contrarotatingpropeller - how it works

The Short but Interesting Life of the AeroproductsDual-Rotation Propeller

Tom Fey

Sixth Annual Aircraft Engine Historical Society ConventionIndianapolis, Indiana

July 16-18, 2009

• Fundamentals of the Aeroproducts design

• Piston engine contra-rotating drive trains: R-4360, V-3420

• Operation principles of the dual rotation prop for piston applications

Aircraft Powerplant First Flight Fisher XP-75 V-3420-B Nov. 17, 1943Republic XP-72 R-4360-4 June 26, 1944Boeing XF8B-1 R-4360-10 Nov. 27, 1944Curtiss XBTC-2 R-4360-8a January 1945

• Turbine engine contra-rotating drive trains: Allison T-40

• Operation principles of the dual rotation prop for turbine applications

Aircraft Powerplant First FlightConvair Tradewind XP5Y XT40-A-4A April 18, 1950Douglas A2D Skyshark XT40-A-2 May 26, 1950XA2J Super Savage T40-A-6 Jan. 4, 1952Convair Tradewind R3Y-1 T40-A-10 Feb. 25, 1954

Werner J. “Pete” Blanchard 1900 - 1948

Charles S.J. MacNeil

1910 - 1944

Engineering Projects Inc.; six years of development.

Bought by GM in 1940 and renamed Aeroproducts

Unique propeller system because oil supply, oil pump, oil filter, pressure release valve, and governor all contained inside prop regulator body rigidly attached to backside of propeller hub. Prop can be changed in 20 minutes.Manufactured 73 props in month of Dec. 1941

12,500 props in month of Feb. 1944

Regulator body

R-3350 nose case

Anti-rotationbracket

Prop governor control linkage,bellcrank, and tie rod

Prophub

The Outside of a Single Rotation Aeroproducts PropellerA642-G8 Aeroprop on Douglas Skyraider

BlueBlue = Non-rotating components fixed in place by anti-rotation bracket attached to engine nose case

The Inside of the Aeroproducts

Propeller

Gold parts are non-rotating, locked stationary to engine

Black (regulator and hub) parts rotate with the propeller, generating its own hydraulic pressure

Control ringtranslates fore or aft to set the governor control via fulcrum and spring set that oppose centrifugal force on the spool valve

Governor

Pressure Control Valve and Oil Filter

Oil Pump

Increase Pitch Tube

High Pressure Feed From Oil Pump

Decrease Pitch Tube

Stainless steel pressure tubing and steel mounting

pads are cast integrally into the aluminum

regulator body

Blade can move up to 5° per second via 1000 psi oil

Torque Unit

• Forged and machined steel thrust member w/ integral ribs

• Steel camber sheet roll-welded and brazed to thrust member

• Hollow root accepts torque unit

Aeroproducts Hollow Steel Propeller Blades

Centrifugal force wants

to throw piston

outward

Centrifugal force on piston is

resisted by spring whose

force is moderated

by the moveable fulcrum

Aeroproducts Propeller Governor

Capable of governing prop to ± 1 rpm

UnderspeedNeed to increase revs by lowering blade pitch

OverspeedNeed to decrease revs by increasing blade pitch

• Dual output shafts are geared together at engine, spin at crankshaft speed, and rotate in opposite directions as viewed from tail

• Inboard prop rotation: counter clockwise• Reduction ratio: 2.458 to 1• Gearbox weight: 390 lbs.• Extension shafts and bearings: 135 lbs.• Has own oiling system in the gearbox• Gears made by Cadillac; 99.5% efficient

Allison V-3420-BPropeller Reduction Gearbox

Farman Gear Set Pinion Axles Held Stationary in Red Ring Gear

Pratt & Whitney Dual-Rotation

Reduction Gear

Fixed

Werner J. Blanchard and Charles S.J. MacNeil, Dayton, Ohio, assignors, by mesneassignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware

• Activity Factor: approx. 100 • Pitch range: 35° (28° to 63°)• Weight: 780 lbs.

(763# dry + 17# grease/fluid)• Blade Angle Differential: 1.5° finer

pitch on inboard prop• Max. Prop RPM: 1220

Aeroproducts AD7562Dual rotation prop used on piston-powered aircraft

P-75AXF8B-1

NomenclatureAD7562-A1

A =AeroproductsD =Dual rotation7 =70 spline inboard shaft5 = 50 spline outerboard shaft6 = 6 blades2 = Blade shank sizeA = Major design specification5 = Minor design specification

• Constant speed is maintained by inboard prop regulator• Outboard propeller pitch is indirectly slaved to inboard pitch• Outboard prop requires a “fixed” component to drive oil pump

and an adjustable component to translate pitch change information from the inboard prop to the outboard prop

Aeroproducts AD7562

InboardOutboard

Control of Outboard Propeller

Instead of the centrifugal governor of the inboard prop, the outboard prop used a distributor valve to direct fluid flow to above or below the torque piston.

The position of the distributor valve is set by a cam.

The cam is adjusted by a coordinating linkage from the master gear of the inboard prop

Elements in pink rotate with the inboard propeller.

Elements in yellowrotate with the outboard propeller.

When the prop is onspeed, the orange planet gears essentially spin in place with no relative angular movement (indexing) between the inboard and outboard components, just opposite rotationBecause the props rotate in opposite directions, power

gear (11) drives the oil pump for the outboard prop

Inboard and Outboard Components for Coordination of Props

Coordination Signal to Initiate Blade Pitch Change in Outboard Prop

When inboard master gear (7) moves in response to blade pitch change, that movement is transferred by the ring gear (8) and pinion(10) back to the cam (12)

This “re-indexes” the cam, the distributor valve moves off the neutral position to provide flow to one side of the torque piston and change outboard blade pitch

Feedback to Terminate Blade Pitch Change in Outboard Prop

When outboard master gear (16) moves in response to blade pitch change, that movement is transferred by the transfer shaft (18) back to the cam via gear (19) which is linked to follower gear (24)

This “re-indexes” the cam and distributor valve back to the neutral “onspeed” position

Coordinator Assembly

P-75A

Fisher P-75A EagleFirst flights

XP-75: Nov. 17, 1943 (8 built)P-75A: Sept. 15, 1944 (6 built)

Allison V-3420 B-10 with remote dual-rotation gearbox

P-75A Powertrain

AD7562-X5, 13 ft. 1 in. diameter#70 spline inboard, #50 spline outboard

• Sad remains of crashed P-75A AD7562 X5A prop. Outboard prop and shaft sheared off by impact.

• Inboard spinner failure or gun tube separation fouled the props, destroyed the transmission between the props, caused the regulator to rotate 30°, loss of oil through open ports, and blades to go flat pitch

Three of the 5 P-75A Eagles crashed in flight test; program cancelled Nov. 8, 1944

Republic XP-72

First Flight:XP-72 #1 (single rotation): Feb. 2, 1944

XP-72 #2 (dual rotation): June 26, 1944

Republic XP-72

Actual XP-72 engine was

single stage, single speed

R-4360-3

Remote, fluid drive, first stage supercharger intended for XP-72

R-4360-8 (single stage, variable speed)shown

Republic XP-72

Propeller: AeroproductsAD7562-X14, 13 ft. 7 in. diameter

Both prototypes reportto have achieved 490 mph @ 25,000 ft

Dual rotation aircraft flew only a short time; in-flight fire at altitude resulted in belly landing and extensive damage; not rebuilt

Republic XP-72Aeroproducts AD7562-X14 in test cell driven by Allison V-3420

Nose cowling contained a contravane behind the spinner fan to straighten the airflow downstream of the spinner fan and into the engine

Boeing XF8B-1 “Five - In- One Fighter”

Span: 54 ftEngine: R-4360-10 Gross Weight: 18,263 lbsInternal bomb bay

Fighter - Interceptor - Torpedo Bomber - Dive Bomber - Horizontal Bomber

R-4360-10, two stage, variable speed supercharger, SAE #50, #70 prop shafts, 3000 hp, 3785 lbs

Aeroproducts AD7562-8 propeller, 13’ 5 11/16” ft diameter, 13.5 inches between blade sets, approx. 865 pounds, governing range was 610 to 1150 prop rpm, held to +/- 5 rpm, pitch change rate 4.2 ° / sec.

Boeing XF8B-1

From Aeropinion; “Magazine for and by the employees of Aeroproducts”

Experimental Installation of Aeroprop Contra-Prop on Vought XF4U-4 Corsair

Engine: P&W R-2800-18W

Propeller: AD7562-X5, 12’ 7” diameter, 864 lbs.

Performance was noted as being 8 mph slower @ 26,000 ft. and rate of climb 300 ft/min slower than the 667 lb 4-blade, 13 foot diameter Hamilton Standard Hydromatic prop.

Picture in William Green’s book; see bibliography

Curtiss XBTC-2 Experimental Bomber Torpedo Aircraft

Engine: P&W R-4360-8aPropeller: AD7562-14, 13’ 6” diameterFirst flight January, 1945

Initially used Curtiss Electric contra-prop, however vibration and stress tests revealed this prop to be a poor match for this particular installation, so the Aeroprop was fitted in mid-1945. Additional pictures in Bob Kowalski book, see bibliography