Electrical Static on Aircraft

[yshij]

Is anyone over there who knows how aircraft discharges itself before touching down on the runway? I think when aircraft flies in sky or pass through a static charged cloud, the aircraft could be fully charged because of friction or through direct transfer. The fully static charged aircraft could cause sparks or fires when it touchs down if the static is not discharged.

 

[astroclone]

I believe the aircraft stops off at the little aircraft's room.

A little humor never hurts, especially for engineers.

 

[IRstuff]

Many of the older planes had trailing edge "bleeders", long wires, insulated except that the tip. Since electric field is magnified with sharp structures, you can cause small charges to generate enough field to cause breakdown, thus dissipating the charge.

TTFN

 

[butelja]

Are these "bleeders" the things that look similar to small flexible antenna, usually attached to the ailerons? Also, you mention older planes used them. What about newer planes?

 

[IRstuff]

>yes
>haven't really been looking too much at new planes, so I don't know for sure.

TTFN

 

[harryr]

aircraft use trailing edge(wings,rudders,flaps,etc) to mount devices called static wicks which are flexable, carbon filled, small diameter tublar devices with many small
hair like whiskers at the end that is opposite the attachment point.
Helicopters attach these to the main and tail rotors in addition to the structure.
There is an empirical relationship (estimate) that the airlines use to estimate the number of wicks required to dissipate a static charge which is a function of air speed
and wing span.
Even with wicks there have been cases where helicopters using cables and hooks (logging operations for example)
where it is hovering to ground level where a ground person grabs the hook and receives a tremendous shock. Enough in some cases to require hospitalization.
The next time you are around an aircraft you can see the wicks on the wings trailing edge and horizontal stabilizer.
the most common problem with commerical and civil aircraft
not protected with wicks is noise (static) on the headset.

 

[mbakerfl]

HarryR is absolutely correct. And yes, these are still being used on new aircraft.
Mike Baker
Baker aerospace Designs, Inc.
info@bakeraerospacedesigns.com