Beechcraft King Air 90
1964, Beech introduced the Model 90 Beech King Air. It quickly
established itself as the industry standard in corporate jetprops.
During our production
of Northwestern Air Lease
a multitude of the King Air 90’s on board systems are reviewed.
Below is an overview.
The engine is a reverse flow, free-turbine engine. Air enters
through an intake screen and passes into a three-stage axial
centrifugal compressor driven by a single-stage reaction turbine. Another
single-stage reaction turbine counter-rotating with the first drives
the propeller through a two-stage reduction gear. Fuel is sprayed into
the annular combustion chamber by fourteen individual removable fuel
nozzles mounted around the gas generator case. A low voltage ignition
unit and coil igniter plugs are used to start combustion. The fuel
control unit schedules fuel flow to maintain the power set by
the gas generator
Power Levers. The accessory section and integral oil tank are located
on the aft end of the gas generator.
Propulsion Systems and Controls
Operated by three sets of controls:
Power Levers: control engine power from idle to take-off
power by adjusting the N1 speed governor in the FCU. Increasing
results in increased
Propeller Levers: Control the constant speed propellers
through the Primary Governor.
Condition Levers: 3 position lever; CUT-OFF, LOW-IDLE, and
All three work in conjunction with the fuel control unit to control
engine power. Propeller reversing is accomplished by lifting the power levers over
the IDLE detent. The levers override the Secondary Flight Idle Stop
and control engine power through the beta and reverse range.
The fuel system has a total capacity of 384 usable gallons, consisting
of 131 gallons in each wing tank and 61 gallons in each main take.
Both the right and left had systems are independent of each other
connected only by the cross-feed system. Fuel under pressure is
supplied to each engine by a submerged boost pump in each main
The direct current, 24 volt electrical system consists of a single,
24-volt, 40 ampere/hour, nickel-cadmium battery mounted in the
right center section
and two, 200-ampere starter generators controlled by solid state
Conventional dual controls are provided and nose steering is
accomplished by use of the individually adjustable rudder pedals.
on the rudder, elevator and left aileron are adjustable from
Optional electric elevator trim is thumb-actuated by a switch
on the pilot’s control wheel.
UP - 0%
APPROACH – 35%
DOWN – 100%
The landing gear is retracted and extended by a 28-volt split
field motor. Safety switches are incorporated to prevent
inadvertent gear retraction
on the ground and to avoid gear up landings. Visual indication
of the landing gear position is provided by individual
gear. Gear Unsafe lights are installed.
Hydraulic disk brakes on each main wheel are controlled
via pilot toe pressure on either set of rudder pedals.
The pressurization form the cabin comes from a mechanically
driven supercharger connected to the left engine accessory
air to air heat exchanger
removes the heat from this air prior to entering the