Rocket recovery system failure modes

A compilation of reasons why your rocket may no longer be in one piece

1. The chute shroud lines being the same length as the shock cord, therefore the shock cord could go tight without ensuring the chute was completely out of the bay.
2. Poor shock cord attachment at motor end or nose end.
3. Poor Nomex placement results in burnt chute/shock cord
4. Chute tangles are reduced with use of a swivel.
5. Shock cords about 5m to reduce shock loads.
6. Place chute so that nose and tail sections don't bash each other on decent.
7. Ensure chute compartment is sufficiently sealed so that it can pressurise, primarily between the altimeter bay which should be well vented.
8. Motor retention inadequate, resulting in motor being ejected rather than chute.
9. Flight computer must signal continuity on pad.
10. Flight computer can signal continuity but have damaged capacitor so not fire, ground test firing circuit if possible.
11. Use redundant systems, two flight computers.
12. Don't use smokeless powder, it is too pressure sensitive. Blackpowder substitutes behave differently and should be avoided
13. Make sure e-matches are well clamped in screw terminals.
14. Use acceleration tolerant switches, key switches are good.
15. Align switches perpendicular to axis to avoid acceleration effects.
16. Shock cord not strong enough, assume 20g loads (probably excessive)
17. Use kevlar cord (heat resistant) next to ejection charge and nylon cord or tape to reduce shock load.
18. Use good knots, bowlines, barrel knots and fig 8 for cord, tape knots and overhands for tape.
19. Use tape to pad kevlar cord where it leaves body tube to avoid tube damage "zipper effect"
20. Ground test every deployment three times, to check for repeatability
21. Ejection charges are best mounted centrally on bulkheads, use eyenuts on the end of studding if required.
22. Only use masking tape to adjust fits, other tape generally binds worse.
23. Check friction in joints, it can change.
24. Use a rape alarm so you can find the debris
25. Compartments vented so that reduced ambient pressure doesn't cause premature separation.
26. Vent altimeter bays symmetrically to avoid false readings from wind.
27. Ensure ejection charge not going to change due to acceleration (ie use wadding).
28. Use nylon shear pins (M2) to stop main deploying at drogue deployment.
29. A shear pin can be used to stop the drag on the fins at motor burn out causing separation, has this ever happened?