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  • We've become accustomed to seeing stealth aircraft  now for almost 30 years from the F117 night hawk  

  • to the B2 bomber to the F-35 but what about  helicopters. They are an integral part of the  

  • military but the majority of them are hardly what  you would call stealthy and ever since the advent  

  • of radar-guided and heat-seeking missiles they  have been more vulnerable than their faster-fixed  

  • wing cousins. Although we've had hints ofblack ops stealthy helicopter with the raid  

  • on bin Ladins compound in 2011, there isn't  the rotary equivalent of the F-35 in service

  • But one was developed over 20 years ago and its  mission was to do then for helicopters what the  

  • F-35 has done now for fixed-wing aircraft with  stealth, sophisticated digital battlefield field  

  • electronics, advanced networked sensorshigh performance and firepower. Even though  

  • it was praised by the military, just two  prototypes were ever built. This is the  

  • story of America's first and so far last stealth  helicopter, the BoeingSikorsky RAH-66 Comanche

  • This video is sponsored by Brilliant The story of the Comanche starts  

  • back in the early 1980's with the US  Army looking at replacing the OH-58  

  • Kiowa and OH-6 Cayuse scout helicopters with  something more survivable but also capable  

  • of attacking lightly defended targets. Attack helicopters had come about during  

  • the Vietnam war when gun platforms had been  fitted the Bell UH-1 Iroquois or the Huey  

  • to give them some form of protection when  flying troops into battle but it soon became  

  • apparent that a dedicated platform would be  required to make a true attack Helicopter

  • The first attempt was the 1962 Bell Model 207  Sioux Scout, this introduced the key features of  

  • the modern attack helicopter, the tandem cockpitchin-mounted gun and stub wings for weapons.  

  • Whilst the US Army liked it they thought it was  too small and underpowered. Bell replied with the  

  • Model 209 AH-1 Cobra which used the same enginetransmission and rotor systems as the Huey

  • The AH-1 Cobra was light, manoeuvrable  and effective but lightly armoured and was  

  • susceptible to enemy fire which in the mid-1970s  led to the development of the McDonnell Douglas  

  • Apache AH-64 as a replacement for the CobraThis was more like an airborne tank, very well  

  • armoured with a wide array of weapons but this  lacked the light manoeuvrability of the Corba

  • By the early 80s the US Army was looking for  a light attack and reconnaissance helicopter  

  • but one which would be heavily armoured and use  stealth technology to defeat more sophisticated  

  • radar and heat-seeking missiles allowing  to not only act as a forward scout for  

  • the more heavily armed Apaches but also  attack smaller targets when it found them

  • This resulted in the LHX or light  helicopter experimental program  

  • but as a portent of things to come this  took nearly a decade to come to a conclusion  

  • and award the contract to build the advanced armed  reconnaissance and attack helicopter prototypes  

  • to Boeing-Sikorsky in 1991 with a development  budget of $2.6 Billion. 1200 were to be built  

  • at a cost of $28 million per helicopter. The program was going be the next  

  • generation helicopter and would introduce  advanced new and untried design features.  

  • This would take the stealth knowledge gained  from previous programs like the F-117 night hawk  

  • as well as introducing the concept of the digital  battlefield using networked sensors to instantly  

  • transmit the location and strength of the enemy  back to mobile headquarters directing the battle

  • To do this many new technologies would have to  be developed. The fuselage for example was a  

  • composite made up of 350 parts, a big reduction  compared to the 6000+ parts for a normal  

  • metal helicopter of a similar size. It used the flat faceted construction first seen  

  • on the F-117 to reflect radar signals away and was  coated in radar and infra-red absorbent materials  

  • which reduced the Comanches radar cross-section to  360 times less than that of the Apache AH-64 and  

  • half that of a hellfire missile allowing it to get  five times closer than an Apache before detection

  • To help reduce the radar cross-section the wheels  and weapons including the chin-mounted Gatling gun  

  • retracted into the body which also had the  benefit of making it more aerodynamic and faster

  • It was constructed with Kevlar and graphite  armour that could withstand heavy machinegun  

  • fire from up to 23mm shells and it  would also be more crash-resistant

  • As helicopters operate close to the ground and at  slower speeds than attack aircraft the first thing  

  • that most people know when one is approaching is  the loud chop, chop, chop sound from the rotors.  

  • This is caused by the interaction of the  airflows from the main rotor and the tail rotor.  

  • So on the Comanche, the tail rotor was  an enclosed ducted fan to reduce airflow  

  • interaction and help reduce the sound, this was  also tilted over to be less radar reflective

  • The tail ducted fan was also very powerful  and along with sophisticated control systems  

  • allowed the helicopter to change its angle of  direction whilst it was travelling in a straight  

  • line. The effect of this was that it could fly  sideways at speed or even backwards and aim its  

  • weapons without having to change course. It also had the benefit in that the tail  

  • fan blades would be protected during low-level  manoeuvres at night and when flying at treetop  

  • level, a time when it's difficult for the pilot to  see obstacles like tree branches, something that  

  • could damage normal tail rotors and bring down  the helicopter. The composite tail fan blades  

  • could also withstand hits from 12.7mm rounds. To further reduce the sound, the main rotor had  

  • five composite blades downward-canted which had  less of a regular beating sound and more of a hum  

  • that was half the noise of a regular helicopter  and could blend into the background better

  • To defeat heat-seeking missiles the engine exhaust  from the twin T800 turboshaft engines would be  

  • channelled along the tail to exit by the fan where  it would be cooled by the fresh air from the fan

  • The powerful engines and streamlined body made  the Comanche very fast at 324km/h, 201mph

  • The Comanche had extensive electronic  countermeasures and fire control systems including  

  • a 2nd generation long-range Forward-Looking  Infrared Sensor to spot targets which could then  

  • be illuminated with a laser to guide missiles. It  could be fitted with the longbow millimetre radar  

  • based on that of the Apache above the  rotor to look over hill crests and trees

  • Data from these could fed the automatic  target identification and tracking system  

  • and forward it to others in the force  a bit like the F-35 does now to provide  

  • near real-time intelligence. The crew had  helmet-mounted displays and a night vision  

  • system and the separate crew cabins which were  sealed again chemical and biological attack

  • The triple-redundant fly-by-wire flight  control electronics were fault-tolerant  

  • so that if part of it was damaged in an attackbackup systems could instantly over take over

  • The first prototype started flying in  1996 with a second joining it in 1999  

  • but as development and tests went by, more  and more problems started to crop up. The  

  • sheer number of new systems and technologies  being brought together in one aircraft meant  

  • that BoeingSikorsky were playing an increasing  costly game of whack-a-mole to iron out problems  

  • which weren't helped by the Army shifting the  goalposts and adding new feature requests

  • The Army want more weapons so stub wings were  added with hard points for more missile but this  

  • then made it hundreds of kilos heavier and  less aerodynamic but no one at the time had  

  • figured this out until it was loaded with weapons. The Comanche was far more reliant on software for  

  • all its systems but this was proving to be buggysensors were unreliable and the radar absorbing  

  • body was susceptible to corrosion from rainAll of this, the changing requirements and poor  

  • management slowed the project causing cost overuns  which ended up tripling the development costs

  • One example was the Army's request that the range  of the helicopter which was designed to be a scout  

  • be raised so that it could be flown across  the Atlantic and yet it was designed with a  

  • narrow body so that it could be more  easily transported by plane or ship

  • As the cost went up, budget cuts from the  so-called peace dividend after the fall of  

  • the Soviet Union put more pressure on the  program which was designed to fight a war  

  • against an enemy which no longer existed, so  large numbers of reconnaissance helicopters  

  • were seen as no longer necessary. Afghanistan and the war on terror  

  • moved the focus away from cold war era  design goals even though other stealth  

  • and UAV programs were given more money but the  stealth helicopter was seen as a niche project

  • Over the lifetime of the program, the total  number on order was gradually cut more and more  

  • which meant the unit cost of each went up and up  which emboldened the project critics to push for  

  • even more cuts saying they were now too expensive. In 2002 it was estimated that by 2008 the Comanche  

  • would be taking 40% of the army's  aviation budget, money that could  

  • be put to better use funding development and  renovation of the existing helicopter fleet

  • But in 2004 the Comanche project  was abruptly cancelled by the Army,  

  • the development cost had risen to $6.5 billion  

  • and the cancellation fees to Boeing and Sikorski  added another $500 million to the final bill

  • So like many other forward-thinking programs, the  RAH-66 Comanche ended up as another museum piece  

  • with both the prototypes now located at the US  Army Aviation Museum at Fort Rucker, Alabama

  • Time will tell if a future stealth helicopter  will see the light of day in the US  

  • or maybe other countries might be looking  to take on the challenge and create the  

  • worlds first operational stealth helicopter. One of the feature requests was for the Comanche  

  • to control UAV reconnaissance drones which  ironically helped hastened it's cancellation  

  • because it was realized that they didn't need the  Comanche to act as sort a data middleman and as  

  • drone technology advanced they could be controlled  more directly from regional headquarters

  • The future of UVA's and helicopter drones  will need skilled people to design,  

  • build and operate these new aircraft and  our sponsors for this video Brilliant  

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We've become accustomed to seeing stealth aircraft  now for almost 30 years from the F117 night hawk  

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B2 中高級 美國腔

美洲丢失隐形直升机(America's lost stealth helicopter - RAH 66 Comanche)

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    joey joey 發佈於 2021 年 06 月 14 日
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