Can the cavity of a Military Air Transport Case be the outside minus two walls?

Answer: No. Ribs, corner wrap and lid overlap all take space; a 1120 mm cavity against 1176 mm outside leaves 28 mm per side, the wall being 3.2 mm.

Is a 3.2 mm wall enough for drops?

Answer: It passes a 1.2 m edge drop and a 0.9 m corner drop; performance comes from rib pitch and corner thickness, not overall wall.

Do more tie-down points make the case safer?

Answer: Not alone. Points must sit in solid corner material and align with rail pitch; extra points on thin panels transmit nothing.

What tests back up an IP67 claim?

Answer: Thirty minutes at 1 m depth, thirty minutes of rain at 100 mm per hour, repeated after ten thermal cycles.

Which tolerances deserve to be tight?

Answer: Lid joint gap and insert position. Those drive sealing and tie-down; 3 mm of length error changes nothing.

Specifying a Military Air Transport Case: Size, Wall and Load

Quick answer: A Military Air Transport Case is specified from the cavity outward: packed envelope to inside size, a per-side allowance to outside size, a 3.2 mm base wall, rib pitch at 45 times that, then stack and tie-down checks.

Sizing a Military Air Transport Case from the Inside Out
Wall Thickness and Rib Pitch
Load Rating and Stack Checks
Tie-Down and Lifting Points
Sealing Class Temperature Range and Tolerances
FAQ

1. Sizing a Military Air Transport Case from the Inside Out

Specify the cavity first: packed envelope plus cushioning. The outside adds wall, rib height, corner wrap and shrinkage; reverse the order and the lid land absorbs a 10 to 15 mm error.

From a 1120 × 420 × 310 mm cavity, 28 mm per side — 3.2 mm wall, 9 mm rib, 12 mm corner wrap, 3.8 mm shrinkage — gives 1176 × 476 mm. A 26 mm base with 13.8 mm feet and a 30 mm lid with 17.8 mm overlap give 366 mm.

Item	Value	Basis
Cavity	1120 × 420 × 310 mm	Envelope plus cushioning
Allowance	28 mm per side	3.2 + 9 + 12 + 3.8
External size	1176 × 476 × 366 mm	Cavity plus allowance

Two cases span 952 mm on a 1200 mm pallet; at 1210 mm only one fits, adding 30 percent to shipping volume. Gross mass is 56.3 kg: 38 kg contents, 15.2 kg case, 3.1 kg insert.

2. Wall Thickness and Rib Pitch

Wall thickness on a Military Air Transport Case is a set of numbers: 3.2 mm base panel, 4.6 mm corners and floor, a 1.44 ratio near the limit of rotational moulding.

Military air transport case: four olive green cases on a workshop conveyor, handles and latches visible, one open case on a pallet with grey foam

Rib pitch caps at 45 times the wall, 145 mm at 3.2 mm: seven ribs across 1120 mm, three across 420 mm, 9 mm high, 7 mm root, 1.5 degrees of draft. The lid runs 3.6 mm with 160 mm pitch.

A 1200 mm edge drop dents 0.4 mm at 145 mm pitch and 0.8 mm at 190 mm. Shot weight: 2.36 square metres at 3.2 mm takes 7.1 kg, or 7.9 kg with 11 percent build-up.

3. Load Rating and Stack Checks

Payload and bearing are separate. A Military Air Transport Case rated 38 kg with a 15.2 kg body weighs 56.3 kg, feeding both stack and tie-down sums.

Five high, four cases press 225 kg on the bottom lid, limited to 1.5 mm; after 72 hours the reading is 1.1 mm, and a sixth layer leaves 0.6 mm.

Condition	Value	Part	Criterion
Five-high stack	225 kg	Lid centre	Within 1.5 mm
Edge drop	1.2 m	Bottom edge	No puncture
Corner drop	0.9 m	Bottom corner	Latches hold

Die-cast corners 8 mm thick take 90 kg each, 720 kg across eight. The lid fails first.

4. Tie-Down and Lifting Points

Six points at 1500 N cover 3313 N from 56.3 kg at 6 g; M8 inserts break at 2600 N, a 1.7 factor. Centres sit 95 mm from the end face and 40 mm above the base, on 25.4 mm rail pitch.

Four lifting points take vertical or 60 degree slings, breaking at 400 kg against 100 kg working; each leg carries 0.58 of the load, 32.6 kg here.

5. Sealing Class Temperature Range and Tolerances

Write IP67 plus the proof: 30 minutes at 1 m, 30 minutes of rain at 100 mm per hour. Silicone at Shore A 62, compressed 22 to 28 percent, sets 25 percent after 24 hours at 70 °C. Groove: 7.2 mm wide, 5.5 mm deep, 6.5 mm cord.

Storage spans -46 °C to 71 °C, operation -40 °C to 60 °C, with IP67 re-tested after ten cycles.

Item	Tolerance	Method
External size	±3.0 mm	Tape, three readings
Lid joint gap	Within 1.5 mm	Feeler gauge
Insert position	±0.6 mm	Dedicated gauge

Holding the outside to ±1.5 mm forces secondary straightening and adds 8 to 12 percent to unit cost for a dimension stacking never uses.

Conclusion

Three numbers hold the specification: outside size from the cavity, rib pitch at 45 times the wall, and the 1.5 mm lid deflection allowed five high. Miss one and the case either cannot be moulded or cannot fly stacked. Draw them with a tolerance table that tightens only mating faces, and it is release-ready as a Military Air Transport Case specification.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.