[Federal Register Volume 60, Number 111 (Friday, June 9, 1995)]
[Notices]
[Pages 30751-30754]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-14172]
Federal Register / Vol. 60, No. 111 / Friday, June 9, 1995 /
Notices
[[Page 30751]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
Advisory Circular 25-7, Flight Test Guide for Certification of
Transport Category Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of changes to advisory circular.
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SUMMARY: This notice describes the changes to Advisory Circular (AC)
25-7, ``Flight Test Guide for Certification of Transport Category
Airplanes,'' that accompany Amendment 25-84, published elsewhere in
this issue of the Federal Register.
FOR FURTHER INFORMATION CONTACT:
Donald K. Stimson, Flight Test and Systems Branch, ANM-111, Transport
Airplane Directorate, Aircraft Certification Service, FAA, 1601 Lind
Avenue SW., Renton, WA 98055-4056; telephone (206) 227-1129; facsimile
(206) 227-1320.
SUPPLEMENTARY INFORMATION:
Discussion
On May 22, 1990, the Aerospace Industries Association of America,
Inc. (AIA) and the Association Europeenne des Constructeurs de Materiel
Aerospatial (AECMA) jointly petitioned the FAA and the European Joint
Aviation Authorities (JAA) to harmonize certain airworthiness
requirements that apply to transport category airplanes. In their
petition, a summary of which was published in the July 17, 1990,
edition of the Federal Register (55 FR 137), AIA and AECMA also
recommended changes to Advisory Circular (AC) 25-7, ``Flight Test Guide
for Certification of Transport Category Airplanes,'' to ensure that the
harmonized standards would be interpreted and applied consistently.
Part 25 of the Federal Aviation Regulations (FAR) prescribes the
United States airworthiness standards for transport category airplanes.
Advisory Circular (AC) 25-7 provides guidelines that the FAA has found
acceptable for flight testing transport category airplanes to
demonstrate compliance with those airworthiness standards. Revisions to
part 25, in response to the AIA/AECMA petition, were proposed by the
FAA in Notice of Proposed Rulemaking (NPRM) 94-15, which was published
in the Federal Register on April 22, 1994 (59 FR 19296). The proposed
revisions to AC 25-7 were published in the same issue of the Federal
Register as NPRM 94-15 (59 FR 19303).
Amendment 25-84, which resulted from publication of Notice 94-15,
is published elsewhere in this issue of the Federal Register. The
changes to AC 25-7 that accompany Amendment 25-84 are detailed below.
Copies of the affected pages will be available for distribution shortly
after publication of this notice.
Revisions to AC 25-7 to Accompany Amendment 25-84
1. Replace Paragraph 16.a With the Following
a. Section 25.119(a) states that the engines are to be set at the
power or thrust that is available eight seconds after initiating
movement of the power or thrust controls from the minimum flight idle
position to the go-around power or thrust setting. The procedures given
are for the determination of this maximum thrust for showing compliance
with the climb requirements of Sec. 25.119.
2. Replace Paragraph 16.b.(3) With the Following
(3) For the critical air bleed configuration, stabilize the
airplane in level flight with symmetric power on all engines, landing
gear down, flaps in the landing position, at a speed of 1.3 VS0,
simulating the estimated minimum climb limiting landing weights at an
altitude sufficiently above the selected test altitude so that the time
to descend to the test altitude with the throttles closed equals the
appropriate engine r.p.m. stabilization time determined in paragraph
(2). Retard the throttles to the flight idle position and descend at
1.3 VS to approximately the test altitude; when the appropriate
time has elapsed, rapidly advance the power or thrust controls to the
go-around power or thrust setting. The power or thrust controls may
first be advanced to the forward stop and then retarded to the go-
around power or thrust setting. At the applicant's option, additional
less critical bleed configurations may be tested.
3. Add the Following Sections to Paragraph 20.a
(1) The maximum forces given in the table in Sec. 25.143(c) for
pitch and roll control for short-term application are applicable to
maneuvers in which the control force is only needed for a short period.
Where the maneuver is such that the pilot will need to use one hand to
operate other controls (such as during the landing flare or a go-
around, or during changes of configuration or power resulting in a
change of control force that must be trimmed out) the single-handed
maximum control forces will be applicable. In other cases (such as
takeoff rotation, or maneuvering during en route flight), the two-
handed maximum forces will apply.
(2) Short-term and long-term forces should be interpreted as
follows:
(i) Short-term forces are the initial stabilized control forces
that result from maintaining the intended flight path following
configuration changes and normal transactions from one flight condition
to another, or from regaining control following a failure. It is
assumed that the pilot will take immediate action to reduce or
eliminate such forces by re-trimming or changing configuration or
flight conditions, and consequently short-term forces are not
considered to exist for any significant duration. They do not include
transient force peaks that may occur during the configuration change,
change of flight conditions, or recovery of control following a
failure.
(ii) Long-term forces are those control forces that result from
normal or failure conditions that cannot readily be trimmed out or
eliminated.
4. Add the Following Sections to Paragraph 20
d. Acceptable Means of Compliance. An acceptable means of
compliance with the requirement that stick forces may not be excessive
when maneuvering the airplane is to demonstrate that, in a turn for
0.5g incremental normal acceleration (0.3g above 20,000 feet) at speeds
up to VFC/MFC, the average stick force gradient does not
exceed 120 lbs/g.
e. Interpretive Material. (1) The objective of Sec. 25.143(f) is to
ensure that the limit strength of any critical component on the
airplane would not be exceeded in maneuvering flight. In much of the
structure, the load sustained in maneuvering flight can be assumed to
be directly proportional of the load factor applied. However, this may
not be the case for some parts of the structure, e.g., the tail and
rear fuselage. Nevertheless, it is accepted that the airplane load
factor will be a sufficient guide to the possibility of exceeding limit
strength on any critical component if a structural investigation is
undertaken whenever the design positive limit maneuvering load factor
is closely approached. If flight testing indicates that the design
positive limit maneuvering load factor could be exceeded in steady
maneuvering flight with a 50-pound stick force, the airplane structure
should be evaluated for the anticipated load at a 50-pound stick force.
The airplane will be considered to have been overstressed if limit
strength has been exceeded in any critical [[Page 30752]] component.
For the purposes of this evaluation, limit strength is defined as the
larger of either the limit design loads envelope increased by the
available margins of safety, or the ultimate static test strength
divided by 1.5.
(2) Minimum Stick Force to Reach Limit Strength. (i) A stick force
of at least 50 pounds to reach limit strength in steady maneuvers or
wind-up turns in considered acceptable to demonstrate adequate minimum
force at limit strength in the absence of deterrent buffeting. If heavy
buffeting occurs before the limit strength condition is reached, a
somewhat lower stick force at limit strength may be acceptable. The
acceptability of a stick force of less than 50 pounds at the limit
strength condition will depend upon the intensity of he buffet, the
adequacy of the warning margin (i.e., the load factor increment between
the heavy buffet and the limit strength condition), and the stick force
characteristics. In determining the limit strength condition for each
critical component, the contribution of buffet loads to the overall
maneuvering loads should be taken into account.
(ii) This minimum stick force applies in the en route configuration
with the airplane trimmed for straight flight, at all speeds above the
minimum speed at which the limit strength condition can be achieved
without stalling. No minimum stick force is specified for other
configurations, but the requirements of Sec. 25.143(f) are applicable
in these conditions.
(3) Stick Force Characteristics. (i) At all points within the
buffet onset boundary determined in accordance with Sec. 25.251(e), but
not including speeds above VFC/MFC, the stick force should
increase progressively with increasing load factor. Any reduction in
stick force gradient with change of load factor should not be so large
or abrupt as to impair significantly the ability of the pilot to
maintain control over the load factor and pitch attitude of the
airplane.
(ii) Beyond the buffet onset boundary, hazardous stick force
characteristics should not be encountered within the permitted
maneuvering envelope as limited by paragraph 20.e.(3)(iii). It should
be possible, by use of the primary longitudinal control alone, to pitch
the airplane rapidly nose down so as to regain the initial trimmed
conditions. The stick force characteristics demonstrated should comply
with the following:
(A) For normal acceleration increments of up to 0.3g beyond buffet
onset, where these can be achieved, local reversal of the stick force
gradient may be acceptable, provided that any tendency to pitch up is
mild and easily controllable.
(B) For normal acceleration increments of more than 0.3g beyond
buffet onset, where these can be achieved, more marked reversals of the
stick force gradient may be acceptable. It should be possible for any
tendency to pitch up to be contained within the allowable maneuvering
limits without applying push forces to the control column and without
making a large and rapid forward movement of the control column.
(iii) In flight tests to satisfy paragraphs 20.e.(3) (i) and (ii),
the load factor should be increased until either:
(A) The level of buffet becomes sufficient to provide a strong and
effective deterrent to further increase of load factor; or
(B) Further increase the load factor requires a stick force in
excess of 150 pounds (or in excess of 100 pounds when beyond the buffet
onset boundary) or is impossible because of the limitations of the
control system; or
(C) The positive limit maneuvering load factor established in
compliance with Sec. 25.337(b) is achieved.
(4) Negative Load Factors. It is not intended that a detailed
flight test assessment of the maneuvering characteristics under
negative load factors should necessarily be made throughout the
specified range of conditions. An assessment of the characteristics in
the normal flight envelope involving normal accelerations from 1g to
zero g will normally be sufficient. Stick forces should also be
assessed during other required flight testing involving negative load
factors. Where these assessments reveal stick force gradients that are
unusually low, or that are subject to significant variation, a more
detailed assessment, in the most critical of the specified conditions,
will be required. This may be based on calculations provided these are
supported by adequate flight test or wind tunnel data.
5. Replace Paragraph 21.a.(e) With the Following
(3) Section 25.145(c) contains requirements associated primarily
with attempting a go-around maneuver from the landing configuration.
Retraction of the high-lift devices from the landing configuration
should not result in a loss of altitude if the power or thrust controls
are moved to the go-around setting at the same time that flap/slat
retraction is begun. The design features involved with this requirement
are the rate of flap/slat retraction, the presence of any flap gates,
and the go-around power or thrust setting.
(i) Flap gates, which prevent the pilot from moving the flap
selector through the gated position without a separate and distinct
movement of the selector, allow compliance with these requirements to
be demonstrated in segments. High lift device retraction must be
demonstrated beginning from the maximum landing position to the first
gated position, between gated positions, and from the last gated
position to the fully retracted position.
(ii) The go-around power or thrust setting should be the same as is
used to comply with the approach and landing climb performance
requirements of Secs. 25.121(d) and 25.119, and the controllability
requirements of Secs. 25.145(b)(3), 25.145(b)(4), 25.145(b)(5),
25.149(f), and 25.149(g). The controllability requirements may limit
the go-around power or thrust setting.
6. Replace Paragraph 21.c.(3)(i)(E) With the Following
(E) Engine power at flight idle and the go-around power or thrust
setting.
7. Replace Paragraph 21.c.(4)(ii) With the Following
(ii) The airplane should be trimmed at a speed of 1.4 VS.
Quickly set go-around power or thrust while maintaining the speed of
1.4 VS. The longitudinal control force should not exceed 50 lbs.
throughout the maneuver without changing the trim control.
8. Replace Paragraph 21.c.(6)(ii) With the Following
(ii) Test procedure: With the airplane stable in level flight at a
speed of 1.1 VS for propeller driven airplanes, or 1.2 VS for
turbojet powered airplanes, retract the flaps to the full up position,
or the next gated position, while simultaneously setting go-around
power. Use the same power or thrust as is used to comply with the
performance requirement of Sec. 25.121(d), as limited by the applicable
controllability requirements. It must be possible, without requiring
exceptional piloting skill, to prevent losing altitude during the
maneuver. Trimming is permissible at any time during the maneuver. If
gates are provided, conduct this test beginning from the maximum
landing flap position to the first gate, from gate to gate, and from
the last gate to the fully retracted position. (The gate design
requirements are specified within the rule.) Keep the landing gear
extended throughout the test. [[Page 30753]]
9. Revise the First Sentence of Paragraph 23.a by Replacing ``Landing
Approach (VMCL)'' by ``Approach and Landing VMCL and
VMCL-2).'' Revise the Second Sentence in the Same Paragraph by
Replacing ``VMCL'' with ``VMCL and VMCL-2''
10. Replace Paragraph 23.b.(2)(iii) With the Following
(iii) During determination of VMCG, engine failure recognition
should be provided by:
(A) The pilot feeling a distinct change in the directional tracking
characteristics of the airplane, or
(B) The pilot seeing a directional divergence of the airplane with
respect to the view outside the airplane.
11. Replace Paragraph 23.b.(3) With the Following
(3) Minimum Control Speed During Approach and Landing (VMCL)--
Sec. 25.149(f).
(i) This section is intended to ensure that the airplane is safely
controllable following an engine failure during an all-engines-
operating approach and landing. From a controllability standpoint, the
most critical case usually consists of an engine failing after the
power or thrust has been increased to perform a go-around from an all-
engines-operating approach. Section 25.149(f) requires the minimum
control speed to be determined that allows a pilot of average skill and
strength to retain control of the airplane after the critical engine
becomes inoperative and to maintain straight flight with less than five
degrees of bank angle. Section 25.149(h) requires that sufficient
lateral control be available at VMCL to roll the airplane through
an angle of 20 degrees, in the direction necessary to initiate a turn
away from the inoperative engine, in not more than five seconds when
starting from a steady flight condition.
(ii) Conduct this test using the most critical of the all-engines-
operating approach and landing configurations, or at the option of the
applicant, each of the all-engines-operating approach and landing
configurations. The procedures given in paragraph 23.b.(1)(ii) for
VMCA may be used to determine VMCL, except that flap and trim
settings should be appropriate to the approach and landing
configurations, the power or thrust on the operating engine(s) should
be set to the go-around power or thrust setting, and compliance with
all VMCL requirements of Secs. 25.149 (f) and (h) must be
demonstrated.
12. Add the Following New Sections to Paragraph 23.b.(3)
(iii) For propeller driven airplanes, the propeller must be in the
position it achieves without pilot action following engine failure,
assuming the engine fails while at the power or thrust necessary to
maintain a three degree approach path angle.
(iv) At the option of the applicant, a one-engine-inoperative
landing minimum control speed, VMCL(1 out), may be determined in
the conditions appropriate to an approach and landing with one engine
having failed before the start of the approach. In this case, only
those configurations recommended for use during an approach and landing
with one engine inoperative need be considered. The propeller of the
inoperative engine, if applicable, may be feathered throughout. The
resulting value of VMCL(1 out) may be used in determining the
recommended procedures and speeds for a one-engine-inoperative approach
and landing.
13. Replace and Re-Designate Paragraphs 23.b.(4), 23.b.4(ii), and
23.b.4(ii)(A) With the Following
(4) Minimum Control Speed With One Engine Inoperative During
Approach and Landing (VMCL-2)--Sec. 25.149(g).
(iii) Conduct this test using the most critical approved one-
engine-inoperative approach or landing configuration (usually the
minimum flap deflection), or at the option of the applicant, each of
the approved one-engine-inoperative approach and landing
configurations. The following demonstrations are required to determine
VMCL-2:
(A) With the power or thrust on the operating engines set to
maintain a minus 3 degree glideslope with one critical engine
inoperative, the second critical engine is made inoperative and the
remaining operating engine(s) are advanced to the go-around power or
thrust setting. The VMCL-2 speed is established by the procedures
presented in paragraph 23.b.(1)(ii) for VMCA, except that flap and
trim setting should be appropriate to the approach and landing
configurations, the power or thrust on the operating engine(s) should
be set to the go-around power or thrust setting, and compliance with
all VMCL-2 requirements of Secs. 25.149(g) and (h) must be
demonstrated.
14. Add the Following New Section to Paragraph 23.b.(4)
(ii) For propeller driven airplanes, the propeller of the engine
inoperative at the beginning of the approach may be in the feathered
position. The propeller of the more critical engine must be in the
position it automatically assumes following engine failure.
(iii)(C) Starting from a steady straight flight condition,
demonstrate that sufficient lateral control is available at VMCL-2
to roll the airplane through an angle of 20 degrees in the direction
necessary to initiate a turn away from the inoperative engines in not
more than five seconds. This maneuver may be flown in a bank-to-bank
roll through a wings level attitude.
(iv) At the option of the applicant, a two-engines-inoperative
landing minimum control speed, VMCL-2(2 out), may be determined in
the conditions appropriate to an approach and landing with two engines
having failed before the start of the approach. In this case, only
those configurations recommended for use during an approach and landing
with two engines inoperative need be considered. The propellers of the
inoperative engines, if applicable, may be feathered throughout. The
values of VMCL-2 or VMCL-2(2 out) should be used as guidance
in determining the recommended procedures and speeds for a two-engines-
inoperative approach and landing.
15. Add the Following New Section to Paragraph 23.b
(5) Autofeather Effects. Where an autofeather or other drag
limiting system is installed and will be operative at approach power
settings, its operation may be assumed in determining the propeller
position achieved when the engine fails. Where automatic feathering is
not available, the effects of subsequent movements of the engine and
propeller controls should be considered, including fully closing the
power lever of the failed engine in conjunction with maintaining the
go-around power setting on the operating engine(s).
16. Replace Paragraph 29.b.(3)(i) With the Following
(i) The pitch control reaches the aft stop is held full aft for two
seconds, or until the pitch attitude stops increasing, whichever occurs
later. In the case of turning flight stalls, recovery may be initiated
once the pitch control reaches the aft stop when accompanied by a
rolling motion that is not immediately controllable (provided the
rolling motion complies with Sec. 25.203 (c)).
17. Replace Paragraph 29.b.(3)(ii) With the Following
(ii) An uncommanded, distinctive and easily recognizable nose down
pitch that cannot be readily arrested. This nose down pitch may be
accompanied [[Page 30754]] by a rolling motion that is not immediately
controllable, provided that the rolling motion complies with
Sec. 25.203(b) or (c) as appropriate.
18. Remove Paragraph 29.b.(3)(iii) (and Redesignate Paragraph 29.b.(3)
(iv) and (v) as 29.b.(3) (iii) and (iv), Respectively
(iii) A roll that cannot be readily arrested with normal use of
lateral/directional control.
19. Replace Paragraph 29.d.(3)(i) With the Following
(i) The airplane should be trimmed for hands-off flight at a speed
20 percent to 40 percent above the stall speed, with the appropriate
power setting and configuration. Then, using only the primary
longitudinal control, establish and maintain a deceleration (entry
rate) consistent with that specified in Secs. 25.201(c)(1) or
25.201(c)(2), as appropriate, until the airplane is stalled. Both power
and pilot selectable trim should remain constant throughout the stall
and recovery (angle of attack has decreased to the point of no stall
warning).
20. Replace Paragraph 29.d.(3)(iii) With the Following
(iii) In addition, for turning flight stalls, apply the
longitudinal control to achieve airspeed deceleration rates up to 3
knots per second. The intent of evaluating higher deceleration rates is
to demonstrate safe characteristics at higher rates of increase of
angle of attack than are obtained from the 1 knot per second stalls.
The specified airspeed deceleration rate, and associated angle of
attack rate, should be maintained up to the point at which the airplane
stalls.
21. Replace Paragraph 29.d.(3)(iv) With the Following
(iv) For those airplanes where stall is defined by full nose-up
longitudinal control for both forward and aft c.g., the time at full
aft stick during characteristics testing should be not less than that
used for all speed determination. For turning flight stalls, however,
recovery may be initiated once the pitch control reaches the aft stop
when accompanied by a rolling motion that is not immediately
controllable (provided the rolling motion complies with
Sec. 25.203(c)).
22. Add the Following New Section to Paragraph 29.d.(3)
(vi) In level wing stalls the bank angle may exceed 20 degrees
occasionally, provided that lateral control is effective during
recovery.
Issued in Renton, Washington, on March 9, 1995.
Ronald T. Wojnar,
Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 95-14172 Filed 6-8-95; 8:45 am]
BILLING CODE 4910-13-M
