Covering form of preliminary or final report

Date of event:	2023.01.14
Incident number:	CZ-23-0017
Report:	Final report
Place of event:	meadow near Lanžhot
Registration mark:	Accident
Weight category MTOM::	<2250 kg
Type of operation:	Other
Plane / SFM:	Helicopters
Type of plane / SFM:	Robinson R 22 BETA II
Health effects of event:	Without injury
PDF document:

Description:

SUMMARY

Synopsis

On 14 January 2023, the AAII was notified of an accident of the Robinson R 22 BETA II helicopter. The pilot with an instructor on board was conducting a training flight to obtain an instructor rating on the type. Upon arrival over the selected area and after checking it, the crew performed a practice landing with a simulation of a malfunctioning tail rotor control. The pilot released the foot pedals, and the instructor simulated a tail rotor failure by fixing the foot pedals. After a successful landing, the crew chose the same procedure for the subsequent take-off. According to the crew’s testimony, in the run-up phase, the helicopter spontaneously spun in the air cushion to the right around its vertical axis. The instructor failed to stop the right rotation despite the left pedal supposedly being fully depressed. The helicopter overturned after hitting the ground and remained lying on its left side. It was destroyed. The crew were not injured.

Factual Information

The pilot with an instructor on board was conducting a training flight to obtain an instructor rating on the type. Upon arrival over the selected area and after checking it, the crew performed a practice landing with a simulation of a malfunctioning tail rotor control. The pilot released the foot pedals, and the instructor simulated a tail rotor failure by fixing the foot pedals. After a successful landing, the crew chose the same procedure for the subsequent take-off. According to the crew’s testimony, in the run-up phase, the helicopter spontaneously spun in the air cushion to the right around its vertical axis. The instructor failed to stop the right rotation despite the left pedal supposedly being fully depressed. The helicopter overturned after hitting the ground and remained lying on its left side.

Analyses
Helicopter Crew

The pilot was qualified to fly the helicopter and both helicopter crew members were qualified to fly. The pilot was smoothly fulfilling individual tasks prescribed by the approved FI (H) syllabus without any issues. As an experienced professional pilot of the air rescue service, he had, among other things, experience in piloting helicopters enabling him to carry out emergency procedures training with simulation of tail rotor control malfunction.

The instructor was an experienced pilot and had experience in training pilots and sufficient habits in practicing emergency procedures, including correcting any errors. He had practical experience in flying helicopters enabling him to conduct emergency procedure drills with simulated tail rotor control malfunction.

The crew did not comply with the Flight Manual when practising emergency procedures. In simulating a tail rotor control malfunction during flight, the crew were probably inspired by experience with performing this action on other types of helicopters. It made no sense to perform a take-off with a simulated failure of one of the helicopter’s control elements, and even if successfully executed, it would be counterproductive to subsequent pilot training.

History of the Flight

The pilot carried out pre-flight preparation for the specific flight together with the instructor in the appropriate scope and quality. The crew probably decided no sooner than during the flight to perform a take-off with simulated tail rotor control failure.

Critical Situation

The critical situation occurred immediately after the decision to perform a take-off with simulated tail rotor control failure. An undesirable change in the helicopter pitch occurred during an attempted take-off of the helicopter and, according to the traces found at the take-off site and the skid landing gear, the rear part of the left landing gear skid came into contact with the ground. The skid dug into the soft surface of the grassy area and further lifting of the collective lever in an attempt to lift the helicopter from the ground without the possibility of adequate response by foot control intervention led to the helicopter’s spinning along its vertical axis with subsequent contact of the tail strut and the tail rotor blade with the ground. The resulting forces led to the destruction of the transmission shaft and flexible cross (hardy) couplings. During the destruction of the transmission shaft, the inertial forces caused the tail beam to break and the shaft elements to be thrown out of the beam after the breakage of cross couplings. At the same time, the tail beam was broken into several parts. The helicopter became uncontrollable and after the main rotor blades touched the ground, it rolled over on its left side and remained lying on the ground.

Helicopter

Upon investigation of the place of accident and subsequent detailed technical investigation of the helicopter in the operator’s hangar, no facts that would indicate that the air accident had been caused by a technical defect of the aircraft were detected.

The helicopter was operated within the range of the authorised weight and centre-of-gravity position, which ensured sufficient range of control for its safe piloting.

Helicopter controls were all right. The helicopter crew had not experienced any problems with the helicopter controls during previous flights on that day.

The helicopter engine was operating normally at the time of the accident with respect to the flight mode at maximum power output. This corresponded to the fact that when the engine revolutions were abruptly slowed down during a violent stop when the rotating surfaces came into contact with the ground, both belts on the drive pulley shifted by one groove. There was enough fuel in the helicopter’s tanks for the flight. Other working fluids were used in accordance with the manufacturer’s recommendations and in sufficient quantities.

It may be concluded from the findings described above that until the time of the accident, the propulsion system of the main rotor and the tail rotor operated without faults and the individual control elements were functional. Also, damage to the tail beam by the rotating transmission shaft indicates that the engine was operating until the rotating surfaces touched the ground. The expert examination confirmed that all damage to the individual elements of the transmission shaft occurred after the rotating surfaces came into contact with the ground and until that time the propulsion system and the tail rotor control were fully functional and free of defects.

Weather Effects

The weather conditions allowed the entire flight to be performed according to VFR rules and had no effect on the occurrence and course of the incident.

 

Conclusions/Causes

The cause of the accident was a mishandled take-off attempt with a simulated tail rotor control malfunction in violation of the Flight Manual.

Safety Recommendations

With regard to the possibility of serious injury to the crew in case of failure to pilot the helicopter during the emergency procedures training, it is desirable that the flight of the helicopter during the above-mentioned activity is monitored by a responsible person who would activate the airport rescue units or the Integrated Rescue System units in case of an accident.

Safety Recommendation CZ-2024-003

In view of the circumstances of the air accident, the Air Accidents Investigation Institute recommends the operator CZ/ATO - 017 to consider modifying the Operating Manual by adding the principle that emergency procedure drills should be conducted at controlled airports or at airports (ARV areas) where the service providing information about known air traffic (RADIO) is provided.

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