# Boeing E-6 Mercury

The Boeing E-6 Mercury (formerly Hermes) is an airborne command post and communications relay based on the Boeing 707-300. The original E-6A manufactured by Boeing's defense division entered service with the United States Navy in July 1989, replacing the EC-130Q. This platform, now modified to the E-6B standard, conveys instructions from the National Command Authority to fleet ballistic missile submarines (see communication with submarines), a mission known as TACAMO ("Take Charge And Move Out").
The E-6B model deployed in October 1998 has the ability to remotely control Minuteman ICBMs using the Airborne Launch Control System. The E-6B replaced Air Force EC-135Cs in the Looking Glass role, providing command and control of U.S. nuclear forces should ground-based control become inoperable. With production lasting until 1991, the E-6 was the final new derivative of the Boeing 707 to be built.

## Design and development

Like the E-3 Sentry Airborne Warning and Control System aircraft, the E-6 is adapted from Boeing's 707-320 airliner. Rolled out at Boeing's Renton Factory in December 1986, the first E-6 made its maiden flight in February 1987, when it was flown to nearby Boeing Field in south Seattle for fitting of mission avionics. It was delivered to the Navy for testing in July 1988.
The E-6B is an upgrade of the E-6A. It includes a battlestaff area and updated mission equipment. The flight deck systems were later replaced with an off-the-shelf 737 Next Generation cockpit. This greatly increases the situational awareness of the pilot and saves significant cost over the previous custom avionics package. The first E-6B was accepted in December 1997. All 16 E-6A aircraft were modified to the E-6B standard, with the final delivery taking place in December 2006.
The E-6 cannot use the probe-and-drogue in-flight refueling method that most other US Navy aircraft use. It uses a flying boom receptacle on the upper-forward fuselage, making it, like the Navy's Boeing P-8 Poseidon aircraft, reliant upon specific U.S. Air Force aircraft (KC-135 Stratotanker, KC-10 Extender, and KC-46 Pegasus) for in-flight refueling.

## Operational history

Codenamed Looking Glass, the E-6 is United States Strategic Command's (USSTRATCOM) Airborne Command Post (ABNCP). It is designed to take over in case the Global Operations Center (GOC), located at Offutt Air Force Base, Nebraska, is destroyed or incapable of communicating with strategic forces. The term "Looking Glass" is used because the ABNCP "mirrors" the abilities of the US Strategic Command GOC to control nuclear forces.
The E-6A, which was initially named Hermes, entered service with squadron VQ-3 in August 1989. A second squadron, VQ-4, received its first E-6As in January 1991, allowing the EC-130Q to be phased out in June 1991. The E-6A was renamed Mercury in autumn 1991 by request of the Navy. Sixteen E-6A planes were delivered from 1988 to 1992.
The E-6 fleet is based at Tinker Air Force Base, Oklahoma, and operated by Fleet Air Reconnaissance Squadron 3 (VQ-3), VQ-4, and VQ-7.
In 2021, one of the E-3D Sentry aircraft that had been in service with the Royal Air Force was purchased for conversion into a dedicated E-6 trainer. This was done as a means to extend the life of the operational fleet by reducing the need for E-6s to be used for training missions.

### Replacement

In 2015, both the Air Force and Navy realized that they needed new aircraft to serve the missions of both the E-4 and the E-6. At one point, they considered building one plane to replace both aircraft, but by 2020, the Navy decided to go its own way and develop an aircraft specifically for the TACAMO mission, under the E-XX TACAMO program. The Air Force independently pursued an E-4 replacement under the Survivable Airborne Operations Center program.
The Navy selected a variant of the Lockheed EC-130J, specifically one derived from the lengthened C-130J-30. Initial orders were placed in late 2020 with development beginning in earnest in 2022. Delivery of the first aircraft is expected in FY26. The Navy expects the E-6 to fulfill the TACAMO role into the 2030s as the E-XX is transitioned into service.
In October 2024, the replacement aircraft was officially named E-130J.

## Specifications (E-6B)

Data from Jane's all the world's aircraft, 1992–93 The US Navy – Fact File: E-6B Mercury Airborne Command Post
General characteristics
* Crew: 22
* Length: 150 ft 4 in (45.82 m)
* Wingspan: 148 ft 4 in (45.21 m)
* Height: 42 ft 5 in (12.93 m)
* Wing area: 283.4 sq ft (26.33 m$^2$)
* Empty weight: 172,795 lb (78,378 kg)
* Max takeoff weight: 342,000 lb (155,129 kg)
* Powerplant: 4 × CFM International CFM56-2A-2 turbofan engines
Performance
* Maximum speed: 522 kn (601 mph, 967 km/h) dash speed
* Cruise speed: 455 kn (524 mph, 843 km/h) at 40,000 ft (12,192 m)
* Range: 6,600 nmi (7,600 mi, 12,200 km)
* Combat range: 6,350 nmi (7,310 mi, 11,760 km)
* Endurance: on station at 1,000 nmi (1,200 mi; 1,900 km)
** 10 hours 30 minutes unrefueled
** 28 hours 54 minutes with one refueling
** 72 hours maximum with multiple refuelings
* Service ceiling: 40,000 ft (12,000 m)
* Wing loading: 112.13 lb/sq ft (547.5 kg/m$^2$)
* Thrust/weight: 0.281
* Critical field length: 6,700 ft (2,042 m)
* Max effort take-off run: 5,400 ft (1,646 m)
* Landing run at max landing weight: 2,600 ft (792 m)
Avionics
* AN/ARC-182 VHF/UHF TxRx
* AN/ARC-190 HF
* AN/AIC-32 Crew Intercom
* triplex Litton LTN-90
* LTN-211 VLF/Omega
* Smiths SFM 02 digital/analog flight management system
* AN/APS-133 colour weather radar