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Helicopter down outside Leicester City Football Club

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Helicopter down outside Leicester City Football Club

Old 28th Nov 2018, 14:40
  #841 (permalink)  
 
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Originally Posted by chopjock
TeeS


How long does it take to VTOSS using CatA profile V a "Corner" profile?
Well I would be able to calculate that pretty accurately for the VTOL profile as the test pilots have produced the graphs but I can't compare it to your 'Corner' profile as that would depend on your gut feeling about when to stop your acceleration in order to miss the stadium roof and hence what speed you would reach and therefore what your rate of climb would be.

Cheers
TeeS
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Old 28th Nov 2018, 18:49
  #842 (permalink)  
 
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Chopjock is a drone operator.
{and has flown as a passenger in an R22 once}.
So be gentle.
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Old 28th Nov 2018, 19:03
  #843 (permalink)  

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Originally Posted by chopjock
TeeS


How long does it take to VTOSS using CatA profile V a "Corner" profile?
Surely you don't think that Vtoss is in any way related to the tail rotor?

Here's an example of a pilot trying to fly your proposed technique:
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Old 28th Nov 2018, 19:35
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Originally Posted by ShyTorque
Surely you don't think that Vtoss is in any way related to the tail rotor?
I was giving a time period in which to answer a question.


Here's an example of a pilot trying to fly your proposed technique:
https://www.youtube.com/watch?v=N6vWraEkVkY
That was all too slow, nothing like "my technique". No back up, no firm acceleration and no zoom climb...
I wonder how in that video it would have turned out if that Bell had attempted a Cat A departure profile?
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Old 28th Nov 2018, 19:43
  #845 (permalink)  

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If he had attempted a Cat A departure profile and had insufficient power to fly away, which is exactly what happened, he would have been able to fly safely back down to the departure point.
Maybe the point that Cat A departure profiles are designed for exactly this reason has so far escaped your understanding.
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Old 28th Nov 2018, 20:12
  #846 (permalink)  
 
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Like this...
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Old 28th Nov 2018, 20:37
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You've got it at last Chopjock, that is a perfect demonstration of a class 1 profile (it wasn't called that then). From the hover the pilot flying accelerates the aircraft and the pilot monitoring calls 'groundspeed' when he sees the ground moving past the window and then 'airspeed' when the ASI just begins to fluctuate. At that point, the pilot flying adjusts the attitude and power to climb almost vertically whereupon the pilot monitoring calls '20 feet', '40 feet' and 'rotate' as the radalt shows 50'. At that point, the pilot flying initiates a further acceleration and is committed to fly away - before this point, in the event of an engine failure (or other emergency) the take off is rejected.

This profile allows the S61 to depart from a very short runway providing class 1 performance in the same way that the vertical profile provides. It does not allow a departure with obstructions that would be found in a stadium environment!

Cheers

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Old 28th Nov 2018, 20:47
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Ok a Class 1 profile takes about 12 to 15 seconds of "exposure" time to Vtoss. A Cat A profile takes about 30 seconds or more. If neither can survive a tail rotor failure during this time, then which is the lesser of the two evils? I would suggest a shorter exposure time...
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Old 28th Nov 2018, 20:51
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Laddy....if you think 15 seconds means squat considering the rarity of a Tail Rotor failure.....you ought to stay home in bed all day and pray a Police Helicopter doesn't join you.
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Old 28th Nov 2018, 20:57
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Originally Posted by SASless
Laddy....if you think 15 seconds means squat considering the rarity of a Tail Rotor failure.....you ought to stay home in bed all day and pray a Police Helicopter doesn't join you.
Multiply by how often did they do this and was it after 15 seconds when this tail rotor failed?
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Old 28th Nov 2018, 21:18
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JimL......There cannot be two such on the Forum.....the odds against that are just too far out there for it to be possible.
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Old 28th Nov 2018, 21:31
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Originally Posted by chopjock
Ok a Class 1 profile takes about 12 to 15 seconds of "exposure" time to Vtoss. A Cat A profile takes about 30 seconds or more. If neither can survive a tail rotor failure during this time, then which is the lesser of the two evils? I would suggest a shorter exposure time...
Again, you're missing the point. The one you linked to showing a S-61 is a "clear area" profile. It needs a specified minimum distance of clear area to operate from. If there is sufficient distance available (such as existed at Penzance before Tescos built a supermarket on it), it would be flown. If not, from a shorter and confined area surrounded by high obstacles (such as Leicester City ground), it can't be flown because the required obstacle clearance or stopping distance can't be guaranteed and a landing following any loss of power would almost certainly end up in the stands.
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Old 28th Nov 2018, 22:01
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Originally Posted by ShyTorque
Again, you're missing the point. The one you linked to showing a S-61 is a "clear area" profile. It needs a specified minimum distance of clear area to operate from. If there is sufficient distance available (such as existed at Penzance before Tescos built a supermarket on it), it would be flown. If not, from a shorter and confined area surrounded by high obstacles (such as Leicester City ground), it can't be flown because the required obstacle clearance or stopping distance can't be guaranteed and a landing following any loss of power would almost certainly end up in the stands.
I understand what you are saying. The linked S61 video shows a large helicopter in a large (ish) space with a clear reject area, so scale it down to a smaller helicopter in a smaller space and a smaller reject area. Risk flaring into the stands in 15 seconds of exposure v spinning out of control at 400 feet with no airspeed and 30 seconds + of exposure?
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Old 28th Nov 2018, 22:40
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Care to explain why the size of your chopper is improved by a lack of its length?

Last edited by SASless; 28th Nov 2018 at 23:44.
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Old 28th Nov 2018, 23:37
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Not really relevant but I think the specific S-61 profile shown was called an oblique in Bristow days? I think we operated Cat A or Cat A with dump on the 61 providing we could dump down to Cat A weight with the contents of the centre tank.
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Old 29th Nov 2018, 00:27
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On reading the posts on gear retraction and minimum forward airspeed for aerodynamic control why is gear retract based on height should it not be on airspeed i.e. minimum airspeed for control if TR failure then it's down to help cushion the landing.

I believe autorotates are difficult to judge especially at night how about a belly air bag, triggered by under carriage compression rate or a G sensor and why has no one thought of anyway of adding anti torque at low speed if TR failure. Maybe a smallish parachute fired sideways to slow the spin triggered by a yaw rate and time sensor. Just a bit of brain storming.
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Old 29th Nov 2018, 02:12
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Chop, more people have crashed doing your corner departure (because it relies on a performance guess rather than tested data) than crashes from TR failures doing Cat A take offs.
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Old 29th Nov 2018, 05:32
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Originally Posted by Thomas coupling
Chopjock is a drone operator.
{and has flown as a passenger in an R22 once}.
So be gentle.
Ahh! now it make sense. TC you must be lovin the last bunch of posts. We all on Chopjocks little hook!
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Old 29th Nov 2018, 06:00
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CHOPJOCK, I am not going to trash your ideas because sometimes, lack of doctrinal thinking and dogma can be the mother of invention. However, I sorry but in this instance you are "droning" up the wrong tree.

You see the TR is there to stop the torque applied to the rotor head, spinning the fuselage once the undercarriage friction with the ground is not longer present. To make the TR efficient, it is placed a long way down the tailboom to give some leverage. This provides the added advantage of "Keel" surface. That is to say the surface of the fuselage and tailboom combined, when pushed through the air at speed, provides an element of anti-torque reaction all on its own. However, this "Keel" surface is not really effective until the forward airspeed is well above 70-80 KIAS. Now I am not a Test Pilot so my numbers here are just a guess but you can get the idea. The more power you apply to the rotor head, the more "torque" is trying to spin you.
So armed with this new knowledge, you can understand that what you propose, scuttling across the football pitch then zooming over the stand, you will still be below the speed where any benefit from the keel surface is not present. Added to the requirement to apply lots of power, to accelerate quickly, and you can understand that a TR failure anytime during your procedure would leave you, at worse case, moving forward across the ground, spinning like a an angel with a broken wing towards the obstacles in front of you. This set of circumstances is extremely difficult to resolve.

In recognition of the critical role the TR plays, especially in the low speed, low height part of the flight envelope, the certification requirements for the TR system are very comprehensive and the design failure rate much lower than other systems that may for example, be duplicated. This is why this accident is so significant if indeed it proves to be some kind of design fault.

This problem, the heavy reliance on the TR, has plagued designers and performance systems since Sikorsky donned his pork pie hat. It is nothing new.

Many factors come into play when a TR malfunction occurs and the actions of the pilot are just one aspect. Design characteristics, Power Setting, airspeed, height, wind direction etc all have a influence on the outcome.

I understand your concern, hanging around in the low speed envelope increases the exposure to the impact of a TR failure and you are certainly correct in this assumption. However, your proposal does not solve the problem as the exposure remains critical throughout your proposed take-off envelope and marginally improves as speed (>80 KIAS guess) and height is gained.

If you are a Drone Pilot and you do it for a living, big respect. I had a drone for my Daughters Wedding this year and it and the operator were awesome.

I hope this post helps you to understand why so many are perplexed by your proposal.
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Old 29th Nov 2018, 06:10
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TC

He is actually a helicopter pilot, having done his PC's for the past 7 years or so ( he is actually a very good handling pilot, including a successful landing with a stuffed tail rotor in an Enstrom and an engine failure in a Hu 369) He is a single engine pilot so is asking why one has to climb quite so high when in a single you wouldn't. I suppose I can understand what he is saying, but he may have a hypothetical point are the manufacturers concentrating too much on engine failures rather than the plethora of other problems.
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