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Wake Turbulence Separation and helicopters

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Wake Turbulence Separation and helicopters

Old 25th Apr 2021, 08:33
  #41 (permalink)  
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Terrain safe - just 40 years of helicopter experience, mostly military, and a fair bit in very turbulent conditions in mountains. I have also operated in and around FW - FJ and ME - and never encountered anything more than a burble from wake turbulence - even in and out of LHR.

Jumpseater - good point, I'll follow that up.
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Old 25th Apr 2021, 09:14
  #42 (permalink)  

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Originally Posted by terrain safe View Post
The question could also be; Do you know of any studies or trials which prove the rules are not required?
Surely, if that was the case there would be no need to post this thread.

But some operators routinely fly helicopters in very close formation with much larger fixed wing, as here for example:






Last edited by ShyTorque; 25th Apr 2021 at 09:31.
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Old 25th Apr 2021, 19:40
  #43 (permalink)  
 
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Originally Posted by [email protected] View Post
Terrain safe - just 40 years of helicopter experience, mostly military, and a fair bit in very turbulent conditions in mountains. I have also operated in and around FW - FJ and ME - and never encountered anything more than a burble from wake turbulence - even in and out of LHR..
I've been a controller for over 30 years and after applying the rules never had a problem either. So therefore the rules work well and keep everyone safe.

ShyTorque But these 2 aircraft are in the same wake turbulence category and so require no wake turbulence spacing between them. I don't think that this is done for smaller helicopters (but accept that it's mission dependant rather than size).
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Old 26th Apr 2021, 00:52
  #44 (permalink)  

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Originally Posted by terrain safe View Post
I've been a controller for over 30 years and after applying the rules never had a problem either. So therefore the rules work well and keep everyone safe.

ShyTorque But these 2 aircraft are in the same wake turbulence category and so require no wake turbulence spacing between them. I don't think that this is done for smaller helicopters (but accept that it's mission dependant rather than size).
Iím surprised to hear they are in the same category. A Blackhawk weighs 10 tons and a C-130 weighs up to seven times as much. Yet I have heard that an AW139 (approx. 6.5 tonnes) will now require wake turbulence separation from helicopters such as a 109, max weight 3.175 tonnes.
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Old 26th Apr 2021, 08:24
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Originally Posted by ShyTorque View Post
I’m surprised to hear they are in the same category. A Blackhawk weighs 10 tons and a C-130 weighs up to seven times as much. Yet I have heard that an AW139 (approx. 6.5 tonnes) will now require wake turbulence separation from helicopters such as a 109, max weight 3.175 tonnes.
Light: 7000 kg or less.
Medium: between 7000 kg and 136000 kg.
Heavy: 136000 kg and more.
A380 has it's own category.

In some countries the B757 is weighed as a heavy when flying in front of another aircraft, and meduim flying behind.

Do keep in mind that these are MTOW. And there has been some talk about changing/adding more categories.

By local rules I meant the rules the local CAA has decided on, besides what ICAO say.
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Old 26th Apr 2021, 09:01
  #46 (permalink)  
 
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So in the U.K. alone depending where you fly from you could receive “caution wake turbulence, the recommended spacing is...” or separation applied (or not) variably based on CAA MATS Part 1, USAF, RAF, individual MATS Part 2 eg RECAT/CREDOS/TBS rules each subtly different from ICAO never minding local rules on what constitutes an intersection, relevant proximate runway or taxying near a runway. No wonder the question comes up.

Are there any examples of helicopter incidents due to fixed wing wake turbulence? I don’t remember any.
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Old 26th Apr 2021, 11:13
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Originally Posted by Dan Dare View Post
Are there any examples of helicopter incidents due to fixed wing wake turbulence? I donít remember any.
Me neither..... and I've seen VFR helicopters joining in very tightly behind heavies counting on us to use "reduced runway separation".

The fun part is, we can only use "reduced runway separation" when the braking action isn't affected....... which makes a lot of sense when no. 2 is a helicopter....
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Old 26th Apr 2021, 14:00
  #48 (permalink)  

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Even more so when a helicopter is mandated to use a runway that it doesn't need and then given mandatory separation...

The traditional "Standard Helicopter Join" of approaching at ninety degrees to the centre of the active runway seems to have been totally forgotten.
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Old 26th Apr 2021, 15:02
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Originally Posted by ShyTorque View Post
....
To be fair, the design of the runway, including obstacle free zones etc. are designed for all aircraft, those doesn't really change just because you're in a helicopter. Though we agree a helicopter can land on a dime, and won't need a runway.... the runway is still the part of the airport "designed for the landing and departure of aircraft". Unless helipads have been established.

But yes, we can ask for a lot from you guys, and it's appreciated.
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Old 26th Apr 2021, 21:28
  #50 (permalink)  

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jmmoric,

We realise it's not the fault of the ATCO on the day. But with DOC about £30 a minute for a light twin heli, we're very much aware of how things could often be carried out in a more expeditious way without compromising safety.
An ATCO who has never seen how helicopters operate once away from an airfield, would really not understand how small an area of real estate a modern helicopter needs to take off and land, even whilst complying with with Class 1 performance standards. For example, an AW109 only needs an operating area of approx. 50 feet x 50 feet.

Last edited by ShyTorque; 28th Apr 2021 at 20:17. Reason: To correct meaning!
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Old 28th Apr 2021, 17:13
  #51 (permalink)  
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The fun part is, we can only use "reduced runway separation" when the braking action isn't affected....... which makes a lot of sense when no. 2 is a helicopter....
Another indication that FW rules have been applied to helicopters without any real thought.
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Old 28th Apr 2021, 20:05
  #52 (permalink)  
 
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Crab, the research clearly needs to be done to focus on RW, and, based on what you and ShyTorque have said, it sounds like there is an opportunity for a more flexible approach to be applied to RW.

We need someone to fund the research though. Neither ICAO nor the CAA have the money. That means either a university with a research grant (and many of their sources of cash dried up when we left the EU) or business; BHA?
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Old 28th Apr 2021, 20:20
  #53 (permalink)  

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Originally Posted by [email protected] View Post
Another indication that FW rules have been applied to helicopters without any real thought.
Maybe some days the air is more slippery
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Old 14th May 2021, 11:37
  #54 (permalink)  
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By way of closing the loop, so to speak, I have had a great response from the CAA following an email question I sent.

There is little empirical evidence that FW wake turbulence affects helicopters in any major way and one study, done by the well-renowned Gareth Padfield in the late 90s, seems to be the basis for applying FW separation criteria to RW.

The problem is that it is theoretical, using vortex simulation algorithms and a Lynx Mk 3 s handling characteristics - a good place to start but it assumes a lot of 'worst-case' scenarios (no vortex dissipation and no pilot intervention for several seconds for instance) and uses a Helicopter handling qualities standard (ADS33) to predict the disturbances in pitch, roll and yaw caused by interaction with the vortices.

Again, good place to start but there seems to have been no attempt to follow it up with real-world testing so anyone reading the study - presented at the 25th European Helicopter Forum - would think that any encounter with any wake vortex would be very hazardous, not something backed up by any empirical data and certainly not confirmed by any anecdotal evidence from real encounters.

Once such a safety protocol is put in place, it becomes near impossible to roll it back or water it down without a huge amount of effort and evidence and the RW industry isn't interested in fighting it's corner here it seems.

It was a useful exercise asking the question and I really wasn't expecting anything to change but I scratched the itch.

Many thanks to Rob at the CAA and to all who have contributed.
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