Covering form of preliminary or final report

Date of event:	2023.10.21
Incident number:	CZ-23-1264
Report:	Final report
Place of event:	Nymburk
Registration mark:	Air accident
Weight category MTOM::	<2250 kg
Type of operation:	Other
Plane / SFM:	Sports flying machine
Type of plane / SFM:	Tanarg neo 912S/BioniX2
Health effects of event:	The fatal injuries
PDF document:

Description:

SUMMARY

Synopsis

On 21 October 2023, the AAII was notified of an air accident of the Tanarg neo 912S/BioniX2 powered hang glider (PHG). The pilot, with another person on board (hereinafter the “passenger”) seated in the back seat of the PHG, was conducting an experience flight organised by the pilot training centre. This was the pilot’s second scheduled 20-minute flight of the day. After taking off from runway 27 at LKNYMB, the aircraft continued its flight along the River Elbe to the area east of Poděbrady and from there back to the town of Nymburk. Upon arriving at the south-eastern edge of the town, in the area known as Ostrov Park, he made a 180 degree right-hand turn with a subsequent transition to a left-hand turn. Whilst performing a left-hand turn, the PHG entered a left-hand spiral dive and, during the steep descent, crashed into the ground on the left bank of the River Elbe near the Nymburk lock chamber. Following the collision, fuel exploded and the PHG then caught fire. The fire probably triggered the USH 520 ballistic parachute rescue system.

The crew died in the crash. Due to the crash to the ground and subsequent fire, the PHG was totally destroyed. No damage was caused to a third party property.

Factual information

Description of the critical flight based on an analysis of data recorded by a smartwatch.

The first data from the smartwatch log are recorded at 09:16:16, when the PHG was located on the eastern outskirts of Nymburk at an altitude of 1,711 ft (210 m AGL) and continued its flight along the River Elbe northwards past the town of Poděbrady, which it flew over at an altitude of 1,955 ft (280 m AGL). At 09:22:30, on the eastern outskirts of Poděbrady, it turned 180° and continued back towards Nymburk, flying over a field north of the River Elbe. At 09:27:52, at an altitude of 2,085 ft (320 m AGL), it was flying over the bed of the River Elbe, which it left at 09:28:39 at an altitude of 2,058 ft (310 m AGL) and continued its flight westwards at an altitude of 2,005 ft (290 m AGL) as far as Kolínská Street on the eastern edge of the town of Nymburk, where at 09:29:30 it initiated a right-hand turn of approximately 180° at an altitude of 2,004 ft (290 m AGL) and, whilst doing so, flew over an area known as Ostrov Park. The parameters of the right-hand turn are given in Table 2, and its horizontal profile is shown in Figure 4. At 09:29:55, at an altitude of 1,988 ft (290 m AGL), the PHG smoothly entered a left-turn turn, which changed into a steep left-hand spiral at 09:30:02. The parameters of the left-hand turn are given in Table 3 and its horizontal profile is shown in Figure 5. The recording ends at 09:30:09 at an altitude of approximately 95 m AGL.

Analyses

The critical situation arose at 09:30:02, when the left-hand turn changed into a steep left-hand spiral. The final seven seconds of the data recorded by the pilot’s smartwatch clearly show that the PHG made a course change of approximately 340 degrees whilst in a spiral and lost approximately 190 metres of altitude. During this manoeuvre, a vertical descent rate of up to 48 m∙s-1 was recorded. The data recording from the smartwatch stopped at an altitude of approximately 95 m AGL. Below this altitude, the PHG flight was filmed by a camera positioned on the premises of SK Polaban Nymburk. In the footage, which lasts about a second, it is clear that the PHG was moving at a steep angle to the ground, but without any rotation. It can be inferred from this – and this has been confirmed by the findings of the forensic medical examination – that the PHG pilot continued to fly right until the end in an attempt to recover the steep, rapid descent of the glider. The parameters of the left-hand spiral far exceeded the permitted angles of roll and pitch, and, given the low altitude, did not allow for a safe recovery.

Some witnesses agreed in their statements that they had heard the engine running erratically and had seen the PHG flying relatively slowly through a left-hand turn before entering a steep left-hand spiral, during which it crashed into the ground.

Probable conditions leading to a critical situation.

Based on the findings set out above, the Commission concluded that the pilot was likely dealing with a problem with the power unit during a left-hand turn and was unable to manage the transition to an unpowered gliding flight.

Alternatively, after the loss of power and subsequent loss of speed in a left-hand turn, he pulled the control bar sharply in to regain the speed needed for a gliding flight. The passenger may have been so taken aback by this situation that he instinctively grabbed the dual control bars, thereby effectively preventing the pilot from operating the PHG. This dangerous situation was confirmed to the Commission by some experienced PHG instructors, during whose training sessions some students had gripped the control bar tightly and literally ‘froze’ in that position. A situation in which the pilot was unable to fully control the PHG was simulated during a test flight.

Conclusions/Causes

Pilot

·         He was fit to fly;

·         He had little experience in terms of flying;

·         He flew only one type of PHG, which he was very familiar with;

·         After less than five months of flying experience, he was not a suitable candidate for conducting experience flights with another person on board;

·         He offered another person on board and enabled him to fly the PHG, even though he was not a qualified instructor;

·         Whilst performing a left-hand turn, he was unable to prevent the occurrence of a critical situation in which the PHG transitioned from a left-hand turn into a steep spiral dive, during which the operational limits were exceeded;

·         Given the current altitude above ground level, he was unable to prevent the aircraft from hitting the ground;

·         Presumably in an attempt to recover a steep spiral dive, he did not deploy the ballistic parachute rescue system.

 

Operator

·         It did not have any procedures in place for this type of flight, as no regulation of the Light Aircraft Association of the Czech Republic requires them.

 

Light Aircraft Association of the Czech Republic

·         It has no regulations stipulating the conditions and requirements for performing this type of flight.

 

Powered hang glider

·         It had a valid technical certificate and was airworthy;

·         It had a valid liability insurance;

·         It was filled with the required amount of all working fluids;

·         All the controls were functional;

·         All the damage was caused solely by the PHG hitting the ground;

·         The impact with the ground at a steep angle caused damage to the wing and landing gear;

·         The subsequent fuel fire destroyed all parts of the PHG made of flammable materials, and the extreme heat also damaged some of the metal structural components;

·         Upon investigation at the place of air accident and subsequent technical investigation of the PHG wreckage in the AAII hangar, no facts that would indicate that the air accident had been caused by a technical defect were detected;

·         The fuel samples failed to meet the quality standard because they contained particles of mechanical impurities;

·         The use of contaminated fuel may have contributed to the power unit failing to operate reliably during a critical phase of the flight;

·         According to the expert examination, the engine was free of any defects.

 

Weather conditions

·         Weather conditions had no effect on the occurrence and progress of the air accident.

 

Causes

The cause of the air accident was the pilot’s failure to control the PHG during a left-hand turn, during which the PHG, for reasons that remain unclear, entered a steep left-hand spiral dive which the pilot was unable to recover due to insufficient altitude.

Safety recommendation CZ-26-0004

In light of the finding that the operator of the pilot training centre conducted specific paid experience flights solely as flights with another person on board in accordance with the operating directive UL-1: Rules for the operation of sports flying devices, the Air Accidents Investigation Institute recommends the Light Aircraft Association of the Czech Republic to amend the operating directive UL 1: Rules for the operation of sports flying devices, Chapter 5. Specific procedures for the operation of sports flying devices, paragraph 5.3. Two-seat sports flying devices by specifying the requirements and conditions under which paid experience flights with another person on board may be conducted.

 

Attached final report in PDF file is in original Czech language.