Caution wake turbulence

[Austintatious]

Video I found!

 

 

[carusoam]

See if you can find a similar video of a Cirrus following a heavy helicopter op....

It is amazing how powerful the rotating wind is following heavy aircraft... and how long it stays around... on a windless day...

Standing in the wind thrown off by an R22... it’s a breeze.  An R44... is more of a strong wind...

You can literally feel the difference in the weight of the aircraft...

When the R22 air taxis by... you walk over to close up doors... the R44... You jog to get there to close the doors...  

Nice visible lesson regarding vortex safety.., thanks for sharing!

Best regards,

-a-

[bradp]

Flew 1000 feet under a crossing A380 headed into Houston a couple of weeks ago.  Got my picker factor going and got all my occupants to buckle in just in case.  That’s a really big bug on the windscreen. 

 

Also remember that there is no separation requirement from ATC (just advisory) for same runway departures for those of us that fly out of airports with transport category jets / military etc.  

[steingar]

I'll definitely remember that video next time I take off behind an Anotov.

[0TreeLemur]

1 hour ago, steingar said:

I'll definitely remember that video next time I take off behind an Anotov.

And the music to that video....

[Hank]

On 4/4/2019 at 8:07 AM, bradp said:

Also remember that there is no separation requirement from ATC (just advisory) for same runway departures for those of us that fly out of airports with transport category jets / military etc.  

I always sit for a very long three minutes before taking the runway after any airliner, even a "small" CRJ. Sometimes it feels like forever . . . And I advise Tower why I'm not pulling out as soon as they clear me for takeoff.

[bradp]

Yup last time I told tower at RDU I needed 2 min behind a 737 departure, they got pissed at me and told me wake turn sep is not required (for them).  I told them it is for me and I’d happily go to the naughty corner until there was a break in departures.  

[Yetti]

https://www.aopa.org/news-and-media/all-news/2015/february/04/cirrus-caught-in-rotor-wash

[M016576]

On 4/5/2019 at 7:54 AM, bradp said:

Yup last time I told tower at RDU I needed 2 min behind a 737 departure, they got pissed at me and told me wake turn sep is not required (for them).  I told them it is for me and I’d happily go to the naughty corner until there was a break in departures.  

The other option would be to rotate before the 737’s rotation point, then turn away from his flight path.  That would keep you clear of the 737’s wake turbulence.

obviously, if you’re on an ifr clearance, you might not be able to avoid the 737’s wake turbulence.  And 2 minutes is certainly prudent.

[jaylw314]

7 hours ago, M016576 said:

The other option would be to rotate before the 737’s rotation point, then turn away from his flight path.  That would keep you clear of the 737’s wake turbulence.

obviously, if you’re on an ifr clearance, you might not be able to avoid the 737’s wake turbulence.  And 2 minutes is certainly prudent.

Taking off from PDX 3 times, each time they've cleared me to make a crosswind turn south over the parallel runway after passing the tower.  This keeps me out of the way of any wake turbulence from either runway.  I'll have to remember to thank them next time if that's not what happens elsewhere...

[Mooney in Oz]

On 4/5/2019 at 12:07 AM, bradp said:

Also remember that there is no separation requirement from ATC (just advisory) for same runway departures for those of us that fly out of airports with transport category jets / military etc.  

For those who regularly fly into airports with parallel runway ops and transport category jets, please be extremely cautious particularly when the other runway's threshold is slightly further away causing arrivals on that runway to be higher than your aircraft and the prevailing wind is from that direction which may result in the wake being carried by the wind and descend into your path.  Some years ago at Sydney an A380 on final for 34L almost upended a SAAB 340 on final for 34R at a low altitude.  The A380 was slightly in front and about 100 feet higher than the SAAB with a 10 to 20 knot westerly blowing.

Very nasty.

[Bob - S50]

Knocking the cobwebs off, if I remember right, when wingtip vortices reach the ground in calm air they tend to spread out at about 3 - 5 mph.  So in addition to what M016576 said, in calm conditions, vortices will tend to move away from the runway.  Under light crosswinds of about 3 mph, one vortice will tend to hang over the runway, and under strong winds, the wind will tend to break up the vortices.  And also if I remember right, when airborne, votices tend to descend at about 500 fpm.  So staying even with or above the previous aircraft flightpath should keep us clear too.

[Yetti]

So what is the rule for other GA Prop planes.   I took off behind a Bonanza pretty quickly once and was wondering if I was too close.   Never felt anything, but I think I out climbed him by a small bit.

[M016576]

53 minutes ago, Yetti said:

So what is the rule for other GA Prop planes.   I took off behind a Bonanza pretty quickly once and was wondering if I was too close.   Never felt anything, but I think I out climbed him by a small bit.

Wingtip vortices (wake turbulence) severity is directly related to the weight of the aircraft, the aspect ratio of the wing and the angle of attack of the wing.  The biggest vortices occur with a very heavy aircraft operating at a high angle of attack (very slow).

really, the wingtip vortices are a side effect of generating lift (and the creation of induced drag).  The heavier the weight, the higher the AoA, the more lift being generated... the bigger the vortices.  In a little, light aircraft, like our mooney’s, or a bonanza, we do have wing tip vortices, but they are very small (pretty much insignificant for another aircraft).  

 

[Hank]

I've done steep turns below Va and felt slight jiggles hitting my own wake. Taking off after a Bo or another Mooney isn't an issue, I've done both many times. CRJ? I wait two minutes (120 seconds) before moving onto the runway. 

[Yetti]

40 minutes ago, M016576 said:

Wingtip vortices (wake turbulence) severity is directly related to the weight of the aircraft, the aspect ratio of the wing and the angle of attack of the wing.  The biggest vortices occur with a very heavy aircraft operating at a high angle of attack (very slow).

really, the wingtip vortices are a side effect of generating lift (and the creation of induced drag).  The heavier the weight, the higher the AoA, the more lift being generated... the bigger the vortices.  In a little, light aircraft, like our mooney’s, or a bonanza, we do have wing tip vortices, but they are very small (pretty much insignificant for another aircraft).  

 

I was thinking that too, then watching the AN2 video.   I know it swings a big ole prop, but not much longer than a Mooney

 

[M20F]

Wake turbulence is like wind shear, very rare but when you find it you know it.  Don’t let the rarity make you a statistic.  

[FloridaMan]

Friend lost a partner and four friends in a Baron that crashed due to wake turbulence. They faulted the controller. IFR approach on a parallel runway with inadequate separation. 

I got rushed by a controller at ICT in my F a few years back to take off behind an A320. Winds were straight down the runway and I could see the cloud of exhaust coming towards me. I aborted, braked and flat-spotted a tire. "Unable," deviate, whatever you need to feel comfortable crossing under or behind a heavier aircraft. I got thumped hard in smooth air by an MD88 that'd crossed two minutes ahead of me. 

Controllers do not see what you see and there is often latency or inaccuracy in their data. 

You know the joke: What does a pilot have in common with an air traffic controller? If the pilot screws up, the pilot dies. If the controller screws up, the pilot dies. 

[DXB]

I haven't worried too much about taking off behind a big jet because generally their takeoff roll is so much longer. Once airborne, I try to sidestep a bit to the upwind side of the runway.  Asking for an early turn away from the climb path of the jet might help too. 

What scares me more are heavy-ish planes with short takeoff distances (e.g. a skydiving operations caravan) and now that Antonov in the video.   

Landing also scares me much more - even if you visually capture exactly where the plane touches down (not always easy) and land long beyond it, it's nearly impossible for me to visualize the flight path well enough to ensure staying above it.  

Edited April 9, 2019 by DXB

[M016576]

On 4/7/2019 at 10:23 AM, Yetti said:

I was thinking that too, then watching the AN2 video.   I know it swings a big ole prop, but not much longer than a Mooney

 

 

The AN-2 Colt is much heavier than a mooney (4-5 times heavier... ~12000lbs) I know, it doesn’t look it- but it is) and tends to fly very slow at a high AoA, and with low wing loading on its biplane type structure- hence it should (and does) have “big” wingtip vortices in relation to that small aircraft that was taking off behind it. A mooney, bonanza or single engine Cessna has nothing close to that size of a wake turbulence profile- even though the wingspans are similar.  We just don’t create nearly as much lift, even at what we would consider a “high” angle of attack.

as for the propwash (and Jetwash for that matter)- that tends to break up relatively quickly, due to the randomness of the wash itself.  Don’t get me wrong- If you fly 3000’-6000’ through a turbojet wash- you’re going to feel it in a big way (probably “life altering” if you’re not ready for it).

In relation to a propeller- the size (length) of a prop directly dictates how fast it can spin and still create thrust in an efficient manner.  The tips can’t get going any faster than the upper transonic region- as once the prop gets supersonic, the compressibility of air at those speeds becomes a huge factor in prop efficiency.  The ability for the prop to output enough thrust to make the power required to drive it worth the weight of the motor becomes increasingly out of balance. This is the main reason why you’ll never see a supersonic prop aircraft (although it may be theoretically possible given a light and powerful enough motor.. that I don’t know... I have never heard or seen one- but that certainly doesn’t mean an airplane like that wasn’t built at one point).

supersonic props and the drag/weight associated with a prop led to jet engine design- where great lengths are taken to slow and compress a subsonic (or supersonic) air mass in the inlet->compressor sections... then light that air mass on fire and ride the explosion.... and if you’re really lucky- maybe throw 2-3lbs a second of raw fuel into the exhaust and use the excess bleed air and some igniters to light that on fire too.  Then you can really get going quickly!

Edited April 9, 2019 by M016576

[Marauder]

I have experienced “life altering” wake turbulence twice. The first time as a stupid new pilot still learning what “wake turbulence” meant. A couple of C-130s were flying an oil burner route near my airport. I convinced myself that climbing up through the area they flew through a few minutes earlier would be fine. Was I wrong...

The second time happened more recently and in my Mooney. I was doing an early evening flight on a perfectly calm day. I was showing a friend the area over by the Susquehanna river when we were rocked severely.

I wasn’t sure initially what caused it but then I saw a helicopter above us on the other side of the river and surmised his wake had crossed the river and that was what we hit. Wake turbulence is certainly not to be messed with.


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