Vortex Wake

[niknak]

How do you guys feel about the application of vortex wake?

At our place, we have an allocated area for helicopter training, which is less than 600m from the centreline of the longest runway and parralell to it.
The type of helicopters utilising the area varies from light up to and including AS332, whilst the fixed wing traffic is anything from light aircraft up B767s.

Fundementally, the training area is within the runway strip and therefore we should technically treat the heicopter as if it is departing from the runway, and apply vortex wake spacing every time a fixed wing aircraft departs, (arrival spacing is advisory). But we don't, simply because the management culture is "it has always been like that, and nobody has complained yet".

Personally, I always try and apply some delay, but this ineviatebly leads to moans and groans.

There hasn't been a problem yet, and amazingly, the CAA's erstwhile aerodrome and atc inspectors haven't commented on it, but I know that when the worst happens, it's the atco in the seat who will be blamed.

[NickLappos]

Most helicopters are almost immune to typical wake vortex issues, since the blade loading is so high that little change in lift is created by the wake. Unlike light fixed wing, which can be flipped upside down, helicopters have blade loadings that are almost like high speed jets.

[Aesir]

It´s the fixed wing guys that have to worry about the vortices from the helicopters, expecially in x-wind conditions if the AS-332 is departing I wouldn´t want to be departing after it in anything smaller than a 737.

[The Nr Fairy]

I remember seeing an "I Learnt About Flying From That" article in Pilot, or some such other magazine, where a police ASU pilot describes his Twin Squirrel's encounter with the wake from a landing A320.

Mind you he did fly through or very close to the disturbed air, a damn sight closer than 600m.

May we ask which airfield in particular ?

[Helinut]

Nr Fairy,

UK airports which handle both Pumas and 767s is a pretty short list I think.

Nick,

In the UK we have a big problem with a perceived wake vortex hazard affecting helicopters using major airports. It started with LHR (see the current thread on LHR in Rotorheads), but it is growing to other places.

Operational experience is that it is not a problem but academics with the ear of the CAA say "there may be a problem". The CAA want "more research" but they and the airfield operators are not prepared to pay for it.

Your thoughts on the effect of wake vortex on heles sounds very useful. Is there a source or paper or person who could give more information that could then be fed to the CAA??

[NickLappos]

Helinut,

I do recall the FAA looking for data on this. Basically, it is the question, not the facts that create the controversy. The questions centered around the threat to helos hovering or on the ground and subjected to wake turb from departing or landing heavies. I have never heard of a helo getting in trouble in those circumstances. I think there is a theoretical case, but for helicopters the effects of turbulence are vastly reduced.

It is possible to establish a "guilty until proven innocent" approach and restrict operations with no evidence, but we KNOW the regulators would never do that!

[The Nr Fairy]

Helinut:

Missed the Puma reference. Know I know where he means.

[Jed A1]

We have a training area that is very much the same (not in the UK). I have never felt the slightest upset from a departing fixed wing.

We adopt the principle that if we start the climb out from a point before the fixed wing rotates, with our climb angle being steeper and the fixed wing wake always descending then we shall never meet. Similarly with the approach ours being steeper, we shall always be above the fixed wing wake.

However, we have had complaints that regional turboprops feel the effects of flying through our (Enstrom & B206) wake!