Covering form of preliminary or final report

Date of event :	2021-04-25
Incident number :	CZ-21-0141
Report :	Final report
Place of event :	7.5 km SE of Znojmo
Registration mark :	Accident
Weight category MTOM: :	<2250 kg
Type of operation :	Recreational and sport aviation
Plane / SFM :	Gliders
Type of plane / SFM :	Ventus cM
Health effects of event :	With injury
PDF document :

Description:

Synopsis
On 25 April 2021, the AAII was notified of an air accident of the Ventus cM glider 7.5 km southeast of Znojmo. The glider pilot was unable to find a suitable thermal lift, was unable to start the glider engine and attempted to land on a field in close proximity to a vineyard. During the landing manoeuvre, the glider broke a concrete post in the vineyard fence with its wing. The pilot sustained severe injuries. The glider was destroyed.

Event Flight
The pilot planned a flight along the following flight route: Břeclav – České Budějovice – Pilsen – Břeclav. At 9:00, at LKBA, he assembled the glider, conducted pre-flight preparation, including engine inspection, and installed two freshly charged batteries in the glider. The glider took off from LKBA using the engine at 9:54. The pilot set out for the planned 700-km-long route at 10:04.
Near the town of Znojmo, after about 50 minutes of flying, the pilot was unable to find a suitable thermal lift and that is why he decided to start the engine at the altitude of approximately 400–500 m AGL. The engine only cranked during the first start attempt. The pilot attempted to start the engine three times, but in vain.
After the third unsuccessful attempt to start the engine, at the altitude of approximately 200 m AGL, the pilot decided to land on a field.
The pilot made three left-hand turns during which the glider was descending at an increased vertical speed until the critical phase of the flight. The first two turns were made near the vineyard and the third above the vineyard. In his testimony, he said he had not been aware of the vineyard.
Because of the low altitude, he did not have time to retract the engine or extend main landing gear wheel. When making the last turn into wind, the glider lost uplift pressure due to a low speed and “slid down the wing”.
Just above the ground, the pilot levelled the glider, and the glider, in a right roll, crashed into a concrete post in the vineyard fence with the right half of its wing and broke it. Having broken the concrete post, it was rotating for about 13 m and then crashed against the ground. It then bounced off for cca 4.5 m. It kept moving by way of skidding for cca 12 m until full stop.

Damage to Aircraft:
The glider was completely destroyed as a result of the accident.
Glider damage scope:

broken fuselage at two places (front part and engine attachment point),
longitudinal fuselage rupture in its upper part,
tearing the right half of the wing out of the fuselage,
broken right half of the wing,
deformed wing flaps,
deformed hinges in the right and left wing halves,
deformed elevator hinges,
deformed engine mount,
torn off instrument panel, broken instruments,
deformed pedal controls,
deformed roll control,
broken cab canopy, smashed organic glass canopy.

Glider Pilot

Male, aged 56 years

Meteorological Information
The available data on the weather situation and development show that in the air accident area near the village of Vrbovec, a north-west wind was blowing at the speed of 10–12 kt with gusts of up to 23 kt. Visibility was over 10 km. There was no precipitation. The sky was mostly clear, covered with low clouds of SC type, and sometimes there were also cumuliform clouds. The temperature was around 11 °C. There was no frost. Turbulence was weak.

Wreckage and Impact Information
The air accident site was located 7.5 km SE of Znojmo between the villages of Derflice and Vrbovec. It was a field with low-grown grain.
The fragments of the right half of the wing, the lower fuselage and the organic cabin canopy were scattered between the broken concrete post and the point of glider fuselage stopping.
The first collision with the ground resulted in damage to the front and lower part of the fuselage and breaking of the right half of the wing. The glider bounced off and the pilot cab canopy as well as front and lower parts of the fuselage were damaged after the second contact with the ground and fuselage skidding. The detached broken right half of the wing remained wedged under the glider fuselage.
The wreckage of the glider was located in the field approx. 5 m from the vineyard fence. The engine was in the extended position. The gear wheel was retracted. The left half of the wing was not damaged.

Analyses
Activities before the critical flight
The Commission was provided with records in the daily aircraft logbook. On 23 and 24 April 2021, the pilot carried out two overflights lasting 5:35 hrs and 7:15 hrs, respectively. On 25 April 2021, he planned a 800-km-long flight lasting approx. 8 hrs. It may be assumed that the previous two flights could have caused his overall fatigue and thus affected the pilot’s concentration during the critical flight.

Event Flight
The critical flight phase was analysed with the use of flight data records, an analysis of the meteorological situation, glider flight trajectory on the map, and pilot’s testimony.
The pilot, according to his testimony, conducted due pre-flight preparation, including inspection of engine operation. He installed two fully charged batteries in the glider. At 9:54, he took off from LKBA using an engine. After approx. 50 minutes of flying on the route, he was unable to find a suitable thermal lift and that is why he decided (according to his testimony) to start the engine at the altitude of approximately 400–500 m.

Pilot’s decision-making process when selecting an area for emergency landing
The pilot made three left-hand turns. The flight data show that during these turns, the glider was descending at an increased vertical speed. The pilot made the first turn north of the vineyard, the second while heading towards the vineyard, and the third above the vineyard. By making the turns, the pilot lost situational awareness of the fact that his trajectory was directed above the vineyard. In his testimony, he confirmed that he had not been aware of the vineyard.
At the point of entering into the first turn, at 10:46:24, the Znojmo airport, located in the flight heading, was approx. 4.5 km far away. Considering the prevailing meteorological conditions – wind direction and speed, flight altitude, and also the distance from Znojmo airport, the glider was able to reach Znojmo airport with a vertical descent according to the flight data record. During the check of the flight altitude profile between the first turn initiation point and Znojmo airport, an altitude change of approximately 13 m was detected. At the same time, the flat area offered sufficient number of surfaces suitable for an emergency landing.
Compliance with the procedure to continue on the flight course to the area/s suitable for emergency landing into the terrain due to the prevailing meteorological conditions – north-westerly flow, should have preceded the in-flight engine start. This decision would have reduced the pilot’s strain and stress level. In the event of an unsuccessful engine start, he would have been able to continue in approach to landing without dangerous manoeuvres at low altitude and low speed.
The pilot assumed a successful engine start. At the moment he realised that the engine would not start, he did not have time either to retract the engine into the fuselage, or to extend the landing gear due to the low altitude above the terrain.

Starting the engine during flight
The pilot stated that he followed the same procedure for starting the engine as he had done on the ground. However, he noted that the engine had already been started once that day, and stated verbatim as follows: “The engine had already run that day.”
The AAII Commission has ascertained from the testimony of witness No. 2, a pilot of the same type of glider, that a retracted engine in the fuselage can be considered “cold” after a period of more than about 30 minutes in a METAR-comparable environment (approx. 10 °C). For this reason, the engine start-up procedure should be performed according to the manual in its entirety, i.e. as with a “cold engine”. This start-up assumes enriching of the fuel mixture by “squeezing the rubber bulb”.
The critical moment occurred at 10:49:38 when the aircraft, with a vertical descent speed of 3 m∙s-1 and Gspd of 136 km∙h-1 on a 129° heading with the engine extended, continued to fly with a tailwind component of approximately 21 km∙h-1. At 10:49:44, the pilot continued in a left-hand turn on a 360° heading in descent of 2 m∙s-1. The glider’s Gspd dropped to 28 km∙h-1due to strong headwind. The recorded IAS according to the .igc file flight record was 60.1 km∙h-1.
The pilot noticed the effect of wind direction and wind speed only at low altitude when initiating a landing manoeuvre in an attempt to turn the glider into the wind direction. The glider “slid down the wing” after turning into wind at stall speed. The pilot partially “levelled” the glider and broke a concrete vineyard fence post with the right half of the wing in a right bank.
The loss of glider speed at low altitude due to the increased aerodynamic drag of the deployed inoperative engine and the effect of a strong headwind component made it impossible to complete a safe manoeuvre to avoid the fence post.
The glider struck the ground after breaking the concrete post at a distance of approximately 13 m. It then bounced off for cca 4.5 m. It kept moving on the field by way of skidding for cca 12 m until full stop.

Condition of the wreckage after the accident

The destruction of the fuselage and the right wing half of the glider after impact is indicative of a high energy transfer.
The flap control lever was in the position for Low speed range.
CB position on the control board
- Emergency switch was pushed in.
- The battery switch was switched to BATT 2, but its CB was in the pulled position – electrical circuit disconnected. This type of battery switch is very unlikely to be switched by impact or to be switched by inadvertent tampering,
- while the pilot did not operate with any CB after the accident. He was unable to explain why some CBs were pulled out and some pushed in.
The gear wheel was retracted.

Aircraft

The glider underwent regular annual maintenance, including an airworthiness review on 6 March 2021 with no findings.
There had been no defects during the flights preceding the critical event flight.
According to the pilot’s statement, the glider was refuelled with 15 litres of fuel before the flight.
A check fuel sampling had drained more than 1 litre of fuel.
The fuel level in the fuel tank was sufficient to start the engine.
Technical condition of the glider had no impact on emergence of the air accident.

Weather
The pilot did not correctly assess the effect of wind direction and wind speed during the critical phase of the flight. During the last turn at low altitude over the vineyard, he attempted to turn the glider into wind.

Conclusions
Pilot

had a valid Pilot Licence;
held valid medical certificate;
also had rich flying experience on this glider type;
had completed two long flights of 5:35 hrs and 7:15 hrs in the two previous days;
had conducted pre-flight preparation the morning before the critical flight;
installed charged batteries in the glider and checked the engine;
took off from LKBA using an engine;
approximately 50 minutes of flight, he did not join a thermal lift;
did not set a flight direction to Znojmo airport or the selected emergency landing area;
initiated the engine start procedure at an altitude of approx. 400–500 m AGL;
failed to execute the in-flight engine start procedure as on the ground because: “The engine had already run that day.” He disregarded the temperature of the “cold” engine in the engine start procedure relative to the length of the flight and the temperature of the surrounding atmosphere;
made three unsuccessful attempts to start the engine;
performed the first turn at an altitude of approx. 200 m AGL north of the vineyard, of which he was unaware;
performed the second turn over the vineyard;
made the third turn above the vineyard;
went with the glider into a low-level slip after losing speed;
partially levelled the slip out and in a right bank broke a concrete post in the vineyard fence with the right half of the wing;
was seriously injured, yet able to call for help with his mobile phone.

Aircraft

Technical condition of the glider had no impact on emergence of the air accident.
The flight manual of the given type indicates an identical procedure for starting the engine in flight and on the ground, taking into account the engine temperature and the need to enrich the fuel mixture.

Weather

Meteorological conditions did not affect the flight.

Aircraft Accident Cause
The cause of the accident was the pilot’s decision-making process resulting in not continuing the flight towards an area suitable for an emergency landing and in not considering the engine temperature in the engine start-up procedure before initiating the engine start-up procedure. High stress levels, loss of situational awareness and possibly general fatigue were contributory factors.

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