How do you calculate the descent rate needed to fly a CDFA on a non-precision approach?

To calculate the required descent rate, multiply your groundspeed (in knots) by the approach's published vertical descent angle (VDA) in feet per nautical mile, then divide by 60 to convert to feet per minute. For example, flying 90 knots on a 3.0-degree angle yields approximately 450 feet per minute (using the standard rule-of-thumb factor of about 5 for a 3-degree angle). Most instrument approach procedure charts include a table of groundspeed-to-descent-rate conversions to make this calculation straightforward during preflight planning.

What's the difference between a Continuous Descent Final Approach and the traditional dive-and-drive method?

The traditional dive-and-drive method has pilots descend rapidly to the minimum descent altitude (MDA) after the FAF and then fly level until either the runway environment is in sight or the missed approach point is reached, which can create an unstabilized, steep final descent to landing. CDFA, by contrast, maintains a constant glide angle all the way to the vicinity of the MDA/missed approach point, after which a go-around is initiated if the runway environment is not clearly in sight. The FAA endorses CDFA because it keeps the aircraft in a consistently stabilized approach configuration, reducing workload and the risk of inadvertent descent below MDA.

Continuous Descent Final Approach (CDFA) Technique and Stabilized Approach Criteria

Q: What is the Continuous Descent Final Approach (CDFA) technique?

The CDFA technique involves flying a non-precision instrument approach as a constant-angle, continuous descent from the final approach fix (FAF) altitude down to the missed approach point, rather than using the traditional "dive and drive" level-off at the minimum descent altitude. This mirrors the stabilized profile of a precision approach and is recommended by the FAA because it significantly reduces the risk of Controlled Flight Into Terrain (CFIT). The Instrument Flying Handbook describes CDFA as a best practice that improves situational awareness and simplifies go-around decision-making.

Every year, controlled flight into terrain (CFIT) claims lives on instrument approaches, and a disproportionate number of those accidents occur on non-precision approaches flown with the old "dive-and-drive" technique — a method that demands abrupt level-offs, last-second decision-making, and brief periods of dangerously low, slow flight very close to the ground. The Continuous Descent Final Approach (CDFA) technique is the FAA-endorsed answer to that hazard. By flying a smooth, constant-angle descent from the final approach fix (FAF) all the way to the missed approach point (MAP), CDFA mirrors the stabilized profile of an ILS glide slope and allows pilots to apply a single, unambiguous go/no-go decision rule at the MAP. Understanding CDFA — and the broader stabilized approach criteria it supports — is essential for the instrument rating knowledge test, the practical test, and every IFR flight you will ever make.

This article covers what CDFA is, how to fly it, the math behind the descent angle and vertical speed, and the stabilized approach standards that every instrument pilot must internalize. It is grounded in the Instrument Flying Handbook (FAA-H-8083-15) and the Instrument Procedures Handbook (FAA-H-8083-16).

What CDFA Is — and What It Replaced

Non-precision approaches (NPA) — VOR, NDB, LOC, LNAV, and others — traditionally provided only lateral course guidance. Vertical guidance, if published, was advisory only. Pilots using the old dive-and-drive method would descend rapidly at the FAF to the Minimum Descent Altitude (MDA), level off, and then fly horizontally at MDA until either acquiring the runway environment or reaching the MAP. That level segment at MDA is the dangerous part: the aircraft is flying at minimum obstruction clearance altitude with very little energy margin, limited forward visibility, and a landing decision compressed into the final few seconds before the MAP.

CDFA replaces that level-off with a continuous, stabilized descent computed to arrive at (or just above) the MDA at approximately the MAP — or at the published Threshold Crossing Height (TCH) if the procedure provides it. The pilot calculates a target vertical speed or uses published vertical angle information (often labeled as "VGSI" or a degree angle on the approach chart), flies that constant gradient from the FAF to the MAP, and treats the MDA operationally like a decision point for go/no-go purposes: if visual references required by 14 CFR 91.175 are not acquired by the time the aircraft reaches MDA, the pilot immediately executes a missed approach — no level-off, no searching, no pressing on. It is worth noting that MDA remains, legally and definitionally, a Minimum Descent Altitude, not a Decision Altitude; CDFA borrows the discipline of a DA decision without changing the regulatory character of the MDA.

How to Fly CDFA — The Core Mechanics

Determining the Descent Angle

Many approach charts now publish a Vertical Descent Angle (VDA) in the profile view, typically 3.00° for approaches designed to align with a standard VASI or PAPI. When the VDA is not published, you can calculate an approximate descent gradient using a simple formula:

Required Vertical Speed (fpm) = Ground Speed (knots) × Descent Angle Factor

For a 3° descent angle, the factor is approximately 5.0 times your ground speed in knots. So if you are flying a ground speed of 90 knots on final, the required rate of descent is roughly 90 × 5.0 = 450 fpm, which you would use directly for practical purposes. At 120 knots, that becomes about 600 fpm. The Instrument Procedures Handbook provides tables that eliminate the mental math burden — familiarize yourself with those tables before your checkride.

Timing the Descent

The key discipline in CDFA is starting the descent at the right moment. On a procedure where the FAF is a fix you cross at a published altitude, begin the descent immediately upon station passage or GPS fix crossing. Do not delay. Even a 10-second late start at 90 knots covers a quarter-mile of ground — enough to significantly compress your decision window at the MAP. Use the published FAF crossing altitude as your last level-off altitude before initiating the continuous descent.

The MDA as a Decision Gate

Under CDFA, some operators and procedures build in a small margin above the published MDA to account for descent rate and reaction time at the moment of the go-around decision. The FAA does not codify a single universal add-on figure in the cited handbooks — specific margin values vary by operator, aircraft, and procedure. Because the aircraft is still descending when it reaches MDA, a pilot who delays the go-around call may dip below MDA before the aircraft responds. Building in an appropriate margin, consistent with operator guidance, helps ensure the missed approach is initiated before the aircraft actually breaks the MDA floor. The Instrument Procedures Handbook discusses this general principle; it is not "cheating" — it is smart energy management. Importantly, the aircraft must never descend below the published MDA unless the requirements of 14 CFR 91.175(c) are met: the runway environment is in sight, the flight visibility meets the published minimum, and the aircraft is in a position to make a normal descent to landing using normal maneuvers.

Stabilized Approach Criteria

CDFA is valuable precisely because it produces a stabilized approach — and the concept of stabilization is one of the most safety-critical ideas in all of instrument flying. A stabilized approach is one in which, by a defined gate, the aircraft is established on the correct flight path with all parameters within defined limits and essentially no corrections required except small, smooth adjustments.

The Stabilization Gate

The FAA and industry best practices establish the stabilization gate as a specific altitude above the runway threshold. This 1,000-foot-in-IMC figure is a widely used industry best-practice benchmark (traced to Flight Safety Foundation and FAA guidance for turbine operations) rather than a single number codified across every FAA handbook for all instrument operations, so treat it as a well-established standard rather than a fixed regulatory value. In visual meteorological conditions (VMC), the gate may be as low as 500 feet AGL. By the stabilization gate, all of the following must be true:

On the correct vertical profile: The aircraft must be on or very close to the desired descent angle — glideslope, VGSI, or computed CDFA gradient — with no large deviations.
On the correct lateral track: Course deviation indicator (CDI) centered or within one dot, aircraft aligned with the final approach course.
Configured for landing: Landing gear extended (if applicable), flaps at the approach or landing setting specified in the POH/AFM, checklist complete.
At the correct airspeed: Approach speed (Vref or published approach speed) established, with only small deviations — typically ±10 knots is considered the outer limit, with tighter standards preferred.
At the correct power setting: Power stabilized and consistent with maintaining the desired airspeed and descent rate; not in a high-power or idle configuration inconsistent with the phase of flight.
Correct descent rate: Sink rate consistent with the computed approach angle, and never exceeding what would allow a normal landing flare. Very high sink rates — often cited as greater than 1,000 fpm in the final approach segment — are a red flag requiring immediate go-around consideration.

Executing a Go-Around for Stabilization Failure

If any stabilization criterion is not met at the gate, the only correct action is a go-around. This is not optional, and it is not a sign of pilot failure — it is the application of sound aeronautical decision-making (ADM). The Instrument Flying Handbook is explicit: a go-around should be executed whenever the approach does not meet stabilized criteria, at any point in the approach, including after the MAP if landing is not assured. Pride and schedule pressure are two of the most common hazardous attitudes (as described in the Risk Management Handbook, FAA-H-8083-2) that cause pilots to press on with an unstabilized approach. The result is a disproportionate share of runway excursions, hard landings, and CFIT events.

Why CDFA Matters — Safety and Regulatory Context

The FAA promotes CDFA through the Instrument Procedures Handbook because the technique addresses the fundamental risk model of NPAs. Studies of CFIT accidents consistently show that the dive-and-drive technique creates a period of flight at or below MDA with degraded situational awareness, high workload, and reduced time to respond to unexpected obstacles or missed visual cues. CDFA eliminates that segment entirely. By treating the MDA operationally similar to the Decision Altitude (DA) used on precision approaches, CDFA imposes a discipline: you either have the required visual references and are in position to land, or you go missed. Period.

Additionally, CDFA makes crew resource management (CRM) more effective. With a predictable, constant-angle descent, monitoring pilot callouts are easier to script and verify. Deviations from the desired gradient are immediately apparent to both crew members rather than ambiguous during a level-off segment.

Key Numbers and Rules

Standard VDA: 3.00° is the standard Vertical Descent Angle for most non-precision approaches aligned with a VASI or PAPI.
Descent rate rule of thumb: Ground speed (knots) × 5.0 ≈ required fpm for a 3° descent.
CDFA margin above MDA: Some operators build in a margin above published MDA to account for descent rate and reaction time; the FAA does not specify a single universal figure in the cited handbooks.
IMC stabilization gate: 1,000 feet AGL above the runway threshold elevation (a widely used industry best-practice benchmark).
VMC stabilization gate: 500 feet AGL (commonly cited industry standard).
Airspeed tolerance: Approach speed ± 10 knots is a typical outer limit; smaller deviations are preferred.
Maximum sink rate caution: Sink rates in excess of approximately 1,000 fpm in the final approach segment warrant immediate reassessment or go-around.
14 CFR 91.175(c): Governs the legal requirements — flight visibility, runway environment in sight, and position for normal landing — before descending below MDA or DA.

Common Test Traps

Confusing MDA with DA: MDA applies to non-precision approaches; DA (formerly DH) applies to precision approaches and APV approaches. Under CDFA, MDA is used like a DA in terms of decision-making, but it remains an MDA in regulatory terms — the aircraft must not descend below it unless 91.175(c) requirements are met.
Assuming CDFA means you can land below MDA: CDFA changes how you reach the MDA; it does not lower the MDA or grant any authority to descend below it without required visual references.
Forgetting the margin above MDA: Test questions sometimes probe whether pilots understand that initiating a go-around exactly at MDA may result in momentary excursion below MDA due to inertia. A reasonable margin, per operator guidance, is the safety answer.
Stabilization criteria apply to visual approaches too: The FAA does not limit stabilized approach criteria to IFR. Expect questions about the 500-foot gate in VMC and what to do if criteria are not met.
Dive-and-drive is not prohibited by regulation — but CDFA is the endorsed technique: Some candidates assume that dive-and-drive is illegal. It is not per se illegal, but CDFA is strongly recommended by the FAA, and examiners expect you to understand and endorse the CDFA methodology.