Maneuvering with One Engine Inoperative (AMEL, AMES)

Red line (VMC): promises directional control only — there is no requirement under either certification standard that the airplane be able to climb at VMC (AFH 13-2).

Blue line (VYSE): promises the best rate of climb with one engine inoperative — and above the single-engine absolute ceiling it yields the minimum rate of sink (AFH 13-1).

Neither speed promises performance you have not verified in the AFM/POH chart for today's weight and density altitude.

VSSE — safe, intentional one-engine-inoperative speed — is the minimum speed at which the critical engine may be intentionally rendered inoperative (AFH 13-1). Simulating a failure below VSSE "introduces a very high and unnecessary training risk," and in-flight simulated failures below 3,000 feet AGL are to be introduced with a smooth throttle reduction so the engine stays running and instantly available (AFH 13-35). If the examiner cuts an engine below VSSE, that is a debrief item, not a maneuver.

• Identify — primarily through the control inputs required to maintain straight flight, not the engine gauges. Rudder pressure is on the side of the operating engine, so the dead foot is the dead engine. Gauge confirmation "may or may not be possible, depending upon the failure mode" (AFH 13-32).
• Verify — retard the throttle of the engine you believe has failed. No change in performance is the verification (AFH 13-32).
• Feather — bring the corresponding propeller control fully aft. The blades take up to 10 seconds to fully feather (AFH 13-5, 13-31).

VMC increases with:

• More power on the operating engine — highest at takeoff power and sea level; falls with altitude on normally aspirated engines
• A windmilling propeller at low pitch/high rpm on the failed engine
• Aft CG — shortens the rudder's moment arm
• Reduced weight — less bank-induced side force to oppose the yaw
• Landing gear retracted — extended gear aids directional stability
• Less bank toward the operating engine — "more than 3 knots for each degree of bank reduction" between 5° and wings-level

These are the certification conditions in historical 14 CFR 23.149 (AFH 13-24, 13-25). Flaps in the takeoff position, takeoff trim, and ground effect negligible round out the condition set. Task X.B has the full treatment.

A windmilling propeller at low blade angles can cost you as much as parasite drag equal to the entire airframe's — "a propeller windmilling at high speed in the low range of blade angles can produce parasite drag as great as the parasite drag of the entire airframe" (AFH 13-3, 13-4). Feathered, that same propeller contributes only a small part of total drag. The classic trap is psychological: a windmilling prop looks like it is still producing thrust, which produces "a reluctance to feather" (AFH 13-36).

Bank approximately 2° toward the operating engine — actual values run 1.5° to 2.5° by model — with the ball displaced one-third to one-half of a ball width toward the operating engine (AFH 13-28, 13-29). The ball isn't centered because with an engine inoperative, a centered ball no longer indicates zero sideslip, and no flight deck instrument directly indicates it (AFH 13-27). The AFM/POH single-engine performance charts were flown at zero sideslip, so this predetermined attitude is the only one that delivers charted performance.

More, briefly. Use at least 5° and a maximum of 10° of bank toward the operating engine initially to stop the yaw and ensure directional control, held only momentarily. Then reduce to the zero-sideslip bank for climb, because "climb performance suffers when bank angles exceed approximately 2 or 3°" (AFH 13-31, 13-32). Rudder stops the yaw first — correcting the roll with aileron before rudder increases drag and adverse yaw and further degrades directional control (AFH 13-31).

Try switching tanks first — "many cases of power loss are related to fuel starvation, where restoration of power may be made with the selection of another tank" (AFH 13-34). Cruise altitude buys time to work an orderly inventory of gauges and switches:

• Tank selection
• Boost pump, for suspected vapor
• Mixture
• Carburetor heat or alternate air
• Individual magnetos
• Reduced power setting

Leave the engine running if there is any doubt as to needing it — but heavy vibration, smoke, blistering paint, or large trails of oil is a critical situation: feather it, secure it, divert, and declare (AFH 13-34).

• Altitude ±100 feet, or minimum sink rate if applicable
• Airspeed ±10 knots
• Selected headings ±10° (CA.X.A.S7)

"Minimum sink rate if applicable" is the escape hatch when the airplane is above its single-engine ceiling — you are then graded on holding VYSE and accepting the drift down, not on holding altitude.

The single-engine service ceiling is the altitude at which the airplane can no longer maintain a 50 fpm rate of climb with one engine inoperative; the single-engine absolute ceiling is the altitude at which climb is no longer possible (AFH 13-11).

For contrast, the all-engine service ceiling is based on 100 fpm (AFH 13-11). Expect the examiner to note that because of engine and propeller wear, turbulence, and pilot technique, "the airplane may not maintain altitude even at its published single-engine ceiling" (AFH 13-34).

You are drifting down and that is acceptable — hold VYSE to minimize the rate of altitude loss. The drift-down rate "is greatest immediately following the failure and decreases as the single-engine ceiling is approached" (AFH 13-34). Dragging the nose up to chase altitude bleeds airspeed toward VMC and is how these accidents end. Divert to the nearest suitable airport, declare the emergency for priority handling, and plan the descent to arrive at a runway.

Zero thrust is a power setting on one engine such that the drag from its rotating propeller equals that of a stopped, feathered propeller (AFH 13-29). It is a training substitute that reproduces the drag of a feathered prop without actually feathering. It is not free: the engine is still turning, still consuming fuel, still needing temperature management, and the instructor normally closes its cowl flap, leans the mixture, and clears the engine occasionally (AFH 13-36).

1. Aileron alone, no rudder — requires an 8–10° bank toward the operating engine, ball displaced well toward the good engine, large sideslip, "climb performance greatly reduced." Instructors should not normally demonstrate it (AFH 13-28).
2. Wings level, ball centered — large rudder input, moderate sideslip toward the inoperative engine, reduced climb, and VMC significantly higher than published because no horizontal component of lift is helping the rudder (AFH 13-28).
3. Rudder and aileron in combination — about 2° of bank, one-third to one-half ball toward the good engine: zero sideslip and maximum climb performance (AFH 13-29).

Because most of it does not, and that is exactly the point the examiner is testing. "Other than closing the cowl flap of the failed engine, none of these items, if left undone, adversely affect airplane climb performance" (AFH 13-33). Complete the memory items first, then work the printed securing checklist deliberately and without undue haste — rushing raises "a distinct possibility of actuating an incorrect switch or control." Fly the airplane first; the checklist never outranks aircraft control (AFH 13-32, 13-33).

Most singles use a non-feathering, oil-pressure-to-increase-pitch design. Multiengine props are typically full feathering, counterweighted, oil-pressure-to-decrease-pitch: governor oil pressure drives the blades toward low pitch/high rpm, away from feather. "The only thing that keeps these propellers from feathering is a constant supply of high-pressure engine oil" — deliberate, so the prop can feather after a loss of oil pressure or governor failure. Pull the control aft and the counterweights, plus a spring or a high-pressure air charge in the dome, drive the blades to feather (AFH 13-5).

Below roughly 800 rpm the drop in centrifugal force lets small anti-feathering lock pins in the hub move into place and block feathering (AFH 13-7). So if a propeller is going to be feathered, it must be done before rpm decays below about 800. Feathering and starting a feathered reciprocating engine on the ground are strongly discouraged by manufacturers because of the stress and vibration involved.

Follow the AFM/POH; typically:

1. Ignition on
2. Throttle at low idle
3. Mixture rich
4. Propeller control to a high rpm position
5. Engage the starter — the engine windmills, oil pressure moves the blades out of feather, and it starts

Reduce rpm immediately and give it several minutes to warm up while watching cylinder head and oil temperatures (AFH 13-6).

An unfeathering accumulator stores engine oil under air or nitrogen pressure; moving the prop control out of feather releases it to the hub, driving the blades toward low pitch so the prop windmills and starts without the electric starter. Governor pressure recharges it moments later (AFH 13-6).

Feather only at altitudes and positions "where safe landings on established airports may be readily accomplished if the propeller will not unfeather," and plan unfeathering and restart to be completed no lower than 3,000 feet AGL (AFH 13-36). At some field elevations that floor is above the airplane's single-engine service ceiling, so level flight may not be possible while you are on one engine — brief that before you go.

Not automatically. "If there is a performance loss when the throttle of the affected engine is retarded, some power is still available" — consider letting it run until you have a safe altitude and airspeed for single-engine flight. Shutting down an engine that can still produce partial power may increase the risk of an accident (AFH 13-33). A related trap: an engine failure at a low power setting or in a descent is deceiving, with none of the dramatic yaw. If you suspect one, advance both mixtures, propellers, and throttles significantly — to takeoff settings if necessary — to identify the failed engine correctly (AFH 13-33).

Only when prolonged single-engine flight is unavoidable. "If a suitable airport is close at hand, there is no need to consider crossfeed." When an airport is not available, crossfeed makes otherwise unusable fuel available to the operating engine and lets you balance consumption to avoid wing heaviness. Selector positions and boost pump usage "differ greatly among multiengine airplanes," so the AFM/POH procedure is not optional knowledge — and crossfeed is terminated prior to landing, with the operating engine returned to its main tank (AFH 13-34).

Treat it like any other high-workload air work: before slowing or simulating a failure, "the area surrounding the airplane should first be cleared for possible traffic" (AFH 13-19). In practice:

• Clearing turns in both directions, with a deliberate look above, below, and behind — the nose-high single-engine attitude hides traffic ahead and low
• Pick a practice area clear of arrival and departure corridors, and away from VFR checkpoints and charted routes
• Announce on the practice-area or CTAF frequency; use flight following if it is available
• Keep the scan running through the maneuver — see-and-avoid is still your responsibility under 14 CFR 91.113(b) no matter what the airplane is doing

An examiner who never sees you look outside has a finding regardless of how well the airplane was flown.

Because asymmetric thrust plus a low, slow, distracted pilot is the classic multiengine loss-of-control accident, and a twin has no spin recovery to fall back on — Task X.B covers the VMC/VS convergence and spin entry in detail. Here the question is what you do about it:

• Do this work high — the same 3,000 feet AGL floor that applies to feathering and restart (AFH 13-36)
• Never intentionally fail an engine below VSSE (AFH 13-1)
• VYSE, not altitude, is what you protect — chasing altitude bleeds speed toward VMC
• Accept the drift down and divert; pressing toward terrain on one engine is how these become CFIT