The Boeing E-4 Advanced Airborne Command Post (AACP), the current “Nightwatch” aircraft, is a strategic command and control military aircraft operated by the United States Air Force (USAF). The E-4 series are specially modified from the Boeing 747-200B for the National Emergency Airborne Command Post (NEACP) program. The E-4 serves as a survivable mobile command post for the National Command Authority, namely the President of the United States, the Secretary of Defense, and successors. The four E-4Bs are operated by the 1st Airborne Command and Control Squadron of the 595th Command and Control Group located at Offutt Air Force Base, near Omaha, Nebraska. An E-4B when in action is denoted a “National Airborne Operations Center”.
Nicknamed the “Doomsday plane” due to its ability to withstand a nuclear blast, the iconic blue and white E-4B serves two purposes: to provide a secure and survivable command center in the event of a nuclear war and to transport defense secretaries around the world.
Two of the original 747-200 airframes were originally planned to be commercial airliners. When the airline did not complete the order, Boeing offered the airframes to the United States Air Force as part of a package leading to a replacement for the older EC-135J National Emergency Airborne Command Post (NEACP). Under the 481B NEACP program the Air Force Electronic Systems Division awarded Boeing a contract in February 1973 for two unequipped aircraft, designated E-4A, powered by four P&W JT9D engines, to which a third aircraft was added in July 1973. The first E-4A was completed at the Boeing plant outside Seattle, Washington in 1973. E-Systems won the contract to install interim equipment in these three aircraft, and the first completed E-4A was delivered in July 1973 to Andrews Air Force Base, Maryland. The next two were delivered in October 1973 and October 1974. The third E-4 differed by being powered by the GE F103 engine, which was later made standard and retrofitted to the previous two aircraft. The A-model effectively housed the same equipment as the EC-135, but offered more space and an ability to remain aloft longer than an EC-135.
In November 1973, it was reported that the program cost was estimated to total $548 million for seven 747s, six as operational command posts and one for research and development. In December 1973, a fourth aircraft was ordered; it was fitted with more advanced equipment, resulting in the designation E-4B. On 21 December 1979, Boeing delivered the first E-4B (AF Serial Number 75-0125), which was distinguished from the earlier version by the presence of a large streamlined radome on the dorsal surface directly behind the upper deck. This contains the aircraft’s SHF satellite antenna.
By January 1985 all three E-4As had been retrofitted to E-4B models. The E-4B offered a vast increase in communications capability over the previous model and was considered to be ‘hardened’ against the effects of nuclear electromagnetic pulse (EMP) from a nuclear blast. Hardening the aircraft meant that all equipment and wiring on board was shielded from EMP.
The E-4B fleet has an estimated roll-out cost of approximately US$250 million each. In 2005 the Air Force awarded Boeing a five-year, US$2 billion contract for the continued upgrade of the E-4B fleet. In addition to the purchase and upgrade costs, the E-4 costs nearly $160,000 per hour for the Air Force to operate.
The E-4B is designed to survive an EMP with systems intact and has state-of-the-art direct fire countermeasures. Although many older aircraft have been upgraded with glass cockpits, the E-4B still uses traditional analog flight instruments, as they are less susceptible to damage from an EMP blast.
The E-4B is capable of operating with a crew up to 112 people including flight and mission personnel, the largest crew of any aircraft in US Air Force history. With in-flight aerial refueling it is capable of remaining airborne for a considerable period, limited only by consumption of the engines’ lubricants. In a test flight for endurance, the aircraft remained airborne and fully operational for 35.4 hours, however it was designed to remain airborne for a full week in the event of an emergency. It takes two fully loaded KC-135 tankers to fully refuel an E-4B. The E-4B has three operational decks: upper, middle, and lower.
Middle and upper decks
The flight deck contains stations for the pilot, co-pilot, and flight engineer, plus a special navigation station not normally found on commercial Boeing 747s. A lounge area and sleeping quarters for flight and maintenance crews are located aft of the flight deck. The flight crew consists of an aircraft commander, co-pilot, navigator, and flight engineer.
The middle deck contains the conference room, which provides a secure area for conferences and briefings. It contains a conference table for nine people. Aft of the conference room is a projection room serving the conference room and the briefing room. The projection room had the capability of projecting computer graphics, overhead transparencies, or 35 mm slides to either the conference room or the briefing room either singularly or simultaneously. The projection screens have since been replaced with flat screen displays.
The battle staff includes various controllers, planners, launch system officers, communications operators, a weather officer, administrative and support personnel, and a chief of battle staff. The Operation Looking Glass missions were commanded by a general officer with two staff officers, while the National Airborne Operations Center (NAOC) may rendezvous and embark a member of the National Command Authority (NCA) from an undisclosed location. There are at least 48 crew aboard any E-4B mission.
Behind the projection room is the operations team area containing the automatic data processing equipment and seats and console work areas for 29 staff members. The consoles are configured to provide access to or from the automated data processing, automatic switchboard, direct access telephone and radio circuits, direct (“hot”) lines, monitor panel for switchboard lines, staff, and operator inter-phone and audio recorder.
The aft compartment at the end of the main deck is the Technical Control (Tech Control) area. This area was the nerve center for all communications and communications technicians. Typically 3 of the 6 crew positions were occupied here by specialized US Air Force technicians that were responsible for the proper monitoring and distribution of all communications power, cooling, and reliability. The Technical Controller No. 1 (Tech 1, TC1) was the direct interface with the aircraft Flight Engineer and Flight Crew. This position was also the main focal point for all communications related issues. The Technical Controller No. 2 (Tech 2, TC2) was responsible for maintaining all ultra high frequency communications between the aircraft and the Nightwatch GEP (Ground Entry Points). These GEP’s provided 12 voice lines to the aircraft which were used in the day-to-day operations of the mission. Secure Voice was also provided. The SHF Operator (or technician) maintained the SHF satellite link and provided other worldwide communications services probably having replaced a lot of the UHF capabilities.
The rest area, which occupies the remaining portion of the aft main deck, provides a rest and sleeping area for the crew members. The rest area contains storage for food and is also used for religious ceremonies.
Within the forward entry area is the main galley unit and stairways to the flight deck and to the forward lower equipment area. This area contains refrigerators, freezers, two convection ovens, and a microwave oven to give stewards the capability to provide more than 100 hot meals during prolonged missions. Additionally, four seats are located on the left side of the forward entry area for the security guards and the stewards.
Behind the forward entry area is the National Command Authority (NCA) area, which is designed and furnished as an executive suite. It contains an office, a lounge, a sleeping area, and a dressing room. Telephone instruments in this area provide the NCA with secure and clear worldwide communications.
The briefing room contains a briefing table with three executive seats, eighteen additional seats, a lectern, and two 80-inch flat screen LED monitors flush mounted to the partition.
The communications control area is divided into a voice area and a data area. The voice area, located on the right side of the compartment, contains the radio operator’s console, the semi-automatic switchboard console, and the communication officer’s console. The data area, located on the left side of the area, contains the record communications console, record data supervisor’s console, high speed DATA/AUTODIN/AFSAT console, and LF/VLF control heads. The E-4B can communicate with the ground over a wide range of frequencies covering virtually the entire radio communications spectrum from 14 kHz to 8.4 GHz. Ground stations can link the E-4B into the main US ground-based communications network.
The flight avionics area contains the aircraft systems power panels, flight avionics equipment, liquid oxygen converters, and storage for baggage and spare parts.
The forward lower equipment room contains the aircraft’s water supply tanks, 1200 kVA electrical power panels, step down transformers, VLF transmitter, and SHF SATCOM equipment. An AC/DC powered hydraulic retractable airstair is located in the forward right side of the forward lower equipment area, installed for airplane entry and exit. In the event of an emergency, the air stair can be jettisoned. The aft lower lobe contains the maintenance console and mission specific equipment.
The lower trailing wire antenna (TWA) area contains the aircraft’s 5-mile-long (8.0 km) TWA reel – which is used by up to 13 communications links – the antenna operator’s station, as well as the antenna reel controls and indicators. Much attention has been given to hardening this area against EMP, especially as the TWA, essential for communicating with Ohio-class ballistic missile submarines, is also particularly effective in picking up EMP.
- E-4A: Three aircraft produced (s/n 73–1676, 73–1677, and 74-0787), powered by Pratt & Whitney JT9D-7R4G2 engines. No bulge to house equipment on top of fuselage. These were later converted to E-4Bs.
- E-4B: One built (s/n 75-0125) and equipped with 52,500-lb CF6-50E2 engines. Has nuclear electromagnetic pulse protection, nuclear and thermal effects shielding, advanced electronics, and a wide variety of communications equipment.
|Capacity||up to 108 mission crew|
|Length||231 ft 4 in (70.51 m)|
|Wingspan||195 ft 8 in (59.64 m)|
|Heigh||63 ft 5 in (19.33 m)|
|Wing area||5,500 sq ft (510 m2)|
|Empty weight||410,000 lb (185,973 kg)|
|Gross weight||800,000 lb (362,874 kg)|
|Max take off weight||833,000 lb (377,842 kg)|
|Power plant (Dry thrust)||4 × General Electric F103 turbofan engines, 52,500 lbf (234 kN) thrust each|
|Power plant (Thrust with afterburner)|
|Maximum speed (Sea level)|
|Maximum speed (High altitude)||523 kn (602 mph, 969 km/h)|
|Ferry range||6,200 nmi (7,100 mi, 11,500 km)|
|Service ceiling||45,000 ft (14,000 m)|
|Rate of climb|
|Wing loading||150 lb/sq ft (730 kg/m2)|
|Design load factor|
- United States Air Force – 4 E-4B.