The BEST TURBOPROP explanation video! By Captain Joe and PRATT & WHITNEY

Summary

In this engaging video, Captain Joe delves into the intricacies of the Pratt and Whitney PT6 turboprop engine, renowned for its reliability and power. He explains its unique reverse-flow design, the 'suck, squeeze, bang, blow' principle, and how it differs from standard jet engines. From the cold section's compressor stages to the hot section's combustion and turbine mechanisms, the video offers a detailed look at the PT6's operation. Highlighting its free turbine feature, which aids in handling high torque, Joe also touches on maintenance benefits and the PT6E series' advanced electronic controls, showcasing the engine's enduring legacy in aviation.

Takeaways

• 😀 The Pratt and Whitney PT6 turboprop engine is renowned for its reliability, power, advancement, and widespread sales in its class.
• 🔧 The PT6 operates on a reverse flow free turbine design, which is unique compared to standard jet engines.
• 🌀 It follows the 'suck, squeeze, bang, blow' principle, but unlike jet engines, it lacks a bypass, relying solely on exhaust gases to turn the propeller.
• 🌪️ The engine intakes air from the back, with a low-pressure axial compressor followed by a centrifugal compressor that significantly increases air pressure and temperature.
• 🔥 In the combustion chamber, 14 fuel nozzles inject jet fuel, which ignites and expands, driving the compressor turbine and the gas generator.
• 🔄 The PT6 features a free turbine design where the power turbine spins independently and in the opposite direction of the compressor turbine, which helps manage torque.
• ⚙️ The power turbine transfers energy to the propeller through a reduction gearbox, allowing for large propellers at slower, more efficient speeds.
• 🛫 The PT6's compact design, short power shaft, and counter-rotating elements contribute to a lighter structure with fewer vibration issues, making it ideal for rough runways.
• 🔧 Maintenance is facilitated by the independent shafts, allowing for easy access to the gas generator section when the power section is removed.
• 🌟 The latest PT6E-66XT model introduces a dual-channel integrated electronic propeller and engine control system, enhancing precision, performance, and efficiency.
• 🚁 The PT6 engine is trusted to power a wide range of aircraft, including planes, helicopters, and other vehicles, as evidenced by the extensive list provided in the video.

Q & A

What is the main topic of the video?

The main topic of the video is an explanation of how the Pratt and Whitney PT6 turboprop engine works, its unique features, and its relevance in the aviation industry.

What makes the PT6 engine unique among other gas turbine engines?

The PT6 engine is unique as it is a reverse flow free turbine turboprop engine, which means it operates from back to front, unlike standard jet engines, and it does not have a bypass compared to airliner engines.

How does the PT6 engine's cold section function?

The cold section of the PT6 engine functions by sucking in outside air through the inlet duct, directing it towards the compressor, and then through a series of low-pressure axial compressor stages and stator blades to increase air pressure and temperature.

What is the role of the centrifugal compressor in the PT6 engine?

The centrifugal compressor in the PT6 engine further increases the air pressure and temperature after the air has passed through the axial compressor stages, acting similarly to a turbocharger's spin wheel in a car.

How does the combustion process in the PT6 engine differ from a typical car engine?

In the PT6 engine, the combustion process is continuous from engine start until shutdown, and it does not use spark plugs. Instead, it relies on hot compressed air to self-ignite the fuel-air mixture, with spark igniters assisting during cold engine starts.

What is the purpose of the power turbine in the PT6 engine?

The power turbine in the PT6 engine converts the kinetic energy from the exhaust gases into mechanical power, which then turns the power shaft at a high speed, ultimately driving the propeller through a reduction gearbox.

Why is the PT6 engine considered easy to start, especially in cold weather?

The PT6 engine is easy to start because it has a free turbine design, meaning the power turbine shaft spins freely and is not connected to the gas turbine shaft. This allows the starter to only accelerate the gas generator during startup.

What is the significance of the accessory gearbox in the PT6 engine?

The accessory gearbox in the PT6 engine is significant as it reduces the high RPM from the gas generator shaft to a lower speed suitable for running mounted accessories such as the fuel control unit and other systems.

How does the PT6 engine's free turbine design benefit maintenance?

The free turbine design allows for the entire power section, including the propeller, to be removed for easier access to the gas generator section, simplifying maintenance procedures.

What is the PT6E series engine's new feature in general aviation?

The PT6E series engine introduces a dual-channel integrated electronic propeller and engine control system, a first in general aviation, enhancing precision, performance, and efficiency.

Why is the PT6 engine suitable for rough runway surfaces?

The PT6 engine is suitable for rough runway surfaces because its reverse flow design allows foreign objects to be diverted by inertial separators in the inlet, making it ideal for bush planes that often land on uneven terrain.

Outlines

00:00

🚁 Introduction to the PT6 Turboprop Engine

The video script introduces viewers to the Pratt and Whitney PT6 turboprop engine at the EAA Air Venture in Oshkosh. It promises an explanation of the engine's workings, its uniqueness, and a connection to Dom Toretto's Dodge Charger from The Fast and the Furious. The PT6 is highlighted as a reliable, powerful, and advanced engine, with a focus on its reverse flow free turbine design, which differs from standard jet engines by propelling air from back to front. The script sets the stage for a detailed exploration of the engine's components and functions.

05:01

🔧 Inside the PT6 Engine: Components and Functions

This paragraph delves into the technical aspects of the PT6 engine, detailing its components and their functions. The engine operates on the principle of 'suck, squeeze, bang, blow' but without a bypass, unlike standard jet engines. The unique reverse flow design is emphasized, with air intake from the rear and propulsion via exhaust gases. The cold section includes the low-pressure axial compressor and a centrifugal compressor, which significantly increase air pressure and temperature. The hot section involves combustion with 14 fuel nozzles and a continuous process from startup to shutdown, facilitated by spark igniters during cold starts. The gas generator, consisting of the compressor, combustion chamber, and turbine, is described, along with the power turbine and its role in converting air speed into mechanical power through a reduction gearbox, suitable for large propellers.

10:03

🛫 The Advantages of the PT6's Free Turbine Reverse Flow Design

The final paragraph of the script discusses the advantages of the PT6 engine's free turbine reverse flow design. It explains how the counter-rotation of the power turbine helps manage torque forces, especially during high power changes, preventing potential issues like flipping over an aircraft. The design contributes to a shorter and lighter engine, ideal for rough runway surfaces and easy maintenance. The script also mentions the accessory gearbox, fuel control unit, and the electronic propeller and engine control system introduced in the latest PT6E series. The video concludes by listing various aircraft that utilize the PT6 engine, emphasizing its widespread trust and reliability in the aviation industry.

Keywords

💡EAA Air Venture

EAA Air Venture is an annual event held in Oshkosh, Wisconsin, known as 'The World's Greatest Aviation Celebration.' It is a gathering of aviation enthusiasts and professionals, featuring aircraft displays, forums, and workshops. In the video's context, it serves as the backdrop for the discussion on the Pratt and Whitney PT6 engine, highlighting the event's significance in the aviation community.

💡Pratt and Whitney

Pratt and Whitney is a renowned aerospace manufacturer specializing in aircraft engines and auxiliary power units. The company is a key player in the aviation industry, known for its innovative and reliable engines. In the video, Pratt and Whitney is the sponsor and the manufacturer of the PT6 engine, which is the main subject of the discussion.

💡PT6 Engine

The PT6 engine is a family of turboprop engines produced by Pratt and Whitney Canada. It is widely recognized for its reliability, power, and advanced technology. The video provides an in-depth explanation of how the PT6 engine works, emphasizing its unique design and its status as one of the most sold engines in its class.

💡Reverse Flow

In the context of the PT6 engine, 'reverse flow' refers to the unique design where air intake and exhaust are reversed compared to traditional gas turbine engines. This design allows the PT6 to be more compact and efficient. The video explains how this feature contributes to the engine's performance and reliability.

💡Free Turbine

A 'free turbine' is a type of turboprop engine configuration where the power turbine is not mechanically linked to the gas generator. This allows for independent operation and better control of the engine. The video describes how the PT6 engine benefits from this design, particularly in terms of torque management and maintenance.

💡Gas Turbine Engine

A gas turbine engine is a type of internal combustion engine that uses a gas turbine to develop work. It operates on the 'suck, squeeze, bang, blow' principle, which is explained in the video. The PT6 engine, while following this principle, has its unique aspects that set it apart from standard jet engines.

💡Axial Compressor

An axial compressor is a device that increases the pressure of a gas through the use of an axial-flow principle. In the PT6 engine, the axial compressor is part of the cold section and is responsible for compressing the air before it enters the combustion chamber. The video details the stages of the axial compressor and its role in the engine's operation.

💡Centrifugal Compressor

A centrifugal compressor is a type of dynamic compressor that uses the centrifugal force to increase the pressure of the gas. In the PT6 engine, the centrifugal compressor is a single stage that further compresses the air after it has passed through the axial compressor stages. The video describes its function and how it contributes to the engine's efficiency.

💡Combustion Chamber

The combustion chamber is where the fuel-air mixture is ignited to produce high-pressure, high-temperature gases that drive the turbine. In the PT6 engine, the combustion chamber is part of the hot section, and the video explains how the continuous combustion process works and its significance in the engine's operation.

💡Torque

Torque, in the context of engines, refers to the rotational force that can cause a change in the rotational speed of the engine's components. The video discusses how the PT6 engine's design helps manage the high torque, especially during power changes, to prevent potential issues like flipping over an aircraft.

💡Reduction Gearbox

A reduction gearbox is a mechanical device that reduces the speed of rotation from the engine to a more suitable speed for the propeller. In the PT6 engine, the reduction gearbox is crucial for matching the high-speed output of the power turbine to the optimal propeller speed. The video explains the reduction ratio and its importance in the engine's performance.

💡Propeller

A propeller is a device with a rotating axis that is used to convert rotary motion into thrust. In the video, the propeller is discussed in relation to the PT6 engine's ability to drive large propellers, which is facilitated by the reduction gearbox. The propeller's size and the torque it can handle are highlighted as key features of the engine's capabilities.

💡Gas Generator

The gas generator is the core part of a gas turbine engine, which includes the compressor, combustion chamber, and turbine. It is responsible for generating the high-energy gas flow that drives the engine. The video explains how the gas generator in the PT6 engine operates and its importance in the overall engine design.

💡Jet Fuel

Jet fuel is a type of aviation fuel designed for gas turbine engines. In the video, the role of jet fuel in the PT6 engine's combustion process is discussed, highlighting how it is injected into the combustion chamber and ignites to produce the energy needed to drive the engine.

💡Shaft Horsepower

Shaft horsepower is a unit of measurement for the power delivered by a rotating shaft. The PT6 engine is noted for its range of output power, from 550 to 1700 shaft horsepower, as mentioned in the video. This wide range makes the engine suitable for various types of aircraft and applications.

Highlights

Introduction to the Pratt and Whitney PT6 turbo engine as one of the most reliable, powerful, advanced, and widely sold engines in its class.

Explanation of the unique reverse flow free turbine turbo prop engine design of the PT6.

The PT6 engine's operation principle following 'suck, squeeze, bang, blow' without a bypass, unlike standard jet engines.

Description of the PT6's cold section, including the air intake and low-pressure axial compressor stages.

Details on the centrifugal compressor and its function in heating and pressurizing air to 300 degrees Celsius and 10 bar.

The combustion process in the PT6 engine involving 14 fuel nozzles and controlled, vectored combustion.

How the high-pressure compressor turbine drives the compressor stages at 39,000 RPM.

The energy transfer from hot gas to the compressor turbine and then to the power turbine in the PT6 engine.

The function of the power turbine and its role in converting air speed into mechanical power for the propeller.

The significance of the reduction gearbox in adjusting the power shaft's speed to drive the propeller effectively.

The free turbine design allowing the power turbine to spin independently from the gas generator for better torque management.

Advantages of the PT6's reverse flow design, including a shorter engine length and reduced vibrations.

How the PT6 engine's design makes it suitable for rough runway surfaces and easy maintenance.

Introduction of the PT6E series and its dual-channel integrated electronic propeller and engine control system.

The PT6 engine's broad application in various aircraft, helicopters, and vehicles, emphasizing its reliability.

A summary of the PT6 turboprop engine's components, features, and its status as an iconic engine in the aviation industry.

Closing remarks with a thank you to Pratt & Whitney and a call to action for viewers to engage with the channel.

Transcripts

dear friends and followers welcome back

to my channel and lovely greetings from

the EAA Air Venture here in Oshkosh at

the Pratt and Whitney booth in today's

video we'll be talking about one of the

most reliable most powerful most

advanced and most sold engine in its

class the Pratt and Whitney pt6 turbo

engine I'll explain how the engine works

why it's so unique and what Dom

toretto's Dodge Charger from The Fast

and Furious movie has to do with it

clear probe and let's get started

today's video is brought to you by Pratt

Whitney powering sustainable Aviation

with Dependable engines let's first get

a fundamental understanding of the pt6

engine now the pt6 works like most other

gas turbine engine but is in one aspect

uniquely different as it is a reverse

flow free turbine turbo prop engine what

that means you'll see in a minute as

I'll mention each section individually

now it follows the same principle of

suck squeeze bang blow but the pt6 does

not have a bypass compared to the

standard jet engine on an airliner which

makes up more than 80 percent of the

forward pushing thrust now within the

pt6 it's only the exhaust gases that

make the propeller turn and instead of

pushing the air through the engine from

front to back the pt6 does it from back

to front so we're not starting thing

here instead we have to start at the

back of the engine right here so

initially the outside air gets sucked in

via the inlet duct which on many pt6

driven planes you see below the

propeller now the air is directed below

the engine towards the inlet screen

where the steel mesh protects the engine

from large debris entering so in this

part known as the cold section the

outside air gets sucked in and then

directed towards the compressor now the

first part is the low pressure axle

compressor which comprises three stages

for the small pt6 engines or four stages

for the larger pt6 engines but why low

pressure now very basically speaking the

inlet sucks in the outside air more or

less like a powerful vacuum cleaner the

first stage has the largest compressor

blades which accelerate the air or put

kinetic energy into it and right after

the rotary blades are a set of stator

veins meaning they are stationary or

fixed in place and Aid in increasing the

air pressure this accelerating and

increasing of air pressure process

repeats itself two or three more times

as the air gets forced further inwards

now at the same time the diameter

Narrows with each axial compressor stage

each followed by a set of stator blades

now to give you a perspective the air

entered at let's say 15 degrees Celsius

at the inlet with one bar outside

pressure and once it passed through the

first four compressor stages the air got

heated to 180 degrees Celsius and

increased to 4 Bar in air pressure

think of your bicycle pump remember how

warm it gets as you pump air into your

tires after the last set of stator veins

the heated compressed and accelerated

air enters the single stage centrifugal

compressor now compare this to the spin

wheel of the turbocharger in your car if

you don't have a Turbocharger in your

car this is what it looks like now at

this point the air has a temperature of

approximately 300 degrees Celsius and a

pressure of roughly 10 bar that means it

went in with one bar at the inlet and

forcing it through a compressor which is

not longer than 30 centimeters the

pressure is 10 times higher now the

already relatively hot and compressed

air then gets guided around this Bend

via a pipe diffuser which makes sense

because initially the flow Direction was

parallel along the compressor shaft then

the centrifugal compressor changed its

direction by 90 degrees to the shaft and

after the diffuser it is yet again

parallel as it enters the combustion

chamber liner so this completes the end

of the Cold section OD compressor stage

we've sucked in the air squeezed it

together and now the air enters the hot

section as the air exits the diffuser

and enters the combustion chamber liner

it passes by the 14 fuel nozzles which

inject jet fuel into the combustion

chamber now the fuel air mixture then

ignites instantly which leads to a

controlled and vectored combustion

meaning the hot expanding gases are

confined in the combustion chamber and

want to vacate the chamber as quickly as

possible it is then guide around this

Bend so briefly into the opposite

direction it came from and then flows

directly onto the high pressure

compressor turbine so this is a single

stage axial flow turbine and as you can

clearly see here the turbine is the

driving force of the compressor stages

as they are both mounted on the same

shaft spinning at approximately 39 000

revolutions per minute or 650 rounds per

second so the three components I just

mentioned the compressor the combustion

chamber and the compressor turbine

complete the gas generator does that

make sense now two more things I need to

mention in regards to the combustion

chamber the combustion of the fuel air

mixture is continuous from the engine

start until shutdown meaning because of

the hot compressed air entering the

combustion chamber it will also

self-ignite the mixture as long as fuel

flow is given also there are no spark

plugs as you would have in your car to

ignite the fuel air mixture but during

engine start you can hear that Infamous

clicking sound those are a set of spark

igniters on both sides of the combustion

chamber assisting the engine's startup

when the core is still relatively cold

on to the next stage so we can estimate

that a little more than half of the

energy from the hot gas exiting the

combustion chamber was absorbed or used

to spin the compressor turbine now the

remaining Gas Energy is then guided into

the power turbine the gas passes yet

again a set of stator veins which

accelerate the gas velocity and then

hits the first axial power turbine very

simply speaking think of a hair dryer

being the gas generator blowing onto a

windmill which is our power turbine that

converts air speed into kinetic or

mechanical Power the extracted energy

from the gas stream then turns the power

shaft and Spins it up to 33 000

revolutions per minute the exhaust gases

then Escape through these two side

mounted ducts in the power turbine

housing which are somewhat of the

signature of the pt6 engine letting

other Pilots know what this plane is

powered by so now we have 33 000

revolutions per minute which is way too

fast to drive a propeller now instead

the power shaft is then connected to a

two-stage planetary output reduction

gearbox which turns the propeller at a

speed of 1700 to 2200 revolutions per

minute outputting a reduction ratio of

approximately 15 to 1 which allows for

the largest propellers within the

general aviation industry to be mounted

for example the Pilates Porter comes

with a 2.7 meters in diameter propeller

and at 1700 pounds of torque so the

power turbine blades the power turbine

shaft and the reduction gearbox make up

the power section of the pt6 an

important note I mentioned at the

beginning that it's a free turbine what

is meant by that now if you haven't

noticed it yet the power turbine turns

in the opposite direction of the

compressor turbine why is that if you

look closely in between the first axial

power turbine and the compressor turbine

you'll notice they are not connected

with each other meaning the power

turbine shaft spins freely and is not

connected with the gas turbine shaft yet

again think of a hairdryer blowing onto

a windmill now the counter rotation also

serves its purpose remember when Dom

Toretto revved the engine of his tuned

up Dodge Charger now the immense torque

nearly bent the frame of his car so

during excessive power changes for

instance during takeoff and go around

the excess torque could if the power

turbine the gas generator and the

propeller would all spin in the same

direction potentially flip over your

plane and all pilots flying the pt6

engine in a single-engine aircraft know

how strong the torque forces still are

despite the counter rotation

but there are some great advantages that

come with the free turbine reverse flow

turbo prop engine design the overall

length of only 1.8 meters of the power

unit is relatively short compared to

others and keep in mind the pt6 and

various models can output from 550 up to

1700 shaft horsepower the reverse flow

also allows for a shorter power shaft

resulting in a lighter structure and

fewer vibration problems and due to the

fact that a compressor intake is at the

back of the engine foreign objects can

be diverted by inertial separators in

the inlet making the engine ideal for

rough Runway surfaces hence the Cessna

Caravan or the Pilates Porter which are

well known as Bush planes because they

hardly ever land on a Tarmac Runway also

the three turbine allows for both shafts

to run at different speeds and during

engine startup the starter has to

accelerate only the gas generator making

the engine easy to start particularly in

cold weather also because both shafts

are independent it aids in maintenance

by allowing the entire power section to

be removed along with the propeller

exposing the gas generator section for

easier access okay now that we've spoken

about the main engine components I would

like to direct your attention to the

rear and front part of the engine at the

rear part we have the accessory gearbox

directly connected to the gas generator

shaft reducing 39 000 RPM to as low as

4000 RPM to run the mounted accessories

for instance the fuel control unit which

controls the amount of fuel needed in

accordance with the thrust and propeller

lever position right in front of that is

the high pressure fuel pump bringing up

the necessary pressure for the fuel

nozzles on the other side we have two

scavenge oil pumps responsible for

proper lubrication of the reduction

gearbox both shafts and the accessory

gearbox and the large thing here is the

starter and Generator which is connected

to the airplane's battery and then spins

up the gas generator for engine start

and then acts as an electric power

generator once the engine is running

then at the front we have the propeller

interface unit which respectively

controls the propellers RPM now here we

have a glimpse of the Pratt and

Whitney's latest

p26e66x T engine model it's part of the

pt6e series engine family the first to

offer a dual Channel integrated

electronic propeller and engine control

system in general aviation in summary it

has all the trusted components that have

made the pt6 the iconic engine it is

today plus many new features for the

optimal combination of precision

performance and efficiency and lastly

this is a list of planes helicopters and

other vehicles that trust the power and

reliability of this engine and as you

can see this is long and growing and

this sums up my explanation of how the

pt6 turbo pulp engine works I really

hope you enjoyed this video and got a

few takeaways from this incredible

engine a huge thank you to Pratt Whitney

and their team here at the standard

Oshkosh for allowing us to record this

video and on that bombshell here's your

checklist for today subscribe to my

channel and check activate the

notification Bell check follow my

Instagram account check and perform a

touch and go at my website check and

don't forget a good pilot is always

learning especially at the air Venture

here in oscos wishing you all the best

your Captain Joe

[Music]

thank you