How is Engine Failure Determined as a Cause in an Aircraft Accident Investigation?

          Turbine engines and reciprocating engines are different in terms of operation and crash investigation.  An investigator who is an expert in one may not be an expert in the other.  Reciprocating engines, or “recip” engines, generally are more problematical because of their nature of operation.  They have close tolerances and normal wear patterns that give little clues as to what caused the aircraft to go down, if the engine was turning when it was going down, and what it was doing at the point of impact.  It’s much easier to examine the propeller to find such things.  Turbine engines are different in that they have rotating fans that are very crushable in an accident situation.  These blades do not have wear from normal use like reciprocating internal parts.  A turbine engine has far fewer metal-to-metal rotating parts.[1]  Now we have a pattern we can look at to better determine the engine parameters at the point of impact, a good thing for crash investigation.

            Reciprocating engines have a good track record, but don’t kid yourself, they cannot be neglected.  It has redundant features, such as dual ignition systems.  But let’s say you change both magnetos at the same time.  You want to get all the life and utility you can out of your expensive, precious magnetos.  You also live fairly close to the coast, where salty water getting on aircraft is not uncommon.  You would ideally fly the magnetos untill one quits.  Would you ever try this with one ignition system?  Can you see where redundancy can actually be a compromise of safety?  An accident actually occurred where both magnetos had shorted because of salt water and age.  Turbine engines have an outstanding level of safety and redundancy.  Also, turbines are maintained better than piston engines.  They were designed to, and frequently do, fly all day, every day for years.