Slow Flight, the Twenty Seventeen Rule Change, and Flying the Back Side of the Power Curve Without the Stall Horn in Your Ear

Slow flight changed in 2017, and many pilots never updated how they fly it. Under the current Airman Certification Standards (ACS), slow flight is flown at an airspeed just above the stall warning - roughly five to ten knots above where the horn or light activates - so the warning stays quiet. The old Practical Test Standards (PTS) did the opposite, asking you to fly with the stall horn blaring, and flying it that way on a checkride today will cost you.

What Changed in the 2017 Slow Flight Rule?

For decades, slow flight meant slowing until the stall warning was screaming and then maneuvering - turns, climbs, descents - with the horn on. The old PTS required an airspeed where any further increase in angle of attack or load factor would cause an immediate stall. The horn was the target.

In 2017, the FAA replaced the PTS with the ACS, and slow flight flipped. Now you fly at a speed where the stall warning is not activated - about five to ten knots above where it triggers. The horn is no longer your target; it’s your warning that you’ve gone too slow and need to add a little speed back.

Why Did the FAA Make This Change?

The FAA looked at the accident data, and loss of control in flight was - and remains - the number one killer in general aviation. The old method trained pilots to spend long stretches ignoring the stall warning, conditioning them to tune out the exact sound designed to save their lives.

That’s backwards from what you want close to the ground. The current standard teaches you to treat the horn as a hard floor: if it goes off, you’ve gone too deep into the regime, and you recover a touch of airspeed.

What Does Slow Flight Actually Teach You?

The point was never to prove you can dance on the edge of a stall. It’s to teach you how the airplane feels and behaves when it’s slow, dirty, and working hard - which is exactly how it feels on final approach. Every landing you make is a slow flight maneuver.

Understanding the Back Side of the Power Curve

In cruise, speed and power move together: add power to go faster, reduce power to go slower. That’s the front side of the power curve.

In the slow flight regime, it inverts. The airplane is at such a high angle of attack that induced drag is enormous. Pitch up to hold altitude and you slow down, drag climbs even more, and you need more power just to keep from sinking. Down here, power controls altitude and pitch controls airspeed.

This is the single biggest thing students fight. Instinct says pull back to stop a descent, but pulling back only makes you slower, draggier, and sinkier. The fix for a sink is a handful of throttle, not a handful of yoke. It’s the same trap that catches pilots on a low, dragged-in approach who haul back instead of adding power - and mush into the ground short of the runway, or worse, stall-spin turning base to final.

How Do I Fly Slow Flight to the Current Standard?

1. Clear the area. Two clearing turns, ninety degrees each way, eyes outside for traffic. Pick an altitude with room to recover - at least 1,500 feet AGL for practice, more while you’re getting comfortable. Examiners want to see you clear the area every single time.

2. Set up the airplane. Reduce power, add carb heat if your airplane needs it and conditions call for it, and add flaps in stages if the maneuver calls for landing configuration (it often does). As you slow, feed in back pressure to hold altitude, add right rudder as power comes up, and trim. An out-of-trim slow flight maneuver is one you’ll fight the whole time.

3. Establish the airspeed. Sneak down until you hear the first chirp of the horn, then add a hair of power and pitch to back off until it goes quiet and stays quiet. In a trainer like a Cessna 172 or Piper Cherokee, that often lands somewhere in the mid-forties of knots - but fly your airplane, at your weight, in your configuration. Find where the horn stops and live just above it.

4. Hold it. Maintain altitude, heading, and airspeed at once, on the back side of the curve where the controls feel like mush. Pitch for airspeed, power for altitude, rudder to stay coordinated. When the examiner asks for a turn, climb, descent, or flap change, do it while holding all of that together.

What Are the Slow Flight Tolerances?

For the private pilot ACS, you hold:

• Altitude: ±100 feet
• Heading: ±10 degrees
• Airspeed: +10 knots and −0 knots

Look hard at that airspeed tolerance. Plus ten, minus zero. You can be a little fast, but you cannot be one knot slow - because slow is toward the stall. The tolerance itself is telling you which way the danger lives.

What Are the Most Common Slow Flight Mistakes?

Chasing altitude with the yoke. You sink, you pull, you sink more. On the back side of the curve, the throttle is your altitude control - your hand should reach for it before the yoke.

Forgetting the rudder. High power, low airspeed, and high angle of attack mean maximum left-turning tendency. Asleep feet mean a skidding, uncoordinated airplane - the exact setup that turns a stall into a spin. Step on the ball and keep it centered.

Flying it the old way. Diving until the horn blares and maneuvering with it screaming does not meet the current standard. Experienced pilots adding a rating get dinged on this because they learned it in 1998 and never updated. No shame - just retrain the sight picture: horn quiet, just above it.

Not trimming. An out-of-trim airplane in slow flight exhausts you and magnifies every other error. Trim off the pressure and you free up bandwidth to hold heading and listen.

Getting task saturated. When the examiner stacks tasks, slow down your hands, not the airplane. One smooth input at a time: roll into a shallow bank - no more than about 15 to 20 degrees - keep the ball centered, adjust power, and fly it deliberately.

Where Does This Show Up in Real Flying?

Picture a cross-country to an unfamiliar airport. A slower airplane is ahead of you in the pattern, and Tower asks you to extend your downwind and follow him. Now you’re slow, configured, and low, dividing your attention between flying and spotting your traffic - eyes outside, not on the panel.

That’s slow flight happening in real life at 800 feet with a distraction pulling your attention off the instruments. Drill it until your hand finds the throttle when you sink and your feet keep the ball centered, and this is a non-event. Treat it as a checkride box you crammed and forgot, and this is where loss of control in the pattern happens. That’s not drama - that’s the accident data.

Your Practical Takeaway

Go up to a safe altitude and re-fly slow flight the current way. Find the speed where your stall warning first chirps in landing configuration, note it, then fly just above it - horn quiet - doing turns, climbs, and descents, holding altitude with power and airspeed with pitch, feet alive on the rudder. Do it until it’s boring, because the day you need it you won’t have time to think.

If it’s been a while, take an instructor along the first time. Everything here lives in the ACS and the FAA’s Airplane Flying Handbook, both free to download and worth reading cover to cover.

Key Takeaways

• Slow flight changed in 2017 when the FAA moved from the PTS to the ACS - the stall warning should now stay silent, roughly 5 to 10 knots above where it activates.
• The change targets loss of control, the leading cause of GA fatalities, by teaching pilots to respect the stall horn rather than ignore it.
• On the back side of the power curve, power controls altitude and pitch controls airspeed - the fix for a sink is throttle, not yoke.
• Private pilot ACS tolerances are ±100 feet altitude, ±10 degrees heading, and +10/−0 knots airspeed - you can be fast, never slow.
• Every landing is a slow flight maneuver; proficiency here is the direct antidote to stall-spin accidents in the pattern.