NATOPS Chapter 11 Flight Characteristics HSM-50

Question 1

Blade tips move at ________.

Answer 1

725 ft/sec or Mach .65 (65% of the speed of sound)

Question 2

The MH-60R is considered to be in ground effect below what altitude?

Answer 2

RADALTs of at or below 45 ft. Helicopters are generally considered to be in ground effect within one rotor diameter of the ground.

Question 3

Flapping fixes _____________. By reducing lift on the _________ blade and increasing it on the ___________ blade by flapping _________.

Answer 3

Asymmetrical distribution of lift

Advancing

Retreating

Flapping down

Question 4

Phase lag is felt ______ degrees from where the inputs are put in.

Answer 4

90*

Question 5

Define blowback

Answer 5

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

Question 6

Translational lift is at approximately what?

Answer 6

17kts.

Question 7

Transitioning to forward flight with tail winds will cause you to see _________ when you have relative winds of zero.

Answer 7

More power required versus.

Question 8

STAB begins programming at what?

Answer 8

30 KIAS. Below 30 KIAS, collective position, airspeed, lateral acceleration, and pitch rate inputs do not affect STAB position.

Question 9

Methods to eliminate Blade Stall?

DRAAGS
SCAARG

Answer 9

Decrease Collective Pitch
Rotor Rpm increase
Airspeed reduce
Altitude reduce
Gross weight reduce
Severity of maneuver (reduce)

Question 10

Blade Stall happens when

Answer 10

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.

Question 11

Weather vaning is what?

And occurs when?

Answer 11

Winds push on the tail and cause the helicopter to rotate into the wind.

120* to 240*

Question 12

What is tail rotor vortex ring state?

What region does it occur in?

Answer 12

The tail rotor operates in its own airflow. Causing unpredictable yaw rates

210* to 330*

Question 13

Main rotor disc vortex interaction is what?

Occurs in What region?

Answer 13

Main rotor vortex is directed onto the rotor changing the AOA on the tail rotor.

280* to 330* and possibly 030* to 080*

Question 14

How can you recover from LTE?

Answer 14

Lowering collective

Forward cyclic

In a hover, applying full left pedal.

Question 15

Vortex ring state occurs when?

When are they worst?

Answer 15

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.

Question 16

How do you recover from vortex ring state?

Answer 16

Decrease collective pitch

Increase forward airspeed

Enter autorotation if altitude permits.

Question 17

Regions of prop during autorotative state?

Answer 17

Prop region- 30%
Autorotative-45%
Stall region - 25%

Question 18

Prop region creates _______.

Answer 18

Usable lift

Question 19

The autorotative region creates __________________.

Answer 19

Lift and rotational forces.

Achieved at descent rates between 3125 and 4450 fpm at gross weights of 19,000 lbs.

Question 20

Stall region creates only ___________.

Answer 20

Drag forces

Question 21

When does static Rollover occur?

Answer 21

28*

Question 22

Critical rollover occurs at?

Answer 22

12*

Question 23

How does aircraft respond to rotor blade Stall?

Answer 23

Increased vibs

Pitch up

Roll left

Question 24

Why does a heavier helo auto slower than a lighter helo?

Answer 24

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.

Question 25

Order of preference with abnormal vibrations?

Answer 25

Runway

Large deck

Small deck

Running landing not recommended. Land on a spot.

Question 26

What type of drag is dominant at slow speeds and in a hover?

Answer 26

Induced

Question 27

Securing one engine allows a/c to operate at ___ speeds, where drag is ___, while operating a single engine at a more efficient power setting

Answer 27

Slower, reduced

Question 28

__ 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

Answer 28

Left, 30 deg, 75 KIAS

Question 29

Airspeed for moderate turbulence

Answer 29

blade stall - 15 knots

Question 30

Airspeed for light turbulence

Answer 30

blade stall - 10 knots

Question 31

Tail Rotor Spar Loading

Answer 31

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

Question 32

When executing high roll rate maneuvers to the left, you should

Answer 32

Lower collective concurrently with maneuver initiation to control transient torque increases and reduce high TR spar loads

Question 33

Speed for translational lift

Answer 33

17 KIAS

Question 34

Normal Hover Attitude

Answer 34

4 to 5 degrees nose up, 2 to 3 degrees left wing down

Question 35

Rotor Downwash

Answer 35

For an MH-60R at 21,700 lbs on a standard day, downwash can exceed 50 knots.

Question 36

Autorotation Entry

Answer 36

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.

Question 37

Autorotation Descent

Answer 37

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).

Question 38

Autorotational Recovery

Answer 38

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%)

Question 39

Dynamic Rollover

Answer 39

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.

Question 40

Saltwater Deterioration TGT

Answer 40

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.

Question 41

Saltwater Ingestion Notes

Answer 41

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.

Question 42

What causes ground resonance?

Answer 42

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.

Question 43

Tail Rotor Driveshaft Vibrations

Answer 43

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.