JMR (Joint Multi-Role) & FVL (Future Vertical Lift) Programs

[VTOLicious]

Looks neat

 

[sferrin]

of course an unloaded rotor that is spinning is providing lift as air is being propelled down (Newton not Bernuli) so there is augmenting lift from an unloaded rotor.

This is almost painful to read. Find an engineer friend who can explain to you why this is impossible.

 

[jsport]

of course an unloaded rotor that is spinning is providing lift as air is being propelled down (Newton not Bernuli) so there is augmenting lift from an unloaded rotor.

This is almost painful to read. Find an engineer friend who can explain to you why this is impossible.

If the blade is not locked, and the apparent consencous is the blade is not completely unloaded as the Karem person exclamed then air is being forced down even to the determent of the flying wings . Mostly drag yes (especially if no blade angle) but air is still ibeing force down, quite limited and not useful lift but it is there.

the engineer added that... if the blade is locked than all drag otherwise lift (Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..), is added.. BTW the engineer does not care for the Karem tech personnally.

 

[sferrin]

of course an unloaded rotor that is spinning is providing lift as air is being propelled down (Newton not Bernuli) so there is augmenting lift from an unloaded rotor.

This is almost painful to read. Find an engineer friend who can explain to you why this is impossible.

If the blade is not locked, and the apparent consencous is the blade is not completely unloaded as the Karem person exclamed then air is being forced down even to the determent of the flying wings . Mostly drag yes (especially if no blade angle) but air is still ibeing force down, quite limited and not useful lift but it is there.

the engineer added that... if the blade is locked than all drag otherwise lift (Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..), is added.. BTW the engineer does not care for the Karem tech personnally.

Ask them how the blade can help lift the aircraft without added load to the mast. Now if you're just saying that the blade is lifting itself, and not helping lift the aircraft, then yes, you could have that condition however it will increase drag. Can't get something for nothing.

 

[jsport]

of course an unloaded rotor that is spinning is providing lift as air is being propelled down (Newton not Bernuli) so there is augmenting lift from an unloaded rotor.

This is almost painful to read. Find an engineer friend who can explain to you why this is impossible.

If the blade is not locked, and the apparent consencous is the blade is not completely unloaded as the Karem person exclamed then air is being forced down even to the determent of the flying wings . Mostly drag yes (especially if no blade angle) but air is still ibeing force down, quite limited and not useful lift but it is there.

the engineer added that... if the blade is locked than all drag otherwise lift (Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..), is added.. BTW the engineer does not care for the Karem tech personnally.

Ask them how the blade can help lift the aircraft without added load to the mast. Now if you're just saying that the blade is lifting itself, and not helping lift the aircraft, then yes, you could have that condition however it will increase drag. Can't get something for nothing.

When Karem says offload the rotor of course that is 'not pure offload' (as impossible if rotor is still attached to the craft) as pointed out earlier and as a consensous. Air speed is spinning a non-torque applied rotor resulting in lift. However small. lift is of the whole craft as long as everything remains attached. Never claimed something for nothing.

 

[sferrin]

However small. lift is of the whole craft as long as everything remains attached.

Yeah, that can't happen without loading the rotor.

 

[djfawcett]

I believe the disconnect in this debate is from the definition of Off Load. When Karem says Off Load (reduce the collective-pitch on the rotor), they do not mean all load is removed. They mean the majority of the load is transferred to the wing. I suspect they need some load on the rotor for aero-elastic reasons. One other misconception is that during loss of power the Karem vehicle can simply glide and land like an airplane thereby making it far safer than autorotation. First and foremost. the wing is sized for cruise, which mean whether landing is in the desert or jungle your approach speed will be north of 100 kts making for one messy landing. The wing is not sized to glide around like a Piper Cub. With that being said, the Karem vehicle will also have to autorotate unless the pilot wants a total life changing experience.

 

[jsport]

However small. lift is of the whole craft as long as everything remains attached.

Yeah, that can't happen without loading the rotor.

Again Just said ...Air speed is spinning a non-torque applied rotor resulting in lift.

Again Just said...When Karem says offload the rotor of course that is 'not pure offload' this is is going in circles.........................

 

[sferrin]

However small. lift is of the whole craft as long as everything remains attached.

Yeah, that can't happen without loading the rotor.

Again ...Air speed is spinning a non-torque applied rotor resulting in lift. The engineer knows this stuff.

Ask your engineer friend how lift gets transferred to the rest of the aircraft without applying a load.

 

[yasotay]

[/QUOTE]
this is is going in circles.........................
[/QUOTE]

Just so. Gentlemen (and ladies if it be so), might I recommend that we leave it at an agreement to disagree.

Unless of course you all are having fun with this. Then I will shrug and watch the badminton match continue. B)

 

[jsport]

However small. lift is of the whole craft as long as everything remains attached.

Yeah, that can't happen without loading the rotor.

Again ...Air speed is spinning a non-torque applied rotor resulting in lift. The engineer knows this stuff.

Ask your engineer friend how lift gets transferred to the rest of the aircraft without applying a load.

As long is there is a rotor attached the helicopter( for hundredth time) there is load. The Karem engineer was speaking in absolutes. However, the blade is being spun w/ no added torque and therefore lifting ....

Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..),

 

[sferrin]

However small. lift is of the whole craft as long as everything remains attached.

Yeah, that can't happen without loading the rotor.

Again ...Air speed is spinning a non-torque applied rotor resulting in lift. The engineer knows this stuff.

Ask your engineer friend how lift gets transferred to the rest of the aircraft without applying a load.

As long is there is a rotor attached the helicopter( for hundredth time) there is load. The Karem engineer was speaking in absolutes. However, the blade is being spun w/ no added torque and therefore lifting ....

Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..),

Doesn't matter if it's free-wheeling (like every autogyro ever built), if it's providing lift to the aircraft it's not an unloaded rotor. Ask yourself how any lift from the rotor would get to the aircraft to be lifting the aircraft.

 

[jsport]

However small. lift is of the whole craft as long as everything remains attached.

Yeah, that can't happen without loading the rotor.

Again ...Air speed is spinning a non-torque applied rotor resulting in lift. The engineer knows this stuff.

Ask your engineer friend how lift gets transferred to the rest of the aircraft without applying a load.

As long is there is a rotor attached the helicopter( for hundredth time) there is load. The Karem engineer was speaking in absolutes. However, the blade is being spun w/ no added torque and therefore lifting ....

Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..),

Doesn't matter if it's free-wheeling (like every autogyro ever built), if it's providing lift to the aircraft it's not an unloaded rotor. Ask yourself how any lift from the rotor would get to the aircraft to be lifting the aircraft.

As long is there is a rotor attached the helicopter( for hundredth time) there is load. The Karem engineer was speaking in absolutes. However, the blade is being spun w/ no added torque and therefore lifting ....

Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant..),

 

[sferrin]

As long is there is a rotor attached the helicopter( for hundredth time) there is load. The Karem engineer was speaking in absolutes. However, the blade is being spun w/ no added torque and therefore lifting ....

If there is lifting there is load. That's what lift is. If you don't understand that I don't see any reason to continue this discussion.

 

[jsport]

As long is there is a rotor attached the helicopter( for hundredth time) there is load. The Karem engineer was speaking in absolutes. However, the blade is being spun w/ no added torque and therefore lifting ....

If there is lifting there is load. That's what lift is. If you don't understand that I don't see any reason to continue this discussion.

me thinks your the one doesnt understand even a dead lifts..for the millionth time. load hasnt been the issues for hours.

 

[apparition13]

This argument really looks like a misunderstanding of some sort.

Speed And Size Drive Advanced Options For U.S. Army’s Armed Scout

Oct 18, 2019

Graham Warwick | Aviation Week & Space Technology


To achieve high speed, “we reduce drag significantly and unload the rotor to the wing,” says Berger. “The swiveling tail rotor means we do not have the edgewise drag of a tail rotor. We store all the ordnance inside, stow the gun and fair the targeting turret.” The AR40 has side-by-side seating. This improves crew coordination and provides additional room behind the cockpit for mission equipment or a cabin for personnel. “It’s space for free,” he says.

Are the Sikorsky blades completely "unloaded " in winged based flight? Where are large wings. Do they use no main rotor for completely horizontal flight?

Not an engineer, but purely on the language of the Berger quote, I don't read Berger as saying the rotor is 100% unloaded to the wing, I read Berger as saying some percentage of the rotor (lift) is unloaded to the wing. Is that what this whole argument is about?

Or is it over what the force generated by the rotor is doing, if 100% of the lift is provided by the wings? There's still a load on the rotors, but that "load" (100% of the rotor's force) is being used to propel the vehicle forwards rather than being split between lift and propulsion, right?

 

[_Del_]

It's really only an issue when someone decides that “we reduce drag significantly and unload the rotor to the wing” really means "Complete unload and eliminated retreating stall means they are flying a pure airplane+being augmented by a spinning rotor. " which is more efficient... and then argues with everyone for pages on why it is both completely unloaded and augmenting lift saying everyone else is autistic and should do more homework. Otherwise, I think you've found the crux of the issue.

 

[jsport]

have been saying for days the it was not possible to completely unload while being accused that i was argueing for such complete unloading...

 

[jsport]

AW&ST April 20 2020

 

[fredymac]

Another view of "CHITA". I'm not sure how the antitorque works on this.

https://twitter.com/x/status/1255171416179253249

Modular wind tunnel model, the Compound Helicopter Interactional Aerodynamics, or CHITA, was developed by @CCDC_AVM Technology Development Directorate with @NASA to de-risk future rotorcraft such as FARA and FLRAA

 

[VTOLicious]

Another view of "CHITA". I'm not sure how the antitorque works on this

I'm pretty sure it has a swiveling tail rotor (propulsor), as seen on the Karem AR40

 

[TomcatViP]

Look better at those strange Pods

 

[Gripen287]

Another view of "CHITA". I'm not sure how the antitorque works on this.

Hello, all. I'm a long-time visitor, first time poster. I've thoroughly enjoyed the FARA and FLRAA discussion here, and one of the reasons I began visiting these forums was the Comanche thread.


Looking at the Comanche's transmission, I usually find myself asking myself whether an "anti-torque" system is needed per se. The Comanche is interesting in that it employs a split-torque gearbox without a final planetary reduction stage, as pictured below.



Correct me if I'm mistaken, but without a fixed ring gear to transmit reactive torque from the main rotor into the fuselage, the tail rotor/fan mainly serves to provide yaw control as opposed to yaw stability. Since some means of yaw control is still required, I can see how this would not necessarily drive a shift in helicopter design away from traditional arrangements. For example, the MI-26 and CH-53K utilize split-torque transmissions and have large tail rotors (although I'm not sure whether or not either has a final planetary reduction stage).

With respect to compound designs, however, I imagine that there could be significant advantages to obviating the need for an anti-torque tail rotor, contra-rotating main rotors, or a swiveling drive train and providing relatively clean airflow into a propulsor.

It may be weight prohibitive, but I think a transmission with a parallel hybrid arrangement could be beneficial for a design like CHITA. Utilizing a split-torque transmission like the RAH-66's pictured above, a clutched, constant-speed propuslor could be powered via the fan output. At low speed, yaw control would be provided by a pair of of electric motors on the main rotor drive shaft. A first motor would apply torque to the main rotor driveshaft directly. A second motor would drive the main rotor driveshaft via a 1:1 set of reversing gears. Accordingly, low speed yaw control would be provided via differential torque between the two motors, much like utilizing differential collective pitch between contra-rotating rotors. In a slowed rotor design like CHITA, the rotors could also be declutched from the transmission and driven solely by the electric motors during high speed flight, the majority of engine power therefore going to the propulsor in high speed flight.

Thought I'd share my thoughts to see where I'm mistaken and/or provoke discussion of alternative "anti-torque" solutions.

 

[Gripen287]

Look better at those strange Pods

Could be puffer jets. CHITA also has twin fenestrons.

 

[VTOLicious]

Look better at those strange Pods

Could be puffer jets. CHITA also has twin fenestrons.

View attachment 632628

Indeed... However, those ducted fans appear way to small to provide sufficient anti torque... CHITA's main rotor might be tip driven and the (electric) ducted fans are supposed to provide yaw control only... I have no idea what those pods are for.

 

[VTOLicious]

Another view of "CHITA". I'm not sure how the antitorque works on this.

Looking at the Comanche's transmission, I usually find myself asking myself whether an "anti-torque" system is needed per se. The Comanche is interesting in that it employs a split-torque gearbox without a final planetary reduction stage, as pictured below.
Correct me if I'm mistaken, but without a fixed ring gear to transmit reactive torque from the main rotor into the fuselage, the tail rotor/fan mainly serves to provide yaw control as opposed to yaw stability...

You can't drive a rotor shaft without receiving a corresponding counter torque. That's against physics.

 

[_Del_]

Indeed... However, those ducted fans appear way to small to provide sufficient anti torque... CHITA's main rotor might be tip driven and the (electric) ducted fans are supposed to provide yaw control only... I have no idea what those pods are for.

Have to think they're electric. Didn't Bell's EDAT do the same thing? They had four fans, but there was something about retaining yaw authority with multiple fans out.

 

[VTOLicious]

Indeed... However, those ducted fans appear way to small to provide sufficient anti torque... CHITA's main rotor might be tip driven and the (electric) ducted fans are supposed to provide yaw control only... I have no idea what those pods are for.

Have to think they're electric. Didn't Bell's EDAT do the same thing? They had four fans, but there was something about retaining yaw authority with multiple fans out.

EDAT was discussed here: https://www.secretprojects.co.uk/threads/bell-model-525-«-relentless-».14495/post-380017

 

[_Del_]

EDAT

So if one of four installed small fans sufficiently maintains "some" yaw authority in EDAT, why could two smaller fans (perhaps even at higher rpm) not provide yaw authority?

 

[TomcatViP]

I see the Pods holding collapsible pusher rotors deploying downward (canted). The wing is perfectly placed to hold a straight drive shaft (much more easy Airbus you fool! ) connected to the gear box actuating the rear propeller.
If I am right, we can forsee several other application for those.

The ducted fans might be there for high speed and trim only (think stealth).

 

[_Del_]

Spinning rotors, spinning prop, but they're worried about having a control surface on the tail for trim because it might affect signature?

 

[TomcatViP]

It's all about balance: if you fly with your disc rotor spinning at at an appropriate frequency parallel to the line of sight of a radar (terrain hugging), your RCS might drop significantly. Then you have traded your big rotor RCS for that of a rear mounted, airframe shielded, magnitude smaller propulsive rotor that is less subject to aerodynamics loads and can be built out of more radio transparent materials.

 

[Gripen287]

Another view of "CHITA". I'm not sure how the antitorque works on this.

Looking at the Comanche's transmission, I usually find myself asking myself whether an "anti-torque" system is needed per se. The Comanche is interesting in that it employs a split-torque gearbox without a final planetary reduction stage, as pictured below.
Correct me if I'm mistaken, but without a fixed ring gear to transmit reactive torque from the main rotor into the fuselage, the tail rotor/fan mainly serves to provide yaw control as opposed to yaw stability...

You can't drive a rotor shaft without receiving a corresponding counter torque. That's against physics.

Yes. Transmission aside, however, the fuselage does not drive the rotor shaft, the engines do. Ask yourself where along the driveshaft the reactive torque component from the main rotor is transmitted into the fuselage. In the vast majority of helicopters it's via the ring gear of the final reduction stage, which is consequently the lowest rpm, highest torque (and thus counter torque) stage in the transmission.


In a split torque transmission like the Comanche's the reactive torque is borne as a torsional load back through the drivetrain. Consequently, the blades of the Comanche's fan can operate at a much lower angles of attack in forward flight and thus absorbs far less engine power.

 

[yasotay]

Given this is a government experimental engineering effort I expect we will see a number of configurations in the coming year(s).

 

[fredymac]

Popular Mechanics comparison of Valor vs Defiant.

https://www.popularmechanics.com/mi...9508/defiant-vs-valor-black-hawk-replacement/

 

[Rhinocrates]

Lightened to bring out a little more detail. That dark ring around the tail could be an annular exhaust?

 

[TomcatViP]

If it's fully annular as it looks to be, it's probably denoting a swiveling section. I can't see yet how it will arc a full 90 degree but probably that It can travel laterally and up and down a certain margin for swift move (vectoring thrust).

 

[_Del_]

Images describe a "modular windtunnel model". I honestly just assumed it was an artifact reflecting that modularity. It does look a bit odd, and lacks visible means of intake/efflux, so I like the annular exhaust theory in second place, as well.

 

[yasotay]

It is likely there will be a number of variations to the "model" in the coming years.

 

[VTOLicious]

Vertical Mag Rotor Radio: Dan Parsons talking with Steve Weiner, the chief engineer for X2 at Sikorsky, and chief test pilot Bill Fell.

https://www.verticalmag.com/news/ro...edium=email&utm_term=top-story&utm_content=V1