Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page i

FAA discussion of the cargo testing

as described in the final rule comments

Supplement to Docket No. FAA-2014-0780

Prepared by:

Steven Fox, P.E.

Federal Aviation Administration

Senior Aerospace Engineer

Airframe Branch, ANM-120S

Seattle Aircraft Certification Office

Work (425) 917-6425
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page ii

General issues related to the industry testing and issues raised by the commenters

As stated in the final rule preamble:

Opposition to NPRM (79 FR 71037, December 1, 2014): Inadequate Testing

Cargo Airline Association, Atlas Air, NACA, IATA, Kalitta, and the Michigan Senate criticized 

the tests discussed in the NPRM (79 FR 71037, December 1, 2014) that confirmed the FAA’s 

determination that loading containers in the offset position is an unsafe condition, arguing they 

were unrealistic or inconclusive. In general, the commenters claimed that the tests used 

configurations of intermodal containers and their restraints that are different from those used in 

service and applied pass-fail criteria that were unnecessarily stringent.

We do not agree that the tests were unrealistic or inadequate. A detailed discussion of the 

commenters’ technical concerns regarding the tests is included in the AD docket.

=====================================================================

The following is a discussion of the testing methods used by the industry team of engineers from 

Atlas Air, Kalitta Air (Kalitta), United Parcel Service (UPS), and Boeing (hereafter referred to as 

the industry team). This discussion is limited to aspects of the testing necessary to address issues 

raised by commenters, and is not intended to be a comprehensive discussion of the relevant tests. 

Also included is an FAA response to the specific concerns of several commenters about the 

validity of the testing.
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page iii

Contents

Background..................................................................................................................................... 1

What is a ULD and how is it certified for use on the Boeing Model 747?................................. 1

What is the “Offset Method” for loading intermodal containers? .............................................. 1

What prompted the industry team to start testing? ..................................................................... 1

What are some of the requirements for showing compliance? ................................................... 2

What are the CG effects used for testing? .................................................................................. 3

What is the method to develop a test configuration to assess the CG for critical loading 

conditions for cargo inside the intermodal container?................................................................ 5

What was learned from the baseline testing of an empty intermodal container offset and 

restrained only by a net to a pallet in Oscoda, Michigan? .......................................................... 7

What Further Testing Was Done?............................................................................................... 7

Comments on the rule ................................................................................................................... 11

The lateral CG testing method .................................................................................................. 11

Lack of testing an offset intermodal container strapped directly to the airplane...................... 11

Use of too many straps in the Arlington testing ....................................................................... 12

Testing nonconformance to NAS 3610..................................................................................... 12

The effect of shifting comparisons ........................................................................................... 12

Testing not reflective of typical airline loading........................................................................ 13

Lack of consideration for energy-absorbing straps and nets during testing ............................. 13

Test results not made public permitting adequate comments................................................... 14
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 1

Background

What is a ULD and how is it certified for use on the Boeing Model 747?

As discussed in the final rule preamble, the Boeing 747 cargo airplanes are equipped with a 

cargo loading system, which is part of the airplane’s type design and consists of roller trays, 

guides, latches, and locks that restrain the cargo to the airplane for flight loads. A unit load 

device (ULD) is a device for grouping and restraining cargo for transit. The types of ULDs 

permitted by the Boeing weight and balance manuals (WBMs) meet the standards of National 

Aerospace Standard (NAS) 3610 (“Cargo Unit Load Devices – Specification For”). In 

accordance with NAS 3610, the ULD pallet-net combination restrains the cargo to the pallet. The 

airplane guides, latches, and locks restrain the pallet to the airplane.

The final rule preamble has a complete discussion of this topic. NAS 3610 defines the 

configurations and test requirements for these permitted ULDs. In the case of a netted pallet, 

NAS 3610 prescribes applied loads that the netted pallet must be capable of withstanding and the 

locations around the perimeter of the pallet where the restraints are to be used. NAS 3610 also 

prescribes test parameters for the specified limits for the center of gravity (CG) (Section 3.10.1)

to be used for the testing. These NAS 3610 configurations, load cases, and CG limits were used 

by Boeing to design the capability of the Boeing Model 747 cargo loading system (CLS) and to 

develop the required instructions in the Boeing Model 747 WBMs for loading these ULDs. The 

final rule preamble discusses this subject, including that an intermodal container does not meet 

the requirements of NAS 3610 and is not allowed as a certified ULD under the Boeing WBMs.

What is the “Offset Method” for loading intermodal containers?

The FAA has become aware that some operators, both domestic and foreign, are not loading 

intermodal containers in the center of the airplane, but rather in the standard left and right pallet 

positions. When loaded in this manner, the 8-foot, 6-inch, height of the intermodal container 

interferes with the fuselage, so some operators have been transporting these intermodal 

containers shifted inboard, off of the FAA-approved TSO pallets, and attached to the pallet only 

with a net and/or straps. This method of transport is referred to as the “offset method.” The 

practice of offsetting the intermodal containers results in the certified pallet-net combination 

having slack in the net by the amount of the offset.

What prompted the industry team to start testing?

The Seattle Aircraft Certification Office (SACO) first became aware of offset intermodal

containers being transported on Boeing 747s in September 2013, and reached preliminary 

conclusions that the method was noncompliant and unsafe in October 2013. The SACO then 

issued a memorandum concerning this practice on November 8, 2013. A copy of this memo was 

submitted to the docket by Kalitta as background (Kalitta comment, Appendix A). This 
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 2

prompted the industry to perform tests to show that using the offset method could be shown to 

comply with the applicable airworthiness standards.

What are some of the requirements for showing compliance?

As discussed in the November 8, 2013, SACO memorandum, the intermodal container loaded 

using the offset method does not comply with the Boeing WBMs. The intermodal container

loaded using the offset method does not comply with NAS 3610 because of slack in the net. The 

offset method precludes “adequately encompass[ing] the cargo” and does not provide for “proper 

support and restraint of the cargo” (NAS 3610 paragraph 3.4). NAS 3610 has no provisions to 

meet the standard by supplementing the required net with straps. Demonstrating that the 

intermodal container complies with NAS 3610 is not possible, for the reasons stated above.

As discussed in the final rule preamble, carrying intermodal containers using the offset method 

would require either restraining the containers directly to the airplane, which is the only currently 

approved method, or changing the type certificate with an associated WBM supplement shown to 

comply with the applicable airworthiness standards.

The industry team attempted to demonstrate that the offset practice could be shown to be

compliant with the applicable airworthiness standards: those listed on the Type Certificate Data 

sheet for the Boeing 747 (A20WE).

Some of these requirements for showing compliance are restated below:

§25.301 Loads.

. . .

(b) Unless otherwise provided, the specified air, ground, and water loads must be 

placed in equilibrium with inertia forces, considering each item of mass in the 

airplane. These loads must be distributed to conservatively approximate or closely 

represent actual conditions. Methods used to determine load intensities and 

distribution must be validated by flight load measurement unless the methods 

used for determining these loading conditions are shown to be reliable.

. . .

§25.305 Strength and deformation.

(a) The structure must be able to support limit loads without detrimental 

permanent deformation. At any load up to limit loads, the deformation may not 

interfere with safe operation.

(b) The structure must be able to support ultimate loads without failure for at least 

3 seconds. However, when proof of strength is shown by dynamic tests simulating 

actual load conditions, the 3-second limit does not apply. Static tests conducted to 

ultimate load must include the ultimate deflections and ultimate deformation 

induced by the loading. When analytical methods are used to show compliance 

with the ultimate load strength requirements, it must be shown that—
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 3

(1) The effects of deformation are not significant;

. . .

§25.307 Proof of structure.

(a) Compliance with the strength and deformation requirements of this subpart 

must be shown for each critical loading condition. Structural analysis may be used 

only if the structure conforms to that for which experience has shown this method 

to be reliable. In other cases, substantiating tests must be made to load levels that 

are sufficient to verify structural behavior up to loads specified in §25.305.

. . .

For the intermodal container restrained using the offset method, an applicant must show that the 

intended payload will remain attached to the airplane’s cargo loading system during all loads

specified in subpart C of Title 14 Code of Federal Regulations (14 CFR) part 25 so that the 

container cannot impact the fuselage frames, which could cause them to fail, contrary to the 

requirement of 14 CFR 25.305(b)(1). These loads must be applied in all directions – that is, 

vertical, lateral, and longitudinal – because airplanes may encounter all of these loads during 

operations. For showing compliance, in this case, where experience has not shown analysis to be 

reliable, 14 CFR 25.307(a) requires substantiating tests.

As stated in 14 CFR 25.301(b), these loads must be distributed to “conservatively approximate or 

closely represent actual conditions.” In this case, closely representing actual conditions would 

require testing each individual intermodal container loaded with the contents that are to be 

transported on each flight. Then for each flight flown, the actual cargo (container and contents) 

would have to conform to those configurations tested and certified. This is impractical. 

Therefore, typically, applicants choose to perform tests using a “conservatively approximate”

method.

The intended total gross weight of the intermodal container loaded using the offset method on a 

pallet can readily be determined for certification. The distribution of that weight inside the 

intermodal container must also be investigated because the CG of the cargo within the container 

can have a significant effect on the applied loads at the locations on the airplane where the 

container is restrained. This change in location of the CG could result in failures of the cargo 

loading system’s restraints. An industry standard procedure for conservatively approximating 

these effects is to test loading objects with approximately uniform density within the container, 

and then vary the locations of the objects to produce a change in the CG for the intended 

certifiable weights.

What are the CG effects used for testing?

For certification testing, the CG for the cargo used in testing must vary in the lateral, 

longitudinal, and vertical directions of the airplane to address a range of realistic flight scenarios. 
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 4

Different centers of gravity are critical for different flight load cases (14 CFR 25.307(b)) and 

must be addressed in the testing.

There are two different CG effects that must be addressed in testing intermodal containers loaded 

using the offset method:

(1) the airline’s offset placement of the intermodal container 9 inches inboard on the pallet,

which creates a 9-inch lateral shift in the CG for the intermodal container itself and its 

cargo; and

(2) the unknown and potentially shifting CG of the cargo inside the intermodal container.

These effects must be considered in combination. Because the intermodal containers are 

typically locked before the operators receive them, operators have no means to determine, or 

control during flight, the CG of the cargo within the locked container.

Figure 1: Photograph showing shifted cargo during transport,

which can change the CG locations
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 5

Figure 2: Photograph showing carriage of liquid cargo, which can move within the plastic 

containers, changing the CG during flight

What is the method to develop a test configuration to assess the CG for critical loading 

conditions for cargo inside the intermodal container?

Since operators have no ability to control the cargo inside the locked intermodal container, it is 

nearly impossible to predict the CG of those contents. A simple method to address this

uncertainty is to test using a triangular shaped distribution of cargo. This is analogous to a pile of 

gravel inside the intermodal container sloped to the top on one side and tapering off to the 

bottom on the other. The FAA has approved the use of this method.

The diagram below shows the location of the CG (⊕ inside the triangle) for this triangularshaped assumed cargo as defined by simple plane geometry.
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 6

Figure 3: Location of the CG (the ⊕ inside the triangle) for triangular-shaped cargo

When the cargo is distributed in the shape of a right triangle, the CG is one-third the distance 

from the right angle.

1 In this diagram, the base of the triangle is the 8-foot width of the 

intermodal container. In an 8-foot wide intermodal container, the CG of uniformly distributed 

cargo is in the center of the container, 48 inches from the edges of the container. The triangular 

distribution of cargo results in a CG that is 16 inches from the center of the container (the CG of 

cargo uniformly distributed in an 8-foot wide intermodal container).

 1 Timoshenko, Stephen, and James M. Gere. “Appendix B, Properties of Plane Areas.” Mechanics of Materials. 

New York: Van Nostrand Reinhold, 1972. 503. Print.
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 7

Width of the intermodal 8 feet x 12 inches/foot = 96 inches

CG for uniform distribution 1⁄2 of 96 inches = 48 inches

CG for triangular distribution 1⁄3 of 96 inches = 32 inches

Triangular distribution distance from center 48 inches – 32 inches = 16 inches

When the two effects described previously are combined, the resulting shift of the CG is 25 

inches (9 inches for the offset of the container, and 16 inches for the potential shift of the cargo 

inside the container).

What was learned from the baseline testing of an empty intermodal container offset and 

restrained only by a net to a pallet in Oscoda, Michigan?

One of the first tests explored by Kalitta in Oscoda, Michigan, in late 2013 involved restraining

an empty intermodal container loaded using the offset method and using only the restraints 

defined in NAS 3610: a pallet and net combination. Again, the restraints described in NAS 3610

do not have provisions for additional straps; in fact, the word “strap” does not appear in the 

document. Also, the CG of an empty intermodal container is in the center of the container, so this 

test did not address the second effect discussed previously.

Kalitta’s test was a lateral outboard test. This test simulated the airplane encountering a gust on 

the side of the airplane so that, because of its inertia, the offset container shifted outboard. This 

test involved gradually tilting the offset container, restrained to the pallet only by a net, in a test 

rig to an angle that imposed a side load on the container that is comparable to the gust load 

referenced in the airworthiness standards. This test failed early on, well before the required side 

load was achieved. The test demonstrated that the slack in the net introduced underneath the 

offset intermodal container on the inboard side renders the net ineffective. Based on this failure, 

the offset container restrained using the pallet-net combination described in NAS 3610 was 

shown not to comply with 14 CFR 25.305(b)(1). Similarly, the test demonstrated that the 

requirement for “proper support and restraint of the cargo” (NAS 3610 paragraph 3.4) was not 

met.

Although the FAA, Boeing, and the other airline engineers had not participated in this Kalitta 

testing, the FAA, Boeing, and the other airline engineers accepted the test failure results as 

shown by Kalitta. The industry team subsequently abandoned the use of the pallet-net

combination for all future testing referenced in the preamble of the final rule. The FAA agreed 

with the industry team to delete the ineffective net for future testing. The result of this decision is 

that the NAS 3610 standard was no longer applicable for these tests.

What Further Testing Was Done?

Two more sets of tests of offset intermodal containers were accomplished by an industry team

consisting of engineers from Atlas Air, Boeing, Kalitta, and UPS. One set of tests was performed 

in March 2014, in Oscoda, Michigan, and another in May 2014 at Arlington, Washington. These
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 8

tests explored the use of cargo straps to restrain the offset intermodal container to a pallet 

without the net required by NAS 3610 and without restraints from the container to the airplane 

itself (the cargo loading system restrained the pallet to the airplane). The purpose of these tests 

was to determine whether using straps to restrain the offset intermodal container only to a pallet 

could be shown to comply with the applicable airworthiness requirements.

March 2014 testing in Oscoda, Michigan

The industry team chose to address the CG effect of the cargo inside the locked intermodal 

container using the industry practice described above as the triangular distribution of cargo. For 

the testing in Oscoda, Michigan, the two CG effects (9 plus 16 inches) added up to 25 inches. 

This is documented in the industry test plan prepared by Kalitta in Report 13-0160ER, 

Revision 3, Section 2.2:

The test weight Center of Gravity (CG) within the ISO 1CC container will be 

adjusted to accommodate a lateral CG shift up to 16 inches. The longitudinal and 

vertical CG locations are unplanned, but will be determined during testing. The 

ISO 1CC container shall then be restrained on the TSO-C90 PGA pallet with the 

16 inch CG shift oriented in the same direction as the 9 inch lateral shift of the 

container on the pallet. The final configuration of weight, center of gravity, 

shoring and restraint straps will be documented in a final test report which will 

contain all of the data results from the testing outlined within in the document.

After several test failures, the industry team reconsidered using the test method involving the 

triangular distribution of cargo and elected to attempt a vertical load test with NO CG shift of the 

cargo within the intermodal container. A vertical load test simulates a gust that pushes the 

airplane down, so that, because of its inertia, the offset container shifts upward. Only the CG

effect of offsetting the container was tested. The objective of this test was to better understand, 

by comparison, the effects of the CG distribution of cargo inside the container. This test failed by 

breaking the vertical locks of the cargo loading system, resulting in the container being 

unrestrained. After this test failure, the industry team in Oscoda ceased further testing until new 

test procedures were developed.

As discussed previously, for certification testing, the CG for the cargo used in testing must vary 

in the lateral, longitudinal, and vertical directions of the airplane to address a range of realistic 

flight scenarios. The required longitudinal and vertical CG shifts used in the Oscoda testing were 

not adequately tested for this purpose because the testing was incomplete when tests were halted 

after multiple failures. The industry team did not create a report documenting the failed results.

May 2014 testing in Arlington, Washington

The industry team conducted another set of tests of offset containers that also failed. Because 

intermodal containers are typically locked when operators receive them, operators cannot 

determine or adjust the CG of their contents. To address this, the industry team decided to 

attempt to develop a method to predict the direction of the deviation from the container’s 

centerline of the lateral CG of the cargo inside the container. The industry team balanced the 
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 9

intermodal container on a fulcrum located along the longitudinal center line of the intermodal 

container and documented whether the intermodal container tipped, and in which direction. This 

direction could then be placarded on the container as “outboard” on the airplane for loading. This 

method could be used to counteract the CG effect of the offset container and reduce the 

combined CG effects discussed previously.

When the industry team used this method to perform a vertical load test of an offset intermodal 

container, the vertical locks of the cargo loading system failed. The reason for the failure was 

that the offset of the container resulted in slack in the straps located in the center of the container. 

Because of this slack, the straps located at the ends of the container carried most of the load

imposed by restraining the container to the pallet. (See Figures 4, 5, and 6.) The locks that failed 

first were those that were closest to the end of the pallet where these straps were attached. These 

failures resulted in cascading failures of adjacent locks. In flight, this would result in the

container becoming unrestrained.

The effects of the cargo shifting in flight inside the intermodal container were not explored. 

Further, the required range of changes in the longitudinal and vertical centers of gravity was not 

investigated by the industry team. After the vertical testing failures, the industry team elected to 

stop further testing. The industry team did not create a report documenting the failed results.

Figure 4: Computer drawing showing intermodal container

offset on a pallet and restrained by straps to the pallet
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 10

Figure 5: Photo taken in Oscoda, Michigan,

showing intermodal container strapped to a pallet, and inverted to prepare for vertical testing

Figure 6: Photo taken in Arlington, Washington,

showing intermodal container strapped to a pallet, and inverted to prepare for vertical testing
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 11

Comments on the rule

The lateral CG testing method

Several commenters (Atlas Air, Cargo Airline Association (CAA), and Kalitta) asserted that the 

test by the industry team in March 2014, in Oscoda, Michigan, used a container that was offset 

on a pallet, with a CG shift exceeding the limit allowed by the WBM by nearly three times, 

which caused a grossly imbalanced load, which then caused the test to fail. The WBM limits the 

CG lateral deviation to 10 percent of the width of the pallet (9.6 inches). Kalitta stated that the 

load packed inside the container was actually 16 inches off-center, and the container was set nine 

inches off the pallet. Kalitta stated that the total CG deviation was, therefore, 25 inches.

The commenters are correct that the test used a 25-inch lateral CG offset; however, they fail to

acknowledge the combined effect described above resulting from the carriage of the offset 

intermodal container with an unknown CG of the contents of the container. The testing did use 

the industry team’s CG deviation as defined in the team’s test plan in its attempt to show that this 

configuration complies with the airworthiness standards, even though it exceeds the limits 

specified in the WBM. But the vertical test failure in Oscoda occurred during a test of a container 

with the CG of its contents located in the center of the container. Therefore, the second CG effect 

was eliminated.

Lack of testing an offset intermodal container strapped directly to the airplane

The CAA stated that the Arlington testing was not conducted with the intermodal container 

configured within the CG allowable limits of TSO C-90 and did not use the original strap 

configuration tested in Oscoda. The CAA and NACA also stated that the test did not consider the 

configuration actually used by the airlines. For example, there was never a test conducted with 

the ULD tied directly to the aircraft.

The CAA’s conclusions are incorrect. By design, the Arlington test was not conducted in 

accordance with the TSO standard and did not use the original strap configuration tested in 

Oscoda because the industry team was attempting to show that it is possible to load offset 

containers in a manner that complies with the applicable airworthiness standards, even though 

they do not comply with the TSO. As discussed previously, the strap configuration tested in 

Oscoda failed. No testing was conducted with the ULD tied directly to the aircraft because that is 

not the retention method the industry team was attempting to show compliant. The industry team 

was attempting to substantiate its desired configuration of an offset intermodal container 

restrained only to a pallet that, in turn, is restrained only by the cargo loading system. The 

industry team did not propose to test the configuration that operators may have previously used.
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 12

Use of too many straps in the Arlington testing

Kalitta asserted that the test in Arlington used 65 percent more cargo straps (a total of 96) than 

are normally used (58), which caused local areas of higher stress that caused the pallet to bend 

and the cargo loading system locks to break.

The commenter is correct regarding the number of straps used. However, the failure of the locks 

was not attributable to the number of straps. As discussed previously, the locking failure was 

caused by overloading of the cargo loading system locks located near the corners of the pallet; 

straps in the center of the container were unable to perform their function of carrying loads

because of slack in those straps.

Testing nonconformance to NAS 3610

Three commenters (CAA, Kalitta, and the Michigan Senate) stated that the first test in Oscoda

was not performed in accordance with the NAS 3610/AS361002

standards, which govern the

loading of ULDs, and the results are, therefore, invalid.

The commenters are correct that the tests were not performed in accordance with the referenced 

standards. As described in the background section of this document, the intermodal container 

loaded using the offset method is not a ULD as defined in NAS 3610. Therefore, the testing 

requirements for a ULD are not applicable. The industry team chose not to test in accordance 

with the NAS 3610/AS36100 standards, because the intermodal container would have to be

concentrically loaded on the pallet and restrained only with the corresponding net. The use of 

straps to restrain cargo to the pallet is not permitted in NAS 3610.

The objective of the industry team’s testing was to show that using the offset intermodal 

container complies with the applicable regulations described in the Background section of this 

document. This practice could then be the basis for a Supplemental Type Certificate (STC) 

Weight and Balance supplement. As discussed previously, the testing was unsuccessful.

The effect of shifting comparisons

The CAA asserted that the excessive shifting of the offset intermodal containers was not 

compared to the shifting of an intermodal container restrained by a certified pallet-net ULD. The 

CAA further stated that Kalitta has performed such additional testing, and the shifting of cargo 

restrained by a net far exceeds that of the same cargo also restrained by straps. The CAA asserted 

that the strap configuration is superior to the net configuration with respect to shifting and is 

therefore a preferable, safer method for transporting intermodal containers than using just nets 

alone.

The FAA disagrees with the CAA’s assertions. As discussed in the NPRM, a pallet-net 

combination restraining a concentrically loaded intermodal container can be located only on the 

 2 AS36100 is a later version of NAS 3610.
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 13

centerline of the airplane because it would otherwise interfere with the fuselage frames. At this 

location, the container is at least four feet from the fuselage frames. The testing of offset 

intermodal containers was performed to determine whether intermodal containers could be 

loaded using the offset method to the left or right of the centerline and still enable the airplane to 

meet the applicable airworthiness standards. At these locations, much smaller shifting could 

result in the container impacting the fuselage frames.

Testing not reflective of typical airline loading

Several commenters (Atlas, CAA, Kalitta, and the Michigan Senate) contended that the FAA has

reached conclusions from the cargo load testing conducted last year based on atypical loading of 

the cargo.

The commenters are incorrect. As discussed in the Background section of this document, the 

industry team’s testing was intended to demonstrate that loading offset intermodal containers can 

be shown to comply with the applicable airworthiness standards, which require that testing 

“conservatively approximate” actual conditions. The industry team chose the weight of the cargo 

inside the container to be tested based on the team’s desired payloads. The team determined the 

CG deviation for that cargo by using the triangular distribution method because the actual 

loading of the locked containers is uncontrolled.

Lack of consideration for energy-absorbing straps and nets during testing

IATA asserted that the loads that might impact the fuselage frames would be reduced by the 

energy absorbed by the net, thus the impact damage to the fuselage frames would be reduced. 

IATA further stated that in-flight observations confirm that the net acts as a de facto braking

device while it absorbs energy through elongation, so that irrespective of the type of cargo 

carried, it sometimes comes in soft contact with the fuselage, but never to impact. IATA also 

stated that cargo loading system (CLS) failure is not specified as a case for ULD certification, 

which considers only ULD failure, and that a CLS failure certainly justifies complete 

investigation.

The FAA found that IATA provided no data to substantiate its claims and no evidence of how 

much energy would be absorbed by the net elongation such that it would eliminate the unsafe 

condition. It is unknown whether IATA conducted in-flight observations, including observations 

of any offset intermodal container configurations. Further, the offset method introduces slack in 

the net, which is not accounted for in NAS 3610 ULD testing. Any reduction in energy absorbed 

by the net would occur only after the intermodal container shifted sufficiently to eliminate the 

slack. Following the first test failure in Oscoda, the industry team determined that the slack in the 

net was so great that the net was ineffective, and the team did not use the net in later testing. In 

all vertical tests the industry team completed, the cargo loading system vertical locks failed, 

which resulted in the offset intermodal container becoming unrestrained. This is unsafe.
Docket No. FAA 2014 0780 FAA Discussion of Offset Intermodal Container Testing

July 9, 2015 Page 14

Test results not made public permitting adequate comments

IATA commented that since the test results were not made public, IATA did not have full 

opportunity to review and comment.

As noted previously, the industry team did not document the failed testing in a test report; 

therefore, there is no test report to make public. However, IATA represents two of the industry 

team members, Atlas Air and UPS. Additional information regarding the tests may be available 

from them.