1-g Stall Speed as the Basis for Compliance With Part 25 of the Federal Aviation Regulations

Part II

Department of Transportation

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Federal Aviation Administration

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14 CFR Part 1, et al.

1-g Stall Speed as the Basis for Compliance With Part 25 of the Federal

Aviation Regulations; Proposed Rule

Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 1, 25, 36, and 97

[Docket No. 28404; Notice No. 95-17]

RIN 2120-AD40

1-g Stall Speed as the Basis for Compliance With Part 25 of the

Federal Aviation Regulations

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking.

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SUMMARY: The Federal Aviation Administration (FAA) proposes to redefine

the reference stall speed for transport category airplanes as the 1-g

stall speed instead of the minimum speed obtained in a stalling

maneuver. The proposed changes would: provide for a consistent,

repeatable reference stall speed; ensure consistent and dependable

maneuvering margins; provide for adjusted multiplying factors to

maintain approximately the current requirements in areas where use of

the minimum speed in the stalling maneuver has proven adequate; and

harmonize the applicable regulations with those proposed for the

European Joint Aviation Requirements-25 (JAR-25). These changes would

result in a higher level of safety for those cases in which current

methods would result in artificially low operating speeds.

DATES: Comments must be received on or before May 17, 1996.

e of

the minimum speed in the stalling maneuver has proven adequate; and

harmonize the applicable regulations with those proposed for the

European Joint Aviation Requirements-25 (JAR-25). These changes would

result in a higher level of safety for those cases in which current

methods would result in artificially low operating speeds.

DATES: Comments must be received on or before May 17, 1996.

ADDRESSES: Comments on this notice may be mailed in triplicate to:

Federal Aviation Administration, Office of the Chief Counsel,

Attention: Rules Docket (AGC-10), Docket No. 28404, 800 Independence

Avenue SW., Washington, DC 20591; or delivered in triplicate to: Room

915G, 800 Independence Avenue SW., Washington, DC 20591. Comments

delivered must be marked Docket No. 28404. Comments may be examined in

Room 915G weekdays, except Federal holidays, between 8:30 a.m. and 5:00

p.m. In addition, the FAA is maintaining an information docket of

comments in the Transport Airplane Directorate (ANM-100), Federal

Aviation Administration, Northwest Mountain Region, 1601 Lind Avenue

SW., Renton, WA 98055-4056. Comments in the information docket may be

examined weekdays, except Federal holidays, between 7:30 a.m. and 4:00

p.m.

FOR FURTHER INFORMATION CONTACT: Don Stimson, Flight Test and Systems

Branch, ANM-111, Transport Airplane Directorate, Aircraft Certification

Service, FAA, 1601 Lind Avenue SW., Renton, WA 98055-4056; telephone

st Mountain Region, 1601 Lind Avenue

SW., Renton, WA 98055-4056. Comments in the information docket may be

examined weekdays, except Federal holidays, between 7:30 a.m. and 4:00

p.m.

FOR FURTHER INFORMATION CONTACT: Don 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:

Comments Invited

Interested persons are invited to participate in this proposed

rulemaking by submitting such written data, views, or arguments as they

may desire. Comments relating to any environmental, energy, or economic

impact that might result from adopting the proposals contained in this

notice are invited. Substantive comments should be accompanied by cost

estimates. Commenters should identify the regulatory docket or notice

number and submit comments in triplicate to the Rules Docket address

above. All comments received on or before the closing date for comments

will be considered by the Administrator before taking action on this

proposed rulemaking. The proposals contained in this notice may be

changed in light of comments received. All comments received will be

available in the Rules Docket, both before and after the comment period

closing date, for examination by interested persons. A report

summarizing each substantive public contact with FAA personnel

concerning this rulemaking will be filed in the docket. Persons wishing

the FAA to acknowledge receipt of their comments must submit with those

comments a self-addressed, stamped postcard on which the following

statement is made: ``Comments to Docket No. 28404.'' The postcard will

be date stamped and returned to the commenter.

Availability of the NPRM

antive public contact with FAA personnel

concerning this rulemaking will be filed in the docket. Persons wishing

the FAA to acknowledge receipt of their comments must submit with those

comments a self-addressed, stamped postcard on which the following

statement is made: ``Comments to Docket No. 28404.'' The postcard will

be date stamped and returned to the commenter.

Availability of the NPRM

Any person may obtain a copy of this notice by submitting a request

to the Federal Aviation Administration, Office of Public Affairs,

Attention: Public Inquiry Center, APA-230, 800 Independence Avenue SW.,

Washington, DC 20591; or by calling (202) 267-3484. The notice number

of this NPRM must be identified in all communications. Persons

interested in being placed on a mailing list for future rulemaking

documents should also request a copy of Advisory Circular No. 11-2A,

Notice of Proposed Rulemaking Distribution System, which describes the

application procedure.

Background

The stalling speed (V2) is defined as the minimum speed

demonstrated in the performance stall maneuver described in Sec. 25.103

of 14 CFR part 25 (part 25) of the Federal Aviation Regulations (FAR).

VS has historically served as a reference speed for determining

the minimum operating speeds for transport category airplanes. Examples

of minimum operating speeds that are based on VS include the

takeoff safety speed (V2), the final takeoff climb speed, and the

landing approach speed. The airworthiness standards of part 25 define

these speeds as multiples of VS. For example, V2 must be at

least 1.2 times VS, the final takeoff climb speed must be at least

1.25 times VS, and the landing approach speed must be at least 1.3

times VS.

The speed margin, or difference in speed, between VS and each

minimum operating speed provides a safety ``cushion'' to ensure that

normal operating speeds are sufficiently higher than the speed at which

the airplane stalls

For example, V2 must be at

least 1.2 times VS, the final takeoff climb speed must be at least

1.25 times VS, and the landing approach speed must be at least 1.3

times VS.

The speed margin, or difference in speed, between VS and each

minimum operating speed provides a safety ``cushion'' to ensure that

normal operating speeds are sufficiently higher than the speed at which

the airplane stalls. Using multiplying factors applied to VS to

provide this speed margin, however, assumes that VS provides a

proper reference stall speed. Since VS is the minimum speed

obtained in the stalling maneuver, it can be less than the lowest speed

at which the airplane's weight is still supported entirely by

aerodynamic lift. If VS is significantly less than this speed,

applying multiplying factors to VS to determine the minimum

operating speeds may not provide as large a speed margin as intended.

A proper reference stall speed should provide a reasonably

consistent approximation of the wing's maximum usable lift. Maximum

usable lift occurs at the minimum speed for which the lift provided by

the wing is capable of supporting the weight of the airplane. This

speed is known as the 1-g stall speed because the load factor (the

ratio of airplane lift to weight) at this speed is equal to 1.0 ``g''

(where ``g'' is the acceleration caused by the force of gravity) in the

direction perpendicular to the flight path of the airplane. A speed

lower than the 1-g stall speed represents a transient flight condition

that, if used as a reference for the deriving minimum operating speeds,

may not provide the desired speed margin to protect against

inadvertently stalling the airplane.

For jet transport airplanes, the minimum speed obtained in the

stall maneuver of Sec

direction perpendicular to the flight path of the airplane. A speed

lower than the 1-g stall speed represents a transient flight condition

that, if used as a reference for the deriving minimum operating speeds,

may not provide the desired speed margin to protect against

inadvertently stalling the airplane.

For jet transport airplanes, the minimum speed obtained in the

stall maneuver of Sec. 25.103 usually occurs near the point in the

maneuver where the airplane spontaneously pitches nose-down or where

the pilot initiates recovery after reaching a deterrent level of

buffet, i.e., a vibration of a magnitude and severity that is a strong

and effective deterrent to further speed reduction. Early generation

transport airplanes, which had fairly straight

wings, typically pitched nose-down near the 1-g stall speed. The

minimum speed in the maneuver was easy to note and record, and served

as an adequate approximation of the speed for maximum lift.

For the recent generation of high speed transport airplanes with

swept wings, however, the minimum speed obtained in the stalling

maneuver can be substantially lower than the speed for maximum lift.

Furthermore, the point at which the airplane pitches nose down or

exhibits a deterrent level of buffet is more difficult to distinguish

and can vary with piloting technique. As a result, the minimum speed in

the stalling maneuver has become an inappropriate reference for most

modern high speed transport airplanes for establishing minimum

operating speeds since it may: (1) Be inconsistently determined, and

he point at which the airplane pitches nose down or

exhibits a deterrent level of buffet is more difficult to distinguish

and can vary with piloting technique. As a result, the minimum speed in

the stalling maneuver has become an inappropriate reference for most

modern high speed transport airplanes for establishing minimum

operating speeds since it may: (1) Be inconsistently determined, and

(2) represent a flight condition in which the load factor perpendicular

to the flight path is substantially less than 1.0 g.

In recent years, advanced technology transport category airplanes

have been developed that employ novel flight control systems. These

flight control systems incorporate unique protection features that are

intended to prevent the airplane from stalling. They also prevent the

airplane from maintaining speeds that are slower than a small

percentage above the 1-g stall speed. Because of their unique design

features, the traditional method of establishing VS as the minimum

speed obtained in the stalling maneuver was inappropriate for these

airplanes. The FAA issued special conditions for these airplanes to

define the reference stall speed as the 1-g stall speed for the flight

requirements contained in subpart B of part 25 and the noise

requirements contained in part 36 of the FAR.

In these special conditions, the multiplying factors used to

determine the minimum operating speeds were reduced in order to

maintain equivalency with acceptable operating speeds used by previous

jet transports. Since the 1-g stall speed is generally higher than the

minimum speed obtained in the stalling maneuver, retaining the current

multiplying factors would have resulted in higher minimum operating

speeds for airplanes using the 1-g stall speed as the reference stall

speed. However, increasing the minimum operating speeds would impose

costs on operators because payloads would have to be reduced to comply

with the regulations at the higher operating speeds

um speed obtained in the stalling maneuver, retaining the current

multiplying factors would have resulted in higher minimum operating

speeds for airplanes using the 1-g stall speed as the reference stall

speed. However, increasing the minimum operating speeds would impose

costs on operators because payloads would have to be reduced to comply

with the regulations at the higher operating speeds. Based on the

service experience of the current fleet of jet transports, the costs

imposed would not be offset by a commensurate increase in safety.

Several airplane types with conventional flight control systems

have also been certificated using the 1-g stall speed as the reference

stall speed. Because of the potential deficiencies in using the minimum

speed demonstrated in the stalling maneuver, the FAA has been

encouraging applicants to use the 1-g stall speed in lieu of the

minimum speed obtained in the stalling maneuver. Applicants generally

desire to use 1-g stall speeds because the 1-g stall speeds are less

dependent on pilot technique and other subjective evaluations. Hence,

1-g stall speeds are easier to predict and provide a higher level of

confidence for developing predictions of overall airplane performance.

Again, reduced multiplying factors are applied to the 1-g stall speeds

to obtain minimum operational service. Using 1-g stall speeds ensures

that the airplane's minimum operating speeds will not be unreasonably

low.

Discussion of the Proposals

s. Hence,

1-g stall speeds are easier to predict and provide a higher level of

confidence for developing predictions of overall airplane performance.

Again, reduced multiplying factors are applied to the 1-g stall speeds

to obtain minimum operational service. Using 1-g stall speeds ensures

that the airplane's minimum operating speeds will not be unreasonably

low.

Discussion of the Proposals

The FAA proposes to define the reference stall speed in Sec. 25.103

as a 1-g stall speed, rather than the minimum speed obtained in the

stalling maneuver. This action would provide a consistent basis for use

in all type design certification requirements for transport category

airplanes. The FAA proposes to introduce the symbol VSR to

represent this speed and to indicate that it is different than the

minimum speed obtained in the stalling maneuver, VS.

In addition, the FAA proposes to reduce the multiplying factors

that are used in combination with the reference stall speed to

determine the minimum operating speeds by approximately 6 percent. This

change would result in minimum operating speeds equivalent to those for

most current jet transports since the 1-g stall speed for these

airplanes is approximately 6 percent higher than the minimum speed

obtained in the stalling maneuver. Demonstrating a minimum stalling

speed more than 6 percent slower than the 1-g stall speed, which is

possible under the current standards, would provide an unacceptable

basis for determining the minimum operating speeds. The proposed

standards would prevent this situation from occurring. In this respect,

the proposed standards would provide a higher level of safety than the

existing standards.

However, the reduced factors would allow lower minimum operating

speeds to be established for those airplanes that have a minimum speed

in the stalling maneuver approximately equal to the 1-g stall speed

rating speeds. The proposed

standards would prevent this situation from occurring. In this respect,

the proposed standards would provide a higher level of safety than the

existing standards.

However, the reduced factors would allow lower minimum operating

speeds to be established for those airplanes that have a minimum speed

in the stalling maneuver approximately equal to the 1-g stall speed.

One particular class of airplanes for which this applies are airplanes

equipped with devices that abruptly push the nose down (e.g., stick

pushers) near the angle of attack for maximum lift. These devices are

typically installed on airplanes with unacceptable natural stalling

characteristics. The abrupt nose down push provides an artificial stall

indication and acceptable stall characteristics, and prevents the

airplane from reaching a potentially hazardous natural aerodynamic

stall. The minimum speed obtained in this maneuver is approximately

equal to the 1-g stall speed.

Traditionally, the existing multiplying factors have been applied

to these airplanes. The proposal to define the reference stall speed as

the 1-g stall speed would not affect these airplanes, but reducing the

multiplying factors would allow lower minimum operating speeds to be

established. Therefore, this proposal would allow these airplanes to be

operated at speeds and angles-of-attack closer to the pusher activation

point than has been experienced in operational service.

The FAA considers this reduction in operating speeds for pusher-

equipped airplanes to be acceptable, provided the pusher reliably

performs its intended function and that unwanted operation is

minimized. The FAA intends to propose an acceptable method of

addressing these concerns in an upcoming revision to Advisory Circular

(AC) 25-7

on

point than has been experienced in operational service.

The FAA considers this reduction in operating speeds for pusher-

equipped airplanes to be acceptable, provided the pusher reliably

performs its intended function and that unwanted operation is

minimized. The FAA intends to propose an acceptable method of

addressing these concerns in an upcoming revision to Advisory Circular

(AC) 25-7. In this material, the FAA will provide criteria for pusher

reliability, the effects of design and manufacturing tolerances on the

pusher activation point, design features such as phase advance and

filtering, and the affects of atmospheric turbulence and windshear.

In addition to proposing to define the reference stall speed as the

1-g stall speed and to reduce the multiplying factors for establishing

the minimum operating speeds, the FAA also proposes to require

applicants to demonstrate adequate maneuvering capability during the

takeoff climb, en route climb, and landing approach phases of flight.

During a banked turn, a portion of the lift generated by the wing

provides a force to help turn the airplane. To remain at the same

altitude, the airplane must produce additional lift. Therefore, banking

the airplane (at a constant speed and altitude) reduces the stall

margin, which is the difference between the lift required for the

maneuver and the maximum lift capability of the wing. As the bank angle

increases, the stall margin is reduced proportionately. This bank angle

effect on the stall margin can be determined analytically, and the

multiplying factors applied to VSR to

ore, banking

the airplane (at a constant speed and altitude) reduces the stall

margin, which is the difference between the lift required for the

maneuver and the maximum lift capability of the wing. As the bank angle

increases, the stall margin is reduced proportionately. This bank angle

effect on the stall margin can be determined analytically, and the

multiplying factors applied to VSR to

determine the minimum operating speeds are intended to ensure that an

adequate stall margin is maintained.

In addition to the basic effect of bank angle, however, modern wing

designs also typically exhibit a significant reduction in maximum lift

capability with increasing Mach number. The magnitude of this Mach

number effect depends on the design characteristics of the particular

wing. For wing designs with a large Mach number effect, the maximum

bank angle that can be achieved while retaining an acceptable stall

margin can be significantly reduced. Because the effect of Mach number

can be significant, and because it can also vary greatly for different

wing designs, the multiplying factors applied to VSR are

insufficient to ensure that adequate maneuvering capability exists at

the minimum operating speeds.

To address this issue, the FAA proposes to require a minimum bank

angle capability in a coordinated turn without encountering stall

warning or any other characteristic that might interfere with normal

maneuvering. This requirement would be added to Sec. 25.143 as a new

paragraph (g). The proposed minimum bank angles were derived by adding

a 15 degree allowance for wind gusts and inadvertent overshoot to a

maneuvering capability the FAA considers necessary for the specific

cases identified in the proposed new paragraph. These proposed maneuver

margin requirements are intended to ensure that the level of safety in

maneuvering flight is not reduced by the proposed change to the

reference stall speed and the reduction in the multiplying factors used

to determine the minimum operating speeds

to a

maneuvering capability the FAA considers necessary for the specific

cases identified in the proposed new paragraph. These proposed maneuver

margin requirements are intended to ensure that the level of safety in

maneuvering flight is not reduced by the proposed change to the

reference stall speed and the reduction in the multiplying factors used

to determine the minimum operating speeds.

Consistent with the proposed maneuver margin requirements, the FAA

proposes adding Secs. 25.107(c)(3), 25.107(g)(2), and 25.125(a)(2)(iii)

to reference Sec. 25.143(g) in the list of constraints applicants must

consider when selecting the minimum takeoff safety speed, final takeoff

speed, and reference landing speeds, respectively. The normal all-

engines-operating takeoff climb speed selected by the applicant must

also provide the minimum bank angle capability specified in the

proposed Sec. 25.143(g).

Section 25.145(a) requires that there be adequate longitudinal

control available to promptly pitch the airplane's nose down from at or

near the stall in order to return to original trim speed. The intent of

this requirement is to ensure sufficient pitch control for a prompt

recovery if the airplane is inadvertently slowed to the point of stall.

The FAA proposes to change the wording of this requirement to replace

``VS'' with ``the stall,'' ``Sec. 25.103(b)(1)'' with

``Sec. 25.103(a)(6),'' and ``at any speed'' with ``at any point.''

These changes would be consistent with the proposed change to the

definition of the reference stall speed and the proposed re-formatting

of Sec. 25.103.

Although Sec. 25.145(a) must be met both with power off and with

maximum continuous power, there is no intention to require flight test

demonstrations of full stalls at engine powers above that specified in

Sec. 25.201(a)(2)

at any point.''

These changes would be consistent with the proposed change to the

definition of the reference stall speed and the proposed re-formatting

of Sec. 25.103.

Although Sec. 25.145(a) must be met both with power off and with

maximum continuous power, there is no intention to require flight test

demonstrations of full stalls at engine powers above that specified in

Sec. 25.201(a)(2). Instead of performing a full stall at maximum

continuous power, compliance may be assessed by demonstrating

sufficient static longitudinal stability and nose down control margin

when the deceleration is ended at least one second past stall warning

during a one knot per second deceleration. The static longitudinal

stability during the maneuver and the nose down control power remaining

at the end of the maneuver must be sufficient to assure compliance with

the requirement.

Section 25.207 requires that a warning of an impending stall must

be provided in order to prevent the pilot from inadvertently stalling

the airplane. The warning must occur at a speed sufficiently higher

than the stall speed to allow the pilot time to take action to avoid a

stall. The speed difference between the stall speed and the speed at

which the stall warning occurs is known as the stall warning margin.

The FAA proposes amending the size of the stall warning margin required

by Sec. 25.207(c) because of the change in definition of the reference

stall speed.

Currently, the stall warning must begin at a speed exceeding

VS by seven knots, or a lesser margin if the stall warning has

enough clarity, duration, distinctiveness, or other similar properties.

Requiring the same seven knot warning margin to be provided relative to

VSR would result in an increase to the minimum operating speeds.

This increase in the minimum operating speeds would be necessary to

meet the maneuvering margin requirements proposed in Sec. 25.143(g),

which are defined relative to the stall warning speed

gh clarity, duration, distinctiveness, or other similar properties.

Requiring the same seven knot warning margin to be provided relative to

VSR would result in an increase to the minimum operating speeds.

This increase in the minimum operating speeds would be necessary to

meet the maneuvering margin requirements proposed in Sec. 25.143(g),

which are defined relative to the stall warning speed. However, as

discussed previously, requiring an increase to the minimum operating

speeds would impose costs to airplane operators that cannot be

justified by service experience.

On the other hand, if the stall warning margin were reduced to

retain approximately the same stall warning speed, the warning would

occur only one or two knots prior to reaching the 1-g stall speed.

Although reaching the 1-g stall speed is not likely to be a

catastrophic occurrence, the FAA considers such a small stall warning

margin to be unacceptable. The FAA proposes requiring a stall warning

margin of at least 3 knots or 3 percent, whichever is greater, relative

to VSR. The FAA considers this margin to represent a reasonable

balance between providing the pilot with enough warning to avert an

impending stall, and providing adequate maneuvering capability at the

minimum operating speeds. This proposal would retain the existing level

of safety.

The FAA proposes to require a larger stall warning margin for

airplanes equipped with devices that abruptly push the nose down at a

selected angle of attack (e.g., stick pushers). Inadvertent operation

of such a device, especially close to the ground, can have more serious

consequences than a comparable situation in which the pilot of an

airplane without the device inadvertently slows to VSR. Therefore,

the FAA proposes adding Sec. 25.207(d) to require the stall warning,

for airplanes equipped with one of these devices, to occur at least 5

knots or 5 percent, whichever is greater, above the speed at which the

device activates

the ground, can have more serious

consequences than a comparable situation in which the pilot of an

airplane without the device inadvertently slows to VSR. Therefore,

the FAA proposes adding Sec. 25.207(d) to require the stall warning,

for airplanes equipped with one of these devices, to occur at least 5

knots or 5 percent, whichever is greater, above the speed at which the

device activates. This proposal is intended to retain the existing

level of safety for airplanes equipped with such devices.

The FAA proposes to add a new paragraph, Sec. 25.207(e), to require

that, in a slow-down turn with load factors up to 1.5 g and

deceleration rates up to 3 knots per second, sufficient stall warning

must exist to prevent stalling when recovery is initiated not less than

one second after stall warning occurs. The FAA considers the proposed

requirement necessary to provide adequate stall warning during a

dynamic maneuver, such as a collision avoidance maneuver. In addition,

this new paragraph would provide a quantitative requirement with which

to assess whether ``sufficient margin to prevent inadvertent stalling *

* * in turning flight'' has been provided as required by

Sec. 25.207(a). This proposal would increase the level of safety during

maneuvering flight.

The FAA proposes to add a new paragraph, Sec. 25.207(f), to require

that stall warning be provided for abnormal airplane configurations

likely to be used following system failures. This proposal adds a

requirement currently contained in JAR-25 and is consistent with

current transport airplane designs. There would be no impact on the

existing level of safety.

On modern jet transports, the natural buffet or vibration caused by

the airflow separating and reattaching itself to the wing as the

airplane approaches the

ing, or by adjusting

flight test data obtained at some other setting.

The tolerances associated with the stall warning system must also

be considered in relation to the proposed minimum maneuvering

requirements of Sec. 25.143(g). As proposed, Sec. 25.143(g) would

require that the airplane be capable of reaching a minimum bank angle

during a coordinated turn without encountering stall warning. Because

the proposed requirements already provide the capability to overshoot

the intended bank angle by 15 degrees, the small differences in the

speed at which the stall warning system operates due to system

tolerances are not as critical. Therefore, the FAA intends for the

minimum bank angles in the proposed Sec. 25.143(g) to apply at the

designed nominal setting of the stall warning system. To ensure that

large production tolerances do not adversely impact the airplane's

maneuvering capability free of stall warning, the bank angle capability

specified in the proposed Sec. 25.143(g) should not be reduced by more

than two degrees with the stall warning system operating at its most

critical tolerance. Applicants would be expected to demonstrate this

capability either by flight test with the system set to its critical

tolerance, or by analytically adjusting flight test data obtained at

some other setting.

To be consistent with the proposed revision of the definition of

the reference stall speed, the FAA proposes to incorporate reduced

multiplying factors throughout part 25, where appropriate, in

requirements that use speeds based on a multiple of the reference stall

speed. The FAA also proposes numerous minor wording and structural

changes to various sections to improve editorial clarity and to

harmonize with the wording and structure proposed for JAR-25.

The FAA proposes to add the nomenclature ``final takeoff speed''

and ``reference landing speed'' and the abbreviations ``VFTO'' and

``VREF'' to denote these speeds, respectively, to part 1 of the

FAR

speed. The FAA also proposes numerous minor wording and structural

changes to various sections to improve editorial clarity and to

harmonize with the wording and structure proposed for JAR-25.

The FAA proposes to add the nomenclature ``final takeoff speed''

and ``reference landing speed'' and the abbreviations ``VFTO'' and

``VREF'' to denote these speeds, respectively, to part 1 of the

FAR. These terms and abbreviations, which are commonly used in the

aviation industry, would be referenced throughout the proposed

amendments to part 25. The reference landing speed would be defined as

the speed of the airplane, in a specified landing configuration, at the

point where it descends through the landing screen height in the

determination of the landing distance for manual landings. The term

``landing screen height'' refers to the height of the airplane at the

beginning of the defined landing distance. This height is normally 50

feet above the landing surface (see Sec. 25.125(a)), but approvals have

been granted for steep approaches that use a landing screen height of

35 feet. The final takeoff speed would be defined as the speed of the

airplane that exists at the end of the takeoff path in the en route

configuration with one engine inoperative.

The FAA also proposes to add the abbreviations VSR, VSR0,

and VSR1 to part 1, and use them in part 25 to denote the

reference stall speed corresponding to different airplane

configurations. In addition, the FAA proposes adding the abbreviation

VSW to part 1 to refer to the stall warning speed.

The FAA proposes to amend Sec

eoff path in the en route

configuration with one engine inoperative.

The FAA also proposes to add the abbreviations VSR, VSR0,

and VSR1 to part 1, and use them in part 25 to denote the

reference stall speed corresponding to different airplane

configurations. In addition, the FAA proposes adding the abbreviation

VSW to part 1 to refer to the stall warning speed.

The FAA proposes to amend Sec. C36.9(e)(1) by replacing ``1.3

VS + 10 knots'' with ``VREF + 10 knots'' and by removing the

words ``or the speed used in establishing the approved landing distance

under the airworthiness regulations constituting the type certification

basis of the airplane, whichever speed is greatest.'' The words

proposed to be deleted would no longer be necessary because VREF

would denote the speed used in establishing the approved landing

distance under the airworthiness regulations constituting the type

certification basis of the airplane. Also, VREF would refer to the

speed at the landing screen height, regardless of whether that speed

for a particular airplane is 1.3 VS, 1.23 VSR, or some higher

speed.

In the same manner, the FAA proposes to amend Sec. 97.3(b) by

replacing ``1.3 VS0'' with ``VREF.'' As noted above,

VREF would refer to the speed at the landing screen height used in

establishing the approved landing distance under the airworthiness

regulations constituting the type certification basis of the airplane,

regardless of whether that speed for a particular airplane is 1.3

VS, 1.23 VSR, or some higher speed.

These proposals have been discussed extensively with the European

Joint Aviation Authorities (JAA) with the intent of harmonizing the

certification requirements related to stall speed for transport

category airplanes. The JAA intend to introduce an equivalent proposal

to amend the Joint Aviation Requirements-25 (JAR-25). JAR-25 prescribes

the airworthiness standards for transport category airplanes that are

accepted by the aviation regulatory authorities of 23 European nations

rities (JAA) with the intent of harmonizing the

certification requirements related to stall speed for transport

category airplanes. The JAA intend to introduce an equivalent proposal

to amend the Joint Aviation Requirements-25 (JAR-25). JAR-25 prescribes

the airworthiness standards for transport category airplanes that are

accepted by the aviation regulatory authorities of 23 European nations.

When it is published, the JAA proposal will be placed in the docket for

this rulemaking.

Regulatory Evaluation Summary

Preliminary Regulatory Evaluation, Initial Regulatory Flexibility

Determination, and Trade Impact Assessment

Proposed changes to Federal regulations must undergo several

economic analyses. First, Executive Order 12866 directs that each

Federal agency shall propose or adopt a regulation only upon a reasoned

determination that the benefits of the intended regulation justify its

costs. Second, the Regulatory Flexibility Act of 1980 requires agencies

to analyze the economic effect of regulatory changes on small entities.

Third, the Office of Management and Budget directs agencies to assess

the effects of regulatory changes on international trade. In conducting

these analyses, the FAA has determined that this proposed rule: (1)

Would generate benefits that justify its costs and is not a

``significant regulatory action'' as defined in the Executive Order;

(2) is not significant as defined in DOT's Regulatory Policies and

Procedures; (3) would not have a significant impact on a substantial

number of small entities; and (4) would not constitute a barrier to

international trade. These analyses, available in the docket, are

summarized below.

Regulatory Evaluation Summary

Costs

The proposed requirements would apply to future type certificated

transport category airplanes and generally would not impose significant

additional costs on manufacturers. One major manufacturer demonstrated

adherence to the 1-g stall speed basis in recent FAA special conditions

ional trade. These analyses, available in the docket, are

summarized below.

Regulatory Evaluation Summary

Costs

The proposed requirements would apply to future type certificated

transport category airplanes and generally would not impose significant

additional costs on manufacturers. One major manufacturer demonstrated

adherence to the 1-g stall speed basis in recent FAA special conditions

applicable to several models of advanced technology airplanes. Other

manufacturers have requested certification to the 1-g stall speed basis

through equivalent safety findings for airplanes with conventional

flight control systems.

Cost estimates provided by manufacturers generally did not vary

significantly. Data provided by a manufacturer of part 25 small

airplanes, however, showed costs several hundred thousand dollars

higher than the norm. That manufacturer estimated that short-term costs

(mostly non-recurring) to convert to the new stall speed basis would be

over $1 million and that increased costs on a program-by-program basis

would ``be substantial.'' Because of the gross nature of these

estimates and because of the inability to segment them on a per-

certification basis, they have not been incorporated into this

analysis. The FAA invites manufacturers to provide detailed cost

estimates during the public comment period.

Although several sections of part 25 would be revised by the

proposal, only five merit analysis: Sections 25.103 (Stall speed),

25.107 (Takeoff speeds), 25.125 (Landing), 25.143 (General) (under

Controllability and Maneuverability), and 25.207 (Stall warning).

Section 25.103 (Stall Speed)

The proposal to redefine the reference stall speed as a 1-g stall

speed could result in a net reduction in certification costs for part

25 large airplanes. In some recent airplane designs, manufacturers have

used the 1-g stall speed as the reference stall speed

125 (Landing), 25.143 (General) (under

Controllability and Maneuverability), and 25.207 (Stall warning).

Section 25.103 (Stall Speed)

The proposal to redefine the reference stall speed as a 1-g stall

speed could result in a net reduction in certification costs for part

25 large airplanes. In some recent airplane designs, manufacturers have

used the 1-g stall speed as the reference stall speed. Calculation of

the reference stall speed (VSR) is within the range of

instrumentation currently available and additional instrumentation

would not be required. Existing techniques to determine minimum speed

in the stalling maneuver require six to eight independent stalls at

various flap settings; determination of 1-g stall speed could require

approximately half as many. Cost-savings could be in the range of

$50,000 to $100,000 per type certification.

Recent part 25 small transport category airplane certifications, on

the other hand, have not been based on the 1-g stall speed.

Consequently, additional instrumentation and analysis would be

required. Incremental one-time costs for a part 25 small airplane

design would be approximately $70,000. However, cost savings

attributable to reduced testing could be realized in future

certifications (see previous paragraph re part 25 large airplanes).

Section 25.107 (Takeoff Speeds)

The proposed changes to this section, by virtue of the new

maneuvering requirements of Sec. 25.143(g), could affect airplane

operators if the proposed maneuvering requirements necessitate higher

takeoff/climb speeds and lower passenger/cargo capacity on length-

limited runways. Because of the myriad combinations of airplanes,

runways, passenger/cargo loads, etc., the FAA is unable to estimate

potential capacity limitations. The FAA invites interested parties to

provide estimates of such effects during the public comment period.

Section 25.125 (Landing)

As in the case of Sec

te higher

takeoff/climb speeds and lower passenger/cargo capacity on length-

limited runways. Because of the myriad combinations of airplanes,

runways, passenger/cargo loads, etc., the FAA is unable to estimate

potential capacity limitations. The FAA invites interested parties to

provide estimates of such effects during the public comment period.

Section 25.125 (Landing)

As in the case of Sec. 25.107 above, the proposed changes to this

section could potentially affect operators by virtue of the new

maneuvering requirements in Sec. 25.143(g). Again, the FAA invites

interested parties to submit cost estimates during the public comment

period.

Section 25.143 (General)

Incremental costs that would be incurred by manufacturers to

determine minimum maneuvering margins are estimated to total

approximately $150,000 per part 25 large airplane type certification

and approximately $50,000 per part 25 small airplane type

certification.

Section 25.207 (Stall Warning)

Incremental costs that would be incurred by manufacturers to

provide sufficient stall warning at the various proposed slow-down

speeds and configurations are estimated to total approximately $120,000

per part 25 large airplane type certification and approximately

$200,000 per part 25 small airplane type certification.

Total Costs

Manufacturers of part 25 large airplanes have already incurred the

major portion of the start-up costs to convert to a 1-g stall speed

system and would therefore experience lower incremental costs than

manufacturers of part 25 small airplanes. The estimated costs to meet

the revised standards would total approximately $195,000 per part 25

large airplane type certification (costs associated with Secs. 25.143

and 25.207 reduced by the midpoint of the cost-savings range of

Sec. 25.103). Assuming 500 airplanes produced under one type

certification, this would equate to $390 per airplane.

Manufacturers of part 25 small airplanes would experience one-time

costs of $70,000 in conjunction with Sec. 25.103

imately $195,000 per part 25

large airplane type certification (costs associated with Secs. 25.143

and 25.207 reduced by the midpoint of the cost-savings range of

Sec. 25.103). Assuming 500 airplanes produced under one type

certification, this would equate to $390 per airplane.

Manufacturers of part 25 small airplanes would experience one-time

costs of $70,000 in conjunction with Sec. 25.103. In addition, costs

for each future type certification would total approximately $250,000

(attributable to Secs. 25.143 and 25.207), or about $500 per airplane

over a 500 airplane production run. A portion of these costs may be

offset by reduced testing requirements per revised Sec. 25.103. The

potential operating costs of proposed Secs. 25.107 and 25.125 have not

been estimated in this evaluation; the FAA invites interested parties

to provide cost estimates during the public comment period.

Benefits

Redefining the airplane reference stall speed as the 1-g stall

speed would result in a higher level of safety in those cases where

current methods could result in artificially low operating speeds. New

requirements for minimum maneuvering margins would assure that safe

margins are obtained at the minimum operating speeds, thus diminishing

the possibility of inadvertent stalls at critical flight stages.

A review of National Transportation Safety Board accident reports

for the years 1983-1992 does not indicate that any accidents have been

caused by inconsistent/inappropriate reference stall speeds. There were

several accidents in which inadvertent stalls were cited as a

contributing factor, but pilot error (e.g., airspeed not properly

maintained) was the probable cause rather than inherent problems with

the reference stall speed. In spite of the absence of directly aligned

accidents, the FAA postulates that, without the revisions in stall

speed as proposed or effected through special conditions, safety could

reach unacceptably low levels

lls were cited as a

contributing factor, but pilot error (e.g., airspeed not properly

maintained) was the probable cause rather than inherent problems with

the reference stall speed. In spite of the absence of directly aligned

accidents, the FAA postulates that, without the revisions in stall

speed as proposed or effected through special conditions, safety could

reach unacceptably low levels. The benefits associated with avoiding a

single accident would far exceed the costs of the proposed rule.

Regulatory Flexibility Determination

The Regulatory Flexibility Act of 1980 (RFA) was enacted by

Congress to insure that small entities are not unnecessarily or

disproportionately burdened by Government regulations. The RFA requires

agencies to determine whether proposed rules would have ``a significant

economic impact on a substantial number of small entities'' and, in

cases where they would, to conduct a Regulatory Flexibility Analysis.

As prescribed in implementing FAA Order 2100.14A, the size threshold

for a small aircraft manufacturer is one having 75 or fewer employees.

Since there are no manufacturers of part 25 airplanes with 75 or fewer

employees, the proposed rule would not have a significant economic

impact on a substantial number of small entities.

International Trade Impact Assessment

The proposed rule would not constitute a barrier to international

trade, including the export of U.S. airplanes to foreign markets and

the import of foreign airplanes into the U.S. Instead, the proposed

changes would harmonize with corresponding proposals of the European

Joint Aviation Authorities, thereby lessening restraints on trade.

Federalism Implications

tional Trade Impact Assessment

The proposed rule would not constitute a barrier to international

trade, including the export of U.S. airplanes to foreign markets and

the import of foreign airplanes into the U.S. Instead, the proposed

changes would harmonize with corresponding proposals of the European

Joint Aviation Authorities, thereby lessening restraints on trade.

Federalism Implications

The amended regulations proposed in this rulemaking would not have

substantial direct effects on the States, on the relationship between

the national government and the States, or on the distribution of power

and responsibilities among the various levels of government. Therefore,

in accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

preparing a Federalism Assessment.

Conclusion

Because the proposed changes to redefine the reference stall speed

for transport category airplanes as the 1-g stall speed are not

expected to result in substantial economic cost, the FAA has determined

that this proposed regulation would not be significant under Executive

Order 12866. Because this is an issue which has not prompted a great

deal of public concern, the FAA has determined that this action is not

significant under DOT Regulatory Policies and Procedures (44 FR 11034,

February 25, 1979). In addition since there are no small entities

affected by this proposed rulemaking, the FAA certifies, under the

criteria of the Regulatory Flexibility Act, that this rule, if adopted,

will not have a significant economic impact, positive or negative, on a

substantial number of small entities. An initial regulatory evaluation

of the proposal, including a Regulatory Flexibility Determination and

Trade Impact Analysis, has been placed in the docket. A copy may be

obtained by contacting the person identified under FOR FURTHER

INFORMATION CONTACT.

List of Subjects

14 CFR Part 1

Air transportation.

14 CFR Part 25

act, positive or negative, on a

substantial number of small entities. An initial regulatory evaluation

of the proposal, including a Regulatory Flexibility Determination and

Trade Impact Analysis, has been placed in the docket. A copy may be

obtained by contacting the person identified under FOR FURTHER

INFORMATION CONTACT.

List of Subjects

14 CFR Part 1

Air transportation.

14 CFR Part 25

Aircraft, Aviation safety, Reporting and recordkeeping

requirements.

14 CFR Part 36

Agriculture, Aircraft, Noise control.

14 CFR Part 97

Air traffic control, Airports, Navigation (air), Weather.

The Proposed Amendments

Accordingly, the Federal Aviation Administration (FAA) proposes to

amend 14 CFR parts 1, 25, 36, and 97 of the Federal Aviation

Regulations (FAR) as follows:

PART 1--DEFINITIONS AND ABBREVIATIONS

1. The authority citation for part 1 is revised to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

2. Section 1.1 is amended by adding new definitions in alphabetical

order to read as follows:

Sec. 1.1 General definitions.

* * * * *

Final takeoff speed means the speed of the airplane that exists at

the end of the takeoff path in the en route configuration with one

engine inoperative.

* * * * *

Reference landing speed means the speed of the airplane, in a

specified landing configuration, at the point where it descends through

the landing screen height in the determination of the land distance for

manual landings.

* * * * *

3. Section 1.2 is amended by adding new terms in alphabetical order

to read as follows:

Sec. 1.2 Abbreviations and symbols.

* * * * *

VFTO means final takeoff speed.

* * * * *

VREF means reference landing speed.

* * * * *

VSR means reference stall speed.

VSR0 means reference stall speed in the landing configuration.

VSR1 means reference stall speed in a specific configuration.

VSW means speed at which onset of natural or artificial stall

warning occurs.

* * * * *

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

O means final takeoff speed.

* * * * *

VREF means reference landing speed.

* * * * *

VSR means reference stall speed.

VSR0 means reference stall speed in the landing configuration.

VSR1 means reference stall speed in a specific configuration.

VSW means speed at which onset of natural or artificial stall

warning occurs.

* * * * *

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

4. The authority citation for part 25 is revised to read as

follows:

Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 22704.

5. Section 25.103 is revised to read as follows:

Sec. 25.103 Stall speed.

(a) The reference stall speed, VSR, is a calibrated airspeed

as defined in paragraph (c) of this section. VSR is determined

with--

(1) Engines idling, or, if that resultant thrust causes an

appreciable decrease in stall speed, not more than zero thrust at the

stall speed;

(2) Propeller pitch controls (if applicable) in the takeoff

position;

(3) The airplane in other respects (such as flaps and landing gear)

in the condition existing in the test in which VSR is being used;

(4) The weight used when VSR is being used as a factor to

determine compliance with a required performance standard;

(5) The center of gravity position that results in the highest

value of reference stall speed; and

(6) The airplane trimmed for straight flight at a speed selected by

the applicant, but not less than 1.13 VSR and not greater than 1.3

VSR.

(b) Starting from the stabilized trim condition, apply elevator

control to decelerate the airplane so that the speed reduction does not

exceed one knot per second.

enter of gravity position that results in the highest

value of reference stall speed; and

(6) The airplane trimmed for straight flight at a speed selected by

the applicant, but not less than 1.13 VSR and not greater than 1.3

VSR.

(b) Starting from the stabilized trim condition, apply elevator

control to decelerate the airplane so that the speed reduction does not

exceed one knot per second.

(c) The reference stall speed, VSR, is a calibrated airspeed

determined in the stalling maneuver. VSR may not be less than a 1-

g stall speed. VSR is expressed as:

[GRAPHIC][TIFF OMITTED]TP18JA96.000

where--

VCLMAX = Speed occurring when lift coefficient is first a maximum.

In addition, if the stalling maneuver is limited by a device that

commands an abrupt nose down pitch (e.g., a stick pusher), VCLMAX

may not be less than the speed existing at the instant the device

operates; and

nZW = Flight patch normal load factor (not greater than 1.0) at

VCLMAX.

6. Section 25.107 is amended by revising paragraphs (b)(1)

introductory text, (b)(2) introductory text, (c)(1) and (c)(2), and by

adding new paragraphs (c)(3) and (g) to read as follows:

Sec. 25.107 Takeoff speeds.

* * * * *

(b) * * *

(1) 1.13 VSR for--

* * * * *

(2) 1.08 VSR for--

* * * * *

(c) * * *

(1) V2MIN;

(2) VR plus the speed increment attained (in accordance with

Sec. 25.111(c)(2)) before reaching a height of 35 feet above the

takeoff surface; and

(3) A speed that provides the maneuvering capability specified in

Sec. 25.143(g).

* * * * *

(g) VFTO, in terms of calibrated airspeed, must be selected by

the applicant to provide at least the gradient of climb required by

Sec. 25.121(c), but may not be less than--

(1) 1.18 VSR; and

(2) A speed that provides the maneuvering capability specified in

Sec. 25.143(g).

7. Section 25.111 is amended by revising paragraph (a) introductory

text to read as follows:

Sec. 25.111 Takeoff path.

(g) VFTO, in terms of calibrated airspeed, must be selected by

the applicant to provide at least the gradient of climb required by

Sec. 25.121(c), but may not be less than--

(1) 1.18 VSR; and

(2) A speed that provides the maneuvering capability specified in

Sec. 25.143(g).

7. Section 25.111 is amended by revising paragraph (a) introductory

text to read as follows:

Sec. 25.111 Takeoff path.

(a) The takeoff path extends from a standing start to a point in

the takeoff at which the airplane is 1,500 feet above the takeoff

surface, or at which the transition from the takeoff to the en route

configuration is completed and VFTO is reached, whichever point is

higher. In addition--

* * * * *

8. Section 25.119 is amended by revising the section heading and

paragraph (b) to read as follows:

Sec. 25.119 Landing climb: All-engines-operating.

* * * * *

(b) A climb speed of not more than VREF.

9. Section 25.121 is amended by revising paragraphs (c)

introductory text, (d) introductory text, (d)(2) and (d)(3), and by

adding paragraph (d)(4) to read as follows:

Sec. 25.121 Climb: One-engine-inoperative.

* * * * *

(c) Final takeoff. In the en route configuration at the end of the

takeoff path determined in accordance with Sec. 25.111, the steady

gradient of climb may not be less than 1.2 percent for two-engine

airplanes, 1.5 percent for three-engine airplanes and 1.7 percent for

four-engine airplanes, at VFTO and with--

* * * * *

o read as follows:

Sec. 25.121 Climb: One-engine-inoperative.

* * * * *

(c) Final takeoff. In the en route configuration at the end of the

takeoff path determined in accordance with Sec. 25.111, the steady

gradient of climb may not be less than 1.2 percent for two-engine

airplanes, 1.5 percent for three-engine airplanes and 1.7 percent for

four-engine airplanes, at VFTO and with--

* * * * *

(d) Approach. In a configuration corresponding to the normal all-

engines-operating procedure in which VSR for this configuration

does not exceed 110 percent of the VSR for the related all-

engines-operating landing configuration, the steady gradient of climb

may not be less than 2.1 percent for two-engine airplanes, 2.4 percent

for three-engine airplanes, and 2.7 percent for four engine airplanes,

with--

(1) * * *

(2) The maximum landing weight;

(3) A climb speed established in connection with normal landing

procedures, but not more than 1.4 VSR; and

(4) Landing gear retracted.

10. Section 25.125 is amended by revising paragraph (a)(2) to read

as follows:

Sec. 25.125 Landing.

(a) * * *

(2) A stabilized approach, with a calibrated airspeed of VREF,

must be maintained down to the 50 foot height. VREF may not be

less than--

(i) 1.23 VSR0,

(ii) VMCL established under Sec. 25.149(f); and

(ii) A speed that provides the maneuvering capability specified in

Sec. 25.143(g).

* * * * *

11. Section 25.143 is amended by adding a new paragraph (g) to read

as follows:

Sec. 25.143 General.

* * * * *

ed approach, with a calibrated airspeed of VREF,

must be maintained down to the 50 foot height. VREF may not be

less than--

(i) 1.23 VSR0,

(ii) VMCL established under Sec. 25.149(f); and

(ii) A speed that provides the maneuvering capability specified in

Sec. 25.143(g).

* * * * *

11. Section 25.143 is amended by adding a new paragraph (g) to read

as follows:

Sec. 25.143 General.

* * * * *

(g) The maneuvering capabilities in a constant speed coordinated

turn at forward center of gravity, as specified in the following table,

must be free of stall warning or other characteristics that might

interfere with normal maneuvering:

----------------------------------------------------------------------------------------------------------------

Maneuvering

bank angle

Configuration Speed in a Thrust/power setting

coordinated

turn

----------------------------------------------------------------------------------------------------------------

Takeoff.................................. V2........................ 30 deg. Asymmetric WAT-limited.1

Takeoff.................................. V2+XX 2................... 40 deg. All-engines-operating

climb.3

En route................................. VFTO...................... 40 deg. Asymmetric WAT-limited.1

Landing.................................. VREF...................... 40 deg. Symmetric for -3 deg. flight

path angle.

----------------------------------------------------------------------------------------------------------------

\1\ A combination of weight, altitude, and temperature (WAT) such that the thrust or power setting produces the

minimum climb gradient specified in Sec. 25.121 for the flight condition.

\2\ Airspeed approved for all-engines-operating initial climb

ric for -3 deg. flight

path angle.

----------------------------------------------------------------------------------------------------------------

\1\ A combination of weight, altitude, and temperature (WAT) such that the thrust or power setting produces the

minimum climb gradient specified in Sec. 25.121 for the flight condition.

\2\ Airspeed approved for all-engines-operating initial climb.

\3\ That thrust or power setting which, in the event of failure of the critical engine and without any crew

action to adjust the thrust or power of the remaining engines, would result in the thrust or power specified

for the takeoff condition at V2, or any lesser thrust or power setting that is used for all engines-operating

initial climb procedures.

12. Section 25.145 is amended by revising paragraphs (a)

introductory text, (a)(1), (b)(1), (b)(4), (b)(6), and (c) introductory

text to read as follows:

Sec. 25.145 Longitudinal control.

(a) It must be possible, at any point between the trim speed

prescribed in Sec. 25.103(a)(6) and the stall, to pitch the nose

downward so that the acceleration to this selected trim speed is prompt

with--

(1) The airplane trimmed at the trim speed prescribed in

Sec. 25.103(a)(6);

* * * * *

(b) * * *

(1) With power off, flaps retracted, and the airplane trimmed at

1.3 VSR1, extend the flaps as rapidly as possible while

maintaining the airspeed at approximately 30 percent above the

reference stall speed existing at each instant throughout the maneuver.

* * * * *

(4) With power off, flaps retracted, and the airplane trimmed at

1.3 VSR1, rapidly set go-around power or thrust while maintaining

the same airspeed.

* * * * *

(6) With power off, flaps extended, and the airplane trimmed at 1.3

VSR1, obtain and maintain airspeeds between VSW and either

1.6 VSR1 or VFE, whichever is lower.

ll speed existing at each instant throughout the maneuver.

* * * * *

(4) With power off, flaps retracted, and the airplane trimmed at

1.3 VSR1, rapidly set go-around power or thrust while maintaining

the same airspeed.

* * * * *

(6) With power off, flaps extended, and the airplane trimmed at 1.3

VSR1, obtain and maintain airspeeds between VSW and either

1.6 VSR1 or VFE, whichever is lower.

(c) It must be possible, without exceptional piloting skill, to

prevent loss of altitude when complete retraction of the high lift

devices from any position is begun during steady, straight, level

flight at 1.08 VSR1 for propeller powered airplanes, or 1.13

VSR1 for turbojet powered airplanes, with--

* * * * *

Sec. 25.147 [Amended]

13. Section 25.147 is amended in paragraphs (a) introductory text,

(a)(2), (c) introductory text, and (d) by revising the expression ``1.4

VS1'' to read ``1.3 VSR1''.

Sec. 25.149 [Amended]

14. Section 25.149 is amended in paragraph (c) introductory text by

revising the expression ``1.2 VS'' to read ``1.13 VSR.''

Sec. 25.161 [Amended]

15. Section 25.161 is amended in paragraphs (b), (c)(1), (c)(2),

(c)(3) and (d) introductory text by revising the expression ``1.4

VS1'' to read ``1.3 VSR1''; and in paragraph (e)(3) by

revising the expression ``0.013 VS02'' to read

``0.013VSR02''.

Sec. 25.175 [Amended]

16. Section 25.175 is amended in paragraphs (a)(2), (b)(1)

introductory text, (b)(2) introductory text, (b)(3)

introductory text and (c)(4) by revising the expression ``1.4

VS1'' to read ``1.3 VSR1'', in paragraph (b)(2)(ii) by

revising the expression ``VMO+1.4 VS1/2'' to read

``(VMO+1.3 VSR1)/2'', in paragraph (c) introductory text by

revising the expressions ``1.1 VS1'' to read ``VSW'' and

``1.8 VS1'' to read ``1.7 VSR1'', in paragraph (d)

introductory text by revising the expressions ``1.1 VS0'' to read

``VSW'' and ``1.3 VS0'' to read ``1.7 VSR0'', and in

paragraph (d)(5) by revising the expression ``1.4 VSO'' to read

``1.3 VSR0''.

Sec. 25.177 [Amended]

read

``(VMO+1.3 VSR1)/2'', in paragraph (c) introductory text by

revising the expressions ``1.1 VS1'' to read ``VSW'' and

``1.8 VS1'' to read ``1.7 VSR1'', in paragraph (d)

introductory text by revising the expressions ``1.1 VS0'' to read

``VSW'' and ``1.3 VS0'' to read ``1.7 VSR0'', and in

paragraph (d)(5) by revising the expression ``1.4 VSO'' to read

``1.3 VSR0''.

Sec. 25.177 [Amended]

17. Section 25.177 is amended in paragraph (c) by revising the

expression ``1.2 VS1'' to read ``1.13 VSR1''.

Sec. 25.181 [Amended]

18. Section 25.181 is amended in paragraphs (a) introductory text

and (b) by revising the reference ``1.2 VS'' to read ``1.13

VSR''.

19. Section 25.201 is amended by revising paragraphs (a)(2) and

(b)(4) to read as follows:

Sec. 25.201 Stall demonstration.

(a) * * *

(2) The power necessary to maintain level flight at 1.5 VSR1

(where VSR1 corresponds to the reference stall speed with flaps in

the approach position, the landing gear retracted, and the maximum

landing weight).

(b) * * *

(4) The airplane trimmed for straight flight at the speed

prescribed in Sec. 25.103(a)(6).

* * * * *

20. Section 25.207 is amended by revising paragraphs (b) and (c),

and by adding new paragraphs (d), (e), and (f) to read as follows:

Sec. 25.207 Stall warning.

* * * * *

(b) The warning must be furnished either through the inherent

aerodynamic qualities of the airplane or by a device that will give

clearly distinguishable indications under expected conditions of

flight. However, a visual stall warning device that requires the

attention of the crew within the cockpit is not acceptable by itself.

If a warning device is used, it must provide a warning in each of the

airplane configurations prescribed in paragraph (a) of this section at

the speed prescribed in paragraphs (c) and (d) of this section.

istinguishable indications under expected conditions of

flight. However, a visual stall warning device that requires the

attention of the crew within the cockpit is not acceptable by itself.

If a warning device is used, it must provide a warning in each of the

airplane configurations prescribed in paragraph (a) of this section at

the speed prescribed in paragraphs (c) and (d) of this section.

(c) When the speed is reduced at rates not exceeding one knot per

second, with engines idling and throttles closed, stall warning must

begin, in each normal configuration, at a speed, VSW, exceeding

the reference stall speed by not less than three knots or three

percent, whichever is greater. For the purposes of this paragraph, the

reference stall speed is as defined in Sec. 25.103, except that

Sec. 25.103(a)(5) does not apply. Stall warning must continue

throughout the demonstration, until the angle of attack is reduced to

approximately that at which stall warning is initiated.

(d) In addition to the requirements of paragraph (c) of this

section, when devices that abruptly push the nose down at a selected

angle of attack (e.g., stick pushers) are installed, the stall warning

must occur at a speed not less than five knots or five percent,

whichever is greater, above the speed at which the device activates.

(e) In slow-down turns up to 1.5g at entry rates up to 3 knots per

second, with the flaps and landing gear in any normal position, the

stall warning margin must be sufficient to allow the pilot to prevent

stalling when recovery is initiated not less than one second after the

onset of stall warning.

ve knots or five percent,

whichever is greater, above the speed at which the device activates.

(e) In slow-down turns up to 1.5g at entry rates up to 3 knots per

second, with the flaps and landing gear in any normal position, the

stall warning margin must be sufficient to allow the pilot to prevent

stalling when recovery is initiated not less than one second after the

onset of stall warning.

(f) Stall warning must also be provided in each abnormal

configuration of the high lift devices that is likely to be used in

flight following system failures (including all configurations covered

by Airplane Flight Manual procedures).

Sec. 25.231 [Amended]

21. Section 25.231 is amended in paragraph (a)(2) by revising the

word ``altitude'' to read ``attitude'' and by revising the expression

``80 percent of VS1'' to read ``75 percent of VSR1''.

Sec. 25.233 [Amended]

22. Section 25.233 is amended in paragraph (a) by revising the

reference ``0.2 VS0'' to read ``0.2 VSR0''.

Sec. 25.237 [Amended]

23. Section 25.237 is amended in paragraphs (a), (b)(1), and (b)(2)

by revising the reference ``0.2 VS0'' to read ``0.2 VSR0''.

24. Action 25.735 is amended by revising paragraphs (f)(2) and (g)

to read as follows:

Sec. 25.735 Brakes.

* * * * *

(f) * * *

(2) Instead of a rational analysis, the kinetic energy absorption

requirements for each main wheel brake assembly may be derived from the

following formula, which must be modified in the case of unequal

braking distribution, which assumes an equal distribution of braking

between main wheels:

KE=0.0443 (WV2/N)

where--

KE=Kinetic energy per wheel (ft.-lb.);

W=Design landing weight (lb.);

V=VREF/1.3

VREF=Airplane steady landing approach speed, in knots, at the

maximum design landing weight and in the landing configuration at sea

level; and

N=Number of main wheels with brakes.

case of unequal

braking distribution, which assumes an equal distribution of braking

between main wheels:

KE=0.0443 (WV2/N)

where--

KE=Kinetic energy per wheel (ft.-lb.);

W=Design landing weight (lb.);

V=VREF/1.3

VREF=Airplane steady landing approach speed, in knots, at the

maximum design landing weight and in the landing configuration at sea

level; and

N=Number of main wheels with brakes.

(g) The minimum speed rating of each main wheel-brake assembly

(that is, the initial speed used in the dynamometer tests) may not be

more than the V used in the determination of kinetic energy in

accordance with paragraph (f) of this section, assuming that the test

procedures for wheel-brake assemblies involve a specified rate of

deceleration, and, therefore, for the same amount of kinetic energy,

the rate of energy absorption (the power absorbing ability of the

brake) varies inversely with the initial speed.

Sec. 25.773 [Amended]

25. Section 25.773 is amended in paragraph (b)(1)(i) by revising

the expression ``1.6 VS1'' to read ``1.5 VSR1''.

Sec. 25.1001 [Amended]

26. Section 25.1001 is amended in paragraphs (c)(1) and (c)(3) by

revising the expression ``1.4 VS1'' to read ``1.3 VSR1''.

Sec. 25.1323 [Amended]

27. Section 25.1323 is amended in paragraph (c)(1) by revising the

expression ``1.3 VS1'' to read ``1.23 VSR1'' and in paragraph

(c)(2) by revising the expression ``1.3 VS0'' to read ``1.23

VSR0''.

Sec. 25.1325 [Amended]

28. Section 25.1325 is amended in paragraph (e) by revising the

expressions ``1.3 VS0'' and ``1.8 VS1'' to read ``1.23

VSR0'' and ``1.7 VSR1'', respectively.

Sec. 25.1587 [Amended]

29. Section 25.1587 is amended in paragraph (b)(2) by revising the

expression ``VS'' to read ``VSR''.

PART 36--NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS

CERTIFICATION

30. The authority citation for part 36 continues to read as

follows:

paragraph (e) by revising the

expressions ``1.3 VS0'' and ``1.8 VS1'' to read ``1.23

VSR0'' and ``1.7 VSR1'', respectively.

Sec. 25.1587 [Amended]

29. Section 25.1587 is amended in paragraph (b)(2) by revising the

expression ``VS'' to read ``VSR''.

PART 36--NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS

CERTIFICATION

30. The authority citation for part 36 continues to read as

follows:

Authority: 42 U.S.C. 4321 et seq., 49 U.S.C. 106(g), 40113,

44701-44702, 44704, 44715; sec. 305, Pub. L. 96-193, 94 Stat. 50,

57; E.O. 11514, 35 FR 4247, 3 CFR, 1966-1970 comp., p. 902.

31. Appendix C to part 36, Section C36.9 is amended by revising

paragraph (e)(1) to read as follows:

Appendix C to Part 36--Noise Levels for Transport Category and Turbojet

Powered Airplanes Under Sec. 36.201

* * * * *

Sec. C36.9 Approach Reference and Test Limitations

* * * * *

(e) * * *

(1) For subsonic airplanes a steady approach speed of VREF +

10 knots must be established and maintained over the approach measuring

point.

* * * * *

PART 97--STANDARD INSTRUMENT APPROACH PROCEDURES

32. The authority citation for part 97 is revised to read as

follows:

Authority: 49 U.S.C. 106(g), 40103, 40106, 40113, 40114, 40120,

44502, 44514, 44701, 44719, 44721-44722.

33. Section 97.3 is amended by revising the first two sentences of

paragraph (b) introductory text to read as follows:

Sec. 97.3 Symbols and terms used in procedures.

* * * * *

(b) Aircraft approach category means a grouping of aircraft based

on a speed of VREF at the maximum certificated landing weight.

VREF and the maximum certificated landing weight are those values

as established for the aircraft by the certification authority of the

country of registry. * * *

* * * * *

Issued in Washington, DC on November 29, 1995.

Thomas E. McSweeny,

Director, Aircraft Certification Service.

[FR Doc. 96-415 Filed 1-17-96; 8:45 am]

BILLING CODE 4910-13-M