Low NR Hind
Purveyor of Egg Liqueur to Lucifer
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.
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.
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
)
HF
(SS I hope your version was tongue in cheek
)
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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.
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.
Purveyor of Egg Liqueur to Lucifer
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/hrvats...52004/mi24.asp
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/hrvats...52004/mi24.asp
Avoid imitations
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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 .
Or "BS" might mean something else
.
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SilsoeSid
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.
the rotor speed would need to be in the region of 1800rpm for a highish quality 30fps video speed.
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.
Purveyor of Egg Liqueur to Lucifer
The craft appears to have 5 blades. This means that the rotor speed can be 1800/5 = 360 RPM.
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'.
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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.
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.
Last edited by ShyTorque; 21st May 2007 at 14:27.
Purveyor of Egg Liqueur to Lucifer
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.
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.
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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.
But the idea of a heli flying at slow speeds and nearly stopping in midair with out the big fan rotating is quite amazing.
But the idea of a heli flying at slow speeds and nearly stopping in midair with out the big fan rotating is quite amazing.
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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.
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.
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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
OA
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...
Mickjoebill
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...
Mickjoebill
Do I get a prize?
Purveyor of Egg Liqueur to Lucifer
You should be able to figure out then how railway sleepers can appear stationary when filmed from a moving train...
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 ?