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Sikorsky SB-1 flies for first time

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Sikorsky SB-1 flies for first time

Old 22nd Jul 2021, 23:41
  #321 (permalink)  
 
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Originally Posted by IFMU View Post
Totally wrong. The coax limitation for yaw is in autorotation. They leave room for differential collective on top of collective.
"Leaving room" doesn't leave much margin when operating in the mountains of Afghanistan. The question isn't can it yaw at all, but how fast can the helicopter yaw at its limits? Fast yaw has not been demonstrated to date.
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Old 23rd Jul 2021, 09:25
  #322 (permalink)  
 
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Originally Posted by noneofyourbusiness View Post
There is a major difference between a prop and a tail rotor. Answer how the side force is counter-acted when both rotors are tilted in the same direction. Don't just give an arm wave. The reaction torque from a pusher prop is a pure torque. The torque from a tail rotor provides side thrust and moments (above the cg). Conventional helicopters have a much smaller roll torque from the engines. Did you ever take a physics class?

When you get an answer from your bosses at Sikorsky, I am willing to learn and be educated.
I've got no Sikorsky bosses anymore. I moved to another UTC division when they closed Schweizer. I was the responsible engineer for the X2 flight controls though. And yes I've studied physics. Still use it at my space job. You?

You had mentioned the UH60 high tail rotor before. The torque would be the thrust from the tail rotor times the lever arm. Really no torque from the engines as you say. The torque from the X2 propeller would be the power it absorbs times 5252 divided by RPM. I'll leave it to the student to do the math.
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Old 23rd Jul 2021, 17:29
  #323 (permalink)  
 
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The S300 - now spun off as a separate business?. I am retired from my day job, mechanical engineer, same industry as you, passing my time working on an invention.

Clearly the Raider rolled side to side pretty quickly when it crashed, with the rotors not parallel. You say the design is intended to keep the rotors parallel, I believe you.

I wasn't comparing a tail rotor torque to the pusher prop torque. Clearly most engine power goes through the prop at high speeds, unlike the tail rotor. I was just trying to point out, the tail rotor is a flight control device, but the pusher prop isn't. There is high speed flight, and there is low speed flight with the pusher disengaged. For high speed flight, what keeps the x2 type design going straight forward, if the main rotors are canted to offset prop reaction torque? Are the vertical stabilizers enough? Secondly at hover, is the only difference between a sideways movement and a roll, the degree of tilt of the rotors?

I never worked flight controls, so I may miss the obvious. I appreciate your input.

Last edited by noneofyourbusiness; 23rd Jul 2021 at 17:51.
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Old 24th Jul 2021, 02:42
  #324 (permalink)  
 
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For high speed flight, what keeps the x2 type design going straight forward, if the main rotors are canted to offset prop reaction torque?
Think in terms of a fixed wing Cessna with two wing fuel tanks. One full, and one empty. You have to put in enough aileron to react the unbalanced fuel load, but the airplane still goes straight. Same as a helicopter using cyclic to balance other forces and moments. They can be prop torque, tail rotor twisting moment, unbalanced fuel/crew loading, or whatever.

Sikorsky pretty much destroyed Schweizer. Somebody bought the 269/300 type certificate and I think they are building them again. Probably with chinese parts but I don't know.
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Old 29th Jul 2021, 14:41
  #325 (permalink)  
 
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Originally Posted by noneofyourbusiness View Post
For high speed flight, what keeps the x2 type design going straight forward, if the main rotors are canted to offset prop reaction torque?
The cant itself will be largely irrelevant for straight flight because it is only relative to the fuselage. The only small effect would probably result from slightly increased drag of the rotors on the side where the rotors need to produce a bit more lift to counter the torque. On the other hand you will have a drag force on the opposite side resulting from the fuselage being displaced to the opposite side by the torque and the resulting cant.
But realistically this will be negligeable and be easily countered with a tiny bit of crab.
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Old 11th Sep 2021, 15:42
  #326 (permalink)  
 
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SB-1 FLRAA Proposal Submitted

It has been rather boring in the waning days of summer (coming not too soon) until this gem dropped on Verticalmag:

https://verticalmag.com/news/sikorsk...x-to-u-s-army/

This has a number of things to comment on:

“Today, Team DEFIANT completed and submitted the proposal for the U.S. Army’s FLRAA competition
Amazing that for the first time in the FLRAA program Sikorsky-Boeing actually met a schedule. Proves they are better at writing fiction than they are at program management and cutting metal (actually molding composites).

“We’re very excited to be at this point. It’s been a long journey in a very short period of time.”
It has been EIGHT years since the FLRAA concept demonstrators were selected. Five years is a normal development cycle so where did the "very short time" come from?

Army’s need for an advanced rotorcraft capable of at least 230 knots and preferably capable of cruising 280 knots, much faster than traditional rotorcraft.
Data gathered in the ensuing flight test campaign, including level flight at 230 knots, was incorporated into the team’s FLRAA proposal.
Defiant X delivers speed where it matters
This ignores the original goal of the FLRAA requirements to have a 250 kt minimum cruise speed. The final requirements were changed once the shortfalls of the SB concept were known. What does "speed where it matters" even mean? For a long range assault aircraft (the LRAA in FLRAA) where high speed matters is in the cruise segment of a mission getting to the objective. This shaves hours off a mission. Where does SB think speed matters more?

while operating in the same footprint as the BLACK HAWK,
Was that a requirement in the final RFP? If it was? Why? Who cares?

Defiant X also has a tricycle-style landing gear with one wheel under the cockpit and two wheels aft whereas the operational prototype Defiant sported two front wheels and a tail wheel that protruded down from its tail boom.
What!!! The original concept made sense as it at least tried to keep the pusher prop out of the dirt. Going to a nose gear can only be a last resort to move the cg forward to reduce rotor loads at the sacrifice of operability. You strike the pusher on the ground flaring into a hot LZ, you are there for the duration.

Relative to the images released is it just me or does the gap between the rotors been significantly increase?




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Old 11th Sep 2021, 16:51
  #327 (permalink)  
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Amazing

“Amazing that for the first time in the FLRAA program Sikorsky-Boeing actually met a schedule.”

Sikorsky and Boeing saved a lot of RFP response time by not having to compile and analyze hundreds of hours of flight testing like Bell had to. Smart move by the Defiant program not to waste time and money in unnecessary flight testing to prove concept viability.
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Old 11th Sep 2021, 20:49
  #328 (permalink)  
 
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Originally Posted by CTR View Post
“Amazing that for the first time in the FLRAA program Sikorsky-Boeing actually met a schedule.”

Sikorsky and Boeing saved a lot of RFP response time by not having to compile and analyze hundreds of hours of flight testing like Bell had to. Smart move by the Defiant program not to waste time and money in unnecessary flight testing to prove concept viability.
If there is any sanity in this world, this RFP submission is the beginning of the end of the ABC concept.
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Old 15th Sep 2021, 03:25
  #329 (permalink)  
 
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Sikorsky and Boeing saved a lot of RFP response time by not having to compile and analyze hundreds of hours of flight testing
Didn't SB get millions $ more than Bell to fund this phase? Don't they have to account for this money? Time to check SB leaders 1offshore accounts.
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Old 3rd Oct 2021, 16:10
  #330 (permalink)  
 
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SB Admits Technical Defeat

The latest Sikorsky-Boeing printed infomercial (attached) spends the whole "article" minimizing technical requirements/capabilities and initial cost by emphasizing the current boogieman of long term sustainment costs as a reason why the SB-1 should be selected for FLRAA. So basically ignore the tangibles of lower speed, shorter range, and higher acquisition costs of the SB-1 versus the Bell V-280 for an unknown promise of lower life cycle costs. This approach attempts to fearmonger using the F-35 unaffordability fiasco that has been in the headlines. What is so pathetic is the S-B team, along with Sikorsky parent LM, have failed repeatedly to control acquisition costs, meet schedules, and provide a sustainable spec compliant product. Additionally, this team are the poster childes for what they are warning about by supplying legendary acquisition failures including the Cyclone, Comanche, and CH-53K (Sikorsky); the KC-46, Starliner, and 737Max (Boeing); and of course the F-35 and F-22 (LM).

As a counterpoint the Bell V-280 has incorporated and demonstrated changes learned from earlier tiltrotors to simplify construction, reduce risk and cost, improve operability and (stunningly) met program requirements.

You almost have to feel sorry the S-B team as they grasp at this last straw to save themselves.

Sponsored Content: An acquisition strategy for the Future Long-Range Assault Aircraft: Focus on the mission - POLITICO
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Old 5th Oct 2021, 22:54
  #331 (permalink)  
 
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What about the CH-46, CH-47, SH-3, UH-60, and all their derivatives that have been operational for about six decades? Does The Sultan judge these to be legendary acquisition failures as well?
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Old 6th Oct 2021, 00:26
  #332 (permalink)  
 
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If it looks right, it'll fly right.
And that thing don't look right.
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Old 6th Oct 2021, 03:49
  #333 (permalink)  
 
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What about the CH-46, CH-47, SH-3, UH-60, and all their derivatives that have been operational for about six decades? Does The Sultan judge these to be legendary acquisition failures as well?
Heli

All the types mentioned are 50+ year old designs developed when Sikorsky and Boeing had competent engineering and management. The latest string of problematic designs from both companies shows they have lost the expertise needed to field a design worthy of being selected for FLRAA. The pathetic SB-1 testing program confirms this.
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Old 6th Oct 2021, 14:57
  #334 (permalink)  
 
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The choice of words by “the sultan” are interesting… it’s almost sounds as if he is afraid to loose his job because of the competition….

To me both programs are plain silly for a tactical vertical lift machine. They will never be able to replace a simple, cheap Blackhawk in terms of survivability/agility and especially costs. I don’t get why it is so important for the army to fly fast… is it plain envy to the airforce guys? It’s nice for semi-strategic movements to get the Christmas presents quickly from the main base to the various FOBs, but it will be interesting to see if a Valor OR defiant will still fly 200+ Kts, Limited to 20-30ft AGL due to a radar threat, or if they then slow down to half of that, like any other helicopter…. Then the government has payed an awful lot of money for the slightly quicker transport of MREs….
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Old 6th Oct 2021, 19:18
  #335 (permalink)  
 
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Choice of words are interesting indeed: “ when Sikorsky and Boeing had competent engineering and management.“.

But wait, what does the new Bell Invictus replicate?……..why, its the Boeing/Sikorsky Comanche! What is interesting is that the Bell Invictus design has dropped the copy of the canted, ducted fan tail of Comanche in favor of a conventional canted tail. Wondering why they did that as the Comanche ducted fan was quite powerful-good for 100 kias right sideward flight and capable of flying forward at 80 kias, swapping ends to fly backwards at 80 kias while staying in formation with the photo chase, then after the Ch Test Pilot from Euro-Copter was suitably impressed, Mr. Lappos returned it to a conventional, nose in front mode. Why would you drop such a capability? ( But then, truth be told, this was SA’s third ducted tail, with previous successful efforts on the S-67 and S-76 preceding, so for Bell it was going to be a first, and doubly so for the canted aspect, which had been flown on the S-61R and CH-53D before productionizing on the S-70 and CH-53E lines ).
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Old 6th Oct 2021, 19:51
  #336 (permalink)  
 
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John

Remind me how many $billion the development portion of the Comanche was projected to overrun the original budget when cancelled? Wasn't the projected recurring unit cost $70m in 2005 dollars? You do make a point how will SB produce a more complex design in 2025 for under $70m apiece? What about FARA? How is the Raider X going to be cheaper than the 2005 Comanche? I think the goal for FARA is under $30m apiece in 2025 dollars? Thats a long way from $70m.

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Old 6th Oct 2021, 21:20
  #337 (permalink)  
 
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Originally Posted by JohnDixson View Post
Choice of words are interesting indeed: “ when Sikorsky and Boeing had competent engineering and management.“.

But wait, what does the new Bell Invictus replicate?……..why, its the Boeing/Sikorsky Comanche! What is interesting is that the Bell Invictus design has dropped the copy of the canted, ducted fan tail of Comanche in favor of a conventional canted tail. Wondering why they did that as the Comanche ducted fan was quite powerful-good for 100 kias right sideward flight and capable of flying forward at 80 kias, swapping ends to fly backwards at 80 kias while staying in formation with the photo chase, then after the Ch Test Pilot from Euro-Copter was suitably impressed, Mr. Lappos returned it to a conventional, nose in front mode. Why would you drop such a capability? ( But then, truth be told, this was SA’s third ducted tail, with previous successful efforts on the S-67 and S-76 preceding, so for Bell it was going to be a first, and doubly so for the canted aspect, which had been flown on the S-61R and CH-53D before productionizing on the S-70 and CH-53E lines ).
I’m usually content to let people carry on in pissing contests, but thought I’d add for the record that Bell flew a ducted tail rotor on the Model 222 and the Model 407, so has that flight test data to use. The 525 also has a canted tail rotor, so they have some experience with that effect as well. As for the reasons why it was dropped, I assume it was power required in a hover, weight, and/or drag. There are some agility and acoustic advantages to a ducted tail rotor for sure, but when you are weight and or power limited (as even the Army seems to admit is a common concern for FARA competitors) it’s hard to beat lower disk loading for conversion of HP to thrust and less airframe structure in tail for weight and drag.

A few seconds of searching can dig up the 407 tail fan and there are images of the 222 one with a little more digging.
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Old 7th Oct 2021, 00:06
  #338 (permalink)  
 
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Originally Posted by casper64 View Post

To me both programs are plain silly for a tactical vertical lift machine. They will never be able to replace a simple, cheap Blackhawk in terms of survivability/agility and especially costs. I don’t get why it is so important for the army to fly fast… is it plain envy to the airforce guys? It’s nice for semi-strategic movements to get the Christmas presents quickly from the main base to the various FOBs, but it will be interesting to see if a Valor OR defiant will still fly 200+ Kts, Limited to 20-30ft AGL due to a radar threat, or if they then slow down to half of that, like any other helicopter…. Then the government has payed an awful lot of money for the slightly quicker transport of MREs….
Sadly I think this take is very much on the money.
The Army does not have any coherent vision of what the next conflict may look like, so they chose to raise the bar on some well recognized aircraft performance metrics, even though these are militarily irrelevant.
Other less visible parameters, such as hours of maintenance per flight hour, even though more relevant, seem to have been ignored entirely.
I expect the entire effort to be cancelled, joining a long list of aborted Army development efforts.
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Old 7th Oct 2021, 02:17
  #339 (permalink)  
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Originally Posted by etudiant View Post
Sadly I think this take is very much on the money.
The Army does not have any coherent vision of what the next conflict may look like, so they chose to raise the bar on some well recognized aircraft performance metrics, even though these are militarily irrelevant.
Other less visible parameters, such as hours of maintenance per flight hour, even though more relevant, seem to have been ignored entirely.
I expect the entire effort to be cancelled, joining a long list of aborted Army development efforts.
Based on this logic, the US Army should have stayed with the Huey like the US Marines.

The Bell (independent of Boeing) V-280 Valor is not a V-22 when it comes to cost per flight hour. The V-280 is based on Bell developed commercial aircraft technology, not 40 year old V-22 military technology. Commercial customers care a lot more about cost per flight hour than the military.
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Old 7th Oct 2021, 06:32
  #340 (permalink)  
 
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Originally Posted by CTR View Post
Based on this logic, the US Army should have stayed with the Huey like the US Marines.

The Bell (independent of Boeing) V-280 Valor is not a V-22 when it comes to cost per flight hour. The V-280 is based on Bell developed commercial aircraft technology, not 40 year old V-22 military technology. Commercial customers care a lot more about cost per flight hour than the military.
No, you can have some speed increase with modern rotor systems, clearly range increase is interesting, but this can also be achieved with more modern engines/technologies. And clearly subjects like C4I, operation in DVE, etc are relevant… I just don’t see the “speed thing” and it’s crazy configurations to reach this goal, with all its drawbacks as really relevant.
Regarding “commercial technology” you mean that aircraft that is 20 years in development and still not certified and will be crazy expensive as well, only filling a niche market?
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