V-280 wins US ARMY FLRAA contract

[noneofyourbusiness]

Hold onto your butt.



Remember that the S-97 pusher is wet clutched so it does not stop rotating. Defiant used a dry clutch to attempt to demonstrate the safety aspect of stopping it during ground ops. Unfortunately that clutch sh*t the bed and the Army knows all about it.

At a gas turbine company, I sometimes worked on design of high power aerospace clutches. The wet clutch is always superior to a dry clutch. It is possible to design the Raider wet clutch to be unclutched while idling on the ground, so it sounds like the Raider clutch design is a botch job. A brake would still be needed on the prop, and the clutch plates would need to have spring separators, to make sure the plates separated when the clamp force was removed. A dry clutch has a much much greater wear rate of the clutch plates. Therefore the plates have to be very thick. Then the clamp load has to be massively increased because there are fewer plates. So the dry clutch ends up just as large or larger than the wet clutch. Oil must continuously be supplied to the clutch bearings even with a "dry" clutch. Likely Sikorsky did not account for the very high wear rate of the dry clutch plates. Think of needing 1.5 inch thick plates instead of .125 inch thick clutch plates. The thermal management of the dry clutch requires shielding around the red hot dry clutch plates, to keep from coking the bearings oil, or even starting a fire. Cooling air is required, and the best source here is engine bleed air. Do everything right, and the dry clutch still has a much shorter clutch plate life than a wet clutch.

The Sikorsky X-wing clutch design, scaled to size, would work just fine.

[CTR]

Another large benefit of a wet clutch over a dry clutch is more predictable coefficient of friction. The highest risk of damage in this clutch application is during engagement with the main rotors spinning and the propeller stopped. This must be achieved smoothly to prevent damage to the drive system.

With a dry clutch, the coefficient of friction is higher than on a wet clutch, and dry friction can change significantly with wear and temperature. This makes safety engaging a dry clutch in this application much more problematic.

[SplineDrive]

At a gas turbine company, I sometimes worked on design of high power aerospace clutches. The wet clutch is always superior to a dry clutch. It is possible to design the Raider wet clutch to be unclutched while idling on the ground, so it sounds like the Raider clutch design is a botch job. A brake would still be needed on the prop, and the clutch plates would need to have spring separators, to make sure the plates separated when the clamp force was removed.

[paragraph removed]

The Sikorsky X-wing clutch design, scaled to size, would work just fine.

Raider's prop is just a foot or so from the YT706 exhaust, so it likely always spins, by design, to prevent excessive heating on the prop blades (if the prop were braked).

"X-Wing"... there's a technological dead end we haven't heard of in a long, long time.

[noneofyourbusiness]

Raider's prop is just a foot or so from the YT706 exhaust, so it likely always spins, by design, to prevent excessive heating on the prop blades (if the prop were braked).

"X-Wing"... there's a technological dead end we haven't heard of in a long, long time.
And the clutch design was fantastic, well before my time. Comparing it to some other "modern" clutches. Does JSF ring a bell?

I think is more likely to be an oversight in design to let the blades keep rotating on the ground. Not sure you would get much cooling effect with a relatively slow rpm rotation of the blades. The engine would be at ground idle condition, so maybe the exhaust is relatively cool.

If Sikorsky always needed to have the clutch engaged, there would be no reason to have a clutch.

I am guessing whoever designed the clutch wasn't aware you need spring separators to "unstick" the clutch plates. And maybe Sikorsky did not want to add the weight of a brake.

If Sikorsky needed to always keep the clutch engaged, there would be no reason to have a clutch.

[noneofyourbusiness]

Another large benefit of a wet clutch over a dry clutch is more predictable coefficient of friction. The highest risk of damage in this clutch application is during engagement with the main rotors spinning and the propeller stopped. This must be achieved smoothly to prevent damage to the drive system.

With a dry clutch, the coefficient of friction is higher than on a wet clutch, and dry friction can change significantly with wear and temperature. This makes safety engaging a dry clutch in this application much more problematic.
Exactly.

[SplineDrive]

And the clutch design was fantastic, well before my time. Comparing it to some other "modern" clutches. Does JSF ring a bell?

I think is more likely to be an oversight in design to let the blades keep rotating on the ground. Not sure you would get much cooling effect with a relatively slow rpm rotation of the blades. The engine would be at ground idle condition, so maybe the exhaust is relatively cool.

If Sikorsky always needed to have the clutch engaged, there would be no reason to have a clutch.

I am guessing whoever designed the clutch wasn't aware you need spring separators to "unstick" the clutch plates. And maybe Sikorsky did not want to add the weight of a brake.

If Sikorsky needed to always keep the clutch engaged, there would be no reason to have a clutch.

“Declutching” down to a slow rpm basically eliminates the blade tip noise from the prop which, like a tail rotor, is far worse than the main rotor noise. Being low to the ground, blade tip erosion from a slow spinning prop is also improved. I think for a combat scout there are operational reasons to prefer a clutchable prop. Reduced power loss from prop profile drag as well. Is all this worth the cost/weight/complexity of a clutchable prop? Completely fair question. Raider included the technology as a demonstrator. I guess it’s possible it is eliminated on Raider-X as not being worth the penalties. We’ll have to see.

[60FltMech]

With upturned exhaust on H-60 rotor blades need to be positioned on centerline to avoid “charring” during rotor brake starts. I suppose even slowly rotating the pusher prop would help, but seems to be a recipe for disaster for personnel operating around the aircraft.

I’ve heard that the pusher on Raider X is electric driven, I assume clutching of the drive system would still be required?

I used to be pretty solid in the co-axial camp but the more I hear about the challenges associated with maturing the technology the less suitable it appears.

Would be interesting to see the engineering challenges both designs face discussed in detail by some of the members that have engineering backgrounds, think I’ll start a new thread on that in a bit.

FltMech

[noneofyourbusiness]

“Declutching” down to a slow rpm basically eliminates the blade tip noise from the prop which, like a tail rotor, is far worse than the main rotor noise. Being low to the ground, blade tip erosion from a slow spinning prop is also improved. I think for a combat scout there are operational reasons to prefer a clutchable prop. Reduced power loss from prop profile drag as well. Is all this worth the cost/weight/complexity of a clutchable prop? Completely fair question. Raider included the technology as a demonstrator. I guess it’s possible it is eliminated on Raider-X as not being worth the penalties. We’ll have to see.
Certainly there are good reasons to have a clutched prop. Sikorsky has sold this as a major advantage. Either 1) they did not execute the design well or 2) Your concern, that they may have had to keep the prop engaged for blade cooling reasons.

[noneofyourbusiness]

With upturned exhaust on H-60 rotor blades need to be positioned on centerline to avoid “charring” during rotor brake starts. I suppose even slowly rotating the pusher prop would help, but seems to be a recipe for disaster for personnel operating around the aircraft.

I’ve heard that the pusher on Raider X is electric driven, I assume clutching of the drive system would still be required?

I used to be pretty solid in the co-axial camp but the more I hear about the challenges associated with maturing the technology the less suitable it appears.

Would be interesting to see the engineering challenges both designs face discussed in detail by some of the members that have engineering backgrounds, think I’ll start a new thread on that in a bit.

FltMech
They would not necessarily need a clutch. They could drive, with a variable speed motor, the prop pretty much any speed they want down to very low rpm. The lower the rpm they want, the heavier the motor, unless they added a gearbox and clutch to the motor. An electric generator is also required with the electric motor, so this is very energy inefficient (perhaps 70%) compared to a mechanical drive (98-99%), and heavy. Additional cooling would be required the handle the energy losses of the electric motor and generator.

[noneofyourbusiness]

A man named "spyclip" posted this on The Drive. Seems very knowledgeable, probably a former engineering insider at Sikorsky:

Spyclip
1 July, 2022

No vibration issues? Are you serious? The vibration is the entire reason they have flown only a few dozen hours in 3 years of flight testing and only allowed a single sortie flown by Army test pilots at low speed. The AVC system approach has been a complete failure (again, just like S-97), and the dynamics of another insufficiently stiff fuselage for the propulsor drive shaft make the SB1 just as much of a paint shaker as S-97. Pilots can't even read their instruments in these designs due to the vibration. SB1 has hit absolutely ZERO of its own self imposed targets in demonstration. Sikorsky's own target was a cruise speed of 250 kt at MCP, while in the end they could only manage a momentary 247 kt at CRP (130%). Swing and a miss on drag estimates, and vibration levels at high speed put a cap on that. To date they have not demonstrated any Vector Control maneuvers despite touting it in every single mention of the technology. Go watch the videos, there is no level acceleration or deceleration - its always nose down gaining speed like a normal helicopter. And they most certainly have not shown Defiant holding nose high or nose low attitude in hover, much less any ADS-33 level 1 handling maneuvers outside of a lumbering slalom. V-280 demonstrated high rate level 1 hover pitch, roll, and yaw multiple times. Sikorsky hasn't even done a hover pedal yaw turn in Defiant because they have next to no yaw authority with differential torque and it would be embarrassingly slow.

]https://www.thedrive.com/the-war-zone/raider-x-lockheed-martin

[CTR]

What Lockheed and Boeing lack in engineering successes, they make up with a strong lobbying presence in Washington, and US representatives willing to bend to their will.

[noneofyourbusiness]

"Spyclip" at secret projects:

8 May 2023 (https://www.secretprojects.co.uk/threads/jmr-joint-multi-role-fvl-future-vertical-lift-programs.13812/post-596045)

History suggests that RaiderX will suffer the exact same performance issues as all other rigid rotor coaxial designs. Its hard to imagine a situation where the Army would select a fundamentally flawed platform, especially in this case where the aircraft will be given to the Army to do the test flying. Think about how Sikorsky has, to date, still never let an Army XP be PIC on the S-97. And also how there were no Army XP on Defiant until the absolute last minute on a single sortie before it went radio silent and likely retired.

There'll be no place to hide the weenie this time.

With the competitive prototype aircraft both designed around a single engine, RaiderX will be objectively outperformed by Invictus in flight test. If the Army pivots, as expected, to a twin with a larger footprint allowable then it negates the entire CP aircraft exercise and all the losing bidders for the demo will have a field day in court. Combined with the ongoing schedule slips of T901, I do not see how this entire SNAFU does not get canceled before EOY 2023.

https://www.secretprojects.co.uk/threads/jmr-joint-multi-role-fvl-future-vertical-lift-programs.13812/page-63

[CTR]

This is the first I ever saw this type of parody humor. When playing the video on a phone, you may need to hold the phone vertically to see the full image.

All the audio is in German, but the close caption is a parody of what Hitler would say about Bell winning FLRAA, if he was in charge of Sikorsky.

https://www.captiongenerator.com/v/2284390/hitler-reacts-to-the-bell-v-280-winning-flraa.

[Stuart Sutcliffe]

This is the first I ever saw this type of parody humor. When playing the video on a phone, you may need to hold the phone vertically to see the full image.

All the audio is in German, but the close caption is a parody of what Hitler would say about Bell winning FLRAA, if he was in charge of Sikorsky.
It may be the first time you have seen this particular video clip being used this way, but it has been used thousands of times like this over many, many years, to the point of being tiresome.

[CTR]

It may be the first time you have seen this particular video clip being used this way, but it has been used thousands of times like this over many, many years, to the point of being tiresome.

Stuart,

To each their own. Humor is a very personal thing. I however, found it hilariously funny in a Steinfeld episode way. It was also almost spot on accurate in the engineering technical aspects.

Finally, after the legal and political actions of Lockheed following their loss to Bell, any feeling of shame in laughing at their current situation is nonexistent.

[Lonewolf_50]

It may be the first time you have seen this particular video clip being used this way, but it has been used thousands of times like this over many, many years, to the point of being tiresome.
I thought it was both funny and spot on. One of the better applications of that meme show.

[Copter Appreciator00]

The Bell V-280 was always better than the Sikorsky SB-1, faster and more fuel efficient and smaller. BUT i wonder if the V280, which will be closer to battle spaces than the V-22, but i thought of an issue which made my spill my drink. The V280 will be the successor to the UH-60 and likely the UH-1Y, so it will fly and land closer to the enemy just as the black hawk did, so the likelihood of bullets strikes. WHAT IF, while in forward flight, one of the rotating mechanism for one of the two rotors systems was damaged by a bullet impact, and one of the rotating thing could not pivot - ??? If a helicopter gets hit, it can do auto rotate, or just lower its speed and land. But if the Valor gets hit in helicopter mode, it can land. I think the driveshaft is what tilts the rotor housing, but could the propellors be stuck in forward mode... is this a possible malfunction? What happens then, Valor can't land with the props forward..

[Commando Cody]

The Bell V-280 was always better than the Sikorsky SB-1, faster and more fuel efficient and smaller. BUT i wonder if the V280, which will be closer to battle spaces than the V-22, but i thought of an issue which made my spill my drink. The V280 will be the successor to the UH-60 and likely the UH-1Y, so it will fly and land closer to the enemy just as the black hawk did, so the likelihood of bullets strikes. WHAT IF, while in forward flight, one of the rotating mechanism for one of the two rotors systems was damaged by a bullet impact, and one of the rotating thing could not pivot - ??? If a helicopter gets hit, it can do auto rotate, or just lower its speed and land. But if the Valor gets hit in helicopter mode, it can land. I think the driveshaft is what tilts the rotor housing, but could the propellors be stuck in forward mode... is this a possible malfunction? What happens then, Valor can't land with the props forward..

I suspect that Valor will use the same methodology used by the V-22 if the proprotors can't be raised for whatever reason. If they are stopped in the 12-4-8 o'clock position, the blades don't hit the ground. If they are rotating, they are designed to break off at the hub and the direction of rotation is such that the blades are thrown clear of the aircraft.

Also be aware that autorotation is not always that gentle of a landing. That's why in training and testing helos are not required to demonstrate autorotation all the way to the ground.

[CTR]

WHAT IF, while in forward flight, one of the rotating mechanism for one of the two rotors systems was damaged by a bullet impact, and one of the rotating thing could not pivot - ??? If a helicopter gets hit, it can do auto rotate, or just lower its speed and land. But if the Valor gets hit in helicopter mode, it can land. I think the driveshaft is what tilts the rotor housing, but could the propellors be stuck in forward mode... is this a possible malfunction? What happens then, Valor can't land with the props forward..

No aircraft systems are ballistic proof, they are only ballistic tolerant. But based on published photos, the V-280 will incorporates a fully redundant pylon conversion actuator design, like the V-22. In the event of any single actuator part jamming, the aircraft can still covert to approximately 48 degrees (half normal full range). This angle is sufficient for a STOL landing without the blades contacting the ground.

[Sam W]

From Quad A:

First flight of the prototype now scheduled for 2026. Slippage from 2025 blamed on LM protest.

[CTR]

From Quad A:

First flight of the prototype now scheduled for 2026. Slippage from 2025 blamed on LM protest.

My contacts at Bell told me what happened when LM filed their protest. For three months there was no funding to keep the Bell engineering teams on FLRAA together to continue working. So, with the exception of management, almost all engineers, had to find homes on other programs. Most went to FARA, which was understaffed.

When the LM protest was finally denied, it took time to bring the engineers back, and get everyone back up to speed. The situation was even worse with FLRAA suppliers. They also had to find homes for their engineers on other programs. However, many of these engineers did not return.

So if anyone wonders how a three month delay turns into a year, now you know.

[chopper2004]

https://www.defensenews.com/industry/techwatch/2024/04/25/us-army-to-field-long-range-combat-aircraft-to-first-unit-in-fy31/?fbclid=IwZXh0bgNhZW0CMTEAAR2ZwpqVQD_-Qc2V1c_T5ZC87tv9NRYkP0pRPQx3CKAJm9AuenC30RrFIKM_aem_AWqzg-_tvFrr98FfSVMoh2-KDXUwkaO5DQu5CmgxvyKznCzhiEfSPgSWI_ktXqV4AH5Zp4PswUcDkuoc5wc 7lKeu

cheers