World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0000658871
Reproduction Date:

Title: Turboshaft  
Author: World Heritage Encyclopedia
Language: English
Subject: Lycoming T53, Lycoming T55, Lycoming LTS101, Rolls-Royce Spey, HAL/Turbomeca Shakti
Collection: Aircraft Engines, Gas Turbines, Motorcycle Engines
Publisher: World Heritage Encyclopedia


Schematic diagram showing the operation of a simplified turboshaft engine. The compressor spool is shown in green and the free / power spool is in purple.

A turboshaft engine is a form of gas turbine which is optimized to produce shaft power rather than jet thrust.

In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust and convert it into output shaft power. They are even more similar to turboprops, with only minor differences, and a single engine is often sold in both forms.

Turboshaft engines are commonly used in applications that require a sustained high power output, high reliability, small size, and light weight. These include helicopters, auxiliary power units, boats and ships, tanks, hovercraft, and stationary equipment.


  • Overview 1
  • History 2
  • See also 3
  • References 4
  • External links 5


A turboshaft engine may be made up of two major parts assemblies: the 'gas generator' and the 'power section'. The gas generator consists of the compressor, combustion chambers with ignitors and fuel nozzles, and one or more stages of turbine. The power section consists of additional stages of turbines, a gear reduction system, and the shaft output. The gas generator creates the hot expanding gases to drive the power section. Depending on the design, the engine accessories may be driven either by the gas generator or by the power section.

In most designs, the gas generator and power section are mechanically separate so they can each rotate at different speeds appropriate for the conditions, referred to as a 'free power turbine'. A free power turbine can be an extremely useful design feature for vehicles, as it allows the design to forego the weight and cost of complex multiple-ratio transmissions and clutches.

The general layout of a turboshaft is similar to that of a turboprop. The main difference is a turboprop is structurally designed to support the loads created by a rotating propeller, as the propeller is not attached to anything but the engine itself. In contrast, turboshaft engines usually drive a transmission which is not structurally attached to the engine. The transmission is attached to the vehicle structure and supports the loads created instead of the engine. In practice, though, many of the same engines are built in both turboprop and turboshaft versions, with only minor differences.

An unusual example of the turboshaft principle is the Pratt & Whitney F135-PW-600 turbofan engine for the STOVL F-35B - in conventional mode it operates as a turbofan, but when powering the LiftFan, it switches partially to turboshaft mode to send 29,000 horsepower forward through a shaft[1] (like a turboprop) and partially to turbofan mode to continue to send thrust to the main engine's fan and rear nozzle.

Large helicopters use two or three turboshaft engines for redundancy. The Mil Mi-26 uses two Lotarev D-136 at 11,400 hp each,[2] while the Sikorsky CH-53E Super Stallion uses three General Electric T64 at 4,380 hp each.[3]

Early turboshaft engines were adaptations of turboprop engines, delivering power through a shaft driven directly from the gas generator shafts, via a reduction gearbox. Examples of direct-drive turboshafts include marinised or industrial Rolls-Royce Dart engines.

Austin 250hp gas turbine, sectioned.


The first examples of a gas turbine engine design ever considered for armoured fighting vehicles, the BMW 003-based GT 101, were tested in Nazi Germany's Panther tanks in mid-1944.[4] The first true turboshaft engine for helicopters was built by the French engine firm Turbomeca, led by the founder, Joseph Szydlowski. In 1948, they built the first French-designed turbine engine, the 100-shp 782. Originally conceived as an auxiliary power unit, it was soon adapted to aircraft propulsion, and found a niche as a powerplant for turboshaft-driven helicopters in the 1950s. In 1950, this work was used to develop the larger 280-shp Artouste, which was widely used on the Aérospatiale Alouette II and other helicopters. This was following the experimental installation of a Boeing T50 turboshaft in an example of the Kaman K-225 synchropter on December 11, 1951, as the world's first-ever turboshaft-powered helicopter of any type to fly.[5] Since 1984 the US Army has operated the M1 Abrams tank. Designed and built in the late 1970s, this tank makes use of a gas turbine engine compared to most tanks using reciprocating diesels. The engine has considerably fewer parts, mechanically is very reliable and reduced exterior noise and runs on virtually any fuel; petrol (gasoline), diesel fuel, aviation fuels. Similarly, the Swedish Stridsvagn 103 was the first tank to utilize a gas turbine. In this case as a secondary, high-horsepower "sprint" engine to augment the primary piston engine's performance.

See also


  1. ^ Warwick, Graham. " F-35B - The STOVL Challenges" Aviation Week & Space Technology, December 09, 2011. Accessed: April 10, 2014.
  2. ^ "Mi-26 HALO", September 21, 1999. Accessed: April 10, 2014.
  3. ^ "About the GE T64" BGA-aeroweb, May 17, 2012. Accessed: April 10, 2014.
  4. ^ Kay, Antony, German Jet Engine and Gas Turbine Development 1930-1945, Airlife Publishing, 2002
  5. ^ "Smithsonian National Air and Space Museum - Kaman K-225". NASM. Retrieved January 14, 2015. 

External links

  • Wikibooks: Jet propulsion
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.