Slow Flight, the 2017 Rewrite of the Airman Certification Standards, and Why the Stall Warning Horn Should Stay Silent on Your Checkride

Since 2017, the Airman Certification Standards (ACS) require you to fly slow flight without the stall warning horn going off. You establish and maintain a slow airspeed roughly 5 to 10 knots above the stalling speed - slow enough that any increase in angle of attack, load factor, or reduction in power would cause an immediate stall, but with the horn silent. If you were taught to pull the nose up until the horn blares and hold it there, you’re practicing the old standard, and an examiner is looking for the exact opposite.

What Changed in the 2017 ACS Slow Flight Standard?

For decades, slow flight was taught one way: slow the airplane down, add power to hold altitude, and keep raising the nose until the stall warning horn came on. Then you’d fly right there - horn blaring, on the ragged edge - demonstrating control at what was called minimum controllable airspeed, the absolute slowest the airplane could go before it quit flying.

The problem was the lesson it taught. That maneuver rehearses being comfortable with the stall horn. It parks a student - sometimes with only 15 or 20 hours - in a flight regime with almost no margin, where a gust, a distraction, or a slightly uncoordinated turn drops you into a full stall.

More importantly, it builds a habit. It teaches that flying with the horn on is normal, a place you can just live for a while.

When the ACS replaced the old Practical Test Standards (PTS) in 2017, slow flight was rewritten. The new standard: you fly at a speed just above the point where the stall warning activates. If the horn comes on, you’re too slow - add a little power, lower the nose a hair, and get the airspeed back up to where the airplane is talking to you but not warning you.

Why Did the FAA Change the Slow Flight Standard?

The change was about accidents, not academics. Loss of control in flight was, and still is, one of the leading causes of fatal general aviation accidents.

And those stall-spin accidents don’t usually happen up at altitude doing air work. They happen down low, in the pattern - on the base-to-final turn, when a pilot overshoots the centerline, cranks in too much bank, feeds in a little bottom rudder to bring the nose around, and stalls a wing at 300 feet with nowhere to go.

The FAA looked hard at those numbers. The old maneuver was teaching pilots that the horn was a familiar friend. The new standard teaches that the horn is a hard boundary. That difference in reflex is the entire point of the change.

How Do I Fly Slow Flight to the Current ACS Standard?

Here are the ACS tolerances you’re held to during the maneuver:

• Altitude: within 100 feet of assigned altitude
• Airspeed: +10 / −0 knots (target just above stall warning)
• Heading: within 10 degrees
• Bank: within 10 degrees when turning

Now the actual technique, step by step:

1. Clear the area. Do clearing turns in both directions. You’re about to be nose-high and slow with a big blind spot over the cowling.

2. Pick an altitude with real room. Forget the numbers for a second - give yourself air underneath you, because if this goes wrong and you stall, you want altitude to recover.

3. Reduce power and slow down. As airspeed bleeds off, feed in back pressure to hold altitude - and trim off that pressure as you slow. Students who never trim end up wrestling the yoke and chasing altitude, and the whole maneuver falls apart. Trim as you go.

4. Configure as specified. The examiner may want it clean or in landing configuration with full flaps (and gear down if you have retractable gear). Know both, and run your checklist - fly it like a professional.

5. Manage the high-angle-of-attack handling. The controls get mushy and the nose points way up. You’ll need a lot of power to hold altitude, and in most training airplanes that means real right rudder - especially in a left turn, where uncoordinated flight wants to bite. Keep the ball centered. Fly with your feet.

6. Settle onto the target. Ease the nose up until you hear the very first chirp of the horn, then release a touch of back pressure so it goes quiet. Settle right there, just below the chirp. You’re on the back side of the power curve, mushing along, and the horn is silent.

7. Do the work. The examiner will have you hold altitude, turn to a heading, maybe climb, descend, or change configuration - all while keeping airspeed pinned, the ball centered, and the horn quiet.

8. If the horn comes on, don’t panic and don’t yank. Add a whisper of power and relax a hair of back pressure. Small corrections. This maneuver rewards a light touch and punishes a heavy hand.

9. Recover cleanly. Full power, pitch for airspeed, flaps up in stages, back to cruise. Smooth and deliberate.

Why Do So Many Students Fail Slow Flight on the Checkride?

Because many students learned the maneuver from an instructor who learned it the old way. Muscle memory is powerful, and plenty of experienced CFIs - even great ones with thousands of hours - still teach out of habit: pull it back until the horn chirps and hold it there.

So the student shows up on checkride day, the examiner asks for slow flight, and the student does exactly what they practiced. They slow down, keep pulling until the horn comes on, and hold it there proudly - thinking they’re nailing it.

The examiner is looking for the opposite. They want you to establish and maintain that slow airspeed without activating the stall warning. A horn going off through the whole maneuver isn’t a demonstration of the standard - it’s a deviation from it, and depending on the examiner and how the rest of the ride is going, that can be a conversation you don’t want to have.

The checkride isn’t a test of whether you can fly the airplane to its absolute limit. It’s a test of whether you can fly to a standard - precisely, on purpose - and explain what you’re doing and why. The skill being tested isn’t bravery. It’s control and awareness at low airspeed, with a margin you’re deliberately maintaining.

Why This Matters Long After the Checkride

Picture it. You’re on downwind at a nontowered field on a nice day. You add your first notch of flaps, slow to pattern speed, and turn base. A Cessna ahead is slow to clear the runway, so you extend your base, and now you’re a touch high and a touch fast. You overshoot the extended centerline on your turn to final. It happens to everybody.

The pilot who trained the old way - comfortable with the horn going off - cranks in bank to salvage the turn and pulls to bring the nose around. When the horn sounds, some quiet part of their brain says, that’s fine, I fly with the horn on all the time. That’s the setup for a base-to-final stall-spin. That’s the accident.

The pilot who trained to the current standard has a different relationship with that horn. It’s a hard boundary, not a familiar friend. When it chirps, the reaction is immediate and automatic: reduce the angle of attack, get the margin back, go around if you have to. A silent horn during slow flight training builds a habit where the warning means something - where it triggers action instead of comfort.

That was never really about the maneuver. It was about the reflex it builds in you.

What Should I Do to Prepare?

Go find the current Airman Certification Standards for your certificate - it’s free on the FAA website. Read the slow flight task word for word. Look specifically at the note about performing the maneuver without a stall warning.

Then go fly it that way with your instructor. If your CFI has been teaching it the old way out of habit, have that conversation - a good instructor will respect you for bringing the book and asking to get on the same page.

Take ownership of the book. The ACS is not a secret. The examiner is working from it, and so should you. It is maddening to fumble a maneuver - or fail a ride - over which version of a standard you happened to be taught.

Key Takeaways

• Since 2017, the ACS requires slow flight to be flown just above the stall warning, with the horn silent - not on the edge of a stall like the old PTS.
• Target an airspeed roughly 5 to 10 knots above stall speed, where any further increase in angle of attack, load factor, or power reduction would cause an immediate stall.
• Hold ACS tolerances: ±100 feet altitude, +10/−0 knots airspeed, ±10 degrees heading and bank.
• Trim as you slow, use right rudder at high angle of attack, and keep the ball centered - uncoordinated slow flight is where a stall-spin bites.
• The real goal is a reflex: treat the stall horn as a hard boundary that triggers action, not a familiar sound you fly comfortably alongside.