Sikorsky SB-1 flies for first time
CTR
From a synopsis of the FLRAA requirements:
So minimum to be considered is 250 with desired 280. The Marines minimum is 280 with desired 320 kts.
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.
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 22:31.
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 
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.
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.
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.
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.
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.
With all respects to Carly Simon ;-)
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 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.
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.
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!
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!
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!
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 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.
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.
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.
Last edited by CTR; 13th Dec 2019 at 18:01.
