Zzz wrote:

CamTom12 wrote:
Except that vertical accelerations can change AOA. It all depends on how active the air is, I guess.

Gust factors and sinking air does change AOA, which is why the aircraft loses lift. The rapid change in relative wind may occur faster than the AOA indicator can respond ... which means it ain't really "real time", just a bit delayed. Kinda like our pitot static system ASI and VSI.

I believe this just emulated the downwind turn debacle.... sideways

Rob wrote:I believe this just emulated the downwind turn debacle.... sideways

Haha kinda. That's always entertainment.

But, to be fair, the downwind turn myth is actually somewhat germane. The premise of the DTM of course being that pilots mistake the downwind of "robbing their airspeed" when it is merely a visual illusion of increasing groundspeed causing pilots to bank and pull more aggressively, the unluckiest ones into an accelerated stall.

My statement about vertical acceleration assumes dirty air: the combination of downdrafts and updrafts and mechanical like rotors. Isn't it the same reason maneuvering speed decreases as weight decreases? You get a greater acceleration through the medium vertically, and thus a greater change in AOA, the lighter you are (F=ma, anyone?) It is possible for a downdraft to accelerate you to a point where when you emerge from the descending air, your AOA will be well beyond critical. Is there debacle potential here? I hope so. You and I always end up PMing when there is.

Zzz wrote:

CamTom12 wrote:In a situation like that, your AoA very likely hasn't changed - you're just flying through a sinking parcel of air. Had the runway been part of your sinking air pocket, I bet the landing would have felt completely normal!

It's important to use other indicators, visual cues and "seat of the pants" cues to recognize updrafts and downdrafts.

Except that vertical accelerations can change AOA. It all depends on how active the air is, I guess.

So very true. It really depends on the size of the air packet you're in. And depending on the refresh rate of your AoA (I'm sure there's some filtering in most) or even the responsiveness of your airspeed indicator (the column of air in the pitot lines and the mass of the gears/needle filters a bit), you may not even indicate passing through the boundary of the sinking/rising air pocket. If it's big enough to envelop the aircraft, once you're in it, you're in it. Much like a headwind or tailwind don't show up on your airspeed indicator.

But if you're in intermittent gusts, anything that pushes the airplane up or down against the free stream air should show as an AoA change.

If this was Wed. June 21st, I can understand the wind. I was departing from Harvey S43 about 7AM headed SE and was clocking 154 kts ground speed at 9500 feet. Maules don't go that fast. IAS was about 120 kts.

Guessing the winds down the Stehiken river could have been "brisk".

TD

Yes Wednesday June 21st, once over the lake white caps everywhere, I knew the landing was going to be fun.
Went yesterday again windy but not as much as the week before.
Both times though the mountain crossing were real smooth, which was nice.