GB2158797A - An aerodynamic flexible fairing - Google Patents
An aerodynamic flexible fairing Download PDFInfo
- Publication number
- GB2158797A GB2158797A GB08511742A GB8511742A GB2158797A GB 2158797 A GB2158797 A GB 2158797A GB 08511742 A GB08511742 A GB 08511742A GB 8511742 A GB8511742 A GB 8511742A GB 2158797 A GB2158797 A GB 2158797A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fairing
- flexible
- rotor
- aerodynamic
- foam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000006260 foam Substances 0.000 claims abstract description 19
- 238000005299 abrasion Methods 0.000 claims abstract description 6
- 238000010073 coating (rubber) Methods 0.000 claims abstract description 4
- 229920003225 polyurethane elastomer Polymers 0.000 claims description 2
- 229920005830 Polyurethane Foam Polymers 0.000 abstract description 4
- 239000000463 material Substances 0.000 abstract description 4
- 239000011496 polyurethane foam Substances 0.000 abstract description 4
- 229920006311 Urethane elastomer Polymers 0.000 abstract description 3
- 238000010521 absorption reaction Methods 0.000 abstract description 2
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 6
- 229920001971 elastomer Polymers 0.000 description 5
- 239000005060 rubber Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 238000001746 injection moulding Methods 0.000 description 2
- 230000033001 locomotion Effects 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000009545 invasion Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C7/00—Structures or fairings not otherwise provided for
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/32—Rotors
- B64C27/33—Rotors having flexing arms
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/32—Rotors
- B64C27/46—Blades
Abstract
A flexible fairing 1 for covering rotor connections on a rotor wing aircraft comprises a flexible polyurethane foam material which could maintain its aerodynamic shape while in flight yet be compliant enough to allow for changes in blade pitch without adding significant torsional stiffness to the connector. In addition, a flexible urethane rubber coating may be used to protect the foam faring from abrasion or moisture absorption. <IMAGE>
Description
SPECIFICATION
An aerodynamic flexible fairing
Technical field
The present invention relates to aerodynamic structures and in particular fairings.
Background art
A recent development in rotor hub design for rotary wing aircraft has introduced a rotor connector in place of the torque tube. Typically, the rotor connector contains one or more structural members, a pitch shaft and a push rod assembly. The inboard end ofthis assembly is fixed to the main rotor hub by a spherical bearing mounted to fix the center of pitch rotation and react the push rod load in shear. While the outboard portion attaches to the rotor blade.
Through the operation of the push rod and pitch shaft, it is possible to alter the pitch of the rotor blade to conform to a particular flight mode. This may be done by applying torque to the inboard portion of the pitch shaft via the push rod rotating or twisting the pitch shaft such that it changes the pitch of the rotor blade connected at the outboard end of the pitch shaft.
Rotor connectors of this type are about 3 to about 5 feet in length and since they are not aerodynamic in design, they generate aerodynamic drag when in use. In addition, if they are not covered, they are subject to attack by foreign objects and erosion by the elements. In the past, when a structure was non-aerodynamic, a rigid aerodynamic fairing would be used to both protect the structure as well as to conform into an aerodynamic shape, thus producing additional lift. However, such a rigid structure would not be able to withstand the bending and twisting motions associated with these novel rotor connectors.Therefore, what is needed in the art is a flexible compliantfairing which is capable of maintaining its aerodynamic shape in flight and will not lose its structural integrity when subjected to the twisting forces associated with the changes in blade pitch.
Disclosure of invention
The present invention is for a flexible fairing which is useful in forming an aerodynamic form about the rotor connectors. Said fairings may be formed of flexible urethane foam which will hold its shape when under centrifugal and aerodynamic loading.
The urethane foam fairing should add no significant increase in stiffness in either bending or torsion of the flex beams when the blade pitch is changed. In addition, the fairing may include a flexible urethane coating to protect the foam fairing from abrasion, moisture absorption and other contamination.
Other features and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.
Brief description of drawings
The drawing illustrates a flexible fairing of the present invention.
Best mode for carrying out the invention
The foam which may be used to practice this invention may be any flexible urethane foam that is capable of being formed into an aerodynamic shape and will substantially retain its shape under the forces produced in flight and blade pitch changes.
The foam should have good moisture resistance and be compliant enough to allow the outboard end to rotate through a pitch change of up to about t30" to the normal axis without cracking or significantly contributing to the torsional stiffness of the rotor connector. A significant increase in the stiffness may result in higher pitch rod or control loads which could lead to undesirable handling qualities of the aircraft. In addition, such increased stiffness may require the use of heavier, stronger components due to the higher stresses resulting in a less desirable product.
The particular polyurethane foam which is used will depend upon the particular stresses and torsional stiffnesses desired for a particular aircraft. It is apparent that a larger rotor connector which required larger structural members having inherent in zit a highertorsional stiffness could accommodate a less compliant polyurethane fairing. Typical polyurethane foams which may be used to practice this invention are available in several densities, i.e. 3
Ibs. per cubic ft., 6 Ibs. per cubic ft., 10 Ibs. per cubic ft., etc. These foams are typically two component systems, A and B, wherein part A is the urethane base material and part B is the catalyst.The particularfoam selected should also not deteriorate (crack, crumble, become brittle, etc.) when operating at temperatures of from about -65"F (-47.8"C) to about150"F(65.5"C).
These foams are typically closed cell and are characterized by compression-deflection data. It is believed that any urethane foam system which, when processed, will result in a compressivemodulus of foam about 50 to about 175 psi will result in an acceptable fairing. However, it should be pointed out that the particular rotor system will determine the particularfoam requirements.
Any of the conventional techniques which may be used to form the fairing, i.e. injection molding directly over the rotor connector superstructure or forming the fairing in two or more sections and fitting them about the rotor connector may be used.
It should be pointed out that in the injection molding technique, it may be desirable to protect the area between the pitch shaft and the flex beam from invasion by the foam which may increase the apparent torsional stiffness of the connector.
However, the foam may be permitted to encompass the pitch shaft providing that it does not bond to the shaft and a low friction (Teflon type) surface is placed between them. In the alternative, a clearance around the pitch shaft may be necessary to permit freedom of motion of the pitch shaft during flight, or under dynamic loads.
Due to the susceptibility of the polyurethane foam to moisture damage and abrasion, an abrasion and moisture resistant polyurethane rubber coating is recommended. This may be done by applying the rubber in the form of a liquid or using the rubber in sheet form. The particular urethane rubber should have substantially the same flexible qualities as the foamso that when the rotor pitch is altered and the fairing twists, the abrasion coating does not separate from the foam. Although it is believed that a number of urethane rubbers may be used, one such material is PR 1592, a liquid rubber available from Products
Research & Chemical Corporation. This material may be applied directly onto the foam fairing by brushing, squeegeeing, etc. in the liquid form or it may be cast into sheet form and then attached to the foam with an adhesive. It may also be possible, when using rubber sheet stock, to co-cure the foam and the rubber coating together. This may be done by lining the mold with the rubber sheet stock and then injecting the foam into the lined mold forming a complete fairing in one curing step.
The figure illustrates a flexible fairing 1 which is shaped about the rotor connector 10 which comprises two flexbeams 20 and a pitch shaft 30.
It is believed that the novel fairing disclosed herein results in an aerodynamic, protective cover for rotor connectors. The fairing will not only add additional aerodynamic iift to the aircraft, but it will also protect it from erosion by the elements or foreign object damage which could seriously damage the aircraft and possibly cause the aircraft to crash.
Claims (2)
1. In a rotary wing aircraft having a flexible rotor connector comprising one or more flex beams, a pitch shaft and a means for applying torque to the shaft to alter the pitch of the rotor wherein the improvement comprises enclosing the rotor connector inside an aerodynamic, flexible foam fairing.
2. The article of claim 1 wherein the fairing is coated with an abrasion resistant, flexible, polyurethane rubber coating
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/610,373 US4580944A (en) | 1983-05-17 | 1984-05-15 | Aerodynamic flexible fairing |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8511742D0 GB8511742D0 (en) | 1985-06-19 |
| GB2158797A true GB2158797A (en) | 1985-11-20 |
| GB2158797B GB2158797B (en) | 1987-06-24 |
Family
ID=24444769
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08511742A Expired GB2158797B (en) | 1984-05-15 | 1985-05-09 | An aerodynamic flexible fairing |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE3515968C2 (en) |
| FR (1) | FR2564419B1 (en) |
| GB (1) | GB2158797B (en) |
| IT (1) | IT1208540B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2727832A1 (en) | 2012-10-31 | 2014-05-07 | Eurocopter Deutschland GmbH | Rotor head of a rotary wing flying machine and method of manufacturing and assembling such a rotor head |
| US9415866B2 (en) | 2013-04-03 | 2016-08-16 | Sikorsky Aircraft Corporation | Low drag rotor system |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3261407A (en) * | 1964-08-05 | 1966-07-19 | Lockheed Aircraft Corp | Helicopter rotor system |
| US3411348A (en) * | 1966-06-30 | 1968-11-19 | W C Dillon & Company Inc | Electronic dynamometer |
| US3331444A (en) * | 1966-12-28 | 1967-07-18 | Piasecki Aircraft Corp | Fairing assembly |
| FR2397325A1 (en) * | 1977-07-13 | 1979-02-09 | Aerospatiale | ROTOR HUB, IN PARTICULAR FOR THE MAIN ROTOR OF A HELICOPTER |
| DE2758086C2 (en) * | 1977-12-24 | 1983-12-01 | Messerschmitt-Bölkow-Blohm GmbH, 8000 München | Rotor for a rotary wing aircraft with a hingeless blade connection |
| DE2806119B2 (en) * | 1978-02-14 | 1980-06-04 | Messerschmitt-Boelkow-Blohm Gmbh, 8000 Muenchen | Rotor blades, in particular for rotary wing aircraft |
| US4403918A (en) * | 1979-04-03 | 1983-09-13 | Schramm Buford J | Hubless, hingeless and bearingless helicopter rotor system |
| US4427340A (en) * | 1982-06-24 | 1984-01-24 | Bell Helicopter Textron Inc. | Soft inplane bearingless helicopter rotor |
-
1985
- 1985-05-03 DE DE3515968A patent/DE3515968C2/en not_active Expired - Fee Related
- 1985-05-09 GB GB08511742A patent/GB2158797B/en not_active Expired
- 1985-05-14 FR FR8507300A patent/FR2564419B1/en not_active Expired
- 1985-05-15 IT IT8520721A patent/IT1208540B/en active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2727832A1 (en) | 2012-10-31 | 2014-05-07 | Eurocopter Deutschland GmbH | Rotor head of a rotary wing flying machine and method of manufacturing and assembling such a rotor head |
| US9415866B2 (en) | 2013-04-03 | 2016-08-16 | Sikorsky Aircraft Corporation | Low drag rotor system |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2564419A1 (en) | 1985-11-22 |
| GB2158797B (en) | 1987-06-24 |
| DE3515968A1 (en) | 1985-11-21 |
| IT1208540B (en) | 1989-07-10 |
| FR2564419B1 (en) | 1987-11-20 |
| DE3515968C2 (en) | 1995-07-13 |
| IT8520721A0 (en) | 1985-05-15 |
| GB8511742D0 (en) | 1985-06-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19970509 |