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Sikorsky SB-1 flies for first time

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Sikorsky SB-1 flies for first time

Old 15th Jan 2020, 00:01
  #141 (permalink)  
 
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Originally Posted by CTR View Post
Sultan has yet to realize that in the US Army and DOD in general, political motives almost always trump technological realities.

Sikorsky from the start of the FVL technology demonstrator selection was favored by the US Army to be the ultimate supplier for the UH-60 replacement. With all the resources of Sikorsky and Boeing combined, how could they fail? Then Bell all alone, using advanced design tools and proven tilt rotor technology, screwed that all up and succeeded beyond expectations. Does anyone think that if the situation was reversed, and Bell was two years behind schedule, that the US Army would select Bell to proceed to the next stage and build a prototype? Of course not. If Bell had failed as badly in producing a demonstrator aircraft as Sikorsky and Boeing have done, the competition would be over and the SB>1 Defiant would be moving forward in development all alone.

Sultan, what is just, fair and technically correct has no place in the administration of the FVL contracts.
Lots of tradition for that kind of politically adjusted decision making. The C-5 and the F-111 were the prime examples used to illustrate this back in the 1960s,
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Old 17th Jan 2020, 21:11
  #142 (permalink)  
 
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Update

https://www.verticalmag.com/news/sik...ant-100-knots/


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Old 17th Jan 2020, 23:47
  #143 (permalink)  
 
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For 100kt, the fuselage angle is noticeably nose-down - what will it look like at 280kt?
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Old 18th Jan 2020, 00:10
  #144 (permalink)  
 
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Wow. . . .100 knots. The fuselage angle indicates the tail prop is probably generating little or no thrust which means the fuselage has to tilt to get any non vertical thrust. A shame the program it was developed for completed last month.
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Old 25th Jan 2020, 19:52
  #145 (permalink)  
 
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Good afternoon, folks. I'm a semi-new member. It seems that there is a bit of anti-SB-1 sentiment, and i'll rant my ideas on it. ALot of us want to see Bell Helicop-- er, Bell Flight, prevail in the FVL FLRAA or whatever it's called now. They're kind of an underdog i.e. they've had their machines in various entries over the years, and lost out to the AH-64 and UH-60 i.e. bid programs for Turkey, Taiwan, South Korea, Greece, etc, other countries, and the dominance of the AW139 in civil and militaries, the seeing the dead end of the ARH-70 bid, the Bell 210/412 not being picked over the Lakota UH-72... It would be great to see Bell prevail, especially as the Navy went with the AW-119 for the TH-57 replacement despite the idea of replacing a Bell 206 with a 407 seemed like a sure bet. Seems like Leonardo is winning everything these days!! I also secretly kick my table leg when I see on heli Hub that some other county Air ambulance replaces their Bell 412 with a $&@ Airbus H135/145 or Leo-Agusta Westland-Boeing whatever AW139. If only the Bell 525 had been ready in time for the UH-1N replacement... grrr.
It's good to see the AH-1Z get some foreign interest, like the Czech Republic's order and Bahrain' s pending sale, with Morocco and Romania showing interest. bell was able to make a sale to pakistan - but the AH-1Zs are currently in storage due to political order.
I believe the winged and plane-propped V-280 will have the range and speed advantage, and will be agile enough at the X. I simply don't see the SB>1 being as fuel efficient with the twin rotors and pusher prop, but may be nearly as fast as Valor due to raw power, but if Raider S-97 and Raider X are examples, it will be very agile at the X. We have to be aware that Sikorsky has a strong contender in the SB-1. However, I am sure Bell has their cards lined up for the FVL, with the V-280 building on the V-22 to make a strong case for tilt-rotors, and their B360 Invictus has the least complex approach to FARA, which may be a good thing. Go Bell Flight!
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Old 26th Jan 2020, 15:38
  #146 (permalink)  
 
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Originally Posted by Ascend Charlie View Post
For 100kt, the fuselage angle is noticeably nose-down - what will it look like at 280kt?
It would be near level body to minimize drag at speeds greater than ~180-200 knots. Looks like at least several of the shots had the aircraft flying in "helicopter mode" with the main rotor producing horizontal force and the prop freewheeling. The earlier XH-59A, with it's comparatively poor rotor aerodynamics, and limited power/weight ratio compared to some modern X-2 aircraft, could do 156 knots as a pure helicopter. Given the advancements and installed power in the more recent aircraft, they should have an even larger "helicopter mode" flight envelope to work in before prop thrust "airplane mode" flight is required. So if the prop driveline of SB>1 isn't ready yet, they still have plenty of flight envelope to explore.
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Old 26th Jan 2020, 16:48
  #147 (permalink)  
 
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Because it is in flight test, they will be doing flights at many different power settings on the rotor, prop, plus horizontal tail position. Each one will give a different attitude for a given airspeed. There is no reason it won't fly level body throughout the envelope once they have it mapped out.
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Old 26th Jan 2020, 16:53
  #148 (permalink)  
 
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IFMU: gee, what's with the common sense and rational thought in a post?
Are you sure you are in the right place?
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Old 27th Jan 2020, 16:40
  #149 (permalink)  
 
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Originally Posted by Copter Appreciator00 View Post
if Raider S-97 and Raider X are examples, it will be very agile at the X.
Sikorsky's marketing team is certainly earning their paychecks....I'm still at a loss with regards to these repeated sentiments from people.

40 years after XH-59, 10 years after X2, and 5 years after first flight on S-97 and the most extreme maneuvering we have seen is footage of Raider plodding around lazy strafing circles played back at 1.5X speed on Sikorsky youtube videos.

I simply don't see the SB>1 being as fuel efficient with the twin rotors and pusher prop, but may be nearly as fast as Valor due to raw power
The fastest hot-rod, all-engine X2 squeaked past 260 kt in a shallow dive. The V-280 has reportedly flown in excess of 310 kt (and recall the XV-15 reached 345 kt in a shallow dive). The odds an edgewise-rotor-flight ship even sniffs the speeds of a tiltrotor flying on a wing with remotely the same installed power is essentially zero.
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Old 27th Jan 2020, 20:47
  #150 (permalink)  
 
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If the Army specs a high rate roll reversal at high speed (low rotor rpm) to simulate SAM avoidance the ABC concept is finished. The S-97 crash at full rpm showed how even moderate roll rates will cause the rotors to collide.
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Old 27th Jan 2020, 21:02
  #151 (permalink)  
 
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Originally Posted by The Sultan View Post
If the Army specs a high rate roll reversal at high speed (low rotor rpm) to simulate SAM avoidance the ABC concept is finished. The S-97 crash at full rpm showed how even moderate roll rates will cause the rotors to collide.
The crash was a result of the wrong set of control laws being active, not the rate of input... the crash isn’t representative of how well the aircraft will maneuver. Most rotary wing platforms are capable of blade to “something” strikes if control laws drive the aircraft to a bad state.
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Old 28th Jan 2020, 12:57
  #152 (permalink)  
 
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Originally Posted by The Sultan View Post
If the Army specs a high rate roll reversal at high speed (low rotor rpm) to simulate SAM avoidance the ABC concept is finished. The S-97 crash at full rpm showed how even moderate roll rates will cause the rotors to collide.
My instructors at Fallon and Nellis, regarding SAM evasion by helicopters, would be laughing pretty hard at your understanding of how slow aircraft deal in modern SAM avoidance.
high rate roll reversal at high speed (low rotor rpm) to simulate SAM avoidance
And that was with tech that is about 30 years old.
Missile seeker heads have not gotten worse in the interim.
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Old 28th Jan 2020, 15:12
  #153 (permalink)  
 
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Originally Posted by Lonewolf_50 View Post
My instructors at Fallon and Nellis, regarding SAM evasion by helicopters, would be laughing pretty hard at your understanding of how slow aircraft deal in modern SAM avoidance.
Lone

The FLRAA is a 280+ Kt aircraft and not a 30 yr old 120 kt or slower design. I believe the avoidance technique is still to pop chaff and flares and then be somewhere else when the missile arrives. Kind of defeats the purpose to fly straight and level after deploying countermeasures.

From a countermeasures description:

Once the presence of a "live" IR missile is indicated, flares are released by the aircraft in an attempt to decoy the missile; some systems are automatic, while others require manual jettisoning of the flares.

The aircraft would then pull away at a sharp angle from the flare (and the terminal trajectory of the missile) and reduce engine power in attempt to cool the thermal signature. Optimally, the missile's seeker head is then confused by this change in temperature and flurry of new signatures, and therefore follows the flare(s) rather than the aircraft.=13.33px
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Old 28th Jan 2020, 15:31
  #154 (permalink)  
 
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Originally Posted by The Sultan View Post
Lone

The FLRAA is a 280+ Kt aircraft and not a 30 yr old 120 kt or slower design.
Sorry, 280 knots is still slow.
There is a rate change that takes a lot more speed to make a difference to a seeker head with tech that is two generations older than what is available now.
What feels like a radical maneuver in that cockpit looks pathetic to the seeker head.
(Granted, I am sure that old OV-10 Bronco hands may have a tew things to say about this).
I believe the avoidance technique is still to pop chaff and flares and then be somewhere else when the missile arrives.
I expect that's still true. Without various countermeasures and a change in all three axes, evasion isn't even a useful term.
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Old 28th Jan 2020, 16:19
  #155 (permalink)  
 
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Originally Posted by SplineDrive View Post
The crash was a result of the wrong set of control laws being active, not the rate of input... the crash isn’t representative of how well the aircraft will maneuver. Most rotary wing platforms are capable of blade to “something” strikes if control laws drive the aircraft to a bad state.
From my reading of the accident report the wrong set of control laws increased the roll input to cyclic command by a factor of 2.5 which led to over control resulting in a couple of roll reversals causing the blades to collide. The “instantaneous” roll rates achieved during the event were never higher than would be expected in aggressive flight maneuvers. One selling point of the ABC was the rotors were so stiff it would be impossible for them to deflect enough to collide even in the most severe maneuvers. The 97 accident shows this is not true and will be a governing constraint limiting the agility of an aircraft billed as being highly maneuverable.
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Old 28th Jan 2020, 16:22
  #156 (permalink)  
 
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Lone,

To be fair, it was the Army themselves (and Sikorsky over the years with their presumed greater hover maneuverability) who had been touting the value of exceeding ADS-33 requirements and the (preposterous) idea of dodging threats from slow speed/hover.

It was always the knock against tiltrotors, hence why the V280 added massive amount of flapping to address the V22's relative sluggishness. Bell always argued the survivability was not from dancing around a seeker, but flying high above the threat, faster, and eliminating the time time on station. The Army should really have recalled the AH-64 fights in Najaf to remember why the doctrine immediately changed from lobbing munitions from a stand off hover to constant high speed strafing attacks.
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Old 21st Feb 2020, 00:03
  #157 (permalink)  
 
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Update today. Sikorsky sounds nervous. Go to breakingdefense.com

“We’re flying it before we’re buying it,” McCarthy said this morning. “There’s nothing better than putting hours against the platform and learning.”

"The SB>1 Defiant compound helicopter has only 11 hours of flight testing, versus over 160 for Bell’s V-280 Valor"

"But what has the actual aircraft done in flight? Fell said that Defiant has flown backwards, sideways, banked at a 45-degree angle, and flown forward in level flight as fast as 150 mph (130 knots).

"But that’s not halfway to the 322 mph (280 knots) that the Army wants. Even the Army’s minimum requirement for top speed is 265 mph (230 knots).

"When will the Defiant fly at its top speed? “A few months,” Fell said. That’s a remarkably short timespan compared to how long it’s taken to get it this point."
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Old 21st Feb 2020, 02:22
  #158 (permalink)  
 
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The aforementioned article:

https://breakingdefense.com/2020/02/...korsky-boeing/

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Old 21st Feb 2020, 11:36
  #159 (permalink)  
 
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Another article.

https://www.verticalmag.com/news/sik...er-tail-rotor/

I like this part:

If the tail boom, which includes no hydraulics, took a direct hit and literally fell off, the aircraft would still be able to operate as a helicopter. All control surfaces aft of the engine outlet are controlled by electronic actuators.
So advanced it doesn’t have a CG! What a joke, Hope they briefed the DOD with more accurate info. This thing would back flip like anything else. Even if you only lost tail thrust good luck making it back to base at 90 or so knots.
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Old 21st Feb 2020, 13:06
  #160 (permalink)  
 
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Originally Posted by SansAnhedral View Post
The Army should really have recalled the AH-64 fights in Najaf to remember why the doctrine immediately changed from lobbing munitions from a stand off hover to constant high speed strafing attacks.
Heh, are you referring to the 2003 raid by 11th Aviation Regiment, or a different fight?
The Army requirements for Comanche had some very tough to meet lateral movement numbers. I'll offer that "shoot it from a hover" was being been abandoned in the midl to late 90's in at least a part of the Army's recon / attack community.
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