Turbopropeller Applications

The Turbopropeller Age
Complexities of the turbopropeller:
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Constant engine speed
High horsepower = high blade loadings
Very narrow rpm range requires very rapid blade pitch response
Feathering
Reversing (Beta mode)
Negative torque detection and response
De-Icing
Prop braking
Starting
T-40A-10
5,260 Horsepower
Wt: 3000 lbs.
• Dual power output shafts spin at turbine
speed (14,000 rpm), driving the bull gear in
the reduction gearbox.
• Reduction ratio: 15.688 to 1 (2.675 to 1 via
spur gears ; 5.857 to 1 via planetary gears)
• 26 clutch plates transmit 2600+ hp per power
section
First Test Cell Run of T-40 with
Dual-Rotation Propeller
June 4, 1948
T-40
Reduction
Gearbox
15.688 to 1
• Prop gearbox has a friction type propeller brake on the first stage reduction
gear to stop prop during feathering. Held “off” by oil pressure, prop speed
drops, springs push friction surfaces together. Outer member of the brake
has a helical thread; self-energizes putting more force on brake if props try
to reverse direction
• Accessories are driven by a gear set off the first stage reduction gear
Generator drive
Starter drive gears
Tachometer drive
Hydraulic pump
• Engines could be started:
By de-clutching the props and having the starters start one power
unit or the other
Once sufficient power was made by the running unit, the second
power unit was started by clutching-in the second unit
In flight, unfeather the prop, then the windmilling props could be
clutched in to start one or both power units
• Spring loaded, helically-splined safety coupling disengages power section if
-600 hp is generated at 100% rpm
Aeroproducts Dual Rotation Turbo Propeller Assembly
Outboard
prop
Inboard
prop
Red drive coupling connects the inner prop regulator body to the
“stationary” regulator housing of the outer propeller, locking them together,
thus providing the “fixed” portion of the outer propeller unit
Green control coupling connects master gear of the inboard propeller to the
control ring of the outboard propeller, thereby transmitting changes in pitch
setting to the regulator of the outer prop
Components in the Turbo Propeller Assembly
• Seven lanes of slip rings for each prop for electrical governing
control and blade de-icing
• Dual 0.072 c.i. / rev. hydraulic pumps for blade change operation
• Electric feathering pump (0.7 hp, 9000 rpm) provides 210 c.i. / min. @
400 psi for feathering and blade change when prop is stationary
• Centrifugal switch to detect rpm and energize or de-energize
feathering pumps
• Pressure control valve, flow control valve, and equal area valve that
maintain 600 psi differential between system and torque units
• Pressure reducing valve that reduces pressure for selector valve
• Solenoid valve driven by alternator/tachometer that biases flow to top
or bottom of torque unit piston based on electronic speed sensing
• Governor assemblies
Overspeed governor
Underspeed governor
Selector valve to select beta mode
Distributor valve manually controlled from cockpit for feathering,
starting, and Beta mode
Rotary piston translate linear to rotary motion, activating selector
valve
Inboard regulator
AD8664 FN-67
Outboard regulator
Inboard
prop
Onspeed
condition
• Separate centrifugal governors for underspeed (906 rpm) and overspeed
(913 rpm) control. Severe underspeed is considered 890 rpm.
• Solenoid valve cycles @ 20 times per second, alternating flow to one side
or the other of the torque piston. Dwell bias towards one or the other is
set by the tachometer/alternator on the gearbox via electronic governor
Inboard prop
Overspeed Condition
Outboard Propeller Regulator: Feathering
Douglas A2D Skyshark
Prop: AD8664 FN-47
Diameter: 14 ft.
Weight: 1516 lbs.
Runs @ 913 rpm
Solidity: 33%
Allison XT-40-A-2
5,500 shp
Wingspan: 50 ft.
Weight: 17,592 lbs
Max. Speed: 500 mph
Max. Climb: 7960 fpm
62 prop sets made
• AD8664 FN-47 prop on
test stand; strain gauges
on lower 2 blades
• Note lighter colored prop
spinner nose. This was
fiberglass as it was
intended to mount a
fixed radar antennae of
120 degree cone in the
spinner dome. Antennae
dish was to be mounted
on a support rod that
extended through the
hollow bore of the
propeller shafts.
2 prototypes and 6
production A2D aircraft
were flown
Persistent problems
with engine, gearbox,
and propeller control
resulted in cancellation
of production contract in
Sept. 1954
One A2D flew test with
Allison for several years
Used by permission from Brian Lockett
Chino, CA
1993
Now resides, restored but disassembled, in Idaho Falls, ID
Convair XP5Y-1, R3Y-1, -2 Tradewind
Engines: Allison T-40-A-10
Props: AD8664FN-67
Prop Diameter: 15 ft.
Cruise: 308 kt
XP5Y-1
Full feathering, reversing,
prop brake, external
electrical deicing
12 prop sets for XP5Y-1
R3Y-1
R3Y-2 Bowloader
Buried engine installation in XP5Y-1 required 3
piece extension shafting; engine was 21.5 feet long
Engine and Propeller Control Diagram
• Airframe-mounted electronic prop governor contained 25 vacuum tubes
Convair R3Y-2 Bowloader
“The Flying LST”
R3Y-2 Tradewind Refueling Grumman F9F Panthers
Pilots commented that the relatively straight flow, smoother air coming off the
contra-rotating propellers made in-flight refueling easier than behind tankers
equipped with single rotation propellers
• Eleven Tradewind aircraft and 88 prop sets were made
• Chronic problems with engines, reduction gearbox, and props caused
several in flight emergencies including 2 cases of departed props /
gearboxes which resulted decommissioning in April 1958
• Total combined fleet flight time was 3302 hours; maximum single
airframe had 716 hours of operation
North American XA2J-1
Super Savage
Max. speed 451 mph
Engines: Allison T-40A-6
5,035 hp + 1225 lbs thrust
Props: AD8664FN-B1
Diameter: 15 ft.
Prop Weight: 1446 lbs., dry
Max. RPM: 914 rpm
Governing: Electro-hydraulic
Deicing: Internal and external
electric, 120 volt
Components of AD8664FN-B1 as Used on XA2J-1
Inboard slip ring assembly
Vibration Testing
“Pineapple” contains electronic
brushes and slip rings to
transmit signals from carbon
strain gauges to the cable
Propeller Vibration Test
Aeroproducts Dual Rotation AD7562
Allison Torque Stand, Indianapolis, IN, June 25 - 30,1943
• All six blades instrumented with carbon resistance strain
gauges on blade shank (0 and 90°) as well as 7, 12, 17, 22,
27, 32, 37, 42, 47, and 52 inches from blade tip
• Driven by V-3420-B4 with 2.46 : 1 reduction ratio
• Engine run from 1400 to 3000 rpm, up to 45 in. Hg MAP, 201
p.s.i. BMEP
• Data acquired on Miller oscilligraph and Variable Area
recorder (film recorder).
AD7562, Outboard Prop, 12 inches from tip
Vibratory change in stress (p.s.i.)
Manifold Pressure
Strain
(p.s.i.)
1400
Engine RPM
3000
Summary of Report on AD7562 prop:
Outboard prop maximum stress:
8000 p.s.i., 2300 rpm, 22 inches from the tip
Inboard prop maximum stress:
9000 p.s.i., 2650 rpm, 37 inches from the tip
Prop hub maximum stress:
3800 p.s.i., 2960 rpm, 0° station, 2nd order vibration,
outboard hub
Maximum stress occurred as blades pass each other, however
these stresses were considered moderate and the prop/blade
combination safe for use
Other reports cite failures before test end due to vibratory
stress: stresses of 27,000 p.s.i. are unsafe and excessive
P-51H
XP-72
References and Contributors
R-4360: Pratt & Whitney’s Major Miracle, Graham White, Specialty Press, 2006, ISBN1-5807097-3
R-2800: Pratt & Whitney’s Dependable Masterpiece, Graham White, SAE, 2001, ISBN 0-76800272-9
Boeing XF8B-1 Five in One Fighter, Naval Fighters #39, Rick Koehnen, 2005, ISBN 0-942612-655
The Boeing XF8B-1 Fighter: Last of the Line, Jared A. Zichek, Schiffer Military Press, 2007, ISBN 07643-2587-6
Curtiss XBTC-2 Eggbeater, Naval Fighters #77, Bob Kowalski, 2007, ISBN 0-942612-77-9
Convair XPY-1 & R3Y-1/2 Tradewind, Naval Fighters #34, Steve Ginter, 1006, ISBN 0-942612-34-5
Douglas Skyshark A2D Turbo-Prop Attack, Naval Fighters #43, Gerry Markgraf, 1997, ISBN0942612-43-4
Famous Fighters of World War II, William Green, Doubleday, 1975, ISBN 0-385-12395-7
The Allison Engine Catalog 1915-2007, Technical Series #8, John. M. Leonard , Rolls Royce
Heritage Trust Allison Branch, 2008, ISBN 978-1-872922-38-6
Wings Magazine, Vol. 24, #3, June 1994 (color side view drawing of XP-72)
Operating Guide Navy Model T40-A-10 revised 1 November 1957
U.S. Army Engineering Division Report ENG-52-580-33-5, 3-Nov-1943
Aeroproducts Technical Manuals:
AD7652 (NASM)
AD8664 FN-47 (NASM)
AD8664 A1, A2 (RRHT-Allison Branch)
John Leonard, Bruce Vander Mark, Kim McCutcheon, RRHT-Allison Branch
Thank You!