Wake turbulance...or how to write off a private jet

[IBob]

Emirates Airbus A380 wake turbulence sends private jet into uncontrolled descent

[eightyknots]

That's really bad. Is a review of the 1,000 feet separation on the cards?

 

 

[Birdseye]

Wake turbulence/vortex is a fickle beast. Many moons ago, an exec jet I was directing to the ILS at Heathrow reported that he had just 'flown into a brick wall'. Flying at 7000' he had hit severe turbulence as he crossed the track of a DC8-63 that had passed about 25 miles ahead of him. He was shaken and stirred!

 

 

[dutchroll]

You can get wake turbulence under the right conditions with 2000ft separation too. Also ATC are generally pretty good at issuing wake turbulence cautions where aircraft of greatly different size pass close to each other. The A380 is particularly problematic, hence its "super" callsign suffix which was specially created for it because it can't fit into the wake turbulence category of "heavy"!

 

Pilot's just need to be really aware of it, especially in the vicinity of an A380.

 

 

[SDQDI]

10,000 feet is a lot of height loss!

 

 

[dutchroll]

10,000 feet is a lot of height loss!

This is true, but you really can get some very high rates of descent with loss of control/upset recovery in a jet at high altitude, depending on the scenario.

In documented jet upset recovery cases, height loss of more than 10,000 ft is not uncommon at all. Sometimes much greater.

 

 

[facthunter]

More applicable to near limit cruising levels where you cannot expect to achieve less height loss, safely... Being below the level of the "causal" aircraft would presumably be worse than being above it. Being prepared would help but structural considerations exist as well. Perhaps more training and revised procedures needed. "Tortured air" is what keeps aircraft up there especially with super heavies. The energy takes a while to dissipate in stable air. More research needed to predict it accurately . Nev

 

 

[Bats]

... Being below the level of the "causal" aircraft would presumably be worse than being above it.

I suspect so, presumably any atmospheric disturbance that would result in wake turbulence or vortices ascending, would also dissipate it. That said it was one of life's little disappointments to learn that wake turbulence is to be found close behind and above a paraglider flying in smooth ridge lift.

 

 

[facthunter]

In that case the "datum" is ascending so it's not so surprising. Also the very extreme energy of the Jumbo supporting it's weight by deflecting an air mass to stay there gives the larger downwards effect locally. ( Not unlike a "rotary wing" helicopter in that respect. Heavier than Air needs a reaction to air to fly ( a Dynamic). Nev

 

 

[Birdseye]

Two mechanisms in play here I think, firstly the general turbulence (often referred to as the slipstream) from the aircraft passing through the air and secondly the wake vortices. Those with gliding experience will have aware that you have to get low (or high) enough when behind the tug to avoid the slipstream.

 

 

[DrZoos]

Victor 1 under the approach to Sydney might be up fr review too?

 

 

[Icarus]

Is wind direction available to ATC along the flight paths? If so ,could the vulnerable aircraft be positioned upwind slightly of the 380?

 

 

[Birdseye]

Impractical, even if they had the real time wind info.

 

 

[dutchroll]

Is wind direction available to ATC along the flight paths? If so ,could the vulnerable aircraft be positioned upwind slightly of the 380?

You can actually ask for a small lateral offset (2nm would likely be sufficient) to avoid wake turbulence from an aircraft above and in front of you on the same route if you're getting bumped around by it. It's just like asking for a weather deviation.

In Australian Oceanic controlled airspace you can offset up to 2nm right without a clearance at cruise altitude, though the aircraft must have automatic route offset capability in its navigation system (which most modern FMCs do) and if you're radar or ADSB identified you have to inform ATC you're doing it. Some other countries don't allow this though, so you have to be careful when you're crossing FIR boundaries.

 

 

[IBob]

Well, I say we do something about these Irish funerals???

 

 

[boleropilot]

I suspect so, presumably any atmospheric disturbance that would result in wake turbulence or vortices ascending, would also dissipate it. That said it was one of life's little disappointments to learn that wake turbulence is to be found close behind and above a paraglider flying in smooth ridge lift.

hey Bats - I've got a couple of hundred paraglider flights under my belt - and I gotta say I was VERY surprised to hear about the level of turbulence a friend encountered behind a big tandem - they were in the same thermal at around the same height and he thought it was just a bit bumpy - and then it got REAL bumpy - and it was smooth as after he buggered off from behind the tandem - and then the penny dropped - he was flying a competition glider so that would not have helped...

 

taking off a full minute behind another Drifter and I still got a bit squirrelly just after lift-off - it's out there folks...and it's invisible

 

sounds to me like the pilot of the bizjet should get a medal - if the aircraft was written off it's not just because the seats are wrecked - that aircraft suffered major structural damage and it's a miracle it stayed in one piece and they managed to get it on the ground...

 

 

[facthunter]

it's a real hazard alright. Not something to be brushed off. IF you are maintaining a TRACK being upwind is the place to be. The turbulence moves with the airmass. The track stays fixed in one place and you maintain it by an external reference. You need the wind information for flight planning and IS available and easily determined in flight . You use changing wind components when determining Ground Nautical miles/ 1,000 Kg fuel to get best range/ economical level for cruise and alternates which may require vastly different levels. Engine out and depressurised are at different to cruise levels to normal cruise. planned level. Nev

 

 

[poteroo]

It doesn't have to be an A380 either!

 

We fly quite a bit of formation in RVs here, and we never have any vortice induced upsets when there is even a 2-3 kt x/w on the runway and on its' approach and departure ends. But when it's a beautiful winters late afternoon, and the surface inversion has commenced, beware the uncommanded roll when entering the vortices from a preceding RV. We have had some quite attention grabbing events coming down final. The last element has sometimes gone round due to an upset - yet we are not close in terms of spacing between elements. Not that we are flying fast either - 70KIAS down final

 

Because we breakup into elements of 2, with sometimes 4 elements landing in formation but at 300m intervals, it has become a point of debate as to how best to manage it. Do the leading elements fly low, but then extend their float to touchdown well into the runway? Or, do we fly a slightly 'diagonal' path to touchdown?

 

This probably isn't of concern in a PC9 because of the wing loading and speed, but it certainly is a situation we brief for in certain weather.

 

happy days,

 

 

[Birdseye]

A light crosswind is the optimum condition for vortex problems. In still air, the vortices will normally diverge towards the edge of the runway at 3 to 5 kts (that speed is as far as I recall), bring in a similar strength crosswind and one vortex will effectively sit on the runway. In the days when large jets did circuit training, it was common on a calmish day to see a vortex cause an indication on the anemometer after a few seconds or so. Then again there is always the exception. The aircraft I first soloed and the CFI that took me on my GFT were both written off in a vortex incident about 2 years later. That was on a quite breezy day.

 

 

[Bats]

hey Bats - I've got a couple of hundred paraglider flights under my belt - and I gotta say I was VERY surprised to hear about the level of turbulence a friend encountered behind a big tandem - they were in the same thermal at around the same height and he thought it was just a bit bumpy - and then it got REAL bumpy - and it was smooth as after he buggered off from behind the tandem - and then the penny dropped - he was flying a competition glider so that would not have helped...

Hi Bolero - in my case a good mate and I were using up the last of the afternoon ridgelift on a coastal dune before adjourning for a debrief at the pub below. My mate, who drives airliners for a living, when not also playing with his RV, turned in close behind me to take some photos, believing that as his wing was a good half span above mine, he was clear of any turbulence. Got his attention in a big way when a chunk of wing collapsed, whilst he had the toggles loosely in one hand! The clunk when the penny dropped was clearly audible....

 

 

[boleropilot]

wing collapses are always fun - being a careful fella I flew a big Gin Bolero (and the penny drops again!), DHV1 so as safe as you can get - the guy mentioned above was in a 2-3 - I had a test flight in a 2 and it scared me!

 

on another occasion I was flying not far from my mate at about the same altitude and we both got whacked by some rough stuff - my Bolero just shuddered a bit, he was fighting madly to stay in the air - nearly pulled the handle

 

for those who don't know paraglider talk, DHV is the glider rating for performance - 1 is like a donkey, 3 is like a racehorse on steroids with a cracker up its clacker....being chased by a randy donkey!