Retirement

The Nighthawk proved too costly for the US Air Force to maintain and carry out sorties with rising fuel costs and budget cuts. In early 2007, the US Air Force decided to retire the aircraft. Don Logan of Lockheed F-117 Nighthawks: A Stealth Fighter Roll Call tells us that instead of scrapping the airframes or donating the aircraft to aviation museums, the entire  Nighthawk fleet was returned to the climate controlled hanger where they were developed at the Tonopah Test Range. At Tonopah, the F-117's wings were removed for ease of storage. The first four prototype YF-117A aircraft were sent to museums to be on display.

In Action

The F-117, "being a coalitions workhorse, logged nearly 1,300 combat sorties while flying 6,905 combat flying hours". During their missions, F-117A pilots delivered over 2,000 tons of precision-guided ordnance with a hit rate of better than 80 percent. The success is attributed to the element of surprise made relevant again by the use of stealth. During the Gulf War, Iraq was left virtually defenseless against American attacks. Cruise missiles by day and Nighthawk bombing runs by night made continuous blows on the Iraqi air defense systems, cities, and oil refineries. No other aircraft in the US arsenal was this effective in it's rate of success at the time.

Innovations

Perhaps the most interesting piece of technology on the Nighthawk that paved the way for its use in future military and commercial aircraft were the composite dual vertical tail fins. Made of a thermoplastic graphite material, Maloney says this was the first use of a composite for a primary aircraft structure. As mentioned, this enabled the Nighthawk to have a lighter tail section which assisted in moving the aircraft's center of gravity forward, always preferred due to better maneuverability. Composite materials were found to further decrease the Nighthawk's radar signature over traditional metals used in prior aircraft, likely due to the nature of heat conduction with air friction being lower in comparison to metal. All of the aircraft's antennae were retractable, and the mid air refueling inlet which allowed the nighthawk to receive fuel without landing (thus increasing its range)  had a door that slides over it to reduce exposure to radio waves. The engine intake was covered with a composite grid panel that provided sufficient airflow while maintaining stealth.
 

 

 

Materials and Technologies

The skin of the aircraft was covered in Radar Absorbing Material, or RAM, which was a material designed to absorb any excess radar waves that had been developed alongside the Nighthawk for the F-117 specifically. This material that was composed of ferrite and polymer was applied in tiles on the skin of the aircraft, on the cockpit windows in the form of film, as well as the engine inlet covers. The exhaust stream was directed upward and spread along the exhaust duct in an attempt to reduce the aircraft's infrared heat signature, which could just as easily give the Nighthawk's position away to the enemy.
 

Design

The aircraft fuselage had a prismatic shape which reduced its radar cross section by a large margin. No other plane before the Nighthawk ever employed such a design and as such, aerodynamic disadvantages became apparent. The design had to compromise some maneuverability and controllability in order to reduce its radar detection. The result of the Nighthawk design provided a radar cross section similar to the size of a bird.

The aircraft benefitted from two General Electric F-404 turbofan engines with no fuel afterburners. In contrast to the afterburning turbojet engines used on fighters during this time, the Nighthawk employed turbofan engines to reduce noise and heat signature, increase thrust at lower speeds, and eliminate the hot, loud, fuel consuming afterburner systems. Even though the Nighthawk was designated F-117, with the F signifying a fighter role, Maloney says it's design focused on surprise ground attack missions rather than mid air dogfights against other aircraft. The Nighthawk also employed a variety of smaller technologies in addition to the design of the aircraft to further reduce its radar cross section.
 

Purpose

The HAVE Blue project was top secret, and stealth technology "did not officially exist" to the general public. The entire project was to remain in complete secrecy, and no information about it was allowed to be shared outside of the members in the development team in hopes of keeping the technology secret from the Soviet Union and other enemies. On November 1st, 1975, Lockheed was awarded a US 1.5 million dollar contract by DARPA to develop an aircraft that used the low radar cross section design, and would be called the Experimental Survival Test bed, or XST. Skunk Works got started right away on the project using the flat panel design as the concept behind the development. With the entire project developed under complete secrecy, the general public does not know exactly when the Nighthawk was first put into active service.

Origins

Crickmore tells us that the "HAVE Blue" project was born in the mid 1970's when the Defense Advanced Research Projects Agency, or more commonly referred to as  DARPA, started to seek a manufacture for a new fighter aircraft that employed stealth technology. Lockheed wasn't even on DARPA's radar, because Lockheed was entering a period of financial turmoil due to their failed attempts at re-entering the commercial aviation market with their L-1011 Tri-Star.

Skunk Works, a division of Lockheed that specializes in advanced projects, was given permission by the US Central Intelligence Agency to talk with DARPA on the topic of stealth development, because of their upcoming A-12 and D-21 aircraft that would benefit greatly from the technology. Lockheed could be involved in the project but with no government financial aid.