10 Minute Helicopter Videos (10/28/22) Flashcards
What makes you fall faster in an autorotation?
- Higher density altitude
- Higher weight
- Out of trim
- Turning
- Aft cyclic
In an autorotation, what if you don’t reduce blade pitch (drop collective)?
Blades will cone upwards and break
Why doesn’t rotor reverse in an autorotation?
Because if pitch was left high, then the blades would cone and break before they reversed
More Lift: Larger ______ and less ______ _____?
Angle of attack, induced flow
Less Lift: Smaller ______ and more ______ _____?
Angle of attack, induced flow
What speed does Transverse Flow Effect happen?
10-15 knots
What speed does Effective Translational Lift happen?
16-24 knots
Gyroscopic precession
Force felt 90 degrees ahead of rotation
If you want to drift left, where does the force need to be applied?
Rear of rotor, force will be felt 90 degrees ahead of rotation (right side), causing left drift
What does ETL speed depend on? (3 things)
- Blade size
- Area
- RPM
What speed occurs at the lowest point on the total drag curve?
Max rate of climb airspeed
Looking at a rotor from above, there are three regions, starting at the center and moving outwards, what is each region called
- Stall region (25%)
- Driving region (45% lift producing)
- Driven region (30%)
Which direction does the R22 rotor turn?
Counter Clockwise
What are several ways that you can compensate for translating tendency? (4 things)
- Left cyclic
- Rigging of flight controls
- Transmission mounting
- Flight management computer
What is another name for vortex ring state?
Settling with power
What are three requirements for vortex ring state?
- less than ETL
- greater than 300 FPM descent
- 20% to 100% power applied
Why do you need power for vortex ring state to occur?
You need power in order to produce some downflow and create the vortices. If you have no power than you only have upflow
What flight situations are conducive to vortex ring state? (6 things)
- Steep approaches
- Downwind/tailwind approach
- Formation approach
- Poor attitude control in OGE
- Descent from OGE hover
- Hover above max hover ceiling (high DA)
Height/Velocity curve: Why are there two upper curves?
Changing density altitude
Height/Velocity curve: What is shown by the lower curve?
High speed, low altitude, not enough reaction time
What is the height/velocity curve based on? (2 things)
- Max gross weight
- Average, proficient pilot
What is dynamic rollover?
The tendency of a helicopter to continue rolling when the critical angle is exceeded.
What are the three parts of a dynamic rollover?
- Pivot point
- Exceeding critical angle
- Rolling motion
What are some causes of dynamic rollover? (4 things)
- Tiedowns
- Skid contact
- Stuck landing
- Slope T/O and Landing
Best actions to avoid dynamic rollover (2 things)
- Focus and slow down
- Lower collective if the situation doesn’t feel right
What are three types of rotor systems?
- Rigid
- Semi rigid
- Fully articulated
Describe a rigid rotor (Movement, advantages, disadvantages, what type of helicopter has this type of rotor)
- Only feathering
- Simple and cost effective
- Blades absorb all of the forces
- Red bull helicopter
Describe a semi rigid rotor (Movement, advantages, disadvantages, what type of helicopter has this type of rotor)
- Flap and feather
- Simple and cost effective
- Subject to mast bumping
- R22
Describe a fully articulated rotor (Movement, advantages, disadvantages, what type of helicopter has this type of rotor)
- Flap, feather, lead/lag
- Coriolis affect is absorbed by the hinges
- Apache
What are the different types of drag? (4 types)
- Parasite (exponential up)
- Induced (exponential down, lift)
- Profile (gradually up)
- Total (combination of them all)
What is the low point of the total drag curve?
Max rate of climb
What are the four parts of the lift equation?
- Coefficient of lift
- Surface area of rotor
- Air density
- Velocity
How does speed affect lift?
Lift quadruples as speed doubles
What is the main thing that effects the coefficient of lift?
Shape of the airfoil
How does surface area effect lift?
More area, more lift
As the rotor cones, what happens to the CG of the blades? What happens to the surface area?
CG moves inward, surface area decreases
How can you avoid mast bumping? (2 things)
- Don’t do a low-g pushover
- Keep weight on the rotor
What is the main advantage of a symmetric rotor?
The center of pressure has very little forward/aft movement with changing angles of attack
What is the center of pressure?
It is the center of the aerodynamic forces
As the velocity of air increases in a venturi, what happens?
Pressure and temperature drop
What are three causes of retreating blade stall?
- Airspeed above Vne
- To much forward cyclic
- Collective angle to high
What are four symptoms of retreating blade stall?
- Vibrations
- Vertical bounce
- Flight control feedback
- Uncommanded pitch up, roll to left side
Describe retreating blade stall
Down flap on the retreating side increases angle of attack leading to a stall.
What does the term “bucket speed” mean in a helicopter?
It is the speed at the bottom of the lift drag curve. This is basically the speed where you have a lot of power available.
What is the acronym for a confined area approach/landing?
PWOTFEEL
- Power/performance
- Winds
- Obstacle
- Terrain/Turbulence
- Forced Landing Area
- Exit
- Enter
- Landing
When should you consider a go around in a confined area approach?
Before ETL (10-12 KIAS)
What is transient torque spike? (Long definition)
When a decrease in RPM is sensed, the fuel governor shoots fuel into the engine to try and maintain rotor RPM. This results in a torque spike.
What are some factors that amplify torque spike? (5 things)
- Rate of movement
- Magnitude of movement
- Power applied
- Airspeed
- Weight
What is transient torque spike? (Short definition)
Aerodynamic phenomenon that occurs given lateral cyclic
Describe the string theory in relation to transient torque spike
Think of a string attached to the cyclic. You want to keep tension in the string. If you move the cyclic to the right (away from the collective) then you have to raise the collective.
Vbe
Velocity best endurance
Greatest airborne time per unit of fuel consumed
Vy
Max rate of climb per unit time
Vx
Max rate of climb per unit distance
Vbr
Velocity best range, most miles per gallon
LTE
Loss of tail rotor effectiveness
Describe LTE
Uncontrolled, rapid, right yaw that can cause loss of control
What are different types of tail rotor issues? (4 things)
- Wind (LTE)
- Mechanical limit (Physical stop)
- Mechanical failure (Fixed pitch/stuck pedal)
- Emergency (Loss of components)
When are you “OGE”
Height that is one rotor diameter above the ground.
Autorotation, why do you put the collective down?
Because it allows the upward flow of air to keep the rotor spinning in the direction that is was spinning.
Autorotation, what would happen if you held the collective up?
The rotor would eventually stop, cone up, and break
Anything that makes you fall faster will do what to the RPM in an autorotation?
Increase the RPM
What increases the RPM in an autorotation? (4 things)
- Weight
- Density altitude
- Out of trim
- Turning (left turn- little increase, right turn- big increase)
What does aft aft cyclic do to RPM in an autorotation? What does forward cyclic do?
Increase RPM, decrease RPM
In an autorotation with excessively high RPM, what happens to the regions of the rotor?
- Driving region expands and the driven region shrinks.
