Wire strike protection system

{{multiple image |direction=vertical |align=right

|image1=ILA 2010 Samstag 138.JPG |caption1=Upper WSPS cutter

|image2=ILA 2010 Samstag 070.JPG |caption2=Lower WSPS cutter

|footer=The wedge shape and reinforced windshield strip direct the wire to the sharpened cutter blades.}}

Between 1974 and 1979 wire strike accidents accounted for 8% of United States Army Aviation aircraft damage, 6% of aircraft-related injuries, and 16% of aircraft-related fatalities.{{rp|9}} For the ten years from 1970, 208 civil helicopters were also involved in wire strike accidents; 88 were destroyed (42%) and 37 (11%) of the 331 people involved were killed.{{cite report |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800024873.pdf |title=Civil Helicopter Wire Strike Assessment Study |volume=1 |author1=Tuomela, Clyde H. |author2=Brennan, Mark F. |publisher=National Aeronautics and Space Administration |date=October 1980 |access-date=2 April 2020}}{{rp|5;7}} The commonest cause of civil helicopter aerial accidents between 1975 and 1977 was striking wires and poles.{{rp|1}}

Bristol Aerospace developed a WSPS qualified for the Bell OH-58 Kiowa under contract to the Canadian Armed Forces in May 1979.{{cite report |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a086857.pdf |archive-url=https://web.archive.org/web/20210604124134/https://apps.dtic.mil/dtic/tr/fulltext/u2/a086857.pdf |url-status=live |archive-date=June 4, 2021 |title=Investigation of Helicopter Wire Strike Protection Concepts |author=Burrows, LeRoy T. |date=June 1980 |publisher=US Army AVRADCOM |access-date=2 April 2020}}{{rp|9}} Nelson Chan invented WSPS, and was granted patents in 1980.{{cite patent |country=CA |number=1079182 |status=patent |title=Cable-cutting device |pubdate=10 June 1980 |pridate=7 December 1978 |inventor=Nelson Chan |assign1=Canada Minister of National Defence}}{{cite patent |country=US |number=4215833 |status=patent |title=Cable-cutting device |pubdate=5 August 1980 |fdate=16 January 1979 |pridate=7 December 1978 |inventor=Nelson Chan |assign1=Canada Minister of National Defence |url=https://patents.google.com/patent/US4215833A/}} Bristol staged a series of 52 tests of the WSPS by mounting it on the fuselage of a wrecked Kiowa; the fuselage was loaded onto a flatbed truck and driven into wires at speeds ranging from {{convert|15|to|60|mph|knot km/hour|abbr=on}}, yaw angles ranging from 0 to 45°, and a variety of cables that were typically used in overhead power and telecommunication transmission lines, including a {{convert|3/8|in|abbr=on|adj=on}} 7-strand steel cable with a tensile strength exceeding {{convert|10000|lb|kg|abbr=on}}.{{rp|9–10}}

Because the Bristol testing did not determine the effectiveness of the lower fuselage-mounted cutter, and was a ground-based test that did not evaluate how a wire strike with the cutter would affect aircraft attitude during flight, the United States Army Research Laboratory conducted supplemental pendulum swing tests at the Impact Dynamics Research Facility located at Langley Research Center with a Kiowa in October 1979.{{rp|11}} An additional deflector to protect the skids, landing gear, and tail boom (including the rotor and vertical stabilizer) was also tested, but was found to be ineffective.{{rp|11;15–19;41}}

During the Langley tests, an OH-58 was attached to the end of a {{convert|196|ft|adj=on}} long cable, pulled back, and released to swing through wires mounted horizontally at a height of approximately {{convert|22|ft}}.{{rp|14}} Similar pendulum tests were subsequently performed at Langley for Bell UH-1H{{cite report |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a122220.pdf |archive-url=https://web.archive.org/web/20210607172334/https://apps.dtic.mil/dtic/tr/fulltext/u2/a122220.pdf |url-status=live |archive-date=June 7, 2021 |title=Verification Testing of a UH-1 Wire Strike Protection System (WSPS) |author=Burrows, LeRoy T. |date=November 1982 |publisher=US Army AVRADCOM |access-date=2 April 2020}} and AH-1S helicopters in 1981 and 1982.

All small to medium {{efn|OH-58, UH-1, OH-6, AH-1, UH-60 and AH-64}} United States Army helicopters were fitted with WSPS in a retrofit programme that was completed in 1992;{{cite report |url=http://www.tc.faa.gov/its/worldpac/techrpt/ar0825.pdf |title=Safety Study of Wire Strike Devices Installed on Civil and Military Helicopters |author1=Nagaraj, Vengalattore T. |author2=Chopra, Inderjit |date=September 2018 |publisher=Air Traffic Organization, Operations Planning Office of Aviation Research and Development, Federal Aviation Administration, United States Department of Transportation |access-date=2 April 2020}} between 1996 and 2002 the US Army had no fatal wire strike accidents. In civil helicopter operations, wire cutters were thought to be most effective for agricultural flights.{{rp|37–38}} Of the 208 wire strike accidents in the 1970s, almost half could have been avoided with wire cutters and other recommended mechanical upgrades.{{rp|45}}

File:Bell AH-1S Cobra 0-17109 (10562355843).jpg

The system is typically mounted around the front of American military helicopters,{{cite report |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a123188.pdf |archive-url=https://web.archive.org/web/20210607172334/https://apps.dtic.mil/dtic/tr/fulltext/u2/a123188.pdf |url-status=live |archive-date=June 7, 2021 |title=Verification Testing of an AH-1S Wire Strike Protection System (WSPS) |author=Burrows, LeRoy T. |date=December 1982 |publisher=US Army Aviation Research and Development Command (AVRADCOM) |access-date=2 April 2020}} rescue helicopters and of civilian helicopters involved in agricultural work. It is effective when the helicopter strikes the wires at angle of less than 90 degrees and at speeds more than {{convert|30|knot|mph km/h|}}. The system is designed to cut a {{convert|3/8|in|adj=on||}} steel cable with a breaking strength of {{convert|12000|lb|kg|abbr=on}}.

The WSPS developed by Bristol, which is typical of most cable cutters today, consists of a roof-mounted cutter, a lower cutter fitted to the fuselage,{{efn|multiple fuselage cutters can be used}} and a deflector fitted to the middle of the windshield to guide the cable into the cutters.{{rp|9}} Sometimes a windshield wiper protector frame is used to stop the cables from catching on wiper motor shafts.[http://www.helicopterpage.com/html/unique.html WSPS]{{Unreliable source?|date=December 2018}} As installed, the OH-58 WSPS developed by Bristol weighs {{convert|16.3|lb|abbr=on}} and requires 40 man-hours to install.{{rp|15}}

Wire Strike Protection System is a registered trademark of Magellan Aerospace, the parent company of Bristol via acquisition.{{cite web |url=https://magellan.aero/wp-content/uploads/WSPS%20General-1.pdf |title=Wire Strike Protection System™ |website=Magellan Aerospace |access-date=2 April 2020}} Dart Aerospace markets an equivalent apparatus under the name Cable Cutter System.{{cite web |url=https://www.dartaerospace.com/en/gear-up/cable-cutters.html |title=Cable Cutters |website=DART Aerospace |access-date=2 April 2020}} Cable cutting systems to protect helicopters have been developed by other manufacturers, including MD Helicopters (1981),{{cite patent |country=US |number=4407467 |status=patent |title=Tactical wire-cutter system for helicopters |pubdate=4 October 1983 |pridate=24 August 1981 |invent1=Charles F. Emigh |invent2=Morris Goldin |assign1=McDonnell Douglas Helicopter Co |url=https://patents.google.com/patent/US4407467A/}} Custom Air (1987),{{cite patent |country=US |number=4826103 |status=patent |title=Active cable-cutting assembly for aircraft |pubdate=2 May 1989 |pridate=28 April 1987 |inventor=James M. McKown |assign1=Custom Air Inc. |url=https://patents.google.com/patent/US4826103A/}} Airbus Helicopters (2008{{cite patent |country=FR |number=2935956 |status=patent |title=Dispositif sectionneur de cables |pubdate=2 May 1989 |pridate=28 April 1987 |inventor=Gerald Claeys |assign1=Airbus Helicopters SAS |url=}} and 2011),{{cite patent |country=FR |number=2982844 |status=patent |title=Dispositif sectionneur de cables, et aeronef |pubdate=14 March 2014 |pridate=18 November 2011 |invent1=Marc Denante |invent2=Lacroix Pierre Prudhomme |assign1=Airbus Helicopters SAS}} and Bell Helicopter (2014).{{cite patent |country=US |number=9725165 |status=patennt |title=Cable cutter system |pubdate=8 August 2017 |pridate=3 October 2014 |invent1=Michael Smith |invent2=Chen-Ho Tho |invent3=Anand Kumar Marimuthu |assign1=Bell Helicopter Textron Inc. |url=https://patents.google.com/patent/US9725165B2/}} Another invention aims to protect the rotor by equipping the control rods with cutting edges.{{cite patent |country=US |number=5286170 |status=patent |title=Helicopter wire strike cutter |pubdate=15 February 1994 |pridate=24 November 1992 |inventor=William W. Brannon|url=https://patents.google.com/patent/US5286170A/}}

• Wire cutter (jeep)

{{notes}}

{{Reflist}}

• [http://www.helicopterpage.com/html/unique.html www.helicopterpage.com - WSPS (How Helicopters Work)] {{Unreliable source?|date=December 2018}}
• [http://ihst.rotor.com/portals/54/industry_reports/wirestrikes_20050055.pdf Wire Strike Accidents in General Aviation: Data Analysis 1994 to 2004] – Page 33
• [http://www.rotorywing.com/downloads/index.php?file=2&sort=1 Wire Strike Protection System, MDHS 500 Maintenance Manual]
• [http://www.magellan.aero/media/press-releases/Recent/2011%20-%20March%208/Magellan%20Aerospace%20Announces%20New%20Bell%20Helicopter%20Wire%20Strike%20Protection%20System%20Development.pdf Magellan Aerospace Announces New Bell Helicopter Wire Strike Protection System Development]
• {{youtube|id=rm6MwIdY4TA |title=Wire Strike Protection System (WSPS) - The Cutting Edge of Helicopter Safety}}. Marketing video from Magellan/Bristol that includes development of WSPS. Clips from flatbed and pendulum testing are shown.
• {{youtube|id=6YsHHx1CZz0 |title=Un hélicoptère percute des lignes de haute tension}}. Video of a helicopter wire strike that occurred during a rescue exercise. The helicopter was equipped with a WSPS.

;Prior art

• {{cite patent |country=DK |number=38811C |status=patent |title=Flyvemaskine |pubdate=29 May 1928 =|fdate=7 October 1926 |pridate=7 October 1926 |inventor=Jacob Christian Hansen-Ellehammer |assign1=Fabrikant af Motorer og Motorkøretøjer}}
• {{cite patent |country=DE |number=739409C |status=Grant |title=An einem Flugzeug angebrachte Vorrichtung zum Zerstoeren von Sperrdraehten |pubdate=24 September 1943 |gdate= |fdate= |pridate=16 March 1939 |inventor= |invent1=Georg Baierle |invent2=Gustav Leutner}}
• {{cite patent |country=US |number=2335952A |status=Grant |title=Cable cutting device for use on aircraft |pubdate=7 December 1943 |gdate= |fdate=23 March 1942 |pridate=29 April 1940 |inventor=James Martin}}
• {{cite patent |country=AU |number=6573374A |status=Grant |title=Improvements in and relating to cable specification or other line cutting devices |pubdate=21 August 1975 |gdate= |fdate= |pridate=2 March 1973 |inventor= |invent1=William Ronald Smith |invent2=Sydney Langford Howlett |assign1=Commonwealth of Australia}}

{{Helicopters and rotorcraft}}

Category:Aircraft components

Category:Aviation safety

Category:Helicopter equipment

Strike protection system