NATOPS Chapter 11 Flight Characteristics HSM-50 Flashcards
Blade tips move at ________.
725 ft/sec or Mach .65 (65% of the speed of sound)
The MH-60R is considered to be in ground effect below what altitude?
RADALTs of at or below 45 ft. Helicopters are generally considered to be in ground effect within one rotor diameter of the ground.
Flapping fixes _____________. By reducing lift on the _________ blade and increasing it on the ___________ blade by flapping _________.
Asymmetrical distribution of lift
Advancing
Retreating
Flapping down
Phase lag is felt ______ degrees from where the inputs are put in.
90*
Define blowback
In a hover the advancing blade sees more lift than the retreating blade. Causing the rotor to be tilted aft.
Pilot input, gust alleviation function of SAS 2, and attitude hold functions will counter this
Translational lift is at approximately what?
17kts.
Transitioning to forward flight with tail winds will cause you to see _________ when you have relative winds of zero.
More power required versus.
STAB begins programming at what?
30 KIAS. Below 30 KIAS, collective position, airspeed, lateral acceleration, and pitch rate inputs do not affect STAB position.
Methods to eliminate Blade Stall?
DRAAGS
SCAARG
Decrease Collective Pitch Rotor Rpm increase Airspeed reduce Altitude reduce Gross weight reduce Severity of maneuver (reduce)
Blade Stall happens when
The retreating blade has increased is AOA so much that it has stalled.
The blade tip is traveling at rotational speed minus forward airspeed of helicopter.
Each blade will pass through the blade stall region until controlled; forms at root of blade.
All other causal factors are increased significantly by low rotor rpm.
Weather vaning is what?
And occurs when?
Winds push on the tail and cause the helicopter to rotate into the wind.
120* to 240*
What is tail rotor vortex ring state?
What region does it occur in?
The tail rotor operates in its own airflow. Causing unpredictable yaw rates
210* to 330*
Main rotor disc vortex interaction is what?
Occurs in What region?
Main rotor vortex is directed onto the rotor changing the AOA on the tail rotor.
280* to 330* and possibly 030* to 080*
How can you recover from LTE?
Lowering collective
Forward cyclic
In a hover, applying full left pedal.
Vortex ring state occurs when?
When are they worst?
Measurable at Descent rates greater than 700 fpm between 0 - 20 kias
Worst at Descent rates of 1500 fpm and 5 - 10 kias
Fully developed characterized by unstable pitch and roll oscillations, little or no cyclic authority, and decent rates up to 6000fpm.
How do you recover from vortex ring state?
Decrease collective pitch
Increase forward airspeed
Enter autorotation if altitude permits.
Regions of prop during autorotative state?
Prop region- 30%
Autorotative-45%
Stall region - 25%
Prop region creates _______.
Usable lift
The autorotative region creates __________________.
Lift and rotational forces.
Achieved at descent rates between 3125 and 4450 fpm at gross weights of 19,000 lbs.
Stall region creates only ___________.
Drag forces
When does static Rollover occur?
28*
Critical rollover occurs at?
12*
How does aircraft respond to rotor blade Stall?
Increased vibs
Pitch up
Roll left
Why does a heavier helo auto slower than a lighter helo?
Higher collective pitch is required to control Nr of heavy aircraft. This results in more lift from the rotors and a slower rate of descent.
Order of preference with abnormal vibrations?
Runway
Large deck
Small deck
Running landing not recommended. Land on a spot.
What type of drag is dominant at slow speeds and in a hover?
Induced
Securing one engine allows a/c to operate at ___ speeds, where drag is ___, while operating a single engine at a more efficient power setting
Slower, reduced
__ roll rates of __ deg/second in forward flight above __ KIAS, can combine with induced tail rotor gyroscopic and flapping loads to cause excessive tail rotor spar loading
Left, 30 deg, 75 KIAS
Airspeed for moderate turbulence
blade stall - 15 knots
Airspeed for light turbulence
blade stall - 10 knots
Tail Rotor Spar Loading
Left roll rate increases blade AOA, driving torque up and main rotor precession loads can contribute further
Left roll rates (above 30 deg/sec in forward flight above 75 KIAS) can combine with induced tail rotor gyroscopic and flapping loads to cause excessive spar loading
When executing high roll rate maneuvers to the left, you should
Lower collective concurrently with maneuver initiation to control transient torque increases and reduce high TR spar loads
Speed for translational lift
17 KIAS
Normal Hover Attitude
4 to 5 degrees nose up, 2 to 3 degrees left wing down
Rotor Downwash
For an MH-60R at 21,700 lbs on a standard day, downwash can exceed 50 knots.
Autorotation Entry
Delay in lowering collective can result in catastrophic loss of Nr within 2 seconds. Generally, higher airspeeds up to max of 100 are preferred because more energy can be put into spinning rotor at the end.
Autorotation Descent
Minimum rate of decent achieved at 75 KIAS. (Increase or decrease from here increases ROD).
Increasing up to 95 KIAS will increase glide distance.
(Practice autorotations are generally shot 5 KIAS above ideal airspeed to allow aircraft to slow to the optimal condition).
Autorotational Recovery
Stab will program down, helping helicopter slow even more.
In actual auto-rotational flare, pilot may choose to allow Nr to increase above optimum for descent to attain more kinetic energy for recovery. (For practice, keep at 100, engines won’t respond to power pull until Nr back at 100%)
Dynamic Rollover
Not defined by a single number. Can occur within 2 seconds when unable to counter with full opposite cyclic. (1/5 the effectiveness of cyclic vs airborne).
Many contributing factors, but largest is buildup of angular velocity of helicopter CG about the wheel touching the ground.
Rolling moment to the right will be increased by tail rotor.
Smooth reduction of collective is the most effective means of countering dynamic rollover.
Saltwater Deterioration TGT
While operating in a salt spray environment for any time, a TGT rise of 20 degrees or more for a constant torque is an indication of engine degradation and possible salt encrustation.
40 degrees… an indication of engine degradation which could result in compressor stalls.
Saltwater Ingestion Notes
The amount of salt spray on the windshield is the best indicator of the environment that the engines are subjected to.
Probability of ingestion greatest at 8-12 Kts.
At 15-20 kts and higher, salt spray is generated but blown below engines so little ingestion occurs.
Nonlinear relationship with salt and hover altitude for a given wind condition:
30 ft little buildup
15-20 moderate
Even at 5 feet, winds have to be 8-12 to cause a deterioration of engine performance.
What causes ground resonance?
Ground resonance is precipitated by a blade badly out of track, or a malfunctioning damper which feeds aircraft motion back into the rotors, creating a large unbalance and inertial forces.
Tail Rotor Driveshaft Vibrations
Could be caused by a failing IGB/TGB. Felt as a buzzing in the pedals or a tickling of the nose like that of a feather.
