Rough air flying do you get light in the seat?

[GrantR]

All of this talk about a gyro having to stay at 1g has me a little confused. In rough air I have noticed on many occasion getting light in the seat or even coming up a bit out of the seat. Saturday when I flew, this was the roughest air I have flown a gyro in and it had me a bit surprised when I got light and came up out of the seat a few times. The onset of this lightness is so sudden that if the nose was to suddenly pitch down, I don’t think human reaction time could possibly be fast enough to correct it quick enough.

Needless to say my gyro did maintain a level keel each time with out have to do anything. Floating the stick was interesting as it would bounce back and forth with the thermals. The Offset gimbal is neat. Holding it firm the gyro still maintained a level attitude with really no noticeably pitch changes. I did have one slight pitch up. All of this was with 75% to 100% throttle. I also watched the rotor tach a bit and the RRPM fluctuations were very small during these less than 1 g bumps.

So this leaves me a bit confused. I know the rotor relies on the weight of the gyro pulling down on it to maintain RRPM and lift. Increase the weight increase the RRPM decrease the weight lower the RRPM.

So when flying in strong updrafts and downdrafts. It only makes since if you enter a strong downdraft that you will feel a lightness in the seat for a second or so and more weight in the seat in a updraft as the gyro transitions to the new airmass.

So is this considered unloading the rotor?

If I were to chop power and pull back the stick to try to restore 1 g, the lightness would be gone. So I don’t really see a way around it other than don’t fly at 2pm in 97 degree weather!

What I am describing is nothing like being tossed up out of the seat in a Ultralight fixed wing.

[Friendly]

Unnerving at times, but lucky for me I always land back in the seat. That was good altitude quick in your video for 97 degree weather

[Redbaron]

do a sharp bank grant, about 2 gees lol if it takes back pressure your gyro is g-load stable! my disk loading is lighter than yours and it bounces a bit nothing bad


:wave:All of this talk about a gyro having to stay at 1g has me a little confused. In rough air I have noticed on many occasion getting light in the seat or even coming up a bit out of the seat. Saturday when I flew, this was the roughest air I have flown a gyro in and it had me a bit surprised when I got light and came up out of the seat a few times. The onset of this lightness is so sudden that if the nose was to suddenly pitch down, I don’t think human reaction time could possibly be fast enough to correct it quick enough.

Needless to say my gyro did maintain a level keel each time with out have to do anything. Floating the stick was interesting as it would bounce back and forth with the thermals. The Offset gimbal is neat. Holding it firm the gyro still maintained a level attitude with really no noticeably pitch changes. I did have one slight pitch up. All of this was with 75% to 100% throttle. I also watched the rotor tach a bit and the RRPM fluctuations were very small during these less than 1 g bumps.

So this leaves me a bit confused. I know the rotor relies on the weight of the gyro pulling down on it to maintain RRPM and lift. Increase the weight increase the RRPM decrease the weight lower the RRPM.
lol if you were truely weightless in your gyro you would want enought down force on your stab to pitch your nose up! if your nose pitches forward then your at risk for a bunt! I'm no means an expert grant, maybe a dumbass but my disk loading is alot lighter than yours. throw your gyro into a hard bank load that baby up to about 2 gees if it requires back pressure she is g load stable! you still get bumps atleast I do but the main thing is she is pitch stable!


So when flying in strong updrafts and downdrafts. It only makes since if you enter a strong downdraft that you will feel a lightness in the seat for a second or so and more weight in the seat in a updraft as the gyro transitions to the new airmass.

So is this considered unloading the rotor?

If I were to chop power and pull back the stick to try to restore 1 g, the lightness would be gone. So I don’t really see a way around it other than don’t fly at 2pm in 97 degree weather!

What I am describing is nothing like being tossed up out of the seat in a Ultralight fixed wing.

[Alan_Cheatham]

A gyro can fly through brief moments of zero-g flight without a problem. What gets one into trouble is when going through zero-g with a machine that has a significantly offset thrust line and the engine throttled up causing a strong pitching moment on the airframe which the rotor at zero-g can no longer compensate for.

.

[bmoore2156]

Grant,
The way I understand it is.... As long as your rotor has enough inertia to maintain rrpm on the way back down, you will be ok as long as it's center line thrust.
I found myself in a situation the other day that I hope to avoid in the future.
We had a nice north wind that was 15G20 kts. The north wind where I fly is the smoothest and I wouldn't think of flying if it were easterly.
I was flying in the smooth air about 1200' agl when I spotted some elk and went down for a closer look. I got down to about 500' agl and started a turn to maintain visual sight with the elk. My path took me behind a hill where the air was boiling over. I am not sure if the wind picked up for a short time or I just flew into it but I was very glad that my RAF was CLT. Several ups and downs later I was looking for the quickest path back to smooth air and it was naturally a downwind turn. I had to stay in the bumpyness for longer than I wanted, to avoid the downwind turn. I didn't want to loose precious altitude at that point. I noticed my rrpms were from 330 to 360 during the bumps.
I hope to avoid this mistake in the future.
Brad

[Passin' Thru]

A gyro can fly through brief moments of zero-g flight without a problem. What gets one into trouble is when going through zero-g with a machine that has a significantly offset thrust line and the engine throttled up causing a strong pitching moment on the airframe which the rotor at zero-g can no longer compensate for.
.
Precisely! And when that happens with one of those stock "unmentionable" gyros, it can go negative very quickly and all too often, someone dies.

Grant, as Brad mentioned, due to its enertia the rotor changes speed at a considerabley slower rate than your butt gets slammed up and down! One thing that amplifies your "seat of the pants" sensation is the spring board effect of the rotor coning. (don't think about that too much, -it'll scare you!;))

All of this talk about a gyro having to stay at 1g has me a little confused.
Often what we are trying to say is "maintain positive G rotor loading". Think about it like this; as you burn off fuel, the rotor load decreases, right? Also, you can go considerably less than 1 G and still have positive rotor loading.

One word of caution; Where you live you are coming into the season when you have a lot of thunderstorms and Towering Cummulus. Some folks call them "Anvil Heads". Do not fly near those things, especially do not fly under one. Those thing have vertical winds that have been measured at over 200 mph!
I have read of instances where aircraft were sucked up from beneath into the center rising column and broken up and spit ot in pieces.
Also, even a few miles down wind of one you can encounter some serious hail.

Enjoy your nice little gyro, but be safe!;)

[ckurz7000]

...I was looking for the quickest path back to smooth air and it was naturally a downwind turn. I had to stay in the bumpyness for longer than I wanted, to avoid the downwind turn....

I almost dare not say it for fear of breaking loose another endless discussion, but you don't lose any more altitude in a downwind turn than you would turning the other direction.

-- Chris.

[Chopper Reid]

Lightness in the seat is not any cause for alarm unless you are deliberately using forward stick to go negative.

In rough air, as long as the stick is held so it has positive feel [a touch of backstick] then you will not have a problem. If you fly a HTL like myself, reducing throttle will help keep the ride a bit smoother. You are flying through a parcel of air and some air is rising, some falling and when you transition from one to another, you will experience a reaction of some sorts.

A downwind turn is not going to help much in rough air unless you are traveling through a weather front. If you get caught in a big thermal etc, the easiest way out is to throttle back smoothly, and heel the gyro over so the wind is now not under the rotors and start a descending turn out. You do not need to do a 90* heel over, 45* is plenty.

Unless you are an competent pilot, keep up at an altitude that if you were to loose some height from any maneuver, you are not going to conflict with the ground !! In rough air, the rules regarding turns into or out of the wind go out of the window and even more so close to the ground eg, below 200 ft AGL.

[All_In]

I've been wondering about this! Thanks for teaching me more...

[birdy]

I never fly in ruff air. :)
Not high anyway. My fear of hights wont let me.

But, two facts about ruff air; [generaly speakn]
the higher you go, the stronger the wind currents
and the faster you go, he harder you hit the bumps.
So stay low n slow.

OK, ill shuddup now. :(

[Resasi]

As I understand, and from advice I received from Ernie at RFD when I was purchasing my DW's, disc loading also plays a part in the reaction of the gyro in situations like these.

The lower the disc loading the greater the reaction to turbulence, updrafts and thermals you may encounter, and why he recommends a disc loading range of 1.4-1.6 for his blades.

Those who have gone on about their nice 'floaty' blades with low disc loading will react more and get bounced around more, and the blades will slow down quicker (this may just apply to light blades. I would like clarificaiton.)in lightly loaded situations ie when you start getting light in the seat.

[GrantR]

Thanks, Guys. This is what I expected/ hoped to hear! :) Pete I do not fly when T storms are close. I am well aware of what they can do. One took down 2 trees on my backyard the other day!

[cgmg]

My first blades on my Air Command were what I thought was 23' McCutchens. Flying on thermally active days always scared the bejeebers out of me, due to the light-in-the-seat, and down hard effects. As Grant experienced, the nose didn't pitch up and down much at all, just that weird response to thermals.

Turns out there was a reason I should have been scared: Air Command sold me 25' blades, not 23'. My AC weighed 354 empty, and I then weighed about 135 pounds. I'm actually afraid to calculate what the disc loading was, but it had to be too light for my all-up weight.

Fortunately for us, I think, Cathy flapped the McCutchens and ruined them. Ernie recommended either 22' or 23', depending on what kind of performance I wanted. We bought the 23 footers, and what a difference! People can say what they want about McCutchens, I loved my Dragon Wings!

As my flight time increased, I also increased the type of thermally active days I flew in. It took quite a bit of stronger thermal activity to match that same 25' McCutchen effect I experienced early on.

So for those of you who don't hold much thought on how important disc loading is, I'm telling you experience says it does.

[choppergabor]

Hey Grant are you sure you didn't eat beans before that flight? There could be other reasons you catapult out of that darn seat ya know..... Just checking to make sure you have all your facts right and don't mislead the forum here buddy. Keep damn chilies in the can before flight.

[jcarleto]

Grant...I have your solution...gain about 100 pounds. You'll load up the blades so much it'll take a hurricane to bump you out of the seat! :D

[GrantR]

I have 23 foot dragon wings. They spin right about 336 rpm in level flight. I think My disc loading is around 1.8 to 1.2. Ernie told me my blades are fine at the rpms they spin. I like the climb rate!

Gabor you know beans are the musical fruit:) John Then I couldn't climb as good :(

[scottessex]

Hmmmm, I think it is OK, as long as you don't get "light in the loafers"
That is what I have heard.

[jcarleto]

Well, Grant..that's always the rub. Comfort vs. performance. One is always going to suffer the other.

[Doug Riley]

In a gyro with a pitch-stable airframe (i.e. one with a reasonable prop thrustline location and a properly designed and adjusted H-stab), floating the stick in turbulence is neither necessary nor desirable. A pitch-stable gyro is, in effect, a giant gimbal-head torque bar, with the net rotor thrust aft of the pivot point (i.e. the CG). The H-stab plays the role of the spring when necessary. Hold the stick normally in this type of gyro and let the tail surfaces do the work.

Stick-floating in a pitch-UNstable gyro can be a life-saver. It's not 100% effective in that role, though.

[GrantR]

Doug,

Why would floating the stick be non desirable? I could not tell much difference between floating it and not other than when floating it the stick would kick back and forth with the thermals. My H stab is a flat plate with a 2 foot root chord, 1 foot tip and 4 foot span 6 sq ft in size and set level on the keel. My gyro feels very dampened.

[Doug Riley]

Grant, an up- or down-draft changes the rotor disk's angle of attack (AOA). We'd like to smooth out those changes, which means limiting them as much as possible and restoring the original disk AOA as fast as we can.

The H-stab (and rotor thrustline behind CG) do this by weathervaning the frame into the up- or down-drafts. The rotor will only follow this weathervaning if the stick is held at a constant position relative to the frame. "Floating" it de-couples the rotor from the frame. That's a very good thing if the frame is UNstable, but it defeats your stability mechanism if the frame IS stable.

When I first started flying Dominators, I floated the stick in turbulence, as I'd done for years in my (unstable) Air Command. It gradually downed on me that the nose was rising or dipping in the CORRECT direction to smooth out the AOA changes (the Air Command's nose usually went in the wrong direction). Nose motion, by itself, doesn't accomplish anything unless the rotor disk follows. I was making that impossible by letting the rotor head move independently of the frame. I then tried holding the stick still -- and found that the aircraft held airspeed better in the rough stuff.

Do NOT use this technique if you don't know for sure that your gyro is pitch-stable. "Float when in doubt."

[WaspAir]

A downwind turn is not going to help much in rough air unless you are traveling through a weather front. If you get caught in a big thermal etc, the easiest way out is to throttle back smoothly, and heel the gyro over so the wind is now not under the rotors and start a descending turn out. You do not need to do a 90* heel over, 45* is plenty.
Thermals are rising columns of air, and are often surrounded by sinking air (there has to be sink nearby or you'd run out of air somewhere!). If you fly into a thermal, you'll get a kick in the seat as your aircraft is pushed up, so positive g is the initial response. The thermal itself, since it's lifting you higher, rarely causes any safety issues (unless you are so high that you're getting pushed up into the cloud base, it's just free altitude, so glider pilots slow down and circle to prolong it). Left to its own devices, mother nature tries to turn you out of thermals and center you in the sink nearby. The strength of the lift varies significantly across the thermal, stronger in the center and weaker at the edges for a typical shape. As you enter lifting air, it's normal to have slightly stronger lift on one side or the other, and that will naturally tend to bank you away from the stronger core and into the sinking air. Encountering the sink rather than the thermal is usually source of that "unbearable lightness of being". However, these areas are usually not very large, and almost any steady heading will take you out of it quickly; allowing the aircraft to wander where it wants will usually put you in the strongest sink as you will be banked toward the side with most rapid downward flow . Glider pilots speed up when they encounter sink so that the time spent in it and the altitude loss is minimized, expecting to pass out of it in a matter of seconds, and they use the stick to resist any banking tendency felt along the way.

It is common to encounter sink-lift-sink on a given heading as you pass through the region surrounding the thermal, the thermal itself, and then back through the surroundings. The glider rule is fast through the sink, slow in the lift, and fast through the sink again. Light airplane pilots tend to do the opposite in a sometimes futile effort to maintain constant altitude, pulling up to fight the sink and pushing to fight the lift; this maximizes time in the sink while minimizing time in the lift.

[All_In]

I'll be a little better pilot now. Thank you Doug, I learned form that great explanation.

[GrantR]

Doug how do I determine if my gyro is pitch stable? Greg's Stability tests? I think my gyro is I have the TL going through my butt :)

[Doug Riley]

Grant, first check your thrustline location by double hang test. If your prop thrustline is near, on or below the CG, you're on your way to confirming pitch stability. If it's way high, proceed with caution.

To sure, though, do the flight tests. Most pitch-unstable gyros will show their true colors in a simple banked turn with a high throttle setting -- if you need FORWARD stick pressure to maintain airspeed, the gyro lacks angle-of-attack pitch stability. If you need back pressure, you have more evidence that it's stable -- but finish the tests to nail it for sure.

If your gyro tests out pitch-stable, you really have the choice of using stick-floating or not in turbulence. Again, I found that the Dominator did a better job compensating for turbulence if the stick was held normally. I would expect that to be the case in general with stable gyros, though lots of variables are in play from one gyro to another.

[Friendly]

Grant, first check your thrust line location by double hang test. If your prop thrust line is near, on or below the CG, you're on your way to confirming pitch stability. If it's way high, proceed with caution.

To sure, though, do the flight tests. Most pitch-unstable gyros will show their true colors in a simple banked turn with a high throttle setting -- if you need FORWARD stick pressure to maintain airspeed, the gyro lacks angle-of-attack pitch stability. If you need back pressure, you have more evidence that it's stable -- but finish the tests to nail it for sure.

If your gyro tests out pitch-stable, you really have the choice of using stick-floating or not in turbulence. Again, I found that the Dominator did a better job compensating for turbulence if the stick was held normally. I would expect that to be the case in general with stable gyros, though lots of variables are in play from one gyro to another.

Doug,
I am missing something? If you make a banked turn, how would you not need the back stick to make the turn and how would this not slow the gyro down?
Also you mentions something about the HS at the proper angle. There is plenty of information on the forum about the CLT but very little about the H/S incident. Would you expound on this more?

[Doug Riley]

Mark, it'd take a long post to cover these topics completely. Quickie version:

Turns: You need more rotor thrust to accomplish a turn -- some of the rotor thrust is holding you up in the sky as usual, but you need some extra thrust to pull the gyro through the turn.

You can obtain more thrust from the rotor by either holding its disk angle of attack the same and increasing its airspeed, or by increasing its AOA and holding airspeed.

Say your rotor's thrustline is in the UNstable position -- forward of the CG. In that case, when you roll into a turn, stick fixed, the gyro will start to descend for lack of enough thrust to hold you level. Airspeed will increase. This will increase rotor thrust and start to pull you through the turn. With rotor thrust ahead of CG, though, it'll also pull the nose up. That will slow you down (stick fixed). The upswing of the nose will also pull the bottom end of the trim spring down, causing a tendency for the stick to move aft. For both reasons, you'll need to push forward on the stick to hold airspeed. If you fail to push forward, you'll slow down and may mush out of the turn.

A stable gyro -- one with rotor thrustline aft of CG -- will react in the opposite way. If you roll into a bank stick-fixed, the gyro will again dive initially. The result will be more airspeed. This will boost rotor thrust and commence the turn. However, with rotor thrust aft of CG, the extra rotor thrust will pull the TAIL up and the nose down. This will cause an increased diving tendency until/unless the pilot pulls aft on the stick. IOW, the stable gyro manipulates you into adding back stick in a turn. You won't slow down from trimmed speed (unless you over-do the back stick); you'll just avoid speeding up.

As for the H-stab, its incidence must be adjusted to compensate for the nose-up or nose-down tendencies of the airframe. If you have 300 lb. of prop thrust and a HTL of 3 inches, for example, you'll need your H-stab to make 75 foot-lb. (300 lb. x 1/4 foot) of nose-up torque at wide-open throttle, at any airspeed (including zero). You can guesstimate H-stab incidence based on standard lift curves and the size and leverage of the H-stab. Your final incidence setting will be based on flight test results. You may have to adjust it a few times before you get the best outcome.

If the airframe has no nose-up or nose-down tendencies (prop thrust and frame drag perfectly centered on the CG and frame drag also centered aft of CG), then you will need very little to zero stab incidence -- maybe 1 degree negative at most.

[GrantR]

Doug,

I do a lot of of full power turns as I gain altitude inside the field and I seem to notice always having to add in back stick in a turn or the airspeed increases in the turn. Maybe at the next flyin I can do a Double hang test. I plan on going out after work and I will confirm this for sure but I do not remember ever having to push forward to maintain airspeed.

Thanks for the tips and explanation of how this works!

[Redbaron]

ditto! high and hot equals bumpy! :sad:

I never fly in ruff air. :)
Not high anyway. My fear of hights wont let me.

But, two facts about ruff air; [generaly speakn]
the higher you go, the stronger the wind currents
and the faster you go, he harder you hit the bumps.
So stay low n slow.

OK, ill shuddup now. :(

[birdy]

Floatn the stick ina clt machine dose smooth the ride, coz as the load changes, so dose the disc AOA, so you fly through the bumps, instead of over um.
The ruffer the air you fly in, the more youll notice it.

[GrantR]

Doug,

I went flying today and did your test to see what happened, I climbed up to 500 feet and held the stick firm while at 50 mph ASI straight and level and went into a 30 or so degree bank keeping the stick firmly locked from moving fore or aft and the power set at full throttle. The gyro started to gradually drop the nose and speed up and it kept on lowering the nose and speeding up until I added back pressure. I did the test 4 times and a few at 6000 rpm and it did the same thing every time. I let the airspeed peg 70 (that’s as high as my asi goes )and the wind was really blowing before adding in back stick.

So I guess I have a stable machine!

[Redbaron]

she is g-load stable! :rolleyes:

[GrantR]

Doug,

One other thing I noticed was my trim changes with power during straight and level flight. At full power if the gyro is trimmed to say 50mph and I reduce power the gyro lowers the nose slightly and speeds up. My H stab is mounted with zero incidence to the keel.

[Doug Riley]

Grant:

Both those test outcomes point to stability with respect to disk angle of attack and power setting, respectively. The "turn" test alone isn't 100% reliable; some gyros with pretty vicious pitch instability will pass that part of the test (though my lowrider Air Command and the lowrider SxS Air Command failed it).

Run the full battery of tests on Greg Gremminger's Magni Web site to sure you have static stability with respect to (1) power setting (2) airspeed and (3) disk angle of attack. G-load and disk angle of attack are equivalent things at a given airspeed if you don't have collective pitch.

Assuming you do, you can decide for yourself if stick-floating is necessary or helpful. My view is that it's an unnecessary complication if the gyro is pitch-stable. It's just one more thing that earns gyros the undeserved "tricky to fly" rep.

[All_In]

This has been a great thread. I learned a lot!

Thank you!

[birdy]

Bout as tricky as pushn a barrow Doug. ;)
But your rite, most of the time one dont need to float the stick, coz most of the time it aint ruff.
But wen it is, a floated stick will AOA react much faster n the frame, so the rotors dont catch as much air.

[All_In]

Thank you Birdy!!! This really did filled in some holes in my understanding of procedures, you guys rock!

[RockyMeLad]

Yo Grant,

I like your videos. You're coming along nicely.

Around here I usually fly about 300-500AGL max away from the airport...
especially later in the day. There is both up and down air in about equal proportions when I fly in a sorta straight line. Holding "steady", the Bee will rise and fall a bit (maybe 50ft), but hold a constant average height. I only have about 1.2 loading, but seldom get any hard "bumps", just smooth rise and fall. I can definitely feel the change in "seat of the pants" calibration, but have not actually come off the seat. Although early in my gyro flying, even "getting light" got my attention. I've also come to realize that the seat belt/harness won't let me go very far either, so not to worry.

As for your flaring high, the secret is practice. Get comfortable at a reasonable speed, then gradually change your approach speed and get a feel for the subtle change in flare timing. Eventually you should be able to consistently land "dead stick" where you want from various heights. Just remember that you can add power for safety while you're learning. Bending birds is not sanctioned.

[NoWingsAttached]

Grant

I, too, was flying in Georgia last Saturday and had lots of ups and downs! It was well into the day, so the thermals were really kicking it up several notches. When I first took off I went from 200ft AGL to about 800 ft in about 15 seconds in a thermal at the end of the runway - so a climb rate of 2400fps, at 3200 adjusted ground alt. Fastest I've ever climbed out in my little Bee, but I am still a low-timer. I expected, and got, the drops as well as the lifts. All I know is "keep it level" when it goes up or down.