AF Form 3640: Non-Precision Computations – Official Guide

AF Form 3640: Non-Precision Computations – Official Guide – U.S. Air Force aircrew and flight operations personnel rely on standardized tools for safe and compliant instrument approaches. AF Form 3640, titled NonPrecision Computations, is a specialized form used to document calculations for non-precision approaches (NPAs). These approaches provide course guidance but lack the vertical precision of an ILS or other precision systems.

This article explains the purpose of AF Form 3640, how it fits into Air Force flight operations, when to use it, and where to download the official PDF. It targets USAF pilots, navigators, flight planners, and instructors operating under current Air Force instructions.

What Is AF Form 3640?

AF Form 3640 is an official U.S. Air Force form (formerly categorized under AF IMT) designed specifically for recording non-precision computations. It supports record-keeping and reference during flight planning and mission execution for instrument approaches that do not provide electronic glidepath guidance.

Key details:

  • Full Title: Non-Precision Computations
  • Purpose: To systematically document the mathematical calculations required for safe execution of non-precision instrument approaches.
  • Release/Revision: The form dates back to its original release on July 1, 1993, with the current version available through official Air Force e-Publishing channels.
  • Companion Forms: It is often used alongside AF Form 3642 (Circling Computations) and other flight planning documents.

Non-precision approaches include procedures such as VOR, NDB, LOC-only, or certain RNAV/GPS approaches without vertical guidance. These require crews to calculate and apply minimum descent altitudes (MDA), visibility minimums, and timing or distance information to reach the missed approach point (MAP) safely.

Why Non-Precision Computations Matter in USAF Operations?

In modern aviation, precision approaches (like ILS CAT I/II/III) are preferred for their lower minimums and automated glidepath. However, many airfields—especially austere, deployed, or contingency locations—offer only non-precision procedures. Air Force crews must be proficient in these to maintain operational flexibility and safety.

AFMAN 11-202 Volume 3 (Flight Operations) governs general flight rules, including instrument procedures. It addresses non-precision approaches, minimum descent altitudes, and requirements for continuous descent final approach (CDFA) techniques where applicable. Supplements from MAJCOMs (such as ACC or AFDW) provide additional guidance on derived decision altitudes (DDA) and related computations.

Accurate computations help crews:

  • Determine timing from the final approach fix (FAF) to the MAP.
  • Apply wind corrections and true airspeed adjustments.
  • Calculate visibility and ceiling requirements.
  • Ensure compliance with obstacle clearance and protected airspace.
  • Support debriefs, training, and safety investigations.

Proper documentation on AF Form 3640 creates an auditable record, which is critical for standardization, training, and regulatory compliance.

When and How to Use AF Form 3640?

Aircrew typically complete the form during preflight planning for missions involving non-precision approaches. It is especially relevant for:

  • Initial qualification or currency training.
  • Operations at airports without precision approach capability.
  • Contingency or tactical scenarios.
  • Instructor/evaluator oversight of student computations.

General process (based on standard Air Force practices):

  1. Gather approach plate data (MDA, HAT, visibility, timing, etc.) from approved FLIP or digital charts.
  2. Perform required calculations (e.g., ground speed, timing, descent rates).
  3. Record step-by-step computations on the form.
  4. Review and verify with the other crew member or instructor.
  5. Retain for records or mission paperwork as directed by unit SOPs.

The form includes dedicated blocks for specific data fields, notes, and signatures. Always follow the instructions printed on the form itself and any MDS-specific guidance in AFMAN 11-2 series publications (e.g., for C-130, KC-135, or fighter aircraft).

Important Notes:

  • Non-precision approaches generally have higher minimums than precision ones.
  • Many units now emphasize CDFA techniques, which may involve briefing a Derived Decision Altitude (DDA) approximately 100 feet above the published MDA to avoid descending below it while maintaining a stabilized descent.
  • Crews must comply with higher headquarters supplements and local directives, which may impose additional restrictions.

How to Download the Official AF Form 3640 PDF?

The most current and authorized version is available directly from the Air Force e-Publishing site:

Official Download Link: https://static.e-publishing.af.mil/production/1/af_a3/form/af3640/af3640.pdf

Always download forms from the official AF e-Publishing portal (e-publishing.af.mil) to ensure you have the latest revision and to maintain compliance with DAFI 33-360 (Publications and Forms Management).

Tips for users:

  • Check the revision date on the form.
  • Use Adobe Acrobat or compatible software for digital filling when authorized.
  • Some units may integrate these computations into electronic flight bags (EFBs) or mission planning software, but manual forms remain essential for training and backup.

Best Practices for Non-Precision Approach Planning

  • Cross-reference computations with aircraft-specific performance data.
  • Account for environmental factors (wind, temperature, pressure altitude).
  • Brief the approach thoroughly, including the missed approach procedure.
  • Use approved aids (EFBs, flight manuals) while maintaining proficiency with manual calculations.
  • Document any deviations or special conditions.

Staying current with AFMAN 11-202V3 and related instructions is essential, as guidance on instrument operations evolves.

Conclusion

AF Form 3640 remains a foundational tool for U.S. Air Force aircrew performing non-precision computations. Whether you are a seasoned instructor pilot or a new aviator building instrument proficiency, mastering this form supports mission success and flight safety in diverse operational environments.

For the official form and the most up-to-date instructions, visit the Air Force e-Publishing website and consult your unit flight standards or operations officer. Safe flying starts with thorough planning and accurate computations.

Related Resources:

  • AFMAN 11-202 Volume 3 – Flight Operations
  • AF e-Publishing Forms Index
  • MDS-specific Volume 3 manuals (e.g., AFMAN 11-2C-XXX)

This guide is for informational purposes and does not replace official Air Force instructions or directives. Always refer to current publications and chain of command for authoritative guidance.

Keywords: AF Form 3640, Non-Precision Computations, Air Force instrument approaches, AFMAN 11-202V3, USAF flight planning, non-precision approach worksheet, download AF Form 3640.

(Last updated with current Air Force references as of 2026.)