New Multirole V/STOL being developed

[Birdog8585]

Video
There have been a lot of concepts surface in this department but IMHO this one seems to have the most potential to gain traction. Nicely done CAD video BTW.

My only concern would be the complexity of the rotor system and there in lie my question for the helo bubas. It would appear to the layperson (me) that by removing the inner portion of the rotor blade ‘bite’ by covering it up with his enclosure disc, would reduce the amount of lifting capacity left to the exposed portion of the blade. Does that hold true or would it provide the same amount of lift if it were left unexposed?

 

[MasterBates]

Couple main problems.

The way they showed an auto to a confined area, that's total shenanigans unless this thing has some wicked high inertia head.

Engines not being used in current mode- dead weight. Dead weight = reduced cargo/fuel capacity.

I'm not buying the "one engine in helo mode gets home from any place" without some hard data to back it up. Most heavy rotorcraft are on the dicey side single engine to start with, and they don't have 2 dead engines and a wing they are lugging around either.

The losing the blade at the hub is not as bad as you would think, as the outer portions of the rotor make more lift per foot of span than the inner part due to the higher airspeed/tangential velocity at the outer points of the hub.

I forget the exact number, but a good chunk of the 60's blade is not making lift in the faster parts of it's flight envelope, and some portions even have reversed flow.

 

[MasterBates]

Also, just from a "looks like" standpoint, the fenestron in that is really small for the apparent size of the aircraft.

 

[GFS]

New Multirole V/STOL being developed Reply to Thread

The last 1/3rd of the rotor blade (outboard) is the working part of the blade the inner 2/3rds basically holds the last 1/3rd out there. the inboard 2/3rds is turning too slow to be effective (save auto rotation)... Now as far as complicated retraction system it astoundingly simple..... Single engine performance, the usual statement is "the good engine will take you to the scene of the crash" that's because the average aircraft is built to close to the lower limits of the flight envelope. This aircraft is designed with each engine having the power to fly the aircraft at gross weight. That's the beauty of the engines finally decided on for the project, Williams Fan Jets lots of power at less than 400 pounds. Easy to carry.... Most other aircraft both the engines share the load of the flight envelope. To loose loose one of them is trouble... Auto-rotation into a confined area always made me appreciate practice,practice, and more practice. But as we can see the the video-graph-er is not a rotor craft pilot, his confined area landing would be quite a feat.....

 

[NozeMan]

The last 1/3rd of the rotor blade (outboard) is the working part of the blade the inner 2/3rds basically holds the last 1/3rd out there. the inboard 2/3rds is turning too slow to be effective (save auto rotation)... Now as far as complicated retraction system it astoundingly simple..... Single engine performance, the usual statement is "the good engine will take you to the scene of the crash" that's because the average aircraft is built to close to the lower limits of the flight envelope. This aircraft is designed with each engine having the power to fly the aircraft at gross weight. That's the beauty of the engines finally decided on for the project, Williams Fan Jets lots of power at less than 400 pounds. Easy to carry.... Most other aircraft both the engines share the load of the flight envelope. To loose loose one of them is trouble... Auto-rotation into a confined area always made me appreciate practice,practice, and more practice. But as we can see the the video-graph-er is not a rotor craft pilot, his confined area landing would be quite a feat.....

Allows another rotorhead to weigh in:

The dome (AWACS thingy that holds the rotor blades) at the top of the aircraft looked awfully thing in the video. How "thick" does it need to be to allow full articulation of the rotorblades? I think it would have to be fairly signifacant.....and would it have any aerodynamic benefit? I think this would be a hinderance in fixed wing and rotary wing modes.

Second, how does the big ass wing under the "dome" affect the rotor blades during autorotation? I would think that large wing would block a significant amount of airflow that would be aiding the rotor blades in this phase of flight.

What is the radius of the dome compared to the length of each rotor blade?

 

[MasterBates]

Ok, so the fans are 800# thereabouts. I know you aren't going to throw full specs out, but what weight class is this thing in? H60? HH65? H1?

There has been quite a few times in the 60B where I would have killed for 800# less dead weight (mostly electronics we weren't using) and that thing is in the 22-24K range with 2 1900ish SHP motors.

 

[HokiePilot]

Second, how does the big ass wing under the "dome" affect the rotor blades during autorotation? I would think that large wing would block a significant amount of airflow that would be aiding the rotor blades in this phase of flight.

Also, the down wash from the rotor blades onto the outer parts of the wings would cause a big problem. The wings would have to be bulked up to resist the loads and the hover power would be huge.

I think it is an interesting concept I just won't believe it until I see it.

 

[NozeMan]

Also, the down wash from the rotor blades onto the outer parts of the wings would cause a big problem. The wings would have to be bulked up to resist the loads and the hover power would be huge.

More flashbacks from Aero.....shudder......

 

[busdriver]

Most of it has been covered already. The concept is interesting, but the dimensions in the animation would never work. What strikes me more than the obviously flawed animation is that Ray Prouty has said that the gains from using a wing on a helo in cruise are about equally offset by the losses in a hover. He went so far as to say you'd be better off allowing a compound helicopter to turn it's main rotor into an auto gyro.

The concept of retractable rotor blades is not new to this project. A team from a university that I can't remember was working on this recently, in their system a spring system would extend the blades with an increase in rotor rpm. Their premise was flawed, saying you'd retract them for hover (confined area) and extend them for cruise. The real advantage would be extending them in a hover to make a proper helo, and retract and slow them for forward flight, using small wings to offset the loss in lift while countering the retreating blade stall problem. The extended disc in a hover could dwarf the small wings and offset the hover losses due to down wash on the wing.

 

[GFS]

New Multirole V/STOL being developed Reply to Thread

OK let me answer some of these questions all very reasonable.one was how thick the disc... well believe it or not it does not have to be very thick because of blade anomalies. 1-airfoil design for less leading,lagging,and flapping.. most of these anomalies are outside the disc... what might shock you is the fact that helicopter rotor blades operate in the range of minus 3 degrees (mostly auto rotation) to plus 6 degrees up (realistically in flight we use 2 to 3 1/2,degrees up) Based on gross weight obviously. 4 to 6 degree pull of pitch would be a very dramatic departure. The wing below the rotor obviously disturbs the airflow as does the wing of the v-22, armament wings on the Hawk, and the platform for the MD500. and by lowering the flaps the wing area is reduced. by the way the increase in airflow over the wing (boundary layer) dramatically improves transitional lift, the size of the fenestron can be reduced because of the size of the rudder on this proto type.. Mr Prady and Mr Alexander know each other and I am comfortable with the respect for each others talents. Mr Alexander being awarded by the FAA for his 71 years of contributions to the aviation and aerospace industry, two great and talented men..

 

[Beans]

by the way the increase in airflow over the wing (boundary layer) dramatically improves transitional lift

The rest of your response makes sense, but in the excerpt above I think you're trying to say the acceleration of flow over the top of the wing improves translational lift. That has nothing to do w/ the boundary layer, which is only inches thick (unless the wing's stalled, but then it's just separated flow, which isn't really a boundary layer, but I digress...) and a deceleration of flow.

 

[GFS]

Beans,
The down force on the wing accelerates the airflow over the wing.. With no air movement aircraft stationary no boundary layer( very very limited for the movement of air to be exact). Now with the down thrust from the rotor system and the rush of air over the airfoil wala increased boundary layer and the aircraft is still in one position.... now move forward at 10 miles an hour,and you get the benefits of the airflow... Al gfs

Beans, you are right I should have said that the increase in airflow over the wing gives the WING more lift Thus ASSISTING the helicopter mode in its performance win win.. Sorry!! crow is not bad to eat the meat is fine but the feathers get cought in ones throut........Al gfs

 

[busdriver]

As I said interesting concept, I look forward to seeing how things progress and what the final compromise between the interests of helo and fixed wing flight pan out.

As to the size of the fenestron, I fail to see how the size of the rudder affects anti-torque requirements since the greatest demand on the tail rotor is in a hover/sideward flight. Furthermore, given that you will have a fairly high torque head since you'll have to counter the downwash on the wing. But in any event, even if the fenestron gets much bigger is doesn't invalidate the concept.

 

[HAL Pilot]

 

[Birdog8585]

As to the size of the fenestron, I fail to see how the size of the rudder affects anti-torque requirements since the greatest demand on the tail rotor is in a hover/sideward flight. Furthermore, given that you will have a fairly high torque head since you'll have to counter the downwash on the wing.

I'm still a little lost on how the rudder will act to counter torque in a hover too. Will the flight control surfaces on the wings be configured in such a way during a hover to counter the torque? (i.e. - routing air from the rotor in a unique anti-torque way) I understand how the V-22 configures to reduce wing area in a hover but the Proprotors spin in opposing directions for torque counteraction.

Damn geek-ass engineering curse....must.....under...stand....head...going...to...explode :banghead_