Rotorcraft Picketing / lashing equipment safety factor

[chesmit]

Dear Sir

Helicopter tiedown in wind speeds of up to 80kts (on land only). Ref. Defstan 970 (part 308/309). Safety factors for attachment points and structure are 1.25 and 1.5 respectively.
WHAT SAFETY FACTOR is required for the lashings / cable equipment? Can you ID a spec?
Generally we use a factor of between 3 or 6 when personnel safety is involved.

Regards
Che Smit

 

[Sparweb]

I'll speculate that since there are no direct airworthiness requirements for the tie-downs, that standard practices for industrial cables apply. That is: a cable or rope assembly has a minimum breaking strength specified by the manufacturer or by whoever put it together for you, and a working load is usually the breaking strength divided by 5 or so. The working load should not be exceeded in service.

I'm not an expert in these matters, but since nobody else had any suggestions...

Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout