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HIGH PERFORMANCE AND COMPLEXAIRPLANESTransition to a complex airplane, or a high performanceairplane, can be demanding for most pilots without pre-vious experience. Increased performance and increasedcomplexity both require additional planning, judgment,and piloting skills. Transition to these types ofairplanes, therefore, should be accomplished in asystematic manner through a structured course oftraining administered by a qualified flight instructor.

A complex airplane is defined as an airplane equippedwith a retractable landing gear, wing flaps, and acontrollable-pitch propeller. For a seaplane to beconsidered complex, it is required to have wing flaps anda controllable-pitch propeller. A high performanceairplane is defined as an airplane with an engine of morethan 200 horsepower.

WING FLAPSAirplanes can be designed to fly fast or slow. Highspeed requires thin, moderately cambered airfoils witha small wing area, whereas the high lift needed for lowspeeds is obtained with thicker highly camberedairfoils with a larger wing area. [Figure 11-1] Many

attempts have been made to compromise thisconflicting requirement of high cruise and slowlanding speeds.

Since an airfoil cannot have two different cambers atthe same time, one of two things must be done. Eitherthe airfoil can be a compromise, or a cruise airfoil canbe combined with a device for increasing the camber ofthe airfoil for low-speed flight. One method for varyingan airfoil’s camber is the addition of trailing edge flaps.Engineers call these devices a high-lift system.

FUNCTION OF FLAPSFlaps work primarily by changing the camber of theairfoil since deflection adds aft camber. Flap deflectiondoes not increase the critical (stall) angle of attack, andin some cases flap deflection actually decreases thecritical angle of attack.

Deflection of trailing edge control surfaces, such as theaileron, alters both lift and drag. With ailerondeflection, there is asymmetrical lift (rolling moment)and drag (adverse yaw). Wing flaps differ in thatdeflection acts symmetrically on the airplane. There isno roll or yaw effect, and pitch changes depend on theairplane design.

Straight

Elliptical

Tapered

Sweptback

Delta

Figure 11-1. Airfoil types.

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Pitch behavior depends on flap type, wing position,and horizontal tail location. The increased camberfrom flap deflection produces lift primarily on the rearportion of the wing. This produces a nosedownpitching moment; however, the change in tail loadfrom the downwash deflected by the flaps over thehorizontal tail has a significant influence on thepitching moment. Consequently, pitch behaviordepends on the design features of the particular airplane.

Flap deflection of up to 15° primarily produces liftwith minimal drag. The tendency to balloon up withinitial flap deflection is because of lift increase, but thenosedown pitching moment tends to offset the balloon.Deflection beyond 15° produces a large increase indrag. Drag from flap deflection is parasite drag, andas such is proportional to the square of the speed. Also,deflection beyond 15° produces a significant noseuppitching moment in most high-wing airplanes becausethe resulting downwash increases the airflow over thehorizontal tail.

FLAP EFFECTIVENESSFlap effectiveness depends on a number of factors, butthe most noticeable are size and type. For the purposeof this chapter, trailing edge flaps are classified as fourbasic types: plain (hinge), split, slotted, and Fowler.[Figure 11-2]

The plain or hinge flap is a hinged section of the wing.The structure and function are comparable to the othercontrol surfaces—ailerons, rudder, and elevator. Thesplit flap is more complex. It is the lower or undersideportion of the wing; deflection of the flap leaves thetrailing edge of the wing undisturbed. It is, however,more effective than the hinge flap because of greaterlift and less pitching moment, but there is more drag.Split flaps are more useful for landing, but the partiallydeflected hinge flaps have the advantage in takeoff.The split flap has significant drag at small deflections,whereas the hinge flap does not because airflowremains “attached” to the flap.

The slotted flap has a gap between the wing and theleading edge of the flap. The slot allows highpressure airflow on the wing undersurface to energizethe lower pressure over the top, thereby delaying flowseparation. The slotted flap has greater lift than thehinge flap but less than the split flap; but, because ofa higher lift-drag ratio, it gives better takeoff andclimb performance. Small deflections of the slottedflap give a higher drag than the hinge flap but lessthan the split. This allows the slotted flap to be usedfor takeoff.

The Fowler flap deflects down and aft to increase thewing area. This flap can be multi-slotted making it themost complex of the trailing edge systems. This

system does, however, give the maximum liftcoefficient. Drag characteristics at small deflectionsare much like the slotted flap. Because of structuralcomplexity and difficulty in sealing the slots, Fowlerflaps are most commonly used on larger airplanes.

OPERATIONAL PROCEDURESIt would be impossible to discuss all the many airplanedesign and flap combinations. This emphasizes theimportance of the FAA-approved Airplane FlightManual and/or Pilot’s Operating Handbook(AFM/POH) for a given airplane. However, whilesome AFM/POHs are specific as to operational use offlaps, many are lacking. Hence, flap operation makespilot judgment of critical importance. In addition, flapoperation is used for landings and takeoffs, duringwhich the airplane is in close proximity to the groundwhere the margin for error is small.

Since the recommendations given in the AFM/POH arebased on the airplane and the flap design combination,

Plain Flap

Split Flap

Slotted Flap

Fowler Flap

Figure 11-2. Four basic types of flaps.

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the pilot must relate the manufacturer’s recommenda-tion to aerodynamic effects of flaps. This requires thatthe pilot have a basic background knowledge of flapaerodynamics and geometry. With this information, thepilot must make a decision as to the degree of flapdeflection and time of deflection based on runway andapproach conditions relative to the wind conditions.

The time of flap extension and degree of deflection arerelated. Large flap deflections at one single point in thelanding pattern produce large lift changes that requiresignificant pitch and power changes in order tomaintain airspeed and glide slope. Incrementaldeflection of flaps on downwind, base, and finalapproach allow smaller adjustment of pitch and powercompared to extension of full flaps all at one time. Thisprocedure facilitates a more stabilized approach.

A soft- or short-field landing requires minimal speed attouchdown. The flap deflection that results in minimalgroundspeed, therefore, should be used. If obstacleclearance is a factor, the flap deflection that results inthe steepest angle of approach should be used. Itshould be noted, however, that the flap setting thatgives the minimal speed at touchdown does notnecessarily give the steepest angle of approach;however, maximum flap extension gives the steepestangle of approach and minimum speed at touchdown.Maximum flap extension, particularly beyond 30 to35°, results in a large amount of drag. This requireshigher power settings than used with partial flaps.Because of the steep approach angle combined withpower to offset drag, the flare with full flaps becomescritical. The drag produces a high sink rate that mustbe controlled with power, yet failure to reduce powerat a rate so that the power is idle at touchdown allowsthe airplane to float down the runway. A reduction inpower too early results in a hard landing.

Crosswind component is another factor to beconsidered in the degree of flap extension. Thedeflected flap presents a surface area for the wind toact on. In a crosswind, the “flapped” wing on theupwind side is more affected than the downwindwing. This is, however, eliminated to a slight extentin the crabbed approach since the airplane is morenearly aligned with the wind. When using a wing lowapproach, however, the lowered wing partiallyblankets the upwind flap, but the dihedral of the wingcombined with the flap and wind make lateral controlmore difficult. Lateral control becomes more difficultas flap extension reaches maximum and thecrosswind becomes perpendicular to the runway.

Crosswind effects on the “flapped” wing become morepronounced as the airplane comes closer to the ground.The wing, flap, and ground form a “container” that isfilled with air by the crosswind. With the wind striking

the deflected flap and fuselage side and with the flaplocated behind the main gear, the upwind wing willtend to rise and the airplane will tend to turn into thewind. Proper control position, therefore, is essentialfor maintaining runway alignment. Also, it maybe necessary to retract the flaps upon positiveground contact.

The go-around is another factor to consider whenmaking a decision about degree of flap deflectionand about where in the landing pattern to extendflaps. Because of the nosedown pitching momentproduced with flap extension, trim is used to offsetthis pitching moment. Application of full power inthe go-around increases the airflow over the“flapped” wing. This produces additional liftcausing the nose to pitch up. The pitch-up tendencydoes not diminish completely with flap retractionbecause of the trim setting. Expedient retraction offlaps is desirable to eliminate drag, thereby allowingrapid increase in airspeed; however, flap retractionalso decreases lift so that the airplane sinks rapidly.

The degree of flap deflection combined with designconfiguration of the horizontal tail relative to thewing requires that the pilot carefully monitor pitchand airspeed, carefully control flap retraction tominimize altitude loss, and properly use the rudderfor coordination. Considering these factors, the pilotshould extend the same degree of deflection at thesame point in the landing pattern. This requires that aconsistent traffic pattern be used. Therefore, the pilotcan have a preplanned go-around sequence based onthe airplane’s position in the landing pattern.

There is no single formula to determine the degree offlap deflection to be used on landing, because alanding involves variables that are dependent on eachother. The AFM/POH for the particular airplane willcontain the manufacturer’s recommendations forsome landing situations. On the other hand,AFM/POH information on flap usage for takeoff ismore precise. The manufacturer’s requirements arebased on the climb performance produced by a givenflap design. Under no circumstances should a flapsetting given in the AFM/POH be exceededfor takeoff.

CONTROLLABLE-PITCH PROPELLERFixed-pitch propellers are designed for best efficiencyat one speed of rotation and forward speed. This typeof propeller will provide suitable performance ina narrow range of airspeeds; however, efficiencywould suffer considerably outside this range. Toprovide high propeller efficiency through a widerange of operation, the propeller blade anglemust be controllable. The most convenient

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way of controlling the propeller blade angle is bymeans of a constant-speed governing system.

CONSTANT-SPEED PROPELLERThe constant-speed propeller keeps the blade angleadjusted for maximum efficiency for most conditionsof flight. When an engine is running at constantspeed, the torque (power) exerted by the engine at thepropeller shaft must equal the opposing load providedby the resistance of the air. The r.p.m. is controlled byregulating the torque absorbed by the propeller—inother words by increasing or decreasing theresistance offered by the air to the propeller. In thecase of a fixed-pitch propeller, the torque absorbedby the propeller is a function of speed, or r.p.m. If thepower output of the engine is changed, the engine willaccelerate or decelerate until an r.p.m. is reached atwhich the power delivered is equal to the powerabsorbed. In the case of a constant-speed propeller,the power absorbed is independent of the r.p.m., forby varying the pitch of the blades, the air resistanceand hence the torque or load, can be changed withoutreference to propeller speed. This is accomplishedwith a constant-speed propeller by means of agovernor. The governor, in most cases, is geared tothe engine crankshaft and thus is sensitive to changesin engine r.p.m.

The pilot controls the engine r.p.m. indirectly by meansof a propeller control in the cockpit, which isconnected to the governor. For maximum takeoffpower, the propeller control is moved all the wayforward to the low pitch/high r.p.m. position, and thethrottle is moved forward to the maximum allowablemanifold pressure position. To reduce power for climbor cruise, manifold pressure is reduced to the desiredvalue with the throttle, and the engine r.p.m. is reducedby moving the propeller control back toward the highpitch/low r.p.m. position until the desired r.p.m. isobserved on the tachometer. Pulling back on thepropeller control causes the propeller blades to moveto a higher angle. Increasing the propeller blade angle(of attack) results in an increase in the resistance of theair. This puts a load on the engine so it slows down. Inother words, the resistance of the air at the higher bladeangle is greater than the torque, or power, delivered tothe propeller by the engine, so it slows down to a pointwhere the two forces are in balance.

When an airplane is nosed up into a climb from levelflight, the engine will tend to slow down. Since thegovernor is sensitive to small changes in engine r.p.m.,it will decrease the blade angle just enough to keep theengine speed from falling off. If the airplane is noseddown into a dive, the governor will increase the bladeangle enough to prevent the engine from overspeeding.This allows the engine to maintain a constant r.p.m.,and thus maintain the power output. Changes in

airspeed and power can be obtained by changingr.p.m. at a constant manifold pressure; by changingthe manifold pressure at a constant r.p.m.; or bychanging both r.p.m. and manifold pressure. Thusthe constant-speed propeller makes it possible toobtain an infinite number of power settings.

TAKEOFF, CLIMB, AND CRUISEDuring takeoff, when the forward motion of theairplane is at low speeds and when maximum powerand thrust are required, the constant-speed propellersets up a low propeller blade angle (pitch). The lowblade angle keeps the angle of attack, with respect tothe relative wind, small and efficient at the low speed.[Figure 11-3]

At the same time, it allows the propeller to “slice itthin” and handle a smaller mass of air per revolution.This light load allows the engine to turn at maximumr.p.m. and develop maximum power. Although themass of air per revolution is small, the number ofrevolutions per minute is high. Thrust is maximum atthe beginning of the takeoff and then decreases as theairplane gains speed and the airplane drag increases.Due to the high slipstream velocity during takeoff,the effective lift of the wing behind the propeller(s)is increased.

As the airspeed increases after lift-off, the load on theengine is lightened because of the small blade angle.The governor senses this and increases the blade angleslightly. Again, the higher blade angle, with the higherspeeds, keeps the angle of attack with respect to therelative wind small and efficient.

Angle of Attack

ChordLine

Plane ofPropellerRotation

Angle of Attack

Chord Line(Blade Face)

STATIONARY FORWARD MOTION

Plane of PropellerRotation

Forward Airspeed

RelativeWind

RelativeWind

Figure 11-3. Propeller blade angle.

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For climb after takeoff, the power output of the engineis reduced to climb power by decreasing the manifoldpressure and lowering r.p.m. by increasing the bladeangle. At the higher (climb) airspeed and the higherblade angle, the propeller is handling a greater mass ofair per second at a lower slipstream velocity. Thisreduction in power is offset by the increase in propellerefficiency. The angle of attack is again kept small bythe increase in the blade angle with an increasein airspeed.

At cruising altitude, when the airplane is in level flight,less power is required to produce a higher airspeedthan is used in climb. Consequently, engine power isagain reduced by lowering the manifold pressure andincreasing the blade angle (to decrease r.p.m.). Thehigher airspeed and higher blade angle enable thepropeller to handle a still greater mass of air persecond at still smaller slipstream velocity. At normalcruising speeds, propeller efficiency is at, or nearmaximum efficiency. Due to the increase in bladeangle and airspeed, the angle of attack is still smalland efficient.

BLADE ANGLE CONTROLOnce the pilot selects the r.p.m. settings for thepropeller, the propeller governor automatically adjuststhe blade angle to maintain the selected r.p.m. It doesthis by using oil pressure. Generally, the oil pressureused for pitch change comes directly from the enginelubricating system. When a governor is employed,engine oil is used and the oil pressure is usuallyboosted by a pump, which is integrated with thegovernor. The higher pressure provides a quicker bladeangle change. The r.p.m. at which the propeller is tooperate is adjusted in the governor head. The pilotchanges this setting by changing the position of thegovernor rack through the cockpit propeller control.

On some constant-speed propellers, changes in pitchare obtained by the use of an inherent centrifugaltwisting moment of the blades that tends to flatten theblades toward low pitch, and oil pressure applied to ahydraulic piston connected to the propeller bladeswhich moves them toward high pitch. Another type ofconstant-speed propeller uses counterweights attachedto the blade shanks in the hub. Governor oil pressure

and the blade twisting moment move the blades towardthe low pitch position, and centrifugal force acting onthe counterweights moves them (and the blades)toward the high pitch position. In the first case above,governor oil pressure moves the blades towards highpitch, and in the second case, governor oil pressure andthe blade twisting moment move the blades toward lowpitch. A loss of governor oil pressure, therefore, willaffect each differently.

GOVERNING RANGEThe blade angle range for constant-speed propellersvaries from about 11 1/2 to 40°. The higher the speedof the airplane, the greater the blade angle range.[Figure 11-4]

The range of possible blade angles is termed thepropeller’s governing range. The governing range isdefined by the limits of the propeller blade’s travelbetween high and low blade angle pitch stops. As longas the propeller blade angle is within the governingrange and not against either pitch stop, a constantengine r.p.m. will be maintained. However, once thepropeller blade reaches its pitch-stop limit, the enginer.p.m. will increase or decrease with changes inairspeed and propeller load similar to a fixed-pitchpropeller. For example, once a specific r.p.m. isselected, if the airspeed decreases enough, thepropeller blades will reduce pitch, in an attempt tomaintain the selected r.p.m., until they contact theirlow pitch stops. From that point, any furtherreduction in airspeed will cause the engine r.p.m.to decrease. Conversely, if the airspeed increases,the propeller blade angle will increase until thehigh pitch stop is reached. The engine r.p.m. willthen begin to increase.

CONSTANT-SPEEDPROPELLER OPERATIONThe engine is started with the propeller control in thelow pitch/high r.p.m. position. This position reducesthe load or drag of the propeller and the result is easierstarting and warm-up of the engine. During warm-up,the propeller blade changing mechanism should beoperated slowly and smoothly through a full cycle.This is done by moving the propeller control (with the

Fixed GearRetractableTurbo RetractableTurbine RetractableTransport Retractable

Aircraft Type Design Speed(m.p.h.)

Blade AngleRange

PitchLow High

160180

225/240250/300

325

111/2°15°20°30°40°

101/2°11°14°10°

10/15°

22°26°34°40°

50/55°

Figure 11-4. Blade angle range (values are approximate).

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manifold pressure set to produce about 1,600 r.p.m.)to the high pitch/low r.p.m. position, allowing ther.p.m. to stabilize, and then moving the propellercontrol back to the low pitch takeoff position. Thisshould be done for two reasons: to determinewhether the system is operating correctly, and tocirculate fresh warm oil through the propellergovernor system. It should be remembered that theoil has been trapped in the propeller cylinder sincethe last time the engine was shut down. There is acertain amount of leakage from the propellercylinder, and the oil tends to congeal, especially ifthe outside air temperature is low. Consequently, ifthe propeller isn’t exercised before takeoff, there isa possibility that the engine may overspeedon takeoff.

An airplane equipped with a constant-speed propellerhas better takeoff performance than a similarly poweredairplane equipped with a fixed-pitch propeller. This isbecause with a constant-speed propeller, an airplane candevelop its maximum rated horsepower (red line on thetachometer) while motionless. An airplane with a fixed-pitch propeller, on the other hand, must accelerate downthe runway to increase airspeed and aerodynamicallyunload the propeller so that r.p.m. and horsepower cansteadily build up to their maximum. With a constant-speed propeller, the tachometer reading should come upto within 40 r.p.m. of the red line as soon as full power isapplied, and should remain there for the entire takeoff.

Excessive manifold pressure raises the cylindercompression pressure, resulting in high stresses withinthe engine. Excessive pressure also produces highengine temperatures. A combination of high manifoldpressure and low r.p.m. can induce damagingdetonation. In order to avoid these situations, thefollowing sequence should be followed when makingpower changes.

• When increasing power, increase the r.p.m. first,and then the manifold pressure.

• When decreasing power, decrease the manifoldpressure first, and then decrease the r.p.m.

It is a fallacy that (in non-turbocharged engines) themanifold pressure in inches of mercury (inches Hg)should never exceed r.p.m. in hundreds for cruisepower settings. The cruise power charts in theAFM/POH should be consulted when selecting cruisepower settings. Whatever the combinations of r.p.m.and manifold pressure listed in these charts—they havebeen flight tested and approved by the airframe andpowerplant engineers for the respective airframe andengine manufacturer. Therefore, if there are powersettings such as 2,100 r.p.m. and 24 inches manifoldpressure in the power chart, they are approved for use.

With a constant-speed propeller, a power descent canbe made without overspeeding the engine. The systemcompensates for the increased airspeed of the descentby increasing the propeller blade angles. If the descentis too rapid, or is being made from a high altitude, themaximum blade angle limit of the blades is notsufficient to hold the r.p.m. constant. When thisoccurs, the r.p.m. is responsive to any changein throttle setting.

Some pilots consider it advisable to set the propellercontrol for maximum r.p.m. during the approach tohave full horsepower available in case of emergency.If the governor is set for this higher r.p.m. early in theapproach when the blades have not yet reached theirminimum angle stops, the r.p.m. may increase tounsafe limits. However, if the propeller control is notreadjusted for the takeoff r.p.m. until the approach isalmost completed, the blades will be against, or verynear their minimum angle stops and there will be littleif any change in r.p.m. In case of emergency, boththrottle and propeller controls should be moved totakeoff positions.

Many pilots prefer to feel the airplane respondimmediately when they give short bursts of thethrottle during approach. By making the approachunder a little power and having the propeller controlset at or near cruising r.p.m., this result canbe obtained.

Although the governor responds quickly to any changein throttle setting, a sudden and large increase in thethrottle setting will cause a momentary overspeedingof the engine until the blades become adjusted toabsorb the increased power. If an emergencydemanding full power should arise during approach,the sudden advancing of the throttle will causemomentary overspeeding of the engine beyond ther.p.m. for which the governor is adjusted. Thistemporary increase in engine speed acts as anemergency power reserve.

Some important points to remember concerningconstant-speed propeller operation are:

• The red line on the tachometer not only indicatesmaximum allowable r.p.m.; it also indicatesthe r.p.m. required to obtain the engine’srated horsepower.

• A momentary propeller overspeed may occurwhen the throttle is advanced rapidly for takeoff.This is usually not serious if the rated r.p.m. isnot exceeded by 10 percent for more than3 seconds.

• The green arc on the tachometer indicates thenormal operating range. When developing

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power in this range, the engine drives the pro-peller. Below the green arc, however, it is usuallythe windmilling propeller that powers theengine. Prolonged operation below the green arccan be detrimental to the engine.

• On takeoffs from low elevation airports, themanifold pressure in inches of mercury mayexceed the r.p.m. This is normal in most cases.The pilot should consult the AFM/POHfor limitations.

• All power changes should be made smoothlyand slowly to avoid overboosting and/oroverspeeding.

TURBOCHARGINGThe turbocharged engine allows the pilot to maintainsufficient cruise power at high altitudes where there isless drag, which means faster true airspeeds andincreased range with fuel economy. At the same time,the powerplant has flexibility and can be flown at a lowaltitude without the increased fuel consumption of aturbine engine. When attached to the standardpowerplant, the turbocharger does not take anyhorsepower from the powerplant to operate; it isrelatively simple mechanically, and some models canpressurize the cabin as well.

The turbocharger is an exhaust-driven device, whichraises the pressure and density of the induction airdelivered to the engine. It consists of two separatecomponents: a compressor and a turbine connected bya common shaft. The compressor supplies pressurizedair to the engine for high altitude operation. Thecompressor and its housing are between the ambientair intake and the induction air manifold. The turbineand its housing are part of the exhaust system andutilize the flow of exhaust gases to drive thecompressor. [Figure 11-5]

The turbine has the capability of producing manifoldpressure in excess of the maximum allowable for theparticular engine. In order not to exceed the maximumallowable manifold pressure, a bypass or waste gate isused so that some of the exhaust will be divertedoverboard before it passes through the turbine.

The position of the waste gate regulates the output ofthe turbine and therefore, the compressed air availableto the engine. When the waste gate is closed, all of theexhaust gases pass through and drive the turbine. Asthe waste gate opens, some of the exhaust gases arerouted around the turbine, through the exhaust bypassand overboard through the exhaust pipe.

The waste gate actuator is a spring-loaded piston,operated by engine oil pressure. The actuator, whichadjusts the waste gate position, is connected to thewaste gate by a mechanical linkage.

The control center of the turbocharger system isthe pressure controller. This device simplifiesturbocharging to one control: the throttle. Once thepilot has set the desired manifold pressure, virtually nothrottle adjustment is required with changes in altitude.The controller senses compressor dischargerequirements for various altitudes and controls the oilpressure to the waste gate actuator which adjusts thewaste gate accordingly. Thus the turbochargermaintains only the manifold pressure called for by thethrottle setting.

GROUND BOOSTING VS. ALTITUDETURBOCHARGINGAltitude turbocharging (sometimes called “normal-izing”) is accomplished by using a turbocharger thatwill maintain maximum allowable sea level manifoldpressure (normally 29 – 30 inches Hg) up to a certainaltitude. This altitude is specified by the airplanemanufacturer and is referred to as the airplane’scritical altitude. Above the critical altitude,

EXHAUST GASDISCHARGE

WASTE GATEThis controls the amount of exhaust through the turbine. Waste gate position is actuated by engine oil pressure.

TURBOCHARGERThe turbocharger incorporates a turbine, which is driven by exhaust gases, and a compressor that pressurizes the incoming air.

THROTTLE BODYThis regulates airflow to the engine.

INTAKE MANIFOLDPressurized air from the turbocharger is supplied to the cylinders.

EXHAUST MANIFOLDExhaust gas is ducted through the exhaust manifold and is used to turn the turbine which drives the compressor.

AIR INTAKEIntake air is ducted to the turbocharger where it is compressed.

Figure 11-5.Turbocharging system.

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the manifold pressure decreases as additional altitudeis gained. Ground boosting, on the other hand, is anapplication of turbocharging where more than thestandard 29 inches of manifold pressure is used inflight. In various airplanes using ground boosting,takeoff manifold pressures may go as high as 45inches of mercury.

Although a sea level power setting and maximumr.p.m. can be maintained up to the critical altitude,this does not mean that the engine is developing sealevel power. Engine power is not determined just bymanifold pressure and r.p.m. Induction airtemperature is also a factor. Turbocharged inductionair is heated by compression. This temperature risedecreases induction air density which causes apower loss. Maintaining the equivalent horsepoweroutput will require a somewhat higher manifoldpressure at a given altitude than if the induction airwere not compressed by turbocharging. If, on theother hand, the system incorporates an automaticdensity controller which, instead of maintaining aconstant manifold pressure, automatically positionsthe waste gate so as to maintain constant air densityto the engine, a near constant horsepower outputwill result.

OPERATING CHARACTERISTICSFirst and foremost, all movements of the powercontrols on turbocharged engines should be slow andgentle. Aggressive and/or abrupt throttle movementsincrease the possibility of overboosting. The pilotshould carefully monitor engine indications whenmaking power changes.

When the waste gate is open, the turbocharged enginewill react the same as a normally aspirated enginewhen the r.p.m. is varied. That is, when the r.p.m. isincreased, the manifold pressure will decrease slightly.When the engine r.p.m. is decreased, the manifoldpressure will increase slightly. However, when thewaste gate is closed, manifold pressure variation withengine r.p.m. is just the opposite of the normallyaspirated engine. An increase in engine r.p.m. willresult in an increase in manifold pressure, and adecrease in engine r.p.m. will result in a decrease inmanifold pressure.

Above the critical altitude, where the waste gateis closed, any change in airspeed will result in acorresponding change in manifold pressure. This istrue because the increase in ram air pressure with anincrease in airspeed is magnified by the compressorresulting in an increase in manifold pressure. Theincrease in manifold pressure creates a higher massflow through the engine, causing higher turbine speedsand thus further increasing manifold pressure.

When running at high altitudes, aviation gasoline maytend to vaporize prior to reaching the cylinder. If thisoccurs in the portion of the fuel system between thefuel tank and the engine-driven fuel pump, anauxiliary positive pressure pump may be needed in thetank. Since engine-driven pumps pull fuel, they areeasily vapor locked. A boost pump provides positivepressure—pushes the fuel—reducing the tendency tovaporize.

HEAT MANAGEMENTTurbocharged engines must be thoughtfully andcarefully operated, with continuous monitoring ofpressures and temperatures. There are two tempera-tures that are especially important—turbine inlettemperature (TIT) or in some installations exhaust gastemperature (EGT), and cylinder head temperature.TIT or EGT limits are set to protect the elements in thehot section of the turbocharger, while cylinder headtemperature limits protect the engine’s internal parts.

Due to the heat of compression of the induction air, aturbocharged engine runs at higher operatingtemperatures than a non-turbocharged engine. Becauseturbocharged engines operate at high altitudes, theirenvironment is less efficient for cooling. At altitudethe air is less dense and therefore, cools lessefficiently. Also, the less dense air causes thecompressor to work harder. Compressor turbinespeeds can reach 80,000 – 100,000 r.p.m., addingto the overall engine operating temperatures.Turbocharged engines are also operated at higherpower settings a greater portion of the time.

High heat is detrimental to piston engine operation. Itscumulative effects can lead to piston, ring, andcylinder head failure, and place thermal stress on otheroperating components. Excessive cylinder headtemperature can lead to detonation, which in turn cancause catastrophic engine failure. Turbochargedengines are especially heat sensitive. The key toturbocharger operation, therefore, is effective heatmanagement.

The pilot monitors the condition of a turbochargedengine with manifold pressure gauge, tachometer,exhaust gas temperature/turbine inlet temperaturegauge, and cylinder head temperature. The pilotmanages the “heat system” with the throttle, propellerr.p.m., mixture, and cowl flaps. At any given cruisepower, the mixture is the most influential control overthe exhaust gas/turbine inlet temperature. The throttleregulates total fuel flow, but the mixture governs thefuel to air ratio. The mixture, therefore, controlstemperature.

Exceeding temperature limits in an after takeoff climbis usually not a problem since a full rich mixture cools

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with excess fuel. At cruise, however, the pilot normallyreduces power to 75 percent or less and simultaneouslyadjusts the mixture. Under cruise conditions,temperature limits should be monitored most closelybecause it’s there that the temperatures are most likelyto reach the maximum, even though the engine isproducing less power. Overheating in an enrouteclimb, however, may require fully open cowl flaps anda higher airspeed.

Since turbocharged engines operate hotter at altitudethan do normally aspirated engines, they are moreprone to damage from cooling stress. Gradualreductions in power, and careful monitoring oftemperatures are essential in the descent phase. Thepilot may find it helpful to lower the landing gear togive the engine something to work against while poweris reduced and provide time for a slow cool down. Itmay also be necessary to lean the mixture slightly toeliminate roughness at the lower power settings.

TURBOCHARGER FAILUREBecause of the high temperatures and pressuresproduced in the turbine exhaust systems, anymalfunction of the turbocharger must be treated withextreme caution. In all cases of turbocharger operation,the manufacturer’s recommended procedures shouldbe followed. This is especially so in the case ofturbocharger malfunction. However, in those instanceswhere the manufacturer’s procedures do notadequately describe the actions to be taken in the eventof a turbocharger failure, the following proceduresshould be used.

OVERBOOST CONDITIONIf an excessive rise in manifold pressure occurs duringnormal advancement of the throttle (possibly owing tofaulty operation of the waste gate):

• Immediately retard the throttle smoothly to limitthe manifold pressure below the maximum forthe r.p.m. and mixture setting.

• Operate the engine in such a manner as to avoid afurther overboost condition.

LOW MANIFOLD PRESSUREAlthough this condition may be caused by a minorfault, it is quite possible that a serious exhaust leak hasoccurred creating a potentially hazardous situation:

• Shut down the engine in accordance with therecommended engine failure procedures, unlessa greater emergency exists that warrants contin-ued engine operation.

• If continuing to operate the engine, use the low-est power setting demanded by the situation andland as soon as practicable.

It is very important to ensure that correctivemaintenance is undertaken following anyturbocharger malfunction.

RETRACTABLE LANDING GEARThe primary benefits of being able to retract thelanding gear are increased climb performance andhigher cruise airspeeds due to the resulting decrease indrag. Retractable landing gear systems may beoperated either hydraulically or electrically, or mayemploy a combination of the two systems. Warningindicators are provided in the cockpit to show the pilotwhen the wheels are down and locked and when theyare up and locked or if they are in intermediatepositions. Systems for emergency operation are alsoprovided. The complexity of the retractable landinggear system requires that specific operating proceduresbe adhered to and that certain operating limitations notbe exceeded.

LANDING GEAR SYSTEMSAn electrical landing gear retraction system utilizes anelectrically driven motor for gear operation. Thesystem is basically an electrically driven jack forraising and lowering the gear. When a switch in thecockpit is moved to the UP position, the electric motoroperates. Through a system of shafts, gears, adapters,an actuator screw, and a torque tube, a force istransmitted to the drag strut linkages. Thus, the gearretracts and locks. Struts are also activated that openand close the gear doors. If the switch is moved to theDOWN position, the motor reverses and the gearmoves down and locks. Once activated the gear motorwill continue to operate until an up or down limitswitch on the motor’s gearbox is tripped.

A hydraulic landing gear retraction system utilizespressurized hydraulic fluid to actuate linkages to raiseand lower the gear. When a switch in the cockpit ismoved to the UP position, hydraulic fluid is directedinto the gear up line. The fluid flows throughsequenced valves and downlocks to the gearactuating cylinders. A similar process occurs duringgear extension. The pump which pressurizes the fluidin the system can be either engine driven orelectrically powered. If an electrically powered pumpis used to pressurize the fluid, the system is referredto as an electrohydraulic system. The system alsoincorporates a hydraulic reservoir to contain excessfluid, and to provide a means of determining systemfluid level.

Regardless of its power source, the hydraulic pump isdesigned to operate within a specific range. When asensor detects excessive pressure, a relief valve withinthe pump opens, and hydraulic pressure is routed backto the reservoir. Another type of relief valve preventsexcessive pressure that may result from thermal expan-sion. Hydraulic pressure is also regulated by limit

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switches. Each gear has two limit switches—onededicated to extension and one dedicated to retraction.These switches de-energize the hydraulic pump afterthe landing gear has completed its gear cycle. In theevent of limit switch failure, a backup pressure reliefvalve activates to relieve excess system pressure.

CONTROLS AND POSITION INDICATORSLanding gear position is controlled by a switch in thecockpit. In most airplanes, the gear switch is shapedlike a wheel in order to facilitate positive identificationand to differentiate it from other cockpit controls.[Figure 11-6]

Landing gear position indicators vary with differentmake and model airplanes. The most common types oflanding gear position indicators utilize a group oflights. One type consists of a group of three greenlights, which illuminate when the landing gear is downand locked. [Figure 11-6] Another type consists of onegreen light to indicate when the landing gear is downand an amber light to indicate when the gear is up. Stillother systems incorporate a red or amber light toindicate when the gear is in transit or unsafe forlanding. [Figure 11-7] The lights are usually of the“press to test” type, and the bulbs are interchangeable.[Figure 11-6]

Other types of landing gear position indicators consistof tab-type indicators with markings “UP” to indicatethe gear is up and locked, a display of red and whitediagonal stripes to show when the gear is unlocked, ora silhouette of each gear to indicate when it locks inthe DOWN position.

LANDING GEAR SAFETY DEVICESMost airplanes with a retractable landing gear have agear warning horn that will sound when the airplane isconfigured for landing and the landing gear is notdown and locked. Normally, the horn is linked to thethrottle or flap position, and/or the airspeed indicatorso that when the airplane is below a certain airspeed,

configuration, or power setting with the gear retracted,the warning horn will sound.

Accidental retraction of a landing gear may beprevented by such devices as mechanical downlocks,safety switches, and ground locks. Mechanicaldownlocks are built-in components of a gear retractionsystem and are operated automatically by the gearretraction system. To prevent accidental operation ofthe downlocks, and inadvertent landing gear retractionwhile the airplane is on the ground, electricallyoperated safety switches are installed.

A landing gear safety switch, sometimes referred to asa squat switch, is usually mounted in a bracket on oneof the main gear shock struts. [Figure 11-8] When thestrut is compressed by the weight of the airplane, theswitch opens the electrical circuit to the motor ormechanism that powers retraction. In this way, if thelanding gear switch in the cockpit is placed in theRETRACT position when weight is on the gear, thegear will remain extended, and the warning horn maysound as an alert to the unsafe condition. Once theweight is off the gear, however, such as on takeoff, thesafety switch will release and the gear will retract.

Many airplanes are equipped with additional safetydevices to prevent collapse of the gear when theairplane is on the ground. These devices are calledground locks. One common type is a pin installed inaligned holes drilled in two or more units of thelanding gear support structure. Another type is aspring-loaded clip designed to fit around and hold twoor more units of the support structure together. Alltypes of ground locks usually have red streamerspermanently attached to them to readily indicatewhether or not they are installed.

EMERGENCY GEAR EXTENSION SYSTEMSThe emergency extension system lowers the landinggear if the main power system fails. Some airplanes

Figure 11-6. Typical landing gear switches and positionindicators.

Figure 11-7. Typical landing gear switches and positionindicators.

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have an emergency release handle in the cockpit,which is connected through a mechanical linkage tothe gear uplocks. When the handle is operated, it

releases the uplocks and allows the gears to free fall, orextend under their own weight. [Figure 11-9]

Safety Switch

Landing GearSelector Valve

Lock ReleaseSolenoid

Lock-Pin

28V DCBus Bar

Figure 11-8. Landing gear safety switch.

Hand Pump Compressed Gas

Hand Crank

Figure 11-9.Typical emergency gear extension systems.

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should then turn on the battery master switch andensure that the landing gear position indicators showthat the gear is down and locked.

External inspection of the landing gear shouldconsist of checking individual system components.[Figure 11-10] The landing gear, wheel well, andadjacent areas should be clean and free of mud anddebris. Dirty switches and valves may cause falsesafe light indications or interrupt the extension cyclebefore the landing gear is completely down andlocked. The wheel wells should be clear of anyobstructions, as foreign objects may damage the gearor interfere with its operation. Bent gear doors may

Figure 11-10. Retractable landing gear inspectioncheckpoints.

On other airplanes, release of the uplock isaccomplished using compressed gas, which is directedto uplock release cylinders.

In some airplanes, design configurations makeemergency extension of the landing gear by gravityand air loads alone impossible or impractical. In theseairplanes, provisions are included for forceful gearextension in an emergency. Some installations aredesigned so that either hydraulic fluid or compressedgas provides the necessary pressure, while others use amanual system such as a hand crank for emergencygear extension. [Figure 11-9] Hydraulic pressure foremergency operation of the landing gear may beprovided by an auxiliary hand pump, an accumulator,or an electrically powered hydraulic pump dependingon the design of the airplane.

OPERATIONAL PROCEDURESPREFLIGHTBecause of their complexity, retractable landing gearsdemand a close inspection prior to every flight. Theinspection should begin inside the cockpit. The pilotshould first make certain that the landing gear selectorswitch is in the GEAR DOWN position. The pilot

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be an indication of possible problems with normalgear operation.

Shock struts should be properly inflated and thepistons clean. Main gear and nose gear uplock anddownlock mechanisms should be checked for generalcondition. Power sources and retracting mechanismsshould be checked for general condition, obviousdefects, and security of attachment. Hydraulic linesshould be checked for signs of chafing, and leakageat attach points. Warning system micro switches(squat switches) should be checked for cleanlinessand security of attachment. Actuating cylinders,sprockets, universals, drive gears, linkages and anyother accessible components should be checked forcondition and obvious defects. The airplane structureto which the landing gear is attached should bechecked for distortion, cracks, and general condition.All bolts and rivets should be intact and secure.

TAKEOFF AND CLIMBNormally, the landing gear should be retracted afterlift-off when the airplane has reached an altitudewhere, in the event of an engine failure or otheremergency requiring an aborted takeoff, the airplanecould no longer be landed on the runway. This proce-dure, however, may not apply to all situations. Landinggear retraction should be preplanned, taking intoaccount the length of the runway, climb gradient,obstacle clearance requirements, the characteristics ofthe terrain beyond the departure end of the runway, andthe climb characteristics of the particular airplane. Forexample, in some situations it may be preferable, in theevent of an engine failure, to make an off airport forcedlanding with the gear extended in order to takeadvantage of the energy absorbing qualities of terrain(see Chapter 16). In which case, a delay in retractingthe landing gear after takeoff from a short runway maybe warranted. In other situations, obstacles in the climbpath may warrant a timely gear retraction after takeoff.Also, in some airplanes the initial climb pitch attitudeis such that any view of the runway remaining isblocked, making an assessment of the feasibility oftouching down on the remaining runway difficult.

Premature landing gear retraction should be avoided.The landing gear should not be retracted until apositive rate of climb is indicated on the flightinstruments. If the airplane has not attained a positiverate of climb, there is always the chance it may settleback onto the runway with the gear retracted. This isespecially so in cases of premature lift-off. The pilotshould also remember that leaning forward to reach thelanding gear selector may result in inadvertent forwardpressure on the yoke, which will cause the airplane todescend.

As the landing gear retracts, airspeed will increase andthe airplane’s pitch attitude may change. The gear may

take several seconds to retract. Gear retraction andlocking (and gear extension and locking) isaccompanied by sound and feel that are unique to thespecific make and model airplane. The pilot shouldbecome familiar with the sounds and feel of normalgear retraction so that any abnormal gear operation canbe readily discernable. Abnormal landing gearretraction is most often a clear sign that the gearextension cycle will also be abnormal.

APPROACH AND LANDING The operating loads placed on the landing gear athigher airspeeds may cause structural damage due tothe forces of the airstream. Limiting speeds, therefore,are established for gear operation to protect the gearcomponents from becoming overstressed during flight.These speeds are not found on the airspeed indicator.They are published in the AFM/POH for the particularairplane and are usually listed on placards in thecockpit. [Figure 11-11] The maximum landingextended speed (VLE ) is the maximum speed at whichthe airplane can be flown with the landing gearextended. The maximum landing gear operating speed(VLO) is the maximum speed at which the landing gearmay be operated through its cycle.

The landing gear is extended by placing the gearselector switch in the GEAR DOWN position. As thelanding gear extends, the airspeed will decrease andthe pitch attitude may increase. During the severalseconds it takes for the gear to extend, the pilotshould be attentive to any abnormal sounds or feel.The pilot should confirm that the landing gear hasextended and locked by the normal sound and feel ofthe system operation as well as by the gear positionindicators in the cockpit. Unless the landing gear hasbeen previously extended to aid in a descent to trafficpattern altitude, the landing gear should be extendedby the time the airplane reaches a point on the down-wind leg that is opposite the point of intendedlanding. The pilot should establish a standardprocedure consisting of a specific position on thedownwind leg at which to lower the landing gear.Strict adherence to this procedure will aid the pilot inavoiding unintentional gear up landings.

Figure 11-11. Placarded gear speeds in the cockpit.

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Operation of an airplane equipped with a retractablelanding gear requires the deliberate, careful, andcontinued use of an appropriate checklist. When onthe downwind leg, the pilot should make it a habit tocomplete the landing gear checklist for that airplane.This accomplishes two purposes. It ensures thataction has been taken to lower the gear, and itincreases the pilot’s awareness so that the gear downindicators can be rechecked prior to landing.

Unless good operating practices dictate otherwise, thelanding roll should be completed and the airplaneclear of the runway before any levers or switches areoperated. This will accomplish the following: Thelanding gear strut safety switches will be actuated,deactivating the landing gear retract system. Afterrollout and clearing the runway, the pilot will be ableto focus attention on the after landing checklist and toidentify the proper controls.

Pilots transitioning to retractable gear airplanes shouldbe aware that the most common pilot operationalfactors involved in retractable gear airplane accidentsare:

• Neglected to extend landing gear.

• Inadvertently retracted landing gear.

• Activated gear, but failed to check gear position.

• Misused emergency gear system.

• Retracted gear prematurely on takeoff.

• Extended gear too late.

In order to minimize the chances of a landing gearrelated mishap, the pilot should:

• Use an appropriate checklist. (A condensedchecklist mounted in view of the pilot as areminder for its use and easy reference can beespecially helpful.)

• Be familiar with, and periodically review, thelanding gear emergency extension procedures forthe particular airplane.

• Be familiar with the landing gear warning hornand warning light systems for the particularairplane. Use the horn system to cross-check thewarning light system when an unsafe conditionis noted.

• Review the procedure for replacing light bulbsin the landing gear warning light displays for theparticular airplane, so that you can properlyreplace a bulb to determine if the bulb(s) in thedisplay is good. Check to see if spare bulbs areavailable in the airplane spare bulb supply as partof the preflight inspection.

• Be familiar with and aware of the sounds andfeel of a properly operating landing gear system.

TRANSITION TRAININGTransition to a complex airplane or a highperformance airplane should be accomplished througha structured course of training administered by acompetent and qualified flight instructor. The trainingshould be accomplished in accordance with a groundand flight training syllabus. [Figure 11-12]

This sample syllabus for transition training is to beconsidered flexible. The arrangement of the subjectmatter may be changed and the emphasis may beshifted to fit the qualifications of the transitioningpilot, the airplane involved, and the circumstances ofthe training situation, provided the prescribedproficiency standards are achieved. These standardsare contained in the practical test standardsappropriate for the certificate that the transitioningpilot holds or is working towards.

The training times indicated in the syllabus are basedon the capabilities of a pilot who is currently activeand fully meets the present requirements for theissuance of at least a private pilot certificate. The timeperiods may be reduced for pilots with higherqualifications or increased for pilots who do not meetthe current certification requirements or who have hadlittle recent flight experience.

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1. Operations sections of flight manual2. Line inspection3. Cockpit familiarization

1. Flight training maneuvers2. Takeoffs, landings and go-arounds

1. Aircraft loading, limitations and servicing2. Instruments, radio and special equipment3. Aircraft systems

1. Emergency operations2. Control by reference to instruments3. Use of radio and autopilot

As assigned by flight instructor

1. Performance section of flight manual2. Cruise control3. Review

1. Short and soft-field takeoffs and landings2. Maximum performance operations

As assigned by flight instructor

Ground Instruction Flight Instruction Directed Practice*

1 Hour—CHECKOUT

1 Hour 1 Hour

1 Hour 1 Hour 1 Hour

1 Hour 1 Hour 1 Hour

* The directed practice indicated may be conducted solo or with a safety pilot at the discretion of the instructor.

Figure 11-12.Transition training syllabus.

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