Originally Posted by riff_raff
(Post 10575778)
Haven't seen the actual RFI document yet. Responses to some sections are due Nov. 22 and responses to other sections are due Jan. 1. Be interesting to see if they get any proposals for innovative propulsion/aero concepts that meet their objectives and truly merit funding. Giving serious funding to small companies to rapidly develop innovative concepts applicable to AURA objectives is also a good way to keep the existing JMR/FVL teams on their toes.
After being in this business for a couple of decades, I can tell you that if the 295+ knot speed is firm, it won't be an edgewise flow rotor. It's possible to hit those speeds, but not efficient enough to have good range and be a balanced platform. The shipboard compatibility requirements and exactly which hangers it needs to fit in will also heavily drive the design for AURA. |
Originally Posted by SplineDrive
(Post 10576230)
I think the industry is getting a little tired. One of these programs needs to become a fully funded program of record and not a one-off cost share project. .
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Upon successful PSTB endurance envelop expansion, we expect to be positioned to quickly expand the aircraft flight envelope later this summer I have been following these programs for going on 10 years now, and have been suspicious of most of the claims from a technical standpoint nearly the entire time (hell just look at my post history). I cannot fathom how there has been almost zero pressing done by the aerospace and defense community and media journalists regarding the repeated failures, complete opacity, and outright lying that has come from Sikorsky throughout. Nearly weekly there are news stories regarding FVL with headlining pictures displaying Defiant and breathless commentary about how its a leading contender for FLRAA. Does anyone else feel like they are taking crazy pills reading these pieces year in and year out? Will Defiant even fly again by year end now? Even the laughable historical lifetime combined flight rate for all ABC aircraft of 1 hour / month far exceeds what Defiant has achieved thus far. |
Originally Posted by SansAnhedral
(Post 10577628)
Today is the first day of fall. And yet again, Sikorsky misses another milestone with this program. Literally every single date, whether it was contractually driven or self-imposed, has been missed or slipped by both the Defiant and Raider teams. It's simply mind boggling.
I have been following these programs for going on 10 years now, and have been suspicious of most of the claims from a technical standpoint nearly the entire time (hell just look at my post history). I cannot fathom how there has been almost zero pressing done by the aerospace and defense community and media journalists regarding the repeated failures, complete opacity, and outright lying that has come from Sikorsky throughout. Nearly weekly there are news stories regarding FVL with headlining pictures displaying Defiant and breathless commentary about how its a leading contender for FLRAA. Does anyone else feel like they are taking crazy pills reading these pieces year in and year out? Will Defiant even fly again by year end now? Even the laughable historical lifetime combined flight rate for all ABC aircraft of 1 hour / month far exceeds what Defiant has achieved thus far. Hence all news reports are slightly massaged press releases, rather than independent opinions. Bad for the industry and bad for the tax payer, but short term profitable. Imho, the relevant precedent is the pre WW2 French defense industry, it produced some truly superb gear such as the Char 2bis, was hugely profitable and an abject failure from a national perspective. |
Sept 2019 was suppose to be the conclusion of the FVL assault tech demo phase. It looks like the Marines are sticking to that with their AURA schedule of having RFI response in by Jan 2020. Defiant will obviously have no positive influence on whatever Boeing submits. Meanwhile the V-280 is racking up flights doing demo’s or training with a lot of low altitude fully converted high speed passes and helicopter mode agility maneuvers. Quite impressive relative to speed, low acoustic signature, and looks. |
Interesting article regarding recent SB1 model wind tunnel testing
NFAC tests next-generation military helicopter | Aerotech News & Review “From the NFAC perspective, the wind tunnel test was successful,” Wang said. |
2019 is a little late to do wind tunnel testing on a design done in 2015. It would appear these tests were trying to determine how to fix the problems uncovered on the S-97 and carried over to the Defiant which has limited it to basically 200 kts (60 kts short of the X-2). We should know at AUSA in four days if they are making design mods to the Defiant to get closer to the 280 kt cruise required or scrapping the program outright. |
Originally Posted by SansAnhedral
(Post 10591226)
Interesting article regarding recent SB1 model wind tunnel testing
NFAC tests next-generation military helicopter | Aerotech News & Review One wonders if a seemingly unnecessary qualifying statement like that has some implications. Stuff like that happens in the VTOL business. I remember the Rockwell XV-12, a design based on the concept that a jet flux could entrain considerable ambient air, enough to add about 20% to the lift produced. It worked fine in scale models, but not when scaled up to full size. Perhaps something similar is happening here. |
Progress?
From the second day AUSA press release: The SB>1 Defiant is back in the air, reaching speeds of 20 knots on its fourth test flight. It should reach the Army-mandated minimum speed of 230 knots by the end of March, “if we have no other significant things we learn along the way,” Boeing program manager Ken Eland said here this morning. |
Originally Posted by The Sultan
(Post 10595641)
From the second day AUSA press release: I guess this might be considered progress. A good PR headline would have been “SB-1 Doubles Flight Envelope in One Leap.” So six months to get to 20 knots and another 4 to 6 weeks before they will attempt a fifth flight. They also state they will reach 230 kts plus by March, but hedge by saying what year. |
Originally Posted by The Sultan
(Post 10595641)
From the second day AUSA press release: I guess this might be considered progress. A good PR headline would have been “SB-1 Doubles Flight Envelope in One Leap.” So six months to get to 20 knots and another 4 to 6 weeks before they will attempt a fifth flight. They also state they will reach 230 kts plus by March, but hedge by not saying what year. https://cimg7.ibsrv.net/gimg/pprune....aa81d63247.gif |
Who Writes This Stuff?
Just think someone at Sikorsky/Boeing is congratulating themselves with getting this info in the press: https://breakingdefense.com/2019/10/...-inches-ahead/ They seem to think their continued “development” of the Defiant until the end of 2020 will be beneficial to the programs it was applicable to. Problem is the Marines want responses on their program no later than January and the Army in the first quarter of 2020 while they will still be struggling to get above 120 knots. Got to wonder if the Marines/Army will say enough and save a billion dollars or so by selecting the V-280 derived offering from Bell and fast track development and fielding. |
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Any New Flight Test Status Updates?
Any new Sikorsky Defiant flight test status news? It has been a month with no press releases or leaked intel. Just curious, not trolling or looking to rehash history. |
Originally Posted by CTR
(Post 10619111)
Any new Sikorsky Defiant flight test status news? It has been a month with no press releases or leaked intel. Just curious, not trolling or looking to rehash history. |
Fairings look more like they will add drag.
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Originally Posted by The Sultan
(Post 10619382)
Fairings look more like they will add drag.
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IFMU Did the fairings on the S-97 work out as expected? The 97 is 50+ knots short of design speed not due to its horrendous vibration, but because of drag. As referenced elsewhere Sikorsky was back in the wind tunnel this year trying to come up with a solution. As the SB-1 fairings look even worse than the 97 it appears that testing was a bust. Will be surprised if they make it much past 200 knots, which is now 80 knots short of the new minimum cruise for the FLRAA. |
Thanks for the Update
Splinedrive, Thanks for the link to the video. It didn’t come up on my usual searches. Sultan, I believe the 280 KT requirement is a USMC AURA spec, not currently a US Army spec. It would be a shame however if the Army for a second time opted out of a Tiltrotor aircraft. |
Fairings can be pretty large and bluff body looking and still reduce drag, so I’m confident that SB>1’s rotor fairings will be an improvement over the comparatively inelegant metal structure that are the rotor hubs. Raider’s hubs are a different structural solution and fair more compactly.
I don’t think Raider is 50+ knots off it’s target speed... it was never advertised to hit the speeds of the X-2 Demonstrator. And I can think of ways that vibration can limit top speeds if the high 4P vibes leak into the drivetrain or other components that have loads that directly scale with speed. So it’s performance miss could be both drag and vibration limited. That said, it’s still a sleek airframe with one of the slickest engine installations I’ve ever seen. |
If the Army opts out of a tilt rotor then they’ll be settling for an ITE upgraded Blackhawk or somehow decide an S-92 variant is what they wanted all along.
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CTR From a synopsis of the FLRAA requirements: The Army wants the FLRAA to have a top speed of 250 knots, or more than 285 miles per hour, and potentially up to 280 knots, or more than 320 miles per hour. The maximum speed of the Army’s latest iteration of the Black Hawk, the UH-60M, is still under 200 miles per hour. |
Spline All of the attention the Army has given the V-280 indicates they are ready for a tilt rotor. Add to that that the Marines spec for a new medium can only be met by a tilt rotor the Army will not want to cede leadership of the program. As for the 92: the last military variant worked out to $200M apiece, far above the $42m target FLRAA unit cost. On the 97 the max speed was suppose to be 240 knots which in the commercial world requires you to demo 267 knots (+11%). The 97 struggles to get above 180kts and the refined scout/attack derivative is now billed as having only a 205 kt top speed. So I stand by the 50 kts short. |
Originally Posted by The Sultan
(Post 10619382)
Fairings look more like they will add drag.
Aerodynamics by looking at pictures. Scrap all CFD and wind tunnel.... Folks never cease to amaze me. |
Whilst aerodynamics is a complex subject well above the pay grade of most mere mortals, you don’t need a wind tunnel to determine a brick is aerodynamically challenged :} |
Originally Posted by Bell_ringer
(Post 10620332)
Whilst aerodynamics is a complex subject well above the pay grade of most mere mortals, you don’t need a wind tunnel to determine a brick is aerodynamically challenged :} |
Originally Posted by The Sultan
(Post 10620069)
Spline All of the attention the Army has given the V-280 indicates they are ready for a tilt rotor. Add to that that the Marines spec for a new medium can only be met by a tilt rotor the Army will not want to cede leadership of the program. As for the 92: the last military variant worked out to $200M apiece, far above the $42m target FLRAA unit cost. On the 97 the max speed was suppose to be 240 knots which in the commercial world requires you to demo 267 knots (+11%). The 97 struggles to get above 180kts and the refined scout/attack derivative is now billed as having only a 205 kt top speed. So I stand by the 50 kts short. As for speed, I see how you got 50 knots short now... it has definitely missed the target very significantly. The Raider-X has grown in gross weight and drag more than horsepower, so I fully expect a slower cruise and top speed. So much so that the complexity of the configuration isn't worth the cost and payload hit if a slick and optimized conventional helicopter can achieve similar speed targets. Defiant might have enough installed power to make its targets... let's see if it has the funding and patience also required. |
Originally Posted by SplineDrive
(Post 10620522)
Defiant might have enough installed power to make its targets... let's see if it has the funding and patience also required.
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How much did Sikorsky pay for this? From this week, but same old video. Apparently no real progress in 9 months of flight testing. |
Originally Posted by The Sultan
(Post 10636831)
How much did Sikorsky pay for this?
https://m.youtube.com/watch?v=YK26VfUyMlc From this week, but same old video. Apparently no real progress in 9 months of flight testing. |
Anticipation is making me wait. It’s keeping me waiting....
Anticipation is making me wait. It’s keeping me waiting.... With all respects to Carly Simon ;-) Landing gear still down and pusher prop still not turning. |
Popular Science: what credibility do you give to that mag? None, but it appears the best Sikorsky can pay to publish bogus feel good stories. |
Originally Posted by CTR
(Post 10637350)
Landing gear still down and pusher prop still not turning. |
Originally Posted by SplineDrive
(Post 10638072)
I wonder how that propellor gearbox likes sitting stationary in a vibrating environment? In a non-rotating state, some of the gear mesh and bearing rolling element contacts are direct metal-metal with no fluid film separating the surfaces. Could eventually get fretting damage. Presumably they’re doing something to keep the transmission at a reasonable operating temperature when it’s not spinning so when power is quickly clutched in, the system isn’t cold.
The tail is a severe vibratory environment on any rotorcraft. More so on an ABC type with inherently brutal vibration levels. As all this is common knowledge, you would think Sikorsky would run the tail at no thrust while they expand their hover envelope if they could. Points to a serious drive system issue. |
Originally Posted by The Sultan
(Post 10638163)
The tail is a severe vibratory environment on any rotorcraft. More so on an ABC type with inherently brutal vibration levels. As all this is common knowledge, you would think Sikorsky would run the tail at no thrust while they expand their hover envelope if they could. Points to a serious drive system issue. |
The X2 vibe levels were not brutal, and in fact were most benign at hover. This is when you would not be spinning the rear gearbox.
Please name one gearbox where the oil is warmed up prior to running it up. I've never seen that in any helicopter or car. One of my friends flew hueys in Antarctica and they would drain the oil out of the gearbox and engine so they could bring it inside overnight, but other than that I think you guys just like making things up! |
Originally Posted by IFMU
(Post 10638234)
The X2 vibe levels were not brutal, and in fact were most benign at hover. This is when you would not be spinning the rear gearbox.
Please name one gearbox where the oil is warmed up prior to running it up. I've never seen that in any helicopter or car. One of my friends flew hueys in Antarctica and they would drain the oil out of the gearbox and engine so they could bring it inside overnight, but other than that I think you guys just like making things up! |
Originally Posted by SplineDrive
(Post 10638242)
A transmission isn’t usually hit with MCP torque 15 seconds after it starts the first rotation. If the clutching process is going to take a few minutes (same as starting turbines, going to flight idle, checking the lists, ready for take off, go) well, sure. But I imagine that the desire is to clutch the prop in at a much faster rate than that.
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Originally Posted by The Sultan
(Post 10638163)
Good point. Another design flaw to add to the list. I have seen a bearing which had Brinelling (subtle impact damage to balls and races due to installation or handling errors) which spalled at locations around the circumference of the races at ball spacing intervals well before the overhaul/inspection interval. We have also seen what happens to an Airbus 225 when a transmission is dropped during shipping and the bearings not replaced (not proven, but a leading contender to have resulted in separation of the rotor). The tail is a severe vibratory environment on any rotorcraft. More so on an ABC type with inherently brutal vibration levels. As all this is common knowledge, you would think Sikorsky would run the tail at no thrust while they expand their hover envelope if they could. Points to a serious drive system issue. Words fail me... |
Truth is somewhere in between polar positions
For the purpose of safety my group designed a concept for de clutching a conventional anti torque tail rotor on the ground. Of course unlike the X-2 concept we needed to re engage the tail rotor prior to take off. There was never a concern on bearing fretting when de clutched. We didn’t brake to halt rotation, we used max pitch to dissipate inertia. Therefore there was always go to be creep from clutch drag and external forces. This was actually a concern to some, but we didn’t want the added weight and complexity of a brake. Our tail gearbox was splash lube. Getting to an acceptable operating temperature came quickly after less than a couple minutes. Less than the time to complete preflight. On the X-2 they can engage after take off and wait a bit if required before increasing pitch. We never got beyond the test bench stage. No technology issues. Just cost and weight impacts were unacceptable. |
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