Pratt & Whitney JT8D
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| A JT8D pictured mounted on a McDonnell Douglas DC-9 operated by DHL at the Portland International Jetport in 2004 | |
| Type | Turbofan |
| Manufacturer | Pratt & Whitney |
| First run | 1964 |
| Major applications | Boeing 727 McDonnell Douglas DC-9 |
| Developed from | Pratt & Whitney J52 |
| Variants | Volvo RM8 |
The Pratt & Whitney JT8D is a low-bypass (0.96 to 1) turbofan jet engine, introduced by Pratt & Whitney in February 1964 with the inaugural flight of Boeing's 727. It was a modification of the Pratt & Whitney J52 turbojet engine, which powered the US Navy A-6 Intruder attack aircraft. The Volvo RM8 is an afterburning version that was license-built in Sweden for the Saab 37 Viggen fighter. A "fixed" version for powerplant and ship propulsion is known as the FT12.
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[edit] Design
The JT8D is an axial-flow front turbofan engine incorporating dual-spool design. There are two coaxially-mounted independent rotating assemblies: one rotating assembly for the low pressure compressor (LPC) which consists of the first six stages (i.e. six pairs of rotating and stator blades, including the first two stages which are for the bypass turbofan), driven by the second (downstream) turbine (which consists of three stages); and a second rotating assembly for the high-pressure compressor (HPC) section, which has seven stages. The high-pressure compressor is driven by the first (upstream) turbine, which has a single stage.
The front-mounted bypass fan has two stages. The annular discharge duct for the bypass fan runs along the full length of the engine, so that both the fan air and exhaust gases can exit through the same nozzle. This arrangement allows some noise attenuation, in that the still-hot fast-moving turbine exhaust is shrouded in much-cooler and slower-moving air (from the bypass fan) before interacting with ambient air. Thus the JT8D noise levels were significantly reduced from previous non-turbofan engines, although the low bypass ratio meant that high noise levels were still produced.
Eight models comprise the JT8D standard engine family, covering the thrust range from 12,250 to 17,400 pounds-force (62 to 77 kN) and power 727, 737-100/200, and DC-9 aircraft. More than 14,000 JT8D engines have been produced, totaling more than one-half billion hours of service with more than 350 operators making it the most popular of all low-bypass turbofan engines ever produced.
Within the fan inlet case, there are anti-icing air bosses and probes to sense the inlet pressure and temperature. Similar units exist throughout the engine to check temperatures and pressures.
At the 13th (i.e. the final) compressor stage, air is bled out and used for anti-icing. The amount is controlled by the Pressure Ratio Bleed Control sense signal (PRBC). The diffuser case at the aft end of the compressor houses the 13th stage. Its increasing cross-sectional area allows the compressed air to slow down before entering one of the engine's nine burner cans. Again, there are two bosses to extract 13th stage air for anti-icing, de-icing of fuel, and airframe (cabin pressurization) use. Not all the compressed air enters the burner cans at the fuel-ignition point; some bypasses the can completely and cools the first turbine stage, and some is gradually introduced into the burner can's perimeter in such a way that the burning fuel is held near the can's centerline.
There are nine combustion chambers positioned in a can-annular arrangement. Each chamber has three air inlet hole sizes: the smallest is for cooling, the medium is for burning and the large for forming an air blanket.
The Kawasaki C-1, a Japanese military transport, is powered by the JT8D-M-9, manufactured by Mitsubishi.
[edit] Update programs
In response to environmental concerns that began in the 1970s, the company began developing a new version of the engine, the JT8D-200 series.[1] Designed to be quieter, cleaner, more efficient, yet more powerful than earlier models, the -200 Series power-plant was re-engineered with a significantly higher bypass ratio (1.74 to 1) covering the 18,500 to 21,700 pound-force (82 to 97 kN) thrust range and powering the McDonnell Douglas MD-80 series. This increase was achieved by increasing bypass fan diameter (from 39.9 to 49.2 inches) and reducing fan pressure ratio (from 2.21 to 1.92.)[citation needed] Overall engine pressure ratio was also increased from 15.4 to 21.0[2].Since entering service in 1980, more than 2,900 of the -200 series engines have been produced.
The JT8D-217 and -219 engine(s) were tested in 2001 and were deemed suitable replacements for the old TF33 engines on military and commercial aircraft as part of the Super 27 re-engining program. The updated engines offer reduced (Stage-3) noise compliance standards without the need for hush kits, enhanced short field performance, steeper and faster climb rates with roughly a 10% reduction in fuel burn for extended range.
Pratt & Whitney, in a joint venture with Seven Q Seven (SQS) and Omega Air, has developed the JT8D-219 as a re-engine powerplant for Boeing 707-based aircraft.[3] Northrop Grumman has the -219 to re-engine the United States Air Force’s fleet of 19 Joint Surveillance Target Attack Radar System (E-8 Joint STARS) aircraft, which will allow the JSTARS more time on station due to the engine's 17% [4]greater fuel efficiency. NATO also plans to re-engine their fleet of E-3 Sentry AWACS aircraft. The -219 is publicized as being half the cost of the competing 707 re-engine powerplant, the CFM-56, for reasons of geometrical and balance similarity to the engine it is replacing and the associated relative up-front wing modification costs of the two choices[4][3].
There have been on- and off-again discussions of using the engine for the B-52H, which is programmed for use until 2040.
[edit] Variants and applications
- JT8D-5, operating on the McDonnell Douglas DC-9-10 Aircraft
- JT8D-7, operating on the Boeing 727-100 and some 727-200 aircraft
- JT8D-9, operating on the Boeing 737-100 and 737-200, McDonnell Douglas DC-9-30 and the Sud Aviation Caravelle (10B, 10R, 11R, and 12 models only) aircraft
- JT8D-9A, which is another version of the JTD8-9, operating on the Boeing 737-100, 737-200, 727-200 and McDonnell Douglas DC-9-30 aircraft
- JT8D-11, operating on the Boeing 727-200 and McDonnell Douglas DC-9-40 aircraft
- JT8D-15, operating on the Boeing 727-200 and 737-200 aircraft, Dassault Mercure and McDonnell Douglas DC-9-30, -40 and -50 aircraft
- JT8D-17, operating on the McDonnell Douglas YC-15, Boeing 727-200 aircraft and 737-200 aircraft
- JT8D-17R & S, operating on the Boeing 727-200 Advanced aircraft and McDonnell Douglas DC-9-50 aircraft
- JT8D-209, used on some McDonnell Douglas MD-81s
- JT8D-217A/C, used to power the McDonnell Douglas MD-81/MD-82/MD-88 and MD-87
- JT8D-219, used to power the McDonnell Douglas MD-82/MD-83 and MD-88 and are being fitted to the USAF's E-8C J-STARS Aircraft
[edit] Accidents
- 22 August 1985 – British Airtours Flight 28M - an engine failed during take-off from Manchester Airport, the fire spreading into the cabin, resulting in 55 fatalities aboard the Boeing 737-236 Advanced. The uncontained engine failure was later traced to an incorrectly repaired combustor causing the turbine disc to shatter and puncture the wing fuel tanks. [1]
- 06 July 1996, An engine explosion happened on an MD-88, Delta Air Lines Flight 1288, just prior to take-off at Pensacola, Florida, U.S.A. A loose turbine blade penetrated the rear of fuselage (close to the point to where the engines are mounted), decapitating two passengers in seats 37A and 37C.
- 15 April 2008, a DC9-51 operated by Hewa Bora Airways crashed and burned at Goma following an engine fire
[edit] Specifications (JT8D-200)
General characteristics
- Type: Turbofan
- Length: 120.0 - 154.1 in
- Diameter: 49.2 in
- Dry weight: From 3200 lb (JT8D) to 4740 lb ( JT8D-219)
Components
- Compressor: Axial flow, 2-stage fan, 6-stage LP, 7-stage HP
- Turbine: 3-stage
Performance
- Maximum Thrust: 21,700 lbf
- Overall pressure ratio: 16:1
- Power-to-weight ratio:
[edit] See also
Related development
Related lists
[edit] References
- Notes
- ^ Gunston 2006, p.169.
- ^ Pratt & Whitney website, accessed 14 October 2007
- ^ a b Flug Revue, May 12, 2002
- ^ a b Re-engining the E-8 JSTARS, May 14, 2008
- Bibliography
- Gunston, Bill (1999). The Development of Piston Aero Engines, 2nd Edition. Sparkford, Somerset, England, UK: Patrick Stephens, Haynes Publishing. ISBN 0-7509-4478-1.
[edit] External links
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