C-20 Gulfstream IV

Gulfstream IV / G400 C-20F/G/H/J GIV-SP / G350 / G450
A Gulfstream IV of the Royal Netherlands Air Force
Role	Business jet
Manufacturer	Gulfstream Aerospace
Status	Active service
Primary users	United States Air Force United States Army United States Navy National Oceanic and Atmospheric Administration
Produced	1985-present
Number built	870
Unit cost	GIV: US$36 million (1996) G350: US$34.9 million (2012) G450: US$41 million (2015)
Developed from	Gulfstream III
Variants	Gulfstream V Gulfstream G350/G450

The Gulfstream IV (or G-IV or GIV) and derivatives are a family of twinjet aircraft, mainly for private or business use. The aircraft was designed and built by Gulfstream Aerospace, a General Dynamics company based in Savannah, Georgia, United States from 1985 until 2003. Power is two Rolls-Royce RB.183 Tay turbofans. In October 2016, Gulfstream announced it will end production of the G450 and deliver the last in early 2018, as the G500 is starting to be delivered. 870 GIV/GIV-SP/G450 have been produced.

Gulfstream, in collaboration with Grumman, began work on the Gulfstream IV in March 1983 as a re-engined, stretched fuselage derivative of the Gulfstream III. A decision to redesign the wing structure for weight reduction presented an opportunity for an aerodynamic redesign of the wing to reduce cruise drag and increase range. Wing contour modifications had to be restricted to the forward 65% of wing chord so that no redesign of the control surfaces would be necessary. Modification of the inboard wing would have entailed a redesign of the fuselage floor structure, consequently this region of the wing was not modified. Outboard wing modifications were aimed at reducing the peak subcritical pressure coefficient and moving it aft in an effort to reduce shock strength and increase shock sweep. The Gulfstream IV wing has a weaker, more swept outboard shock resulting in a lower cruise drag. Other benefits arising from this design are a lower root bending moment due to the more inboard center of pressure, a lower stall speed due to washout and a larger fuel volume due to increased chord. These aerodynamic improvements result in an increase in range of over 300 nautical miles.

In addition to the innovative wing design, the Gulfstream IV also became the first business jet to have an entire glass cockpit. The first GIV made its maiden flight on September 19, 1985. The model received type certification from the FAA on April 22, 1987. The G-IV entered into service with serial number 1000 in 1987 and was upgraded to the special purpose GIV-SP version at serial number 1214 in 1993. It was later redesignated G400 at serial number 1500.