What are the most common errors students make during instrument approach procedures?

The most frequently observed errors include failure to brief the approach thoroughly before beginning, late configuration changes that create an unstabilized approach, over-controlling the glideslope or localizer (chasing the needle with large pitch or bank inputs), and descending below decision altitude or MDA without the required visual references established under 14 CFR §91.175. Poor missed approach execution—hesitation, incomplete climb checklist, or deviation from the published procedure—is also a common and often under-critiqued error category.

What is the difference between decision altitude and minimum descent altitude on an instrument approach?

Decision altitude (DA) is used with precision approaches, such as an ILS, and is expressed as a mean sea level altitude at which the pilot must either have the required visual references to continue to a landing or execute a missed approach. Minimum descent altitude (MDA) is used with non-precision approaches; the pilot may not descend below MDA unless the runway environment is in sight and a normal landing can be made from the current position, as required by 14 CFR §91.175. The two terms are not interchangeable on FAA knowledge tests or in the cockpit.

How should a flight instructor critique a student who descended below minimums on an instrument approach?

The Aviation Instructor's Handbook (FAA-H-8083-9) calls for critique that is specific, objective, and constructive, but when a student descends below DA or MDA without legal visual reference, the instructor must address it directly and cite the specific regulatory requirement in 14 CFR §91.175. The critique should explain exactly what altitude the student reached, what visual references were or were not established at that point, and the safety and legal consequences of continuing. This category of error goes beyond a technique correction and requires the student to internalize the regulatory boundary before being authorized to conduct further approaches in actual IMC.

Critiquing Common Errors in Instrument Approach Procedures

Critiquing a student's instrument approach procedure is one of the most demanding—and most consequential—skills a flight or ground instructor develops. The Aviation Instructor's Handbook (FAA-H-8083-9) is explicit that effective critique must be specific, timely, objective, and constructive. Vague feedback like "that approach was rough" teaches nothing and frustrates the student. Precise feedback like "you crossed HIKED intersection 180 feet high on the glideslope, applied a full-dot correction that overshot, and then abandoned the ILS to duck under the clouds at 200 feet above decision altitude" gives the student an exact mental movie to replay and correct. In instrument flying, where controlled flight into terrain (CFIT) is persistently one of the leading causes of fatal general aviation accidents, that precision is not a nicety—it is a safety imperative.

The Instructor's Analytical Framework

Before critiquing individual errors, an instructor must build a mental model of what a correct approach looks like so that deviations register immediately. The Instrument Flying Handbook (FAA-H-8083-15) describes a fully stabilized approach as one in which the aircraft is on the correct track and glidepath, in the correct configuration, at the correct airspeed, and with appropriate power—all criteria met simultaneously and maintained continuously from at least 1,000 feet above the airport in IMC conditions (500 feet in VMC). Any approach that fails even one of those criteria by the final approach fix should be evaluated critically, and any approach that remains unstabilized at those altitudes should result in a go-around.

The best critique framework is the What–Why–How method described in FAA-H-8083-9: describe what the specific deviation was (quantify it where possible), identify why it most likely occurred (cognitive overload, improper scan, wind correction error, checklist omission), and prescribe how to fix it with a concrete, actionable technique. This structure keeps critique educational rather than judgmental and gives the student a clear path forward.

Category-by-Category Error Analysis

1. Incomplete or Absent Approach Briefing

An approach begins on the ground with chart review and in the air with a thorough briefing before the initial approach fix. If the student has not identified the inbound course, the final approach fix altitude, the decision altitude (DA) or minimum descent altitude (MDA), the missed approach point, the missed approach procedure, and the runway environment visibility requirements, the approach is already mentally behind before the aircraft ever turns inbound. Critique this by conducting a full briefing debrief after the flight: ask the student to recite each element from memory. If they cannot, the next session should begin with repeated briefing drills on different approaches before any flying occurs.

2. Late or Missequenced Configuration Changes

The Airplane Flying Handbook (FAA-H-8083-3) emphasizes that all configuration changes—gear extension, flap selection, power reduction—should be completed before the final approach fix on a precision approach so that the pilot can devote full attention to glideslope and localizer tracking. Students who extend gear or select flaps after crossing the FAF are forced to simultaneously chase the glideslope, correct for new trim forces, and verify configuration, resulting in classic task saturation. When critiquing, cite the exact fix where the change was required and the actual fix (or altitude) at which it occurred. A concrete time-distance anchor prevents the student from underestimating the error.

3. Glideslope Deviation and Over-Control

On an ILS, deviating above the glideslope and then applying an aggressive pitch-down correction is the most commonly observed precision approach error. Students treat the glideslope indicator like an attitude indicator and respond to each dot of deviation with a large pitch change, which introduces a lag-correct-overshoot cycle. The Instrument Flying Handbook recommends small pitch changes—often as little as half a bar width of pitch—followed immediately by re-trimming to hold the new attitude, then observing the result before correcting again. When critiquing, describe the deviation in dots (a full-scale deflection is approximately 2.5° from center on most ILS installations), the magnitude of the pitch correction applied, and the resulting overshoot. Ask the student to demonstrate the technique on a BATD or AATD before the next flight.

4. Localizer Overshoot and Bracketing Failure

Wind correction errors on the localizer fall into two types: students who apply no wind correction and drift continuously off-course, and students who apply excessive correction, overshoot the centerline, and then over-bank to re-intercept—a process that compounds with each oscillation. The appropriate correction bank for a localizer deviation inside the FAF is generally no more than half the number of degrees of heading correction required, applied smoothly and released early. Critique should reference the specific bank angles observed, the heading flown versus the inbound course, and the timing of the correction relative to the needle movement.

5. Improper Descent on Non-Precision Approaches

On non-precision approaches using the constant-descent final approach (CDFA) technique recommended by FAA-H-8083-16, students often fail to establish the correct descent rate before the FAF, arriving at MDA too early or too late. Arriving early means leveling off at MDA and flying level while searching for the runway—a technique that, while technically legal, increases workload and reduces energy management options. Arriving late means a steep, rushed descent that sacrifices stabilization. Critique should include the calculated required descent rate (which is determined from approach chart data: altitude to lose divided by the time available based on groundspeed) versus the actual rate observed.

6. Descending Below Minimums Without Legal Visual Reference

This is the single most safety-critical error category. Under 14 CFR §91.175, a pilot operating under IFR may not operate below DA on a precision approach or below MDA on a non-precision approach unless the runway environment is clearly visible and the aircraft is in a position from which a normal landing can be made. The AIM further clarifies that if only approach lights are visible (without the red terminating bars or red side-row bars), the pilot may descend to no lower than 100 feet above the touchdown zone elevation—not to the runway surface. Any tendency to duck under minimums must be addressed immediately, firmly, and with explicit regulatory citation. This is not a technique error; it is a legal and safety violation that, if not corrected, disqualifies the student from a certificate.

7. Missed Approach Execution Errors

Instructors frequently spend so much energy critiquing the descent phase that they neglect the missed approach. Common errors include hesitation at the missed approach point, failure to simultaneously apply full power and establish a positive climb attitude, and deviation from the published missed approach procedure. The priority sequence—power, pitch, clean up, communicate—must be internalized as muscle memory. Critique should specify the altitude at which the missed approach was initiated relative to the missed approach point or DA, the climb rate achieved, and whether the published procedure was followed correctly.

Key Numbers and Regulatory Anchors

Stabilized approach criteria: All parameters met by 1,000 feet AGL in IMC, 500 feet AGL in VMC (FAA-H-8083-15).
Approach lights only visible: May descend to no lower than 100 feet above TDZE under 14 CFR §91.175(c)(3).
DA vs. MDA: Decision altitude (DA) applies to precision approaches; minimum descent altitude (MDA) applies to non-precision approaches. These terms are not interchangeable.
ILS full-scale deflection: Approximately 2.5° from the localizer centerline; glideslope full-scale is approximately 0.7° above or below the published angle.
Missed approach point: On a non-precision approach, the MAP is defined by a fix, a distance from a facility, or a timing element—not by reaching MDA.

Common Test Traps

The Flight Instructor Instrument knowledge test distinguishes carefully between DA and MDA; using one term where the other is correct will cost points.
A stabilized approach requires all criteria to be met simultaneously—airspeed within limits, on glidepath, correct configuration, appropriate power, and correct track. Meeting only some criteria does not constitute a stabilized approach.
Approach lights alone do not authorize descent to the runway; only the red terminating bars or red side-row bars (or other runway environment elements listed in §91.175) permit descent below the 100-foot buffer.
The missed approach must be initiated no later than the missed approach point; initiating it early is not a violation, but the student must still comply with the published procedure from that point.
Critiquing only the final segment of an approach misses the compounding nature of instrument approach errors—brief the student that errors at the initial approach fix amplify by the time the aircraft reaches minimums.