Posted by jb92563 on Monday, February 6, 2012 @ 12:56 PM:
I am in the process of getting an annual and I apparently have Grade 8 bolts holding the prop to the flange.
The Inspector would like to see them changed out for AN or NAS Bolts.
Does anyone know if this is original equipment or did my Bolts get changed out for grade 8 at some point?
Is anyone using AN Bolts and Bushings? What size?
I saw that the Operating Handbook indicated M 8 Bolts but it did not specify if they were Grade 8 or better.
[Edit by jb92563 on Monday, February 6, 2012 @ 12:58 PM]
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Posted by SteveBeaver on Monday, February 6, 2012 @ 01:37 PM:
Surely there is no such thing as an AN or NAS metric bolt? Why would a French airplane built in Germany need American bolts?
Posted by jb92563 on Monday, February 6, 2012 @ 02:11 PM:
Sounds like my Bolt is non standard then.
I don't know how Metric bolts are graded for strength, so since mine is marked Grade 8 I presume its not original and I will go ahead an
look for a suitable AN or NAS replacement from Aircraft Spruce.
I doubt I would be able to find a suitable M8 replacement and the prop flange and prop is now sized for my current US bolts.
Good catch by my A&P, as I'd rather not watch my nice new prop leave me in flight.
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Posted by Collin on Monday, February 6, 2012 @ 05:08 PM:
Hi,
The std bolts are M8 8.8 grade. 10.9 would be the next grade stronger.
New 8.8 bolts are still available, but heads need to be drilled for safety wire.
Collin
Posted by jb92563 on Monday, February 6, 2012 @ 05:41 PM:
What about the low profile bushing/nut on the engine side of the prop flange that the bolts connect into.
Mine must have been changed out as well to accommodate my grade 8 bolts.
I dont know if there is enough clearance to use regular lock nuts.
I will have to take my prop off and measure everything to see if I can get something that will work.
It seems odd that someone changed them out.
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Posted by jb92563 on Tuesday, February 7, 2012 @ 11:50 AM:
Just a thought, is a grade 8.8 M8 bolt of similar strength to a US Grade 8 bolt?
Perhaps their idea was to match the strength of the original M8 bolt?
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Posted by eugenio on Tuesday, February 7, 2012 @ 03:55 PM:
8.8 bolts are the standard in gliders and motorgliders. They have more or less the same strenght of standard AN bolts. The same bolts are used on all VW conversions here in Europe, the same as in the US you use the AN5.
8.8 and 10.9 bolts are high strenght bolts, while low strenght are 4.6 and 5.6. Breaking strenght for 8.8 bolts is 800N/mm2 while for 10.9 is 1000N/mm2.
Tell your inspector that the engine, the aircraft and the propeller are certified with that bolts, so the modification is to change them with AN bolts instead of UNI/DIN Bolts.
European norms UNI 5931, DIN 912, ISO 4762 for allen bolts, UNI 5737, DIN 931, ISO 4017 for hexagonal head bolts.
Eugenio
