Try this one other way, do you think the aircraft tracks perfectly to the direction it's pointing when you are turning?
Slowflight Question
- Thread starter Funkeruski
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Try this one other way, do you think the aircraft tracks perfectly to the direction it's pointing when you are turning?
If you turn away from the wind, which will be closer to the wind, the planes motion track or the direction it's pointing?
jesse
Touchdown! Greaser!
I'm with you there.
Correct. What has happened to the relationship of the mean aerodynamich chord and the relative wind?
skidoo
Line Up and Wait
What wind are you referring to? Wind is relative. But, you are not being clear as to what any wind is relative to...
skidoo
Line Up and Wait
No, you don't perceive the 'yaw' difference between where the plane is pointing and where the plane is going?
'0' tolerance; as I said at the very beginning of all this, it's all small small insignificant components.
skidoo
Line Up and Wait
Well, based on that, I would say there is no such thing. No mater how close you get, there will still be some small, error...
Captain
Final Approach
There is no 'yaw' difference between where you're pointing and where your going. In level flight your 'pointing' up a bit and 'going' level. There's no yaw in straight level flight. In a turn there is yaw but its a function of lift being offset from the vertical and pulling the nose around.
Think of a fighter jet with a HUD. They have a flight path marker. It displays where the plane is going. There is also a water mark that displays where the planes nose is. Seldom are the two on top of each other. If you maneuver the plane to put the FPM over the numbers and nothing changes then the plane will impact the numbers.
In level flight the water mark is a couple degrees above the horizon (more if slow, less if fast) and the FPM is on the horizon. In a level turn the water mark is a few degrees above the horizon and the FPM lags behind it and is on the horizon. If you pushed over into negative G's then the FPM would be above the water mark.
Think of a fighter jet with a HUD. They have a flight path marker. It displays where the plane is going. There is also a water mark that displays where the planes nose is. Seldom are the two on top of each other. If you maneuver the plane to put the FPM over the numbers and nothing changes then the plane will impact the numbers.
In level flight the water mark is a couple degrees above the horizon (more if slow, less if fast) and the FPM is on the horizon. In a level turn the water mark is a few degrees above the horizon and the FPM lags behind it and is on the horizon. If you pushed over into negative G's then the FPM would be above the water mark.
flyingcheesehead
Touchdown! Greaser!
Yes - But the airplanes we fly are small enough, and propeller powerplants responsive enough, that they'll quickly re-accelerate to 95 KIAS.
The problem with wind shear for airliners is that if they encounter a large shear at a low enough altitude on final, they may not have enough altitude left to maintain flying airspeed (by pushing the nose down) before their engines spool back up and accelerate that big mass back up to the desired speed at the desired altitude or glidepath.
However, you don't create any wind shear by turning.
flyingcheesehead
Touchdown! Greaser!
The angle of attack increased due to increased load factor, meaning that the airplane's path slightly lags the direction it's actually pointed. So what? It's relative wind that matters.
So, let's say you're doing a 60-degree steep turn from upwind to downwind. When the airplane's nose is pointed directly downwind, its path will be lagging slightly - But the relative wind felt by the airplane will be the same as it was when the plane was pointed upwind.
I'm going to point out right here that we're all speaking in terms of vertically unaccelerated turns (level or steady state climb/descent) lest someone try to bring that added wrinkle into the equation unnecessarily...
denverpilot
Tied Down
Yes - But the airplanes we fly are small enough, and propeller powerplants responsive enough, that they'll quickly re-accelerate to 95 KIAS.
The problem with wind shear for airliners is that if they encounter a large shear at a low enough altitude on final, they may not have enough altitude left to maintain flying airspeed (by pushing the nose down) before their engines spool back up and accelerate that big mass back up to the desired speed at the desired altitude or glidepath.
However, you don't create any wind shear by turning.
I'd be careful thinking that it's only a large aircraft problem.
I've survived a windshear (actually microburst) encounter on final in a Skyhawk. The only option was pitch to appropriate pitch for a Vx climb and full throttle and wait until we hit the ground. The ground luckily happened to be a runway.
The aircraft was accelerating but not fast enough to overcome the tremendous force of the microburst.
I was weeks from my Private checkride and the CFI in the right seat and I remember it clearly to this day, as do his two kids who were in the back seat.
Microbursts can overcome the ability of even a light propellor aircraft to climb out. In fact after many conversations about it over the years we've concluded that the prop airstream was about all we were flying on when we smacked the runway threshold at just over 500 FPM down, stall horn screaming, CFI holding the pitch attitude between a deeper stall and a normal climb out, dancing on a pin.
Hardest "arrival" in a light aircraft I've ever encountered. The gear "sprung" out and tried to shove us off the ground again but the wing was completely finished flying at that point. A tooth smashing "squish".
THEN we started really accelerating.
Full power, now rolling down the runway ready to basically do a T&G. Power chop and lots of brakes...And I'm serious when I say "survived". There were no other options left that day.
We put the airplane away and went home. And I was glad we didn't kill my CFI's kids that day.
That yaw is a shift of chord with regards to the relative wind; an inefficiency when turning off wind, an advantage into the wind.
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Captain
Final Approach
That yaw is a shift of chord with regards to the relative wind; an inefficiency when turning off wind, an advantage into the wind.
Dancing emoticons not withstanding...a plane turns the exact same way in still air as it does in an airmass moving at 30 kts or 300 kts or 1000 kts. Think about it...due to the Earths rotation alone we are all traveling close to 1,000 mph at the equator. The air is moving with us (more or less) so that speed isn't felt.
That's why I was waiting for the whole East / West argument to support how gravity and inertia were a factor. You never brought that up.
West and East are irrelevant to the subject of a downwind turn. You said the ground does not matter and I said that it does because gravity makes everything a ground reference maneuver because it's always pulling.
Captain
Final Approach
Okay, that's where your off. Gravity pulls everything to the center of the Earth. Horizontal movement does not effect this. Fire a gun level and drop a bullet from your hand at the same time and you'll find both bullets hit the ground at the same time.
East / West does affect centrifugal forces. If you're Eastbound then the speed of the Earths rotation is added to your speed so you weigh less. If you're Westbound then your speed is subtracted from the speed of the Earths rotation and you weigh more. Ever notice the space shuttle and space station and satellites all orbit in a Easterly direction? There is a reason for that.
Never mind space craft. From a plane perspective, doing a standard rate turn in an airmass that is not moving with reference to the surface is the EXACT same as doing a standard rate turn in an airmass that is moving at 800 kts. Fact. Can Not Dispute. Please just wrap your head around that or decide that you you will live the rest of your life believing what ever your think is true.
skidoo
Line Up and Wait
Since the OP was satisfied with answers through post 5, and because we have since been discussing insignificant stuff,
But it is relevent because the aircraft weighs more going West than it does going East...
But it is relevent because the aircraft weighs more going West than it does going East...
Correct, but not in the same place and one travels an arc to get there.
Here would be a cool orbital experiment... in low earth orbits fire N,S,E,& W while simultaneously dropping and study the paths and landing spots in relationship to each other.
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Captain
Final Approach
I'm punching out. Sorry.
skidoo
Line Up and Wait
How high was the aircraft when the burst occurred? I'm just wondering if it was say 200 feet, if rather than pulling close to stall, that you would have applied full power and pushed to get more airspeed, and then when you got to 50 feet or so, pull back to arrest the descent. I wonder if the net result would have been less than 500 ft/min descent at touchdown... At least in my 182, It seems that there isn't much climb ability with full flaps at near stall speed.
skidoo
Line Up and Wait
I don't blame you for that even though you have been the most correct here...
denverpilot
Tied Down
The outflow effects started as soon as we turned final. The aircraft was at idle power and still not descending (or losing airspeed) which should have been a big clue.
We were set up for just about a power-off descent with full flaps (30) in a Skyhawk.
About the time the CFI told me to get the power off (umm... It is!) the downward portion of the microburst hit.
Power was back at 3/4 when the CFIs hand hit the back of mine and pushed the power to full. He'd just come from the early sim training after the Delta crash in Dallas and he recognized it for what it was.
At this point he said "my aircraft but stay on the controls" and did push the nose down for the last 100 feet or so. I started calling out airspeeds. The lowest I called was 40 knots. Of course the stall horn was blaring. Power is maxed this entire time.
Adding to the problem, this is Denver on a warm day. At sea level this may have been a low-approach with puckered butts. Or a more controlled landing with wild power setting changes.
Both of us could clearly see that whereas my original aiming point was well beyond the runway threshold, the spot that wasn't moving was the very edge of the pavement. CFI pitched up gingerly as the speed inched upward toward Vx.
We touched down with roughly five feet to spare inside the threshold. Tail was over the grass.
Now we've just hit the transition point to a tailwind and the "non-bounce". The wing is not flying at all. Groundspeed is gaining rapidly but ASI is still well below Vx as we roll very rapidly down the runway but with the drag of producing lift removed, we're about to liftoff speed when the power is unceremoniously chopped and heavy braking applied.
Looking down the runway we see the windsock straight out away from us. A flagpole at the approach end had indicated the EXACT opposite. Straight out toward us. Classic microburst.
We taxied in and the phrase I remember was "airplane doesn't want to go flying today and I'm not going to fight it".
The previous landing had been squirrelly. Later we realized this was the edge of a thunderstorm inflow line that was feeding a building storm barely developed almost 22 miles West. (Storm was near KBDU, we were at KEIK.)
Amazing experience. One that I learned never to mess with t-storms in the building stage on a relatively dry unstable day, even if 20+ miles away, and one I'd definitely prefer not to repeat.
skidoo
Line Up and Wait
I guess that would have been hard to push for airspeed in that situation. That was too close for comfort!
It is nice to see informative and helpful responses!
This story brings back a memory of my launching a hang glider on the back side of Green Mountain just outside of Denver. I carried that kite on my back up the mountain and as I approached the top, the breezes started shifting, once up the hill, then next down the hill, then calm. I did not want to carry it back down, so I quickly set it up and waited for the next breeze up hill, and launched. That was a mistake. I didn't get the lift I normally would have expected and then about 50 off the ground, the ground approached rapidly. So, I flared maximum, arms outstretched, hit the ground with an immediate stop, no sliding or such. I was fortunate that speed must have been slowed just enough that no damage occurred except for a pulled muscle on my arm. About 5 minutes later, the winds started howling down the hill and all over Denver, some of the strongest winds I had ever seen around Denver that day.
denverpilot
Tied Down
Ouch!
Love watching folks off Green Mountain and Lookout Mountain launch points, but I'm way too chicken to do that stuff without a roll cage around me.