Low NR Hind

[hoodie]

All the weight of gearbox and MRB, and for what (http://www.break.com/index/helicopter-blades-stop-moving.html)? :}

Clearly the Russians have their own Area 51ski alien anti-gravity technology. :ok:

[Heli-kiwi]

Looks like the govenor is doing a pretty good job though..

[SilsoeSid]

I think this is part of an early 90's experiment into stopping the blades in flight and using the winglets, to enable faster flight.

Miniature thrusters were placed on the winglets to increase forward speed and operated just prior to a retreating blade stall condition which just happened to be the optimum winglet lift speed (Vo).

If you notice when the aircraft slows down, the airframe begins to rotate. This is because the tail rotor is kept engaged for yaw control, and is more effective at the slower air speeds. Once a boundary speed (Vrt) is reached without the rotors engaged, the TRT causes a virtually uncontrollable spin.

The movement of the blades that can be seen, is caused by the secondary rotor brake creeping. It is a very weak brake and is brought into operation only once when the blades haved stopped (Vrs). This weakness in brakeability is to facilitate a rapide re-engagement.

Unfortunately the experiments were halted due to the increasing loss of aircraft, as when trying to revert to normal rotary flight, 3 aircraft were lost.
This was due to;
i. early re-engagement of the rotors causing blade loss,
ii. too late re-engagement of the rotors causing lift loss,
iii. thruster failure and failure of rapid re-engagement system.

At least the ejection system temporarily developed at the time for the Hind, using Havok design, proved to be a success.

:hmm:

[Aser]

Another "RIGID" rotor
http://www.youtube.com/watch?v=DFCsFTnW5y4

;)

[Hummingfrog]

I think that you will find that this stationary rotor is a visual effect caused by the flicker rate of the video camera and the RRPM of the Hind being very similar so you get the same effect as viewing a moving object under stroboscopic lights - it looks stationary. The clue is that the tail rotor is also moving slowly because it is not at the same RPM as the head.

HF

(SS I hope your version was tongue in cheek:E )

[hoodie]

Thanks for clearing that up!

[Tractor_Driver]

Gee, thanks Hummingfrog,

the other 339 readers of the thread all thought we were watching a genuinely stopped rotor. It's good to know that someone knows something about helicopters.

[as355f1]

Hummingfrog , your reply amused me more than the video, well done :D

[SilsoeSid]

Hummingfrog,

Although your answer may make sense to those 'not in the know' about these and other experimental aircraft, it is fundementaly flawed.

To match the frame rate and thus give the impression of being stationary, the rotor speed would need to be in the region of 1800rpm for a highish quality 30fps video speed. Even if the frame rate was reduced to a level at which 'stuttering' would begin to occur, 25fps, the rotor speed would have to be 1500rpm. As you must be aware, these rotor speeds are impossible due to many factors, the main one being the tip speed, let alone the problems when forward speed is introduced. (The only helicopters with blade rpms that high are radio controlled models.)

I would estimate the Hinds MR speed to be considerably less than 500rpm, which even at that speed would require a shutter speed of 8.33 fps. You will of course realise that this is a ridiculously slow speed for video.

As mentioned before, the tail rotor is moving because it is the only method of yaw control available with either the main rotors rotating or stationary.


By the way, after the 'G' model, the winglets were increased in size to help performance in Afghanistan. However by this time the project was over.

Also, in '75 another branch of this project was experimenting with a fenestron for the Mil-24, which was a bit more succesful, however, when bringing the 2 projects together politics got in the way and again it fell by the wayside.

http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1052004/pictures/05.jpg
http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1052004/mi24.asp

[ShyTorque]

Isn't this the "BS" derivative? "Blade Stealth" They need to be quiet because they use this derivative for spraying those chemtrails, by night.

Or "BS" might mean something else :E .

[Dave_Jackson]

SilsoeSid
the rotor speed would need to be in the region of 1800rpm for a highish quality 30fps video speed.
The craft appears to have 5 blades. This means that the rotor speed can be 1800/5 = 360 RPM.



OK it's time to get serious.

The video was a training film for interrogators, when the Russians were fighting in Afghanistan.

A person's rate of blinking increases when nervous. The interrogators would start by making the captive very nervous. When the prisoner said that the rotors on the overhead helicopter had stopped turning the interrogators knew that it was time to start the questioning.

[SilsoeSid]

The craft appears to have 5 blades. This means that the rotor speed can be 1800/5 = 360 RPM.

Sorry Dave, but that is a ridiculous calculation to make and a basic PoF error when it comes to these matters. Besides, using your calculations the frame speed would be 6fps, again resulting in a very stuttered video clip, which of course it isn't.

ShyTorque, being Russian, of course the technology is named in reverse.
The Stealth Blade project was a very serious matter in the late 70's/80's. Many a time, Lynx patrolling along the IGB would be flying alongside a Hind, yet not until they actually saw the aircraft did they know it was there, it arrived unheard!
So to some degree the Soviet Stealth Blade must have been operative and relatively effective.

It also highlights the different working ethos between the East and West.
The Soviets had 'Blade Stealth' (BS),
Whereas we had the 'British Experimental Blade Project' (BERP)
http://www.whl.co.uk/history_timeline4.cfm

It just goes to show that although we worked on technology that was a very serious matter, especially given we were in the Cold War era, the British still maintained that loveable schoolboy sense of humour.


On the ground, still think we should have had a different tactical refuelling method, in that the Forward Refuelling and Arming Points (FARPs) were replaced by smaller detachments, less detectable close to the frontlines and called these units, 'Forward Arming and Refuelling Teams'.

[ShyTorque]

Sid,

It's a little known fact that during the Cold War, the AAC Lynx were actually employed on Anti Stealth Blade Operations (ASBOs). Those Lynx blades were designed to be used as noise decoys, to draw enemy fire away from the RAF helicopters, coming along in the next valley, bringing in the troops. The AAC were never told this, in the interests of maintaining the morale of the crews.
Hence your very credible story about the Russian helicopter, which was able to sneak up behind. Noise / quiet are only relative, after all.

Similarly, the Gazelle was occasionally provided as cover for the Lynx. These aircraft were regarded as completely expendable, so were only given to lower ranks to fly and single manned. The Gazelles were known as Little 'Elicopters Sadly Beyond Operational Stuff, or LESBOS for short.

Fortunately for the AAC, it all went for a ball of chalk when the "BUBWAN" Chinooks arrived in theatre. (Big, Ugly Buggers, What A Noise).

P.S. I think that if the crossing of the IGB had ever occurred, there would have been more than a few FARTS coming up from the rear. ;)

[SilsoeSid]

I did hear this ST, thanks for confiming it.

The advantage of having the Gazelle around, as some form of cover or indeed early warning, was that as they were basically of airfix form, the were not able to be picked up on RADAR.

This became a bit of a problem for 'peacetime' flying and especially when not in the BAOR Theatre for civilian controllers. This problem was overcome, again with British ingenuity, by issueing the crews with a radar reflective device.

Cunningly, this was disguised as an 'Aircrew Survival Knife' which allowed the Gazelle to show up on a RADAR screen, yet could also quickly be discarded when the Soviet hordes bolted westwards and stealth was once more the order of the day.

That is why;
1. Gazelle crews carry a 'survival knife on their flying suit.
2. The 'Survival Knife' couldn't even assist survival in the grocery department of Marktkauf.

[gwelo shamwari]

Looks as if all they have done is edited/synked in the camera shutter with the rotation of the main rotor. This is can be pretty much done on a basic home PC these days with the right software and a bit of time.

:cool: But the idea of a heli flying at slow speeds and nearly stopping in midair with out the big fan rotating is quite amazing.:ok:

[SilsoeSid]

Hi TGZ,

The whole problem with the project was this slow speed capability, ie none. Which is why it was so crutial to re-engage the rotors quickly.

As mentioned before, this was its downfall. When it slowed down too much the yaw forced a spin which in most cases, without sufficient height was uncontrollable. In the vid here, you can see he nearly lost it, but managed to boost the thrusters (@25 secs) during the recovery and was able to gain height and fly away from what was without doubt impending disaster.

[Overt Auk]

I understand that Red Ken is a big fan of the technology and is trying to persuade the operaters of Batersea to offer a discount to fixed rotor craft as they will obviously cause less disturbance to the newts.
OA

[mickjoebill]

Frame rate is somewhat irrelevant.
Synching the shutter speed/duration of each frame to rotor revs is what its all about.
For a small fee I'll stop the blades on any heli
Except you all know how to do it now:}
It also works with many subjects that are at constant speed with constant intervals.
You should be able to figure out then how railway sleepers can appear stationary when filmed from a moving train...:8
Mickjoebill

[Twisted Rigging]

For a small fee I'll stop the blades on any heli
Except you all know how to do it now
Rotorbrake? :rolleyes: Do I get a prize?

[SilsoeSid]

You should be able to figure out then how railway sleepers can appear stationary when filmed from a moving train...

Railways sleepers are stationary, aren't they? It's the train that moves!
Isn't he whole point of a railway sleeper to be still, in order to maintain the tracks integrity ?

Is this a Soviet stealth train related project ?

[HELOFAN]

Actually it isnt the helicopter moving , its the pilot controlling the earth around him.

Its all relative, the rotors dont need to move for lift , they are there for balance.

:ok:

HF

[ShyTorque]

I'm just trying to work out what railway sleepers look like, as filmed from a stopped rotor helicopter, when a Russian stealth train runs across them.

On a conveyor belt......

[SilsoeSid]

ST,
From a stationary railway sleeper, this is what a rotor blade looks like!

http://i52.photobucket.com/albums/g11/silsoesid/r22blades.jpg

[ShyTorque]

That one always keeps coming back :ok:

[SilsoeSid]

For those not in the know, this was the joint US/Aus Helicopter Return Project-Experimental Study. (HeRPES)

Because of the increasing loss of the R22/44 series of helicopters, it was thought that the re-design of the basic rotor blade would enable aircraft in a navigational embarrassment situation, to be able to 'rotor profile shift'. A kind of shape shifting using pneumatic cells along the trailing edges.

This would allow the aircraft to return to it's point of origin with the minimum amount of navigational workload for its pilot. However the project was eventually cancelled as it was realised that the most common time for navigational embarrassment was after the point of no return, resulting in the aircraft being lost anyway due to lack of fuel!

[HELOFAN]

How the facts continually get mixed up.

This main rotor & tail rotor ( look close ) was designed by an Australian aviation design technology team based near Perth Western Australia.

It was mainly influenced by the Australian Aborigines boomerang principle.

But instead of the head being fixed like in earlier designs & having anti clockwise patterns , the rotor head is controllable allowing for a more controllable flight & right hand ( clock wise ) patterns .

HF

[SilsoeSid]

Helofan, I remember that head issue. If I remember correctly some of the the technical problems were associated with the aircraft being tested either in the US or Australia.

Due to the inevitable admin cook-ups they often had the clock-wise rotors in the US and the anti-clockwise rotors in Australia. As with the water going down the plughole principle, the aircraft had to be in the correct hemisphere for it to operate in the correct sense.

The British suggested that to overcome this problem, the project set up an operating base near to the Equator. As it happened, the British Army exercise near to the Equator in Kenya and with the Kenyans permission they would supply the security required, as long as our boffins could have an input into the project.

After the relevant clearances were given, the Kenyan New Operating Base (KNOB) was set up in Nanyuki. This was a highly successful unit, until a few months later, just when the big breakthroughs were happening, the Kenyan Landowners and Arrowhead Polishers (KLAP) reclaimed the land for the development of the Kenyan University - Nanyuki Town. ( := )

The project then returned to the original test bases in Perth and New Mexico, the British pulled out first, and it all went downhill from there!

[HELOFAN]

Mate,
I get the feeling you were working on the project as well.

Now just to figure who you are and we can finish off a few cold ones.

Now If we could get the funding for the 3 bladed varient , we would have ourselves a winner.

HF
;)