Oil blockage caused Kunene air crash

A CATASTROPHIC engine failure as a result of a blockage in an oil supply line has been identified as the probable cause of the plane crash that claimed the life of experienced pilot Wolfgang Rapp at a landing strip in the Twyfelfontein area in December last year.

The 57-year-old Rapp – a seasoned pilot who had clocked up some 6 600 hours of flying experience – was killed on impact when a fixed-wing microlight aircraft of which he was the sole occupant crashed shortly after take-off from an airstrip at Rag Rock Camp in the Kunene Region on December 5 last year. The crash took place in good weather.Rapp was also in good health and had a wealth of experience as a licensed commercial pilot, microlight pilot and instructor, and also hot-air balloon pilot, to fall back on if anything was to go wrong with the flight on which he embarked late on the afternoon of December 5.What went wrong with that flight however happened so soon after the Tecnam P92 fixed-wing microlight had taken off from the Rag Rock airstrip, that Rapp had no time to arrest the stall and fall that the aircraft went into when its engine stopped seconds after take-off, the official report on the cause of the crash indicates.The report, compiled by aircraft-accident investigator Ericsson Nengola, was released by the Ministry of Works, Transport and Communications’ Directorate of Aircraft Accident Investigations on Tuesday.In the report Nengola described the crash and the events that preceded it: “Two eyewitnesses who witnessed the accident stated that the pilot spent most of the morning hours maintaining and test flying the aircraft.He then decided to do one longer flight test in the afternoon.”Shortly after take-off, the engine coughed once, followed by a loud bang.There was no smoke or fire observed.”The aircraft sharply turned to the left while climbing, followed by an uncommanded nose dive attitude.The rate of descent increased uncontrollably and it (the aircraft) smashed onto the terrain at a steep angle and a near vertical attitude.”The plane had risen only some 60 to 70 feet above ground level before the engine stopped, the aircraft banked sharply to the left and it nose-dived into the ground.A major part of Nengola’s report focuses on the condition of the aircraft’s engine after the crash.When the engine was examined, it was found that part of it was completely dry and showed signs of extreme overheating.Two of the engine’s four cylinders as well as the rear part of the engine’s crankshaft were completely dry and had seized, the report states.No signs of an oil-pump failure could be found, however.From the state that the engine was found in, Nengola concluded that the engine “most probably experienced oil starvation which led to a catastrophic failure”.He also concluded that the most likely cause of this was an obstruction in the oil pipes that feed oil to the engine.Nengola stated that according to a Microlight Association of Namibia inspector who is highly experienced in the Rotax 912 S engine – the type of engine that Rapp’s plane was fitted with – Rapp had phoned him a week or two before the incident to inform him that he had to re-route the plane’s oil cooler and oil pipes, as a new covering for the plane’s engine was a bit different from the old one.The Rotax engine installation manual stipulates that the engine’s oil pipe has to be able to withstand a certain level of pressure and should not be bent in a radius of less than 70 millimetres, the report states.It also states that it is possible that the oil pipe of Rapp’s aircraft had folded to form a partial or complete obstruction.”This (obstruction) is the most likely cause of the engine failure,” it states.Nengola strongly recommended in the report that owners of Tecnam P92 aircraft and planes fitted with Rotax 912 engines and approved persons who maintain this type of aircraft should “strictly adhere” to the specifications prescribed by the engine manufacturer in its installation manual.The crash took place in good weather.Rapp was also in good health and had a wealth of experience as a licensed commercial pilot, microlight pilot and instructor, and also hot-air balloon pilot, to fall back on if anything was to go wrong with the flight on which he embarked late on the afternoon of December 5.What went wrong with that flight however happened so soon after the Tecnam P92 fixed-wing microlight had taken off from the Rag Rock airstrip, that Rapp had no time to arrest the stall and fall that the aircraft went into when its engine stopped seconds after take-off, the official report on the cause of the crash indicates.The report, compiled by aircraft-accident investigator Ericsson Nengola, was released by the Ministry of Works, Transport and Communications’ Directorate of Aircraft Accident Investigations on Tuesday.In the report Nengola described the crash and the events that preceded it: “Two eyewitnesses who witnessed the accident stated that the pilot spent most of the morning hours maintaining and test flying the aircraft.He then decided to do one longer flight test in the afternoon.”Shortly after take-off, the engine coughed once, followed by a loud bang.There was no smoke or fire observed.”The aircraft sharply turned to the left while climbing, followed by an uncommanded nose dive attitude.The rate of descent increased uncontrollably and it (the aircraft) smashed onto the terrain at a steep angle and a near vertical attitude.”The plane had risen only some 60 to 70 feet above ground level before the engine stopped, the aircraft banked sharply to the left and it nose-dived into the ground.A major part of Nengola’s report focuses on the condition of the aircraft’s engine after the crash.When the engine was examined, it was found that part of it was completely dry and showed signs of extreme overheating.Two of the engine’s four cylinders as well as the rear part of the engine’s crankshaft were completely dry and had seized, the report states.No signs of an oil-pump failure could be found, however.From the state that the engine was found in, Nengola concluded that the engine “most probably experienced oil starvation which led to a catastrophic failure”.He also concluded that the most likely cause of this was an obstruction in the oil pipes that feed oil to the engine.Nengola stated that according to a Microlight Association of Namibia inspector who is highly experienced in the Rotax 912 S engine – the type of engine that Rapp’s plane was fitted with – Rapp had phoned him a week or two before the incident to inform him that he had to re-route the plane’s oil cooler and oil pipes, as a new covering for the plane’s engine was a bit different from the old one.The Rotax engine installation manual stipulates that the engine’s oil pipe has to be able to withstand a certain level of pressure and should not be bent in a radius of less than 70 millimetres, the report states.It also states that it is possible that the oil pipe of Rapp’s aircraft had folded to form a partial or complete obstruction.”This (obstruction) is the most likely cause of the engine failure,” it states.Nengola strongly recommended in the report that owners of Tecnam P92 aircraft and planes fitted with Rotax 912 engines and approved persons who maintain this type of aircraft should “strictly adhere” to the specifications prescribed by the engine manufacturer in its installation manual.