Wake Vortex

[Cylinder Head]

Rotorheads,
I am putting together some training material for students to help them undertand the above and I'd be grateful to hear from single engine helicopter pilots of any practical examples of Wake Vortex, that you have experienced. Your own experiences please, not hearsay!
Particularly:
What were you flying?
What aircraft type caused the vortex?
Where were you relative the vortex inducing aircraft - height, position and flight stage?
How did your helicopter behave?
How did you respond?
What did you learn from the experience?
Many Thanks
CH

[HeliStudent]

Cylinder Head you probably have these publications already but in case you don't,

http://www.faa.gov/training_testing/training/media/wake/04SEC2.PDF

http://upl-aopa.lu/docs/Waketurbulence.pdf

SKYbrary - Wake Vortex Turbulence (http://www.skybrary.aero/index.php/Wake_Vortex_Turbulence)

http://www.airservicesaustralia.com/wp-content/uploads/wake.pdf

[Gemini Twin]

I just doesn't a common operating environment were the two types would mix but there will be a few I suppose.

[Ascend Charlie]

While flying over mascot on a dead calm day, I have observed the twin wingtip vortices from the heavy jets as they land on 34 L and R, the lines on the water were plain to see.

In my daily job, I am often sitting in the hover next to a runway when an A320 or B737 takes off or lands. I usually put it on the ground until it is gone, and sit and watch the adjacent windsock for any signs that the vortex has passed by - never seen a thing. On calm days, days when the cross wind would blow it onto me, days when it would blow it away from me - never seen a thing, the grass doesn't move, no twitch in the rotor disc - nothing.

HOWEVER! I would NEVER fly across the track or parallel to one. I have seen the videos of vortex tests, read the reports etc.

But you asked for first-hand knowledge, and I can say that I have never seen any. Flying through the wash of the lead aircraft in the formation causes a bit of a burble, but doesn't tip me upside down.

[agodesign]

Flying a photo flight in a R22. The flight required extensive hovering below the approach end of the major Runways 4 L&R in Honolulu Hawaii. Working with the tower they allowed me to hover below 500' about 1 NM from the runway. Of course this could only be done in between landing aircraft.

When an airplane was on final I was given instructions to stay north of the approach path. This flight took about 1:30 mins to complete, so as you can imagine there were multiple approaches during the filming. I imagine that during this time lots of different types of fixed wings. There is another runway that the smaller traffic use, the 4's were longer and generally only used for the bigger aircraft.

When instructed that a plane was on final I would bring the R22 to a hover near the ground and wait. Once the plane passed over head I was back the the OGE hover moving between the filming locations. I remember that I was in the OGE hover for the filming shortly after being cleared, and the helicopter went through what I can only describe as a large wobble. Similar to a boat that is in rough seas. It happened so fast that there was nothing to do, it only lasted a couple seconds, then back to normal.

It was a bit of a surprise, but did not seem to worrisome. Although 7 years later I still remember it, so must have been a bit unusual. Don't remember the exact plane, but it was something big heavy and slow.


AGO

[mickjoebill]

For a bit of fun,

When the traffic is heading for 27R at Heathrow, proceed to 213 Waye ave Hounslow, stand under the telephone pole that has 25 cables radiating from it and wait for the vortex of heavy jets to play a tune...

Marvellous!


http://s13.postimg.org/s8mzknc2b/Google_Earth_Image.jpg (http://postimg.org/image/s8mzknc2b/)

Mickjoebill

[MightyGem]

single engine helicopter pilots
Why just single engine pilots? The only wake turbulence I've experienced is my own(when orbiting) and from other helicopters when fairly close astern in flight or when they hover taxi past.

ATC where I work refuse to let us taxi/depart for wake turbulence even for small biz jets. The windsock is between us and the runway, and like Ascend Charlie, I've never seen it twitch for any turbulence, even from a Beluga.
http://juantadeo.files.wordpress.com/2011/09/a300-600st-beluga-landing.jpg

[RVDT]

Many moons ago.............................long before t'interweb.

H369 passes behind a Fokker F27 with a partial flap configuration.

The helicopter rolled that far it was decided to carry on to complete the roll!

Saw the result - twisted tailboom.

[Cylinder Head]

Thanks for your answers guys - bit disappointed that so few responded - oh wait - that probably means most pilots have not experienced a problem. Now this may well be because of the protocol of grounding everyone within three quarters of a kilometre, I accept.

I am particularly interested because the our ATC interpretation of the current guidelines is that no helicopter should be allowed to hover or hover taxi within 760 m of a runway where a heavier category of aircraft may have created a vortex. This effectively means our whole airport is locked down for skidded helicopters for 3 minutes everytime a heavier cat aircraft takes off or lands. The actual text suggests that crossing a runway should be treated as a departure from that runway. It does not mention operations that do not involve crossing the area of potential vortex.

I have no problem with being prevented from taking off or landing or crossing a runway where a heavier cat aircraft has been - that is only sensible but I think its over the top to apply this same policy to a training square well away from the runway and any potential vortex when there is no intention og going any where near the affected area.

Can I turn the question around - please post if you have ever been a helicopter pilot of small singles operating at airports where heavier cat aircraft operate and you have never experienced wake vortex.

CH

[Flying Bull]

Hi cylinder head,

https://maps.google.de/maps?q=d%C3%BCsseldorf+flughafen&hl=de&ie=UTF8&ll=51.291956,6.782126&spn=0.00832,0.022724&sll=51.290171,6.783972&sspn=0.00832,0.022724&t=k&om=1&radius=0.59&hq=d%C3%BCsseldorf+flughafen&z=16

on bottom (zoom in) you see a helicopter station.
Well, flying from there you got informed by ATC - watch out for wake turbulence - but we´re cleared to cross the runway system behind landing aircraft or cross in the middle (normally climbing to around 1.000 feet isch) before we do.
If the weather is crab we cross lower and sometimes feel a little wiggle - but we´re flying helicopters with an empty weight above what most SE have as a maximum....
Had some heart accelerating moments crossing behind a Seaking in a Gazelle.....
I think, due to the turning blades instead of the fixed ones on airplanes - together with hinges on the rotorsystem (or flexible blades), the effects of wake vortexes are less on helicopters - but still there and be avoided if possible.
Another reason is, that helicopters normaly approach or depart 90°isch from runway systems, so that we don´t fly in the vortextube, just cross them and therefor have only a short shake without to much of a rolling experiance, which you can have in a light type aircraft.

[Cylinder Head]

Thanks Flying Bull, very interesting. You tend to confirm my suspicion that as long as you don't cross the vortex or attempt to take-off through it, little effect is actually apparent.
CH

[MightyGem]

I am particularly interested because the our ATC interpretation of the current guidelines is that no helicopter should be allowed to hover or hover taxi within 760 m of a runway where a heavier category of aircraft may have created a vortex.

Yes, that's the same problem that we have. It's because of the word "shall" that appears in the ATC regs regarding wake separation for departing aircraft; ie, there "shall" be the required gap between aircraft. The word "shall" dictates that they must enforce it. Having said that, a previous airport that we operated out of, gave us the advise, but when we replied, "roger, request immediate departure", they were happy to let us go.

On approach to land, however, it's different. Threy give you the recommended spacing, and it's up to you whether you abide by it.

[Fun Police]

only one mention noticed so far, but in my experience it is much more common to wind up flying through ones own wake turbulence which generally does not amount to much more that a "bump". however, on one occasion the conditions were such that it caused a brief encounter with vortex ring state. not a nice feeling but in a B2 (or other articulated rotor system) not a huge deal as a bit of a poke with the cyclic took care of it. (i rarely fly into airports that are shared by heavy jets)
it's not uncommon while doing production longline work such as seismic and you are looking for your pickup point in the bush.

[newfieboy]

On spray ops at the moment. Not uncommon to fly through my own vortex regularly considering the tight turns and calm conditions. No big deal in long ranger or B2, just a bit of a bump.

[army_av8r]

I'm assuming we are discussing a helicopter flying through a relatively large fixed wing wake turbulence? If that is the case, I flew perpendicular across the lead in lights at Honolulu international airport, during the busy part of the afternoon. after holding north of the centerline for traffic I was cleared to cross the extended centerline and proceed "feet wet" south of the field. I pulled in the torque and crossed the centerline, when suddenly the helicopter was "grabbed" and thrown pretty violently downward as if i hard hit a pocket of strong turbulence. aircraft went to ~0.0G and maybe even slightly Negative G. this was at 200 Feet above the water. As quickly as it started, it let us go. and the aircraft recovered to straight and level. It was at this point i realized what I had just done and put the puzzle pieces together in my head... oops. aircraft was an OH-58D with the Bell "soft-in-plane" rotor system, im not sure of the size of the fixed wing traffic because it was already on the runway and basically out of sight. but my guess would be 747 or larger. probably the hardest spank i have felt inflight with this helicopter. luckily we went perpendicular to the FW flight path and minimized the duration. probably lost 100ft total but started at 200AGL, which made things interesting.