Travel News - Lightning strike leads to cracked windshield?

UA flight from MSN to ORD got struck by lightning and made an emergency landing after the pilots discovered a cracked windshield. Did the lightning strike cause the cracked windshield? I thought that planes got hit by lightning all the time?

Link (http://www.channel3000.com/news/28171006/detail.html)

Each Airliner get hit by lightning, on average, once a year.

Cracked windshields are not that unusual. They're usually caused by a fault in the windshield heat which causes a hot spot on the window. As long as the cracks don't impair the pilot's vision, and icing conditions can be avoided, the airplane can continue to fly until the windsheild can be replaced.

Each Airliner get hit by lightning, on average, once a year.

Cracked windshields are not that unusual. They're usually caused by a fault in the windshield heat which causes a hot spot on the window. As long as the cracks don't impair the pilot's vision, and icing conditions can be avoided, the airplane can continue to fly until the windsheild can be replaced.

Interesting, thanks. So, other than impairing the pilot's vision, there's little risk of an actual break?

Probably just a coincidence:
http://www.avherald.com/h?article=43dd9a7e&opt=0

UA flight from MSN to ORD got struck by lightning and made an emergency landing after the pilots discovered a cracked windshield. Did the lightning strike cause the cracked windshield? I thought that planes got hit by lightning all the time?

Link (http://www.channel3000.com/news/28171006/detail.html)

Lightening, which is a discharge, produces intense heat and pressure, accompanied by a shock wave, either of which can crack a windshield depending on the loacation of the strike and propagation path of the charge.

Lightening, which is a discharge, produces intense heat and pressure, accompanied by a shock wave, either of which can crack a windshield depending on the loacation of the strike and propagation path of the charge.

Yeah, I understand that. I was just surprised that airplane windshields aren't designed to withstand them considering how frequent lightning strikes are.

They are designed to withstand them. Building are designed to withstand earthquakes, too, but there's always one bigger than the design specs.

Yeah, I understand that. I was just surprised that airplane windshields aren't designed to withstand them considering how frequent lightning strikes are.
Sometimes things happen that are beyond the design criterion.

Each Airliner get hit by lightning, on average, once a year.

Cracked windshields are not that unusual. They're usually caused by a fault in the windshield heat which causes a hot spot on the window. As long as the cracks don't impair the pilot's vision, and icing conditions can be avoided, the airplane can continue to fly until the windshield can be replaced.
I disagree with your contention that it;s safe to fly a plane with a cracked windshield.
Windshield isn't just for view. The windshield has to be able to withstand the pressure difference between the interior and exterior of the plane.
Seriousness of the crack depends on the type of crack and its location. A crack on the side would be more serious. When the crack is in the front, the pressure of the air ramming into the windshield would either keep it in place or allow the crack to propagate. But a window on the side does not have the excess pressure to balance the interior pressure. It's possible that you could fly the plane with the crack. But it's not a good practice. Of course, you have to keep flying if when it happens in air. But it should be replaced before it takes off again.
This is what common sense tells me. Heck, you aren't even allowed to drive a car with a crack in a windshield.

I disagree with your contention that it;s safe to fly a plane with a cracked windshield.

I've been an airline pilot for over 20 years. Every airliner that I've flown has allowed dispatch with a cracked windshield under certain conditions (windshield heat off for the cracked pane, no flight in icing conditions, and a max airspeed of 235 knots under 10,000'). The windshields are made up of multiple layers. It's not a single pane of glass.

I've flown many airliners with cracked windshields, the most recent being a 7+ hour flight over the South China Sea just last week. That airplane flew for about 17 hours, over three flights, with the cracked before the windshield was replaced.

I was booked on a United 747 from ORD to Hong Kong. The flight was delayed until the next day due to a cracked windshield. The next day, the flight was operated with a different aircraft.

Depends on which panes of the windsheild are cracked. On the one's that I've flown, it can not be the inner-most pane that is cracked but that's not the one that typically cracks. The cracks usually occur in the outer panes when there's a malfunction in the windshield heat which causes a hot spot with the uneven thermal expansion causing the cracks.

There are limitations on where and how big a crack can be. A single ply crack can be out near the edge of a windshield and be acceptable for further operations. Bring that crack into the area that the manual defines as the 'pilot's field of view', or several cracks in the same area, and a windshield change can become mandatory very quickly.

A crack due to a lightning strike is kind of rare due to the airframe being a better conductor around the windshield area unless it somehow happens to enter the heating element embedded between the layers. So far, all the cracked/shattered windshields I have seen have involved only one layer that failed, but have generally been caused by an issue with the heating element.

I've been an airline pilot for over 20 years. Every airliner that I've flown has allowed dispatch with a cracked windshield under certain conditions (windshield heat off for the cracked pane, no flight in icing conditions, and a max airspeed of 235 knots under 10,000'). The windshields are made up of multiple layers. It's not a single pane of glass.

I've flown many airliners with cracked windshields, the most recent being a 7+ hour flight over the South China Sea just last week. That airplane flew for about 17 hours, over three flights, with the cracked before the windshield was replaced.

Please pay attention to my words. Some cracks may not pose a significant safety hazard. But you cannot say "It's safe to fly an aeroplane with a crack in the windshield", if it's not always safe to fly a plane with every crack. The location and nature of the crack has to be taken into account.
Just because it might be or it is sometimes under specific consitions, doesn't mean that it is always so.

With all respect for your skills, a pilot is a pilot, not an expert on every aspect of aircraft. If it were so, there would be no need for different specialisations in aviation. Crack propagation is a specialised field, that's way beyoond the expertise of a pilot unless they have undertaken advanced/graduate studies in theory of elasticity, theory of stress analysis and analysis of structures, not just elastic structures but non elastic structures too.
Sure

Depends on which panes of the windsheild are cracked. On the one's that I've flown, it can not be the inner-most pane that is cracked but that's not the one that typically cracks. The cracks usually occur in the outer panes when there's a malfunction in the windshield heat which causes a hot spot with the uneven thermal expansion causing the cracks.

Did I not say seriousness of a crack depends on the type of crack and its location. You cannot make a blanket statement "it's safe to fly a plane with a crack in the windshield". All you can say, is "it may be safe to dry a plane with a crack in its windshield." There is a difference.
I don;t know why you are contradicting my statement.

Depends on which panes of the windsheild are cracked. On the one's that I've flown, it can not be the inner-most pane that is cracked but that's not the one that typically cracks. The cracks usually occur in the outer panes when there's a malfunction in the windshield heat which causes a hot spot with the uneven thermal expansion causing the cracks.

That's one way a crack can development. Mechanical and thermal shock is another. Composite panels, made of a number of layers, are difficult to analyse. To isolate one layer from another, different layers have to be separated by visco-elastic layers, which in case of a windshield, have to have high transmissibility and low reflectivity, which can tolerate shear, so that shock can be isolated and propagation of a crack from one layer to the next can be prevented.
Composie plates/teams is my specialty, I cannot fly a plane though. I would not argue with you about how to fly a plane.

Depends on which panes of the windsheild are cracked. On the one's that I've flown, it can not be the inner-most pane that is cracked but that's not the one that typically cracks. The cracks usually occur in the outer panes when there's a malfunction in the windshield heat which causes a hot spot with the uneven thermal expansion causing the cracks.

Thanks, Larry, as always. I always appreciate your wisdom.