Wake Turbulence Separation and helicopters
Crab, fully acknowledge the issue that you're describing but the requirements for separation are sourced from ICAO and have been reinforced in recent years by research undertaken by the FAA and EUROCONTROL; albeit that research focused on fixed wing.
The CAA did some work on RW wake turbulence a few years ago (which resulted in a minor amendment to the ICAO materials, I think a note was added) but it focused on RW AS generates of wake, not how they react to wake. I believe that there was a plan to do some (UK) research on this aspect a few years ago but the funding application fell through.
The CAA did some work on RW wake turbulence a few years ago (which resulted in a minor amendment to the ICAO materials, I think a note was added) but it focused on RW AS generates of wake, not how they react to wake. I believe that there was a plan to do some (UK) research on this aspect a few years ago but the funding application fell through.
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whowhenwhy - as I mentioned earlier, every helicopter pilot knows the dangers of another helicopter's rotor wash but despite being of similar strength, especially things like S-92 and Merlin, to a large FW, the vortices do not persist and dissipate in a very short distance from the aircraft.
Even if you do encounter the wake of another helicopter, there is no loss of control or stall, it usually just affects your power required briefly.
There seems to be a dearth of evidence or any research to produce such evidence that would lead you to apply a FW safety protocol to a RW aircraft.
As I mentioned, a 3 min hold is complete overkill for a helicopter to transition after a heavy or super FW has rolled or gone around.
Even if you do encounter the wake of another helicopter, there is no loss of control or stall, it usually just affects your power required briefly.
There seems to be a dearth of evidence or any research to produce such evidence that would lead you to apply a FW safety protocol to a RW aircraft.
As I mentioned, a 3 min hold is complete overkill for a helicopter to transition after a heavy or super FW has rolled or gone around.
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Originally Posted by [email protected]
I am led to believe that the FAA don't apply wake turbulence separation to helicopters on approach behind a FW.
Originally Posted by [email protected]
As I mentioned, a 3 min hold is complete overkill for a helicopter to transition after a heavy or super FW has rolled or gone around.
The 3 minutes hold is again a requirement by the rules, and some countries allow for the pilots to accept separation to a preceding heavier departure (but I think it has been removed in DOC4444?)... there is no standard phraseology for it though, and I've heard people saying that if the pilot just says he is "ready", it means he will take the wake turbulence separation himself.... though I personally don't like that interpretation.
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ATC usually provide the recommended spacing for VFR approaches but mandate the time for departures - haven't ever heard of allowing the pilot to make his own decision on a departure.
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Originally Posted by [email protected]
ATC usually provide the recommended spacing for VFR approaches but mandate the time for departures - haven't ever heard of allowing the pilot to make his own decision on a departure.
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I don't understand why there should be 'local rules' - surely any difference from ICAO procedures would have to be sanctioned nationally by the CAA.
Any controller is going to play by the rules since it is their licence on the line - it is the rules that need clarifying on this matter.
We have a very good relationship with our local ATC but the increase in traffic now many covid restrictions have been lifted has brought the situation into sharper focus.
Any controller is going to play by the rules since it is their licence on the line - it is the rules that need clarifying on this matter.
We have a very good relationship with our local ATC but the increase in traffic now many covid restrictions have been lifted has brought the situation into sharper focus.
it is the rules that need clarifying on this matter
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The rules are quite clear, any controller should know exactly which rules they’re applying
Originally Posted by [email protected]
The rules do not stipulate FW separation to be applied to RW - it is just assumed.
Originally Posted by [email protected]
The rules do not stipulate FW separation to be applied to RW - it is just assumed.
https://publicapps.caa.co.uk/docs/33...0117928886.pdf
So a controller shall apply those separations, and they are drummed in under training. Also note separation standards required for parallel runways in said documents. Then ask how does that work with a parallel taxiway and a heli taxiing with skids, eg MD’s Robbo’s,...
A controller has to use those separations, so if you’re at an airfield where rotary has to use the runway for departures and the traffic mix is different weight/wake vortex categories, (and speeds), it can be as frustrating for controllers as it is for the engine drivers...
As others have pointed out, the rules (certainly for the UK) are clearly set out in the national procedures manual. It is unfortunate that at aerodromes where RW mix with larger FW operations those procedures do appear to penalise the RW operations, in some cases quite significantly. Sadly, simply being unhappy with that and posting here doesn't change things. But there is a process for changing things, at your home base, at least, if your ATC people support it. Many national procedures can be varied to take account of local conditions and features....if the variations are published in the local Manual of ATS. To get something into the local procedures it will have to be approved by the CAA and I imagine this will require something along the lines of a safety argument showing that the variation is at least as safe as following the 'standard' rules. Whilst this takes some work and effort, if there are benefits to be gained by both RW operators and ATC (and, probably, the airport), maybe it's worth doing. I've no idea how such things are viewed these days, or how practical it is at your base and with your aircraft, but there may be other possibilities which do not require some of the separations to be applied. In the past I recall one airport where RW (although not larger ones) hover/air-taxied from the apron to a designated point in a grass area, from which they transitioned and set course largely as desired. The point was quite specifically not a FATO and was outside the runway strip - no wake turbulence separation is specified and a caution was issued if the aircraft was going to pass behind or through the recent path of another aircraft. Seemed to work OK, I'd go further and say it worked well for everyone, but maybe it's been stopped in the intervening time.
Thread Starter
Thanks for all the replies - I know what the rules say but the whole argument for wake vortex separation is based on FW encounters with it not RW and especially the dangers to a FW with a small wingspan getting trapped in the vortex and losing control.
It doesn't mention the dangers to RW because they don't know if there are, it is all based on FW research.
Rather than do the studies to see exactly what effects a wake vortex has on a RW, it has just been assumed and read across - the MATS manual specifies FW susceptibility but only mentions helicopters as a generator of wake vortex, not a potential victim.
It seems to me that classifying helicopters in the same way as FW is all about their ability to generate wake, not their susceptibility ie a S92 is far more dangerous to a light FW than an R 22 dues to its weight and therefore downwash strength.
I'm not expecting this situation to change because once you apply a safety measure, no matter how pointless, the amount of work to get it removed in our risk-averse world is unlikely to be completed and fought at every turn.
I have written to the CAA but I won't be holding my breath - I will be advised to read MATS and pointed out that the rules are the rules.
Meanwhile I'll just lose time and revenue waiting for an almost non-existent threat to my aircraft to dissipate, even in conditions where it is physically impossible to affect me.
It doesn't mention the dangers to RW because they don't know if there are, it is all based on FW research.
Rather than do the studies to see exactly what effects a wake vortex has on a RW, it has just been assumed and read across - the MATS manual specifies FW susceptibility but only mentions helicopters as a generator of wake vortex, not a potential victim.
It seems to me that classifying helicopters in the same way as FW is all about their ability to generate wake, not their susceptibility ie a S92 is far more dangerous to a light FW than an R 22 dues to its weight and therefore downwash strength.
I'm not expecting this situation to change because once you apply a safety measure, no matter how pointless, the amount of work to get it removed in our risk-averse world is unlikely to be completed and fought at every turn.
I have written to the CAA but I won't be holding my breath - I will be advised to read MATS and pointed out that the rules are the rules.
Meanwhile I'll just lose time and revenue waiting for an almost non-existent threat to my aircraft to dissipate, even in conditions where it is physically impossible to affect me.
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Well I rather hoped that some educated ATC er would point me in the direction of the evidence used to establish these rules with helicopters rather than just pointing out what MATS says.
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Originally Posted by [email protected]
Well I rather hoped that some educated ATC er would point me in the direction of the evidence used to establish these rules with helicopters rather than just pointing out what MATS says.
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Done all that Callum, the geography doesn't lend itself to any areas for circuit arrivals and departures away from FW. We do have manoeuvring areas for ground cushion work but that is it.
Originally Posted by [email protected]
Well I rather hoped that some educated ATC er would point me in the direction of the evidence used to establish these rules with helicopters rather than just pointing out what MATS says.
1) why apply the same separation criteria, whether it be distance based or time based, between a FW and a RW?
2) what alleviations are allowed to disregard wake turbulence separation when wind conditions - ie strong crosswind away from other traffic - mean the wake cannot possibly persist and be affecting other traffic?
The answers are above, really: 1) because the rules require it; 2) none, because the rules require it.
You're not going to get a response here that helps any more than that, I'm afraid, because it's not within the gift of those posting here to change it. It doesn't matter whether they want to, or not, they don't have the authority. I'd be staggered if any airfield operator was prepared to sign off a safety case that changes any of that, without clear documented evidence from a higher authority, so your best bet would be lobbying via the CAA, & the BHA perhaps.
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alfaman - yes, the answers were what I was expecting, I just wanted to know if anyone had any inside knowledge of studies or trials that actually support the rules as they stand.
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Originally Posted by [email protected]
alfaman - yes, the answers were what I was expecting, I just wanted to know if anyone had any inside knowledge of studies or trials that actually support the rules as they stand.
Originally Posted by [email protected]
alfaman - yes, the answers were what I was expecting, I just wanted to know if anyone had any inside knowledge of studies or trials that actually support the rules as they stand.
If a change were to be proposed, there may be a baseline platform data of military ops, as, as I understand it UK mil aren’t ‘restricted’ in the same manner. How to access that data, if it exists and if it would be considered meaningful are way above my pay grade. But if you wanted a place to start with examples of safe operations, that might be a path to follow.