Son of CV-22B Osprey: Air Force Research Lab contracts Bell for high speed VTOL study

RavenOne

ACCESS: Secret
Joined
Jun 18, 2008
Messages
454
Reaction score
764

Attachments

  • 33597031-7FD4-4E52-8D04-54490146833B.png
    33597031-7FD4-4E52-8D04-54490146833B.png
    140.9 KB · Views: 134

Archibald

ACCESS: Above Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
6,661
Reaction score
5,425
Waaaaait a minute... so the plan is
- to start from something like a V-280 (where the engines don't tilt, just the props)
- folds the props in flight, along the nacelles
- and then go full Learjet / bizjet style ? with turbofans in rear nacelles ?

Daring enough, it may work... or not.

Before quadcopters (and many other drones / aerodynamic heresies / abominations) flew I wouldn't have bet on folding props in flight.

With algorithms to tame instability, however, even cast irons and pigs could fly so maybe it is possible ?

Seriously - I kind of like the idea.
A- Liftoff V-280 style
B- then lit the turbofans, gradually accelerate to 150-200-250 miles per hour: fast enough to fly like a Learjet, except a Learjet with huge wingtip propellers (!)
1- with the props, first, disconnecting from the turbines
2- then windmill / feather the props as if the turbine was dead (as done on piston and tuboprop aircraft for decades and decades)
3- gradually fold the blades along the nacelles
4- fly like a F-89 Scorpion: an aircraft that is proof that having huge wingtip pods is not a major issue.

What is really interesting is
a) we know that propellers-and-jet aircraft flies well since the 1940's at least (Ryan Fireball, B-36H...)
b) we know that helicopter-with-jet can also fly pretty fast (XH-59 flew at 250 mph, Cheyenne, many others)
c) the Bell V-280 is the necessary step beyond the CL-84 (tilt-wing) and V-22 (tilt-turbines) to make this happen: it is kind of "tilt-propellers-only"
 
Last edited:

stealthflanker

ACCESS: Top Secret
Senior Member
Joined
Feb 12, 2010
Messages
927
Reaction score
797
Folded Rotor like that is arguably the most optimum solution for getting tiltrotor to high subsonic speed.
 

Archibald

ACCESS: Above Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
6,661
Reaction score
5,425
Yes. I would add that a tilt-rotor the V-280 way (engines don't tilting) will have an easier time pulling that trick, than a V-22 with its big, moving engines. Probably safer too, having the engines not moving: only the props.
 

TomcatViP

Hellcat
Joined
Feb 12, 2017
Messages
4,543
Reaction score
3,967
I guess you have noticed the tip Pods house only electrical engines (I haven't read yet FlightGlobal report).
 

AeroFranz

ACCESS: Top Secret
Senior Member
Joined
May 4, 2008
Messages
2,376
Reaction score
393
the hard parts are:
1) fold the props in flight, and vice versa. Bell demonstrated this in a full-scale wind tunnel in 1972
2) you need a convertible engine that can switch from turbofan to turboshaft, or some comparable hybrid-electric arrangement. GE has produced a convertible TF34 (meant for RSRA, IIRC) but it never flew AFAIK
 

TomcatViP

Hellcat
Joined
Feb 12, 2017
Messages
4,543
Reaction score
3,967
Only my own understanding so far @Archibald
But there is no inlets to be seen on the wing Pods, the straight line b/w the two inge line on the Pods is too close to flapperons to host a cross shaft (something that would be absolutely needed in any other case) and the rear fuselage engine location clearly excludes any mechanical connection b/w the turbofans and the rotor pods.
 

Hood

ACCESS: Top Secret
Staff member
Senior Member
Joined
Sep 6, 2006
Messages
2,542
Reaction score
2,872
If only they could solve the ground erosion and hot-air ingestion issues with jet vectored-thrust, it would seem simpler to return to all-jet V/STOL.
At least electric motors reduce the amount of dead weight during horizontal flight, although batteries are not light so it would be interesting to see how they would compare with a small turbofan or turboprop engine.
 

Archibald

ACCESS: Above Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
6,661
Reaction score
5,425
Would it be possible to use the turbofans on the rear to provide electric power to electric engines ? via an APU maybe ?

Because batteries for aircraft... ugh. I think it would take quite a heavy mass of lithium batteries to lift a Learjet-V280 hybrid (weighing 12 to 15 metric tons).
Now if some kind of APU or the turbofans themselves could provide power, things may be different...

If only they could solve the ground erosion and hot-air ingestion issues with jet vectored-thrust, it would seem simpler to return to all-jet V/STOL.
I see your point, as I said earlier, maddening instability is much less an issue than in the 60's - Falcon 9 stage 1, Starship, Quadcopters... this would leave hot gases reingestion, as you say.
But there is a third issue that won't go away: fuel consumption and the lack of efficiency of jets for vertical flight (that disc loading thing too).
 
Last edited:

Archibald

ACCESS: Above Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
6,661
Reaction score
5,425
fold the props in flight, and vice versa. Bell demonstrated this in a full-scale wind tunnel in 1972
Interesting, where did you got that ? Back then XV-15 hadn't flown yet, so it was probably premature, but this date in interesting nonetheless !
 

yasotay

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Oct 19, 2006
Messages
2,835
Reaction score
1,532
From the previous discussion here - https://www.secretprojects.co.uk/th...tical-lift-programs.13812/page-43#post-455568

Bell has been working on the "stop-fold" technology for some time now. Sikorsky did a significant amount of work on this as well, when they were looking at tilt rotor technology. Both the USAF and the USMC are interested in going faster/further than traditional tilt rotor can likely operate, but without the challenge of even higher disc loading associated with some of the other options for faster VTOL. Fan-in-wing is possibly the other option for high speed and relatively low disc loading.
From the article - “At least our initial thinking in AFSOC is that we’re looking at a generation beyond current tiltrotor technology,” said Lieutenant General James Slife, commander of AFSOC, last September. “We’re not just looking at marginal improvements, in terms of speed, range and reliability, but we’re looking at a generational movement for a vertical take-off and landing capability going into the future. I think it’ll be probably something quite different than the V-22.”
This was mentioned earlier in (sic) the thread mentioned above.
Also - “There are a number of technology and drive system proposals out there that look like they may be within the realm of possibility; that they could provide like a generational step ahead in technology, get us up into jet speed kind of capabilities,” Slife said. “When you look at the future operating environment, where range and access are going to be challenging across the board… I think whatever comes next is going to have to be a generation [ahead] yet again.”
I think it is Northrop who has the "fan-in-wing" technology, that might be able to have similar disc-loading. I suppose some of the ideas for EVTOL might be an option, but suspect that they might not scale up very well.

The big difference is that now technology is available for more efficient electrical power generation for the prop-rotors than when the original work was done. This also makes for a lighter aircraft (potentially) as you do not need heavy, damage resistant gearing and shafts to provide power for the prop-rotors. More efficient generator technology is being worked for a number of reasons for rotorcraft (ASE and other energy systems). The engine is likely the challenge at this point.

Then there is this - https://www.futureflight.aero/news-...y-400-vtol-aircraft-military-support-missions

Of note though - slightly less than $1M (US) means this is a small study to inform the USAF of what is likely perceived as one of the less risky technology options.
 
Last edited:

Grey Havoc

ACCESS: USAP
Senior Member
Joined
Oct 9, 2009
Messages
16,722
Reaction score
6,285
Yes, yet another example of 'Back to the Future'.

Here's some of Sikorsky's past work in the area:

Lockheed did a fair bit of work along the same lines as well, a number of the resulting designs can be found here:


EDIT: I think Hughes was another company that worked on such designs, but I can't track down the relevant thread/s at the moment.
 
Last edited:

stealthflanker

ACCESS: Top Secret
Senior Member
Joined
Feb 12, 2010
Messages
927
Reaction score
797
Ha finally.. potentially another aircraft using FSW which would get a mass production.
 

F-14D

I really did change my personal text
Senior Member
Joined
Oct 4, 2007
Messages
1,869
Reaction score
434

Moose

ACCESS: Top Secret
Senior Member
Joined
Jul 4, 2010
Messages
1,538
Reaction score
646
Turbine in the fuselage, electric motors for the folding rotors? Or is Bell still sticking with driveshafts?
Looks like the kind of thing that SOCCOM wants to replace the Osprey
I'm guessing that's exactly who Bell's pitching to.
 

helmutkohl

ACCESS: Top Secret
Staff member
Senior Member
Joined
Nov 29, 2010
Messages
860
Reaction score
1,471

alertken

ACCESS: Top Secret
Joined
Jan 20, 2007
Messages
654
Reaction score
311
Bell/Boeing Osprey: 1983 origin: USMC IOC 13/6/07. Mega-$. Who here would welcome a posting to Opnl.Reqts? Dead before they know you got it wrong.
 

yasotay

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Oct 19, 2006
Messages
2,835
Reaction score
1,532
@Moose - I suspect that Bell will pitch low(er) risk driveshafts initially with an option for hybrid electric in future versions as that technology becomes more mature.
 

shin_getter

ACCESS: Top Secret
Joined
Jun 1, 2019
Messages
522
Reaction score
561
It seems to me that separated lift system, direct drive shaft on turbine, with electrical distributed propulsors control is a pretty good idea for hybrid VTOL. You are not paying for a huge generator/electrical distribution system and you are also not paying for mechanical complexity in the lift rotor for control.

The primary engine can be scaled for efficient cruise with extra power needs for take off and landing from batteries.
 

yasotay

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Oct 19, 2006
Messages
2,835
Reaction score
1,532
@shin_getter - Agree completely. I think that Bell most likely has something like this in mind. This is a way for them to advance their hybrid electric work with DoD funds, vice their IRAD. They could make a compelling argument that it would reduce the weight of the aircraft significantly. Since the US DoD buys aircraft by the pound, this might be attractive to the government. DoD could point out to Congress they are helping to reduce the carbon foot print AND protecting our grandchildren. Win, win!
 

autoeac

ACCESS: Restricted
Joined
Jan 25, 2011
Messages
23
Reaction score
13
I like the idea of electric motors for the rotors. Battery weight is still an issue but the jet engines could recharge the batteries while inflight. I also think the plane could take off vertically tethered to an electric or a fuel line until it's 50 or 100 feet in the air. Hovering, the line replenishes the fuel and then the plane is released.
 

Attachments

  • Teathered.jpg
    Teathered.jpg
    194.8 KB · Views: 72

yasotay

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Oct 19, 2006
Messages
2,835
Reaction score
1,532

A couple more bits on the effort here.
 

yasotay

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Oct 19, 2006
Messages
2,835
Reaction score
1,532




 
Last edited:

Spyclip

ACCESS: Restricted
Joined
Jun 18, 2021
Messages
26
Reaction score
49
I like the idea of electric motors for the rotors. Battery weight is still an issue but the jet engines could recharge the batteries while inflight. I also think the plane could take off vertically tethered to an electric or a fuel line until it's 50 or 100 feet in the air. Hovering, the line replenishes the fuel and then the plane is released.


US20210147043A1-20210520-D00001.png
 

Conspirator

ACCESS: You don't have clearance to know......
Joined
Jan 14, 2021
Messages
179
Reaction score
61
you could have some sort of locking mech after the engines for V-TOL are shut down so it spins down, locks into a certain position. and the rotors fold into molded slots? better aerodynamics that way. and actually the learjet type design is kinda smart you have adequet storage space for electronics/ cargo/ bombs/ troops and with the two fuselage mounted jet engines, if they are powerful enough they could get it up to subsonic velocity. its a good possibility
 

Moose

ACCESS: Top Secret
Senior Member
Joined
Jul 4, 2010
Messages
1,538
Reaction score
646
you could have some sort of locking mech after the engines for V-TOL are shut down so it spins down, locks into a certain position. and the rotors fold into molded slots? better aerodynamics that way. and actually the learjet type design is kinda smart you have adequet storage space for electronics/ cargo/ bombs/ troops and with the two fuselage mounted jet engines, if they are powerful enough they could get it up to subsonic velocity. its a good possibility
One of The War Zone's videos is of a 1972 NASA video demonstrating rotors locking in a desired configuration.
View: https://www.youtube.com/watch?v=yFPePHjB9Es

The closeup image at the top of their article may have "slots" for the rotors along the nacelle, but it seems to be more for getting smooth airflow over the exposed rotors rather than trying to get them out of the air stream entirely.

Their HSVTOL Light goes for lighter weight and simplicity by just having the rotors fold back
View: https://www.youtube.com/watch?v=5cjGTIFJcx4
 

yasotay

ACCESS: Top Secret
Top Contributor
Senior Member
Joined
Oct 19, 2006
Messages
2,835
Reaction score
1,532
I wonder how they will deal with the air flow effects of the blade twist at high speed in relation to the nacelles and the wing joint.
 

Conspirator

ACCESS: You don't have clearance to know......
Joined
Jan 14, 2021
Messages
179
Reaction score
61
I wonder how they will deal with the air flow effects of the blade twist at high speed in relation to the nacelles and the wing joint.
it would kinda be like a Helo rotor where the pitch is ajustable. you could also do this for the VTOL
 

Similar threads

Top