da40 stable unstable and abnormal approaches

DA40 – STABLE, UNSTABLE & ABNORMAL APPROACHES

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Introduction

Statistics indicate that a significant number of accidents occur during approach and landing.

This lesson covers:► “Stabilized Approach” concept ► How to recognize Abnormal and Unstable approaches.


Elements of a Stabilized Approach

1. Aircraft is on the correct flight path.

2. Only small heading and pitch changes are required to maintain correct flight path.

3. Aircraft is maintaining target airspeed.

4. Aircraft is in proper landing configuration.

5. Descent rate is appropriate to ground speed.

6. Power setting is appropriate for aircraft configuration.

7. All briefings and checklists have been performed.

8. ILS approaches are flown within 1 dot (LOC & GS).

9. Visual approaches are ‘wings level’ at 500 ft Height Above Touchdown (HAT).

10. Approaches with unique features require special briefing.


Stabilized Approach Definition

A stabilized approach is any approach that incorporates the elements just described.

In short, the airplane:► Is on correct flight path, at correct airspeed and in correct

configuration► Has power setting and descent rate appropriate to

configuration and ground speed► All briefings and checklists are complete by height above

touchdown specified in SOPs.


Stabilized Approach Concept 1

A stabilized approach is characterized by a constant angle and rate of descent from a specific altitude to the point where the landing maneuver begins.

Other characteristics are proper airspeed and power control, an appropriate descent rate and correct ground track.



Touchdown

Aiming point (descent angle intersects ground)

Distance traveled in flare



Too high – Above glide slope

Too low – Below glide slope

Proper angle – On glide slope

• When moving straight towards an object or point, it appears stationary.• Aiming point is point that does not move in the windscreen. • Other points appear to move outward as you approach aiming point.• Important pilot skill when landing:

– Ability to accurately determine True Aiming Point from any distance out on final approach.



A stabilized approach is facilitated if true aiming point coincides with desired touchdown point.

With a constant airspeed, glidepath is adjusted with power.

Airplane must be configured for landing and trimmed for approach airspeed.



Target is to complete briefings and stabilize the approach by 500 ft HAT:► Go-around is mandatory if approach not stabilized by 200 ft

HAT.

In an airliner, all appropriate briefings and checklists should be complete and approach stabilized before:► 1,000 ft HAT in Instrument conditions► 500 ft HAT in Visual conditions.


Unstable Approach Definition

Unstable approach; any approach where there are significant variations in: ► Airspeed or power setting► Approach angle► Descent rate► Ground track.

Approach is also considered unstable if:► Airplane is not properly configured► Briefings and checklists not complete by target height.


Why Approaches Become Unstable

An approach can be come unstable due to:► Failure to establish appropriate descent power setting► Failure to establish appropriate descent angle and rate► Failure to properly trim airplane in final approach► Improper use of elevator or power to manage glidepath► Over-controlling airplane► Failure to complete checklists in timely manner► Improper correction for wind drift.


Configure the airplane for a go-around / missed approach:• Apply full power• Control pitch attitude change• Establish positive rate of climb• Accelerate to Vy (66 knots)• Set Flaps T/O• Accelerate to 73 knots• Set Flaps UP• Trim airplane for normal climb.

Climb to published Missed Approach Altitude or VFR Pattern Altitude.

At 800 ft AGL call for “Flaps Up, After Takeoff Checklist”

Establish climb at Vy (73 Kt)

IFR Approach:• At DH/MDA commit to landing or execute the Missed

ApproachVFR Approach:

• Commit to landing or execute a go-around if required• PF “Go-Around”

Unstable Approach Solution

• Only one solution to unstable approach: Immediately execute a go-around!


Abnormal Approaches

Abnormal approaches different from unstable approaches.

We will discuss causes of abnormal approaches; and what can we do to correct the situation.

If at any time, you doubt safety of approach, execute immediate go-around.


Abnormal Approach Causes

An equipment failure may require an abnormal approach procedure, but if properly executed, the approach will be fully stabilized.

An abnormal approach can become an unstable approach.

LANDING WITH A FLAT MAIN TIRE1. Approach ……………………………………………………….

NORMAL2. Wing Flaps ………………………………………………………….

FULL3. Touchdown …………………………………..

GOOD MAIN TIRE FIRST a. Hold airplane off flat tire as long as possible with aileron control

4. Directional Control …………………………………………..MAINTAIN a. Use brake on good wheel as required.


Abnormal Approaches

Abnormal Approach conditions:► Flaps UP; approach and landing► Landing without elevator control► Landing with flat main wheel tire.


Airliner Abnormal Approaches

The more complex and technically advanced an airplane is, the more things can go wrong.

In an airliner, some of the things that characterize an abnormal approach are:► One engine inoperative► Autospoilers or autobrakes inoperative► Flap asymmetry► Elevator trim problems► Contaminated runways / braking action problems.


Flaps UP Landing

Landing with flaps UP is not a major problem:► Trim for normal approach airspeed► Control descent angle and rate with power► Use normal 3° glidepath► Less power is required because there is less drag with flaps

retracted (fully UP)► A longer final approach may be required.


Trim for level flight at 65 knots IAS with flaps set to Takeoff.

Do not change the elevator trim setting:► Control glide angle by adjusting power.

To round out for landing, adjust elevator trim towards full nose up as power is reduced to idle.

Landing Without Elevator Control


Landing With a Flat Tire

Use these procedures if a landing must be made with a flat main or nose tire.

Landing with a Defective Tire on the Main Landing Gear

CAUTION A defective (e.g. burst) tire is not usually easy to detect. The damage normally occurs during takeoff or landing, and is hardly noticeable during fast taxing. It is only during the rollout after landing or a lower taxiing speeds that a tendency to swerve occurs. Rapid and determined action is then required.

1. Advise ATC 2. Land the airplane at the edge of the runway that is located on the side of the intact tire, so

that changes in direction which must be expected during rollout due to the braking action of the defective tire can be corrected on the runway.

3. Land with one wing low. The wing on the side of the intact tire should be held low. 4. Direction should be maintained using the rudder. This should be supported by use of the

brake. It is possible that the brake must be applied strongly – if necessary to the point where the wheel locks. The wide track of the landing gear will prevent the airplane from tipping over a wide speed range. There is no pronounced tendency to tip even when skidding.

CAUTION


Common Approach / Landing Mistakes

Landing Mistakes include:► Final approach too low or too high ► Overshooting final approach course ► Airspeed too slow► Flare too low, too rapid or too high ► Floating while in landing flare► Ballooning or bouncing► Porpoising or wheelbarrowing► Touching down in a drift or crab.

Many flight path deviations can be corrected by prompt action.

Remember, if you doubt that the approach can continue safely, execute a go-around.


Causes:► Turn to final approach started

too late► Incorrect compensation for

tailwind on base leg► Insufficient bank angle during

turn to final.

Caution:► DO NOT attempt to correct this

error, a fatal stall/spin may result.

Remedy:► Execute a go-around.

Overshooting the Final Approach Course


• Caution:– Do not increase pitch without

increasing power– Do not retract flaps.

• Remedy:– Add considerable power– Maintain airspeed– Increase pitch– Regain correct glide path.

Final Approach Too Low

Intercept normal glidepathResume normal approachWrong (dragging it in with high

power / high pitch altitude)

Add power, Nose up, Hold altitudeNormal approach path

• Causes:– Insufficient power– Flaps extended early– Base leg too low– Wind speed misjudged.


Final Approach Too High

No flaps

Full flapsSteeper descent angle

Increased rate of descent

• Caution:– Trim airplane to maintain target

airspeed.• Remedy:

– Increase flap extension– Reduce power– Adjust pitch to maintain target

airspeed.

• Causes:– Insufficient descent rate– Too much power– Base leg too close to runway

threshold– Insufficient flap extension.


Airspeed Too Slow

• Causes:– Inattention to target airspeed– Incorrect trim setting– Attempting to control descent

rate with pitch instead of power.

• Remedy:– Increase power to accelerate and

reduce sink rate– Execute go-around.


Flare Too High

• Causes:– Poor height judgment– Flare too rapid– Excessive nose-up pitch

change.

• Remedy:– Hold pitch attitude constant or

decrease slightly– Add small amount of power.


• Causes:– Poor height judgment– Pulling the elevator control

backward too fast.

Flare Too Low / Too Rapid

• Caution:– Sudden increase in angle of

attack may cause accelerated stall

– May result in hard landing and/or bounce.

• Remedy:– Prompt, positive increase in

power– May require go-around.


Floating While in Landing Flare

• Causes:– Excessive airspeed on final

approach– Diving at runway if too high

on final.

• Remedy:– Proper airspeed control– Careful pitch control and height

judgment as speed dissipates– Execute go-around.


Ballooning

• Causes:– Misjudging sink rate– Too rapid flare– Excessive airspeed on final

approach.

• Remedy:– Hold landing attitude– Allow airplane to decelerate– Apply power as necessary or

execute go-around.


Bounced Landing

Small AOA

Decreasing AOA

Rapid increase in AOANormal AOA

• Causes:– Excessive sink rate at

touchdown– Insufficient flare and improper

touchdown attitude.

• Remedy:– Adjust pitch to obtain landing

attitude– Apply power as necessary or

execute go-around.


• Causes:– Improper recovery from

bounced landing– Improper airspeed control– Inadequate flare resulting in

nose wheel touching first.

Porpoising

Decreasing AOA

Rapid increase in AOA

Normal AOA

Decreasing AOA

Rapid increase in AOA

Normal AOA

• Remedy:– Increase pitch and add power– Recover from bounce or execute

go-around.


Wheelbarrowing

• Causes:– Insufficient flare resulting in

touching down on nose wheel– Too much speed– Forcing airplane onto runway

by pushing nose down.

• Remedy:– Reduce power– Smoothly apply back pressure on

elevator– Execute go-around.


Touchdown in a Drift or Crab

Weight

Inertia force

Force resisting side motion

C of G

• Cause:– Improper correction for a

crosswind.

• Caution:– Ground loop may result if drift or

crab is excessive.• Remedy:

– If slight, aileron into wind, use rudder and brake to gain directional control

– If severe, execute go-around.


Summary

A superior pilot uses superior knowledge and judgment to avoid the necessity of demonstrating superior skill!

DA40 – STABLE, UNSTABLE & ABNORMAL APPROACHES

da40 stable unstable and abnormal approaches

Documents

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approach altitude

missed approach vfr

unstablean approach

safety of approach

ifr approach

abnormal approach procedure

unstable approaches