Design Spec's
The JT8D is an axial flow, dual spool, low bypass ratio, fully ducted turbofan. It's specification depends on the dash model.

Take Off Thrust:
Pounds of thrust 84 deg F (28.9'C)
JT8D-7,-7A, -7B: 14,000 lbs thrust
JT8D-9, -9A: 14,500 lbs thrust
JT8D-11: 15,000 lbs thrust
JT8D-15,15A: 15,500 lbs thrust
JT8D-17,-17A: 16,000 lbs thrust
Pounds of thrust to 77 deg F (25'C)
JT8D-17R,-17AR: 16,400 / 17,400 lbs thrust (reserve take of thrust)

Bypass Ratio:
1:1 (approx.)

Total Airflow:
315 to 331 lb/sec

Compression Ratio:
LPC 4.2 to 4.4
HPC 3.8 to 4
Overall 15.8 to 17.5

Dry Weight:
3,205 to 3,500 LB

Configuration:
Full length annular duct
6 Stage front (LP) compressor including 2 fan stages
7 Stage rear (HP) compressor
Combustion section 9 combustion chambers
1 Stage front compressor drive turbine
3 Stage rear compressor drive turbine
7 Main bearings

Dimensions:
42.5 inches (Dia) 123.6 inches (length)

Direction References:
A standard directional reference makes it easy to locate components and parts of the engine. Look at the engine from the rear, left and right sides and clock angular positions. The top of the engine is referred to as the 12:00 (twelve o'clock) the bottom is 6:00.