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Sources: wikimedia.org and ar15.com

Holdback bars are used to hold a carrier plane at full thrust until the catapult pulls it for launch.

Older bars (right) use a disposable shearable block (item 5) between the bar and the plane.

How does the reusable holdback bar (left) work?

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    $\begingroup$ I've always wondered about it, researched it, and thought to share it. $\endgroup$ – ymb1 Jan 20 at 6:13
  • $\begingroup$ Are turbine engines like propellers where they do not generate full thrust at static conditions? At least, if their blade pitch is too high. Actually, I guess that doesn't matter since there is the catapult that will be pulling it along. $\endgroup$ – DKNguyen Jan 20 at 21:40
  • $\begingroup$ @DKNguyen: In general, it's the highest when static, also see here. $\endgroup$ – ymb1 Jan 21 at 15:23
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Source: YouTube

The bar is placed between a tong-like (two hooks) device on the aircraft, and when released, the body of the holdback bar envelops the hooks (note the disappearing red paint on the tips of the hooks) forming a collet.

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On the inside, as the plane pulls on the bar (1), the walls (2) compress a chamber filled with hydraulic fluid (3). The fluid pushes into a channel and pushes against a sphere (4). At the right pulling force, the sphere is pushed which allows the fluid to fire the piston (5) freeing the inserted hooks from the bar.

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Source: YouTube


Reference: Repeatable release holdback bar, US Navy patent US4101099A

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