Downwind turns demystified.

[Birdy2]

Yes, i know, its a badly flogged horse, but theres sumthn that is dangerous bout turning downwind, specialy at low altitudes.
A good friend of mine who is new to gyros, [and flyn generaly] has found out the hard way that there IS a danger. He's got a compleatly totaled machine to prove it. [ with the only things salvageable be'n the 912 and the stick grip.] But, thank whoever you like, he didnt get a single scratch. :yes:
He has just over 100 hours in a machine i'd describe as a perfect mustering machine, a real pochet rocket. Single open machine with 26' extru blades and a trusty 912. Perfect. He's wot sum people call gifted wen it came to flyn, coz he 'clicked' so early in his flyn time, with beautifuly smooth exicution of every manouver he did, and was careful and precise.
So, why did this bloke smash this machine while do'n nuthn but a routine turn?
To put it simply, he chose the wrong time to turn down wind.
His mistake wasnt coz he was incompitant, complacent or reckless. It was coz he turned downwind INTO A STRONG WIND SHEAR. [ this machine could climb at better than 1800 fpm.]
This air he hit was decending fast, at less than 200' alt and as it neared the ground, it accelerated in the same direction he was traveling, downwind. So the further he flew into it, the stronger the virtical component became, AND the stronger the tail wind got till he reached the point where he had no AS, No lift and no alt, no options, but he had a dangerously high ground speed. A ground speed that ment that if there was contact, it was over. If you touch the ground at this point you have very little control over wot happens next, coz if the power is still on, you wont slow down, but if you chop power, you have no rudder authority, and the rotors, with the strong tail wind, will be next to usless in as far as keeping you upright goes. This is a pretty scarey picture. Scootn along at probably 60 odd kmh with next to no directional control. Itd be scarey in the middle of an airstrip, but its happened to me plenty of times in tall timber country, which is where it happened to this bloke.
Theres nuthn any training, machine modification, or warning devise could have done to prevent this from happening. Coz it was caused by ignorance It would have happened to anyone, in any aircraft in the same situation if they didnt know bout these gremlins. The only thing that 'could' have had sum bearing on a better outcome would have been if id told him bout these f^%$# invisable gremlins.
I dont know if its fate or sumthn, but as i drove home from my own mustern job [ after striken a few of these little basterds] i remember thinkn to meself, 'id better ring ol mate tnite and hava yarn bout these before he hits one.'
Too late of course coz wen i got home, Liz said ### just rang, and he's got bad news. :(

I wont say any more bout this incident but to say he contacted the ground, so ill leave the rest to your imagination. [ and no, i wont mention his name :omfg:]


So, to those who recon theres no difference between up and down wind turns, watch your step.
Your rite, to a point.
If you keep a constant AS, bank angle and power setting, AND THE WIND IS ALSO CONSTANT AND HORISONTAL, then yes, there is no difference.
But wen mum nature recons you need a wakeup, you'll certainly be woken up.
If you know wot to do, your likely to get out of it, but if your ignorant to wot nature is capable of, then youll get caught every time.


Iv said it before and ill say it again, how many accidents happen wen the craft turned upwind?

[Gyrodes]

Birdy, Thanks for posting that and sorry about the old mates machine, good to hear he is not hurt and can tell ya what happened.
Des Garvin

[SamL]

I hope it wasn't the light blue Rosco we all saw at the Nationals Birdy :nervious:
As long as it was only the machine that broke, then thats fine. ( I guess :'( )

Sam.

[Brian]

I'm really sorry to hear that Birdy, of course, the old timers will tell you that the 50 & 100 hours are real danger times. Why, ?? a bit like what happens when you pick the wrong time to turn downwind!! The text books will tell you that it DOESN'T MATTER WHICH WAY YOU TURN BECAUSE ITS ALL THE FLAMIN SAME. No, its not all the same and Birdy has just described the whole event with beautiful articulation.

I'm really pleased to hear ****** walked away okay!!!!!

I have been a bit like you Birdy, struck a few of these 'gremilins' from time to time , scraped my backside along the paddock doing what feels like a million miles an hour, using every bit of ability/ nous/ whatever and every time you mentioned it happened when you turned downwind, you get howled down by the so called experts [DRIPS UNDER EXTREME PRESSURE ] who haven't encountered the conditions described by Birdy. I reckon you ought to right a book Birdy, would be a best seller !! :yes:

[Birdy2]

A book ????
Bloodyell, it took me 4 hours to rite that one post mate, i dont recon id live long enuff to rite a book. Besides, wot would i put init :blahblah: :bored: :chuckel:

[bones]

A book ????
Besides, wot would i put init :blahblah: :bored: :chuckel:


Actually this is fairly well off topic, but i think if we all get together and sent a few stories of things that have hapened, and seen, it would make a real good read, damn i got near a full chapter from just one visit to the NT, more to come next year i'm sure.

[ken watson]

I think the names say it all.....DOWNwind.......UPwind. Goin down, climbing up. Have hit that fast wind that feels like a lull, ground coming up fast and going past fast and max power doesnt do much. I think the fact that your balls are rising up through your neck eventually helps the machine climb. The tail wind also makes a coarse pitched prop cavitate and so response seems slower. Ken

[Brian]

A book ????
Bloodyell, it took me 4 hours to rite that one post mate, i dont recon id live long enuff to rite a book. Besides, wot would i put init :blahblah: :bored: :chuckel:


Yep, 4 hours to the page, its not going to be quick but it would be a 'must read!! It wouldnt matter what you wrote about, just the way you say stuff is enjoyable to read or listen too.

[gbw]

"If you know wot to do, your likely to get out of it, but if your ignorant to wot nature is capable of, then youll get caught every time."

Birdy,

So what do you do? Turn back down wind, full throttle and stick just slighty back? Bounce off grass tussocks?
Your mate must have done something right to come out OK. Glad that he did.

Graham

[Birdy2]

Was wundern if anyone was go'n to ask that Graham. :yes:
It all depends on the depth of the sh1t your in once you realise your init, and your 'familuarity' of the machine's capabilities.
If you are well aquainted with the machine, and your own ability, then you shouldnt fly DW any lower than an alt that you KNOW you can safly do a quick 180* turn, WITHOUT power before you hit the ground with the AS your at.
This alt min will give you room to manuver if you hit one of these gremlins, and the 'engine out' part of it will simulate pretty closely the effect of hitn one. IOW, if you dont recon your high enuf to chop power and turn bac into the wind, your too low. Itll differ between machine typs and pilot skill levels, but its the bare min you should fly DW.
Sumthn like the ferel has consistantly turned 180* DW without power from 50' easly for years, but sumthn as hardmouthed as a Magni would JUST make it from 200', if your ready for it.
If your puttn along at your min DW alt and you feel it starting to drop, start turning immeadiately while you have room, if it turns out to be just one of them little holes, you have nuthn to fear, you just streighten out and fly off. But if is one of these bursts, then your ready for it and have already taken action to avoid it.
If, however, you find yourself too low by the time you realise in the sh1t, then all you can do is hold the throttle full open, and keep the machine JUST off the ground WITH THE STICK and hope like hell your machine has the power to fly out. Any attempt to hold alt will only deepn the sh1t level coz all your do'n is traden AS for alt, and in this situation , AS is better than alt. And, wen your JUST off the ground, you only have to contend with the increasing tail wind component, coz at ground level, the air cant go any lower, so theres no down draft component.
Also, tryn to turn out of it would have a very low success rate, coz you could well be turning into a stronger tail wind, deepening the sh1t, and any deviation from streight will cost you AS and alt, 2 things you wont have any of to spare.
At NO time do you stop flyn, coz the machine will happily crash if you let it.
If you dont have the power to stay off the ground, and you make contact, chop the throttle and try your best to hold it streight with rudder AND stick, and again, hope like hell.
OL mate survived without a scratch coz, even wen he knew he was dusted, he still TRYED to keep it upright. IOW, he was still 'flyn' it after the rotors took off, and the machine was in pices. Soon's the movement and noise stopped, he unbuckled and got out of wot was left of the machine.

The best defence against these basterds is to stay well above YOUR/YOUR MACHINE'S danger zone.

Note; im no expert at this sorta thing, so dont take this post as gospel. Its only the observations iv gained after bout 3000 hours of mustern with these hazards.

[gbw]

"Note; im no expert at this sorta thing,"

I think you are a bit experterer than me!!

Thanks for that. All that typing your finger must be near wore out...

Graham

[Brian]

"Note; im no expert at this sorta thing,"

I think you are a bit experterer than me!!

Thanks for that. All that typing your finger must be near wore out...

Graham


Not a truer word said, the lad can fly and he's a lot smarter than the average. :raving: :raving: :hug:


Graham, the severity of these downers or microbursts, whatever you want to call them, vary greatly, however, Birdy has said it well.
As your experience grows, you will find you can 'feel' the gyro telling you that the conditions exist as you start the turn and if you're smart, you will heed the warning.

[Mitch]

Sorry to hear about ole Mate........ Birdy send him my best wishes.

Brian, Mate clean up that avitar, who are those blokes hugging :hug: :hug:

Mitch.

[Brian]

Brian, Mate clean up that avitar, who are those blokes hugging :hug: :hug:

Mitch.


Not sure brother ::) :wave: not sure why it went blurry , got to give it another go. :chuckel: Think it was someone I met up with at easter. :blowme:

[Gyrodes]

Better leave it as is or Mitch might not like it. Des Garvin

[hatrack]

Birdy. Great speil. Down to earth, (sorry!), but informative. Great stuff for us low hour newbies. We dont know these rarer situations well because we just havent encountered them yet. I havent had any bad experiences yet but respect Mother Nature and am aware of what can happen from armchair piloting with Gyronews, ASRA website, and this forum. I practice DW turns in circuit, on downwind leg as engine outs, to taste the bitch. It's no use practicing emergency landings in perfect conditions only. Am always doing DW touch and go's too. Mate, you could have a regular post focusing on specific experiences to pass on to us newer guys. That way we might become better equipped without learning the hard way.
Cheers, Hatrack.

[Brian]

Birdy. Great speil. Down to earth, (sorry!), but informative. Great stuff for us low hour newbies. We dont know these rarer situations well because we just havent encountered them yet. I havent had any bad experiences yet but respect Mother Nature and am aware of what can happen from armchair piloting with Gyronews, ASRA website, and this forum. I practice DW turns in circuit, on downwind leg as engine outs, to taste the bitch. It's no use practicing emergency landings in perfect conditions only. Am always doing DW touch and go's too. Mate, you could have a regular post focusing on specific experiences to pass on to us newer guys. That way we might become better equipped without learning the hard way.
Cheers, Hatrack.



It is very informative as gyros tend to be flown low and sometimes /usually, fairly aggressively leading to an opening there when turning downwind. You may fly for years before finding a real pearler that catches you unawares.

[russ]

He's wot sum people call gifted wen it came to flyn, coz he 'clicked' so early in his flyn time, with beautifuly smooth exicution of every manouver he did, and was careful and precise.


From readin this, it then followed you was hands on with this guy........ie training.

Ok........so you were'nt, at any stage. My mistake, my opologies.

[ back under me rock ]

[Birdy2]

Apology accepted russ.:D
So, do you still want me to pass your critisisms of the method of instruction to the lads CFI?:beer:
Afterall, it was his instruction that failed him, init?:bored:

[oh, sorry, it would only apply if i was his instructer................ yeh rite, moron.]:rolleyes:

[SamL]

Glad to see you 2 blocks are finally making up.
One final comment, as usual.
"There is nothing to fear from down wind turns, as its your machines airspeed that keeps you flying, not the horizontal wind direction. What can, and will catch you out is vertical wind direction.
But, again it has nothing to do with flying upwind, or down wind, and it makes no difference to the machine, as it dosn't know the difference. :D

Regards SamL....

[Gyrodes]

Ah Sam you are treading on quicksand there using words like you did in the opening sentence above:Bat1::cheers: Des

[Drifter]

"There is nothing to fear from down wind turns, as its your machines airspeed that keeps you flying, not the horizontal wind direction. What can, and will catch you out is vertical wind direction.
But, again it has nothing to do with flying upwind, or down wind, and it makes no difference to the machine, as it dosn't know the difference.

Except that the closer to the ground you are the more likely you will be influenced by ground reference and thats where pilots have come unstuck.

[bones]

Orrrrrrr frig here we go again, :censored::chainsaw::Bat1::anger:

[Brian]

Sam is correct, however there can be other factors that come into play.

Down low is an entirely different ball game to 500 or 1000 ft or higher. Even at 20 ft AGL, there are days when you can turn anyway you want without a drama, then there are those odd times when you can feel all is not well when going to do that 'downwind turn'.

I got to say that at low level, downwind is where you strike the most problems, I have very rarely fought to gain altitude into any breeze where as I have some very vivid memory of scooting downwind at ground level with climb power and 40 knots on the ASI knowing that any turn will put me into the ground.

Its an interesting topic and one that causes much huffing and puffing by the text book experts and can cause many days of argument.
It was particularly interesting when Birdy started this same subject on the US forum, that it raised no controversy.

I tend to go with the hight theory as I never experienced in a FW, the same reaction as I have found in a gyro and in the FW, I tended to muster around 300 to 500 feet and found I had little problems except in days when it got windy and even a small angle of bank turn was extremely interesting and could well need lots of aileron and rudder controll,

[Birdy2]

But, again it has nothing to do with flying upwind, or down wind, and it makes no difference to the machine, as it dosn't know the difference.
Sam, mate, your missn the point.
Of course the machine dont know wether its turn'n up or down wind. To the machine, it just turned into a downer, thats it.
The st1t only hits the fan IF you make contact with the ground.
Like i said, it dont matter if you turned up into a downer, coz your ground speed will be zilch and if you get overpowered, you just land with buggerall GS.
Its a different critter wen the wind is up your clacker tho init.

There is another gremlime at the 10-20' level that can catch the unwary, [wind or no wind]but you never need to wurry bout it, coz its generaly not a hazard to you blokes.

[SamL]

Fellers, I 2 have experienced what you are taking about. (In Trikes and Gyros')
"Airspeed is Airspeed" and flying in horizontal winds, (upwind or down) wont make a hoot to your machines.
BUT, If you enter a body of desending air, then you 2 will desend in it. This air is what I'am calling vertical winds, and they come in the form of standing waves, rotors, ground effect, thermals, wind shear, and many other names. If that air is already desending then you 2 will desend even if you push out to 80 Knots. Its known as vectors.
It gets interesting because the ground speed is much much higher, airspeed is usually increased to counter it. Also your climb is just not what you would usually get, and use to.
All because of that body of desending air. The exact same thing can (if conditions are right) happen up wind.
I use a VSI on my gyro and have had my machine flying at 3000 ft, pushing 60 knots and desending at 800ft per min+. I have also flown my old trike heading cross wind, down a creek line on a 15knot day. I was unable to climb out 2 up,(with my mate Alf(also a pilot)) as the rotors comming off the 50 meter bank were holding me down. But once the creek turned down wind, and I finally got far enough away from that bank, then up I popped climbing at 500 ft per minute (down wind).
What all this means is we should all think twice about flying low on windy thermally days, especially if there are trees, hills, mountains around.

Thats probably more that 2 cents.:mrhappy
But hopefully it helps clear things up for some of our more junior pilots.
Regards SamL......

[Mitch]

G'Day Gents,

This is a good thread.

Sam, very well articulated and relating your experiences along with the 'Mustering Pilots' really paints a picture.

"What all this means is we should all think twice about flying low on windy thermally days, especially if there are trees, hills, mountains around."

The caution you gave is well received by this low hrs pilot.:D

Birdy,

Don't do it Mate!.....get the Gremlin out there....

."There is another gremlime:confused: (What's a grem lime?):D at the 10-20' level that can catch the unwary,( I'm unwary:o) [wind or no wind]but you never need to wurry bout it, (when someone tells me I don't "Never" need to worry, I worry!)F:censored:K! coz its generaly not a hazard to you blokes." (Generally not a hazard! It's a Gremlin! :eek::Bat1::beer::D )

Spit it out Mate, tell us about the Gremlin:blink:

Cheers,

Mitch

[Birdy2]

"Airspeed is Airspeed" and flying in horizontal winds, (upwind or down) wont make a hoot to your machines.
Sam, i know.
I think everyone knows.
If you never touched the stick or throttle, youll be follown the air.
IOW, if its blown from behind you, your GS will increase, in frunt itll decrease, from above [down draft] youll go down and from under you, youll go up. Thats all logical.
We can cancel all these little bumps if we want to, with the stick n power, to a point. Its wen you hit a strong wind and your machine's highest performace rate is less than the wind, your go'n to go which ever way the wind is blown. Same with wind from any direction.
But its the wind thats go'n down that tends to bend machines, coz sumtimes you dont have the power to counter the strength of the downer, and you hit the ground, and this WILL generaly bend things if you have substantial GS. Ie; a tail wind.

Virticaly decending wind will only go down to ground level, at which time it has to 'fan out' like an upsidedown mushroom. If you happen to be over powered by the strength of the downer to the point that it takes you down to ground level, your in abit of trouble.
If you happen to get to ground level where the air mass is spreadn AWAY from you, your in real trouble, coz not only did the downer overpower you, you will have a rapidly increaseing tail wind component to deal with as well, which you cant coz youv already been overpowered.
These little gems BTW, can happen wether its windy or not, coz we're talkn bout thermaly powered wind.
The most dangerous time to be flyn low is on a hot still day over flat country with no thermal triggers.
This situation gives the most power to thermal activity coz the air stratifies and builds up masses of energy, and wen sumthn does trigger a thermal, like a mob of cattle moven off, or a car driven under you, then all that stored heat takes off real quick in a concentrated columb.
And we all know that wot goes up must come down.
If air is riseing rapidly, then air surrounding it must decend rapidly to replace it.

Ground speed has nuthn to do with the hazard level, till you hit it.
0 GS= no damage [ headwind]
high GS= big mess. [tail wind]
Simple.

What all this means is we should all think twice about flying low on windy thermally days, especially if there are trees, hills, mountains around.
Or to put it more simply, dont fly past YOUR/ your machine's limits.


"What all this means is we should all think twice about flying low on windy thermally days, especially if there are trees, hills, mountains around."
Mitch, while mountains on windy days can get kinda rough, they aint anywhere near as scary as flat country ona hot day.
Wind in mountains is predictable. After a while you can 'see' wot the air is do'n coz you can see the things that will cause turbulance, rolls, shears n stuff.
On a hot still day you cant 'see' jack sh1t, coz the triggers aint as obvious, and can change from one hour to the next. But you know theres plenty of stored thermal energy buildn up down there just waitn to scare the crap outa you.:D

Don't do it Mate!.....get the Gremlin out there....
Nuthn unusual, just anatha 'hole' youll find down low.
Again, you will find um on any day, cept strong wind days, and are strongest on still days over 'green inland' country.
And the holes are BIG.
Ona hot still day, the air below 20' can get very thin.
Above 20' it can be more than 20c cooler and dryer than ground level. This hotter low air, coupled with the humidity from the green vegitation at ground level mean the DA is significantly higher down there than it is at 20', meaning wen you drop low enuff to get into it and your AS was at cruise or lower, you can quickly find yourself dropn like a rock and behind the curve.
But again, it only gets real messy if your go'n DW and you contact the deck.

[Mitch]

G'Day Fellas,

Just come home from the better part of the day at Cranbourne airfield.
My gyro is hangered there now and ready to go next time out.

Elise and Jillian (Airfield owner) helped strap up the blades (Patroney's) and fit to the rotor head. The blades are heavy but they so much better than the Bensen's. This is the first time in over two years since I flew off Cranbourne, having only recently re-soled at Lameroo.

Interestingly, after setting up and doing the 'mother' of all pre-flights, I asked Jillian, what she thought the wind was blowing at...gusting 15-25 knots. I spin the blades up, (Elise was not there, gone to Launie, soon to return) took to the air and flew a circuit, landed, touch and go and off to the training area for some low level comparisons with Lameroo.

I had felt that southerly gusting about in the circuit. It was not comming over the Mt's, so It was was no problem, until.....low in the training area where off to my right a large stand of thick forrested Gum. The wind was comming at 90 degrees, spilling off the trees and causing a good deal of turbulance. I did a down wind turn at 100 feet, kept the power on nose up a little, wow! I was scooting along . Had 50 knots IAS but with that 20 knots up me date...whoosh!! I think I lost 10 feet in the turn.

This was my first real experience in blowy conditions. I dived down to 20 feet off the deck and flew S & L for a while but was not experiencing the same level of comfort I was having at Lameroo Sunday afternoon. Jillian's cattle dead ahead so back on the stick and wop, wop, wop, Butterfly popped up to 300 ft and I joined the circuit at 500.

Much better away from the tall green stuff and Mts today. Blustery but bloody beautiful.

Lameroo with it's wind and wide open paddocks, was a very different experience than today, with Mts and small paddocks, powerlines and roads, fences everywhere, dams and creeks BUT....I had geese and ducks for company and spoted one Tassy WedgeTail (endangered species) off in the distance. Nil aircraft. I reckon the Patroney's are the 'duck's nuts'. If the AK's ( Jeff Henley-Smith's) are anything like them then I understand why many of the boys recommend them too.

There was a Lightwing that had a bad landing yesterday (crashed) and sustained about $10,000 worth of damage.

My gyro is hangered along with one other and the bloke is a Pilot and has a gyro...how about that.

Thanks to all you blokes for discussing this topic.
Revision is priority on my list and I'll be keeping an eye open for any sneeky Gremlins or other nasties.

I enjoyed flying my gyro today because of you blokes who contribute to this and other forums...Thanks Fellas.

Oh yeah, I got my Dr to give me the OK to fly and I had no trouble tapping the blades up myself, (mainly because I had 20 knots blowing thru them before I even got going) and kept the disk tilted into the wind whilst taxiing 45 mtrs to the club house. Did the smart thing and let them wind down almost all the way, before reaching up and helping them stop.
So the thread on blade management came in very handy too.

Gyros....to much fun to be legal!

Mitch:cheers:

[Birdy2]

:d :d :d ;)

[bones]

So that be why you wouldnt answer your phone today you low down mungrel you wer out flying ayy
Good on ya does it fel good :confused: :anger:
Good for you matey

[Mitch]

Sorry Bones,

I hope ringing you back last night, left you less angry:anger: and confused :confused:.

Thank Peg for sending thru the news letter. I'll ring you after I have a good read. Elise thanks you for not talking all night.:D

Hope your :cool:Xenon gets here this week.:cheers:

Birdy what is (:d) ......ditto ? Dunno:confused:
Gonna ring ole Mate today and find out how he is. Shame he didn't get to chill out at Indiana for a while.:(


Mitch

[vicgrin]

Hi Birdy
Just to go back a bit you said if you are well aquainted with the machine, and your own ability, then you shouldnt fly DW any lower than an alt that you KNOW you can safly do a quick 180* turn, WITHOUT power before you hit the ground with the AS your at.
Without power, why without power ???????

[Fencing Wire]

Hi Birdy
Just to go back a bit you said if you are well aquainted with the machine, and your own ability, then you shouldnt fly DW any lower than an alt that you KNOW you can safly do a quick 180* turn, WITHOUT power before you hit the ground with the AS your at.
Without power, why without power ???????

Not presuming to answer for Birdy, but if the donk goes quiet, then you've got no power. And you should always fly as if the donk is gunna go quiet at any second. Consequently, if you are flying DW, you need to have enuff altitude to be able to turn into the wind to land if the donk quits. :blahblah::blahblah::blahblah:

Donks and women are at their most dangerous when they are quiet. :beer:

[Birdy2]

Close FW:D

Vicgrin, noone should ever fly anywhere, up,down or xwind, at an alt lower than they can comfortably land if the woman/noise stops.
If your flyn DW, then you gota give yourself room to be able to turn 180* so you land into wind.

But my referance to it in the instance you gave above was to give an indication of how fast you can drop if you hit one of these things with WOT.
Obviously if you hit one, and your dropn like a rock, your throttle will be wide open as you turn back into wind.
If you simulate the turn in calm air, with the power off, the decent rate will be similar to a 180 with WOT wen in a burst, so it will give you an indication of your/your machine's min alt while flyn DW.

Birdy what is (:d) ......ditto ? Dunno
Buggered if i know Mitch, i pressed 3 of them green smily thingys and got 3 (:d) ?????
Im haven abito trouble with this new setup.:mad:

[vicgrin]

Ok, I was thinking that in all instances like you discribed you had to do your turns with out power.
exuse my ignorance but WOT is with out throtle?

[marko66]

Hi Vicgrin

I'm pretty sure that WOT is usually meant to mean WIDE OPEN THROTTLE a thing I really hate :D :mrhappy damn i wish the 308 was running well it brings back memories, will have to fire the bike up tommorrow and see what WOT means again :cool: :D

Regards Mark

[Birdy2]

Sorry Vic, yeh, WOT=wide open throttle.

[mceagle]

THE FOLLOWING FROM THE US FORUM, MAKES FOR INTERESTING READING FOR THOSE THAT ARE INTERESTED.

For a gyro that flies low (10-30 meters) above trees during strong wind conditions, it is not out of the question to expect a wind gradient of 5 mph between the rotor and the airframe. This wind gradient is fairly consistent in this alt range, so bobbing up and down does not take you out of the gradient.
The upwind-to-downwind turn under gradient conditions is a little more difficult to understand so I will start with the steady state conditions of upwind flight vs. downwind flight.
Mark said: “Also the flying down wind thing needing more throttle is back on again to, dont know why but it does, about 300 rpm more”
This is not the first time people have reported needing more power when flying downwind vs. upwind.
Due to the wind gradient, when flying upwind, the rotor apparent headwind is higher than the indicated airspeed. But when flying downwind, the rotor apparent headwind is lower than the indicated airspeed.
When flying in the 40-60 mph range, rotor drag goes down with airspeed. IOW, a rotor has less drag at 50 mph than at 40 mph. So, even though the pilot THINKS he is flying at 45 mph, the rotor is actually flying at a different airspeed. This explains very nicely Marks observation that he needed 300 more RPM flying downwind than flying upwind.

Back to the upwind-to-downwind turn discussion. This is a little more difficult to visualize because the gyro doesn't really fly in a "big mass of moving air", like we always like to explain in this kind of discussions. The gyro is flying in layers of moving air. Look at the picture below again. The top gyro, flying at 45 mph and with the rotor flying at 50 mph, is now going to make a 180 degree turn and still fly at 45 mph, BUT, the rotor is now transitioning from a 50 mph headwind to a 40 mph headwind. This is like being hit from the back by a gust of wind that takes away 10 mph from your airspeed. What's going to happen? The gyro is sinking until the pilot has a chance to increase power and pull back on the stick to transition to the new and less efficient rotor airspeed.

That is the whole explanation. I will post a chart that shows the wind gradient over trees and over open planes. Trees create a very significant friction with the wind and that makes for a very significant wind gradient in the first 10-40 meters (depending on wind intensity).
There is one more aspect to flying in a steep wind gradient that I haven’t mentioned above. When flying upwind, a gyro has a better climb rate than normal because you are constantly climbing into layers of faster head winds. You are getting free energy, if you will.
The opposite is true for flying downwind. When climbing downwind, you are constantly flying into layers of higher BACK winds. This requires much more power to climb than normally because the gyro has to accelerate all the time, in addition to climbing.

This has nothing to do with the downwind turn discussion per-se, but it adds to the pilot’s perception of having more power available flying upwind than downwind. It is harder to make up for lost altitude when flying in a downwind gradient.

Dr. Barry Gardiner of the UK Forestry Commission did a lot of research in the field of atmospheric science. http://www.bwea.com/pdf/trees/Barry_Gardiner.pdf
(actually a presentation) gives the information we need for this discussion. This is a very interesting reading but if you want to go straight to the most relevant data go to page 30. The graphs on page 30 show the boundary layer and wind profiles over trees and open spaces. As you can see, the wind gradient over trees is greatest in the boundary layer between 10 and 30 meters. The exact shape of the boundary layer depends on many factors but, in general, a stronger wind would result in a thicker (taller) boundary layer. This graph shows that a 5 mph gradient over 2 meters is not out of the question but regardless of the numbers the existence of this phenomenon cannot be disputed.
Udi

[Birdy2]

Where did ya find that Tim, i been tryn to say that for ages.:)
Ol Udi is alot better with the inglish lingo n ill ever be.:D

[mceagle]

Yes, Udi certainly has a way of putting things.
Those that have worked stock in windy conditions have always known that there is a difference in up-wind and down-wind flying conditions, and these are often blokes with thousands of hours who DO know how to fly, despite what some of their "peers" say.
We all know that we are flying in a moving mass of air but we cannot ignore the fact that low level turbulance and wind shear is mostly ground related and does not flow along with the mass of air that the gyro is flying in. As such we are affected by ground related features whether we like it or not, especially if you are at stock working height.

[Birdy2]

"As such we are affected by ground related features whether we like it or not, "
Yup, and its this that causes others to assume any incident is caused by 'ground referencing'.
two vastly different things.
Ones pilot error, the other is a phisical reality.

Mind you, it wasnt this that brung ol mate down.

[Brian]

Its great to see some really great stuff coming out and explaining some conditions that can sometimes exist down low [under 300 ft AGL]

While most gyros dont fly that low, some attempt it, some get away with it, then there are some that go anywhere from changing the pants scare to a flat out body slam.

There was a very good article I think in the Pacific Flyer that explained "a climbing downwind turn " a few years ago, I would like to see this article re printed in the gyro news as it would help most pilots understand the difference between down wind and up wind flying a whole lot better as it was a very well explained article.

In the crash comics, it now has been proved that wind shear was the cause of air liners smacking the runway when playing cat and mouse with thunderstorms when a headwind of say 20 knots goes to a tailwind of similar speed at low level and even jets have not been able to power their way out of a 40 knot change of wind direction.

[Drifter]

Yup, and its this that causes others to assume any incident is caused by 'ground referencing'.


Trouble is, its very hard to refute, the statistics held by the ASTB which suggest that the majority of incidents incurred by aircraft ( not just gyros) who have come unstuck after turning downwind. Those surviving pilots have all indicated that their actions or lack of action, where influenced by and large by ground reference. They tended not to believe their instruments.

[Birdy2]

Drifter, for a start, most mustern pilots never look at instruments.
And i wouldnt be suprised if most GA and rec DW incidents would be coz of pilot error[ ground referancing]. Mainly coz low alt is sumthn they aint accustmed to, cept wen they are on a streight landing approach, into wind. Flyn low DW is a little unnerving coz they can 'see' how fast they are go'n.
But wen you live down ere, its as common as walkn.
Only the pilot knows wot happened, and he's only fooln himself if he made a boo boo but blamed sumthn else.

But your rite, who's ever heard of a plane crashn coz he turned upwind?
Generaly, if your headn upwind and you contact the deck, its like a normal landn, and usualy no one gets hurt cept maybe the AC, and unless sumone dies, itll never make the news.

[Drifter]

Its a shame this topic had drifted off the original intent. Perhaps in hindsight there should have been a separate topics dealing with either flight at very low levels, or flight conditions in convective air.

I am currently trying to put together a series of articles from material gained from the net which describes low level flight conditions, but mostly they are poorly described or have ineffective graphics.

[Gyrodes]

Brian,
Start diggin mate and find it so we can all share this knowledge. May just save some unaware pilot one day.

There was a very good article I think in the Pacific Flyer that explained "a climbing downwind turn " a few years ago, I would like to see this article re printed in the gyro news as it would help most pilots understand the difference between down wind and up wind flying a whole lot better as it was a very well explained article.

Just send it to Art, he will buy you a beer for it:D:cheers:

There yuz are something different :confused:Cheers Des

[Birdy2]

"Its a shame this topic had drifted off the original intent."
????????
It did get drifted, by Russ, but its still on topic now. We are still talkn bout DW turns n low level stuff.

[Drifter]

Birdy the topic is Downwind turns demysterfied... Yet we have expressed a number of views on the convectional effects, early thermal cells, trapped layers etc.... which is clearly beyond the topic header.

[Birdy2]

I know, but people gota understand that its the ;convectional effects, early thermal cells, trapped layers etc... That make the difference between a regular no brainer DW turn [ generaly at higher alts] and one thatll have you tastn your ass.
In constant low level or higher alt gusty winds, it dont make a difference which way the wind is blown, coz if you hit a strong downer, so wut, your way off the ground and its nuthn to ride it out.
Its only the virtical component at low level, coupled with a tail wind that makes things risky. Not coz of the tail wind per say, but the fact that if you DO happen to touch the ground, its guna hurt more if your traveln DW than UW.
The ' Downwind turns demystified.' was an attempt to seperate the facts from the common gospel truths.
I was tryn to educate WHY sum people do get caught out, and its nuthn to do with ground referancing.[ as is commonly believed]

If you recon this thread is a wast of compooter space, then ignor it.

and i wont bother anyone bout it agin.

[Fencing Wire]

If you recon this thread is a wast of compooter space, then ignor it.

and i wont bother anyone bout it agin.

Dave,
Any day you learn sumthin, its a good day (specially if it don't kill ya). I learn't heaps from this discussion. Just your explanation of the "downers" and how they work was well worth the thread, and explained a lot of things. Just cause most of us leave our machines in the shed on days when you and Brian are hard at it doesn't mean we aren't gunna get caught sometime. At least now, we've got some idea what to look for and how to react.

You sure aint botherin us. (well, most of us, anyway). :beer:

Cheers

[Gyrodes]

Dave,
This old hole digger conciders that your writtings are worth copy and paste to be refered to any time in the future. With your easy no bull shit explanations are just so easy to understand. If some one don't understand your explanations it is obviously he don't want to. So just keep goin the way ya are for us not so experianced ones that apreciate your veiws. Just keep it commin :cheers: Des the hole digga

[Drifter]

Birdy, Its not my view that these posts are a waste of time. All I wanted to point out is that the topic header was "down wind turns demystified", yet we ended up talking about flying in convection or inversion layer effected parcels of air. Something which can occur whether you are upwind, downwind, cross wind or even in potentially still wind conditions.

All of these subjects are of real interest to the members.

Drifter

[Birdy2]

Yes Drifter, but nun of it matters if theres no danger.
And everythns relitive, coz its the convection or inversion layer effected parcels of air dopwn low that can make a seemingly simple DW turn turn to sh1t.
So as far as i can see, it belongs on this thread, you cant talkn bout one without the other, coz everythns effectn everythn else.

Thanx Des n FW.
Just cause most of us leave our machines in the shed on days when you and Brian are hard at it doesn't mean we aren't gunna get caught sometime
And thats the only reason its on the forum.
Its out there, waitn for all of us, so the more we know the longer we'll fly.;)

[Drifter]

Yes Drifter, but nun of it matters if theres no danger.
And everythns relitive, coz its the convection or inversion layer effected parcels of air dopwn low that can make a seemingly simple DW turn turn to sh1t.

Its out there, waitn for all of us, so the more we know the longer we'll fly.;)

Birdy it all matters regardless of whether there's any danger likely to be involved or not. Its called education.