What would you do?

Just a word of support for London Info. Yesterday I was IFR OCAS down the east coast from Scotland at FL70. London Info asked for confirmation that I planned to descend to remain below the London TMA – which was affirmative, but a good prompt nevertheless. One day that might save someone the £200 class…

Yes this is the way LI is supposed to reduce CAS busts without revealing they can see you on radar It’s a “great system”; the airspace regulator holds all the cards, you can never see them, but LI is allowed to offer you little guess opportunities warnings which, if you call them right, mean that you win a little prize (not get busted). Hey ho…

Peter wrote:

But, if you get it wrong, you might die.

There’s a lot I can do and get it wring and die. The trajectories of wingtip vortices isn’t rocket science. The big birds touch down at the same point every time. The vortices will slowly go down, hit the ground and dissipate. With a GA aircraft just stay above the path, and land just inside, Cross wind will take them away, head wind will blow them back. Tail wind is a bit of a problem, and you can fly straight into them getting too close.

I’ve experienced the same on a golf course just short of Tenerife airport. Swooshing noise and then sometimes you saw it hit a tree!

LeSving wrote:

Just the slightest cross wind will blow any remnant of vortices off the runway in seconds.

Recently I was in the car park of Europe’s busiest airport, which is about <1000m from the touchdown zone. It was sunny and no perceptible wind. There was this loud and strange swishing sound, not out of place from a netflix sci-fi series. I could not tell where the sound was coming from, I thought I was going a little nuts. It continued to happened about 30secs after each arrival like clockwork. I stayed for a bit as I quite amazed. The very light cross allowed the wake to drift right down over the centre line, minimally disturbed.

However if your were at they same position I was on the glide path, then the vortex was the least of your worries.

I once went though the wake of 767 that was on base while I departed on upwind in a pa31. (different but very close airports). A very solid thump but no control problem.

Just a word of support for London Info. Yesterday I was IFR OCAS down the east coast from Scotland at FL70. London Info asked for confirmation that I planned to descend to remain below the London TMA – which was affirmative, but a good prompt nevertheless. One day that might save someone the £200 class…

The same controller was then in dialogue over several minutes with another aircraft over the Channel who was unaware of Danger areas. The controller exercised commendable patience speaking slowly and clearly, coordinated with Plymouth Military and advised the pilot he could safely proceed direct destination. Well done sir.

But, if you get it wrong, you might die.

The wind aloft could be quite different from the reported runway wind.

Three minutes sounds an awful lot behind an ATR, or any aircraft for that matter. Just the slightest cross wind will blow any remnant of vortices off the runway in seconds. Remember, 2 knots is 1 m/s. In 1 min, the vortices would have moved 60 meters, way off your path. I rather try to visualize/predict them, following the wind, then counting minutes.

For London Info, I strongly back up what Peter says. I operate from a grass strip and NEED London info to open my flight plan, nothing is more annoying than it being clogged up with pointless basic service aircraft. I open flight plan and immediately leave.

(Tongue in cheek) If you feel anxious without being on a frequency then talk to Farnborough, Solent, Lydd, whoever takes your fancy, or you could try tuning in 121.5. Also; some people aren’t aware that if you turn the radio off, the aircraft will keep flying. :-)

If Guernsey follows UK procedures exactly for the wake turbulence, the ATCO should have advised ‘Caution wake Turbulence, the recommended distance is 4 miles’, based on an ATR-72. It is only a recommendation for VFR traffic, and 4 miles should be a lot less than 3 minutes. At busier airports, significantly more than 4 miles could result in you being held off on base leg, as you would potentially be caught up by the next speedier arrival.
As others have said, flying above the flight path of the ATR is an option until you have the 4 miles. Until the nosewheel of the preceding aircraft is also on the ground (not just touched-down), then wake-turbulence is still taken to be being generated.