ANALYSIS OF ACCIDENT TO SIKORSKY S-76C++ HELICOPTER-25 MAY 2017
The helicopter S-76C ++ was involved
in an accident on 25th May 2017 during the flight. It was a VIP Flight from a Helipad at an elevation of 2000 Ft. There were four passengers and two crew
members onboard the helicopter at the time of accident. Both the pilots were well experienced and duly qualified to operate the subject flight.
The helipad was prepared in an open ground measuring 118.6 M X 110 M where, an area measuring 75 M X 75M was barricaded for the helipad. There were obstructions all around the helipad.
The requirements for Touchdown and Lift-off Area (TLOF), Final Approach and Take-off area (FATO) and Safety Area as per CARs was available at the Helipad. However the adequate length of take-off climb surface of 8% slope was not available because of obstructions.
The helicopter landed at the helipad at 1105 Hrs. The temperature at the time of departure (Approx. 1200 Hrs.) was around 40 degrees with visibility fair and variable winds of 3 to 5 knots from northerly direction.
The maximum AUW permitted for flight at Mean Sea Level 2000 feet and at Temperature of 40 degrees as per Flight Manual is 10400 Lbs. The All up weight (AUW) for the flight calculated by the crew was 10891 Lbs. as against the actual Wt. of 11183 Lbs calculated by the Inquiry Team.
The required rejected take-off distance, for the maximum permissible take-off weight permitted at Critical Decision Point (CDP) of 45Kts comes out to be 1250 feet approx. as per the performance data available in the flight manual. This rejected take-off distance was not available at the temporary landing ground.
From the above it can be inferred that the landing area was not suitable to carry out safe operations in Category A as well as Category B due to inadequate take-off climb slope caused by close proximity of obstructions around the Helipad.
After the helicopter picked up and came to hover, the Captain turned heading towards Northerly direction, and thereafter hovered out of ground effect to proceed for the take-off. The PIC had stated that after few seconds into hover when the helicopter was around the edge of the helipad, co-pilot called out rotor RPM 102%.
This was acknowledged by PIC and he continued to apply power to gain height and also moved forward to cross the obstacle (High tension wires) for take-off. The helicopter did not gain height even after the application of extra power. During this time the helicopter had crossed the barricaded area and was engulfed by the dust which was kicked up due to strong rotor downwash caused by the main rotor, this further obscured the vision of the crew.
As the helicopter was transiting in the process of take-off with max collective, the co-pilot called out, close proximity of cables and rotor RPM drop at 93%. The helicopter started sinking instead of climbing to cross over the obstacles.
The PIC immediately called for raising the undercarriage to avoid entanglement with high tension cables. However, in the process, the helicopter belly hit the high tension cables and helicopter lost the yaw control and turned right. Subsequently, the main rotor blades hit through a tree and also the roof of a truck and sheared off. The 5 tail rotor blades also hit the roof of a hut and sheared off. Thereafter the helicopter crash landed and settled on the ground between truck and a hut.
The PIC had earlier operated flight from the same landing area in December 2016, and the temperatures were much lower and could manage the take-off with low power requirements.
It was evident from the media video coverage that, as the helicopter hovered out of ground effect to proceed for take-off, it got engulfed in dust which reduced visibility of the PIC.
Analysis by Aviation Safety Management Society of India
The pilots failed to carry out proper risk assessment before Take Off which is essential particularly when flying VIP’s. The Helipad was unsuitable since it did not provide for adequate distance to clear the obstructions.
The knowledge of the Pilots about the adverse effects on the performance of the Helicopter in high temperature conditions appears to be inadequate. The
Density Altitude of the Helipad with an elevation of 2000 Ft and surface Temperature of 40 Degrees was almost 5480 Ft which increased the power
requirement for Take Off thus reducing the reserve of power as well as reduced the all up weight which could be lifted by the helicopter. There was an error in calculation of the All Up weight by the pilot.
Actual All Up weight was found to be 11183 Lbs. whereas the Pilot had calculated the Weight as 10891 Lbs. The calculation of the pilot was almost 300
Lbs. less than the actual. In high temperature and calm wind conditions, the reserve of power further reduced. The lack of knowledge on the part of the pilots about the rules, regulations and procedures related to Performance Class 1, CAT “A” Operations is quite evident.
The pilots lacked Situational awareness about the surface conditions which were dusty, in the immediate vicinity of the helipad and high tension cables and other obstructions in the takeoff path. The Captain gives the impression of being over confident, unprofessional , complacent and bit casual in calculations of all up weight of the helicopter, power available, power required, reserve of power and technique of taking off, climb and obstacle clearance from
restricted areas with obstructions in close vicinity.
The Pilot should have gone to the beginning of the helipad to make use of the full length of the helipad rather than taking off from the center of the
helipad. The action on the part of the pilot to gain height in hover before initiating take off further reduced the reserve of power for takeoff.
While moving forward for takeoff, the helicopter was engulfed in dust bowl which must have made the pilot uncomfortable during critical phase of transition. Possibly in panic due to the approaching HT cables, the pilot raised collective to cross the obstruction. However, since the helicopter speed was below transition, application of more power resulted in the rotor RPM dropping and coning angle of the blades increasing. This resulted in helicopter striking the cables in front and crash land.
The District administration failed to prepare the helipad as per the guidelines and the helipad area had loose dust which led to the dust rising due to rotor downwash. The takeoff time was around noon, temperature was in the region of 40 degree C. Even if the water was sprinkled to prevent dust from rising, the direct hot sun with 40 degree temperature was enough to dry up the wet sand. The sprinkling of the water should have been done just 10 mts before the arrival of the VIP.
It also appears that the pilots were not aware of the handling characteristics of their Helicopter while operating near its max limits and also they failed to appreciate the power, weight ratio and the height of the obstruction which they were supposed to cross. The Pilots although well experienced and qualified did not factor high all up weight, elevation of the helipad, high density altitude, dusty helipad and high obstructions.
The Pilots had landed at the same Helipad about a year back in the month of Dec when temperature are low and hence the density altitude is low. In addition, the Pilots had landed on this helipad just an hour before the time of accident .During the approach, pilots should have assessed the Helipad environments and general performance of the Helicopter. May be the operation at the helipad a year back and landing of the Helicopter an hour before the time of accident gave the pilots a false sense of complacency.
For every flight it is essential to plan and carry out good preparations related to the flight, particularly for VIP flights under marginal conditions. Make sure that you are fully situationally aware and have good knowledge about your Helicopter, its performance, limitations, Systems, Emergencies and operating procedures.
In depth knowledge of the terrain, obstructions around the Helipad, Surface conditions of and around the helipad, weather and environmental conditions, is essential.
Correct technique of Take Off, Approach and landing from Helipads particularly restricted, dusty Helipads (As far as possible, Dusty Helipads should not be accepted) should be known to the Pilots.
Make sure that the water is sprinkled just half an hour before the arrival of VIP so that no dust gets kicked up due to rotor down wash during takeoff or landing.
Professional Risk assessment, comprehensive Pre Flight Briefing, Good CRM, Knowledge of Rules, Regulations and Procedures, high standards of Knowledge and Skill Levels, remaining alert and Situationally Aware particularly during critical phases of the flight and avoidance of overconfidence and complacency, are essential for Safety of Aviation Operations.
Never be complacent, overconfident and do not indulge in show off or eagerness to impress VIP.
High temperature conditions obtained during summer months will lead to high Density Altitude, high requirement of power, less reserve of Power, reduced load carrying ability and maneuverability, longer takeoff and landing runs due to higher TAS and Ground speed.
Pilots must be careful in calculating the Density Altitude, Reserve of Power and load carrying capacity.
The Load and Trim Sheet must be accurately prepared keeping in mind Power Available, Power Required, all up Weight and CG Limits. No casual attitude should be displayed.
Please do not accept any additional load beyond capacity even if the request comes directly from VIP. Have courage of conviction and inform the VIP politely that you are placing the safety of VIP on highest priority and hence cannot accommodate the additional load.
Even if you have made a mistake in calculating max all up weight and you realize it after pick up to hover, do not hesitate to sit down and offload. It is better to sit down, reduce weight and face little embarrassment then to crash land attempting to take off with additional load. If you have made a mistake, do not aggravate the situation by attempting to take off (Under false belief and misplaced hope that you will be able to take off) in order to save little embarrassment.