SSC-Natick Press ReleaseU.S. Army Soldier Systems
Public Affairs Office
Contact: Public Affairs Office
Date: July 11, 2008
utilized to improve sling load operations
NATICK, Mass. --
Helicopters have long played a role in getting needed supplies to
Soldiers in the field. One way this is accomplished is through sling
loading. Sling loading is where a helicopter hovers while some type
of cargo, whether it is food, ammunition or other needed equipment,
is attached underneath. The load is fastened to a cargo hook via a
A few years back, during Operation Iraqi Freedom (OIF), air assault
troops noticed a problem with sling load operations during
brownouts, when blowing sand significantly decreased visibility for
aircrews and ground personnel.
Scott Ullery, project officer, Natick Soldier Research, Development
and Engineering Center (NSRDEC), said that it can be difficult for
pilots to hover and hold steady enough for ground personnel to
connect a load to the cargo hook. In brownout conditions, with no
visual references, hovering over the load can be extremely
Air assault troops attempted to fix the problem using an existing
polyester round sling as a pendant, providing additional separation
between the helicopter and the traditional sling set attached to the
load. The configuration allowed the helicopter to land beside the
load but lacked the required strength and durability.
"It turned out to be a viable concept, but the material was not very
durable. It was catching and tearing," said George Moorachian,
senior aerospace engineer, NSRDEC.
Other approaches were examined but an early solution using a braided
line didn't hold up well against sand. After a source selection
process, development resulted in a more viable pendant design that
used stronger materials and an extruded outer shell to protect it
from foreign debris.
Soon a new problem arose. The initial delivery of the newly
developed pendant failed first article testing. The production
pendants were not able to meet the required strength level, which
the design exceeded during development.
"The situation was, the unit had an urgent need and the first
contract lot was not deliverable," said Ullery. "Once we realized
there was a problem, [everyone] tried to react as quickly as
As the pendants were for the 101st Airborne Division, the
contracting had been done out of Fort Campbell, Ky.
The contracting officer and the subject matter experts agreed that
it wasn't feasible to cancel the contract and try to select a new
manufacturer. Ullery said they realized by the time a new source
selection could be done, it was possible the unit could be back from
Therefore, it was decided to look at all information available, and
use Lean Six Sigma (LSS) process and statistical tools to try and
determine where the problem might be.
"We looked at the actual [strength] testing process from beginning
to end," Ullery said, "and had an independent lab conduct additional
tests." Results varied, he continued, and we were able to
statistically prove that the initial results were incorrect. The
pendants, however, still did not meet the strength requirements.
The manufacturer and the subject matter experts also reviewed every
step involved with the production of the pendant.
"We looked at production process areas where defects might
inadvertently be introduced," stated Ullery. Areas such as
machinery, linking items together, anything where there might be
potential to have something not work, were observed, evaluated, and
One area identified as potentially contributing to the reduced
strength was found where production personnel were stripping some
polyurethane off the eye area of the pendants using a knife. This
posed a risk to the underlying fibers.
Ullery said they used a LSS tool called, 'Poke-yoke." Basically,
Poke-yoke is mistake-proofing your process.
We found an alternate way to remove the polyurethane so that there
would no longer be the potential for the fibers to get cut,
commented Ullery. It's an iterative process, and as the pendants
were produced, we continued to test and monitor the batches to find
out where the strength was.
The end result was that the pendant met its strength requirement and
the 101st Airborne Division received what they needed for
"The item is much more reliable for the user," Ullery said. "The
design of the pendant was proven, and what we found is that the
problem was a production issue that we were able to find and correct
using the tools of Lean Six Sigma."
He also commented that they wouldn't have been able to uncover the
problem if the manufacturer hadn't been so willing to participate.
"They stepped up and it was really beneficial," he said.
Moorachian commented that although there is a tradeoff with the
pendant, because the load is further back so it projects more drag
and reduces fuel efficiency, overall the general feedback from the
users has been pretty good.
The U.S. Army Combined Arms Support Command is currently examining
user requirements for improving helicopter operations, including
sling load operations.
"It [the pendant] is something the user is happy with," said
Ullery said, "Everyone worked together to ensure success."