35 votes
Accepted

Why do we refer to "power" for turboprop engines and "thrust" for turbojet/fan engines?

Ultimately what you want from all three types of engines is quantification of thrust available to push an airplane through the sky. The turbofan/jet engines are self contained and produce thrust ...
user avatar
  • 16.6k
33 votes
Accepted

Can you identify this engine?

It appears to be a Rolls Royce Viper turbo jet engine made in 1966. The maker's mark (BSB) derives from Bristol Siddeley, formed from Armstrong Siddeley (the company that originally developed the ...
user avatar
28 votes

What is the difference between turbojet and turbofan engines?

Turbojets and turbofans are very similar indeed: both are turbine engines; both create thrust from jet exhaust; and both have a rotating implement in front that can be called a fan. Although in the ...
user avatar
  • 57.8k
25 votes

What is the difference between turbojet and turbofan engines?

In a turbojet, all the air goes through the engine proper, through the combustion chamber and all the stages of compressor and post-combustion turbine blades. In a turbofan, some of the air is just ...
user avatar
24 votes

Why do we refer to "power" for turboprop engines and "thrust" for turbojet/fan engines?

Jet engines directly produce thrust by exhausting gas (and in a modern turbo fan also moving a lot of air around them), so fuel flow rate is directly related to the thrust that is generated. In a ...
user avatar
  • 96k
21 votes
Accepted

Which jet engines have the highest thermal efficiency?

Thermal efficiencies are very rarely quoted for aviation gas turbines. The metrics of interest are specific fuel consumption, and power to weight ratio. While a higher thermal efficiency will increase ...
user avatar
  • 4,353
21 votes

Are centrifugal turbojets easier to make than axial ones?

Centrifugal is easier to make. It's just a big vacuum cleaner with a kerosene burning furnace behind it instead of an electric motor. You have a one piece impeller, as opposed to numerous little ...
user avatar
  • 104k
16 votes

What is the difference between turbojet and turbofan engines?

Completely different design philosophies They are both turbine engines, and that is where the similarity ends. In a turbojet, the compressor-burner-turbine package is optimized to make thrust. A ...
user avatar
16 votes

Do jet aircraft have a better glide ratio than propeller aircraft in general? If so, why?

"Glide performance" is measured by "Lift-to-drag ratio": In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the amount of lift generated by a wing or vehicle, divided by ...
user avatar
  • 25.6k
12 votes
Accepted

Do turbine engines contain engine oil and fire-extinguishing fluid?

For turbofan engines used on passengers aircraft, oil system and fire sensor system are part of the engine. This is not the case for fire extinguishers which are manufactured by third parties and ...
user avatar
  • 67.7k
12 votes

How come a turboprop can't reach speeds as high as a turbofan?

The attributes of the incoming air for combustion matter less than how the thrust is generated. Many turbofans operate past Mach 1, but a turboprop's thrust comes practically entirely from the ...
user avatar
11 votes

Can a turbojet jet or turbofan powered aircraft land and take off from water?

Yes, they can. In service today: The Canadair CL415 is a turboprop water bomber with water landing capabilities (typically, water skimming capabilities, to skim across a lake and refill). The ...
user avatar
  • 8,567
10 votes

Why do we refer to "power" for turboprop engines and "thrust" for turbojet/fan engines?

To expand on what Dave said, the term Power is used for turboprops because the thrust produced by the prop is a function of horsepower applied to the prop, that is, torque @ RPM. The gas generator ...
user avatar
  • 104k
10 votes

Why were turbojets the first kind of turbo-engines, instead of turboprops?

Propeller planes already existed, and turboprops were an answer to a question that was not asked in times of war. The main driving factor behind development of the turbojet was to provide great ...
user avatar
  • 57.8k
9 votes

Do jet aircraft have a better glide ratio than propeller aircraft in general? If so, why?

A few reasons: if we're talking glide range from altitude, then jets certainly can glide longer! They fly MUCH higher than most props do, even turboprops! Second, propellers are draggy when they're at ...
user avatar
  • 2,414
9 votes
Accepted

Do jet fighters use Turbojet engines, and do cargo/passenger aircraft use Turbofan engines?

No Turbojets were mainly used in the Fourties and Fifties. As soon as pressure ratios had become high enough to allow adding a fan stage, turbofans replaced them. And the distinction is less between ...
user avatar
8 votes
Accepted

Why is a turbofan engine less efficient when air leaks over fan blade tips?

If it was to leak, it's still going through the intake to the compressor or bypass duct. This is incorrect. A "leak" would cause the compressed air to circle around the fan and exit again from the ...
user avatar
  • 31.5k
8 votes
Accepted

Are there cases of a thrust reverser used on a turbojet engine?

Yes. The Rolls-Royce/Snecma Olympus 593 [Wikipedia] were pure turbojets and they had thrust reversers. Source: Wikimedia Also, T/R on Concorde were also used in flight (If I remember correctly, ...
user avatar
8 votes
Accepted

Why were turbojets the first kind of turbo-engines, instead of turboprops?

The development of turboprops and jets were going on more or less concurrently before and during the initial stages of WWII -their first test runs were within years of each other. You have to ...
user avatar
  • 98.6k
8 votes
Accepted

What causes the horn-like noise during the start-up of some jet engines?

Almost all jet engines will have one or more "resonance" conditions where the combination of turbine RPM, mechanical elasticity and aeroelasticity constructively reinforces to cause ...
user avatar
  • 332
8 votes

Do jet fighters use Turbojet engines, and do cargo/passenger aircraft use Turbofan engines?

Pretty much all "jet" aircraft designed since the 1960s (if not the late 1950s) have used turbofan engines, and bypass ratios have tended to increase over that time frame, as higher bypass ...
user avatar
  • 14.3k
8 votes
Accepted

What does "time at temperature" mean in the maintenance manual of the J79 engine?

It means the time the engine has been operating at the indicated Exhaust Gas Temperature (EGT). These are limitation graphs for startup and running to prevent thermally damaging the hot section of ...
user avatar
5 votes

Why do we refer to "power" for turboprop engines and "thrust" for turbojet/fan engines?

The real reason is that, by definition, a jet engine does not output any kind of power but outputs the thrust force instead. Turbopropeller engines do not output a thrust force but rather output a ...
user avatar
5 votes

Can a gas turbine be able to switch from torque to thrust?

The main way to convert a gas turbine to provide thrust rather than shaft horsepower is to attach a large fan or propeller in place of the previous load. For example, the GE CF6, which powers aircraft ...
user avatar
  • 69.7k
5 votes
Accepted

How does an engine work when an airplane has $v=0$ on the ground?

To start the engine, the fan blades have to be spun up. This is typically handled by either blowing air through them from some outside source, and/or by using an APU to generate power to drive the ...
user avatar
  • 14.9k
5 votes
Accepted

Why is thrust available constant with speed for turbojet engines, when it varies with speed for turboprop engines?

Turboprops and turbojets - or, more broadly, jets - produce thrust in somewhat different ways. First of all, let's address the way thrust is produced. Per Newton's 2nd and 3rd laws, force equals ...
user avatar
  • 17.7k

Only top scored, non community-wiki answers of a minimum length are eligible