[SystemSafety] Anyone for a trip to Dubai?

[Bernd Sieker]

On 15 February 2017 11:26:07 CET, paul_e.bennett at topmail.co.uk wrote:
>On 15/02/2017 at 9:42 AM, "John J SPRIGGS"  wrote:         
>
>	OK, it is not functional safety, but why don’t “drones” have
>ducted propellers, or at least some form of guard around them? 
>	JohnConsidering that thrust efficiency is usually improved by
>ducting, I have 
>wondered that myself. It would also aid general safety when people are
>
>in closer proximity than they should be.

The short answer is "weight".

The safety argument is worth considering, and many small drones have optional prop guards. But as to thrust efficiency, longer blades increase efficiency more per unit weight than ducts. This is the reason propeller airplanes have open propellers instead of ducts. Ducts are only useful when blade length is restricted, e.g. by clearance or tip speed considerations.

>
>Regards
> Paul E. Bennett IEng MIET
> Systems Engineer
> -- 


Bernd
-- 
Sent from Kaiten Mail. Please excuse my brevity.