Francis Scott Key Bridge in Baltimore collapses

[TuFun 437]

 

[Paul K 1,336]

Dreadful to watch. There's a plume of smoke above and to the left just before she hits the bridge support - engine going full astern, maybe.

The conspiracy people are already at work, of course.🙄

Edited March 26 by charliearon
edit out attempted swear!

[Paul K 1,336]

Another video, showing the power failure aboard the ship as it approached the bridge, and how that might have contributed to the collision.

https://www.youtube.com/watch?v=qZbUXewlQDk

[HiFlyer 9,361]

1 minute ago, Paul K said:

Another video, showing the power failure aboard the ship as it approached the bridge, and how that might have contributed to the collision.

https://www.youtube.com/watch?v=qZbUXewlQDk

Just got back home after glancing at the story this morning. My theory was power failure.

Either way, some insurance company(s) are about to get hit, hard!

[Bob Scott 7,721]

I started college on a Navy scholarship, and as part of that deal I took a naval ship systems course...I remember learning about a phenomena called "transverse thrust" or "propwalk" that results when you back down a ship with the screw in reverse.  When the ship is moving forward, there's not a lot of yaw moment from the water being pushed aft by the screw(s) (think P-factor in a plane), but when the screw rotation is reversed, it pushes a large and asymmetric volume of water up against the two sides of the hull, creating a large differential in hydrodynamic pressure, and as a result, forcing the stern to translate laterally off to one side.  On ships with multiple, counter-rotating screws, it's not a huge deal, but on a ship with a single large screw like the MV Dali, it certainly is.

As part of my Navy midshipman training, I was stationed aboard the 46,000-ton USS Mars out in the West Pacific for about half of my first summer in college.  One morning right around dawn we found ourselves in the middle of a fleet of small fishing vessels in the Phillippine Sea.  When we started seeing small radar contacts popping up at short range all around us, the young Lt jg that had the conn called "all stop", and was quickly overridden by the ship's executive officer, who immediately called for "all ahead full" and had us push it up to 15 knots to get more water flowing over the rudder and give the ship the increased rudder authority needed to maneuver around/through that gaggle of fishing boats.  If you hit something with a vessel that large, regardless of whether you're going 3 knots or 15, it's gonna make a big mess...better to keep the speed up so you can steer around trouble.

From watching the video, it sure looks like they lost power for an entire minute, which probably felt like a friggin' lifetime underway in the harbor channel at night.  Then about the time they got power back, they apparently backed it down hard (evidenced by the thick diesel smoke plume from the stack that started soon after the lights came back on) and the stern swung around hard to port, steering the ship's track hard over to starboard.  With the combination of slow speed and flow under the transom being further disrupted by the screw in reverse, the rudder effectiveness would have been diminished, very possibly to the point where it could not counteract the large yawing moment from the transverse thrust.

When I was stationed at Andrews AFB in DC in the late 90s, some guy jumped up on top of the Woodrow Wilson bridge threatening to jump.  The WW bridge, like the Francis Scott Key bridge in Baltimore is part of a major artery in the local road network--it carries the DC Beltway (I-495) across the Potomac on the south side of the city.  They closed that bridge for about 8 hours, and the traffic impacts were just unbelievable.  As if Baltimore didn't already have enough problems, this is gonna bork traffic there for months, if not years.

 

[threexgreen 3,139]

24 minutes ago, Bob Scott said:

When we started seeing small radar contacts popping up at short range all around us, the young Lt jg that had the conn called "all stop", and was quickly overridden by the ship's executive officer, who immediately called for "all ahead full" and had us push it up to 15 knots to get more water flowing over the rudder and give the ship the increased rudder authority needed to maneuver around/through that gaggle of fishing boats.  If you hit something with a vessel that large, regardless of whether you're going 3 knots or 15, it's gonna make a big mess...better to keep the speed up so you can steer around trouble.

Titanic...

[Paul K 1,336]

2 hours ago, Bob Scott said:

I started college on a Navy scholarship, and as part of that deal I took a naval ship systems course...I remember learning about a phenomena called "transverse thrust" or "propwalk" that results when you back down a ship with the screw in reverse.  When the ship is moving forward, there's not a lot of yaw moment from the water being pushed aft by the screw(s) (think P-factor in a plane), but when the screw rotation is reversed, it pushes a large and asymmetric volume of water up against the two sides of the hull, creating a large differential in hydrodynamic pressure, and as a result, forcing the stern to translate laterally off to one side.  On ships with multiple, counter-rotating screws, it's not a huge deal, but on a ship with a single large screw like the MV Dali, it certainly is.

 

I'll bet you are exactly right in this. Well said.

[DavidP 1,412]

1 hour ago, Paul K said:

I'll bet you are exactly right in this. Well said.

As a practising marine pilot of 20 years experience it is exactly right.

[Paul K 1,336]

3 hours ago, DavidP said:

As a practising marine pilot of 20 years experience it is exactly right.

David, thanks for that - with the internet awash with conspiracy idiocy, it is refreshing to read people who actually know what they are talking about.

I was an engineer officer, so I couldn't see what was going on up top - though in this case, I probably would have been very grateful for that! Transverse thrust was something we knew of, but it really was the concern of those upstairs on the other end of the telegraph. It explains why M.V. Dali is seen turning in towards the pier in the last moments.

With the loss of life, a tragic accident. I have a feeling we'll get the initial investigative reports very soon.

Edited March 27 by Paul K

[stans 703]

No need for conspiracy theories, it was a mechanical failure and, unfortunately, this time it happened as this boat was approaching the bridge.

[Paul K 1,336]

4 hours ago, stans said:

No need for conspiracy theories,

Try telling the fantasists that.

Yesterday I saw one that said it couldn't have been an accident, because the ship hit the exact point that would cause the bridge to collapse. She was completely oblivious to the idea that there was no other point that the ship could have hit - it would have passed underneath, and we would never have heard of M.V. Dali. I just can't grasp conspiracy fantasists' mental processes and idiotic logic at times.

[Adrian123 1,015]

12 minutes ago, Paul K said:

Try telling the fantasists that.

Yesterday I saw one that said it couldn't have been an accident, because the ship hit the exact point that would cause the bridge to collapse. She was completely oblivious to the idea that there was no other point that the ship could have hit - it would have passed underneath, and we would never have heard of M.V. Dali. I just can't grasp conspiracy fantasists' mental processes and idiotic logic at times.

Space may be the final frontier, but it's made in a Hollywood basement

[Bob Scott 7,721]

28 minutes ago, Paul K said:

Try telling the fantasists that.

Yesterday I saw one that said it couldn't have been an accident, because the ship hit the exact point that would cause the bridge to collapse. She was completely oblivious to the idea that there was no other point that the ship could have hit - it would have passed underneath, and we would never have heard of M.V. Dali. I just can't grasp conspiracy fantasists' mental processes and idiotic logic at times.

Last night my wife showed me an internet video from yet another soldier in the conspiracy clown army, who was whipping himself into a lather over the bright flashes on the NE end of the collapsing span, concluding that they must be explosive charges set to demolish the bridge.

Of course it was actually electrical arcing as the high voltage electric cables that ran along the bridge were being torn loose and faulting.  But hey, don't try to tell the clown that...

[charliearon 3,024]

I'm blaming it all on Godzilla!

 

[DD_Arthur 1,050]

2 hours ago, charliearon said:

I'm blaming it all on Godzilla!

Now there’s a theory we can all get behind!😆