SLOW FLIGHT

Slow Flight Lesson by wifiCFI


Objective

To determine that the applicant exhibits satisfactory knowledge, risk management, and skills associated with maneuvering during slow flight.

Knowledge

The applicant demonstrates understanding of: 

Aerodynamics associated with slow flight in various aircraft configurations, to include:

The relationship between angle of attack, airspeed, load factor, power setting, aircraft weight and center of gravity, aircraft attitude, and yaw effects.

Risk Management

The applicant demonstrates the ability to identify, assess and mitigate risks, encompassing: 

Inadvertent slow flight and flight with a stall warning, which could lead to loss of control. 

Range and limitations of stall warning indicators (e.g., aircraft buffet, stall horn, etc.). 

Failure to maintain coordinated flight. 

Effect of environmental elements on aircraft performance. (e.g., turbulence, microbursts, and high density altitude). 

Collision hazards, to include aircraft, terrain, obstacles, and wires. 

Distractions, loss of situational awareness, and/or improper task management.

Slow Flight (AFH C9)

Slow flight is when the airplane AOA is just under the AOA which will cause an aerodynamic buffet or a warning from a stall warning device if equipped with one. 

A small increase in AOA may result in an impending stall, which increases the risk of an actual stall. In most normal flight operations the airplane would not be flown close to the stall-warning AOA or critical AOA, but because the airplane is flown at higher AOAs, and thus reduced speeds in the takeoff/departure and approach/ landing phases of flight, learning to fly at reduced airspeeds is essential. 

In these phases of flight, the airplane’s close proximity to the ground would make loss of control catastrophic; therefore, the pilot must be proficient in slow flight.

The objective of maneuvering in slow flight is to understand the flight characteristics and how the airplane’s flight controls feel near its aerodynamic buffet or stall-warning. 

It also helps to develop the pilot’s recognition of how the airplane feels, sounds, and looks when a stall is impending. 

These characteristics include: 

Degraded response to control inputs 

Difficulty maintaining altitude

Practicing slow flight will help pilots recognize an imminent stall not only from the feel of the controls, but also from visual cues, aural indications, and instrument indications. 

For pilot training and testing purposes, slow flight includes two main elements: 

Slowing to, maneuvering at, and recovering from an airspeed at which the airplane is still capable of maintaining controlled flight without activating the stall warning, 5 to 10 knots above the 1G stall speed is a good target.

Performing slow flight in configurations appropriate to takeoffs, climbs, descents, approaches to landing, and go-arounds. 

Slow flight should be introduced with the airspeed sufficiently above the stall to permit safe maneuvering, but close enough to the stall warning for the pilot to experience the characteristics of flight at a very low airspeed.

Flying below L/D Max (minimum drag speed) or Back Side of the Power Curve

Larger inputs in power or reducing the AOA will be required for the airplane to be able to accelerate. 

Since slow flight will be performed well below L/DMAX, the pilot must be aware that large power inputs or a reduction in AOA will be required to prevent the aircraft from decelerating. 

It is important to note that when flying on the backside of the power curve, as the AOA increases toward the critical AOA and the airplane’s speed continues to decrease, small changes in the pitch control result in disproportionally large changes in induced drag and therefore changes in airspeed. 

As a result, pitch becomes a more effective control of airspeed when flying below L/DMAX and power is an effective control of the altitude profile.

Performing the Maneuver- Set Up

Slow flight should be practiced in straight-and-level flight, straight-ahead climbs and climbing medium-banked (approximately 20 degrees) turns, and straight-ahead power off gliding descents and descending turns to represent the takeoff and landing phases of flight. 

Slow flight training should include slowing the airplane smoothly and promptly from cruising to approach speeds without changes in altitude or heading, and understanding the required power and trim settings to maintain slow flight. 

It should also include configuration changes, such as extending the landing gear and adding flaps, while maintaining heading and altitude.

Performing the Maneuver- Maneuvering

When the desired pitch attitude and airspeed have been established in straight-and-level slow flight, the pilot must maintain awareness of outside references and continually cross-check the airplane’s instruments to maintain control. 

The pilot should also practice climbs and descents by adjusting the power when stabilized in straight-and-level slow flight. 

The pilot should note the increased yawing tendency at high power settings and counter it with rudder input as needed. 

Performing the Maneuver- Recovery

To exit the slow flight maneuver, follow the same procedure as for recovery from a stall: apply forward control pressure to reduce the AOA, maintain coordinated flight and level the wings, and apply power as necessary to return to the desired flightpath. 

As airspeed increases, clean up the airplane by retracting flaps and landing gear if they were extended. 

A pilot should anticipate the changes to the AOA as the landing gear and flaps are retracted to avoid a stall.

Private Pilot ACS Standards

Clear the area. 

Select an entry altitude that will allow the Task to be completed no lower than 1,500 feet AGL (ASEL) or 3,000 feet AGL (AMEL). 

Establish and maintain an airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in a stall warning (e.g., aircraft buffet, stall horn, etc.). 

Accomplish coordinated straight-and-level flight, turns, climbs, and descents with landing gear and flap configurations specified by the evaluator without a stall warning (e.g., aircraft buffet, stall horn, etc.). 

Maintain the specified altitude, ±100 feet; specified heading, ±10°; airspeed +10/-0 knots; and specified angle of bank, ±10°.

Commercial Pilot ACS Standards

Clear the area. 

Select an entry altitude that will allow the Task to be completed no lower than 1,500 feet AGL (ASEL) or 3,000 feet AGL (AMEL). 

Establish and maintain an airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in a stall warning (e.g., aircraft buffet, stall horn, etc.). 

Accomplish coordinated straight-and-level flight, turns, climbs, and descents with landing gear and flap configurations specified by the evaluator without a stall warning (e.g., aircraft buffet, stall horn, etc.). 

Maintain the specified altitude, ±50 feet; specified heading, ±10°; airspeed +5/-0 knots; and specified angle of bank, ±10°.

Common Errors

Failure to adequately clear the area 

Inadequate back-elevator pressure as power is reduced, resulting in altitude loss

Excessive back-elevator pressure as power is reduced, resulting in a climb followed by a rapid reduction in airspeed 

Insufficient right rudder to compensate for left yaw 

Fixation on the flight instruments 

Failure to anticipate changes in AOA as flaps are extended or retracted 

Inadequate power management 

Inability to adequately divide attention between airplane control and orientation 

Failure to properly trim the airplane 

Failure to respond to a stall warning

FAA Sources Used for This Lesson

Private Pilot Airmen Certification Standards

Commercial Pilot Airmen Certification Standards

Airplane Flying Handbook (AFH) Chapter 9

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