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Even though most people in the industry have heard of MIL-STD-810, understanding the details and nuances of the standard is key to its successful use.

DAVID LIPPINCOTT, CHIEF TECHNOLOGY OFFICER CHASSIS PLANS

 

The MIL-STD-810 standard continues to be a fixture in today’s military system design realm. But understanding what the standard is almost as important as understanding what it isn’t. What is the purpose of MIL-STD-810? The standard states: “…the environmental management and engineering processes described in this standard can be of enormous value in generating confidence in the environmental worthiness and overall durability of materiel system design.” What does that mean and how are vendors applying the standard?

It’s important to understand that MIL-STD-810 is not a specification per se but a standard. A specification provides for absolute criteria which must be satisfied to “meet the spec”. MIL-STD-810 as a standard provides methods for testing material for use in various environments but provides no absolute environmental limits. As stated in the Standard, “It is important to note that this document does not impose design or test specifications.” MIL-STD-810 is simply a collection of recommended tests and procedures to confirm that an item being tested will perform its function reliably under certain stated conditions. 810 provides guidelines for negotiations between the customer and vendor as to how to test an item. Figure 1 shows a display system after being put through 810G testing Method 510.5 for blowing sand and dust side by side with a display system actually sent back from use in Afghanistan to be refurbished. Note how the two look quite similar.

Figure 1 Display system on left after being put through 810G testing for blowing sand and dust. System on right looks similar and it’s an actual system returned from field use in Afghanistan.

The customer or program manager and vendor collaborate on-or the program manager can simply dictate-a set of test criteria an item must pass and the physical parameters the item is tested to. With a test plan in place, the item is tested per the recommendations of the standard and the test plan, operationally examined, and the test results documented. For example, the program manager and vendor can agree the item will be used in a humidity- and temperature-controlled environment at sea level, devise a test plan to assure function in those conditions, and “meet MIL-STD-810G”. Not exactly what most people think of when they consider MIL-STD-810G.

810 in Historical Context
Prior to 1940, formalized environmental testing was practically non-existent. World War II brought with it the requirement for new military hardware including clothing, weapons, vehicles, and so forth, to be operated worldwide, in desert to jungle to artic conditions. As a result, improper packaging, handling, transportation, storage and extreme environmental conditions resulted in extensive damage to equipment and vehicles. We’ve all heard stories of uniforms rotting off soldiers stationed in the South Pacific.

During the war years, environmental testing at Wright Field, Ohio, was greatly increased to fill this gap in formalized testing. However, there were few standard tests and each of the laboratories conducted tests on items within their jurisdiction as they saw fit. In 1945, the Army Air Force released specification No. 41065 titled “Equipment: General Specification For Environmental Test Of” which comprised 7 pages and provided guidance for testing for high and low temperature, humidity, high altitude, salt spray, vibration, sunshine, sand and dust and rain. This specification finally codified testing procedures allowing industry to provide standardized testing services.

Through the late 40’s and into the 50’s, the Navy released several specifications for testing aircraft electrical systems with the end result being the release of MIL-T-5422 (BuAir). The Army Air Force re-issued 41065 as MIL-E-5272 (USAF) and coordinated with the Navy MIL-T-5422 specification. Both documents contained almost identical test procedures and it was decided that combining the documents into one would be advantageous.

In December, 1961, the first draft of MIL-STD-810 was circulated within the Air Force for coordination and the final Standard was released June 14, 1962. The original MIL-STD-810 was 66 pages long and included 17 Methods. In June, 1964, MIL-STD-810A was released to include the very latest engineering input. The ‘A’ revision is slightly longer at 77 pages but still only includes 17 Methods. There have been 7 revisions since the original document and MIL-STD-810G is the current revision since October, 2008.

Current MIL-STD-810G Version
The current revision, MIL-STD-810G, is 804 pages long and includes 28 Methods including 5 new Methods since revision F. New also in 810G is a 53-page section for World Climatic Regions Guidance. MIL-STD-810G is divided into three parts as detailed in the table in Figure 2. There are 28 Methods included in Part Two of 810G with 5 new Methods since revision F. The decimal number references the Method revision so 500.5 for Low Pressure has undergone 5 revisions since the original publication of the standard in 1962. When a new Method is published, it starts at an integral number such as the new-in-‘G’ Method 526 for Rail Impact.

What MIL-STD-810G brings to the party for most companies is the experience of specifying a test program. For example, what temperatures would be experienced in a desert setting? The customer and vendor could research and make an educated guess as to the temperature environment in, say, Afghanistan. Or they can simply take advantage of the work that has gone into MIL-STD-810G and the previous revisions where these high and low temperature extremes are documented.

Chassis Plans manufactures rackmount and transit case mounted computers and LCD displays. As such, there’s a particular set of appropriate test Methods they test to and which are appropriate for manufacturers of similar devices. These 29 test Methods range from everything from 506.5 Rain test to the 511.5 Explosive Atmosphere test to the 524 Freeze / Thaw Test. See online version of this article for a complete list of these tests.

Simple and Complex
Many of these Methods are fairly straight forward. For example, Method 500.5, Low Pressure, is used to simulate high altitudes for high ground elevation sites or transportation in aircraft. The Method is also applicable to rapid or explosive decompression. For the tests, the item is placed in a pressure chamber which allows the pressure to be lowered to simulate high altitudes. Failure modes of the equipment may include fluid leakage, electrical arcing, mechanical distortion, and so forth.

Other Methods can be quit complex. For example, Method 522.1, Ballistic Shock, discusses shock propagation through a vehicle in which electronics may be installed. The physics of such shock propagation are not particularly well understood and simulation can be difficult and misleading. The best way to perform the test may be to mount the equipment in the actual vehicle and shoot it with appropriate non-exploding ammunition. This is an expensive test and generally not available at civilian test labs.

RFQ Specification Confusion
Often an opportunity to bid will be posted by a military customer wherein the statement “Must meet MIL-STD-810G” is included. What exactly does that mean? There are 28 distinctly different Methods included in 810G. Perhaps a major program such as the F-35 Joint Strike Fighter will be tested to most of the 28 Methods but should it be subjected to Method 526 for Rail Impact-for transport on rail cars? Items such as rackmount computers or LCD displays should be tested to an appropriate sub-set of Methods but certain Methods, such as Method 509.5 (Salt Fog), are certainly not applicable and would destroy the unit under test. On the other hand, a sealed fanless computer might have a requirement to be tested for Salt Fog and it would survive. What Methods in MIL-STD-810G the customer wants the product to meet should be documented within the RFQ. Figure 3 shows an F-35B Lightning II undergoing ice evaluation testing at the 96th Test Wing’s McKinley Climatic Laboratory at Eglin Air Force Base, Florida.

Figure 3 An F-35B Lightning II undergoes ice evaluation testing at the 96th Test Wing’s McKinley Climatic Laboratory at Eglin Air Force Base, Florida (Photo by Michael D. Jackson, F-35 Integrated Test Force).

Vendors freely use the phrase “Meets or designed to meet MIL-STD-810G”. Which Methods are they referring to? Often a vendor will test to Method 514.6 (Vibration), Procedure II, for Loose Cargo Transportation and claim “Meets MIL-STD-810G”. For this Method, the item is packaged for shipment, either in a transit case or cardboard box with appropriate packaging material and subjected to 1-inch peak-to-peak circular motion at a frequency of 5 Hz. This simulates the item under test being transported in the open bed of a truck where it is not tied down or restrained. Not a hard test to pass, especially if the product routinely survives handling by UPS. Does that mean the product “Meets MIL-STD-810G”? Yes, you could say that but only in a very limited sense.

To be accurate, a vendor should reference the Method(s) and limits their device was tested to. Pre-testing may be sufficient to satisfy a Program Manager’s requirements in which case the product would be in conformance with the Standard. “Designed to Meet” can be construed as a statement by the company’s engineers that they have made their best efforts to assure the design will conform with appropriate parts of the Standard but, until the item is actually tested, there are no guarantees. In any case, a product cannot “meet” MIL-STD-810G without input from the customer to determine which Methods and environmental considerations are appropriate for their particular program. It is legitimate to state a product has been tested per Method ‘xxx’ with stated conditions to indicate to interested customers the product has a chance of surviving in the field.

MIL-STD-810 Here to Stay
Like it or not, MIL-STD-810 is here to stay and will be updated periodically as new requirements, technology, testing methods and computational analysis capabilities are introduced. There transpired 11 years between revisions E and F and 8 years between revisions F and G. Program Managers need to communicate their testing requirements more clearly. Contracting Officers need to quit using a broad “Meets MIL-STD-810G” requirement. Vendors need to be forthcoming with what Methods in 810 they have actually tested to. “Designed to Meet” doesn’t really mean much given that compliance with 810G is a contract between a customer and vendor. MIL-STD-810 binds two entities together in a complex relationship for the greater good.

MIL-STD-810G is a compendium of suggested tests and not an absolute specification to which assemblies can be tested and said to “meet the spec”. The Standard is 804 pages of the collected wisdom and experience of many engineers over many years verifying that military equipment will function reliably in the incredibly harsh conditions of the battle field. Chassis Plans offers military grade computers, LCD displays and Zero Clients, many of which have been tested per MIL-STD-810G. Working closely with multiple customers, Chassis Plans has tested various products to the requirements of MIL-STD-810G to meet the customer’s specific application and mission requirements.

Chassis Plans
San Diego, CA
(858) 571-4330
www.chassis-plans.com