USS JFK CV67

Who: Paul Montgomery, Boiler/Eng Controls USS JFK CV67 (79-81) Military Contractor

Where: Aboard USS JFK [3]

• Length: 1,052 feet
• 4 steam turbines
• Holds 80+ aircraft

What: An emergency stop test of the aircraft carrier USS JFK [2]

• Typically, large ships generally coast to a stop.
• Typically, it takes about 5 miles for a military aircraft carrier to coast to a stop.
• If they have to stop suddenly in an emergency, the engineers in the engine room “full reverse” the props.
• The balance is to apply as much reverse power to the props as possible without breaking something in the full drive train and/or the actual props.
• The water around the props will begin to boil – cavitate. [1]
• The aircraft carrier can accomplish an emergency stop within a few ship’s lengths.
• In an “emergency stop test,” EVERYTHING is firmly secured and strapped down. [2]

. . . . .

“An object in motion tends to stay in motion.”  That is Newton’s first law of motion.  Once something gets moving, it wants to stay moving.  When it comes to an aircraft carrier, the ship will stay in motion for about five miles — that is the distance from here to ______ — before it coasts to a stop.

The ship can be stopped a lot faster, but it takes a lot of skill to accomplish that in an emergency.  It can be done in a couple of ship lengths by a “full-reverse” of the props, but the water around the props begins to boil, and the generated shock waves can accomplish a lot of damage to the machinery in the engine compartment.

Here is what Paul Montgomery says about that experience . . . .

• The ship starts shaking.
• The throttleman and boiler console operator are working desperately together to keep from breaking stuff.
• People are calling off times and pressures as everything starts vibrating.
• Dust and dirt falls on you from the pipes and wiring above.
• Hands grab tight to things bolted down to keep standing.
• The props try to catch water so hard that it boils. Yes, the water boils as the pressure is lowered, and it turns to steam.
• 82,655 tons of metal that wants to keep on moving, and it all protests loudly.

Likewise, some sins and sinful situations are hard to stop as they play out in life.  As one tries to manage the by-products of that sin, midst the terrible accompanying decisions.

Like David, he sought to manage his sin with Bathsheba — hoping he could coast the ship to a stop, and then finally David had Uriah killed in battle. Be assured, there were loud protests of the Spirit as to how wrong that decision was.

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Other Information & Links:

1. The static pressure falls below the vapor pressure.  That is why bubbles form when you heat water, and those bubbles then collapse and produce steam vapor.  However, when this propeller phenomenon happens, bubbles and steam vapor are created due to the rapid movement of water, and vapor-filled cavities or voids are formed. Their collapse generates shock waves that can and do damage machinery.
— https://dmsonline.us/bubbles-are-bad-the-cause-and-effects-of-propeller-cavitation/

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2. A Personal Account By Paul Montgomery, Military Contractor

I was present for an emergency stop test in the engine room of the JFK back in the early 80s. I have first-hand knowledge of doing this. . . . Please fasten your seat belts.

A ship has no brakes. Normally it coasts to a stop.

This takes about five miles for a carrier at full speed as someone else alluded to in another answer.

You can do this in a car coming to a red light if you want to. It will irritate the other drivers, but who cares right?

Now imagine a car with no brakes. You coast to a stop just like ships do.

Everything is fine until some guy ruins your day by pulling out in front of you.

What do you do, You have no brakes?

YOU CRAM IT INTO REVERSE AND STEP ON THE GAS.

In cars, that would likely break something even if you have a straight shift, but you can do it if you are:

• In the dirt.
• Aided by brakes.
• Have fancy foot work.

I can hear the comments now. Impossible.

• It’s not.
• I’ve done it.
• Yes it is likely to tear things apart.

I’ll refrain from giving the details of when, where and why I did this. I am not sure what the statute of limitations is.

On an aircraft carrier, you are doing just that when you do an emergency stop. In the engine room, things are absolutely screaming in protest.

• The ship starts shaking.
• The throttleman and boiler console operator are working desperately together to keep from breaking stuff.
• People are calling off times and pressures as everything starts vibrating.
• Dust and dirt falls on you from the pipes and wiring above.
• Hands grab tight to things bolted down to keep standing.
• The ship’s tires start losing grip. That’s the screws (props) as they try to catch water so hard it boils. Yes, the water boils (cavitates). As the pressure is lowered, it turns to steam.
• A few might wet themselves just a little.
• 82,655 tons of metal that wants to keep on truckin’ protests loudly.

And it does not take miles to stop.
It happens in a few ship lengths.
Remember, a mile is only five lengths of a US aircraft carrier.

Yes, it is intense.

We did this without any equipment on the flight deck. No planes. No green, red, yellow, white, blue, brown, or purple shirted guys running around. Everything tied down tight.

Bonus memory

The night I reported to the ship it was dark and rainy. I walked up to the watch at the pier and showed my orders. He pointed toward this dark shadow. I was confused.

“Is the ship behind that warehouse?” I asked.

He laughed and said, “That warehouse is the ship”

You really can’t appreciate the size of a US Carrier until you walk up and get swallowed by it.

3. — https://en.wikipedia.org/wiki/USS_John_F._Kennedy_(CV-67)