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Down Draft / Wind Shear on Final

RV6_flyer

Well Known Member
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I consider myself an experienced pilot with more than 3,000 flight hours and over 1,600 Cross Country hours. I am a commercial rated pilot, built my RV, and have flown it over 16-year. I have over 2,700 RV hours.

Background: Airplane is RV-6, 160 HP, Constant Speed prop, VSO = 41 KTS, VX = 65 KTS, VY = 80 KTS
Normal pattern speed is 65 KTS, decent rate down final = 700 FPM

After a 2.6 hour cross country flight; I experienced an event that was a first for me after 32-years of flying.

ASOS reports Wind 200 @ 14 KTS with gusts to 23 KTS when 10 NM out.
Crossed over the airport and entered left pattern for landing on Runway 21. Update on the ASOS on the radio reports winds 19 with gusts to 29 KTS.

Flying a normal pattern (1,000 AGL TPA) and decent approach profile at a ¼ mile final and 300’ above the runway, I experienced a strong sink rate. Airspeed dropped to 60 KIAS and sink rate was 1,700 FPM. Full power was added and forward pressure used on the stick. The windshield is full of the hill / cliff at the approach end of the runway. Airspeed, Airspeed, Airspeed go through my mind. Full power slowed then arrested the sink rate but there was a slight delay as airspeed went up and I had a positive rate of climb. I am now over the numbers doing 80 KTS and 50 feet in the air. With lots of hours and experience in the airplane, I pulled power for landing. The runway is 3,898 feet long so the excess airspeed was judged not to be an issue. Power pulled to idle, airspeed reduced and a normal one small bounce 3-point tailwheel landing followed.

Shutting down the airplane, I am greeted by the airport fuel attended and welcomed to the airport. Telling him about my landing experience, he reported that the last three airplanes all did go abounds. One of the airplanes did three approaches before it landed.

When I get to the hotel, the landing event goes through my mind. I instinctively pushed forward on the stick when I wanted to go up. I knew that I needed airspeed to climb. Most people will pull back to go up. I was looking at flying straight into a hill or cliff but I needed airspeed. Pulling back would have decreased airspeed, put the aircraft on the backside of the power curve, and a possible stall may have occurred. Two-weeks earlier, my local EAA Chapter 45 had John G. Dye (no relation to Paul “Ironflight” Dye of NASA fame) of Bad Attitude, LLC give a talk about “Upset Recovery.” I remember him saying to start an upset recovery; they teach to Unload the aircraft.

I prefer to use my Superior Judgment to avoid situations that require the use of my Superior Pilot skills. I would like to think that I was required to use my Superior Pilot Skills in this situation. Looking back, I ask what could I have done different? Going around is first thing that comes to my mind. IF I were not so comfortable and familiar in the aircraft, I would have. I should have used higher approach airspeed to compensate for the head wind and the gust component.

Thought I would share this experience so that others may learn something.
 
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I recall reading about some sink rate events here.... I will leave the names out.
Your instinct to PUSH... not PULL is one that will keep you alive. Good job !
Being physically fit is the other key. When your heart rate goes sky high... you want to get tied down, visit the facilities and go eat. A heart attack would spoil all of that...
 
I think this is a perfect example of flying by feel instead of flying by rote. Your airplane speaks to you and you know what it needs without having to sort through logic first. This is what practice and intimacy with your airplane will get you.
 
Just curious, it looks like you said there was a hill/cliff on the approach end of the runway? Had you landed at this airport before? Which airport was it?

Airports like Catalina have warnings about this kind of thing happening when winds are high. I think somewhere I read that a longer landing helps to avoid this as the air doesn't start to sink until it goes over the cliff at the approach end. Maybe this would have been an option? RV's can have pretty steep decent angle on final, so if you had been aware of the situation, a high final and long landing might have helped ?

Thx
 
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Something similar happened to me back in 2009. My outcome wasn't as pretty, though. I was on short final, just crossed the fence at about 50 feet when I got hit by a windshear. That was the first (hopefully last) plane I ever destroyed. Thank God nobody was hurt, but it sure gave me a new respect for windshear.
 
I don't think you should beat yourself up about landing promtly.
I see it this way: Once you got thru the bad patch, and into the more protected air at the runway, you evaluated the situation and forged ahead.
Did you really want to go thru that final approach turbulence again?
Get-Down Itis can be a problem, but maybe your OODA loop runs fast enough.
 
Just curious, it looks like you said there was a hill/cliff on the approach end of the runway? Had you landed at this airport before? Which airport was it?

Airports like Catalina have warnings about this kind of thing happening when winds are high. I think somewhere I read that a longer landing helps to avoid this as the air doesn't start to sink until it goes over the cliff at the approach end. Maybe this would have been an option? RV's can have pretty steep decent angle on final, so if you had been aware of the situation, a high final and long landing might have helped ?

Thx


Borger, Texas. KBGD This is a typical RON stop for me when going coast to coast.

Have landed there maybe 20 times the past 16-years. 2nd time using RWY 21 and both were within last 30-days. Typically RWY 17 - 35 are what the winds favor.
 
Any landing where the aircraft is still usable afterwards is always a *Great* landing! ;)

I've got much fewer hours under my belt, but have experienced a few episodes of big sink on short final/flare before and the instinct to push the nose down and recover airspeed has saved my butt. Much better to be only a few feet AGL and still flying than... the... uh, alternative!
 
I'm not familiar with that runway Condor, but I would agree with you that I'd have kept a little higher approach speed to compensate for gusts, and planned to take it out once I had the runway made. The headwinds will give you more time over the runway to take it out, and you'll need a lot less pavement for your overall landing. Because of the effective extra length, I'd also shoot a steeper approach, or at least shifted my aim point away from the nasty cliff at the threshold - just because nasty cliffs and airplanes don't like each other. I don't ever give away runway length on take-off, but I'll land long when I know I have way more pavement than I need - if there is a reason.
 
Our airport has a drop off on one end too. With 14G20 down the runway, a downdraft near the end is a certainty. A steeper than normal approach and a bit more speed is the way to go.
Thanks for the reminder.
 
I'm not familiar with that runway Condor, but I would agree with you that I'd have kept a little higher approach speed to compensate for gusts, and planned to take it out once I had the runway made. The headwinds will give you more time over the runway to take it out, and you'll need a lot less pavement for your overall landing. Because of the effective extra length, I'd also shoot a steeper approach, or at least shifted my aim point away from the nasty cliff at the threshold - just because nasty cliffs and airplanes don't like each other. I don't ever give away runway length on take-off, but I'll land long when I know I have way more pavement than I need - if there is a reason.

Plus one for Paul's method/thought process.
 
You had two ASOS readings which gave you a five to ten knot increase in both the base speed and the gust speed. This information is always old, and depending on the system it can be as much as a trailing fifteen minutes. So you know the winds where getting worse, you did not mention the timestamp intervals so no progression can be estimated.

So with that stated, the winds were getting worse, and potentially quickly. Therefore my answer if you still wanted to do the approach would have been the following:
-- Increase speed by half of the gust factor; so 15 knots over 65 would have meant an approach speed of 80 knots.
-- 6% descent angle, assume no wind, would mean a descent rate of 800 FPM.
-- In a single engine airplane, chop power abeam the numbers and do a very short turn in and descent with power at idle.

Tim
 
It is situations such as this where having angle of attack guidance would be worth its weight in gold.
 
I once held off to allow a formation of 3 T6 harvards to land ahead of me. Quite a mistake in hindsight as I needed full power to make the threshold.

I have never had a cliff face approach but THANK YOU for posting. I can visualize the sinking air flowing off the runway. This will stay in the memory banks.
 
Condor,

I add half the steady-state wind speed PLUS all of the gust to my final approach speed.

So for example winds 15G30 would result in a 22.5 mph increase in vref.
 
If you're familiar with using Google Earth take a look at the elevation profile along the approach to that runway. The land surface at 1 mile out is about 220 feet lower than the threshold, and at 1/4 mile out its still about 150 feet lower. A big drop, practically guaranteed to produce a downdraft on a windy day.
 
Borger

Last time I flew into Borger, I was flying in my Cub and essentially gliding in, low on fuel. Two things I noticed about the area was that "giant" rocky chasm to the north of the airport and town (or that how it looked knowing I was low on fuel approaching the airport). The other was that 60,000' tall green thunderstorm to the west.

That was a sporty day for me, but I wonder if these two features might have been contributors to the sink you experienced. Any of those giant panhandle thunderstorms around? Wind must have been southerly as you landed to the south, so not sure how the wash/valley to the north would have interacted so significantly with the wind. (BTW, no downdraft in the Cub for me that day, and I landed in the perpetual 20+ mph southerly panhandle wind.)
 
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Just a thought, Add 1/2 the wind +all the Gust to approch speed

As a former a/l pilot we always added 1/2 half the wind + all the gust to our approch airspeed. Always seem to work.
 
Condor,

I add half the steady-state wind speed PLUS all of the gust to my final approach speed.

So for example winds 15G30 would result in a 22.5 mph increase in vref.

I like that version now after converting back to power flying from gliding and having a very bad landing when I used the "add 1/2 the gust factor" to the approach speed. :(

Desert winds and turbulence can give some unexpected situations.

Sedona is famous (infamous?) for crashes into the slopes at the end of their runways. A friend's son operated tourist flights there and was trained to aim for, and land, 1/3 the way down the runway when it was windy.

Given that headwinds shorten the landing distance needed this sounds much safer for windy desert locations than the usual "aim for the numbers" approach.
 
What was the weather, Micro burst from a cell above?

Again from desert gliding training, always land towards the storm cell in case it does turn into a microburst, even if it is presently a tailwind.

Only had to do it once, and it did work. :)
 
Sedona, AZ is another place to watch out for. A number of accidents have occurred under similar circumstances to the OP. Even our one way 1700' grass strip (land E, TO W) has a canyon off of the approach end that creates a significant down air + tail wind component when the wind is from the NW. It was never much of an issue with my RV-3A with a C/S prop knowing what to expect, but it's much more of an issue with my RV-12. Having an AOA in the 12 does help.

Years ago, Van even got surprised by it in his RV-4.
 
after a 5 hr x/c flight back from Laramie we were unable to land in Troutdale, OR. I was actually cleared to land from 5 miles out but the ceiling in the gorge went to zero. we turned around and landed at hood river. winds were 25 from the west, right down the runway. the east end of the runway has tall trees. my approach was high so I did a 360?. that worked fine. the turbulence on short final and wind shear had me with full stick forward, full power, maybe 50' AGL. way before I intended, we were on the ground. I realized i was focused on hitting the numbers. with that wind I didn't need even half the runway. talking with the locals I learned they all land long on those days. in 15 years of flying that was the closest I had ever come to crashing, 60 miles from home.
 
downdraft

Post number 15 is basically correct. However the surface wind speeds are in knots and the example used statute.
The starting point for calculation should be 1.25 x the stall speed in the configuration planned. Many add 5 or 10 knots to this under normal conditions. 10 knots allows for a 10 knot steady wind or a 5 knot gust. Any significant wind, 1/2 the steady wind plus all the gust factor is added, usually to a maximum of 20 knots additive.
There are two very different theories on downdrafts. The first is what Gary did, lower the nose and fly out of the downdraft. That works some of the time. The second theory, mostly for larger turbojet aircraft, is to SLOW ALL THE WAY TO THE STICK SHAKER, and fly on the edge of the stick shaker until the aircraft starts to climb. This procedure evolved from downburst accidents such as Dallas and JFK. I have flown these accident profiles in several aircraft simulators. The most memorable was the JFK profile in a Falcon 20. The airplane became nearly uncontrollable at 600' AGL and I abandoned the approach at that point.
In Garys case it is likely that the constant speed prop saved the day. I think with most fixed pitch props he might not have made the runway.
 
This can happen to anybody anywhere with the right, or better said wrong, weather conditions. It happened to me on on December 26, 2012 at St. Simons Island (KSSI) Georgia while landing a beautiful RV-9A. I too consider myself an experienced pilot (+25yrs) with more than 2,500hrs, over 1,000hrs of cross country Commercial rated SEL, MEL, IR pilot. Mine wasn't pretty either.

Background: Airplane RV-9A, 180Hp, Constant Speed Prop. I had completed my BFR in this airplane 12 days before the incident.

We were on short final after a 3hr flight from Bay Minette, AL and had just crossed the fence at about 50 feet when we got hit by a severe downdraft. I had just enough time to shove the throttle full forward when we were slammed to the ground about 80' short on the displaced runway and just 4" left of centerline. We slid straight down the runway for 400ft before skidding off to the left. The aircraft caught fire and we were barely able to get out before the fire engulfed the airplane completely destroying it. That was also my first (hopefully last) plane I ever destroyed.

Incredibly, we walked away with just very minor injuries but it sure gave me a new respect for the weather, wind shear and how incredibly well designed the RV-9A is.

:cool:
 
Wind must have been southerly as you landed to the south, so not sure how the wash/valley to the north would have interacted so significantly with the wind.

The surface wind flowing from the south would flow over the flat airport and then follow the topography downward into the wash. This is a common pattern on airports located on top of mesas (or next to canyons). If you're not careful you fly into the edge of the mesa rather than onto its top.

I'd certainly agree that other causes such as thunderstorms could also have been at play.
 
"...A steeper than normal approach and a bit more speed is the way to go..."

Actually, the prudent thing to do is probably delay your landing for a bit. It is not wise to mess with mother nature...and those "downdrafts" can EASILY exceed even the stellar performance of the RV series. Knowing the aircraft and having lots of experience is great but good judgement is better...
 
Sedona, AZ

Is famous for the dreaded sink on short final too. Some refer to it as the USS Sedona because it looks like an aircraft carrier, built on a mesa top. always fly the airplane they say!
 
Windshear. gust

I relate a short story to you... there was this Learjet flying an approach to a Southwest airport and there were thunderstorms all over the area and reports of turbulance... 4 miles behind him was a Delta flight... There was a small cell located on the localizer and the Lears speed was 170 knots indicated. They reported the ride was really rough but landed with out further incident. The Delta flight went through the same area at REF or 1.3 VSO...Tracking the localizer... Unfortunately they did not make it..All the power... all the downdraft... and 300 folks perished.

This flight started the big up tick in Microburst. Until this time most airlines just reported Severe or Extreme turbulance.. which is what most crews would associate with a Thunderstorm... If you have ever flown through one you'll agree..

But the microburst scene and Windshear on approaches were a thing to be studied.

In our little planes that are easily upset... let me relate this to you.

Your in a 18 foot boat along side the Queen Mary... Calm seas... all is good

Now you in 2 foot seas... your bouncing around and the Queen Mary is still sitting still..

Lets increase it to 8 foot seas.... your sunk.... the Queen Mary is just starting to rock a bit...

Sure were rated for 6 G's... and most airlines do not even make it to 2.0 G's.

but it takes a lot more to upset the BIG BOAT....

Take the Advice... 1/2 the wind.... All the gust... to your 1.3 VSO airspeed.
It will give make all your flight controls more effective...and your landing distance will not be any longer than in a calm wind day.

Go back to your private pilot handbook...
1.3 Vso is reserved for Short field landing. At the hypothetical 50 foot obstruction over the end of the runway.... not all the way down final... At the 50 foot point you start a flare slowly to the touchdown. There will be no float..
For what it is worth... my .02 C

Smilin' Jack
 
re: post #29

The wind shear accident mentioned in this post was
Delta at DFW, Aug 2, 1985. While there is a discrepancy in the total fatalities, the NTSB lists the total at 135. There were survivors.
While the Delta accident certainly intensified wind shear research, the actual start of wind shear research in the US followed to a large degree a much earlier accident, Eastern Airlines at JFK, June 24, 1975.
I can say with absolute certainty that wind shear measuring equipment was in use at Ft. Lauderdale in 1982, three years before the Delta accident.
I flew the JFK profile in a Flight Safety simulator in around 1980. This is the first wind shear training that I personally experienced.
 
:mad:Do not confuse "upset recovery" with a loss of airspeed due to wind shear. Upset or departure is defined as "I put in a control input, and the airplane doesn't do that." I.e. I roll right and nothing happens, or something else happens.

When they talk about "unload to recover", you're unloading to get AOA off the wing, and accelerate for airspeed and thus controllability. Assuming the ground is not a factor, if it is.... We're playing a different game and max performing the wing for lift.

Unloading on short final with a rapid loss of airspeed will get you killed. If you find yourself suddenly riding the elevator down, you should be max power and pitching for stall plus a few knots. You're not in an upset recovery, you're trying to get on top of the lift curve (and not beyond it) where you can minimize the rate of decent.

No airline on the planet teaches "unload" for windshear recovery. You push the throttle through the firewall, and squeeze every amount of lift you can from that wing.

PS, if you know the wind is gusting you should be adding a correction factor to your final approach speed and/or using less flaps.
 
You are correct. It was 1985 I tried to remember the date exactly but guessed. Sorry.
It was a friends Lear
ahead of the Delta flight. They had lots of talks with the NTSB and FAA

It really is not fair to talk about the technique used on Jets for windshear I don't think when compairing it to an RV. In the Jets were told to pitch to the shaker with all the throttle and let the computer take care of the power. There is a slight climb advantage in the jet. But i would if ever slamed by windshear in a light aircraft do basically the same ....power and pitch. And pray for the best.
Numerous public safety agencies responded to the crash, including the Dallas/Fort Worth Airport Department of Public Safety, the Texas Department of Public Safety, the Irving Fire Department, the Irving Police Department and all available third watch personnel from the Dallas Police Department's Northwest Patrol Division and the Northeastern Sector of the Fort Worth Police Department's Patrol Division.

After a long investigation, the National Transportation Safety Board deemed the cause of the crash to be attributable to pilot error (for decision to fly through a thunderstorm), combined with extreme weather phenomena associated with microburst-induced wind shear.[2][3]

The NTSB attributed the accident to lack of the ability to detect microbursts aboard aircraft – the radar equipment aboard aircraft at the time was unable to detect wind changes, only thunderstorms. After the investigation, NASA researchers at Langley Research Center modified a Boeing 737-200 as a testbed for an on-board Doppler weather radar. The resultant airborne wind shear detection and alert system was installed on many commercial airliners in the United States after the FAA mandated that all commercial aircraft must have on-board windshear detection systems.[4]

I believe the first windshear training I had was in 1992 at Flight Safety in our CE650. But of course yearly since then,


Jack
 
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GalinHdz
Sure glad you were able to exit the9A before the flames got too intense.
In a situation like that, it would be easy to twist the airframe enough to make it impossible to unlatch the canopy.
Not to mention a head strike that delayed the process of fleeing with haste n
Well done.. You were lucky.
 
:mad:Do not confuse "upset recovery" with a loss of airspeed due to wind shear. Upset or departure is defined as "I put in a control input, and the airplane doesn't do that." I.e. I roll right and nothing happens, or something else happens.

When they talk about "unload to recover", you're unloading to get AOA off the wing, and accelerate for airspeed and thus controllability. Assuming the ground is not a factor, if it is.... We're playing a different game and max performing the wing for lift.

Unloading on short final with a rapid loss of airspeed will get you killed. If you find yourself suddenly riding the elevator down, you should be max power and pitching for stall plus a few knots. You're not in an upset recovery, you're trying to get on top of the lift curve (and not beyond it) where you can minimize the rate of decent.

No airline on the planet teaches "unload" for windshear recovery. You push the throttle through the firewall, and squeeze every amount of lift you can from that wing.

PS, if you know the wind is gusting you should be adding a correction factor to your final approach speed and/or using less flaps.

In my earlier post about having an angle of attack indicator for guidance, I was too lazy to expand my explanation. You did a great job in explaining windshear recovery in relatively few words.

Regards,
 
You mention the winds, but nothing about the temperature/dewpoint spread. What was it if you recall? With the weather we've had in the midwest the last couple days there has been a pretty strong pressure gradient and spread in the temp/dewpoint. This is a combination that increases chances of windshear. Was there any virga in the area by chance?

Others have mentioned the increase to approach speed due to headwind component and gust factor, others have discussed the proper escape from windshear.

I'm not going to armchair QB because you had a safe outcome. However, there is something I would stress: Don't hesitate to go around. It's a natural reaction to just get the plane on the ground and be done with it but sometimes the safest thing to do is get back in the air and either wait for conditions to improve or go somewhere that has better conditions. This has become a large area of emphasis in the airline world because most of the recent accidents in our industry have involved unstable approaches, many with no adverse weather conditions.

When I was working on my ratings one of my instructors had extensive glider experience. He was by far the best instructor I had and his different perspective taught me a lot about reading the terrain and the clouds to anticipate where you would have rises and sink. With some practice it wasn't difficult to catch updrafts along the bluffs in a cherokee on a hot day and climb at idle power. Lots of fun.
 
GalinHdz
Sure glad you were able to exit the9A before the flames got too intense.
In a situation like that, it would be easy to twist the airframe enough to make it impossible to unlatch the canopy.
Not to mention a head strike that delayed the process of fleeing with haste n
Well done.. You were lucky.

I had a dislocated left index finger and, since I was in the right seat, it was VERY hard to unlock the slider canopy so we could get out. Yes, we were VERY lucky it didn't twist the airframe and we got out in time. Once we got out there was no way we were going anywhere near the airplane to try using the fire extinguisher.

:cool:
 
Well done Condor. If it was note worthy to you, it must have been quite an event.
Our home field is 2000' long with serious trees on both ends as well as tree's in our community park which sit on the south east end of the field beside the first 400' of that approach end. Those trees are well over 100' tall.
The preferred landing is to the east even with some tailwind. The tree's are set back a little farther. The west landing forces you to make a very steep approach to clear the tree's. If the wind is out of the southwest, you have to deal with the burble off of the park trees as well.
The runway is not long enough to land long to avoid the park tree burble unless the wind is really up and into you. It is also slightly down hill.

Recently, one of our friends got bit by this. The "bottom fell out" on him causing a hard landing in his RV7, bent gear, prop strike, etc.... Six months of hard work and I escorted him on his first flight a couple weeks ago. He got back on the horse and is doing fine.

Point being, you don't need gusty conditions to produce this kind of event and there are many airports with hangars, trees, and other obstacles that can cause this same effect.
 
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