Table Of ContentFAA Aviation Rulemaking Advisory
Committee
FTHWG Phase 2
Topic 1 Envelope Protection
Topic 2 Adaptation for Flight in Icing
Topic 6 Stability
Topic 7 Side Stick Controls
Topic 9 Wet Runway Stopping
Topic 10 Runway Excursion Hazard
Topic 11 Stall In Ground Effect
Topic 12 Steep Approach
Topic 13 Out of Trim
Topic 14 Tailwind-Crosswind
Recommendation Report – Rev A
April, 2017
FTHWG Phase 2 Final Recommendation Report – Rev A 1 April, 2017
Table of Contents
List of Abbreviations 4
Executive Summary 5
Organization of this Report 6
Background 7
A. What is the underlying safety issue addressed by the CS/FAR? 8
B. What is the task? 9
C. Why is this task needed? 9
D. Who has worked the task? 10
E. Any relation with other topics? 11
Historical Information 11
A. What are the current regulatory and guidance material CS 25 and FAR 25? 14
B. What, if any, are the differences in the existing regulatory and guidance material CS 25 and
FAR 25? 14
C. What are the existing CRIs/IPs (SC and MoC)? 14
D. What, if any, are the differences in the Special Conditions (CRIs/IPs) (SC and MoC) and what
do these differences result in? 14
Consensus 14
Recommendation 19
A. Rulemaking 21
1. What is the proposed action? 21
2. What should the harmonized standard be? 22
3. How does this proposed standard address the underlying safety issue (identified under #1)? 22
4. Relative to the current FAR, does the proposed standard increase, decrease, or maintain the
same level of safety? Explain. 23
5. Relative to current industry practice, does the proposed standard increase, decrease, or
maintain the same level of safety? Explain. 23
6. Who would be affected by the proposed change? 24
7. Does the proposed standard affect other HWG’s and what is the result of any consultation
with other HWGs? 24
B. Advisory Material 26
1. Is existing FAA advisory material adequate? If not, what advisory material should be
adopted? 26
2. To ensure harmonization, what current advisory material (e.g., ACJ, AMJ, AC, policy letters)
needs to be included in the rule text or preamble? 26
Economics 26
A. What is the cost impact of complying with the proposed standard? 26
B. Does the HWG want to review the draft NPRM prior to publication in the Federal Register? 27
ICAO Standards 27
How does the proposed standard compare to the current ICAO standard? 27
Attachment A ARAC Tasking from Federal Register 28
Attachment B Proposed Regulatory Material 31
Attachment C Proposed Guidance Material 58
Appendix 1 Topic 1 Envelope Limiting Final Report 195
Appendix 2 Topic 2 Adaptation for Flight in Icing Final Report 262
Appendix 3 Topic 6 Stability 310
FTHWG Phase 2 Final Recommendation Report – Rev A 2 April, 2017
Appendix 4 Topic 7 Side Stick Controllers 350
Appendix 5 Topic 9 Wet Runway Stopping Performance Interim Report 392
Appendix 6 Topic 10 Runway Excursion Hazard Classification 434
Appendix 7 Topic 11 Stall in Ground Effect Final Report 465
Appendix 8 Topic 12 Steep Approach Landing Final Report 494
Appendix 9 Topic 13 Out of Trim Final Report 519
Appendix 10 Topic 14 Tailwind/Crosswind Final Report 542
FTHWG Phase 2 Final Recommendation Report – Rev A 3 April, 2017
List of Abbreviations
AC Advisory Circular
AFM Airplane Flight Manual
ALPA Airline Pilots Association
ANAC Agência Nacional de Aviação Civil (Brazil)
AOA Angle of Attack
APC Airplane-Pilot Coupling
ARAC Aviation Rulemaking Advisory Committee
CFR Code of Federal Regulations
CRI Certification Review Item
CS Certification Specification
EASA European Aviation Safety Agency
EFCS Electronic Flight Control System
ELOS Equivalent Level of Safety
EPF Envelope Protection Function
EU OPS European Union Operations
FAA Federal Aviation Administration
FAR Federal Aviation Regulation (now referred to as 14CFR, for Title 14, Code of Federal
Regulations)
FBW Fly-by-Wire
FCHWG Flight Controls Harmonization Working Group
FCTLS Flight Controls
FTHWG Flight Test Harmonization Working Group
FTG Flight Test Guide
FWP Flight Working Paper
HALF High Angle of Attack Limiting Function
HQ Handling Qualities
HQRM Handling Qualities Rating Method
HUD Heads-Up Display
ICAO International Civil Aviation Organization
IP Issue Paper
JAA Joint Airworthiness Authorities
NPA Notice of Proposed Amendment
NPRM Notice of Proposed Rulemaking
NTSB National Transportation Safety Board
NZ Normal Load Factor
OEM Original Equipment Manufacturer
PIL Pilot in the Loop
PIO Pilot Induced Oscillation
PFC Porous Friction Course
SAIB Safety Alert Information Bulletin
SAL Steep Approach Landing
SC Special Condition
SME Subject Matter Expert
STPCM Strategies for Protection against Thrust Control Malfunctions
TALPA ARC Takeoff and Landing Performance Assessment Aviation Rulemaking Committee
TCCA Transport Canada Civil Aviation
Vmin1g Minimum steady flight speed for a given aeroplane configuration corrected to 1g with the high
Angle of Attack Protection system operating
VSR Reference Stall Speed
VSW Stall Warning Speed
FTHWG Phase 2 Final Recommendation Report – Rev A 4 April, 2017
Executive Summary
Pursuant to ARAC tasking given at the 20 March, 2014 FAA assigned to ARAC a tasking to use the
Flight Test Harmonization Working Group (FTHWG) to develop recommended standards in the areas of
Fly-by-Wire flight controls, takeoff and landing performance, and guidance material for assessing
certain aspects of handling qualities.
While transport airplanes incorporating fly-by-wire systems and flight envelope protection features have
been certified and in service since the late 1980’s, the basis on which the airworthiness was determined
has always been Special Conditions (SC’s) and Certification Review Items (CRI’s) in Europe. The
technical content of these individual SC’s and CRI’s was written specifically in response to a proposed
configuration architecture and list of features from each applicant. As a result, while the intended level
of safety has been rather consistent, the particular content of the SC’s and CRI’s was not harmonized
across authorities nor across airplane models, nor could it have been expected to be, given the
circumstances. This tasking provides an opportunity to look across the industry and across the
authorities to achieve a single safety standard (a harmonized set of regulations) and a consistent means
of compliance which is intended to be applicable to the architectures represented in the current fleet of
transport airplanes as well as those reasonably envisioned by the FTHWG team. These fly-by-wire tasks
included use of envelope protection features, adaptation for flight in icing for angle-of-attack protected
airplanes, dealing with configurations which do not exhibit static (speed) stability, dealing with airplanes
having auto-trim functions in compliance to the out-of-trim maneuvering characteristics, and side stick
controls.
For the other topics, the relevant safety issues were identified and addressed. These included
harmonization of standards and procedures for certifying steep approach landing, for the assignment of
safety hazard classifications for systems failures involving runway excursions, for evaluation and
presentation of gusts in crosswind and tailwind testing, for wet runway stopping performance and for the
reduction of flight test risk from stalling in ground effect.
The FTHWG undertook this tasking beginning in June of 2014 and worked diligently throughout the
period.
Throughout the deliberations, the FTHWG ensured that every member had an equal voice, that all
dissenting opinions were documented and dispositioned, and that recommendations for new or modified
requirements and guidance material were properly vetted within the group. Though not without its
challenges, the FTHWG reached a majority consensus on the intent, and the structure of both proposed
regulations and proposed guidance which is harmonized for every topic considered. Some topics
required new regulations, some only modified regulations, some only modifications to the guidance
material. Some disagreements were encountered concerning some specific words, some specific test
conditions, and these are documented.
The consensus decisions and the recommendations are included in the individual reports as Appendices
to this report and summarized here. Proposed changes to 14CFR25 and related guidance material is
included and color-coded to illustrate the source (topic) of each change.
FTHWG Phase 2 Final Recommendation Report – Rev A 5 April, 2017
Organization of this Report
This report is a summary of the work of the Flight Test Harmonization Working Group (FTHWG),
pursuant to tasking in the Federal Register dated 11 April, 2014. Because the tasking was very broad,
the FTHWG decided that the best course of action was to conduct the technical deliberations on each
topic individually, being cognizant of the very close interactions between the topics. As a result, the
output of the Working Group is provided in the form of individual reports for each topic. The FTHWG
believes they have coordinated the various recommendations to the point that they are compatible with
each other.
This report serves as a “wrapper” for those individual reports, and includes a summary. For that reason,
in each section of this report, the items of interest will be grouped by topic. Each of the individual topic
reports is included as an Appendix to this report. The recommended harmonized regulatory and
guidance material is collected in Attachments B and C, respectively, of this report and represents the
sum total of the recommended material from each of the individual topic reports, color-coded by topic,
so that the reader can easily see from which topic a particular change proposal came.
As the work progressed, the Working Group adopted the topic numbers from the original list of topics as
identifiers for each topic. As a result, the individual reports, included as Appendices to this report are
not numbered sequentially (i.e., they are listed as Topics 1, 2, 6, 7, 9, 10, 11, 12, 13, and 14), although
the Appendix numbers are sequential (i.e. 1-10). It should not come as a surprise, for example, that
Appendix 3 contains the report for Topic 6, etc.
Preface to Rev. A of this Report
The original tasking called for an end date of the Phase 2 activities of April, 2017, and the original
scheduling of the tasks was done respecting this date. That schedule was subsequently modified to
January, 2017, to allow for both TAE and ARAC review of the recommendations by April. The
RevNew version of this report met the January date and included the work which had been concluded at
that time, along with reference to some work not yet concluded, and recommended next steps.
Notwithstanding the report submittal in January, the Working Group had already scheduled a meeting
for March, and was working well via teleconferences, so the work on the unfinished items continued. At
the same time, the April TAE and ARAC meetings were cancelled. Therefore, Rev A incorporates the
results of the continued work on the part of the Working Group into the report so that the more complete
work of Phase 2 can be considered by TAE and ARAC at their next opportunity to meet.
The new material in Revision A is limited to:
• Topic 1 (Envelope Limiting): additional guidance material which had been drafted but
not vetted (and therefore not included in RevNew) when the original report was released.
• Topic 10 (Runway Excursion Hazard Classification): an additional dissenting opinion
from EASA which came to the attention of the FTHWG only after the RevNew report
had been written and approved.
• Topic 12 (Steep Approach Landing): additional detail has been added after reaching
majority/dissenting opinions around the issues of the degree of flight path angle variation
and associated screen heights for demonstration flight tests, as well as the use of other
FTHWG Phase 2 Final Recommendation Report – Rev A 6 April, 2017
mitigating factors (like AFM limitations) to set acceptable limits on demonstrated angle
and screen height.
There are no changes to any other sections of the report as a result of Revision A. Revision markings
for Revision A changes are provided for all substantive changes with the exception of Attachments B
and C. Attachments B and C are the compilation of all Regulatory and Guidance Material from the
topic reports and the revision markings in those Attachments show all the changes relative to existing
Regulations and Guidance Material. Revision markings for Revision A changes show added text but not
the deleted text.
Background
As a result of the 20 March, 2014 ARAC meeting, FAA has assigned and ARAC has accepted a tasking
which would use the existing Flight Test Harmonization Working Group (FTHWG).
The working group should develop recommended standards in the following topic areas. If there are disagreements
within the working group, these should be documented, including the reasons for the disagreement and rationale
from each party. The following subject areas should be worked upon within this task:
1. Fly-by-wire Flight Controls.
Regulatory requirements and associated guidance material for airworthiness certification of airplane designs using
fly-by-wire technology to remove the need for longstanding, repetitively-used fly-by-wire special conditions.
Specific areas include:
a. Applicability/adaptation of Amendment 25–121 airplane performance and handling characteristics in
icing conditions requirements,
b. Lateral/directional/longitudinal stability,
c. Out of trim requirements,
d. Side stick controls, and
e. Flight envelope protection.
2. Takeoff and Landing Performance.
Regulatory requirements and associated guidance material for airworthiness certification in the following areas
listed below. (Note: This topic area excludes items addressed by the Takeoff and Landing Performance Assessment
Aviation Rulemaking Committee.)
a. Flight test methods used to determine maximum tailwind and crosswind capability. For crosswind
testing, better define intended operational use of demonstrated maximum steady and gusting crosswind performance.
b. Wet runway stopping performance.
Recent landing overruns on wet runways have raised questions regarding current wet runway stopping performance
requirements and methods. Analyses indicate that the braking coefficient of friction in each case was significantly
lower than expected for a wet runway (i.e., lower than the level specified in FAA regulations). Consideration should
also be given to the scheduling of landing performance on wet porous friction course and grooved runway surfaces.
Recommendations may include the need for additional data gathering, analysis, and possible rulemaking.
c. Steep approach landing performance.
Current airplane certification standards are not harmonized among the U.S., Canadian, Brazilian, and European
airworthiness authorities.
d. Guidance material addressing the adverse effects on stall speed in ground effect.
e. Runway excursion hazard classification. Current safety assessments are not harmonized among the U.S.,
Canadian, Brazilian, and European airworthiness authorities.
3. Handling Characteristics. Guidance material for airworthiness certification in the following areas:
a. Guidance material for assessing handling qualities.
Current Advisory Circular 25–7, ‘‘Flight Test Guide for Certification of Transport Category Airplanes,’’ provides
an FAA Handling Quality Rating Method that is intended to provide a systematic way of determining appropriate
minimum handling qualities requirements and evaluating those handling qualities for conditions affecting an
airplane’s flying qualities. The FAA handling quality rating system is not universally accepted within industry, nor
is it accepted by EASA.
FTHWG Phase 2 Final Recommendation Report – Rev A 7 April, 2017
b. Guidance for assessing susceptibility to pilot-induced oscillations/airplane-pilot coupling (PIO/APC).
Guidance provided in Advisory Circular 25–7C for evaluating PIO/APC is also not well accepted by airplane
manufacturers, is not harmonized with EASA, and has been superseded to some extent in recent certification
programs. Modified guidance is needed to both simplify and standardize the methods for evaluating an airplane’s
susceptibility to PIO/APC.
The FTHWG, in planning this work statement divided the tasking as given into 12 topics, as follows:
1. Topic 1 Flight Envelope Protection
2. Topic 2 Adaptation for Flight in Icing for high angle of attack limiting function airplanes
3. Topic 6 Stability
4. Topic 7 Side Stick Controls
5. Topic 9 Wet Runway Stopping Performance
6. Topic 10 Runway Excursion Hazard Classification
7. Topic 11 Stall in Ground Effect
8. Topic 12 Steep Approach Landing
9. Topic 13 Out of Trim
10. Topic 14 Tailwind/Crosswind
11. Topic 15 Pilot Induced Oscillation (PIO)
12. Topic 16 Handling Qualities Rating Method (HQRM)
The initial presumption during planning was that because many of these topics involve different
populations of Subject Matter Experts, many could be worked simultaneously. This presumption was
valid for the technical SME’s involved, but turned out to be not valid for others on the Working Group.
In reality, most of the members of the working group were interested in all of the topics. This fact,
together with the realization that the planning was more than a bit optimistic led to a re-planning effort.
In the summer of 2016, it became clear that the work involved in the tasking was significantly more
involved than originally planned. FTHWG asked for, and was granted the following modifications to
the plan:
1. Defer Topic 15 (PIO) to Phase 3, planned to begin in March, 2017.
2. Defer Topic 16 (Handling Qualities Rating Method) to Phase 3, planned to begin in March,
2017.
3. Split Topic 9: Provide an interim report addressing the safety aspects outlined in Topic 9 by
11 January, 2017 (included in this report), planning to complete tasks 2 and 3 in July, 2017.
It is noted that the initial due date for this work was given in the tasking as 11 April, 2017. About a year
into the work, it was realized that the planning to the 11 April, 2017 date did not include necessary time
for review by TAE and similarly by ARAC. As a result, the working due-date was backed up to 11
January, 2017. As that date approached and the early 2017 TAE meeting date became more firm, the
due date for release to TAE was re-negotiated to be 25 January, 2017. As noted above, the RevNew
version of this report was submitted on time. Since that time, the FTHWG has continued to work and
has produced Revision A, for consideration by TAE and ARAC.
A. What is the underlying safety issue addressed by the CS/FAR?
The stated motivation for the Fly-by-Wire tasks (Topics 1, 2, 6, 7, and 13) is to remove the need for
repetitively used Special Conditions. The FTHWG believes that the recommended proposals will allow
that to happen, and that the result will be a single, harmonized set of standards which will have the effect
FTHWG Phase 2 Final Recommendation Report – Rev A 8 April, 2017
of ensuring a consistent safety standard across authorities. The standard of safety used by the working
group is a composite of that taken to be the current airworthiness requirements applied to conventional
(not-flight-envelope-protected) configurations and the various SC’s and CRI’s applied to current fly-by-
wire, protected types.
The underlying safety issues addressed by the other topics are detailed in each of the topic reports and
are summarized below.
Topic Underlying Safety Issue Reference for more detail
1 Envelope Protection Lack of harmonized standard Appendix 1
2 Adaptation for Flight in Icing Lack of harmonized standard Appendix 2
6 Stability Lack of harmonized standard Appendix 3
7 Side Sticks Lack of harmonized standard Appendix 4
9 Wet Runway Stopping Several accidents and incidents have Appendix 5
raised questions regarding landing
performance on wet runways. There
has been evidence that airplanes could
not obtain the expected wheel braking
performance during these accidents
and incidents as defined by CFR
25.109
10 Runway Excursion Hazard Failures in certain systems could cause Appendix 6
a runway excursion.
11 Stall IGE The need for improved awareness and Appendix 7
understanding of ground effects on
stall angle-of-attack and maximum lift
coefficient.
12 Steep Approach Lack of harmonized standard Appendix 8
13 Out of Trim Lack of harmonized standard Appendix 9
14 Tailwind-Crosswind Neither 14CFR25 and CS25 mandate Appendix10
an evaluation on the effects of gusts
on handling qualities during takeoff
and landing.
For tailwinds above 10 kts, the two
standards consider gusts in different
ways.
B. What is the task?
From the general tasking statement above, individual work plans for each topic were developed and
further refined in the FTHWG Phase 1 report, dated 30 January, 2014. These specific work plans appear
in each individual topic report, in the Appendices to this report.
C. Why is this task needed?
FTHWG Phase 2 Final Recommendation Report – Rev A 9 April, 2017
For the fly-by-wire tasks (Topics 1, 2, 6, 7, and 13), an appropriate harmonized safety standard simply
did not exist. As a result, as new airplane configurations and architectures appeared, each was certified
to SC’s and CRI’s which were written specifically to address each configuration and architecture. The
industry appeared to be diverging, with each manufacturer using a custom certification standard. The
result was increased administrative burden on both the manufacturers and the authorities.
Topic Why is this task needed? Reference for more detail
1 Envelope Protection Lack of harmonized standard Appendix 1
2 Adaptation for Flight in Icing Lack of harmonized standard Appendix 2
6 Stability Lack of harmonized standard Appendix 3
7 Side Sticks Lack of harmonized standard Appendix 4
9 Wet Runway Stopping There has not been a discussion as to Appendix 5
the factors affecting the ability of the
airplane to create wet runway wheel
braking due to the tire ground
interaction nor whether the
combination of the CFR 25 methods
and operating requirements could be
improved.
10 Runway Excursion Hazard Authorities do not have a Appendix 6
common/harmonized policy/guidance
for classifying systems failures that
could cause runway excursions.
11 Stall IGE Inaccurate accounting of ground Appendix 7
effect stall for takeoff speed schedule
development may impact maximum
performance flight tests such as V
MU
and abused takeoff demonstrations.
12 Steep Approach Lack of harmonized standard Appendix 8
13 Out of Trim Lack of harmonized standard Appendix 9
14 Tailwind-Crosswind Harmonize the presentation of Appendix10
crosswinds in the AFM and remove
risks of different interpretation. For
tailwinds, to harmonize the
compliance methodology.
D. Who has worked the task?
This task has been worked by the Flight Test Harmonization Working Group (FTHWG) specialists in
Aerodynamics, Stability and Control, Flight Test, and Airplane Performance from the following
organisations:
- Authorities : FAA, EASA, TCCA, JCAB*, CAAI*
- Manufacturers : Airbus, Boeing, Bombardier, Dassault, Embraer, Gulfstream, Textron
- Airlines : American Airlines, Delta Airlines*
- Labour Union: ALPA
- Airport Authoritites* (for Topic 12, Steep Approach)
FTHWG Phase 2 Final Recommendation Report – Rev A 10 April, 2017
