# a question from ground school

#### bryancobb

##### Junior Member
I was tauqht... Induced draq is that portion of total draq that is created when lift is beinq produced. It varies with the amount of lift beinq produced.

By definition, straiqht & level at 100kts in a particular machine needs the exact same amount of lift as that machine straiqht & level at 50kts. Induced draq is the same.

#### WaspAir

##### Supreme Allied Gyro CFI
I was tauqht... Induced draq is that portion of total draq that is created when lift is beinq produced. It varies with the amount of lift beinq produced.

By definition, straiqht & level at 100kts in a particular machine needs the exact same amount of lift as that machine straiqht & level at 50kts. Induced draq is the same.
It is not dependent on lift alone. For an airfoil at steady airspeed, as in a fixed wing aircraft, induced drag varies inversely with the square of the airspeed, and its graph is a rapidly decreasing curve with respect to speed. That's because higher speed flow will produce the same lift with a lower angle of attack, and that is a lower induced drag situation. Parasitic drag, however, will rapidly increase with airspeed. The variation in the sum of those two is what permits flight at two airspeeds with the same high power setting -- one "behind the curve" with low speed and high AOA, and one at high speed with a low AOA, even though both conditions use high power and create the same lift. Induced drag dominates at the lower speed and parasitic drag dominates at the higher speed.

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#### XXavier

##### Member
This is another terribly worded question.
First, rrpm increases slightly with more forward speed (a small but real effect).
Second, airspeed seen by the retreating blade is NOT higher with more forward speed (remember disymmetry of lift?), so you can't make a blanket comment about "any station at any moment".
Perhaps they could have asked a question about total drag of the whole rotor system instead of a blade . . . but this one is not well thought out.
True... I stand corrected...

#### PanamaPaul

##### Newbie
EVERYONE
These discussions are great and needed for new gyro pilots, I am leaning a great deal reading this one, please keep it going. ******

#### Vance

##### Gyroplane CFI
another off the sport pilot question bank.

another off the sport pilot question bank.

What precaution should be taken while taxiing a gyroplane?
A. The cyclic stick should be held in the neutral position at all times
B. Avoid abrupt control movements when blades are turning.
C. The cyclic stick should be held slightly aft of neutral at all times.

I found this question confusing.

The answer they want is B.

I was taught to taxi with the blades stopped on smooth surfaces.

When the blades are slowing and not providing lift abrupt control inputs won't do much.

A and C are also wrong because with most gyroplanes I have flown the cyclic should be full forward when taxiing.

At the air show I taxied with the blades turning to get out of the way and part of how I stop them in the correct place (front and back) is an abrupt control input.

#### JEFF TIPTON

##### Senior Member
B. Avoid abrupt control movements when blades are turning.
I wonder if the bank of questions are geared toward a McCullough J-2 or the Air & Space 18.

#### WaspAir

##### Supreme Allied Gyro CFI
I wonder if the bank of questions are geared toward a McCullough J-2 or the Air & Space 18.
Definitely NOT for the questions cited in this thread so far. Addressing them in the order they came up,

1. I've never even seen a pitch oscillation in either model; PIO is not an issue.

2. There is no such thing as "flap" for the J-2 or 18A. They are each pre-spun to more than 120% of flight rpm while sitting still, before any take-off roll is even begun, and they lose rpm (not gain it) during the roll. There is no rotor management to be done when flying these aircraft.

3. Collective pitch is not varied during flight (except for a small rpm-trimming adjustment available on some 18As with an STC), so one won't be "adjusting a pitch angle" for steering.

4. Both are swash-plate controlled systems, not head-tilting, and you're not going to create problems with stick position during taxi. I often taxi the 18A without touching the stick at all; it doesn't really matter where it is. Abrupt stick movements on the ground are simply not a concern. For the 18A in particular, you can apply the rotor brake for taxi, and that puts it into flat collective pitch, so the rotor won't be doing anything at all.

These questions appear to me to aimed at Bensen-style fixed collective teetering rotor systems for which rotor management is a big deal, but the questions are just very badly written.

#### Vance

##### Gyroplane CFI
Another question from the sport pilot gyroplane bank.

Another question from the sport pilot gyroplane bank.

Here is one that is clearly aimed at an 18 A or McCulloch J2 and people with experience limited to a two blade semi rigid rotor system may feel lost.

If ground resonance is experienced during rotor spin-up, what action should you take?

A. Taxi to a smooth area.

B. Make a normal takeoff immediately.

C. Close the throttle and slowly raise the spin-up lever.

C is the answer they want.

This is odd because Sport Pilot only allows two blade semi rigid rotor systems and the 18A and J2 have too high a gross weight to be sport pilot.

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#### WaspAir

##### Supreme Allied Gyro CFI
Answer C applies to the J-2 only; it's the only one with a "spin-up lever". Raising it adds collective pitch, disengages the transmission, and removes tension from the clutch belts. The 18A has push-buttons and a hydraulic pump handle instead (raising the pump handle won't increase collective pitch so it doesn't work like the J-2 lever).

This question is especially strange, given that I've never heard of anybody getting even the slightest hint of ground resonance in a J-2.

P.S. It's "McCulloch", like the chain saw brand (same guy behind both companies), not "McCullough", if anybody cares about such details.

#### okaneco1

##### Member
another question

another question

Maybe poorly written, I didn't write the questions

Remember there is a correct answer and then there is the FAA correct answer.
These questions fall into the correct answer catagory

During flight, if the wind conditions became very gusty, what would the proper action be to avoid possible oscillating and/or porpoising?

#### Vance

##### Gyroplane CFI
I reduce power and slow to maneuvering speed when I encounter turbulence.

Without the possible answers the FAA answer is hard to determine.

#### okaneco1

##### Member
This is not a FAA test

This is not a FAA test

Vance, this is not a FAA test. Please answer as honest as possible with the your answer as you see it.

#### Vance

##### Gyroplane CFI
I thought I had James.

I fly along the coastal mountains of California where there frequently AIRMET (Airmen's Meteorological Information) for moderate turbulence and sometimes a SIGMET (Significant Meteorological Information) for severe turbulence.

Our entire flight in the Cavalon from Santa Maria, California to Spanish Fork, Utah had an AIRMET for moderate to severe turbulence.

When we encounter turbulence I reduce power and slow to 70kts; maneuvering speed; Vb (design speed for maximum gust intensity).

I use the rudder pedals to keep the yaw string as straight as possible.

We were seeing wind shear as much as 15kts and rising or descending air over 1,000 feet per minute.

It is not unusual to encounter unexpected turbulence even when there is no AIRMET and the response is the same, reduce power and reduce speed to Vb.

Most air speed indicators are marked for Vb with a green arc. If it is not I feel it is a useful thing to do. I feel a red arc for Vne also has value.

This is not to be construed as flight instruction. It is just what I do when I encounter turbulence. Flight instruction is progressive and more complex.

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#### WaspAir

##### Supreme Allied Gyro CFI
Another thought to consider -- what is your target for aircraft control in strong turbulence and wildly varying local airmass movement? Holding altitude, holding airspeed, holding something else? (Face it, you can't keep all the numbers where you want them at the same time when the atmosphere is feeling argumentative!)
My preference is to hold attitude, accepting altitude and speed excursions as you get blasted about. Chasing speed, or chasing altitude, is a great deal of work and can lead to still greater excursions, perhaps including oscillation.

#### C. Beaty

##### Gold Supporter
Here’s yet another reason for providing aerodynamic compensation for propeller torque.

During turbulence, gusts roll the airframe in those cases where the rotor is called upon to balance propeller torque. It makes no difference whether the rotor is offset to one side or not; the rotor thrust vector must pass to one side of the CG by the same amount in either case.

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#### oldsparky

##### Newbie
what is the first action to take if oscillation occurs in flight?
that question has been been answered.

What is the 2nd action to take is the next question.

answer, put an effective horizontal stabilizer on the gyro, then you wont have to ask question 1

thats been my experience after flying (?) a parsons with a bit of bent tin for a stabilizer, and flying my own gyro with a foil section stabilizer.
Having a reference in line of sight to the forward horizon is also useful to pick up early sign of oscillation.

cheers bruce