Gulfstream IV

==Design==
[[File:VH-MBP Gulfstream Aerospace G-IV-X Gulfstream G450 (6486143227).jpg|thumb|G450 updated flight deck]]

Compared to 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.<ref>Chandrasekharan, R.M., Murphy, W.R., Taverna, F.P. and Boppe, C.W., "Computational Aerodynamic of the Gulfstream IV Wing", AIAA paper 85-0427, presented at the AIAA 23rd Aerospace Sciences Meeting, Reno Nevada, January 1985.</ref>

At 12,420 lbs, the [[Rolls-Royce RB.183 Tay|Rolls-Royce Tay]] fanjet engines provided more thrust than the 11,400&nbsp;lbs of the Gulfstream III. Speed, noise levels, emissions, fuel economy, range, and cargo capacity were also markedly improved over the earlier model.<ref name=WAW220336>{{cite journal | journal = [[Ward's|Ward's Auto World]] | volume = 22 | number = 3 | publisher = Ward's Communications | date = March 1986 | page = 36 | title = Everybody takes a number | first = David C. | last = Smith }}</ref>

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.<ref>Boppe, Charles W., "Computational Aerodynamic Design: X-29, the Gulfstream Series and a Tactical Fighter", SAE paper 851789, 1985 Wright Brothers Award Paper, presented at the Aerospace Technology Conference & Exposition, Long Beach California, October 1985.</ref>
In addition to the wing redesign, the Gulfstream IV also became the first business jet to have an entire glass cockpit.<ref name=thomas>{{cite web |publisher= stratos jet charters| first = Joel | last = Thomas |title= History of the Gulfstream Aerospace Corporation |url= https://www.stratosjets.com/history-of-gulfstream-aerospace-corporation/ |date= 19 May 2014}}</ref>

The G400 has a large cabin, long range of 4,350 nautical miles (8,060&nbsp;km) and the same comfort and design that characterize the G series. Maximum cruise height and speed are 45,000&nbsp;ft and [[Mach number|Mach]] 0.85. Earlier models were fitted with Honeywell's SPZ 8000 Avionics package. The SPZ 8400 Avionics Package was an option, becoming standard on later models. Its second-hand price was below $15 million (~${{Format price|{{Inflation|index=US-GDP|value=15000000|start_year=2009}}}} in {{Inflation/year|US-GDP}}) in 2009.<ref name="flagship"/> Gulfstream had also considered making a {{cvt|5.5|m|ft|0}} longer, 24-27 seat model for airline use.<ref name=WAW220336/>