I always thought the tailhooks were there to help navy pilots land on carriers. They grab onto lines on the deck to help the jet decelerate, otherwise the jets would only skim over and either hit the water, or be unable to safely land.
Some runways are miles long, but the navy doesn't have any carriers that big.
That's the main use of the hooks but they actually are used to secure (along with wheel chocks) the planes to the deck if they are parked there, I think in this case the plane was parked on deck but slid off the edge and was caught by the emergency cable.
Is this true?
Some runways are miles long, but the navy doesn't have any carriers that big.