Confined Area Takeoff and Maximum Performance Climb (ASES, AMES)

Purpose: departing a body of water too small for a straight-line takeoff run into the wind. The technique the handbook offers: begin the takeoff run headed downwind, then turn to complete the takeoff into the wind — put the seaplane on the step on a downwind heading, then make a step turn into the wind to finish (FAA-H-8083-23 ch. 4).

First lesson: exercise caution when using this technique, since wind and centrifugal force are acting in the same direction and could result in the seaplane tipping over. The water area must be large enough to permit a wide step turn, and winds should be light.

That is the whole risk brief in two sentences, and it is the reason this maneuver is instructor-supervised long after a student can fly a normal water takeoff.

• Establish a pitch attitude to maintain the recommended obstacle clearance airspeed or VX, ±5 knots, until the obstacle is cleared or until the airplane is 50 feet above the surface (S12)
• Then establish a pitch attitude for VY and accelerate to VY ±5 knots after clearing the obstacle or at 50 feet AGL if simulating an obstacle (S13)
• Retract flaps, if extended, after a positive rate of climb has been verified or per the manufacturer (S14)
• Maintain VY ±5 knots to a safe maneuvering altitude (S15), with directional control and proper wind-drift correction throughout (S16)
• Analyze and correct common errors related to this Task (S18) — the skill element that turns the whole Task from flying into teaching
• Plus the seaplane-specific skills: verify the assigned/correct takeoff path, taxi into position utilizing maximum available takeoff area, retract the water rudders, maintain the most efficient planing/lift-off attitude and correct for porpoising and skipping, and avoid excessive water spray on the propeller(s)

Damage. Water rudders are normally retracted before applying takeoff power. The buffeting and dynamic water pressure during a takeoff can cause serious damage if the water rudders are left down (FAA-H-8083-23 ch. 4).

Teach it as a checklist item with a consequence attached, not as a memorized step — a student who knows why will notice a missing item on a busy confined-area departure. The mirror-image habit is on landing: the water rudders are also retracted for landings and lowered again once the seaplane settles into a displacement taxi.

That the water is often not the limiting factor. In some cases the water area may be adequate but surrounding high terrain creates a confined area. The terrain may also block winds, resulting in a glassy water situation as well. Such conditions may lead to a dangerous situation, especially when combined with a high density altitude (FAA-H-8083-23 ch. 4).

Three planning items that follow, all worth making a student say out loud:

• If the departure path leads over high terrain, consider circling back over the water after takeoff to gain altitude
• If air temperatures have increased since landing, make the proper allowance for reduced takeoff performance due to the change in density altitude — and consider spending the night to take advantage of cooler temperatures the next morning
• Consider leaving some cargo or passengers behind if takeoff safety is in question. It is far better to make a second trip than to end your takeoff in the trees along the shore

This is the real content of the Task: it is a judgment maneuver with a flying component, and the ACS grades your ability to teach the judgment.

Because the penalty compounds. High, hot, and humid conditions reduce engine power and propeller efficiency, and the seaplane must also attain a higher water speed in order to generate the lift required for takeoff. This increase in water speed means overcoming additional water drag. All of these factors combine to increase takeoff distances and decrease climb performance (FAA-H-8083-23 ch. 4).

The instructor-depth reason water drag makes it worse than in a landplane: drag increases as the square of speed on the floats, and as weight increases the floats sink deeper, creating more wetted area and more drag during initial acceleration (FAA-H-8083-23 ch. 4, ch. 5).

Teaching consequence: in high density altitude conditions, consider not only the length of the water run, but the room required for a safe climbout as well. In a confined area, the climbout is usually the binding constraint.

Four phases: the displacement phase, the hump or plowing phase, the planing (on the step) phase, and the lift-off (FAA-H-8083-23 ch. 4).

The mechanism, at instructor depth:

• Displacement — the floats displace a volume of water weighing exactly as much as the seaplane; the submerged surface is the wetted area, and it is the major source of drag
• Plowing — hydrodynamic lift pushes the float bows up, moving the center of buoyancy aft; combined with full back elevator forcing the rear of the floats deeper, this creates more wetted area and more drag, which is why the seaplane accelerates so slowly here. The peak is the hump
• Planing — past the hump, weight is supported entirely by hydrodynamic lift; relaxing back pressure lets the float rock up onto the step, reducing wetted area, which allows acceleration, which increases hydrodynamic lift
• Lift-off — at flying speed; sometimes you gently help the floats unstick with a little aileron to lift one float, or a small amount of back pressure

The narration line that teaches the whole thing: "Full back through the hump, then ease it onto the step and let it accelerate."

The aerodynamics and both the nose-low and nose-too-high mechanisms are covered under Task II.L — teach them on the ground before this flight, not during it. What this Task adds is the part that happens at 40 knots on the step.

Correction, as the student flies it: apply timely back pressure to prevent the bows from digging in, and maintain it until porpoising stops. If porpoising does not stop by the time the second oscillation occurs, reduce the power to idle and hold the elevator control back firmly so the seaplane settles with no further instability. Never try to "chase" the oscillations — this usually makes them worse and results in an accident (FAA-H-8083-23 ch. 4).

That last sentence is why this is an instructor problem. Chasing is the instinctive response, so a student under startle will do it, and each cycle is more severe than the last — uncorrected it noses the seaplane into the water, with extensive damage or possible capsizing.

Your trigger is unusually clean because the handbook counts it for you: the second oscillation. Brief it as a number, not a judgment — "if it's still porpoising on the second cycle, I'm taking it" — then say "I have the flight controls" (AIH ch. 9) and close the throttle. Don't wait to see whether the student's back pressure is going to work on cycle three; by then the amplitude has doubled and the correction that worked on cycle one no longer does.

Task II.L carries the definitions and the trim-limit mechanism. In the airplane you need one discriminator the student can apply in under a second, and the handbook gives you a body sensation: a skip gives the body vertical "G" forces, similar to bouncing a landplane. Porpoising is a rocking chair type forward and aft motion feeling (FAA-H-8083-23 ch. 4).

Teach it that way — up-and-down is a skip, back-and-forth is a porpoise — because it's the only cue available with the airplane already moving. Say it on the ground, then name it out loud the first time each one happens: "that's a skip — feel the vertical." Naming it in the moment is what makes the cue stick (law of intensity).

Correction: increase back pressure on the elevator control and add sufficient power to prevent the floats from contacting the water. Then establish the proper pitch attitude and reduce power gradually to allow the seaplane to settle gently onto the water.

The instructor's reason to insist on the distinction is that the two have different urgency. Skipping oscillations do not tend to increase in amplitude, as in porpoising — so a skip gives you time to coach, and you should. But skipping subjects the floats and airframe to unnecessary pounding and can lead to porpoising, and once it does, the divergent problem takes over and your second-oscillation trigger applies. A student who misidentifies a porpoise as a skip will coach themselves right through the window in which the correction still works.

Because the "correct" planing attitude is not one fixed picture. The upper and lower limits of these pitch angles are established by the design of the seaplane; however, changing the seaplane's gross weight, wing flap position, or center of gravity location also changes these limits (FAA-H-8083-23 ch. 4):

• Increased weight increases float displacement and raises the lower limit considerably
• Extending the wing flaps frequently trims the seaplane to the lower limit at lower speeds, and may lower the upper limit at high speeds
• A forward center of gravity increases the possibility of high angle porpoising, especially during landing

The instructional consequence the handbook states directly: pilots must learn and practice the correct pitch attitudes for takeoff, planing, and landing for each type of seaplane until there is no doubt as to the proper angles. So teach the attitude by sight picture and by the conditions that shift it — a student who learned the picture at light weight will find it wrong on a loaded confined-area departure.

Two techniques, and the confined area usually chooses for you (FAA-H-8083-23 ch. 4):

• Controlled weathervaning — before adding power, use the water rudders to set up a heading somewhat downwind of the aim point, with the lead angle sized to the wind, so the seaplane weathervanes to the desired heading as it gains enough speed for the air rudder and ailerons to become effective. Use full aileron into the wind as the run begins, maintaining enough to keep the upwind wing from lifting.
• The downwind arc — a curved path starting somewhat into the wind and turning gradually downwind, using centrifugal force to balance the wind force, adjustable by varying rudder pressure. The tightest part of the downwind arc is when the seaplane is traveling at slower speeds.

Throughout: pick a spot on the shore as an aim point, because there are no clear reference lines for directional guidance and waves may make it appear that the water is moving sideways when it is not — the water is nearly stationary and the waves are only up-and-down motion.

The consequence of getting it wrong is named: the downwind float submerges, the wingtip catches, and the seaplane waterloops — in a fully developed waterloop it may be severely damaged or may capsize. Keep in mind that the allowable crosswind component for a floatplane may be significantly less than for the equivalent landplane.

Unlike the AFH's landplane Tasks, the Seaplane Handbook prints no numbered common-error list — so build yours from the failure modes it does describe (FAA-H-8083-23 ch. 4). Name the error, then give one corrective phrase:

• Surveying the water but not the climbout — "Where does the departure path go?" The handbook's own warning is that the water area may be adequate but surrounding high terrain creates a confined area
• Ignoring density altitude since the landing — "What has the temperature done?" Make the proper allowance for reduced takeoff performance due to the change in density altitude
• Water rudders left down — buffeting and dynamic water pressure during a takeoff can cause serious damage
• Failing to use the maximum available takeoff area (S6) — the seaplane version of not backtaxiing
• Nose too low through the hump, producing excessive water spray on the propeller(s) — "Full back through the hump"
• Chasing a porpoise instead of applying steady back pressure — never try to "chase" the oscillations
• Under-correcting in crosswind, letting the upwind wing lift — full aileron into the wind as the run begins
• Premature lift-off at high AOA, the nose-too-high porpoise, which ends in a stall and a nose-down drop into the water
• Leaving VX before the obstacle (or never establishing it), which busts S12

Teach the list as a diagnostic order: planning errors happen before the run, technique errors on the step, and standard errors in the climb.