Water and Seaplane Characteristics, Seaplane Bases, Maritime Rules, and Aids to Marine Navigation (ASES, AMES)

I work outside-in:

• Size, location, and protection — protected water shelters you from wind and swell; unprotected areas add both
• Surface wind and waves — read direction and strength from the water itself; wave systems have direction and height, and a swell system encountered on the step can itself initiate porpoising (FAA-H-8083-23 ch. 4)
• Current — it's stronger than intuition suggests: a 5-knot current can carry the seaplane against a 25-knot wind (FAA-H-8083-23 ch. 4), so plan taxi and sailing with both vectors
• Debris, sandbars, islands, and shoals — floating and partially submerged hazards, plus depth
• Vessel traffic and wakes — a boat wake crossed on the step can trigger skipping (FAA-H-8083-23 ch. 4)

The AMES layer: with two engines you also have differential power to aid steering on the water (FAA-H-8083-23 ch. 4), which changes your taxi options in wind.

Porpoising is a rhythmic pitching motion caused by dynamic instability in forces along the float bottoms while on the step — an incorrect planing attitude sets off a cyclic oscillation that steadily increases in amplitude unless the proper pitch attitude is reestablished. Nose too low builds a water crest under the bows that the floats ride over and dig into again; nose too high can also porpoise, or cause a premature lift-off at extreme AOA, stall, and a nose-down drop (FAA-H-8083-23 ch. 4).

Correction:

• Apply timely back pressure and hold it until the porpoising stops
• If it hasn't stopped by the second oscillation: power to idle, elevator control held firmly back, and let the seaplane settle with no further instability
• Never chase the oscillations — that makes them worse (FAA-H-8083-23 ch. 4)

Limits shift with gross weight, flap position, and CG — a forward CG increases the chance of high-angle porpoising, especially during landing (FAA-H-8083-23 ch. 4).

Skipping is instability from landing at excessive speed with the nose at too high a pitch angle — at the upper trim limit the seaplane enters a cyclic oscillation on touching the water and bounces across the surface like a skipped stone. It can also occur crossing a boat wake while taxiing on the step or during takeoff.

Telling them apart by feel: a skip gives vertical G forces like a bounced landplane landing; porpoising is a rocking-chair, forward-and-aft motion.

Correction: increase back pressure and add sufficient power to keep the floats off the water, establish the proper pitch attitude, then reduce power gradually and settle on.

Skipping oscillations don't grow in amplitude the way porpoising does, but they pound the floats and airframe — and can lead to porpoising (FAA-H-8083-23 ch. 4).

Through drag and its phases:

• Displacement (at rest and idle taxi): buoyancy carries the weight and the wetted area — the float surface below the waterline — is the drag driver; heavier means deeper means more wetted area
• Plowing: hydrodynamic lift raises the bows while the aft floats dig deeper, and water drag peaks at "the hump" just before the planing attitude
• The step: the specially shaped forward float bottom converts motion into hydrodynamic lift, wetted area shrinks, and acceleration to lift-off becomes possible without additional power (FAA-H-8083-23 ch. 4)

Hull differences matter to handling too: with the engine shut down, most flying boats sail backward and toward wherever the nose points, because a hull gives proportionally less keel effect than floats (FAA-H-8083-23 ch. 4).

• Charts: seaplane landing areas use symbols like land airports with an anchor in the center; tick marks mean fuel and services, a double ring means military (FAA-H-8083-23 ch. 1)
• Directories: the Chart Supplement lists data on record with the FAA for all open-to-the-public airports, seaplane bases, and heliports (AFH glossary) — including services and operating restrictions
• At night: the rotating beacon for a lighted water landing area alternates white and yellow; a double white flash alternating with yellow marks a military seaplane base (FAA-H-8083-23 ch. 1)

Restrictions extend onto the water itself: when circling the landing area, note buoys marking preferred channels, hidden dangers, or off-limits areas such as no-wake zones and swimming beaches (FAA-H-8083-23 ch. 6). Services at many bases are minimal, which the ACS flags as its own risk (AA.I.H.R4).

• General: keep clear of all vessels insofar as possible and avoid impeding their navigation; give way to anything with the right-of-way
• Crossing: the aircraft or vessel to the other's right has the right-of-way
• Head-on: each alters course to the right
• Overtaking: the one being overtaken has the right-of-way; the overtaking craft keeps well clear
• Special circumstances: when risk of collision exists, proceed with careful regard for circumstances including the limitations of the respective craft (91.115)

And the jurisdiction point examiners like: under Coast Guard regulations a seaplane on the water is a vessel — inshore of the demarcation line you follow the Inland Rules, seaward of it the International Rules, and all seaplanes must carry a current copy of the rules when operating in international waters (FAA-H-8083-23 ch. 1).

Both bind you because a seaplane on the water is a vessel:

• Naval vessel protection zone — a 500-yard regulated area of water surrounding any large U.S. naval vessel (greater than 100 feet in length), in effect whether the vessel is underway, anchored, moored, or in a floating dry dock (33 CFR 165.2015, 165.2025, 165.2030). Within the zone, operate at the minimum speed necessary to maintain a safe course and proceed as directed by the Coast Guard, the senior naval officer present in command, or the official patrol; no vessel or person may come within 100 yards of the naval vessel unless authorized — request authorization on VHF-FM channel 16
• No-wake zones — locally designated areas, marked by buoys, where vessels must hold to a minimum speed that produces no wake — typically near docks, marinas, and swimming areas. For a seaplane that means displacement (idle) taxi through them: step taxi throws a wake. Note them while circling the landing area, along with other off-limits areas (FAA-H-8083-23 ch. 6)

The U.S. buoyage system is built for vessels running channels to and from the sea, so read it from seaward:

• Can buoys — cylindrical, black or green, odd-numbered, mark the left (port) side of the channel approaching from seaward
• Nun buoys — conical, red, even-numbered, mark the right side: "red, right, returning" to home port
• Black and white vertically striped buoys mark the middle of the channel or fairway
• Daybeacons — the shallow-water equivalent, markers on pilings
• Numbers increase from seaward toward the coast; only the more important buoys are lighted (FAA-H-8083-23 ch. 1)

Practical caution: the mooring chain may be several times the water depth, so the buoy can float a good distance from its charted spot and from the hazard it marks — don't cut close to one (FAA-H-8083-23 ch. 1). Nautical charts come from NOAA's Office of Coast Survey, and Coast Guard light lists describe the lighted aids (FAA-H-8083-23 ch. 1).