4.20-4.25

IDENTIFY the characteristics and causes of tides and tidal currents.

Tides are the regular rising and falling of ocean water, mostly caused by the Moon’s gravity pulling on Earth’s oceans, with help from the Sun’s gravity. Currents are the side-to-side water movements connected to tides.As Earth rotates, different places move in and out of these bulges → we get two high tides and two low tides every lunar day (24 hr 50 min).

Flood current

Ebb current

slack water

water moving toward shore (filling up like a bathtub).

water moving away from shore (draining).

when the current is barely moving, usually when it’s switching direction.

LIST the reference publications used to predict tides and tidal currents

US Waters

outside US Waters

ALL

NOAA Tides and Currents website (real-time and predicted data)  NOAA’s official electronic programs (CO-approved)

Admiralty Total Tide (ATT) — used worldwide for computing tides and currents

Predictions are based on “reference stations” along your route — you check each one for the times and heights of tide

DESCRIBE the effect current has on your ship in restricted waters and open ocean

In restricted waters (

in open ocean

s (like a narrow channel or harbor), even a small current can push you sideways into the pier, shoals, or other ships. You might have to steer at an angle (“crab” the ship) to move straight.

currents still affect you but you have more space to adjust course gradually. They can change your arrival time, fuel use, and formation position with other ships.

Tide graphs and current graphs are like the “heartbeats” of the ocean

they show how the water level and movement change over time.

Tide graph

vertical movement (rise and fall of water height)

Peaks = high tide o Valleys = low tide Slope of the line tells you how fast it’s changing — steeper = faster change.

Current graph

horizontal movement (speed and direction)

Above the zero line =

Below the zero line =

Crossing the zero line =

flood current (toward shore) o

ebb current (away from shore) o

slack water (no movement).

components of small boat

Sponson – The inflatable tube around the outside. Adds stability and acts like a shock absorber. (If you’ve ever seen a big rubber bumper on a dock, this is like that, but all around the boat.)

 Keel – The backbone of the boat that runs along the bottom center. Helps the boat go straight and gives it strength.

 Flag Staff / Bow Post / Jack Staff – Poles for flying flags (important for signals).

 Sampson Posts – Strong vertical posts for tying lines or attaching equipment.

 Transom – The flat back of the boat where outboard engines or equipment mount.

 Hoisting Sling – Straps used to lift the boat with a crane or davit.

 Life Lines – Safety ropes around the boat so crew/passengers can grab on

Coxswain –

 Engineer / Sternhook –

 Bowhook –

 Boat Officer –

 Optional crew:

The “driver” and in charge of the boat when no Boat Officer is present. Responsible for safety, navigation, and boat handling in all weather. Knows the Rules of the Road. 

Keeps the engine running, does repairs underway, fuels the boat, checks the battery. Also helps tie up the boat from the stern.

Assists Coxswain, stands lookout, helps with lines and fenders, can drive if Coxswain is out. Often the SAR swimmer.

Directs Coxswain, ensures safety rules are followed, responsible for everyone aboard. Required in foul weather, poor visibility, unfamiliar harbors, large liberty party returns, or SAR.

Corpsman (medical), Gunner’s Mate (armed shark watch), Coast Guard LEDET or VBSS team for law enforcement boarding.

Mechanical (Slewing Arm Davit – SLAD)

Gravity (Double Pivot Gravity Davit)

Cranes

Uses powered arms to swing and lower the boat. 

Uses the boat’s weight and pulleys to lower it. Can also lift small boats, especially heavier or special craft.

special terms

Fall – Heavy cable used to raise/lower the boat.  Monkey Lines – Knotted ropes for crew to hold onto during lowering (must hold 80% of their body weight).  Sea Painter – Rope from the ship’s bow to the boat, keeping it alongside until ready to leave.  Steadying Lines – Keep the boat from twisting while lowering/raising.

DISCUSS planning speed, pivot turns, and how to prevent chine tripping and causing a small boat to become airborne.

Planing speed – The speed where the boat lifts slightly out of the water and skims across it. Faster and smoother but less stable in rough seas.  Pivot turn – A sharp 180° turn in place. Useful for quick maneuvering but risky if done too fast.  Chine tripping – When a boat skids sideways in a high-speed turn and the outside edge (chine) digs into the water, flipping the boat outward.  Prevent airborne maneuvers – Adjust speed for sea state; if you hit a wave too fast, the boat can launch into the air, leading to engine overspeed or crew injury.

DISCUSS the communications between aircraft, flight control and ships with respect to UHF, light signals, hand signals, and signal flags."

Think of this like a “multilingual conversation” between the ship and the helicopter. They can’t just shout to each other, so they use multiple communication methods:

comms betwwen aircraft and ships

UHF Radio – The pilot and ship talk over dedicated aircraft frequencies. Like a walkie-talkie but specific to aviation.  Light Signals – If radios fail or noise is too loud, they use colored lights to send instructions.

Example: “Waveoff” lights tell the pilot to abort landing.

 Hand Signals – The Landing Signalman Enlisted (LSE) stands in a bright yellow jacket on deck and uses body language like waving arms to guide the helicopter pilot.

 Signal Flags – The ship raises certain flags to tell everyone what’s going on. Example: Hotel Flag means helicopter ops in progress, so other ships know to stay clear.

DISCUSS the envelope necessary for air operations

The “envelope” is the safe range of wind direction, wind speed, and ship movement where helicopter operations can happen safely.

DESCRIBE the responsibilities of the flight deck crew.

TAO/CICWO – Oversees aircraft control from the Combat Information Center.

 Helo Control Officer (HCO) – Directs the helicopter during launch and landing.

 Landing Signalman Enlisted (LSE) – The human traffic controller on deck, guiding the pilot visually.

 Chock & Chain Crew (Blue) – Runs in after landing to chain the helo down so it doesn’t slide

.  Fueling Team (Purple) – Handles fuel safely and refuels the helo.

 Crash & Salvage Crew (Red) – Firefighters/rescue team in case something goes wrong.

 Flight Deck Safety Officer (White) – Watches over all operations for safety

DESCRIBE the Crash Crew equipment.

Crash crews have gear to fight fires, cut into a helicopter if needed, and rescue people. This includes:  Firefighting hoses & foam systems – to smother fuel fires.  Rescue tools – cutters, axes, spreaders to break into an aircraft fuselage.  Protective gear – suits that protect against heat and flames. Basically, it’s like having a mini fire department right on the flight deck.

DESCRIBE the considerations for conducting a HIFR/VERTREP."

 HIFR (Helicopter In-Flight Refueling) – When the helicopter can’t land (deck blocked or seas too rough), the ship sends up a fuel hose while the helo hovers.  VERTREP (Vertical Replenishment) – Moving cargo via helicopter, often between ships at sea.

DISCUSS the purpose and use of Polar Plots

Polar plots are safety maps that show where the ship can point in relation to the waves while doing helicopter ops.  They help avoid situations where waves splash the deck or hit the helicopter rotor.  They show safe “zones” for the ship’s heading to reduce risk in bad weather. Think of it like a compass chart with green “safe zones” and red “danger zones” for operating a helicopter.

DISCUSS the purpose, capabilities, limitations, and ship lighting configuration for NVG operations."

Night Vision Goggle (NVG) ops require very dim lighting so the goggles work.  Purpose: Allow night flying without blinding pilots.  Capabilities: Fly and land in near-darkness.  Limitations: Any bright light can blind NVG users temporarily.  Ship Lighting: Navigation lights dimmed, stern light turns blue, no white lights topside.

DISCUSS the purpose of use a Flight Plan.

A flight plan is like a roadmap for the day’s air operations:  Who’s flying.  When they’re flying.  Where they’re going.  What missions they’ll do. It keeps everyone on the same page so there are no surprises.

DISCUSS FOD and importance of a FOD walkdown.

FOD (Foreign Object Debris) – Any loose object that can get sucked into helicopter engines or damage equipment. Example: a bolt, screwdriver, or even a soda can. FOD Walkdown – Before flying, everyone walks the deck to pick up any loose objects. It’s like vacuuming before you turn on a fan — you don’t want things flying into it.

DISCUSS terms and definitions used to define weather events

Meteorology: the study of the weather, especially in forecasting. Weather: the way the atmosphere is behaving. The state of the Earth’s atmosphere with respect to temperature, humidity, precipitation, visibility, cloudiness, wind, and barometric pressure. Day-to-day state of the atmosphere at a given time and place. Atmosphere: the relatively thin shell of air, water vapor, and suspended particulates surrounding the Earth

DESCRIBE weather elements and how they are measured

Temperature – measured with a thermometer in °C or °F. Humidity – measured as relative humidity (%) with a hygrometer or psychrometer. Air pressure – measured with a barometer in inches of mercury (inHg), millibars (mb), or psi. Wind speed & direction – measured with an anemometer and wind vane (or combined as an aerovane). Clouds – observed visually; classified by form and height.

IDENTIFY the information available on Naval Oceanography Center weather messages

NAVMETOCCOMINST 3144.1 requires ships to take regular weather observations.

DESCRIBE the responsibilities of the OOD in heavy weather

Decision-making process should consider:  Vessel’s motion limits.  Present and future weather using all available resources.  Alternative routes (shortest distance vs. routes that use wind, sea, current, topography).  Adjustments for navigational restrictions. Avoid placing seas directly on the bow, stern, or beam.

DISCUSS formation of fog and ice

Fog types (formed by cooling):  Radiation fog – clear nights, high humidity, ground cools and air near it hits dew point.  Advection fog – warm moist air moves over cold surface (often water).  Upslope fog – warm moist air moves up a slope and cools

Fog types (formed by evaporation):

 Steam fog – cold dry air over warmer water, moisture evaporates and condenses (looks like steam).  Frontal/precipitation fog – warm air lifted over cold air, moisture evaporates into cold layer, raising humidity to dew point

ice

Topside icing – water spray freezes on ship surfaces, adding dangerous weight and making ship top-heavy.  Ice accretion rate depends on water temp, air temp, and wind speed (e.g., 45°F water + 25°F air + 30kts wind = 1" ice/hour).  Ice reduces stability, damages gear, and can block radar/comms.

DISCUSS how tropical cyclones are formed and techniques on how to avoid them

Formation: Need warm ocean water, moist air, and low wind shear. Tropical cyclones form over warm tropical seas where rising warm, moist air creates a low-pressure area. As air spirals inward, it rises, cools, and condenses, releasing heat that fuels the storm. Rotate counterclockwise in the Northern Hemisphere (cyclonic rotation). Avoidance techniques: Do not cross forecasted track (“crossing the T”). In Northern Hemisphere: Dangerous semicircle: put true wind on starboard bow (045°R), make max headway. Navigable semicircle: put true wind on starboard quarter, make max headway.

DESCRIBE the characteristics of the different types of fronts

Cold front: like an aggressive bulldozer of cold air plowing under warm air — pushes it up fast, makes big puffy storm clouds and sudden downpours.  Warm front: warm air slowly climbs over cold air like a ramp, making long, steady rain or drizzle and low clouds.  Occluded front: a cold front catches a warm front, lifting all warm air off the ground — weather can be messy with mixed rain and clouds.  Stationary front: neither air mass moves much — can cause days of gray, wet weather.

DESCRIBE the requirements for logging and reporting weather information

NAVMETOCCOMINST 3144.1: ships must take and report regular weather observations.  Fleet Commander can exempt; OTC may designate a guard ship.  Reports are legal records for accident investigation and stored for climatology.  Reports include: position, present weather, wind speed/direction, sea height, swell, water temp, pressure, air temp.  Significant observations during “minimize” conditions: o Winds > 25 kts, seas ≥ 12 ft, moderate/heavy precipitation, visibility < 1 NM, volcanic ash, et

DISCUSS the requirement for submitting and contents of an OTSR report

OTSR (Optimum Track Ship Routing): advisory service to minimize heavy weather exposure.  Request sent via MOVREP at least 72 hours before departure.  Daily OTSR reports include: date/time, position, course/speed, RPM, wind direction/speed, sea direction/period/height, barometer, sea temp, remarks.  Recommendations/diversions sent during transit based on ship’s limits.

IDENTIFY the importance of the Global Positioning System in regard to navigational history

Before GPS, sailors used the sun, moon, stars, and horizon angles to figure out where they were. In the 1920s, they started using radio signals from land-based stations to help navigate. Then came satellites — which made it possible to send accurate navigation signals from space anywhere in the world. The U.S. military made GPS mainly so it could deliver weapons exactly where they needed to go and so all branches used one common navigation system.

IDENTIFY the common uses of the Global Positioning System

Navigation — knowing the ship’s position, course, and speed precisely.

2. Data collection — logging location of events, surveys, and research.

3. Targeting — guiding weapons to exact coordinates.

4. Mine hunting — marking precise locations of hazards so they can be avoided or removed.

STATE the advantages and disadvantages of the Global Positioning System

Advantages:  Accurate, instant 3D position and velocity.  Standard time provided.  24/7 coverage, all weather.  Passive system (unlimited users). Disadvantages:  Antenna masking.  Electromagnetic interference.  Jamming.  Spoofing.

LIST the three major segments of the Global Positioning System

Space Segment — 31 satellites in 6 orbital planes at ~20,200 km altitude. 2. Control Segment — Master Control Station, monitor stations, and ground antennas. 3. User Segment — receivers that calculate position.

IDENTIFY how a GPS receiver determines its correct position using satellites as reference points

Satellites orbit Earth twice a day, sending time and position. Receiver measures the time signal took to arrive → distance to each satellite.

 Trilateration: o 3 satellites → latitude, longitude, altitude. o 4th satellite → corrects clock error for more precision. Uses speed of light for distance calculation.

LIST factors that affect Global Positioning System accuracy

Receiver navigation mode.

 Ionospheric conditions.

 Satellite geometry (Dilution of Precision).

 User range accuracy effects.

DESCRIBE sources of Global Positioning System errors

User clock bias.  Satellite clock bias.  Atmospheric interference.

IDENTIFY the procedures to interpret Global Positioning System navigation data

use position, velocity, and time outputs; verify with other nav systems. Check position in latitude/longitude. Check course over ground (COG) and speed over ground (SOG). Compare with charts and radar to verify it makes sense. Never trust GPS as your only source — cross-check to avoid disasters like the USS Lamoure County grounding

IDENTIFY the principles of chart datums

A datum is like the “lens” your GPS uses to look at the Earth. Different lenses show slightly different shapes and sizes, so a point’s coordinates can shift. GPS uses WGS 84, but if your chart uses a different datum, your position could appear off — sometimes by hundreds of meters — unless you correct for it.

STATE chart datum mismatch and its impact on modern navigation

If your GPS is set to WGS 84 but your chart is based on another datum, your “X marks the spot” might actually be somewhere else in real life. That’s how ships can run aground even though GPS says they’re in safe water.

IDENTIFY the limitations of commercial Global Positioning System receivers

Civilian GPS units are accurate enough for most uses but lack military encryption and anti-spoofing features. They’re more vulnerable to jamming and can’t do ionospheric corrections as precisely as military receivers.