Bell 525 Relentless
The commercial Bell 525 Relentless mid-size helicopter is directly competitive with the Sikorsky H-60/S-70 Blackhawk. The Bell's 525 “Relentless” super-medium class twin turbine helicopter is attempting to raise the bar for technology.
Based on a clean sheet design incorporating advancements in engine, airframe, drive system and avionics designs, the Bell 525 meets current FAA and EASA safety standards — including bird strike protection, drive system loss of lubrication, fatigue, and damage tolerance. Operators benefit from improved fuel efficiency and lower direct operating costs. Designs released by the airframer show a 20-passenger configuration, using four rows of five seats each. Fielding a military variant of the 525 “is being discussed” but for now will take a backburner as Bell concentrates on gaining certification for the civil design. Discussion of a militarized 525 is “almost inevitable” due to its rugged airframe that meets all the latest amendments to FAA Part 29 certification requirements and its FBW flight controls.
Certification of the 525 has been repeatedly delayed due to Bell's struggles with the helicopter's development. Bell’s 525 Relentless, its first super medium commercial helicopter, entered development with a projected first flight in 2014. Bell Helicopter had hoped to complete the certification process for the 525 in 2017, but a crash in 2016 delayed certification as well as first deliveries to customers. The 06 July 2016 crash in Ellis County that killed two pilots, it appears the main rotor struck the front and back of the helicopter, causing the helicopter to break up in mid-flight. The signatures indicate that the main rotor struck both the tailboom and the nose. The aircraft broke up in flight and impacted terrain near Italy, Texas. The two test pilots received fatal injuries, and the helicopter was destroyed.
The NTSB determined [NTSB case number DCA16FA199] that the probable cause of the accident was a severe vibration of the helicopter that led to the crew’s inability to maintain sufficient rotor rotation speed (Nr), leading to excessive main rotor blade flapping, subsequent main rotor blade contact with the tail boom, and the resultant in-flight breakup. Contributing to the severity and sustainment of the vibration, which was not predicted during development, were (1) the collective biomechanical feedback and (2) the attitude and heading reference system response, both of which occurred due to the lack of protections in the flight control laws against the sustainment and growth of adverse feedback loops when the 6-hertz (Hz) airframe vibration initiated. Contributing to the crew’s inability to maintain sufficient Nr in the severe vibration environment were (1) the lack of an automated safeguard in the modified one-engine-inoperative (OEI) software used during flight testing to exit at a critical Nr threshold and (2) the lack of distinct and unambiguous cues for low Nr. About 21 seconds into the test, the main rotor blades flapped low enough to impact the tail boom, severing it and causing the in-flight breakup of the helicopter.
Since the 525 Relentless returned to the air in July 2017 after the fatal crash of flight test vehicle 1 a year before, by March 2018 Bell has flown both of its remaining super-medium twins, FTV2 and 3, nearly an additional 200 flight-test hours. The two aircraft have accumulated approximately 290 hours in total between them. The first production-representative Bell 525, fitted with an oil-and-gas interior made its first Helicopter Association International’s annual Heli-Expo in Anaheim, California in January 2019. The Bell 525 has made significant strides in flight test activity, completing major development testing requirements. The program is transitioning to certification flight testing. By alte 2019 four test ships were flying with a fifth slated to join the program soon. Overall, test aircraft have accumulated 1,300 flight hours through the middle of September. Approximately six production aircraft are already in work at Bell’s Amarillo, Texas assembly facility.
The Bell 525 delivers a generational leap forward with fly-by-wire which greatly increases safety through reduced pilot workload and enhanced situational awareness. The Bell 525 is powered by two 1,800-shp GE Aviation GE CT7-2F1 engines which received FAA type certification in Fall 2019. The Bell 525 is powered by two electronically controlled GE CT7-2F1 engines. These engines provide a dual-channel FADEC system and 2000 SHP that deliver exceptional performance along with a maximum cruise speed of 160 kts (296 kph). Pilots stay aware of their surroundings at all times flying the Bell 525 with Garmin’s top-of-the-line G5000H avionics suite featuring a touch screen interface and synthetic vision technology. Large displays and visualizations of the terrain, potential obstacles and other aircraft keep pilots aware. The flight deck layout also gives crew superior over-the-nose visibility and comfort with side stick controllers.
The flagship Bell 525 model offers unparalleled performance and situational awareness across a diverse range of missions. Creating a class of its own, the 525 offers record-setting speed, payload and range for enhanced pilot operation, along with elevated comfort and versatility for passengers. Designed to meet the newest FAA certification standards, the 525 will be the most thoroughly tested aircraft in the rotorcraft market.
Three baseline interiors configure the Bell 525 for 8, 10 or 12 passengers, making it easy to accommodate individual needs. These versatile configurations include table space, beverage holders and general storage space to keep passengers comfortable and productive on the go. Power outlets, two-tone leather seats, fresh air vents, color-matched carpet and electrochromic windows allow owners to match their unique style.
The Bell 525 offers long range and high speed, covering distances up to 500 nautical miles and speeds pushing 175 kts, setting new standards in rotorcraft performance. As the first commercially certified fly-by-wire (FBW) helicopter, the Bell 525 is the future of vertical flight. The continuously active FBW control laws are there when you need them, while the pilot is always in direct control of the aircraft. The system makes flying repeatable, simple and intuitive. With triple redundant systems, the Bell 525 provides reliability for your pilots and passengers when they’re far away from home.
Nothing makes travel more stressful than a grounded aircraft. Maintenance is simpler than that of legacy aircraft, with an efficient MSG-3 maintenance program and long overhaul cycles. Integrated Vehicle Health Management provides extensive aircraft monitoring along with predictive diagnostic tools to improve flight safety and optimize availability.
|Max Gross Weight||20,500 lb / 9,299 kg|
|Max Gross Weight (External Load)||21,500 lb / 9,752 kg|
|Max Cruise Speed||160 kts 296 km/h|
|Max Range||580 nm 1,074km|
|Engines||2x GE CT7-2F1|
2 Flight Crew + 16 Passengers
2 Flight Crew + 20 Passengers
|Standard Fuel||641 US gal 2,426 liters|
|Passenger Cabin Height||54 in 137 cm|
|Passenger Cabin Floor Area||88 ft2 8.2 m2|
|Baggage Compartment Volume||128 ft3 3.6 m3|
|Hover Ceiling IGE||10,700 ft 3,261 m|
|Hover Ceiling OGE||8,100 ft 2,469 m|
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