CA 12-12b 25 MAY 2010 Page 1 of 13 Section/division Accident and Incident Investigation Division Form Number: CA 12-12b AIRCRAFT INCIDENT REPORT AND EXECUTIVE SUMMARY Reference: CA18/3/2/1035 Aircraft Registration ZS-RSO Date of Incident 14 January 2014 Time of Accident 0630Z Type of Aircraft Robinson R44 II (Helicopter) Type of Operation Private Pilot-in-command Licence Type Private Age 22 Licence Valid Yes Pilot-in-command Flying Experience Total Flying Hours 161.2 Hours on Type 60.0 Last point of departure Nelspruit Aerodrome-FANS (Mpumalanga Province) Next point of intended landing Nelspruit Aerodrome-FANS (Mpumalanga Province) Location of the incident site with reference to easily defined geographical points (GPS readings if possible) Private property farm Rocky drift, Mpumalanga province, (GPS position: South 25° 22.37.8’ East 030° 59.46.6’, elevation 3 605 ft) Meteorological Information Surface wind; light and variable, Temperature; 28°C , CAVOK Number of people on board 1 + 1 No. of people injured 0 No. of people killed 0 Synopsis The pilot and passenger were engaged on a private flight in the Nelspruit area when the incident happened. During the flight the helicopter lost engine power within 3 seconds. The pilot auto rotated the helicopter, identified the landing strip and the helicopter was landed safely without further incident. The investigation established that due to the fact that the connecting rod converts the pistons reciprocating motion into the rotational motion of the crankshaft, the failure could be attributed to undetermined overload during such conversion. Probable Cause Successful forced landing following an engine stoppage or failure during flight. Contributory factors: Connecting rod failure. Oil supply failure which caused oil pressure drop. ASP Date Release Date
Transcript
CA 12-12b 25 MAY 2010 Page 1 of 13
Section/division Accident and Incident Investigation Division Form Number: CA 12-12b
AIRCRAFT INCIDENT REPORT AND EXECUTIVE SUMMARY
Reference: CA18/3/2/1035
Aircraft Registration ZS-RSO Date of Incident 14 January 2014 Time of Accident 0630Z
Type of Aircraft Robinson R44 II (Helicopter) Type of Operation Private
Pilot-in-command Licence Type Private Age 22 Licence Valid Yes
Pilot-in-command Flying Experience
Total Flying Hours
161.2 Hours on Type 60.0
Last point of departure Nelspruit Aerodrome-FANS (Mpumalanga Province)
Next point of intended landing Nelspruit Aerodrome-FANS (Mpumalanga Province)
Location of the incident site with reference to easily defined geographical points (GPS readings if possible) Private property farm Rocky drift, Mpumalanga province, (GPS position: South 25° 22.37.8’ East 030° 59.46.6’, elevation 3 605 ft) Meteorological Information Surface wind; light and variable, Temperature; 28°C , CAVOK
Number of people on board 1 + 1 No. of people injured 0 No. of people killed 0
Synopsis
The pilot and passenger were engaged on a private flight in the Nelspruit area when the incident happened. During the flight the helicopter lost engine power within 3 seconds. The pilot auto rotated the helicopter, identified the landing strip and the helicopter was landed safely without further incident. The investigation established that due to the fact that the connecting rod converts the pistons reciprocating motion into the rotational motion of the crankshaft, the failure could be attributed to undetermined overload during such conversion.
Probable Cause
Successful forced landing following an engine stoppage or failure during flight. Contributory factors: Connecting rod failure. Oil supply failure which caused oil pressure drop. ASP Date Release Date
CA 12-12b 11 JULY 2013 Page 2 of 13
Section/division Accident and Incident Investigation Division Form Number: CA 12-12b
AIRCRAFT INCIDENT REPORT
Name of Owner : Delta Zulu Consultants CC
Name of Operator : Delta Zulu Consultants CC
Manufacturer : Robinson Helicopter Company
Model : R44 II
Nationality : South African
Registration Marks : ZS-RSO
Place : Private property farm Rocky drift, Mpumalanga
province
Date : 14 January 2014
Time : 0630Z
All times given in this report are Co-ordinated Universal Time (UTC) and will be denoted by (Z). South
African Standard Time is UTC plus 2 hours.
Purpose of the Investigation:
In terms of Regulation 12.03.1 of the Civil Aviation Regulations (1997) this report was compiled in the
interest of the promotion of aviation safety and the reduction of the risk of aviation accidents or incidents and
not to establish legal liability.
Disclaimer:
This report is produced without prejudice to the rights of the CAA, which are reserved.
1. FACTUAL INFORMATION 1.1 History of Flight
1.1.1 The pilot and passenger were on a private flight in the Nelspruit area when the
incident happened. During the flight the helicopter lost engine power within 3
seconds. This was followed by moderate to severe vibrations which were reported
by the pilot. During power loss the manifold pressure indicator increased to above
25”, while oil pressure dropped to the red line which indicates the minimum oil
pressure, followed by a sudden engine stoppage.
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1.1.2 The pilot auto rotated the helicopter, identified the landing strip and the helicopter
was landed safely without further incident.
1.1.3 The incident occurred during morning light conditions at a geographical position
determined to be South 25°22’37.8” East 030°59’46.6 ’ at an elevation of
approximately 3 605 feet above mean sea level (AMSL).
1.2 Injuries to persons
Injuries Pilot Crew Pass. Other
Fatal - - - -
Serious - - - -
Minor - - - -
None 1 - 1 -
1.3 Damage to aircraft
1.3.1 The helicopter sustained no damage.
Figure 1 shows the helicopter after landing safely.
1.11.1 The helicopter was not equipped with a flight data recorder (FDR) or a cockpit voice
recorder (CVR), nor was it required to be fitted to this helicopter type according to
regulatory requirements.
1.12 Wreckage and Impact Information
1.12.1 The helicopter landed safely without further damage.
1.13 Medical and Pathological Information:
1.13.1There was no evidence that physiological factors or incapacitation affected the
performance of the pilot.
1.14 Fire:
1.14.1 There was no evidence of pre- or post-impact fire.
1.15 Survival aspects:
1.15.1 Both occupants were properly restrained by the helicopter’s safety harnesses. The
cockpit/cabin area remained intact during the incident. Nobody was injured in the
incident, which was associated with a low kinetic energy during the forced landing
sequence.
1.16 Tests and research
1.16.1 Following the incident, the aircraft was transported to an approved maintenance organisation. The engine was placed on a stand where a visual inspection was conducted. There was no visible leak, damage or anomaly on the outside of the engine.
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Pistons and Rings: The affected piston was visually inspected and no damage or scratches could be seen. Piston and ring failures can be caused by improper packing during assembly. There were no indications of heat distress failures, such as could be due to fuel contamination or improper engine operation. Cylinder: A visual inspection of the cylinder revealed no damage or abnormalities inside or outside. Valves: The valves were visually inspected and no damage, anomalies or scratches could be seen. Connecting rod bushing: The connecting rod bushing for the incident connecting rod failed which resulted in a connecting rod failure and as a result the bottom of the engine casing was damaged (please see photos below).
. Figure 2: View of the engine before disassembly
Figure 3 and 4: shows the oil sump after removal from the engine and metal
particles which were found coming from the connecting rod.
Figure 7: shows the failed connecting rod which failed at rod small end.
1.17 Organizational and management information
1.17.1 The last mandatory periodic inspection that was carried out on the helicopter prior to
the incident flight was certified on 28 October 2013 at 1626. 9 airframe hours. The
aircraft maintenance organisation (AMO) that performed the last maintenance on
the helicopter was in possession of a valid AMO Approval certificate. The last AMO
inspection was carried out on 17 May 2013. AMO certificate was issued on 30 May
2013 with an expiry date of 31 May 2014. AMO was approved for Category rating
B&E.
1.17.2 This was a private flight.
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1.18 Additional information
1.18.1 Research: Asian Economic and Association Society-Journal of Asian Scientific Research 2(11): 737-741:
Connecting rod (CR) is a conversion of the pistons reciprocating motion into the rotational motion of the crankshaft. It has two ends, one of its ends is connected to the piston by the piston pin, and the other end moves in a circular shape or revolves with the crankshaft and is separated in a way that it allows it to get clamped around the crankshaft. They are produced by using casting or forging and materials such as steel, but it can be aluminium or titanium which is used for making up or producing them for high performance engines, or of ductile cast iron for low cost. The analysis of CR consists of two conditions, the maximum stretch condition and the maximum compression condition. The load is applied to inner surfaces of big end and small end. The load distribution is second-degree parabola in axial direction and cosine in radial direction. The deformation of the connected rod under tensing and compression loading is displayed in figures below respectively. In suction stroke, it is indicated that it undergoes high tensile stresses cyclic load. The stress distribution and deformation of CR at the maximum stretch condition are shown in Figure below:
Figures above shows the deformation of the connected rod
The results show that the medial surface of small end will be the critical surface whereby damage will initiate at the maximum stretch condition. The stresses are high at the CR shank, but stress distribution is relatively uniform.
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Above: is the picture of a connecting rod.
1.18.2 The connecting rod (CR) is the main moving parts and an important component of engine. If the reliability is not strong enough, fatigue failure of the CR would occur, thereby leading to component fracture and engine failure. So much so that CR fracture. It will lead to engine fault as well as serious outcome.
Reference: The Open Mechanical Engineering Journal, 2013, 7, 14-17 by School of Transportation and Vehicle
Engineering, Shandong University of Technology, Zibo 255049, China 1.19 Useful or effective investigation techniques
1.19.1 None.
2. ANALYSIS
2.1 Man
The pilot was appropriately licensed for the flight. He had a total of 161.2 hours, with 60.0 of those being on type. The pilot flies this particular aircraft on a regular basis. His flying medical certificate was valid and issued without restrictions. During flight the pilot reported that the engine RPM dropped and within three seconds the engine stopped completely. The pilot auto rotated the helicopter and landed safety on an open private farm without further incident.
When the engine began to vibrate, the pilot attempted to identify and rectify the problem. He was not successful as there was very little time from the first indication of engine trouble to when the engine stopped completely. Under these circumstances, the pilot had no choice but to conduct a forced landing, which was successful.
2.2 Aircraft
The helicopter was properly maintained and no mechanical defect or malfunction
was reported prior to the flight that contributed or had caused the incident. The
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serviceability of the helicopter was discussed with the pilot during an interview with
him on the day of the accident and no reference was made to any mechanical
defects that could have induced or caused the incident.
The aircraft was removed to an approved facility. The engine was removed from the
aircraft so that further investigations could be conducted. The engine was put on a
work bench and was visually inspected. This revealed no damage to the outside of
the engine. During disassembly of the engine it was found that the connecting rods
on numbers 5 and 6 cylinders had failed. The cause of the failure could not be
conclusively determined.
Connecting rods are responsible for a significant number of catastrophic engine
failures. When a rod failed in flight, it punched a hole in the crankcase and caused
loss of engine oil and subsequent oil starvation. This explains the pilot’s report that
the oil pressure indicator dropped to the red line, which is the minimum oil pressure
indicator.
The cause of the connecting rod failure could not be conclusively determined, but
the investigation suggests that due to the fact that the connecting rod converts the
piston’s reciprocating motion into rotational motion of the crankshaft, the failure
could be attributed to undetermined overload during such conversion.
Examination of the engine showed that it contained sufficient lubricating oil and that the oil filter screens were free of metal particles or other contamination. This indicates that the engine was not releasing metal prior to the failure. Thus imminent failure would not have been detectable during routine maintenance activity. Oil supply and engine maintenance were not factors in the failure. The main rotor, tail rotor, and accessory gearbox sections of the engine did not contribute to the engine failure.
The damage to the connecting rod and cylinder number five suggests that the associated connecting rod failed first in the sequence. It then penetrated the cylinder sleeve as the engine continued to operate. The failure initiated a chain of overload failures for each of the remaining connecting rods in rapid succession until the engine stopped operating. Due to the severity of damage to the fracture surfaces of connecting rod number five, the mode of failure could not be determined.
2.3 Mission:
The pilot and passenger were on a private scenic flight when the incident occurred.
When the aircraft started experiencing an engine problem the pilot immediately
executed a successful forced landing.
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2.4 Environment:
This flight was conducted at an open flat private farm. The wind was light and
variable with no gusts. Following the identified vibrations the pilot auto rotated the
helicopter, identified the landing area and the helicopter was landed safely without
further incident.
3. CONCLUSION
3.1 Findings
3.1.1 The pilot was in possession of a valid aviation medical certificate issued by a
CAA- approved medical examiner.
3.1.2 The pilot had the helicopter type endorsed in his licence.
3.1.3 The helicopter had a valid Certificate of Airworthiness at the time of the accident
and had flown 48.7 hours since the last maintenance inspection was certified on 28
October 2013.
3.1.4 During flight the helicopter lost engine power within 3 seconds. The pilot auto
rotated the helicopter, identified the landing area and the helicopter was landed
safely without further incident.
3.1.5 The helicopter operator was operating under Part 91 at the time of the accident.
3.1.6 Following the incident, the aircraft was removed to an approved maintenance organisation. The engine was placed on a stand where a visual inspection was conducted. There was no visible leak, damage or anomaly on the outside of the engine.
3.1.7 The investigation suggests that due to the fact that connecting rod converts the
piston’s reciprocating motion into the rotational motion of the crankshaft, the failure
could be attributed to undetermined overload during such conversion.
3.1.8 The damage to the connecting rod and cylinder number five suggests that the
associated connecting rod failed first in the sequence. It then penetrated the
cylinder sleeve as the engine continued to operate.
3.1.9 The failure initiated a chain of overload failures for each of the remaining connecting rods in rapid succession until the engine stopped operating. Due to the severity of damage to the fracture surfaces of connecting rod number five, the mode of failure could not be determined.
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3.2 Probable cause:
3.2.1 Successful forced landing following an engine stoppage or failure during flight.
3.3 Contributory factors:
3.3.1 Connecting rod number five failed for undetermined reasons. This failure initiated a sequence that resulted in the overload failure of the remaining connecting rods.
3.3.2 Oil supply failure which caused oil pressure drop.
3.3.3 When the engine failed, the pilot had little time to prepare for the forced approach due to the low altitude of the aircraft.
