Stabilized Constant Descent Angle NPA’s

Overview• What is a Stabilized Constant Descent Angle

(SCDA) Non- Precision Approach (NPA)?• Why do we need it?• How do we fly it?• Considerations?

Legal-Applicability• CBAAC No. 0238 is primarily applicable to

operators under Subparts 703, 704 and 705 of the Canadian Aviation Regulations (CARs) who may be authorized through Ops Spec 019, 303, or 503 respectively to conduct SCDA NPA procedures at reduced approach ban visibility values RVR, or ground visibility at aerodromes south of 60 degrees North Latitude (60°N Lat), and to use the Minimum Descent Altitude (MDA) as a Decision Altitude (Height) DA(H).

SCDA Training Program• The operator should ensure that flight crews

receive ground and simulator or flight training that addresses SCDA NPA procedure proficiency.

• The operator should have SOPs incorporating SCDA NPA procedures.

Background• Precision Approach

– An approach with both lateral and vertical information used to guide the aircraft to a Decision Height

• Non Precision Approach– An approach with only lateral information

used to guide the aircraft to a minimum descent altitude

Decision Height• A specified height in the precision approach

or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach to land has not been established.

Minimum Descent Altitude• The altitude above sea level (ASL) specified

in the Canada Air Pilot (CAP) or the route and approach inventory for a nonprecision approach, below which descent shall not be made until the required visual reference to continue the approach to land has been established.

Stabilized approach• a final approach flown to achieve a constant

rate of descent, at an approximate 3 degree descent flight path angle, with stable airspeed, power setting, and attitude, with the aircraft configured for landing.

Types of NPA’s• Step Down• Constant Descent Angle • Stabilized Descent Angle

Traditional NPA• Step Down Technique

– Also referred to as “Dive and Drive”MAP FAF

What is a CDA?• means stabilized constant-descent-angle non-

precision approach.MAP FAF

What is a SCDA?• means stabilized constant-descent-angle non-

precision approach.MAP FAF

The Approach

• Initial Approach– From the IAF to the IF (if defined)– Obstacle clearance 1,000 ft.

• Intermediate Approach– From the IF to the FAF – Obstacle clearance 500 ft.

• Final Approach– From the FAF to the MDA– Obstacle clearance 200 ft.

Traditional NPA Workload

FAF

Final Approach Segment

3.3 nm

Stabilized Constant Descent Final Approach Workload

FAF

Final Approach Segment

3.3 nm

Advantages of the SCDA• Increased safety by employing the concepts

of stabilized approach criteria and procedure standardization.

• Improved pilot situational awareness (SA) and reduced pilot workload.

• Improved fuel efficiency by minimizing the low-altitude level flight time.

Advantages of the SCDA• Reduced noise level by minimizing the level

flight time at high thrust settings. • Procedural similarities to precision approach

operations. • Reduced probability of infringement on

required obstacle clearance during the final approach segment.

Statistics*

*Flight Safety Foundation Approach and Landing Accident Reduction Task Force

Stabilized Approach• Aircraft on the correct flight path• Only minor changes required to maintain the

correct flight path• Airspeed between Vref and Vref +20 and

power properly set• Aircraft properly configured for landing• Sink rate no greater than 1,000 fpm• All briefings and checklists complete

SCDA Criteria• The approach is flown to straight-in minima.• The approach design should permit a final

approach segment descent angle of 2.9 to 3.5 degrees.

• The final approach course shall not be more than 15 degrees from runway centreline.

Approach Considerations• Don’t forget temperature corrections • Take minimum altitudes at step-down fixes

into account when planning the final descent angle

Missed Approach• When flown correctly, the position where a

missed approach is commenced following an SCDA NPA to MDA will occur before the published MAP.

• The missed approach climb will normally occur some distance before reaching the published MAP.

Missed Approach

• Missed approach can begin before the MAP• Missed approach must begin at the MAP• For obstacle clearance, delay any turns

stated in the published missed approach procedure until the aircraft crosses the MAP

Missed Approach Profile on Step Down

Missed Approach Profile on a SCDA

Missed Approach Profile on a CDA

Missed Approach• Time required for a decision (reaction time);• Rate of descent at commencement of the

missed approach;• Pilot technique;• Aircraft performance; and• Baro altimeter lag.

CAP depiction

Questions???