To simplify fuel operations, the Department of Defense (DOD)
has adopted a single-fuel concept (SFC) that requires U.S.
forces to use only one fuel while deployed. Although the concept
has merits, it also has shortcomings. The challenge is to develop
a policy that will best meet all military fuel needs.
Evolution of the SFC
Waxing and fuel filterability problems with the North Atlantic Treaty Organization’s
(NATO’s) standard diesel fuel, F54, during cold weather created severe
problems for the engines of M1 Abrams main battle tanks and other gasoline turbine-powered
equipment when they were introduced to U.S. forces in Germany in 1981. [Diesel
fuel typically has a high paraffin hydrocarbon content, which prevents it from
flowing at low temperatures. Waxing refers to this situation, in which the paraffin
hydrocarbons in the fuel congeal and wax-like particles are formed that can either
coat the surfaces they contact or plug fuel filters.]
The interim fix for these problems involved blending the F54 diesel fuel with
aviation kerosene turbine fuel (either JP5 or JP8) to lower both the waxing tendency
and the viscosity of the diesel fuel. This blended fuel, known as the “M1
fuel mix,” was used for all diesel-fueled equipment in forward areas from
November through April annually. Other NATO countries soon adopted the blend
(50 percent F54 and 50 percent JP8 or JP5), which subsequently was given the
NATO code number F65. These fixes for the low-temperature operability problems
more than likely served as the genesis for the SFC.
The subsequent requirement for blending of fuels created logistics problems that
prompted the Army to adopt JP8 as an alternative to diesel fuel in 1986, circumventing
the need to blend other fuels with diesel. DOD issued a directive on fuel standardization
in March 1988 that specified JP8 as the primary fuel for air and land forces.
Testing and Field Trials
Users expressed concerns about using JP8 as a substitute for diesel fuel. These
concerns included whether JP8 would burn hotter, if it would increase fuel consumption,
and if it would be compatible with existing systems. As a result, the Army conducted
many tests in the laboratory and on engine dynamometers, in addition to field
and fleet tests, to validate using aviation kerosene turbine fuels in diesel
engines and to dispel concerns. [Dynamometers measure mechanical power and assess
engine durability and performance.]
Of the many successful fleet tests, one was particularly noteworthy. This 10,000-mile
durability test was conducted with several commercial utility cargo vehicles
(CUCVs) at the General Motors Desert Proving Ground in Mesa, Arizona, where they
were exposed to round-the-clock operations in continuously hot climates. The
test revealed no significant impacts on vehicle performance or fuel-injection
pump wear, and no measured differences in engine operating temperatures were
noted, which dispelled the fears of engines overheating because of supposedly
hotter burning fuels.
Field Artillery Battalion soldier from Fort Stewart,
Georgia, prepares to refuel a 155 millimeter howitzer
during a “refuel on the move” exercise
One of the more significant and comprehensive
tests of JP8 was a field de-monstration conducted at Fort Bliss,
Texas, from October 1988 through July 1991. This field demonstration
in-volved about 2,800 diesel-powered vehicles and pieces of
equipment that consumed over 4.7 million gallons of JP8. The
demonstration proved successful: no catastrophic failures were
attributed to JP8. In fact, no major differences in procurement
costs, fuel consumption, oil change intervals, or component
replacements were identified when compared to historical data
for the same fleet of vehicles and equipment using diesel fuel.
Implementation of the SFC Since 1990
When approved by the combatant commander, the primary fuel support for air and
ground forces in overseas theaters will be a single, kerosene-based fuel. The
SFC was first implemented in December 1989, when JP5 was used as the single fuel
during Operation Just Cause in Panama.
In August 1990, DOD implemented the SFC by providing Jet A1 (JP8 without its
three mandatory additives) for U.S. forces in Operations Desert Shield and Desert
Storm. During those operations, some Air Force units were located on bases where
only JP4, which could not be used in ground vehicles and equipment, was available.
Some Army units requested diesel fuel instead of JP8 because JP8 did not make
acceptable smoke in the M1 Abrams’ exhaust-system smoke generators. Further
compounding the problems was the lack of training of ground units, which would
have reduced their initial concerns about using aviation fuels in ground vehicles
and equipment. Despite these problems, the SFC was considered a success.
The SFC was im-plemented next for combat operations in Somalia, Haiti, and the
eastern Balkans with the same success that it had achieved duringOperations Desert
Shield and Desert Storm.
|A fuel specialist
with the 127th Area Support Battalion, Division Supply
Command, 1st Armored Division, signals the pump truck
operator to stop the flow while another fuel specialist
prepares to unhitch the fuel line from a UH–60
Black Hawk helicopter at Baghdad International Airport.
During Operations Desert Shield and Desert Storm, certain families
of engines that used fuel-lubricated, rotary-distribution,
fuel-injection pumps experienced some op-erational problems
that resulted in hot-starting difficulty and gradual loss
of power. (Hot starting refers to restarting a vehicle while
its engine is still hot.) Usually, the engines that experienced
the most problems were the General Motors 6.2-liter and 6.5-liter
engines, which use the commercially manufactured Stanadyne
fuel-injection pump. These engines power smaller tactical
wheeled vehicles, such as CUCVs and high-mobility, multipurpose,
wheeled vehicles (HMMWVs). The Stanadyne fuel-injection pump
is used on a variety of other engine systems that provide
power to combat support and combat service support equipment.
Causes of the problems with the engines included—
• Sustained operation during high temperatures.
• Failure to retrofit the Stanadyne fuel-injection pump with elastomer
drive governor weight retainer assemblies.
• Improperly manufactured replacement parts.
• Unauthorized oils and fluids added to Jet A1 fuel.
• Use of Jet A1 that did not contain corrosion inhibitor and lubrication-enhancing
additives.The viscosity of the Jet A1 fuel being supplied by Saudi Arabia under
a host nation support agreement was very low, as was the sulfur content, which
compounded the hot-starting problems.
Ironically, none of these problems occurred during the extensive testing at Fort
Bliss. In hindsight, the test at Fort Bliss used JP8, which has a higher viscosity
than the Jet A1 fuel typically refined in the Middle East, and temperatures at
Fort Bliss were at least 15 degrees Fahrenheit lower than those encountered in
Of the many types of fuel-injection pumps manufactured commercially, such as
the single-cylinder pump, the inline pump, and the distributor pump, the rotary-distribution,
fuel-injection pump is the most sensitive to the lubricating quality of the fuel.
This pump is inexpensive and is used in a wide variety of commercial and military
equipment typically powered by light-duty diesel engines. In these pumps, the
fuel provides the needed lubrication to the internal moving components. When
the lubricity (lubricating quality) of the fuel becomes marginal or insufficient,
the pump components will wear.
If fuel viscosity is sufficiently high, the fuel will physically separate the
injection system’s sliding components, preventing wear. With a lower viscosity,
the potential for wear increases significantly because the surfaces of the sliding
parts can begin to interact. However, certain additives to the fuel will generate
surface films that provide the needed wear protection. The viscosity of fuel
decreases as the fuel temperature increases, thus decreasing
the fuel’s ability to lubricate the injection system and increasing users’ dependence
on lubricious surface films to control component wear. American Society for Testing
and Materials (ASTM) D 975, Standard Specification for Diesel Fuel Oils, sets
the current industry standard for the minimum viscosity of grades 1–D and
low sulfur 1–D diesel fuel at 1.3 square millimeters per second (mm2/s)
at 40 degrees Celsius. While the viscosity of JP8 at 40 degrees Celsius is not
identified in the JP8 specification (MIL–DTL–83133E), the observed
range of viscosity varies from 1.0 to 1.7 mm2/s at 40 degrees Celsius. Obviously,
using a fuel with viscosity lower than 1.3 mm2/s will accelerate the potential
for component wear. Of the four major manufacturers of rotary-distribution, fuel-injection
pumps, Stanadyne Automotive Corporation is the only one that provides factory
retrofit kits for lessening the potential for wear and hot restart problems when
using low viscosity fuel.
Another adverse effect resulting from using low-viscosity fuels in rotary-distribution,
fuel-injection fuel pumps is the increased potential for internal leakage. A
combination of low-viscosity fuel and increased clearances between surfaces due
to wear (resulting from insufficient lubricity) can result in increased internal
fuel leakage that reduces the amount of fuel delivered to the combustion chamber.
More internal leakage in the pumping sections occurs at low engine speeds, causing
hot-starting and hot-idle problems. Some of these problems surfaced during the
latter stages of Operations Desert Shield and Desert Storm.
Major Problems Since 9/11
With the recent major combat operations in Afghanistan and Iraq, fuel-related
problems have increased significantly as a result of using low-viscosity fuels
as the single fuel. In Afghanistan, much of the aviation kerosene that initially
was procured was Russian TS1 aviation kerosene because the neighboring refineries
produce aviation kerosene as TS1 instead of Jet A1 or JP8. The Russian TS1 aviation
kerosene is similar to Jet A1, but it is more volatile because it has a lower
flash point and a lower viscosity.
|A fuel specialist
with the 127th Area Support Battalion, Division Supply
Command, 1st Armored Division, takes a fuel sample
for testing at Baghdad International Airport.
The fuel being used in Iraq is JP8. However, in both Afghanistan
and Iraq, the ground vehicles and equipment are being used
much more extensively than they would be used in normal service.
Considering this added use, the hot temperatures that typically
prevail in the Middle East, and the increasing engine-power
demands imposed by the increased weights of up-armor kits,
it is no wonder that the ground vehicles and equipment that
have rotary-distribution, fuel-injection pumps have had many
fuel-related engine problems.
An article in the July 2004 issue of National Defense magazine, “Army Ponders
New Diesel Engine for Humvee Trucks,” notes that maintenance nightmares
have been experienced in Iraq because engines regularly break down and often
must be replaced after only 1,000 to 2,000 miles of operation. Much of the blame
for this is placed on the bolted-on armor protection that adds weight to the
vehicles. However, the inability of the rotary-distribution, fuel-injection pumps
to operate satisfactorily for sustained periods of heavy-duty operation is probably
a contributing factor, especially when low-viscosity fuel is used in a hot environment.
Interestingly, the fuel-injection pumps in many, if not all, of the HMMWVs operating
in Southwest Asia have been retrofitted with Stanadyne’s Arctic Fuel Conversion
Retrofit Kit. This kit apparently has done little to offset the significant increases
in maintenance that have been experienced recently.
Rethinking the SFC
Combat operations that occur in higher temperature environments certainly will
intensify the operational and maintenance problems of diesel-powered vehicles
and equipment with fuel-lubricated fuel-injection pumps. Since almost half of
the Army’s diesel vehicles and equipment have rotary-distribution, fuel-injection
pumps, a solution is urgently needed.
Despite the maintenance and readiness problems it has created,
the SFC has created many benefits. One fuel is considerably
easier to manage than multiple fuels.
The functions of fuel storage, transportation, and distribution can be tailored
for maximum efficiency. Using a single fuel lessens the possibility of dispensing
the wrong fuel. Using JP8 as the single fuel has enhanced long-term storage
stability, improved cold weather vehicle operation, reduced
engine combustion component
wear, and reduced fuel system corrosion problems.
The most recent version of DOD Directive 4140.25, DOD Management
Policy for Energy Commodities and Related Services, stipulates
that “. . . it is imperative
that combat support and combat service support vehicles and equipment be capable
of receiving support (i.e., fittings, nozzles, etc.), achieving and sustaining
acceptable operational performance using both kerosene-based turbine fuel and
diesel fuels to the maximum extent practical.” Policy directives may
not always match reality, which is the case with the large numbers of diesel-fuel-consuming
vehicles and equipment with rotary-distribution, fuel-injection pumps.
Certainly, the significant increases in maintenance requirements that have
been experienced in Afghanistan and Iraq strain an individual’s understanding
of the phrase “sustaining acceptable operational performance.” This
is not saying that the SFC doctrine is flawed, but some changes are urgently
Ironically, a strategy research project completed in April 1996 at the Army
War College identified some possible problems with the SFC and gave
several recommendations. Two of the more significant recommendations were—
• The fuel pumps on all new equipment must be compatible with JP8.
• All future military equipment must be designed to use JP8 as the primary
fuel source.Both of these recommendations are as relevant today as they were
DOD Directive 4140.25 requires that acceptable operational performance be
achieved with both kerosene-based turbine fuels and diesel fuels. However,
type must predominate over the other, and, since compression-ignition engines
essentially designed and manufactured for diesel fuel consumption, the predominant
fuel naturally would be diesel. An engine’s fuel pump must be JP8 compatible
in all types of operating conditions, not just in environments with cold
to moderate temperatures.
Because of the large number of existing vehicles and equipment that use the
fuel-lubricated, rotary-distribution, fuel-injection pumps, one approach
would be to make the
SFC doctrine more flexible by requiring use of diesel fuel when systems operate
for sustained periods in a high-temperature environment. This change would
least affect the Air Force because it typically operates from fixed sites
removed from direct combat operations so that two fuel distribution and storage
systems are easier to implement. The Army and Marine Corps would be affected
more because they require one fuel distribution system for ground equipment
and a second for helicopters and both systems require intense protection
This dual-system option is complicated further by doctrine calling for highly
mobile, distributed, autonomous combat units.
Another, albeit more complicated, approach would be to require that the rotary-distribution,
fuel-injection pumps be replaced with pumps that are less sensitive to fuel
viscosity and lubricity, such as the common rail or pump-line nozzle systems.
Failure to recognize and act on the problems inherent in the use of kerosene-based
fuel with rotary-distribution, fuel-injection pumps will only serve to decrease
operational readiness and increase maintenance costs over time. ALOG
E. Le Pera is the president of Le Pera and Associates of Harrisonburg, Virginia.
He is a graduate of the University of Delaware and had 36 years of Government
The author wishes to thank Emilio S. Alfaro of the Air Force Petroleum Office
and Edwin C. Owens of the Southwest Research Institute for their assistance
in developing this article.