Sikorsky X2 coaxial heli developments.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
CEFOSKEY, the rotor retard idea would work since the machine would turn to keep the same airspeed for each rotor system. Transient performance would also be good as the rotor inertia was transferred to the fuselage during braking, until forces reached equilibrium. However, you would lose some power and generate heat - particularly in HOGE where you might not want to (pusher prop tail might force lots of peddal work in strong winds). Still in principle rotor retard works better than the tip brakes, since the rotor retard system would directly control yaw rate while the tip brakes only controlled yaw torque.
That does raise an interesting point about the differential collective in X2 though: Does the system only produce a good yaw rate control, in all flight regimes, because of the yaw laser gyro in the control system? Nick, has commented that S69 was not as positive in yaw as a tail rotor.
That does raise an interesting point about the differential collective in X2 though: Does the system only produce a good yaw rate control, in all flight regimes, because of the yaw laser gyro in the control system? Nick, has commented that S69 was not as positive in yaw as a tail rotor.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Tip brakes (and tail rotors) consume additional power. Differential collective has very little effect on power consumption.
The blades on the two rotors of a coaxial are set so that they always cross at a specific azimuth, to minimize vibration. This rules out the use of a rotor brake, since the brake would slow both rotors.
This is a concept for yaw control on a coaxial rotorcraft. It does not brake or consume additional power and it does not require differential collective. Unfortunately, it does not maintain a fixed blade crossing at a specific azimuth.
OTHER: Miscellaneous - Thoughtless Idea - Coaxial Transmission w/ Yaw Control
Dave
The blades on the two rotors of a coaxial are set so that they always cross at a specific azimuth, to minimize vibration. This rules out the use of a rotor brake, since the brake would slow both rotors.
From the Department of Demented Designs
Where the lights are never turned off ~ because the light never really came on.
Where the lights are never turned off ~ because the light never really came on.
This is a concept for yaw control on a coaxial rotorcraft. It does not brake or consume additional power and it does not require differential collective. Unfortunately, it does not maintain a fixed blade crossing at a specific azimuth.
OTHER: Miscellaneous - Thoughtless Idea - Coaxial Transmission w/ Yaw Control
Dave
Last edited by Dave_Jackson; 2nd Apr 2008 at 17:37. Reason: The bad news added in 'red'.
Join Date: Mar 2008
Location: Austin, TX
Age: 65
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
This is a concept for yaw control on a coaxial rotorcraft. It does not brake or consume additional power ...
Bob
Join Date: Jul 2004
Location: Huntsville AL
Age: 51
Posts: 139
Likes: 0
Received 0 Likes
on
0 Posts
Just a thought
I had a similar idea to Daves without the gears. When I worked for Erickson we had a test cell that would run one engine and one main gearbox at the same time. Power that was being absorbed by the cell was redirected to the input of the gearbox that was not occupied by the engine. Why not use this for yaw control on a coaxial? I was thinking more along the lines of a motor/generator on each mast. When you apply a field current to one as a generator it will create a drag on that rotor mast. The energy absorbed by that generator would be sent to the motor on the opposite mast to recoup the lost power. In an of itself it me not be perfect as the motor/generators would obviously add weight and complexity it could also be useful as a hybrid drive of sorts. During cruise flight equal current could be drawn from both systems to charge a battery pack which could be used as additional boost of power in the case of engine failure. You could even use it for normal operations and scale down the engine such that a max power take off may require both engine and battery power and then the smaller engine package is left to carry the load during cruise. Of course that wouldnt be such a great thing for an aircraft destined for long hover times as sooner or later you are going to run out of battery power!!
Like I said,...just a thought
Max
Like I said,...just a thought
Max
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
This might be of some interest for those who want to look deeper into the subject.
The July 26, 2001 posting by H-43 mentions the only problem that I have heard of; that of the systems linkages not knowing whether to apply CW or CCW yaw at low collective settings. I understand that this is applicable to Intermeshing and Coaxial.
http://www.unicopter.com/0742.html#Yaw
Relyon,
True but the power is going into thrust.
Dave
The July 26, 2001 posting by H-43 mentions the only problem that I have heard of; that of the systems linkages not knowing whether to apply CW or CCW yaw at low collective settings. I understand that this is applicable to Intermeshing and Coaxial.
http://www.unicopter.com/0742.html#Yaw
Relyon,
While admittedly an interesting concept it does use power, no matter how little that may be. It takes energy to move mass which to my knowledge can't be avoided.
Dave
Originally Posted by CEFOSKEY
The idea of rotor momentum is what allows yaw control on fixed-collective coaxial RC helicopters. However, this is controlled via variable differential Nr through the throttle of two seperate motors.
-- IFMU
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Bat1, i was just wondering about "ping"ing this thread again... 
I suspect that having generated much good publicity on the potential for high speed helicopters X2 has been handed back to the engineering development team for the various ground/tethered test activities which precede a test flight. Machines are now just too complicated for the jump in and see what happens approach of the past. It will probably undergo some strain guage durability proofing to demonstrate that everything is behaving the way that FEA said it should.
With Nick finally giving in to Dave, and moving over to the dark side of lateral symmetry, i'm not sure how us X2 fans will get our fix.
I suspect that having generated much good publicity on the potential for high speed helicopters X2 has been handed back to the engineering development team for the various ground/tethered test activities which precede a test flight. Machines are now just too complicated for the jump in and see what happens approach of the past. It will probably undergo some strain guage durability proofing to demonstrate that everything is behaving the way that FEA said it should.
With Nick finally giving in to Dave, and moving over to the dark side of lateral symmetry, i'm not sure how us X2 fans will get our fix.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Brilliant Stuff, "Genau"...
Cefoskey, anything serious or just a few cracks showing that the fatigue duty cycle was not correctly predicted? You have to expect these on a new concept of design. Which areas are giving problems, i'm guessing the rotor mast?
Cefoskey, anything serious or just a few cracks showing that the fatigue duty cycle was not correctly predicted? You have to expect these on a new concept of design. Which areas are giving problems, i'm guessing the rotor mast?
Join Date: Mar 2008
Location: Cincy
Age: 45
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
Seriously gauss rifle
If there going fancy they need to work on the overall look. Cigars rarely look intimidating, unless some one is trying to put it out in your eye
If there going fancy they need to work on the overall look. Cigars rarely look intimidating, unless some one is trying to put it out in your eye
Join Date: Mar 2008
Location: Cincy
Age: 45
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
if you do a google image search on light transport helicopter you get Uh-1 style helicopters. So I bet that would be the niche to fill. As for cigar shape the model does not look functional for combat, more like a pressurized exec heli fast and comfy
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
The April 2008 issue of Rotor & Wing has an article and six pictures of the X2.
This is the text of the article.
This is one of the pictures.
.jpg)
Dave
This is the text of the article.
This is one of the pictures.
Dave
Join Date: Mar 2008
Location: England... what's left of it...
Posts: 161
Likes: 0
Received 0 Likes
on
0 Posts
Thanks, interesting. Do you have the other four pics to hand? I hope it all happens mostly to schedule, can't wait to see it fly.
Mention made of minimizing the drag of the hub assy. itself... which I was just thinking looks relatively svelte in the photo.
Join Date: Mar 2008
Location: England... what's left of it...
Posts: 161
Likes: 0
Received 0 Likes
on
0 Posts
OD,
The photos omit the weather-vaning hub fairing, which was not displayed at heli-expo. We were discussing this a few pages back.
The photos omit the weather-vaning hub fairing, which was not displayed at heli-expo. We were discussing this a few pages back.
Ta
. I shall look.
Originally Posted by Dave_Jackson
The April 2008 issue of Rotor & Wing has an article and six pictures of the X2.
-- IFMU