National Commission for the
Certification of Crane Operators
Committed to Quality, Integrity, and Fairness in Testing since 1995

CERTIFICATIONS

Mobile Crane Operator

Written Exam - Answers to Sample Questions

Manitowoc - Lattice Boom Truck Crane (LBT)

Following are the answers to the Manitowoc LBT sample questions:

Sample Item #1

Configuration On Fully Extended Outriggers Extension 40-ft. jib
Counterweight 95,400-lb. + 25,000-lb. Ext. Off-set / Angle 5-degrees
Main Boom 140-ft. Block 5,000-lb., 4-parts of line
Main Boom Angle 60.3-degrees Ball 500-lb., 1-part of line, 15-ft. below tip
Radius N/A Rigging 1,000-lb.
Other Boom Butt Mounted Auxiliary Drum Main Rope 2-lb./ft.
Other N/A Aux. Rope  2-lb./ft.

Note: For line in use, deductions for wire rope length beneath boom/jib point shall be based on boom/jib point-elevation column listed on the boom/jib capacity chart. Round boom/jib point elevation to the nearest whole number.

What is the net capacity when lifting from the main boom over the side?
(Click on each answer for explanation of why it is correct or incorrect.)

A. 39,100 lb.
Incorrect. No excess rope deduct.

B. 38,030 lb.
Correct. 

Gross Capacity
52,000
Jib
4,700
Block
5,000
Ball
500
Rigging
1,000
Main Rope
1,040
Aux Rope
30
Aux Drum
1,700
Total Deducts
13,970
Net Capacity
38,030

 
C. 31,230 lb.
Incorrect. Used 78,400 lb. + 25,000 lb. counterweight.

D. 42,730 lb.
Incorrect. No jib deduct.

Sample Item #2

Configuration On Fully Extended Outriggers Extension 30-ft. jib
Counterweight 95,400-lb. + 25,000-lb. Ext. Off-set / Angle 25-degrees
Main Boom 100-ft. Block 2,650-lb., 4-parts of line, 10-ft below tip
Main Boom Angle N/A Ball 500-lb., 1-part of line
Radius 105-ft. Rigging 375-lb.
Other N/A Main Rope 2-lb./ft.
Other N/A Aux. Rope  2-lb./ft.

Note: For line in use, deductions for wire rope length beneath boom/jib point shall be based on boom/jib point-elevation column listed on the boom/jib capacity chart. Round boom/jib point elevation to the nearest whole number.

What is the net capacity when lifting off the jib over the rear?
(Click on each answer for explanation of why it is correct or incorrect.)

A. 26,029 lb.
Incorrect. Used 5 degree offset chart.

B. 25,375 lb.
Incorrect. No main or aux rope deducts.

C. 25,129 lb.
Correct.

Gross Capacity
28,900
Block
2,650
Ball
500
Rigging
375
Main Rope
80
Aux Rope
166
Total Deducts
3,771
Net Capacity
25,129

  
D. 21,229 lb.
Incorrect. Deducted jib.

Sample Item #3

Configuration On Fully Extended Outriggers Extension 40-ft. jib
Counterweight 95,400-lb. + 25,000-lb. Ext. Off-set / Angle 15-degrees
Main Boom 140-ft. Block 5,000-lb., 4-parts of line
Main Boom Angle 68.5-degrees Ball 500-lb., 15-ft. below tip
Radius N/A Rigging 800-lb.
Other N/A Main Rope 2-lb./ft.
Other N/A Aux. Rope  2-lb./ft.

Note: For line in use, deductions for wire rope length beneath boom/jib point shall be based on boom/jib point-elevation column listed on the boom/jib capacity chart. Round boom/jib point elevation to the nearest whole number.

What is the net capacity when lifting off the main boom over the rear?
(Click on each answer for explanation of why it is correct or incorrect.)

A. 73,200 lb.
Incorrect. Gross capacity.

B. 66,304 lb.
Incorrect. No deducts for jib, ball, or aux rope.

C. 60,374 lb.
Incorrect. Used 360 degree chart.

D. 61,074 lb.
Correct.

Gross Capacity
73,200
Jib
4,700
Block
5,000
Ball
500
Rigging
800
Main Rope
1,096
Aux Rope
30
Total Deducts
12,126
Net Capacity
61,074