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propellers

B

Brado78

Senior member
Hey Gang, I love flying, but I don't like turbo props because I am always afraid that the propeller might fly off and hit the fuselage ,What would happen?, would the blade disintegrate on impact,or will it cut through the fuselage like a hot knife through butter?
 
Brado78 said:
Hey Gang, I love flying, but I don't like turbo props because I am always afraid that the propeller might fly off and hit the fuselage ,What would happen?, would the blade disintegrate on impact,or will it cut through the fuselage like a hot knife through butter?
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Like a hot knife through butter. But that's probably better, get hit with a spinning propeller and die quickly. That death spiral into the inevitable fiery crash would be a bitch.
 
I can't recall the last time I heard of a prop failing without some sort of impact. Air Canada had an event a few years ago, but that's because the landing gear failed.

The thing you should be worried about are disk failures in any jet engine. There are many times more of those in an engine, they're solid metal, and they weigh a heck of a lot more than a prop blade. https://en.wikipedia.org/wiki/Turbine_engine_failure

Could be a sampling bias though. There are many fewer commercial turboprops relative to turbofan.
 
You'll be fine. Loud as hell though! I survived sitting at this seat:



My window pane was rattling, I don't know if that's normal, I just put my elbow on it to make it stop.

(I think the AC incident mentioned earlier was on the same model of plane lol)

That was a fun trip, was my first time on a plane.
 
drinkmorejava said:
The thing you should be worried about are disk failures in any jet engine. There are many times more of those in an engine, they're solid metal, and they weigh a heck of a lot more than a prop blade. https://en.wikipedia.org/wiki/Turbine_engine_failure
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yeah that can be nasty
here's a A380 AF66 where the fan disc failed
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lsMl6so.jpg
 
lmao! Found this while doing a search for the above picture. "prank" IED:

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I wonder how many watts of allah ackbar that makes? 😛 The toilet paper rolls are a nice touch.
 
When I was in Job Corp, the day before I was to leave to go back home for Christmas vacation I watched the first Final Destination at the theater on campus. Talk about rattling one's nerves before your flight in the morning.

Now that I know a lot about aviation I know that flying is one of the safest forms of travel there is. You are more apt to get in a car crash then being involved in an aviation mishap.

If turbulence is an issue with you, get a seat in the middle of the A/C with the wings.
 
I don't know about the mechanics of props, but I'm sure the bolt/s are a reverse thread that goes against the rotation of the propeller.

One A/C I really don't want to fly on is a MD-11. The jack screw has to be greased will otherwise you won't have your ailerons. I think it was the MD-11 or MD-80. And I believe Allegiant flies those.

Here it is. MD-83. https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261
 
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John Connor said:
I don't know about the mechanics of props, but I'm sure the bolt/s are a reverse thread that goes against the rotation of the propeller.

One A/C I really don't want to fly on is a MD-11. The jack screw has to be greased will otherwise you won't have your ailerons. I think it was the MD-11 or MD-80. And I believe Allegiant flies those.

Here it is. MD-83. https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261
Click to expand...

All kinds of bad things happen if you don't properly maintain an airplane. The official NTSB cause was "Alaska Airlines' insufficient lubrication of the jackscrew assembly." Of course there were contributing factors (as with all accidents), but the fault was on Alaska Airlines.

Everyone's forgotten about that now and thinks Alaska is a great airline...
 
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Like a lot of FAA requirements, the requirement for losing propellers is relatively simple:
https://www.ecfr.gov/cgi-bin/text-i...96ab1278&mc=true&node=se14.1.25_1905&rgn=div8
"Design precautions must be taken to minimize the hazards to the airplane in the event a propeller blade fails or is released by a hub failure. The hazards which must be considered include damage to structure and vital systems due to impact of a failed or released blade and the unbalance created by such failure or release."

Actual certification is a lot more complex. Often there are advisories discussing a pre-approved means of compliance, but even those aren't necessarily straightforward. Here's the advisory for the above propeller regulation:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/0a7294b17805f84e862569b300547865/$FILE/AC 25.905-1.pdf

Notice the lack of requirements protecting occupants. Like many failure-related issues, the important thing is that the airplane can land safely.

When it comes to failures, it's usually all about the probability vs. the level of hazard (https://en.wikipedia.org/wiki/AC_25.1309-1). The probability of getting hit by a blade is extremely low. You're more likely to win millions of dollars in the lottery.
 
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<----------Retired A&P mechanic

Old school wood props are one piece and bolted through the center with a hub or plate assy. Torqued and safety wired on.

Small single & light twin engine planes have hub assemblies with the blades joined internally via cuffs, boots, (differs per manuf) the hubs are fastened to the power plant and torqued and saftied.

Large turbo props are very sophisticated reversing assemblies with complicated electro-hydraulic hub & blade systems.

You don't see many blade/hub separations

Lots of pertinent pics here;

https://www.google.com/search?hl=en....13.1996.0..0j0i10i24k1.0._iA7rEGyrik#imgrc=_
 
I'd imagine they use a bolt pattern kinda like a car wheel, and probably have some kind of locking mechanism so the force is not only on the bolts. Just my guess though.
 
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