9
$\begingroup$

I know that fuel filters on aircraft engines have some features that avoid the bowl from detachment during flight, and that they can be secured using safety wire as shown below.

Safetied gascolator

I've also heard that installing safety wire is very time consuming. Is that true?
What is your experience with installation & safetying of fuel filter bowls?

$\endgroup$
2
  • 1
    $\begingroup$ Here is a video describing installation of lockwire (safety wire) in general. The most common use indirect; the lockwire holds the screws so they can't shake loose. $\endgroup$
    – Jan Hudec
    Feb 10 '15 at 10:56
  • $\begingroup$ @JanHudec That's essentially how they're used on the fuel strainers too - the bail nut is what's holding the bowl in place, and the wires hold the bail nut (and the bail) so it can't shift in flight and let the bowl fall off. $\endgroup$
    – voretaq7
    Feb 10 '15 at 19:04
16
$\begingroup$

Safety wire is almost never "efficient", but efficiency is not the goal: Safety is.
You want to be certain that once the fuel strainer has been secured it's not going to fall off in flight (which will result in the engine being starved of fuel).

On many light aircraft that's accomplished by wrapping safety wire on the fuel strainer to ensure it can't come loose in flight:
Fuel strainer safety wiring

A skilled mechanic who works with safety wire every day can safety a fuel strainer in about a minute - probably even faster. It's pretty impressive to watch.

A bungling incompetent like me who does it maybe once a year takes about 5 minutes, often punctuated with "colorful metaphors" and comments about the questionable parentage of the engineer responsible for the fuel strainer.

Either way, in the grand scheme of things that's not a lot of time spent on securing a flight-critical component.


Because there are far more bungling incompetents than skilled mechanics (and because even good mechanics are frequently not fond of safety wire) there are other fuel strainer designs which don't use safety wire.
The one I linked to uses a bayonet lock for the bowl, and a cotter pin to keep it from coming loose in flight. Anyone can bend a cotter pin in a couple of seconds, and as effective as the safety wire technique, if not moreso.

$\endgroup$
4
  • 2
    $\begingroup$ Much easier if you use a safety wire twisting tool. Not cheap, but much more efficient and less wire jabs... $\endgroup$
    – user7272
    Feb 10 '15 at 9:41
  • $\begingroup$ @Muzza Yeah, I don't know anyone who twists safety wire by hand, except for the first twist or two after a fastener. It's almost impossible to get a good uniform twist without using safety wire pliers, and if the twist is sloppy you've got to cut the wire off and start over… $\endgroup$
    – voretaq7
    Feb 10 '15 at 19:07
  • $\begingroup$ I have seen some filters that have a ratchet mechanism to secure the filter bowl instead of safety wire and are supposed to be easier to remove and install. Are they really better than safety wire? what is your experience with these type of mechanisms? $\endgroup$
    – Aerochar
    Feb 11 '15 at 19:01
  • $\begingroup$ @Aerochar I've never seen a "ratchet" mechanism so I'm not entirely sure what you're referring to. The bayonet-lock one I linked to is kind of like what you find on modern SLR camera lenses (line up two tabs and rotate about 30 degrees until it stops in position) except there's no locking tab like most camera lenses have: That functionality is accomplished with the cotter pin. Personally I like that idea better than safety wire as it seems less error prone (like I said, anyone can bend a cotter pin - twisting safety wire is an art form). $\endgroup$
    – voretaq7
    Feb 11 '15 at 20:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.