And what country can preserve its liberties if their rulers are not warned from time to time that their people preserve the spirit of resistance? Let them take arms. The remedy is to set them right as to facts, pardon and pacify them. What signify a few lives lost in a century or two? The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants.
Static electricity. One night we're hoisting to a 42' CG boat, they are training a new guy on the boat. The helo blades (3 of them) are generating static electricity all the time, I lower the basket to the stern of the boat, the new guy reaches for the basket and a big blue spark (static electricity) jumps 6 inches - foot from the basket to the NG's hand. He jumps back. The helo blades are still generating static elect, so when he reaches for it... pow! again. Happened 3 times before his trainer came out and grabbed the basket and got bit only once. He held on until the basket was sitting on the deck and the helo was then grounded. The next cycle the NG did it right.
With a bridging outfit at Ft Carson. Ribbon bridge. We were training on dumping our bays of bridge on land then hooking them to a chinook to be flown to teller reservoir to be dropped and connected. Same thing happened to a couple of guys that were trying to hook up to the chinook, big flash of blue and the guys knocked back. Good times.
For planning purposes, we always figured the typical passenger jet was hit by lightning once a year. More for planes that live in tropics, less for those that fly northern latitudes. That's how a lightning bolt exits the aircraft - leaves from a point, usually on the ends of the wings, or the horizontal stabilizer back near the rear of the aircraft.
The trick is keeping the lightning bolt from bothering anything on the plane.
What SiGraybeard said. There is a new section in the aircraft maintenance manual for the big iron called L/HIRF (Lightning/High Intensity Radiated Field). I've seen bizjets come back with scorched static wicks and melted diffuser strips on the radome and the pilots were unaware of a strike. Modern composite fairings have a micro-thin stainless steel mesh just beneath the paint and the fuel tank area of the wing is coated with aluminium loaded paint to dissipate a strike.
Aluminum body airplanes are in effect a Faraday cage so usually the people and avionics inside are not affected. Newer composite airplanes have more of an issue with discharging static buildup. It is a form of St. Elmo's fire first seen on sailing ships long ago.
That wingtip strike exited from a static wick. Most commercial aircraft have several of them on the wing tips, horizontal stab and the vertical stab. In spite of that it is not unusual to have to blend out strikes on the airframe. Most often they show up where rivets attach skin to frame. Sometimes they are so deep you have to replace the rivet. Composites usually have flame spray aluminum, metallic mesh, or conductive epoxy that acts as a conductor to move the lightning strike to an area with a static wick where it can discharge.
Early in my Naval aviation career, in the mid 70's, we were flying a training mission off the coast of Florida in a P-3C. St. Elmo's fire was quite active arcing off the windshield wipers. Suddenly, we took a lightning strike to the radome. A huge ball of static electricity, about the size of a basketball, formed behind the flight engineers seat and started traveling down the aisle of the plane. It passed through the torso of one of the crew and knocked him on his azz then continued down the aircraft and finally exited out the tail of the plane. As a parting gesture, it blew the cover off the magnetic anomaly detector (MAD boom). Over the course of a 20 year career, I've experienced several lightning strikes and seen the results of other flights as well. Always a scary situation.
Blame gremlins (not the little American Motors cars of yesteryear).
ReplyDeleteNow that is some downright weird shit?
ReplyDeleteStatic discharger?
ReplyDeleteStatic electricity.
ReplyDeleteOne night we're hoisting to a 42' CG boat, they are training a new guy on the boat. The helo blades (3 of them) are generating static electricity all the time, I lower the basket to the stern of the boat, the new guy reaches for the basket and a big blue spark (static electricity) jumps 6 inches - foot from the basket to the NG's hand. He jumps back. The helo blades are still generating static elect, so when he reaches for it... pow! again. Happened 3 times before his trainer came out and grabbed the basket and got bit only once. He held on until the basket was sitting on the deck and the helo was then grounded.
The next cycle the NG did it right.
It was a BIG blue spark! :-)
Working with LSB in Okinawa, they'd let the newbie climb up the cargo net to trip the hook.
DeleteIn that hot tropic air, a few went flying.
😁
With a bridging outfit at Ft Carson. Ribbon bridge. We were training on dumping our bays of bridge on land then hooking them to a chinook to be flown to teller reservoir to be dropped and connected. Same thing happened to a couple of guys that were trying to hook up to the chinook, big flash of blue and the guys knocked back. Good times.
DeleteFor planning purposes, we always figured the typical passenger jet was hit by lightning once a year. More for planes that live in tropics, less for those that fly northern latitudes. That's how a lightning bolt exits the aircraft - leaves from a point, usually on the ends of the wings, or the horizontal stabilizer back near the rear of the aircraft.
ReplyDeleteThe trick is keeping the lightning bolt from bothering anything on the plane.
What SiGraybeard said. There is a new section in the aircraft maintenance manual for the big iron called L/HIRF (Lightning/High Intensity Radiated Field). I've seen bizjets come back with scorched static wicks and melted diffuser strips on the radome and the pilots were unaware of a strike. Modern composite fairings have a micro-thin stainless steel mesh just beneath the paint and the fuel tank area of the wing is coated with aluminium loaded paint to dissipate a strike.
ReplyDeleteAl_in_Ottawa
Aluminum body airplanes are in effect a Faraday cage so usually the people and avionics inside are not affected. Newer composite airplanes have more of an issue with discharging static buildup. It is a form of St. Elmo's fire first seen on sailing ships long ago.
ReplyDeleteThat wingtip strike exited from a static wick. Most commercial aircraft have several of them on the wing tips, horizontal stab and the vertical stab. In spite of that it is not unusual to have to blend out strikes on the airframe. Most often they show up where rivets attach skin to frame. Sometimes they are so deep you have to replace the rivet. Composites usually have flame spray aluminum, metallic mesh, or conductive epoxy that acts as a conductor to move the lightning strike to an area with a static wick where it can discharge.
ReplyDeleteEarly in my Naval aviation career, in the mid 70's, we were flying a training mission off the coast of Florida in a P-3C. St. Elmo's fire was quite active arcing off the windshield wipers. Suddenly, we took a lightning strike to the radome. A huge ball of static electricity, about the size of a basketball, formed behind the flight engineers seat and started traveling down the aisle of the plane. It passed through the torso of one of the crew and knocked him on his azz then continued down the aircraft and finally exited out the tail of the plane. As a parting gesture, it blew the cover off the magnetic anomaly detector (MAD boom). Over the course of a 20 year career, I've experienced several lightning strikes and seen the results of other flights as well. Always a scary situation.
ReplyDelete