Approval of Flight Management Systems in Transport Category Airplanes

AC 25-15 · FAA

Public domain · FAAAdvisory Circulars

Overview

The Approval of Flight Management Systems in Transport Category Airplanes (AC 25-15) is a public-domain FAA advisory circular, republished here as a free chaptered HTML edition with a linked table of contents and the official PDF.

Publisher: FAA
Document: AC 25-15
Pages: 28
Chapters: 2

Key points

This advisory circular (AC 25-15) provides guidance for the airworthiness approval of flight management systems (FMS) in transport category airplanes.
The guidance material is not mandatory and outlines a method of compliance with the rules, which applicants may choose to follow or propose an alternate method.
The AC addresses system design aspects, characteristics, and the criticality of system failure cases for FMS, emphasizing the integration of various onboard performance and navigation sensors.
A comprehensive certification plan is required for applicants, detailing compliance with applicable regulations and including necessary substantiating data and tests.
The FMS must be integrated with other onboard systems to ensure safe operation within the airplane's approved flight envelope, with specific navigation accuracy criteria for different operational areas.

Frequently asked questions

What is the purpose of AC 25-15?

The purpose of AC 25-15 is to provide guidance material for the airworthiness approval of flight management systems (FMS) in transport category airplanes.

Is compliance with the guidance in AC 25-15 mandatory?

No, compliance with the guidance in AC 25-15 is not mandatory; it is issued for guidance purposes and applicants may choose to follow an alternate method if acceptable to the FAA.

What should a certification plan include according to AC 25-15?

A certification plan should include how the applicant plans to comply with applicable regulations, a listing of substantiating data and necessary tests, a comprehensive system description, and an estimated time schedule.

What are the navigation accuracy criteria mentioned in AC 25-15?

The navigation accuracy required for computed position can vary significantly and must meet specific criteria for different operational areas, such as the U.S. National Airspace System and other international specifications.

What does AC 25-15 say about system failure conditions?

AC 25-15 states that various types of system failure conditions must be addressed, and the failure of the FMS should not degrade the integrity of other safety-related systems installed in the airplane.

Appendix 1

11/20/89 AC 25-15 Appendix 1 APPENDIX I TABLE·I COMPUTED PERFORMANCE CRITERIA COCKPIT FMS COMPUTES FMS ERRORS PARAMETER FMS CONTROLS READABILITY TO THE AFM RESULTING FROM TO THE VALUES WITHIN: SENSOR ACCURACY COMPUTED COMMANDS WITHIN (STEADY STATE*): EPR .01 See Note 1 See Note 2 See Note 3 THRUST SET .1 See Note 1 See Note 2 See Note 3 RPM (%} EGT (C} I + 8 LIMITING 1 t O, -1.0 + .5 + 1 RPM (%} IAS (KTS) 1 +5, -2 + I + 2

v,' VR v2

1 + 2, -0 + 2@ 100 KTS +5, -0 See Note 4 See Note 4 T.O. & LOG 10 DISTANCE {FEET) PERF. See Note 5 See Note 5 See Note 5 LIMIT WT Dual systems displays may differ by the extremes of the sum of columns 3 and 4.

*Control accuracy on "steady state" basis; gusts and other short term disturbances may exceed these during transients.

NOTE 1: Computes thrust setting values to an accuracy that does not introduce appreciable error in the displayed value of the thrust setting parameter when compared to the value shown on the thrust setting charts contained in the AFM.

Typically± .005 EPR or± .25% RPM.

NOTE 2: Errors introduced by sensor inaccuracy may not exceed those associated with the accuracies/readabilities historically deemed acceptable for the display of parameters used in setting thrust by means of reference charts contained in the AFM. Typically± ,005 EPR or± .25% RPM.

NOTE 3: Controls all engines to computed comands with an accuracy equal to or better than the pilot's ability to set thrust manually without undue concentration or effort when relying on the thrust setting information contained in the AFM. Typically .01 EPR or .5% RPM. For single serve systems see paragraph 5f(2}(i} of this AC.

NOTE 4: Not shorter than the distance determined by the AFM.

NOTE 5: Not greater than the weight determined from the AFM.

Next: Appendix 1 →

Appendix 1

AC 25-15 11/20/89 Appendix 1 TABLE 2 LOW ALTITUDE SPEED COMMAND TOLERANCES (STILL AIR) MODE CONDITION TRANSITION IAS (KTSl STEADY STATE IAS TAKEOFF CRITICAL ENGINE Before 35 feet, as close FAILURE vEF < v as practical to the speed profile demonstrated durir~ performance tests .

CRITICAL ENGINE FAILURE +5 < VEF < (V +X) vEF -5 (Note 1.) VEF -2 (Note 2.) V 2 2 CRITICAL ENGINE FAILURE +5 VEF > (V + X) (V + X) -S (Note 3.) (V + X) -2 2 2 2 +5 All Engines N/A (V + X) -2 Operating (Note4.)

+5 TAKEOFF, Critical Engine (V + X) -5 (Note 3.) (V + X) -2 2 2 NOISE Failure During THRUST Thrust Cutback CUTBACK All Engines +5 Operating (V + X) -2 (V + X) -2 (tfote 4.)

+5 +5 LANDING Critical Engine (Vm +XX) -5 (Note 5.) VREF +XX) -2 APPROACH Failure During GO-AROUND Transition (Initiated +5 +5 at Vm + All Engines (VREF +XX} -5 (Note 6.) VREF +XX) -2 XX during Operating stabilized approach) +5 LANDING All Engs Operating N/A Vg~F +XX) -5 APPROACH & Critical Engine (Note 7.)

Failure NOTES: 1. Less than VEF -2 not to exceed 10 sec.; less than V not to exceed 5 sec; Not less than V -2 2. Not less than V 3. less than (V + X) -2 not to exceed 10 sec.

4. Except in pitch limited conditions 5. Less than (VREF +XX) -2 not to exceed 10 sec.; less than l.2V not to exceed 5 sec.; Not less than l.2V -2 6. Less than (VREF +XX) -2 not to exceed 10 sec.; Not less than l.2Vs 7. ~o~ less than l.3V 8. X = All engine speeij additive from the AFM 9. XX= ~anding approach wind speed/gust additive