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Author Topic: Boeing-Sikorsky SB-1 Defiant  (Read 27255 times)

Offline sferrin

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #90 on: October 04, 2018, 05:18:50 am »
Thoughts?

Quote
But compound helicopters might be much more agile at low speeds and in tight quarters — the conditions in which most crashes and shoot-downs occur. When you compare a compound helicopter like the SB>1 Defiant to a traditional helicopter, “not only do you not sacrifice maneuverability,” Boeing’s Rotte told me, “you actually have enhanced maneuverability.”

Why? Because they combine traditional helicopter rotors for vertical lift (albeit a sophisticated low-drag, low-vibration version) with a pusher propeller or “propulsor” for high speed. Low to the ground or in tight quarters, you can use the propulsor to maneuver without tilting the whole aircraft the way a traditional helicopter has to do. Higher up, where you do have room to tilt the whole aircraft, you can use both traditional helicopter maneuvers and the propulsor together to maneuver in ways a conventional helicopter can’t.

“It’s really good to get to the objective area in a combat operation quickly, but if you get there (and) you’re not maneuverable… you’re not survivable,” Sikorsky’s Koucheravy said. With a compound helicopter, “I get in and get out much more quickly, and in the face of enemy fire, I can maneuver, I can turn,” he told me. “The propulsor on this aircraft gives you a new independent power vector that no helicopter has ever had” — and, while he didn’t say so outright, no tiltrotor, either.

Source:
https://breakingdefense.com/2018/10/sb1-defiant-will-be-worth-the-wait-sikorsky-boeing/

I thought the propulsor only went one way (Well, two ways technically...).

Though the coaxial rotors might give more of a push when input is provided.

Actually, wasn't the entire reason why Kamov used coaxials because they needed to fit a helicopter on a ship with minimal space? Specifically, the rotors would have provided better lift. Does that mean the SB>1 can carry more for its size?

EDIT: Actually, I can kinda get the point for the SB>1 being able to land better, since it takes less space than the V-280.

You're right on the Kamov design.  The Sikorsky design uses counter rotating rotors to prevent roll off at high speed.  With helicopters you lose more lift the faster you go on the retreating blade side.  That's also why they're using rigid rotors (so they can keep the height reasonable without risking the blades becoming intertwined). The AH-56 avoided roll off by using a wing and unloading the rotor.
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Offline TomS

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #91 on: October 04, 2018, 07:36:22 am »
Thoughts?

Quote
But compound helicopters might be much more agile at low speeds and in tight quarters — the conditions in which most crashes and shoot-downs occur. When you compare a compound helicopter like the SB>1 Defiant to a traditional helicopter, “not only do you not sacrifice maneuverability,” Boeing’s Rotte told me, “you actually have enhanced maneuverability.”

Why? Because they combine traditional helicopter rotors for vertical lift (albeit a sophisticated low-drag, low-vibration version) with a pusher propeller or “propulsor” for high speed. Low to the ground or in tight quarters, you can use the propulsor to maneuver without tilting the whole aircraft the way a traditional helicopter has to do. Higher up, where you do have room to tilt the whole aircraft, you can use both traditional helicopter maneuvers and the propulsor together to maneuver in ways a conventional helicopter can’t.

“It’s really good to get to the objective area in a combat operation quickly, but if you get there (and) you’re not maneuverable… you’re not survivable,” Sikorsky’s Koucheravy said. With a compound helicopter, “I get in and get out much more quickly, and in the face of enemy fire, I can maneuver, I can turn,” he told me. “The propulsor on this aircraft gives you a new independent power vector that no helicopter has ever had” — and, while he didn’t say so outright, no tiltrotor, either.

Source:
https://breakingdefense.com/2018/10/sb1-defiant-will-be-worth-the-wait-sikorsky-boeing/

I thought the propulsor only went one way (Well, two ways technically...).

Though the coaxial rotors might give more of a push when input is provided.

Actually, wasn't the entire reason why Kamov used coaxials because they needed to fit a helicopter on a ship with minimal space? Specifically, the rotors would have provided better lift. Does that mean the SB>1 can carry more for its size?

EDIT: Actually, I can kinda get the point for the SB>1 being able to land better, since it takes less space than the V-280.

The improved landing characteristics come from a bunch of things.  Smaller rotor span compared to tiltrotors and even conventional helicopters helps, both in terms of where it fits and in how it flies at speed.  Not having a tail rotor can apparently allow faster turns, especially when coupled with the smaller diameter and very rigid main rotors.

Also the ability of the tail propulsor to reverse pitch in flight can brake the aircraft for a rapid transition from forward flight to hover or landing.  Normally, a quick stop in a helicopter involves a nose-high flare maneuver where the troops get tossed around in the back, pilots can lose situational awareness, and worst case you can get either a tail strike or a settling with power situation.  Not needing to pitch up can make a quick insert simpler and safer all around.

The following article about flying the X2/S-97 is pretty interesting.  Granted it's by a Sikorsky employee, but it seems pretty candid.

http://digitaledition.rotorandwing.com/april-may-2018/x2-from-the-pilots-view/

Offline yasotay

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #92 on: October 04, 2018, 11:13:47 am »
I suspect that at high speed the V-280 will have better roll, possibly pitch and yaw.  At low speed I would give SB>1 better pitch and roll.  Yaw rate will depend on how much flexibility the V-280 has in the prop-rotors.  Both are big aircraft. 

Offline TomcatViP

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #93 on: October 04, 2018, 02:42:06 pm »
@TomS:
Don't forget also that S-97 and SB-1 are sons of the Advancing Blade Concept design where the symmetry of having two blades advancing simultaneously in the relative wind allows an increase in blade maximal admissible momentum that results in a superior value of the blade loading and stability.
The concept fielded by Sikorsky is not only to have contra-rotating rotors or "rigid" rotors. Primarily, It's the ABC.

     
« Last Edit: October 05, 2018, 06:29:49 am by TomcatViP »

Offline Triton

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #94 on: October 08, 2018, 08:28:21 pm »
"Sikorsky-Boeing SB-1 Defiant Prototype Complete, Except For Main Rotors"
by Dan Parsons | October 8, 2018

Source:
https://www.rotorandwing.com/2018/10/08/sikorsky-boeing-sb-1-defiant-prototype-complete-except-main-rotors/

Quote
Installation of its eight 30-foot-long rigid rotor blades is all the SB-1 Defiant needs to be a complete compound helicopter scheduled for a first flight before the end of the year.

“Defiant has been completely built, minus the rotor blades,” Rich Koucheravy, Sikorsky’s future vertical lift director, said Oct. 8 at the Association of the U.S. Army’s annual expo in Washington, D.C. “We have run nearly all of the aircraft systems, so not only have the individual components been put through bench testing, but now we’ve got the aircraft completely configured. We’ve run the engines, we’ve run the electrical system. We’ve run the hydraulics. We’ve even turned the transmission without blades.”

Half of the aircraft’s eight 30-foot rigid rotors will arrive at Sikorsky’s West Palm Beach, Florida, flight test facility by Oct. 9, said Boeing FVL Program Manager Ken Eland. The other four will arrive by next weekend.

Prior to first flight and during ground runs, engineers will gain hundreds of hours of system performance data from the powertrain systems test bed, which is essentially a replica of the Defiant that stays bolted to the ground and contains all of the dynamic systems configured exactly as they are in the aircraft. It has been run twice without the eight rigid rotor blades installed, according to Ken Eland, Boeing’s FVL program manager. It’s aft propulsor blades are installed.

The main rotor blades for the test bed have been delivered to West Palm Beach, but have not been installed, Eland said. The plan is to run the powertrain test bed once more before installing the blades. At that point, the test bed will start at zero and will be run a total 200 hours before the Defiant takes off, Eland said.

Koucheravy said the test bed should be fully up and running before the end of October. It will operate concurrently with Defiant ground runs, which should begin in November. The companies are eyeing a first flight in December.

“Between Sikorsky and Boeing, we have worked tremendously hard over the past six months to remove as much risk … from the program to get our aircraft up in the air,” Koucheravy said. “We remain on a path to complete the build of Defiant shortly and get it in the air by the end of the year.”

If the Defiant breaks contact with the ground in December, it will be about a year later than originally planned. That delay was primarily due to problems with automating the layering of fibers to create the central spar of the blades.

“We took the approach to automate the core part of this blade, so the spar is very long. It’s very thick and it’s composite material,’ Eland said. “To set the precedent for the future, of being a low-cost aircraft, we went right in with an automated approach to doing that. It was actually tooling for the rotor blades that set that back for a while.”

Because Boeing was developing the rotor lamination process — called automatic fiber placement — as it went, it took two years to build the first rotor spar. The last one took just 11 days, Eland said.

The same rotor configuration has flown in smaller scale on Sikorsky’s experimental X2 aircraft and on the S-97 Raider. The airfoil design is proven, said Randy Rotte, Boeing's director of business development for cargo helicopters and future vertical lift programs.

“It’s not about the airfoil challenges there,” Rotte said. “It really was about the process that we embarked upon — by the way at the request of the Army — to improve the manufacturing readiness level of that process and the discoveries we made on how to do that, which, yes, took us way longer than we expected because we ran into unexpected challenges.”

If Defiant lifts off in December, Eland said it could be flying at upward of 200 kt by mid-2019 as part of a gradual, phased flight test program that has been worked out in cooperation with the Army. A six-month “window is not an unrealistic time period for us to get there.”

“The true answer is when the aircraft says it’s ready, we’ll get there,” Eland said. “It’s a little hard to predict with what we’re doing. We have a revolutionary technology. … Expanding the flight envelope is going to be step-by-step to make sure that we do it safely and properly. To assign timelines to it at this time would be a little naive on my part.”
« Last Edit: October 08, 2018, 08:41:16 pm by Triton »

Offline TomS

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #95 on: October 09, 2018, 06:48:34 am »
That's a smarter spin to put on the SB-1 timeline.  They are saying that the bulk of the delay was due to de-risking the manufacturing processes for the main rotors. They basically built the production tooling, rather than going for hand-built test articles that wouldn't be production-representative.
« Last Edit: October 09, 2018, 11:42:24 am by TomS »

Online fightingirish

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #96 on: October 09, 2018, 10:36:15 am »
Quote from: Dan Parsons / @SharkParsons
So ... Boeing has a revised attack variant of their dual coax-rigid rotor design. Here it is hovering next to Defiant
[...]
Revised from the original concept. Notice new design has internal weapons stores that stow flush to fuselage to reduce drag in forward flight.
Twitter: https://twitter.com/SharkParsons/status/1049313887861002240
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Offline yasotay

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #97 on: October 09, 2018, 12:35:18 pm »
That's a smarter spin to put on the SB-1 timeline.  They are saying that the bulk of the delay was due to de-risking the manufacturing processes for the main rotors. They basically built the production tooling, rather than going for hand-built test articles that wouldn't be production-representative.

Yup.  I noted an article that originally noted higher risk and unproven stuff was appended to take those comments out.

Offline Aeroengineer1

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #98 on: October 11, 2018, 09:59:53 pm »
Still, 11 days to build a spar is actually pretty high for AFP.  I wonder what is in that flow time.  The layup itself should not take more than a day or so.  An AFP machine should be able to lay down on the order of 2-10lbs of material an hour, and the spar should weigh on the order of around 80-110lbs for this blade (very rough guesses here based upon what I know on the S-97 blade).  Even if we go to the high end of the weight, combined with the low end of the laydown rate, this should be able to be done in 2-4 days depending on if they are running two or three shifts.  I would imagine that at most, Boeing Mesa is running 2 shifts.  The cure, demold and deflash around a day.  Machining should be around 2 days, with potential to get that down a lot depending on fixturing and the actual machine being used for the process.  There may be some post machining installations of bushings, though most of that time will be in cure if they do not elevate the cure temp (which is almost always done, unless you do not need the parts fast).  This set of bushings, though, I imagine that they would be installed after the blade assy.

Each blade assy should take around 2-4 days, though could be faster if all the components have a good fit.  There will be some machining of the final assy, and that would be a day.  Final assembly of weight cups, balance and paint another 2 days or so. 

I come up with an overall flow time of around 9-13 days, and I think that this is high, especially once they are getting to the last blades.  The layup of the skins, and core machining would all be happening in parallel.

Offline yasotay

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Re: Boeing-Sikorsky SB-1 Defiant
« Reply #99 on: October 12, 2018, 02:41:37 pm »
Could it just be caution with a new process?  They are delayed a year due to rotor blade issues. Something about it is very new to two companies very familiar with making rotor blades.