Crating and Packaging Aerospace Hardware
Good aerospace packaging starts from the part's risks: corrosion, electrostatic discharge, contamination, and shock. Choose the preservation method and inner packaging for those risks, then the crate or box for the load and route, and write all of it into the purchase order.
Start with the part's failure modes
Packaging fails when it protects against the wrong thing. List the part's sensitivities before choosing materials.
| Sensitivity | Example parts | Packaging response |
|---|---|---|
| Corrosion | Alloy steel shafts, bare aluminum, bearings | Preservative, VCI, watervaporproof barrier with desiccant |
| ESD | PCBAs, harnesses with sensitive devices, sensors | Dissipative inner contact, static shielding outer layer |
| Contamination | Oxygen and propellant system parts, optics, cleanroom hardware | Cleanroom compatible film, double bag, sealed in a clean area |
| Shock and vibration | Machined assemblies, instruments, large weldments | Cushioning, blocking and bracing, crate, indicators |
| Surface damage | Finished, anodized or lapped surfaces | Protective caps, interleaving, no contact with fasteners or wood |
The logistics hub shows how packaging connects to shipping and receipt.
MIL-STD-2073-1 preservation methods
When a defense contract invokes MIL-STD-2073-1, the method code tells the packager exactly what protection to apply. The top level families are:
| Method | Protection |
|---|---|
| 10 | Physical protection only |
| 20 | Preservative coating |
| 30 | Waterproof protection |
| 40 | Watervaporproof protection |
| 50 | Watervaporproof protection with desiccant |
Sub-methods add detail; for example, MIL-STD-2073-1E lists Method 51 as a heat sealed watervaporproof bag with desiccant and Method 52 as a container holding such a bag. Contract packaging data blocks also specify cleaning and drying procedure, wrap, cushioning and unit container codes. Pull the current revision from the DoD ASSIST database before applying it, and do not guess sub-method content from memory.
Crates and boxes: ASTM D6039 and D6251
For wood shipping containers, two ASTM specifications cover most aerospace needs.
| Spec | Covers | Load range in scope | Notes |
|---|---|---|---|
| ASTM D6039/D6039M | Open and covered wood crates | Net loads not exceeding 4,000 lb (1,814 kg) | Style A heavy duty for severe handling and multiple trips; Style B light duty |
| ASTM D6251/D6251M | Wood-cleated panelboard shipping boxes | General materials up to 1,000 lb (454 kg) depending on box type | Multiple types, classes and styles reflecting different performance |
Open crates suit items that are not readily damaged and need little weather protection; ASTM D6039 suggests a shroud or covered crate when environmental protection is needed. Heavier items need an engineered crate designed for the load, with skids sized for forklift entry and lift points marked.
Blocking and bracing matter more than the crate walls. The item should be fastened to the crate base through its own mounting points or a shipping fixture, never just wedged with foam. Machined interfaces should be covered, and nothing should bear on finished surfaces.
ISPM 15 for wood packaging in export
Wood packaging that crosses borders must meet ISPM 15. The common heat treatment (HT) schedule requires the wood core to reach at least 56 °C for at least 30 minutes. Approved methyl bromide fumigation (MB) is the other traditional treatment, but many countries restrict it.
Compliant wood carries a mark with the IPPC symbol, the ISO two-letter country code, a producer or treatment provider code issued by the national plant protection organization, and the treatment code, typically applied on two opposite sides. Kiln drying alone is not an approved treatment unless the core temperature requirement is met.
Practical rule: if a crate might ever leave the country, including a return trip from a foreign test site, build it with ISPM 15 marked lumber from the start. Processed wood products such as plywood are generally outside the standard, but confirm with the destination's rules.
ESD packaging
ANSI/ESD S20.20 requires ESD protective packaging to be defined for moving sensitive items within, between and out of ESD protected areas, and it points to ANSI/ESD S541 for packaging materials. Inside a protected area, low charging and dissipative packaging is the minimum. Outside it, the package needs low charge generation, dissipative or conductive material in contact with the item, and a structure that provides electrostatic discharge shielding.
For defense work, MIL-PRF-81705 covers barrier materials. Type I is marked EMI and static shield and Type III is marked static shield; commercial metal-in shielding bags are commonly qualified to Type III. Authorized sources are on the qualified products list QPL-81705. Pink polyethylene by itself is dissipative only and does not shield.
Corrosion protection: VCI, desiccant and humidity cards
- VCI. Volatile corrosion inhibitor papers release a vapor that protects nearby metal surfaces. MIL-PRF-3420 covers VCI wraps, with Class 2 medium duty and Class 3 light duty. Confirm compatibility with non-ferrous metals and with any coating or lubricant on the part.
- Desiccant. MIL-D-3464 covers bagged desiccants for packaging use. Desiccant quantity is calculated in units based on container size and barrier type; a commonly cited definition is that one unit adsorbs at least 3 g of water vapor at 20 percent RH and 6 g at 40 percent RH at 25 °C. Desiccant only works inside a sealed watervaporproof barrier.
- Humidity indicator cards. Cards to MIL-I-8835 change color with relative humidity, letting receiving check whether the barrier held. Keep them from touching bare metal; some card chemistry can stain it.
Cleanroom and precision cleaned parts
For contamination critical hardware, packaging is part of the cleaning process. IEST-STD-CC1246 defines product cleanliness levels for particles and nonvolatile residue; the purchase order should state the level for the part and require packaging film compatible with it. Packaging film vendors rate their film against CC1246 levels, so ask for the film's rating rather than assuming.
The usual practice is double bagging: the inner bag is sealed in the clean area immediately after cleaning and verification, and the outer bag protects the inner bag in handling. Receiving removes the outer bag at the entry to the clean area and the inner bag inside it. Label each bag with part number, cleanliness level, cleaning date and the cleaning record reference. Material compatibility matters for oxygen service hardware; follow the program's oxygen cleaning specification. See precision and oxygen cleaning.
Shock and tilt indicators
Indicators do not prevent damage; they document it and trigger inspection. Impact indicators change color when an impact exceeds a rated level of amplitude and duration, and their sensitivity is chosen by package weight and the item's fragility. Tilt indicators show whether a package was tipped; one common single plane device turns red past 80 degrees. Recording data loggers go further and capture time, peak shock, temperature and humidity.
Place indicators where the handler can see them, note their condition on the bill of lading at pickup and delivery, and train receiving to stop and document before opening an activated package.
What to write on the purchase order
- Packaging level: commercial, or MIL-STD-2073-1 with method codes.
- Inner packaging: ESD material standard, VCI, desiccant and humidity card, cleanliness level of film.
- Crate or box standard and style, or a crate drawing for heavy items.
- ISPM 15 compliance for any export or possible export.
- Shock and tilt indicators, or a data logger for high value hardware.
- Marking: part number, quantity, handling symbols, center of gravity and lift points for heavy crates.
- Photographs of the packed item before closing the crate.
Quote crating and packaging
Packaging is quoted best with the item's weight, dimensions, sensitivities and destination in hand. Request a crating quote and we will match it to qualified suppliers and flow down your packaging requirements. A person replies within 1 business day. For export controlled hardware, see controlled programs.
Questions
Is pink anti-static bag enough for shipping circuit boards?
Usually not outside an ESD protected area. Pink polyethylene is low charging and dissipative but does not shield against discharge. ANSI/ESD S541 calls for a discharge shielding structure when sensitive items leave a protected area, which is why metal-in static shielding bags or shielding containers are used. For defense work, MIL-PRF-81705 barrier materials from the qualified products list are often specified.
Does a crate need ISPM 15 marking for a domestic shipment?
No, ISPM 15 applies to wood packaging in international trade. Many aerospace shippers use ISPM 15 marked lumber anyway, because crates get reused and hardware can travel to foreign launch or test sites. If there is any chance the crate will cross a border, build it compliant from the start rather than re-crating later.
How much desiccant does a package need?
It depends on the barrier, the enclosed volume, the dunnage and the storage time. MIL-D-3464 bagged desiccant is sold in units, with one unit commonly defined as adsorbing at least 3 g of water vapor at 20 percent RH. MIL-STD-2073-1 gives the method for calculating units. Desiccant inside an unsealed or permeable bag saturates quickly and protects nothing, so seal the barrier first.
Why double bag precision cleaned parts?
The inner bag keeps the part at its cleanliness level and should only be opened in an equivalent clean environment. The outer bag takes the handling, dust and fingerprints during shipping and is removed at the clean area entrance. This lets receiving check labels and seals without exposing the part. State the cleanliness level and bagging requirement on the purchase order.
Are shock indicators accurate enough to prove a carrier dropped a crate?
They show that an impact exceeded a threshold, not the exact force, so they are evidence rather than measurement. Combined with notes on the delivery receipt and photographs, they support a claim and tell receiving to inspect more deeply. For high value or very sensitive hardware, recording data loggers capture the time and size of each event and give much stronger evidence.
Related
Sources
- MIL-STD-2073-1E with Change 2, Standard Practice for Military Packaging (PDF copy from ASSIST)
- DLA Small Business, packaging training slides (MIL-STD-2073-1 preservation methods)
- ASTM D6039/D6039M-18, Standard Specification for Open and Covered Wood Crates
- ASTM D6251/D6251M-23, Standard Specification for Wood-Cleated Panelboard Shipping Boxes
- IPPC, UK heat treatment standards for wood packaging (56 °C core for 30 minutes)
- ISPM 15 overview (treatments, marking)
- ESD Association forum, ANSI/ESD S541 packaging requirement clause 6.2
- DLA Packaging, ESD sensitive items acceptable materials
- McMaster-Carr, MIL-PRF-3420 corrosion-inhibiting wrap classes
- EverySpec, MIL-D-3464E Desiccants, Activated, Bagged, Packaging Use and Static Dehumidification
- Campbell Scientific, desiccant unit definition per MIL-D-3464E
- AGM Container Controls, MIL-I-8835 humidity indicator card
- IEST-STD-CC1246E Product Cleanliness Levels (ANSI webstore)
- SpotSee, ShockWatch impact and TiltWatch tilt indicators for packaging (PDF)
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