5 ms·

Bolts can get unscrewed with vibrations. So probably a design error, they did not use the correct type of bolt (the one with the safety pin).

gregoriol 3y ago
Don't they have many ways to prevent bolts from unscrewing? I know at least a few by doing mechanical stuff on motorcycles, and it seems that other planes don't have such problems (at least not within 2 months after the last inspection).
- aredox 3y ago
  There are washers, or thread lock glue, but it is still a question of correct execution: has the glue been applied? Was the glue batch used before its shelf life? Were the parts degreased before glue application? Or did anyone decided to cut corners by using an old batch/skipping degreasing/not putting glue because they were late on delivery?
  - MarkMarine 3y ago
    safety wire and cotter pins are preferred methods on aircraft.
    - lobsterthief 3y ago
      Yes. For mission-critical bolts and nuts, absolutely safety wire and cotter pins should be used.
      - MarkMarine 3y ago
        The engineers at Bell also thought that blind bolts you couldn’t inspect in dailies should be wired.
somewhereoutth 3y ago
My understanding is that the bolts did have castle nuts and retaining wires in the design. So either they were incorrectly fitted, or the bolts themselves were under specified with regard to strength.
- stevehawk 3y ago
  ah. i've been wondering what the method of securing the bolts would have been and have not seen anyone mention it. torque values or threadlocker is rarely enough for the FAA. it's usually safety wire, castle nuts, lock washers, etc.
- aziaziazi 3y ago
  Not sure what happened from “the design” to “the field”. The two loosen bolts in the picture are not castle nuts.
- 0xbadc0de5 3y ago
  The door hinge bolt had a castellated nut and pin, but the screws holding the hinge mount to the airframe apparently had no retaining wire. See leaked photo at: https://twitter.com/ByERussell/status/1744460136855294106/photo/1 https://twitter.com/ByERussell/status/1744460136855294106/ph...
- MarkMarine 3y ago
  Those bolts aren’t drilled for safety wire.

gregoriol 3y ago

Don't they have many ways to prevent bolts from unscrewing? I know at least a few by doing mechanical stuff on motorcycles, and it seems that other planes don't have such problems (at least not within 2 months after the last inspection).

aredox 3y ago
There are washers, or thread lock glue, but it is still a question of correct execution: has the glue been applied? Was the glue batch used before its shelf life? Were the parts degreased before glue application? Or did anyone decided to cut corners by using an old batch/skipping degreasing/not putting glue because they were late on delivery?
- MarkMarine 3y ago
  safety wire and cotter pins are preferred methods on aircraft.
  - lobsterthief 3y ago
    Yes. For mission-critical bolts and nuts, absolutely safety wire and cotter pins should be used.
    - MarkMarine 3y ago
      The engineers at Bell also thought that blind bolts you couldn’t inspect in dailies should be wired.

somewhereoutth 3y ago

My understanding is that the bolts did have castle nuts and retaining wires in the design. So either they were incorrectly fitted, or the bolts themselves were under specified with regard to strength.

stevehawk 3y ago
ah. i've been wondering what the method of securing the bolts would have been and have not seen anyone mention it. torque values or threadlocker is rarely enough for the FAA. it's usually safety wire, castle nuts, lock washers, etc.
aziaziazi 3y ago
Not sure what happened from “the design” to “the field”. The two loosen bolts in the picture are not castle nuts.
0xbadc0de5 3y ago
The door hinge bolt had a castellated nut and pin, but the screws holding the hinge mount to the airframe apparently had no retaining wire. See leaked photo at: https://twitter.com/ByERussell/status/1744460136855294106/photo/1 https://twitter.com/ByERussell/status/1744460136855294106/ph...
MarkMarine 3y ago
Those bolts aren’t drilled for safety wire.