Episode # 108

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Dave Higdon
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Re: Episode # 108

Postby Dave Higdon » Mon Dec 08, 2008 5:23 pm

OK, folks, my comments about landing before the touchdown point of a heavy caused so much reaction -- rightfully reactions of horror -- that it seems to me a brief caveat is in order here...and believe me, from my perspective, all of your collective advise and admonitions are on-point and well-taken.

In the cases at the root of my comments, my landing short of the heavy's touchdown point always occured when ATC vectors put in a position well behind and below the glideslope of the heavy ahead of me; landing well short kept me from the unpleasant and unsafe act of flying through where we'd expect to find wake turbulence...and my touchdown points were always at least a couple thousand feet behind the jet's touchdown point. To fly through the wake at 1,100, 1,200 agl in an attempt to land beyond the jet's touchdown point was and remains something I'd rather not do.

If the controllers instructions vectored me into a turn to final already above the jet's glidepath, I'd be equally averse to flying through that wake to get below the trashy air and land short; so in those instances, have always either landed long or, when that wasn't practical, requested another shot at the runway and I'd go around the patch again on the theory, belief, that the wake would no longer be present.

And when departing behind such jets, it's always been really easy to rotate well before the prior aircraft's rotation point and, with ATC's OK usually in hand, turn out immediately to avoid any chance of a wake encounter.

So appreciate the worries and the good advise. But rest assured, I haven't lost my respect for wake turbulance -- and no more of my mind than it takes to do this podcast every week with the likes 8-) of Jeb and Jack :lol: ...

Hope this helps put to rest the (valid) rumors of my mental capacities... ;)

Dave

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lucaberta
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Re: Episode # 108

Postby lucaberta » Mon Dec 08, 2008 5:54 pm

Dave Higdon wrote:OK, folks, my comments about landing before the touchdown point of a heavy caused so much reaction -- rightfully reactions of horror -- that it seems to me a brief caveat is in order here...and believe me, from my perspective, all of your collective advise and admonitions are on-point and well-taken.

it's because we l-o-v-e you, Dave! :D

In the cases at the root of my comments, my landing short of the heavy's touchdown point always occured when ATC vectors put in a position well behind and below the glideslope of the heavy ahead of me; landing well short kept me from the unpleasant and unsafe act of flying through where we'd expect to find wake turbulence...and my touchdown points were always at least a couple thousand feet behind the jet's touchdown point.

not sure I follow you here, still, Dave.

If you're landing on the exact same runway as a jet, you should be aiming at the exact same point on the runway. The aiming markers are 1000' after the piano keys, and that's where the touchdown should happen. with the piano keys overflown at 50'. If you're landing couple of thousand feet behind the jet ahead, you're either touching down on the grass before the runway begins, or the schmuck flying the HMT ahead of you got his landing wrong... :lol:

Granted, us in light planes can aim well before the piano keys and nail a short field landing right on the piano keys, but would you do that at an airport with a long runway and commercial traffic lined up on final? Last time I flew a light into heavy iron land was last January, a C172 IFR into KSMF in between MD80s and B737s. The tower very much appreciated our keeping 100 knots until we passed the piano keys, and we then hovered on the runway for a few thousand feet bleeding off airspeed, landed just before the high-speed exit and taxied to the GA apron. I just don't see us light planes pilot slowing down to do a short slick landing on a very very long runway...

And remember also that the wave turbulence vortex can still be affecting light planes after touching the ground, for up to a minute. They just don't dissipate right away the moment they touch the ground. So for me, being lower and behind something a lot heavier than me it's a clear no go.

To fly through the wake at 1,100, 1,200 agl in an attempt to land beyond the jet's touchdown point was and remains something I'd rather not do.

agree. It's easier to do a 360 in the downwind and lose a minute or two before coming in for landing. That is, if the tower is still able to slot us in!

Hope this helps put to rest the (valid) rumors of my mental capacities... ;)

now, if it's the rumors around your mental capabilities that we should be talking about, I better open up a new thread... :D :D

Ciao, Luca
(yes, lucaberta is just my nick on forums, Luca is the first name and Berta is the initial part of my last name)
Last edited by lucaberta on Tue Dec 09, 2008 7:24 am, edited 1 time in total.
Luca Bertagnolio, CPL/ASEL/AMEL/ASES/IR

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Greg Bockelman
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Re: Episode # 108

Postby Greg Bockelman » Tue Dec 09, 2008 6:55 am

Dave Higdon wrote:In the cases at the root of my comments, my landing short of the heavy's touchdown point always occured when ATC vectors put in a position well behind and below the glideslope of the heavy ahead of me; landing well short kept me from the unpleasant and unsafe act of flying through where we'd expect to find wake turbulence...and my touchdown points were always at least a couple thousand feet behind the jet's touchdown point. To fly through the wake at 1,100, 1,200 agl in an attempt to land beyond the jet's touchdown point was and remains something I'd rather not do.


Dave, with all due respect, if you keep this up, you may be setting yourself up for a nasty surprise some day. If the heavy was doing it properly, he would be on a 3 degree glideslope and aiming for the fixed distance marker that is 1000 feet down the runway. Now if he was a tad fast, he may float a bit and touch down further down the runway, but they are always aiming for 1000 feet down the runway. It would seem like if you were aiming for the numbers when the heavy was aiming at 1000 feet or further down the runway you would be a safe distance but you would be wrong.

As you and I hope everyone here knows, the vortexes flow down and out from the wingtip. If you touch down 1000 feet behind the heavy, you are really only about....MAYBE 50 feet lower than the heavy at the same point on the ground. Not a good place to be. Point is, if you are below the glidepath of a heavy you WILL fly through the plane of his vortecies

Also, I would rather encounter the wake at 1,000 or 1,200 feet than at 500 or 100 or God Forbid, less. If you think it will be an issue, go around, sidestep the final a bit, or use another runway.

Hope this helps put to rest the (valid) rumors of my mental capacities... ;)

Dave


Not so sure about that, David. :D

You ALWAYS, ALWAYS, ALWAYS want to stay ABOVE any potential wake turbulence. If landing behind a heavy, you ALWAYS want to be ABOVE his glide path. If landing behind a departing heavy, you want to touch down before his rotation point. If taking off behind a landing heavy, plan to rotate AFTER his touchdown point. If taking off behind a departing heavy, plan the departure so as to be off the ground BEFORE his rotation point, and if necessary, sidestep to the upwind side of the runway to avoid his wake turbulence.

There really aren't that many absolute rules in aviation but this comes close.

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tonycondon
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Re: Episode # 108

Postby tonycondon » Tue Dec 09, 2008 11:12 pm

I can understand the situation, but really the only guarantee is to stay above the wake. Sure you've managed to come in under it before, but you have no way of knowing how close you are to the wake.


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