Boeing Gas Turbines
Compiled by Kimble D. McCutcheon and Doug Culy
Published 31 Oct 2023; Revised 6 Nov 2023


Boeing T50-BO-12 in Gyrodyne QH-50D (Wiki)		 When the turbojet was finally revealed in 1943, U.S. Army Air Forces became interested in powering large aircraft with them. Boeing realized that if large jet-powered military aircraft proved successful, the airlines would want them, so Boeing began planning large jet-propelled aircraft. In order to understand these new engines, Boeing questioned several gas turbine manufacturers, but got conflicting accounts of the new technology; thrust, life, operating temperatures and fuel economy estimates varied wildly. To gain better data, Boeing started its own jet propulsion research in June 1943.

 

Introduction

Boeing built and tested various gas turbine components in a purpose-built area at Boeing's Seattle, Washington Plant. There, engineering spaces, machine shops, assembly facilities and component test cells were constructed. Small axial- and centrifugal-flow compressors were built and tested, and finally the assembly and testing of complete experimental power units resulted in the construction of two small gas turbines. The Model 500 turbojet was assembled in 1947, and the Model 502 turboprop was assembled in 1949.

While this work started as a research endeavor to explore the characteristics of gas turbine engines, Boeing realized that these engines might produce an income stream. Development of the two engines proceeded through the late-1940s. The first engine to run was the Model 500, and the Model 502 quickly followed. Boeing announced these two engines in 1947. The Model 500 turbojet was considered suitable as a large jet engines starter and also for missile, glide bomb, and small aircraft propulsion. The Model 502 turboprop was offered for use in light aircraft, although it was anticipated that early use would be as an auxiliary power unit in large aircraft and as a ground power unit. These engines benefited from the close cooperation among Boeing's several engineering groups, including acoustics, vibration, electronics, process, and metallurgy, each with its own laboratory and specialists. These groups, together with Boeing's jet propulsion laboratory, resulted in a research organization considered by Boeing to be unparalleled at that time by any other U.S. aircraft gas turbine concern.

Development

The Model 500 was a single-shaft turbojet with a single-entry centrifugal compressor, two can-type combustors, and a single-stage axial turbine. The Model 500, first run in 1947, was rated at 150 lbt, had a 1.3 lb/hp/hr sfc, and weighed 85 lb. By 1954, the thrust was 195 lb, and engine weight was 120 lb. Compressor and turbine modifications achieved the performance increases. Boeing continued developing and marketing this engine, but it found no applications. Boeing's small engine work then became focused on free-turbine turboprops and turboshaft engines, derived from the Model 500.

The Model 502 was initially a turboprop and later a turboshaft engine. The 502 used a 500 power section, but a single-stage free power turbine and gearbox were added. First run in 1947, the 502 weighed 140 lb and produced 120 shp with a 1.8 lb/hp/hr sfc. In 1949, Boeing delivered six engines to the Navythat produced 160 shp with a 1.5 lb/hp/hr sfc. The refined engine had an aerodynamic upgrade, thickened turbine blades, compressor structural changes, a new accessory section/gearbox, and a more reliable fuel control system.

The Model 502-10C turboshaft increased output from 120 to 240 shp with a 1.02 lb/hp/hr sfc, but weight also increased to 320 lb. Production cost and time between overhauls was on par with reciprocating engines. By 1965, the Model 502-10VC turboshaft was producing 300 shp at a 0.98 lb/hp/hr sfc.

 

 

Marine Power

Boeing Model 540 Cycle Parameters
Turbine Inlet Temperature1,550°F
Airflow1.615 lb/sec
Overall Pressure Ratio4.15
Compressor Efficiency0.74%
Gas Generator Turbine Efficiency (T-T)85%
Power Turbine Efficiency (T-S)80%
Gas Generator Speed54,600 rpm
Power Turbine Speed34,500 rpm
Boeing Model 540 Weight Breakdown
Gas Producer Section60 lb
Output Section40 lb
Propeller Drive Assembly35 lb
Transom Mounting Bracket30 lb
Starter and Alternator27 lb
Remaining Accessories10 lb
Shroud8 lb
(T-T) = Through-turbine efficiency measurement.
(T-S) = Measurement involves stopping a small flow portion.

In 1947, while the U.S. Navy Bureau of Ships was looking for a naval vessel power plant; the Model 502 acquired the T50 military designation. Boeing received the first Model 502 production contract during 1950 for engines to be used in Navy minesweepers using two 502-6 engines that drove an electric generator through a combining gearbox. The turboshaft 502 also served in air-start carts, fire truck water pumps, truck and traction power.

Boeing 540 (Culy)

The Model 540. In mid 1959, Boeing prepared layout designs of several alternative outboard gas turbine engines for marine use, with the U.S. Navy’s needs particularly in mind. In mid 1960, a go-ahead was made to build a demonstrator, making use of some existing test-rig components that had been designed to evaluate improved small-engine technologies. The goal was a 100-shp free turbine outboard engine delivering 1.0 lb/hp/hr sfc, using commercial off-the-shelf components as much as possible. The demonstrator was mounted on a Mercury Model 800 outboard propeller drive unit. The demonstrator was running in a 20-ft boat by the fall of 1961, and a proposal to the Navy was made in March 1962.

The engine featured a monorotor gas generator (centrifugal compressor and radial-inflow turbine) and an axial power turbine. In the demonstrator, a radial turbine was used for the power turbine, and all rotors were hogged out of forgings; but they were to be cast in the production engine. Most of the controls and accessories were off-the-shelf items. A single reverse-flow thumb-type (stickeing out radially) combustor was used. A single-stage offset layshaft gear set provided 5.82:1 reduction. Early in its testing, the engine delivered its output goals

Boeing expected to easily grow the engine to 150 shp with 0.88 lb/shp/hr sfc at 1,775°F turbine inlet temperature. Production engine weight was estimated to be 180 lb, development engines were expected to weigh 210 lb, and the demonstrator weighed a few pounds more than that.

The Navy wanted a commercially available engine, and Boeing had discussions with a prominent outboard engine manufacturer, which expressed interest. However, Boeing would not commit to marketing a commercial engine, and the Navy did not accept the proposal. The Boeing engineers on the program were extremely disappointed; the demonstrator was shelved in 1962. So ended the Model 540, a beautiful and simple engine that would have revolutionized the boat engine market. Boeing had done its homework, and was envisioning using the 540 basic engine for auxiliary power unit, pumping, generating, etc., but there was no follow-through.

Aircraft Power Firsts

On 10 Dec 1951, a Model 502-2E (YT50) replaced the standard Lycoming O-435-A2 piston engine in a Kaman K-225, becoming the first gas turbine to power a helicopter. In 1952, the Navy became interested in pilotless helicopters for Anti-Submarine Warfare surveillance. Kaman did the initial experimentation and the Navy initiated a competitive procurement; on 6 Apr 1961, Gyrodyne of Long Island, New York, won with its proposal for the DSN-3, powered by a Model 502 (T50-BO-4) turboshaft producing 270 shp. Later, the DSN-3 was fitted with a 300 shp Model 502-10VC (T50-BO-8A) and was redesignated the QH-50C. The Model 502-10VC was the first U.S. 200 - 350-shp class to pass a 150-hour type test.

In November 1952, Boeing, Cessna, Army and Air Force installed a 210 hp Model 502-8 (XT50-BO-1) turboprop in a Cessna XL-19B; this was the first turboprop-powered light airplane. On 16 July 1953, the XL-19B set a light plane altitude world record of 37,063 feet. In 1960, the 300 shp Model 502-10F turboprop powered the Army's rocket-launched Radioplane RP-77D, a radio-controlled aerial gunnery target. On 24 Mar 1954, a Kaman HTK-2 equipped with two 502-2 engines became the first twin-turbine helicopter to fly. When Model 502 production ceased in 1965, about 1,500 turboshaft, turboprop, and ground power unit engines had been built.

 

 

In early 1954, Model 520 series engine design began as a joint Navy/Boeing project. The initial helicopter version was the 430 hp Model 520-2 (T60-BO-2). This engine's gas generator had a double-entry centrifugal compressor, two reverse-flow combustion chambers, a single radial inflow turbine, and a single axial free turbine driving the power takeoff. The new double-entry compressor provided an airflow and pressure ratio increase of about 25% over the Model 502.

Three turboshaft and two turboprop Model 520 versions were rated from 430 to 550 shp with sfcs from 0.72 to 0.65 lb/hp/hr. By 1960, the Model 520-2 had passed its 50-hour Preliminary Flight Rating Test (PFRT), but the Navy's projected applications never happened and the 520 Series was never produced.

The 365 shp Model 550 (T50), introduced in the early 1960s, descended from the Model 502. Initially an improved and lighter Model 502 the 550 featured a single axial stage ahead of the single-sided centrifugal compressor stage, two new reverse-flow can-type combustors, and a radial inflow turbine driving the compressor. The Model 550's rated power increased by 65 shp and its weight decreased by 84 lb compared to the earlier Model 502-10VC; sfc also decreased from 0.98 to 0.80 lb/hp/hr. The Model 550-1 (T50-BO-12) entered production in the mid-1960s and powered the Gyrodyne QH-50D drone. Model 550 production continued until April 1968.

Despite its successes, by 1965 Boeing's Turbine Division had lost money for 17 straight years. Boeing was unwilling to commit the resources necessary to save the Division, plus, it needed capital and engineering resources for its new Model 747 airplane project. On 25 Jan 1966, Boeing announced plans to phase out its gas turbine engine operations over several years. Production commitments were to be met and a commitment made to support the 1,200 engines in service. On 7 Dec 1966, the Caterpillar Tractor Co. took over development and support. Boeing completed the last Model 550-1 (T50-BO-12) in April 1968. On 1 Mar 1969, Steward-Davis, Inc., a major turbine overhaul and repair facility located in Long Beach, California, took over development, manufacture, sales and service of Model 502 and T50-BO-10/12 engines.

Boeing Gas Turbine Data

 

 

 

 

 

 

 

Acknowledgements

Many thanks to Douglas Culy for the Boeing Model 540 information and images.

References

Leyes, Richard A. II and William A. Flemming The History of North American Small Gas Turbine Aircraft Engines (Reston, Virginia: AIAA, 1999) 51 -62.
Wilkinson, Paul H. Aircraft Engines of the World (New York, New York: Paul H. Wilkinson, 1948 to 1966/67).

 

Send mail to with questions or comments about this web site.
This website depends on cookies to make it function. If you continue to browse, scroll, click or otherwise interact, you are providing implicit acknowledgement of and agreement to this.
Copyright © 2002-2024 Aircraft Engine Historical Society, Inc.      Home