FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesEasy
A technician is fabricating a new fluid line using a standard AN flared fitting. To what angle should the tubing end be flared for proper mating with the fitting?
- A45°
- B37°
- C60°
- D30°
Show answer & explanationAnswer & explanation
Correct answer: B. 37°
Standard AN (Air Force-Navy) flared fittings used in aircraft hydraulic and fuel systems require a 37° flare angle. Older automotive-style fittings commonly use a 45° flare, which is not compatible with AN fittings.
Why the other options are wrong
- A. This is the standard automotive flare angle, not used for AN fittings.
- C. This angle is not used for standard fluid line flares.
- D. This angle is not a standard flare specification.
AN Flare Angle
The standard flare angle used on aircraft AN fluid line fittings to ensure a proper leak-free seal.
- AN fittings use a 37° flare
- Automotive/45° flares are incompatible with AN fittings
- Flared fittings rely on a metal-to-metal seal
Memory trick: AN = 'A Narrow' 37° cone for a tight aircraft seal.