Guide to Reciprocating Engine Accident Investigation
i. Abst.
The plane Piper Navajo Chieftain PA31-350 of the air company Air Nunavut Limited crashed shortly after take-off during the time it was achieving its climb to the appropriate altitude. It was observed by the pilot that the plane’s right engine developed mechanical failures and was incapacitated to provide sufficient thrust required to maintain the plane’s climb thereby causing the plane to crash. This report forms the critical analysis on the basis of the reciprocating engine investigations for the plane and other investigative subtitles necessary.
Reciprocating engines operate mechanically by a to-and-fro motion of the pistons in which the energy generated is transformed via a connecting rod into rotational motion of the crankshaft (Kamimoto, 2009).
The plane under study was found to be operating a reciprocating engine which is as well-known as piston engines. This is a heat driven engine which uses pressure on a number of the reciprocating pistons to generate motion. One major type of this kind of operational engines is the internal combustion engine (ICE), which is widely used in automobiles industry (Gupta).
The engine has a role for a full operation to generate the required horse power for the motion in the air to be achieved optimally (Bansal, 2001). Components of the engine consist of single or several pistons which are located inside cylinders. In the cylinders, a pressurized hot gas is injected or it can either be ignited through a fuel-air mixture or probably it could be produced due to contact with the heat exchangers at high temperatures (Florio, 2006). The injected pressurized hot gas in the cylinder pushes down the piston inside the cylinder and then it is brought back to its normal position by use of a flywheel or power from other adjacent pistons in connection to it through a similar shaft. A stroke movement by the pistons makes the engine to exhaust the gases but in some instances, the piston is powered in both the directions of stroke inside the cylinder a situation known as double action (Gonzales, 2010). The various details of the atmospheric conditions are tabulated and can also play some significant role in determining the main route cause of the engine failure (Pravas Mahapatra, 2007).
Power = Peff x Lp x Ap x n/2
Where: Ap = piston head area
Lp = length of piston stroke
n/2 = power stroke per minute, n = rpm.
For Nc = number of cylinders, the equation is;
In-Depth Analysis of Case Study
IHP = Peff x Lp x Ap x n/2 x Nc
The total displaced volume is calculated by,
Vx = Ap . Lc . Nc ≡ IHP = Peff x Vx x n/2 (IHP :internal horse power)
Engine power equations; Brake Horse Power (BHP)
BHP = IHP – FHP (FHP: Frictional Horse Power)
BHP = 2 x π x RPM x torque
BHP = ηmech . Peff x Vx x RPM = Peff x Vx x RPM
Engine efficiency;
BHP/ ?f x Q = ηth = 1/ (?f /BHP x Q)
The diagram indicates that the exhaust starts (after 5) while the pressure in the cylinder is well above atmospheric. The exhaust stroke ends at near-atmospheric pressure (by virtue of the inertia of piston).
iv. Findings from the case study.
From the case study, it is evident that the pilot claimed to have performed feathering to the plane. Feathering is a procedure performed to the plane which is known as the setting of the propeller blades to a particular pitch and making them more of streamlined to the direction of flight (Thomas R. Yechout, 2002). This is done so as to maintain the movement of the plane in the air in case there is an occurrence of engine failure by enabling the propellers to rotate more freely due to laminar flow of air currents. It enables the aircraft to stay in control by the pilot and reduces yawing when the feathering procedure is done appropriately (Lewis, 2006).
It is clear that the aircraft propellers were not feathered after the accident occurred which typically suggest that the plane was not previously feathered. Due to the engine failure, there was no thrust power generated by the propellers and consequently, could be subjected to the frictional force due to air currents and additional compressional forces acting on the engines which caused a significant yawing effect hence the crushing (Cooper, 2007).
A properly feathered propeller has its blades positioned to the actually required angle by the pilot and thereby they are streamlined to the airflow in the direction of flow. When the propellers are feathered appropriately, the frictional force, drag and compressional forces are greatly reduced hence the yawing effect becomes negligible and minimal chances of crushing.
The exhaust mufflers and exhaust pipe accidentally became disconnected. The steel collars also had incorrect installation order (Administration, 2010). An intensive monitoring of the aircraft could ensure that the connection of the heat exchangers and the exhaust pipe were properly connected and any evident misappropriate connection cancelled out.
Components and Features of Reciprocating Engines
The aircraft engine cowl was damaged making the engine to be exposed to air. The cowl is a removable metal that covers the aircraft engine and performs the function of forming parallel lining with the wing or fuselage (Soares, 2005).
Causes of the engine failure leading to plane crash could be probably caused by engine combustion chamber component melting causing infectivity, the bearing could be faulty or the components of powertrain getting damaged. There was the disconnection of the exhaust pipe from the cylinder muffles which consequently led to the buildup of the exhaust fumes inside the engine cowl. Accumulation of the fumes which were at high temperatures caused the engine cowl getting damaged by the flame. The spark plugs were worn out and from the investigations, we found out that they became damaged by high heat intensity (Bolton, 2004).
Loose engine magneto which is a constituent component of the engine with other attachments like hardware components, the gasket and some other stud threads. The aircraft engine oil should be regularly sampled to the laboratory for checking if there could be any contaminants present. In these laboratory samples, small pieces of the engine worn out parts can be identified thus creating a route path to identifying the engine problems and thereby minimizing engine failure.
The engine valves could be possibly ineffective caused by sticking together making fuel flow uncontrolled (Xin, 2011). The cam followers could have been broken away from their shafts. Breakage of the cam followers is brought by broken governor idle gear teeth crushing into the cam follower chambers (Senft, 2005).
The aircraft was to be properly and extensively checked and the technician to ensure that the plane was in a proper condition for operation. Most worn out parts of the aircraft ought to have been replaced prior to issuing a take-off (Thomas W Wild). Replacement of most of the worn out parts could be important since the operation of the aircraft is nearly efficient a hundred percent.
i. Introduction to turbine engine accident investigations.
Turbine engines is an engine that rotates while converting the kinetic energy of flowing fluids through it and they include the following; turbojet engine, turboprop engine, turbofan engine and lastly the turboshaft engine (El-Sayed, 2008). Aircraft highlighted in the case study was more likely to be operating on turboprop plane engine.
The engine is connected to a propeller through a gearing system produces power to spin a shaft which in turn connects to the propeller via the gearbox. The propeller thereby rotates creating differential pressures due to eddies of air currents hence generating thrust to create motion for the aircraft (Vennard, 2008).
Propeller Systems and Feathering Procedure
There are a number of turbine engine accident related investigations. Turbine engine failure is an incidence which takes place when the engines occasionally stop producing thrust and power for the aircraft. Some aspects that are unique with the turbo engines are that they can be shut down in case of a cause for alarm for instance low oil pressure or high temperatures in oil (Ward, 2010). The chances of the turbine engine to be on fire can happen if there is fuel flow control has surpassed a fault in the system and combustor receives an excess of fuel and this can cause the fire which is likely to spread to the exhaust system.
Mechanical failures can arise in the engine; damage to some components of the turbine engine, oil leakage in the engine system and aircraft fuel contamination. In aircraft maintenance regulations, the turbo engines are very critical thus the maintenance and management operations are so intense to the level of ensuring the aircraft have no risk factor imposed to the engine systems (Treager, 2002).
Turbine engines are engineered such that the aircraft can land safely on a single operative engine by managing the plane swiftly without crushing. In more obvious occasions, the turbine engines are presumed to be safer relative to the reciprocating engines (Colin R. Ferguson, 2015).
In conclusion, reciprocating engine accident on the aircraft under case study was majorly caused due to human error and negligence of the responsible parties.
References.
Administration, F. A. (2010). Aircraft Inspection and Repair.
Bansal, D. R. (2001). Mechanical Engineering (O.T.). Elsevier.
Bolton, J. (2004). Classical Physics of Matter. Bristol and Philadelphia.
Colin R. Ferguson, A. T. (2015). Internal Combustion Engines. John Wiley & Sons, Inc.
Cooper, J. R. (2007). Introduction to Aircraft Aeroelasticity and Loads. In J. R. Cooper. New York: John Wiley & Sons, Inc.
El-Sayed, A. F. (2008). Aircraft Propulsion and Gas Turbine Engines. CRC Press.
Florio, F. D. (2006). Air Worthiness. In An Introduction to Aircraft Certification.
Gonzales, K. H. (2010). Future Fuels for General Aviation. John Wiley & Sons, Inc.
Gupta, B. (n.d.). Theory of Machines. In Kinematics and Dynamics. New Delhi: I.K International Publishing House Pvt. Ltd.
Kamimoto, C. A. (2009). Flow and Combustion in Reciprocating Engines. In C. A. Kamimoto. Springer-Verlag Berlin Heidelberg.
Lewis, B. L. (2006). Aircraft Control and Simulation. In B. L. Lewis. New York: John Wiley & Sons, Inc.
Pravas Mahapatra, R. D. (2007). Aviation Weather Surveillance Systems. In Advanced Radar And Surface Sensors. American Institute of Aeronautics and Astronautics.
Senft, J. R. (2005). Mechanical Efficiency of Heat Engines. Canada: The Woodbridge Company Ltd.
Soares, C. (2005). Gas Turbines. In C. Soares, A Handbook of Air, Land and Sea Applications. Elsevier.
Thomas R. Yechout, S. L. (2002). Introduction to Aircraft Flight Mechanics. In S. L. Thomas R. Yechout, Performance, Static Stability, Dynamic Stability, and Classical Feedback Control.
Thomas W Wild, M. a. (n.d.). Aircraft Powerplants, Eighth Edition. McGraw Hill.
Treager. (2002). Aircraft: Gas Turbine Engine Technology. McGraw Hill Pvt. Limited.
Vennard, J. (2008). Aircraft Gas Turbine Engines. In Operation, Components and Systems. Wexford.
Ward, T. A. (2010). Aerospace Propulsion Systems. John Wiley & Sons, Inc.
Xin, Q. (2011). Diesel Engine System Design. Edinburgh: Elsevier.
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