View Full Version : Steep turns and hitting your own wake...
grumpyoldgeek
16th Apr 2007, 21:32
Please excuse the general aviation related question. You folks have been helpful in the past and I hope the question isn't too distracting.
Do you perform the classic steep turn maneuver as part of your transport proficiency testing? If so, if you fly a steep turn in a large transport aircraft, will you hit your wake as you come around to your starting point?
gearpins
16th Apr 2007, 22:02
I have got hit by it once!!
calm winter sky during descent radar requested us to level off at fl150 and orbit present position:} feel like a dog biting its own tail!!!
Brian Abraham
17th Apr 2007, 01:16
Recall one aerodynamicist writing that if you hit your own wake it means you have descended during the turn. Naturally depend what the airmass itself is doing I guess. Could possible be the beginning of an argument such as the famous "downwind turns".
Dan Winterland
17th Apr 2007, 01:57
Wake descends at about 200fpm as a reult of the downwash induced by the wing. If you flew a rate 3 turn, it would take 40 seconds. If you hit your own wake, it would mean you have descended about 133' in the turn.
Contract Con
17th Apr 2007, 05:52
Gday,
how about on a hot thermally summers day?
Does the wake still descend at such a rate?
I remember hitting the wake regularly doing steep turns, moons ago in G.A types.
Cheers,
Con:ok:
compressor stall
17th Apr 2007, 06:53
Have to disagree with the wake descending @ 200fpm statement.
Many moons ago (most likely in the same aircraft Contract Con alluded to) we would regularly fly in company out to an island. I felt the wake of the preceeding aircraft when they were up to two miles ahead.
With both aircraft on autopilot with working alt holds, the front one would throttle back and we would speed up and when arriving in "company" we'd be almost exactly the same height - certainly not the 150 feet or so difference as suggested by that rule.
And for the record, yes a good feeling to hit it on your check rides! ;)
In t'RAF it used to be the 'test' of a perfect max rate turn. I have flown a few (60deg) in 737 and 727 simulators - and never 'hit' my wake - but I guess the 'wake' from a sim is small:)
GOLF_BRAVO_ZULU
17th Apr 2007, 08:21
Having initially descended beneath line of flight, doesn't the wake then reverse to ascend above it? The analogue being hill lee-waves.
Brian Abraham
17th Apr 2007, 09:20
Not a heavy metal driver or operated where wake turbulence avoidance was an issue but is not this analogous to flying an ILS "on glide slope". The wake of the previous aircraft will have descended below the glide slope thus giving you a smooth ride. From what I read, some following a heavier type, like to keep 1/2 to 1 dot high to avoid surprises. Wake avoidance material I read says at altitude, vortices sink at a rate of 300 to 500 feet per minute and stabilize about 500 to 900 feet below the flight level of the generating aircraft.
BOAC - I can recall some heavy 'wakes' following a sim. :sad:
OverFlare
17th Apr 2007, 09:51
Like BOAC, have done 60 deg turns in the sim, but only once or twice. I certainly don't recall any wake. But then it was all I could do to concentrate on holding altitude and speed so I might have missed it!
It's not something we do very often unfortunately.
I would be very surprised if this is even simulated.I don't recall seeing Wake Turb even simulated from preceeding aircraft!
Hey you lot - the comment about 'wake' in the sim was TIC - as picked up by Brian:)
merlinxx
17th Apr 2007, 17:28
What does it smell like?
Just checked and there are in fact two versions on later sims. One is a simple wake vortex that can be place in the sky ahead of the aircraft on command from the IOS. The second more sophisticated model ties in with TCAS and attaches a wake to a TCAS target (that flies a simple course, altitude and airspeed) with a set of scenarios.
Old Smokey
18th Apr 2007, 07:43
ZFT, some wake turbulence is simulated, by the instructor!:E
If a student has done a perfect or near-perfect steep turn in the simulator, I have been known to inject 2 to 3 seconds of light turbulence just as they roll out on a 360° turn.... a small ego boost to the student you see..:ok:
Amazing how many (all?) thought that it was real;)
Perhaps I'm guilty of originating an aviation myth, well, I had to leave my mark somewhere:hmm:
Regards,
Old Smokey
Old Smokey
A wise head at the IOS does make all the difference.
Yet another mark to add to a long list I suspect.
Brgds,
ZFT