KCLE
Posts: 673
Joined: Fri Feb 23, 2001 11:03 am

What's The Deal With The JT8D?

Sat Jun 02, 2001 9:25 am

While spotting at CLE, a person will see many MD-80s in a short amount of time, so, there are a lot of JT8D turbofans here. While taxiing, i noticed the engines' main intake turbines weren't moving. Why is this, and do these main intake turbines ever turn?
 
wilcharl
Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: What's The Deal With The JT8D?

Sat Jun 02, 2001 10:42 am

Those "turbines" are the inlet guide vanes. The turbine section is located aft of the combusters. There was talk of this earlier. If you ever want to freak out a pax on a DC-9 tell them the airline has decided to institute fuel saving measures by shuting the engines off during the decent and gliding in, if he doesnt believe you tell him to look @ the engine, they will look out the window and see the IGV's and freak out.  Smile
 
Monocleman
Posts: 133
Joined: Fri Apr 27, 2001 10:21 am

RE: What's The Deal With The JT8D?

Sat Jun 02, 2001 11:32 am

Can you really see the engines from the cabin? In a 737 last row you can see the very tip of the horizontal stabilizer if you try but I thought the engines were located too far aft to see them.
-Will
 
wilcharl
Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: What's The Deal With The JT8D?

Sat Jun 02, 2001 11:36 am

yeah the last row of a DC-9 you get a view of nothing, just forward of that you get a ncie view of the cowling, if you sit in row about 25(on an FL DC-9) you can get a nice view of the engine. whats great is a night flight on a 717 when the strobes fire you can look back and see the live fan of the BR-715
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: What's The Deal With The JT8D?

Sat Jun 02, 2001 10:51 pm

Just a clarification.

In simplistic terms, the "turbines" are downstream of the combustion chamber of the engine. They extract power to run the compressor and/or propeller or fan (if applicable) at the other end of the engine. In jet engines the turbines are at the rear and the compressor is at the front. Not always the case with turboprop engines like the PT-6 where the air flow starts at the rear of the engines and ends at the exhaust stacks at the front of the engine.

Guide vanes are usually incorporated thoughout the engine to optimize the direction of the air to allow the proper angle over the compressor and turbine blades which are really small airfoils. The engine is optimized usually at one critical power setting.

Many modern jet engines utilize variable guide vanes to allow optimization at several power settings.

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