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bunds during a power-off glide with inding gear and wing flaps extended, ith the most forward center of gravity osition approved at the maximum eight, and regardless of weight. (e) It shall be possible, without the use
the primary means of longitudinal introl, to control the descent of the airane with the use of all other normal ght and power controls to a zero rate of Scent and to an attitude suitable for a ntrolled landing without requiring exptional strength, skill, or alertness on e part of the pilot, or without exceeding e operational and the structural limitains of the airplane. 1 F.R. 3339, May 22, 1956, as amended by ndt. 3–5, 24 F.R. 7066, Sept. 1, 1959] 3.110 Lateral and directional control. (a) It shall be possible with multigine airplanes to execute 15-degree nked turns both with and against the operative engine from steady climb at ! Vs, or Vy for the condition with: (1) Maximum continuous power on e operating engines, (2) Rearmost center of gravity, (3) (i) Landing gear retracted and (ii) Landing gear extended. (4) Wing flaps in most favorable climb sition, (5) Maximum weight, 6) The inoperative propeller in its nimum drag condition. b) It shall be possible with multisine airplanes, while holding the wings el laterally within 5 degrees, to execute Iden changes in heading in both ditions without dangerous charactercs being encountered. This shall be nonstrated at 1.4 Vs, or Vy up to headchanges of 15 degrees, except that the iding change at which the rudder ce corresponds to that specified in 106 need not be exceeded, with: 1) The critical engine inoperative, 2) Maximum continuous power on operating engine(s), }) (i) Landing gear retracted and i) Landing gear extended, D) Wing flaps in the most favorable ib position, i) The inoperative propeller in its imum drag condition, 1) The airplane center of gravity at earmost position,
$ 3.111 Minimum control speed (Vmo).
(a) A minimum speed shall be determined under the conditions specified below, such that when any one engine is suddenly made inoperative at that speed, it shall be possible to recover con
ol of the airplane, with the one engine still inoperative, and to maintain it in straight flight at that speed, either with zero yaw or, at the option of the applicant, with a bank not in excess of 5 degrees. Such speed shall not exceed 1.2 V., with:
(1) Take-off or maximum available power on all engines,
(2) Rearmost center of gravity,
(b) In demonstrating this minimum speed, the rudder force required to maintain it shall not exceed forces specified in $ 3.106, nor shall it be necessary to throttle the remaining engines. During recovery the airplane shall not assume any dangerous attitude, nor shall it require exceptional skill, strength, or alertness on the part of the pilot to prevent a change of heading in excess of 20 degrees before recovery is complete. [21 F.R. 3339, May 22, 1956, as amended by Amdt. 3–2, 22 F.R. 5561, July 16, 1957]
§ 3.112 Requirements.
(a) The means used for trimming the airplane shall be such that, after being trimmed and without further pressure upon or movement of either the primary control or its corresponding trim control by the pilot or the automatic pilot, the airplane will maintain:
(1) Lateral and directional trim in level flight at a speed of 0.9 Vn or at Vc, if lower, with the landing gear and wing flaps retracted;
(2) Longitudinal trim under the following conditions:
(i) During a climb with maximum continuous power at a speed between Vi and 1.4 V81,
(a) With landing gear retracted and wing flaps retracted,
(b) With landing gear retracted and wing flaps in the take-off position.
(ii) During a power approach at 1.5 V.1 and while maintaining a 3-degree angle of descent.
(a) With landing gear extended and released from any speed within the limwing flaps retracted,
its defined in paragraph (a) of this sec(6) With landing gear extended and
tion. wing flaps extended under the forward
§ 3.115 Specific conditions. center of gravity position approved with the maximum weight,
In conditions set forth in this section,
within the speeds specified, the stable (c) With landing gear extended and
slope of stick force versus speed curve wing flaps extended under the most for
shall be such that any substantial change ward center of gravity position approved,
in speed is clearly perceptible to the pilot regardless of weight.
through a resulting change in stick (iii) During level flight at any speed force. from 0.9 Vn to V: or 1.4 Vs, with landing
(a) Approach. The stick force curve gear and wing flaps retracted.
shall have a stable slope and the stick (b) In addition to the above, multi
force shall not exceed 40 lbs. at any engine airplanes shall maintain longi
speed between 1.1 Vs, and 1.8 Vs, with: tudinal and directional trim at a speed
(1) Wing flaps in the landing position, between Vy and 1.4 Vs, during climbing flight with the critical of two or more
(2) The landing gear extended, engines inoperative, with:
(3) Maximum weight, (1) The other engine(s) operating at (4) Airplane trimmed at 1.5 V., and maximum continuous power,
power on as required to maintain & 3 (2) The landing gear retracted, degree angle of descent. (3) Wing flaps retracted,
(b) Climb. The stick force curve (4) Bank not in excess of 5 degrees. shall have a stable slope at all speeds be121 F.R. 3339, May 22, 1956, as amended by tween 1.2 Vs, and 1.6 Vs, with: Amdt. 3-5, 24 F.R. 7066, Sept. 1, 1959)
(1) Wing flaps retracted, STABILITY
(2) Landing gear retracted, & 3.113 General.
(3) Maximum weight, The airplane shall be longitudinally, (4) 75 percent of maximum continudirectionally, and laterally stable in ac ous power, cordance with the following sections. (5) The airplane trimmed at 1.4 V.,. Suitable stability and control "feel"
(c) Cruising. (1) Between 1.3 V's, (static stability) shall be required in
and the maximum permissible speed, the other conditions normally encountered
stick force curve shall have a stable slope in service, if flight tests show such sta
at all speeds obtainable with a stick bility to be necessary for safe operation.
force not in excess of 40 pounds with: $ 3.114 Static longitudinal stability.
(i) Landing gear retracted, In the configurations outlined in (ii) Wing ilaps retracted, $ 3.115 and with the airplane trimmed as
(iii) Maximum weight, indicated, the characteristics of the elevator control forces and the friction
(iv) 75 percent of maximum con
tinuous power, within the control system shall be such that:
(v) The airplane trimmed for level
flight with 75 percent of the maximum (a) A pull shall be required to obtain
continuous power. and maintain speeds below the specified trim speed and a push to obtain and
(2) Same as subparagraph (1) of this maintain speeds above the specified trim
paragraph, except that the landing gear speed. This shall be so at any speed
shall be extended and the level flight which can be obtained without excessive
trim speed need not be exceeded. control force, except that such speeds
(21 F.R. 3339, May 22, 1956, as amended by
Amdt. 3-5, 24 F.R. 7066, Sept. 1, 1959) need not be greater than the appropriate maximum permissible speed or less than $ 3.116 Instrumented stick force me u the minimum speed in steady unstalled
Instrumented stick force measure (b) The air speed shall return to ments need not be made when chante within 10 percent of the original trim in speed are clearly reflected by chanie speed when the control force is slowly in stick forces and the maximum forte
obtained in the above conditions are not excessive. $ 3.117 Dynamic longitudinal stability,
Any short period oscillation occurring between stalling speed and maximum permissible speed shall be heavily damped with the primary controls (1) free, and (2) in a fixed position. § 3.118 Directional and lateral stability.
(a) Three-control airplanes. (1) The static directional stability, as shown by the tendency to recover from a skid with rudder free, shall be positive for all landing gear and flap positions appropriate to the takeoff, climb, cruise, and approach configurations, with symmetrical power up to maximum continuous power, and at all speeds from 1.2 Vs up to the maximum permissible speed for the configuration being investigated. The angle of skid for these tests shall be appropriate to the type of airplane. At greater angles of skid up to that at which full rudder is employed or a control force limit specified in $ 3.106 is obtained, whichever occurs first, and at speeds from 1.2 Voz to Vp, the rudder pedal force shall not reverse.
(2) The static lateral stability, as shown by the tendency to raise the low wing in a sideslip, shall be positive for all landing gear and flap positions with symmetrical power up to 75 percent maximum continuous power at all speeds above 1.2 Vs up to the maximum pernissible speed for the configuration inrestigated but shall not be negative at a speed of 1.2 Voz The angle of sideslip 'or these tests shall be appropriate to the ype of airplane but in no case shall the ideslip be less than that obtained with 10 legrees of bank.
(3) In straight steady sideslips at a speed of 1.2 Vs for all gear and flap posiions and for all symmetrical power onditions up to 50 percent maximum ontinuous power, the aileron and rudder ontrol movements and forces shall ncrease steadily, but not necessarily in onstant proportion, as the angle of sidelip is increased up to the maximum apropriate to the type of airplane. At reater angles up to that at which the ull rudder or aileron control is employed ra control force limit specified by $ 3.106 s obtained, the rudder pedal force shall lot reverse. Sufficient bank shall acompany sideslipping to prevent dearture from a constant heading. Rapid ntry into or recovery from a maximum
sideslip shall not result in uncontrollable flight characteristics.
(4) Any short-period oscillation occurring between stalling speed and maximum permissible speed shall be heavily damped with the primary controls (1) free and (ii) in a fixed position.
(b) Two-control (or simplified) airplanes. (1) The directional stability shall be shown to be adequate by demonstrating that the airplane in all configurations can be rapidly rolled from a 45-degree bank to a 45-degree bank in the opposite direction without exhibiting dangerous skidding characteristics.
(2) Lateral stability shall be shown to be adequate by demonstrating that the airplane will not assume a dangerous attitude or speed when all the controls are abandoned for a period of 2 minutes. This demonstration shall be made in moderately smooth air with the airplane trimmed for straight level flight at 0.9 Vn (or at Vc, if lower), flaps and gear retracted, and with rearward center of gravity loading.
(3) Any short period oscillation occurring between the stalling speed and the maximum permissible speed shall be heavily damped with the primary controls (i) free and (ii) in a fixed position. [21 F.R. 3339, May 22, 1956, as amended by Amdt. 3–5, 24 F.R. 7066, Sept. 1, 1959) $ 3.118–2 Large displacements of flight
controls in directional and lateral stability tests (FAA policies which
apply to $ 3.118). (a) In performing flight tests to determine compliance with $ 3.118, it should be borne in mind that the airplane structural requirements do not provide for large displacements of the flight controls at high speeds. Full application of rudder and aileron controls should be confined to speeds below the design maneuvering speed Vp. The following rules (approximations) will serve as a guide for the maximum permissible control surface deflections at speeds above Vp. (This does not imply that these maximum deflections must be used in the tests at high speeds).
(1) The permissible rudder angle decreases approximately according to the ratio (Vp/V)’, where V is the speed of the test.
(2) The permissible aileron deflection decreases approximately at the ratio (Vp/V), up to the design cruising speed,
§ 3.120 Stalling demonstration.
(a) Stalls shall be demonstrated under two conditions:
(1) With power off, and
(2) With a power setting of not less than that required to show compliance with the provisions of $ 3.85 (a) for airplanes of more than 6,000 pounds maximum weight, or with 90 percent of maximum continuous power for airplanes of 6,000 pounds or less maximum weight.
(b) In either condition required by paragraph (a) of this section it shall be possible, with flaps and landing gear in any position, with center of gravity in the position least favorable for recovery, and with appropriate airplane weights, to show compliance with the applicable requirements of paragraphs (c) through (f) of this section.
(c) For airplanes having independently controlled rolling and directional controls, it shall be possible to produce and to correct roll by unreversed use of the rolling control and to produce and correct yaw by unreversed use of the directional control up until the time the airplane pitches in the maneuver prescribed in paragraph (g) of this section.
(d) For two-control airplanes having either interconnected lateral and directional controls or for airplanes having only one of these controls, it shall be possible to produce and to correct roll by unreversed use of the rolling control without producing excessive yaw up until the time the airplane pitches in the maneuver prescribed in paragraph (g) of this section.
(e) During the recovery portion of the maneuver, it shall be possible to prevent more than 15 degrees roll or yaw by the normal use of controls, and any
loss of altitude in excess of 100 feet or any pitch in excess of 30 degrees below level shall be entered in the Airplane Flight Manual.
(f) A clear and distinctive stall warning shall precede the stalling of the airplane, with the flaps and landing gear in any position, both in straight and turning flight. The stall warning shall begin at a speed exceeding that of stalling by not less than 5 but not more than 10 miles per hour and shall continue until the stall occurs.
(g) In demonstrating the qualities required by paragraphs (c) through (f) of this section, the procedure set forth in subparagraphs (1) and (2) of this para. graph shall be followed.
(1) With trim controls adjusted for straight flight at 1.5Vsų or at the mini. mum trim speed, whichever is higher, the speed shall be reduced by means of the elevator control until the speed is slightly above the stalling speed; then
(2) The elevator control shall be pulled back at a rate such that the airplane speed reduction does not exceed 1 mile per hour per second until a stall is produced as evidenced by an uncontrollable downward pitching motion of the airplane, or until the control reaches the stop. Normal use of the elevator control for recovery shall be allowed after such pitching motion has unmistakably developed. [21 F.R. 3339, May 22, 1956, as amended by Amdt. 3-5, 24 F.R. 7066, Sept. 1, 1959) § 3.120-1 Measuring loss of altitude
during stall (FAA policies which
apply to $ 3.120). To meet the requirements of $ 3.120. pertaining to the maximum loss of altitude permitted during the stall, it is necessary that a suitable method be used for the purpose of measuring such loss during the investigation of stalls. Unless special features of an individual type being investigated render the following instructions inapplicable, the procedure described shall be used for this purpose:
(a) The standard procedure for approaching a stall shall be used as specified in $ 3.120.
(b) The loss of altitude encountered in the stall (power on or power off) shall be the distance as observed on the sensitive altimeter testing installation from the moment the airplane pitches to the
observed altitude reading at which horizontal flight has been regained.
(c) Power used during the recovery portions of a stall maneuver may be that which, at the discretion of the inspector, would be likely used by a pilot under normal operating conditions when executing this particular maneuver. However, the power used to regain level flight shall not be applied until the airplane has regained flying control at a speed of approximately 1.2 Vs. This means that in the investigation of stalls with the critical engine inoperative, the power may be reduced on the operating engine(s) before reapplying power on the operating engine or engines for the purpose of regaining level flight. [Supp. 1, 12 F. R. 3435, May 28, 1947, as amended by Amdt. 1, 14 F. R. 36, Jan. 5, 1949) $ 3.120–2 Indications of stall warnings
(FAA policies which apply to
§ 3.120). (a) No precise and complete description of the various warnings that would comply with $ 3.120 can be given at this time, but the following lists of items may be used as a guide:
(1) Satisfactory items include:
(i) Buffeting, which may be defined as general shaking or vibration of the airplane, elevator nibble, aileron nibble, rudder nibble, audible indications such as oil canning of structural members or covering roughness in riding qualities of the airplane due to aerodynamic disturbances, etc.
(ii) Stall warning instrument, either visual or aural. A visual instrument could be either a light or a dial.
(ii) Stick force, defined as heavy.
(ii) Inability to hold wing level.
When stalled from an excessive climb attitude it shall be possible to recover from this maneuver without exceeding the limiting air speed or the allowable acceleration limit.
§ 3.121-1 Climbing stall flight tests for
limited control airplanes (FAA inter.
pretations which apply to g 3.121). (a) This requirement is intended to draw particular attention to any stall recovery characteristics that might be encountered when a limited control airplane is completely stalled from an extremely nose high attitude, either intentionally or inadvertently. In practice it is possible that the elevator control travel could be limited to such an extent that stalls could not be obtained at the normal rate of deceleration used in testing. However, if the airplane was pulled up into a very steep climbing attitude from reasonably high speed flight either power on or power off, and held in this attitude, excessive pitching may occur. At the same time, the limited elevator travel may retard recovery from the pitched attitude until excessively high speeds are obtained. These characteristics would normally be considered under § 3.106; however, it appears wise to call particular attention to the control characteristics that might result from these flight configurations on limited control airplanes.
(b) Although Form ACA-283-03, item A, (3), (a), indicates that take-off power should be used for these tests, this is not a mandatory requirement. In this regard it is to be noted that although $ 3.121 is entitled “Climbing Stalls”, it specifically states: "... when stalled from an excessive climb attitude", thus a specified application of power is not required. For example, flight tests recently conducted on several aircraft have indicated that the power-off configuration was critical since the stall resulted in greater pitch and less elevator control. The technique used for inducing such stalls consisted of stalling the airplane (power off) in as steep a climbing attitude as possible without falling into a whip stall, or other flight maneuver that might overstress the structure. (Form ACA-283-03 will be revised at the next printing, so that the power found to be critical can be recorded in a space that will be provided for this purpose.) (Supp. 10, 16 F. R. 3284, Apr. 14, 1951) 3.122 Turning flight stalls.
When stalled during a coordinated 30degree banked turn with 75 percent maximum continuous power on all engines, flaps and landing gear retracted, it shall be possible to recover to normal