S97 Raider

[SASless]

The Tilt Rotor has some scaleability issues too doesn't it?

OGE Hover performance for the V-22 remains a limiting factor in helicopter mode....and is quite modest considering the amount of horsepower the engines are capable for producing.

That comes from the compromise that must be made when combining helicopter and airplane performance using Prop-Rotors.

That being the Power Demand that is generated by the Rotor Design itself....hover performance demands huge amounts of power well in excess of that needed for cruise performance and that has been the problem for the Tilt Rotor in the past. The Bell Aircraft was eighteen months behind due to reworking the aircraft to accept 1800 horsepower engines as I seem to remember when preparing for the Demonstration Flights at Fort Rucker back in the Eighties.

The two aircraft used for that "competition" were not production aircraft but were instead technology demonstrators. The Army saw the ABC as having more potential as shown by their decision not to get involved in the Tilt Rotor Contract as did the Navy/USMC and USAF.

Which seems to be the bigger problem for the 97....stresses and weight issues in the Rotor Head/Mast or thrust being produced by the Pusher Prop?

The goal is 265 Knots Dash Speed is it not?

[SansAnhedral]

Well for JHL, the program office actually had settled on a (quad) tiltrotor solution only - it was determined it was basically the only technology that could meet the requirements. It will be interesting to see how that develops when the program is restarted.

Specific V-22 HOGE performance are not an indictment of tiltrotors in general but more of the specific sizing requirements placed on the Osprey driven by shipboard operations. For example, V-280 is purported to have much lower disc loading and improved hover performance due to a suite of improvements in sizing and rotor control. It also comes down to doctrine, does a high speed vertical lift transport asset need to spend long periods of time loitering in a hover?

If the army saw promise in the ABC, then its surprising they chose to put zero funding towards Sikorsky's proposed XH-59B which added a ducted pusher. That snuff was essentially what shelved the concept for 30 years.

All in all, I think that the S97 is at the upper end of the feasible size of an ABC craft, and likely can dash around 230kt, but I am not holding my breath for it to demonstrate some of the severe high-G maneuvers SAC advertises. The X2 which was about half the gross weight seemingly never pulled them off. S-97 also will not achieve anywhere close to the range and cost numbers they have floated.

My theory regarding the slow progression of Raider testing is that they have possibly had some rotor component failures.

[SplineDrive]

Sans, running through the scaling math for beams, it looks like that for a given number of blades, solidity, and load factor, the spacing between the rotors can indeed be a constant proportion as gross weight is sized up. Loads, radius, airfoil thickness, blade stiffness, and tip deflection all change so that the blades are strained the same. I don't think that new materials are required as gross weights increase, though I can certainly imagine that specific pitch bearing joint technologies work well at certain size ranges and may practically constrain the hub design at some point.

I would expect that when actual photos of the SB>1 are released, the inter-rotor spacing is essentially the same as the X2 and S-97 as a percentage of the rotor diameter.

[The Sultan]

OGE Hover performance for the V-22 remains a limiting factor in helicopter mode.

The V-22 met the spec requirements for the program. The performance of the V-22 was primarily controlled by design constraints for shipboard stowage. That constraint is not an issue with the smaller V-280 which is also designed to meet the 6K/95 requirements.

As to the requirements for the V-22 can the 1/2 capable SB1 even fit in the hanger of an LH? It is extremely tall and you cannot fold that second rotor away.

[SansAnhedral]

Sans, running through the scaling math for beams, it looks like that for a given number of blades, solidity, and load factor, the spacing between the rotors can indeed be a constant proportion as gross weight is sized up. Loads, radius, airfoil thickness, blade stiffness, and tip deflection all change so that the blades are strained the same. I don't think that new materials are required as gross weights increase, though I can certainly imagine that specific pitch bearing joint technologies work well at certain size ranges and may practically constrain the hub design at some point.

I would expect that when actual photos of the SB>1 are released, the inter-rotor spacing is essentially the same as the X2 and S-97 as a percentage of the rotor diameter.

Calculations for static beams don't account for aeroelastic tuning concerns, effective airfoil shapes that must fully contain the structure, nor mast/hub sizing for the fixed end of your cantilever.

[IFMU]

Calculations for static beams don't account for aeroelastic tuning concerns, effective airfoil shapes that must fully contain the structure, nor mast/hub sizing for the fixed end of your cantilever.

I'm with spline on this one. He got it right in one.

[SplineDrive]

I implicitly addressed airfoil cross sections by holding them constant, blade tuning to similar fan plots is acheiveable across wide ranges of rotor diameters, and I explicitly addressed what is likely the biggest challenge in hub design. I do believe the design scales. Practical limits of ABC aircraft will be driven by other factors (like Sultan's shipboard observation above).

[SASless]

If the army saw promise in the ABC, then its surprising they chose to put zero funding towards Sikorsky's proposed XH-59B which added a ducted pusher.

Remember what was going on in those years with the Economy?

Military Budgets were affected by those same factors and the draw down from Vietnam Years.

The Army also did not get into the Tilt Rotor business either.

Their Budget was being spent on things like the Blackhawk, Apache, Kiowa, Chinook, Cobra, and Commanche.

The Strategic Focus was Tank Killing in Europe as the Soviet's superiority in numbers of Tanks was seen as the major threat.

The Army spent a lot of money on everything from Lasers, Sand Enhancer, NVG development, and a host of other critical (or thought critical) items and concepts.....besides helicopter research and development.



http://www.history.army.mil/books/DAHSUM/1980/ch11.htm

[SansAnhedral]

Spline claims that:

Loads, radius, airfoil thickness, blade stiffness, and tip deflection all change so that the blades are strained the same.

Exactly how do you propose you achieve stiffness for the same strain within a linearly scaled aero envelope without increasing structure and in turn weight?

An increase in size by a factor of 2 would require a quadratic increase in stiffness (EI), as your material modulus is invariant in our example case. Greater stiffness with the same materials requires more material, and results in larger weight and therefore larger loads. This is a snowball effect. Mach scaling a rotor radius 200% is a cubic function for mass, square function for loads.

A blanket statement like:

blade tuning to similar fan plots is acheiveable across wide ranges of rotor diameters

in light of the immense structural changes required by scaling up is dubious. I've seen it time and time again on trade studies of rigid rotors - from coax to tiltrotor.

In any case, the added mass has a cascading effect on mast moments and rotor hub structure also increasing the sizing in the non-blade rotating system as well.


If rigid rotors in general scaled as easily as you suggest here, then existing conventional medium and heavy helicopters would already implement that rotor system as it offers significantly better control power and a far less complex and costly rotor head assembly. Sikorsky also would not have candidly admitted that X2 technology does not scale beyond the medium class in 2011 (http://www.defensenews.com/story.php?i=7682499)

Edit: The link is now dead, I wonder why? Alt reference (https://goo.gl/BRwGd5)

[SansAnhedral]

Remember what was going on in those years with the Economy?

Military Budgets were affected by those same factors and the draw down from Vietnam Years.

True, but the army was also reeling from the dumpster fire that was the AH-56 program. So I would argue their taste for rigid rotors was not all that well developed.

I've not seen anything published or documented that would illustrate a positive opinion expressed by the Army regarding XH-59A, so I am curious why you say:
The Army saw the ABC as having more potential as shown by their decision not to get involved in the Tilt Rotor Contract

The logical conclusion they did not get involved in either project goes back to your point regarding the budget situation.

[Ian Corrigible]

Well for JHL, the program office actually had settled on a (quad) tiltrotor solution only
Not quite true. Prior to the JHL effort being folded into the JFTL AoA (which included various fixed-wing STOL and V/STOL designs) in late 2010, the concept definition work had been narrowed down to three candidate configurations:
Bell's QTR (with 55 ft diameter rotors)
A conventional tiltrotor (CTR) that Bell had additionally been funded to study in parallel with QTR (with 80 ft diameter rotors)
Karem's OSTR (specifically the TR75, with 75 ft diameter rotors). As you may recall, the Army's "representative" JHL configuration used for wargaming purposes from 2007 on – the High Efficiency Tilt Rotor (HETR) – was very reminiscent of the OSTR.
The three concepts from the original JHL CDA that had already been dropped by this time were the Boeing Advanced Tandem Rotor Helicopter (ATRH), the Sikorsky X2 Technology Crane (X2C) and the X2 Technology High Speed Lifter (X2HSL).

I/C

[SansAnhedral]

Not quite true. Prior to the JHL effort being folded into the JFTL AoA (which included various fixed-wing STOL and V/STOL designs) in late 2010, the concept definition work had been narrowed down to three candidate configurations:
Bell's QTR (with 55 ft diameter rotors)
A conventional tiltrotor (CTR) that Bell had additionally been funded to study in parallel with QTR (with 80 ft diameter rotors)
Karem's OSTR (specifically the TR75, with 75 ft diameter rotors). As you may recall, the Army's "representative" JHL configuration used for wargaming purposes from 2007 on – the High Efficiency Tilt Rotor (HETR) – was very reminiscent of the OSTR.
I/C

I mentioned the quad in parentheses as it was basically the only feasible solution that did not require the implementation of some very low TRL items.

TR75 relies on some very dubious tuning claims, in addition to extremely high risk, high frequency individual blade control.

[Lonewolf_50]

Loads, radius, airfoil thickness, blade stiffness, and tip deflection all change so that the blades are strained the same. I don't think that new materials are required as gross weights increase, though I can certainly imagine that specific pitch bearing joint technologies work well at certain size ranges and may practically constrain the hub design at some point. What about a bearingless rotor?


@etudiant
We don't really have a firm grasp even on conventional rotor systems engineering The 225 in Norway that you cited as an example is a gearbox/transmission issue, not a rotor system issue. (though as CH-53K seems to be finding out, at some point when you get bigger you get some new problems inside the gear box ...)

[SASless]

Theory and Reality are two entirely different concepts!

[Lonewolf_50]

Theory and Reality are two entirely different concepts!SAS, what's that a comment on? :confused: (consider this lupine one confused).

[SplineDrive]

[QUOTE=Lonewolf_50;9755171]What about a bearingless rotor?

A 'bearingless rotor' is rarely totally bearingless, but 'reduced bearing count rotor' doesn't sound as sexy. Same comment applies... there are specific bearing types that are well suited to particular sized components based on loads and motions. It's a matter of seeing which ones package reasonably into your specific hub needs. As far as the flexbeam portion of a bearingless design, my comment on strain levels being relatively constant with rotor diameter still applies. In practice, of course, there are plenty of other design considerations that make a bearingless rotor more or less appropriate for a particular application.

[Lonewolf_50]

What about a bearingless rotor? A 'bearingless rotor' is rarely totally bearingless, but 'reduced bearing count rotor' doesn't sound as sexy. I was under the impression that the AH-1Z/UH-1Y is a true bearingless design, and it is successful. However, I suspect that if one wished to scale that up the design team would encounter, and have to account for, the loads and other issues you pointed to.
It's a matter of seeing which ones package reasonably into your specific hub needs. As far as the flexbeam portion of a bearingless design, my comment on strain levels being relatively constant with rotor diameter still applies. OK, thanks, appreciate the insight.

[SASless]

A quick example....Sikorsky had a design problem with the Rotor Blade Retention design on the S-76A.....despite the Ira best efforts.....they had two failures.

We might also add the Gear Box problems on the EC-225....the Engineers thought they had that sorted out as well but discovered they did not.

Read the latest Report about that in the 225 Thread.

Then say we bring up square windows on the Comet.

The Titanic was unsinkable.

The F-117 Stealth was invisible....till one got shot down and a second one was almo st lost to a pair of SAM's.

The list goes on at great length.

Reality always trumps theory!

[SplineDrive]

Spline claims that:



Exactly how do you propose you achieve stiffness for the same strain within a linearly scaled aero envelope without increasing structure and in turn weight?

An increase in size by a factor of 2 would require a quadratic increase in stiffness (EI), as your material modulus is invariant in our example case. Greater stiffness with the same materials requires more material, and results in larger weight and therefore larger loads. This is a snowball effect. Mach scaling a rotor radius 200% is a cubic function for mass, square function for loads.

A blanket statement like:



in light of the immense structural changes required by scaling up is dubious. I've seen it time and time again on trade studies of rigid rotors - from coax to tiltrotor.

In any case, the added mass has a cascading effect on mast moments and rotor hub structure also increasing the sizing in the non-blade rotating system as well.


If rigid rotors in general scaled as easily as you suggest here, then existing conventional medium and heavy helicopters would already implement that rotor system as it offers significantly better control power and a far less complex and costly rotor head assembly. Sikorsky also would not have candidly admitted that X2 technology does not scale beyond the medium class in 2011 (http://www.defensenews.com/story.php?i=7682499)

Edit: The link is now dead, I wonder why? Alt reference (https://goo.gl/BRwGd5)
Sans, when you double the rotor radius and hold solidity, blade number, and airfoil family constant, you get a fourth order increase in cross section stiffness as part of that scaling. Mass per unit length is a second order scaling which leads to natural frequencies being inversely linear with the radius doubling, which is good, because so does the rotor rpm to hold tip speed constant. That also means that fan plots tend to look similar for each type of rotor, somewhat regardless of diameter. Of course, specific design details like abrasion strip thickness and other details don't scale linearly with rotor radius, so there is some variation in resulting fan plot, but the principle holds. This is true for articulated and rigid rotors.

My previous comments on strains is also true for articlated and rigid rotors and it's why I've been able to use the same materials for all of my rotor designs despite an order of magnitude range in their diameters.

The reason we don't see more rigid rotors is as you alluded... they do weigh more. The flapping hinge, despite the mechanical complexity, is a wonderful elegant invention. A rigid rotor produces high vibration, huge moments, and not always in helpful directions. They're twitchy, high gain beasts. Do they have their applications? I believe yes, but certainly not for every helicopter design.

[SplineDrive]

I was under the impression that the AH-1Z/UH-1Y is a true bearingless design, and it is successful. However, I suspect that if one wished to scale that up the design team would encounter, and have to account for, the loads and other issues you pointed to.
OK, thanks, appreciate the insight.

There is typically an inboard shear bearing between the flexbeam and inboard end of the blade. Often a lag damper is installed there as well. The bearing transmits shears, allows for blade pitch and has some misalignment capability to handle flap and lag motions.

[SansAnhedral]

Sans, when you double the rotor radius and hold solidity, blade number, and airfoil family constant, you get a fourth order increase in cross section stiffness as part of that scaling. Mass per unit length is a second order scaling which leads to natural frequencies being inversely linear with the radius doubling, which is good, because so does the rotor rpm to hold tip speed constant. That also means that fan plots tend to look similar for each type of rotor, somewhat regardless of diameter. Of course, specific design details like abrasion strip thickness and other details don't scale linearly with rotor radius, so there is some variation in resulting fan plot, but the principle holds. This is true for articulated and rigid rotors.

We are actually in agreement on the bulk of what is being discussed from a theoretical standpoint, however the idea that one can actually leverage existing (high) modulus materials used on the X2 and S97 and continue to scale up to achieve a physically manufacturable stated 1:1 cross sectional area increase to yield the required 16x stiffness to maintain strain and loads is the issue at hand. A real physical implementation will always require variations (typically the larger the less efficient the structure due to manufacturing constraints, and achieving scaled stiffness will almost invariably require more material and weight) which make for significant diminishing returns.

Even with bleeding edge UHM materials the weights still increase to a point where hub attachment and inboard structure gets to be the root (no pun intended) of the challenge for a high speed flying vehicle, not to mention the potential ILS issues that are readily apparent with very thick laminates making use of such a high percentage of stiff materials attempting to keep weight down.

[Otterotor]

Originally Posted by Lonewolf_50 http://www.pprune.org/images/buttons/viewpost.gif (http://www.pprune.org/rotorheads/524130-s97-raider.html#post9755203) I was under the impression that the AH-1Z/UH-1Y is a true bearingless design, and it is successful. However, I suspect that if one wished to scale that up the design team would encounter, and have to account for, the loads and other issues you pointed to.
OK, thanks, appreciate the insight.
Originally Posted by Spline Drive:
There is typically an inboard shear bearing between the flexbeam and inboard end of the blade. Often a lag damper is installed there as well. The bearing transmits shears, allows for blade pitch and has some misalignment capability to handle flap and lag motions.


The successful bearingless rotor employed on the brother/sister duo Zulu/Yankee does indeed have a small elastomeric shear bearing at the inboard end of the cuff. It accommodates relative pitch motion between the torsionally rigid cuff and the yoke and reacts shear loads at that point as well. As I understand it, the name 'bearingless' is used to indicate the larger bearings used to accommodate flapping, lead/lag and the large C.F. loaded feathering bearing have all been replaced with fiberglass (composite) flexing virtual hinges. And the center of the yokes (blade station 0.0) are connected rigidly to the mast, eliminating the two bladed mast bumping (teetering rotor) flaw and delivering a significant amount of hub moment (control power) to the mast. Otter :ok:

[riff_raff]

"Bearingless" rotors still have some arrangement that permits adjustment of the blade pitch. Usually a torsionally flexible attachment structure or a laminated elastomeric bearing. However, they do not provide adequate stiffness for rigid rotor systems. Look at the Sikorsky rigid rotor hub designs that use rolling element blade feather bearings.

[SplineDrive]

"Bearingless" rotors still have some arrangement that permits adjustment of the blade pitch. Usually a torsionally flexible attachment structure or a laminated elastomeric bearing. However, they do not provide adequate stiffness for rigid rotor systems. Look at the Sikorsky rigid rotor hub designs that use rolling element blade feather bearings.
Riff, while requiring a different flexbeam arrangement than a conventional flexbeam rotor like AH-1Y/Z, RAH-66, or EC-135, a stiff out of plane rotor can have a flexbeam. The Sikorsky X-Wing used a flexbeam with a torisionally soft I cross section but was stiff in the flap and lag directions.

Sikorsky Archives | X-Wing (http://sikorskyarchives.com/X-WING.php)

If you browse around on Google patents, it's clear Sikorsky continues to examine atypical applications of flexbeam type rotors, including for coaxial aircraft. In fact, if you examine good photos of the S-97, the inboard half of the blade looks proportionally thicker than the X-2 does, and early ground run photos with the hub fairings off show the blade composite wrapping around the outside of the hub structure. They haven't said as much (to my recollection), but Raider might well be a 'rigid' flexbeam rotor, at least flexible in the torsion direction.

[The Sultan]

Spline wrote: The Sikorsky X-Wing used a flexbeam with a torisionally soft I cross section but was stiff in the flap and lag directions.

How did that workout for them?

[The Sultan]

This is relevant to the discussion.

https://www.youtube.com/watch?v=ycXEgIRWGqs

ycXEgIRWGqs

Interesting. It appears superior to the 97 in every way, did not take 2 years to get out of hover, and scrapped in early 70's.

[SansAnhedral]

They haven't said as much (to my recollection), but Raider might well be a 'rigid' flexbeam rotor, at least flexible in the torsion direction.

It absolutely is, and the flexbeams are what I believe have either failed or been giving them issues hence some rumored new builds. Rumor also has it that next month is supposed to finally be higher speed testing, so it would make sense they would want new components.

Having been involved with X2 and seen S97 blade construction, I can say they are quite similar, despite one being detail designed by a supplier and the other being "build to print" by the same folks.

[etudiant]

This is relevant to the discussion.

https://www.youtube.com/watch?v=ycXEgIRWGqs

ycXEgIRWGqs

Interesting. It appears superior to the 97 in every way, did not take 2 years to get out of hover, and scrapped in early 70's.

That may be quite true, but iirc, it was scrapped after a fatal accident which involved the crew getting killed by the main rotor blades.
Solving the rotor stability problem proved more difficult than expected.

[SASless]

The 525 is doomed then I assume....as is the 609 and the Tilt Rotor based upon prototype crashes.

Now of course the Sultan ignores politics and places a focus on just one problem.

It was politics that was fatal to the Cheyenne....not aerodynamics!

He might read his history a bit better!

[IFMU]

It absolutely is, and the flexbeams are what I believe have either failed or been giving them issues hence some rumored new builds. Rumor also has it that next month is supposed to finally be higher speed testing, so it would make sense they would want new components.

Having been involved with X2 and seen S97 blade construction, I can say they are quite similar, despite one being detail designed by a supplier and the other being "build to print" by the same folks.

So, the X2 was a flexbeam rotor?

[SansAnhedral]

So, the X2 was a flexbeam rotor?

As if you didn't know...not exactly "A" (singular) flexbeam, more akin to a beefy composite TT strap or loop.

It really depends on what one considers a "flexbeam" semantically. In the traditional sense like an S-92 tail rotor, Comanche, or Bell 680/H1 style chicken foot yoke/flexbeam? No.

But if you pay close attention, you'll notice even Sikorsky refers to these types of multi-node structures as "flexbeams"

https://www.google.com/patents/US7695249

https://www.google.com/patents/US20150014476

[etudiant]

The 525 is doomed then I assume....as is the 609 and the Tilt Rotor based upon prototype crashes.

It was politics that was fatal to the Cheyenne....not aerodynamics!



I'm unconvinced about that. The political leadership did support a state of the art high end attack helicopter.
There was a consensus that there was a legitimate requirement, but no confidence that the Cheyenne's problems could be fixed. Hence the AH-64, to replace the Cheyenne.

[CTR]

There was a consensus that there was a legitimate requirement, but no confidence that the Cheyenne's problems could be fixed. Hence the AH-64, to replace the Cheyenne.

You are making an incorrect historical omission. The Bell Cobra is the platform that fulfilled the Army's "legitimate requirement ". The Cheyenne was a technical marvel when designed, and would still be today. But could you ever imagine maintaining the complex beast in the rice paddies of South East Asia?

The Bell Cobra may not have been what the Army upper eschelon wanted, but it provided the grunts on the ground in Vietnam the machine they need for a decade before the Apache came around.

[etudiant]

The Cobra was indeed in service at the time, no question. The Cheyenne was to be the clean sheet follow on, faster, more powerful and more capable.
The Apache was launched as a Cheyenne successor after that effort ran into technical problems.

[Lonewolf_50]

The Bell Cobra may not have been what the Army upper eschelon wanted, but it provided the grunts on the ground in Vietnam the machine they need for a decade before the Apache came around. A goodly number of my colleagues who flew in the USMC likewise found the Cobra a capable platform.

[SASless]

After a lot of improvements and growth over the years.

[tartare]

That Cheyenne doco is fascinating.
Forgive my ignorance - but I assume the Apache is ultimately a much more capable aircraft?

[Lonewolf_50]

That Cheyenne doco is fascinating.
Forgive my ignorance - but I assume the Apache is ultimately a much more capable aircraft? IIRC not as fast, but plenty capable. (And it apparently does not have the problem of the blades coming through the cabin ...)
@SASless: IIRC, the Marines flew three (J, T, W) Cobra variants variations (twin engine) before the recent Z model (Viper) made a big change in what a Cobra is. Not sure if there was a single engine model mixed in there in the dim and distant past.

[SASless]

Back in the time of target designation being made by map coordinates given by a very scared guy on the ground (no gps) and either a smoke grenade or perhaps some tracers or muzzle flashes.....or at night tracers or verbal directions and visible light strobe lights/flashlights....there was some discussion as to the effect of having two pilots in an enclosed cockpit versus having two door gunners as well had on efficiency in acquiring targets.

With the advent of hi-tech means of locations, nvg's, FLIR, etc......the two pilot gunship has come into its own!

The USMC also uses their latest UH-1 for gunnery Support as I hear it.

[etudiant]

That Cheyenne doco is fascinating.
Forgive my ignorance - but I assume the Apache is ultimately a much more capable aircraft?

The Army accepted that the Apache would not match the Cheyenne performance. It has not closed the gap since, partly because the design is less capable, partly because weight growth has negated the gains from the improved power train and rotor.
It should be noted that the one attempt in Iraq to engage a large tank formation solely with Apache helicopters was not a success. It is doubtful that the Cheyenne would have done much better.

[SASless]

Apples to Oranges....the Cheyenne was '60's technology and only reached prototype status with three aircraft .

Perhaps that Apache thing was tactics/planning/intel failure generated rather than an aircraft failure!

[etudiant]

Apples to Oranges....the Cheyenne was '60's technology and only reached prototype status with three aircraft .

Perhaps that Apache thing was tactics/planning/intel failure generated rather than an aircraft failure!

No argument about the tactics failure, just that tactics need to adjust to reality and that is difficult to determine in exercises. The Army thought it had the answer, they were mistaken. Iirc, over 30 Apaches got badly shot up in that engagement.
Separately, the Cheyenne was much more advanced than the AH-64.
The combination of a pusher prop, a wing and a rigid rotor allowed much better acceleration and maneuverability than the Apache could offer. Technically, the Apache was two steps backward, but it was more powerful and safer than the Cobra, which was what the Army wanted.

[chopper2004]

http://aviationweek.com/defense/us-army-needs-fvl-light-recon-more-black-hawk-successor


http://i57.photobucket.com/albums/g209/longranger/df-rotorcraft_2_sikorsky_zpszr7rvusx.jpg

[Lonewolf_50]

The USMC also uses their latest UH-1 for gunnery Support as I hear it. Oh yes, they do, and the typical two ship was one Cobra and one Huey when I was last in the area where hot lead was going down range for real. Goodness. :ok:

[Lonewolf_50]

The Army accepted that the Apache would not match the Cheyenne performance. It has not closed the gap since, partly because the design is less capable, partly because weight growth has negated the gains from the improved power train and rotor.
It should be noted that the one attempt in Iraq to engage a large tank formation solely with Apache helicopters was not a success. It is doubtful that the Cheyenne would have done much better.
My friend, the Army Aviation folks spent the better part of two decades trying to convince our two dimensionally, ground bound, and limited colleagues that Army Aviation is a maneuver element not a combat support element nor a DS element like Artillery.

A friend of mine wrote a paper on the problems of the Army "getting" CAS and Rotary Wing aviation. (www.dtic.mil/get-tr-doc/pdf?AD=ADA314357) It may be a bit dated, but the Army changes as slowly as any top heavy organization.

So, once they finally got that acceptance, they had to go an prove it. 11th paid a price for that. (How about let's give the Iraqi's a bit of credit for being a smart, thinking enemy in how they handled that ambush).

[Lonewolf_50]

OK, I get the troop assault and the recon attack.

SAR?

FFS, let's give it a rest.

[tartare]

I'm still in awe of the maneuverability and handling characteristics of the XH-51 in that video.
So - reading back through the thread - essentially you are all debating whether a rigid rotor co-axial design will effectively scale up to the size required by the Raider?

[SansAnhedral]

So - reading back through the thread - essentially you are all debating whether a rigid rotor co-axial design will effectively scale up to the size required by the Raider?

I've debated the following:


The Raider is the upper limit of the ABC technology scalability that will still meet some of its performance goals versus conventional helicopters
Even at S-97 gross weight it will not perform the high-G maneuvers advertised (even X2 never demonstrated the same at 1/2 size)
A flyaway cost for S-97 would not come anywhere close to the purported $15 million price tag


The real feasibility challenge is scaling up 2X again to SB-1 size and meeting any of the maneuverability, speed, and cost targets.

[turboshaft]

That mission variants graphic seems familiar.

http://www.turboshaft.com/images/xh-59a_concepts.jpg (http://www.pprune.org/rotorheads/245168-sikorsky-x2-coaxial-heli-developments-28.html#post5388520)

Note, the 1973 version even includes the "autonomous" variant (RPV as it was back in those days).

[whoknows idont]

OK, I get the troop assault and the recon attack.

SAR?

FFS, let's give it a rest.

Why? Without having given it much thought, using a fast compound for SAR doesn't seem like the worst idea. :confused:

[SplineDrive]

Why? Without having given it much thought, using a fast compound for SAR doesn't seem like the worst idea. :confused:
High speed SAR has been discussed before... at one point it was hoped that a 609 tiltrotor variant with a wider door and retractable hoist would be a good fit for the US Coast Guard. So he range and speed of a twin Raider style aircraft isn't a bad fit for the mission, though making an aircraft that can handle landing on ships in severe sea states isn't something Sikorsky has tackled yet. If that's not part of the mission requirements, then sure, it's worth consideration as an idea.

[CTR]

The Cobra was indeed in service at the time, no question. The Cheyenne was to be the clean sheet follow on, faster, more powerful and more capable.
The Apache was launched as a Cheyenne successor after that effort ran into technical problems.

Just looking at first flight and introduction into service dates can confuse one into thinking that the Cobra came after the Cheyenne. The truth however is found in the program request for proposals and contract awarding dates. The request for proposals and contract award for an interim attack helicopter which Bell won came after the paper competition that Bell lost. After losing to Lockheed Bell built the prototype AH-1 using company funds. Bell recognized that the Cheyenne was not the near term solution the Army desperately needed. Once the Cobra was in service and the Cheyenne was in flight test, there was a de facto fly off competition between them. The Cheyenne with superior performance but fragile and maintenance intensive design, or the Cobra with it's just acceptable performance but rugged durability and commonality with the Huey. While not official, Vietnam changed the Army's perspective on what they needed, which doomed the Cheyenne. When the Apache was designed 10 years later it benefited from the Cobra Lessons Learned.

Performance at the cost of low availability and high maintenance is not always a good trade.

Moving forward to the S-97 thread, I believe there is a lesson to be relearned. Is the added performance provided by the highly complex composite structure, three rotor, fly by wire S-97 worth the lower availablity and higher maintenance when compared to a modern equivalent to a Kiowa?

[SASless]

Is the added performance provided by the highly complex composite structure, three rotor, fly by wire S-97 worth the lower availablity and higher maintenance when compared to a modern equivalent to a Kiowa?


Or a ...... Commanche?

[SplineDrive]

Or a ...... Commanche?
That is a very fair question, no doubt!

[tartare]

So - it would seem that the proven tiltrotor format of the Valor (notwithstanding a static rather than rotating nacelle) appears to be a lot lower risk than the S-97?
With admittedly no expertise whatsoever in this area - the Valor intuitively `looks right'
And as (ironically) Kelly said - "If it looks right..."
Fascinating project - hadn't realised the split into FVL light, medium, heavy and ultra.
Now I see what you mean by the Commanche comment SAS.

[Photonic]

If I can throw a question out here, as a non-expert in this area:

To what extent is the competition between ABC and tilt-rotor designs determined by radar profile? Tilt-rotors obviously presenting a larger target in cruise mode. Or does that not matter anymore, with current AA radar tech being able to pick up anything of that size inbound and flying low?

[CTR]

If I can throw a question out here, as a non-expert in this area:

To what extent is the competition between ABC and tilt-rotor designs determined by radar profile? Tilt-rotors obviously presenting a larger target in cruise mode. Or does that not matter anymore, with current AA radar tech being able to pick up anything of that size inbound and flying low?

On what information do you base your conjecture that the tiltrotor had a higher RCS in cruise?

[Photonic]

On what information do you base your conjecture that the tiltrotor had a higher RCS in cruise?

IIRC, it was an article I read somewhere mentioning the huge forward-facing area of the rotors in cruise mode. I'll see if I can dig it up.

[tottigol]

Obviously there are the wings and the nacelles with engines/gearboxes, but aren't the rotor/propeller blades of composite material?

[Photonic]

Obviously there are the wings and the nacelles with engines/gearboxes, but aren't the rotor/propeller blades of composite material?

Primarily composite, but with other materials that are radar reflective:

"The V-22 is equipped with two counterrotating three-bladed proprotors. The blades are constructed primarily of composite material with a metallic leading edge abrasion strip and integral de-ice blanket. "
V-22 Osprey (http://www.globalsecurity.org/military/systems/aircraft/v-22-propulsion.htm)


Each blade is also wired for green LED lights at the blade tips, for ground crew safety (you may have seen photos of the "green ring" on these things at night). So they're not 100% composite, and whatever metal is in there is spinning to form a disk in cruise mode. A metal leading edge strip would probably light up pretty good.

This was the only info I could find about the radar cross section, from "V-22 crew chief Staff Sgt. Brian Freeman’s letter to Gannett’s Marine Corps Times," quoted in defenseindustrydaily.com:

"Nevertheless, the countermeasures dispensing system was found to have insufficient capacity for longer missions, and radar reflection from the V-22’s total propeller disc area of more than 2,267 square feet rivals that of two Boeing 707s in formation.146 (Given that situation, one can only wonder at the logic behind the development of top-secret "stealth paint" for the fuselage at a cost of $7,500 per gallon; the one aircraft they painted required 10 gallons for a paint job costing $75,000 -- but those huge, whirling discs were still there, bouncing back radar signals with gusto.)"
V-22 Osprey: A Flying Shame? (http://www.defenseindustrydaily.com/v-22-osprey-a-flying-shame-04822/)


Maybe there have been upgrades since then, and I remember seeing something recently about Bell developing new prop/rotor blades. But I think that was mainly for cost-savings? Anyway, it's just something I find interesting when comparing tiltrotor, tiltwing, and more conventional designs for military use.

[CTR]

After all these years it is suprizing to me how many people still don't understand "stealth".

Stealth technology is not limited to detection by radar. Stealth technology includes acoustic detection, thermal signature, and visual detection.

Designing an aircraft to incorporate stealthy radar characteristics is highly dependent on its intended mission. No aircraft is completely invisible to radar. Comprises are made to provide stealth where it makes the greatest mission benefit.

For a B-2 bomber it is penetration at high altitude that is of greatest importance. While on the dogfighting F-22 needs to be concerned all directional aspects need to be considered.

So before dismissing the benefits of Low Observable paint on a V-22, think about the V-22 mission.

[riff_raff]

I believe one advantage of tilt rotors versus helos is their ability to quickly climb and cruise at altitudes beyond MANPADS. There are many things Bell can do to reduce detection of this tilt rotor. They are using composite materials for most of the airframe structures and rotor. The straight single-piece wing makes it easier to manufacture and repair, and also simplifies the interconnect rotor drive system. One major reason for using the non-tilting engine was due to the fact that there were no suitable tilting turboshaft engines available.

[Mee3]

one piece of anything is harder to repair compared to segmented design.

Modern chopper can easily beat manpads in service today in terms of practical ceiling and climb no slower than TRs. The only benefit for current gen of TRs are the range and speed. Anything else is just sell pitch.

[The Sultan]

As to a tilt rotors rotor radar cross section. The rotor blades in airplane mode operate at high angles which provides the same faceting effect as on a F117 to deflect radar from returning to its source. NAVAIR tried a Lawerence Livermore airframe mounted radar blade tracker which worked ok when the target section of the blade was perpendicular to the tracker, but useless with even a few degrees of pitch as the return was deflected. The proposed solution was to add a 360 degree radar reflector to the blade to ensure a return. Obviously this was rejected as stupid. V-22's still use optical trackers for a rare maintenance action.

Note: Radar cross section is closely guarded, has little to do with presented disk area (disk presented solidity somewhat), and something a Staff Sargent would never have a clue of.

[SansAnhedral]

Modern chopper can easily beat manpads in service today in terms of practical ceiling and climb no slower than TRs. The only benefit for current gen of TRs are the range and speed. Anything else is just sell pitch.

Climb no slower? (https://www.verticalmag.com/features/20112-flying-the-v-22-html/) The climb rate in airplane mode is not matched by conventional helicopters, and that's precisely what riff was referring to.

Climb capability is where the Osprey excels, with rates approaching 4,000 feet a minute depending on environmental conditions.

[SansAnhedral]

At AHS today, Mark Miller from SAC mentioned the S-97 has 18 total flight hours to date in 13 flights, which is over the course of 2 years.

Also disclosed they have attained 150kt in level flight and 130kt in a 45 degree bank, which aligns with the footage released recently.

[Mee3]

Climb no slower? (https://www.verticalmag.com/features/20112-flying-the-v-22-html/) The climb rate in airplane mode is not matched by conventional helicopters, and that's precisely what riff was referring to.
Take 609 and 175 for example. They have engines somewhat in the same class. And they both climb about the same.

[SansAnhedral]

Take 609 and 175 for example. They have engines somewhat in the same class. And they both climb about the same.

Curious where you get the idea that the 609 is limited to 1500 fpm climb rate.

[Mee3]

Curious where you get the idea that the 609 is limited to 1500 fpm climb rate.
I never said it is. But if you are implying that 609 RoC is in another class, surely you have done the math and the chance is very slim.

[SansAnhedral]

I never said it is. But if you are implying that 609 RoC is in another class, surely you have done the math and the chance is very slim.

AW themselves (and Bell prior) estimated 2500-3000 fpm climb rate publicly (http://www.ainonline.com/aviation-news/aerospace/2012-02-11/aw609-finally-ready-its-close), and with quite a bit of flight testing completed to date I have heard this is not far from accurate.

A 75-100% increase would indeed be in another class.

[JohnDixson]

The US Army thinking from Vietnam controlled their requirements for hover and climb for the UTTAS. Specifically, they required, from an HOGE hover at design gross weight, and at 4000'Hp/95F, a vertical climb of 500 ft/min utilizing 95% of rated power.

The JMR conditions I believe are now 6000'/95F, but in any case, if their thinking follows past indications, it will be climb from an HOGE hover, not at forward speed that will be a main requirement.

[SansAnhedral]

The likely argument will be that converting from a HOGE hover and accelerating to climb over the same duration for a greater ascent rate would meet the intended performance requirement.

[Lonewolf_50]

Sans, is the JMR requirements document available in the public domain? I would think that it would be.

[The Sultan]

Reported: Shares of industrial and aerospace conglomerate Textron (TXT) jumped more than 3.5% on Thursday as chatter about its possible acquisition by Lockheed (LMT) swept the market.

Lockheed does not appear confident in Sikorsky's ability to pull off the SB1 and is looking to acquire the V280.

[tartare]

Excellent.
I'll be able to feel like a steely eyed killer and say I tool around the skies in a Lockheed C-152. :)
That's quite significant news...

[Mee3]

AW themselves (and Bell prior) estimated 2500-3000 fpm climb rate publicly (http://www.ainonline.com/aviation-news/aerospace/2012-02-11/aw609-finally-ready-its-close), and with quite a bit of flight testing completed to date I have heard this is not far from accurate.

A 75-100% increase would indeed be in another class.
Lets see, that power that wing, does not add up. If they do, fixed wing is out of chart.

[Commando Cody]

Reported:

Lockheed does not appear confident in Sikorsky's ability to pull off the SB1 and is looking to acquire the V280.

This could be quite interesting. when United Technologies sought to divest itself of Sikorsky, there was some interest from Textron to acquire it. However, the US Gov't let it be known that it wouldn't let that happen for antitrust reasons, as owning both Bell and Sikorsky would give it too large a share of the US helicopter industry, in their opinion. Since foreign complanies would not be allowed to acquire this US strategic asset, Lockheed got it because no one else showed interest.

So one would think that this is the exact same scenario, but maybe with the cnbage in Administrations, opinions could change. If this is true, I suspect it's not so much the SB-1 that disappointed Lockheed, as much as the entire technology it's based on since the record is not good in all its iterations so far .

Of course, keep in mind that Lockheed is already a partner with Bell on the V-280.

[SansAnhedral]

Finally some news on the S-97....but not the kind I'm sure Sikorsky prefers. "Hard landing from hover". Crew safe thankfully.

S-97 Raider helicopter makes a hard landing at the Sikorsky Development Flight Center - wptv.com (http://www.wptv.com/news/region-c-palm-beach-county/west-palm-beach/s-97-raider-helicopter-makes-a-hard-landing-at-the-sikorsky-development-flight-center)

http://media2.wptv.com/photo/2017/08/02/WPTV_CHOPPER_INCIDENT_SIKORSKY_1501688098847_63667862_ver1.0 _640_480.png

[The Sultan]

History repeating itself? From Wiki:

The first S-69 built (73-21941) first flew on July 26, 1973. However, it was badly damaged in a low-speed crash on August 24, 1973 due to unexpected rotor forces and insufficient control systems.[2] The airframe was then converted into a wind tunnel testbed

Note: S-69 was first of the Sik coaxials.

Could not tell from photo on landing gear position. Looks like it was up. Question: Who hovers over a runway with the gear up?

[Tailspin Turtle]

History repeating itself? From Wiki:



Note: S-69 was first of the Sik coaxials.

Could not tell from photo on landing gear position. Looks like it was up. Question: Who hovers over a runway with the gear up?

My guess is the "landing" was hard enough to result in maximum landing gear stroking as the first step in reducing the initial sink rate to one that the crew could tolerate without injury.

[IFMU]

Can anybody see signs of the gear? They stick out to the side normally. It almost looks more like the gear failed to extend and they elected to set it down on the taxiway.

[SASless]

Sat it down on the Taxiway with the nose sticking out onto the Runway.....really?

[Lonewolf_50]

What if they were hovering, doing some regular thing in a gear up configuration (for whatever reason, I think this is mostly a test aircraft, isn't it?) and had an engine roll back? That would make you settle. Note, this is speculation.
@SASless: I don't think that's a taxiway. No markings. IF that pic is from the West Palm Beach facility, I don't think there are any taxiways there. (Memory foggy, been since the late 90's that I was there...)

[212man]

What if they were hovering, doing some regular thing in a gear up configuration (for whatever reason, I think this is mostly a test aircraft, isn't it?) and had an engine roll back? That would make you settle. Note, this is speculation.
@SASless: I don't think that's a taxiway. No markings. IF that pic is from the West Palm Beach facility, I don't think there are any taxiways there. (Memory foggy, been since the late 90's that I was there...)

Looks almost certainly to be the westerly of the two parallel taxiways close together almost at the runway centre: https://www.google.nl/maps/place/Sikorsky+Aircraft+Corporation/@26.9075259,-80.3269408,362m/data=!3m1!1e3!4m5!3m4!1s0x0:0x38c798bcb0906333!8m2!3d26.9065 729!4d-80.3191729

[IFMU]

To me it looks like the road that goes to the ILS shack down at the west end of the runway. True that it is not technically a taxiway, so I misspoke. They had a designated area down there for the Comanche to land if they had gear trouble​.

[The Sultan]

had an engine roll back

It would be the engine.

the gear failed to extend

Gear failure to extend is not unheard of on test aircraft. On rotor craft which are stable enough to allow it the solution has been to have ground personnel manually extend the gear.

[Nige321]

Slightly off-topic, what's this, A mile to the north east...?! (https://www.google.nl/maps/place/Sikorsky+Aircraft+Corporation/@26.9282909,-80.3406399,191m/data=!3m1!1e3!4m5!3m4!1s0x0:0x38c798bcb0906333!8m2!3d26.9065 729!4d-80.3191729)

[Vzlet]

A radar cross section testing range? Perhaps from the Comanche era?
ed: Or are you asking about the "diamond" shapes?

[212man]

To me it looks like the road that goes to the ILS shack down at the west end of the runway. True that it is not technically a taxiway, so I misspoke. They had a designated area down there for the Comanche to land if they had gear trouble​.
I don't think the tree-line or water features match up, plus that large pale rectangular feature in the top right of the photo matches with the google image.

[Nige321]

A radar cross section testing range? Perhaps from the Comanche era?
ed: Or are you asking about the "diamond" shapes? The diamond shape 'vehicles'...?

[SansAnhedral]

History repeating itself?
The first S-69 built (73-21941) first flew on July 26, 1973. However, it was badly damaged in a low-speed crash on August 24, 1973 due to unexpected rotor forces and insufficient control systems.[2] The airframe was then converted into a wind tunnel testbed


https://i.imgur.com/s5fWKok.png

https://i.imgur.com/RwDNhDZ.png

https://i.imgur.com/y2zOH6W.png

https://i.imgur.com/150dfsr.png

[Ian Corrigible]

The diamond shape 'vehicles'...?
S-75 ACAP (http://www.sikorskyarchives.com/S-75%20ACAP.php)?

http://www.sikorskyarchives.com/images/images%20s75%20ACAP/S75-10.jpg

I/C

[Self loading bear]

Ian,

I think Nige321 meant this Diamond shaped contraption:

2716

Area 51B?

Cheers 5lB

[etudiant]

These shapes are highly reminiscent of the 'hopeless diamond' shape that eventually resulted in the F-117, albeit more evolved. Radar cross section test dummies for some high speed vehicle perhaps?

[Lonewolf_50]

The Sultan, not sure how much you have ever flown. I suffered an engine roll back in a single engine turboprop trainer. I have had an engine roll back (reduce RPM from flight RPM) in both an SH-2F and an SH-60B in flight. In each case use of the various emergency throttle/lock out procedures restored enough power to fly home without securing the engine. (The SH-60B NATOPS called a "a partial power loss" ... but it's the same thing).

While I've had engines fluctuate while in a hover, I've never lost one (though we certainly trained for that malfunction a lot in the sim ... )

[Lonewolf_50]

@212man Based on the water filled ditch/canal in the background of the photo of the S-97 and the fire truck, and the overhead you presented, it looks like the road at the far right of the overhead you posted. Taxiways in that picture are marked very clearly, while the one in the photo with the fire truck has no markings.

[The Sultan]

Lone,

Point is the 97 is single engine so "an" engine (implies more than one) rolling back is not applicable. Very possible it puked the engine. Question remains with exception of a PR flight why was the gear up (as "confirmed" by articles) when hovering/low speed over a hard surface? They obviously were not doing HV/auto testing. I guess it is always possible they landed after forgetting to lower the gear, but not likely. On the 609 we had a special rig we could land on should the gear fail to extend, do not see similar here.

[pants on fire...]

The Sultan;9850996]It would be the engine.

I thought you had permanently disappeared after your last round of ill informed and totally factually incorrect bashing of the S-92 and individuals on this forum, but then again, maybe your Mother hasn't realized you're back here posting again yet?

It's possible that English isn't your native tongue, or simply that you have never mastered it?

Just for you.
https://en.oxforddictionaries.com/definition/an

It is "AN" engine failure. It is also "AN" engine roll back.

[The Sultan]

Pants

Common definition of "the": used with a singular noun to indicate that it represents a whole species or class.

Since their was only one completed S-97 with only one engine "the" is the proper determiner.

[SplineDrive]

You know there’s a lack of public information when we’re arguing over grammar, lol.

[Jack Carson]

The S-97 Raider has experienced a minor mishap after years of development with a very limited flight envelope. The lack of flight envelope expansion is the issue not this mishap.

[tartare]

Looking at the S-75 ACAP - I see grandfather of Stealth-Blackhawk.

[Lonewolf_50]

@Jack Carson: nicely put
@Sultan: I guess the both of us can drop the handbags now.

As to the damage, I guess it'll buff out. :} :cool:

[SansAnhedral]

Anyone hear any news about possible causes in the last couple of weeks? Component failure, computer/software issues, etc?

Perhaps it threw a pusher prop blade like the iron bird did a while back? Noticed in the videos some personnel far off to the 9 o'clock in the grass possibly looking for something

[IFMU]

Sans,
I have no idea, but am interested also. Tell us about this iron bird prop incident - did I miss the story somewhere? Did they have a dedicated iron bird?

[SansAnhedral]

While shaking the proverbial trees among my industry peers for info on the Raider incident, I was told in passing about the tail rotor prop chucking a blade in the test pit on an iron bird rig a while ago.

Supposedly this was caused by some miscommunication regarding design loads with a supplier, and subsequently slowed progress as all changes were much more thoroughly scrutinized.

Same sources also relayed something that a lot of people have been suspecting - that the vibration is a large issue and the pilots were having difficulty reading displays in flight. Sounds like there is an internal belief that the fuselage may not be stiff enough.

[riff_raff]

Sans-

In this video of a tie-down run of the S-97 you can see how the pusher prop drive is de-clutched as the main rotors come up to speed. If my understanding is correct, doesn't the S-97 de-clutch the prop drive during hover? If so, I can see potential unanticipated vibration and dynamic torsional load issues in the prop drivetrain from friction clutch chatter while accelerating the prop up to speed from a stop. The dynamic torsional effects produced by friction clutch slip/chatter during engagement are very hard to accurately predict. Seems possible that the prop system failed due to operating loads higher than anticipated.

https://youtu.be/VBJZhPbMHlU

[SansAnhedral]

S-97 Raider sustained ?substantial damage' in crash, but program moves forward (http://www.defensenews.com/land/2017/09/11/s-97-raider-sustained-substantial-damage-in-crash-but-program-moves-forward/)

Most interesting takeaway is 20 flight hours in approx 2.5 years. Also explains where that 2nd prototype airframe has been.

[The Sultan]

From the above referenced:

“The neighborhood of the root cause is the complex interaction between the ground, the landing gear, the flight control system and the associated pilot interactions,” he told a few reporters in a phone interview. “If you are familiar with the rotorcraft industry, this is a well-documented complex set of interaction as airplanes transition from operations on the ground to operations in flight.”

So pretty close to what caused them to crash the first XH-59A. It appears #1 is basically finished also like the 59A. You would think Sikorsky would have focused on near ground handling as a lesson learned from the previous program.

Does not bode well for this concept if you can not safely lift to a hover.

[212man]

complex interaction between the ground, the landing gear, the flight control system and the associated pilot interactions
Otherwise known as 'taking off and landing'!

[heli1]

Otherwise known as 'taking off and landing'!

Also known as ground resonance?

[The Sultan]

Heli1

No. Sounds more like what caused the prototype F-22 crashed.

Fighter prototype crash not caused by aircaft flaw - UPI Archives (http://www.upi.com/Archives/1992/10/22/Fighter-prototype-crash-not-caused-by-aircaft-flaw/9777719726400/)

[IFMU]

Vertical released this:
https://www.verticalmag.com/news/sikorsky-reveals-details-s-97-raider-hard-landing-ntsb-publishes-initial-report

Ground resonance is not a factor for rigid rotors. Article says it was a flight controls software issue. I have no idea what they did on Raider. I know for a fact that they did not use the X2 flight controls and software guys on Raider.

[Jack Carson]

Does the Raider use full or limited motion flight controls? The S-76 SHADOW aircraft was used as part of the early development of the Comanche flight control system. The SHADOW utilized a limited motion force control for the cyclic system and a full motion collective. During flight test we did experienced multiple spurious down collective inputs in a hover. All were recovered by the safety pilot in the rear cockpit. The SHADOW flight control system also received inputs from the landing gear struts during takeoff and landing.

[IFMU]

I think all the Sikorsky FBW uses a normal collective and a unique trim sidearm controller. The RAH66 didn't have pedals but everything else has.

I'd flown in the back of the Shadow a few times as a young engineer, including once when my old man was up front for a demo. It was a good aircraft but the technology definitely moved ahead since those days.

At Schweizer we also built a Shadow style FBW 333. We didn't get to do a lot with it but it was a fun project.

[SansAnhedral]

Lockheed Martin Reaffirms Support For Sikorsky?s Raider | Defense content from Aviation Week (http://aviationweek.com/defense/lockheed-martin-reaffirms-support-sikorsky-s-raider)

The fly-by-wire (FBW) Raider was taxiing to its takeoff position when the mishap occurred. The digital flight control system unexpectedly transitioned from simple ground mode to augmented flight mode before the aircraft became airborne. The crew lifted into a hover but, unable to stabilize the helicopter, quickly put it back on the ground, the Raider coming down heavily, upright and level on the runway. The two company test pilots powered down the engine and shut off the electrics before egressing. The Raider suffered substantial damage, but they escaped with minor injuries— the impact-absorbing landing gear, composite airframe and crew seats working as designed.

[SplineDrive]

Lockheed Martin Reaffirms Support For Sikorsky?s Raider | Defense content from Aviation Week (http://aviationweek.com/defense/lockheed-martin-reaffirms-support-sikorsky-s-raider)

... if the FCC was not in the correct flight mode, I suspect there was a substantial amount of excitement packed into the phrase "unable to stabilize the helicopter". Glad the rest of the systems worked as intended and the pilots walked away. Makes it a good landing.

[CTR]

While l wish the Raider team success in achieving their goals, I don't see Lockheed's priority stacking placing them anywhere near the top.

Whenever an accident like this occurs it raises the question "What else have we missed?"
This introspection leads to a deep dive into system design and integration lab regression tests.

If the Raider was Sikorsky's only development program, it would be all hands on deck to get ship two back into flight test. But with getting the CH-53K production ready, the Defiant back on schedule for achieving first flight, and bill paying production programs like the Presidential Helicopter and Blackhawk, where is the Raider program going to find the resources it needs?

[SplineDrive]

If the Raider was Sikorsky's only development program, it would be all hands on deck to get ship two back into flight test. But with getting the CH-53K production ready, the Defiant back on schedule for achieving first flight, and bill paying production programs like the Presidential Helicopter and Blackhawk, where is the Raider program going to find the resources it needs?

Sikorsky appears to be hiring in CT, TX, and WPB, so perhaps they're willing to do all of the above. At this point, what's required to regression check and complete the second Raider aircraft is fairly small potatoes, assuming all the big ticket items were already manufactured and paid for before assembly was halted.

Guess we'll see.

[CTR]

Sikorsky appears to be hiring in CT, TX, and WPB, so perhaps they're willing to do all of the above. At this point, what's required to regression check and complete the second Raider aircraft is fairly small .

Unless Sikorsky can steal experienced Flight Control System specialists from other aerospace companies, they will be hard pressed to man up the teams required to support all their FBW programs.

[IFMU]

Unless Sikorsky can steal experienced Flight Control System specialists from other aerospace companies, they will be hard pressed to man up the teams required to support all their FBW programs.

They have a lot of flight controls talent, and one would have to assume there is some commonality between the systems. They had enough talent they didn't need to keep the X2 guys when they closed Elmira!

[The Sultan]

From FI:

The company has no plans to build a replacement for the first prototype, but that could remain as an option, he says.

97 Ship 1 appears to be a complete write off.

[Lonewolf_50]

Sultan: Might they not repair it, rather than replace it?

[The Sultan]

Lone,

As the gist of the article was that they are concentrating on #2 and #1 was lessons learned the impression was #1 is done. I guess they could move the data plate to a new fuselage (if they had one) and call it 1, but that is cheating.

[SplineDrive]

Lone,

As the gist of the article was that they are concentrating on #2 and #1 was lessons learned the impression was #1 is done. I guess they could move the data plate to a new fuselage (if they had one) and call it 1, but that is cheating.

Right... I haven’t seen anything that indicates AC1 will fly again.

Since it seems clear that development has been slower than ideal, hopefully they can roll the changes made to AC1, over the last couple of years, more cleanly into AC2. Its build was apparently stopped well before completion (for example, just now assembling the transmission) which should be helpful if there was some hardware evolution along the way.

Bet Raider AC2 flies before SB>1 does :-)

[The Sultan]

Spline

A better bet would be will they fly in 2018 or 19? Hover only does not count. They have to go beyond the airport perimeter and do a full circuit.

[CTR]

Bet Raider AC2 flies before SB>1 does :-)

I am predicting Defiant flying first, but only for a limited hover envelope before being pushed back in the hanger to be finished being built and software completed.

Raider Ship 2 will then fly to
expand the flight envelope before risking it on the defiant.

[SplineDrive]

Spline

A better bet would be will they fly in 2018 or 19? Hover only does not count. They have to go beyond the airport perimeter and do a full circuit.

Progress has certainly been slow, but we both know RAIDER has been out of the airport perimeter and done more than hover. As for schedule, we'll see.

[IFMU]

Raider back in flight test:
https://www.verticalmag.com/news/sikorsky-resumes-flight-tests-with-s-97-raider/

[SansAnhedral]

Did it actually fly for a full 90 minutes? That's pretty amazing. That would be almost 10% of the entire flight time that ship 1 saw in its over 2 years worth of flight test.

[CTR]

Raider Ship 2 did fly before the Defiant. What I hadn’t accounted for was Sikorsky and Boeing lobbying to push FVL Capability Set 1 ahead of 3. How Sikorsky can claim however that the S-97 represents a lower risk development than the V-280 is beyond me. Especially since the V-280 has in six months flown more hours and faster than the S-97 achieved in over two years.

In no no way trying to dismiss Sikorsky’s X-2 Technology challenges and achievements. Just getting tired of Washington and defense contractor politics.

[SansAnhedral]

What I hadn’t accounted for was Sikorsky and Boeing lobbying to push FVL Capability Set 1 ahead of 3.

I saw this coming over 3 years ago

https://www.pprune.org/rotorheads/524130-s97-raider-4.html#post8992734

I still maintain that both Sikorsky and Boeing want nothing more than for FVL-M to go away, hence the teaming. Sikorsky wants to sell S97 as FVL-L or as something "off the shelf, ready to go" to replace Kiowa and AAS. They both subsequently convince Uncle Sam that the capability in the medium class can better be accomplished (read: cheaper) with next gen UH-60X and AH-64X to keep those revenue streams alive.

[SplineDrive]

I saw this coming over 3 years ago

https://www.pprune.org/rotorheads/524130-s97-raider-4.html#post8992734

Yup... and the Army retired their scout aircraft and are currently receiving new build mediums. Leading off with the CapSet3 medium aircraft never made much sense.

[SplineDrive]

Raider Ship 2 did fly before the Defiant. What I hadn’t accounted for was Sikorsky and Boeing lobbying to push FVL Capability Set 1 ahead of 3. How Sikorsky can claim however that the S-97 represents a lower risk development than the V-280 is beyond me. Especially since the V-280 has in six months flown more hours and faster than the S-97 achieved in over two years.

In no no way trying to dismiss Sikorsky’s X-2 Technology challenges and achievements. Just getting tired of Washington and defense contractor politics.

I doubt Boeing is pushing for Cap Set 1 to go first. They’re not teamed with Sikorsky on the Cap Set 1 end of the FVL line and I am not aware of a Boeing internal platform that would fullfit the Cap Set 1 requirements very well. Let’s see if they respond to the FARA program that the Army just announced a few days ago.

[SansAnhedral]

Yup... and the Army retired their scout aircraft and are currently receiving new build mediums. Leading off with the CapSet3 medium aircraft never made much sense.

In retrospect, it appears it was dangling the big carrot (4000 aircraft UH-60/AH-64 replacement) to get the OEMs to invest and demonstrate their technology. It also made more sense at the time because it predated the colossal blunder of mothballing the OH-58s.

But now it appears to be a gigantic middle finger to Bell, who to date have done exactly what was asked with their demo - on time and on budget - only to get the Army waffling on whether or not they really are going to go through with CS3 first...or even at all!

I can imagine a scenario where the Army ends up saying "Well we really need that Kiowa replacement because we totally f'ed up by retiring them" and the subsequent procurement of the scouts (especially if they really believe the suspect cost estimates Sikorsky has published on the Raider) eats their budget to such a degree that replacing the mediums will seem like a pipe dream.

It seems unfathomable that the Army would expect OEMs like Bell to absorb the cost of building and flying ANOTHER demonstrator, particularly on this condensed proposed timescale. I don't see how they can afford that - their pockets aren't nearly as deep as LockMart/Boeing.

FARA isnt remotely feasible as a real competition unless the Army is really just looking for a way to buy the S97

[noneofyourbusiness]

The Airbus Racer would be the competitor to Sikorsky Raider, as a demonstrator is being built. Racer and Tiltrotor have much better fuel burn rate than Sikorsky's X2 technology. After the Army had industry fund the JMR demonstrators, it is totally unacceptable to say forget your investment, we really want something else now. Constantly changing their mind could once again leave the Army getting nothing. The Bell V280 clearly is better than the current Black Hawk, or SB1 Defiant, as a transport aircraft.

[SplineDrive]

S-97 was sized to a mission spec closer to ARH, so it’s quite a bit less capable than the FVL CapSet 1 requirements, but FARA seems like it's possibly in between the two. I doubt S-97 meets the FARA requirements, as-is. The industry has invested quite a bit of money in the Valor and the recent group of rigid coaxials. If any of this yields a program, I have some hope the taxpayers will get a decent deal.

As for cost cost of the S-97 or similar aircraft, the physical cost should be predictable. You’re paying for a second rotor system, a moderately more complex transmission, and a more powerful tail drive system. Those are all estimatable. Like most modern aircraft, the real cost variability is in the fly by wire and mission systems integration, and with the advanced “digital quarterback” feel of the FARA spec, any entrant is going to carry a risk there.

[Commando Cody]

In retrospect, it appears it was dangling the big carrot (4000 aircraft UH-60/AH-64 replacement) to get the OEMs to invest and demonstrate their technology. It also made more sense at the time because it predated the colossal blunder of mothballing the OH-58s.

But now it appears to be a gigantic middle finger to Bell, who to date have done exactly what was asked with their demo - on time and on budget - only to get the Army waffling on whether or not they really are going to go through with CS3 first...or even at all!

I can imagine a scenario where the Army ends up saying "Well we really need that Kiowa replacement because we totally f'ed up by retiring them" and the subsequent procurement of the scouts (especially if they really believe the suspect cost estimates Sikorsky has published on the Raider) eats their budget to such a degree that replacing the mediums will seem like a pipe dream.

It seems unfathomable that the Army would expect OEMs like Bell to absorb the cost of building and flying ANOTHER demonstrator, particularly on this condensed proposed timescale. I don't see how they can afford that - their pockets aren't nearly as deep as LockMart/Boeing.

FARA isnt remotely feasible as a real competition unless the Army is really just looking for a way to buy the S97

I agree that that the Army's waffling could prove disastrous. Although Army is getting new/rebuilt medium lift 'copters, they are still basically the same technology and performance as what has been around for 20-30 years, and you have to start moving away from that sometime. The nice thing about CS3 is its widespread applicability.

Aside from Army's replacing UH-60/AH-64, USMC has shown significant interest in it as a replacement for UH-1Y and AH-1Z. USN also might be interested. Although the high speed capabilities aren't as important, to USN, the range and endurance would be and commonality with USN would be a plus. . The UK and Japan have shown interest, and one would think Israel and maybe Australia would be watching closely. The scout mission, though, is pretty unique to the Army. A vehicle for that wouldn't have the appeal elsewhere that the medium lift variant would. As stated, it wold be awful hard to get companies to invest their money on another vehicle when if it's perceived that Army might abandon its latest direction. We have already seen examples of major contractors declining to bid on new programs. Given the already ridiculous and unnecessarily long time Army is stretching FVL out, the ultimate result of doing this could very well be that nobody gets anything.

[Commando Cody]

The Airbus Racer would be the competitor to Sikorsky Raider, as a demonstrator is being built. Racer and Tiltrotor have much better fuel burn rate than Sikorsky's X2 technology. After the Army had industry fund the JMR demonstrators, it is totally unacceptable to say forget your investment, we really want something else now. Constantly changing their mind could once again leave the Army getting nothing. The Bell V280 clearly is better than the current Black Hawk, or SB1 Defiant, as a transport aircraft.

Racer would be a competitor to Sikorsky's X2 technology (as embodied by Raider) in the civil world, but has a couple of limitations in military guise.

First, Army wants to able to load/offload their medium/light helicopters quickly from both sides. With Tilt-Rotor you can do that in a nearly 360º arc around the aircraft, and only slightly less with X2. With the Racer concept, because of the support structure for the props you can only come directly towards it or away in an arc of at best 180º. That brings up the second limitation, you've got to be careful moving near those props until both of them are stopped, which can only happen when on the ground. At least one has to be kept turning with any altitude because the prop[s] are what provides the antitorque force. With X2, the prop can be started/stopped while airborne since it is strictly propulsion, the contra-rotating rotors cancel out the torque. With Tilt-Rotor the issue doesn't arise because the proprotors cancel each other out and also when on the ground the proprotors are up and out of the way.

In civil use, these aren't serious limitation because its no big deal to wait until they're stopped or to approach the doors only from the side/front.

BTW, Bell also has an attack version of the V-280; except for the lack of windows aft of the cockpit, it doesn't look that much different from the transport model. As with all the JMR proposals, to meet the high speed requirement, the main weapons are carried internally.

[SansAnhedral]

The low thrust line mounting of the pusher on the SB1 and S97 would also preclude any sort of flared landing or autorotation without incurring damage to the prop, whether it is disengaged or not.

[IFMU]

The low thrust line mounting of the pusher on the SB1 and S97 would also preclude any sort of flared landing or autorotation without incurring damage to the prop, whether it is disengaged or not.
When I look at the pictures of the S97 on the ground, I see that you can do a flared landing. When I was training my instructor drilled it into my head that before touchdown on an auto, skids should be level. I did a lot of full touchdown autos. Do you really want to land tail first, either power on or in an auto? If landing power on with the prop engaged you can always use beta for deceleration.

[JohnDixson]

The short answer here would seem to be that the Defiant pictures reflect a tail wheel, and assuming the Army crashworthy standards remain at least as rigorous as for the UTTAS design, that gear will be substantial and used for the power off landings.

A proof of the structural strength resultant from these standards occurred during development. A power off landing was added to the flight test card on the power plant/subsystem design test ship. Pilots were the Ch Pilot and a sr test pilot who had done a lot of the CH-54 work. The Ch Pilot was in the second seat. Wind was 0-15 kts and the wind died at the flare, meaning they flared at 65, not 80. Flare effectiveness on ROD was essentially zero-all they accomplished was an attitude change. Tail wheel hit the ground at 42 ft/sec. Damage was: 1) broke the tail wheel rim and cut the tire; 2) Scraped the trailing edge of the stabilator. Happened at about 3:30 PM and with a new wheel/tire and the same stabilator straightened via a pair of vice-grips, that ship flew at 0700 the next morning. There is a video of that landing floating around.

Hasten to add that I’m referring to the Defiant design in the preceding paragraph. I’m not at all certain as to the specifics of the present S-97 landing gear design loads criteria.

[SansAnhedral]

I agree that that the Army's waffling could prove disastrous. Although Army is getting new/rebuilt medium lift 'copters, they are still basically the same technology and performance as what has been around for 20-30 years, and you have to start moving away from that sometime. The nice thing about CS3 is its widespread applicability.

Here is how serious the Army seems about actually going though with FVL CS3 :rolleyes:

https://insidedefense.com/insider/army-announces-potential-black-hawk-buy

[SplineDrive]

Here is how serious the Army seems about actually going though with FVL CS3 :rolleyes:

https://insidedefense.com/insider/army-announces-potential-black-hawk-buy

Saw this link on HeliOps Facebook page... Hopefully a more complete video is released. If the video was shot from the ground, then presumably as much of the demo was done within eyesight as possible. Would be a good time to show off some maneuverability.

https://vimeo.com/282705255/ce17a701de

[IFMU]

Very cool video, thanks!

[SplineDrive]

After a few months of quiet, some more progress with S-97 AC2... finally exceeded 200 knots and demoed some various low speed maneuvers and some decent angle of bank, etc.

Sikorsky Raider Hits 200 knots

[The Sultan]

And it only took 3 years and 4 months from first flight to go 10 knots faster than a 1960’s era Cobra. Meanwhile the V-280 cruised faster on its 300+ mile ferry flight and has already flown 50 knots faster.

[industry insider]

Regardless of your apparent dislike for the Winged S and anything they do Sultan, any technology which advances rotary flight whether it be the FBW of the 525 or the X2 / S-97 concept or the V280, it should be applauded and we should respect those who develop and test it.

[SansAnhedral]

After a few months of quiet, some more progress with S-97 AC2... finally exceeded 200 knots and demoed some various low speed maneuvers and some decent angle of bank, etc.

Sikorsky Raider Hits 200 knots (https://www.youtube.com/watch?v=Elh0IM7Zp2U)

Well this sounds interesting.

"Low acoustics" in high speed mode (skip to 1:34): https://www.youtube.com/watch?v=Elh0IM7Zp2U&t=94s

High speed flyby from the 8/1 video: https://www.youtube.com/watch?v=-rH8KEhfKjo

Did they doctor the sound, or what is going on differently in the promo video? I notice a more nose-low attitude, is that just running rotor-only with a freewheeling prop in that clip?

[SplineDrive]

I think the nose down pass is main rotor thrust only, so a helo mode pass with the prop disengaged. There’s a nice side shot where you can see the exhaust gasses... as close as they are to the prop, I can imagine that you’d never want to have the prop truly stopped and stationary. So it looks like it’s spinning, but probably just from windmilling and or torque from a disengaged wet clutch.

Definitely sounds like a hornets with the prop engaged, but it should be pretty quiet with the prop off.

Well this sounds interesting.

"Low acoustics" in high speed mode (skip to 1:34): https://www.youtube.com/watch?v=Elh0IM7Zp2U&t=94s

High speed flyby from the 8/1 video: https://www.youtube.com/watch?v=-rH8KEhfKjo

Did they doctor the sound, or what is going on differently in the promo video? I notice a more nose-low attitude, is that just running rotor-only with a freewheeling prop in that clip?

[IFMU]

Did they doctor the sound, or what is going on differently in the promo video?
I've never heard the Raider in person. I've spent a lot of time with the X2. The first time Kevin pulled pitch it got very quiet in the TM trailer. All of us looked up from our screens to see what happened. All the data said it was running but the noise went away. Those blades are magic. During the early no prop flights all you could hear outside was the S76 chase. I do not believe that video is doctored.
Excellent job S97 team!

[KqQNr]

I've never heard the Raider in person. I've spent a lot of time with the X2. The first time Kevin pulled pitch it got very quiet in the TM trailer. All of us looked up from our screens to see what happened. All the data said it was running but the noise went away. Those blades are magic. During the early no prop flights all you could hear outside was the S76 chase. I do not believe that video is doctored.
Excellent job S97 team!

There's nothing "magic" about the rotors. I've been very near an H-53E on takeoff and "heard" it make almost no sound, yet on other days during rotor engagement one would have a difficult time speaking to a person right next to them. The effect of relative wind on the acoustic signature is far more likely the factor in rotor noise. Also, at least when X2 was flying, the -76 was generally positioned closer to the TM van than the test article (to the best of my recollection).

[IFMU]

There's nothing "magic" about the rotors. I've been very near an H-53E on takeoff and "heard" it make almost no sound, yet on other days during rotor engagement one would have a difficult time speaking to a person right next to them. The effect of relative wind on the acoustic signature is far more likely the factor in rotor noise. Also, at least when X2 was flying, the -76 was generally positioned closer to the TM van than the test article (to the best of my recollection).
A 53E making no sound? That I've never seen! Or heard I should say.
When they flew the X2 in Elmira, you cannot say the S76 was closer to the X2 trailer. I was there!

[KqQNr]

Fair enough, I was speaking about WPB - and I was there. Re: H-53Es, my point is that if the winds are right, the sound is substantially reduced (but not eliminated). I am sure if you ask the Kilo guys, they will tell you the same thing.

[The Sultan]

https://m.youtube.com/watch?v=d9rnb0AXTVc

Latest V-280 video compilation shows why the 97’s videos are not that impressive.

[IFMU]

Show some confidence and post that in the 280 thread!

[SansAnhedral]

Looks like the full factual NTSB report was released on the S97 "hard landing" back in 2017.

5 seconds of roll oscillations up to 60 degrees (!) followed by rotor intermeshing and destruction. Could have been a far worse outcome. The whole incident reminds of the control issues experienced on XH-59 back in the 70s causing the loss of the first airframe (intermeshing blades in that incident as well) with the 2nd getting airworthy 2 years later.

https://www.verticalmag.com/news/ntsb-releases-more-details-s-97-raider-accident/

Actual report:

https://dms.ntsb.gov/public/62000-62499/62323/624201.pdf

[IFMU]

Thank you for the link. The two accidents are very dissimilar. I found the Raider accident troubling as the flight controls were my job on X2. They should have done a better job in test.

I truly believe anybody who designs FBW helicopter control systems should be a helicopter pilot, regardless of what company they work for.

[SansAnhedral]

Thank you for the link. The two accidents are very dissimilar. I found the Raider accident troubling as the flight controls were my job on X2. They should have done a better job in test.

True, they were somewhat opposite in respect (too low gains (https://www.sikorskyarchives.com/S-69%20(XH-59A).php) in XH-59 vs 2.5x cyclic oversensitivity in S-97 in transition), but still overall the same general issue - cyclic flight control.

[JohnDixson]

Sans, it wasn’t low gain on the 59 ( in the sense of control sensitivity ), but rather low blade range, i.e., total moment capability longitudinally. The hell of that issue was that they’d been up against the forward stop previously.

[CTR]

Reading the accident report I was surprised to discover that the blades contacted each other while still in flight from rapid roll reversals. I had expected to read they contacted each other when the aircraft landed hard. I would’ve expected some level of envelope CLAW protection to prevent actuator commands that could result in upper and lower rotor blade contact from pilot inputs. Even if the cyclic gain was too high, shouldn’t the actuator commands to the rotor have been limited?

[SansAnhedral]

Sans, it wasn’t low gain on the 59 ( in the sense of control sensitivity ), but rather low blade range, i.e., total moment capability longitudinally. The hell of that issue was that they’d been up against the forward stop previously.

Ah I see. Thanks for the correction John, I got the "low gain" quote from the Sikorsky Archives article.

First flight occurred in June, 1973. One month later the first XH-59A aircraft experienced a low speed accident on the flight field. The design team had never dealt with a rotor system as stiff as this before. There was much concern about the extremely high control power that the rotor could develop. As a result, the control system was designed with a very low gain to prevent the controls from being too sensitive. This seemed to work out fine in the initial hover tests. However, when the pilots moved out of hover to transition to forward flight, the aircraft tended to nose up. The pilot inputted more and more forward cyclic to counter this, until the stick was on the forward stop and the aircraft was still nosing up. The pilot reduced the collective to get it back on the ground. The tail contacted the ground first and the aircraft rolled over until the blades struck the ground. The rotor system was destroyed. Both pilots were uninjured.

This set the program back for over a year while the cause of the accident was determined. The conclusion was that the control system gains were too low to cover all flight modes. Aircraft #1 was rebuilt for wind tunnel testing, but was not returned to flight status

[JohnDixson]

The transition to forward flight resulted in the main rotor downwash impacting the low horizontal tail, which is what of course drove the tail down and nose up.
( About a year later, we were to engage that sort of problem in a major way with the original UTTAS tail which if I recall was 60 sq ft. ).

[The Sultan]

From R&W:


The compound helicopter, one of two Sikorsky built initially to satisfy the Army’s need for an armed scout helicopter to replace the OH-58D Kiowa Warrior, now has 55 total flight hours. It has flown to 207 knots in level cruise flight, performed 60-degree banks and risen to 8,000 feet.


Raider is flying almost weekly and at up to 180 knots — well past the sprint speed of a conventional helicopter — on almost every outings, said Chief Test Pilot Bill Fell. The goal was to fly at 220 knots, but the aircraft might not make that benchmark in its current configuration, Fell said.
Sent from my iPad

The above from R&W. Knowing the goals of the program this has to be considered a major setback to both the program and a failure of the ABC concept to produce a leap forward in rotorcraft. Taken with the lack of progress on the SB-1 one has to wonder if Sikorsky would have been better off not building hardware and hope a paper proposal based on empty promises could yield a development contact. Now that they have generated real data it will be hard to put the failure Genie back in the bottle.

[SplineDrive]

From R&W:



The above from R&W. Knowing the goals of the program this has to be considered a major setback to both the program and a failure of the ABC concept to produce a leap forward in rotorcraft. Taken with the lack of progress on the SB-1 one has to wonder if Sikorsky would have been better off not building hardware and hope a paper proposal based on empty promises could yield a development contact. Now that they have generated real data it will be hard to put the failure Genie back in the bottle.


An article a while back had the comment from the Army stating something to the effect of “the Army knows quite a bit about the rigid coaxial configuration”... that may not be a good thing for Sikorsky and Sikorsky-Boeing.

[SansAnhedral]

The compound helicopter, one of two Sikorsky built initially to satisfy the Army’s need for an armed scout helicopter to replace the OH-58D Kiowa Warrior, now has 55 total flight hours. It has flown to 207 knots in level cruise flight, performed 60-degree banks and risen to 8,000 feet.

Wait, 55 flight hours in 4 years of flight testing? :sad:

[The Sultan]

55 hours is the total for the one that hasn’t crashed.

[The Sultan]

Article and video about 97’s “agility.” Looks lumbering at best, must be concerned about getting another upper/lower rotor collision. Not so sure why they spend so much time on fuselage attitude when tilt rotors are superior in every way whether you want a +/- pitch attitude or acceling or deceling with a level fuselage.

https://breakingdefense.com/2019/06/sikorsky-be-nimble-s-97-raider-shows-off-for-army-fara/

[The Sultan]

Just think...this is the best Sikorsky can say about the S-97.

http://digitaledition.rotorandwing.com/july-august-2019/raider-rotor-and-wing-witnesses-first-public-flight-of-sikorskys-fast-attack-prototype/?_ga=2.71933013.731871994.1563801859-1878792707.1544675409

Having to use rotor aero to increase rotor separation to allow “safe” flight thereby resulting in so much drag they can not meet even their new lowered high speed goals does not bode well for this program or the SB-1.

[CTR]

Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?

From Rotor &Wing Article:
A glitch in the code caused the flight control system to miscue during the transition from takeoff to forward flight, and the aircraft began to wobble as the computer lost control of the separation between the counter-spinning rotors. The aircraft responded to pilot inputs more powerfully than it should have, causing the aircraft to slam into the ground. The force of the impact flexed the rotors enough that they made contact and shattered, Fell (Sikorsky Senior Test Pilot Bill Fell) explained.

From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.

[SansAnhedral]

Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?

From Rotor &Wing Article:
A glitch in the code caused the flight control system to miscue during the transition from takeoff to forward flight, and the aircraft began to wobble as the computer lost control of the separation between the counter-spinning rotors. The aircraft responded to pilot inputs more powerfully than it should have, causing the aircraft to slam into the ground. The force of the impact flexed the rotors enough that they made contact and shattered, Fell (Sikorsky Senior Test Pilot Bill Fell) explained.

From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.


It seems abundantly clear that in Bill's and Sikorsky repeated attempts to downplay the incident with the media, numerous reporters are understandably interpreting the blade contact as being a result of the hard landing, and not vice versa - a la the old XH-59 incident (https://www.pprune.org/showthread.php?p=9851191). This was certainly not the case.

I am sure Sikorsky was ruing the day of the NTSB report release. In my previous post (https://www.pprune.org/showthread.php?p=9865968) I had posited that based on the long-range helicopter news footage of the aftermath they could have been looking for possibly thrown components...little did I know they were searching for the outboard few feet of all the blades!

[SplineDrive]

Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?

From NTSB Accident Report:
3.0 VIDEO SUMMARY. Video of the accident sequence of events was reviewed. The video was filmed from the right rear quadrant of the helicopter. It showed the helicopter slowly taxing forward with all 3 landing gear wheels in contact with the ground. As the helicopter approaches the edge of the runway, the tail wheel lifts off the ground followed by the main landing gear lifting off the taxiway simultaneously. As the helicopter gets airborne, the nose pitched upward slightly with a slight right roll. The helicopter then rolls to the left about 20° angle of bank and the left landing gear contacts the ground. A right roll followed that went slightly past horizontal. The roll reversed to the left, exceeding 30° angle of bank, then reversed to the right, and as the helicopter rolled through the vertical plane, the upper and lower rotors intermeshed about the 1 o’clock position (as viewed from the cockpit), creating a cloud of blade fragments and gray dust. The right roll continued, exceeding 60° angle of bank, then reversed to the left, and then landed hard as the helicopter passed through the vertical plane. The rotors continued to turn, decelerating until they come to a stop 43 seconds later.

This one is easy... believe the NTSB.

[henra]

Did the S-97 rotors mesh in the air as described in the NTSB report based on the analysis of the video? Or has Rotor & Wing misquoted the pilots description of events by writing that the rotors meshed as a result of the hard landing?
From Rotor &Wing Article:
...
From NTSB Accident Report:
...
You are not seriously questioning whome to trust more, the NTSB or a Journo, are you?!

[The Sultan]

No he is not seriously questioning the NTSB. He is throwing shade on the effort of Sikorsky to cover up a serious design flaw in the S-97 and the similarly designed SB-1 which allows the rotors to collide in flight at moderate roll rates.

[CTR]

You are not seriously questioning whome to trust more, the NTSB or a Journo, are you?!

Actually, based on my flight test experience, I trust the pilot.

However based on even more experience I have little faith in the media accurately reporting what was stated in an interview.

[Nige321]

No he is not seriously questioning the NTSB. He is throwing shade on the effort of Sikorsky to cover up a serious design flaw in the S-97 and the similarly designed SB-1 which allows the rotors to collide in flight at moderate roll rates.

So what was the actual roll rate at the point of contact?
Define moderate...

You slag SK off at every opportunity.
Why...?

[The Sultan]

I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.

So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?

[SplineDrive]

So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?

I would classify it as an excellent teaching tool for new HQ, control law, dynamics, and aerodynamics engineers 😉

[henra]

I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.
We don't know if the collision of the blades was purely down to roll rate/onset. Could be that the erroneous control system caused more havoc, e.g. by controlling both rotors at different rates or overall throws.
I would not immediately conclude from this mishap that the concept as such is flawed. What seems clear is that the control logic needs some tweaking.
That said the prospect of this happening in flight is not so nice. So Sikorsky needs to make sure that even clumsy control input doesn't lead to such dynamic reduction of rotor diameter in flight...

[Nige321]

I understand the roll rate peaked at 100 deg per second. This is moderate for an air vehicle billed as highly maneuverable. Sikorsky billed the ABC rotors as being so stiff you could narrow the gap between rotors with no chance of them colliding in the extreme maneuvers that the concept was promised to be able to do.

So Nige how would you classify an aircraft that can damage itself in flight when it was not suppose to be able to, exhibiting vibration levels so high that test pilots limit the level flight speeds even in the test environment, and has so much drag that it can not even come close to the originally advertised 250 knots?


Bell 525
The aircraft broke up in flight[14] (https://en.wikipedia.org/wiki/Bell_525_Relentless#cite_note-14) while traveling about 229 mph at an altitude of about 2,000 feet.[15] (https://en.wikipedia.org/wiki/Bell_525_Relentless#cite_note-NTSB_prelim_report-15) In January 2018, the US National Transportation Safety Board (https://en.wikipedia.org/wiki/National_Transportation_Safety_Board) released its findings, saying that the aircraft had suffered from severe inflight vibrations, which resulted in a loss of rotor RPM, subsequent rotor flapping and rotor impact with the tailboom, causing the inflight break-up.

Bell 609
The aircraft broke up in midair after 27 minutes of flight, on a flight plan that included high speed testing.[88] (https://en.wikipedia.org/wiki/AgustaWestland_AW609#cite_note-vertical20151109-88)
[89] (https://en.wikipedia.org/wiki/AgustaWestland_AW609#cite_note-avtoday20151216-89) Investigators consider the most likely cause to be changes in flight control laws and tail changes.

I suppose these don't count...

[Bell_ringer]

Bell 609

Agusta 609, since pedantry seems to be the theme.

[CTR]

Bell 525
I suppose these don't count...

Nigel, I agree with you that Sultan seems in his posts to have a never ending vendetta against Sikorsky. He seems to take pleasure from twisting the knife. But in your efforts to strike back by bringing up the AW609 accidents as a comparison, you distort key facts.

Both the AW609 and the 525 accidents occurred while exploring extreme corners of their flight envelopes. Vdive recovery and simulated loss of an engine at Vmax respectively. The S-97 accident occurred lifting to a hover.

Both AW and Bell kept quiet and made no comments to the media regarding the probable causes of the accidents. And when the reports were published made no attempts to offer “Alternate Truths”. Sikorsky management by their actions following the S-97 crash in my opinion have not respected the name of the company founder.

Note that unlike Sultan, I did not blame the Sikorsky Senior Test Pilot for the misinformation in the article. I have little doubt it was either journalist error or Sikorsky PR editing. Test Pilots deserve our respect.

[The Sultan]

CTR: Never disrespected the pilots. Just stated the obvious that the test pilots in a monitored test environment are unwilling to push out to hit the planned test point. This points to serious loads or other safety issues not simply ride comfort.

Nige: The 525 accident occurred when the ship was well above Vne and the pilot failed to take action to correct rotor rpm droop within the planned response time after simulated engine loss. No traditional helicopter can survive flight above Vne with the rotor rpm decayed to 60% of normal operating rpm.

As to 609 the aircraft had been to the accident speeds and above without incident before they reduced the area of the tail. Also new flight control software to improve high speed stability with the smaller tail had been finalized, but not installed on the fatal flight.

Back to the 97 it was marketed to be physically impossible for the rotors to collide due to their stiffness. This was always thought to be a questionable claim especially when the size grew above the X-2. Collision of the rotors at flight rpm for any reason invalidates the concept. As stated in the NTSB report the control input rates were greater in the accident, not how the rotors were fundamentally controlled.

[The Sultan]

You slag SK off at every opportunity.
Why...?

To point out the hypocrisy of the Sikorsky acolytes in this forum. They continuously ignore the basic truth that Sikorsky’s days of competence are well passed. What technological leap or even competent design have they done in the last 30 years?

The S-92? Just a refuselaged 60 with higher vibration an noisier rotor and a transmission that will fail in 12 minutes after loss of lube (when the requirement for cert is 30 minutes).

The Cyclone? 10+ years late, $200m per aircraft cost for another 60 derivative.

The CH-53K? Another 10 year late program, unit cost exceeding 3 times the original estimate of $35M, and near program ending unsolved problems (main and tail rotors, main transmission, engines, and the structure). IOC is now pushed out to 2023. Who thinks this is a winner?

[Lonewolf_50]

CTR: Never disrespected the pilots.
{and then you write}Nige: The 525 accident occurred when the ship was well above Vne and the pilot failed to take action to correct rotor rpm droop within the planned response time after simulated engine loss. Looks like you just crapped on two dead Bell pilots to me.

What I read in the NTSB report that came out regarding the dampening / vibe isolation (or lack there of) in the collective/power channel tells me that they were set up by the FBW system design.
Granted, those reports provide a particular view/perspective on such things, and are the limit of my understanding of that crash.

Is everyone else at Bell satisfied that the pilots screwed that one up or is that just you?

Regarding your disdain for Sikorsky: we get it. We got it last year too, and the year before.

[henra]

Back to the 97 it was marketed to be physically impossible for the rotors to collide due to their stiffness.
When not limiting the control throws and preventing opposite or differing blade excursions between both discs it can't really be physically impossible. Or the rotor blades would have to be so stiff that they would either break before touching or be so thick that the drag would be ridiculously high. Effectively every Helicopter can chop off his own tail if given enough cyclic authority. Control limits can possibly prevent this but that goes out off the window once control logic runs havoc which apparently was the case here.

[etudiant]

Nige: The 525 accident occurred when the ship was well above Vne and the pilot failed to take action to correct rotor rpm droop within the planned response time after simulated engine loss. No traditional helicopter can survive flight above Vne with the rotor rpm decayed to 60% of normal operating rpm.


If that is so, why has the airframe certification been delayed so much? It seems a pretty extended delay for what you describe as a clear cut pilot error.

[noneofyourbusiness]

Rigid rotor for noise control? We know that people who build ultralight gyrocopters want flexible rotor blades for "ride comfort". If the blades are too stiff, these enthusiasts complain about the flight comfort. If the vibration issue is overcome, do rigid rotors work the air less, and thereby substantially reduce noise? Or not? We know Boeing is pursuing a single main rotor design as a replacement for the Apache, with a pusher propeller. Bell is pursuing a single main rotor design for FARA, which we do not know if it will have a pusher prop. Does the Raider for a special forces variant add a shroud around the pusher prop for further noise reduction? A single main rotor should be quieter than dual counter-rotating rotors.

[CTR]

If that is so, why has the airframe certification been delayed so much? It seems a pretty extended delay for what you describe as a clear cut pilot error.

If you have ever worked in aircraft development and certification you would know nothing is ever simple, rapid, or “clear cut”. Read and learn, all that post simplistic responses on both sides of this discussion.

https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20160706X42741&key=1

[IFMU]

Rigid rotor for noise control? We know that people who build ultralight gyrocopters want flexible rotor blades for "ride comfort". If the blades are too stiff, these enthusiasts complain about the flight comfort. If the vibration issue is overcome, do rigid rotors work the air less, and thereby substantially reduce noise? Or not? We know Boeing is pursuing a single main rotor design as a replacement for the Apache, with a pusher propeller. Bell is pursuing a single main rotor design for FARA, which we do not know if it will have a pusher prop. Does the Raider for a special forces variant add a shroud around the pusher prop for further noise reduction? A single main rotor should be quieter than dual counter-rotating rotors.
A shroud is not needed for noise control. They have a clutch. I can tell you the X2 main rotor is orders of magnitude quieter than any single rotor helicopter that I've heard. I don't believe this is due to stiffness, just awesome aerodynamics. Regarding vibration, the X2 vibes were lower than a UH60 when it was cruising at 250 kts. We got it there using conventional balancing methods cleaned up with AVC.

Ultralight gyros? How is that relevant?

[etudiant]

If you have ever worked in aircraft development and certification you would know nothing is ever simple, rapid, or “clear cut”. Read and learn, all that post simplistic responses on both sides of this discussion.

https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20160706X42741&key=1

Very much on board with all that.
However, it does seem to me that the 525 was cruising to certification when this accident happened. The inquiry has resulted in a material certification delay, rather unexpected had the cause been as obviously pilot error as was suggested above,

[noneofyourbusiness]

A shroud is not needed for noise control. They have a clutch. I can tell you the X2 main rotor is orders of magnitude quieter than any single rotor helicopter that I've heard. I don't believe this is due to stiffness, just awesome aerodynamics. Regarding vibration, the X2 vibes were lower than a UH60 when it was cruising at 250 kts. We got it there using conventional balancing methods cleaned up with AVC.

Ultralight gyros? How is that relevant?
Thanks for your input. A shroud would be useful for when the prop is engaged. It is difficult to believe Sikorsky would sell any noisy helicopters if all they had to do was change the aerodynamics of the blades.

[JohnDixson]

I’m surprised that IFMU didn’t also suggest that SA might also propose an alternative: a compound version of the RAH-66 Comanche for FARA. Now that might get even my attention!

[IFMU]

I’m surprised that IFMU didn’t also suggest that SA might also propose an alternative: a compound version of the RAH-66 Comanche for FARA. Now that might get even my attention!
That doesn't float my boat! I think the Comanche airframe was pretty good as it was.

Adding a shroud is not free. Performance gains from a shroud are sketchy and that is weight where you don't need it.

[JohnDixson]

Indeed it was, but doesn’t the FARA have a 180 kt cruise number?

[SplineDrive]

Indeed it was, but doesn’t the FARA have a 180 kt cruise number?

A compounded RAH-66 would have a wing to help offload the rotor as mu increases... that alone should enable the extra speed for FARA with a usable payload. At 180 knots, it wouldn’t need a pusher. I think Sikorsky’s leadership is pretty clear they want an X-2 in the FARA role, regardless if the complexity makes sense for the requirements or not.

[JohnDixson]

Sorry, wasn’t thinking about a wing, only a pusher. Just dreaming, I think. We did wing on/off maneuverability comparison with the S-67 as a NASA or Army contract ( do not recall the sponsor ).

[SplineDrive]

Sorry, wasn’t thinking about a wing, only a pusher. Just dreaming, I think. We did wing on/off maneuverability comparison with the S-67 as a NASA or Army contract ( do not recall the sponsor ).

I’ve got those reports on the S-67 somewhere, I recall they’re for the Army. They’re on one of the .mil data servers.

[JohnDixson]

The point was, we achieved some additional Nz capability with the wing, but less than some of us were expecting My point re the pusher was based on guessing that the FARA requirement might include a fairly respectable maneuver envelope at the 180 kt point, and having a pusher would provide for a lower rotor Ct/sigma at 180, allowing that maneuverability. I should add that I haven't a clue as to the FARA maneuverability requirements.

[Lonewolf_50]

New pictures of the latest mods on S-97. Interesting comment 'way down inside the article' and they made mention of how much 'pointier' the nose is on this prototype.
Its modular effects launchers are extended but can be folded into the fuselage to reduce drag during flight. Those pods can also be loaded with other munitions, including air-launched drones. They also can be removed to clear space for assault troops or casualty evacuation. If you look at the Army's decision to drop the OH-58D and go with "attack helicopters (AH-64) + drones" as their concept for armed reconnaissance, this is an interesting way to achieve that. You could also just load a few hellfires or other Air to Ground munitions based on the mission. The 3 barrel 20mm is hopefully common to this and the Marine AH-1Z (Viper). Joint logistics and all that ... and note that they got rid of that "tail wheel in the tail" in favor of a more conventional tricycle landing gear configuration.
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1920x1080/raider_sikorsky_chin_gun_and_hellfires_317c0681de860d0103f63 83e0cae0c6b676d2bde.jpg

[The Sultan]

Lone,

Holy S! This is the most insane weapons configuration I have ever seen for the following:

1. Flight crew will not be happy with missiles stowed in the cabin and aimed at the back of their heads during missions. Will be a significant distraction. One bullet igniting a motor and game over.
2. In an emergency at low level it will be difficult to jettison the weapons to reduce weight and/or get rid of things that go boom before impacting the ground.
3. Unlike Airwolf this configuration looks impossible to deploy symmetrically or asymmetrically at high speeds due to high drag and having gaping holes in the side of the cabin. Anything loose in the cabin will end up going through the pusher.
4. The pusher is directly aft of the weapons and will be impinged face on by the back blast of the missiles. Good way to get things blown off.

[Doors Off]

Lone,

Holy S! This is the most insane weapons configuration I have ever seen for the following:

1. Flight crew will not be happy with missiles stowed in the cabin and aimed at the back of their heads during missions. Will be a significant distraction. One bullet igniting a motor and game over.
2. In an emergency at low level it will be difficult to jettison the weapons to reduce weight and/or get rid of things that go boom before impacting the ground.
3. Unlike Airwolf this configuration looks impossible to deploy symmetrically or asymmetrically at high speeds due to high drag and having gaping holes in the side of the cabin. Anything loose in the cabin will end up going through the pusher.
4. The pusher is directly aft of the weapons and will be impinged face on by the back blast of the missiles. Good way to get things blown off.


It is pretty insane. That said, internal weapons carriage has been around for a while and the number of bullets that have hit Hellfires and not ignited motors or warheads, is significant. The risk is high but the likelihood incredibly low.

On the jettison function, I'm thinking the whole doors might go, rather than an open to jettison munition pods. Just a thought.

On the FOD threat to the pusher, via points 3 and 4, I would think that it is of much less consequence to the pusher than that to a tail rotor. You would only lose speed, rather than a total TR drive/control failure. I know which I would prefer to lose.

All great points you have raised. I just saw the pretty pictures until you raised the questions about certain practicalities. Thank you for making me think.

[CTR]

Sikorsky appears to have learned a lesson from Bell after the Defiant fumbles in regards to sticking to promised schedule, and being more open with the press. From the photos it appears their FARA aircraft has progressed well towards first flight. But on close examination of the mast and the weapons carriage, they are obviously wood or plastic mock-ups of real parts. The nose gear reality also looks questionable.

So while I complement Sikorsky on their apparent change in ability to meet schedule and on being more open to the press, I have to wonder how much of the aircraft was just slapped together for a photo op.

[exwessex]

Am I right in thinking that the nose wheel folds to the left?

[The Sultan]

On the FOD threat to the pusher, via points 3 and 4, I would think that it is of much less consequence to the pusher than that to a tail rotor. You would only lose speed, rather than a total TR drive/control failure. I know which I would prefer to lose.


Doors

Impact of weapon exhaust on the tail has always been a concern and looked at very closely. That’s why the weapons are placed on all helicopters I know of where the tail rotor is not directly behind it. On the Raider the pusher is very big and face on to the back blast. If damaged the pusher wouldn’t just stop working, but be significantly out of balance. If the unbalance is large enough you loose the whole tail.

As to one of your other points about internal weapons carriage; name one helicopter where the missiles are mounted inside the occupied space? They are normally mounted externally or in dedicated weapon bays. When working around military helicopters I always paid attention to the “Armed” warnings and avoided standing in front of the missiles (even knowing if one launched it didn’t have to hit you to cause serious damage to the body). Won’t be able to do that in the Raider.

[retoocs]

Am I right in thinking that the nose wheel folds to the left?

You can see the right side door in this picture. https://www.thedrive.com/uploads/2022/06/29/DSC08204-SIKORSKY-RAIDER-X-FARA-CP-JUNE-2022-Photo2-scaled.jpg

[exwessex]

Thanks-that seems more conventional.

[Commando Cody]

One other things these two photos confirm: On an X2, all usable internal space has to be forward of the mast, making the vehicle have to be longer than a conventional helo of comparable cabin/bay size.

[Lonewolf_50]

Lone,

Holy S! This is the most insane weapons configuration I have ever seen for the following:

1. Flight crew will not be happy with missiles stowed in the cabin and aimed at the back of their heads during missions.
2. In an emergency at low level it will be difficult to jettison the weapons to reduce weight and/or get rid of things that go boom before impacting the ground.
3. Unlike Airwolf this configuration looks impossible to deploy symmetrically or asymmetrically at high speeds due to high drag and having gaping holes in the side of the cabin. Anything loose in the cabin will end up going through the pusher.
4. The pusher is directly aft of the weapons and will be impinged face on by the back blast of the missiles. Good way to get things blown off. All thoughts that the FARA team had better address.
From a practical point of view, I am certain that number three is the most pressing. Self FOD is a poor idea, so a procedural 'clean up' has to be implemented or what you suggest will for darned sure happen at least once. Humans are humans, right?
As to number 4, I suspect that the weapons rack can include a CAD type thing that pushes the munition down before the rocket engine fires. But I agree with you that this issue must be addressed by the FARA team.

WTF, I agreed with The Sultan? That means that I am buying the next round! :ok::D:}:E

[The Sultan]

Lone wrote:

I suspect that the weapons rack can include a CAD type thing that pushes the munition down before the rocket engine fires.

On the pushing down this is hard successfully for an aircraft that lives nap of earth.

As to storage of the missiles in the cabin I recommend Holland's "Big Week" about the bombing campaign in Europe (one of, if not the best on the subject). It includes numerous examples on how bombers just vanishing after their load explodes and how devastated the other crews were witnessing it. Sure fortified their belief they would not make it to their going home mission count. Not exactly a moral builder.

[Lonewolf_50]

Lone wrote:
On the pushing down this is hard successfully for an aircraft that lives nap of earth.
If you were a pilot you'd understand how odd that statement looks.
It only takes a few feet of down and then "away from the aircraft" for that exhaust to be below the tail. But if the rocket ignites while still in the rack? Yeah, a problem.
And no, NoE isn't 5 feet off the ground...but as you've never flown it how would you know?

As to the missiles in the cabin: certainly an opportunity for an own goal.
If one does not learn how to use the arm/disarm toggle switch that's been on aircraft since before I got my wings over 40 years ago, yeah, you could shoot yourself
While that's a minor concern it does need to be addressed. Something like an overcenter lock for the door that opens a circuit when doors are closed, but the circuit closes when the doors open/deploy. Many other ways to peel that onion as well, but the concern you raise needs to be addressed in the human factors engineering phase.

[The Sultan]

If you were a pilot you'd understand how odd that statement looks.
It only takes a few feet of down and then "away from the aircraft" for that exhaust to be below the tail. But if the rocket ignites while still in the rack? Yeah, a problem.
And no, NoE isn't 5 feet off the ground...but as you've never flown it how would you know?.

Lone,

While not a pilot (something about having too high of an IQ) I have thousands of hours in the front or left seat of military helicopters so I am very familiar with NOE day and night operations. Drop before ignition is a bad idea and would result in more than a few own goals.

[Lonewolf_50]

Lone,

While not a pilot (something about having too high of an IQ) I have thousands of hours in the front or left seat of military helicopters so I am very familiar with NOE day and night operations. Drop before ignition is a bad idea and would result in more than a few own goals. It is certainly fraught with technical chances for malfunction, yes.

There is ordnance that is released in an unarmed state in a variety of military aircraft. (Arming delays come in a variety of forms, our torps had the low tech solution of a lanyard...). Since most munitions would be guided, the 'drop and ignite' poses little obstacle to the munition getting to its target, but, all of that violated the KISS principle and requires a substantial change in arming and ignition logic . That would make the munitions for the Raider bespoke / non standard with the other users of that munition. That's a bit of a red flag for most people in the acquisition field.

Your point on "there's a better way to carry/deploy those weapons" has merit.

I had envisioned, when I saw the original Raider design, that an internally carried weapons module would be deck / floor mounted and "roll" or "pivot" about 210 - 240 degrees on fore and aft arms. The mount would (in my mind's eye) be a circular or hexagonal rack that could revolve like the cylinder in a revolver-style pistol.
After deployment, it would hang adjacent to and below the edge of the door.
The bottom of the cylinder, or the bottom two positions on the cylinder, would be the only ones that could fire. (that should keep the rocket exhaust below the horizontal stab and pusher prop, but it would take some better modeling and dynamic testing to confirm that).
Yeah, that's a rube goldberg device for sure, but then so is every helicopter out there. :E
That kind of approach would require more moving parts in terms of the door hinge (or a sliding door rather than a hinged door), and of course that leads to more things that could malfunction.
I'd sketch it for you on the back of a napkin if were were in a bar, but this format doesn't lend itself to that kind of illustration.

[SansAnhedral]

A couple of other details that have not been discussed in this thread re:RaiderX gull wing door weapons deployment:

1. The entire rack with stores is hanging from the single-cantilever door, which looks to be operated with short-coupled linear actuators pushing on lugs. This seems like it would be extremely structurally difficult to create a sufficiently stiff deployed-door state - particularly with the major historical vibration problems on every X2 platform ever built.

2. Rotation of the stores rack into the deployed position (~ 90 degrees or so) would also apply torque and spin the seeker heads on guided munitions like AGM-114.

[IFMU]

particularly with the major historical vibration problems on every X2 platform ever built.


The X2 TD was better at 250kts than a UH60 in cruise. I can't comment on its progeny.

[CTR]

SansAnhedral,

Perhaps a weapons bay actuation configuration similar as shown in the attached US Patent is more realistic.

https://pdfpiw.uspto.gov/.piw?PageNum=0&docid=11370544&IDKey=93CF7B8BD2C5%0D%0A&HomeUrl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO2%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D% 25252Fnetahtml%25252FPTO%25252Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526co1%3DAND%2526d %3DPTXT%2526s1%3D11%2C370%2C544.PN.%2526OS%3DPN%2F11%2C370%2 C544%2526RS%3DPN%2F11%2C370%2C544

Maybe Bell will be willing to license the design rights to Sikorsky;-)

[SansAnhedral]

The X2 TD was better at 250kts than a UH60 in cruise. I can't comment on its progeny.

True, at 6000 pounds the X2 AVC did not saturate and maintained right around 0.5 IPS in all directions.

Its unfortunate that a practical/useful platform using X2 technology requires about minimum double that gross weight, which has proved to be a bridge too far for both AVC system designs Sikorsky has built since.

Just like CTR suggested above, perhaps Raider-X will license another recent Bell patent (https://patents.google.com/patent/US11214362B2) in their search for a solution!

[The Sultan]

The X2 TD was better at 250kts than a UH60 in cruise. I can't comment on its progeny.

The vibration in the X2 was brutal. That's why they had active vibration suppression for a single seater where the only goal is to not kill the pilot (all surviving test pilots will say it was great and ready for production no matter how bad it is). Relative to the UH-60, not a good example. It carries vibration suppression devices to make 130+ knots. On the S-97 you could tell from crew comments they were reluctant to go above 190 knots due to vibration as engineers worked to get it tolerable enough so they good dash to their max speed of 230 knots.

[Commando Cody]

The X2 TD was better at 250kts than a UH60 in cruise. I can't comment on its progeny.

I don't have the exact numbers immediately to hand but IIRC, in the entire X2 TD program the total time at 250 knots was only a few minutes. It is interesting the FAI offered Sikorsky the opportunity to take the world helicopter speed record (wingless compounds are classed as helicopters) which involves flying along over a measured course, doing a 180 and then flying the same course in the opposite direction (to account for the effect of wind) and taking the average of the two runs. This would be quite a feather in X2 technology's cap and would give great bragging rights for the technology. However, Sikorsky turned them down.

[Commando Cody]

Sultan:

I may be overlooking something, but I can't recall any existing helicopter that has a dedicated weapons bay for missiles. For FARA, neither competitor can get the speed the Army wants without an internal bay (and retractable gear).

In the case of Raider-X they're using the space that could be used for a cabin on a different version of the a/c', a "B" model used as a light transport. In the case of Invictus, they can be slimmer because there is no interest in using that area for anything other than missile carriage.

Lone Wolf:

I for one think your "revolver" idea is really clever, although eight missiles might be a tight fit. The big bugaboo would be weight, since Army has tight limit on acceptable gross weight for FARA.

[IFMU]

However, Sikorsky turned them down.
That was all on the VP at the time. He was a former Lockheed guy. He just wanted the program done. Too bad, because besides the FAI record there was still engineering and flight test work to do.

[heli1]

Sikorsky would have had to fly straight and level and with the aft propulser free wheeling to qualify for the helicopter speed record attempt. Otherwise Bell could have claimed it years ago with their modified UH-1 and its prodded jet engines.

[retoocs]

Maybe Sikorsky is re-using some previously engineered designs?

https://www.sandboxx.us/wp-content/uploads/2021/01/RAH-66-6.jpg

[CTR]

Maybe Sikorsky is re-using some previously engineered designs?


Very interesting, thanks for the photo. Looking at the gooseneck hinge on the door, and the ball-lock strut attached to the hinge in the door, it does not look like the weapons are actually attached to the door. There must be a secondary mechanism that is actually supporting the weapons rack.

[BLloydK]

Let’s remember the Sikorsky of Lockheed isn’t the Sikorsky of X2 days. The whole concept has lost its way since the triad of Lockheed Boeing and it’s Sikorsky bench warmers have been pushed aside. It started with Raider when the X2 team was pushed aside by its own leadership at the time for the next team to show anyone to include the X2 team it’s easy. So Raider went down the so called experts route chasing Army supposed dreams and requirements instead of letting the original X2 team do the Y next version of the X2.
The X2 was fast, smooth at the time it flew its speed flight. But after that speed flight the X2 team lost control of the X2 destiny to the marketing and program future chasers and the so called next team of Raider.
X2 was to finish its speed test flights and maneuvering flights to close out the modeling of an X2. It went over 250 kts at cruise 71 % power and it had speed and power remaining, vibes were good and the matrix set up for the AVCs was ingenious and set the stage for the Y aircraft. The X2 team had about 9 flights remaining but as mentioned the team was basically shutdown by leadership now chasing their idea of the Raider.

The X2 team wanted to after those 9 close out flights put a new design set of rotor blades on the X2, install a real AFCS system, an active tail and active collective to truely close out the X2 design model. The Y version the X2 team envisioned was a two engine S76 sized aircraft with a gross weight ~ 13 to 14000 lbs. But good things end when good things happen due to so called self proclaimed experts and leaders that have self in mind instead of promoting and supporting the real experts to move forward to get it done and accomplished.

S97 out of the gate was the wrong aircraft, one engine and no power or payload and capability for true over 200 kt speed or margin. Power to weight to drag basic computations didn’t add up and the aircraft structurally was under designed so it couldn’t do the maneuvers planned for such a capable concept. Then SB1 Defiant came along to scale up a design which we all knew wasn’t a viable path for the concept. So in the end what was good and had potential to change the way the helicopter could fly ended back with Raider and with the triad of Lockheed, Boeing and then the Sikorsky tag alongs chasing stupid Army requirements instead of letting the original X2 team follow thru on the concept and a Y platform aircraft so when it was time we could of offered a viable awesome finished product sooner than later.
The goal of the X2 team was accomplish all KPPs with the X platform on the X2 Demonstrator and then move onto the Y version as mentioned. If they were allowed to progress just think in less than 10 years we would be here today with a viable maneuvering and speed demon weapons platform. But here they are still in the big program paper chase with the so many experts of Lockheed and Boeing and Sikorsky now developing a one engine (still waiting the 15 years now ITEP magic engine) Raider X or FARA FLARA or …… and still a true Y Plane of the X2 has never flown to close out and prove the true viable capabilities of the X2 design and platform.

Again the X2 design and the X2 demonstrator met all its KPPs and if the original team was allowed to continue moving forward on its path the full potential as outlined would be a real accomplishment for the industry. As great as the ACH 66 Comanche now the the X2 follows its fate. Shame we don’t let the small selected group do the development for it has proved over and over in history it can be done.

But here you are design by committee, self proclaimed experts, dream requirements half baked and now in competition in a chase. So
good luck with the chase and the big program burdens. Go slow and drag it out and keep changing requirements as the Army leadership changes and the corporate leadership changes. To bad you don’t let the dedicated smart people move forward.

And really sad UTC sold Sikorsky..

[CTR]

BLloydK,

Thank you for one of the most interesting and enlightening posts I have read on PPRUNE in a very long time. Looking forward to your future posts.

[Commando Cody]

Sikorsky would have had to fly straight and level and with the aft propulser free wheeling to qualify for the helicopter speed record attempt. Otherwise Bell could have claimed it years ago with their modified UH-1 and its prodded jet engines.

IIRC, the Bell 533 often flew with a wing, which I believe would disqualify it, the rotor not being the only lift surface. More importantly, the podded jets were not integral to the rotorcraft's lift/propulsion system, which is a requirement, but merely an auxiliary thrust system independent of the helicopter's operation itself. Otherwise you could just hang a big enough jet on anything and just force your way through the air, with no advance in helicopter technology. The X2 TD does not use any auxiliary means of propulsion, the pusher is powered by the vehicle's normal engine/transmission and so would qualify as a helicopter for record purposes.

[Commando Cody]

Sultan:

"Impact of weapon exhaust on the tail has always been a concern and looked at very closely. That’s why the weapons are placed on all helicopters I know of where the tail rotor is not directly behind it. On the Raider the pusher is very big and face on to the back blast. If damaged the pusher wouldn’t just stop working, but be significantly out of balance. If the unbalance is large enough you loose the whole tail."

I wonder if you've hit on another, unannounced, reason why Bell changed the location/type of tail rotor on Invictus. In the initial configuration, the shrouded tail rotor was directly in line with the fuselage. This was no big deal on previous uses of this technology. However, in the case of the Bell 360, this also puts tha air flowing through it would be in line with the exhaust from missile launch. Their studies might have indicated this turbulence could potentially be a problem. Moving it to a conventional design higher up takes it out of this area. Could that be another reason for the move?

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/275x183/bell360orig_eaa76657eef0a4297b49166bac2ac499c17604d5.jpg
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/282x179/bell360mod_ecb1081bf00e223ace933d724dc2e51472d4f672.jpg

[SansAnhedral]

Let’s remember the Sikorsky of Lockheed isn’t the Sikorsky of X2 days. The whole concept has lost its way since the triad of Lockheed Boeing and it’s Sikorsky bench warmers have been pushed aside. It started with Raider when the X2 team was pushed aside by its own leadership at the time for the next team to show anyone to include the X2 team it’s easy. So Raider went down the so called experts route chasing Army supposed dreams and requirements instead of letting the original X2 team do the Y next version of the X2.
The X2 was fast, smooth at the time it flew its speed flight. But after that speed flight the X2 team lost control of the X2 destiny to the marketing and program future chasers and the so called next team of Raider.
X2 was to finish its speed test flights and maneuvering flights to close out the modeling of an X2. It went over 250 kts at cruise 71 % power and it had speed and power remaining, vibes were good and the matrix set up for the AVCs was ingenious and set the stage for the Y aircraft. The X2 team had about 9 flights remaining but as mentioned the team was basically shutdown by leadership now chasing their idea of the Raider.

The X2 team wanted to after those 9 close out flights put a new design set of rotor blades on the X2, install a real AFCS system, an active tail and active collective to truely close out the X2 design model. The Y version the X2 team envisioned was a two engine S76 sized aircraft with a gross weight ~ 13 to 14000 lbs. But good things end when good things happen due to so called self proclaimed experts and leaders that have self in mind instead of promoting and supporting the real experts to move forward to get it done and accomplished.

S97 out of the gate was the wrong aircraft, one engine and no power or payload and capability for true over 200 kt speed or margin. Power to weight to drag basic computations didn’t add up and the aircraft structurally was under designed so it couldn’t do the maneuvers planned for such a capable concept. Then SB1 Defiant came along to scale up a design which we all knew wasn’t a viable path for the concept. So in the end what was good and had potential to change the way the helicopter could fly ended back with Raider and with the triad of Lockheed, Boeing and then the Sikorsky tag alongs chasing stupid Army requirements instead of letting the original X2 team follow thru on the concept and a Y platform aircraft so when it was time we could of offered a viable awesome finished product sooner than later.
The goal of the X2 team was accomplish all KPPs with the X platform on the X2 Demonstrator and then move onto the Y version as mentioned. If they were allowed to progress just think in less than 10 years we would be here today with a viable maneuvering and speed demon weapons platform. But here they are still in the big program paper chase with the so many experts of Lockheed and Boeing and Sikorsky now developing a one engine (still waiting the 15 years now ITEP magic engine) Raider X or FARA FLARA or …… and still a true Y Plane of the X2 has never flown to close out and prove the true viable capabilities of the X2 design and platform.

Again the X2 design and the X2 demonstrator met all its KPPs and if the original team was allowed to continue moving forward on its path the full potential as outlined would be a real accomplishment for the industry. As great as the ACH 66 Comanche now the the X2 follows its fate. Shame we don’t let the small selected group do the development for it has proved over and over in history it can be done.

But here you are design by committee, self proclaimed experts, dream requirements half baked and now in competition in a chase. So
good luck with the chase and the big program burdens. Go slow and drag it out and keep changing requirements as the Army leadership changes and the corporate leadership changes. To bad you don’t let the dedicated smart people move forward.

And really sad UTC sold Sikorsky..

A lot to unpack here, least of which is my sneaking suspicion that we were just graced by a post from an esteemed Sikorsky test pilot.

Based upon the commentary above, it would seem that there is some belief that the increased gross weight of the aircraft would not necessarily guarantee an inherent increased vibration problem that we have witnessed on S97 and SB1.

While I understand and agree with the power limitation and drag issues mentioned on committee-designed Raider and Defiant...had the "Y-2" been built as described, what would have prevented the same vibration-based limitations the contemporary ships have experienced when it comes to ABC/LOC flight with essentially the same rigid rotor system (aside from perhaps much improved fuselage stiffness designs)?

Also was the S-76 sized "Y-2" concept at Sikorsky referred to as ACER (or maybe ASIR) at any point?

[The Sultan]

Bell’s FARA entry looks substantially more complete than Sikorsky’s.

https://www.thedrive.com/the-war-zone/nearly-complete-invictus-armed-scout-helicopter-looks-wicked-in-new-photos

[CTR]

Currently both Sikorsky and Bell state the first flight of the FARA prototypes are being delayed waiting for the customers supplied engine.

Assuming both receive their engines this November, it will be interesting to see if this is really the long pole in their first flight schedules.

[Lonewolf_50]

Lone Wolf:

I for one think your "revolver" idea is really clever, although eight missiles might be a tight fit. The big bugaboo would be weight, since Army has tight limit on acceptable gross weight for FARA.
The idea could be scaled down a bit to a pair of 'three packs' (one for each side) that revolve: top two un armed, bottom one armed, so more of a 'triangle' than a revolver, if they have to meet an internal weight bogey.
Aha, finally see what they are up to with the Invictus/360 sliding armament racks, from the link.

Can anyone explain to me why 360/Invictus/Bell FARA has two pilots? (Or pilot/gunner)
I would think that the automation, helmets, and mission packages developed for a variety of aircraft over last 30 years could be modded and integrated into this weapons system and allow it to be flown/operated by a single pilot. (Like an A-7, F-35, F-16, and so on).
Comments on that?
Did the Army write a hard requirement for 'must be a two seat aircraft' into this future system?

The impression I get from the pictures at The Drive link is that the wings are intended to be lift producing devices, not stub wings for weapons stations.
As depicted, they do not look to be adjustable in pitch (like the Black Hawk Horizontal stab) but basically wings similar to a fixed wing aircraft. And it occurs to me that they might include fuel capacity / tanks that cannot be down in the hull where the missiles / weapons slide in and out on that rack.
An interesting hybrid, to be sure.

[The Sultan]

Invictus’s wings date back to the Bell 533 high speed test aircraft with the main purpose to allow rotor thrust to be used for speed instead of lift.

Invictus is less two pilots than a pilot and a systems/drone manager. Also, when lurking in the trees a second pair of eyes is essential.

[Commando Cody]

Aside from lift, one of the other purposes that has been shown in illustrations is that they provide two more weapons stations. However, they probably couldn't be used for such while staying within the Army's weight limit unless it's acceptable to go over to carry more so long as you meet the requirement when carrying the Army specified load. In any case, using the stations would entail a noticeable performance hit, but it might be an acceptable option in cases where maximum firepower is most important.

Regarding the second crewman, Raider-X also has a crew of two. Don't forget, the original Army requirement for LHX (which eventually became Comanche) specified single pilot. This was eventually dropped when reality stepped in. Like The Sultan said, workload.

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/736x414/bell360wingmsls2_a3da20819491d421bfc326c40ff9202c467a1988.jp g

[Lonewolf_50]

Regarding the second crewman, Raider-X also has a crew of two. Don't forget, the original Army requirement for LHX (which eventually became Comanche) specified single pilot. This was eventually dropped when reality stepped in. Like The Sultan said, workload. I am reasonably aware of the LHX failure, and the risk decisions on missions systems integration on Comanche in terms of cockpit loading, but mission systems in general have come a long way since the 1980's. Army is not good at getting out of old paradigms, and never has been. I will say that I believe that the Apache mafia did as much harm as good in the Comanche's development ... but that's all water under the bridge.

[PPRuNeUser0211]

I am reasonably aware of the LHX failure, and the risk decisions on missions systems integration on Comanche in terms of cockpit loading, but mission systems in general have come a long way since the 1980's. Army is not good at getting out of old paradigms, and never has been. I will say that I believe that the Apache mafia did as much harm as good in the Comanche's development ... but that's all water under the bridge.

I'd say there's a fundamental reality to flying rotorcraft nap of the earth, which is that the pilot flying has a high workload and a no fail task that automation can't cope with yet unless you give it active sensors (trees, wires, ducks and geese). Active sensors come with a freedom of action penalty due to emcon, so that rules out most automation for now, until computer vision gets really good. Maximum allowable time eyes in for a pilot flying at or below 50' is maybe a second or 2 at cruise speeds. Not really an opportunity there to operate anything or assess a sensor picture.

Contrast that with fast jet aircraft at medium level where the pilot can be eyes in for a few more seconds at a time - here automation of flying tasks and sensor fusion has made single pilot ops feasible.

I would say that advances have meant the non flying crew member can be expected to do a lot more: uncrewed teaming brings in a lot of information but we're a long way from that just being neatly dropped as threats on to a map from an EO picture though AI might help get that over the line to warfighting standard in the next decade or so. (Noting that things a helicopter crew care about tend to be harder to find than something a jet monkey cares about).

Tesla's computer vision kit is probably the most advanced real world example and that can't cope with the real world to appropriate safety standards yet, so we can't really expect a niche application for military rotorcraft to be any better tbh. Everyone that has gone one better is essentially relying on an active sensor of some description (typically LIDAR, which at least is relatively low prob of intercept). Active sensor reliance, as mentioned earlier, limits you due to emcon, but also introduces as massive vulnerability for hostile exploitation unless you have a few alternatives. Demoes of uncrewed Blackhawks going from A to B are great, but it's not tactical flying in a warfighting operation with a bad guy vote.

[Lonewolf_50]

OK, I guess the old 'task saturation' bogey is still out there, thanks for the in depth response pba_target. :ok:

[CTR]

The introduction of armed drones has forced the Army to continually redefine mission and crew requirements.

Armed drones helped kill the need for the Comanche, and commanding a squadron of drones may require a FARA second seat.

[Commando Cody]

There are some other reasons for the second crew member in addition to what's in pba_target's comprehensive post:

Aside from strictly nap of the earth operations, there's simply the reality of flying low level in irregular terrain that's going to keep the pilot pretty focused without the complication of trying to read and interpret sensors and programming and launching weapons. Army says it wants to operate FARA in urban environments. There's going to be enough going on in that situation without burdening the pilot with other tasks unrelated to flying and maneuvering the ship. There'd be a lot of right brain/left brain things going on which would Beverly degrade effectiveness. Also, while firing the cannon straight ahead wouldn't be too burdensome, consider what would be involved mentally in maintaining safe flight while simultaneously operating the cannon off-axis, especially against a mobile target.