Air Force Assessment of the Joint Strike Fighter's Aerial
Refueling Method (14-MAR-05, GAO-05-316R).
The Joint Strike Fighter (JSF) acquisition program is estimated
to cost $245 billion to develop and produce three variants of
stealthy fighter aircraft--a conventional takeoff and landing
variant for the Air Force, an aircraft carrier variant for the
Navy, and a short take-off and vertical landing variant for the
Marine Corps and Air Force. A major goal of the JSF program is to
reduce costs by maximizing commonality among variants. However,
the Air Force conventional variant is being designed with a
different aerial refueling method than those used by the two
other JSF variants. U.S. fighters use two different methods for
aerial refueling. Air Force fixed-wing aircraft are all currently
fueled by a boom that extends from a tanker aircraft and is
guided into a receptacle. The Navy and Marine Corps fighters use
a probe that extends from the fighter to receive fuel when
inserted into a drogue, which is a basket-like device on the end
of a hose that extends from the tanker. The Senate Armed Services
Committee directed that we (1) examine the rationale behind the
Air Force refueling decision for its JSF version, (2) determine
the savings if the Air Force decided to change its refueling
method on its JSF, and (3) determine the operational advantages
or disadvantages if the Air Force decided to change its refueling
method. This letter summarizes the information we provided
committee staff on December 16, 2004.
-------------------------Indexing Terms-------------------------
REPORTNUM: GAO-05-316R
ACCNO: A19397
TITLE: Air Force Assessment of the Joint Strike Fighter's Aerial
Refueling Method
DATE: 03/14/2005
SUBJECT: Air Force procurement
Aircraft components
Comparative analysis
Cost effectiveness analysis
Evaluation methods
Fighter aircraft
Military aircraft
Military cost control
Program evaluation
Aircraft refueling methods
Joint Strike Fighter
KC-10 Aircraft
KC-135 Aircraft
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GAO-05-316R
United States Government Accountability Office Washington, DC 20548
March 14, 2005
The Honorable John Warner
Chairman
The Honorable Carl Levin
Ranking Minority Member
Committee on Armed Services
United States Senate
Subject: Air Force Assessment of the Joint Strike Fighter's Aerial
Refueling Method
The Joint Strike Fighter (JSF) acquisition program is estimated to cost
$245 billion to develop and produce three variants of stealthy fighter
aircraft-a conventional takeoff and landing variant for the Air Force, an
aircraft carrier variant for the Navy, and a short take-off and vertical
landing variant for the Marine Corps and Air Force. A major goal of the
JSF program is to reduce costs by maximizing commonality among variants.
However, the Air Force conventional variant is being designed with a
different aerial refueling method than those used by the two other JSF
variants. U.S. fighters use two different methods for aerial refueling.
Air Force fixed-wing aircraft are all currently fueled by a boom that
extends from a tanker aircraft and is guided into a receptacle. The Navy
and Marine Corps fighters use a probe that extends from the fighter to
receive fuel when inserted into a drogue, which is a basket-like device on
the end of a hose that extends from the tanker.
The Senate Armed Services Committee directed that we (1) examine the
rationale behind the Air Force refueling decision for its JSF version, (2)
determine the savings if the Air Force decided to change its refueling
method on its JSF, and (3) determine the operational advantages or
disadvantages if the Air Force decided to change its refueling method.
This letter summarizes the information we provided committee staff on
December 16, 2004.
To determine the Air Force rationale for selecting a refueling method that
is different from the refueling method for the other variants, we reviewed
JSF requirements documents, an evaluation by the JSF contractor of JSF
refueling options, and design alternatives for each option. To assess the
advantages and disadvantages of each method, we reviewed Air Force
assessments of operational lessons learned and mishap reports for aerial
refueling missions. To determine whether there were potential savings if
the Air Force were to change its refueling, we reviewed an Air Force
estimate of savings and the cost of impacts to other assets, such as
tankers, to support this change. We also discussed relevant information
with program officials from the joint JSF program office, the Air Combat
Command, and the Air Mobility
Page 1 GAO-05-316R Joint Strike Fighter Refueling
Command. We conducted our review between August 2004 and January 2005 in
accordance with generally accepted government auditing standards.
Summary
Revising the Air Force's conventional JSF aircraft refueling method from a
boom to a probe and drogue would require modifying most of its current
KC-135 tanker aircraft at an estimated cost of $2.5-$3.5 billion according
to the Air Force. This estimated cost far outweighs the cost savings
gained from having a common JSF refueling configuration estimated to be
about $180 million for the JSF program. However, the Air Force estimate of
costs and savings does not consider the future tanker acquisition and
potential cost savings if the Air Force JSF was refueled by the probe and
drogue method. For example, a Rand Corporation study concluded that tanker
requirements could be reduced from 17 percent to 50 percent depending upon
specific warfighting scenarios if a tanker has the capability to refuel
simultaneously two aircraft with the probe and drogue method. Using the
current inventory of KC-135 tankers as a replacement baseline and a
Congressional Budget Office1 estimate of $150 million for a new tanker, a
17-percent reduction in the number of tankers required could equate to an
estimated savings of $13.7 billion. The Air Force assessment of JSF
refueling requirements did not fully address advantages and disadvantages
of each method to make it clear whether a change is beneficial to DOD.
Background
The Air Force's tanker fleet of KC-10 and KC-135 aircraft provides the
bulk of military aerial refueling services. These are large, long-range
commercial aircraft modified into tankers. See figures 1 and 2.
1Letter to the Honorable John McCain, United States Senate, May 7, 2002,
from Dan L. Crippen, Director, Congressional Budget Office.
Page 2 GAO-05-316R Joint Strike Fighter Refueling
Figure 1: KC-135 refuels a flight of F-15 aircraft with a boom
Source: U.S. Air Force.
Figure 2: KC-10 refuels an F-18 with a probe and drogue
Source: U.S. Air Force.
Each KC-10 has a centerline boom and a drogue so that it can refuel any
U.S. fixed wing aircraft. Further, 20 have been modified with drogue and
hose on each wing that allows two fighters to simultaneously
refuel-commonly called "multipoint." While each KC135 has a boom and can
be configured with a drogue adaptor to refuel probe-equipped fighters, the
configuration must take place on the ground before take-off. There are
currently only enough adapters to configure one-half the KC-135 fleet. The
following table shows the refueling capability of the current Air Force
tanker aircraft.
Table 1: Current U.S. Air Force Tanker Fleet and Refueling Capabilities
KC-10 tanker KC-135 tanker
Number in fleet 59 534
o All equipped with o All equipped for centerline
centerline boom and drogue boom refueling o 20 modified
refueling capability o 20 with drogue multipoint
Capability modified with wing air refueling system o About
refueling pod system for half can be configured for
multipoint drogue refueling centerline drogue refueling
capability
Average age 22 years 44 years
Source: Air Force.
The Air Force is currently evaluating several alternatives including a new
tanker to replace its aging KC-135 fleet. According to its mission need
statement a new tanker should be equipped with a centerline boom and
drogue capability so it can refuel both types of receiver aircraft on the
same mission. Further, it should eventually be capable of refueling
multiple aircraft simultaneously. The current and future tanker force
capabilities are important factors in determining the type of refueling
method selected for the JSF.
Evaluation Results
The Air Force plans to continue its reliance on boom refueling for its
conventional takeoff and landing JSF variant. The operational requirement
document specified that this variant would use the standard Air Force
refueling technique, which is the boom from its existing KC-10 and KC-135
tanker fleet. A JSF program official told us that during the requirements
development process no evaluation was made on using a common refueling
method and the requirement was driven by the existing and planned
refueling assets for each service.
Adopting the probe and drogue method of refueling for the Air Force
conventional takeoff and landing JSF version is technically feasible and
would save the JSF program about $180 million according to an assessment
made by the JSF contractor (Lockheed Martin). Of the total, an estimated
$176.2 million in production savings would accrue because the parts for a
probe system are less expensive than a boom refueling system. However, the
Air Force estimates it would cost between $2.5 billion and $3.5 billion to
modify 415 KC135 tankers to support a fleet of 1,763 Air Force JSF
variants. The cost estimate is based on a budget estimate by Boeing
Wichita, the KC-135 contractor, that the cost to add a multipoint
refueling capability is $6.1 million to $8.4 million per tanker depending
on the production lot size, 5 or 20 tanker aircraft. The Air Force used a
simple ratio to estimate the number of tankers that would need
modification. It assumed that 70 percent of its fighter force in 2020
would be JSFs. Therefore, 70 percent of its tanker force (415 tankers)
should be capable of multipoint refueling.
In addition to the cost to modify the KC-135 tanker, Air Force officials
stated that the boom method is less likely to damage the low observable
feature of the JSF aircraft and, therefore, reduce its vulnerability to
enemy air defenses. Thus, the chance for a successful mission is
increased. In contrast to a stable boom, air turbulences are more likely
to move the drogue basket and strike the JSF aircraft, leaving it more
vulnerable to enemy air defenses because its low observable feature has
been degraded. While the boom method has several operational advantages, a
major disadvantage is its inability to simultaneously fuel two fighters
with the multipoint capability provided with the probe and drogue method.
The advantages and disadvantages associated with each method are shown in
table 2.
Table 2: Analysis of Advantages and Disadvantages for Using Boom and
Drogue Refueling Techniques on the Air Force JSF Variant
Boom Drogue
o No modification of o Permits refueling by half the
existing tankers for KC-135s and the British L1011
multipoint refueling or tanker o Permits multipoint
purchase of additional refueling on 35 US tankers o
boom to drogue adapters Increased JSF variant commonality
Advantages o Less chance to damage o Less time to refuel a 4-aircraft
to JSF low observable JSF flight o Avoids $3.19 million
features o Weighs 4.1 in developmental cost o Improved
pounds less than drogue allied interoperability o Saves
assembly $180 million in JSF total cost o
Could reduce number of new tankers
o Requires $2.5-$3.5 billion
o No refueling with modification to KC-135s o
British L1011 tanker o Requires change in joint common
Loss of $180 million in specifications o Potential to
JSF production and damage JSF low observable features
Disadvantages operations and o Adds 4.1 pounds to aircraft
maintenance savings o weight o Drogue adapter requires
No multipoint refueling preflight reconfiguration of KC-135
o Less JSF variant on the ground o Half of KC-135s
commonality cannot refuel with centerline
drogue
Source: GAO analysis based on DOD data.
In assessing the options for refueling the JSF, Air Force Air Combat
Command did not consider the potential for reducing the number of new
tankers by using multipoint refueling. For example, Rand2 identified three
comprehensive studies3 that concluded that the use of multipoint refueling
could reduce tanker requirements by 17 to 50 percent depending on a
particular scenario. If new tankers with multipoint capability replace all
KC-135 tankers, a 17-percent reduction would reduce the requirement by 91
aircraft (534 x .17 = 91). The Congressional Budget Office estimated that
a new tanker would cost $150 million. Thus, a 91-aircraft reduction would
save an estimated $13.7 billion. Additionally, the multipoint refueling
offers improved operational efficiencies by refueling two aircraft at a
time. However, quantifying the number of new tankers that could be reduced
and the improved operational efficiencies would require a detailed study.
In its estimates of the number of KC-135s needed to be modified to support
an Air Force probe and drogue version, the Air Force did not consider that
some of the KC-135s would be replaced by the new tanker. By contrast, the
JSF contractor, in estimating savings to the JSF program, projected that
170 new tankers may be in the inventory by the year 2020, which would
reduce the number of KC-135s requiring modification. Quantifying this
reduction, however, would require a detailed study. In addition, the Air
Force did not consider the following factors in its projection.
o The Air Force recently delayed delivery of the first JSF aircraft by 1
year. Additional delays could occur in the JSF program given its early
stage in the development process. If this happens, the Air Force would not
need to modify as many KC-135s to support the JSF fleet.
o In December 2004, Air Combat Command officials told us that the Air
Force is considering buying about 250 short takeoff and landing variant
JSFs and about 1,300 conventional takeoff and landing JSFs. This would
reduce the total number of Air Force JSFs to be acquired by 213 and could
reduce the total number of tankers required to refuel the JSF fleet.
Also, the Air Force's belief regarding the adverse low observable effect
caused by the drogue method lacked a technical engineering assessment on
the likelihood and the extent of low observable damage, according to Air
Combat Command officials. It also lacked an operational assessment to
determine the impact on mission success caused by the damage.
Additional factors could also influence decisions about the refueling
method for the Air Force variant of the JSF. First, as the JSF moves
forward in development, the decision to change to a probe and drogue
method will become more costly. Key points when the cost of design change
increases include the critical design review scheduled in fiscal year 2006
and production scheduled to start in fiscal year 2007. Also, JSF
quantities and delivery schedules could change as a result of the
Quadrennial Defense Review in 2005.
2 Bowie, C.J., et al., Enhancing USAF Aerial Refueling Capabilities, Santa
Monica, Calif.: RAND, R-3801-AF, 1990 (for government use only; not
available to the public).
3 Copeland, Donald, et al., Multipoint Refueling Program Cost Benefit
Analysis Final Report, Santa Barbara, Calif.: Frontier Technology, Inc.,
1995 (for government use only; not available to the public).George,
William L., Lt. Col., USAF, Utility of KC-135 Multipoint Modification,
Washington, D.C.: Air Force Studies and Analyses Agency, 1992 (for
government use only; not available to the public).
Conclusions
The advantages and disadvantages of a decision to change the Air Force
variant to the probe and drogue method of refueling can change based on a
wider range of considerations than included in the Air Force's assessment.
If the assessment includes only the JSF and other related legacy systems,
it appears the cost to modify the 415 KC135 aircraft at as much as $3.5
billion is the overwhelming deciding factor and suggests that keeping the
Air Force variant as a boom refueled aircraft is cost effective. However,
if the assessment is expanded to include potential reductions in
quantities of a new Air Force tanker because of efficiencies gained by
multipoint refueling, it is not clear where the larger cost benefit to DOD
lies.
Agency Comments and Our Evaluation
This correspondence is being issued without agency comments because DOD
did not provide comments within the time allotted.
We are sending copies of this report to the Secretary of Defense; the
Director, Office of Management and Budget; and interested congressional
committees. We will also make copies available to others upon request. In
addition, the report will be available at no charge on the GAO Web site at
http://www.gao.gov.
Should you or your staff have any questions on matters discussed in this
report, please
contact me on (202) 512-4163 or Michael Hazard on 937-258-7917. Principal
contributors
to this report were Richard Strittmatter, Dayna Foster, Marie Ahearn, and
Karen Sloan.
Michael J. Sullivan
Director, Acquisition and Sourcing Management
(120376)
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