Negative Gs?

Vance

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I'm not following here, Vance. As I envision the typical dangerous zoom climb, one pulls back, loads up the rotor a bit, and eventually runs out of energy/power to maintain the climb. Pushing forward at that moment (a common fixed-wing pilot stall recovery reflex to regain airspeed) unloads the rotor and that's what awakens the low-g demon. Merely commanding high-g in the climb will not by itself lead to low-g in the aftermath, and doesn't precipitate the problem any more than the take-off did.

Are we talking about a different scenario?
I don't know J.R.

In my opinion using aft cyclic at the top of a zoom climb raises the nose further initiating a back slide. I am already headed down because I have run out of airspeed, reduced the power and my controls feel vague because I have unloaded the rotor.

I am not suggesting that I push the cyclic forward J.R.; just not gently aft as Bryan writes “In a low-G condition, re-loading the rotor SHOULD always be your goal. In almost all low-G events, gentle application of aft cyclic will do that.”

In my opinion if I am approaching zero indicated air speed at the top of a zoom climb aft cyclic will not reload the rotor.

Do you think aft cyclic will reload the rotor at close to zero indicated air speed J.R.?

I recommend to student pilots that they not do zoom climbs.
 

birdy

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Fear and ignorance.

Its amazn the level of fear sumone can show, simply coz they are ignorant.
Its natural.
Sumthn youv been told will kill you will usualy generate fear.
Its a life preservation thing.
And you shouldnt ignor that fear, coz if it scares you, fair chance it can kill you, coz you dont know anythn about it other than that it could kill you.
Your fear is there to protect you from your ignorance.

If, however, you do understand it, your fear suddenly turns to respect.
You realise it could kill you, if you didnt respect the hazard zones. You realise this coz your now eductated.
Not ignorant IOW.

So, unless you understand how itll kill you, your sayn " dont go there, itll kill you" simply shows your level of ignorance.

Better tho, to say, " id never go there" and appear ignorant, than say " dont you go there" and remove all dout.

Life is much more relaxed and productive if you have a healthy respect through knowlage, instead a fear born out of ignorance.
 

WaspAir

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I don't know J.R.

In my opinion using aft cyclic at the top of a zoom climb raises the nose further initiating a back slide. I am already headed down because I have run out of airspeed, reduced the power and my controls feel vague because I have unloaded the rotor.

I am not suggesting that I push the cyclic forward J.R.; just not gently aft as Bryan writes “In a low-G condition, re-loading the rotor SHOULD always be your goal. In almost all low-G events, gentle application of aft cyclic will do that.”

In my opinion if I am approaching zero indicated air speed at the top of a zoom climb aft cyclic will not reload the rotor.

Do you think aft cyclic will reload the rotor at close to zero indicated air speed J.R.?

I recommend to student pilots that they not do zoom climbs.
I am not suggesting that you encourage your students to do zoom climbs, but I think we are picturing different scenarios when we use that term, and aren't quite communicating what either of us intends.

I have in mind a rapid pull up like this unfortunate fellow did in Japan. Notice that he does NOT go vertical, and does NOT exceed about 60 degrees of pitch (by my eyeball measurement, anyway), but it would look and feel like a "zoom", trading airspeed for altitude. This is not the same as pointing your nose straight up like a fixed wing about to do a hammerhead or tail slide with no horizontal motion through the air. I don't see any realistic risk of a tail slide on the sort of profile this poor chap flew. Losing vertical speed, and going to zero on the VSI, certainly, but not stopping or reversing his horizontal motion with respect to the air. I think this sort of milder-pitch accident is far more likely than somebody going a full 90 degrees to the earth and falling back on the same line.

www.youtube.com/watch?v=mWNKvAyKcFc

I note in the bolded portion of your response quoted above that you suggest any further back stick will raise the nose but will not add load to the rotor -- and those two sound contradictory to me, especially since you said you are already moving down, and that has me a little confused (whether that's a higher or lower level, I can't say!).
 

C. Beaty

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If that guy had chopped the throttle before pushing over, propeller torque/thrust wouldn’t have killed him.

Or, he most likely would still be here had he terminated his zoom climb by rolling it over into a turn rather than with a pushover.

Any gyro that depends upon rotor thrust to stay rightside up probably won’t when rotor thrust goes away without a power chop.
 

Wiplash

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Fear and ignorance.

Its amazn the level of fear sumone can show, simply coz they are ignorant.
Its natural.
Sumthn youv been told will kill you will usualy generate fear.
Its a life preservation thing.
And you shouldnt ignor that fear, coz if it scares you, fair chance it can kill you, coz you dont know anythn about it other than that it could kill you.
Your fear is there to protect you from your ignorance.

If, however, you do understand it, your fear suddenly turns to respect.
You realise it could kill you, if you didnt respect the hazard zones. You realise this coz your now eductated.
Not ignorant IOW.

So, unless you understand how itll kill you, your sayn " dont go there, itll kill you" simply shows your level of ignorance.

Better tho, to say, " id never go there" and appear ignorant, than say " dont you go there" and remove all dout.

Life is much more relaxed and productive if you have a healthy respect through knowlage, instead a fear born out of ignorance.
That was beautiful Birdy :hippie:
 

Vance

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I am not suggesting that you encourage your students to do zoom climbs, but I think we are picturing different scenarios when we use that term, and aren't quite communicating what either of us intends.

I have in mind a rapid pull up like this unfortunate fellow did in Japan. Notice that he does NOT go vertical, and does NOT exceed about 60 degrees of pitch (by my eyeball measurement, anyway), but it would look and feel like a "zoom", trading airspeed for altitude. This is not the same as pointing your nose straight up like a fixed wing about to do a hammerhead or tail slide with no horizontal motion through the air. I don't see any realistic risk of a tail slide on the sort of profile this poor chap flew. Losing vertical speed, and going to zero on the VSI, certainly, but not stopping or reversing his horizontal motion with respect to the air. I think this sort of milder-pitch accident is far more likely than somebody going a full 90 degrees to the earth and falling back on the same line.

www.youtube.com/watch?v=mWNKvAyKcFc

I note in the bolded portion of your response quoted above that you suggest any further back stick will raise the nose but will not add load to the rotor -- and those two sound contradictory to me, especially since you said you are already moving down, and that has me a little confused (whether that's a higher or lower level, I can't say!).
The video is a good example of my idea of a zoom climb J.R.

I would have reduced power at the top and have the cyclic neutral.

Even near maximum takeoff weight The Predator will climb out just fine without doing a zoom climb.

I feel a zoom climb like the one in the video is an advanced maneuver without much value other than to show off.

I encourage managing heading, airspeed and altitude. I am focused on smooth control inputs. If they want to learn to fly an airshow I am probably not the right instructor.
 

kyron

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Vance,
Thanks for the video. Its really interesting to watch the rotor in slow motion.
If this was done at a much higher altitude, without the ground being so close, do you think the gyro could have recovered with the correct inputs? or was this an event that could not be corrected? I'm curious (I would not try to do such a maneuver after watching this video - very sobering :help:).
Kyron
 

Vance

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Thoughts that come in the night.

Thoughts that come in the night.

I woke up thinking about zoom climbs and my challenge with my answer to J.R. about what to do at the top of a zoom climb is it would depend on the situation, the aircraft and how the controls felt.

I feel it would be incorrect to suggest that the answer on what to do with the controls would be the same for all gyroplanes in all situations under all conditions. It is not a video game. I can feel things with my body and the feedback from the controls that help to define what to do.

I have done exactly the same thing in the same place on different days with very different results.

In my experience anything that doesn’t work well started several moves back and my response would depend on how I arrived at the situation.

When I am practicing any aggressive maneuver for an airshow I carefully monitor the rotor rpm and the response to control inputs. I gradually expand on the maneuver so I don’t find myself deep into unfamiliar territory. I think about how things feel and why before I increase anything. I don’t do anything in an air show that I haven’t practiced.

I can think of situations I have been in where gentle aft pressure on the cyclic at the top of a zoom climb might be good and many where I feel it would not. Having prescriptive responses to poorly defined situations seems like a bad idea to me.

I don’t fly a SparrowHawk anything like a Cavalon and neither of them is anything like The Predator. The response to divergence from an intended path would be very different in each aircraft.

Reducing power and leaving the cyclic neutral would be my response at the top of an intentional zoom climb with minimal airspeed and low rotor rpm in The Predator. In the Cavalon I would not let her get to near zero air speed and would reduce the power sooner. The Cavalon goes nose up when I reduce power and I feel back pressure would make it worse.

I haven’t practiced for an air show in anything else so I don’t know what that unknown gyroplane can do or how I would respond to a particular situation.

I advise students to avoid zoom climbs because I feel it is an advanced maneuver and requires experience and has little value.

I do not have David’s sense of exactly what to do in every situation because I am still learning and even if I did I don’t know how I would communicate it to the student. I feel there are just too many variables.
 

Vance

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We seem to be corrected Kyron.

We seem to be corrected Kyron.

Vance,
Thanks for the video. Its really interesting to watch the rotor in slow motion.
If this was done at a much higher altitude, without the ground being so close, do you think the gyro could have recovered with the correct inputs? or was this an event that could not be corrected? I'm curious (I would not try to do such a maneuver after watching this video - very sobering :help:).
Kyron
Please see my last post for a better answer.

Kyron is in the same time zone as me and it is 5:17 in the morning. He is one of my practice students and intends to start training with me when he gets a Cavalon.

J.R. posted the video.

I feel it is not clear enough to know what the right thing to do was. Without feeling what the pilot was feeling and how the controls felt I don’t have an answer. I have no time in a gyroplane like the one in the video.

I have watched the video carefully many times and it appears to me the pilot stabs at the controls. If the rotor is already turning slowly because of low gs I feel this exacerbates the problem.

It appears to me the pilot did not anticipate the nose over and reduced the power too late. I don’t know where his thrust line was in relation to his center of gravity or what rotor blades he had. I feel his horizontal stabilizer is too small.

I would advise against that particular maneuver in the Cavalon.

It would be hard to determine exactly when it became a non-recoverable event. In my opinion once the rotor began to diverge the pilot was in trouble. Reducing power sooner probably would have helped. I feel more altitude would not have changed the outcome.

I am off to bed!
 

Jean Claude

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In my opinion, this bad clone of B8 is very HTL, because of too heavy wheels and too low seat. Added to this a inefficient tail, and you get a murderer gyroplane:
Decrease in lift on the top of the climb make disappear the stabilizer torque of pitch. So, nose down starts due to HTL. Then, the flight path is parallel to the disk in spite of the pulled stick, due to the inefficient tail. Nose down continues by HTL without lift. Now negative AoA of the disk adds a nose down torque because of the pulled stick. Engine idling is now too late. END
 
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C. Beaty

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There is no recovery once the pitch over has started, JC. The rotor cannot precess at such a high rate and stalls, usually striking the tail.
 

birdy

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Having prescriptive responses to poorly defined situations seems like a bad idea to me.
i am very confident you will become a very old pilot Vance.
Your attitude is refreshing.
You respect your level of abilities.
You respect the machines limits.
You are constantly trying to deepen you understanding of how and why.
And most importantly, you understand the one thing that seperates aviation from any other motorised transport.
The inconsistancies of air, and how the machine responces are changed in different conditions.
There are no ruel of thumb actions wen your near the edge.
Because the only consistant ruel of thumb in aviation is, the bottom of air is hard.
 

Vance

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Thank you David!

Thank you David!

That is a very nice thing to express, thoughtfully composed and beautifully written.

I have learned a lot from you David.

I have learned something from everyone who posts on the Rotary Wing Forum.

I love the friends I have found here.

I am already a very old pilot.

I love every minute I spend involved with gyroplanes and learn from every flight.

I hope to have many more gyroplane adventures.

I would love to feel I have contributed to making flying gyroplanes a little safer.

I love to share epiphanies with people so I suspect instructing will be a hoot.

THANK YOU!
 

Jean Claude

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There is no recovery once the pitch over has started, JC.
Yes, that's well what I wanted to express. The phenomenas irretrievably accumulate.
 

C. Beaty

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Early helicopters sometimes encountered precession stall of the tail rotor when yawing (pirouetting?) too fast.

The tail rotor would destroy itself by overrunning the flap stops and sometimes striking the tail boom.
 

birdy

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Interesting CB.
At wot yaw rpm did this happen at?
Would modern TRs at 3000 odd rpm be close to same?
What yaw rate could a 30" TR handle at 3000 cycles a sec without stalln?
Id suspect pretty damn high. ;)
 

C. Beaty

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Antiques, Birdy, from the cut-n-try era.

The Sikorsky R-4s and some other early helicopter contraptions sometimes destroyed their tail rotors from yawing too fast.

Delta-3 hinges and a larger margin of available thrust stopped that.
 

Jean Claude

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Video shows that the rotor has not strike the tail, despite the very high rate of pitching. Blade stall seems to me side issue in the PPO.
 

C. Beaty

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Of course, JC. The real problem is to ignore offset propeller thrust and torque.

However, I know of at least 2 instances where the pilot avoided catastrophe by rapidly closing the throttle (“throttle chop”) at the beginning of pushover/torqueover and recovering rotor speed in a vertical sink.

But once the rotor has stalled, rotor rpm is likely too slow for recovery.
 
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