6.2 Load-Chart Readiness Drills

A Repeatable Load-Chart Routine

Load-chart questions reward a fixed routine, not improvisation. Under exam time pressure, the operators who score well solve every chart problem the same way:

1. Confirm configuration — outrigger position, counterweight, boom mode, and which chart applies.
2. Find radius and boom length — use the actual operating radius (load center to centerline of rotation), not the boom length alone.
3. Read gross capacity at the least-favorable cell for that radius/boom-length combination.
4. Subtract deductions in one running total.
5. Compare net capacity to the total suspended load.

If any step fails, the lift is not acceptable — there is no partial credit on the job or on the exam.

Drill 1: Straight Net-Capacity Check

Scenario: Outriggers fully extended, 100 ft of main boom, working radius 40 ft. The chart cell for 40 ft radius at 100 ft boom shows 18,500 lb gross. Deductions: main block 450 lb, overhaul ball 150 lb, stowed jib 700 lb. The load is 15,000 lb plus 600 lb of slings and shackles.

Solve:

• Net = 18,500 − (450 + 150 + 700) = 17,200 lb
• Total suspended load = 15,000 + 600 = 15,600 lb
• 15,600 lb ≤ 17,200 lb → lift is within capacity (about 91% of net; still acceptable, but flag that it is a heavy-percentage lift requiring extra caution).

Drill 2: Between-Rows Rounding

Scenario: The actual working radius measures 47 ft. The chart lists rows at 45 ft (20,000 lb) and 50 ft (17,000 lb) for the current boom length.

Correct method: When the radius is between rows, you must use the next longer radius row, because capacity decreases as radius increases. Use 50 ft → 17,000 lb, not 20,000 lb and not an averaged 18,500 lb.

Why it matters: Interpolating to a higher number, or rounding the radius down, produces a falsely high capacity and is one of the most common ways candidates miss load-chart questions. The conservative read is always the safe and correct read on this exam.

Drill 3: Parts of Line

Scenario: The total line load (load + block + ball + rigging) is 24,000 lb. The wire rope has a rated single-line pull of 9,000 lb.

Solve:

• Minimum parts = 24,000 ÷ 9,000 = 2.67
• Round up to the next whole part → 3 parts of line required.

Key rule: You never round parts of line down. Two parts (18,000 lb capacity) would be overloaded; three parts (27,000 lb capacity) safely carries the 24,000 lb line load. The reeving must also be allowed by the chart for that configuration.

Reading Footnotes and Chart Notes

Footnotes can change or void a capacity before you ever do arithmetic. Read them first.

• Range/area notes: A chart may give different capacities for over-rear, over-side, or 360-degree operation. A capacity valid over the rear can be far lower over the side.
• Defined-arc / restricted-swing notes: Some capacities apply only within a stated work area; swinging outside the arc is prohibited at that weight.
• Outrigger / on-rubber notes: On-rubber (pick-and-carry) charts are separate and far more restrictive; never read an outrigger value for an on-rubber lift.
• Deduction notes: Notes specify exactly which attachments and how much rigging to deduct, and whether stowed jibs still count.
• Asterisks / bold lines: Often mark the boundary between stability-governed and structure-governed values, or note that the value is limited by something other than tipping.

Footnote Triage Table

Fast Net-Capacity Speed Method

Under time pressure, run one subtraction string instead of stacking separate calculations:

Net = Gross − block − ball − jib/attachments − required rigging

Then compare to Total load = load + all below-the-hook hardware.

Write the gross number, then verbally subtract each deduction in one pass: "18,500 minus 450 is 18,050, minus 150 is 17,900, minus 700 is 17,200." This avoids transcription errors and is faster than columnar addition. Finish with a single sanity check: is net at least the suspended load, using the least-favorable chart cell? If yes, the answer choice that matches that net (or the smallest sufficient capacity) is correct; if no, the correct answer is the one stating the lift is not permitted.

Most Common Calculation Mistakes

• Forgetting a deduction — especially a stowed jib or auxiliary boom head that the note still requires you to subtract.
• Counting rigging twice or not at all — know whether the chart deducts rigging from capacity or expects it added to the load; never both, never neither.
• Rounding radius down — always round the working radius up to the next chart row.
• Optimistic interpolation — reading between two cells and choosing the higher value.
• Wrong chart line — using an outrigger value for an on-rubber lift, or the over-rear value for an over-side swing.
• Comparing gross instead of net — the load must be checked against net capacity, not the printed gross number.