Reciprocating Engine Aircraft Accidents Due

Reciprocating Engine Aircraft Accidents Due to Component Failure

The most important component that fails in a reciprocating engine is the human component. We shall first study an accident that was of a big aircraft, Lockheed Super Constellation, L-1049H, N 6917C at Miami Florida. Next we shall look at the causes of accidents from an engine point-of-view. Though it seems clear that most of the accidents are not due to engine problems, there are still problems connected with other parts of aircrafts that cause accidents and for this part of analysis we have decided to use the case history of Cessna. We shall understand that it is pilot error that causes 95% of the accidents for reciprocating engine aircraft, and thus pre-flight inspection is one of their most important duties. The pilot of the aircraft in question is finally responsible for ensuring that the aircraft is safe before each flight, and the checking procedure depends on the complexities of the aircraft and the capabilities of the pilot in question.

Reciprocating engine aircraft accidents due to component failure

Introduction:

The biggest component that fails in a reciprocating engine is the human component. Let us first study an accident that was of a big aircraft, Lockheed Super Constellation, L-1049H, N 6917C at Miami Florida. The accident took place on December 15, 1973 and the aircraft hit the ground 1.25 miles east of the airport and destroyed quite a few homes, automobiles and other property. The occupants of the aircraft were three members of the crew and six persons on the ground were all killed. There were injuries to two others. According to the study by the National Transportation Safety Board the direct cause of the accident was the over-rotation of the aircraft at lift off time and this resulted in the flight being in the aerodynamic region of reversed command and near the stall regime. (Aircraft Accident Report)

At the same time the flight was then at too low a height to permit recovery. Why the aircraft got into this situation was not fully understood by the board, but they felt that there may have been three possible reasons. The first could have been an improper loading of cargo. The second could have been a rear shift of the cargo resulting in a shift of the center of gravity beyond the limits permitted for the aircraft and the third could have been improper coordination of the crew. The deficient coordination by the crew refers to the management of the flight and this required overall control of the flight by the captain, the management of the different controls of flight and power-plant, and both of them could have been combined with the actions of one or more partially incapacitated or unqualified members of the crew. (Aircraft Accident Report)

Analysis:

Now let us look at the causes of accidents from an engine point-of-view. Both turbine engines and reciprocating engines process air in the same manner and that means that they both have intake, compression, combustion and exhaust. In the reciprocating engine one step has to follow the other and in the turbine engine all the processes proceed all at the same time and without any interruption. The other difference is that in the turbine engine there are separate components decided for the particular operation of the cycle, while in the reciprocating engine, all the functions take place in the same combustion chamber. The design of each engine gives certain benefits and advantages, and when the issue is considered from thermal efficiency, reciprocating engines are easily more efficient. They have a complex design, but the engine has had a longer period to be developed and perfected. The general view is that turbine engines have simplicity of motion and this has given a reputation for being more reliable, though it burns more fuel than a reciprocating engine. (Engines: Turbine Reliability: Fact or Friction?)

On the other hand the space required for the reciprocating engine is more while the turbine engine costs more. In terms of weight, the turbine engine is lighter whereas the reciprocating engine is definitely heavier. The question of weight is probably most important when both engines are considered, and certainly turbine engines provide much more power for the weight. In the case of reciprocating engines, the power provided is roughly around one horsepower for one pound of weight while the turbine engines can provide more than six horsepower for every pound of weight. Now let us look at the point on hand - accidents. The view that is taken in this analysis is accident causes as a percentage of total accidents in comparison of two helicopters - the piston powered R22/R24 and the turbine powered Bell 206 and MD 500. The analysis is from NTSB summaries of accidents in United States from January 1993 up to December 1997. During this entire period, only 2% of the R22/R24 met with accidents due to the failure of their engines as compared to 10% of the Bell 206 and MD 500 from the same reason of engine failure. This should make it clear that the reliability of the reciprocating engine has been much higher during the entire period. When one specifically takes the case of R24, this has not met with a single accident due to engine failure during this entire period. (Engines: Turbine Reliability: Fact or Friction?) Since there has not been any engine failure, it is clear that component failures are almost impossible to find.

It has been seen that it is pilot error that causes 95% of the accidents for reciprocating engine aircraft, and thus pre-flight inspection is one of their most important duties. This is a procedure by which the pilot determines that the aircraft is ready for safe flight. Most aircraft flight manuals or pilot's operating handbooks contain sections for conducting a systematic pre-flight inspection. Simple or minor preservation functions and replacing small standard parts are considered to be preventive maintenance. The pilot may carry out preventive maintenance on any aircraft that is owned or operated by the pilot, unless it is used in air carrier service. A reciprocating powered single engine aircraft used for the purpose of pleasure requires at least annual maintenance by means of a certified airframe and power-plant mechanic. (Airplanes and Engines)

There are differences in requirement of maintenance by different aircraft, but it has been seen that most aircraft needs some type of maintenance at least after every 25 hours of flying time, and minor maintenance is required at least once every 100 hours. Of course maintenance is influenced by type of operations, climatic conditions, storage facilities, age and construction of aircraft. Water and dirt in fuel systems are very dangerous and the pilot has to eliminate or prevent contamination. Of the many accidents which have been due to power-plant failure, the reasons for most have been due to inadequate preflight inspection by the pilot, servicing of aircraft which has improperly filtered fuel from small tanks or drums, due to storing aircraft by means of partially filled fuel tanks and lack of proper maintenance or handling. Of all the contaminants, water is considered as the most prevalent and it has been recommended that fuel sumps should be drained during the time of preflight inspections so that flight safety is improved. (Airplanes and Engines)

Though it seems clear that most of the accidents are not due to engine problems, there are still problems connected with other parts of aircrafts that cause accidents and for this part of analysis we have decided to use the case history of Cessna, which is a common aircraft in the country. At 1400 Central Standard Time, on February 3, 2004, a Cessna 208B lost right rudder control after taking off from Columbus Metro Airport in Columbus, Georgia. The flight was operated under Title 14 CFR Part 91 and visual flight rules. The meteorological conditions were suitable for visual flight and there were no filed flight plans. Even with the accident, the pilot and co-pilot were not injured and the airplane was not damaged. (Aircraft: Cessna 180A)

The flight left the airport at 1340 and was going to Auburn-Opelika Airport in Auburn in Alabama. As per the information from the co-pilot, during the take-off roll the co-pilot noticed that the right rudder was not responding to their efforts. Though they should have returned to Columbus, but there was a very high volume of traffic in that airport and they decided to go on to their destination of Auburn-Opelika Airport. While the flight continued, the pilots began to find out more about the problem. They found that there was no response from rudder trim and even when the right rudder pedal was fully deflected, there was still no effect. They examined the matter further and found that the right rudder cable was broken.

This made them aware of the seriousness of their problem and they contacted their Chief Pilot and Director of Maintenance. According to the experts there was nothing that could be done during the flight. The pilot then asked for emergency vehicles to meet them on runway 36 as a precaution. No total emergency was declared. The flight was able to land safely on runway 36 and the pilot was able to complete a normal shutdown. Then the rudder cable was sent to the NTSB materials laboratory and they found that the wire rope portion of the cable was fractured inside the clevis fitting as the forward end of the cable. The strands of the wire rope had separated from each other by a distance of more than one foot from the cable end. At the same time, the separation between strands of the same cable were not so high and even when they were separated, the distance was much less. Then the broken ends were seen through a bench binocular microscope and that showed the wire fractures were aligned with each other and within a distance of 0.02-inch and within a distance of 0.05-inch from the end of clevis fitting. (Aircraft: Cessna 180A)

Almost all of the fractures were on a flat transverse plane and there was no great deformation in a necking form which comes when these crack due to fatigue of the whole wire rope. Some of the wires were broken on a slant plane and they had the necking down deformation to indicate that they had broken down due to high stress. Some of the wires also had fracture shapes that showed a mixture of fatigue and overstress. This required them to be examined more as also the clevis fitting and this showed that the forward ends of the clevis point were all joined together. The space between the points were then measured with calipers and found to be 0.18-inch near the joining point and 0.13 inches from the tip. Then the entire lot was examined visually and the inside portions of the points of the clevis showed that there was some rust colored material there and this happens due to fretting or rubbing damage, near the tips of the points.