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In a discussion on the RWF this project came back to mind...
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Author:  skyguynca [ Sat Feb 27, 2021 8:56 pm ]
Post subject:  In a discussion on the RWF this project came back to mind...
So not sure if you are familiar with flying platforms, specifically the DH-4 De Lackner flying platform.
Image
https://sites.google.com/site/stingrayslistofrotorcraft/de-lackner-dh-4-heli-vector--hz-1-aerocycle

Would be a fun run around low project, maybe even higher but some things need to be changed. Zimmerman and Hiller proved that the rotor below concept to be more stable than the rotor overhead. Just inconvenient around people.

The way I see it, the rotors are rigid so they need more space between them and teetering heads also the addition of collective pitch. They had great success with the first prototypes but when the Army wanted more hp, increased from 40 hp to 75hp (who knows why it could lift 120lbs besides the pilot) they started having blade collisions. I believe this to be from the blades rigidly mounted and failing at higher fwd speeds also with abrupt cyclic inputs. It did not help they were so close together either.

I think with collective it should be able to autorotate, On this I would really consider a BRS since the rotors are below the airframe, and at 150 ft and above the ground the BRS use is feasible. Below that try to autorotate to the ground. Autorotation is something you would have to test at altitude so you could deploy the BRS if it gets out of hand.

Could make an interesting project, could be a lot of fun too.

Opinions and suggestions are deeply appreciated.

David
Author:  Hillberg [ Sat Feb 27, 2021 9:20 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Williams WASP. Who needs rotors?
Author:  skyguynca [ Sat Feb 27, 2021 9:42 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Hillberg wrote:
Williams WASP. Who needs rotors?


Ahhhhh, NO?

Very inefficient and definitely more of a death trap.....well in my opinion

At least this still has rotors. :realcrazy
Author:  Arnie M. [ Sat Feb 27, 2021 11:22 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
.

Just a quick comment for now , maybe more later.

Couple of years ago I read a bit about flying platforms ... then to my surprise I got very interested and spent a lot of time on it.

My memory is rusty but I think it was Stan Hiller that discovered that the shape of the surrounding duct (fenestron) made a huge difference ... I think 30% better lift.

Shape somewhat like a convergent-divergent nozzle ... wide at the top ... narrows down in the middle .... then widens again at the bottom.

Natural stability ... fast forward and drag above the rotors (pilot area) will keep it from tilting too far forward
Author:  Hillberg [ Sun Feb 28, 2021 12:55 am ]
Post subject:  Re: In a discussion on the RWF this project came back to min
skyguynca wrote:
Hillberg wrote:
Williams WASP. Who needs rotors?


Ahhhhh, NO?

Very inefficient and definitely more of a death trap.....well in my opinion

At least this still has rotors. :realcrazy


With a Stanley escape system you'll have zero zero ejection -

Hiller, Williams. Bell Labs, Tyler, Zap are safer then the Lackner lawn mower :laughing

Hiller Museum has two examples and a platform simulator :pbunny
Author:  Girodreamer [ Sun Feb 28, 2021 1:37 am ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Hi David,
I love those plateforms, I don't know anything about them but I'd love to try one ..
a stupid remark : with this it is heasy to install a chute !
Author:  Arnie M. [ Sun Feb 28, 2021 7:10 am ]
Post subject:  Re: In a discussion on the RWF this project came back to min
.

Memory coming back .... I think it was this one that triggered a lot of discussion a few years ago
Author:  Gabor [ Sun Feb 28, 2021 10:09 am ]
Post subject:  Re: In a discussion on the RWF this project came back to min
That guy has some balls.
At times it seemed almost like he was losing control.
:eek
:beefcake
Author:  Arnie M. [ Sun Feb 28, 2021 11:06 am ]
Post subject:  Re: In a discussion on the RWF this project came back to min
.

Professor ankle biter ..

At 1:09 his ankle comes within inches of the props.

(I think he is an actual professor)
Author:  Girodreamer [ Sun Feb 28, 2021 2:06 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min


I could not see the video link
Author:  Arnie M. [ Sun Feb 28, 2021 3:43 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
.

Try this

https://www.youtube.com/watch?v=df8Syrp ... e=emb_logo
Author:  skyguynca [ Sun Feb 28, 2021 5:38 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Arnie M. wrote:
.

Just a quick comment for now , maybe more later.

Couple of years ago I read a bit about flying platforms ... then to my surprise I got very interested and spent a lot of time on it.

My memory is rusty but I think it was Stan Hiller that discovered that the shape of the surrounding duct (fenestron) made a huge difference ... I think 30% better lift.

Shape somewhat like a convergent-divergent nozzle ... wide at the top ... narrows down in the middle .... then widens again at the bottom.

Natural stability ... fast forward and drag above the rotors (pilot area) will keep it from tilting too far forward


Yep, the duct provided 30% more lift. Also it was more stable because the platform was always trying to get back under the CG. If you lean forward the platform moves back under you. They found, and when you watch the news reels footage you will see, that the pilots of flying platforms seem to be leaning forward and looks like they are trying to push repeatedly against something. That is them going from center to forward postion to keep applying a forward tilt to the disk, it is self righting.
Author:  skyguynca [ Sun Feb 28, 2021 5:41 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Hillberg wrote:
skyguynca wrote:
Hillberg wrote:
Williams WASP. Who needs rotors?


Ahhhhh, NO?

Very inefficient and definitely more of a death trap.....well in my opinion

At least this still has rotors. :realcrazy


With a Stanley escape system you'll have zero zero ejection -

Hiller, Williams. Bell Labs, Tyler, Zap are safer then the Lackner lawn mower :laughing

Hiller Museum has two examples and a platform simulator :pbunny


Very true, but also use alot more power. The Lackner, the early 25hp version, never had a problem. Never an accident or crash. It was used to do the initial training for the military pilots before moving up to the 40 or 75 hp versions. Those had a couple of crashes, but the Army by then had decided that personal transport was not the way to go for a battlefield soldier.
Author:  skyguynca [ Sun Feb 28, 2021 5:43 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Girodreamer wrote:
Hi David,
I love those plateforms, I don't know anything about them but I'd love to try one ..
a stupid remark : with this it is heasy to install a chute !



Should be, since the rotors are below you would just install on the top and it should always regardless of position always fire away from the rotor systems. Heck even if you were tumbling it would still fire away from the rotor system. Unless you were in a un-godly fast spin, but too much aircraft and drag for that.
Author:  skyguynca [ Sun Feb 28, 2021 5:45 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Arnie M. wrote:
.

Memory coming back .... I think it was this one that triggered a lot of discussion a few years ago




Yeah, for me this one would be a no. For many reasons.

The main reason I would consider building a variant of the HZ1 Lackner is that the rotors are big enough, and could easily have collective added so the option of autorotation is available, plus BRS could also be used if you decide to fly higher than 100 ft.
Author:  skyguynca [ Sun Feb 28, 2021 5:48 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Arnie M. wrote:
.

Memory coming back .... I think it was this one that triggered a lot of discussion a few years ago



The biggest reason this is a NO, the lift area is too small for the height of the CG above it. Instead of the GG sitting in the middle of a large disk(8ft diameter) right above (16" above props) like the Hiller, it is about 3ft diameter and 5ft above.....too narrow of a cg range, very twitchy.
Author:  Hillberg [ Sun Feb 28, 2021 6:22 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
skyguynca wrote:
Arnie M. wrote:
.

Memory coming back .... I think it was this one that triggered a lot of discussion a few years ago




Yeah, for me this one would be a no. For many reasons.

The main reason I would consider building a variant of the HZ1 Lackner is that the rotors are big enough, and could easily have collective added so the option of autorotation is available, plus BRS could also be used if you decide to fly higher than 100 ft.


With autorotation you'd be fine no chute needed. The biggest drawback with the De Lacker is free public haircuts starting from the ankles -

I've put helicopters down in lots where skids and tails just cleared parked cars as rotors spun above their hoods.

De Lacker needs a bigger circle :laughing
Author:  skyguynca [ Sun Feb 28, 2021 6:57 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
Hillberg wrote:
skyguynca wrote:
Arnie M. wrote:
.

Memory coming back .... I think it was this one that triggered a lot of discussion a few years ago




Yeah, for me this one would be a no. For many reasons.

The main reason I would consider building a variant of the HZ1 Lackner is that the rotors are big enough, and could easily have collective added so the option of autorotation is available, plus BRS could also be used if you decide to fly higher than 100 ft.


With autorotation you'd be fine no chute needed. The biggest drawback with the De Lacker is free public haircuts starting from the ankles -

I've put helicopters down in lots where skids and tails just cleared parked cars as rotors spun above their hoods.

De Lacker needs a bigger circle :laughing



Very true Don, movement on the ground, around people, all hazards but sort of like taxiing a Gruman Tiger or a Piper Arrow, or really any homebuilt helicopter (usually rotors under 8ft at mast top and tips dip to 4 feet).....oh and most definitely a chinook, that front rotor can get within a foot of the gound, the only helicopter I ever operated where you did NOT want to see the paxs approaching from the front.
Author:  Hillberg [ Sun Feb 28, 2021 8:35 pm ]
Post subject:  Re: In a discussion on the RWF this project came back to min
And the left front area with an Enstrom - Buzzzzzzzzzzzz job
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