Propellers and Propeller Systems for Propulsion Investigation

Question: Discuss about thePropellers and Propeller Systems for Propulsion Investigation. Answer: Aircraft accidents could occur due to a number of reasons and propeller damage is one of the best indicators of aircraft accidents. While checking for propeller damages time for overhaul, repair records and operation times are checked whether the repairs are carried out as per the rules and regulations as improper repairs can lead to failures caused by surface discontinuities ( Anderson, 2009). Irregular welding and straightening activities can lead to propeller failure but physical damage to the propeller physical damages are the most destructive. Damages caused by water impact and ground impact are thoroughly investigated in case of propeller damage. Ground impact damage could be determined by evaluating the bending of the blade, slash marks caused by ground, breakage, tip curl, span wise and chord wise scratches. Tip curl shows that the engine was rotating and the power developed by the engine is indicated by the amount of tip curl (Anderson, 2009). If the propeller tips are curled backwards then it suggests that the propeller was rotating with low RPM relative to forward velocity and if the propeller was rotating with high RPM with respect to the speed of the aircraft, then the tip curls in the forward direction. Bending is caused due to crash impact and its direction will be opposite to that of the direction of rotation is the propeller is powered. Low aircraft speed and high power bends the propeller in the forward direction. But if the aircraft creates an impact at right angles to the ground the propeller bends in the backward direction. Vibration, imbalance and improper maintenance also bends the propeller blades (Kroes and Wild, 2010). Misalignments in the crankshaft and bearings are good indicators of bending because problems in the propeller are transmitted to the crankshaft and bearings. If the engine is not rotating then it could break the propeller blade, scratches along propeller blade face is due to propeller rotation. Chord-wise scratches are caused when the propeller rotates at the time of impact, but this sign not necessary indicate that the engine was running it can also be caused due to wind-milling (Kroes and Wild, 2010). Rotation of the propeller can cause slash marks on the ground which could be used to estimate the RPM of the propeller. Some of the good practices which could prevent propellant damages are to regularly check all the parameters like temperature of all bearings and shaft bearings, maintain oil level in the tank at all times, maintain the pressure, perform regular checks near the stem and perform overboard checks, regularly check for leakages, regular hydraulic oil analysis should be carried out, always start the engine at zero pitch angle and always run the engine at constant speed (Anderson, 2015). Propeller installation is a highly complex and expensive procedure which has to be carried out under extreme care and damages due to improper installation should be avoided with the highest priority so as to control propeller damages. Following standard practices and regulations coupled with an effective maintenance routine could reduce propeller damages to a large extent. References Anderson, C.L. (2015). The Effects of Aircraft Certification Rules on General Aviation Accidents. Journal of Aviation Technology and Engineering 4(3), 32-48. Anderson, K. (2009). Propulsion Plant Accident Investigation. Embry-Riddle Aeronautical University. Kroes, M.J. and Wild, T.W. (2010). Aircraft Powerplants (Aviation Technology Series). New Delhi, new Delhi: McGraw-Hill Higher Education.