:39:37, he reported being clear of Class C airspace. The pilot stated he did not see the other aircraft and that the PowerFLARM system did not generate a warning. Approximately 0.6 nautical miles or 8 seconds before the closest point of approach, the pilot initiated a left turn while the Cessna 208B was still about 550 feet above the Cessna 172P. The descent rate was approximately 4,000 feet per minute, and the ground speed was about 180 knots. The Cessna 208B then crossed the flight path of the Cessna 172P from left to right at nearly the same altitude. The Cessna 172P was on a private sightseeing flight from Borkenberge aerodrome, carrying the pilot and three passengers. The pilot was in radio contact with Langen Information and reported that the aircraft was in cruise flight on a heading of approximately 005 degrees, at 109 knots indicated airspeed, and at 2,370 feet above mean sea level. He observed a fast-descending white aircraft from the upper left, behind the A-pillar, in a left turn. He estimated that without evasive action, a collision would have occurred within the next two seconds. The horizontal distance at sighting was about 20 meters, with the other aircraft at the same altitude. He pulled the control yoke fully back and turned fully left, losing sight of the other aircraft. He did not observe any evasive maneuver by the other aircraft and did not receive traffic information from Langen Information. ## Radar Data and Closest Point of Approach Radar data confirmed the pilot's description of the approach. The closest point of approach occurred at 16:39:42 at an altitude of approximately 2,100 feet above mean sea level. The Cessna 208B passed the Cessna 172P from left to right, approximately 30 feet above and 18 meters away. Both aircraft subsequently continued their flights as planned. ## Personnel and Air Traffic Control The pilot of the Cessna 208B was a 30-year-old commercial pilot with a French CPL(A) license issued on 27 January 2010, holding various type ratings and a Class 1 medical certificate valid until 13 August 2021. He had approximately 4,900 hours of total flight experience. The pilot of the Cessna 172P was a 25-year-old private pilot with a PPL(A) license issued by the Bezirksregierung Münster on 18 February 2013, holding a SEP (land) PIC rating and a Class 1 medical certificate with TML and SIC remarks, valid until 22 May 2021. He had approximately 319 hours of total flight experience. The Langen Radar controller was a 27-year-old air traffic controller with a BAF license valid until 1 March 2023 and a Class 3 medical certificate valid until 24 July 2021. He reported that traffic was high and complex, and his sector was combined with two others. His main focus was on IFR traffic, and he only noticed the conflict when the Cessna 208B pilot reported being below Class C airspace. No traffic information was issued because the aircraft had already passed each other. The Langen Information specialist was a 27-year-old flight information specialist with a BAF permit valid until 20 October 2020 and a medical certificate valid until March 2025. She reported high and complex traffic, with 25-30 aircraft on the frequency due to good weather in the northeast. Strong thunderstorms south of Münster required many weather information broadcasts. The Cessna 172P was not affected by the thunderstorms. She saw the Cessna 208B on the radar screen above flight level 100. The Cessna 172P pilot reported staying clear of the drop zone. Due to the large altitude difference, she did not expect a conflict. At the time, the Cessna 208B was below flight level 100 (approximately flight level 91). She also had to provide traffic information to another pilot and deal with weather queries. Around 16:40, the Cessna 172P pilot reported a near miss. ## Meteorological and Airspace Information According to the Cessna 172P pilot, flight visibility was more than 10 kilometers, and the sky was clear. The METAR from Dortmund airport at 16:20 reported variable wind at 3 knots, visibility more than 10 kilometers, no significant cloud below 5,000 feet (CAVOK), temperature 34°C, dew point 14°C, and QNH 1016 hPa. The sun was in the direction of 240 to 250 degrees at an angle of 35 to 40 degrees above the horizon. The aircraft were in Class G airspace at approximately 2,100 feet above mean sea level. Class G is uncontrolled airspace with no separation provided. Flight information service is available on request. Minimum VFR conditions in Class G include 5 kilometers flight visibility above 3,000 feet AMSL or 1,000 feet AGL, and 1.5 kilometers flight visibility (for IAS max 140 knots) or 800 meters for helicopters in or below 3,000 feet AMSL or 1,000 feet AGL, with unobstructed view of the surface. Cloud clearance requirements are 1.5 kilometers horizontal and 1,000 feet vertical above 3,000 feet AMSL or 1,000 feet AGL, and clear of clouds in and below 3,000 feet AMSL or 1,000 feet AGL. Maximum speed is 250 knots IAS.