Wake Turbulence Encounters (RVSM)

[320DRIVER]

Lately, my outfit has had two reports of wake turbulence encounters (equivalent to severe turbulence) due to wake from crossing traffic... in both cases B747s crossing their track perpendicularly at more or less some 20 Nm ahead, 1000 ft above.

In both cases the RVSM Wake Encounter form was filed. Did you ever experience such severe encounters of wake during cruise?

320DRIVER

[PODKNOCKER]

We were 20nm behind and 2000 feet below a B747, we could see the contrail clearly and hit wake turbulence, so it is not just RVSM, the problem has been around for years...a one mile offset usually does the trick.

[Lu Zuckerman]

Wake turbulence can be encountered every where. Many years ago an Air Force B-36 landed at an AF Base and was already chocked in place on the hardstand when an Air Force PBY landed and hit the still active wake turbulence and was flipped upside down and it hit the runway and exploded.

:eek:

[777AV8R]

Yup..agree with Podknocker...an upwind parallel offset of a mile works great.

Have encountered occasional 'bites' on the Pacific to HNL behind traffic ahead..the offset works like a charm

[RAT 5]

The offset works good, as you say, but 320driver's comment was about a perpendicular track crossing scenario. I've never encountered this situation in RVSM, but often at the same FL. To try and avoid this I used to climb +200' until crossing the wake.

It is common when flying N-S across France to be vectored behind traffic entering at the same level off the Atlantic. ATC do not offer type information, (they will if asked) but because they are coming off the ocean they are most likely heavy.

There was a case in USA many moons ago where a DC.9 went to 60 degrees bank at high level after crossing behind a B747. They'd crossed a VOR with suitable separation and track divergance according to the ATC regs' of the day. At that time wake separation only applied to takeoff & landing; in trail and lateral separation applied for airmiss reasons. The 5nm bubble was not broken in the DC.9 case, but there was something wrong. Were the regs ever changed to take note?

I seem to remember an article a couple of years ago into crz wake trubulence behiond a 747. Surprisingly they discovered that after the wake had sunk a few hundred feet and trailed nm or so, it then rose again. Inother words it didn't keep sinking and weakening. I never heard anymore on this research.

One things for sure, 5nm behind & crossing, or 1000' below in trial spills the coffee.

[Georgeablelovehowindia]

In the London TMA, descending in a 757, I was vectored behind and across the path of an outbound company 757, with approx. five miles of separation. The jolt when we crossed the wake was stupendous. BANG! Then the old tub shook and rattled for a few seconds and flew on. An ashen-faced senior cabin crew member shortly after entered the flight deck to demand what the **** was that? I got on the PA to the passengers and explained what had happened but apparently some of them later got off accusing me of colliding with something...