Page 18 - Index

The Big Things About Little Engines
Bigger, faster, stronger...it’s always better, right? Well, maybe so and maybe no.
by Joe Casey
In aviation, smaller can bring some real benefits if there are size constraints. The airplane that can’t fit in your hangar will not do a lot of good. And parasite drag is directly commensurate with the size of the object being hurled though the air. The only thing that overcomes drag
is thrust, and thrust can cost you a bundle. So, smaller can be better from an efficiency standpoint.
Consider faster. Faster sure seems better, but those 30 extra knots that your next “dream airplane” may provide can come at an exponential cost. Not only do the bigger engines require more fuel, they also have a larger engine reserve cost (the engine overhaul cost divided by the TBO expressed in a cost per hour). Speed is expensive.
Stronger also appears better, but strength usually brings his “best friend” weight along for the ride. And weight is not a friend in aviation if you are interested in a good climb rate, fast speed or higher useful load.
Yet, the market almost always prefers bigger, faster and stronger. And a premium is frequently paid by those who simply gravitate to the biggest, fastest and strongest. But herein lies an opportu- nity for those who choose to actually analyze their mission, do the math and approach an airplane purchase without bias. In the world of aviation, there is oftentimes a better deal found in smaller, slower and weaker options, especially when aircraft engines are considered. A puffed-out chest in the airplane buying process can end up costing money for no other reason than feeding an ego.
Let’s consider a practical example. I fly both a -6 powered King Air B100 and a -10 powered King Air B100 regularly. The engines are the exact same design, but the -6 engine is slightly smaller, developing less thrust at higher altitudes. I keep very accurate data for both airplanes and fly both
16 • TWIN & TURBINE
October 2018
PHOTO COURTESY OF DIANNE WHITE