The Birth of the Gulfstream Series of Aircraft

Before the Second World War, Grumman Aircraft had a partnership with New York-based Gillies Aviation to market and sell the company's line of amphibian aircraft. One Gillies' salesmen, a pilot named Henry Schiebel, eventually came to work for Grumman during the war as a company test pilot. In the postwar period as Grumman began to diversify its offerings outside of naval aircraft, Schiebel was the head of the company's transportation department, flying the company's executives on various business trips. At the time, Grumman's civilian offerings were limited to its amphibian line of aircraft from the Widgeon and Goose on the small end of the scale to the Albatross and Mallard on the top end. Because of Schiebel's sales background, he often found himself in the role of pitching one of the amphibians to a civilian customer as the need arose.

Though Schiebel wasn't an engineer, he began working with a small group of engineers that since the mid-1950s in their free time after hours had been putting some effort into coming up with a civilian feederliner that could also be used for corporate and private use. Unlike Grumman's previous offerings, what the engineers had in mind was a land-based aircraft that would offer a level of comfort and performance that justified their forecast one-million dollar price given that most companies in those days could get a good used DC-3 for just over $200,000. Schiebel's job was to bring to the after-hours effort not just a pilot's perspective, but also the perspective of someone who was intimately aware of the needs of civilian owners and operators. 

Their starting point was actually basing their aircraft's cabin cross-section on that of the DC-3. Grumman had several of them in its corporate flight department and everyone agreed that they were the most comfortable aircraft when it came to business travel compared to other types of aircraft available on the market. Their second consideration was the type of powerplant to use- again, all were in agreement that a turboprop would offered good operating economics as well as fuel efficiency that translated into a good operating range. At the time, the Rolls-Royce Dart engine had the most flying time of any turboprop and was well-known in the commercial world as it already powered several successful airliners like the Vickers Viscount. The team was well aware that their biggest competition would be pure jets and the prototype Lockheed Jetstar was already flying. This was long before turbofans entered the picture and the choice of a turboprop, while slower in speed than a pure jet, offered better range. 

By the point that the project had matured to the point that it was time to pitch it to Leroy Grumman, a minor bit of discord developed within the team about whether this new aircraft should have a low-wing or a high-wing. Aerodynamically there were no disadvantages or advantages to either layout. Schiebel, drawing upon his experiences in aircraft sales, pushed for a low-wing layout. Rather amusingly, the debate would be settled by Leroy Grumman himself when he was presented with the project by Schiebel and the adhoc group of engineers. Two models of the design were made- one with a low-mounted wing and one with a high-mounted wing. Both were shown to Grumman and he immediately settled on the low-winged configuration. He then summoned the heads of finance and his lieutenants to view the engineers presentation. Building the aircraft would require an initial investment of $23 million and Grumman himself is reportedly to have said "I'd like to build this airplane before I retire." Some had asked whether a market survey should be done first before committing to the project, but Grumman felt comfortable with the fact that Henry Schiebel had been involved with the project all along and trusted his thoughts on the market for the aircraft. Interestingly a competitor did do a market survey and predicted that Grumman would sell less than 20 of the aircraft.

 

It turned out that after the maiden flight of the Grumman Gulfstream I on 14 August 1958, the company would go on and build approximately 200 Gulfstream Is and launched in iconic line of business aircraft that have become near-synonymous with business aircraft. The Gulfstream I had two features which have been kept in every successive Gulfstream right up to the current Gulfstream 650 that's in flight testing- the characteristic nose/cockpit shape and the large oval windows, the largest of any business aircraft. 

The first Gulfstream Is sold for $845,000 and the first one went to the Sinclair Refining Company and the FAA, responsible for certifying the aircraft, even got two for its own use. By 1963, Grumman was building two Gulfstream Is a month and began work on transitioning the product line to jet power with the Rolls-Royce Spey-powered Gulfstream II which first flew in October 1966. The new Gulfstream jets were built a new plant set up in Savannah, Georgia, by Grumman and though Grumman is no longer involved with the production of Gulfstream jets, the plant in Savannah is still to this day where they are built. 

Source: The Grumman Story by Richard Thruelsen. Praeger Publishers, 1976, p275-279.

The Turboprop B-17 Flying Fortress

In the late-1950s, many of the surplus Boeing B-17 Flying Fortresses that were used by the Navy, Air Force, and Coast Guard in the air-sea rescue role found their way into the hands of several civilian fire bomber operations that for the first time along with surplus Consolidated PB4Y-2 Privateers, offered a quantum leap in performance with the ability to carry significant loads of fire retardant. In fact, prior to the arrival of the B-17s and PB4Y-2s, no other civilian fire bomber then in use even remotely approached the fire retardant capacity of the converted four-engined bombers. In 1960, the first of about two dozen B-17s were converted with bomb bay tanks for aerial delivery of fire retardants.

The bomb bays were fitted with tanks that could carry 2,000 lbs of retardant. The tank was then subdivided into four compartments, each compartment having its own quick-opening door to empty that tank on a forest fire target. The converted B-17s were based on the -F and -G variants primarily (the USAF's air-sea rescue SB-17G, for example). Stripped of all non-essential equipment, the B-17 offered a significant increase in power in the typical-high altitude areas that most forest fires were found. Most of the conversions flew on contracts with the US Forest Service.

However, by the late-1960s many of the fire bomber B-17s were retired from service as aircraft like the Douglas DC-6 and ex-military Douglas C-54s were converted for the role. In addition, the Wright R-1820 Cyclone radial engines of the B-17s were becoming increasingly difficult to support with spare parts. One enterprising outfit got around this issue by re-engining their B-17 fire bomber with four Rolls-Royce Dart turboprops that once belonged to Vickers Viscount. As the Dart engines were much lighter than the Wright Cyclone radials, the nacelles had to be extended far forward to maintain the center of gravity with the propeller spinners being nearly in line with the nose of the B-17. Only one B-17, N1304N, was converted in 1970. Some sources indicate that the aircraft had the nickname "Batmobile" and she was so overpowered, that with both outboard engines shut down and feathered, she was still faster than a stock B-17 and this was while carrying a full load of fire retardant. When the pilots made their drop, they had to shut down and feather the outboard engines to keep from overspeeding the airframe.

This unique and one-of-a-kind B-17 Flying Fortress was unfortunately lost in the same year it was converted. While fighting a forest fire near Dubois, Wyoming, the engines lost power due to excessive ingestion of heated air and smoke from the fire and the aircraft failed to pull out of a retardant drop.

Source: Boeing B-17 Flying Fortress (Warbird Tech No. 7) by Frederick A. Johnsen. Specialty Press, 2002, p97-99.

British European Airways' Dart Dakota

While the Vickers Viscount and its Rolls-Royce Dart turboprop engines underwent an exhaustive test flying program befitting its groundbreaking status as the first turbine-powered production airliner to fly, the Dart engines themselves would also fly on a variety of testbed aircraft to allow not only Rolls-Royce's engineers to gain operating experience with the new engine, British European Airways (BEA) also gained operating experience as well with the Dart Dakota, a conversion of one of the airline's DC-3s with Dart turboprops. Two BEA DC-3s were converted to Dart engines- G-ALXN "Sir Henry Royce" and the other DC-3, G-AMDB "Claude Johnson", BEA's managers, pilots, and maintenance crews gained valuable experience in turbine operations before the arrival of the Vickers Viscount.

One of the unique aspects that made testing the Dart engine challenging was that it was a purely postwar civilian engine program that lacked a large body of military operating experience that in the past made applying civilian versions of military powerplants relatively smooth. Both BEA and Rolls-Royce lacked data on the ideal flight patterns, control methods, and maintenance pitfalls for the Dart engine and the use of the two Dart Dakotas would remedy this situation- rather than flying a test program, BEA's Dart Dakotas would be integrated into BEA's routine operations to see how the engines fared in routine use.

Early model Dart engines (designated Mk. 505s) replaced the Dakota's radial engines and the nacelle installation would approximate that of the Viscount as closely as possible. As the DC-3 was an unpressurized aircraft, it was impractical to operate the Dart Dakota at lower altitudes (which would have been inefficient for the engines) or at higher altitudes (as the passengers would have needed a bulky oxygen supplementation system). As a result, BEA would employ the two Dart Dakotas for freight only services as only the flight deck crew would need oxygen to operate at the at the efficient higher altitudes.

The first scheduled "operational" service was flown on 15 August 1951 when G-ALXN carried 1.5 tons of cargo from BEA's original base at Northolt to Hannover, Germany. Following succesful introductions to service, BEA then deployed the two Dart Dakotas on all-cargo scheduled services out of Northolt to Copenhagen and Milan in addition to Hannover until the end of the trial period in 1952.

Compared to a stock DC-3, the Dart Dakotas had the following performance figures: 202 mph/325 km/h for the Dart Dakota vs. 167 mph/270 km/h with a gross weight of 28000 lbs at an altitude of 25000 feet vs. only 7000 feet for a standard DC-3. Ultimately the trial period was uneconomic, as the Dart Dakotas weren't able to fly as many hours as planned thanks to a shortage of qualified flight crews and trained engineers and maintenance crews. Technical difficulties as well resulted in numerous canceled flights and delays- but these were the very sort of problems BEA, Rolls-Royce, and Vickers wanted to see before the Viscount entered scheduled passenger services.

At the end of the trial period, G-ALXN flew for a total 538 hours in Dart configuration and her sistership G-AMDB flew for 668 total hours. Both aircraft were then reconverted back to standard DC-3 configuration, flying services with BEA until early 1962 when they were passed on to the British independent operators of the day.

Source: A Celebration of the DC-3 by Arthur Pearcy. Airlife Publishing, 1985, p99-100.