US2549886A - Folding rotor blade - Google Patents

Folding rotor blade Download PDF

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Publication number
US2549886A
US2549886A US761975A US76197547A US2549886A US 2549886 A US2549886 A US 2549886A US 761975 A US761975 A US 761975A US 76197547 A US76197547 A US 76197547A US 2549886 A US2549886 A US 2549886A
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blade
pitch
means
axis
hinge
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Expired - Lifetime
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US761975A
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Michel D Buivid
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United Technologies Corp
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C27/00Rotorcraft; Rotors peculiar thereto
    • B64C27/32Rotors
    • B64C27/46Blades
    • B64C27/473Constructional features
    • B64C27/50Blades foldable to facilitate stowage of aircraft

Description

April 24, 1951 M. D. BUlVlD FOLDING ROTOR BLADE Filed July 18, 1947 2 Sheets-Sheet 1 MICHEL D. BUIVID INVENTOR ATTORNEY April 24, 1951 BU|V|D 2,549,886

FOLDING ROTOR BLADE Filed July 18, 1947 2 Sheets-Sheet 2 gr R a (D O G (D I @321 T MIGHEL'D. BUIVID INVENTOR I MK ATTORNEY Patented Apr. 24, 1951 UNITED STATES PATENT OFFICE FOLDING ROTOR BLADE Michel D. Buivid, Milford, Conn assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application July 18, 1947, Serial No. 761,975

Claims. 1

This invention relates to an improved mechanism for folding rotor blades of rotary wing aircraft without injury to the control mechanism.

Accordingly, an object of this invention is to provide a rotorblade mounting assembly which will permit the blade to be folded and the controls to be automatically disengaged by a simple rapid process.

Another object of this invention is to provide a hub assembly for rotary wing aircraft which automatically disengages the pitch control system when the blade is released for folding.

A further object is to provide means for folding rotor blades into a more compact space.

A further object is to provide automatic mechanism to disengage the pitch controls when the rotor blades are folded.

Another object is to provide mechanism which automatically engages the controls only when the blade is properly positioned with respect thereto.

Still another object is to provide a method of folding rotor blades which will simplify ground handling.

The foregoing, and other objects, will be obvious or pointed out in the following specification and claims.

In the drawings:

Fig. 1 is a side elevation of a helicopter with the rotor blades folded according to my invention;

Fig. 2 is a fragmentary perspective View;

Fig. 3 is a plan view showing the blade in the assembled or flight position; and

Fig. 4 is a view of Fig. 3 taken along line 4-4 with parts broken away with the blade lowered.

In my United States Patent No. 2,405,777, I have shown a method of folding the rotor blades to rest upon a jack on the tail cone of the wellknown helicopter configuration of a single main rotor and a torque counteracting tail rotor. The method disclosed in my patent involves two steps; releasing the rotor blade for folding and disconnecting the pitch control mechanism. When the blades are returned to the operative position the pitch control and the blade must be secured. It is the purpose of the present invention to improve upon the mechanism shown in my patent to provide a simple mounting device whereby releasing the blade for folding movement automatically disconnects the pitch control mechanism. When the blades are returned to the flight position, the pitch control mechanism is automatically engaged. This results in a material time saving which is of particular advantage aboard naval vessels where the flight deck must be cleared for further operations as rapidly as possible.

Fig. 1 shows a helicopter N3 of conventional configuration having a single main rotor [-2 and a torque counteracting 'tail rotor l4. The rotor has three blades I6, [8, 20 which are shown in the position they occupy when folded according to my invention. When blade 20 overlies the tail cone the upper taper pin, to be described hereinafter, is released to allow the blade to rest on jack 22. The port'and starboard blades I6, I8 are supported by slings 24 with the chord of the blade generally vertical. This provides a stable support and allows the blades to lie against the tail cone, reducing the probability of damage thereto.

Referring to Figs. 2 through 4, the port blade I6 is mounted in fitting 26 which has an integral mounting cuff 28 with upper and lower sets of ears 30 parallel to the chordline of the blade. Ears 30 are adapted to mesh with ears 32 on the cuff of the sleeve 34 and have holes 36 which align with holes 38 in cars 32. Taper pins 48, 42 pass through the cooperating holes 36, 38 to hold the blade in its flight position. Pins 40, 42 are driven into a tight fit by means of a rawhide mallet and nuts 44, 46 are then used to further draw up on the taper. When the upper taper pin is removed, the blade may be pivoted about the lower pin 42 which acts as a hinge, as shown in Fig. 2. Since the pins are substantially parallel to the chord of the blade, the tip'of the blade may be swung down to ground level when the upper pin 4!! is released. As will appear hereinafter, this feature permits of safe, easy ground handling of the blade.

Sleeve 34 is mounted on internal bearings 33,35 which resist axial movement but permit rotation about the sleeve axle 43 to change the pitch of the blade when the blade is assembled for flight. The rotational movement and position of the sleeve is controlled by the pitch control mechanismithrough push pull rod 5?! which is actuated by the usual rotating and stationary star assembly, not shown, and is connected, by means of pin 52, to the bifurcated'end of the collar arm 54. Collar arm 54 is integral with collar 58 which is mounted on bearing ring nut 37 in aconventional manner. On the upper portion of collar 56 is lug 58 which has tapered hole 61] passing therethrough. A spring loaded device 66 is mounted Within aligned holes in ears 62, 64 on top of sleeve 34 and connects collar ear 58 to sleeve 34 to transmit pitch control movements to the blade of the sleeve 34 with respect to collar 56 without loading the pitch mechanism.

The spring loaded device 66 comprises the central tube 14 which has a latch pin 68 slidably mounted in the left-hand end thereof (Fig. 4) and restrained from movement completely out of the tube by means of an internal shoulder I6 on tube 14 and cooperating shoulder 18 on pin 68. A latch pin 88 has a cylindrical end fixed in the right-hand end of tube 74 by, a pin 8! and projects beyond tube 14 and is slidably received in the hole in ear 64. The free end of pin 88 is suitably tapered to facilitate entry thereof .into the like tapered hOle 68 in lug 58. Inside the tube and between the facing ends of latch pins 68 and 88 is a preloaded safety spring 82, the purpose of which will be more fully described hereinafter. Compression spring 18, outside tube 14, bears against ear 64 and guide plate 12 which seats against an external annular shoulder 83 on tube 14.

As shown in Fig. 3, when the rotor is assembled the middle ear 38 on cuff 28 bears against the end of latch pin 68 and displaces it to the right. This force acting through spring 82 moves pin 88 and tube 14 to the right against the bias of spring 18 which constantly urges the device 66 into the position shown in Fig. 4. The safety spring 82 drives the latch pin 88 into operative engagement with the holes 68 in ear 58 on collar 56. As shown in Figs. 2 and 4, when the upper taper pin 48 is removed and the blade is pivoted about the lower hinge pin 42, the disengaging spring 18 moves the latch pin 88 out of engagement with the collar arm ear 58. The blade and the sleeve are now freely rotatable about the sleeve axis and, therefore, the blade may be folded back against the tail cone of the helicopter without damaging the pitch mechanism.

When the blade is returned to the flight position, the middle ear 38 moves the latch pin 68 inwardly against the force of spring. Should the holes in the ears 64 and 58 be misaligned, the safety spring 82 will compress when latch pin 88 is unable to move into the hole in the ear 58, preventing damage to the mechanism. The taper pin 48 may be driven through the holes 36, 38 in the ears 38, 32 and the blade'may then be rocked about its pitch changing axis until the holes in ears 64, 58 become aligned, at which time the spring 82 drives latch pin 88 into engagement with collar arm ear 58. As an alternative to rocking the blade about its axis, the pitch control stick may be worked until the collar arm becomes aligned with the sleeve and latch pin 88 is driven into engagement with tapered hole 68.

All the blades are mounted in the same manner but it will be obvious that the blade on the starboard side must be folded in the opposite direction with respect to the direction of blade rotation.

This construction permits simple, rapid, and safe ground handling of the blades during the folding process. When the taper pin 48 is removed the blade is free to pivot about hinge pin 42, allowing the blade tip to drop to a crewman waiting on the ground. The crewman now walks the blade back adjacent the tail cone and places it in sling 24. This movement cause the sleeve 34 to rotate on bearings 33, 35 and will also cause further movement of the blade about h nge pin 42. Since the pitch mechanism is disengaged there is no danger of damage to the controls. Since the blade may be moved freely about the hinge pin 42 and/or the pitch changing axis the crewman can conveniently handle the blade safe ly, even in winds of high velocity. When the blade has been placed in the sling it is more secure and less vulnerable. It will be apparent that this device provides a convenient and simple blade folding process which precludes damage to the controls and minimizes the danger of damage to the blades.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim.

1. In a helicopter having a sustaining rotor and a body includin a tail, a blade mounted on said rotor, blade support means cooperating with said tail, and means for folding said blade to lie adja cent said tail on said support means with its chord generally vertical including a hinge in the blade root portion having an axis generally parallel with the chord of the blade.

2. In a helicopter having a sustaining rotor and a body including a tail, in combination, three blades mounted on said rotor, pitch control means for said blades, means for folding said blade including a hinge in the blade root portion of each blade having an axis generally parallel with the chord of the blade, means for automatically releasin said pitch control means upon operation of said folding means, means coacting with said tail and one of said blades to support said one blade over said tail cone, and means cooperating with said tail for supporting the others of said blades adjacent said tail with the chords of said blades generally vertical.

3. In a helicopter, a rotor hub, a variable pitch blade mounted on said hub, blade folding means including a hinge in the root portion of said blade, whereby a combined pivotal movement of said blade about said hinge and about the pitch varying axis of the blade enables the blade to be folded and unfolded, means for locking said hinge with said blade in flight position, manually operable means for varying the pitch of said blade including a member movable with said blade during pitch variation through a limited movement which is less than that required about said pitch varying axis in said blade folding movement, means operatively connecting said member and blade in the flight position of the latter, and mechanism operative in response ,to pivotal movement of said blade about said hinge for controlling said last mentioned means to connect and disconnect said member and blade.

4. In a helicopter, a rotor hub, a variable pitch blade mounted on said hub, blade folding means including a hinge in the root portion of said blade, whereby a combined pivotal movement of said blade about said hinge and about the pitch.

varying axis of the blade enables the blade to be folded, means for locking said hinge with said blade in flight position, manually operable means for varying the pitch of said blade including a member movable with said blade during pitch variation through a limited movement which is less than that required about said pitch varying axis in said blade folding movement, means operatively connecting said member and blade in the flight position of the latter, and mechanism operative in response to folding movement of said amasec blade for operating said connecting means to disconnect said member and blade during the latter part of the blade folding movement.

5. In a helicopter, a rotor hub, a variable pitch blade mounted on said" hub, blade: folding means including a hinge in the root portion of said. blade, whereby a. combined pivotal movement of said blade about said hinge and about the pitch varying axis ofthe blade enables the blade to be folded and unfolded, means for locking said hinge with saidv blade in unfolded position, manually operable means for varying the pitch of said blade including a member movable with said blade during pitch variation through a limited movement which is less than that required about said pitch varying axis in said blade folding movement, means operatively connecting said member and blade in the unfolded position of the latter, and mechanism operated by said blade during unfolding movement thereof for operating said connectin means to connect said member and blade.

6. In a helicopter, a rotor hub, a blade mounted on said hub for pitch changing movement about the longitudinal axis of said blade, means for moving said blade between flight position and a folded position including a hinge in the root portion of said blade having an axis transverse to said pitch changing axis, whereby pivotal movements of said blade about its pitch changing axis and about said hinge axis enable said blades to be moved between said positions, means for locking said hinge with said blade in flight position, manually operable means for changing the pitch of said blade including a member movable with said blade during pitch change through a limited range which is less than the movement required about said pitch changing axis in moving said blade between said flight and folded positions, means operatively connecting said member and blade in the flight position of the latter, and mechanism operative in responsive to folding and unfolding movements of said blade for disconnecting and connecting said member and blade.

7. In a helicopter, a rotor hub, a blade mounted on said hub for pitch changing movement about the longitudinal axis of said blade, means for moving said blade between flight position and a folded position including a hinge in the root portion of said blade having an axis transverse to said pitch changing axis, whereby pivotal movements of said blade about its pitch changing axis and about said hinge aXis enable said blade to be moved between said positions, means for locking said hinge with said blade in flight position, manually operable means for changing the pitch of said blade including a member movable with said blade during pitch change through a limited range which is less than the movement required about said pitch changing axis in moving between said flight and folded positions, means operatively connecting said member and blade in the flight position of the latter, and mechanism operated by said blade as the latter moves about said hinge axis during folding and unfolding movement for disconnecting and connecting said member and blade.

8. In a helicopter, a rotor hub, a blade mounted on said hub for pitch changing movement about the longitudinal axis of said blade, means for moving said blade between a flight position and a folded position including a hinge in the root portion of said blade having an axis transverse to said pitch changing axis, whereby pivotal movements of said blade about its pitch changing axis and about said-hinge, axis. enables said-lblade to be movedbetween the. aforesaidpositions, means for locking saidhinge with said blade in, flight position, manually operablepitch changing mechanism including a member movable with said blade during pitch change through a limited range which is lessthan the movement required about said pitch changing axis in moving said blade between said flight and folded positions, means operatively connecting said member and blade in the flight position of the latter comprising a latch element constantly biased to release said member, said latch element having a portion projecting into the path of said blade as the latter is swung about said hinge axis into flight position for moving said latch element against its bias intoposition to connect said member and blade.

9. In a helicopter, a rotor hub, a stub shaft mounted on said hub, a blade having a root sleeve journalled on said shaft for pitch changing movement about the longitudinal axis of the blade, means for moving said blade between a flight position and a folded position including a hinge between said root sleeve and said blade having an axis transverse to said pitch changing axis, whereby pivotal movements of said blade sleeve and pivotal movements of said blade about said hinge axis enable said blade to be moved between the aforesaid positions, means for locking said hinge with said blade in flight position, manually operable pitch changing mechanism including a member journalled on said stub shaft adjacent said sleeve and movable with said sleeve during pitch change through a limited range which is less than the movement required about said pitch changing axis in moving said blade between said flight and folded positions, aligned apertures in said sleeve and member, a plunger mounted in said sleeve apertures in position to project into the aperture in said member, and means constantly biasing said plunger out of the aperture in said member, said plunger having a portion projecting into the path of said blade as the latter is swung about said hinge axi into flight position, whereby said member and sleeve are operatively connected in the flight position of said blade.

10. In a helicopter, a rotor hub, a stub shaft mounted on said hub, a blade having a root sleeve journalled on said shaft for pitch changing movement of said blade about the longitudinal axis thereof, means for moving said blade between a flight position and a folded position including a hinge between said root sleeve and said blade having an axis transverse to said pitch changing axis, whereby pivotal movements of said sleeve about said pitch changing axis and pivotal movements of said blade about said hinge axis enable said blade to be moved between the aforesaid positions, means for locking said hinge with said blade in flight position, manually operable pitch changing mechanism including a member journalled on said stub shaft adjacent said sleeve and movable with said sleeve during pitch change through a limited range which is less than the movement required about said pitch changing axis in moving said blade between said flight and folded positions, a plunger mounted on said sleeve in position to project into an aperture in said member and operably connect said member and sleeve, means constantly biasing said plunger out of the aperture in said member, said plunger having a portion projecting into the path of said blade as the latter is swung about said hinge axis r V 7 into flight position, whereby said member and sleeve are operatively connected in the flight position of said blade, said plunger including a tubular member having latch pins projecting from the inboard and outboard ends thereof, one of said pins being fixed to said tubula member and the other telescoping therewith, cooperating abutment means on said telescoping pin and tubular member for limiting the telescopin movement therebetween, and a compression spring biasing said telescoping pin in a direction to engage said abutments and project the outboard pin into the path of movement of said blade as the latter i moved about said hinge axis into flight position. I

MICHEL D. BUIVID.

1 V I REFERENCES CITED The following references are of record in the V file of this patent:

UNITED STATES PATENTS Number Name Date 1,994,465 Cierva Mar. 19, 1935 2,110,443 Larsen et al Mar. 8, 1938 2,220,109 Larsen Nov. 5, 1940 2,402,468 Thompson June 18, 1946 2,405,777 Buivid Aug. 13, 1946,

FOREIGN PATENTS Number Country Date 490,151 Great Britain Aug. 10, 1938 325,172 Italy Mar. 2, 1935;

US761975A 1947-07-18 1947-07-18 Folding rotor blade Expired - Lifetime US2549886A (en)

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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2702454A (en) * 1951-06-07 1955-02-22 United Aircraft Corp Transition piece providing a connection between the combustion chambers and the turbine nozzle in gas turbine power plants
US3050274A (en) * 1959-10-01 1962-08-21 United Aircraft Corp Tilting rotor head system
US3053480A (en) * 1959-10-06 1962-09-11 Piasecki Aircraft Corp Omni-directional, vertical-lift, helicopter drone
US3101785A (en) * 1961-06-28 1963-08-27 United Aircraft Corp Blade folding device
US3133715A (en) * 1961-12-22 1964-05-19 Sud Aviation Apparatus for supporting and holding foldable rotor blades of helicopters
US3185409A (en) * 1962-12-10 1965-05-25 Hiller Aircraft Company Inc Foldable rotary wing aircraft
DE1254977B (en) * 1962-01-19 1967-11-23 Sud Aviation Means for selbsttaetigen inserting a conical pin into the hub of a rotor blade for helicopters beiklappbaren
DE1256078B (en) * 1961-12-22 1967-12-07 Sud Aviation Means for manually folding back of rotor blades and its holder, in particular for light helicopters
DE1260317B (en) * 1962-10-15 1968-02-01 Boeing Co An apparatus for folding and unfolding the Drehfluegel a Drehfluegelflugzeuges
DE2631151A1 (en) * 1976-07-10 1978-01-12 Hans Leistner Swivelling aerofoil for aircraft, boat or rocket - has actuator for moving longitudinally for braking or compact
WO1980002408A1 (en) * 1979-05-02 1980-11-13 United Technologies Corp Blade fold restraint system
US4268222A (en) * 1978-04-17 1981-05-19 Societe Nationale Industrielle Aerospatiale Equipment for folding the blades of a main helicopter rotor
US4432696A (en) * 1980-09-25 1984-02-21 Messerschmitt-Boelkow-Blohm Gmbh Rotor structure for a rotary wing aircraft
US4623300A (en) * 1985-09-19 1986-11-18 United Technologies Corporation Helicopter rotor blade securement device
US5211538A (en) * 1991-11-27 1993-05-18 Bell Helicopter Textron Inc. Method for folding helicopter main rotor blades
US20020142057A1 (en) * 1994-07-08 2002-10-03 Herbert Krenchel Extruder for producing bodies of consolidated particulate material
US20040118970A1 (en) * 2002-12-23 2004-06-24 Muylaert Neal W. Apparatus and method for folding helicoptor rotor blades for storage and transport of helicopter
US20040118971A1 (en) * 2002-12-23 2004-06-24 Muylaert Neal W. Tail boom saddle for maintaining helicoptor main rotor blades in a stowed configuration for helicopter stowage and transport
US20040129830A1 (en) * 2002-12-23 2004-07-08 Muylaert Neal W. Tail boom saddle for maintaining helicoptor main rotor blades in a stowed configuration for helicoptor stowage and transport
WO2014024128A3 (en) * 2012-08-07 2014-03-27 Epsilon Engineering Services (Pty) Ltd. A hinge arrangement
US8919692B2 (en) 2009-04-28 2014-12-30 Sikorsky Aircraft Corporation Proximity sensor valve and lock system using same
US20160368598A1 (en) * 2015-05-19 2016-12-22 Alion Science And Technology Corporation Helicopter blade folding apparatus

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1994465A (en) * 1931-06-15 1935-03-19 Autogiro Co Of America Aircraft with rotatively mounted sustaining wings
US2110443A (en) * 1936-02-29 1938-03-08 Autogiro Co Of America Empennage for rotary winged aircraft
GB490151A (en) * 1936-05-08 1938-08-10 Bayerische Flugzeugwerke A G H Improvements relating to folding wings for aeroplanes
US2220109A (en) * 1938-11-04 1940-11-05 Autogiro Co Of America Aircraft sustaining rotor
US2402468A (en) * 1942-11-02 1946-06-18 Earnest W Harrison Aerial and land vehicle
US2405777A (en) * 1943-03-31 1946-08-13 United Aircraft Corp Foldable rotor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1994465A (en) * 1931-06-15 1935-03-19 Autogiro Co Of America Aircraft with rotatively mounted sustaining wings
US2110443A (en) * 1936-02-29 1938-03-08 Autogiro Co Of America Empennage for rotary winged aircraft
GB490151A (en) * 1936-05-08 1938-08-10 Bayerische Flugzeugwerke A G H Improvements relating to folding wings for aeroplanes
US2220109A (en) * 1938-11-04 1940-11-05 Autogiro Co Of America Aircraft sustaining rotor
US2402468A (en) * 1942-11-02 1946-06-18 Earnest W Harrison Aerial and land vehicle
US2405777A (en) * 1943-03-31 1946-08-13 United Aircraft Corp Foldable rotor

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2702454A (en) * 1951-06-07 1955-02-22 United Aircraft Corp Transition piece providing a connection between the combustion chambers and the turbine nozzle in gas turbine power plants
US3050274A (en) * 1959-10-01 1962-08-21 United Aircraft Corp Tilting rotor head system
US3053480A (en) * 1959-10-06 1962-09-11 Piasecki Aircraft Corp Omni-directional, vertical-lift, helicopter drone
US3101785A (en) * 1961-06-28 1963-08-27 United Aircraft Corp Blade folding device
US3133715A (en) * 1961-12-22 1964-05-19 Sud Aviation Apparatus for supporting and holding foldable rotor blades of helicopters
DE1256078B (en) * 1961-12-22 1967-12-07 Sud Aviation Means for manually folding back of rotor blades and its holder, in particular for light helicopters
DE1254977B (en) * 1962-01-19 1967-11-23 Sud Aviation Means for selbsttaetigen inserting a conical pin into the hub of a rotor blade for helicopters beiklappbaren
DE1260317B (en) * 1962-10-15 1968-02-01 Boeing Co An apparatus for folding and unfolding the Drehfluegel a Drehfluegelflugzeuges
US3185409A (en) * 1962-12-10 1965-05-25 Hiller Aircraft Company Inc Foldable rotary wing aircraft
DE2631151A1 (en) * 1976-07-10 1978-01-12 Hans Leistner Swivelling aerofoil for aircraft, boat or rocket - has actuator for moving longitudinally for braking or compact
US4268222A (en) * 1978-04-17 1981-05-19 Societe Nationale Industrielle Aerospatiale Equipment for folding the blades of a main helicopter rotor
WO1980002408A1 (en) * 1979-05-02 1980-11-13 United Technologies Corp Blade fold restraint system
US4284387A (en) * 1979-05-02 1981-08-18 United Technologies Corp. Blade fold restraint system
US4432696A (en) * 1980-09-25 1984-02-21 Messerschmitt-Boelkow-Blohm Gmbh Rotor structure for a rotary wing aircraft
US4623300A (en) * 1985-09-19 1986-11-18 United Technologies Corporation Helicopter rotor blade securement device
US5211538A (en) * 1991-11-27 1993-05-18 Bell Helicopter Textron Inc. Method for folding helicopter main rotor blades
WO1993011037A1 (en) * 1991-11-27 1993-06-10 Bell Helicopter Textron Inc. Method for folding helicopter main rotor blades
US20020142057A1 (en) * 1994-07-08 2002-10-03 Herbert Krenchel Extruder for producing bodies of consolidated particulate material
US20040129830A1 (en) * 2002-12-23 2004-07-08 Muylaert Neal W. Tail boom saddle for maintaining helicoptor main rotor blades in a stowed configuration for helicoptor stowage and transport
US20040118971A1 (en) * 2002-12-23 2004-06-24 Muylaert Neal W. Tail boom saddle for maintaining helicoptor main rotor blades in a stowed configuration for helicopter stowage and transport
US20040118970A1 (en) * 2002-12-23 2004-06-24 Muylaert Neal W. Apparatus and method for folding helicoptor rotor blades for storage and transport of helicopter
US6769644B2 (en) * 2002-12-23 2004-08-03 The Boeing Company Tail boom saddle for maintaining helicoptor main rotor blades in a stowed configuration for helicopter stowage and transport
US6860450B2 (en) * 2002-12-23 2005-03-01 The Boeing Company Apparatus and method for folding helicopter rotor blades for storage and transport of helicopter
US8919692B2 (en) 2009-04-28 2014-12-30 Sikorsky Aircraft Corporation Proximity sensor valve and lock system using same
WO2014024128A3 (en) * 2012-08-07 2014-03-27 Epsilon Engineering Services (Pty) Ltd. A hinge arrangement
US20160368598A1 (en) * 2015-05-19 2016-12-22 Alion Science And Technology Corporation Helicopter blade folding apparatus
US10287009B2 (en) * 2015-05-19 2019-05-14 Alion Science And Technology Corporation Helicopter blade folding apparatus

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