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DEPARTMENT OF THE NAVY -- NAVAL HISTORICAL CENTER
805 Kidder Breese SE -- WASHINGTON NAVY YARD
WASHINGTON DC 20374-5060
E-6A/B MERCURY (TACAMO)
Wing span: 145 feet, 9 inches
Length: 153 feet
Height: 42 feet, 5 inches
Weight: gross takeoff: 342,000 pounds
Ceiling: 42,000 feet
patrol altitude: 25,000-30,000 feet
Speed: 512 knots
Range: unrefueled: 6,700 nautical miles with 16 hours
on-station endurance
Power plant: CFM International F-108-CF-100 (CFM 56-24-2)
turbofan engines
Crew: Four flight crew, five mission crew
Contractor: Boeing
3-View Drawings of an E-6A (download
as .pdf file)
Emphasis in the design and operation of most of today's new
Navy aircraft is on multimission capability. One exception, by
designation and intended role, might seem to be the Boeing E-6A.
Fleet Air Reconnaissance Squadrons (VQs) 3 and 4 operate E-6As
in the same manner as their EC-130s - as TACAMO (take charge and
move out) communications platforms serving as command links to
the fleet ballistic missile submarine force. In spite of their
new military designation, the E-6As, like the EC-130s, are part
of a large family of transports that have been adapted to many
roles. Prototypes of both designs first flew within a month of
each other in the summer of 1954.
Following Boeing's prototype four-jet transport, widely publicized
as the first of the 707 series, the Air Force ordered the first
production models as KC-135 tanker transports. Much modified and
adapted, these still serve the Air Force, and two were transferred
to the Navy in the late 1970s for use in the electronics support
role. Similar in appearance, but considerably redesigned, the
first 707-120 airline transports rolled off Boeing's production
lines in 1957. By the time these were in service, the larger 707-320
series was following, designed for long range transoceanic service.
Both models soon received turbofan engines in place of their original
jets. The Navy's E-6A is the final derivative of the 707-320 series
to be added to the production line, joining its better known E-3A
Sentry AWACS (airborne warning and control system) predecessor.
The first 707-320 series to join the military took on the
duties of the presidential aircraft as "Air Force One"
in 1962, two joining several earlier 707-120s in the VC-137 series.
Ten years later, the two prototypes for what would become the
E-3 were also designated in this series. In addition to the large
radome mounted on struts above the aft fuselage, similar to that
on the prototypes, many detail modifications were made to the
707-320B airframe for the subsequent production E-3As. Particular
attention was paid to hardening the airframe against the effect
of electromagnetic radiation and nuclear blasts. Updated E-3s
serve the Air Force, NATO, and other countries, and are still
being produced today.
With the Navy order for TACAMO versions of the 707-320B airframe,
the E-6A designation was assigned for these airframes, to be built
on the E-3A line. At the same time, C-18 series and E-8A designations
were assigned to ex-airline 707-320Bs purchased and modified as
test aircraft, both for airborne range instrumentation duties
and the JSTARS (joint surveillance target attack radar) program.
The former, as EC-18Bs, feature a bulbous nose radome, while the
latter carry an elongated under-fuselage radome for a multimode
side-looking radar.
The E-6A had its beginnings in studies at the Naval Air Development
Center, Warminster, Pa., looking for an expanded capability airframe
for the TACAMO role. Among several turbofan-powered jet transports,
the basic Boeing 707-320B was particularly attractive because
of the availability of the hardened E-3A airframe in production.
Higher bypass ratio, more fuel efficient GE-SNECMA CFM 56 engines
were being retrofitted to various first-generation, four-jet commercial
transports and would enhance the performance of a TACAMO version.
Space and weight-carrying capability would accommodate the various
communications systems of the EC-130 TACAMO aircraft, including
the long trailing very low frequency antenna and its extension/retraction
system.
Based on the study results, the TACAMO replacement program
got under way; the first two of a planned buy of 16 were ordered
in 1984. Unusual was the concept that major components of the
communications systems in squadron EC-130s would be removed and
reinstalled in the E-6As as they were completed. Many features
of the E-3 airframe were retained, including the in-flight refueling
receptacle for the flying boom refueling system located at the
top of the fuselage aft of the cockpit. A forward cargo door,
as on commercial air freight transports, was installed for purposes
of transporting major spare components to remote sites.
Provisions for the two trailing wire antennas, one extending
from under the mid-fuselage and the other from the tail cone,
are among the obvious changes. Enlarged wing tip pods for special
electronic equipment are also fitted. Not obvious are the structural
changes required to carry the heavy communications systems in
the aft fuselage and the increased level of electromagnetic pulse
and nuclear blast hardening over that already incorporated in
the E-3s.
The first E-6A rolled out in December 1986 and made its first
flight in February 1987. After initial flights at Seattle, Wash.,
it was ferried to the Naval Air Test Center, Patuxent River, Md.,
for further systems development testing. Crew training using contractor-owned
commercial 707-320s began for squadron personnel with no standdown
required for squadron transition - a necessity to maintain the
strategic communications links. Operational test and evaluation
was undertaken by VX-1. Initial deliveries to VQ-3 took place
in August 1989.
The new flight profiles and structural characteristics that
the E-6A introduced to the 707-320 airframe did result in some
unanticipated development challenges. Their resolution will provide
the necessary survivable strategic command link to the submarine-launched
leg of the strategic nuclear triad well into the future. Besides
the command link to the ballistic missile submarines, the E-6A
TACAMO aircraft is involved in a joint mission, to provide the
vital communication link from the National Command Authority (NCA)
to all strategic forces. By 1998, after completion of extensive
modifications, it will also provide an Airborne Command Post for
United States Command in Chief for Strategic Forces (USINCSTRAT)
and theater CINCs.
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15 November 2000
