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Sikorsky SB-1 flies for first time

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Sikorsky SB-1 flies for first time

Old 16th Nov 2019, 17:10
  #101 (permalink)  
 
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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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Old 16th Nov 2019, 21:01
  #102 (permalink)  
 
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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.
So minimum to be considered is 250 with desired 280. The Marines minimum is 280 with desired 320 kts.
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Old 16th Nov 2019, 21:18
  #103 (permalink)  
 
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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.

Last edited by The Sultan; 16th Nov 2019 at 21:31.
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Old 17th Nov 2019, 08:27
  #104 (permalink)  
 
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Originally Posted by The Sultan View Post
Fairings look more like they will add drag.
Find the error....

Aerodynamics by looking at pictures.
Scrap all CFD and wind tunnel....

Folks never cease to amaze me.
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Old 17th Nov 2019, 09:52
  #105 (permalink)  
 
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Whilst aerodynamics is a complex subject well above the pay grade of most mere mortals, you donít need a wind tunnel to determine a brick is aerodynamically challenged
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Old 17th Nov 2019, 10:10
  #106 (permalink)  
 
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Originally Posted by Bell_ringer View Post
Whilst aerodynamics is a complex subject well above the pay grade of most mere mortals, you donít need a wind tunnel to determine a brick is aerodynamically challenged
That actually depends quite a bit on flow direction and Reynolds number
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Old 17th Nov 2019, 15:45
  #107 (permalink)  
 
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Originally Posted by The Sultan View Post
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.
Oh, I agree that the Army is ready for a tilt rotor and that such an aircraft is the right technical solution for long range assault... I'm just suggesting what Sikorsky's next strategy might be.

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.
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Old 17th Nov 2019, 23:47
  #108 (permalink)  
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Originally Posted by SplineDrive View Post
Defiant might have enough installed power to make its targets... let's see if it has the funding and patience also required.
The problem with using excessive power to achieve speed and payload is that there is always a price. SFC (fuel consumption) always suffers. This is one of the limitations of X-2 technology. It is hard to beat getting on wing (as on a Tiltrotor) for maximum range.
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Old 11th Dec 2019, 01:04
  #109 (permalink)  
 
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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.
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Old 11th Dec 2019, 14:11
  #110 (permalink)  
 
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Originally Posted by The Sultan View Post
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.
Popular Science: what credibility do you give to that mag?
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Old 11th Dec 2019, 16:19
  #111 (permalink)  
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Anticipation is making me wait. Itís keeping me waiting....

Anticipation is making me wait. Itís keeping me waiting....

With all respects to Carly Simon ;-)

Landing gear still down and pusher prop still not turning.
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Old 12th Dec 2019, 00:14
  #112 (permalink)  
 
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Popular Science: what credibility do you give to that mag?
Lone,

None, but it appears the best Sikorsky can pay to publish bogus feel good stories.
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Old 12th Dec 2019, 12:47
  #113 (permalink)  
 
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Originally Posted by CTR View Post
Landing gear still down and pusher prop still not turning.
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 theyíre doing something to keep the transmission at a reasonable operating temperature when itís not spinning so when power is quickly clutched in, the system isnít cold.
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Old 12th Dec 2019, 15:15
  #114 (permalink)  
 
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Originally Posted by SplineDrive View Post
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 theyíre doing something to keep the transmission at a reasonable operating temperature when itís not spinning so when power is quickly clutched in, the system isnít cold.
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.
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Old 12th Dec 2019, 15:24
  #115 (permalink)  
 
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Originally Posted by The Sultan View Post
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.
Perhaps they designed in a mitigation and are just testing it as they intend to fly. In any case, thereís probably some learning that will happen at the rear end of the aircraft. Hope they publish some papers!
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Old 12th Dec 2019, 16:57
  #116 (permalink)  
 
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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!
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Old 12th Dec 2019, 17:02
  #117 (permalink)  
 
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Originally Posted by IFMU View Post
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!
A transmission isnít 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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Old 13th Dec 2019, 03:26
  #118 (permalink)  
 
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Originally Posted by SplineDrive View Post
A transmission isnít 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.
We didn't have a clutch on the X2. But you would clutch up the prop at flat pitch, not MCP. Once it was clutched up you would roll in the prop pitch and start ramping up the power. I am not sure I see a valid concern.
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Old 13th Dec 2019, 15:34
  #119 (permalink)  
 
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Originally Posted by The Sultan View Post


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.
Talk about an armchair expert...
Words fail me...

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Old 13th Dec 2019, 16:44
  #120 (permalink)  
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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 didnít 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 didnít 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.

Last edited by CTR; 13th Dec 2019 at 17:01.
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