Hot answers tagged

54

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 weight that would be used in balancing the fan. GE uses units of gr.in. I'm fairly sure that Pratt uses oz.in, snecma uses gr.cm. I'm not sure what RR uses. But ...


38

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 engines. Take a following back-of-the-envelope calculation: disregard incoming airflow velocity and assume a hypothetical fan with a 1 meter diameter rotates at ...


31

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 CT. Where is it located? The compressor turbine is located at the exit nozzle of the annular combustion chamber, and is the first component which enters in ...


29

Very significant. A research on blisk cost estimation with funding and data provided by Rolls-Royce states: Integrally bladed discs, commonly known as blisks, are currently found in axial-flow compressors of gas turbine engines. Fig. 1 shows that blisks require significantly less material because the dead weight from the blade roots, disc lugs, and the disc ...


28

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 hub in this photo: And there is a clear view of the blade root in this photo: U.S. Air Force Senior Airman Steven Valencia, 18th Component Maintenance ...


27

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, they move in the mounts and establish individual lead/lag positions to achieve a balanced disc. It will be understood that turbine wheels rotate at very high ...


25

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 after combustion chamber and the temperature which the first stage of turbine blades is able to resist is a proof of high technology engine. Those blades are ...


24

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 in some electically-actuated propellers) would work, but would also wear away quickly and require frequent maintenance as losing control of a helicopter's main ...


20

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 faster and faster CD-ROM drives, the reduction of vibrations caused by small imbalances in the discs became more and more important. The solution is is shown ...


16

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're building a contra-rotating propeller: Pictured is a Sun Flightcraft contra-rotating gearbox kit for Rotax 503 and Rotax 582 engines. Although more ...


16

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 helicopter blades. Compared to fixed weight attached to the blade, the pendulum configuration allows for shifting of the damping range depending on rotor angular ...


15

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 principle is pretty simple- Align the rotor plane with the (rotating) swash plate, and tilt (or rise) it according to requirements. Source: helistart.com This system ...


14

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 gas temperature is even a few hundred centigrades higher than that. Steel would melt and other materials like titanium would quickly oxidize, and only nickel ...


14

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 blades are loose while the blades are stationary, as the engine start spinning, the centrifugal force pushes the blades out and as a result, they will not be so ...


14

Prop blades from side view at two RPMs Vector diagrams help with visualizing prop blades. Above the vertical vector lines are two RPMs, the horizontal vector lines are the forward velocity (the same for both), and the connecting orange vector lines are the resultant airflows. Note the AOA for the same blade pitch and how it is affected by the airflow at the ...


13

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 several images of blades which look similar to your photos. Compressor blade A search on locatory.com for the part number (B778503) lists the description as C-3 ...


12

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 and swashplateless rotor designs by Ch. Kessler. Link: http://dx.doi.org/10.1007/s13272-011-0001-0 There, I extracted three sources relevant to your question: ...


12

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 be coupled together and the blades could resonate with a large amplitude, causing increased noise and potentially reducing the life of the blades because of ...


12

It's done sometimes, for ultralight aircraft and paramotors. Like this:


11

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 are also required by 14 CFR 33.94 to confirm they do, typically via destructive "blade-off testing." (There are a number of good videos of this testing online: ...


9

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 a jet engine has no need for a tailored reduction in lift towards the tips; instead it tries to maximize the thrust from the available area. The wavy shape is ...


8

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 fail that we considered would pretty much leave all blades in the same place. So without claiming that it could not, ever, ever, no way no how, not in all ...


8

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.


8

Short answer: that fuel saving figure does not depend on the stator stage.[1] The aft stator function is swirl recovery, assuming its weight penalty can be offset. GE's design GE's (part of CFM) patent for that engine was filed in 2020: Unducted thrust producing system architecture US20200308979A1. From the patent, the second set of blades are optional, and ...


7

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 mass flow rate through the rotor and $\Delta v$ is the change of speed of the air. To accelerate the air to that speed, it has to give it kinetic energy. This ...


7

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 glide before blade stall when power is removed, and more time to settle into a landing at the end of the glide. The downside is more sluggish response to power ...


6

Development is in progress, just a matter of time: Source: Helicopters are quieter (translation by Google)


6

It's because the blade's span-wise axis is "swept" relative to its flapping hinge line, so when it flaps, the sweep angle results in the blade's effective AOA changing somewhat (for the advancing blade, reducing; that's what the feathering part means). To picture it, imaging you are standing directly in front of the tail rotor disc watching the advancing ...


6

The final report notes: At the time of each TAI [thermal acoustic imaging], the inspectors attributed the indication to a defect in the paint that was used during the TAI process and allowed the blade to continue the overhaul process and be returned to service. [emphasis mine] The paint being referred to is used for the inspection. Its function is to ...


6

The answer is yes it could be used in that flight profile as the pilot of that AS300 was never in a low G condition with the rotor unloaded during those maneuvers. Once he dropped the concrete, though he’s descending, he’s also accelerating at a high power setting, which is keeping the rotor loaded. However, zero G mast bumping is still a risk that must be ...


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