While tethered to a hover pit, BAE Systems Test Pilot
Graham Tomlinson makes two STOVL conversions in the first
production F-35B 'BF-01' at Fort Worth, TX 5/25/08
5/29/2008 - Fort Worth, TX -- The shaft-driven lift fan propulsion
system that will enable the Lockheed Martin F-35B Lightning
II stealth fighter to perform short takeoffs and vertical landings
(STOVL) operated for the first time in the aircraft during ground
testing on Sunday, May 25. At full power, the F-35B's system
generates more than 40,000 pounds of lifting force, or about
170 percent more than current-generation STOVL fighters.
Pilot Graham Tomlinson of BAE Systems performed two conversions
from conventional (wing-borne) to STOVL (jet-borne) mode with
the aircraft anchored to a specially instrumented hover pit
at Lockheed Martin’s STOVL Operations Test Facility. The
F-35B is conducting a final series of ground tests before its
first flight in the coming weeks.
"The F-35B's STOVL propulsion system operated exactly
as expected, providing the power output that our models forecast
and transitioning very smoothly from conventional to STOVL-mode
and back," said Bobby Williams, Lockheed Martin vice president
and F-35 deputy program manager. "We expect the same kind
of seamless transition when the F-35B begins STOVL-mode flights
in early 2009."
The F-35B combines the profound advantages of stealth and supersonic
speed with the ability to operate from small ships and austere
bases near front lines.
The F-35B STOVL propulsion system has logged more than 1,900
hours of operation on test stands. In 2001 the X-35B, a proof-of-concept
STOVL aircraft using a prototype of the same propulsion system,
completed 14 short takeoffs, 17 vertical takeoffs and 27 vertical
landings. On July 20, 2001, the X-35B became the first aircraft
in history to perform a short takeoff, accelerate to supersonic
speed in level flight and descend for a vertical landing in
a single mission.
The STOVL propulsion system comprises a Pratt & Whitney
F135 turbofan engine, a drive shaft leading from the engine
face to a gear box and clutch connecting to a counter-rotating
Rolls-Royce lift fan located directly behind the cockpit, a
3-bearing swivel duct at the rear that vectors the engine thrust
downward and provides yaw control, and a roll nozzle under each
wing for lateral stability.
During the conversion from conventional flight to STOVL flight,
all doors associated with the STOVL propulsion system begin
to open including the lift fan inlet and exhaust doors, the
roll-nozzle doors, the auxiliary-inlet doors atop the fuselage
(providing increased efficiency to the main engine) and the
aft fuselage 3-bearing swivel duct doors. The 3-bearing swivel
duct begins vectoring engine thrust downward as well. Once all
doors are open, the clutch engages and the lift fan begins turning.
As the lift fan reaches full speed the clutch locks, providing
a direct physical connection between engine and lift fan. The
aircraft control laws then begin using the STOVL propulsion
system to provide aircraft flight control. The system operates
automatically at the touch of a button.
The F-35B will operate in conventional mode during its initial
series of flights to evaluate overall flying qualities and airworthiness.
In preparation for the F-35B’s first flight, pilot Tomlinson
flew the F-35A for the first time on May 28, assessing the aircraft’s
handling at various power settings. In early 2009, the F-35B
will conduct initial STOVL flight operations before moving to
Naval Air Station Patuxent River, Md., for further testing.
Sunday's test marked the first use of the newly constructed
hover pit and its supporting facilities. "Our aim is to
retire technical risk well before we deliver F-35s to the fleet,"
Williams said. "Our investment in facilities like the hover
pit are helping us do just that while building confidence in
the test program."
Source: Lockheed Press Release