tag:blogger.com,1999:blog-10000144.post111869641958168091..comments2024-03-13T09:47:40.487+00:00Comments on Cockpit Conversation: Burning HeartsAviatrixhttp://www.blogger.com/profile/13634111275860140084noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-10000144.post-1310575744957408982015-03-08T18:27:51.200+00:002015-03-08T18:27:51.200+00:00For more info on the concept of the PT-6 or revers...For more info on the concept of the PT-6 or reverse flow (from the above description), contact me.Moosehttps://www.blogger.com/profile/14208762341622466246noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-247347256751710302015-03-08T18:25:53.581+00:002015-03-08T18:25:53.581+00:00Free Turbine - Understand that the term "Free...Free Turbine - Understand that the term "Free Turbine" has nothing to do with where the air goes in and comes out of the engine. On the normal "tractor" aircraft application (Cessna Conquest and Beech King Air), the engine ingests air at the rear and expels it at the front but when the PT6 is turned 180* and mounted pusher style on the Piaggio Avanti or the Beech Starship it now takes in it's airflow in the "front" and exhausts out the "rear" but it's still a "reverse flow" engine.<br />Reverse flow is the internal airflow. Compressed air from the centrifugal flow compressor makes a 180* turn (after the diffuser tubes) to enter the annular combustion chamber. Leaving the combustion chamber, the heated, expanding, airflow makes a second 180* turn before coming to bear on the compressor turbine and then quickly the stators and power turbines as the airflow cools, expands and slows.<br />The "reverse flow" concept was used in many, many of the early jet engines and is still prevalent in smaller engines today. This design concept makes the engine shorter and consequently, weighs less. The traditional turbojet engine like the J79 (F-4) and the J85 (T-38) use only axial flow engines (no centrifugal compressor) and are slim but longer.Moosehttps://www.blogger.com/profile/14208762341622466246noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1164337716140488772007-06-14T03:20:00.000+00:002007-06-14T03:20:00.000+00:00Thanks for your explanation. I've just started stu...Thanks for your explanation. I've just started studying about PT-6 and you answered all of my questions!Unknownhttps://www.blogger.com/profile/18272994316226704786noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1118853877440573052005-06-15T16:44:00.000+00:002005-06-15T16:44:00.000+00:00Nice description. The odd nature of turboprop eng...Nice description. The odd nature of turboprop engines makes them a mystery to most non-pilots, and I can't tell you how many people have said, "Get outa here" when I told them the engines operate in reverse flow.<BR/><BR/>You're right, I'll figure out the aircraft type as we go along, if I haven't already :)Scott Johnsonhttps://www.blogger.com/profile/18076313660049246875noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1118806469903404282005-06-15T03:34:00.000+00:002005-06-15T03:34:00.000+00:00Thanks. I guess all the PT6-powered planes I've se...Thanks. I guess all the PT6-powered planes I've seen have curved exhaust tubes pointing towards the rear; I just assumed maybe some models didn't use them...Jimmy Littlehttps://www.blogger.com/profile/00700283384274714344noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1118783576704741922005-06-14T21:12:00.000+00:002005-06-14T21:12:00.000+00:00Cool, you really did ask questions!Andy: It takes ...Cool, you really did ask questions!<BR/><BR/>Andy: It takes a lot of power to turn a turbine, whether that turbine is compressing air or propelling the airplane. If there were a better way to turn the compressor turbines, then the whole engine would be powered that way. The energy spent in turning the compressor is recouped many times through the advantage of burning compressed air and not ambient pressure air.<BR/><BR/>Going backwards and braking is a function of the propellers, not the engine, so we'll get there later.<BR/><BR/>Jimmy: I remember thinking that myself when I first learned about the airplane, and just accepting it. The diagram does make it look like the exhaust just shoots out the side. There is actually a scooplike exhaust stack that directs the gas towards the rear, stubbier on the older models and longer on the newer ones. I don't know if there are baffles in it or not. There's kind of a grille at the open end, but that may be just to prevent birds from nesting inside.Aviatrixhttps://www.blogger.com/profile/13634111275860140084noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1118782178889547212005-06-14T20:49:00.000+00:002005-06-14T20:49:00.000+00:00"The exhaust is still directed backwards, though a..."The exhaust is still directed backwards, though and its discharge adds an extra twenty-nine horsepower of thrust to the engine output."<BR/><BR/>OK, I'm little slow, but your diagram makes it look like the exhaust goes out sideways at best. How does this exhaust add to the thrust, or was the diagram only an artist's impression? Are there interesting little baffles and such in the exhaust thingies (technical term)?<BR/><BR/>JL (who always wanted to be an aero engineer but ended up a photographer instead...)Jimmy Littlehttps://www.blogger.com/profile/00700283384274714344noreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1118779934218504232005-06-14T20:12:00.000+00:002005-06-14T20:12:00.000+00:00That is so cool.~JefThat is so cool.<BR/>~JefAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-10000144.post-1118778728975524402005-06-14T19:52:00.000+00:002005-06-14T19:52:00.000+00:00"About two thirds of the power generated by the en..."About two thirds of the power generated by the engine goes right back into turning those compressors".<BR/>Isn't that really inefficient? And how do you make it go backwards (ie brake)?<BR/>I think your essays are really helpful (if you want to be a north American pilot). Perhaps you ought to publish?Anonymousnoreply@blogger.com