(i) Airplanes modified by increasing the installed horsepower (maximum takeoff power) by more than 10 percent or 25 horsepower, whichever is less, over the original type certificated airplane installed horsepower rating, will require spin testing.
(a) Airplanes modified by increasing the installed horsepower may accept a derated power schedule in lieu of spin testing. The 10 percent or 25 horsepower, whichever is less, maximum hp difference criteria would apply from sea level to the airplane service ceiling.
This will require a placard of manifold pressure versus pressure altitude (at rated r.p.m.)
corresponding to the maximum allowable horsepower differential between the derated engine and the original type certificated engine.
(ii) Turbocharged and turboprop engine installations will be evaluated as follows:
(A)Determine the maximum power available on the original engine at 10,000 feet pressure altitude.
(B) Determine the value of 75 percent MCP/thrust on the new engine.
(C) If the difference between (a) and (b) exceeds either 10 percent of the original installed horsepower (maximum takeoff power) or 25 horsepower, spin tests will be conducted.
(4) Limited spin matrix. Consider a limited spin matrix if there is either a weight increase greater than ten percent or an inertial increase greater than ten percent, or both. Inertial changes to check are those that may affect the rotational characteristics of the airplane during spin recovery. When considering a 10 percen t change, use the product of the weight and moment arm changes. Examples to consider are the addition of tip tanks, moving the engine forward, and locating the battery in the tailcone.
(5) Subjective reasoning. Again, there is some subjec tivity that needs to be used when deciding on the need to re-evaluate the spin recovery ability of an airplane. The airplane’s service history and the airplane’s original spin recovery performance should be part of the decision. An airplane that typi cally recovers in a ¼ turn does not need the same re-evaluation matrix that an airplane recovering in 7/8 of a turn does. The airplane that recovers in 7/8 of a turn is close to the limit already and may have trouble with normal wear and tear. There is not a clear, easy approach to standardizing the spin requirements for STC’s. The FAA encourages the use of issue papers to document the rational for not requiring spinning. This may help standardize future projects.
r--.....
r--..._ r--...
r--..__ r---..__ r---...
r---...
r--..._ r--..._ r--..__ r---..__ r---..__ r---...
r--..._ Number Flaps Up Appch.(As Flaps GearUp PowerOff C.G.
Aft C.G.
LateralC.G.
11/16/2011 AC 23-8C Figure 23 - Spin Evaluation Configuration Matrix
SPIN EVALUATION CONFIGURATION Flight Condition Spins from Wing Level Attitude Flaps Approp.)
Spin AsRequired Closed Cowl Flaps Test with Normal Spin Controls Left Spin 1 thru 6 1 2 3 4 5 6 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
X X X X
X X X X CowlFlaps Landing GearDown PowerOn Forward Repeat 1 through 6 from a right spin.
Repeat 1 through 6 fromleft and right turning flight.
Test with Abnormal Spin Controls 7 8 9 10 11 12 13 14 15 16 17 18 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Left Spin Aileron Against 7 thru 12 (Repeat 7 through 12 from a right spin) Left Spin Aileron with 13 thru 18 Repeat 13 through 18 from a right spin.
Repeat 7 through 18 from left and right turning flight.
Section 9. Ground and Water Handling Characteristics
1. § 23.231 Longitudinal Stability and Control.
a. Explanation.
(1) Landplanes. For landplanes, §§ 23.231(a) and 23.233 are companion requirements to § 23.75.
(2) Floatplanes. For floatplanes, §§ 23.231(b) and 23.233 are companion requirements to § 23.75.
(3) Amphibians. The requirements for both landplanes and floatplanes apply to amphibians.
b. Procedures.
(1) Landplanes. Landplanes should be operated from all types of runways applicable to the type of airplane. Taxi, takeoff, and landing operations should be evaluated for acceptable characteristics. This should include idle power landings as well as landings and takeoffs with procedures used in §§ 23.75 and 23.51.
(2) Floatplanes. Floatplanes should be operated under as many different water conditions as practical up to the maximum wave height appropriate to the type of airplane. Taxi (both displacement and step), takeoff, and landing operations should be evaluated for acceptable characteristics. This includes idle power landings as well as landings and takeoffs with procedures used under §§ 23.75 and 23.51.
(3) Amphibians. Amphibians should be evaluated in accordance with both items (1) and (2) above.
c. Procedures - Multiengine Airplanes. Evaluate all of the considerations contained in paragraph b(2) plus the effects of one engine loss during water operations.
d. Airplane Flight Manual (AFM). The AFM should include appropriate limitations plus demonstrated wind and sea state conditions.
2. § 23.233 Directional Stability and Control.
a. Explanation.
(1) Crosswind. This regulation establishes the minimum value of crosswind that must be demonstrated. Since the minimum re quired value may be far less than the actual capability of the airplane, higher values may be tested at the option of the applicant. The highest 90-degree crosswind component tested satisfactorily should be put in the AFM as performance information. If a demonstrated crosswind is found limiting, it has to be introduced in Section 2 of the AFM.
(2) Ground Loops. Section 23.233(a) does not preclude an airplane from having a tendency to ground loop in crosswinds, providing the pilot can control the tendency using engine power, brakes, and aerodynamic controls. The operating procedures should be placed in the AFM in accordance with § 23.1585(a).
(3) Controllability. Section 23.233(b) is not related to the crosswind requirement of § 23.233(a). The demonstration of compliance with this requirement is accomplished into the wind. The test pilot is searching for any unus ual controllability problems during landing and must use judgment as to what constitutes "satisfactorily controllable" since, at some point in the landing rollout, the aerodynamic controls may become ineffective.
(4) Taxi Controllability. Section 23.233(c) requires the airplane to have adequate directional controllability for taxi operations on land for landplanes, on water for floatplanes, and on land and water for amphibians.
b. Procedures.
(1) Crosswind.
(a) The airplane should be operated throughout its approved loading envelope at gradually increasing values of crosswind component until a crosswind equivalent to 0.2 VSO is reached. All approved takeoff and landing conf igurations should be evaluated. Higher crosswind values may be evaluated at the discretion of the test pilot for AFM inclusion.
(b) For floatplanes, the use of water rudders or the use of airplane attitude on the water to control weathervaning should be described in the AFM.
(2) Controllability.
(a) A landplane should demonstrate satisfactory controllability during power-off (idle power) landings through landing rollout. Th is may be conducted into the existing wind and should be evaluated at all key loading envelope points.
(b) Although power-off landings are not expressly required for floatplanes under § 23.233(b), it is recommended they be evaluated.
(3) Taxi Controllability.
(a) A landplane should have sufficient directional control available through the use of nose/tail wheel steering, differential braking (if provided), differential power (multiengine airplanes), and aerodynamic control inputs to allow taxiing at its "maximum demonstrated crosswind" value.
(b) A floatplane should have sufficient directional control available through the use of water rudders, airplane attitude (displacement or plow), taxi technique (displacement or step), differential power (multiengine floatplanes) and aerodynamic control inputs to allow taxiing at its "maximum demonstrated crosswind" value. This is not intended to suggest that all of the above must be evaluated at 0.2 VSO, but accepted techniques using one or more of the above must allow controllable taxiing.
(c) Amphibians should exhibit suitable directional controllability on both land and water in accordance with the preceding two paragraphs. In addition, amphibians should have suitable directional controllability to taxi from the water to a land facility and vice-versa unless prohibited by the operating limitations.
c. Data Acquisition and Reduction. The determination of compliance is primarily a qualitative one. However, wind readings (veloc ity and direction) should be taken and compared to the wind component chart (Appendix 7) to determine that the minimum 90-degree crosswind component has been tested.
3. § 23.235 Operation on Unpaved Surfaces.
a. Explanation. This requirement states that the airplane landing gear shock absorbing mechanism must function as intended throughout the expected operating envelope of the airplane.
b. Procedures. During the development and certification flight testing, the airplane should be operated on a variety of runways including those considered to be the worst (in terms of roughness) appropriate to the type of airplane. There should be no evidence of damage to the airplane during these operations.
4. § 23.237 Operation on Water. Allowable water surface conditions should be established during the certification flight testing, depending on the type of aircraft, to ensure safe operation and attainment of the published takeoff and landing performance.
5. § 23.239 Spray Characteristics.
a. Explanation. This rule is intended to ensure that any spray produced during water operation neither excessively interferes with the pilot's visibility nor damages, beyond "normal wear-and-tear," the airplane itself.
b. Procedures.
(1) Taxi, takeoff, and landing. Taxi, takeoff, and landing operations should be conducted throughout the approved loading envelope. Spray patterns should be specifically noted with respect to visibility and their contact areas on the airplane. These areas should be monitored to assure compliance with the rule.
(2) Reversing propellers. Airplanes with reversing propellers should be demonstrated to comply at the highest reverse power expected to be applicable to the airplane operation.
Section 10. Miscellaneous Flight Requirements
1. § 23.251 Vibration and Buffering.
a. Explanation.
(1) Flutter. The test required under this section should not be confused with flutter tests, which are required under § 23.629. Test are typically considered elevated risk and should be carefully planned and conducted.
(2) Test Speeds. Prior to the test, the pilot shou ld coordinate with the airframe engineer to determine that the flutter requirements of § 23.629 have been satisfied and to determine the most critical weight and c.g. for the test. The flight test engineer and pilot should obtain from the airframe engineer the dive equivalent airspeed and Mach number to which the test should be conducted. In the absence of a well-calibrated Mach meter, knowing the Mach number and equivalent airspeed, a schedule of pressure altitude and indicated airspeed should be developed for the test.
(3) Airspeed Determination. Another major considera tion is CAS determination during the test. In this regard, a calibrated, sensitive airspeed indicator should be installed to provide accurate readability. Careful study of the airplane's airspeed position error/correction curve is required with respect to the characteristics of the slope at the high-speed end and how the airspeed calibration was conducted. This is necessary to determine the adequacy of the airspeed position error curve for extrapolating to VD/MD. Refer to appendix 7, figure 5, for compressibility corrections. An expanded Mach number calibrated-airspeed graph may be found in the Air Force "Flight Test Engineering Handbook" (refer to appendix 2, paragraph f(2) of this AC).
(4) Springs. If the airplane incorporates spring devices in any of the control systems, the test should be conducted with the spring devices connected and disconnected. Alternately, if satisfactory spring reliability is shown in accordance with § 23.687, tests with springs disconnected are not required.
(5) Mach Limits. For those airplanes that are ob serving Mach limits, the tests should be repeated at MD speed. Careful selection of the test altitude for both MD and VD tests will help cut down on the number of repeat runs necessary to determine compliance. Attempting to combine the tests at the knee of the airspeed/Mach curve should be approached cautiously since it can result in overshooting the desired speed.
b. Procedures.
(1) Configuration. In the clean configur ation at the gross weight, most critical c.g.
(probably most aft) and the altitude selected for the start of the test, the airplane should be trimmed in level flight at maximum continuous power. Speed is gained in a dive in gradual increments until VD/MD, or VDF/MDF for turbojets, is attained. The airplane should be trimmed, if possible, throughout the maneuver. Remain at the maximum speed only long enough to determine the absence of excessive buffet, vibration, or controllability problems.
(2) Flaps extended. With flaps extended and the airplane trimmed in level flight at a speed below VFE, stabilize at VFE in a shallow dive and make the same determinations as listed in (1) above.
2. § 23.253 High Speed Characteristics.
a. Explanation.
(1) Related Sections. The design dive speeds are established under the provisions of § 23.335, with the airspeed limits established under the provisions of § 23.1505. There is distinction made in both regulatory sections for airplanes that accelerate quickly when upset.
The high-speed characteristics, in any case, should be evaluated by flight demonstration. Section
23.1303(e) gives the requirements for a speed-warning device.
(2) Dynamic Pressure and Mach. In general, the same maneuvers should be accomplished in both the dynamic pressure (q) and Mach (M) critical ranges. All maneuvers in either range should be accomplished at thrust and trim points appropriate for the specific range being evaluated. Some maneuvers in the Mach ra nge may be more critical for some airplanes due to drag rise characteristics.
(3) Flight Crew Duties. The airplane's handling char acteristics in the high-speed range should be investigated in terms of anticipated action on the part of the flight crew during normal and emergency conditions. Consideration should be given to their duties, which not only 107
involve piloting the airplane, but also the operational and navigational duties having to do with traffic control and record keeping necessary to the progress of safe flight.
(4) Upset Axes. The upset criteria of § 23.335(b)(4)(i) is predicated on an upset in pitch while operational evaluation of upsets expected to occur in service should cover pitch, roll, yaw, and critical combinations of multi-axis upsets.
(5) Factors. The following factors are involved in the flight test investigation of high-speed characteristics:
(i) Effectiveness of longitudinal control at VMO/MMO and up to the demonstrated VD/MD speed;
(ii) Effect of any reasonably probable mis-trim on upset and recovery;
(iii) Dynamic and static stability;
(iv) The speed increase that may result from likely mass movement that occurs when trimmed at any cruise speed to VMO/MMO;
(v) Trim changes resulting from compressibility effects. Evaluation should cover Mach tuck, control reversal, or other phenomena associated with high speed;
(vi) Characteristics exhibited during recovery from inadvertent speed increase;
(vii) Upsets due to turbulence (vertical, horizontal, and combination gusts);
(viii) Effective and unmistakable aural speed warning at VMO plus six knots, or MMO plus 0.0lM;
(ix) Speed control during application of devices (power, speed brakes, high-speed spoilers, and so forth); and
(x) Characteristics and controllability during and after failure or malfunction of any stability augmentation system.
(6) Type of Warning. Operational experi ence has revealed that an important and effective deterrent to inadvertent overspeeding is an aural warning device, which is distinctively different from aural warning used for other purposes. Aerodynamic buffeting is influenced by, and is similar to, the effects of turbulence at high speed and is not normally considered to be suitable as an overspeed warning.
(7) Speed Margins. Once it is established whether the airplane limits will be V NE or VMO, appropriate speed margins and markings may be evaluated. The factors outlined in § 23.335 have been considered in establishing minimum speed margins during past type certification programs for the appropriate speeds. The factors to be considered are the following:
(i) Increment allowance for gusts (0.02M);
(ii) Increment allowance for penetration of jet stream or cold front (0.0l5M);
(iii) Increment allowance for production differences of airspeed systems
(0.005M), unless larger tolerances or errors are found to exist;
(iv) Increment allowance for production tolerances of overspeed warning errors
(0.0lM), unless larger tolerances or errors are found to exist;
(v) Increment allowance M, due to speed overshoot from MMO, established by upset during flight tests in accordance with § 23.253, should be added to the values for production differences and equipment tolerances. The minimum acceptable combined value should not be less than that required by § 23.335(b)(4) between MMO and MD. The value of MMO should not be greater than the lowest value obtained from each of the following equations and from § 23.1505:
MMO = MD - M - .005M - .01M or MMO = MD - the Mach increment required by § 23.335(b)(4)
(vi) Altitudes where dynamic pressure (q) is limiting, the allowances of items (i) and (ii) are applicable, and the Mach increment is converted to the units used for the limits;
(vii) At altitudes where q is limiting, the increment allowance for production differences of airspeed systems and production tolerances of overspeed warning errors are three and six knots, respectively, unless larger differences or errors are found to exist; and
(viii) Increment allowance V, due to speed overshoot from VMO established by upset during flight tests in accordance with § 23.253, should be added to the values for production differences and equipment tolerances. The value of VMO should not be greater than the lowest obtained from the following:
VMO = VD - V - 3 knots (prod. diff.) - 6 knots (equip. tol.)
or for VNO airplanes:
VNO = V D - V - 3 knots (prod. diff.) - 6 knots (equip. tol.)
b. Procedures. Using the VMO/VNO, MMO, or the associated design or demonstrated dive speeds determined in accordance with §§ 23.251, 23.335, and 23.1505, the airplane should be shown to comply with the high speed characteristics of § 23.253 and that adequate speed margins exist. The airplane characteristics should be investigated at any speed up to and including VNO, VMO/MMO or VD/MD, as required by § 23.253. The recovery procedures used should be those selected by the applicant, except that the normal acceleration during recovery should not exceed l.5g (total).
(1) C.G. Shift. The airplane should be upset by the c.g shift corresponding to the forward movement of a representative number of passengers depending upon the airplane interior configuration. The airp lane should be allowed to accelerate for three seconds after the calibrated VMO/MMO (not overspeed warning) occurs before recovery is initiated. Note the maximum airspeed. Do not exceed VD /MD.
(2) Inadvertent Control Movement. Simulate an evasive control application when trimmed at VMO/MMO by applying sufficient forward force to the elevator control to produce
0.5g (total) for a period of five seconds, after which recovery should be effected at not more than
l.5g (total). Care should be taken not to exceed VD /MD during the entry maneuver.
(3) Gust Upset.
(i) Lateral Upset. With the airplane trimmed at any likely cruise speed up to VMO/MMO in wings level flight, perform a lateral upset to the same angle as that for autopilot approval, or to a maximum bank angle appropriate to the airplane, whichever is critical.
Operationally, it has been determined that the maximum bank angle appropriate for the airplane should not be less than 45 degrees, need not be greater than 60 degrees, and should depend upon airplane stability and inertia characteristics. The lower and upper limits should be used for airplanes with low and high maneuverability, respectively. Following this, with the controls free, the evaluation should be conducted for a minimum of three seconds after the calibrated value of VMO/MMO (not overspeed warning) or ten seconds, whichever occurs first.
(ii) Longitudinal Upset. Perform a longitudinal upset as follows:
(A) Trim at VMO/MMO using power required for level flight but with not more than maximum continuous power. If the airplane will not reach VMO/MMO at maximum continuous power, push over to VMO/MMO and trim.
(B) If descending to achieve VMO/MMO, return to level flight without changing trim.
(C) Perform a longitudinal upset from normal cruise by displacing the attitude of the airplane in the range between 6-12 degrees, which has been determined from service experience to be an optimum range. The value of displacement should be appropriate to the airplane type and should depend upon airplane stability and inertia characteristics. The lower and upper limits should be used for airplanes with low and high maneuverability, respectively.
(D) The airplane should be permitted to accelerate until three seconds after the calibrated value of VMO/MMO (not overspeed warning).
(iii) Two-Axis Upset. Perform a two-axis upset consisting of a longitudinal upset combined with a lateral upset. Perform a longitudinal upset by displacing the attitude of the airplane as in the previous paragraph, and simultaneously perform lateral upset by rolling the airplane to the 15-25 degree bank angle range, which was determined to be operationally representative. The values of displacement should be appropriate to the airplane type and should depend upon airplane stability and inertia characteristics. The lower and upper limits should be used for airplanes with low and high maneuverability, respectively. The established attitude should be maintained until the overspeed warning occurs. The airplane should be permitted to accelerate until three seconds after the calibrated value of VMO/MMO (not overspeed warning).
(4) Leveling Off From Climb. Perform transition from c limb to level flight without reducing power below the maximum value permitted for climb until the overspeed warning has occurred. Recovery should be accomplished by applying not more than l.5g (total).
(5) Descent From Mach to Airspeed Limit Altitude. A descent should be initiated at MMO and performed at the airspeed schedule defined in MMO until the overspeed warning occurs. The airplane should be permitted to de scend into the airspeed limit altitude where recovery should be accomplished after overspeed warning occurs by applying not more than l.5g (total). The maneuver should be completed without exceeding V D.
Chapter 3. Subpart D--Design and Construction Section 1. General
1. § 23.629 Flutter.
This subject is covered in AC 23.629-1B.
Section 2. Control Systems
1. § 23.671 General.
Reserved.
2. § 23.672 Stability Augmentation and Automatic and Power Operated Systems.
Reserved.
3. § 23.677 Trim Systems.
a. Qualitative Evaluation. Trim should be qualitatively evaluated during all phases of the flight test program. Cockpit control trim devices should be evaluated for smoothness, sense of motion, and ease of operation, accessibility, and visibility of the trim tab indicators (both day and night). Ease in estab lishing and maintaining a trim condition should be evaluated.
b. Electric Trim Background. Electrically-actuated, manually-controlled trim systems have been certificated in several ways, depending on systems design. The simpler systems are tested for failure in flight. More sophisticated systems, which generally incorporate dual-wire, split-actuating switches, may require a dual failure to produce a runaway. Analysis of these systems discloses that one switch could fail closed and remain undetected until a failure occurred in the other switch or circuit to produce a runaway. This is still considered acceptable if the applicant provided a preflight test procedure that will detect such a dormant failure. Service experience dictates that evaluation of fail-safe trim systems by analysis alone is not acceptable and flight testing is required.
c. Explanation.
(1) Fault Analysis. A fault analysis should be evaluated for each trim system.
(2) Single Failure and Back-up System. For a system in which the fault analysis indicates a single failure will cause runaway, flight tests should be conducted. For a system with back-up features, or a redundant system where multiple failures would be required for runaway, the certification team should determine the extent of the flight tests necessary after consideration of the fault analysis and determination of the probability and effect of runaway. In all cases, flight test evaluations should be conducted to determine functional system/airplane compatibility in accordance with § 23.1301.
(3) Failure. For the purpose of a fault analysis, a failure is the first fault obviously detectable by the pilot and should follow probable combinations of undetectable failures assumed as latent failures existing at the occurrence of the detectable failure. When an initial failure also causes other failures, the initial failure and the subsequent failures are considered to constitute a single failure for purposes of fault analysis. Only independent failures may be introduced into the fault analysis to show multiple failure integrity.
(4) Failure Warning. The first indication a pilot has of a trim runaway is a deviation from the intended flight path, abnormal control movements, or a warning from a reliable failure warning system. The following time delays after pilot recognition are considered appropriate:
(i) Takeoff, approach, landing - one second.
(ii) Climb, cruise, descent - three seconds.
(5) Second Set of Controls. If a set of controls and instruments are provided for a second crew member, multi-function systems disconnect or quick-disconnect/interrupt switches, as appropriate, should be provided for both crew members regardless of minimum crew.
d. Definitions.
(1) Disconnect Switch. A switch, which has the pr imary purpose of stopping all movement of the electric trim system, that is located within immediate reach and readily accessible to the pilot. A circuit breaker is not considered to be a disconnect switch.
(2) Quick-Disconnect/Interrupt Switch. A switch or device, which is located on the control wheel on the side opposite the throttles, or on the stick control, that momentarily interrupts all movement of the electric trim system and can be operated without moving the hand from its normal position on the control. The primary purpose of the switch is to stop all movement of the electric trim system.
e. Procedures.
(1) Quick-Disconnect or Interrupt Switch. With a quick-disconnect or interrupt switch located on the pilot’s control wheel or stick, disconnect may be initiated after the delay times given in 23.677c(4).
(2) Disconnect Switch. With a disconnect switch located somewhere on the panel other than the pilot’s control wheel or stick, the time delays given in § 23.677c(4) should be applied prior to corrective action by use of primary controls. In addition to these time delays, an appropriate reaction time to locate the switch and disconnect the systems should be added.
When there are other switches in the immediate area of the disconnect switch, a time increment the same as for the quick disconnect should be added to account for identifying the switch. This effectively doubles the time delay for a cockpit located disconnect switch.
(3) Loads. The loads experienced as a result of the malfunction should normally not exceed an envelope of 0 to +2g. The positive lim it may be increased if analysis has shown that neither the malfunction nor subsequent corrective action would result in a load beyond limit load. In this case, careful c onsideration should be given to the delay time applied, since it may be more difficult for the pilot to reach the disconnect switch.
(4) High Speed Malfunctions. When high speed malfunctions are introduced at V NE or VMO/MMO, whichever is appropriate, the speed excursion, using the primary controls and any speed reduction controls/devices, should not exceed the demonstrated upset speed established under § 23.253 for airplanes with a VMO/MMO speed limitation and a speed midway between VNE and VD for those airplanes certified with a VNE limitation.
(5) Speed Limitations. The use of a reduction of VNE/VMO/MMO in complying with paragraph e(4) of this section is not considered acceptable, unless these new speeds represent limitations for the overall operation of the airplane.
__________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ 11/16/2011 AC 23-8C
(6) Forces. The forces encountered in the te sts should conform to the requirements of § 23.143 for temporary and prolonged application. Also, refer to paragraph 23.143 of this AC.
(i) To allow expansion of the 0 to 2g envelope, the FAA suggests a test procedure that incorporates both control restrained and unrestrained malfunctions. The following test matrix considers the probability of trim runaways, high airframe limit loads, control stick/wheel configuration and absence of an autopilot system. Because rudder trim can be adjusted without the pilot directly in the control loop (that is, feet on the floor), restrained runaways for rudder trim are not considered acceptable. (Refer to table 8 below.)
Table 8 - Trim Systems Requirements Maximum Maximum Force Maximum Axis Time Load(g) Attitude (restrained and Rate of Force (unrestrained) Change unrestrained) Change (unrestrained) (restrained) Pitch recognition structural +/-45 degrees 60 pounds 20 pounds/sec +3 seconds limits NTE
3.5g Roll recognition structural +/-90 degrees 30 pounds 10 pounds/sec +3 seconds limits Yaw recognition structural +/-30 degrees 150 pounds N/A +3 seconds limits (unrestrained only) Note 1: “Restrained” means the pilot is in the control loop (hands on) and “unrestrained” means the pilot is not in the control loop (hands off).
Note 2: Trim systems with a monitor/limiter will be tested at a magnitude just below that required for monitor/limiter trip.
Note 3: NTE is Not to Exceed.
4. § 23.679 Control System Locks.
This subject is covered in AC 23-17.
5. § 23.689 Cable Systems. Section 23.689(f) allows for tab control cables that are not part of the primary control system to be less then 1/8 inch in diameter as long as the airplane is safely controllable with the tabs in the most adverse positions. Flight testing only requires that the tabs be in the most adverse positions associated with the airplane’s operating envelope. This would typically be at the lowest and fastest trimmable operating speeds with the airplane loaded at forward cg. Safely controllable is subjective and has to be determined by an FAA test pilot. If there is disagreement between an applicant and the FAA, a multiple pilot evaluation may be used to make the final compliance determination. Typically, the forces in § 23.143 for “prolonged” use are not used because they are intended for normal operation and are unreasonably low for a failure condition. If the forces are so high that the pilot cannot adequately control the airplane, 113