Fluid Lines and Fittings — practice questions
4% of the exam ≈2 real questions 2 free questions here
Four percent of the weighting: how tubing and fittings are sized, flaring and double flaring, AN fitting color codes, and the flexible hose installation rules. Mostly numbers worth memorizing once.
Where people lose points
- Tube and fitting dash numbers are OUTSIDE diameter in sixteenths of an inch: number 6 is 3/8 inch.
- Aircraft flares are 35° to 37°; a 45° automotive flare must never be used.
- Double flares are for soft aluminum tubing 3/8 inch OD and under.
- Flexible hose gets 5 to 8 percent slack and must not be twisted; a spiraling lay line means it is.
Drill: Fluid Lines and Fittings
2 free questions from this domain, each with an explanation and a cited source. Timed at real exam pace.
2 questions
Pass line: 70%, same as the real exam
See the answer and explanation right after each question.
Questions and answers, explained
All 2 questions above, with the correct answer and why it is correct. Everything here is on fluid lines and fittings.
Rigid metal tubing marked as number 6 has what dimension?
Why: Metal tubing is sized by outside diameter in sixteenths of an inch: number 6 is 6/16 (3/8) inch OD and number 8 is 8/16 (1/2) inch OD. Fitting dash numbers follow the same nominal OD in sixteenths.
Reference AM.I.D.K1 · FAA-H-8083-30B, Ch. 9 (Tubing; Size Identification)
How much slack should be provided when installing a flexible hose?
Why: Flexible hose contracts in length and expands in diameter when pressurized, so the handbook calls for 5 to 8 percent slack. A hose must never be stretched tightly between two fittings, and it must be supported at least every 24 inches.
Reference AM.I.D.K4 · FAA-H-8083-30B, Ch. 9 (Installation of Flexible Hose Assemblies)