How Many Fuel Stops?
 

Just published:

“Last week, a fascinating experimental helicopter from Sikorsky and Boeing made its longest flight yet: It flew from West Palm Beach, Florida to Nashville, Tennessee—a distance of some 805 miles. The two companies behind the futuristic chopper announced the March 21 flight in a press briefing today, saying it was the first time that this helicopter had traveled out of Florida, where all its previous testing had taken place.”

https://www.popsci.com/technology/si...copter-flight/

Anyone know how many a “couple stops” is for fuel?

Another Defiant Embarrasment
 

While truncated the article still has the pertinent information:

https://aviationweek.com/defense-spa...raa-downselect

This is another PR disaster for Team Defiant. They are proud it took them 7 hours to fly 700 miles between West Palm and Nashville….and they required two hot refueling stops to do it! This is not the speed and range the Army is looking for.

Even More Embarrassing
 

From another article lifted from the SB press release:

So they are proud that it was able to fly 700 nautical miles with only two stops/three loads of fuel and not kill anybody. Kind of like aviation records broken in 1910.

Another quote bragged they never got over 50% torque. Translation: May not have made it if we pulled more than 50% torque. This may give us a clue on how screwed up the drive system is.

No worries. The government money printing presses will keep on pumping out until the project goes the way of the Comanche.

For comparison, from Popular Science Feb. 2012:

“With all its tanks full of fuel, the CV-22 Osprey can go about 2100 miles—farther than the MV-22 and much farther than any helicopter. But it might need to refuel, especially during the return from a mission.”

A quote from an SB executive:

He forgot the old truism;

"Familiarity breeds contempt."

And SB have a lot of dirty laundry with which to fuel this contempt, such as:

Boeing;
- KC-46 tanker fiasco. (How could the company that developed aerial refueling have F'ed this up so badly?)
- Starliner, couldn't get to orbit and designers didn't know it is humid in Florida.
- 737 Max

LM/Sikorsky
- F-35 cost and reliability.
- Freedom class LCS. (So bad the Navy is scrapping the entire series at a 1/4 of their life.)
- CH-148 Cyclone (Years behind schedule and $ billion or so overrun)
- CH-53K (Ditto)
- FLRAA demo program

Bell seems a scrappy little startup by comparison!!

Just don't tell the Army about the V-22's painful development... (although it is technically the Bell-BoeingV-22...)

T&C

Good point. The two prototype V-22's that crashed were Boeing controlled and operated V-22's and could be traced to failures at Boeing. The North Carolina V-22 crash in the early days was due to Boeing leaving dead/bad code in the flight controls which responded badly to pressing the FC reset multiple times. So yes most of the V-22 woes were due to Boeing screw ups.

Relative to FLRAA the concept demo phase did what it was suppose to do which was separate bull**** (fix it in production) and capability. The V-280 flew on time to the original schedule, met or exceeded all of the original program goals, and was kept in service after program completion to do govt pilot evaluations and demo new mission capabilities. On the other side, the SB>1 was three years late and had to beg for an extension to the schedule to accomplish anything, met none of the original program goals and reduced to bragging about flying 700 miles without crashing.

Related to familiarity the last experience the Army had with Bell was the OH-58D which up to its senseless termination had by far the highest mission capability rates in combat operations of any Army helicopter. It would have been #1 for all helicopters except for the Bell UH-1N.

One of the happiest days for Bell Valor engineering was when Boeing announced they were parting way with Bell.

One of the saddest days for Sikorsky Defiant engineering was when Boeing announced they were teaming with Sikorsky.

Wasn't Comanche a joint S/B project? As to LCS, a lot of Naval professionals were unimpressed by it at its debut ... but that's not on topic so I'll not pursue that further.

Defiant at Quad A
 

I’m sorry but I can’t help it. Does this rotor make my aircraft look huge?

[img]blob:https://www.pprune.org/f1486203-89c8-407b-8ea4-001d7259bddd[/img]

Quad A Aftermath
 

Does anyone know what happened to the SB-1? Was it:

- Flown home,
- Trucked home,
- Still there awaiting maintenance, or
- Sent to the museum at Ft. Rucker for temporary display like the Comanche?

-

Now that you mentioned Comanche……er…..Invictus. What’s that adage? : “ Imitation is the sincerest form of flattery “ , or something like that. Curious that Invictus started out as , like a 100% look alike copy of Comanche, but then they dropped the canted ducted fan TR for a standard TR. Had they done a ducted fan before and didn’t like it?? Kind of a shame. Back in the day, when we were flying the prototype S-76 Fantail at the Paris Airshow, Nick L gave a ride in the Fantail to the Eurocopter Chief Test Pilot, and during the return flight from Le Bourget to the Paris Heliport at Issy les Moulineaux, Nick flew it at 80 KIAS in a right echelon off the UH-60 that I was flying with video camera/photographer , and on cue Nick kicked the fan around so he was now in formation, but going backwards at 80, and then after a few minutes of that, kicked it around the rest of the way to resume going down the heli-route at 80 with the nose in the correct direction again.. Nick told me later that when he did that, his French companion said the word ( phonetically here ) “ form-ee-dahl-bluh “. SA has the video somewhere.
( But we knew what he meant: Nick and I had a couple of years of high school french ).

John

The government spent around $7 billion on the Comanche before it was cancelled. Bell probably assumed something from that program could be salvaged and the original 360 proposal included the ducted tail fan to meet anticipated RCS requirements. Once it was recognized that low RCS was incompatible with the pusher ABC configuration, the final requirements for RCS on the selected prototypes were relaxed to allow the Raider to compete. With that requirement no longer a constraint Bell wisely reverted to a conventional tail rotor to save cost, save weight, improve reliability, and reduce program risk while still meeting the final program requirements.

I failed to note another capability of the Comanche ducted fan: it was capable of sideward flight to 100 kts ( paced) . Pretty high bar for low speed directional control. So with all those savings reasons for the conventional tail rotor, does it have performance equal to the Comanche?

My understanding is that the current thinking is RAH-66 was over-specified and/or over-capable in terms of maneuvering capabilities, particularly in yaw and that ADS-33 requirements are getting tailored for a better balance of capability, control sensitivity, and weight/etc. Comanche always struggled with weight and the Army is attempting to shove a similar airframe with more weaponry and a little higher speed under the same ~40’ rotor. Giving up un-necessary yaw performance to reduce the weight/complexity of the yaw control system is reasonable. Of course, it’s also required for an ABC style aircraft with integrated prop to even be competitive. Yaw power isn’t a strength of a coaxial design with a lot of mass (prop, gearbox, and oh so very large horizontal stabilizer) at the end of the tail cone.

So neither aircraft will match Comanche’s impressive yaw control power and this is by design and with concurrence of USG customer, that’s pretty clear at this point.

Didn't the Comanche not have a rotating gun turret because of the ability to literally point the nose at the target whenever it needs to?

From an article at the time of the cancellation of the Comanche in 2004:

That works out to $120 million apiece in 2004 dollars! Additionally, as mentioned previously, it was grossly overweight and could not do all of the missions without significant redesign. About the only place they could have cut the required weight was to scrap the ducted fan and revert to a conventional tail rotor. I am sure somewhere at Sikorsky there is a sketch of such a change.

No, Comanche had a conventional turreted cannon that did have the unique feature of being able to swivel towards the tail for stowage in a reduced RCS configuration. So it could fly 100 knots backwards and shoot in all directions for some reason (fall out capability due to other requirements, lol).

My Two Cents, and at the risk of being controversial: the core problem with Comanche (weight wise) was that the original LHX concept was departed from and the Army insisted on a two pilot cockpit, not a single pilot aircraft. But there ya go, that is a part of requirements being established and the US Army's mind set. Not sure if Invictus will run into this as well before all is said and done.

By the way, what the Comanche program produced was a remarkable machine (IIRC, LRIP had in fact commenced when the Army pulled the plug). The Sultan's observation on the price point bears considering - similar issues arose with F-35. I am of the opinion that the "Apache Mafia" in the US Army is what finally killed it, but opinions are like navels ...
:p
I remember being in a room with Togo West (then Secretary of the Army) and a bunch of career Army types. The Secretary threw out this idea (mid 90's, Clinton Administration years, as money kept getting milked out of various DoD budgets) - does the Army really need Comanche? Well, long after he was replaced by someone else, Comanche was still moving forward, one milestone at a time.

V-22 Osprey ran into similar push back over the years at various points, but it made its way through all that in the end.

A couple of thoughts on FARA and Bell's change in tail rotor design:

First, I don't think it's fair to say that Bell changed the design after RCS requirement were lowered because it was realized that low RCS was incompatible with the pusher ABC configuration. That would imply that the requirements were lowered to allow the Raider to compete sometime after Bell showed its initial configuration. At that point, Sikorsky had already shown its design; they'd always said it would be based on Raider. Frankly, it had to be, because Sikorsky has invested so much in X2 technology with not that much to show for it, that they had to go with an X2 design or else abandon it altogether, and frankly, it's all they've got for the future. They can only push S-70 technology so far. On the civil side the S--76 is gone and the S-92 is based on S-70 technology. On the military side, they've basically got further refinements of the H-60 and the CH-53K. Not anything that has got long "legs" except X2 if they can get it to work better than it has so far.

Regarding pusher propeller and RCS, it's worthy of note that except for Bell's 360, all of the candidates used pusher technology, so clearly that wasn't considered an RCS problem by anyone, including the Army, from the get-go. RCS reduction wasn't a constraint even when the RFP went out. Low RCS reduction requirements like Comanche was trying to achieve was not required because top Army along the way finally acknowledged what their operating forces were trying to tell them years ago: Except for highly specialized limited uses (like searching for Bin Laden,and even then the airframe program was terminated early), trying to make a "stealthy" helicopter is a dumb idea. There are all kinds of reasons for this, but here's just one: Why go through all the pain and suffering to reduce RCS on something that the bad guy can just look out the window and see?

Besides, who cares about the pusher when you've got that relatively large mast/hub on an X2?

I suspect there were other reasons why Bell abandoned the fan, maybe something as simple as it looked more like what the Army is used to (although they'd never admit that), and in a competition every bit helps.

As for the admittedly strong resemblance between the planform of Comanche and Invictus, similar requirements can result in similar shapes. Look at the F-14/15 and the MiG-29/SU-27. Bell would not have access to Sikorsky's proprietary data from LHX,and what flight data would be public probably wouldn't be enough to be that much of a driver.

Since the RAH-66 came up, here's a few things about the program. The aircraft flew late and never met its performance and systems goals. It suffered a protracted and delayed development and it was projected that the Comanche if it continued would use up 40% of the entire Army aviation budget. After all the years of work, there didn't seem to be much progress resolving problems including weight and engine power(the engines met the specification, but that wasn't enough power to handle the Comanche's weight growth. It never reached LRIP, in fact only two airframes were ever completed.

A lot of folks involved with the program were so fixated on it that they didn't realize what was happening in the real world. A classic example: Boeing spokesman John Morrocco spoke on the record with the following statement: "The Comanche program is on track and schedule". ...The program cancellation was announced the next day.

Let's hope we don't make the same mistakes with FARA. One thing that should give us pause is that the FARA program manager has publicly stated that an aircraft that meets all the performance requirements in the specification can't be built. His exact words were that the requirements, "...are not compatible with the laws of physics.”

When a helicopter likely to have weight problems (hence the "not compatible with the laws of physics quote") goes through a significant design change, it's a fair bet that the change either reduces weight or improves the conversion of power to thrust or both. In the case of changing a canted fan-in-tail configuration to a canted open tail rotor, you'll get lower weight, lower disk loading, and probably lower drag.

Are you saying the 360 has known weight problems or are you talking about the change to the RAH-66's empennage during development?

I'm saying both 360 and Raider-X are going to struggle with weight when the Army wants a turreted cannon, internal carriage of 8 missiles, higher than normal speeds, a single engine, and a relatively small rotor. Same basic challenges RAH-66 had (aside from the engine selection). Add on top of that a very reduced schedule, and it's not hard to imagine unoptimized structure as well.

Remember what I mentioned about what the FARA Program Manager said. The requirements, "...are not compatible with the laws of physics.” Army is going to have to compromise on something.

Agreed. Will definitely be interesting to see how Bell's 360 performs when the engine is ready and if the Army is willing to wait around for Raider-X to fly. Bell's public photos show a main rotor shaft ready for a main rotor to be mounted and Sikorsky's public photo does not.

Hmm, memory foggy, for some reason I had remembered that #3 got airborne, but if it didn't it didn't. Had not realized that LRIP phase had not begun when the CNX decision was made, thanks for correcting my somewhat faulty memory. I wonder how similar to the A-12 (Navy replacement for A-6 that died thanks to a variety of program problems) the Comanche was in terms of tech risk, over promising and under delivering. Probably good case studies for graduate level acquisition courses ...
Lets, or, let's hope they can weaponize the V-280 Valor effectively enough. :E

In the nearly nine years following rollout, they only managed to finish one more airframe; they were a long way from even considering LRIP. In the case of the A-12 it should be remembered that the team that might actually know how to build such an aircraft walked away from the competition. They decided that the only thing worse than losing the competition was winning it.

Part, but by no means all, of Comanche's problems came when they dumbed down the original specifications so as to insure that no one would offer a Tilt-Rotor. In doing so, they put in weight and power constraints that made a Tilt-Rotor non-competitive, The maximum allowable weight and power allowed made something other than a conventional helicopter non-feasible especially when they changed to give no extra credit for significantly exceeding requirements. Ironically, the weight and power specs had to be relaxed for Comanche anyway. Of course any type of airframe they did build, regardless of technology, likely still would have had many of the systems and avionics problems and deficiencies (like a gun that couldn't hit a target) Comanche had.

Bell has shown a number of concepts and models of heavily armed Valors. It would just take someone (USMC?) to say, "Go ahead, and here's money". Keep in mind that Valor is a much larger craft designed for a different mission. A Tilt-Rotor gunship also has a major oft overlooked advantage over a helicopter. While it's really complicated to do so on a helicopter, it's trivial to fit off-the shelf-ejection seats to a Tilt-Rotor.

Having been “ fairly close “ to both the Army UTTAS and the Comanche Programs, it is important to note the effects of two absolutely different approaches taken by the Army in their management of the two:

1. In the case of UTTAS, the Army took great pains to produce a Material Needs document which then became a detailed specification, which was then an integral part of the Request for Proposal, and which remained unchanged throughout the selection and fly-off competition. This was hardly the case with Comanche, where the goal posts were changed frequently esp.with regard to systems.
2. There was a competitive fly-off, involving competitive evaluations both in engineering at their Engineering Flight Activity at Edwards AFB, a Service Evaluation at Ft. Rucker and an Operational Evaluation at Ft. Campbell, wherein the Army determined the degree to which the competitors met or did not meet their predetermined requirements.

One produced a vehicle that met their requirements, in a timely fashion, and for far, far less investment than the second. Some of us are still wondering why the example set by UTTAS wasn’t followed again for the RAH program.

This is an excellent point and I'm sure the success of UTTAS and AAH helped convince the Army to pursue competitive demonstrators and actively iterate on the requirements of a final FLRAA program to make sure it is not technically over specified and achievable. Gives me some hope that this will be the first successful, completely new Army rotary wing platform in generations.

Let's be honest here... if a tilt rotor had won a down select for LHX, it in all likelihood would have been late, overweight, too expensive, and ultimately canceled as well. The Boeing-Sikorsky team had struggles of their own making, but they would have had the same Army customer that continually shifted requirements and the same design/manufacturing technology of the era.

In retrospect, LHX was a good program to lose, lol.

There have been many historical inaccuracies written regarding the A-12 program cancellation, most written by individuals with limited access to information and biased preconceptions.

Grumman lost the ATA competition due to company arrogance that as manufacturer of the A-6 they could not lose.

Note, MCAIR was equally guilty of arrogance on the ATF contract, thinking that as manufacturer of the F-15 they could tell the USAF how the specifications should be written.

Now the way it was explained to me was that the members of the two A-12 teams were dictated by DoD. One team consisted of a company with extensive stealth experience and partner companies (Grumman, Vought) that built every fixed wing aircraft on carrier decks at the time. The other team consisted of two companies with zero stealth expertise and the leader had no experience in building carrier aircraft whatsoever. The secondary member, who the leader wouldn't listen to (I got that from a member of that team) had carrier experience and was building 1/2 of one of the aircraft on carrier decks. The Navy insisted on a "fixed price" development contract, a type that with new technology always goes wrong. The first team put in its bid, Navy came back and said they really liked the aircraft but wanted the team to lower its bid by a substantial amount. Previously, Grumman had foolishly agreed to such a request back on the F-14 development and made it clear that they were not willing to risk their company on such a situation again. The other companies concurred. Rather than publicly embarrass the government customer (something you never do), the team decided to submit a "cost plus" proposal. As expected, the gov't ruled that this was "non-responsive" and eliminated them, and the team was able to walk away clean. Navy never told the GD/MDD team that the other bidders had left and kept advising them to sharpen their bid if they wanted to win.

In the case of the ATF, Northrop was the leader. Since the ATF competition was not a direct flyoff, it's never been fully explained how the Secretary of the Air Force decided between the two proposals. AF stated that both candidates fully met or exceeded all requirements. It's quite likely that the choice was made based on what has been speculated since then: Lockheed/Boeing's proposal was better documented (MDD conceded this) and was judged lower risk.

Here's a drawing of the Northrop-Grumman ATA proposal. Yes, it looks like a mini B-2, which shouldn't surprise anyone.


https://cimg7.ibsrv.net/gimg/pprune....fbd412cfd3.png

The original requirements for LHX required among other things higher speed, more agility at those higher speeds as well as very good acceleration and greater endurance. The requirements for max weight and required engine power were broader, and there was no requirement for a high degree of "stealth". It appeared that a Tilt-Rotor would ahve a better chance of meeting them , since they well within thee technology's envelope. That's why Bell indicated it would bid a Tilt-Rotor, and while at that point they hadn't committed, it was likely that Boeing might bid one as well. Suddenly, seemingly without warning. Army changed the requirements. The speed and endurance requirements were reduced to that achievable by a conventional helo and it was stated that credit wouldn't be given for performance above that. The maximum weight and engine power allowed were lowered to a point where it would be virtually impossible to build a practical Tilt-Rotor. Given that such a vehicle would be more expensive and with no credit for exceeding specs, it was clear the Army was now saying, "Read my lips: Hel-i-cop-ter". Thus Tilt-Rotor for LHX went away. Ironically, as the program unfolded the power and weight limits for Comanche were relaxed to the point that a Tilt-Rotor probably would have been feasible.

As to whether a Tilt-Rotor would have been late, overweight and too expensive, we'll never know. The V-22 experience was unique. It's kind of hard to stay on schedule and cost when one Administration cancels a program and another one revives it but underfunds EMD and adjusts the program so that the big procurement money won't be required until it is out of office. It's worthy of note that none of the problems have been related to Tilt-Rotor technology itself.

Now as far as avionics and systems go, I suspect there might have been similar problems as to those experienced by the RAH-66, but that's an independent issue.

Fly-offs are the good way to go. History shows us that they lead to programs that are more successful and cost less overall. Their big drawback as far as Washington is concerned is that although they pay off big time in the end, they have a funding "bulge" at the front end to have the flyoff. Plus, with a flyoff, those working in the lofty towers of DC don't get the chance to show the brilliance of their analysis through demonstrating how they don't need to be bothered with the real world.

That's why we don't have them much anymore. The last big ones I can think of were the AAH, F16/17 and A-9/10. The F-22/23 was not really a full flyoff as much as a performance validation of claims, and there will be no flyoff for FLRAA. What we've seen so far has been a demonstration of the capabilities of two technologies without an actual mandate to meet all the performance specified for FLRAA, although in my mind it's obvious which one has a better chance of pulling it off. The winner will be determined by a paper analysis, of which demonstrated capability so far will be one of the factors considered. FARA, though, so far seems to be headed for a good ol' fashioned flyoff. Let's hope so and may the better craft win.

Tilt rotors are plain silly, except for semi-tactical/strategic transport from a ship where higher distances (over a flat sea) can be covered more quickly. I still cannot imagine a tiltrotor doing 100kts NOE…. And with NOE I mean real NOE, so not at a 100ft but 20ft, being agile enough to really follow the terrain like a Huey or Blackhawk could.

Not being a candidate for a Lying Contest....20 feet as a standard minimum height for NOE ffight in a Huey.?

Memory serves it was Three Feet in the Huey long before the Term was NOE and was called "Low Level" or " Contour" flight.

I know for a fact we flew lower than 20 feet above the ground (includes trees, brush, rice paddy dikes and road right-of-ways.....going around or between tall trees sticking up over the rest.

I can benefits to either style aircraft....Sikorsky Comanche or the Bell Tiltrotor but each also have detrimental characteristics to be considered for the Task.

The Tiltrotor puts the important bits higher due to the diameter of the Prop-Rotors in airplane mode....and certainly does in either transition or helicopter mode.

Commanche does not.....as it the Rotor system that is the highest part of the aircraft and it would have the smallest radar cross section compared to the Tilt Rotor.

You must not have seen the “hide-and-go-seek” video of the XV-15 playing with a OH-58 at below tree levels, at times with her belly in the grass. The tiltrotor platform can certainly perform NOE maneuvers and missions if that is part of the design mission set. It certainly was not for the V-22 and it shows (high disk loading and downwash, limited agility in VTOL mode) but those aren’t fundamental to the concept, they’re a fall out of the mission requirements for V-22. Lower disk loading and higher flapping capabilities are known and demonstrated capabilities for a smaller tactical aircraft.

Oh yeah. It got even worse in the 90's as the whole budget shrank and APN 1 programs became scarce.
As I remember it, Navy piggy backed onto the Army Blackhawk Multi Year contract to get CH-60 S built to replace the Phrog(or at least to me that program forward) as the downstream effect of the infamous "Helo Master Plan".
NAVIAR was more or less forced into the "remanufacture of B/F{1}" Seahawks for the R since the "make it new" money wasn't going to be available for mere helicopters (and the Seahawks by then were beginning to show a little of that "ridden hard and put away wet" as a result of how much they got flown).
As I remember it, F-18E/F and E2 upgrades got the "new stuff" money. A-12 was long since dead.
JSF was still in the 'figure it out' stage and got money.
({1} I remember a few conversations with people about that approach having holes in it, and as it worked out, those holes didn't line up...).
Good grief, has it been a quarter of a century ago? :uhoh: