# Pitch Question

#### Vance

##### Gyroplane CFI
I think you might have not read my original post or I may have not articulated it well.
Would you agree that the gyro flys through relative wind and as long as there is wind going through the rotor the gyro does not know the earth is below it or in front of it.
Would you agree the the rotor is tilted back about 9 degrees typically do that the relative wind can spin the rotors?
So if you were in a dive- not a glide- dive dive dive! Lol
And you are let’s say max power max speed a setting that would be fastest available speed in level flight-
Are you still going to climb out of that dive?

I am unable to understand what you are trying to articulate.

The answer to the first question is no; I would not agree that a gyroplane rotor disk is tilted back about nine degrees to the relative wind.

A rotor disk on a gyroplane at near VNE is tilted back just a few degrees to the relative wind.

At very low indicated air speeds the rotor disk may be tilted back as much as fifteen degrees to the relative wind.

Gyroplanes have a power required curve and above or below the minimum power required speed the power required to maintain level flight is increased.

If the power required exceeds the power available the gyroplane will descend even at wide open throttle.

There have been many gyroplane accidents because people did not understand this and imagined a gyroplane climbs with the cyclic.

The control of the cyclic is done with pressure rather than movement and the gyroplane I train in, The Predator will run along nicely level at ninety knots at full power with the cyclic against the forward stop.

The first picture is The Predator at eighty five knots indicated air speed, the second is rounding out with at around twenty five knots indicated air speed and the final picture is touching down at less than five knots of indicated air speed.

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#### Housedr

##### Newbie
In any steady-state flight at any acute angle of your path to the horizontal (whether up, down, or level) that you can achieve, adding power, without any other change, will cause a clockwise rotational motion of the needle on your vertical speed indicator. How far it moves depends on how much power you are able to add.
Fine- no problem with that. Now limit speed to available power, point the gyro ground bound , no stick movement. Where will you wind up?

#### Housedr

##### Newbie
I am unable to understand what you are trying to articulate.

The answer to the first question is no; I would not agree that a gyroplane rotor disk is tilted back about nine degrees to the relative wind.

A rotor disk on a gyroplane at near VNE is tilted back just a few degrees to the relative wind.

At very low indicated air speeds the rotor disk may be tilted back as much as fifteen degrees to the relative wind.

Gyroplanes have a power required curve and above or below the minimum power required speed the power required to maintain level flight is increased.

If the power required exceeds the power available the gyroplane will descend even at wide open throttle.

There have been many gyroplane accidents because people did not understand this and imagined a gyroplane climbs with the cyclic.

The control of the cyclic is done with pressure rather than movement and the gyroplane I train in, The Predator will run along nicely level at ninety knots at full power with the cyclic against the forward stop.

The first picture is The Predator at eighty five knots indicated air speed, the second is rounding out with at around twenty five knots indicated air speed and the final picture is touching down at less than five knots of indicated air speed.
Ok vance. I’m in agreement so far.
does your gyro in these pics know where the ground is? I know YOU know where it is but does the gyro care?

#### Housedr

##### Newbie
Also Vance- for perspective. At full speed in your photo 90:knots
looks like 9 degrees to me - am I off by 1 or 2?

#### Vance

##### Gyroplane CFI
Ok vance. I’m in agreement so far.
does your gyro in these pics know where the ground is? I know YOU know where it is but does the gyro care?

The rotor knows where the ground it when it is in ground effect.

The horizontal stabilizer knows where the ground is when it is in ground effect.

The gyroplane knows where it is in relation to gravity.

The Predator is not alive, she doesn’t care about anything.

#### Vance

##### Gyroplane CFI
Also Vance- for perspective. At full speed in your photo 90:knots
looks like 9 degrees to me - am I off by 1 or 2?

The picture of The Predator at speed is at eighty five knots as I wrote in the post.

I have no pictures of her flying at ninety knots indicated airspeed because I don’t go that fast near the ground.

In the picture the cyclic is close to the forward stop with the rotorhead a zero degrees in relation to the fuselage which is flying slightly nose down.

It is hard to say how much blowback there is. It is likely not seven degrees.

I suspect there is not a way to measure rotor disk angle in a picture of The Predator taken from the ground a quarter mile away when I am flying a thousand feet above the ground.

I posted the pictures of fast and slow flight to help you see the difference and understand the disk is not flying at nine degrees in relation to the relative wind.

The thread was about the fuselage pitching down when the cyclic is moved forward and I feel the question was answered correctly by most who posted.

I responded to your visualization because of the way I interpreted it and I apologize if I misinterpreted it.

It appeared to me to promote a misunderstanding of the function of the cyclic and the throttle that may be at the heart of many gyroplane accidents.

Your further posts have reinforced my perspective.

I felt that misunderstanding was at the heart of the original question.

When I am giving someone a proficiency check ride and the applicant lowers the nose when he finds himself near the upper limit of the practical test standard he usually busts the standard for airspeed soon after.

This is important to the FAA because the NTSB feels that not understanding how the flight controls is causal in many gyroplane accidents.

In my opinion that is the reason for recognition and recovery from low air speed and high rate of descent practical test standard.

Gyroplane safety affects all of us and a better understanding of how to pilot a gyroplane safely is paramount in our efforts to share the fun of flying a gyroplane.

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#### Vance

##### Gyroplane CFI
Fine- no problem with that. Now limit speed to available power, point the gyro ground bound , no stick movement. Where will you wind up?

The way you point the gyroplane at the ground is with forward movement of the cyclic.

#### Housedr

##### Newbie
Ok there is a total lack of communication. And no you did not answer correctly .
We are not in ground effect in the example -
We are not in a PTS
You have evaded answering because you think I don’t understand the physics which I can assure you I do.
So answer only this question then we will move to the point.
you are flying along straight and level A earth below- horizon out front.
foes the gyro know it is straight any level horizon out front or is it flying through relative air- ( any airspeed at this point)

#### Vance

##### Gyroplane CFI
Ok there is a total lack of communication. And no you did not answer correctly .
We are not in ground effect in the example -
We are not in a PTS
You have evaded answering because you think I don’t understand the physics which I can assure you I do.
So answer only this question then we will move to the point.
you are flying along straight and level A earth below- horizon out front.
foes the gyro know it is straight any level horizon out front or is it flying through relative air- ( any airspeed at this point)

I apologize for the lack of communication.

In two of the three pictures the rotor is in ground effect and in one of the pictures the horizontal stabilizer is in ground effect.

In my opinion in aviation we are always flying in a block of air.

The block may be moving in relation to the ground.

I feel that is what makes wind a ground reference term.

Part of the reason for ground reference maneuvers is to teach this concept.

I don’t know what you mean by relative air. Relative to what?

#### Housedr

##### Newbie
Clearly you are poking fun at this point.
The original poster wanted to get an answer and was having a hard time visualizing .
You posted pics of you. Great.
You did not answer his question.
S let me ask it once again-
You are flying along - there is zero ground reference to you (in this example)— this is an example so only answer the question - do not introduce un asked information.

The wind speed is calm so in this example you can’t point to any wind other than relative wind going through the rotors.
Give yourself max available airspeed and power- you can not go faster and climb because you have used all power going forward.
So you can’t push the stick any further forward and you have no more power to climb at that airspeed.
Will the gyro happily travel on its path undisturbed not climbing not losing altitude max airspeed max power?

————————
stop
—————-
Same scenario
This time you are headed to earth in a 30 degree dive
You have max power as in the example above
Max stick forward
Will your gyro suddenly climb now in this configuration where it would only go straight in the above first example?

#### Vance

##### Gyroplane CFI
Clearly you are poking fun at this point.
The original poster wanted to get an answer and was having a hard time visualizing .
You posted pics of you. Great.
You did not answer his question.
S let me ask it once again-
You are flying along - there is zero ground reference to you (in this example)— this is an example so only answer the question - do not introduce un asked information.

The wind speed is calm so in this example you can’t point to any wind other than relative wind going through the rotors.
Give yourself max available airspeed and power- you can not go faster and climb because you have used all power going forward.
So you can’t push the stick any further forward and you have no more power to climb at that airspeed.
Will the gyro happily travel on its path undisturbed not climbing not losing altitude max airspeed max power?

————————
stop

If the forces are in balance and I don’t move the cyclic or change the power the gyroplane will continue at that airspeed and altitude.

In The Predator at 7,500 feet MSL on a standard day I will be flying along at around 90kts and 75% power. The cyclic will not be against the forward stop.

stop
—————-
Same scenario
This time you are headed to earth in a 30 degree dive
You have max power as in the example above
Max stick forward
Will your gyro suddenly climb now in this configuration where it would only go straight in the above first example?

In The Predator I cannot leave maximum power in in a thirty degree dive without exceeding the indicated air speed I feel comfortable with. I will not have the power available to climb at anything over ninety knots and the cyclic will not be against the forward stop.

In the picture I had the hundred knot airspeed indicator pegged and was showing a little over 2,000 feet per minute of descent on the vertical speed indicator. My GPS showed 140 knots of ground speed.

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#### Housedr

##### Newbie
Ok- so we are in agreement after all.
(Max power=max usable)
Full forward stick =full travel to achieve level flight
So in this configuration the gyro flys straight- no climb.
So to the first confusion the gentleman asked why does the nose pitch down when stick is pushed forward.
That once the force is applied to the rotor (in this case forward motion tilting the rotor head down at some degree)
Instantaneously the rotor pitches forward- but the carriage lags behind just a second or so.
Then the carriage seeks angle that it needs for the desired speed- always.
It does not matter if you are diving or climbing- the rotor head angle only determines the speed at which you will fly.
When you see the nose of the gyro drop- you are seeing the carriage seeking the optimum angle it needs for that speed.
If you initiate a dive by pushing forward stick and hold that position and do not change the power setting- you will continue on that flight path.
JJ I hope that makes sense

#### Vance

##### Gyroplane CFI
Ok- so we are in agreement after all.
(Max power=max usable)
Full forward stick =full travel to achieve level flight
So in this configuration the gyro flys straight- no climb.
So to the first confusion the gentleman asked why does the nose pitch down when stick is pushed forward.
That once the force is applied to the rotor (in this case forward motion tilting the rotor head down at some degree)
Instantaneously the rotor pitches forward- but the carriage lags behind just a second or so.
Then the carriage seeks angle that it needs for the desired speed- always.
It does not matter if you are diving or climbing- the rotor head angle only determines the speed at which you will fly.
When you see the nose of the gyro drop- you are seeing the carriage seeking the optimum angle it needs for that speed.
If you initiate a dive by pushing forward stick and hold that position and do not change the power setting- you will continue on that flight path.
JJ I hope that makes sense

It appears to me we are not in agreement about anything and I mean no disrespect Jeff; we just have very different opinions about how a gyroplane flies.

I don’t know what “(Max power=max usable)” means.

The gyroplanes I have flown achieve level flight with power appropriate to the airspeed.

I don’t know what the meaning is of “Full forward stick =full travel to achieve level flight.”

These are not phrases used in The Rotorcraft Flying Handbook that I use as one of my primary references.

I have not flown a gyroplane with rotor system that instantaneously responds to cyclic control inputs. The slow response of a gyroplane rotor to cyclic inputs is often a challenge for new to gyroplane clients compounded by the fuselage lag.

As I wrote in my original post to JJ Campbell; in my opinion the reason the nose of a gyroplane pitches down when forward cyclic is applied is because the rotor thrust vector moves rearward and the center of gravity, generally speaking, seeks to be beneath the rotor thrust vector.

In my opinion based on my flying experience if I lower the nose in a gyroplane by moving the cyclic forward the gyroplane will increase its airspeed speed and if power is not added the gyroplane will descend unless I am below the minimum power required speed.

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#### Housedr

##### Newbie
Vance
you are stuck on a phrase not in the gyro handbook?
Explain this to me.
You said you have not flown a gyroplane that instantaneously responds to cyclic input.
I said the same exact thing you just did not read it.
The carriage lags behind. The cyclic moves instantaneously period.
Explain how that’s not accurate.
In my physics book it suggests that you can mechanically link the rotor to the stick and get instant movement with a delayed reaction.
so now that’s wrong? Explain that

Push the cyclic forward - the rotor disc tilts forward instantly but the carriage lags behind because it takes time for that mass to settle into the new attitude. Push cyclic forward, rotor disc tilts slightly forward carriage lags behind a second then follows by a nose down attitude.
tell me now how your physics is different?

Tell me how you have a level rotor head at full speed? This is not an opinion piece. I would be interested in knowing where you obtain that information. In every case, the rotor will stop spinning once the advancing blade ceases to have an angle sufficient to catch The wind. So tell me how your gyro is capable of having the disc level at full speed and everyone else’s is tilted back at an angle comenserate with the speed.

#### Vance

##### Gyroplane CFI

These are useful qualities in a flight instructor.

I find clients often imagine they understand some aspect of gyroplane flight when they don't and they aren't willing to ask the questions to clarify divergent opinions.

Vance
you are stuck on a phrase not in the gyro handbook?

As a flight instructor I find value in using the correct terminology so that my explanations are not misunderstood and it aligns with any homework I have given the client.

I was not able to find a definition for your equations.

I am not able to agree with an equation that has no meaning to me.

Explain this to me.
You said you have not flown a gyroplane that instantaneously responds to cyclic input.
I said the same exact thing you just did not read it.
The carriage lags behind. The cyclic moves instantaneously period.
Explain how that’s not accurate.
In my physics book it suggests that you can mechanically link the rotor to the stick and get instant movement with a delayed reaction.
so now that’s wrong? Explain that

Push the cyclic forward - the rotor disc tilts forward instantly but the carriage lags behind because it takes time for that mass to settle into the new attitude. Push cyclic forward, rotor disc tilts slightly forward carriage lags behind a second then follows by a nose down attitude.
tell me now how your physics is different?

Tell me how you have a level rotor head at full speed? This is not an opinion piece. I would be interested in knowing where you obtain that information. In every case, the rotor will stop spinning once the advancing blade ceases to have an angle sufficient to catch The wind. So tell me how your gyro is capable of having the disc level at full speed and everyone else’s is tilted back at an angle comenserate with the speed.

You wrote:

that once the force is applied to the rotor (in this case forward motion tilting the rotor head down at some degree)
Instantaneously the rotor pitches forward- but the carriage lags behind just a second or so.”

I wrote; “I have not flown a gyroplane with rotor system that instantaneously responds to cyclic control inputs. The slow response of a gyroplane rotor to cyclic inputs is often a challenge for new to gyroplane clients compounded by the fuselage lag.”

These explanations do not have the same meaning to me. I feel it is important to consider the progressive cyclic response of the rotor control system as a part of understanding the flight controls.

If I assume that you use the word “carriage” to mean the fuselage; we are in agreement that there is a lag in the fuselage response to the change in rotor disk angle.

I have not flown a gyroplane with a “rotor” that responds instantly to rotor control inputs. In my opinion based on my observation the rotor disk angle lags behind the rotor control inputs and the fuselage lags behind the change in the rotor disk angle.

This is often a valuable understanding for a low time pilot flying in gusting winds.

They tend to stab at the cyclic when they feel a gust.

I can shake the cyclic pretty hard with effectively no response from the rotor.

Tell me how you have a level rotor head at full speed? This is not an opinion piece. I would be interested in knowing where you obtain that information. In every case, the rotor will stop spinning once the advancing blade ceases to have an angle sufficient to catch The wind. So tell me how your gyro is capable of having the disc level at full speed and everyone else’s is tilted back at an angle comenserate with the speed.

I don't recall opining that I have a level rotor disk at maximum indicated air speed in The Predator.

When I measure the angle of the rotor head on The Predator when she is on the ground with the cyclic against the forward stop the angle is very near zero degrees. At higher airspeeds The Predator fuselage flies very near the same angle as she is on the ground. Even with the cyclic at the forward stop the rotor disk angle is still tilted back because of blow back. At ninety knots indicated air speed the cyclic is near the forward stop in The Predator.

From The Rotorcraft Flying Handbook Glossary: Blowback- The tendency of the rotor disk to tilt aft in forward flight as a result of flapping.

If a gyroplane's rotor disk is at zero degrees to the relative wind there will be no lift produced and the gyroplane will descend providing the rotor disk with a positive angle of the disk to the relative wind.

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#### WaspAir

##### Supreme Allied Gyro CFI
(Max power=max usable)
Full forward stick =full travel to achieve level flight
So in this configuration the gyro flys straight- no climb.
It seems you have assumed that top speed in level flight is limited by the available forward cyclic control travel, and this description does not match my experience.
I have never held full forward stick for any sustained period, because I don't care to bunt.

Assuming you are trying to answer the original question in this thread, it was about why the nose goes down as a result of forward stick, not when it will respond. Delay or control lag wasn't the question.

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#### Greg Vos

##### Active Member
One might (at first blush) think that the gyro's frame would stay level when the rotor disk is level. That's the way it is in helicopters.

In our gyros, however, we intentionally place the CG far enough forward so that, if the rotor is pulling straight up relative to the horizon (rotor level) and there's no prop thrust, the frame hangs 10-11 degree nose-down. We conduct a "hang test" before we first fly to be sure this is the case.

Why? Because, in level cruising flight, a gyro's rotor is inclined aft around ten degrees. This aft tilt means that the rotor is pulling up-and-back on the gyro at an angle of ten degrees. The gyro's CG must lie on the rotor's up-and-back thrust line, and the frame then flies level in cruise.
I think this post answers the OP. ..the rest .....

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