Free turboprop vs fixed turboprop engines

In this last video of the three-part series on propeller-driven aircraft, I explain the difference between the free turboprop and the fixed single shaft turboprop engine. We look at the schematics of both engine types, how to recognize them on the ground, how they are started, and how they are controlled by the pilot.

[edwinkorteweg]

I have been flying jet airliners for 29 years; Didn't know anything about turboprops. Now I do. Very nice explanation Phillipp. Danke vielmahls.

[felima]

This video series about gasoline, diesel and turboprop engines are by far the best I’ve ever seen. Congratulations Philipp for your great didacticism and thank you for sharing that knowledge with us.

[TIOS]

Thank you for this. I purchased a C441 with TPE331-10 and took the 5 day initial training at SimCom and never learned as much about the engines, let alone the distinction between them and the PT6 as you taught me in a 15 minute video.

[Shilgi]

Thank you Philipp for the thorough explanation, even when thinking one knows everything there’s always something to learn.

[icepdb]

Thank you for the info. If I recall correctly, in CASA C212 aircrafts that uses Garret (now Allied Signal) engines when the emergency shutoff is used the propeller will be to feather condition. And the pilot use the un-feathering pump to get them to plate before startup.

[shannonwittman]

Excellent explanation! I'm not a pilot but am fascinated by the different ways that all internal combustion powerplants operate, converting fuel to usable energy. I personally think that small efficient turboprop engines will eventually replace piston engines in private airplanes; mostly for their increased reliability, lighter weight and fewer moving parts. I can't tell what might be the differences in exhaust emissions.
I did not know there were these two different turboprop engines. Now I will be able to recognize which type of turboprop on an airplane, especially on its startup. Perhaps also the frontal exhaust stacks on a free turboprop?
I wonder if a fixed turboprop engine will exhibit a torque effect, whereas the free turboprop might not -- or perhaps not as pronounced?

[pareagles]

Thanks for a great video. I've learned so much from you!

[Hoekstes]

Very interesting, can’t wait for the new King Air. Did you see the video about Austin’s comments on the G1000?

[joebloggs]

Thank you for this series. Any chance you could do Part 4: Turbojet?

[ndenise]

Unless you have start locks(seaplane) on the PT6. WRT efficiency any time there is a change in state of energy there are losses.

[duncanm]

Do turbofans on airliners make use of a turbine to drive te larger ducted fan or shaft power from the gas producing section?

[diegobeatrice]

Hi, great explanation! One question from a jet jockey with no experience on turboprops but always fascinated by them! If I understood it correctly while operating in the beta range, the torque maintained at a constant value - either low or high idle based on the setting of the condition lever in a free turbine engine, and u vary the thrust by varying the pitch angle on the blades so that is for instance you move the PL forward you increase the blade angle first increasing the mass of airflow accelerated backwards and thus as a reaction the thrust that propels the aircraft forward, and then the HMU - i assume a sort of bottom governor - increases the ff to the engine to compensate for the increase in the required torque to maintain constant value - low or high idle - to drive the prop and the accessories on the AGB and the RGB, like the generator, for instance; and vice-versa. Also my question is, why do u need a beta range while on the ground? can t u operate the prop and the engine in a normal way as when in the forward thrust regime? Thanks for sharing

[sherwinsalvatori]

The free turbine is techically a 2 spool turbine much like a turbofan

[cristoballozano]

Thanks for the video, its great. I have a question...for all variable pitch prop aircraft, you need to adjust different configurations for MAP (InHg) and prop RPM (piston engine), or Torque or HP, Prop RPM, and engine RPM (in the case of a free engine, in a fixed one i think you would only have an RPM gauge for the engine) am i right? Well, are those values unique for each airplane and in real life pilots memorize each configuration for taxi, TO, climb, cruise, descent, and approach?(I also know that those can change with factors like PA and the range you want to reach, etc, and you will have options to choose in AIM for different flight conditions.) But in general, are those specific configurations you need to always follow? Or are there standard configurations that a pilot can use to correctly fly an airplane without choosing one of the manual options? Im interested in learn how to correctly operate engines and props with different airplanes in Xplane 11, but im not sure if i could do that without specific AIM knowledge for each airplane. Thanks a lot

[aeronauticgeek]

Sir, can you tell me what happens if there is no reduction gearbox ?

[tafaragadze]

Now which is more efficient?
Which is more fuel efficient?
Which is more responsive?

[JaymzSim]

So, in the free turboprop model, there are no planetary reduction gears?

[mizzyroro]

Why are fixed turboprop engines so noisy such as the Rolls Royce Dart and the Garrett TPE?

[gokmen]

Poor explanation but thank you for your effort.