Operation of Systems

Answers come from the POH/AFM and the type-specific FSB Report — almost every good answer starts with your airplane's numbers, not generic ones. Differently than at commercial, the ACS expects you to:

• Explain and describe the operation of the aircraft systems and components using correct terminology (AA.I.A.S1)
• Recall immediate action items or memory items (AA.I.A.S2)
• Identify system or component limitations listed in the POH/AFM (AA.I.A.S3)

The knowledge elements sweep every system from landing gear to HUD (AA.I.A.K1–K16), but the evaluator samples; what's graded throughout is whether you answer in your airplane's terms and know where the limitation lives. The systems fundamentals — landing gear, brakes, and anti-skid (K1), powerplant (K2), fuel (K4), oil (K5), hydraulics (K6), flight controls (K12), and pitot-static (K13) — are built card-by-card in the Commercial guide's systems task; the ATP layer on each is your type's architecture and AFM limitations. K9's avionics sweep (ADS-B, CPDLC, GNSS, ELT, EFB) lives in the Instrument and Commercial guides, and TCAS and terrain warning systems are covered under Task I.E. Deferring inoperative equipment (AA.I.A.S4, K17) is exercised under Task II.A — the MEL and CDL cards live there.

Conditioned air is delivered to the cabin continuously; cabin altitude is controlled by regulating how fast that air leaves, through the outflow valve (PHAK ch. 7). The control system provides:

• A cabin pressure regulator — controls cabin pressure to the selected value in the isobaric range and limits it to a preset value in the differential range
• The outflow valve — the working muscle that meters exit air
• A safety valve — combination pressure relief (prevents exceeding the predetermined differential), vacuum relief (lets ambient air in if outside pressure exceeds cabin pressure), and dump valve (flight deck switch dumps cabin air)

A typical system holds a cabin altitude of about 8,000 feet at the airplane's maximum designed cruising altitude. Monitoring instruments: cabin differential pressure gauge, cabin altimeter, and cabin rate-of-climb indicator (PHAK ch. 7).

Structure. The fuselage is designed to withstand a particular maximum cabin differential pressure — the difference between cabin and ambient pressure — set by the structural strength of the cabin and the relationship of cabin size to probable rupture areas such as windows and doors (PHAK ch. 7).

Isobaric range: the system holds a constant cabin altitude as you climb.

Differential control: when the airplane reaches the altitude where the inside-outside difference equals the maximum differential, the system shifts over — any further climb produces a corresponding climb in cabin altitude, because the controller will not let the structural limit be exceeded (PHAK ch. 7).

That's why max operating altitude and max differential are paired limitations in the AFM — know both numbers for your type.

Target reversers: clamshell doors that swivel from the stowed position at the tailpipe to redirect exhaust forward.

Cascade reversers: normally on turbofans, often reversing only the fan air — blocking doors obstruct forward fan thrust and redirect it through cascade vanes.

The flow never fully reverses — the final exhaust path is about 45° from straight ahead, so efficiency is limited, and less than maximum rpm in reverse reduces it further. Reverse thrust is more effective at high speed than at low speed, so use it as soon as prudent after touchdown. Some types pitch nose-up when reverse is selected (worse combined with spoiler pitch-up) and must be firmly on the ground, nosewheel down, first. And remember the contrast with props: idle reverse on a propeller produces large drag; idle reverse on a jet produces very little (AFH ch. 16).

Uncommanded or inadvertent deployment of a thrust reverser while airborne is an emergency (AFH ch. 16). The design protections are layered:

• A lock system to keep reversers from operating in the air
• Another lock preventing operation with the thrust levers out of the idle detent
• An auto-stow circuit commanding reverser stowage any time deployment would be inappropriate — such as during takeoff and while airborne

The ACS names uncommanded reverse procedures explicitly (AA.I.A.K3), so know your AFM's procedure as a recall item: which lever motions are prohibited, what the airplane's controllability penalty is, and any airspeed limits the AFM imposes after a deploy. This is a place where the honest oral answer is your type's procedure, verbatim.

NTS is the automatic backstop for engine failure on a fixed-shaft turboprop: when propeller torque starts driving the engine, the system limits the torque the engine can extract and drives the blades toward feather to reduce drag (AFH ch. 15). The fixed-shaft engine needs it because a failed engine's windmilling propeller drives the compressor, absorbing large amounts of power — a control threat in a twin unless the propeller is feathered immediately. Two cautions for the oral:

• NTS is an emergency backup, not a substitute for feathering with the condition lever
• Contrast with a free power-turbine (split-shaft) engine like the PT6: the propeller isn't on the engine shaft, so it can be feathered with the basic engine still running, and prop rpm is selectable independent of gas generator rpm (AFH ch. 15)

A propeller synchronizer precisely matches rpm between engines. A synchrophaser goes one step further: it matches rpm and compares and adjusts the blade phase angle between propellers (AFH ch. 13). From the pilot's seat they operate similarly — the point of both is noise and vibration reduction. The ACS lists synchronizing and synchrophasing among the propeller knowledge elements alongside feathering, auto-feather, and NTS (AA.I.A.K3); if your type has a phase-control knob, be able to say what it's actually adjusting.

Flight director: computes and displays steering commands on the ADI — it incorporates the attitude display within its system, driven by a mode controller and flight director computer (IFH ch. 5).

Autopilot: can fly those same computed commands, and integrated systems allow more flight director modes as capability grows (IFH ch. 5).

FMS: supplies the navigation and performance problem the autoflight system is solving.

The crew discipline the ACS is probing (AA.I.A.R3 — monitoring and management of automated systems) shows up on the ground first: both pilots should review takeoff data entered in an FMS, or separately compute it and cross-check against the takeoff data card — and recalculate if plans change while taxiing (AFH ch. 16). State your operator's automation policy: who makes mode selections, who verifies, and what gets announced.

It means the evaluator is watching how you use the paper, not whether you can find it. The Task requires demonstrating the systems through the use of the appropriate checklists and normal and abnormal procedures (AA.I.A.S6), and separately requires recall of immediate action items or memory items, if appropriate (AA.I.A.S2) — so you must know which items your AFM designates as memory items, execute those from recall, and then confirm with the checklist. Detection and management of a malfunction (AA.I.A.R1, R2) is graded as a sequence:

1. Recognize from the indications
2. Silence and confirm the alert
3. Memory items, if published
4. The QRH/abnormal checklist
5. The follow-on decisions

Reciting a checklist item-by-item from memory when it isn't a memory item reads as worse discipline, not better.

Most turbojet airplanes capable of Mach-range cruise have some form of trim and autopilot Mach compensating device — a stick puller — to alert the pilot to inadvertent excursions beyond certificated MMO (AC 61-107, para 3-2). Two things the AC is blunt about:

• If a malfunction requires disabling the stick puller, the aircraft must be operated at speeds well below MMO, per the AFM procedures
• The stick puller should never be disabled during normal flight operations — the AC recounts operators disabling airspeed/Mach warnings to run past VMO/MMO, and the chain it invites: flutter, control-surface flow separation, aileron buzz or snatch, Mach tuck, and loss of the airplane (AC 61-107, para 3-2)

Pair this with your type's answer: which protections exist in normal law or with all systems up, and what remains in each degraded mode. That mapping comes from the AFM and the FSB report, and "it depends on the control law" is only a passing answer if you can then say what each law provides.

Three layers beyond the commercial-level anti-ice/deice distinction (that groundwork is in the Commercial guide's systems task):

• Coverage map — the ACS expects anti-ice/deice knowledge across pitot-static protection, turbine inlet, propeller, windshield, and airfoil surfaces (AA.I.A.K10). Know which method protects each surface on your type and what the AFM requires to be on, and when
• Supply side — pneumatic and environmental systems knowledge includes the supply for ice protection systems (AA.I.A.K8): if your protection is bleed-air fed, know where the air comes from and what using it costs (that performance conversation continues in Task I.B)
• Limitations — icing operating limitations are AFM material (AA.I.A.S3), and ground deicing, holdover times, and the clean wing concept are exercised under Tasks I.B and II.A

Systems side: pure AFM material — know your type's detection loops and warnings, and which extinguishing bottles protect the engines, APU, cargo compartments, and lavatories, plus the discharge procedure and any limitations.

Crew side: regulated by 121.417, which requires:

• Emergency training in fire in flight or on the surface, and smoke control procedures with emphasis on electrical equipment and related circuit breakers in cabin areas — including galleys and lavatories (121.417(b)(3)(ii))
• Training in portable fire extinguishers, with emphasis on the type of extinguisher to be used on different classes of fires (121.417(b)(2)(iii))
• A protective breathing equipment (PBE) drill by every crewmember, combatting an actual or simulated fire (121.417(c)(1))
• Recurrent training every 24 calendar months operating each type of installed hand extinguisher (121.417(c)(2))

For the oral: name your type's fire memory items and where the smoke-removal procedure lives.

Three buckets, and know your evacuation duties cold:

• Oxygen — the flight-crew supply quantities and mask-wear rules of 121.333 are covered under Task I.E; the system mechanics (source, quick-donning masks, passenger drop-out) are your type's AFM material
• Exits and equipment — 121.417 requires individual instruction in the location, function, and operation of emergency equipment, including ditching and evacuation equipment and emergency exits in the emergency mode with the evacuation slide/raft pack attached, with emphasis on operating exits under adverse conditions (121.417(b)(2))
• Evacuation duties — training covers emergency assignments and coordination among crewmembers, and evacuation of persons who need the assistance of another person to reach an exit (121.417(b)(1), (b)(3)(iii)); crewmembers serving above 25,000 feet also get physiology training — respiration, hypoxia, duration of consciousness, gas expansion and bubble formation, decompression phenomena (121.417(e))