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Wake Turbulence + 7:00 Am = Not Fun  
User currently offlineGolfhaus From United States of America, joined Aug 2000, 132 posts, RR: 0
Posted (13 years 2 months 3 weeks 2 days 4 hours ago) and read 1176 times:

Hey all,

On an early morning flight last week, I had the "pleasure" of experiencing wake turbulence. Our Dash-8 aircraft apparently got a little too close to a bigger plane as we were descending. The whole ride had been smooth and uneventful to this point, when suddenly we lurched, I'd say, about 50-55 degrees starboard, followed immediately by a lurch to port at about the same intensity. Needless to say, all the folks who were trying to wake up from the little nap they had caught on the plane found a way to do so.

Once on the ground, the captain came out and mentioned to another pilot flying in the cabin, "Did that get your attention? Certainly got mine!" He explained that he got caught in wake turbulence, and the vacationing pilot said, "I thought that's what it was."

My questions: 1) Exactly how close to death did I come this early Monday morning? The captain didn't seem too anxious about the whole situation, but all you pilots are always so level-headed anyway...  Big grin 2) Was the lurch to port a result of passing through the second vortex left behind the plane (2 engines and all that), an overcorrection, or something different that my non-pilot brain can't even think of?

Thanks!

13 replies: All unread, jump to last
 
User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 1, posted (13 years 2 months 3 weeks 2 days 2 hours ago) and read 1099 times:

The danger of upset of this nature is difficult to determine without having observed it from within the aircraft or as a close observer from an exterior viewpoint.

Without doubting your veracity, 50-55 degrees both ways seems to be excessive and, having been through a couple of wake turbulence episodes, it often seems worse on board than it actually is.

As the crew/autopilot handled the situation with just a reverse of direction of roll and return to normal, its doubtful you were in any severe danger, but the experience isn't pleasant and highlights why correct separation is crucial


User currently offlineGolfhaus From United States of America, joined Aug 2000, 132 posts, RR: 0
Reply 2, posted (13 years 2 months 3 weeks 2 days 1 hour ago) and read 1082 times:

I'll concede that my estimates might be a little excessive... it's not like I was expecting it to really know what was going on.  Smile

How far do planes usually have to stay behind each other to keep this sort of thing from happening? Especially in a situation like this, with a turboprop getting tossed around behind a jet?


User currently offlineIainhol From , joined Dec 1969, posts, RR:
Reply 3, posted (13 years 2 months 3 weeks 2 days 1 hour ago) and read 1082 times:

>>How far do planes usually have to stay behind each other to keep this sort of thing from happening? <<

Distant behind is not important what is important is the aircraft following has to stay about the other one, and land past his point.
Iain


User currently offlineEGGD From United Kingdom, joined Feb 2001, 12443 posts, RR: 35
Reply 4, posted (13 years 2 months 3 weeks 2 days 1 hour ago) and read 1070 times:

Wake Turbulence, In my experience can be very un-nerving if it's the first time it happens to you. And when you weren't expecting it it probably seemed very violent, I can remember my first Wake Turbulence, Descending into MAN very shallow, coming in from the Soutwest.

We had just crossed the M5 motorway, at about 2000ft i think (PhilB you know how high  Big grin). We made a short 9 degree bank to the right before a sharp left turn followed by another sharp right turn. We made a couple of Attitude changes before going around, and we were all a bit shaken. I was only about 19 and i can remember this little kid about 5 years old screaming.

I think the airline was Dan Air, i'm not sure what aircraft.

I'm sure at 7:00am it wasn't too appreciated in the Cabin!

EGGD


User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 5, posted (13 years 2 months 3 weeks 2 days 1 hour ago) and read 1065 times:

Ianhol you are wrong.

There are published wake turbulence distance/times for various classes of aircraft following other, larger or more vortex creating aircraft (such as the 757 which is classed as a "heavy").

These distances vary from country to country by a small amount but, generally, they break down into spacing between "heavies" , "medium", "small" and "light".

Similar rules apply to take off but, in both cases, pilots may accept a closer margin at their discretion and the controller is then supposed to say "caution - wake turbulence" to a. remind the pilot and b. place on the tape that the pilot is accepting responsibility AFTER a wake warning.

There have been times when a 747 has caused wake upset to another 747. The most famous was in the early 80s when a Pan Am 747 off JFK was badly rocked by a 747 of Air France, causing minor injuries.


User currently offlineIainhol From , joined Dec 1969, posts, RR:
Reply 6, posted (13 years 2 months 3 weeks 2 days 1 hour ago) and read 1058 times:

PhilB by no means I am wrong, I am speaking from a pilots presecptive, while yours is from a controllers! As a pilot I could not care less about distances when I am following another aircraft, my concern is just staying above them and out of their wake turbulance!
Iain


User currently offlineSxmarbury33 From United States of America, joined Oct 2000, 445 posts, RR: 0
Reply 7, posted (13 years 2 months 3 weeks 2 days ago) and read 1051 times:

Iahohol what your talking about is the wake turbulence avodience taught to general aviation pilots. In class B and to a lessor extent class A airspace (which most of the airlines fly in most of the time) the planes are always in radar contact and the controlers have to space them accordingly. And the tower controler may issue a wake turb advisory and then the wake turb avodience is by the pilot ex staying above his glidepath on final. But a 737 getting vectored to final too closely behind a 757 would get in his wake and in class B airspace you cant just be at any altitude to stay above the 757.

>>How far do planes usually have to stay behind each other to keep this sort of thing from happening? <<

Distant behind is not important what is important is the aircraft following has to stay about the other one, and land past his point.
Iain

Iain distance behind is very important like i said above if they are being vectored to final aircaraft cannot just fly above the aircraft they are following if they are givin an alt restriction of 3000 ft. SO distance behind (spacing) is nessasary.




User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 8, posted (13 years 2 months 3 weeks 2 days ago) and read 1042 times:

Ianhol,

I suggest you refer to ICAO Doc 8643 which categorises aircraft by identification abbreviation and vortex generation.

This document is the basis on which all seps are worked out and any decent pilot knows that he needs to monitor and maintain at least the minimum separation (his job as much as the controller's) and he also knows that certain aircraft and certain conditions generate wake turbulence ABOVE the flightpath of the preceding aircraft.

A number of biz jets have been upset (one or two fatally) whilst following 757s at pilot's discretion and keeping high did not stop them getting into trouble.

There are old pilots and bold pilots, but no old bold pilots.


User currently offlineIainhol From , joined Dec 1969, posts, RR:
Reply 9, posted (13 years 2 months 3 weeks 2 days ago) and read 1036 times:

Classic Airliners.net one upmanship!
Iain


User currently onlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4190 posts, RR: 37
Reply 10, posted (13 years 2 months 3 weeks 1 day 19 hours ago) and read 983 times:

The general rule for wake turbulence is 2 minutes or 4 miles- which ever is greater (if i remember correctly). As long as you werent too close to the ground you werent in too big of danger. Ive been jacked by an overpassing 737's wake turbulence before on a 3 mile base and it wasnt exactly the smoothest thing in the world. I was at 2000 and he was at 3...so it wasnt too big of a deal, just the jolt and roll wasnt the most welcome thing. Iain was talking about landing precautions...which is correct to an extent, but you do need to be careful about those vortexes bouncing off the ground too. Distance/time is of the upmost importance. Give yourself an extra 2 minutes to be safe when following behind the big boys to keep you and your passengers pants clean.


Chicks dig winglets.
User currently offlineSailorOrion From Germany, joined Feb 2001, 2058 posts, RR: 6
Reply 11, posted (13 years 2 months 3 weeks 1 day 18 hours ago) and read 974 times:


This is info for MUC, but as far as I know, most airports in Germany have identical or similar rules.


For approaches to the parallel runway system 08/26, a radar separation minimum of 2.5 NM (instead of 3 NM) is applied on final approach between 30 NM final and threshold provided the following conditions are met:
a) The preceding aircraft approaching on the same RWY is of the same or of a lower weight category. Aircraft of category HEAVY, including B757 as preceding aircraft, are excluded from this procedure;
b) The turn-off points of the runway are visible from the control tower;
c) The runway is dry.


Hope this help,

SailorOrion


User currently offlinePhilB From Ireland, joined May 1999, 2915 posts, RR: 13
Reply 12, posted (13 years 2 months 3 weeks 1 day 15 hours ago) and read 963 times:

SailorOrion,

That is standard DFS approach procedure for parallel runway, minimum separation, approaches in Germany


User currently offlineSailorOrion From Germany, joined Feb 2001, 2058 posts, RR: 6
Reply 13, posted (13 years 2 months 3 weeks 1 day 15 hours ago) and read 959 times:

PhilB.

thanx for pointing that out. I was wondering.

SailorOrion


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