Northrop Tacit Blue

{{Short description|Experimental 1980s USAF aircraft}}  {{Infobox aircraft |name = Tacit Blue |image = File:Tacit Blue in flight.jpg |image_caption = Northrop Tacit Blue in flight |alt = Northrop Tacit Blue in flight |type = Stealth demonstrator |manufacturer = Northrop Corporation |designer = |first_flight = February 5, 1982 |introduction = |retired = 1985 |produced = |number_built = 1 |status = Retired |unit cost = |primary_user = United States Air Force |more_users = |developed_from = |variants = }}

The '''Northrop Tacit Blue''' is a technology demonstrator aircraft created to demonstrate that a low-observable stealth surveillance aircraft with a low-probability-of-intercept radar (LPIR) and other sensors could operate close to the forward line of battle with a high degree of survivability.

==Development== Unveiled by the U.S. Air Force on 30 April 1996, the ''Tacit Blue Technology Demonstration Program'' was designed to prove that such an aircraft could continuously monitor the ground situation deep behind the battlefield and provide targeting information in real time to a ground command center.

[[File:Pave Mover Antenna Array, view 1, prototype for J-STARS antenna, Norden, 1981-1983 - National Electronics Museum - DSC00429.JPG|thumb|left|Pave Mover radar antenna]]

In December 1976, DARPA and the U.S. Air Force initiated the '''Battlefield Surveillance Aircraft-Experimental (BSAX)''' program, which was part of a larger Air Force program called Pave Mover. The BSAX program's goal was to develop an efficient stealth reconnaissance aircraft with a low probability of intercept radar and other sensors that could operate close to the forward line of battle with a high degree of survivability.

Tacit Blue represented the "black" component in the larger "Assault Breaker" program, which intended to validate the concept of massed standoff attacks on advancing armored formations using smart munitions. The Pave Mover radar demonstrators provided the non-stealth portion of the program's targeting system, whereas Tacit Blue was intended to demonstrate a similar but stealth capability, while validating a number of innovative stealth technology advances.<ref>[http://www.ausairpower.net/TE-Assault-Breaker.html Assault Breaker Program Analysis].</ref>

The radar sensor technology developed for Tacit Blue evolved into the radar that was used by the E-8 Joint STARS aircraft.<ref >{{Cite journal |title=Out of the black comes Tacit Blue |author=Ramon Lopez |date=8 May 1996 |journal=Flight Global |url=https://www.flightglobal.com/news/articles/out-of-the-black-comes-tacit-blue-17057/}}</ref>

Tacit Blue was given the cover designation of "YF-117D" by the Air Force.<ref>{{cite book |last1=von Ehrenfried |first1=Manfred "Ductch" |title=Stratonauts: Pioneers Venturing into the Stratosphere |date=2013 |publisher=Springer |location=New York |isbn=978-3319029009 |pages=204 |url=https://books.google.com/books?id=r3W8BAAAQBAJ&q=%22YF-117D%22&pg=PA204}}</ref><ref>{{Cite web |title=Cover Designations for Classified USAF Aircraft |url=https://www.designation-systems.net/usmilav/coverdesignations.html |access-date=2024-04-22 |website=www.designation-systems.net}}</ref>

==Design== thumb|alt=Northrop Tacit Blue Whale|Northrop's B-2 chief engineer John Cashen<ref name="LATimes1993" >{{cite web |last1= Vartabedian |first1=Ralph |title=Job Stress Catches Up With 'Dr. Stealth' of Aerospace : Science: Eccentric genius John Cashen's departure for Australia has many questioning the technology's future |url=https://www.latimes.com/archives/la-xpm-1993-02-26-mn-622-story.html |publisher=L A Times |access-date=28 August 2018 |date=26 February 1993}}</ref> was quoted in 1996 as having said, "You're talking about an aircraft that at the time was arguably the most unstable aircraft man had ever flown."<ref >{{cite web |title=Tacit Blue |url=http://www.news.com/2300-11397_3-6219637-16.html?tag=ne.gall.pg |archive-url=https://archive.today/20120907082056/http://www.news.com/2300-11397_3-6219637-16.html?tag=ne.gall.pg |url-status=dead |archive-date=September 7, 2012 |series=Photos: A brief history of stealth aircraft |work=CNet News |access-date=2 May 2012 |date=November 23, 2007}}</ref><ref name=AFMag/>

Tacit Blue, nicknamed "the whale" (and sometimes also called an "alien school bus" for its only slightly rounded-off rectangular shape),<ref>{{cite news |url=http://foxtrotalpha.jalopnik.com/lockheeds-senior-peg-the-forgotten-stealth-bomber-1534057907 |title=Lockheed's Senior Peg: The Forgotten Stealth Bomber |first=Tyler |last=Rogoway |date=March 1, 2014 |work=Jalopnik}}</ref> featured a straight tapered wing with a V-tail mounted on an oversized fuselage with a curved shape. It was the first stealth aircraft to feature curved surfaces for radar cross-section reduction.<ref >{{Cite book |title=Area 51 |first=Peter W. |last=Merlin |year=2011 |publisher=Arcadia Publishing |isbn=978-0738576206 |page=119 |url=https://books.google.com/books?id=TLPsUdb_Me8C&pg=PA119 }}</ref> Northrop would use this stealth technology on the B-2 bomber. A single flush inlet on the top of the fuselage provided air to two medium-bypass turbofan engines. Tacit Blue employed a quadruply redundant digital fly-by-wire flight control system to help stabilize the aircraft about its longitudinal and directional axes.

==Operational history== thumb|Northrop Tacit Blue cockpit

The aircraft made its first successful flight on February 5, 1982, in Area 51, at Groom Lake, Nevada, flown by Northrop test pilot Richard G. Thomas.<ref name=AFMag>{{cite web |last1=Grier |first1=Peter |title=The (Tacit) Blue Whale |url=http://www.airforcemag.com/MagazineArchive/Pages/1996/August%201996/0896tacit.aspx/ |publisher=Air Force Magazine |access-date=25 August 2018 |date=August 1996}}</ref> The aircraft subsequently logged 135 flights over a three-year period. The aircraft often flew three to four flights weekly and several times flew more than once a day.

Another Tacit Blue test pilot, Ken Dyson, told CNN in 2014 that Northrop had manufactured additional major components for the jet, which amounted to half of a second plane. "If we lost one, we could have a second one up and flying in short order," Dyson said.<ref name=CNN>{{cite web |last1=Patterson |first1=Thom |title=Area 51 Spy Plane and Other Aviation Tales |url=https://www.cnn.com/travel/article/air-force-museum-spy-plane/index.html|publisher=CNN |access-date=25 June 2020 |date=February 2014}}</ref>

After reaching about 250 flight hours, the aircraft was placed in storage in 1985. In 1996, after Tacit Blue was declassified, it was placed on display at the National Museum of the United States Air Force at Wright-Patterson Air Force Base, near Dayton, Ohio and has been on display in the fourth hangar at the museum since June 2016.<ref name=factSheet>[https://web.archive.org/web/20141213195801/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=353 National Museum of the USAF Fact Sheet]</ref>

==Specifications== Data from the [https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195769/northrop-tacit-blue/ National Museum of the United States Air Force] and the [https://www.war.gov/Multimedia/Photos/igphoto/2001236821/ Department of Defense]

{{Aircraft specs |prime units?=kts  |crew=1 |length ft=55 |length in=10 |length note= |span ft=48 |span in=2 |span note= |upper span ft= |upper span in= |upper span note= |height ft=10 |height in=7 |height note= |wing area sqft= |wing area note= |aspect ratio= |airfoil=Clark Y mod.<ref name="Selig">{{cite web |last1=Lednicer |first1=David |title=The Incomplete Guide to Airfoil Usage |url=https://m-selig.ae.illinois.edu/ads/aircraft.html |website=m-selig.ae.illinois.edu |access-date=16 April 2019}}</ref> |empty weight lb= |empty weight note= |gross weight lb=30000 |gross weight note= |max takeoff weight lb= |max takeoff weight note= |fuel capacity= |more general=  |eng1 number=2 |eng1 name=Garrett ATF3-6 |eng1 type=turbofan engines |eng1 lbf=5440 |eng1 note=  |max speed kts=250 |max speed note= |cruise speed kts= |cruise speed note= |stall speed kts= |stall speed note= |never exceed speed kts= |never exceed speed note= |minimum control speed kts= |minimum control speed note= |range nmi= |range note= |combat range nmi= |combat range note= |ferry range nmi= |ferry range note= |endurance= |ceiling ft=25000-30000 |ceiling note=operating altitude |g limits= |roll rate= |climb rate ftmin= |climb rate note= |time to altitude= |lift to drag= |wing loading lb/sqft= |wing loading note= |fuel consumption lb/mi= |power/mass= |thrust/weight=0.36

|more performance= |avionics= }}

==See also== {{aircontent |related= |similar aircraft= *Lockheed Have Blue |lists= * List of experimental aircraft * List of military aircraft of the United States * List of stealth aircraft

|see also= }}

==References== {{reflist}}

==External links== {{commons category|Northrop Tacit Blue}} * [https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195769/northrop-tacit-blue/ Tacit Blue at National Museum of USAF] * [http://news.northropgrumman.com/news/features/tacit-blue%3A-the-creation-of-stealth Tacit Blue: The Creation of Stealth]

Category:Stealth aircraft Category:1980s United States experimental aircraft Category:Code names Tacit Blue Category:V-tail aircraft Category:Low-wing aircraft Category:Twinjets Category:Area 51