Bell 525 Relentless

{{short description|American medium-lift helicopter}} {{Use mdy dates|date=December 2022}}  {{Infobox aircraft | name = Bell 525 Relentless | logo = | logo_size = | image = File:525 GKY (31495047476).jpg | alt = | caption = Prototype of the Bell 525 in flight | long_caption = | other_names = | aircraft_type = Super-medium-lift utility helicopter | aim = | outcome = | related = | national_origin = United States | manufacturer = Bell Textron | design_group = | designer = | builder = | issuer = | status = Under development | owners = | primary_user = | more_users = | service = | major_applications = | proposals = | prototypes = | number_built = | construction_number = | civil_registration = | military_serial = | radio_code = | requirement = | aircraft_carried = | flights = | total_hours = | total_distance = | construction_date = 2015–present | introduction = | retired = | first_flight = 1 July 2015 | initiated = | in_service = | last_flight = | expected = | developed_from = | variants = | developed_into = | preservation = | fate = | predecessors = | successors = | concluded = }}

The '''Bell 525 Relentless''' is an American super-medium-lift helicopter, under development by Bell Textron. The new model was unveiled at the 2012 Heli-Expo in Dallas, Texas in February 2012. It first flew on 1 July 2015.

The Bell 525 is designed to transport up to 19 passengers.<ref name=AWST>{{cite web |last=Osborne |first=Tony |title=Bell Pressing Ahead With Fly-By-Wire 525 Certification |website=Aviation Week Network |date=2018-02-23 |url=http://aviationweek.com/vertical-flight/bell-pressing-ahead-fly-wire-525-certification |access-date=2021-10-22}}</ref> The aircraft is the first fly-by-wire civilian aircraft and suffered a crash of its prototype, and is still slowly working towards certification. As of 2024, Bell is working towards completing flight certification,<ref>{{Cite web |title=Bell aiming to wrap up 525 certification flight tests in first half of 2024 |url=https://verticalmag.com/news/bell-wrap-525-flight-tests-certification-2024/ |access-date=2024-04-26 |website=Vertical Mag |language=en-US}}</ref> and it has secured its first order.

It is a twin turbine engine helicopter with a composite and metal airframe that is in the latter stages of its development.

==Development== Bell's first new project after the Bell 429 and Bell V-22 was the super medium Bell 525, previously known as Project X or Magellan. The helicopter is designed for trips of 50 to 500 nautical miles, and has a 5-blade main rotor powered by twin engines, including digital controls and a Garmin G5000H screen, with planned seating for 16-20 people.<ref name=":1">{{Cite web |date=2015-01-27 |title=New Aircraft Preview: Bell 525 Relentless |url=https://www.bjtonline.com/business-jet-news/aircraft/new-aircraft-preview-bell-525-relentless |access-date=2024-04-26 |website=Business Jet Traveler |language=en}}</ref> The flight software is intended to have features that enable single-pilot operation of the helicopter.<ref name=":1" />

The Bell 525's maiden flight was planned for late 2014.<ref>[http://www.bellhelicopter.com/en_US/News/PressReleases/NewsRelease/NewsRelease.html?ReleaseID=b008f3e9-7358-4ccb-a6a6-567c90dc762b "Bell Helicopter Reveals the Latest in the Bell 525 Program during HELI-EXPO 2014"] {{Webarchive|url=https://web.archive.org/web/20140429204242/http://www.bellhelicopter.com/en_US/News/PressReleases/NewsRelease/NewsRelease.html?ReleaseID=b008f3e9-7358-4ccb-a6a6-567c90dc762b |date=2014-04-29 }}. Bell Helicopter, February 25, 2014. Archive link appears dead.</ref> PHI, Inc. was the launch customer for the type,<ref name="AW_Bigger_Bell">{{cite journal|last=Norris|first=Guy|title=Bigger Bell (web title: Bell Rings In Changes With Super-Medium 525 Relentless)|journal=Aviation Week & Space Technology|date=20 February 2012|publisher=McGraw-Hill|location=New York|volume=174|issue=7|pages=36–37|url=http://www.aviationweek.com/awin/ArticlesStory.aspx?&id=/article-xml/bav_02_20_2012_p05-01-426874.xml}}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> but as of 2016 is no longer the launch customer.<ref>{{cite web |last1=Drew |first1=James |title=VIDEO: Bell relentlessly pursuing 525 despite market troubles |url=https://www.flightglobal.com/news/articles/video-bell-relentlessly-pursuing-525-despite-market-422506/ |website=FlightGlobal |publisher=Reed Business Information |access-date=15 August 2018}}</ref> After a six-month delay, the Bell 525 prototype first flew in July 2015. At that time, Bell predicted certification to be completed by the end of 2017.<ref name="flt-global-video">{{cite web|last1=Perry|first1=Dominic|title=VIDEO: Successful first flight for new Bell 525 Relentless|url=http://www.flightglobal.com/news/articles/video-successful-first-flight-for-new-bell-525-relentless-414250/|website=Flightglobal.com|access-date=August 16, 2015|date=July 2, 2015}}</ref><ref>{{cite web |title=Eclipse Special Edition and Bell Model 525 News from The Weekly of Business Aviation |website=Aviation Week Network |date=2015-07-07 |url=http://aviationweek.com/bca/eclipse-special-edition-and-bell-model-525-news-weekly-business-aviation |access-date=2021-10-22}}</ref> The FAA suggested special rules in May 2016, to address the fly-by-wire concept.<ref>{{cite web|url=https://www.federalregister.gov/articles/2016/05/27/2016-12497/special-conditions-bell-helicopter-textron-inc-bhti-model-525-helicopters-interaction-of-systems-and|title=Federal Register – Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Interaction of Systems and Structures|date=May 27, 2016 |access-date=6 August 2016}}</ref>

===July 2016 crash=== {{main|2016 Bell 525 Relentless prototype crash}}

At approximately 11:48 AM Central Daylight Time on July 6, 2016, the prototype crashed during a test flight near Italy, Texas, killing the two occupants.<ref name=Bell_525_Test_Crash>{{cite news |last1=Ramirez |first1=Domingo |title=Bell helicopter crashes in Ellis County, two reportedly killed |url=http://www.star-telegram.com/news/local/community/fort-worth/article87986262.html |newspaper=Fort Worth Star-Telegram |date=July 6, 2016 |access-date=July 6, 2016}}</ref> The aircraft, registration N525TA, broke up in flight<ref name=DCA16FA199-prelim>{{cite web |url=https://www.ntsb.gov/_layouts/ntsb.aviation/brief2.aspx?ev_id=20160706X42741&ntsbno=DCA16FA199&akey=1 |title=NTSB Identification: DCA16FA199 |publisher=NTSB |access-date=6 August 2016}}</ref> while traveling about {{convert|229|mph|km/h kn|abbr=on}} at an altitude of about {{convert|2000|ft|-2}}.<ref name=NTSB_prelim_report/> During flight testing of the prototype, a severe vibration in the main rotor led to a sequence of events causing the break up of the aircraft. An oscillation in the main rotors of scissoring type caused a 6 hertz vibration in the airfame, which led to a bio-mechanical feedback loop transmitted from the pilot seat to the pilot and controls among other issues. The accident happened during simulated one engine out test, that used special software to lower the output of both engines. There are many other aspects to conditions that led to the accident.<ref>{{Cite web |last=Huber |first=Mark |title=NTSB: Severe Vibration Triggered Bell 525 Breakup {{!}} AIN |url=https://www.ainonline.com/aviation-news/business-aviation/2018-01-17/ntsb-severe-vibration-triggered-bell-525-breakup |access-date=2024-04-26 |website=Aviation International News (AIN)}}</ref>

The crash delayed the expected certification<ref name=NTSB_prelim_report>{{cite web|url=http://www.star-telegram.com/news/business/aviation/sky-talk-blog/article93468772.html|title=NTSB releases preliminary report on Bell Helicopter crash|work=Fort Worth Star-Telegram|access-date=6 August 2016}}</ref> beyond 2017.<ref name="Grady16Jan18">{{cite web|url=https://www.avweb.com/avwebflash/news/NTSB-Cites-Adverse-Feedback-Loops-In-Bell-Crash-230180-1.html|title=NTSB Cites 'Adverse Feedback Loops' In Bell Crash|access-date=17 January 2018|last=Grady|first=Mary|work=AVweb|date=16 January 2018|archive-date=July 20, 2018|archive-url=https://web.archive.org/web/20180720100709/https://www.avweb.com/avwebflash/news/NTSB-Cites-Adverse-Feedback-Loops-In-Bell-Crash-230180-1.html|url-status=dead}}</ref> In February 2018, Bell predicted certification to be completed by late 2018 or early 2019.<ref name=AWST/> In December 2018, 1,300 hours of turn time and 900 hr of flight were accumulated, towards a 2019 US type certification. In early 2019, two helicopters were to be tested in cold weather in Yellowknife, Northwest Territories, Canada, as a third prototype was to validate performance in snowy north continental US.<ref name=Flight18Dec2018>{{cite news |url= https://www.flightglobal.com/news/articles/bell-525-helicopters-head-to-canada-for-cold-weather-454496/ |title= Bell 525 helicopters head to Canada for cold-weather testing |date= 18 Dec 2018 |work= Flightglobal}}</ref>

Bell has worked with the FAA to work towards certifying the new design, and examples of tests include running simulated icing conditions.<ref>{{Cite web |last1=Lynch |first1=Kerry |title=Bell 525 Certification on Horizon This Year {{!}} AIN |url=https://www.ainonline.com/aviation-news/business-aviation/2023-03-05/bell-525-certification-horizon-year |access-date=2024-04-26 |website=Aviation International News}}</ref>

===Intended market=== The helicopter is the largest civilian helicopter made yet by Bell, and can carry 16 passengers and two crew.<ref name=":0">{{Cite web |last1=Lynch |first1=Kerry |title=Bell Lands First Purchase Agreement for 525 Super-medium Helicopter |url=https://www.ainonline.com/aviation-news/business-aviation/2024-03-01/bell-lands-first-purchase-agreement-super-medium-525 |access-date=2024-04-26 |website=Aviation International News}}</ref>

Bell has also pitched the Bell 525 to military customers as a 20-passenger utility and troop transport or search and rescue (SAR) aircraft.<ref>{{Cite web |url=https://www.flightglobal.com/helicopters/pictures-bell-targets-military-market-with-525-helicopter/125199.article |title=PICTURES: Bell targets military market with 525 helicopter|first=Dominic|last=Perry |date=2017-08-25 |website=Flight Global}}</ref> Bell sought to sell the 525 to the United Kingdom for its New Medium Helicopter program, which aims to replace the RAF's Puma (SA330) helicopters,<ref>{{Cite web |url=https://www.janes.com/defence-news/news-detail/bell-touts-ideal-525-for-uk-new-medium-helicopter-requirement |title=Bell touts 'ideal' 525 for UK New Medium Helicopter requirement |website=Janes.com}}</ref> but Bell's proposal did not make it past the pre-qualification questionnaire stage for the UK's medium lift programme.<ref>{{Cite news |last=Jennings |first=Gareth |title=UK downselects New Medium Helicopter contenders |url=https://www.janes.com/defence-news/news-detail/uk-downselects-new-medium-helicopter-contenders |website=Janes.com |date=2022-11-02 |accessdate=2022-12-04}}</ref>

In 2019, Bell displayed the Bell 525 at the Paris Air Show, updating the market on its progress and demonstrating some of the aircraft systems.<ref>{{Cite web |title=Bell Helicopter will showcase a number of updates and aircraft at Paris show |url=https://www.helicopterinvestor.com/news/42813/bell-display-updates-pari-141/ |access-date=2024-04-26 |website=Helicopter Investor |language=en-US}}</ref>

In 2024, Bell announced its first customer for the Bell 525. Norwegian oil company Equinor placed an order for ten. They are expected to operate in the North Sea offshore market and be delivered in the late 2020s. The customer noted its thirty–year relationship with Bell and its products.<ref name=":0" /> In March 2025, Bell stated that certification of the 525 was nearing.<ref>{{cite web |title=Bell Sees 'Strong Path Forward' To 525 Certification |url=https://www.ainonline.com/aviation-news/business-aviation/2025-03-10/bell-sees-strong-path-forward-525-certification |website=Aviation International News |access-date=13 October 2025 |date=March 10, 2025}}</ref>

==Design== thumb|Bell 525 on display at the Paris Air Show of 2019

The Bell 525 is designed to meet a requirement for a medium-lift helicopter. It will be constructed primarily from composites and metal and is to be the first commercial helicopter to incorporate fly-by-wire flight controls,<ref>{{cite journal|journal=Sport Aviation|title=Bell's 525 is Relentless|date=April 2012|page=14}}</ref> with tactile cues. The system is triple redundant, and is developed in two simulator environments.<ref name=mah1/> The 525 is powered by a pair of GE CT7-2F1 turboshaft engines, with a new composite five-blade main rotor system.<ref name=AW_Bigger_Bell/> The cost of the 525 has not yet been determined, but it is expected to be cost competitive on missions between 50 and 400 nmi, performed by helicopters such as the AgustaWestland AW139 and Sikorsky S-92.<ref name=Bell_technical>[http://bell525smt.net/downloads/525_Brochure_062013EN.pdf "Bell 525 Brochure"] {{webarchive|url=https://web.archive.org/web/20131005011832/http://bell525smt.net/downloads/525_Brochure_062013EN.pdf|date=October 5, 2013 }}. ''Bell Helicopter'', February 2012. pdf</ref><ref name="details">[http://www.ainonline.com/aviation-news/hai-convention-news/2012-02-12/relentless-525-be-largest-bell-helicopter "'Relentless' 525 To Be Largest Bell Helicopter"] {{Webarchive|url=https://web.archive.org/web/20140907142010/http://www.ainonline.com/aviation-news/hai-convention-news/2012-02-12/relentless-525-be-largest-bell-helicopter |date=September 7, 2014 }}. ''AINOnline'', February 2012.</ref>

The Bell 525 is designed to fit the emerging "Super-Medium" size category suited ideally to support offshore oil and gas operations.<ref>{{cite web |last1=CFM |first1=In association with |last2=Airshow |first2=In association with Singapore |last3=Recruitment |first3= In association with GOOSE |last4=Trimble |first4= Stephen |title= ANALYSIS: Oil prices create super uncertainty |website=Flight Global |date=2015-02-23 |url=https://www.flightglobal.com/analysis-oil-prices-create-super-uncertainty-/115926.article |access-date=2021-10-22}}</ref> Half of the customers come from that sector.<ref name=mah1>{{cite web |title='Flight Testing' the Bell 525 Relentless |website=Vertical Mag |date=2016-06-30 |url=https://verticalmag.com/features/flighttestingthebell525relentless/ |access-date=2021-10-22}} [https://web.archive.org/web/20140723182823/http://www.verticalmag.com/features/features_article/FlightTestingtheBell525Relentless Archived] on 23 July 2014.</ref> Helicopters under development in the same class are the Airbus Helicopters H175 and the AgustaWestland AW189.<ref name=AW_Bigger_Bell/> The 525 is to be certified in Category A Takeoff class, at maximum gross weight. This involves being able to continue a takeoff (or landing) after one of the helicopter's two turbine engines fails at any point. It should be capable of carrying 19 passengers, more than any existing super-medium helicopter.<ref name=AWST/> It is designed for two pilots with 16 passengers in the standard configuration and two pilots with 20 passengers in high-density seating.<ref>{{cite web |title=Bell 525 Relentless |website=Bell Flight |url=https://www.bellflight.com/products/bell-525 |access-date=2021-10-22}}</ref>

==Specifications (Bell 525)== {{Aircraft specs |ref="Bell 525",<ref>{{cite web|url=https://www.bellflight.com/commercial/bell-525|archive-url=https://web.archive.org/web/20190711185919/http://www.bellflight.com/commercial/bell-525|archive-date=2019-07-11|url-status=dead|title=BELL 525 RELENTLESS|website=bellflight.com}}</ref> Flight Global<ref>{{cite web |last1=CFM |first1=In association with |last2=Airshow |first2=In association with Singapore |last3=Recruitment |first3=In association with GOOSE |last4=Perry |first4=Dominic |title=Bell confident on further 525 performance boost |website=Flight Global |date=2015-09-21 |url=https://www.flightglobal.com/helicopters/bell-confident-on-further-525-performance-boost/118283.article |access-date=2021-10-22}}</ref> |prime units?=imp

|crew=one or two |capacity=16 or 20 passengers <br>{{convert|8200|lb}} useful load |length m= |length ft= |length in= |length note= |height m= |height ft= |height in= |height note= |empty weight kg= |empty weight lb= |empty weight note= |gross weight kg=9300 |gross weight lb=20,500<ref name=AWST/> |gross weight note= |max takeoff weight kg=9300 |max takeoff weight lb=20,500 |max takeoff weight note= |fuel capacity={{convert|2461|liters}} |more general=

|max speed kmh= |max speed mph= |max speed kts=165 |max speed note= |cruise speed kmh= |cruise speed mph= |cruise speed kts=155 |cruise speed note= |range km=1037 |range miles= |range nmi=560 |range note=Max GW, Sea Level, ISA, standard fuel, no reserve, VLRC |ferry range km= |ferry range miles= |ferry range nmi= |ferry range note= |endurance= |ceiling m= |ceiling ft=20000 |ceiling note=with {{convert|12000|ft|m|abbr=on}} hover in ground effect, {{convert|6000|ft|m|abbr=on}} HOGE |g limits= |roll rate= |climb rate ms= |climb rate ftmin= |climb rate note= |time to altitude= |sink rate ms= |sink rate ftmin= |sink rate note= |lift to drag= |disk loading kg/m2= |disk loading lb/sqft= |disk loading note= |fuel consumption kg/km= |fuel consumption lb/mi= |power/mass=

|more performance=

|avionics=* Garmin G5000H }}

==See also== {{aircontent |see also= * Bell 214ST |related= * Bell 360 Invictus |similar aircraft= * AgustaWestland AW189 * Airbus Helicopters H175 * Harbin Z-20 * KAI KUH-1 Surion * NHIndustries NH90 * Sikorsky S-70 |lists= }}

==References== {{Reflist|30em}}

==External links== {{Commons and category|Bell 525}} *[https://www.bellflight.com/products/bell-525 Bell 525 web page] * [http://www.flightglobal.com/news/articles/analysis-bell-525-relentless-cutaway-and-technical-405541/ ANALYSIS: Bell 525 Relentless cutaway and technical description] * [http://www.flightglobal.com/assets/getasset.aspx?itemid=58474 Cutaway drawing of Bell 525] * {{cite news |url= https://www.ainonline.com/aviation-news/business-aviation/2018-01-17/ntsb-severe-vibration-triggered-bell-525-breakup |title= NTSB: Severe Vibration Triggered Bell 525 Breakup |author= Mark Huber |date= January 17, 2018 |work= AINonline}} * {{cite news |url= https://www.flightglobal.com/news/articles/ntsb-report-faults-control-system-gaps-in-fatal-525-444981/ |title= NTSB report faults control system gaps in fatal 525 crash |date= 17 January 2018 |author= Stephen Trimble |work= Flightglobal}}

Category:Aircraft first flown in 2015 525 Relentless Category:Twin-turbine helicopters Category:2010s United States civil utility aircraft Category:2010s United States helicopters Category:Single-rotor helicopters Category:Aircraft with fixed tricycle landing gear