Covering form of preliminary or final report
| Date of event : | 2021-05-11 |
| Incident number : | CZ-20-0178 |
| Report : | Final report |
| Place of event : | Letňany airport |
| Registration mark : | Accident |
| Weight category MTOM: : | <2250 kg |
| Type of operation : | Recreational and sport aviation |
| Plane / SFM : | Airplanes |
| Type of plane / SFM : | Cessna F152 and Robinson R44 |
| Health effects of event : | Without injury |
| PDF document : | 
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Description:
SUMMARY
Overview
On 11 May 2021, the taxiing Cessna F152 aircraft collided with the Robinson R44 helicopter at LKLT. At 11:12 UTC, during taxiing after landing, the pilot of Cessna F152 bumped with the end of the left half of its wing into the standing Robinson R44 OK-BAD helicopter. Nobody was injured. Both the aircraft and helicopter were damaged.
Neither any serious injury nor any damage were sustained during the incident.
Factual Information
The aircraft pilot – student pilot was carrying out a solo flight. With the aid of an interpreter present, the student pilot explained to the summoned patrol of the Police of the Czech Republic that after landing, he had been instructed by the RADIO Letňany to vacate the runway and operating area near the area for parachuting traffic due to the expected parachute drop. As he wanted to respond as quickly as possible, he was heading towards the second paved area with yellow horizontal marking of axis line where there was a helicopter on the left side from his point of view. At the moment when he crossed from the grassy to a paved area, the aircraft was located on the yellow axis line of the paved area, turned about 10° to the left towards the helicopter. Therefore, the student pilot thought he would pass the helicopter safely. Nevertheless, the aircraft bumped with the end of the left half of the wing into the helicopter and damaged it. The impact deflected the aircraft from the direction of movement to the left towards the helicopter. As the aircraft after the first contact with the helicopter continued moving, it also crashed into the upper flashing beacon and then to the tail rotor. Although the brake of the main rotor was applied, the tail rotor spun. This impact deflected the taxiing aircraft from its original direction of movement by approx. 20°.
The helicopter was brought to the paved area of limited parking area for aircraft and other transport and mechanised vehicles (3-A) at 10:50 UTC for take-off at 11:00 UTC.
A small-scale damage was found on Cessna F152 aircraft when inspected at the site of the accident. The damage to the Robinson R44 helicopter was extensive.
No other damage was reported to the AAII commission.
The site of the accident was a paved area south-east of THR RWY 05R at a distance of about 100 m. The said area is a part of the movement area designated in the LKLT airport operation rules The Regulation of Public Domestic and Private International Prague Letňany Airport Ltd as “Area for limited parking of aircraft and other transport and mechanised vehicles (3-A)” in which the maximum time for parking is limited up to 15 minutes.
The left half of the aircraft wing was damaged. The leading edge, the left end arch of the wing and the end of the wing structure in the length of approx. 50 cm were damaged.
The helicopter sustained the following damage due to the impact of the end of the left half of the F152 aircraft wing:
- There was a scratch in the length of about 60 cm on the upper left part of the cabin.
- An anti-collision flashing beacon was broken off from the tail beam.
- Due to impact of the end of the left half of the wing into the tail rotor, the tail rotor rotated while the main rotor was braked.
Analysis
Student pilot competence
The student pilot was qualified in terms of health and qualifications. He had, relatively, little flight experience and knowledge of the principles of airport operation and aircraft movement in the operating area.
Aircraft
The helicopter was airworthy. At the time of the incident, it was not moving and was only brought to the site prior to the planned flight. It was standing on a paved surface, at its right edge, 4.95 m to the left of the surface axis marking. The helicopter was not marked as an obstacle, although it should not have been in the “Area for limited parking of aircraft and other transport and mechanised vehicles (3-A)” for as long as 12 minutes.
The aircraft was airworthy until the event. The landing weight and the centre of gravity were within the permitted limits and had no impact on the occurrence of the incident. At the time of the incident, the aircraft was taxiing to the fuel station after landing.
Weather
The event occurred on a clear day and, from the pilot’s point of view, the sun was to his right, so there could be no loss of visual contact with the surroundings due to glare. The weather had no effect on the cause of the incident.
Regulation of Public Domestic and Private International Prague Letňany Airport Ltd. No. LKLT-SMS-05 (Version 5), Section 3(3.2.) Aircraft Taxiing, states the following:
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The area in which the incident occurred is part of the movement area marked in the LKLT Airport Regulations as “Area for limited parking of aircraft and other transport and mechanised vehicles (3-A)”. Parking of aircraft, transport and mechanised vehicles in this area is limited to maximum of 15 minutes. Part of this area is also the area in the LKLT Airport Regulations marked as “Parachute operation area and probable parachute touch down zone” at which the parachute drop was expected.
On the helipad to the right of the area aimed at by the student pilot with the F152 OK-VYR aircraft, another helicopter was parked for a short time, and another Mi-8 helicopter, likewise not marked as an obstacle, was parked on another paved area.
The student pilot registered the information of the RADIO Letňany dispatcher regarding the clearance of the runway and the area for the parachute operation. In the area between the wind direction and speed indicator pole and the pole with safety cameras, the centre of the drop zone area for the ongoing parachute drop was marked with an orange cross.
The R44 helicopter was brought to the area prior to its flight. It was standing on the right edge of the paved part of the manoeuvring area, with its left side at a distance of 4.95 m from the area axis marking. According to the statement of the technician, the helicopter was brought to the area at 10:50. Its departure was scheduled for 11:00, and at the time of the collision at 11:12 it was not marked as an obstacle. The position of the helicopter outside the axis marking of the area led the student pilot of the F152 aircraft to the mistaken assumption that if he taxied along the axis marking of the area, he would pass the helicopter safely.
These facts led the student pilot to making the erroneous decision about the place of entry into the airport paved area. He approached the axis of the paved area with the aircraft but already during the actual approach, the aircraft was deflected by about 10° from the axis marking of the area towards the helicopter. The aircraft came close to the helicopter so that the end of the left half of the wing collided by about 11cm with the fuselage of the helicopter. The student pilot did not stop after the first collision with the helicopter due to the initial startle. The impact turned the aircraft even further to the left, so the next impact struck the tail beam anti-collision flashing beacon of the helicopter. During the impact that followed, the tail rotor was damaged, spun, and the impact deflected the aircraft by about 30° to the left.
After the last contact of the wing with the helicopter, the student pilot stopped for about 4 seconds (according to the recording from the safety camera) and then continued to drive to the fuel station. According to the traces of contact of the aircraft with the helicopter, it is probable that if the student pilot stopped immediately after the first contact with the helicopter, there would be only slight damage to both, the aircraft and the helicopter.
Causes
The cause of the air-accident was non-compliance with the rules when moving aircraft on the ground while taxiing the aircraft.
The collaborating cause would be the inappropriate positioning of the helicopter not marked as an obstacle on the paved area. The helicopter should have been marked as an obstacle at the time of the incident, because the time limit of 15 minutes of use of “Area for limited parking of aircraft and other transport and mechanised vehicles (3-A)” stipulated in the Regulation of Public Domestic and Private International Prague Letňany Airport Ltd. LKLT-SMS-05 (Version 5) had been already exceeded.Attached final report in PDF file is in original Czech language.