0 G flight condition

N447MR

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If I’m doing 75mph straight and level then proceed to zoom climb under power hard up that curve... as I feel the machine start to slow and reach the apex of the parabola and cut power, is there any dangerous unloading happening?
If I do the same maneuver but chop power to idle before pulling into the zoom climb and ride it out until all airspeed is lost, is there dangerous unloading?
I flew Powered Paragliders for some years. I feel there is an exaggerated similarity. In PPG I hang from string to my wing. Negative G issues are obvious when the strings go slack. I feel the gyro similarly in that I “see” it as hanging from my spinning rotors by string. Yes we have solid connections but we’re still hanging from that wing and the force of us hanging is what maintains the “structure” Of the wing. Without us hanging on it, it doesn’t work.
No more regulation. Take personal responsibility. You don’t get to force your will on others because you think you know better, even if you do.
 

Vance

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If I’m doing 75mph straight and level then proceed to zoom climb under power hard up that curve... as I feel the machine start to slow and reach the apex of the parabola and cut power, is there any dangerous unloading happening?
In my opinion in a full power zoom climb the propeller thrust is unloading the Rotor.
If I do the same maneuver but chop power to idle before pulling into the zoom climb and ride it out until all airspeed is lost, is there dangerous unloading?
In my opinion, no. You will lose some altitude getting back up to speed.
I flew Powered Paragliders for some years. I feel there is an exaggerated similarity. In PPG I hang from string to my wing. Negative G issues are obvious when the strings go slack. I feel the gyro similarly in that I “see” it as hanging from my spinning rotors by string. Yes we have solid connections but we’re still hanging from that wing and the force of us hanging is what maintains the “structure” Of the wing. Without us hanging on it, it doesn’t work.
An object in space rotates around the center of gravity rather than an imaginary sky hook. I feel this is a useful thing to understand.
 

HeliSwede

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If I’m doing 75mph straight and level then proceed to zoom climb under power hard up that curve... as I feel the machine start to slow and reach the apex of the parabola and cut power, is there any dangerous unloading happening?
If I do the same maneuver but chop power to idle before pulling into the zoom climb and ride it out until all airspeed is lost, is there dangerous unloading?
I flew Powered Paragliders for some years. I feel there is an exaggerated similarity. In PPG I hang from string to my wing. Negative G issues are obvious when the strings go slack. I feel the gyro similarly in that I “see” it as hanging from my spinning rotors by string. Yes we have solid connections but we’re still hanging from that wing and the force of us hanging is what maintains the “structure” Of the wing. Without us hanging on it, it doesn’t work.
No more regulation. Take personal responsibility. You don’t get to force your will on others because you think you know better, even if you do.
In my opinion it's dangerous. If you are seeing or feeling any signs of weightlessness (light in the seat) or strings go slack in any aircraft that has a two bladed teetering rotor system and you survive, I would highly recommend never attempt such a maneuver again. I knew a guy who flew into 2 rather severe storms and survived, until he flew into the 3rd one. I also knew a pilot that inadvertently did a loop in a R22 helicopter avoiding power lines and survived, until he intentionally tried to repeat the maneuver. The list goes on. Please be careful out there!

From observing flights that eventually resulted in loss of life, here are the top (5) self induced flight risks I will avoid at all times:
Experimenting with exceeding the recommended flight envelope for the aircraft I am operating
Scud running / inadvertent flight from VFR to IFR
Continued flight with low fuel hoping to make it to the next fuel stop
Skipping a detailed pre-flight / being in a hurry to get in the air
Flying when one is not feeling well, the aircraft has any squawks, the weather is marginal, other red flags
 

Doug Riley

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Vance points out that, in a zoom climb, part of the aircraft's weight is being supported by the propeller thrust. There is therefore that much less weight being supported by the rotor. Consequently, smoothly reducing power during such a climb will add to the rotor's load and reduce the chance of a zero G event. Note that the word here is "reduce," not "eliminate." With enough speed built up, a gyro could reach zero G even at idle power, if the gyro were to trace a ballistic trajectory.

Chopping power in the same circumstances is more troublesome. By supporting part of the aircraft's weight using prop thrust, you've given the rotor less work to do. In response to the reduced load, the rotor will slow down near the top of the zoom. If you suddenly re-apply the full load by chopping throttle, it's possible that the rotor could flap violently. That's what always happens to teetering rotors when you apply more load to them than they are capable of lifting at their current RPM.

These are "thought experiments" only! A zoom climb is an advanced maneuver that low-time gyro pilots should not try at all. Period.

The experienced gyro-aerobatics pilots generally bank out of a zoom (sometimes to 90 deg. bank or more), to keep the rotor loaded. But, again, a zoom is an aerobatic maneuver -- i.e. one that is unnecessary for routine flight.
 

rwdreams

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In a down draft situation, which is the terror of my ppg. What do you hope your muscle memory response would be ? Before you go to low g.
 

N447MR

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In a down draft situation, which is the terror of my ppg. What do you hope your muscle memory response would be ? Before you go to low g.
Big brakes and full throttle! PPG
 
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Vance

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In a down draft situation, which is the terror of my ppg. What do you hope your muscle memory response would be ? Before you go to low g.
In my experience a down draft is unlikely to cause a low g event in a gyroplane unless I am too close to a thunderstorm or beneath virga.

The best response depends on the situation.

In a high thrust line gyroplane if I felt I was in danger of a power push over from a low g event for any reason I would reduce power to idle.

Generally speaking a down draft doesn’t go all the way to the ground because there is no place for the air to go except in a microburst.

Usually there is an updraft near a down draft and I would try to find it.
 

WaspAir

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It's only the entry to a downdraft that might produce a momentary sensation of reduced g-load, and that's over pretty quickly. Once you're in subsiding air, you fly through it like anything else but with reduced climb ability. Most thermal-generated sink is pretty small and you'll find yourself out the other side soon. Around lines of convergence/shear, downwind near a ridge, or in standing mountain lee wave systems, you can get large areas where it's all going down and where a slight change of course may be the best option.
 

fara

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In a down draft situation, which is the terror of my ppg. What do you hope your muscle memory response would be ? Before you go to low g.


You fly through them like normal. Just can't climb as good. Unless its a huge downdraft on lee side of a mountain that can take down anything that flies if pilot does not take proper precautions and does take airplanes or anything else down because the descent rate cannot be overcome by available thrust. In normal downdrafts like you are talking about (I think) the resultant relative wind is still from the front.
 

Burrengyro

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It's only the entry to a downdraft that might produce a momentary sensation of reduced g-load, and that's over pretty quickly. Once you're in subsiding air, you fly through it like anything else but with reduced climb ability. Most thermal-generated sink is pretty small and you'll find yourself out the other side soon. Around lines of convergence/shear, downwind near a ridge, or in standing mountain lee wave systems, you can get large areas where it's all going down and where a slight change of course may be the best option.
Hi Waspair,
There is a small but significant hill (from a wind effect point of view) on the port side of our 06 runway. When coming into land with a strong crosswind from the port side, the gyro can experience a rapid drop in height from this lee side crosswind. I usually approach to land at a higher than normal landing speed to counteract this rapid drop in height, especially in gusting conditions. The drop in g-load can be surprising! John H
 

WaspAir

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Hi Waspair,
There is a small but significant hill (from a wind effect point of view) on the port side of our 06 runway. When coming into land with a strong crosswind from the port side, the gyro can experience a rapid drop in height from this lee side crosswind. I usually approach to land at a higher than normal landing speed to counteract this rapid drop in height, especially in gusting conditions. The drop in g-load can be surprising! John H
A wind shadow from terrain and/or a wind gradient as you get close to the ground, typically on final approach, can surprise the unwary with a loss of airspeed, hurting performance at a time when margins are small. Personally, I have never encountered a low-g hazard from those effects.
 

Burrengyro

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A wind shadow from terrain and/or a wind gradient as you get close to the ground, typically on final approach, can surprise the unwary with a loss of airspeed, hurting performance at a time when margins are small. Personally, I have never encountered a low-g hazard from those effects.
Hi WaspAir,
In my case, it was a sudden sharp drop in height, more than a drop in airspeed. Maybe a hill roll effect. It happened so fast I could not be sure whether it was the classic seat of the pants low g feeling or just squeaky bum time. Most likely a localised weather phenomenon associated with this particular hill and wind direction at the time. At this stage, I'm used to it, but alert to it's effects. The first time I did the gyro licence test, I failed because I over pushed the stick forward when recovering from a sharp zoom climb into an unusual nose-high attitude. That was a well-learned lesson. John H.
 

HeliSwede

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Guys, I can tell you that I have encountered some rather nasty wind conditions caused by wind coming over a row of hangars and/or a row of trees next to a runway on approach. The wind shear and/or turbulent wind rotors coming over those structures can really cause havoc on any aircraft, especially lighter FW and rotorcraft. I'm always on alert when I know such conditions exist and do my best to fly a more shallow extended approaches to landing. This method works well for me, anyway.
I've seen a few aircraft "drop" to the runway and another one hit a wing on the runway due to such turbulence.
Thankfully, most airports I have flown to do not have such problems, but two our local airports 1K1 and KAAO certainly do.
 

Tyger

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Turbulence is one thing but, as Vance and WaspAir said, any negative vertical acceleration from entering a real downdraft can only be momentary, and that's really the topic of this thread.
Hitting a big updraft might be a bigger problem, if you are are near Vne, because it momentarily increases the angle of attack of the blades. But that, also, is another topic.
 

Doug Riley

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Tyger, you're right that the zero or negative disk AAO from entering a downdraft does rather quickly return to positive as the aircraft falls. The short run, however, can be a real problem in some gyros. I know you know this, but bring it up for others.

A gyro with a substantial HTL condition, and no HS, relies on rotor thrust to keep its nose up. A rotor thrustline ahead of the aircraft's CM can counteract the often hundreds of foot-pounds of nose-down torque continually trying to cause a PPO. If you take away the rotor thrust, as you do in a downdraft, you allow the HTL moment to assert itself. Once it starts to do so, PPO begins, and is a statically unstable event -- that is, it's self-amplifying. The resumption of rotor thrust as the craft falls may come too late.

There have been some mysterious losses of gyros with these design flaws that may well have bene traceable to such a sequence of events.
 
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