UAL747 From United States of America, joined Dec 1999, 7901 posts, RR: 30 Posted (6 years 7 months 1 week 4 days 1 hour ago) and read 11549 times:
Ever since I was a kid, I remember riding in the family Cessna 335 and noticing these wire like structures that were on the trailing edge of the wings, and other parts of the aircraft. When I was young, I thought it had something to do with radio, however, as I understand it now, it has to do with static discharge, or rather, getting rid of the static build up on the aircraft. This technology is on most planes I've seen.
1. Why does static build up on the plane?
2. How can you measure the amount of static build up?
3. What would happen if these static ports were not on the aircraft?
4. Is static dangerous?
5. How big are the static ports on an aircraft say the size of the 335 all the way to the 747?
6. How many discharge points does an aircraft have or need?
7. Why are they always on the ends of the wings, and not closer to the fuselage?
8. How did we discover the static "problem".
Also, feel free to give any other explanations you feel necessary.
Thanks,
UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
Woodreau From United States of America, joined Sep 2001, 810 posts, RR: 8 Reply 2, posted (6 years 7 months 1 week 3 days 23 hours ago) and read 11536 times:
Regarding question 3
There is a difference between a static port and static. They are not related. I think you meant to say "static wick" instead of "static port" two different things for two separate systems.
Good judgement comes from experience. Experience comes from surviving bad judgement.
WrenchBender From Canada, joined Feb 2004, 1677 posts, RR: 11 Reply 3, posted (6 years 7 months 1 week 3 days 23 hours ago) and read 11529 times:
1. Why does static build up on the plane?
It's a matter of physics, a mass moving through air will generate static electricity.
2. How can you measure the amount of static build up?
By allowing it to build up and then directing the discharge through a meter.
3. What would happen if these static ports were not on the aircraft?
Change ports to read WICKS see Woodreau's reply, If the static was not constantly bled off through the wicks, the A/C would develop problems with it's navaids and radios. Also massive discharges would occur from the A/C to whatever is available somewhat like lightning to clouds etc.
4. Is static dangerous?
Extremely, CF5/T38 type fighter/trainers have to have their windshields grounded prior to pilots getting out of the cockpit massive amounts of voltage can be built up on short flights. Helicopters can generate 50,000 volts in 1/2 a second, that is why we ground the hoist cable when hoisting people, I once fended off a hoistee when I was working deck crew on Destroyer and lost the use of my arm for about 2 hours, the hoistee also had ahard time walking.
5. How big are the static ports on an aircraft say the size of the 335 all the way to the 747?
The wicks are usually 6 to 8 inches long and placed along the trailing edge of wings(flaps/ailerons) and the tail (rudder)
6. How many discharge points does an aircraft have or need?
As many as it takes Sea King Helicopter 5, Twin Otter 11, etc.
7. Why are they always on the ends of the wings, and not closer to the fuselage?
As long as they are in the air flow they work
8. How did we discover the static "problem".
Not sure, but probaly once they started installing radios that were frequency sensitive.
By the way Static Ports are for measuring Barometric pressure for A/C instrumentaton
UAL747 From United States of America, joined Dec 1999, 7901 posts, RR: 30 Reply 4, posted (6 years 7 months 1 week 3 days 23 hours ago) and read 11520 times:
Yeah, I figured I was a bit off on the use of the word "ports" as it didn't sound correct. "Wick" is much more suited!
Thankks or the info.
UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
Pilotpip From United States of America, joined Sep 2003, 2996 posts, RR: 14 Reply 5, posted (6 years 7 months 1 week 3 days 19 hours ago) and read 11493 times:
This is one of the reasons that an aircraft must be grounded before fueling it. If you remember seeing the huff n' puff being fueled when you were younger the fueler attached a cable to a metal point on the aircraft. This was to ground it. Many larger aircraft have specific studs for this, or a point for a probe similiar to a headset jack. Sometimes, this connection would be continued to the ground (the military still does this) it's not required by my employers or for that matter, any of the companies I fuel.
UAL747 From United States of America, joined Dec 1999, 7901 posts, RR: 30 Reply 6, posted (6 years 7 months 1 week 3 days 18 hours ago) and read 11482 times:
Quoting Pilotpip (Reply 5): This is one of the reasons that an aircraft must be grounded before fueling it. If you remember seeing the huff n' puff being fueled when you were younger the fueler attached a cable to a metal point on the aircraft. This was to ground it. Many larger aircraft have specific studs for this, or a point for a probe similiar to a headset jack. Sometimes, this connection would be continued to the ground (the military still does this) it's not required by my employers or for that matter, any of the companies I fuel.
Actually, I've never seen the plane be fueled. It's based at Wiley Post airport in OKC. Basically we just call when we need to use it, and it's towed out on the apron fueled, but I've seen the pilot test the fuel, that's about it.
UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
Comorin From United States of America, joined May 2005, 4251 posts, RR: 19 Reply 7, posted (6 years 7 months 1 week 2 days 21 hours ago) and read 11424 times:
How does static build up affect instruments or electrical equipment inside a plane? A charged body has no electrical field in its interior, if I remember my college physics right. I suppose it could affect sensors on the surface of the aircraft, and cause misleading readings.
Do the wicks also help in dissipating induced charge buildup from nearby thunderstorms? If so, is this the the primary reason for their existence?
UAL747 From United States of America, joined Dec 1999, 7901 posts, RR: 30 Reply 8, posted (6 years 7 months 1 week 2 days 19 hours ago) and read 11406 times:
Quoting Comorin (Reply 7): I suppose it could affect sensors on the surface of the aircraft, and cause misleading readings.
That is my understanding.
Quoting Comorin (Reply 7): Do the wicks also help in dissipating induced charge buildup from nearby thunderstorms? If so, is this the the primary reason for their existence?
I think from what I understand, is that because of the airflow going so fast over the wing area, this "friction" causes an atom to lose either a proton or an electron, causing the ion to be either positively charged or negatively charged. (Not sure which one happens on wings). Anyway, a build up of these ions on the aircraft surface causes it to have an electrical charge, hence the need for the wicks.
Though, I don't quite understand HOW the wicks actually work.
Any info would be appreciated?
UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
Fly2HMO From United States of America, joined Jan 2004, 8123 posts, RR: 9 Reply 9, posted (6 years 7 months 1 week 2 days 19 hours ago) and read 11400 times:
Think of it as grounding by means of the air...
well sort of
Why if one person has an imaginary friend they're crazy; if many people have the same imaginary friend, its religion?
Oly720man From United Kingdom, joined May 2004, 6081 posts, RR: 12 Reply 10, posted (6 years 7 months 1 week 2 days 13 hours ago) and read 11379 times:
Quoting Fly2HMO (Reply 9): I think from what I understand, is that because of the airflow going so fast over the wing area, this "friction" causes an atom to lose either a proton or an electron, causing the ion to be either positively charged or negatively charged
If an atom lost a proton I'd be worried, that's radioactivity.
The situation arises because friction between the aircraft and the air, as between two bodies, causes local charge separation so, for example the aircraft can become electrically charged positively and the air negatively charged, or vice versa.
The static wicks work because they are a location where the charge can concentrate and have a higher local potential to discharge into the atmosphere. Anyone have one of the piezoelectric gas lighters? Same idea. Squeezing the piezo material causes a charge separation within the material and this manifests itself as a spark from the centre of the lighter to the surrounding metal.
Man City p3 w3 d0 l0 f4 a0 P9 - hey it may never happen again!
Comorin From United States of America, joined May 2005, 4251 posts, RR: 19 Reply 11, posted (6 years 7 months 1 week 2 days 8 hours ago) and read 11344 times:
In still air, electrostatic leakage occurs at sharp edges, because as the radius of a charged surface gets smaller, electrostatic forces increase (I forget the calcs) , causing a concentration of electrons at a tip. This concentration leads to higher ionizing forces in the air near the tip, and helps conduct away the electrons. When you have air rushing by, I suppose there is a constantly renewing supply of either neutral air molecules waiting to be ionized, or ionized air waiting to be neutralized, either of which will enhance the discharge from the wick.
I think the reason wick tips aren't sharper than they are is that you may not want the discharge current to be too high, causing heat damage -but this is speculative.
Dont worry UAL747, we'll all eventually get to the bottom of this!
CRJIAD From United States of America, joined Jun 2005, 32 posts, RR: 0 Reply 12, posted (6 years 7 months 1 week 2 days 4 hours ago) and read 11329 times:
FlyMatt2Bermud From United States of America, joined Jan 2006, 562 posts, RR: 9 Reply 14, posted (5 years 5 months 3 weeks 2 hours ago) and read 10877 times:
Quoting SP90 (Reply 13): What about if the plane get hit by lighting while moving on the ground?
As in a car, as long as the aircraft is solid on rubber tires (nothing to create a ground) not being airborne probably won't make a difference provided the intensity of the lightning isn't too strong.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
CptSpeaking From United States of America, joined Apr 2006, 635 posts, RR: 2 Reply 15, posted (5 years 5 months 2 weeks 6 days 22 hours ago) and read 10827 times:
Quoting Comorin (Reply 7): How does static build up affect instruments or electrical equipment inside a plane? A charged body has no electrical field in its interior, if I remember my college physics right. I suppose it could affect sensors on the surface of the aircraft, and cause misleading readings.
Static buidup can cause major issues with the radios. If the charge isn't being dissipated properly, you'll hear a LOT of static on the radios to the point where it would be difficult to understand any real transmissions. The same is true for nav radios I believe...the static is so bad that the reciever can't hear what it's being told and therefore can't give you a good reading.
Feel free to correct or add on, the details of this interest me as well!
Starlionblue From Greenland, joined Feb 2004, 14991 posts, RR: 69 Reply 16, posted (5 years 5 months 2 weeks 6 days 21 hours ago) and read 10815 times:
Quoting SP90 (Reply 13): What about if the plane get hit by lighting while moving on the ground?
Same as in a car I would guess. Not a problem.
Tact Is For People Who Aren't Witty Enough To Be Sarcastic
Vikkyvik From United States of America, joined Jul 2003, 6052 posts, RR: 26 Reply 17, posted (5 years 5 months 2 weeks 6 days 19 hours ago) and read 10802 times:
Quoting FlyMatt2Bermud (Reply 14): As in a car, as long as the aircraft is solid on rubber tires (nothing to create a ground) not being airborne probably won't make a difference provided the intensity of the lightning isn't too strong.
I'm still a bit unsure on this one, but I thought this was due to the Faraday Cage effect of the metal skin (of the car or airplane). I'm pretty sure that if lightning strikes a car, it's going to get to the ground, be it through the tires or the air (after all, air is already a pretty strong insulator at ~3000 V/cm).
So basically, you'd be safe as long as you weren't touching the skin, or any other conductor that's touching the skin. That's my understanding at least.
~Vik
The spirit of Massachusetts is the spirit of America!
SP90 From United States of America, joined May 2006, 371 posts, RR: 0 Reply 18, posted (5 years 5 months 2 weeks 6 days 2 hours ago) and read 10737 times:
Thanks for the replies guys. It was just a question that popped into my head today after seeing some pretty intense lighting flashes while I was out driving.
Now for those who would like to know about spacecraft grounding, take a look at this.
David L From United Kingdom, joined May 1999, 8950 posts, RR: 45 Reply 19, posted (5 years 5 months 2 weeks 6 days 2 hours ago) and read 10725 times:
Quoting FlyMatt2Bermud (Reply 14): As in a car, as long as the aircraft is solid on rubber tires (nothing to create a ground) not being airborne probably won't make a difference provided the intensity of the lightning isn't too strong.
Is it too simplistic to say that if there's no earth/ground path for a given intensity via, say, the tyres, then the car/aircraft probably isn't going to be struck by lightning anyway?
Bri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4 Reply 20, posted (5 years 5 months 2 weeks 6 days ago) and read 10714 times:
Planes can get struck by lightning. They do build up static potential while flying, as this thread has demonstrated, and they are obviously much closer to the clouds, so an oppositely charged cloud could discharge some potential to an airplane. More common, I would presume, is lightning just taking the path to the ground via the airplane. After all, electricity follows the path of least resistance, and the nice, conductive metal structure of the plane is much less resistive than the air.
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