B/CA Analysis: Gulfstream III - CompAir Logo

B/CA Analysis: Gulfstream III
Gulfstream Aerospace’s G-III is the proud possessor of a name that has been prominent in business
aviation for a quarter century.
By David W. Almy, Richard N. Aarons and John W. Olcott
The airframe manufacturer with the newest name in corporate aviation produces aircraft with the
oldest and possibly most respected hallmark in the business of executive transportation. We’re
referring to Gulfstream Aerospace Corporation, of course, manufacturer of the Gulfstream III
and possessor of the prestigious Gulfstream label since 1978 when Allen Paulson acquired
Grumman American. Paulson called the new company Gulfstream American to capitalize on the
charm of the Gulfstream name and to emphasize the firm’s principal product. But in October
1982 he changed the American to Aerospace to leave no doubt about the nature of his business.
No one knows the exact origin of the Gulfstream designation. Leroy Grumman (who died in
the fall of 1982 at the age of 88) apparently came up with the name on his own, and since a chairman’s
edicts are usually followed, the title stuck. No Roman numerals trailed the aircraft’s identifier
in those early days; there was only one Gulfstream.
When the original first flew on August 14, 1958, it was at somewhat of a financial risk sine the
number of customers — only 19 with firm deposits — was not nearly enough to justify the production
of a new aircraft.
Seemingly, all did not bode well for Grumman, this being the company’s first major investment
in the business aircraft market.
But the aircraft did sell, partially because of the growth of business aviation in the late 1950s
and partially because of an attractive mix of passenger amenities and pilot features. A 2,000-nm
range, 260-knot cruise, spacious cabin, pressurization and above average reliability all contributed
to the turboprop’s success. By the time the last one (number 200) rolled off the line in
April 1969, the Gulfstream had become a classic.
Part of that evolving mystique was and is attributable to the logo stamped on the side of every
Gulfstream engine nacelle ever built. Charles Stewart Rolls and Frederick Henry Royce probably
never dreamed that their names would appear on aircraft engines, but the “double-II” brand and
the dependability of the Dart turbines (and later the Speys) were just as much a part of the
Gulfstream’s character as is the distinct shrill produced by the Rolls-Royce turboprops.
No sooner had the Gulfstream begun its life, however, when the jet age arrived and the thenlargest
and first airplane built solely for the corporate market was psychologically eclipsed by
smaller and faster jets like the Aero, Commander, Lear 23, Sabreliner and JetStar. The
Gulfstream, while certainly a successful and capable aircraft, had lost the imagination of a market
that had been captivated by the turbojet engine.
Grumman was not caught entirely off balance, however. In the fall of 1964 an expectant business
aviation community was told of the Gulfstream II, a new executive aircraft that combined
the successful cabin size of the original Gulfstream with Rolls-Royce Spey turbofan engines in a
logical masterstroke of marketing and engineering.
The first production Gulfstream II (there was no prototype) flew on October 2, 1966. It was
priced at a then record $2 million, but unlike its predecessor, the G-II had sixty launch customers.
Indicative of the loyalty within the Gulfstream “family,” all but four of the launch orders
came from Gulfstream I owners.
B/CA characterized the Gulfstream II as “a ship just a bit larger in cabin size than the prede-
FROM THE JANUARY 1983 BUSINESS & COMMERCIAL AVIATION.
COPYRIGHT © 1983, THE McGRAW-HILL COMPANIES, INC. ALL RIGHTS RESERVED.

cessor Gulfstream, but the only “commonality” with the turboprop (that Grumman will admit to)
is a hydraulic valve in the flap system.”
Capitalizing on their preeminence in the business jet market during the early 1970s, the wise
marketers at Grumman dubbed their G-II “The Ultimate.” Their advertising stylishly echoed
that of Rolls-Royce motorcars. It was a soft sell with a strong machine. There were never any
unsold aircraft on Grumman’s ramp.
But the Gulfstream II was not without problems. Although the reliability and passenger appeal
of the airplane remained unsurpassed throughout the 1970s, the soaring cost of fuel, range (most
transatlantic trips required a fuel stop), public sensitivity to noise and some increasingly formidable
competition necessitated some changes in the G-II design.
The Gulfstream II’s range was subsequently increased by 500 nm through the convenient
addition of tip tanks. Hush kits largely eliminated the granite-splitting crackle of full-power G-II
takeoffs and brought the aircraft in line with FAR Part 36 requirements.
But the problem of fuel efficiency remained. Three options were available: A major aerodynamic
cleanup, use of more efficient engines or a mix of both.
During three years of research and development, two primary areas were targeted for aerodynamic
improvement: the forward fuselage (the cockpit and the nose) and the wing. In addition,
several reengining options were seriously considered, and performance projections were finally
calculated on two-, three-, and four-engine configurations.
Enter, Gulfstream III
Rather than develop an entirely new wing for the follow-on aircraft, soon to be known as the
Gulfstream III, Grumman engineers employed advanced techniques in computational aerodynamics
and blended the results with wind tunnel data to design a modification to the G-II’s airfoil
shape and wing planform. The wing’s chord was extended forward and its leading-edge geometry
was changed, resulting in a thinner, more aerodynamically efficient airfoil section with better
drag characteristics. Wingspan was increased by nine feet for better performance on takeoff and
at altitude, and four-foot winglets were grafted onto the wingtips to lower induced drag.
(Originally, there were four winglets planned for the G-III, one extending upward and one probing
downward from each tip. But the lower, smaller winglets were marginally effective and were
eliminated.)
Although the modified wing was not as efficient as if Grumman’s engineers had started from
scratch, its lower drag rise at high Mach numbers and its ability to sustain the Gulfstream at FL
450 (and higher; the G-III holds the altitude record 52,000 feet — for its weight class) contributed
to a 15- to 17-percent increase in specfic range when compared with the G-II.
A redesigned nose also improved the Gulfstream’s performance by shifting rearward a shock
wave that, in cruise, emanates from the fuselage’s curvature just aft of the cockpit. Consequently,
the G-III enjoys a quieter cockpit than its predecessor since now the shock dances relatively
unnoticed in the region between the cockpit and the passenger cabin.
Despite concerted efforts to find an engine for the G-III with a less voracious affinity for jet A,
none were deemed suitable. Reliability and high-altitude performance were cited as the principal
reasons for retaining the Speys. Statistically, you can expect an inflight shutdown only once in
every 50,000 hours of operation.
In addition, further analysis of specific fuel consumption and power output at altitude indicated
that above FL 410, the venerable Speys, with their very low (0.62:1) bypass ratios, were the
best engines available for the job.
A glance at the Comparison Profile suggests why the G-III does well in upholding the
FROM THE JANUARY 1983 BUSINESS & COMMERCIAL AVIATION.
COPYRIGHT © 1983, THE McGRAW-HILL COMPANIES, INC. ALL RIGHTS RESERVED.

Gulfstream tradition. Ranking or tieing for first in 14 of the 28 categories B/CA used to compare
the G-III against the composite characteristics of its competitors — the Canadair Challenger
CL-600 and the AMD Falcon 50 — the Gulfstream shines in its ability to carry a maximum useful
load of 30,900 pounds. Much of that capacity, however, is used to lift the fuel that provides an
impressive VFR, tanks-full range (with NBAA reserves) of 4,150 nm — tops among the aircraft
considered.
In the categories that relate to fuel flow, the G-III produces numbers that place significantly
below average due to the low bypass ratio and older technology of the Spey engine. Note, however,
that the noise performance of the G-III is only 6 percent below the average on takeoff and 2
percent lower in the approach configuration.
The G-III meets Stage II of the Part 36 noise standards, without the use of any special noiseabatement
procedures. But when Gulfstream’s “flex EPR” technique is followed, whereby a
reduced power setting is used to achieve but not exceed a Part 25 takeoff profile (even with an
engine cut at V1, and no power adjustment), the 90 EPNdB noise footprint can be reduced in
size by as much as 76 percent.
Something More
Competitive performance partially accounts for the G-III’s success, but reliability and flying
qualities play major roles in sustaining the Gulfstream image.
Reliability dominates the G-III design: There is a back-up system for nearly every back-up
system. For example, there are four boost pumps in the fuel system, but the aircraft can operate at
FL 450 with only one functional, provided the cross-flow is open. And yes, there are two means
of providing cross flow between the fuel tanks.
Although the electrical system also enjoyed the redundancy for which Gulfstreams are well
known, Gulfstream Aerospace’s new demonstrator (due out of Gulfstream’s own completion center
in March 1983) as well as aircraft beyond serial number 402 will use two Bendix variablespeed,
constant-frequency AC alternators for their primary sources of electrical power. Each unit
is rated at 23kVA and can carry the aircraft’s total electrical load. Direct current (other than battery
power) will be obtained by means of rectifiers; however, other aspects of the new electrical
system, such as the aircraft I’s split-bus arrangement, will remain the same as on older G-IIIs.
By selecting AC as the primary source of electrical power, Gulfstream Aerospace simplified
the system and saved about 200 pounds of weight. Pilot work load is reduced by more automatic
sensing of anomalies and improved fault-protection logic, and outfitters have a greater latitude in
their selection of special equipment for the aircraft.
The new G-IIIs also will enjoy the advantages of an auxiliary power unit that is approved for
operation at altitudes up to FL 300. The APU can be started up to FL 200 and will have the same
capacity for producing AC as that of the engine-driven Bendix alternators.
Rounding out the revamped G-III electrical system will be a new overhead electrical panel,
with simplified readouts that show percent capacity.
Gulfstream Aerospace’s new demonstrator also will feature dual Sperry ED-800 electronic
flight instrumentation systems as well as Sperry’s Primus 800 multifunctional display. But the
timing of available, FAA-approved hardware prevented Gulfstream Aerospace from selecting an
electronic engine instrumentation and crew alerting system. Howell round-dial instrumentation
with digital readouts, however, will be used in the new demonstrator, serial number 357.
Another advanced feature of serial number 357 will be its three Honeywell ring laser gyros,
which will provide heading reference for the aircraft’s compass and inertial navigation systems. The
Honeywell units save weight and improve reliability by eliminating the use of mechanical gyros.
FROM THE JANUARY 1983 BUSINESS & COMMERCIAL AVIATION.
COPYRIGHT © 1983, THE McGRAW-HILL COMPANIES, INC. ALL RIGHTS RESERVED.

Pilots enjoy the G-III not only for the reliability that its redundant systems provide but for its
favorable flying qualities as well. With sufficient power to climb unrestricted to FL 450 at its
maximum takeoff weight of 68,200 pounds, and with its longer, wingless-enhanced wing providing
comfortable stability and control even at FL 450, the G-III is a pleasure to fly. We were able
to sustain a bank angle of 50- to 55-degrees without exciting a buffet at FL 450 and about 52,000
pounds. And we found the aircraft’s stall behavior at that altitude to be predictable and without
violence as the stick shaker and pusher did their respective jobs of stall warning and protection.
Even with our lack of familiarity with the G-III, we recovered fully by FL 430.
The G-IIIs speed stability and lateral and directional handling characteristics provide a comfortable
platform for approach and landing tasks. The longer wings and winglets significantly
lessen the roll sensitivity and tendency toward wing rocking that is found in the G-II in its
approach configuration.
While it is the passengers who must pass final judgment (since they pay the bills), certainly the
feelings of confidence that come from Gulfstream reliability and pilot praise help sell G-IIIs.
Gulfstream Aerospace’s dedication to the business aviation community as well as the 25-year-old
Gulfstream tradition also are significant factors, no doubt.
Proof of the Gulfstream appeal is the fact that during this past year, while most of the business
aviation industry was wallowing in an economic quagmire, Gulfstream Aerospace’s Savannah
division was running at full capacity.
And Gulfstream’s future looks bright too. Looming large on the horizon is the G-IV, another
twin engine growth version of the G-I that will include one major modification: a new turbofan.
Those resourceful people at Rolls-Royce, enticed by visions of hundreds of retrofitted BAC One
Eleven’s, Fokker F28s, G-IIs and G-IIIs, have come up with a new Spey derivative to match the
Gulfstream airframe. The Rolls-Royce RB183-03 will be a 13,900 pound-thrust turbofan derated
to 12,000 pounds thrust for use in the G-IV. Certification of the Gulfstream IV is expected in
1986, provided Rolls-Royce announces a go-ahead on the RB183-03 this month.
If the past 25 years are any indication, future versions of the Gulfstream are likely to be just as successful
as their predecessors, for that name holds a special place in the annals of business aviation. B/CA
FROM THE JANUARY 1983 BUSINESS & COMMERCIAL AVIATION.
COPYRIGHT © 1983, THE McGRAW-HILL COMPANIES, INC. ALL RIGHTS RESERVED.