# Harrier jet and squash balls **URL:** \ **Category:** Factual Questions\ **Created:** [March 14, 2018, 12:40pm UTC](https://boards.straightdope.com/t/harrier-jet-and-squash-balls/810539 "2018-03-14T12:40:32Z")\ **Posts on this page:** 2\ **Page:** 2
**Author:** ![NBYodo](https://avatars.discourse-cdn.com/v4/letter/n/a9a28c/32.png) [@NBYodo](https://boards.straightdope.com/u/NBYodo)\ **Post date:** [March 17, 2018, 9:31am UTC](https://boards.straightdope.com/t/harrier-jet-and-squash-balls/810539/21 "2018-03-17T09:31:51Z")
> [@Irishman](#): > > I agree with these. There are different levels of functional requirement and different levels of certification depending on usage (at least in NASA), but supply chain documentation is very thorough. For instance, metal parts a traced back through the manufacturer listing the processes applied (heat treatment, etc) all the way back to the source metal. If something fails and they identify it was a bad batch, they want to be able to source _where_ the problem occurred, and what caused the bad batch, and how it missed quality control. > > […] And be able to find all the aircraft that parts made from the same faulty batch were installed on. NM Sent from my SM-N910G using Tapatalk ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [March 17, 2018, 10:35am UTC](https://boards.straightdope.com/t/harrier-jet-and-squash-balls/810539/22 "2018-03-17T10:35:50Z")
> [@Mangetout](#): > > I wouldn’t have thought a bushing or bearing would be made of rubber - those things are normally made of harder materials like metal or ceramic. Maybe a boot or a grommet, assuming the story has any sort of truth to it. control arm bushings in automotive suspensions are usually rubber. they need some flexibility for shock damping. [Previous page](https://boards.straightdope.com/t/harrier-jet-and-squash-balls/810539.md?page=1)