Covering form of preliminary or final report

Date of event :	2021-07-29
Incident number :	CZ-21-0475
Report :	Final report
Place of event :	On a meadow in the vicinity of the village Jablonná, 6,5 km
Registration mark :	Accident
Weight category MTOM: :	<2250 kg
Type of operation :	Recreational and sport aviation
Plane / SFM :	Sports flying machines
Type of plane / SFM :	Fisher Flying HORIZON 1
Health effects of event :	The fatal injuries
PDF document :

Description:

SUMMARY

Synopsis

On 29 July 2021, the AAII was notified of an air accident of the Fisher Flying Horizon 1 UL aircraft on a meadow in the vicinity of the village Jablonná. After taking off, the UL aircraft entered a right spin and crashed into the ground. The UL aircraft was destroyed. The pilot died at the accident site in the UL aircraft wreckage.

Factual Information

The UL aircraft was purchased as a kit and then assembled. The pilot was assembling the UL aircraft on his own for 4 years. It was a UL aircraft with a skid landing gear with which the pilot did not have any experience.

Until the event flight, the pilot flew with gliders and UL aircraft with a nose landing gear. According to a witness, the pilot conducted the last flight on the UL aircraft in July 2019, i.e. two years before the air accident. The pilot wrote down 24 flight hours over the last 2 years in the LAA CR form “Pilot’s licence validity extension”.

According to the testimony of a witness, he was waiting for suitable weather – gentle west breeze. On the critical day, mostly west wind was blowing at the speed of 12 kt (CHMI) / 14 kt (LKPM).

The pilot was training taxiing and running-up first. He only raised the tail wheel during the first take-off run.

During the second take-off run, the UL aircraft lifted from the ground and was slightly turned to the right by the wind after the take-off. According to the testimony of a witness, the pilot levelled the UL aircraft with the horizon at the altitude of approximately 100 m.

The Commission was unable to establish whether the pilot levelled the UL aircraft intentionally at a low altitude or whether the fuel feeding to the engine had been limited and the engine no longer had a sufficient power to climb.

The pilot continued flying at the same altitude with a slight drift to the right.

Probably due to reduced engine power caused by fuel deficiency, the pilot attempted to return to the take-off area. He selected a route he was familiar with more than two years ago, without taking the wind direction and speed into consideration.

During the right turn, probably due to the wind, the UL aircraft turned sharply to the right and entered a right spin.

The wind direction and speed had a negative effect on piloting, especially in the right turn. Given the absence of the Flight Manual, the Commission failed to establish whether or not the pilot had exceeded the wind speed limits.

Tests and Research

The Commission checked the engine condition, including fuel feeding to the engine, in the AAII deposit.

Some parts of the fuel system showed signs of reuse, e.g., fuel filter, fuel hoses, fuel pump for pumping fuel into tanks (refuelling).
The installation of some fuel hoses caused the fuel system malfunction. Some hoses were installed at small radius and were kinked. Solid impurities had been accumulating at the points of kinking, partially preventing the flow of fuel to the engine.

The fuel system check detected contamination at the inlet and outlet of the fuel pump (designed for refuelling) as well as in front of and inside the fuel filter.

The contamination was caused by a 100% natural material Moler-based loose sorbent with the trade name Absodan Plus. The Commission was not able to determine the sorbent origin in the fuel system.

The Commission checked the fuel residues from the cans obtained from the pilot’s home. No impurities were found in the fuel. Also, no contamination was detected by the fuel tank check.

The contamination probably originated in reused components which might have been contaminated.

The test pilot said to the AAII Commission that the fuel filter contamination found in the fuel system during flight tests was visually different from that found after the air accident.

Aircraft

The registration sheet for recording the UL aircraft in the LAA CR register was issued on 15 April 2021.
The report on the flight tests was dated 7 May 2021. The flight tests lasted in total about 5 hours. According to the test pilot’s statement, after refuelling, some issues related to a slight drop in RPMs at the maximum power of the two-stroke engine occurred at the beginning of the second half of flight tests. Contamination of the fuel filter with impurities has been detected. Once the entire fuel system, including the tank, has been thoroughly cleansed and the fuel filter and some fuel system hoses have been replaced, RPMs were no longer decreased.
Some components showed signs of reuse.
Some fuel hoses were found kinked after the air accident.
The UL aircraft fuel system was clogged with loose sorbent, which together with the kinked hoses limited the flow of fuel to the engine.
The test pilot denied that the impurities found during flight tests and the impurities found in the fuel system after the air accident were visually identical.

Weather

The above-mentioned south-west wind could have a negative effect on the course of the event flight, especially during the right turn at a low altitude.

Analysis

Pilot

Had a valid pilot licence;
Held valid medical certificates;
Had a deteriorated health condition due to multiple chronic disease changes;
Had no experience with the UL aircraft with a skid landing gear;
Was waiting for a gentle west breeze;
Flew with this UL aircraft for the first time;
Only raised the tail wheel during the first take-off run;
Took off during the second take-off run;
Levelled the UL aircraft at the altitude of approximately 100 m. The Commission was unable to establish whether the pilot levelled the UL aircraft intentionally at a low altitude or whether the fuel feeding to the engine had been limited and the engine no longer had a sufficient power to climb.
Probably due to reduced engine power caused by fuel deficiency, the pilot attempted to return to the take-off area.
He selected a route he was familiar with in the past, without taking the wind direction and speed into consideration.
During the right turn, probably due to the wind, the UL aircraft turned sharply to the right and entered a right spin.

Aircraft

Some parts of the engine and fuel system showed signs of reuse;
Some hoses were found kinked after the air accident;
The UL aircraft fuel system was clogged with loose sorbent, which together with the kinked hoses limited the flow of fuel to the engine.

Weather

The south-west wind blowing at the above-mentioned speed could have a negative effect on the course of the event flight, especially during the right turn at a low altitude.

Aircraft Accident Cause

The accident was caused by a coincidence and impact of the below-mentioned facts:

The pilot’s decision to perform the first flight after a several year break with the UL aircraft with a skid landing gear which he was not familiar with.
Possible fuel deficiency due to improper installation of fuel system elements and subsequent clogging of the system with loose sorbent.
The wind direction and speed had a negative effect on piloting, especially in the final critical right turn.
The influence of the pilot’s deteriorated health condition on the emergence and development of the emergency situation can be neither excluded nor confirmed.

Safety Recommendations

The AAII issues no safety recommendation.

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