Ch5

Question 1

What do you adjust on a bell 212 to prevent geometric imbalance?

Answer 1

Check answer

Drag braces

Question 2

What is the purpose of the tab on the trailing edge of a blade

Answer 2

Tracking adjustment

Question 3

What do you adjust on a semi-rigid rotor to reduce vibration

Answer 3

Check answer

Dampeners

Question 4

What are the two factors of vibration we are concerned with?

Answer 4

Amplitude and frequency

Question 5

What does BIS stand for and what is it?

Answer 5

-Blade Inspection System
-use of thin wires along the spar that will cause a steady light if broken by a crack
(Flashing light is good, steady=change 9V battery and check again, if still steady, replace blade)

Question 6

What does BIM stand for and what is it?

Answer 6

• Blade Inspection Method
• fill spar (which is pretty much the blade) with nitrogen. Gauge will be yellow and white if no leak (means no crack in spar) and red and black if there is a loss in pressure (means crack in blade)

Question 7

Check question;

What unit of measurement is used for imbalanced vibrations?

Answer 7

Inches Per Second (IPS)

Question 8

What are the CPM ranges of the 3 types of vibration (found as a result of MR imbalance)?

Answer 8

• Low frequency= 0-500
• Med frequency=500-2000
• High frequency=2000 plus

Question 9

If a pilot complains about a tingling in his/her feet, what is it’s cause?

Answer 9

High frequency vibrations in tail rotor

Question 10

What are the methods used to determine track?

Answer 10

• stick method
• flag method
• light reflector method
• pre-track method (manufacturer does this)
• electronic or strobe method (most common)

Question 11

What method is not used to determine track?

Answer 11

Tape method (used for balancing)

Question 12

After alignment, when balancing, blades may only be swept ____ of alignment points

Answer 12

Aft (never want a diving blade)

Question 13

After tracking you must always test…

Answer 13

Autorotation rpm (very important step)

Question 14

What is the purpose of blade alignment?

Answer 14

To align CofP with pitch change axis

Question 15

What is the Astar flex beam made of and what is an advantage of this?

Answer 15

• fibreglass

- not subject to fatigue

Question 16

What is the difference between a fibreglass and composite blade?

Answer 16

Fibreglass has a fibreglass spar and composite has a metal spar

Question 17

What is the MAJOR advantage of a fibreglass blade?

Answer 17

It’s life

Question 18

What are the 2 most common types of rotor heads?

Answer 18

• semi-rigid

- fully articulated

Question 19

What is soft in plane?

Answer 19

Bells version of fully articulated rotor head (same thing)

Question 20

Explain retreating blade stall

Answer 20

The condition of a rotor blade when its operating at an angle of attack greater than the max. angle of lift.
-occurs at high forward speed to the retreating blade and all blades during “settling of power”

Question 20

Why were symmetrical airfoils used on early helicopters?

Answer 20

Lower cost and ease of construction

Question 21

Why was wood used originally for helicopters blades? What shortcomings were found in wooden MR blades?

Answer 21

• because of their lifetime (it’s use depends on its condition)
• a short coming was blades were a matched set (to replace one, had to replace both)

Question 22

What factors affect autorotation rpm?

Answer 22

• gross weight of heli

- density alt.

Question 23

What is a “2 per rev” vibration?

Answer 23

It’s a low frequency vibration caused by the rotor itself

Question 24

A “teeter totter” rotor head is more formally referred to as?

Answer 24

Semi-rigid rotor head

Has seesaw action or flapping axis

Question 25

After tracking adjustments what must be verified on each aircraft?

Answer 25

Check that all blades are traveling within the same tip path plane

Question 26

What is the function of a lead/lag dampener?

Answer 26

Dampens the hunting action of the lead-lag hinge to prevent geometric imbalance

Question 27

How many types of lead-lag dampeners are in use?

Answer 27

3

• hydraulic
• multiple disc
• elastomeric

Question 28

A faulty lead/lag dampener may induce what dangerous condition?

Answer 28

A shuffle with a 1:1 beat of the rotor

Question 29

What is the difference between vertical and lateral vibration?

Answer 29

Vertical vibration is normally associated with track, while lateral vibration is associated with an unbalanced condition