13-1

TAILWHEEL AIRPLANES

Tailwheel airplanes are often referred to as 

conventional gear airplanes. Due to their design and

structure, tailwheel airplanes exhibit operational and

handling characteristics that are different from those of

tricycle gear airplanes. Tailwheel airplanes are not 

necessarily more difficult to takeoff, land, and/or taxi

than tricycle gear airplanes; in fact under certain 

conditions, they may even handle with less difficulty.

This chapter will focus on the operational differences

that occur during ground operations, takeoffs, and 

landings.

LANDING GEAR

The main landing gear forms the principal support of

the airplane on the ground. The tailwheel also supports

the airplane, but steering and directional control are its

primary functions. With the tailwheel-type airplane, the

two main struts are attached to the airplane slightly

ahead of the airplane’s center of gravity (CG).

The rudder pedals are the primary directional controls

while taxiing. Steering with the pedals may be 

accomplished through the forces of airflow or propeller

slipstream acting on the rudder surface, or through a

mechanical linkage to the steerable tailwheel. Initially,

the pilot should taxi with the heels of the feet resting on

the cockpit floor and the balls of the feet on the bottom

of the rudder pedals. The feet should be slid up onto the

brake pedals only when it is necessary to depress the

brakes. This permits the simultaneous application of

rudder and brake whenever needed. Some models of

tailwheel airplanes are equipped with heel brakes rather

than toe brakes. In either configuration the brakes are

used primarily to stop the airplane at a desired point, to

slow the airplane, or as an aid in making a sharp 

controlled turn. Whenever used, they must be applied

smoothly, evenly, and cautiously at all times.

TAXIING

When beginning to taxi, the brakes should be tested

immediately for proper operation. This is done by first

applying power to start the airplane moving slowly 

forward, then retarding the throttle and simultaneously

applying pressure smoothly to both brakes. If braking

action is unsatisfactory, the engine should be shut down

immediately.

To turn the airplane on the ground, the pilot should

apply rudder in the desired direction of turn and use

whatever power or brake that is necessary to control

the taxi speed. The rudder should be held in the 

direction of the turn until just short of the point where

the turn is to be stopped, then the rudder pressure

released or slight opposite pressure applied as needed.

While taxiing, the pilot will have to anticipate the

movements of the airplane and adjust rudder pressure

accordingly. Since the airplane will continue to turn

slightly even as the rudder pressure is being released,

the stopping of the turn must be anticipated and the 

rudder pedals neutralized before the desired heading is

reached. In some cases, it may be necessary to apply

opposite rudder to stop the turn, depending on the taxi

speed.

The presence of moderate to strong headwinds and/or a

strong propeller slipstream makes the use of the 

elevator necessary to maintain control of the pitch 

attitude while taxiing. This becomes apparent when

considering the lifting action that may be created on

the horizontal tail surfaces by either of those two 

factors. The elevator control should be held in the aft

position (stick or yoke back) to hold the tail down.

When taxiing in a quartering headwind, the wing on

the upwind side will usually tend to be lifted by the

wind unless the aileron control is held in that direction

(upwind aileron UP). Moving the aileron into the UP

position reduces the effect of wind striking that wing,

thus reducing the lifting action. This control movement

will also cause the opposite aileron to be placed in the

DOWN position, thus creating drag and possibly some

lift on the downwind wing, further reducing the 

tendency of the upwind wing to rise.

When taxiing with a quartering tailwind, the elevator

should be held in the full DOWN position (stick or

yoke full forward), and the upwind aileron down. Since

the wind is striking the airplane from behind, these

control positions reduce the tendency of the wind to get

under the tail and the wing possibly causing the 

airplane to nose over. The application of these 

crosswind taxi corrections also helps to minimize the

weathervaning tendency and ultimately results in

increased controllability.

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An airplane with a tailwheel has a tendency to 

weathervane or turn into the wind while it is being 

taxied. The tendency of the airplane to weathervane is

greatest while taxiing directly crosswind; 

consequently, directional control is somewhat difficult.

Without brakes, it is almost impossible to keep the 

airplane from turning into any wind of considerable

velocity since the airplane’s rudder control capability

may be inadequate to counteract the crosswind. In 

taxiing downwind, the tendency to weathervane is

increased, due to the tailwind decreasing the 

effectiveness of the flight controls. This requires a

more positive use of the rudder and the brakes, 

particularly if the wind velocity is above that of a light

breeze.

Unless the field is soft, or very rough, it is best when

taxiing downwind to hold the elevator control in the

forward position. Even on soft fields, the elevator

should be raised only as much as is absolutely 

necessary to maintain a safe margin of control in case

there is a tendency of the airplane to nose over.

On most tailwheel-type airplanes, directional control

while taxiing is facilitated by the use of a steerable 

tailwheel, which operates along with the rudder. The

tailwheel steering mechanism remains engaged when

the tailwheel is operated through an arc of about 16 to

18° each side of neutral and then automatically

becomes full swiveling when turned to a greater angle.

On some models the tailwheel may also be locked in

place. The airplane may be pivoted within its own

length, if desired, yet is fully steerable for slight turns

while taxiing forward. While taxiing, the steerable 

tailwheel should be used for making normal turns and

the pilot’s feet kept off the brake pedals to avoid 

unnecessary wear on the brakes.

Since a tailwheel-type airplane rests on the tailwheel

as well as the main landing wheels, it assumes a 

nose-high attitude when on the ground. In most cases

this places the engine cowling high enough to restrict

the pilot’s vision of the area directly ahead of the 

airplane. Consequently, objects directly ahead of the

airplane are difficult, if not impossible, to see. To

observe and avoid colliding with any objects or 

hazardous surface conditions, the pilot should 

alternately turn the nose from one side to the 

other—that is zigzag, or make a series of short S-turns

while taxiing forward. This should be done slowly,

smoothly, positively, and cautiously.

NORMAL TAKEOFF ROLL

After taxiing onto the runway, the airplane should be

carefully aligned with the intended takeoff direction,

and the tailwheel positioned straight, or centered. In

airplanes equipped with a locking device, the tailwheel

should be locked in the centered position. After 

releasing the brakes, the throttle should be smoothly

and continuously advanced to takeoff power. As the

airplane starts to roll forward, the pilot should slide

both feet down on the rudder pedals so that the toes or

balls of the feet are on the rudder portions, not on the

brake portions.

An abrupt application of power may cause the airplane

to yaw sharply to the left because of the torque effects

of the engine and propeller. Also, precession will be

particularly noticeable during takeoff in a tailwheeltype airplane if the tail is rapidly raised from a three

point to a level flight attitude. The abrupt change of

attitude tilts the horizontal axis of the propeller, and

the resulting precession produces a forward force on

the right side (90° ahead in the direction of rotation),

yawing the airplane’s nose to the left. The amount of

force created by this precession is directly related to

the rate the propeller axis is tilted when the tail is

raised. With this in mind, the throttle should always be

advanced smoothly and continuously to prevent any

sudden swerving.

Smooth, gradual advancement of the throttle is very

important in tailwheel-type airplanes, since 

peculiarities in their takeoff characteristics are 

accentuated in proportion to how rapidly the takeoff

power is applied.

As speed is gained, the elevator control will tend to

assume a neutral position if the airplane is correctly

trimmed. At the same time, directional control should

be maintained with smooth, prompt, positive rudder

corrections throughout the takeoff roll. The effects of

torque and P-factor at the initial speeds tend to pull the

nose to the left. The pilot must use what rudder 

pressure is needed to correct for these effects or for

existing wind conditions to keep the nose of the 

airplane headed straight down the runway. The use of

brakes for steering purposes should be avoided, since

they will cause slower acceleration of the airplane’s

speed, lengthen the takeoff distance, and possibly

result in severe swerving.

When the elevator trim is set for takeoff, on 

application of maximum allowable power, the airplane

will (when sufficient speed has been attained) 

normally assume the correct takeoff pitch attitude on

its own—the tail will rise slightly. This attitude can

then be maintained by applying slight back-elevator

pressure. If the elevator control is pushed forward 

during the takeoff roll to prematurely raise the tail, its

effectiveness will rapidly build up as the speed

increases, making it necessary to apply back-elevator

pressure to lower the tail to the proper takeoff attitude.

This erratic change in attitude will delay the takeoff

and lead to directional control problems. Rudder 

pressure must be used promptly and smoothly to 

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counteract yawing forces so that the airplane continues

straight down the runway.

While the speed of the takeoff roll increases, more and

more pressure will be felt on the flight controls, 

particularly the elevators and rudder. Since the tail 

surfaces receive the full effect of the propeller 

slipstream, they become effective first. As the speed

continues to increase, all of the flight controls will

gradually become effective enough to maneuver the

airplane about its three axes. It is at this point, in the

taxi to flight transition, that the airplane is being flown

more than taxied. As this occurs, progressively smaller

rudder deflections are needed to maintain direction.

TAKEOFF

Since a good takeoff depends on the proper takeoff

attitude, it is important to know how this attitude

appears and how it is attained. The ideal takeoff 

attitude requires only minimum pitch adjustments

shortly after the airplane lifts off to attain the speed for

the best rate of climb.

The tail should first be allowed to rise off the ground

slightly to permit the airplane to accelerate more 

rapidly. At this point, the position of the nose in 

relation to the horizon should be noted, then elevator

pressure applied as necessary to hold this attitude. The

wings are kept level by applying aileron pressure as

necessary. 

The airplane may be allowed to fly off the ground

while in normal takeoff attitude. Forcing it into the air

by applying excessive back-elevator pressure would

result in an excessively high pitch attitude and may

delay the takeoff. As discussed earlier, excessive and

rapid changes in pitch attitude result in proportionate

changes in the effects of torque, making the airplane

more difficult to control.

Although the airplane can be forced into the air, this is

considered an unsafe practice and should be avoided

under normal circumstances. If the airplane is forced

to leave the ground by using too much back-elevator

pressure before adequate flying speed is attained, the

wing’s angle of attack may be excessive, causing the

airplane to settle back to the runway or even to stall.

On the other hand, if sufficient back-elevator pressure

is not held to maintain the correct takeoff attitude after

becoming airborne, or the nose is allowed to lower

excessively, the airplane may also settle back to the

runway. This occurs because the angle of attack is

decreased and lift is diminished to the degree where it

will not support the airplane. It is important to hold the

attitude constant after rotation or lift-off.

As the airplane leaves the ground, the pilot must 

continue to maintain straight flight, as well as holding

the proper pitch attitude. During takeoffs in strong,

gusty wind, it is advisable that an extra margin of speed

be obtained before the airplane is allowed to leave the

ground. A takeoff at the normal takeoff speed may

result in a lack of positive control, or a stall, when the

airplane encounters a sudden lull in strong, gusty wind,

or other turbulent air currents. In this case, the pilot

should hold the airplane on the ground longer to attain

more speed, then make a smooth, positive rotation to

leave the ground.

CROSSWIND TAKEOFF

It is important to establish and maintain the proper

amount of crosswind correction prior to lift-off; that is,

apply aileron pressure toward the wind to keep the

upwind wing from rising and apply rudder pressure as

needed to prevent weathervaning.

As the tailwheel is raised off the runway, the holding

of aileron control into the wind may result in the 

downwind wing rising and the downwind main wheel

lifting off the runway first, with the remainder of the

takeoff roll being made on one main wheel. This is

acceptable and is preferable to side-skipping.

If a significant crosswind exists, the main wheels

should be held on the ground slightly longer than in a

normal takeoff so that a smooth but definite lift-off can

be made. This procedure will allow the airplane to

leave the ground under more positive control so that it

will definitely remain airborne while the proper

amount of drift correction is being established. More

importantly, it will avoid imposing excessive side

loads on the landing gear and prevent possible damage

that would result from the airplane settling back to the

runway while drifting.

As both main wheels leave the runway, and ground

friction no longer resists drifting, the airplane will be

slowly carried sideways with the wind until adequate

drift correction is maintained. 

SHORT-FIELD TAKEOFF

Wing flaps should be lowered prior to takeoff if 

recommended by the manufacturer. Takeoff power

should be applied smoothly and continuously, (there

should be no hesitation) to accelerate the airplane as

rapidly as possible. As the takeoff roll progresses, the

airplane’s pitch attitude and angle of attack should be

adjusted to that which results in the minimum amount

of drag and the quickest acceleration. The tail should

be allowed to rise off the ground slightly, then held in

this tail-low flight attitude until the proper lift-off or

rotation airspeed is attained. For the steepest climb-out

and best obstacle clearance, the airplane should be

allowed to roll with its full weight on the main wheels

and accelerated to the lift-off speed. 

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SOFT-FIELD TAKEOFF

Wing flaps may be lowered prior to starting the takeoff

(if recommended by the manufacturer) to provide 

additional lift and transfer the airplane’s weight from

the wheels to the wings as early as possible. The 

airplane should be taxied onto the takeoff surface 

without stopping on a soft surface. Stopping on a soft

surface, such as mud or snow, might bog the 

airplane down. The airplane should be kept in

continuous motion with sufficient power while lining

up for the takeoff roll.

As the airplane is aligned with the proposed takeoff

path, takeoff power is applied smoothly and as rapidly

as the powerplant will accept it without faltering. The

tail should be kept low to maintain the inherent 

positive angle of attack and to avoid any tendency of

the airplane to nose over as a result of soft spots, tall

grass, or deep snow.

When the airplane is held at a nose-high attitude

throughout the takeoff run, the wings will, as speed

increases and lift develops, progressively relieve the

wheels of more and more of the airplane’s weight,

thereby minimizing the drag caused by surface 

irregularities or adhesion. If this attitude is accurately

maintained, the airplane will virtually fly itself off the

ground. The airplane should be allowed to accelerate

to climb speed in ground effect.

TOUCHDOWN

The touchdown is the gentle settling of the airplane

onto the landing surface. The roundout and touchdown

should be made with the engine idling, and the airplane

at minimum controllable airspeed, so that the airplane

will touch down at approximately stalling speed. As

the airplane settles, the proper landing attitude must be

attained by applying whatever back-elevator pressure

is necessary. The roundout and touchdown should be

timed so that the wheels of the main landing gear and

tailwheel touch down simultaneously (three-point

landing). This requires proper timing, technique, and

judgment of distance and altitude. [Figure 13-1]

When the wheels make contact with the ground, the

elevator control should be carefully eased fully back

to hold the tail down and to keep the tailwheel on the

ground. This provides more positive directional 

control of the airplane equipped with a steerable 

tailwheel, and prevents any tendency for the airplane

to nose over. If the tailwheel is not on the ground, 

easing back on the elevator control may cause the 

airplane to become airborne again because the change

in attitude will increase the angle of attack and 

produce enough lift for the airplane to fly.

It is extremely important that the touchdown occur

with the airplane’s longitudinal axis exactly parallel to

the direction the airplane is moving along the runway.

Failure to accomplish this not only imposes severe

side loads on the landing gear, but imparts 

groundlooping (swerving) tendencies. To avoid these

side stresses or a ground loop, the pilot must never

allow the airplane to touch down while in a crab or

while drifting.

AFTER-LANDING ROLL

The landing process must never be considered 

complete until the airplane decelerates to the normal

taxi speed during the landing roll or has been brought

to a complete stop when clear of the landing area. The

pilot must be alert for directional control difficulties

immediately upon and after touchdown due to the

ground friction on the wheels. The friction creates a

pivot point on which a moment arm can act. This is

because the CG is behind the main wheels. 

[Figure 13-2] 

Any difference between the direction the airplane is

traveling and the direction it is headed will produce a

moment about the pivot point of the wheels, and the

airplane will tend to swerve. Loss of directional 

control may lead to an aggravated, uncontrolled, tight

turn on the ground, or a ground loop. The combination

of inertia acting on the CG and ground friction of the

main wheels resisting it during the ground loop may

cause the airplane to tip or lean enough for the outside

Main Gear and Tailwheel

Touch Down Simultaneously

Hold Elevator

Full Up

Normal

Glide

Start Roundout

to Landing Attitude

Figure 13-1.Tailwheel touchdown.

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wingtip to contact the ground, and may even impose a

sideward force that could collapse the landing gear.

The airplane can ground loop late in the after-landing

roll because rudder effectiveness decreases with the

decreasing flow of air along the rudder surface as the

airplane slows. As the airplane speed decreases and the

tailwheel has been lowered to the ground, the steerable

tailwheel provides more positive directional control.

To use the brakes, the pilot should slide the toes or feet

up from the rudder pedals to the brake pedals (or apply

heel pressure in airplanes equipped with heel brakes).

If rudder pressure is being held at the time braking

action is needed, that pressure should not be released

as the feet or toes are being slid up to the brake pedals,

because control may be lost before brakes can be

applied. During the ground roll, the airplane’s 

direction of movement may be changed by carefully

applying pressure on one brake or uneven pressures on

each brake in the desired direction. Caution must be

exercised, when applying brakes to avoid 

overcontrolling.

If a wing starts to rise, aileron control should be

applied toward that wing to lower it. The amount

required will depend on speed because as the forward

speed of the airplane decreases, the ailerons will

become less effective. 

The elevator control should be held back as far as 

possible and as firmly as possible, until the airplane

stops. This provides more positive control with 

tailwheel steering, tends to shorten the after-landing

roll, and prevents bouncing and skipping. 

If available runway permits, the speed of the airplane

should be allowed to dissipate in a normal manner by

the friction and drag of the wheels on the ground.

Brakes may be used if needed to help slow the airplane.

After the airplane has been slowed sufficiently and has

been turned onto a taxiway or clear of the landing area,

it should be brought to a complete stop. Only after this

is done should the pilot retract the flaps and perform

other checklist items.

CROSSWIND LANDING

If the crab method of drift correction has been used

throughout the final approach and roundout, the crab

must be removed before touchdown by applying 

rudder to align the airplane’s longitudinal axis with its

direction of movement. This requires timely and 

accurate action. Failure to accomplish this results in

severe side loads being imposed on the landing gear

and imparts ground looping tendencies.

If the wing-low method is used, the crosswind 

correction (aileron into the wind and opposite rudder)

should be maintained throughout the roundout, and the

touchdown made on the upwind main wheel.

During gusty or high-wind conditions, prompt 

adjustments must be made in the crosswind correction

to assure that the airplane does not drift as it touches

down.

As the forward speed decreases after initial contact,

the weight of the airplane will cause the downwind

main wheel to gradually settle onto the runway.

An adequate amount of power should be used to 

maintain the proper airspeed throughout the approach,

and the throttle should be retarded to idling position

after the main wheels contact the landing surface. Care

must be exercised in closing the throttle before the

pilot is ready for touchdown, because the sudden or

premature closing of the throttle may cause a sudden

increase in the descent rate that could result in a hard

landing.

CROSSWIND AFTER-LANDING ROLL

Particularly during the after-landing roll, special 

attention must be given to maintaining directional 

control by the use of rudder and tailwheel steering,

while keeping the upwind wing from rising by the use

of aileron. Characteristically, an airplane has a greater

profile, or side area, behind the main landing gear than

forward of it. [Figure 13-3] With the main wheels 

acting as a pivot point and the greater surface area

exposed to the crosswind behind that pivot point, the

airplane will tend to turn or weathervane into the wind.

This weathervaning tendency is more prevalent in the

tailwheel-type because the airplane’s surface area

behind the main landing gear is greater than in 

nosewheel-type airplanes.

Point of

Wheel Pivoting

C.G.

Figure 13-2. Effect of CG on directional control.

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Pilots should be familiar with the crosswind component

of each airplane they fly, and avoid operations in

wind conditions that exceed the capability of the 

airplane, as well as their own limitations.

While the airplane is decelerating during the 

after-landing roll, more aileron must be applied to keep

the upwind wing from rising. Since the airplane is

slowing down, there is less airflow around the ailerons

and they become less effective. At the same time, the

relative wind is becoming more of a crosswind and

exerting a greater lifting force on the upwind wing.

Consequently, when the airplane is coming to a stop,

the aileron control must be held fully toward the wind.

WHEEL LANDING

Landings from power approaches in turbulence or in

crosswinds should be such that the touchdown is made

with the airplane in approximately level flight attitude.

The touchdown should be made smoothly on the main

wheels, with the tailwheel held clear of the runway.

This is called a “wheel landing” and requires careful

timing and control usage to prevent bouncing. These

wheel landings can be best accomplished by holding

the airplane in level flight attitude until the main

wheels touch, then immediately but smoothly 

retarding the throttle, and holding sufficient forward

elevator pressure to hold the main wheels on the

ground. The airplane should never be forced onto the

ground by excessive forward pressure.

If the touchdown is made at too high a rate of descent

as the main wheels strike the landing surface, the tail is

forced down by its own weight. In turn, when the tail is

forced down, the wing’s angle of attack increases

resulting in a sudden increase in lift and the airplane

may become airborne again. Then as the airplane’s

speed continues to decrease, the tail may again lower

onto the runway. If the tail is allowed to settle too

quickly, the airplane may again become airborne. This

process, often called “porpoising,” usually intensifies

even though the pilot tries to stop it. The best 

corrective action is to execute a go-around procedure.

SHORT-FIELD LANDING

Upon touchdown, the airplane should be firmly held in

a three-point attitude. This will provide aerodynamic

braking by the wings. Immediately upon touchdown,

and closing the throttle, the brakes should be applied

evenly and firmly to minimize the after-landing roll.

The airplane should be stopped within the shortest

possible distance consistent with safety.

SOFT-FIELD LANDING

The tailwheel should touch down simultaneously with

or just before the main wheels, and should then be held

down by maintaining firm back-elevator pressure

throughout the landing roll. This will minimize any

tendency for the airplane to nose over and will provide

aerodynamic braking. The use of brakes on a soft field

is not needed because the soft or rough surface itself

will provide sufficient reduction in the airplane’s 

forward speed. Often it will be found that upon 

landing on a very soft field, the pilot will need to

increase power to keep the airplane moving and from

becoming stuck in the soft surface.

GROUND LOOP

A ground loop is an uncontrolled turn during ground

operation that may occur while taxiing or taking off,

but especially during the after-landing roll. It is not

always caused by drift or weathervaning, although

these things may cause the initial swerve. Careless use

of the rudder, an uneven ground surface, or a soft spot

that retards one main wheel of the airplane may also

cause a swerve. In any case, the initial swerve tends to

cause the airplane to ground loop.

Due to the characteristics of an airplane equipped with

a tailwheel, the forces that cause a ground loop

increase as the swerve increases. The initial swerve

develops inertia and this, acting at the CG (which is

located behind the main wheels), swerves the airplane

even more. If allowed to develop, the force produced

may become great enough to tip the airplane until one

wing strikes the ground.

If the airplane touches down while drifting or in a crab,

the pilot should apply aileron toward the high wing

and stop the swerve with the rudder. Brakes should be

used to correct for turns or swerves only when the 

rudder is inadequate. The pilot must exercise caution

when applying corrective brake action because it is

very easy to overcontrol and aggravate the situation. If

brakes are used, sufficient brake should be applied on

the low-wing wheel (outside of the turn) to stop the

swerve. When the wings are approximately level, the

new direction must be maintained until the airplane

has slowed to taxi speed or has stopped.

Figure 13-3. Weathervaning tendency.

Profile

Behind Pivot Point

N

W

S

E

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GENERAL

The turbopropeller-powered airplane flies and handles

just like any other airplane of comparable size and

weight. The aerodynamics are the same. The major

differences between flying a turboprop and other

non-turbine-powered airplanes are found in the powerplant and systems. The powerplant is different and

requires operating procedures that are unique to gas

turbine engines. But so, too, are other systems such as

the electrical system, hydraulics, environmental, flight

control, rain and ice protection, and avionics. The

turbopropeller-powered airplane also has the advantage

of being equipped with a constant speed, full feathering

and reversing propeller—something normally not

found on piston-powered airplanes.

THE GAS TURBINE ENGINE

Both piston (reciprocating) engines and gas turbine

engines are internal combustion engines. They have a

similar cycle of operation that consists of induction,

compression, combustion, expansion, and exhaust. In a

piston engine, each of these events is a separate distinct

occurrence in each cylinder. Also, in a piston engine an

ignition event must occur during each cycle, in each

cylinder. Unlike reciprocating engines, in gas turbine

engines these phases of power occur simultaneously

and continuously instead of one cycle at a time.

Additionally, ignition occurs during the starting cycle

and is continuous thereafter. 

The basic gas turbine engine contains four sections:

intake, compression, combustion, and exhaust.

[Figure 14-1]

To start the engine, the compressor section is rotated by

an electrical starter on small engines or an air driven

starter on large engines. As compressor r.p.m.

accelerates, air is brought in through the inlet duct,

compressed to a high pressure, and delivered to the

combustion section (combustion chambers). Fuel is

then injected by a fuel controller through spray

nozzles and ignited by igniter plugs. (Not all of the

compressed air is used to support combustion. Some of

the compressed air bypasses the burner section and circulates within the engine to provide internal cooling.) The

fuel/air mixture in the combustion chamber is then burned

in a continuous combustion process and produces a very

high temperature, typically around 4,000°F, which heats

INTAKE COMPRESSION COMBUSTION EXHAUST

Air Inlet Compression Combustion Chambers Turbine Exhaust 

Cold Section Hot Section

Figure 14-1. Basic components of a gas turbine engine.

Ch 14.qxd 5/7/04 10:08 AM Page 14-1
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the entire air mass to 1,600 – 2,400°F. The mixture of

hot air and gases expands and is directed to the turbine

blades forcing the turbine section to rotate, which in

turn drives the compressor by means of a direct shaft.

After powering the turbine section, the high velocity

excess exhaust exits the tail pipe or exhaust section.

Once the turbine section is powered by gases from the

burner section, the starter is disengaged, and the

igniters are turned off. Combustion continues until the

engine is shut down by turning off the fuel supply. 

High-pressure exhaust gases can be used to provide

jet thrust as in a turbojet engine. Or, the gases

can be directed through an additional turbine to drive a

propeller through reduction gearing, as in a

turbopropeller (turboprop) engine.

TURBOPROP ENGINES

The turbojet engine excels the reciprocating engine in

top speed and altitude performance. On the other hand,

the turbojet engine has limited takeoff and initial climb

performance, as compared to that of a reciprocating

engine. In the matter of takeoff and initial climb

performance, the reciprocating engine is superior to

the turbojet engine. Turbojet engines are most efficient

at high speeds and high altitudes, while propellers are

most efficient at slow and medium speeds (less than

400 m.p.h.). Propellers also improve takeoff and climb

performance. The development of the turboprop

engine was an attempt to combine in one engine the

best characteristics of both the turbojet, and propeller

driven reciprocating engine.

The turboprop engine offers several advantages over

other types of engines such as:

• Light weight.

• Mechanical reliability due to relatively few

moving parts.

• Simplicity of operation.

• Minimum vibration.

• High power per unit of weight.

• Use of propeller for takeoff and landing.

Turboprop engines are most efficient at speeds

between 250 and 400 m.p.h. and altitudes between

18,000 and 30,000 feet. They also perform well at the

slow speeds required for takeoff and landing, and are

fuel efficient. The minimum specific fuel consumption

of the turboprop engine is normally available in the

altitude range of 25,000 feet up to the tropopause.

The power output of a piston engine is measured in

horsepower and is determined primarily by r.p.m. and

manifold pressure. The power of a turboprop engine,

however, is measured in shaft horsepower (shp). Shaft

horsepower is determined by the r.p.m. and the torque

(twisting moment) applied to the propeller shaft. Since

turboprop engines are gas turbine engines, some jet

thrust is produced by exhaust leaving the engine. This

thrust is added to the shaft horsepower to determine

the total engine power, or equivalent shaft horsepower

(eshp). Jet thrust usually accounts for less than

10 percent of the total engine power.

Although the turboprop engine is more complicated

and heavier than a turbojet engine of equivalent size

and power, it will deliver more thrust at low subsonic

airspeeds. However, the advantages decrease as flight

speed increases. In normal cruising speed ranges, the

propulsive efficiency (output divided by input) of a

turboprop decreases as speed increases.

The propeller of a typical turboprop engine is

responsible for roughly 90 percent of the total thrust

under sea level conditions on a standard day. The

excellent performance of a turboprop during takeoff

and climb is the result of the ability of the propeller to

accelerate a large mass of air while the airplane is

moving at a relatively low ground and flight speed.

“Turboprop,” however, should not be confused with

“turbosupercharged” or similar terminology. All

turbine engines have a similarity to normally aspirated

(non-supercharged) reciprocating engines in that

maximum available power decreases almost as a direct

function of increased altitude.

Although power will decrease as the airplane climbs

to higher altitudes, engine efficiency in terms of

specific fuel consumption (expressed as pounds of fuel

consumed per horsepower per hour) will be increased.

Decreased specific fuel consumption plus the

increased true airspeed at higher altitudes is a definite

advantage of a turboprop engine.

All turbine engines, turboprop or turbojet, are defined

by limiting temperatures, rotational speeds, and (in the

case of turboprops) torque. Depending on the

installation, the primary parameter for power setting

might be temperature, torque, fuel flow or r.p.m.

(either propeller r.p.m., gas generator (compressor)

r.p.m. or both). In cold weather conditions, torque

limits can be exceeded while temperature limits are

still within acceptable range. While in hot weather

conditions, temperature limits may be exceeded

without exceeding torque limits. In any weather, the

maximum power setting of a turbine engine is usually

obtained with the throttles positioned somewhat aft of

the full forward position. The transitioning pilot must

understand the importance of knowing and observing

limits on turbine engines. An overtemp or overtorque

condition that lasts for more than a very few seconds

can literally destroy internal engine components. 

Ch 14.qxd 5/7/04 10:08 AM Page 14-2
14-3

TURBOPROP ENGINE TYPES

FIXED SHAFT

One type of turboprop engine is the fixed shaft

constant speed type such as the Garrett TPE331.

[Figure 14-2] In this type engine, ambient air is

directed to the compressor section through the engine

inlet. An acceleration/diffusion process in the twostage compressor increases air pressure and directs it

rearward to a combustor. The combustor is made up of

a combustion chamber, a transition liner, and a turbine

plenum. Atomized fuel is added to the air in the

combustion chamber. Air also surrounds the

combustion chamber to provide for cooling and

insulation of the combustor.

The gas mixture is initially ignited by high-energy

igniter plugs, and the expanding combustion gases

flow to the turbine. The energy of the hot, high

velocity gases is converted to torque on the main shaft

by the turbine rotors. The reduction gear converts the

high r.p.m.—low torque of the main shaft to low

r.p.m.—high torque to drive the accessories and the

propeller. The spent gases leaving the turbine are

directed to the atmosphere by the exhaust pipe.

Only about 10 percent of the air which passes through

the engine is actually used in the combustion process.

Up to approximately 20 percent of the compressed air

may be bled off for the purpose of heating, cooling,

cabin pressurization, and pneumatic systems. Over

half the engine power is devoted to driving the

compressor, and it is the compressor which can

potentially produce very high drag in the case of a

failed, windmilling engine. 

In the fixed shaft constant-speed engine, the engine

r.p.m. may be varied within a narrow range of 96

percent to 100 percent. During ground operation, the

r.p.m. may be reduced to 70 percent. In flight, the

engine operates at a constant speed, which is

maintained by the governing section of the propeller.

Power changes are made by increasing fuel flow and

propeller blade angle rather than engine speed. An

increase in fuel flow causes an increase in temperature

and a corresponding increase in energy available to the

turbine. The turbine absorbs more energy and

transmits it to the propeller in the form of torque. The

increased torque forces the propeller blade angle to be

increased to maintain the constant speed. Turbine

temperature is a very important factor to be considered

in power production. It is directly related to fuel flow

and thus to the power produced. It must be limited

because of strength and durability of the material in the

combustion and turbine section. The control system

schedules fuel flow to produce specific temperatures

and to limit those temperatures so that the temperature

tolerances of the combustion and turbine sections are

not exceeded. The engine is designed to operate for its

entire life at 100 percent. All of its components, such

as compressors and turbines, are most efficient when

operated at or near the r.p.m. design point.

Planetary

Reduction Gears

Air

Inlet

First-Stage

Centrifugal

Compressor

Second-Stage

Centrifugal

Compressor

Reverse-Flow

Annular Combustion

Chamber

Three-Stage

Axial Turbine

Fuel

Nozzle

Igniter

Exhaust

Outlet

Figure 14-2. Fixed shaft turboprop engine.

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14-4

Powerplant (engine and propeller) control is achieved

by means of a power lever and a condition lever for

each engine. [Figure 14-3] There is no mixture control

and/or r.p.m. lever as found on piston engine airplanes.

On the fixed shaft constant-speed turboprop engine,

the power lever is advanced or retarded to increase or

decrease forward thrust. The power lever is also used

to provide reverse thrust. The condition lever sets the

desired engine r.p.m. within a narrow range between

that appropriate for ground operations and flight.

Powerplant instrumentation in a fixed shaft turboprop

engine typically consists of the following basic

indicator. [Figure 14-4]

• Torque or horsepower.

• ITT – interturbine temperature.

• Fuel flow. 

• RPM.

Torque developed by the turbine section is measured

by a torque sensor. The torque is then reflected on a

cockpit horsepower gauge calibrated in horsepower

times 100. Interturbine temperature (ITT) is a

measurement of the combustion gas temperature

between the first and second stages of the turbine

section. The gauge is calibrated in degrees Celsius.

Propeller r.p.m. is reflected on a cockpit tachometer as

a percentage of maximum r.p.m. Normally, a vernier

indicator on the gauge dial indicates r.p.m. in 1 percent

graduations as well. The fuel flow indicator indicates

fuel flow rate in pounds per hour.

Propeller feathering in a fixed shaft constant-speed

turboprop engine is normally accomplished with the

condition lever. An engine failure in this type engine,

however, will result in a serious drag condition due to

the large power requirements of the compressor being

absorbed by the propeller. This could create a serious

airplane control problem in twin-engine airplanes

unless the failure is recognized immediately and the

Power Levers

Condition Levers

Figure 14-3. Powerplant controls—fixed shaft turboprop engine.

Figure 14-4. Powerplant instrumentation—fixed shaft

turboprop engine.

Ch 14.qxd 5/7/04 10:09 AM Page 14-4
14-5

affected propeller feathered. For this reason, the fixed

shaft turboprop engine is equipped with negative

torque sensing (NTS).

Negative torque sensing is a condition wherein

propeller torque drives the engine and the propeller is

automatically driven to high pitch to reduce drag. The

function of the negative torque sensing system is to

limit the torque the engine can extract from the

propeller during windmilling and thereby prevent large

drag forces on the airplane. The NTS system causes a

movement of the propeller blades automatically

toward their feathered position should the engine

suddenly lose power while in flight. The NTS system

is an emergency backup system in the event of sudden

engine failure. It is not a substitution for the feathering

device controlled by the condition lever.

SPLIT SHAFT/ FREE TURBINE ENGINE

In a free power-turbine engine, such as the Pratt &

Whitney PT-6 engine, the propeller is driven by a

separate turbine through reduction gearing. The

propeller is not on the same shaft as the basic engine

turbine and compressor. [Figure 14-5] Unlike the fixed

shaft engine, in the split shaft engine the propeller can

be feathered in flight or on the ground with the basic

engine still running. The free power-turbine design

allows the pilot to select a desired propeller governing

r.p.m., regardless of basic engine r.p.m.

A typical free power-turbine engine has two

independent counter-rotating turbines. One turbine

drives the compressor, while the other drives

the propeller through a reduction gearbox. The

compressor in the basic engine consists of three axial

flow compressor stages combined with a single centrifugal compressor stage. The axial and centrifugal

stages are assembled on the same shaft, and operate as

a single unit.

Inlet air enters the engine via a circular plenum near

the rear of the engine, and flows forward through the

successive compressor stages. The flow is directed

outward by the centrifugal compressor stage through

radial diffusers before entering the combustion

chamber, where the flow direction is actually reversed.

The gases produced by combustion are once again

reversed to expand forward through each turbine stage.

After leaving the turbines, the gases are collected in a

peripheral exhaust scroll, and are discharged to the

atmosphere through two exhaust ports near the front of

the engine. 

A pneumatic fuel control system schedules fuel flow to

maintain the power set by the gas generator power

lever. Except in the beta range, propeller speed within

the governing range remains constant at any selected

propeller control lever position through the action of a

propeller governor.

The accessory drive at the aft end of the engine

provides power to drive fuel pumps, fuel control, oil

pumps, a starter/generator, and a tachometer

transmitter. At this point, the speed of the drive (N1) is

the true speed of the compressor side of the engine,

approximately 37,500 r.p.m.

Reduction

Gearbox

Propeller

Drive Shaft Free (Power)

Turbine Compressor

Turbine

(Gas Producer)

Three Stage

Axial Flow

Compressor

Exhaust Outlet

Air Inlet

Centrifugal

Compressor

Igniter

Fuel Nozzle

Igniter

Fuel Nozzle

Accessory

Gearbox

Figure 14-5. Split shaft/free turbine engine.

Ch 14.qxd 5/7/04 10:09 AM Page 14-5
14-6

Powerplant (engine and propeller) operation is

achieved by three sets of controls for each engine: the

power lever, propeller lever, and condition lever.

[Figure 14-6] The power lever serves to control engine

power in the range from idle through takeoff power.

Forward or aft motion of the power lever increases or

decreases gas generator r.p.m. (N1) and thereby

increases or decreases engine power. The propeller

lever is operated conventionally and controls the

constant-speed propellers through the primary

governor. The propeller r.p.m. range is normally from

1,500 to 1,900. The condition lever controls the flow

of fuel to the engine. Like the mixture lever in a

piston-powered airplane, the condition lever is located

at the far right of the power quadrant. But the condition lever on a turboprop engine is really just an on/off

valve for delivering fuel. There are HIGH IDLE and

LOW IDLE positions for ground operations, but condition levers have no metering function. Leaning is not

required in turbine engines; this function is performed

automatically by a dedicated fuel control unit.

Engine instruments in a split shaft/free turbine engine

typically consist of the following basic indicators.

[Figure 14-7] 

• ITT (interstage turbine temperature) indicator.

• Torquemeter.

• Propeller tachometer.

• N1 (gas generator) tachometer.

• Fuel flow indicator.

• Oil temperature/pressure indicator.

Figure 14-6. Powerplant controls—split shaft/free turbine

engine.

Figure 14-7. Engine instruments—split shaft/free turbine

engine.

Ch 14.qxd 5/7/04 10:09 AM Page 14-6
14-7

The ITT indicator gives an instantaneous reading of

engine gas temperature between the compressor

turbine and the power turbines. The torquemeter

responds to power lever movement and gives an

indication, in foot-pounds (ft/lb), of the torque being

applied to the propeller. Because in the free turbine

engine, the propeller is not attached physically to the

shaft of the gas turbine engine, two tachometers are

justified—one for the propeller and one for the gas

generator. The propeller tachometer is read directly in

revolutions per minute. The N1 or gas generator is read

in percent of r.p.m. In the Pratt & Whitney PT-6

engine, it is based on a figure of 37,000 r.p.m. at 100

percent. Maximum continuous gas generator is limited

to 38,100 r.p.m. or 101.5 percent N1. 

The ITT indicator and torquemeter are used to set

takeoff power. Climb and cruise power are established

with the torquemeter and propeller tachometer while

observing ITT limits. Gas generator (N1) operation is

monitored by the gas generator tachometer. Proper

observation and interpretation of these instruments

provide an indication of engine performance

and condition.

REVERSE THRUST AND BETA RANGE

OPERATIONS

The thrust that a propeller provides is a function of the

angle of attack at which the air strikes the blades, and

the speed at which this occurs. The angle of attack

varies with the pitch angle of the propeller.

So called “flat pitch” is the blade position offering

minimum resistance to rotation and no net thrust for

moving the airplane. Forward pitch produces forward

thrust—higher pitch angles being required at higher

airplane speeds. 

The “feathered” position is the highest pitch angle

obtainable. [Figure 14-8] The feathered position

produces no forward thrust. The propeller is generally

placed in feather only in case of in-flight engine failure

to minimize drag and prevent the air from using the

propeller as a turbine. 

In the “reverse” pitch position, the engine/propeller

turns in the same direction as in the normal (forward)

pitch position, but the propeller blade angle is

positioned to the other side of flat pitch. [Figure 14-8]

In reverse pitch, air is pushed away from the airplane

rather than being drawn over it. Reverse pitch results

in braking action, rather than forward thrust of the airplane. It is used for backing away from obstacles when

taxiing, controlling taxi speed, or to aid in bringing the

airplane to a stop during the landing roll. Reverse pitch

does not mean reverse rotation of the engine. The

engine delivers power just the same, no matter which

side of flat pitch the propeller blades are positioned. 

With a turboprop engine, in order to obtain enough

power for flight, the power lever is placed somewhere

between flight idle (in some engines referred to as

“high idle”) and maximum. The power lever directs

signals to a fuel control unit to manually select fuel.

The propeller governor selects the propeller pitch

needed to keep the propeller/engine on speed. This is

referred to as the propeller governing or “alpha” mode

of operation. When positioned aft of flight idle, however, the power lever directly controls propeller blade

angle. This is known as the “beta” range of operation. 

The beta range of operation consists of power lever

positions from flight idle to maximum reverse.

Power Prop Condition

Reverse

Beta

Idle

Feather Normal

"Forward" Pitch

Feather

"Maximum Forward

Pitch"

Flat Pitch

Reverse Pitch

Fuel

Cut

Off

Reverse

Fuel

Cut

Off

Reverse Feather

Fuel

Cut

Off

Feather

Fuel

Cut

Off

Low

Idle

Flt

Idle

Low

Idle

Flt

Idle

Low

Idle

Flt

Idle

Low

Idle

Flt

Idle

Pull

Up

Figure 14-8. Propeller pitch angle characteristics.

Ch 14.qxd 5/7/04 10:09 AM Page 14-7
14-8

Beginning at power lever positions just aft of flight

idle, propeller blade pitch angles become progressively

flatter with aft movement of the power lever until they

go beyond maximum flat pitch and into negative pitch,

resulting in reverse thrust. While in a fixed shaft/

constant-speed engine, the engine speed remains

largely unchanged as the propeller blade angles

achieve their negative values. On the split shaft PT-6

engine, as the negative 5° position is reached, further

aft movement of the power lever will also result in a

progressive increase in engine (N1) r.p.m. until a

maximum value of about negative 11° of blade angle

and 85 percent N1 are achieved. 

Operating in the beta range and/or with reverse thrust

requires specific techniques and procedures depending

on the particular airplane make and model. There are

also specific engine parameters and limitations for

operations within this area that must be adhered to. It

is essential that a pilot transitioning to turboprop

airplanes become knowledgeable and proficient in

these areas, which are unique to turbine-enginepowered airplanes.

TURBOPROP AIRPLANE ELECTRICAL

SYSTEMS

The typical turboprop airplane electrical system is a

28-volt direct current (DC) system, which receives

power from one or more batteries and a starter/

generator for each engine. The batteries may either be

of the lead-acid type commonly used on pistonpowered airplanes, or they may be of the

nickel-cadmium (NiCad) type. The NiCad battery

differs from the lead-acid type in that its output

remains at relatively high power levels for longer

periods of time. When the NiCad battery is depleted,

however, its voltage drops off very suddenly. When

this occurs, its ability to turn the compressor for engine

start is greatly diminished and the possibility of engine

damage due to a hot start increases. Therefore, it is

essential to check the battery’s condition before every

engine start. Compared to lead-acid batteries, highperformance NiCad batteries can be recharged very

quickly. But the faster the battery is recharged, the

more heat it produces. Therefore, NiCad battery

equipped airplanes are fitted with battery overheat

annunciator lights signifying maximum safe and

critical temperature thresholds.

The DC generators used in turboprop airplanes double

as starter motors and are called “starter/generators.”

The starter/generator uses electrical power to produce

mechanical torque to start the engine and then uses the

engine’s mechanical torque to produce electrical power

after the engine is running. Some of the DC power

produced is changed to 28 volt 400 cycle alternating

current (AC) power for certain avionic, lighting,

and indicator synchronization functions. This is

accomplished by an electrical component called an

inverter. 

The distribution of DC and AC power throughout the

system is accomplished through the use of power distribution buses. These “buses” as they are called are

actually common terminals from which individual

electrical circuits get their power. [Figure 14-9]

Buses are usually named for what they power (avionics bus, for example), or for where they get their power

(right generator bus, battery bus). The distribution of

DC and AC power is often divided into functional

groups (buses) that give priority to certain equipment

5 GEAR WARN

5 TRIM INDICATOR

3 TRIM ELEVATOR

5 TRIM AILERON

5 STALL WARNING

5 ACFT ANN-1

5 L TURN & BANK

5 TEMP OVRD

5 HP EMER L & R

5 FUEL QUANTITY

5 L ENGINE GAUGE

5 R ENGINE GAUGE

5 MISC ELEC

5 LDG LT MOTOR

5 BLEED L

3 WSHLD L

3 LIGHTS AUX

5 FUEL FLOW

POWER DISTRIBUTION BUS

Figure 14-9.Typical individual power distribution bus.

Ch 14.qxd 5/7/04 10:09 AM Page 14-8
14-9

during normal and emergency operations. Main buses

serve most of the airplane’s electrical equipment.

Essential buses feed power to equipment having top

priority. [Figure 14-10]

Multiengine turboprop airplanes normally have

several power sources—a battery and at least one

generator per engine. The electrical systems are

usually designed so that any bus can be energized by

any of the power sources. For example, a typical

system might have a right and left generator buses

powered normally by the right and left engine-driven

generators. These buses will be connected by a

normally open switch, which isolates them from each

other. If one generator fails, power will be lost to its

bus, but power can be restored to that bus by closing a

bus tie switch. Closing this switch connects the buses

and allows the operating generator to power both.

Power distribution buses are protected from short

circuits and other malfunctions by a type of fuse called

a current limiter. In the case of excessive current

supplied by any power source, the current limiter will

open the circuit and thereby isolate that power source

and allow the affected bus to become separated from

the system. The other buses will continue to operate

normally. Individual electrical components are

connected to the buses through circuit breakers. A

circuit breaker is a device which opens an electrical

circuit when an excess amount of current flows.

PRIMARY

INVERTER

SECONDARY

INVERTER

LEFT

MAIN

BUS

RIGHT

MAIN

BUS

LEFT

ESSENTIAL

BUS

RIGHT

ESSENTIAL

BUS

AMPS

0

100

200

300

400 DC

VOLTS

0

28

35

AMPS

0

100

200

300

400

REGULATOR REGULATOR

LEFT

GENERATOR

BUS

BATTERY

CHARGING

BUS

RIGHT

GENERATOR

BUS

LEFT

GENERATOR/

STARTER

LEFT

GENERATOR/

STARTER

G.P.U.

LEFT

BATTERY

RIGHT

BATTERY

OVER

VOLTAGE

CUTOUT

Current Limiter

Circuit Breaker

Bus

Figure 14-10. Simplified schematic of turboprop airplane electrical system.

Ch 14.qxd 5/7/04 10:09 AM Page 14-9
14-10

OPERATIONAL CONSIDERATIONS

As previously stated, a turboprop airplane flies just like

any other piston engine airplane of comparable size

and weight. It is in the operation of the engines and

airplane systems that makes the turboprop airplane

different from its piston engine counterpart. Pilot

errors in engine and/or systems operation are the most

common cause of aircraft damage or mishap. The time

of maximum vulnerability to pilot error in any gas

turbine engine is during the engine start sequence. 

Turbine engines are extremely heat sensitive. They

cannot tolerate an overtemperature condition for more

than a very few seconds without serious damage being

done. Engine temperatures get hotter during starting

than at any other time. Thus, turbine engines have

minimum rotational speeds for introducing fuel into

the combustion chambers during startup. Hypervigilant temperature and acceleration monitoring on

the part of the pilot remain crucial until the engine is

running at a stable speed. Successful engine starting

depends on assuring the correct minimum battery

voltage before initiating start, or employing a ground

power unit (GPU) of adequate output. 

After fuel is introduced to the combustion chamber

during the start sequence, “light-off” and its associated

heat rise occur very quickly. Engine temperatures may

approach the maximum in a matter of 2 or 3 seconds

before the engine stabilizes and temperatures fall into

the normal operating range. During this time, the pilot

must watch for any tendency of the temperatures to

exceed limitations and be prepared to cut off fuel to

the engine. 

An engine tendency to exceed maximum starting

temperature limits is termed a hot start. The temperature rise may be preceded by unusually high initial fuel

flow, which may be the first indication the pilot has

that the engine start is not proceeding normally.

Serious engine damage will occur if the hot start is

allowed to continue.

A condition where the engine is accelerating more

slowly than normal is termed a hung start or false

start. During a hung start/false start, the engine may

1. Before Takeoff

 Checks – Completed

2. Lineup Checks – Completed

 Heading Bug – Runway Heading

 Command Bars – 10 Degrees Up

3. Power – Set

 850 ITT / 650 HP

 Max: 923 ITT / 717.5 HP

7. Ign Ovrd – Off

6. Gear Up

8. After T/O

 Checklist

 Yaw Damp

 – On

9. Climb Power – Set

 850 ITT / 650 HP

 98 – 99% RPM

11. Climb Speed – Set

 Climb Checks –

 Completed

10. Prop Sync – On

These are merely typical procedures. The 

pilot maintains his or her prerogative to 

modify configuration and airspeeds as 

required by existing conditions, as long as 

compliance with the FAA approved Airplane 

Flight Manual is assured.

NOTE:

5. Rotate at 96 – 100 KIAS

4. Annunciators – Check

 Engine Inst. – Check

PRESSURE

ALTITUDE

FT

Sea Level

CLIMB

SPEED

KIAS

139

139

134

128

123

118

113

112

5,000

10,000

15,000

20,000

25,000

30,000

31,000

12. Cruise Checks – Completed

Figure 14-11. Example—typical turboprop airplane takeoff and departure profile.

Ch 14.qxd 5/7/04 10:09 AM Page 14-10
14-11

stabilize at an engine r.p.m. that is not high enough for

the engine to continue to run without help from the

starter. This is usually the result of low battery power

or the starter not turning the engine fast enough for it

to start properly. 

Takeoffs in turboprop airplanes are not made by

automatically pushing the power lever full forward to

the stops. Depending on conditions, takeoff power may

be limited by either torque or by engine temperature.

Normally, the power lever position on takeoff will be

somewhat aft of full forward.

Takeoff and departure in a turboprop airplane

(especially a twin-engine cabin-class airplane) should

be accomplished in accordance with a standard takeoff

and departure “profile” developed for the particular

make and model. [Figure 14-11] The takeoff and

departure profile should be in accordance with the

airplane manufacturer’s recommended procedures as

outlined in the FAA-approved Airplane Flight Manual

and/or the Pilot’s Operating Handbook (AFM/POH).

The increased complexity of turboprop airplanes

makes the standardization of procedures a necessity

for safe and efficient operation. The transitioning pilot

should review the profile procedures before each

takeoff to form a mental picture of the takeoff and

departure process. 

For any given high horsepower operation, the pilot can

expect that the engine temperature will climb as

altitude increases at a constant power. On a warm or

hot day, maximum temperature limits may be reached

at a rather low altitude, making it impossible to

maintain high horsepower to higher altitudes. Also, the

engine’s compressor section has to work harder with

decreased air density. Power capability is reduced by

high-density altitude and power use may have to be

modulated to keep engine temperature within limits.

In a turboprop airplane, the pilot can close the

throttles(s) at any time without concern for cooling the

engine too rapidly. Consequently, rapid descents with

the propellers in low pitch can be dramatically steep.

Like takeoffs and departures, approach and landing

should be accomplished in accordance with a standard

approach and landing profile. [Figure 14-12] 

A stabilized approach is an essential part of the

approach and landing process. In a stabilized approach,

the airplane, depending on design and type, is placed

in a stabilized descent on a glidepath ranging from 2.5

to 3.5°. The speed is stabilized at some reference from

the AFM/POH—usually 1.25 to 1.30 times the stall

speed in approach configuration. The descent rate is

stabilized from 500 feet per minute to 700 feet per

minute until the landing flare.

2. Arrival 160 KIAS

 250 HP Level Flt –

 Clean Config.

3. Begin Before

 Landing Checklist

7. Final

 120 KIAS

 Flaps – As Desired

6. Base

 Before Landing Checklist

 120 – 130 KIAS

8. Short Final

 110 KIAS

 Gear – Recheck

 Down

9. Threshold

 96 – 100 KIAS

11. After Landing Checklist

10. Landing

 Cond. Levers – Keep Full Fwd.

 Power – Beta/Reverse

These are merely typical procedures. The 

pilot maintains his or her prerogative to 

modify configuration and airspeeds as 

required by existing conditions, as long as 

compliance with the FAA approved Airplane 

Flight Manual is assured.

NOTE:

5. 130 – 140 KIAS

4. Midfield Downwind

 140 – 160 KIAS

 250 HP

 Gear – Down

 Flaps – Half

1. Leaving Cruise Altitude

 Descent/Approach

 Checklist

Figure 14-12. Example—typical turboprop airplane arrival and landing profile.

Ch 14.qxd 5/7/04 10:09 AM Page 14-11
14-12

Landing some turboprop airplanes (as well as some

piston twins) can result in a hard, premature

touchdown if the engines are idled too soon. This is

because large propellers spinning rapidly in low pitch

create considerable drag. In such airplanes, it may be

preferable to maintain power throughout the landing

flare and touchdown. Once firmly on the ground,

propeller beta range operation will dramatically reduce

the need for braking in comparison to piston airplanes

of similar weights.

TRAINING CONSIDERATIONS

The medium and high altitudes at which turboprop

airplanes are flown provide an entirely different

environment in terms of regulatory requirements,

airspace structure, physiological requirements, and

even meteorology. The pilot transitioning to turboprop

airplanes, particularly those who are not familiar with

operations in the high/medium altitude environment,

should approach turboprop transition training with this

in mind. Thorough ground training should cover all

aspects of high/medium altitude flight, including the

flight environment, weather, flight planning and

navigation, physiological aspects of high-altitude

flight, oxygen and pressurization system operation,

and high-altitude emergencies.

Flight training should prepare the pilot to demonstrate

a comprehensive knowledge of airplane performance,

systems, emergency procedures, and operating

limitations, along with a high degree of proficiency in

performing all flight maneuvers and in-flight

emergency procedures. 

The training outline below covers the minimum

information needed by pilots to operate safely at high

altitudes.

a. Ground Training

(1) The High-Altitude Flight Environment

(a) Airspace

(b) Title 14 of the Code of Federal Regulations

(14 CFR) section 91.211, requirements for

use of supplemental oxygen

(2) Weather

(a) The atmosphere

(b) Winds and clear air turbulence

(c) Icing

(3) Flight Planning and Navigation

(a) Flight planning

(b) Weather charts

(c) Navigation

(d) Navaids

(4) Physiological Training

(a) Respiration

(b) Hypoxia

(c) Effects of prolonged oxygen use

(d) Decompression sickness

(e) Vision

(f) Altitude chamber (optional)

(5) High-Altitude Systems and Components

(a) Oxygen and oxygen equipment

(b) Pressurization systems

(c) High-altitude components

(6) Aerodynamics and Performance Factors

(a) Acceleration

(b) G-forces

(c) MACH Tuck and MACH Critical (turbojet

airplanes)

(7) Emergencies

(a) Decompression

(b) Donning of oxygen masks

(c) Failure of oxygen mask, or complete loss of

oxygen supply/system

(d) In-flight fire

(e) Flight into severe turbulence or thunderstorms

b. Flight Training

(1) Preflight Briefing

(2) Preflight Planning

(a) Weather briefing and considerations

(b) Course plotting

(c) Airplane Flight Manual

(d) Flight plan

(3) Preflight Inspection

(a) Functional test of oxygen system, including

the verification of supply and pressure, regulator operation, oxygen flow, mask fit, and

cockpit and air traffic control (ATC)

communication using mask microphones

(4) Engine Start Procedures, Runup, Takeoff, and

Initial Climb

(5) Climb to High Altitude and Normal Cruise

Operations While Operating Above 25,000

Feet MSL

(6) Emergencies

(a) Simulated rapid decompression, including

the immediate donning of oxygen masks

(b) Emergency descent

(7) Planned Descents

(8) Shutdown Procedures

(9) Postflight Discussion

Ch 14.qxd 5/7/04 10:09 AM Page 14-12
15-1

GENERAL

This chapter contains an overview of jet powered

airplane operations. It is not meant to replace any

portion of a formal jet airplane qualification course.

Rather, the information contained in this chapter is

meant to be a useful preparation for and a supplement

to formal and structured jet airplane qualification

training. The intent of this chapter is to provide

information on the major differences a pilot will

encounter when transitioning to jet powered airplanes.

In order to achieve this in a logical manner, the major

differences between jet powered airplanes and piston

powered airplanes have been approached by

addressing two distinct areas: differences in

technology, or how the airplane itself differs; and

differences in pilot technique, or how the pilot deals

with the technological differences through the

application of different techniques. If any of the

information in this chapter conflicts with information

contained in the FAA-approved Airplane Flight

Manual for a particular airplane, the Airplane Flight

Manual takes precedence.

JET ENGINE BASICS

A jet engine is a gas turbine engine. A jet engine

develops thrust by accelerating a relatively small mass

of air to very high velocity, as opposed to a propeller,

which develops thrust by accelerating a much larger

mass of air to a much slower velocity.

As stated in Chapter 14, both piston and gas turbine

engines are internal combustion engines and have a

similar basic cycle of operation; that is, induction,

compression, combustion, expansion, and exhaust. Air

is taken in and compressed, and fuel is injected and

burned. The hot gases then expand and supply a

surplus of power over that required for compression,

and are finally exhausted. In both piston and jet

engines, the efficiency of the cycle is improved by

increasing the volume of air taken in and the

compression ratio.

Part of the expansion of the burned gases takes place in

the turbine section of the jet engine providing the

necessary power to drive the compressor, while the

remainder of the expansion takes place in the nozzle of

the tail pipe in order to accelerate the gas to a high

velocity jet thereby producing thrust. [Figure 15-1]

In theory, the jet engine is simpler and more directly

converts thermal energy (the burning and expansion of

gases) into mechanical energy (thrust). The piston or

reciprocating engine, with all of its moving parts, must

convert the thermal energy into mechanical energy and

then finally into thrust by rotating a propeller.

One of the advantages of the jet engine over the piston

engine is the jet engine’s capability of producing much

greater amounts of thrust horsepower at the high

altitudes and high speeds. In fact, turbojet engine

efficiency increases with altitude and speed.

Direction of Flight

Air

Enters

Inlet

Duct Exhaust

Combustion

Drive Shaft

Six-Stage Compressor

TURBOJET ENGINE

Two-Stage

Turbine

Figure 15-1. Basic turbojet engine.

Ch 15.qxd 5/7/04 10:22 AM Page 15-1
15-2

Although the propeller driven airplane is not nearly as

efficient as the jet, particularly at the higher altitudes

and cruising speeds required in modern aviation, one

of the few advantages the propeller driven airplane has

over the jet is that maximum thrust is available almost

at the start of the takeoff roll. Initial thrust output of the

jet engine on takeoff is relatively lower and does not

reach peak efficiency until the higher speeds. The fanjet or turbofan engine was developed to help compensate for this problem and is, in effect, a compromise

between the pure jet engine (turbojet) and the propeller

engine.

Like other gas turbine engines, the heart of the turbofan engine is the gas generator—the part of the engine

that produces the hot, high-velocity gases. Similar to

turboprops, turbofans have a low pressure turbine section that uses most of the energy produced by the gas

generator. The low pressure turbine is mounted on a

concentric shaft that passes through the hollow shaft of

the gas generator, connecting it to a ducted fan at the

front of the engine. [Figure 15-2]

Air enters the engine, passes through the fan, and splits

into two separate paths. Some of it flows around—

bypasses—the engine core, hence its name, bypass

air. The air drawn into the engine for the gas generator

is the core airflow. The amount of air that bypasses

the core compared to the amount drawn into the gas

generator determines a turbofan’s bypass ratio.

Turbofans efficiently convert fuel into thrust because

they produce low pressure energy spread over a large

fan disk area. While a turbojet engine uses all of the

gas generator’s output to produce thrust in the form of

a high-velocity exhaust gas jet, cool, low-velocity

bypass air produces between 30 percent and 70 percent of the thrust produced by a turbofan engine.

The fan-jet concept increases the total thrust of the jet

engine, particularly at the lower speeds and altitudes.

Although efficiency at the higher altitudes is lost (turbofan engines are subject to a large lapse in thrust with

increasing altitude), the turbofan engine increases

acceleration, decreases the takeoff roll, improves initial climb performance, and often has the effect of

decreasing specific fuel consumption.

OPERATING THE JET ENGINE

In a jet engine, thrust is determined by the amount of

fuel injected into the combustion chamber. The power

controls on most turbojet and turbofan powered airplanes consist of just one thrust lever for each engine,

because most engine control functions are automatic.

The thrust lever is linked to a fuel control and/or electronic engine computer that meters fuel flow based

upon r.p.m., internal temperatures, ambient conditions,

and other factors. [Figure 15-3]

In a jet engine, each major rotating section usually has

a separate gauge devoted to monitoring its speed of

rotation. Depending on the make and model, a jet

engine may have an N1 gauge that monitors the low

pressure compressor section and/or fan speed in

turbofan engines. The gas generator section may be

monitored by an N2 gauge, while triple spool engines

may have an N3 gauge as well. Each engine section

rotates at many thousands of r.p.m. Their gauges

therefore are calibrated in percent of r.p.m. rather than

actual r.p.m., for ease of display and interpretation.

[Figure 15-4]

Direction of Flight

Inlet

Air

Exhaust

Combustion

Combustion

Fan Air

Fan Air

Figure 15-2.Turbofan engine.

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15-3

The temperature of turbine gases must be closely

monitored by the pilot. As in any gas turbine engine,

exceeding temperature limits, even for a very few

seconds, may result in serious heat damage to turbine

blades and other components. Depending on the make

and model, gas temperatures can be measured at a

number of different locations within the engine. The

associated engine gauges therefore have different

names according to their location. For instance:

• Exhaust Gas Temperature (EGT)—the temperature of the exhaust gases as they enter the tail

pipe, after passing through the turbine.

• Turbine Inlet Temperature (TIT)—the temperature of the gases from the combustion section of

the engine as they enter the first stage of the turbine. TIT is the highest temperature inside a gas

turbine engine and is one of the limiting factors

of the amount of power the engine can produce.

TIT, however, is difficult to measure. EGT

therefore, which relates to TIT, is normally the

parameter measured.

• Interstage Turbine Temperature (ITT)—the

temperature of the gases between the high

pressure and low pressure turbine wheels.

• Turbine Outlet Temperature (TOT)—like EGT,

turbine outlet temperature is taken aft of the

turbine wheel(s).

JET ENGINE IGNITION

Most jet engine ignition systems consist of two igniter

plugs, which are used during the ground or air starting

of the engine. Once the start is completed, this ignition

either automatically goes off or is turned off, and from

this point on, the combustion in the engine is a

continuous process.

CONTINUOUS IGNITION

An engine is sensitive to the flow characteristics of the

air that enters the intake of the engine nacelle. So long

as the flow of air is substantially normal, the engine

will continue to run smoothly. However, particularly

with rear mounted engines that are sometimes in a

position to be affected by disturbed airflow from the

wings, there are some abnormal flight situations that

could cause a compressor stall or flameout of the

engine. These abnormal flight conditions would usually be associated with abrupt pitch changes such as

might be encountered in severe turbulence or a stall.

In order to avoid the possibility of engine flameout

from the above conditions, or from other conditions

that might cause ingestion problems such as heavy

rain, ice, or possible bird strike, most jet engines are

equipped with a continuous ignition system. This system can be turned on and used continuously whenever

the need arises. In many jets, as an added precaution,

this system is normally used during takeoffs and landings. Many jets are also equipped with an automatic

ignition system that operates both igniters whenever

the airplane stall warning or stick shaker is activated.

FUEL HEATERS

Because of the high altitudes and extremely cold outside air temperatures in which the jet flies, it is possible to supercool the jet fuel to the point that the small

Figure 15-3. Jet engine power controls.

Figure 15-4. Jet engine r.p.m. gauges.

Ch 15.qxd 5/7/04 10:22 AM Page 15-3
15-4

particles of water suspended in the fuel can turn to ice

crystals and clog the fuel filters leading to the engine.

For this reason, jet engines are normally equipped with

fuel heaters. The fuel heater may be of the automatic

type which constantly maintains the fuel temperature

above freezing, or they may be manually controlled by

the pilot from the cockpit.

SETTING POWER

On some jet airplanes, thrust is indicated by an engine

pressure ratio (EPR) gauge. Engine pressure ratio can

be thought of as being equivalent to the manifold

pressure on the piston engine. Engine pressure ratio is

the difference between turbine discharge pressure and

engine inlet pressure. It is an indication of what the

engine has done with the raw air scooped in. For

instance, an EPR setting of 2.24 means that the

discharge pressure relative to the inlet pressure is

2.24 : 1. On these airplanes, the EPR gauge is the

primary reference used to establish power settings.

[Figure 15-5]

Fan speed (N1) is the primary indication of thrust on

most turbofan engines. Fuel flow provides a secondary

thrust indication, and cross-checking for proper fuel

flow can help in spotting a faulty N1 gauge. Turbofans

also have a gas generator turbine tachometer (N2).

They are used mainly for engine starting and some

system functions.

In setting power, it is usually the primary power

reference (EPR or N1) that is most critical, and will be

the gauge that will first limit the forward movement of

the thrust levers. However, there are occasions where

the limits of either r.p.m. or temperature can be

exceeded. The rule is: movement of the thrust levers

must be stopped and power set at whichever the limits

of EPR, r.p.m., or temperature is reached first.

THRUST TO THRUST LEVER

RELATIONSHIP

In a piston engine propeller driven airplane, thrust is

proportional to r.p.m., manifold pressure, and propeller

blade angle, with manifold pressure being the most

dominant factor. At a constant r.p.m., thrust is

proportional to throttle lever position. In a jet engine,

however, thrust is quite disproportional to thrust lever

position. This is an important difference that the pilot

transitioning into jet powered airplanes must become

accustomed to.

On a jet engine, thrust is proportional to r.p.m. (mass

flow) and temperature (fuel/air ratio). These are

matched and a further variation of thrust results from

the compressor efficiency at varying r.p.m. The jet

engine is most efficient at high r.p.m., where the

engine is designed to be operated most of the time. As

r.p.m. increases, mass flow, temperature, and efficiency also increase. Therefore, much more thrust is

produced per increment of throttle movement near the

top of the range than near the bottom.

One thing that will seem different to the piston pilot

transitioning into jet powered airplanes is the rather

large amount of thrust lever movement between the

flight idle position and full power as compared to the

small amount of movement of the throttle in the piston

engine. For instance, an inch of throttle movement on

a piston may be worth 400 horsepower wherever the

throttle may be. On a jet, an inch of thrust lever

movement at a low r.p.m. may be worth only 200

pounds of thrust, but at a high r.p.m. that same inch of

movement might amount to closer to 2,000 pounds of

thrust. Because of this, in a situation where

significantly more thrust is needed and the jet engine

is at low r.p.m., it will not do much good to merely

“inch the thrust lever forward.” Substantial thrust lever

movement is in order. This is not to say that rough or

abrupt thrust lever action is standard operating

procedure. If the power setting is already high, it may

take only a small amount of movement. However,

there are two characteristics of the jet engine that work

against the normal habits of the piston engine pilot.

One is the variation of thrust with r.p.m., and the other

is the relatively slow acceleration of the jet engine.

VARIATION OF THRUST WITH RPM

Whereas piston engines normally operate in the range

of 40 percent to 70 percent of available r.p.m., jets

operate most efficiently in the 85 percent to 100

percent range, with a flight idle r.p.m. of 50 percent to

60 percent. The range from 90 percent to 100 percent

in jets may produce as much thrust as the total

available at 70 percent. [Figure 15-6]

SLOW ACCELERATION OF THE JET

ENGINE

In a propeller driven airplane, the constant speed

propeller keeps the engine turning at a constant r.p.m.

within the governing range, and power is changed by

varying the manifold pressure. Acceleration of the

Figure 15-5. EPR gauge.

Ch 15.qxd 5/7/04 10:22 AM Page 15-4
15-5

piston from idle to full power is relatively rapid,

somewhere on the order of 3 to 4 seconds. The

acceleration on the different jet engines can vary

considerably, but it is usually much slower.

Efficiency in a jet engine is highest at high r.p.m.

where the compressor is working closest to its

optimum conditions. At low r.p.m. the operating cycle

is generally inefficient. If the engine is operating at

normal approach r.p.m. and there is a sudden

requirement for increased thrust, the jet engine will

respond immediately and full thrust can be achieved in

about 2 seconds. However, at a low r.p.m., sudden full

power application will tend to overfuel the engine

resulting in possible compressor surge, excessive

turbine temperatures, compressor stall and/or

flameout. To prevent this, various limiters such as

compressor bleed valves are contained in the system

and serve to restrict the engine until it is at an r.p.m. at

which it can respond to a rapid acceleration demand

without distress. This critical r.p.m. is most noticeable

when the engine is at idle r.p.m. and the thrust lever is

rapidly advanced to a high power position. Engine

acceleration is initially very slow, but changes to

very fast after about 78 percent r.p.m. is reached.

[Figure 15-7]

Even though engine acceleration is nearly

instantaneous after about 78 percent r.p.m., total time

to accelerate from idle r.p.m. to full power may take as

much as 8 seconds. For this reason, most jets are

operated at a relatively high r.p.m. during the final

approach to landing or at any other time that

immediate power may be needed.

JET ENGINE EFFICIENCY

Maximum operating altitudes for general aviation

turbojet airplanes now reach 51,000 feet. The

efficiency of the jet engine at high altitudes is the primary reason for operating in the high altitude environment. The specific fuel consumption of jet engines

decreases as the outside air temperature decreases for

constant engine r.p.m. and true airspeed (TAS). Thus,

by flying at a high altitude, the pilot is able to operate

at flight levels where fuel economy is best and with the

most advantageous cruise speed. For efficiency, jet airplanes are typically operated at high altitudes where

cruise is usually very close to r.p.m or exhaust gas temperature limits. At high altitudes, little excess thrust

may be available for maneuvering. Therefore, it is

often impossible for the jet airplane to climb and turn

simultaneously, and all maneuvering must be accomplished within the limits of available thrust and without sacrificing stability and controllability.

ABSENCE OF PROPELLER EFFECT

The absence of a propeller has a significant effect on

the operation of jet powered airplanes that the transitioning pilot must become accustomed to. The effect is

due to the absence of lift from the propeller slipstream,

and the absence of propeller drag.

ABSENCE OF PROPELLER

SLIPSTREAM

A propeller produces thrust by accelerating a large

mass of air rearwards, and (especially with wing

mounted engines) this air passes over a comparatively

large percentage of the wing area. On a propeller

driven airplane, the lift that the wing develops is the

sum of the lift generated by the wing area not in the

wake of the propeller (as a result of airplane speed) and

the lift generated by the wing area influenced by the

propeller slipstream. By increasing or decreasing the

speed of the slipstream air, therefore, it is possible to

increase or decrease the total lift on the wing without

changing airspeed.

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Percent Maximum Thrust

Percent Maximum R.P.M.

VARIATION OF THRUST WITH R.P.M.

(Constant Altitude & Velocity)

Figure 15-6. Variation of thrust with r.p.m.

8

6

4

2

60% 100%

Time to Achieve Full Thrust (sec.)

R.P.M.

78%

Figure 15-7.Typical Jet engine acceleration times.

Ch 15.qxd 5/7/04 10:22 AM Page 15-5
15-6

For example, a propeller driven airplane that is allowed

to become too low and too slow on an approach is very

responsive to a quick blast of power to salvage the

situation. In addition to increasing lift at a constant

airspeed, stalling speed is reduced with power on. A jet

engine, on the other hand, also produces thrust by

accelerating a mass of air rearward, but this air does

not pass over the wings. There is therefore no lift bonus

at increased power at constant airspeed, and no

significant lowering of power-on stall speed.

In not having propellers, the jet powered airplane is

minus two assets.

• It is not possible to produce increased lift

instantly by simply increasing power.

• It is not possible to lower stall speed by simply

increasing power. The 10-knot margin (roughly

the difference between power-off and power-on

stall speed on a propeller driven airplane for a

given configuration) is lost.

Add the poor acceleration response of the jet engine

and it becomes apparent that there are three ways in

which the jet pilot is worse off than the propeller pilot.

For these reasons, there is a marked difference between

the approach qualities of a piston engine airplane and a

jet. In a piston engine airplane, there is some room for

error. Speed is not too critical and a burst of power will

salvage an increasing sink rate. In a jet, however, there

is little room for error.

If an increasing sink rate develops in a jet, the pilot

must remember two points in the proper sequence.

1. Increased lift can be gained only by accelerating

airflow over the wings, and this can be

accomplished only by accelerating the entire

airplane.

2. The airplane can be accelerated, assuming

altitude loss cannot be afforded, only by a rapid

increase in thrust, and here, the slow acceleration

of the jet engine (possibly up to 8 seconds)

becomes a factor.

Salvaging an increasing sink rate on an approach in a

jet can be a very difficult maneuver. The lack of ability

to produce instant lift in the jet, along with the slow

acceleration of the engine, necessitates a “stabilized

approach” to a landing where full landing

configuration, constant airspeed, controlled rate of

descent, and relatively high power settings are

maintained until over the threshold of the runway. This

allows for almost immediate response from the engine

in making minor changes in the approach speed or rate

of descent and makes it possible to initiate an

immediate go-around or missed approach if necessary.

ABSENCE OF PROPELLER DRAG

When the throttles are closed on a piston powered

airplane, the propellers create a vast amount of drag,

and airspeed is immediately decreased or altitude lost.

The effect of reducing power to idle on the jet engine,

however, produces no such drag effect. In fact, at an

idle power setting, the jet engine still produces

forward thrust. The main advantage is that the jet pilot

is no longer faced with a potential drag penalty of a

runaway propeller, or a reversed propeller. A

disadvantage, however, is the “free wheeling” effect

forward thrust at idle has on the jet. While this

occasionally can be used to advantage (such as in a

long descent), it is a handicap when it is necessary to

lose speed quickly, such as when entering a terminal

area or when in a landing flare. The lack of propeller

drag, along with the aerodynamically clean airframe

of the jet, are new to most pilots, and slowing the

airplane down is one of the initial problems

encountered by pilots transitioning into jets.

SPEED MARGINS

The typical piston powered airplane had to deal with

two maximum operating speeds.

• VNO—Maximum structural cruising speed,

represented on the airspeed indicator by the

upper limit of the green arc. It is, however,

permissible to exceed VNO and operate in the

caution range (yellow arc) in certain flight

conditions.

• VNE—Never-exceed speed, represented by a red

line on the airspeed indicator.

These speed margins in the piston airplanes were

never of much concern during normal operations

because the high drag factors and relatively low cruise

power settings kept speeds well below these maximum

limits.

Maximum speeds in jet airplanes are expressed

differently, and always define the maximum operating

speed of the airplane which is comparable to the VNE

of the piston airplane. These maximum speeds in a jet

airplane are referred to as:

• VMO—Maximum operating speed expressed in

terms of knots.

• MMO—Maximum operating speed expressed in

terms of a decimal of Mach speed (speed of

sound).

To observe both limits VMO and MMO, the pilot of a jet

airplane needs both an airspeed indicator and a

Machmeter, each with appropriate red lines. In some

general aviation jet airplanes, these are combined into

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15-7

a single instrument that contains a pair of concentric

indicators, one for the indicated airspeed and the other

for indicated Mach number. Each is provided with an

appropriate red line. [Figure 15-8]

A more sophisticated indicator is used on most

jetliners. It looks much like a conventional airspeed

indicator but has a “barber pole” that automatically

moves so as to display the applicable speed limit at all

times. 

Because of the higher available thrust and very low

drag design, the jet airplane can very easily exceed its

speed margin even in cruising flight, and in fact in

some airplanes in a shallow climb. The handling

qualities in a jet can change drastically when the

maximum operating speeds are exceeded.

High speed airplanes designed for subsonic flight are

limited to some Mach number below the speed of

sound to avoid the formation of shock waves that begin

to develop as the airplane nears Mach 1.0. These shock

waves (and the adverse effects associated with them)

can occur when the airplane speed is substantially

below Mach 1.0. The Mach speed at which some

portion of the airflow over the wing first equals Mach

1.0 is termed the critical Mach number (MACHCRIT).

This is also the speed at which a shock wave first

appears on the airplane.

There is no particular problem associated with the

acceleration of the airflow up to the point where Mach

1.0 is encountered; however, a shock wave is formed at

the point where the airflow suddenly returns to

subsonic flow. This shock wave becomes more severe

and moves aft on the wing as speed of the wing is

increased, and eventually flow separation occurs

behind the well-developed shock wave. [Figure 15-9]

If allowed to progress well beyond the MMO for the

airplane, this separation of air behind the shock wave

can result in severe buffeting and possible loss of

control or “upset.”

Because of the changing center of lift of the wing

resulting from the movement of the shock wave, the

pilot will experience pitch change tendencies as the

airplane moves through the transonic speeds up to and

exceeding MMO. [Figure 15-10]

For example, as the graph in figure 15-10 illustrates,

initially as speed is increased up to Mach .72 the wing

develops an increasing amount of lift requiring a nosedown force or trim to maintain level flight. With

increased speed and the aft movement of the shock

wave, the wing’s center of pressure also moves aft

causing the start of a nosedown tendency or “tuck.” By

Mach .83 the nosedown forces are well developed to a

point where a total of 70 pounds of back pressure are

required to hold the nose up. If allowed to progress

unchecked, Mach tuck may eventually occur.

Although Mach tuck develops gradually, if it is

Figure 15-8. Jet airspeed indicator.

M=.72 (Critical Mach Number) 

M=.77

Supersonic

Flow

M=.82

Normal Shock Wave

Subsonic

Possible 

Separation

Supersonic

Flow

Normal Shock

Normal Shock

Separation

Maximum Local Velocity

Is Less Than Sonic

Figure 15-9.Transonic flow patterns.

70

60

50

40

30

20

10

0

10

20

0

0.3 0.4 0.5 0.6 0.7 0.8 0.9

Stick Force in Pounds

Mach Number

Pull

Push

Figure 15-10. Example of Stick Forces vs. Mach Number in a

typical jet airplane.

Ch 15.qxd 5/7/04 10:22 AM Page 15-7
15-8

allowed to progress significantly, the center of

pressure can move so far rearward that there is no

longer enough elevator authority available to

counteract it, and the airplane could enter a steep,

sometimes unrecoverable dive.

An alert pilot would have observed the high airspeed

indications, experienced the onset of buffeting, and

responded to aural warning devices long before

encountering the extreme stick forces shown.

However, in the event that corrective action is not

taken and the nose allowed to drop, increasing airspeed

even further, the situation could rapidly become

dangerous. As the Mach speed increases beyond the

airplane’s MMO, the effects of flow separation and

turbulence behind the shock wave become more

severe. Eventually, the most powerful forces causing

Mach tuck are a result of the buffeting and lack of

effective downwash on the horizontal stabilizer

because of the disturbed airflow over the wing. This is

the primary reason for the development of the T-tail

configuration on some jet airplanes, which places the

horizontal stabilizer as far as practical from the

turbulence of the wings. Also, because of the critical

aspects of high-altitude/high-Mach flight, most jet

airplanes capable of operating in the Mach speed

ranges are designed with some form of trim and

autopilot Mach compensating device (stick puller) to

alert the pilot to inadvertent excursions beyond its

certificated MMO.

RECOVERY FROM OVERSPEED

CONDITIONS

The simplest remedy for an overspeed condition is to

ensure that the situation never occurs in the first place.

For this reason, the pilot must be aware of all the

conditions that could lead to exceeding the airplane’s

maximum operating speeds. Good attitude instrument

flying skills and good power control are essential.

The pilot should be aware of the symptoms that will be

experienced in the particular airplane as the VMO or

MMO is being approached. These may include:

• Nosedown tendency and need for back pressure

or trim.

• Mild buffeting as airflow separation begins to

occur after critical Mach speed.

• Actuation of an aural warning device/stick puller

at or just slightly beyond VMO or MMO.

The pilot’s response to an overspeed condition should

be to immediately slow the airplane by reducing the

power to flight idle. It will also help to smoothly and

easily raise the pitch attitude to help dissipate speed (in

fact this is done automatically through the stick puller

device when the high speed warning system is

activated). The use of speed brakes can also aid in

slowing the airplane. If, however, the nosedown stick

forces have progressed to the extent that they are

excessive, some speed brakes will tend to further

aggravate the nosedown tendency. Under most

conditions, this additional pitch down force is easily

controllable, and since speed brakes can normally be

used at any speed, they are a very real asset. A final

option would be to extend the landing gear. This will

create enormous drag and possibly some noseup pitch,

but there is usually little risk of damage to the gear

itself. The pilot transitioning into jet airplanes must be

familiar with the manufacturers’ recommended procedures for dealing with overspeed conditions contained

in the FAA-approved Airplane Flight Manual for the

particular make and model airplane.

MACH BUFFET BOUNDARIES

Thus far, only the Mach buffet that results from

excessive speed has been addressed. The transitioning

pilot, however, should be aware that Mach buffet is a

function of the speed of the airflow over the wing—

not necessarily the airspeed of the airplane. Anytime

that too great a lift demand is made on the wing,

whether from too fast an airspeed or from too high an

angle of attack near the MMO, the “high speed buffet”

will occur. However, there are also occasions when the

buffet can be experienced at much slower speeds

known as “low speed Mach buffet.”

The most likely situations that could cause the low

speed buffet would be when an airplane is flown at too

slow a speed for its weight and altitude causing a high

angle of attack. This very high angle of attack would

have the same effect of increasing airflow over the

upper surface of the wing to the point that all of the

same effects of the shock waves and buffet would

occur as in the high speed buffet situation.

The angle of attack of the wing has the greatest effect

on inducing the Mach buffet at either the high or low

speed boundaries for the airplane. The conditions that

increase the angle of attack, hence the speed of the

airflow over the wing and chances of Mach buffet are:

• High altitudes—The higher the airplane flies,

the thinner the air and the greater the angle of

attack required to produce the lift needed to

maintain level flight.

• Heavy weights—The heavier the airplane, the

greater the lift required of the wing, and all other

things being equal, the greater the angle of

attack.

• “G” loading—An increase in the “G” loading of

the wing results in the same situation as

increasing the weight of the airplane. It makes

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no difference whether the increase in “G” forces

is caused by a turn, rough control usage, or turbulence. The effect of increasing the wing’s

angle of attack is the same.

An airplane’s indicated airspeed decreases in relation

to true airspeed as altitude increases. As the indicated

airspeed decreases with altitude, it progressively

merges with the low speed buffet boundary where prestall buffet occurs for the airplane at a load factor of

1.0 G. The point where the high speed Mach indicated

airspeed and low speed buffet boundary indicated airspeed merge is the airplane’s absolute or aerodynamic

ceiling. Once an airplane has reached its aerodynamic

ceiling, which is higher than the altitude stipulated in

the FAA-approved Airplane Flight Manual, the airplane can neither be made to go faster without activating the design stick puller at Mach limit nor can it be

made to go slower without activating the stick shaker

or stick pusher. This critical area of the airplane’s

flight envelope is known as “coffin corner.”

Mach buffet occurs as a result of supersonic airflow on

the wing. Stall buffet occurs at angles of attack that

produce airflow disturbances (burbling) over the upper

surface of the wing which decreases lift. As density

altitude increases, the angle of attack that is required to

produce an airflow disturbance over the top of the wing

is reduced until the density altitude is reached where

Mach buffet and stall buffet converge (coffin corner).

When this phenomenon is encountered, serious consequences may result causing loss of airplane control.

Increasing either gross weight or load factor (G factor)

will increase the low speed buffet and decrease Mach

buffet speeds. A typical jet airplane flying at 51,000

feet altitude at 1.0 G may encounter Mach buffet

slightly above the airplane’s MMO (.82 Mach) and low

speed buffet at .60 Mach. However, only 1.4 G (an

increase of only 0.4 G) may bring on buffet at the optimum speed of .73 Mach and any change in airspeed,

bank angle, or gust loading may reduce this straightand-level flight 1.4 G protection to no protection at all.

Consequently, a maximum cruising flight altitude must

be selected which will allow sufficient buffet margin

for necessary maneuvering and for gust conditions

likely to be encountered. Therefore, it is important for

pilots to be familiar with the use of charts showing

cruise maneuver and buffet limits. [Figure 15-11]

The transitioning pilot must bear in mind that the

maneuverability of the jet airplane is particularly critical, especially at the high altitudes. Some jet airplanes

have a very narrow span between the high and low

speed buffets. One airspeed that the pilot should have

firmly fixed in memory is the manufacturer’s recommended gust penetration speed for the particular make

and model airplane. This speed is normally the speed

that would give the greatest margin between the high

and low speed buffets, and may be considerably higher

1 2 3 .1 .2 .3 .4 .5 .6 .7 .8

Load Factor – G Indicated Mach Number

Sea Level

5,000

10,000

15,000

20,000

Pressure Altitude – 25,000 Ft.

30,000

35,000

40,000

45,000

MMO

19,000 Lbs.

11,000

18,000

17,000

16,000

15,000

14,000

13,000

12,000

A

C B

D

Figure 15-11. Mach buffet boundary chart.

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than design maneuvering speed (VA). This means that,

unlike piston airplanes, there are times when a jet

airplane should be flown in excess of VA during

encounters with turbulence. Pilots operating airplanes

at high speeds must be adequately trained to operate

them safely. This training cannot be complete until

pilots are thoroughly educated in the critical aspects of

the aerodynamic factors pertinent to Mach flight at

high altitudes.

LOW SPEED FLIGHT

The jet airplane wing, designed primarily for high

speed flight, has relatively poor low speed

characteristics. As opposed to the normal piston

powered airplane, the jet wing has less area, a lower

aspect ratio (long chord/short span), and thin airfoil

shape—all of which amount to less lift. The sweptwing

is additionally penalized at low speeds because the

effective lift, which is perpendicular to the leading

edge, is always less than the airspeed of the airplane

itself. In other words, the airflow on the sweptwing has

the effect of persuading the wing into believing that it

is flying slower than it actually is, but the wing consequently suffers a loss of lift for a given airspeed at a

given angle of attack.

The first real consequence of poor lift at low speeds is

a high stall speed. The second consequence of poor lift

at low speeds is the manner in which lift and drag vary

with speed in the lower ranges. As a jet airplane is

slowed toward its minimum drag speed (VMD or

L/DMAX), total drag increases at a much greater rate

than lift, resulting in a sinking flightpath. If the pilot

attempts to increase lift by increasing pitch attitude,

airspeed will be further reduced resulting in a further

increase in drag and sink rate as the airplane slides up

the back side of the power curve. The sink rate can be

arrested in one of two ways:

• Pitch attitude can be substantially reduced to

reduce the angle of attack and allow the airplane

to accelerate to a speed above VMD, where steady

flight conditions can be reestablished. This

procedure, however, will invariably result in a

substantial loss of altitude.

• Thrust can be increased to accelerate the airplane

to a speed above VMD to reestablish steady flight

conditions. It should be remembered that the

amount of thrust required will be quite large. The

amount of thrust must be sufficient to accelerate

the airplane and regain altitude lost. Also, if the

airplane has slid a long way up the back side of

the power required (drag) curve, drag will be

very high and a very large amount of thrust will

be required.

In a typical piston engine airplane, VMD in the clean

configuration is normally at a speed of about 1.3 VS.

[Figure 15-12] Flight below VMD on a piston engine

airplane is well identified and predictable. In contrast,

in a jet airplane flight in the area of VMD (typically 1.5

– 1.6 VS) does not normally produce any noticeable

changes in flying qualities other than a lack of speed

stability—a condition where a decrease in speed leads

to an increase in drag which leads to a further decrease

in speed and hence a speed divergence. A pilot who is

not cognizant of a developing speed divergence may

find a serious sink rate developing at a constant power

setting, and a pitch attitude that appears to be normal.

The fact that drag increases more rapidly than lift,

causing a sinking flightpath, is one of the most

important aspects of jet airplane flying qualities.

STALLS

The stalling characteristics of the sweptwing jet

airplane can vary considerably from those of the

Minimum

Power

Required

L/DMAX

Figure 15-12.Thrust and power required curves.

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normal straight wing airplane. The greatest difference

that will be noticeable to the pilot is the lift developed

vs. angle of attack. An increase in angle of attack of the

straight wing produces a substantial and constantly

increasing lift vector up to its maximum coefficient of

lift, and soon thereafter flow separation (stall) occurs

with a rapid deterioration of lift.

By contrast, the sweptwing produces a much more

gradual buildup of lift with no well defined maximum

coefficient and has the ability to fly well beyond this

maximum buildup even though lift is lost. The drag

curves (which are not depicted in figure 15-13) are

approximately the reverse of the lift curves shown, in

that a rapid increase in drag component may be

expected with an increase in the angle of attack of a

sweptwing airplane.

The differences in the stall characteristics between a

conventional straight wing/low tailplane (non T-tail)

airplane and a sweptwing T-tail airplane center around

two main areas.

• The basic pitching tendency of the airplane at

the stall.

• Tail effectiveness in stall recovery.

On a conventional straight wing/low tailplane airplane,

the weight of the airplane acts downwards forward of

the lift acting upwards, producing a need for a

balancing force acting downwards from the tailplane.

As speed is reduced by gentle up elevator deflection,

the static stability of the airplane causes a nosedown

tendency. This is countered by further up elevator to

keep the nose coming up and the speed decreasing. As

the pitch attitude increases, the low set tail is immersed

in the wing wake, which is slightly turbulent, low

energy air. The accompanying aerodynamic buffeting

serves as a warning of impending stall. The reduced

effectiveness of the tail prevents the pilot from forcing

the airplane into a deeper stall. [Figure 15-14] The

conventional straight wing airplane conforms to the

familiar nosedown pitching tendency at the stall and

gives the entire airplane a fairly pronounced nosedown

pitch. At the moment of stall, the wing wake passes

more or less straight rearward and passes above the

tail. The tail is now immersed in high energy air where

it experiences a sharp increase in positive angle of

attack causing upward lift. This lift then assists the

nosedown pitch and decrease in wing angle of attack

essential to stall recovery.

In a sweptwing jet with a T-tail and rear fuselage

mounted engines, the two qualities that are different

from its straight wing low tailplane counterpart are the

pitching tendency of the airplane as the stall develops

and the loss of tail effectiveness at the stall. The

handling qualities down to the stall are much the same

as the straight wing airplane except that the high, T-tail

remains clear of the wing wake and provides little or

no warning in the form of a pre-stall buffet. Also, the

tail is fully effective during the speed reduction

towards the stall, and remains effective even after the

wing has begun to stall. This enables the pilot to drive

the wing into a deeper stall at a much greater angle

of attack.

At the stall, two distinct things happen. After the stall,

the sweptwing T-tail airplane tends to pitch up rather

than down, and the T-tail is immersed in the wing

wake, which is low energy turbulent air. This greatly

reduces tail effectiveness and the airplane’s ability to

counter the noseup pitch. Also, the disturbed,

relatively slow air behind the wing may sweep across

the tail at such a large angle that the tail itself stalls. If

this occurs, the pilot loses all pitch control and will be

unable to lower the nose. The pitch up just after the

stall is worsened by large reduction in lift and a large

increase in drag, which causes a rapidly increasing

Lift Coefficient

Angle of Attack

Straight

Wing

Sweptwing

Figure 15-13. Stall vs. angle of attack—sweptwing vs. straight

wing.

Figure 15-14. Stall progression—typical straight wing

airplane.

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descent path, thus compounding the rate of increase of

the wing’s angle of attack. [Figure 15-15]

The pitch up tendency after the stall is a characteristic

of a swept and/or tapered wings. With these types of

wings, there is a tendency for the wing to develop a

strong spanwise airflow towards the wingtip when the

wing is at high angles of attack. This leads to a

tendency for separation of airflow, and the subsequent

stall, to occur at the wingtips first. [Figure 15-16] The

tip first stall, results in a shift of the center of lift of the

wing in a forward direction relative to the center of

gravity of the airplane, causing the nose to pitch up.

Another disadvantage of a tip first stall is that it can

involve the ailerons and erode roll control.

As previously stated, when flying at a speed in the area

of VMD, an increase in angle of attack causes drag to

increase faster than lift and the airplane begins to sink.

It is essential to understand that this increasing sinking

tendency, at a constant pitch attitude, results in a rapid

increase in angle of attack as the flightpath becomes

deflected downwards. [Figure 15-17] Furthermore,

once the stall has developed and a large amount of lift

has been lost, the airplane will begin to sink rapidly

and this will be accompanied by a corresponding rapid

increase in angle of attack. This is the beginning of

what is termed a deep stall.

As an airplane enters a deep stall, increasing drag

reduces forward speed to well below normal stall

speed. The sink rate may increase to many thousands

of feet per minute. The airplane eventually stabilizes

in a vertical descent. The angle of attack may approach

Pre-Stall

Stall

Figure 15-15. Stall progression sweptwing airplane.

Spanwise Flow of Boundary

Layer Develops at High CL

Initial Flow Separation

at or Near Tip

Area of Tip

Stall Enlarges

Stall Area Progresses

Inboard

Figure 15-16. Sweptwing stall characteristics.

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90° and the indicated airspeed may be reduced to zero.

At a 90° angle of attack, none of the airplane’s control

surfaces are effective. It must be emphasized that this

situation can occur without an excessively nose-high

pitch attitude. On some airplanes, it can occur at an

apparently normal pitch attitude, and it is this quality

that can mislead the pilot because it appears similar to

the beginning of a normal stall recovery.

Deep stalls are virtually unrecoverable. Fortunately,

they are easily avoided as long as published limitations

are observed. On those airplanes susceptible to deep

stalls (not all swept and/or tapered wing airplanes are),

sophisticated stall warning systems such as stick

shakers and stick pushers are standard equipment. A

stick pusher, as its name implies, acts to automatically

reduce the airplane’s angle of attack before the airplane

reaches a fully stalled condition.

Unless the Airplane Flight Manual procedures

stipulate otherwise, a fully stalled condition in a jet

airplane is to be avoided. Pilots undergoing training in

jet airplanes are taught to recover at the first sign of an

impending stall. Normally, this is indicated by aural

stall warning devices and/or activation of the airplane’s

stick shaker. Stick shakers normally activate around

107 percent of the actual stall speed. At such slow

speeds, very high sink rates can develop if the

airplane’s pitch attitude is decreased below the

horizon, as is normal recovery procedure in most

piston powered straight wing, light airplanes.

Therefore, at the lower altitudes where plenty of

engine thrust is available, the recovery technique in

many sweptwing jets involves applying full available

power, rolling the wings level, and holding a slightly

positive pitch attitude. The amount of pitch attitude

should be sufficient enough to maintain altitude or

begin a slight climb.

At high altitudes, where there may be little excess

thrust available to effect a recovery using power alone,

it may be necessary to lower the nose below the

horizon in order to accelerate away from an impending

stall. This procedure may require several thousand feet

or more of altitude loss to effect a recovery. Stall

recovery techniques may vary considerably from

airplane to airplane. The stall recovery procedures for

a particular make and model airplane, as

recommended by the manufacturer, are contained in

the FAA-approved Airplane Flight Manual for

that airplane.

DRAG DEVICES

To the pilot transitioning into jet airplanes, going faster

is seldom a problem. It is getting the airplane to slow

down that seems to cause the most difficulty. This is

because of the extremely clean aerodynamic design

and fast momentum of the jet airplane, and also

because the jet lacks the propeller drag effects that the

pilot has been accustomed to. Additionally, even with

the power reduced to flight idle, the jet engine still

produces thrust, and deceleration of the jet airplane is a

slow process. Jet airplanes have a glide performance

that is double that of piston powered airplanes, and jet

pilots often cannot comply with an air traffic control

request to go down and slow down at the same time.

Therefore, jet airplanes are equipped with drag devices

such as spoilers and speed brakes.

The primary purpose of spoilers is to spoil lift. The

most common type of spoiler consists of one or more

rectangular plates that lie flush with the upper surface

of each wing. They are installed approximately

parallel to the lateral axis of the airplane and are hinged

along the leading edges. When deployed, spoilers

deflect up against the relative wind, which interferes

with the flow of air about the wing. [Figure 15-18] This

both spoils lift and increases drag. Spoilers are usually

installed forward of the flaps but not in front of the

ailerons so as not to interfere with roll control.

Initial Stall

Deep Stall

Pre-Stall

Relative Wind

Relative Wind

Relative Wind

Pitch Attitude

Flightpath Angle to the Horizontal

Angle of Attack

Figure 15-17. Deep stall progression.

Figure 15-18. Spoilers.

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Deploying spoilers results in a substantial sink rate

with little decay in airspeed. Some airplanes will

exhibit a noseup pitch tendency when the spoilers are

deployed, which the pilot must anticipate.

When spoilers are deployed on landing, most of the

wing’s lift is destroyed. This action transfers the

airplane’s weight to the landing gear so that the wheel

brakes are more effective. Another beneficial effect of

deploying spoilers on landing is that they create

considerable drag, adding to the overall aerodynamic

braking. The real value of spoilers on landing, however, is creating the best circumstances for using

wheel brakes.

The primary purpose of speed brakes is to produce

drag. Speed brakes are found in many sizes, shapes,

and locations on different airplanes, but they all have

the same purpose—to assist in rapid deceleration. The

speed brake consists of a hydraulically operated board

that when deployed extends into the airstream.

Deploying speed brakes results in a rapid decrease in

airspeed. Typically, speed brakes can be deployed at

any time during flight in order to help control airspeed,

but they are most often used only when a rapid deceleration must be accomplished to slow down to landing

gear and flap speeds. There is usually a certain amount

of noise and buffeting associated with the use of speed

brakes, along with an obvious penalty in fuel consumption. Procedures for the use of spoilers and/or

speed brakes in various situations are contained in the

FAA-approved Airplane Flight Manual for the particular airplane.

THRUST REVERSERS

Jet airplanes have high kinetic energy during the

landing roll because of weight and speed. This energy

is difficult to dissipate because a jet airplane has low

drag with the nosewheel on the ground and the engines

continue to produce forward thrust with the power

levers at idle. While wheel brakes normally can cope,

there is an obvious need for another speed retarding

method. This need is satisfied by the drag provided by

reverse thrust.

A thrust reverser is a device fitted in the engine

exhaust system which effectively reverses the flow of

the exhaust gases. The flow does not reverse through

180°; however, the final path of the exhaust gases is

about 45° from straight ahead. This, together with the

losses in the reverse flow paths, results in a net efficiency of about 50 percent. It will produce even less if

the engine r.p.m. is less than maximum in reverse.

Normally, a jet engine will have one of two types of

thrust reversers, either a target reverser or a cascade

reverser. [Figure 15-19] Target reversers are simple

clamshell doors that swivel from the stowed position at

the engine tailpipe to block all of the outflow and

redirect some component of the thrust forward.

Cascade reversers are more complex. They are

normally found on turbofan engines and are often

designed to reverse only the fan air portion. Blocking

doors in the shroud obstructs forward fan thrust and

redirects it through cascade vanes for some reverse

component. Cascades are generally less effective than

target reversers, particularly those that reverse only

fan air, because they do not affect the engine core,

which will continue to produce forward thrust.

On most installations, reverse thrust is obtained with

the thrust lever at idle, by pulling up the reverse lever

to a detent. Doing so positions the reversing

mechanisms for operation but leaves the engine at idle

r.p.m. Further upward and backward movement of the

reverse lever increases engine power. Reverse is

cancelled by closing the reverse lever to the idle

reverse position, then dropping it fully back to the

forward idle position. This last movement operates the

reverser back to the forward thrust position.

Reverse thrust is much more effective at high airplane

speed than at low airplane speeds, for two reasons:

first, the net amount of reverse thrust increases with

speed; second, the power produced is higher at higher

speeds because of the increased rate of doing work. In

other words, the kinetic energy of the airplane is being

destroyed at a higher rate at the higher speeds. To get

maximum efficiency from reverse thrust, therefore, it

should be used as soon as is prudent after touchdown.

When considering the proper time to apply reverse

thrust after touchdown, the pilot should remember that

TARGET OR CLAMSHELL REVERSER

CASCADE REVERSER

Figure 15-19.Thrust reversers.

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some airplanes tend to pitch noseup when reverse is

selected on landing and this effect, particularly when

combined with the noseup pitch effect from the

spoilers, can cause the airplane to leave the ground

again momentarily. On these types, the airplane must

be firmly on the ground with the nosewheel down,

before reverse is selected. Other types of airplanes

have no change in pitch, and reverse idle may be

selected after the main gear is down and before the

nosewheel is down. Specific procedures for reverse

thrust operation for a particular airplane/engine

combination are contained in the FAA-approved

Airplane Flight Manual for that airplane.

There is a significant difference between reverse pitch

on a propeller and reverse thrust on a jet. Idle reverse

on a propeller produces about 60 percent of the reverse

thrust available at full power reverse and is therefore

very effective at this setting when full reverse is not

needed. On a jet engine, however, selecting idle

reverse produces very little actual reverse thrust. In a

jet airplane, the pilot must not only select reverse as

soon as reasonable, but then must open up to full power

reverse as soon as possible. Within Airplane Flight

Manual limitations, full power reverse should be held

until the pilot is certain the landing roll will be

contained within the distance available.

Inadvertent deployment of thrust reversers is a very

serious emergency situation. Therefore, thrust reverser

systems are designed with this prospect in mind. The

systems normally contain several lock systems: one to

keep reversers from operating in the air, another to

prevent operation with the thrust levers out of the idle

detent, and/or an “auto-stow” circuit to command

reverser stowage any time unwanted motion is

detected. It is essential that pilots understand not only

the normal procedures and limitations of thrust

reverser use, but also the procedures for coping with

uncommanded reverse. Those emergencies demand

immediate and accurate response.

PILOT SENSATIONS IN JET FLYING

There are usually three general sensations that the pilot

transitioning into jets will immediately become aware

of. These are: inertial response differences, increased

control sensitivity, and a much increased tempo

of flight.

The varying of power settings from flight idle to full

takeoff power has a much slower effect on the change

of airspeed in the jet airplane. This is commonly called

lead and lag, and is as much a result of the extremely

clean aerodynamic design of the airplane as it is the

slower response of the engine.

The lack of propeller effect is also responsible for the

lower drag increment at the reduced power settings and

results in other changes that the pilot will have to

become accustomed to. These include the lack of

effective slipstream over the lifting surfaces and

control surfaces, and lack of propeller torque effect.

The aft mounted engines will cause a different reaction

to power application and may result in a slightly nosedown pitching tendency with the application of power.

On the other hand, power reduction will not cause the

nose of the airplane to drop to the same extent the pilot

is used to in a propeller airplane. Although neither of

these characteristics are radical enough to cause

transitioning pilots much of a problem, they must be

compensated for.

Power settings required to attain a given performance

are almost impossible to memorize in the jets, and the

pilot who feels the necessity for having an array of

power settings for all occasions will initially feel at a

loss. The only way to answer the question of “how

much power is needed?” is by saying, “whatever is

required to get the job done.” The primary reason that

power settings vary so much is because of the great

changes in weight as fuel is consumed during the

flight. Therefore, the pilot will have to learn to use

power as needed to achieve the desired performance.

In time the pilot will find that the only reference to

power instruments will be that required to keep from

exceeding limits of maximum power settings or to

synchronize r.p.m.

Proper power management is one of the initial problem

areas encountered by the pilot transitioning into jet

airplanes. Although smooth power applications are still

the rule, the pilot will be aware that a greater physical

movement of the power levers is required as compared

to throttle movement in the piston engines. The pilot

will also have to learn to anticipate and lead the power

changes more than in the past and must keep in mind

that the last 30 percent of engine r.p.m. represents the

majority of the engine thrust, and below that the

application of power has very little effect. In slowing

the airplane, power reduction must be made sooner

because there is no longer any propeller drag and the

pilot should anticipate the need for drag devices.

Control sensitivity will differ between various

airplanes, but in all cases, the pilot will find that they

are more sensitive to any change in control

displacement, particularly pitch control, than are the

conventional propeller airplanes. Because of the higher

speeds flown, the control surfaces are more effective

and a variation of just a few degrees in pitch attitude in

a jet can result in over twice the rate of altitude change

that would be experienced in a slower airplane. The

sensitive pitch control in jet airplanes is one of the first

flight differences that the pilot will notice. Invariably

the pilot will have a tendency to over-control pitch

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during initial training flights. The importance of

accurate and smooth control cannot be overemphasized, however, and it is one of the first techniques the

transitioning pilot must master.

The pilot of a sweptwing jet airplane will soon become

adjusted to the fact that it is necessary and normal to

fly at higher angles of attack. It is not unusual to have

about 5° of noseup pitch on an approach to a landing.

During an approach to a stall at constant altitude, the

noseup angle may be as high as 15° to 20°. The higher

deck angles (pitch angle relative to the ground) on

takeoff, which may be as high as 15°, will also take

some getting used to, although this is not the actual

angle of attack relative to the airflow over the wing.

The greater variation of pitch attitudes flown in a jet

airplane are a result of the greater thrust available and

the flight characteristics of the low aspect ratio and

sweptwing. Flight at the higher pitch attitudes requires

a greater reliance on the flight instruments for airplane

control since there is not much in the way of a useful

horizon or other outside reference to be seen. Because

of the high rates of climb and descent, high airspeeds,

high altitudes and variety of attitudes flown, the jet

airplane can only be precisely flown by applying

proficient instrument flight techniques. Proficiency in

attitude instrument flying, therefore, is essential to

successful transition to jet airplane flying.

Most jet airplanes are equipped with a thumb operated

pitch trim button on the control wheel which the pilot

must become familiar with as soon as possible. The jet

airplane will differ regarding pitch tendencies with the

lowering of flaps, landing gear, and drag devices. With

experience, the jet airplane pilot will learn to anticipate

the amount of pitch change required for a particular

operation. The usual method of operating the trim

button is to apply several small, intermittent

applications of trim in the direction desired rather than

holding the trim button for longer periods of time

which can lead to over-controlling.

JET AIRPLANE TAKEOFF AND CLIMB

All FAA certificated jet airplanes are certificated under

Title 14 of the Code of Federal Regulations (14 CFR)

part 25, which contains the airworthiness standards for

transport category airplanes. The FAA certificated jet

airplane is a highly sophisticated machine with proven

levels of performance and guaranteed safety margins.

The jet airplane’s performance and safety margins can

only be realized, however, if the airplane is operated in

strict compliance with the procedures and limitations

contained in the FAA-approved Airplane Flight

Manual for the particular airplane.

The following information is generic in nature and,

since most civilian jet airplanes require a minimum

flight crew of two pilots, assumes a two pilot crew. If

any of the following information conflicts with FAAapproved Airplane Flight Manual procedures for a

particular airplane, the Airplane Flight Manual

procedures take precedence. Also, if any of the

following procedures differ from the FAA-approved

procedures developed for use by a specific air operator

and/or for use in an FAA-approved training center or

pilot school curriculum, the FAA-approved

procedures for that operator and/or training

center/pilot school take precedence.

V-SPEEDS

The following are speeds that will affect the jet

airplane’s takeoff performance. The jet airplane pilot

must be thoroughly familiar with each of these speeds

and how they are used in the planning of the takeoff.

• VS—Stall speed.

• V1—Critical engine failure speed or decision

speed. Engine failure below this speed should

result in an aborted takeoff; above this speed the

takeoff run should be continued.

• VR—Speed at which the rotation of the airplane

is initiated to takeoff attitude. This speed cannot

be less than V1 or less than 1.05 x VMCA

(minimum control speed in the air). On a

single-engine takeoff, it must also allow for the

acceleration to V2 at the 35-foot height at the end

of the runway.

• VLO—The speed at which the airplane first

becomes airborne. This is an engineering term

used when the airplane is certificated and must

meet certain requirements. If it is not listed in the

Airplane Flight Manual, it is within

requirements and does not have to be taken into

consideration by the pilot.

• V2—The takeoff safety speed which must be

attained at the 35-foot height at the end of the

required runway distance. This is essentially the

best single-engine angle of climb speed for the

airplane and should be held until clearing

obstacles after takeoff, or at least 400 feet above

the ground.

PRE-TAKEOFF PROCEDURES

Takeoff data, including V1/VR and V2 speeds, takeoff

power settings, and required field length should be

computed prior to each takeoff and recorded on a

takeoff data card. These data will be based on airplane

weight, runway length available, runway gradient,

field temperature, field barometric pressure, wind,

icing conditions, and runway condition. Both pilots

should separately compute the takeoff data and

cross-check in the cockpit with the takeoff data card.

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15-17

A captain’s briefing is an essential part of cockpit

resource management (CRM) procedures and should

be accomplished just prior to takeoff. [Figure 15-20]

The captain’s briefing is an opportunity to review crew

coordination procedures for takeoff, which is always

the most critical portion of a flight. 

The takeoff and climb-out should be accomplished in

accordance with a standard takeoff and departure

profile developed for the particular make and model

airplane. [Figure 15-21]

TAKEOFF ROLL

The entire runway length should be available for

takeoff, especially if the pre-calculated takeoff

performance shows the airplane to be limited by

runway length or obstacles. After taxing into position

at the end of the runway, the airplane should be aligned

in the center of the runway allowing equal distance on

either side. The brakes should be held while the thrust

levers are brought to a power setting beyond the bleed

valve range (normally the vertical position) and the

engines allowed to stabilized. The engine instruments

should be checked for proper operation before the

brakes are released or the power increased further. This

procedure assures symmetrical thrust during the

takeoff roll and aids in preventing overshooting the

desired takeoff thrust setting. The brakes should then

be released and, during the start of the takeoff roll, the

thrust levers smoothly advanced to the pre-computed

takeoff power setting. All final takeoff thrust

adjustments should be made prior to reaching 60 knots.

The final engine power adjustments are normally made

by the pilot not flying. Once the thrust levers are set for

takeoff power, they should not be readjusted after 60

knots. Retarding a thrust lever would only be

necessary in case an engine exceeds any limitation

such as ITT, fan, or turbine r.p.m.

CAPTAIN'S BRIEFING

I will advance the thrust levers.

Follow me through on the thrust levers.

Monitor all instruments and warning lights on the takeoff 

roll and call out any discrepancies or malfunctions 

observed prior to V1, and I will abort the takeoff. Stand by 

to arm thrust reversers on my command.

Give me a visual and oral signal for the following:

• 80 knots, and I will disengage nosewheel 

steering.

• V1, and I will move my hand from thrust to yoke.

• VR, and I will rotate.

In the event of engine failure at or after V1, I will continue 

the takeoff roll to VR, rotate and establish V2 climb speed.

I will identify the inoperative engine, and we will both 

verify. I will accomplish the shutdown, or have you do it on 

my command.

I will expect you to stand by on the appropriate 

emergency checklist.

I will give you a visual and oral signal for gear retraction 

and for power settings after the takeoff.

Our VFR emergency procedure is to.............................

Our IFR emergency procedure is to..............................

Figure 15-20. Sample captain’s briefing.

• Set Takeoff Thrust Prior

 to 60 Knots

• 70 Knots Check

• V1/VR

• Rotate Smoothly

 to 10° Nose Up

• Positive Rate

 of Climb

• Gear Up

• V2 + 10 Knots

 Minimum

Altitude Selected to Flap Retraction

(400 Ft. FAA Minimum)

(or Obstacle Clearance Altitude)

Close-In Turn

Maintain:

• Flaps T.O. & Appr.

 • V2 + 20 Knots

Minimum

• Maximum

 Bank 30°

Straight Climbout:

• V2 + 10 Knots

• Retract Flaps

• Set Climb Thrust

• Complete After-Takeoff

 Climb Checklist

Rollout:

• V2 + 20 Minimum

• Set Climb Thrust

• Accelerate

• Retract Flaps

• Complete After-Takeoff Climb Checklist

NORMAL TAKEOFF

Figure 15-21.Takeoff and departure profile.

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If sufficient runway length is available, a “rolling”

takeoff may be made without stopping at the end of the

runway. Using this procedure, as the airplane rolls onto

the runway, the thrust levers should be smoothly

advanced to the vertical position and the engines

allowed to stabilize, and then proceed as in the static

takeoff outlined above. Rolling takeoffs can also be

made from the end of the runway by advancing the

thrust levers from idle as the brakes are released.

During the takeoff roll, the pilot flying should

concentrate on directional control of the airplane. This

is made somewhat easier because there is no torqueproduced yawing in a jet as there is in a propeller

driven airplane. The airplane must be maintained

exactly on centerline with the wings level. This will

automatically aid the pilot when contending with an

engine failure. If a crosswind exists, the wings should

be kept level by displacing the control wheel into the

crosswind. During the takeoff roll, the primary

responsibility of the pilot not flying is to closely

monitor the aircraft systems and to call out the proper

V speeds as directed in the captain’s briefing.

Slight forward pressure should be held on the control

column to keep the nosewheel rolling firmly on the

runway. If nosewheel steering is being utilized, the

pilot flying should monitor the nosewheel steering to

about 80 knots (or VMCG for the particular airplane)

while the pilot not flying applies the forward pressure.

After reaching VMCG, the pilot flying should bring

his/her left hand up to the control wheel. The pilot’s

other hand should be on the thrust levers until at least

V1 speed is attained. Although the pilot not flying

maintains a check on the engine instruments

throughout the takeoff roll, the pilot flying (pilot in

command) makes the decision to continue or reject a

takeoff for any reason. A decision to reject a takeoff

will require immediate retarding of thrust levers.

The pilot not flying should call out V1. After passing

V1 speed on the takeoff roll, it is no longer mandatory

for the pilot flying to keep a hand on the thrust levers.

The point for abort has passed, and both hands may be

placed on the control wheel. As the airspeed

approaches VR, the control column should be moved to

a neutral position. As the pre-computed VR speed is

attained, the pilot not flying should make the

appropriate callout and the pilot flying should

smoothly rotate the airplane to the appropriate takeoff

pitch attitude.

ROTATION AND LIFT-OFF

Rotation and lift-off in a jet airplane should be considered a maneuver unto itself. It requires planning, precision, and a fine control touch. The objective is to

initiate the rotation to takeoff pitch attitude exactly at

VR so that the airplane will accelerate through VLOF

and attain V2 speed at 35 feet at the end of the runway.

Rotation to the proper takeoff attitude too soon may

extend the takeoff roll or cause an early lift-off, which

will result in a lower rate of climb, and the predicted

flightpath will not be followed. A late rotation, on the

other hand, will result in a longer takeoff roll,

exceeding V2 speed, and a takeoff and climb path

below the predicted path.

Each airplane has its own specific takeoff pitch

attitude which remains constant regardless of weight.

The takeoff pitch attitude in a jet airplane is normally

between 10° and 15° nose up. The rotation to takeoff

pitch attitude should be made smoothly but

deliberately, and at a constant rate. Depending on the

particular airplane, the pilot should plan on a rate of

pitch attitude increase of approximately 2.5° to 3° per

second.

In training it is common for the pilot to overshoot VR

and then overshoot V2 because the pilot not flying will

call for rotation at, or just past VR. The reaction of the

pilot flying is to visually verify VR and then rotate. The

airplane then leaves the ground at or above V2. The

excess airspeed may be of little concern on a normal

takeoff, but a delayed rotation can be critical when

runway length or obstacle clearance is limited. It

should be remembered that on some airplanes, the

all-engine takeoff can be more limiting than the engine

out takeoff in terms of obstacle clearance in the initial

part of the climb-out. This is because of the rapidly

increasing airspeed causing the achieved flightpath to

fall below the engine out scheduled flightpath unless

care is taken to fly the correct speeds. The

transitioning pilot should remember that rotation at the

right speed and rate to the right attitude will get the

airplane off the ground at the right speed and within

the right distance.

INITIAL CLIMB

Once the proper pitch attitude is attained, it must be

maintained. The initial climb after lift-off is done at

this constant pitch attitude. Takeoff power is

maintained and the airspeed allowed to accelerate.

Landing gear retraction should be accomplished after

a positive rate of climb has been established and

confirmed. Remember that in some airplanes gear

retraction may temporarily increase the airplane drag

while landing gear doors open. Premature gear

retraction may cause the airplane to settle back

towards the runway surface. Remember also that

because of ground effect, the vertical speed indicator

and the altimeter may not show a positive climb until

the airplane is 35 to 50 feet above the runway.

The climb pitch attitude should continue to be held and

the airplane allowed to accelerate to flap retraction

speed. However, the flaps should not be retracted until

Ch 15.qxd 5/7/04 10:22 AM Page 15-18
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obstruction clearance altitude or 400 feet AGL has

been passed. Ground effect and landing gear drag

reduction results in rapid acceleration during this phase

of the takeoff and climb. Airspeed, altitude, climb rate,

attitude, and heading must be monitored carefully.

When the airplane settles down to a steady climb,

longitudinal stick forces can be trimmed out. If a turn

must be made during this phase of flight, no more than

15° to 20° of bank should be used. Because of spiral

instability, and because at this point an accurate trim

state on rudder and ailerons has not yet been achieved,

the bank angle should be carefully monitored throughout the turn. If a power reduction must be made, pitch

attitude should be reduced simultaneously and the

airplane monitored carefully so as to preclude entry

into an inadvertent descent. When the airplane has

attained a steady climb at the appropriate en route

climb speed, it can be trimmed about all axes and the

autopilot engaged.

JET AIRPLANE APPROACH AND

LANDING

LANDING REQUIREMENTS

The FAA landing field length requirements for jet

airplanes are specified in 14 CFR part 25. It defines the

minimum field length (and therefore minimum

margins) that can be scheduled. The regulation

describes the landing profile as the distance required

from a point 50 feet above the runway threshold,

through the flare to touchdown, and then stopping

using the maximum stopping capability on a dry

runway surface. The actual demonstrated distance is

increased by 67 percent and published in the FAAapproved Airplane Flight Manual as the FAR dry

runway landing distance. [Figure 15-22] For wet

runways, the FAR dry runway distance is increased by

an additional 15 percent. Thus the minimum dry

runway field length will be 1.67 times the actual

minimum air and ground distance needed and the wet

runway minimum landing field length will be 1.92

times the minimum dry air and ground distance

needed.

Certified landing field length requirements are

computed for the stop made with speed brakes

deployed and maximum wheel braking. Reverse thrust

is not used in establishing the certified FAR landing

distances. However, reversers should definitely be

used in service.

LANDING SPEEDS

As in the takeoff planning, there are certain speeds that

must be taken into consideration during any landing in

a jet airplane. The speeds are as follows. 

• VSO—Stall speed in the landing configuration.

• VREF—1.3 times the stall speed in the landing

configuration.

• Approach climb—The speed which guarantees

adequate performance in a go-around situation

with an inoperative engine. The airplane’s weight

must be limited so that a twin-engine airplane

will have a 2.1 percent climb gradient capability.

(The approach climb gradient requirements for 3

and 4 engine airplanes are 2.4 percent and 2.7

percent respectively.) These criteria are based on

an airplane configured with approach flaps, landing gear up, and takeoff thrust available from the

operative engine(s).

• Landing climb—The speed which guarantees

adequate performance in arresting the descent

and making a go-around from the final stages of

landing with the airplane in the full landing configuration and maximum takeoff power available

on all engines.

The appropriate speeds should be pre-computed prior

to every landing, and posted where they are visible to

both pilots. The VREF speed, or threshold speed, is used

VREF = 1.3 VS

50 Ft. TD

Actual Distance 60% 40%

FAR (Dry) Runway Field Length Required

1.67 x Actual Distance

FAR (Wet) Runway Field Length Required

1.15 x FAR (Dry)

or

1.92 x Actual Distance

15%

Figure 15-22. FAR landing field length required.

Ch 15.qxd 5/7/04 10:22 AM Page 15-19
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as a reference speed throughout the traffic pattern. For

example:

Downwind leg—VREF plus 20 knots.

Base leg—VREF plus 10 knots.

Final approach—VREF plus 5 knots.

50 feet over threshold—VREF.

The approach and landing sequence in a jet airplane

should be accomplished in accordance with an

approach and landing profile developed for the particular airplane. [Figure 15-23]

SIGNIFICANT DIFFERENCES

A safe approach in any type of airplane culminates in a

particular position, speed, and height over the runway

threshold. That final flight condition is the target

window at which the entire approach aims. Propeller

powered airplanes are able to approach that target from

wider angles, greater speed differentials, and a larger

variety of glidepath angles. Jet airplanes are not as

responsive to power and course corrections, so the

final approach must be more stable, more deliberate,

more constant, in order to reach the window accurately. 

The transitioning pilot must understand that, in spite

of their impressive performance capabilities, there are

six ways in which a jet airplane is worse than a piston

engine airplane in making an approach and in

correcting errors on the approach.

• The absence of the propeller slipstream in

producing immediate extra lift at constant

airspeed. There is no such thing as salvaging a

misjudged glidepath with a sudden burst of

immediately available power. Added lift can

only be achieved by accelerating the airframe.

Not only must the pilot wait for added power but

even when the engines do respond, added lift

will only be available when the airframe has

responded with speed.

• The absence of the propeller slipstream in

significantly lowering the power-on stall speed.

There is virtually no difference between poweron and power-off stall speed. It is not possible in

a jet airplane to jam the thrust levers forward to

avoid a stall.

• Poor acceleration response in a jet engine from

low r.p.m. This characteristic requires that the

approach be flown in a high drag/high power

1. Reset Bug to VREF

2. Review Airport Characteristics

3. Complete Descent and Begin

 Before Landing Checklist

Abeam Runway Midpoint

• Flaps T/O Approach

• VREF + 20 Minimum

1500' Above

Field Elevation 

• Complete Before

 Landing Checklist

• Maximum Bank 30°

• Clear Final Approach Rollout

• Reduce Speed to VREF

• Altitude Callouts

• Stabilized in Slot

DO NOT MAKE FLAT

APPROACH

Touchdown

• Extend Speed

 Brake

• Apply Brakes

• Thrust reverser or

 Drag Chute as

 Required

Fly VREF

Abeam Touchdown Point

• Gear Down

Turning Base

• Flaps Land

• Initially Set Fuel Flow to 400 Lb./Engine

• Start Descent

• VREF + 10 Minimum on Base

APPROACH PREPARATIONS

Figure 15-23.Typical approach and landing profile.

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15-21

configuration so that sufficient power will be

available quickly if needed.

• The increased momentum of the jet airplane

making sudden changes in the flightpath

impossible. Jet airplanes are consistently heavier

than comparable sized propeller airplanes. The

jet airplane, therefore, will require more indicated airspeed during the final approach due to a

wing design that is optimized for higher speeds.

These two factors combine to produce higher

momentum for the jet airplane. Since force is

required to overcome momentum for speed

changes or course corrections, the jet will be far

less responsive than the propeller airplane and

require careful planning and stable conditions

throughout the approach.

• The lack of good speed stability being an

inducement to a low speed condition. The drag

curve for many jet airplanes is much flatter than

for propeller airplanes, so speed changes do not

produce nearly as much drag change. Further, jet

thrust remains nearly constant with small speed

changes. The result is far less speed stability.

When the speed does increase or decrease, there

is little tendency for the jet airplane to re-acquire

the original speed. The pilot, therefore, must

remain alert to the necessity of making speed

adjustments, and then make them aggressively in

order to remain on speed.

• Drag increasing faster than lift producing a high

sink rate at low speeds. Jet airplane wings

typically have a large increase in drag in the

approach configuration. When a sink rate does

develop, the only immediate remedy is to

increase pitch attitude (angle of attack). Because

drag increases faster than lift, that pitch change

will rapidly contribute to an even greater sink

rate unless a significant amount of power is

aggressively applied.

These flying characteristics of jet airplanes make a

stabilized approach an absolute necessity.

THE STABILIZED APPROACH

The performance charts and the limitations contained

in the FAA-approved Airplane Flight Manual are

predicated on momentum values that result from

programmed speeds and weights. Runway length

limitations assume an exact 50-foot threshold height at

an exact speed of 1.3 times VSO. That “window” is

critical and is a prime reason for the stabilized

approach. Performance figures also assume that once

through the target threshold window, the airplane will

touch down in a target touchdown zone approximately

1,000 feet down the runway, after which maximum

stopping capability will be used. 

There are five basic elements to the stabilized

approach.

• The airplane should be in the landing

configuration early in the approach. The landing

gear should be down, landing flaps selected, trim

set, and fuel balanced. Ensuring that these tasks

are completed will help keep the number of

variables to a minimum during the final

approach.

• The airplane should be on profile before

descending below 1,000 feet. Configuration,

trim, speed, and glidepath should be at or near

the optimum parameters early in the approach to

avoid distractions and conflicts as the airplane

nears the threshold window. An optimum

glidepath angle of 2.5° to 3° should be

established and maintained.

• Indicated airspeed should be within 10 knots of

the target airspeed. There are strong relationships

between trim, speed, and power in most jet

airplanes and it is important to stabilize the speed

in order to minimize those other variables.

• The optimum descent rate should be 500 to 700

feet per minute. The descent rate should not be

allowed to exceed 1,000 feet per minute at any

time during the approach.

• The engine speed should be at an r.p.m. that

allows best response when and if a rapid power

increase is needed.

Every approach should be evaluated at 500 feet. In a

typical jet airplane, this is approximately 1 minute

from touchdown. If the approach is not stabilized at

that height, a go-around should be initiated. (See

figure 15-24 on the next page.)

APPROACH SPEED

On final approach, the airspeed is controlled with

power. Any speed diversion from VREF on final

approach must be detected immediately and corrected.

With experience the pilot will be able to detect the very

first tendency of an increasing or decreasing airspeed

trend, which normally can be corrected with a small

adjustment in thrust. The pilot must be attentive to poor

speed stability leading to a low speed condition with

its attendant risk of high drag increasing the sink rate.

Remember that with an increasing sink rate an apparently normal pitch attitude is no guarantee of a normal

angle of attack value. If an increasing sink rate is

detected, it must be countered by increasing the angle

Ch 15.qxd 5/7/04 10:22 AM Page 15-21
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of attack and simultaneously increasing thrust to

counter the extra drag. The degree of correction

required will depend on how much the sink rate needs

to be reduced. For small amounts, smooth and gentle,

almost anticipatory corrections will be sufficient. For

large sink rates, drastic corrective measures may be

required that, even if successful, would destabilize

the approach.

A common error in the performance of approaches in

jet airplanes is excess approach speed. Excess

approach speed carried through the threshold window

and onto the runway will increase the minimum

stopping distance required by 20 – 30 feet per knot of

excess speed for a dry runway and 40 – 50 feet for a

wet runway. Worse yet, the excess speed will increase

the chances of an extended flare, which will increase

the distance to touchdown by approximately 250 feet

for each excess knot in speed.

Proper speed control on final approach is of primary

importance. The pilot must anticipate the need for

speed adjustment so that only small adjustments are

required. It is essential that the airplane arrive at the

approach threshold window exactly on speed.

GLIDEPATH CONTROL

On final approach, at a constant airspeed, the glidepath

angle and rate of descent is controlled with pitch

attitude and elevator. The optimum glidepath angle is

2.5° to 3° whether or not an electronic glidepath

reference is being used. On visual approaches, pilots

may have a tendency to make flat approaches. A flat

approach, however, will increase landing distance and

should be avoided. For example, an approach angle of

2° instead of a recommended 3° will add 500 feet to

landing distance.

A more common error is excessive height over the

threshold. This could be the result of an unstable

approach, or a stable but high approach. It also may

occur during an instrument approach where the missed

approach point is close to or at the runway threshold.

Regardless of the cause, excessive height over the

threshold will most likely result in a touchdown

beyond the normal aiming point. An extra 50 feet of

height over the threshold will add approximately 1,000

feet to the landing distance. It is essential that the

airplane arrive at the approach threshold window

exactly on altitude (50 feet above the runway).

THE FLARE

The flare reduces the approach rate of descent to a

more acceptable rate for touchdown. Unlike light

airplanes, a jet airplane should be flown onto the

runway rather than “held off” the surface as speed

dissipates. A jet airplane is aerodynamically clean

even in the landing configuration, and its engines still

produce residual thrust at idle r.p.m. Holding it off

during the flare in a attempt to make a smooth landing

will greatly increase landing distance. A firm landing

is normal and desirable. A firm landing does not mean

a hard landing, but rather a deliberate or positive

landing.

For most airports, the airplane will pass over the end

of the runway with the landing gear 30 – 45 feet above

the surface, depending on the landing flap setting and

the location of the touchdown zone. It will take 5 – 7

seconds from the time the airplane passes the end of

Figure 15-24. Stabilized approach.

Stop Rollout Touchdown

1,000'

Threshold

Window

50' VREF

500'

Window

Check for

Stabilized

Approach

Stabilized Approach

on Course on Speed

2.5° - 3° Glidepath

500 - 700 FPM

Descent

1,000'

Window

Flare

Ch 15.qxd 5/7/04 10:22 AM Page 15-22
15-23

the runway until touchdown. The flare is initiated by

increasing the pitch attitude just enough to reduce the

sink rate to 100 – 200 feet per minute when the landing

gear is approximately 15 feet above the runway

surface. In most jet airplanes, this will require a pitch

attitude increase of only 1° to 3°. The thrust is

smoothly reduced to idle as the flare progresses.

The normal speed bleed off during the time between

passing the end of the runway and touchdown is 5

knots. Most of the decrease occurs during the flare

when thrust is reduced. If the flare is extended (held

off) while an additional speed is bled off, hundreds or

even thousands of feet of runway may be used up.

[Figure 15-25] The extended flare will also result in

additional pitch attitude which may lead to a tail strike.

It is, therefore, essential to fly the airplane onto the

runway at the target touchdown point, even if the

speed is excessive. A deliberate touchdown should be

planned and practiced on every flight. A positive

touchdown will help prevent an extended flare.

Pilots must learn the flare characteristics of each model

of airplane they fly. The visual reference cues observed

from each cockpit are different because window

geometry and visibility are different. The geometric

relationship between the pilot’s eye and the landing

gear will be different for each make and model. It is

essential that the flare maneuver be initiated at the

proper height—not too high and not too low.

Beginning the flare too high or reducing the thrust too

early may result in the airplane floating beyond the

target touchdown point or may include a rapid pitch up

as the pilot attempts to prevent a high sink rate

touchdown. This can lead to a tail strike. The flare that

is initiated too late may result in a hard touchdown.

Proper thrust management through the flare is also

important. In many jet airplanes, the engines produce a

noticeable effect on pitch trim when the thrust setting

is changed. A rapid change in the thrust setting requires

a quick elevator response. If the thrust levers are

moved to idle too quickly during the flare, the pilot

must make rapid changes in pitch control. If the thrust

levers are moved more slowly, the elevator input can

be more easily coordinated.

Touchdown

On Target

Extended

Flare

10 Knots Deceleration

on Ground (Maximum Braking)

10 Knots Deceleration

in Flare

200 Ft. (Dry Runway)

500 Ft. (Wet Runway)

2,000 Ft. (Air)

Figure 15-25. Extended flare.

Ch 15.qxd 5/7/04 10:22 AM Page 15-23
15-24

TOUCHDOWN AND ROLLOUT

A proper approach and flare positions the airplane to

touch down in the touchdown target zone, which is

usually about 1,000 feet beyond the runway threshold.

Once the main wheels have contacted the runway, the

pilot must maintain directional control and initiate the

stopping process. The stop must be made on the

runway that remains in front of the airplane. The

runway distance available to stop is longest if the

touchdown was on target. The energy to be dissipated

is least if there is no excess speed. The stop that begins

with a touchdown that is on the numbers will be the

easiest stop to make for any set of conditions.

At the point of touchdown, the airplane represents a

very large mass that is moving at a relatively high

speed. The large total energy must be dissipated by the

brakes, the aerodynamic drag, and the thrust reversers.

The nosewheel should be flown onto the ground

immediately after touchdown because a jet airplane

decelerates poorly when held in a nose-high attitude.

Placing the nosewheel tire(s) on the ground will assist

in maintaining directional control. Also, lowering the

nose gear decreases the wing angle of attack,

decreasing the lift, placing more load onto the tires,

thereby increasing tire-to-ground friction. Landing

distance charts for jet airplanes assume that the

nosewheel is lowered onto the runway within 4

seconds of touchdown.

There are only three forces available for stopping the

airplane. They are wheel braking, reverse thrust, and

aerodynamic braking. Of the three, the brakes are most

effective and therefore the most important stopping

force for most landings. When the runway is very

slippery, reverse thrust and drag may be the dominant

forces. Both reverse thrust and aerodynamic drag are

most effective at high speeds. Neither is affected by

runway surface condition. Brakes, on the other hand,

are most effective at low speed. The landing rollout

distance will depend on the touchdown speed and what

forces are applied and when they are applied. The pilot

controls the what and when factors, but the maximum

braking force may be limited by tire-to-ground

friction.

The pilot should begin braking as soon after

touchdown and wheel spin-up as possible, and to

smoothly continue the braking until stopped or a safe

taxi speed is reached. However, caution should be used

if the airplane is not equipped with a functioning

anti-skid system. In such a case, heavy braking can

cause the wheels to lock and the tires to skid.

Both directional control and braking utilize tire ground

friction. They share the maximum friction force the

tires can provide. Increasing either will subtract from

the other. Understanding tire ground friction, how

runway contamination affects it, and how to use the

friction available to maximum advantage is important

to a jet pilot.

Spoilers should be deployed immediately after

touchdown because they are most effective at high

speed. Timely deployment of spoilers will increase

drag by 50 to 60 percent, but more importantly, they

spoil much of the lift the wing is creating, thereby

causing more of the weight of the airplane to be loaded

onto the wheels. The spoilers increase wheel loading

by as much as 200 percent in the landing flap

configuration. This increases the tire ground friction

force making the maximum tire braking and cornering

forces available.

Like spoilers, thrust reversers are most effective at

high speeds and should be deployed quickly after

touchdown. However, the pilot should not command

significant reverse thrust until the nosewheel is on the

ground. Otherwise, the reversers might deploy

asymmetrically resulting in an uncontrollable yaw

towards the side on which the most reverse thrust is

being developed, in which case the pilot will need

whatever nosewheel steering is available to maintain

directional control.

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