FAA Airline Transport Pilot (ATM)Aircraft Performance and Weight and BalanceHard
A cargo compartment floor has a maximum floor loading limit of 100 lb per square foot. A pallet weighing 2,400 lb has a footprint of 4 feet by 5 feet. What must be done before this pallet can be loaded in that compartment?
- AThe pallet may be loaded as is, since its total weight is within the compartment's maximum cargo weight limit
- BThe pallet must be split into two smaller loads of 1,200 lb each placed on the same footprint
- CA load-spreading device must be used to increase the contact area to at least 24 square feet
- DThe pallet must be relocated forward of the aft cargo hold regardless of contact area
Show answer & explanationAnswer & explanation
Correct answer: C. A load-spreading device must be used to increase the contact area to at least 24 square feet
The pallet's loading is 2,400 lb ÷ (4 ft × 5 ft = 20 sq ft) = 120 lb/sq ft, which exceeds the 100 lb/sq ft floor limit. To comply, the contact area must be increased to at least 2,400 ÷ 100 = 24 sq ft, typically by using load-spreading dunnage or a pallet with a larger footprint.
Why the other options are wrong
- A. Total compartment weight limits and floor loading (psf) limits are separate; this load exceeds the psf limit even if total weight is acceptable.
- B. Splitting the weight without changing the footprint does not change the pounds per square foot value.
- D. Relocating the load doesn't address the floor loading limit unless the new location has a different structural rating.
Floor Loading Limit
The maximum weight per square foot a cargo compartment floor structure can bear, independent of the compartment's total weight limit.
- Floor loading (psf) = load weight ÷ contact area
- Must not exceed structural floor loading limit
- Load-spreading devices (dunnage/pallets) increase contact area to reduce psf
Memory trick: Spread the load like peanut butter — thinner spread means less pressure per spot.