What is the purpose of the lay line printed along a flexible hose?
- To mark the minimum bend radius
- To show whether the hose is twisted
- To show the direction of fluid flow
- To mark where to cut the hose
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B. To show whether the hose is twisted
If the lay line spirals around the hose after installation, the hose has been twisted, which can loosen fittings and shorten hose life. The line also carries the hose identification, but it does not indicate flow direction.
Reference: FAA-H-8083-30, Fluid Lines and Fittings (flexible hose installation)
What is the diameter of an AN4 bolt?
- 1/8 in
- 4/32 in
- 1/2 in
- 1/4 in
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D. 1/4 in
The number after AN gives the diameter in sixteenths of an inch, so AN4 is 4/16, or 1/4 in. Reading the number as eighths gives 1/2 in.
Reference: FAA-H-8083-30, Aircraft Materials, Hardware and Processes (aircraft bolts; identification and coding)
How should safety wire be installed on a bolt head?
- So that it pulls in the tightening direction
- So that it pulls in the loosening direction
- With slack so it can flex under vibration
- Through the bolt threads behind the nut
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A. So that it pulls in the tightening direction
Safety wire is routed so that any tendency of the fastener to loosen puts the wire in tension and pulls it tighter. Wire left slack will chafe and break under vibration.
Reference: FAA-H-8083-30, Aircraft Materials, Hardware and Processes (safety wiring methods)