Blade Stall Flashcards
The retreating blade stall places a limit on?
Maximum foward speed of a helicopter
Conditions likely to lead to retreating blade stall include?
High aircraft foward speed
High load factors
Steep turns
Abrupt control movements
Flight in turbulence
High density altitude or high altitude
Main reasons for limitations of foward airspeed
Gross weight increases, which reduces VNE
Increased density altitude reduce VNE
With an engine failure there is a tendency for the aircraft to enter a?
Left descending turn
Stalled region
Slow close to the hub
Attempts to slow the blade down
Driven region
Induced drag is at its worst near the blade tips
Driving region
Total reaction leans foward providing force in the plane of rotation
Drives the blades
Provides rotor thrust
Requirements to develop Vortex ring state
A low or zero airspeed
A rate of descent in the region of 400-800ft/min
Symptoms of vortex ring state
Aircraft vibrations
Random yawing rolling and pitching
Increase rate of descent
Reduction in cyclic stick effectiveness
Recovery technique from vortex ring state
Cyclic foward to increase airspeed
Brief pause to allow airspeed to build up
Apply power
During auto rotations best range is achieved by
Low rotor rpm, high collect pitch at best range speed
Driving region in autorotation distribution over the rotor disc is
Displaced towards the retreating blade
Coming angle will decrease if
Thrust decreases, or centrifugal force (rrpm) increases
One of the main causes of hunting in a main rotor system is
Geometric imbalance
VNE is
IAS which will decrease with height
