Accident Overview
On 8 March 2015, a Robinson R44 Raven I helicopter, registration OK-ADT, sustained damage when its main rotor blade struck the tail boom during landing on a paved area at the northeastern edge of the village of Prasek near Nový Bydžov. The helicopter was operated by T-air spol. s r.o. and was used primarily for training and recreational flights. The pilot, who held a valid private pilot license for helicopters with a Robinson R44 rating, was uninjured.
Flight History
The pilot arrived at the parking location at 12:00 UTC and performed a preflight inspection in accordance with the flight manual. The flight departed at 12:30 UTC and, after 1 hour and 30 minutes, the pilot conducted a landing at a prearranged site with the landowner's consent. The approach was made from the north over a fence bordering the company premises. According to the pilot's statement, during the landing the helicopter "settled more on the skids" because of higher fuel load, and he applied forward cyclic. He reported being unaware of any damage at that time. After engine shutdown and exiting the helicopter, the pilot discovered the damage and arranged ground transport to a repair facility.
Aircraft Information
The Robinson R44 Raven I (serial number 2235, built 2012) is a light, single-engine, four-seat helicopter with a fixed skid landing gear and a Lycoming O-540 piston engine. The fuel tanks (176 liters total) were filled with approximately 160 liters of AVGAS 100 LL before the first flight of the day; after landing, about 70 liters remained. The helicopter had a total flight time of 506 hours and 24 minutes and 1,315 landings. It had valid certificates of airworthiness and insurance. No technical faults were recorded in the logbooks. The last 100-hour inspection was on 6 November 2014, after which the helicopter flew 52 hours and 48 minutes up to the accident. On the accident day, two flights totaling 1 hour and 30 minutes were conducted.
Meteorological Conditions
The area was under the influence of a ridge of high pressure from the northeast, with warm air flowing from the southeast. The estimated conditions at the accident site: surface wind variable 2–4 knots, visibility more than 10 kilometers, few cumulus clouds with base 4,500–5,000 feet AGL, no turbulence. No precipitation was reported.
Examination and Findings
The landing site was a paved area approximately 30 by 90 meters within a commercial yard. The helicopter touched down with the rear part of the skids first, causing an unusual movement. The pilot responded by pushing the cyclic forward, which induced a pitching motion, followed by an instinctive aft cyclic input. This resulted in a main rotor blade striking the tail boom, causing damage to the tail boom, tail rotor drive shaft, tail rotor control rod, and tail rotor guard. The main rotor blade was also damaged. A technical inspection confirmed no mechanical failure of the helicopter's systems; the damage was solely due to the blade impact.
Cause
The official investigation determined the cause to be an inadequate control input during an unusual movement of the helicopter after the skid landing gear contacted the ground during touchdown. The flight manual for the Robinson R44 contains a caution advising pilots not to apply aft cyclic during touchdown or ground slide to avoid possible blade strike to the tail cone.
Safety Recommendations
No safety recommendations were issued by the Czech Accident Investigation Institute (ÚZPLN) in view of the nature of the accident.