In this case, the power is defined as the total amount of power usefully employed in propelling the aircraft at the assumed used conditions of weight, speed, and lift-drag ratio. The Wright 3350 turbocompound engines that powered the Lockheed aircraft are among the most powerful reciprocating engines ever developed for aircraft use. The weights used in this ratio are the dry, uninstalled engine weights as given in reference 205 . The turbine engines in the Boeing aircraft develop nearly four times as much power for each pound of engine weight as do the reciprocating engines that power the Lockheed aircraft. The jet propulsion system avoids the compressibility problem that limits the speed at which the propeller may be efficiently employed, is light in weight for a given amount of power as compared with a reciprocating engine, and can be successfully produced in single units capable of generating very large amounts of power jet propulsion systems also require much less maintenance than do reciprocating engines and may be operated for many thousands of hours without major overhaul.
Engine failures are also relatively rare with jet propulsion systems.