Best practice is to use all metal locknuts firewall forward or some other type of locking fastener that is not a nylock.
I have seen FAA Inspectors and DARs not accept nylock nuts firewall forward even though Certificated Hartzell props come with nylock nuts. Some of the other accessories that bolt to our engines may also come with nylock nuts. I have done follow up inspections after FAA Inspectors and accepted nylocks that the FAA Inspector wanted changed even though they are not best practice for use forward of the firewall.
Anything that I do firewall forward will have metal lock nuts or some other type of locking fastener that is not a nylock.
As someone else quoted, AC43.13-1B, chapter 7, Section 4, 7-64:
f. Fiber or nylon locknuts are constructed with an unthreaded fiber or nylon locking insert held securely in place. The fiber or nylon insert provides the locking action because it has a smaller diameter than the nut.
Fiber or nylon self-locking nuts are not installed in areas where temperatures exceed 250 ?F. After the nut has been tightened, make sure the bolt or stud has at least one thread showing past the nut. DO NOT reuse a fiber or nylon locknut, if the nut cannot meet the minimum prevailing torque values. (See table 7-2.)
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BOLD added by me to the above.]
For an airworthiness certificate to be issued to an Experimental Aircraft, the Experimental aircraft MUST be in a condition for SAFE operation. Safe will be in the eyes of the inspector or DAR and sometimes there will not be a WRITTEN regulation.
Here are some links to best practice of not using nylock's forward of the firewall.
http://exp-aircraft.com/library/alexande/hardware.html
http://www.vansairforce.com/community/showthread.php?t=12842&page=2
See post # 13 in above thread.
Joe Norris is the expert on where things are in writing and the regulations. I expect he will make a post to this thread.
From the FAA training seminars that all FAA and DAR Inspectors must go to:
The Applicant must show and the FAA Inspector or the DAR must find that the aircraft meets the requirements for the certificate requested. They also say that it must be in a condition for safe operation.
IF you build your aircraft to BEST practices and can show the FAA Inspector or DAR that you are using best practices, more than likely the Airworthiness Certificate will be issued for UNLIMITED duration. IF you cannot show, you may not get the Airworthiness Certificate, you may get one of limited duration, or you may get a longer flight test period to PROVE that the aircraft can be operated safely.
Change of subject:
Would an FAA Inspector or DAR issue an airworthiness certificate to an Experimental Aircraft that has the shoulder belts hand sewn to the structure? Is that a condition for safe operation if the builder cannot show that it is at least as strong as a factory belt? (Note: There is NO REGULATION that I know of that REQUIRE safety belts in Amateur Built Aircraft.)
I spent a little bit of my time showing you links to best practice of NOT using nylock nuts forward of the firewall. Now it is your turn to show me links that best practice includes the builder using nylocks for stuff he does forward of the firewall.
