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Dreadful accident - should have been avoided

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Dreadful accident - should have been avoided

Old 21st Oct 2015, 22:39
  #21 (permalink)  
 
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Snoop Long life !

Originally Posted by Machinbird
I pulled back on the stick which turned the aircraft away from over the runway and in seconds I was in control again.

The fix was simple. All I had to do was throw out the mental concept of remaining over the runway. I hope this little story helps others.
Your experience is easy to include in the basics, and so precious ! I hope our regulators and flightcheckers will read and follow your wise example without delay

Last edited by roulishollandais; 22nd Oct 2015 at 12:48. Reason: flightcheckers
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Old 24th Oct 2015, 10:08
  #22 (permalink)  
 
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Not sure how accurate or representative that test on the AN2 was
The aircraft descended then would heve made a big pitch and power change to go to a climb.
I don't know enough about vortices generation? When they are at their maximum but this AN2 took off on a steady climb maybe 30 seconds ahead of the crash aircraft.
A true test would have had smoke emanating from the crash point and the aircraft 30 seconds ahead.
Again in the high altitude tests the AN2 should have been in a climb attitude with the chase aircraft 30 seconds behind which it was not on the test.
But a good example of taking off behind a much larger aircraft and the dangers of doing so.

Pace
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Old 24th Oct 2015, 14:05
  #23 (permalink)  
 
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I've had several occasions in the last few days, where consideration of wake turbulence was necessary for safe flight, both landing behind, and taking off after another aircraft. In the case of landing (behind a departing Dash 8) I recognized it as being appropriate to land short, and be firmly on the ground before its rotation point. In a few other cases, considering the crosswind, to assure all of my operations were upwind of the location of the expected wake.

As long as you are comfortable about list moment maneuvering, it's entirely fine to approach or depart offset to the runway centerline, to avoid a wake turbulence area.
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Old 24th Oct 2015, 18:10
  #24 (permalink)  
 
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Also

With any threat of downdraughts speed is your friend so don't climb away hanging on the stall! If the runway is long enough rotate at a slightly higher rotate speed

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Old 24th Oct 2015, 22:31
  #25 (permalink)  
 
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The problem is wake vortex turbulence not downdrafts.
The vortices naturally decend so staying low is a bad idea.
Rather give them plenty of time to dissipate and use best rate of climb speed to get above them.
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Old 24th Oct 2015, 23:29
  #26 (permalink)  
 
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Rather give them plenty of time to dissipate
Yes.

and use best rate of climb speed to get above them.
Ahhh, not so fast... Yes, above wake turbulence is the most desirable place to be, but trying to get there can end badly. Most of us do not fly aircraft with that kind of climb capability. I will not fly through a zone I think could contain wake turbulence, so I would not be climbing through it! I will be either waiting the full wait, or determining a path which will take me around the risk area, not through it!

The tactics of wake turbulence avoidance are well documented, and worthy of review.
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Old 25th Oct 2015, 09:17
  #27 (permalink)  
 
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In a light aircraft if taking off behind a jet transport at a large airport it's no problem to get airborne well before the point that the jet did, and then turn left or right immediately climbing out at close to 90 degrees to the runway heading (with ATC permission of course).

We used to do this, and ATC appreciated it as it helped keep up the flow rate.
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Old 25th Oct 2015, 10:10
  #28 (permalink)  
 
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I have often wondered about wake turbulence away from the immediate runway. In Los Angeles some heavy commercial traffic inbound route over the SMO VOR fly downwind east to downtown LA, turn base south towards Long Beach and final back towards the LAX, there is a VFR route directly below the base leg that tracks the LA river (the schwartznegger one) with an altitude restriction of 1700 if I remember correctly, however the CAT turning final appear no more that 2000ft above the transiting GA . What is the safe vertical clearance to allow WT to dissipate in a no wind situation from slow and heavy CAT? I read a story in Canada I believe where a GA transiting a terminal area was vectored below a jet and had a in flight break up due to WT.
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Old 25th Oct 2015, 11:08
  #29 (permalink)  
 
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What is the safe vertical clearance to allow WT to dissipate in a no wind situation from slow and heavy CAT?
I don’t know how far away in time and distance you need to be to be “safe” (it depends on your aircraft) but I have experienced serious wake 1,000’ below and 5 minutes after a heavy jet. I suspect in ideal circumstances it could go much lower/longer.

I think atmospheric conditions play a large part: vortices appear to last much longer and keep intensity in a stable layer or where there is no preexisting turbulence.
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Old 25th Oct 2015, 12:11
  #30 (permalink)  
 
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You can encounter wake turbulence in any part of the sky, from any preceding aircraft, though at higher altitudes, and your flying faster, the effect will be more manageable. I'm very pleased to hit my own wake turbulence following a well flown loop.

Encountering wake from a "heavy" ahead of you should always be considered, and avoided, but if you're flying at Va or just slower than, and a thousand feet or so up, you'll have a chance to limit it to a really rough ride, rather than being slammed out of control into the ground.
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Old 25th Oct 2015, 12:47
  #31 (permalink)  
 
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I still stress with any down draughts wake turbulence or other wise you do not want to be hanging in the sky near the stall.

Taking off with that possibility even turning to avoid i personally would get the aircraft cleaned up quickly and some excess speed in case you need that extra energy. Remember its not just wake turbulence which can cause air currents which will slam you into the ground I used to operate at an airfield where the winds from a certain direction would curl over a hanger with the same effects

Hitting wake turbulence at high speed is a different matter. I am sure we have all experienced that crash with air currents caused by unexpected wake turbulence from another aircraft and there excess speed is your enemy

Pace

Last edited by Pace; 25th Oct 2015 at 12:58.
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Old 25th Oct 2015, 19:02
  #32 (permalink)  
 
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http://www.caa.co.uk/docs/33/20130121SSL15.pdf

I'm sure most have found this anyway but it gives some useful info.
Having been hit with wake turbulence in a 737 and we were following a 320 we rolled 30 degrees very very quickly.

Scared the poop out of me and the skipper.
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Old 27th Oct 2015, 12:17
  #33 (permalink)  
hum
 
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Helicopter Wake

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Old 27th Oct 2015, 12:26
  #34 (permalink)  
 
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It might be obvious but I'll point it out anyway; WT is far worse when the generating aircraft's wing is at high alpha, with a big pressure difference between lower and upper surfaces. So much more danger fom an aircraft landing or taking off than from one in the cruise

Hence the danger is a double whammy - WT is far more serious from a landing or taking off aircraft, and by definition if you hit it then you are low down and slow.
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Old 27th Oct 2015, 14:32
  #35 (permalink)  
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To further Shaggy's thoughts, and more for amusement than useful, I have noticed as an airline pax, that on final, with lots of flap out, the wingtip vortex has moved from the wingtip, to the outboard end of the extended flaps. A retired aerodynamisist friend confirmed that the wingtip vortex is not always produced at the wingtip.

In any case, understand where to expect them, and actively avoid!
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