United States General Accounting Office

GAO Report to Congressional Committees

September 1997 ELECTRONIC

WARFARE

Towed Decoys Could

Improve Survivability

of Current Navy

Aircraft

GAO/NSIAD-97-94

GAO United States

General Accounting Office

Washington, D.C. 20548

National Security and

International Affairs Division

B-272628 

September 4, 1997

Congressional Committees

We have completed our review of the Department of Defense’s (DOD)

acquisition plans for the ALE-50 towed decoy system and the Radio

Frequency Countermeasures System (RFCM), which includes a more

advanced towed decoy. The RFCM is part of the Integrated Defensive

Electronics Countermeasures System being developed for some Navy and

Air Force aircraft. Our objective was to determine whether towed decoys

could improve the survivability of these aircraft. In addition, because

Congress has expressed concern for F/A-18C/D survivability, we are

issuing this report to bring to your attention the opportunity towed decoy

systems offer to potentially enhance survivability of the F/A-18C/D.

Results in Brief DOD’s effort to improve the survivability of its aircraft through the use of

towed decoys has demonstrated positive results. According to test reports

and test officials, the ALE-50 has done very well in effectiveness testing

and the future RFCM decoy system is expected to be even more capable.

The Air Force is actively engaged in efforts to field towed decoy systems

on a number of its current aircraft, including the F-15, F-16, and B-1, while

the Navy is planning towed decoys only for its future F/A-18E/F.

In the year 2010, almost 50 percent of the Navy’s tactical fighter inventory

will still be current generation fighter aircraft such as the F/A-18C/D, even

if new F/A-18E/Fs are procured at the rates desired by the Navy between

now and then. Hence, improving the survivability of the F/A-18C/D, as well

as other current Navy and Marine Corps aircraft, potentially offers the

opportunity to save additional aircraft and aircrew’s lives in the event of

future hostilities and also addresses congressional concerns expressed for

F/A-18C/D survivability.

Background Traditionally, DOD’s combat aircraft have used on-board electronic warfare

devices called jammers for self-protection against radar-controlled

weapons, including missiles and anti-aircraft artillery. These jammers emit

electronic signals from the aircraft to try to impede or deny the threat

radar’s ability to locate the aircraft. DOD’s existing self-protection jamming

systems for its tactical aircraft have limitations against certain threats, and

these threats are expected to be improved. DOD has modified existing

systems, such as the Air Force’s ALQ-131 used on the F-16 and the

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ALQ-135 on the F-15, and has developed a newer system, the Navy’s

Airborne Self-Protection Jammer (ASPJ), which is being used on some

F-14D and F/A-18C/D aircraft. As we have previously reported, however,

testing after deployment has shown that the modified jammer systems

have had problems,1

 while operational testing of ASPJ and other jammers

showed they were unable to meet effectiveness criteria against certain

classified threats.2

In an attempt to overcome the limitations of the on-board jammers, the

services are acquiring two new towed decoy systems, the ALE-50 and the

RFCM, to enhance survivability against the radar-controlled threats. The

ALE-50 towed decoy system is in production, while the future RFCM system

is in development. The ALE-50’s towed decoy component generates and

emits its own signals that are intended to lure an incoming radar-guided

weapon away from the aircraft by presenting a more attractive target. To

provide further improvement for selected Air Force and Navy aircraft, the

RFCM is to provide more sophisticated techniques than the ALE-50. A

jamming device called the techniques generator carried onboard the

aircraft produces jamming signals that are transmitted by fiber optic cable

to the RFCM decoy for transmission.

Both decoys are single use systems. Once deployed from the aircraft, the

decoy’s tow line is severed prior to return to base. Each aircraft is to carry

multiple decoys, so if one is destroyed by enemy fire or malfunctions,

another can be deployed. Therefore, substantial inventories of decoys are

required to sustain potential combat operations. The services expect that

these decoys will improve survivability of their aircraft against

radar-controlled threats compared to the current technique of emitting the

jamming signals directly from the aircraft.

Towed Decoys Can

Enhance Survivability

Classified test results show that the ALE-50 towed decoy offers improved

effectiveness against radar-controlled threats, including some threat

systems against which self-protection jammers have shown little to no

effectiveness.3

 Moreover, the future RFCM decoy system is expected to

further improve survivability due to its more sophisticated jamming

techniques.

1

Electronic Warfare: Need to Strengthen Controls Over Air Force Jammer Programs

(GAO/NSIAD-90-168, July 11, 1990) and Electronic Warfare: Most Air Force ALQ-135 Jammers

Procured Without Operational Testing (GAO/NSIAD-95-47, Nov. 22, 1994).

2

Airborne Self-Protection Jammer (GAO/NSIAD-97-46R, Jan. 29, 1997.)

3

Performance against specific threat systems is considered classified.

Page 2 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
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Recognizing the potential offered by these towed decoy systems to

overcome the limitations of using just on-board jammers, such as the ASPJ,

the Air Force is actively pursuing the use of towed decoys for its current

aircraft. It has done the necessary modifications to add the ALE-50 to the

F-16, an aircraft slightly smaller than the Navy’s F/A-18C/D, and to the B-1,

a much larger aircraft. The Air Force is also considering use of the RFCM

decoy system on the F-15, which will use its existing on-board jammer

instead of the techniques generator, and on the B-1, as well as several

other aircraft. The Navy plans to equip only its future F/A-18E/F aircraft

with a decoy system.

The ALE-50 decoy system is to be used by the Air Force on 437 F-16 and 

95 B-1 aircraft. In addition to the ALE-50 components such as the launcher

and controller installed on the aircraft, the Air Force plans to procure

17,306 ALE-50 decoys to meet operational requirements. The Navy plans to

buy 466 ALE-50 decoys. These will be used for F/A-18E/F testing and

contingencies after the aircraft’s deployment until the RFCM decoy is

available. The ALE-50 program cost is estimated at about $1.2 billion.

The Navy’s estimated RFCM cost for its F/A-18E/F aircraft is about

$2.6 billion. The Navy’s plan is to procure enough RFCM systems and spares

to equip and support 600 of its planned buy of 1,000 F/A-18E/F aircraft. For

600 F/A-18E/F aircraft, the number of decoys to be procured to meet

operational needs is 18,000. (These estimates predate the May 1997

decision of the Quadrennial Defense Review (QDR) to recommend a

reduction in the number of F/A-18E/Fs.)

The future RFCM decoy system is also being considered by the Air Force for

its B-1 aircraft, part of its F-15 fleet, and several other Air Force manned

and unmanned aircraft. If the Air Force buys the RFCM system for the B-1

and the F-15, which would use its existing onboard jammer instead of the

RFCM techniques generator, the estimated cost, including 9,107 decoys, is

about $574 million.

Current Navy Aircraft

Will Not Be Provided

With Towed Decoys

In contrast with the Air Force, which intends to use decoys to improve the

survivability of its current aircraft, current Navy combat aircraft will be at

a comparative survivability disadvantage since they will not be provided

with a decoy system. In particular, because F/A-18E/Fs will not be

replacing all of the C/D models in the Navy/Marine Corps inventory in the

foreseeable future, adding a towed decoy system to the F/A-18C/D

Page 3 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
B-272628 

potentially offers the opportunity to save additional aircraft and aircrew’s

lives in the event of hostilities.

In the year 2010, more than 600 of the Navy’s tactical fighter inventory

objective of 1,263 aircraft will still be current generation fighters such as

the F/A-18C/D. This will be true even if F/A-18E/Fs are procured at the

Navy’s desired rates of as high as 60 per year. At the post-QDR suggested

rate of 48 per year, almost 50 percent of the current generation aircraft will

still be in the fleet in the year 2012.

DOD and the Navy have done studies to determine whether towed decoys

could improve the survivability of the F/A-18C/D. DOD’s Joint Tactical

Electronic Warfare Study and an analysis conducted by the Center for

Naval Analyses concluded that the addition of a towed decoy system to the

F/A-18C/D would provide a greater increase in survivability for that

aircraft than any jammer, including the ASPJ.

In limited flight testing on the F/A-18C/D, the Navy demonstrated the

ALE-50 decoy could be deployed from either a wing station or the

centerline station of the aircraft. While the Navy acknowledges that towed

decoys can enhance aircraft survivability, it does not consider these flight

tests to have been successful because of the following suitability concerns.

According to the Navy (1) the tow line can come too close to the

horizontal tail or the trailing edge flap when deployed from a wing station,

making it unsafe or (2) the tow line can be burned off by the engine

exhaust or separated by abrasion if deployed from the centerline station.

The Navy’s report on the wing station testing stated that tow line

oscillation led to lines breaking on several flights, but did not state that the

decoy system was a flight safety risk nor that there was any contact with

the horizontal tail or flaps. Concerning the centerline station tests, several

tow lines were burned off or otherwise separated from the aircraft by

abrasion during maneuvering flights. A reinforced tow line later solved

these problems and the Navy is continuing testing on the F/A-18C/D from

the centerline station. Based on these test results, the Navy now intends to

deploy the ALE-50 decoy from the centerline of the fuselage of the

F/A-18E/F.

The Navy also maintains that even if the decoy could be successfully

deployed from the F/A-18C/D wing or centerline station, for actual

operations, it could not afford to trade a weapon or fuel tank on a wing or

centerline station for a towed decoy system. Further, the Navy considers

Page 4 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
B-272628 

modification of the C/D model’s fuselage for internal carriage of the decoy

to be unaffordable due to volume, weight, power, and cooling constraints

that would have to be addressed.

The Air Force has modified a wing pylon to successfully deploy towed

decoys from the F-16’s wing while avoiding major aircraft modifications

and without sacrificing a weapons station or a fuel tank. The Navy,

however, has not done the technical engineering analyses to determine the

specific modifications necessary to accommodate a towed decoy on the

F/A-18C/D either from the wing or the centerline without affecting the

carriage capability unacceptably.

Survivability of F/A-18

Aircraft Has Been a

Congressional

Concern

Congress has expressed concerns regarding F/A-18C/D survivability. The

Report of the Senate Appropriations Committee on the National Defense

Appropriations Act for Fiscal Year 1997 directed the Navy to report on the

advantages and disadvantages of using various electronic warfare systems

to improve F/A-18C/D survivability. In addition, Congress provided

$47.9 million in fiscal year 1997 funding not requested by DOD to buy 36

additional ASPJs for 3 carrier-deployed squadrons to meet contingency

needs.

The Navy could have addressed the congressional concern for C/D

survivability in the required report by including analysis of the

improvement offered by incorporating the ALE-50 and RFCM towed decoy

systems. In completing the required report, however, the Navy did not

include any analysis of survivability benefits from using towed decoys

because it maintains, as described above, that there are unacceptable

impacts associated with towed decoys on the F/A-18C/D.

Agency Comments

and Our Evaluation

In commenting on a draft of this report, DOD agreed that towed decoy

systems could enhance aircraft survivability, but stated the Navy had

conducted an engineering analysis that concluded any installation option

of a towed decoy on the F/A-18C/D has unacceptable operational and/or

safety of flight impacts. In response to our request for this analysis, the

Navy provided us with a paper discussing the feasibility of installing a

towed system on the F/A-18C/D. This paper concluded that the options

considered had risks or created operational concerns but did not conclude

that these options were unacceptable. Furthermore, the paper did not

consider all possible options.

Page 5 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
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With regard to the safety of flight issue, the Navy stated that the decoy or

towline might contact aircraft control surfaces such as the flaps or the

horizontal stabilizers if deployed from a wing station. The Navy’s summary

of wing station test results, however, does not show any evidence of such

contact. The Navy has expressed no concern about a safety of flight issue

when deploying the decoy along the aircraft’s centerline and continues to

fly test missions with the towed decoy, deploying it from a pod on the

centerline of an F/A-18D aircraft. Furthermore, the Navy intends to install

the system in the fuselage and deploy towed decoys from the centerline of

the E/F model aircraft. In addition, the Air Force incorporated the ALE-50

on to the F-16 without loss of a weapon station or fuel tank and without

having to undertake major aircraft modifications, demonstrating that it is

possible to adapt a towed decoy system to an existing aircraft without

creating unacceptable tactical impacts.

DOD did not concur with the recommendations that were set forth in a

draft of this report. In the draft, we had suggested that (1) in preparing its

congressionally required report, DOD consider F/A-18C/D aircraft upgraded

with RFCM and ALE-50 towed decoy systems and (2) the Navy do the

necessary engineering analyses of the modifications needed to integrate

towed decoys into F/A-18C/D and other current Navy aircraft. DOD

completed the congressionally required report without implementing our

first draft recommendation. We continue to believe, however, that the

Navy needs to explore ways to improve the survivability of its current

aircraft and, therefore, should do a detailed engineering analysis of the

modifications needed to adapt the towed decoy to the F/A-18C/D. DOD’s

comments are reprinted as appendix I in this report.

Recommendation We recommend that the Secretary of Defense direct the Secretary of the

Navy to make a detailed engineering analysis of the modifications needed

to adapt the towed decoy to the F/A-18C/D.

Matters for

Congressional

Consideration

In light of the demonstrated improvement in survivability that analyses

and test results indicate towed decoy systems can provide, and

recognizing that in the year 2010 almost 50 percent of the Navy’s tactical

fighter inventory will still be current generation fighter aircraft such as the

F/A-18C/D, Congress may wish to direct the Navy to find, as it has done for

its F/A-18E/F and the Air Force has done for the F-16, cost-effective ways

to improve the survivability of its current aircraft.

Page 6 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
B-272628 

Scope and

Methodology

To accomplish our objective of determining whether towed decoys could

improve survivability of Air Force and Navy aircraft, we examined DOD and

contractor analyses of adding towed decoy systems and reviewed Air

Force and Navy ALE-50 test results from testing on a variety of aircraft.

We interviewed officials from the Office of the Secretary of Defense, the

Navy, and the Air Force involved in the acquisition and testing processes

of towed decoy systems. We also interviewed contractor personnel

involved in the development, integration, and/or production of towed

decoy systems.

We performed our work at the Offices of the Secretaries of Defense, the

Navy, and the Air Force; F-15, F-16, and B-1 System Program Offices at the

Air Force Material Command, Wright-Patterson Air Force Base, Ohio;

F/A-18 and Tactical Air Electronic Warfare Program Offices at the Program

Executive Office for Naval Tactical Aviation, Naval Air Systems Command,

Washington, D. C.; the 53rd Wing and Air Force Operational Test and

Evaluation Detachment, Eglin Air Force Base, Florida; and selected

contractor locations, including McDonnell-Douglas Aircraft,

Lockheed-Martin, and Rockwell International.

We performed our review from February 1996 to July 1997 in accordance

with generally accepted government auditing standards.

We are sending copies of this report to the Secretaries of Defense, the

Navy, and the Air Force; the Director, Office of Management and Budget;

and other congressional committees. We will make copies available to

others upon request.

Please contact me on (202) 512-2841, if you or your staff have any

questions concerning this report. Major contributors to this report are

listed in appendix II.

Louis J. Rodrigues

Director, Defense Acquisitions Issues

Page 7 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
B-272628 

Congressional Addressees

The Honorable Strom Thurmond

Chairman

The Honorable Carl Levin

Ranking Minority Member

Committee on Armed Services

United States Senate

The Honorable Ted Stevens

Chairman

The Honorable Daniel K. Inouye

Ranking Minority Member

Subcommittee on Defense

Committee on Appropriations

United States Senate

The Honorable Floyd D. Spence

Chairman

The Honorable Ronald V. Dellums

Ranking Minority Member

Committee on National Security

House of Representatives

The Honorable C.W. Bill Young

Chairman

The Honorable John P. Murtha

Ranking Minority Member

Subcommittee on National Security

Committee on Appropriations

House of Representatives

The Honorable Richard C. Shelby

Chairman

The Honorable J. Robert Kerrey

Vice Chairman

Select Committee on Intelligence

United States Senate

Page 8 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
B-272628 

The Honorable Porter J. Goss

Chairman

The Honorable Norman D. Dicks

Ranking Minority Member

Permanent Select Committee on Intelligence

House of Representatives

Page 9 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix I 

Comments From the Department of Defense

Note: GAO comments

supplementing those in the

report text appear at the

end of this appendix.

See comment 1.

See comment 2.

See comment 1.

See comment 3.

Page 10 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix I 

Comments From the Department of Defense

Page 11 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix I 

Comments From the Department of Defense

See comment 1.

Page 12 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix I 

Comments From the Department of Defense

See comment 2.

See comment 2.

See comment 2.

See comment 4.

See comment 3.

Page 13 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix I 

Comments From the Department of Defense

GAO Comments Following are our comments on the Department of Defense’s (DOD) letter

dated May 5, 1997.

1. Our draft report included references to the comparability of F/A-18E/F

and C/D survivability, and it was provided to DOD for comment prior to the

decision to produce the F/A-18E/F. As DOD states, this decision has now

been made. Consequently, we have deleted references to the comparability

of the F/A-18E/F and C/D models. The issue of F/A-18C/D survivability

remains important, however, because E/F models will not replace all of

the current C/D models in the inventory in the foreseeable future.

2. Test results for towed decoys on the F/A-18C/D and other information

provided by DOD and the Navy do not support DOD’s statements. The safety

of flight issue, according to the Navy, arises from the concern that the

decoy or towline might contact aircraft control surfaces such as the flaps

or the horizontal stabilizers if deployed from a wing station. The Navy’s

summary of wing station test results does not show any evidence of such

contact. According to the test report, the Navy did find that aircraft

vortices behind the wing created aerodynamic instability in the towline,

but the report does not conclude that this potentially jeopardized aircraft

flight safety. Additionally, the Navy has expressed no concern about a

safety of flight issue when deploying the decoy along the aircraft’s

centerline, and use of a reinforced towline appears to have eliminated the

burnoff/abrasion problem. Thus, the Navy continues to fly test missions

with the towed decoy, deploying it from a pod on the centerline of an

F/A-18D aircraft, and intends to install the system in the fuselage and

deploy towed decoys from the centerline of the E/F model aircraft. This

evidence indicates that Navy concerns about a high degree of difficulty,

and severe volume, weight, power, cooling, and aircraft aerodynamics

issues associated with installing towed decoys may not be insurmountable.

As for unacceptable tactical impacts associated with towed decoy

installation, the Air Force has overcome this problem on the F-16, and we

presume that the Navy may also be able to find an integration solution for

the F/A-18C/D that avoids unacceptable tactical impacts if it continues to

pursue alternatives. The Navy did not abandon towed decoy installation

for the F/A-18E/F because of early problems with abrasion and heat

breaking the towline. Instead, it pursued alternatives. The solutions for the

F-16 and F/A-18E/F do not have to be the only alternatives considered for

the F/A-18C/D.

Page 14 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix I 

Comments From the Department of Defense

3. The Navy and DOD did provide us with additional information intended

to bolster its broad assertion of unsuitability. However, the information

provided was not an “engineering analysis” (implying a technical

document of some depth), but is instead a rather superficial “installation

feasibility study” that while identifying risk areas associated with installing

the towed decoy on the F/A-18C/D does not conclude that all installation

options have unacceptable operational and/or safety of flight impacts.

4. According to the Navy’s feasibility study, 220 pounds is the weight of the

towed decoy system mounted in a pod. According to the same study, if the

system’s launch controller is mounted in the aircraft’s fuselage, the

bring-back weight is reduced by only 140 pounds. In any case, since

studies and test results indicate the ALE-50 system can provide significant

improvements in survivability, the Navy needs to determine whether loss

of a relatively small amount of bring-back weight is worth the increased

risk of losing aircraft to radar-guided missiles.

Page 15 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
Appendix II 

Major Contributors to This Report

National Security and

International Affairs

Division, Washington,

D.C.

Michael Aiken

Terrell Bishop

Paul Latta

Terry Parker

Charles Ward

(707143) Page 16 GAO/NSIAD-97-94 Electronic Warfare/Towed Decoy Systems
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