Wake Turbulence

Front. · Post by **Front.** » Mon Oct 30, 2006 8:14 pm

It's always been a question for me. Quite a few times now have i gotten a "caution wake turbulence departing seneca also in the circuit" by ATC and i was wondering, how can i be cautious of Wake Turbulence?

Fly to the side of his flight path? Climb at Best Angle and get above his flight path? Or just fly normally and see what happens ... lol.

Like how do you know you're in "wake turbulence." is it like ordinary turbulence?

Another question was how come if you're told to taxi to position and wait and you're departing behind a seneca, why is it favourable to be in position before the seneca applies full power? I heard because of wake turbulence, but how does wake turbulence affect the position of your aircraft when lining up?

Thanks !

lilfssister · Post by **lilfssister** » Mon Oct 30, 2006 8:19 pm

Wake turb from a Seneca???

You can avoid it by lifting off before the point the heavier aircraft lifted off from, and flying above their climb profile. Or waiting for 3 minutes (if a light behind a medium) before take-off.

Front. · Post by **Front.** » Mon Oct 30, 2006 8:28 pm

apparently yes lol... I don't know. I listen to tower.

square · Post by **square** » Mon Oct 30, 2006 8:30 pm

a seneca is like two cherokees dont sweat it. but if you're trailing behind a westjet or something, liftoff BEFORE their lift off point, land PAST their touchdown point (also approach above their approach path) or just wait. don't try to duck under their turbulence though, it falls.

Front. · Post by **Front.** » Mon Oct 30, 2006 8:40 pm

yea that I know. Especially when i try to get into CYXX with a 737

. Normally it's them chasing me though lol.

How about the other question, the thing that you have to be lined up before the plane infront of you takes off "due to wake turbulence." My previous instructor told me that and wasn't really clear on why.

justplanecrazy · Post by **justplanecrazy** » Mon Oct 30, 2006 9:21 pm

First off, there is very little wake turbulence behind a seneca and no reason what so ever to issue a cautionairy, I'm hoping you mixed up your aircraft and are refering to something else. The only time ATC is required to issue a cautionairy is when the aircraft ahead is a heavy or heavier weight class of aircraft. A Seneca is a light and no where near the weight requirement of a medium. Maybe you're flying in a field with only lights and the controller wants to see what it feels like to give a cauitionairy but really there is no reason for this.

Second, wake turbulence profile is down and outwards from the wingtips only. If you stay right down the same flight path, in theory you shouldn't experience any wake even if you're right behind and lower then the aircraft ahead. If you're ever worried about it, use your best angle and runway heading, as long as you rotate prior to their rotation point, you'll be fine. A cessna at best angle will out climb any regular medium departure profile or have 4 miles seperation by the time they run into it and 4 miles is the radar wake seperation standard.

Third, if you want to feel a very light version of wake turbulence, do a 720 steep turn on a calm day. You'll feel your aircraft hit the wake from the first turn as it comes around 360 degrees. It's the same thing right behind a heavies wingtip, only much more pronounced as in your aircraft twirling like a tumbleweed. Wasn't there an incident over NYC where a plane had his tail ripped off by wake, shortly after 9-11. It's not something to mess with but only with significantly heavy or heavier aircraft.

Fourth, the reason we taxi you to position and wait behind a departing medium (not a seneca), has nothing to do with where it is best for you to be for wake turbulence. We taxi you to position for no other reason then to let you get ready for take-off and not have the delay of you rounding the corner later. We're not telling you to taxi to position due wake turbulence, we're telling you to wait due wake turbulence. If you're taking an intesection, and we have no traffic, then we'll put you in position and as 3 min's are about to count down, we give you your clearance. If you're taking it from the threshold, we only need to give you a cautionairy but some guys will still tell you to wait, just to provide a mile or two of seperation first. A heavy still requires 2 min's sep from the threshold. The only thing to be cautious about is jetblast or prop wash. We won't taxi you to position right behind an Airbus that's about to get take off clearance, but we will taxi you to position as soon as he's passed your intersection or, if you're at the threshold, once he's on the roll. The jet blast and prop wash areas are quite small and you have to be really close to be affected. A jumbo jet's danger area is only 1600' at take off thrust. Remember there is no such thing as wake turbulence no matter how big the aircraft, until his nose wheel leaves the ground. Engines, and props produce jetblast and propwash not wake turbulence.

Clodhopper · Post by **Clodhopper** » Tue Oct 31, 2006 8:05 am

justplanecrazy wrote:Second, wake turbulence profile is down and outwards from the wingtips only. If you stay right down the same flight path, in theory you shouldn't experience any wake even if you're right behind and lower then the aircraft ahead.

I certainly hope this isn't advice you offer to everyone. Even a slight crosswind will start drifting one of the vortices over the center of the runway, which could be deadly if you're just rotating in a small GA or light airplane behind a medium or heavy.

Best bet is rotate and climb before and above the departed a/c ahead. Approach and land above and beyond the landed a/c ahead.

Wake turbulence starts as soon as the larger a/c begins to rotate and increase its angle of attack.

justplanecrazy · Post by **justplanecrazy** » Tue Oct 31, 2006 9:01 am

bob sacamano · Post by **bob sacamano** » Tue Oct 31, 2006 9:01 am

Not sure why this has changed, but during my ATC days we didn't give wake turbulance cautions with these little guys, mind you, the smallest thing at pearson was a light twin, and we never issued it back then.

These days, I hear some ATC issue wake turbulance cautions behind navajos and metros.

justplanecrazy · Post by **justplanecrazy** » Tue Oct 31, 2006 9:05 am

bob sacamano wrote:Not sure why this has changed, but during my ATC days we didn't give wake turbulance cautions with these little guys, mind you, the smallest thing at pearson was a light twin, and we never issued it back then.

These days, I hear some ATC issue wake turbulance cautions behind navajos and metros.

Up until now a Metro was a medium. The new weight class moves him to a light. A Navajo has always been a light and a Seneca has always been an ultra light. I guess, you end up getting guys issuing cautionaires for things like that due to having very little flight experience but they definatly aren't required to do it for the same weight class.

Clodhopper · Post by **Clodhopper** » Tue Oct 31, 2006 9:15 am

justplanecrazy wrote:Thank you son for your wake turbulence 101 lesson. Try taking a reading comprehension class and rereading what I wrote before you tell me that I don't know what I'm talking about.

If you stay right down the same flight path, in theory you shouldn't experience any wake even if you're right behind and lower then the aircraft ahead. If you're ever worried about it, use your best angle and runway heading, as long as you rotate prior to their rotation point, you'll be fine.

I'm telling them to do exactly what you're telling them but instead of going into great detail about something that they should have learned in the first 5 minutes of class I decided to explain what they're not told. Explaining that even if you're right behind and below the aircraft, you shouldn't experience any wake. In other words, don't wait and then climb runway track, climb runway heading and allow yourself to be drifted by the same crosswinds that are drifting the vortices. I often see instructers do strange things like sit on the runway until the jet that departed is 1 mile or 2 off the end and then climb runway track. This is the worse position possible because if you wait for 1 or 2 miles, you don't have the 4 mile radar sep that has been proven to allow the wake to dissipate enough to not be a danger and you're also allowing the wake to drift as you said. If you're going to depart right behind a heavier aircraft, go right away, rotate as soon as possible and climb at your best angle and runway heading not track. If you don't want to go right away, ask the controller to give you 4 miles or an early turn before you accept your clearance to position or take-off.

There are times when you can't out climb the aircraft ahead. ie an F18 unrestricted to FL___. If you ever have that happen, you should still be fine as the aircraft will have travelled a lot further than 4 miles by the time you pass through his vertical flight path 1 mile off the end and the wake should have dissapated significantly. But I guess, you just tell your students that they should just outclimb that vertical path rather than explain to them where the true danger areas are.

The reason I threw in the "if your ever worried about it" rider is there are times when you're departing with a wake turbulence cautionairy that we have to give, but there is no reason to worry about it or there times when you should worry about it and you receive no cautionairy. Look at a Pilatous behind a JS31, or a BE20 behind a B350. It seems ridiculous to have to give a cautionairy for that and not a JS31 behind a B727. Now Clodhopper, go back to reading your FTGU, you might pass your private test this time. Why the hell do I bother saying anything on this freaking forum. Cat was right, the 200hr wonders know best, don't argue with them.

JPC,

An apology because I simply misread what you had typed. Yes, if you allow the drift to carry you along the same 'flight path' you should theoretically avoid the wake turbulence and, at sufficient distance, it will dissipate to the point where it doesn't matter. My points are merely reiterated for the takeoff/landing roll and initial climb/final approach. When on the runway, you can't exactly "follow" the flightpath, you're limited to centerline, and any crosswind will put the vortices onto the runway. By all means, the more time/distance between aircraft in flight, the less the wake...

Don't be so quick to hurl insults...its a discussion forum for that exact reason: to discuss.

I never said I knew best, and I also don't insult someone if something they say doesn't make complete sense. Maybe try clarifying beforehand. And you wonder why low-time people are so afraid to ask questions? Because if they get more than one answer, each answer is shot to pieces by someone who thinks their way is best...and then the low-timer is left even more confused.

BTD · Post by **BTD** » Tue Oct 31, 2006 9:20 am

To answer another one of your questions, wake tubulence feels different from "ordinary turbulence". Wake turbulence feels more like you are riding on a wave. It is much smoother if you are following straight behind the other aircraft.

Kind of like water skiing or wake boarding behind a boat. The way you slide down the wake. If you are going straight across the wake then it will feel more like normal turbulence.

BTD

Clodhopper · Post by **Clodhopper** » Tue Oct 31, 2006 9:24 am

Here's a pretty good link to show just how far out, with a good crosswind, a wing-tip vortex will travel from the aircraft...starts off slow but the real show is in the last 10 seconds (almost 30 seconds after the plane passes by).

NASA Wake Turbulence Testing

Nothing fancy, just blowing smoke, but it helps.

And if you're interested in another shot, watch Die Hard 2, at the end where all the planes are coming into land, one of them passes through some billowing smoke and the vortex is clearly seen.

Strong stuff.

mellow_pilot · Post by **mellow_pilot** » Tue Oct 31, 2006 9:34 am

BTD wrote:To answer another one of your questions, wake tubulence feels different from "ordinary turbulence". Wake turbulence feels more like you are riding on a wave. It is much smoother if you are following straight behind the other aircraft.

Kind of like water skiing or wake boarding behind a boat. The way you slide down the wake. If you are going straight across the wake then it will feel more like normal turbulence.

BTD

Hey BTD! Hows it going?

I'm gonna assume you mean following a light, or hitting your own in a steep turn? Taking on the wake of a 767 in a 150 would be slightly less docile... I know you must remember the 'wake turbulence demo' from EMT3!

Hedley · Post by **Hedley** » Tue Oct 31, 2006 10:24 am

Wake turbulence from a light aircraft is generally quite small, but can be quite disconcerting in another light aircraft if you are unlucky enough to enter it before it's had a chance to dissipate.

Maybe I'm not much of a pilot compared to you guys, but I had an unpleasant experience during a formation landing in a Pitts behind our 421 that taught me that even a little 7,000 pound twin can create vortices that you really want to avoid during the flare.

BTD · Post by **BTD** » Tue Oct 31, 2006 5:14 pm

Not too bad Mellow. And yourself?

Yes I do mean following a light. However, turbulence does work the same way with a heavy, it will just roll you much quicker. So it will definately snap you around, but it is not just bumps like on a normal day.

I was just answering another of the questions that was overlooked.

If you do get there though, forget about what you are behind, just focus on the recovery.

As I recall as well the NYC wake turbulence accident was not directly related to the wake turbulence but the F/Os back an forth deflection of the rudder in response to the encounter. Thats what I RECALL anyway.

BTD

Front. · Post by **Front.** » Tue Oct 31, 2006 7:36 pm

thanks for all the responses. Now it makes more sense. Cool Video !

And JPC, i agree it should of been taught in the 5 min of class, but my instructor was retard enough to not explain anything about wake turbulence, at all (you know who you are).

ozone · Post by **ozone** » Tue Oct 31, 2006 8:12 pm

one of the scariest experiences yet while flying was encountering wake turbulence. I had only about 10 hours solo. I was on downwind following a dash 7 and dash 8. I thought I gave lots of spacing. Flying along in a C-152 all of a sudden I was in a 90 degree bank and was heading 90 degrees off of downwind. I had no control at all for a few seconds. Scared the shit out of me! Needless to say after recovering I extended my downwind more than enough in that circuit! I now respect wake turbulence. Just lucky that didn't happen on final!

bezerker · Post by **bezerker** » Tue Oct 31, 2006 8:35 pm

BTD, your last post said that it can snap you around, and I want to emphasise that fact as opposed to your earlier post, which made it sound to me like hitting a wake can be similar to a soothing shiatsu massage.

Many years ago I hit the wake of a 727 at 90 degres in a Cessna 402. I was almost knocked out when my skull hit the ceiling. The 727 was downwind and probably in the worst config for wake turbulence, slow, and probably with some slat and flap. Probably the hardest 'jolt' I have experienced to date in an aircraft (and I have flown in the mountains and I have done a few ulgy landings). I felt lucky the wings didn't snap off that old pig. The only kind of 'wave' my mind associates with that experience is a tsunami.

Not too long ago, when passing 1,000' below an opposite direction heavy up in the flight levels, the medium jet I was in had a few hair raising moments. Captain Collins fought the roll for about a second before he gave up and we had a fairly signifigant angle of bank develop with little time to react after being so rudely awakened. Again, the only 'wave' I would compare that experience to would be one of those 'tubes' that you see the pro surfers get chewed up in.

Avoid it if you can....

BTD · Post by **BTD** » Wed Nov 01, 2006 5:32 am

Bezerker, in no way did I mean to belittle a wake turbulence encounter with a larger aircraft. If I did, I take it back. I was just trying to describe how the wake turbulence feels rather than what it does, as was asked in the first post.

I had the opportunity, while doing some formation flying, to find the wave and sort of "ride" it along. However, both aircraft were identical and both are light aircraft. It was quite interesting.

Following a larger aircraft the wake is the same just significantly more violent and like you said can be quite nasty.

In no way do I mean to say that a wake tubulence encounter is like a massage.

BTD

Fr8 dawg · Post by **Fr8 dawg** » Wed Nov 01, 2006 7:36 am

Maybe the tower was refering to a Seneca graduate ego wake turbulence.
Huge.

mellow_pilot · Post by **mellow_pilot** » Wed Nov 01, 2006 9:25 am

I was trying to think of where I might have encountered wake before. Other than the old 360 and hitting your own, I've been through the wake of a tow plane while gliding numerous times. The thing with gliders is their wingspan will often be great enough that passing through the tug's wake is not really an issue. Even though they are significantly lighter. Given that the distance is only 150-250 feet from the ass end of the tug, you get quite the shake. I think there may be some added bumps from the propwash not being entirely settled.

justplanecrazy · Post by **justplanecrazy** » Wed Nov 01, 2006 9:53 am

Clodhopper wrote:
JPC,

Don't be so quick to hurl insults...its a discussion forum for that exact reason: to discuss.

I never said I knew best, and I also don't insult someone if something they say doesn't make complete sense. Maybe try clarifying beforehand. And you wonder why low-time people are so afraid to ask questions? Because if they get more than one answer, each answer is shot to pieces by someone who thinks their way is best...and then the low-timer is left even more confused.

Well Clodhopper don't you look like the little angel. You wrote a reply to my post saying "UUUUUUUUUUHHHHHHHHHH you're an idiot I hope you don't tell everyone that," then complain about me defending myself after you go back and edit your post to not seem so demeaning. Get a life and teach your high morals to yourself before you start trying to tell me I'm the asshole. It's no wonder Cat doesn't post on here anymore. You guys had the opportunity to learn from someone with a ton of experience and skill and you chase him away by telling him he's an idiot after he posts a significant training technique. Well pretty soon you guys will be happy as pigs in shit because I really don't care to post here anymore either. No matter what I say some 200hr wonder will contradict me and no not discuss it but make a post telling me I'm an idiot just like you did. Soon it will be 200hr wonders teaching 200hr wonders, just like the real world instructing. And you wonder why people with experience don't post here?

-Enjoy JPC

Hedley · Post by **Hedley** » Wed Nov 01, 2006 10:06 am

why people with experience don't post here

well ... I post here, but I have skin thicker than an elephant's and an ego almost as large as a Seneca grad's

mellow_pilot · Post by **mellow_pilot** » Wed Nov 01, 2006 10:40 am

I think my buddy Steve said it best, "Calm the @#$! down!"