Wind shear
The last two weeks have been totally routine. Even the weather has barely changed.
A steady diet of clear skies and light winds has taken some of the sting out of spending more than week living out of a hotel, covering for a pilot whose normal run starts and ends in Aberdeen.
Only the afternoon turbulence intrudes on flying Nirvana. The 310 is notorious for it's annoying dutch roll tendencies in even the lightest of turbulence, making hard work out of every atmospheric ripple.
But as evening comes on and the air turns glassy smooth, as it has done every day for the past two weeks, life is good.
It's the kind of weather that lulls me into near total relaxation. The airplane perfectly trimmed, staying on course and altitude with no input from me, the engines droning on with both propellers in near-perfect synchronization, the setting sun reflecting off of the hundreds of lakes the slip beneath me as I fly the same route day after day.
Approaching Fargo the sunset is particularly spectacular thanks to the haze created by the numerous grass fires and the first rain I have seen in more than a week.
Fargo itself is dry, the rain is still well to the West filtering the last rays of sunlight. I look at the rain and don't like what I see. It has the look of a windy, turbulent mess.
Not to worry, it is still well West of the airport and the winds are light and the air perfectly smooth.
Pre-landing checks are complete and the airplane is in perfect trim, exactly on speed with gear and flaps down flying hands off down the glide path with the power set to 17 inches of manifold pressure. It is magic. Nothing left to do but ease out the last bits of power and flare.
My thoughts turn to the landing and I decide to work for an absolute greaser. The evening is too pretty, the air too cool and smooth to ruin the moment with anything less than a gentle chirp of the tires against pavement.
At 300 feet I place my hands on the controls, add full flaps and adjust the trim. It is still perfectly smooth.
At 200 feet my world, quiet and serene just a few seconds earlier, tilts instantly and distinctly off it's axis. I am stunned.
The first jolt of turbulence is strong enough that I bang my head against the top of the cabin. I am now fighting to control an airplane that just a few feet ago was in perfect harmony with the atmosphere. Now, that same atmosphere is trying to kill me.
I am starting to drop below the glide path. Out of the corner of my eye I catch the airspeed indicator. I have lost 15 knots in the span of a second, perhaps two.
I add power but we are still sinking and my airspeed is still low. It is a fight to keep the wings level and the thought of crashing runs through my head.
I shove the propellers and throttles full forward. Finally, I am no longer sinking and I am getting my airspeed back. I am suddenly deeply in love with the 310 as 570 horsepower begins to carry me toward salvation.
Satisfied that the worst is over I ease the throttles back.
The wind, which was light and slightly from the left just a few seconds ago is now raging and almost 90 degrees to my right. I contemplate going around but by now everything is once again back under control so I fight the wind down to the runway and instead of the greaser I was contemplating what seems like an hour ago settle for an inelegant, albeit it safe, thunk.
From start to finish the entire saga has lasted perhaps 15 seconds.
As I taxi in I report the wind shear to tower. I am strangely annoyed when they reply that they just noticed a wind shift and leave it at that. Even a quick "wind now 360 at 21 knots" while I was on final approach would have alerted me to the possibility of the wind shear that was waiting for me.
I've been fortunate enough to have encountered wind shear enough that I can recognize it when it happens. Usually it's benign, perhaps a five knot swing or so, and occurs on windy, gusty days so I'm already locked and loaded to deal with it.
What made this encounter so shocking was there was no warning, I just happened to arrive over the runway at the same time the wind was shifting more than 90 degrees. Three minutes earlier or later and I'm sure it would have been a totally unremarkable approach and landing.
After dropping my freight I fired back up and launched into moderate turbulence which lasted until 5,300 feet. Like a light switch the atmosphere was suddenly perfectly smooth again and stayed that way for the 45-minute trip back to Aberdeen on a beautiful spring evening.
The learning continues.
A steady diet of clear skies and light winds has taken some of the sting out of spending more than week living out of a hotel, covering for a pilot whose normal run starts and ends in Aberdeen.
Only the afternoon turbulence intrudes on flying Nirvana. The 310 is notorious for it's annoying dutch roll tendencies in even the lightest of turbulence, making hard work out of every atmospheric ripple.
But as evening comes on and the air turns glassy smooth, as it has done every day for the past two weeks, life is good.
It's the kind of weather that lulls me into near total relaxation. The airplane perfectly trimmed, staying on course and altitude with no input from me, the engines droning on with both propellers in near-perfect synchronization, the setting sun reflecting off of the hundreds of lakes the slip beneath me as I fly the same route day after day.
Approaching Fargo the sunset is particularly spectacular thanks to the haze created by the numerous grass fires and the first rain I have seen in more than a week.
Fargo itself is dry, the rain is still well to the West filtering the last rays of sunlight. I look at the rain and don't like what I see. It has the look of a windy, turbulent mess.
Not to worry, it is still well West of the airport and the winds are light and the air perfectly smooth.
Pre-landing checks are complete and the airplane is in perfect trim, exactly on speed with gear and flaps down flying hands off down the glide path with the power set to 17 inches of manifold pressure. It is magic. Nothing left to do but ease out the last bits of power and flare.
My thoughts turn to the landing and I decide to work for an absolute greaser. The evening is too pretty, the air too cool and smooth to ruin the moment with anything less than a gentle chirp of the tires against pavement.
At 300 feet I place my hands on the controls, add full flaps and adjust the trim. It is still perfectly smooth.
At 200 feet my world, quiet and serene just a few seconds earlier, tilts instantly and distinctly off it's axis. I am stunned.
The first jolt of turbulence is strong enough that I bang my head against the top of the cabin. I am now fighting to control an airplane that just a few feet ago was in perfect harmony with the atmosphere. Now, that same atmosphere is trying to kill me.
I am starting to drop below the glide path. Out of the corner of my eye I catch the airspeed indicator. I have lost 15 knots in the span of a second, perhaps two.
I add power but we are still sinking and my airspeed is still low. It is a fight to keep the wings level and the thought of crashing runs through my head.
I shove the propellers and throttles full forward. Finally, I am no longer sinking and I am getting my airspeed back. I am suddenly deeply in love with the 310 as 570 horsepower begins to carry me toward salvation.
Satisfied that the worst is over I ease the throttles back.
The wind, which was light and slightly from the left just a few seconds ago is now raging and almost 90 degrees to my right. I contemplate going around but by now everything is once again back under control so I fight the wind down to the runway and instead of the greaser I was contemplating what seems like an hour ago settle for an inelegant, albeit it safe, thunk.
From start to finish the entire saga has lasted perhaps 15 seconds.
As I taxi in I report the wind shear to tower. I am strangely annoyed when they reply that they just noticed a wind shift and leave it at that. Even a quick "wind now 360 at 21 knots" while I was on final approach would have alerted me to the possibility of the wind shear that was waiting for me.
I've been fortunate enough to have encountered wind shear enough that I can recognize it when it happens. Usually it's benign, perhaps a five knot swing or so, and occurs on windy, gusty days so I'm already locked and loaded to deal with it.
What made this encounter so shocking was there was no warning, I just happened to arrive over the runway at the same time the wind was shifting more than 90 degrees. Three minutes earlier or later and I'm sure it would have been a totally unremarkable approach and landing.
After dropping my freight I fired back up and launched into moderate turbulence which lasted until 5,300 feet. Like a light switch the atmosphere was suddenly perfectly smooth again and stayed that way for the 45-minute trip back to Aberdeen on a beautiful spring evening.
The learning continues.
posted by Will at 2:34 PM
2 Comments:
I learn something new every time I read your posts. Keep up the good work.
I have a question regarding how you were set up when the sheer got you. You said you were at 17" and the implication is that props were somewhere less than full forward as you needed to go to full forward on the 15 knot drop in airspeed. In addition you were at full flaps. My question: do you normally go to full forward at some point prior to the landing? I'm just thinking of the "deer on the runway" scenario with full flaps and less than full RPM.
Thanks Sean.
Good question on the props. I tend to not bring them full forward until I'm below about 110 knots, usually around the last 100-200 feet.
If it's a gusty day or a low instrument approach I'll bring them full forward at the final approach fix.
But on nice days I leave them at cruise until just before touchdown. They create a heck of a racket and a high-rpm/low manifold pressure combination is tough on the engines, not to mention adding a fair bit of drag, so I like to wait until the airspeed is low enough that they're out of the governing range.
I've been re-thinking that approach a bit after Thursday's deal. :-)
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