Covering form of preliminary or final report
| Date of event : | 2020-08-13 |
| Incident number : | CZ-20-0493 |
| Report : | Final report |
| Place of event : | Garden at the eastern edge of Žamberk |
| Registration mark : | Accident |
| Weight category MTOM: : | <2250 kg |
| Type of operation : | Recreational and sport aviation |
| Plane / SFM : | Helicopters |
| Type of plane / SFM : | Robinson R 44 RAVEN I |
| Health effects of event : | Without injury |
| PDF document : | 
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Description:
SUMMARY
Synopsis
On 13 August 2020, the AAII was notified of an air accident of the R 44 RAVEN I helicopter in a garden at the eastern edge of Žamberk. After a stopover at his private property after about a 30-minute break, the pilot conducted take-off with a fully occupied helicopter. Having taken off, while hovering at the altitude of approx. 2–3 m AGL, the helicopter started left-spinning. The pilot lost control of the helicopter, which, several spins later, crashed into a tree standing in the close proximity of the take-off place. Once the rotating surfaces touched an obstacle, the helicopter tilted sharply and having fallen on the ground, remained lying on the left side. The helicopter was damaged heavily due to its collision with an obstacle and crash on the ground. The pilot and passengers left the helicopter cabin unaided, and were not injured.
The Police of the Czech Republic, the FRS, and the AAII inspectors arrived at the location of the air accident and the AAII inspectors performed professional investigation of the location. The wreckage of the helicopter was transported to the operator’s hangar for expert examination.
Factual Information
After a break of about 30 minutes, the pilot, together with three other people, boarded the helicopter cabin for a recreational flight. After boarding the helicopter, he reminded the passengers of the obligation to fasten their seatbelts properly and began starting the engine. In his testimony the pilot said exactly: “I started the engine and performed the check of the instruments all of which showed the values of parameters in the green fields and everything was in good order, fine. Then I lifted the helicopter up off the ground and everything was fine. I raised the helicopter about 2 m above the ground. At this altitude, the helicopter began to spin, and I depressed the left pedal, but it was only a little and the helicopter kept rotating and then began to spin around the axis. I levelled the rotation up with the right pedal. The helicopter stopped turning but I was already close to the tree and the main blade of the rotor crashed into a tree in the garden and we fell to the ground. Once on the ground, we all unfastened our seatbelts and got out. I immediately asked the entire crew if everyone was okay. No-one was injured.”
Analyses
The pilot planned to take off directly from the landing site. The key take-off parameters differed from the take-off of the previous flight. Namely, there was a significant change in the take-off gross weight and in the centre of gravity of the helicopter and also a probable change in wind speed. Under the given conditions, the take-off could be performed without the influence of the ground effect in accordance with the flight manual. With regard to the total weight of the helicopter, this method of take-off was very demanding for piloting, requiring perfect coordination of the movements of the individual control elements. The pilot had memorised in his training that during the lifting of the collective lever, the reaction torque from the left-handed support rotor must be sufficiently compensated by the deflection of the left pedal. Poor coordination of movements between the deflection of the left pedal, the lever of the cyclic and collective control caused the helicopter to start rotating slowly to the left around the vertical axis while hanging at an altitude of about 2 to 3 m above the ground and moving away uncontrollably from the take-off point. The pilot did not respond to the situation in time and correctly.
The critical situation occurred when the helicopter turned slowly to the left by about 90° from the originally planned north-western direction of take-off and the tail propeller was affected by crosswinds or gusts of wind. The helicopter began spinning uncontrollably to the left. The intensity of the rotation could have been increased by a subconscious slight reduction of the collective. At this stage of the flight, the pilot lost control of the helicopter, and the helicopter, probably after a few 360° turns, crashed into the branches of a full-grown tree with the end of the tail beam and the blades of the main rotor. After the contact of the rotating surfaces with a fixed obstacle, the helicopter tilted to the left and fell to the ground. The impact of the ski type landing gear on the ground caused its significant destruction on the left side and in the rear. The helicopter overturned after hitting the ground and remained lying on its left side. The pilot and passengers got out of the cockpit on their own. The helicopter was considerably damaged to a very large extent due to its contact with an obstacle and the subsequent impact on the ground.
Conclusions/Causes
The cause of the air accident was an inappropriately chosen method of take-off and subsequently mismanaged piloting of the helicopter in hovering. A gust of wind and a little experience of the pilot with the take-off of a helicopter at the limit of the maximum take-off weight could have been joint influences in the cause of the accident.
Safety Recommendations
Given the circumstances of the air accident, the AAII issues no safety recommendations.
Attached final report in PDF file is in original Czech language.