User Guide

213
Flight Instruction
212
Flight Instruction
Over the years, both the King Air and PT6 families developed
ever bigger and stronger members, but the family resemblances are
strong. The Super King Air B200 featured in this release of FLY! is a
far cry from the old “straight 90,” but its heritage is evident at a
glance; and its mighty 850-hp PT6-A-42s are similarly close to their
original 500-hp ancestor. In fact, the PT6-A series is the most wide-
ly distributed light turboprop engine in aviation history, with tens of
thousands of units in the field…not to mention quite a few more tur-
boshaft versions in helicopters. While it’s still built in Canada, the
program now is owned by Pratt & Whitney.
AIRCRAFT AND COCKPIT TOUR
As you approach the Super King Air, you’ll see that it’s still,
basically, “just an airplane.” It may, however, be a bigger one than
any you’ve flown thus far; we’ll discuss some of its features on a
quick walkaround, then move into the cockpit.
What strikes everyone at first glance is that big T-tail. Why
have the horizontal stabilizer and elevator all the way up there?
For a couple of reasons. The most obvious is that this location gets
them up out of the downwash of the wing and the propeller slip-
stream; thus, the trim changes with power or aircraft configuration
(landing gear and flaps) are minimized.
A secondary reason is that this location allows the horizon-
tal surfaces to act as an “endplate” for the vertical fin and rudder,
making these more effective and thus allowing them to be small-
er. They’re still pretty good-sized, of course; they need to be able
to handle a potential situation with a windmilling prop on one side
and 850 feisty ponies on the other! Without the horizontal up
there, however, the vertical fin and rudder would have to be quite
a bit taller - to the point that getting the airplane into some typical
corporate hangars could be problem.
A look at the engines and their nacelles tells the educated eye
at a glance that this is a PT6-A powered airplane. There are two
clues. The most obvious is that, at rest, the propeller blades are
feathered. This is because the PT6-A is what’s called a free turbine
engine. (Unfortunately, this proves to be an oxymoron at mainte-
nance or overhaul time.) What it means is that the turbine stages
that drive the gearbox and propeller are not connected mechani-
cally to those that drive the engine’s compressor section. When the
engine is started, its core section (called the gas generator) can come
up to speed right away, without being affected by propeller loads.
Why is this the case? And, for that matter, if turbines are so
simple, why do they cost so much (over $250,000 each on the
Super King Air)? Because their internal parts operate in a very
demanding thermal environment, often requiring the use of exot-
ic and expensive alloys (that we’ll dub “unobtainium”). True, the
temperatures and pressures in a piston engine are similar to those
in a turbine - but they occur only during the combustion (“burn”)
stroke, allowing the relatively massive components to cool off dur-
ing the other three strokes. By contrast, the little turbine blades -
they’re each smaller than a postage stamp - are continually
immersed in the stream of hot gas, with no chance for a rest.
THE SUPER KING AIR AND ITS ENGINES - A
BIT OF HISTORY
Turboprops - generally pretty large ones - started appearing
on airliners in the 1950s, as the airlines’ demands for higher per-
formance, less maintenance, and more economical operation out-
stripped the capabilities of the big radial piston engines available
until then. Initially, however, there were no small engines and no
small business turboprop airplanes. The smallest turboprop air-
plane in general use, starting in 1958, was the admittedly magnif-
icent Grumman Gulfstream, powered by a pair of 1019-hp Rolls
Royce Dart airline turboprops - but with a seating capacity of up
to 21 and a gross weight of up to 36,000 lbs, it was out of reach
of all but the largest corporations.
Meanwhile, however, north of the border, the engineers at
United Aircraft of Canada, Ltd., were developing a very versatile
compact gas turbine for both aviation and industrial purposes.
Their PT6 series has found its way into everything from firefighting
pumps to Andy Granatelli’s Indy car (which had such fabulous
performance it was subsequently disqualified). More importantly,
the availability of the aviation version of the PT6 prompted Beech
Aircraft to develop an appropriate airframe to go with it. The first
King Air 90, which appeared in 1965, was developed from an ear-
lier piston-powered model (the Queen Air 88) and sported a pair
of PT6-A-6’s cranking out 500 hp each. It became the archetypal
small to medium business and corporate turboprop, a position it
continues to occupy.