US3717317A - Method and devices for improving the longitudinal stability of helicopters - Google Patents

Method and devices for improving the longitudinal stability of helicopters Download PDF

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Publication number
US3717317A
US3717317A US00092631A US3717317DA US3717317A US 3717317 A US3717317 A US 3717317A US 00092631 A US00092631 A US 00092631A US 3717317D A US3717317D A US 3717317DA US 3717317 A US3717317 A US 3717317A
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Prior art keywords
helicopter
axis
stabilizer
lever
horizontal stabilizer
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Expired - Lifetime
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US00092631A
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English (en)
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B Certain
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Airbus Group SAS
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Airbus Group SAS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C27/00—Rotorcraft; Rotors peculiar thereto
    • B64C27/32—Rotors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C27/00—Rotorcraft; Rotors peculiar thereto
    • B64C27/82—Rotorcraft; Rotors peculiar thereto characterised by the provision of an auxiliary rotor or fluid-jet device for counter-balancing lifting rotor torque or changing direction of rotorcraft
    • B64C2027/8263—Rotorcraft; Rotors peculiar thereto characterised by the provision of an auxiliary rotor or fluid-jet device for counter-balancing lifting rotor torque or changing direction of rotorcraft comprising in addition rudders, tails, fins, or the like
    • B64C2027/8281—Rotorcraft; Rotors peculiar thereto characterised by the provision of an auxiliary rotor or fluid-jet device for counter-balancing lifting rotor torque or changing direction of rotorcraft comprising in addition rudders, tails, fins, or the like comprising horizontal tail planes

Definitions

  • the invention relates to a method and to devices for improving the longitudinal stability of helicopters, in which an incipient tendency for the nose of the helicopter to pull up is compensated by generating a diving moment responsively to a hinged stabilizer actuated as a result of the inertia of a weight attached thereto.
  • This phenomenon of instability which is commonplace on rotorcraft equipped with such so called rigid rotors, is attributed to a coupling effect between the motions of the blades due to .drag and to blade twist.
  • said diving moment is generated by the inertia of a pendular weight, the action of which is thus proportional to the increase in the load factor but independent of the aerodynamic forces.
  • the invention further relates to devices for performing such method that include in particular a horizontal stabilizer positioned at the rear end of a helicopter fuselage, which stabilizer is pivotally mounted about a horizontal shaft and is fast with a weight the inertia of which deflects said stabilizer in response to incipient longitudinal divergence from the flight path, such deflection being appropriate to counter said divergence.
  • said weight is supported on the end of a lever arm substantially parallel to the chord of the stabilizer airfoil, said lever being directly or indirectly connected to a return spring which, by acting with respect to the instantaneous fulcrum of said stabilizer together with the aerodynamic forces exerted against the latter, balances the moment generated by said weight, the rating of the spring being determined by the maximum stabilizer deflection setting at which stability is desired.
  • a horizontal stabilizer of this kind is mounted on top of a vertical stabilizer
  • the lever arm and its pivotal elements are arranged to form a support for said horizontal stabilizer on an intermediate part pivotally mounted on top of the vertical stabilizer, said intermediate part being rigid with means for setting it angularly with respect to the upper edge of the vertical stabilizer, which angular setting means permit adjustment of the balancing position of the horizontal stabilizer, the latter being set to provide negative lift in normal flight.
  • the horizontal stabilizer support is formed by an inverted channel section which caps the intermediate part, which part is formed in turn by braced flanges.
  • the liaison between the horizontal stabilizer support and said flanges is provided by two divergent links which are mounted, on the one hand, on two upper shafts fast with the upper parts of the inner flanges and, on the other, on two subjacent shafts which are more widely spaced than said upper shafts and are rigid with said support.
  • This balancing pendular articulation system permits stable pivotal motion of the horizontal stabilizer, which is normally at negative incidence, about the first-mentioned two shafts which are connected to the vertical stabilizer, the other two articulation shafts rigid with the horizontal stabilizer support being preferably included in a plane parallel to the plane containing the chord of said horizontal stabilizer airfoil.
  • One of the flanges is fast with a balancing-positionsetting bellcrank which is attached to a tie rod formed by a bracket supported on the vertical stabilizer.
  • the corresponding articulation is associated to a damper possibly positioned between the two flanges and having its body portion fast with one thereof, the other flange being equipped with an arrangement of adjustable stops positioned in registry with contacting surfaces formed on the side of the horizontal stabilizer support.
  • the instantaneous fulcrum about which the horizontal stabilizer rotates and which is at all times located at the intersection of two planes defined respectively by the shafts rigid with the flanges and by the shafts rigid with the supports, is caused to shift rearwardly along a locus which is a circular arc as the motions required to achieve the desired stabilization take place.
  • the position at which the instantaneous fulcrum coincides with the aerodynamic center is the position at which the system is in a state of equilibrium.
  • a weight secured to the rear ofa formed section rigid with the root of each stabilizer element.
  • a spring connected between the forward part of this element and an associated end of a horizontal rocker arm fast with the tail boom balances the moment generated mainly by said weight.
  • Pivotal motion of the said formed sections responsively to the inertia of the associated weights, in order to cause the horizontal stabilizer to react at the onset of a pitch-up divergence by the machine, takes place about the axis of a tube carrying the two horizontal stabilizer elements and is limited by two stops.
  • Possible industrial applications of the invention are to be found in the field of helicopters, and more particularly helicopters having rotors with flexible blades devoid of hinges.
  • FIG. 1 schematically illustrates the location of the subject device of the invention on top of a vertical stabilizer on a helicopter
  • FIG. 2 shows in side elevation a horizontal stabilizer equipped with a deflecting system according to the invention
  • FIG. 3 is a section taken through the line III--III of FIG. 2
  • FIG. 4 is a section taken along the line IV-IV of FIG. 2
  • FIG. 5 is a section taken along the line V-V of FIG.
  • FIG. 6 is a section taken along the dash line VIVI of FIG. 2
  • FIG. 7 is a section taken through the line VII-VII of FIGS. 2 and 8
  • FIG. 8 is a side elevation view which is the reverse of that of FIG. 2;
  • FIG. 9 is a section taken through the line IX-IX of FIG. 8
  • FIG. 10 is a fragmental showing, in corresponding fashion to FIG. 1, of an alternative arrangement for a stabilizing device according to this invention
  • FIG. 11 shows in side elevation on an enlarged scale a control arrangement applicable to the embodiment of FIG. 10
  • FIG. 12 is a plan view corresponding to FIG. 11, with partial cutaway and FIG. I3 is a section taken through the line XIII-XIII of FIG. 11.
  • the vertical stabilizer D of a helicopter l-I having a rotor R carries at its top a horizontal stabilizer E for stabilizing the longitudinal attitude of the helicopter, more particularly when said attitude tends to be disturbed by gusts or sudden changes in the cyclic pitch of the rotor blades.
  • FIG. 2 in which the top 1 of the helicopters vertical stabilizer D receives an element 2 forming a horizontal stabilizer E.
  • This arrangement is effected by means of a support 4 formed by an inverted channel section having its web applied against the lower surface 3 of element 2 and secured thereto by screws 5 and 6 and blocks 7 and 8 permitting precise mutual positioning of support 4 and airfoil 2.
  • the web and flanges of support 4 are suitably cut to shape. and there is secured to the rear end of support web 9, by means of bolts 10 and 11, a weight 12 made of heavy alloy and of size appropriately adjusted'thickness-wise.
  • the flanges l3 and 14 of support 4 are form'edwith corresponding openings 15 and 16 shaped substantially as trapeziums having their longer bases respectively forming the upper edges of said openings.
  • such attachment is effected, on the one hand, upon a shaft 21 extending through one of said spacer means and restrained in lugs 22 of said flanges and in the sides of a clevis 23 fixed to the top of stabilizer D, in the forward region thereof.
  • the attachment system is completed, on the other hand, by having flange l8 bear at its rear a bellcrankforming extension 25 which is bolted at 26 and 27 to rear lugs on flange 18.
  • bellcrank 25 The tapering end of bellcrank 25 is secured by a bolt and nut 28 to a slotted portion 29 of a bracket 30 secured by bolts and nuts 31 to a clevis 32 likewise carried on the crest line 1 of vertical stabilizer D.
  • Bolt 28 is movable along slot 33 of bracket 30 in order to enable the equilibrium position of horizontal stabilizer E to be set, the need for which setting will become apparent hereinafter.
  • vertical stabilizer D Adjacent the rear end of its crest line 1, vertical stabilizer D carries a bracket 35 from which extends a threaded rod 34 associated to a nut and locknut, said rod terminating in an eye 36 into which is hooked the end of a spring 37.
  • the rating of spring 37 is determined by the maximum angular setting of the horizontal stabilizer for which stability is desired, and the other end of spring 37 engages in a groove 38 formed in the middle region of a spacer pin 39 extending through the flanges 13 and 14 of horizontal stabilizer support 4 (FIGS. 6 and 9).
  • the lower part 40 of bracket 30 (FIG. 5) forms a yoke between the arms of which spring 37 freely extends, each yoke arm being provided with a bolt and nut 31.
  • the hinge coupling between stabilizer E and stabilizer D which is an indirect coupling, is accomplished through the agency of the intermediate member formed by flanges 17 and 18, the angular positions of which are adjustable about shaft 21 and which are associated to two links 41 and 42 (see FIGS. 2, 3 and 4). Links 41 and 42 are hingedly connected to the forward upper ends respectively of flanges 17 and 18 through the medium of spacer pins 43 and 44.
  • Links 41 and 42 splay out downwardly from pins 43 and 44 and are interconnected in corresponding pairs by pins 45 and 46 supported in bearings 47 and 48, the latter being fast with lower portions of the side plates or flanges l3 and 14 of support 4 by means of securing lugs 49.
  • Pivotal motion of links 41, 42 about upper pins 43 and 44 is facilitated by needle-bearings 50 and bores 51 in the link ends, said needle-bearings being spaced as required by central cylindrical distance-pieces 52 and flanged washers 53 and 54 pivotal motion of said links about the lower pins 45 and 46 is likewise facilitated by identical needle-bearings driven into bores in the other ends 55 of said links and maintained in spaced relationship by a central distance-piece 52 and two flanged bushes 56 and 57.
  • a peg 58 (FIG. 3) equipped with a flag marker may be inserted through aligned holes 59 in flanges l3 and 14 of support 4 and in the lugs 49 of bearings 47 and 48, and thereafter in the link 42, these last holes lying in the plane containing pins 44 and 46.
  • Peg 58 shown in the engaged position in FIG. 3, is designed to restrain the stabilizer support 4 in relation to flanges 17 and 18 when the resting position of equilibrium of the horizontal stabilizer has been set subsequent to suitable adjustment of the mass of material required to form the weight referred to precedingly.
  • a damper (not shown) is positioned between the two flanges 17 and 18, the body portion of the damper being screwed through the medium of a base to flange 18 (shown in dash lines in FIG. 2).
  • the facing opening 19 in flange 17 provides passage for the hinge-pin of such pivotal damper, which hinge-pin is made fast with a crank to which is hingedly connected a link having its other end pivotally connected to an appropriately configured end of one of pins 45 or 46.
  • a linkage system of this kind is shown in dot-dash lines in FIG. 2.
  • a system of lengthwiseadjustable stops 61 and 62 (FIG. 8) screwed into and restrained by nuts and locknuts in a bracket 63 fast with flange 18, which bracket and stops project into the cutout 16 above the lower edge thereof, which edge bears a bracket 64 carried internally on the facing flange 14 of support 4. That surface of bracket 64 which faces the tips of stops 61 and 62 bears linings cooperating with said tips.
  • peg 58 is removed after setting the equilibrium position of horizontal stabilizer E that is required in stable flight (by setting a degree of negative lift on said stabilizer to balance the diving moment which is generated by the component of pull exerted at the aerodynamic center of the rotor and by the drag exerted against the fuselage) having regard for the reciprocal actions of weight 12 and spring 37.
  • the longitudinal stability improving device is mounted on the helicopter tail boom P in the form of two horizontal half-stabilizers E, projecting from either side of boom P.
  • FIGS. 11 and 12 only one horizontal stabilizer element 66 is shown in addition to the tail boom skin 65.
  • a tapering channel-section 68 Secured to the root 67 of element 66 is a tapering channel-section 68 having its open side facing skin 65. Attached to the rear end of channel section 68 is a weight 69 made of heavy alloy. Forward thereof is disposed, on the web of section 68, a damper 70 the axle of which carries a crank 72 pivotally connected to a link 73 which is in turn pivotally connected to a hinge-pin 71 fixed to skin 65.
  • section 68 The forward end of section 68 is provided with means for attaching the looped end of a spring 69a, through the agency of retention means threaded over a bolt 75.
  • the other end of spring 69a (FIG. 13) is attached to a metal strip welded to a threaded rod 76 which is secured by a nut and locknut to one end of a substantially horizontal transverse arm 77 which is fulcrumed by means of a hinge-pin in a clevis 78 rigid with the undersurface of tail boom skin 65.
  • Arm 77 accordingly forms a rocker arm interconnecting the two stabilizer elements.
  • T- sections 79 the webs 80 of which are cut to match the shape of skin 65 and welded over their entire lengths thereto, and the flanges 81 of which have bolted into slots therein two brackets 82 and 83 faced with elastic linings 84 against which the sides of channel section 68 bear alternately.
  • the two stabilizer elements 66 are fast with a common tubular spar 85 which is carried in antiafriction bearings 86 supported in associated housings in the tail boom and by means of which said elements are capable of pivotal motion.
  • the two horizontal stabilizer halves are identically devised and are positioned symmetrically with respect to the helicopter fore-aft axis.
  • the stabilizer elements could be provided with aerodynamic control surfaces known as tabs, capable of being deflected with respect to the chord line of the airfoil section of such stabilizer in order to cancel the effect of an aerodynamic pitching-up moment about the instantaneous fulcrum of said stabilizer element.
  • a device for improving the longitudinal stability of a helicopter having a rotor provided with flexible blades deprived of articulations for flapping and leadlag oscillations, in which at least one horizontal stabilizer element is hingedly mounted on said helicopter on a first axis parallel to pitch axis of said helicopter and is rigid with a weight, said weight being situated at one extremity of a lever arm nearly parallel to the airfoil chord of said stabilizer element said lever being attached to a return spring, an intermediate member being interposed between helicopter body and hinge of said stabilizer element, said intermediate member being itself hingedly mounted on a second axis parallel to said first axis, the improvement according to which said lever is forming a horizontal stabilizer Supporting element straddling said intermediate member constituted of cross-braced flanges, supported by said second axis on the first hand and attached, on the other hand, by an interconnecting arm to a slotted bracket, said second axis and said bracket being affixed to crest line of a vertical stabilizer of a
  • a flange supporting a damper body and adjustable stop means situated in front of contact surfaces formed in said lever, said damper having a movable part mechanically connected to said lever.
  • a device for improving longitudinal stability of a helicopter having a rotor provided with flexible blades deprived of articulations for flapping and lead-lag oscillations, in which at least one horizontal stabilizer element is hingedly mounted on said helicopter on a first axis, parallel to pitch axis of said helicopter, said horizontal stabilizer element being fast with a weight situated at one end of a lever arm nearly parallel to airfoil chord of said stabilizer element, said lever arm being attached to a return spring, the improvement according to which said stabilizer element is supported by a spar carried as an axle in a bearing housing inserted in a helicopter tail boom, said stabilizer element having a root portion fast with a lever supporting at its rear end a high-density weight and attached at its forward end to a spring itself attached at one extremity of an arm hingedly fixed to said tail-boom, said forward end being rockable between two adjustable abutment means rigid with said tail boom.
  • damper means having its stationary portion supported by said lever and its movable portion attached to pivot means rigid with said tail boom.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Aviation & Aerospace Engineering (AREA)
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  • Aerodynamic Tests, Hydrodynamic Tests, Wind Tunnels, And Water Tanks (AREA)
  • Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
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US00092631A 1969-11-27 1970-11-25 Method and devices for improving the longitudinal stability of helicopters Expired - Lifetime US3717317A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR6940879A FR2067224B1 (enExample) 1969-11-27 1969-11-27

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US3717317A true US3717317A (en) 1973-02-20

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US00092631A Expired - Lifetime US3717317A (en) 1969-11-27 1970-11-25 Method and devices for improving the longitudinal stability of helicopters

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US (1) US3717317A (enExample)
DE (1) DE2056730C3 (enExample)
FR (1) FR2067224B1 (enExample)
GB (1) GB1328540A (enExample)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3902688A (en) * 1974-03-15 1975-09-02 Textron Inc I-tail empennage
US4247061A (en) * 1978-07-12 1981-01-27 United Technologies Corporation Helicopter with stabilator detuned in antisymmetric vibration modes from main rotor wake excitation frequency
US20080203222A1 (en) * 2007-02-22 2008-08-28 Johnson Edward D Yaw Control System and Method
US8602351B2 (en) 2009-09-17 2013-12-10 Textron Innovations Inc. Removable horizontal stabilizer for helicopter
US9527577B2 (en) 2014-01-27 2016-12-27 Airbus Helicopters Deutschland GmbH Rotorcraft with a fuselage and at least one main rotor
US9703294B2 (en) 2015-05-05 2017-07-11 Airbus Helicopters Advanced control relationship for a deflectable stabilizer
US11230392B2 (en) 2019-12-10 2022-01-25 James D Gaston Apache helicopter stabilizer bearing replacement kit
US11498136B1 (en) 2020-08-12 2022-11-15 James D Gaston Black Hawk bushing removal and reamer device

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3935925A1 (de) * 1989-10-27 1991-05-16 Messerschmitt Boelkow Blohm Passiver flatterdaempfer
DE3935893A1 (de) * 1989-10-27 1991-05-02 Messerschmitt Boelkow Blohm Daempfung von dynamischen instabilitaeten

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2630985A (en) * 1950-12-07 1953-03-10 United Aircraft Corp Helicopter stabilizer
US2941792A (en) * 1957-06-03 1960-06-21 United Aircraft Corp Aircraft flight path stabilizer
US3027948A (en) * 1958-01-24 1962-04-03 Kellett Aircraft Corp Stabilization of rotary wing aircraft
US3081052A (en) * 1957-06-03 1963-03-12 United Aircraft Corp Variable stabilizing means

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2630985A (en) * 1950-12-07 1953-03-10 United Aircraft Corp Helicopter stabilizer
US2941792A (en) * 1957-06-03 1960-06-21 United Aircraft Corp Aircraft flight path stabilizer
US3081052A (en) * 1957-06-03 1963-03-12 United Aircraft Corp Variable stabilizing means
US3027948A (en) * 1958-01-24 1962-04-03 Kellett Aircraft Corp Stabilization of rotary wing aircraft

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3902688A (en) * 1974-03-15 1975-09-02 Textron Inc I-tail empennage
US4247061A (en) * 1978-07-12 1981-01-27 United Technologies Corporation Helicopter with stabilator detuned in antisymmetric vibration modes from main rotor wake excitation frequency
US20080203222A1 (en) * 2007-02-22 2008-08-28 Johnson Edward D Yaw Control System and Method
US7644887B2 (en) * 2007-02-22 2010-01-12 Johnson Edward D Yaw control system and method
US8602351B2 (en) 2009-09-17 2013-12-10 Textron Innovations Inc. Removable horizontal stabilizer for helicopter
US8882031B2 (en) 2009-09-17 2014-11-11 Textron Innovations Inc. Removable horizontal stabilizer for helicopter
US9527577B2 (en) 2014-01-27 2016-12-27 Airbus Helicopters Deutschland GmbH Rotorcraft with a fuselage and at least one main rotor
US9703294B2 (en) 2015-05-05 2017-07-11 Airbus Helicopters Advanced control relationship for a deflectable stabilizer
US11230392B2 (en) 2019-12-10 2022-01-25 James D Gaston Apache helicopter stabilizer bearing replacement kit
US11498136B1 (en) 2020-08-12 2022-11-15 James D Gaston Black Hawk bushing removal and reamer device

Also Published As

Publication number Publication date
FR2067224A1 (enExample) 1971-08-20
DE2056730C3 (de) 1979-08-02
DE2056730A1 (de) 1971-06-03
GB1328540A (en) 1973-08-30
DE2056730B2 (de) 1978-11-30
FR2067224B1 (enExample) 1974-05-24

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