The Gulfstream II (G-II) is an American twin engine business jet designed and built by Grumman and then in succession, Grumman American and finally Gulfstream American. Its Grumman model number is G-1159 and its US military designation is C-11 Gulfstream II. It has been succeeded by the Gulfstream III. The first Gulfstream II flew on October 2, 1966.

The Gulfstream II is a twin-jet swept wing corporate transport designed to provide high speed and long range capability without sacrificing the airport performance, reliability, and other operational advantages of its predecessor, the turboprop Gulfstream I. Preliminary design of the wing was influenced by both cruise and low speed considerations. The aft-mounted engine location was selected after extensive analysis and design iterations considering aerodynamic, structural, and ground clearance requirements. Airfoil geometry was developed to maximum sweep benefit from the selected planform. The interference problem at the wing-body juncture was treated by modification of the airfoil shape and thickness over the inner third of the wing span. The basic airfoils for the main area of the wing are similar to those of the Grumman A-6 Intruder aircraft and utilize NASA 6-series thickness distributions combined with an in-house mean line. A buffet boundary commensurate with the M=.85 speed capability was attained by incorporating a row of co-rotating vortex generators on the outer wing panel. In developing the wing contours, attention was paid to the aircraft's low speed requirements by tailoring the leading edge radius to preclude leading edge separation. The high lift configuration, consists of a one piece, single-slotted Fowler flap of 30% chord. Stall initiation on the basic wing was found to occur at midspan but spread rapidly to the tip, particularly at large flap deflections. The addition of an upper surface fence at about midspan provided a strong pitch down at the stall, without sacrificing maximum lift, and also afforded an adequate margin between initial and tip stall.

The high angle of attack investigations on the Gulfstream II indicated that stable trim conditions existed up to 45 degrees angle of attack. The elevator deflection required to trim to the primary stall at most forward center of gravity was sufficient to trim a deep stall at the aft center of gravity, but recovery from deep stall was immediate upon forward stick motion, and more than adequate nose-down elevator control was available. The acceptability of the Gulfstream II high angle of attack characteristics and the absence of a deep stall influence on configuration sizing and arrangement was attributed to the mitigating influence of the nacelle-wing overlap on nacelle contribution. Configuration buildup studies revealed the adverse nacelle influence on tail pitching moment contribution above 30 degrees angle of attack was not unduly severe and no appreciable effect on elevator or stabilizer effectiveness was found.

It was found in flight testing that the stall characteristics were satisfactory but did not preclude stall penetrations to the point of secondary stall pitchup. Rather than pursue a lengthy flight test research effort, and in view of the excellent primary stall behavior, it was decided to mechanically limit the extent of stall penetration with a stick shaker and stick pusher.

During installation of the Aviation Partners Inc. winglets (as the G-IISP), the vortex generators and midspan fence were removed and replaced with six leading edge vortilons similar to those found on the Gulfstream IV.

Variants

Gulfstream II

Twin-engined executive, corporate transport aircraft, with accommodation for up to 14 passengers, powered by two Rolls-Royce Spey RB.168 Mk 511-8 turbofan engines.  Received FAA Type Certificate A12EA on October 19, 1967.

Gulfstream II TT

Modified version with tip tanks. FAA certified May 13, 1977.

Gulfstream IIB

Modified version, the wingleted wings of the Gulfstream III were fitted to the body of the Gulfstream II. FAA certified on September 17, 1981.

Gulfstream II SP

Aircraft modified by the addition of Aviation Partners winglets. FAA certified under STC ST00080SE on April 22, 1994.

VC-11A

VIP transport version for the US Coast Guard. One built.