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54 votes

Which manufacturer produced this fan blade?

GE Aviation Clue 1. Parts designed at the Lynn MA plant have part numbers of the form xxxxTxxPxx, where x is a digit. 4922T12P01 fits that pattern. The gr.in is another clue. That refers to a ...
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  • 5,258
38 votes
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Why does each fan blade have a different mass and frequency?

Because manufacturing processes are not perfect, and the minute differences between parts as-designed and as-produced are amplified by the high rotational speeds and large diameters of modern jet ...
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33 votes

Can you identify this jet turbine stage?

What is this turbine part? This assembly is part of the turbine used to rotate the compressor section of a Pratt & Whitney PT6, a free turbine turboprop. It's known as compressor turbine or just ...
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28 votes
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Why are the fan blades mounted loosely?

The blades are loose in their "Fir Tree" blade mounts so that they can self balance. They are called "fir tree" because they are v shaped. As the rotation speed and centrifugal force increases, ...
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  • 32.4k
28 votes

Which manufacturer produced this fan blade?

That looks very much like a TF-34 fan blade. The TF-34 is used on the A-10 Thunderbolt and S-3B Viking. The root style is known as "pinned" or "clevis". You can see a blade being pinned into the rotor ...
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  • 3,711
25 votes

Why are aircraft turbine blades made of nickel alloys?

Not all turbine blades are made of nickel alloy, some blades are made of such family of alloys but clearly not all. Some blades are actually made of ceramic materials. The turbine is always located ...
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24 votes

In helicopters, why not have electric motors controlling blade pitch?

How would you communicate with (and power) these motors? The main rotor is spinning constantly - Wires won't work, they would wrap around the shaft and be shredded. A slip ring and brushes (as used ...
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  • 67.4k
21 votes

Why are the fan blades mounted loosely?

I's like to expand the answers on how this could reduce vibrations, as it was mentioned in a comment. Therefore, I'd like to look at something completely different: When computers were equipped with ...
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  • 7,157
16 votes

Is possible to stick two '2-blade' propellers to get multi-blade propeller?

Sure, this is not only possible, but even has some advantages over single-plane propellers. The catch is you ideally want the two to spin in opposite directions to cancel out torque and vibration. You'...
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  • 11k
16 votes

What are those ball-shaped things on some helicopter blades?

The devices are pendulum (or pendular) absorbers: Vibration suppression of helicopter blades by pendulum absorbers - Imao Nagasaka. The pendulum absorbers are used for suppressing the vibrations in ...
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  • 21.6k
15 votes

Why are the fan blades mounted loosely?

There are a few reasons for assembling the blades loosely in the gas turbine engine. The loose attachment of the fan blades allow for the easy installation/removal of the fan blades. Though the ...
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  • 98.7k
15 votes

In helicopters, why not have electric motors controlling blade pitch?

Because it would be too complicated (and failure prone) compared to the present system and would offer no great advantages. First, for all the complexity in the helicopter upper controls, the ...
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  • 98.7k
15 votes
Accepted

What are the design principles that result in thin, long-span, narrow chord main rotor blades?

Unlike with fixed-wing aircraft, there are very few structural limitations on the planform of helicopter blades. Pic above was used in this answer and shows the centrifugal force acting on the blades....
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  • 58.8k
14 votes

Why are aircraft turbine blades made of nickel alloys?

Their main advantage is higher strength at elevated temperatures. With elevated I mean temperatures up to 1200°C, which is what you will find in modern, film-cooled high-performance turbines where the ...
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13 votes

What engine are these fan blades from?

Turbine Blade The turbine blade (part number 1475M35P01) is from the High Pressure Turbine (HPT) a CFM56-3 according to this ATSB report on performance testing of the engine. The report contains ...
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12 votes

In helicopters, why not have electric motors controlling blade pitch?

I went on a little search on my university library database, and found a review paper. I'm not sure if you can access it without paying. Active rotor control for helicopters: individual blade control ...
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  • 12.1k
12 votes

Why does each fan blade have a different mass and frequency?

There are advantages in the blades not being "perfectly identical". If all the vibration frequencies were exactly the same, when the blades were assembled to make the complete fan the vibrations would ...
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  • 2,985
12 votes

Is possible to stick two '2-blade' propellers to get multi-blade propeller?

It's done sometimes, for ultralight aircraft and paramotors. Like this:
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  • 10.4k
11 votes
Accepted

Are engine casings expected to contain turbofan blade fragments?

We don't yet know how or why the engine casing failed to contain the fan blade on Southwest 1380. But yes: Not only are the engines designed to contain blade failures at fan red-line speeds, but they ...
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  • 2,134
11 votes

What causes ram air turbines with more blades to spin slower than turbines with two blades?

The windmilling prop extracts energy from the mass flow through the propeller disk area. An 8-bladed prop can extract more energy from the mass flow, and does this at lower RPM than the 2-bladed prop. ...
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  • 58.8k
9 votes
Accepted

Do fan blades use bell shaped lift distribution curves?

The bell shaped lift distribution has been used on the Horten flying wings in order to reduce lift at the outer, rearward parts of the wing for stability and better controllability. The fan blade of ...
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8 votes
Accepted

What would happen if the blades of a variable pitch prop did not all have the same pitch?

Never say never, but that's not a prop malfunction that I've heard of or that was ever addressed in the turboprops that I've flown. We had various prop malfunctions, but the ways that things could ...
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  • 42.2k
8 votes

What engine are these fan blades from?

The part number on the turbine blade shows it comes from a CFM56-3 series (Boeing 737 classic). No hits on the compressor blade, but it looks similar to one from the same engine.
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  • 5,687
7 votes

Why don't helicopters prefer shorter rotors with more blades?

The rotor works by accelerating air downwards, therefore creating an upward reaction force on the blades that lifts the craft. The lift force is equal to $$L = \dot{m}\Delta v$$ where $\dot{m}$ is ...
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  • 54.2k
7 votes
Accepted

What causes a helicopter to autorotate farther?

In general, regardless of the number of blades, the more blade inertia, relative to blade area, the better for autorotation safety because the inertia buys you more time to establish the autorotative ...
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  • 108k
7 votes

There is any kind of advantage and disadvantages in making the blades of a helicopter off-center?

There is a theoretical advantage of an L shaped rotor blade insofar as it behaves like a swept wing, and so it's able to operate at a higher mach number where its velocity is highest, at the tip. The ...
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  • 108k

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