Tractor-Engine Thrust-Component Lift

Manipulation of engine thrust for aircraft control in normal and usual flight is steering the direction the aircraft motion by pitch control. This is vectoring of primary thrust for sustaining required motion causing flight.  Vectored-Thrust consists of engine thrust force components directed forward in the direction of motion and outward as lift to control aircraft attitude.

Usual consideration for vectored-thrust has been in reference to ducting thrust for increased maneuverability, re-directing with powerful engines for slowed or hovering flight. However, all thrust is a force vector. Change of engine power when in flight at a body angle is changing this vectored force and the related force components.

The location and alignment of engine attachment to the aircraft determines how the engine thrust reacts. Most aircraft have engine attachment determined at an optimum body angle for a designed cruise indicated-airspeed.

Aircraft flight requires a small positive wing angle of attack at all times to cause generation of aerodynamic lift from its passage within the airmass.

Increased angle of attack by slowed indicated-airspeed causes the engine generated thrust to be at an increased small angle upwards from the direction of motion resulting in, and increase of, the outward component vector of thrust as a small lift force. This engine thrust lifting acts on the effective center of gravity through a moment arm from the engine attachment and contributes to the total aircraft lift outward from the top of the machine.

Forward mounted (tractor) engines will have vectored-thrust causing nose-up pitch effect. Aft mounted (pusher) engines will have this component vectored-thrust causing nose-down pitch effect.

Design engineers attach the engines to minimize control effects of this vectored-thrust as much as possible throughout the power range of the engines.

As a pilot, there is no way to know the feel of the effects of any specific aircraft control without actually flying the aircraft through the total range of design operational airspeed while being aware of the existence of changing outward engine vectored-thrust.

All level or climbing constant indicated-airspeed maneuvering requires added thrust. It then follows with tractor engines there will be added vectored-thrust lifting as climb angle during this type maneuvering. Conversely, reduced thrust for descending flight will reduce or eliminate this lifting thrust requiring elevator-pitch change to maintain a constant angle of attack indicated-airspeed.

For a level, constant indicated-airspeed turn, it requires increasing vectored-thrust lift to counter the reduced vertical component of aerodynamic lift. This means increased engine thrust coordinated to maintain level flight.

Thrust vectoring still requires use of flight control surfaces, but to a lesser extent. The ailerons and rudder input for banked coordination is always required in a turn.

In a turn, there is no need for elevator input until exceeding the angle of bank that maximum engine power can carry. If elevator input is required, there will be increased angle of attack and slowed indicated-airspeed during that portion of the turn.

Most usual flight at indicated-airspeed well above Vy allows making level turns with aft elevator input, but in all cases there will be slowing. Up to now, this method of turn has been the most usual way of teaching turns.

The main purpose of learning to use vectored-thrust for turns is to reduce the reliance of elevator input when maneuvering. Low and slow maneuvering flight as is normal for approaches becomes critical if using elevator input because of the ease or likelihood of causing rapid increase of stall indicated-airspeed.

Control technique, using engine thrust and minimum or no elevator input, for slow indicated-airspeed maneuvering essentially eliminates the potential of a stall.

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Simply Aircraft Control

So, what’s the problem? It’s getting back to basics…Flight Control.


All texts discuss aerodynamic lift as the source of lift for balanced flight. That typically means considering a large vector from the center of lift located approximately one-fourth back from the leading edge and out from the center of the aircraft. Additionally, there is consideration of aerodynamic lift by the horizontal stabilizer and elevator for pitch control to maintain the balance.

However, in real life there is always a small nose-up angle of the aircraft into the relative wind required for all flight. Rarely, if ever, is there a discussion or even consideration of any lift caused by a component of engine thrust in normal flight, however for very high-powered aircraft we generally recognize that large climb angles are primarily from engine thrust to the extent, vertical flight is totally from engine thrust lifting.

The small engine lifting force of usual flight acts over a lever arm (moment) from its attachment to the fuselage back to the effective center of gravity and changes with any engine power change. Therefore, there is cause for question of what really is happening with control of normal flight when power is changed.


Controlled flight is continuous balance of forces affecting the aircraft. Begin with analyzing a steady-state level flight.

In level constant indicated-airspeed flight, with a body angle, there is a small outward component of engine vectored-thrust as lift contributing to the setting of aerodynamic elevator-load/lift (elevator trimmed) for the angle of attack indicated-airspeed.

Both the thrust-lift and elevator-load/lift have moment arms that act at the effective center of gravity. Small forces (elevator-pitch and engine-pitch) at these areas affect both the angle of attack, and being forces, cause small changes of loading so change the location of the effective center of gravity.

We are suspended and balanced in space. The aircraft does not know the earth is below. All net forces are opposite and equal. The constant velocity within the airmass is with a set sustaining engine generated thrust, causing the wing and body aerodynamic lift forces, while the small component of engine vectored-thrust lift and elevator-pitched aerodynamic loading contribute to the total lift and load by acting from a distance along their moment arms.

Tractor aircraft; engines mounted forward of the effective center of gravity.

As an example, a small aircraft at Vy level flight with approximately 160 pounds of thrust sustaining the flight.  There will be at least 6-degrees nose up angle of attack to the direction of motion. The trigonometric sine of 6 degrees is .1, so that means a lifting force of 16 pounds (160 x .1 = 16) from vectored-thrust outward at the nose. The engine of this aircraft is approximately 10 ft. forward of the center of lift. This is the moment arm for the 16 pounds of lift so is causing 160 foot/pounds of lift at the center of lift. (16 # x 10 ft. lever arm = 160 ft.lbs.) The elevator-pitch acting 20 ft. aft will require an opposing aerodynamic 8 lbs. of positive load to balance the current attitude. (8 # x 20 ft. lever arm = 160 ft.lbs.)

Pusher aircraft; engines mounted aft of the effective center of gravity.

An example of a small aircraft at Vy level flight with 160 lbs. of sustaining thrust will have at least a 6-degree nose up attitude. This means an engine lifting force at the rear of 16 lbs pitching the nose down. This lifting acting over the 20 feet from tail to the effective center of gravity equals 320ft.lbs. of lifting.

For level elevator-pitch trimmed flight, the elevator is set to compensate for that lifting with equal and opposite loading. This then is aerodynamic loading at the elevator of 16 lbs x 20 ft. = -320 ft.lbs. for balancing the aircraft attitude.


Tractor aircraft; engines mounted forward of the effective center of gravity.

An increase of thrust from steady-state level trimmed flight will increase the lift component of engine vectored-thrust. The added thrust causes balance change, so changes the direction of motion, but does not change the angle of attack so indicated-airspeed is changed only by possible increased elevator loading caused by increased downwash.

The added engine-lift moment arm causes a climb-pitch with changed direction of motion and the excess forward thrust is overcoming gravity by increasing altitude. The direction of engine thrust changes as the horizontal thrust component moves up to a climb angle in the new direction of motion. The increased angled component of excess thrust is pushing the aircraft up an inclined path of increasing altitude.

There has been no change of angle of attack, only change in direction of motion. The indicated-airspeed has possibly changed a small amount depending on elevator location vs. downwash flow.  This is climb-pitch.

Let’s reduce thrust back to maintain level flight. We are level again, just a little higher than where we started. We have the same sustaining power setting and original indicated-airspeed. The only control input has been change of power.

Pusher aircraft; engines mounted aft of the effective center of gravity.

Adding excess thrust with aft mounted engines will increase the nose-down pitch effect and requires simultaneous aft elevator-pitch to oppose the change of angle of attack. The resulting excess thrust effect causes a changed direction of motion with a climb-pitched attitude, increasing altitude, and with required coordinated elevator-pitch to sustain a constant indicated-airspeed.

So we are still balanced. Coordinated elevator-pitch has kept the angle of attack constant. The control input has required both change of power and elevator-pitch.

Now we again have two kinds of pitch; climb-pitch, and elevator-pitch. That figures, we call climb angle plus angle-of-attack our aircraft pitched angle. Angle of attack now is body angle. Wing angle of attack is different. As a pilot, we have two distinct kinds of aircraft pitch, neither of which we can distinguish inflight. The indicated-airspeed reading tells us we are within operating limitations. We coordinate control as what-ever-it-takes.


Tractor aircraft; engines mounted forward of the effective center of gravity.

Let’s do a turn. Before we start the turn, think in terms of a turn as being a climb on a different plane. As we roll into a bank, let’s just add power to maintain level flight. Don’t touch the elevator. There will now be a thrust setting that gives the outward component of engine vectored-thrust (lift) necessary to maintain the required total lift. Excess thrust is coordinated to maintain a constant vertical component of lift causing level turning flight. The airplane thinks its climbing without increased altitude.

Continue increase of the roll angle while coordinating with increasing power to maintain level flight, until you reach maximum power. You now know, for the present conditions, the maximum angle of bank for level flight the aircraft can attain.

Why not pull on the elevator for the turn? You can, and it is fine if your indicated-airspeed will allow it, but that changes angle of attack, slows you down, and adds loading to the wings causing added aerodynamic lifting. At low indicated-airspeed and low altitude, people stall aircraft by inadvertently pulling too much.

Pusher aircraft; engines mounted aft of the effective center of gravity.

Turning now must consider increased nose-down pitching effect (effective pitch trim) plus the reduced vertical lift of a banked attitude.

As we roll into a bank, we must add simultaneous coordinated power to maintain level flight and aft elevator-pitch only to maintain constant angle of attack.

Adjustment of elevator-pitch must be continually coordinated to retain a constant angle of attack as power is increased. It is the excess thrust coordinated to maintain a constant vertical component of lift at this same angle of attack causing level turning flight.

Continue increase of the roll angle while coordinating with increasing power and elevator-pitch to maintain constant indicated-airspeed level flight, until you reach maximum power. You now know, for the present conditions, the maximum angle of bank for level flight the aircraft can attain.

Let’s learn to remember the phase of flight we are in before pulling the control wheel. If not pulling, the aircraft will never stall. If pulling in a turn, when reaching maximum power, quit adding additional aft elevator-pitch at least before reducing to minimum safe flight indicated-airspeed.

When in a banked attitude, it is difficult to visualize the extent of nose-up pitch attitude. There is reduced control feel when slowed, but it is necessary to realize you cannot see it and pulling the elevator in steep turns can easily result in stall.

Moral: Let’s teach how not to stall. The stall exercises are nice and the Student really needs to know how to make an immediate recovery (stalls typically happen when low and slow) if a stall occurs. But, if your Student knows why aircraft stall (pulling on the wheel), and has been taught techniques of flight without relying on pulling, and is very aware of what can happen when pulling even when forced to land in trees, rocks or house-tops, and doesn’t let ego keep him continuing when screwing up an approach, guess what? Maybe there won’t be so many “stall and crash” incidents!

I digress, now back to level coordinated level flight.


Tractor aircraft; engines mounted forward of the effective center of gravity.

We need to talk descent. There becomes a difference in control when reducing power for descent.

That bit of engine vectored-thrust lifting that contributes to the trimmed angle of attack starts to disappear. Going to idle for a descent will almost eliminate that outward component of vectored-thrust. That means it’s like a nose down elevator trimming effect from sustained level or excess powered climbing or turning flight.

The angle of attack reduced in this manner allows acceleration. Going down with gravity, an aircraft will accelerate quickly. (A 6-degree nose down attitude will allow gravity component thrust increase to almost equal the sustaining engine power!)

O.K. that explains why these airplanes accelerate when reducing power below level sustained power. Now, throughout all descent maneuvering, with changing thrust settings, you are now going to have an effect on the angle of attack.

You are now aware something is going to happen with changing of thrust and the related engine vectored-thrust lifting.

Let’s be sure we get this right. In descent, increased thrust will still cause lift at the engine, and at the same time increases angle of attack allowing deceleration to balance with the current elevator-pitch. Anytime reducing thrust more when below sustaining thrust will always decrease angle of attack and allow some rapid acceleration from gravity-component thrust.

The elevator-pitch continues its aerodynamic lifting as set, so in descent it will be continually necessary to coordinate a change of elevator-pitch for constant indicated-airspeed control when changing thrust.

Descent maneuvering requires coordination of both kinds of pitch control to maintain a constant indicated-airspeed.

Remember though, if leveling you are back to the level and climb condition at the current elevator-pitched angle of attack. There is again that contribution of engine lifting as part of the angle of attack.

Pusher aircraft; engines mounted aft of the effective center of gravity.

In all regimes of flight, reduced thrust from coordinated level, climbing or turning flight will always reduce the engine nose-down pitching effect resulting in attitude pitch-up and deceleration from an increased angle of attack. Power increase will cause reduced angle of attack and acceleration.

It requires continuous coordinated elevator-pitch input to adjust control to maintain a constant angle of attack indicated-airspeed with every power change.

Descent...Difference where it counts:

Tractor aircraft; engines mounted forward of the effective center of gravity.

So the question always asked. What controls lift and what controls indicated-airspeed? It depends on where you are and what you fly. Aircraft with engines mounted forward of the center of lift, for level and climb, it’s easy, power is lift (climb) and elevator-pitch (angle of attack) is indicated-airspeed.

In descent, power increase causes pitch-up with increased angle of attack and slowing, while power decrease will cause some pitch-down, decreased angle of attack with acceleration. In all cases of descent, for constant indicated-airspeed coordination of elevator pitch is required.

Pusher aircraft; engines mounted aft of the effective center of gravity

Engines mounted aft of the center of lift, both engine thrust-component pitch and elevator-pitch must always be continually coordinated for constant angle of attack indicated-airspeed.

Reducing power in descent causes pitch-up, increases angle of attack and deceleration, while increased power will cause pitch-down with decreased angle of attack and acceleration.


Tractor aircraft; engines mounted forward of the effective center of gravity.

This also explains a little of why adding lots of power for a go-around gives so much pitch-up, but go up to a safe altitude and play with this. If you aren’t pulling on the elevator on a go-around, the radical pitch-up is not going to cause a stall. It’s just an uncomfortable attitude. You are very likely pushing the control wheel by now.

Pusher aircraft; engines mounted aft of the effective center of gravity.

This explains why adding lots of power for a go-around the nose will pitch down and requires coordinated aft elevator input to stop descent and initiate climb.

Elevator control:

Elevator control or trim is pilot input. An undesired autopilot input causing extreme nose up elevator input is pilot control. Any maneuver resulting in a stall is from some sort of pilot input. Inattention to flying the aircraft is not an excuse for a stall.

It goes on and on but, if the Student is not taught specific aircraft control in the first few hours, there is no way to learn the rest…”what to do with the machine”!

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Slow Flight Maneuvering

All slow indicated-airspeed flight has an angled nose-up attitude in the direction of motion. In the steep banked descending turn, the angled motion is toward the surface so visual referencing is very different from the usual sighting expected with wings level flight.

It is almost impossible to reference the nose high attitude and related motion as being slow or extreme. This turning maneuver must be a learned attitude with drilled understanding of response to be expected. Quite simply, always be ready to reduce bank and add power throughout any steep turn.

This type maneuvering requires cautious use of aft elevator-pitch input. Slow indicated-airspeed means there is little room for increased angle of attack before approaching wing critical angle-of-attack. A pilot must understand low altitude slow indicated-airspeed maneuvering has definite limitations.

Engine thrust-component lift acting at its attachment is primary for increasing pitch in this situation. Adding power from a reduced power condition in a descending turn will cause engine thrust-component lifting and increased angle of attack.

This maneuvering requires understanding the effect of vectored-thrust. The engine thrust is always forward in the direction the aircraft is pointed. In slower indicated-airspeed flight there is a body angle of attack above the direction of motion. This angle causes thrust-component force vectors in the direction of motion and outward from the top of the machine, both from the point of engine attachment.

The component of thrust in the direction of motion sustains that motion and if in excess will cause changed direction for climb and turn or if negative excess, descent. This is normal flight, always expected when maneuvering.

The thrust-component created from angle of attack is vectored thrust out the top of the engine attachment. It then contributes in some way to the pitched attitude of the aircraft.

In level flight at any slower indicated-airspeed, the effect of engine pitched vectored-thrust along with coordinated elevator-pitch sets the angle of attack for the present condition. This means, the engine is supplementing angle of attack pitch control.

What Happens With a Power Change?

From stabilized level flight, increased power is excess power. There is increase of both the horizontal and any vertical components of thrust. The vertical thrust component will increase pitch, causing lifting the nose. The elevator-pitch remains constant so there is no change of angle of attack, the aircraft changes direction of motion and climbs.

There is now a climb angle with horizontal motion and increased altitude of moving further away from the surface. The excess horizontal thrust is causing the continued motion in a new direction. The increased vertical thrust has caused climb. The indicated-airspeed angle of attack remains constant unless affected by increased downwash over the wings. In this situation, added power has caused climb angle.

Decreasing power from the level, constant indicated-airspeed condition is negative excess. This reduces the force components of thrust. There is reduced engine vertical pitch so its contribution to angle of attack decreases slightly allowing some acceleration.

The airplane begins descending allowing addition of a horizontal component of gravity as thrust for sustaining the aircraft aerodynamic lift at the new indicated-airspeed. To reduce back to the original angle of attack indicated-airspeed, it is necessary to coordinate more elevator nose-up pitch. With that, we have now stabilized the aircraft in descent at the previous indicated-airspeed.

The conditions of descent are slightly different. When operating in descent, an increase of power will change the outward vectored-thrust as usual, but now the pitch change it causes will first increase the angle of attack until slowing to the level flight indicated-airspeed called for with the combination of current elevator-pitch and thrust. At that point, it has reached level flight for this condition, any additional thrust becomes excess thrust and will cause climb at this new slower indicated-airspeed.

The added nose-up elevator-pitch when initiating the descent and renewed thrust pitch have added to cause a new and greater angle of attack allowing more slowing of indicated-airspeed.

The conditions of elevator trimmed, slow indicated-airspeed during descending flight dramatically changes with large increases of power. Without reduced elevator-pitch when adding power in descent, it is possible to cause inadvertent high angles of attack. This is a common contributing factor to the occurrence of descending low altitude turning stall.

Slow indicated-airspeed maneuvering with descending turns is continuation of these same effects from power change and its affect on angle of attack. There is always the same response for any power change in descent whether wings level or turning.

There is a changed visual presentation when maneuvering in turns. The attitude of the aircraft with reference to the surface becomes misleading. A high angle of attack is obvious when the wings are level. However, in a descending turn the angled nose attitude visually appears to be much lower. In actuality, it is lower.  However, the set angle of attack is high so requires careful elevator control.

This condition of visual awareness becomes hidden more and more as bank angle increases. A pilot must consciously consider these attitudes when controlling in steep banked descending turns. Only with awareness, will there be safe control.

Base Leg to final Turn Overshoot and Stall

The base leg to final approach turn has a history of inadvertent stalls. This turn is the time a pilot is attempting to direct the aircraft toward the runway end while aligning over the extended runway centerline.

Attaining appropriate alignment requires previous positioning on the downwind leg, to allow sufficient space for visually controlling the ground tracking of the descending base leg and final approach turns to roll out on the extended centerline of the landing runway.

Conditions that can cause misalignment of the final turn are common, and usually the result of improper initial downwind positioning for the turn by the pilot.

Often it is flying the downwind too close to the runway, so there is not sufficient ground track to make the turn normally.

A strong crosswind on downwind can cause the aircraft to be drifted toward or away from the runway. Continued drifting, when flying the base leg and the base to final turn, also can lead to an overshooting condition.

Any condition of wind or maneuvering misjudgment can create the situation of overshooting or undershooting the final approach tracking.

When substantial overshoot becomes obvious, there is a strong tendency for a pilot to hold fixed steep bank angle and attempt to increase the turn rate with rudder. Even with added indicated-airspeed for approach wind conditions, this easily becomes an inadvertent cross-controlled situation.

At the same time, in this banked attitude the pilot may try to pull the nose up with aft elevator-pitch input, as an added attempt to increase the rate of turn.

The aircraft would now be in a steep cross-controlled turn, and at the same time, the indicated-airspeed decreasing due to probable back elevator-pitch input.

Any added aft elevator input will simultaneously increase “g” loading, rapidly approaching the increased wing critical angle-of-attack. When controlling the descent rate with the back elevator-pitch input, continuing this steep banked condition can cause a low altitude stall.

It is interesting to be aware that pulling the elevator-pitch control is what caused the aircraft to stall. The attitudes attained in the steep cross-controlled turn will not cause stall. The aircraft will respond with continued descent.

During all this time, an unaware pilot, fixated on attaining the landing approach positioning, is attempting to direct the aircraft to the landing spot.

The slower indicated-airspeed used during approaches reduces control input resistance, and a steep bank angle does not have the appearance of a nose-high attitude. The reduced control feel and visual feedback sensing may not alarm the pilot while concentrating on correcting the aircraft tracking.

Adding to the confusion can be a common mental attitude of pilots, that when the runway is in sight, nothing interferes with the landing. The last thing likely to come to mind is going-around…even if briefed before the approach.

What Has Been Happening?

The pilot is flying without conscious awareness of control input. Wrong positioning has the pilot using unusual or extreme control while being distracted with an assumed importance of needing to “make” the runway and landing. There are any number of distractions that could exist. Fly your airplane first!

An understanding of control during this kind of maneuver needs to be firmly entrenched in pilot training. Increasing the turn rate with the descending steep turn must be with increased engine vectored-thrust lifting by adding power. In the steep turn, the  engine lifting forces are pulling the turn and lifting the nose over its moment arm, the fuselage, so actually decreasing some aerodynamic loading. It often requires reduced elevator control to allow continued safe indicated-airspeed.

Remember that power at slower indicated-airspeed has the direction of thrust angled slightly upward. A V1.3 or Vy approach will be with a sustaining 6 to 8 degrees nose-up from direction of motion.

Now when operating at lower power settings, added power causes vectored thrust-component lifting and nose-up pitch. This initial pitching will contribute to the elevator-pitched trim setting allowing even slower indicated-airspeed until reaching the new level flight sustaining thrust called for with both the previous added elevator-pitch and increased engine-pitch. This condition is calling for slower indicated-airspeed but if not increasing with more elevator-pitch, the aircraft will slow to the angle of attack as set and become very nose-high slow flight. 

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Lift and Control

(The aerospace engineer asks: Are you sure the lift forces are caused by rapid displacement of the air? This sounds more like buoyancy, as occurs with balloons, which are lighter than air. Aren't they caused by the pressure differences above and below the wing? See wikipedia article on lift:)

An aircraft moving through space displaces more than its own volume of airmass. The resulting pressures of rapid flow displacement of the air from motion causes a reaction from the aerodynamic form of the machine, creating reactive forces directed outward from the machine as lift.

Buoyancy is displacement of sufficient volume of air mass but does not necessarily require motion.

An airfoil requires motion through the mass, which with proper flow diversion and displacement creates the pressure differential to cause lift.

Not noted by any source I have seen is that in reduced indicated-airspeed flight there is more mass displaced under the wing than over. Most discussion involves the flow over the top as the mass replaces itself. As a pilot, I don’t really care. I don’t really even want to think about it. Things one can do nothing about are complicating the whole operation of the aircraft.

There is a lot of discussion about all this. Little or none is necessary consideration by a pilot for flight. The engineer is definitely concerned that the thing be built to cause lift. The pilot…just pushes the throttle and the machine flies. He is already convinced it will work. It flew in, it will fly out.

I don’t mean to belittle the designers. It is just that the system has gotten into so much of the technical aspects of design the actual operational control has been forgotten, if ever known.

There has always been the argument that the more one knows about how and why, the better or safer one can operate. It’s kind of hard to disagree. It is just that when actually operating, it is too late to wonder how they built the thing. I have never heard of anyone worrying about that in flight.

Most of the technical aspects of design theory have been added to ground schooling knowledge in attempts to make flight safer. Over the past 40-50 years the typical management and regulator has become more and more intellectually sophisticated. Their focus has been increased knowledge of why, but the airplane is still the same machine as always.

There is so called increased complexity of modern machines and added instrumentation in attempts to improve the ability to do more with them.

The problem is, they are still the same machines. The operation and control is the same. The first 5-10 hours of training should teach all the control that will ever need to be known. After that, it’s what to do with the machine.

Yes, the more sophisticated instrumentation and power systems allow flying faster, further and in more complicated conditions…the control of the machine remains the same.

I just cannot find a book that correctly explains the basics of machine control. 

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Axes of Rotation and Center of Gravity

Now it’s rotation about the axes. There is much writing about the importance of weight and balance. One can’t argue that. The loading of an aircraft must be within the designed limits to allow safe flight.

Weight and balance is based on the mass weight of the static aircraft and the placement of the center of gravity of this mass is required to be within certain limits as required by control design.

At the same time, understand that for positive stability it requires the center of mass to be slightly forward of the center of aerodynamic lift.

With all the consideration and importance of loading within design limits, it really has little to do with flight.

The basis of loading placement limits is on the design ability of the horizontal stabilizer and elevator to safely control the angle of attack pitch for this particular aircraft.

That’s fine. Now at takeoff, we know the elevator can cause enough load/lift over its moment arm to balance the aircraft safely for flight.

Immediately upon becoming airborne, there become small load or lift forces related to the elevator position. These forces are acting outward from the tail area and add or reduce the total load of the aircraft.

A typical situation is some small loading at the elevator. This loading causes an effective center of gravity for the flight in its current condition. This is the center of loading affecting the flight.

The axes of rotation have moved slightly.

Don’t even think about this. A pilot has no way of knowing when or where this occurs and doesn’t care. This is an engineer consideration for design. Just be aware all the things you read about center of gravity for flight are not necessarily so. 

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Energy and Energy Sources

Energy is the ability of a source to cause work (force times distance) and comes from position, heat, or chemistry as potential energy, and from motion as kinetic energy.

You cannot create or destroy energy, but only convert it from one form to another. Potential energy transforms to kinetic energy and kinetic energy transforms to potential energy.

Potential energy is a function of the position or content of an object, and kinetic energy a function of the motion of its mass. This is a simplification of the mechanics of energy used for discussion of flight performance.

These manifestations of energy, motion and position, allow understanding the response when maneuvering an aircraft. For flight, reference is to an arbitrary aircraft attitude controlled above the surface.

Potential energy is energy in a form not yet released. Fuel and altitude are sources of potential energy. Burning fuel causes rapid expansion of gases causing motion by reaction as thrust through a jet engine or a reciprocating engine and propeller. Gravity is the natural attraction of earth’s mass to the aircraft mass and causes motion (thrust) directed toward the surface of the earth.

Kinetic energy is mass in motion, reacting from these thrust forces. The motion of your airplane is its kinetic energy.

Energy is not consumed, but only changes state. Potential energy becomes kinetic energy plus frictional losses of heat energy. Aircraft kinetic energy in flight becomes potential energy of altitude (climbing or zooming up), and in turn again becomes kinetic energy through descent (diving).

Engines develop this thrust force by burning fuel to extract the potential energy. The resulting energy of burning fuel is expansion of gases pushing a piston, turning a crankshaft and propeller to accelerate the mass-of-the-air. The accelerating of mass-of-the-air (blasting air) causes a reactive thrust force of aircraft motion, kinetic energy.

This all occurs with large heat energy losses.

Similarly, the jet engine develops thrust force by burning fuel. The resulting energy is expansion of gases turning a turbine and compressor, accelerating the mass-of-the-air. Thrust is the reaction to accelerating this mass-of-air (blasting air).

Remember; thrust is a vectored force directed to push (pusher) or pull (tractor) transforming into kinetic energy of the machine’s motion. All aircraft have engines for developing the power to generate thrust directed to cause motion (kinetic energy).

Your aircraft at altitude is a source of potential energy. The aircraft weight as affected by gravity’s acceleration and directed by the flight controls produces thrust force effect…with descent.

Velocity of the aircraft mass is its kinetic energy. The air friction and displacement resistance to aircraft momentum is a decelerating frictional effect causing drag and slowing.

Flight control is energy management directing the conversion of energy from one state to the other.

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How Airplanes Fly

What makes an aircraft fly? Money!

How does an airplane fly?

Do not worry too much about how. Engineers designed your airplane to be aerodynamic and manufacturers built it to fly. It is a big chunk of aluminum sitting there. You cannot change that. You just deal with it. If started and turned loose, it could fly by itself.

What is all the fuss about?

Your job, as the pilot, is the utilization of energy through thrust to enable safe, controlled flight. Your airplane uses the potential energy from fuel, converted by the engine for power, to develop thrust to attain and sustain the kinetic energy of motion for flight at altitude where there becomes related potential energy of gravity from position.

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Transfer of energy

It is the thrust, from the reaction of blasting large volumes of the mass-of-the-air, which pushes or pulls your aircraft.

Usual discussion in the industry has always related to jet engine motivation with thrust and reciprocating engine motivation with power. In both cases, it is the thrust. However, this book will use the term power interchangeably for thrust as they both cause the same results. Power causes thrust.

Both Engine and gravity power convert potential energy into thrust. The reactive force of developing thrust causes acceleration. That becomes the kinetic energy of motion. If accelerated to sufficient indicated-airspeed, the aircraft becomes airborne.

Just as in the beginning, you start the engine and turn it loose. All you do as the pilot is guide the thing down the runway with a high power setting allowing acceleration.

When attaining sufficient indicated-airspeed to generate lift greater than the weight, the airplane lifts becoming airborne.

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Now What is Going to Happen?

First, you become airborne. Well, the design of the airplane is to do that, if it goes fast enough. Now it is in the air. It requires control and direction to go somewhere. It needs to climb to some higher altitude, so it does not run into anything.

You have lots of power. You became airborne after accelerating to a selected indicated-airspeed. Now you are climbing. You are converting excess energy of engine thrust climbing to increase the gravitational potential energy of altitude.

We now have available power sources from both, the engine and gravity. The engine consumes potential energy of fuel with combustion causing thrust for motion (kinetic energy), and gravity consumes potential energy of altitude causing thrust for motion (kinetic energy) with descent.

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Becoming Airborne; Flight

Is your aircraft indicated-airspeed still accelerating?


The moment you became airborne the airplane quit accelerating. Now you are just climbing at the indicated-airspeed at which it left the ground.

Why is that? Why did it quit accelerating?

You entered a new world…flight.

The instant of becoming airborne, your aircraft begins operating in three dimensions. It can now go up and down.

Back on the runway, it was almost like driving a car. You just pushed the throttle to accelerate but steered with the rudder pedals.

Now, it has changed to flight with three dimensions of travel and you will remain in flight, until landing back on the surface. The instant of becoming airborne, the generated aerodynamic lift has become equal to the weight of the airplane. With the initial takeoff power unchanged, there is now sustaining thrust for balanced lift and also some excess-thrust causing climb

In flight, the elevator-pitched angle of attack above the direction of motion does not allow acceleration. This means when the angle-of-attack remains constant the excess lift component of thrust is causing climb angle and the excess forward component of thrust sustains the increasing altitude over time. There is the direction of motion, both horizontal, and away from the surface.

The aircraft mass has attained a balance of lift force with gravity force. It does not weigh anything! It is at a sustained indicated-airspeed of motion at which all forces are balanced. Thrust equals drag and lift equals load. The excess thrust-component forward is sustaining the travel at a climb angle, so altitude is increasing.

The indicated-airspeed is constant at an elevator-pitched angle of attack generating the aerodynamic lift sustaining the aircraft load. The engine thrust-component lift and the elevator aerodynamic load/lift are balancing the climb attitude.

The excess power thrust-component forward is causing the aircraft climb at a rate commensurate to the excess applied power.

In a climb attitude there is increased drag. The actual excess engine power required for a climb must be sufficient to sustain both, the increased vertical lift for climb angle and increased drag. The aircraft will then be at its elevator-pitch trimmed constant indicated-airspeed in a direction of motion angled away from the surface with increasing altitude.

The increased drag from climb angle is the rearward component of gravity. At a six-degree climb angle, the rearward component of gravity is .1 (sine 6°=.1) times the mass weight of the aircraft. For a 1600-pound aircraft, that is 160 pounds of drag opposite the direction of motion. At Vy angle of attack of 6 degrees plus the climb angle, there is now a total of 320 pounds of drag opposite the direction of motion. The twelve-degree attitude, 6-degree Vy and 6-degree climb angle is sustained with 160 pounds of sustaining thrust and 160 pounds of excess thrust from the engine and propeller.


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Gravity Effects

Both, Thrust and Gravity cause lift. If you did not add thrust when maneuvering, what would happen?

You would descend, wouldn’t you?

Why is that?

Well, gravity is always out there, and it is a substantial force, directed vertically from the center of mass to the surface. If your vertical component of lift opposing gravity is not equal to the weight of the machine, then gravity will add to maintain the necessary sustaining thrust for the indicated-airspeed but you are going to descend…every time.

The coordinating thrust sources for maneuvering come from the engine and gravity. If there is not enough thrust available from the engine, gravity coordinates the sustaining force, but always with descent.

Gravity will always balance the engine thrust to the sustaining indicated-airspeed for the current aircraft angle-of-attack and always by burning altitude with descent.

For this reason, there is restricted maneuvering of most aircraft because of their limited engine power.

You can maneuver the aircraft into any attitude, but can only attain or sustain that attitude if there is sufficient thrust.

An attitude that engine thrust alone cannot sustain will result in descent from gravity , causing the aircraft to continue to fly, but at some different attitude and altitude.

You can do nothing. If unable to sustain the airplane indicated-airspeed because of engine generated thrust limitations, gravity does it for you, and always with descent.

It requires care when utilizing the downward directed gravity force. The acceleration force of gravity is very large.

The equivalent vertical thrust of gravity is equal to the weight of the aircraft. The normal maximum rated engine thrust of your aircraft is probably not even one-third the aircraft weight. Gravity is very strong.

If you insist on manually forcing control into an attitude the machine does not have the thrust to sustain, it will decelerate into a stall and then still descend, uncontrolled!

In all cases, you will descend. Just be sure there is altitude below.

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Zoom and Dive

Exercises in zoom and dive will allow a pilot to become familiar with the coordination of energy exchanges in different regimes of flight.

Simple wings level constant powered zoom can begin from a beginning trimmed level indicated-airspeed. Input of aft elevator-pitch zooms the aircraft up allowing the indicated-airspeed to approach minimum (critical angle of attack). Releasing the elevator-pitch allows the nose to drop, and the resulting dive allows indicated-airspeed to resume toward the original elevator trimmed indicated-airspeed.

A second procedure could be with added climb power, zooming again following the same procedure as before. The release of elevator-pitch will allow a diving descent, and now will have to be coordinated with reducing the power back to the original level flight sustaining thrust. The power has caused greater altitude increase during the zoom and rapid acceleration in the dive.

This has been an energy exchange of kinetic energy to potential energy of increased altitude then exchanged back to the original kinetic energy of motion.

Continuing this type maneuvering, with initial diving by pushing the elevator-pitch for descent, there will be descent with a rapid increase of indicated-airspeed. Note how rapidly acceleration occurs from the large thrust effect of gravity added to the sustaining engine thrust.

As indicated-airspeed increases toward Vne, gradual release of the elevator-pitch input will allow the increased kinetic energy in the aircraft to cause climb and reduce indicated-airspeed back toward the starting indicated-airspeed and altitude.

Note that with the different energy losses involved, it will not regain the original altitude. The set elevator trimmed angle of attack and related sustaining engine thrust will resume the previous indicate-airspeed, just at a different altitude.

The two types of maneuvers zoom/dive and dive/zoom have different results. With an initial zoom, the aircraft returns to its original altitude. The initial dive maneuver has both engine and gravity thrust adding with considerable acceleration and related energy loss throughout so does not recover to the original altitude.

Turning maneuvers of zoom/dive and dive/zoom will show similar behavior. These turning maneuvers will allow familiarity with the control required in different steep angled turns.

A useful turning maneuver is a technique of climb and dive turning. It will enhance a pilots understanding of energy management for control to become proficient in altitude-exchange turns.

Continuing this into steep banked turning and practiced in different powered conditions, from maximum to idle, this turning is useful in unusual or emergency very low altitude maneuvering situations.

The turn begins by using full engine power into a climbing, banked attitude while allowing the nose to begin dropping as the banked angle increases. Pitch control of the aircraft allows the nose to drop through the horizon as indicated-airspeed approaches minimum, similar to entry of the lazy-eight maneuver. Coordinated rudder at this time will side-pitch the nose down, and indicated-airspeed will begin increasing.

Recovery of descent and heading is coordinated to roll out of the turn leveled at the desired altitude and heading, and with the power coordinated to sustain the original indicated-airspeed.

An exercise beginning from level flight trimmed hands-off and with only rudder steering for turns, without touching the control wheel, the aircraft can be slowly banked into a steep turn. Descent will occur with increasing descent rate. Reversing rudder as the wings level the aircraft will recover itself and start a climb. This has become a lazy-8 maneuver.

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High Altitude Stall Recovery

Stall recovery at any time requires release of aft elevator input to allow increasing indicated-airspeed.  Often in slowed flight, the elevator trim is set to maintain a higher angle of attack.  This requires positive pilot input to assure positive reduction of angle of attack.

Response time and altitude loss at high altitudes, due to the reduced density can require a minimum altitude loss of fifteen hundred or more feet and the related time for this change to occur.

The aircraft is falling in the stalled condition and if not allowed to increase indicated-airspeed with reduced angle of attack, the aircraft will quickly accelerate into a high-speed stalled descent. This continued stall is occurring because the pilot is holding the the control wheel aft. If that happens with reduced power, the ram effect into the engines can quickly create large nose-down pitch forces.

Recovery then can only occur with added engine thrust which eliminates the ram effect and simultaneously causes thrust-component lifting, pitching up, at the engine attachments.

There will now be that portion of thrust-component lifting again contributing to angle of attack for a new reduced indicated-airspeed as called for by the elevator position.  This procedure requires coordination of down elevator pitch with increased power.

In all cases, at higher altitudes in low-density air, this takes unusual amounts of time and altitude for recovery.

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