Appendix 6 A6-5 Figure 5. Probability Guidelines for Combined Occurrence Flight Conditions
LFE OFE NFE
HQR METHOD ELEMENT ISOLATED PROBABILITY
OF OCCURRENCE (at limit boundary) Generally associated with practical, routine operation and/or prescribed conditions, whether all-engine or engine inoperative.
Generally associated with warning onset: outside the normal flight envelope.
The most outside flight envelope, generally associated with airplane design limits or EFCS protection limits.
Normal Flight Envelope:
Operational Flight Envelope:
Limit Flight Envelope:
A. FLIGHT ENVELOPE 10 ° 10 -3 10 -5
Refer to figures 6 & 7.
Several of the flight parameter values may be necessary in combination in order to assign a given flight envelope. For the more influential flight parameters, such as AOA, speed, and Nz, the flight envelope may be determined by fewer or even one of the parameter values. Since the flight envelopes cover ranges of parameters (e.g., Flaps UP: Nz LFE = 1.6 - 2.5) and are not just single point values, the above target probabilities for OFE and LFE might vary slightly depending on expected airplane behavior and assigned task within the range.
B. ATMOSPHERIC DISTURBANCE LEVEL
LIGHT: Turbulence that momentarily causes 10 0 slight, erratic changes in altitude and/or attitude (pitch, roll, yaw).
Crosswinds up to 10 kts.
MODERATE: Turbulence that is similar to light 10 -3 turbulence but of greater intensity.
Changes in altitude and/or attitude occur. Usually causes variations in indicated airspeed. Crosswinds up t o 2 5 k t s .
Appendix 6 A6-6
HQR METHOD ELEMENT ISOLA TED PROBA BILITY OF OCCURRENCE (at limit boundary)
SEVERE: Turbulence that causes large, abrupt 10-5 deviations in altitude and/or attitude.
Usually causes large variations in Indicated airspeeds. Crosswinds substantially in excess of the minimum required crosswind to be demonstrated safe for takeoff and landing.
C. Flight Control System Failure State
Normal Operation: 10 0 Probable Failures: 10 0 - 10-5 Improbable Failures: 10 -5 - 10-9
D. Combination Guidelines
The above occurrence probability guidelines apply in isolation and should be modified when obvious interrelationships exist according to the design or intended or expected operation of the airplane. For example, a severe windshear event may generate an operational flight envelope or limit flight envelope escape task at 100, not 10-3 or 10-5 as shown above, in the limit since the operational procedure for escape would be to pull toward the AOA limit in windshear, perhaps experiencing overshoots of the steady value. Similarly, an airplane may experience overspeed, from VMO cruise, into the OFE due to a gust, in which case the OFE task probability would be 100, not 10-3 in the limit. This probability adjustment concept would also apply to EFCS failure cases where, for example, loss of warnings or exposure to reduced airplane stability might contribute to excursions outside the normal flight envelope (NFE) or OFE, in which case the envelope probability might be appropriately increased.
The following steps can assist in the determination of combined occurrences required to determine the minimum applicable HQ Rating shown in figure 12:
(1) Determine an occurrence probability value (see figures 9 & 10) considering the combination of factors for Flight Envelope (Xe), Atmospheric Disturbance (Xa), and EFCS failure state (Xc) (after making necessary adjustments for interrelationships, as noted above).
(2) Ignore events whose occurrences are less frequent than 10 -9.
(3) For those combinational conditions occurring more frequently than 10 -9, determine a “Flight Condition” value using only the combination values of EFCS Failure State (Xc) and Flight Envelope (Xe). Group this result (Xc+Xe) into a category of either “Probable Flight Condition” (10º - 10-5 ) or “Improbable Flight Condition” (10º - 10-9 ).
(4) Select or develop appropriate task(s) from figure 11.
Appendix 6 A6-7
(5) Using this task(s), determine the minimum applicable HQ Rating shown in figure 12 with the given Flight Envelope and Atmospheric Disturbance, plus “Flight Condition” determined from step (3).
Figure 6. Flaps UP Flight Envelopes
Appendix 6 A6-8
Figure 7. Flaps DOWN Flight Envelopes
Appendix 6 A6-9
Figure 8. Pilot Ratings
FAA COMPARISON HQ FAA DEFINITION CH* MIL STANDARD
RATING LEVEL QUAL
Satisfactory
Full performance criteria met with routine pilot effort and attention
1-3.5
SAT
Adequate
Adequate for continued safe flight and landing:
full or specified reduced performance met, but with heightened pilot effort and attention.
3.5-6.5
ACCEPT
Controllable
Inadequate for continued safe flight and landing, but controllable for return to safe flight condition, a safe flight envelope, and/or reconfiguration so that HQ are at least ADEQUATE.
6.5-8.0
CON
NOTE: *Cooper-Harper Rating
Appendix 6 A6-10 Figure 9. Probability Combination Leading to HQ Rating
Analyze Failures/Determine EFCS Operating State (Xc) Probability
-- Predicted failure rates/check failure co-dependence
-- Equipment Inoperative Dispatch under MEL
-- Service Difficulty Records (continuing airworthiness)
Assume Envelope Probabilities (Xe) and Atmospheric Probabilities (Xa) for Scenario
Modify the Envelope Probability (to Xem) if Co-dependent with Atmospheric Condition (See figure 5, Section D.) If not Co-dependent, Xem = Xe
Continue with Cases Xc + Xa + Xem 10 -9
Develop: “Flight Condition” (Xc + Xem)
-- PROBABLE FLIGHT CONDITION: -5 (Xc + Xem) < 0
-- IMPROBABLE FLIGHT CONDITION: -9 (Xc + Xem) < -5
Develop Tasks/Ensure HQ Requirements Met
(Xc) (Xa) (Xe) (S-SAT,A-ADQ,C-CON) FLIGHT CONDITION + ATMOSPHERIC + ENVELOPE REQUIREMENTS FOR FAA
R A T I N G
-- Flight Test
-- Simulator (high risk and specific atmospheric conditions)
Appendix 6 Figure 10. Probability Guidelines to Determine HQ Requirements EFCS FAILURE RATE - 10Xc
PROBABLE FAIL IMPROBABLE FAIL T -1 -2 -4 -5 -7 -8 -9 IMPROB FLT COND *Based on -8 (Xe+Xc) EFCS PROBABILITY -10x PROB FLT COND* Xe Xc FLIGHT ENVELOPE &
ATMOSPHERIC DISTURBANCE -2 **Gust intensity variations may be expected with altitude and between u, v, waxes
NFE OFE LFE ENVELOPE FLIGHT
LIGHT MOD SEVERE ATMOSPHERIC
DISTURBANCE oug GUST** 14 20 fps
SMALL RAMP INCR & JFK DEN MSY DFW (TO&L) SHEAR 10 18 25 33 45 kts XWIND A6-11
Appendix 6 A6-12 Figure 11. General HQ Task Categories
A. TRIM & UNATTENDED OPERATION Characteristics of the airplane to stay at or depart from an initial trim or unaccelerated condition.
Dynamic and flight-path response to pulse (3 axes) Dynamic and flight-path response to atmospheric disturbance Spiral stability (e.g., release at 40 bank)
B. LARGE-AMPLITUDE MANEUVERING Generally, these are open-loop maneuvers in which the pilot attempts a significant change in airplane path, speed, or attitude in order to evaluate safe airplane capability, but not reflecting the normal, daily commercial use of the airplane. Maneuvers may be initiated outside the NORMAL FLIGHT ENVELOPE and transition flight envelopes. Most of these maneuvers are representative of engineering airworthiness stability and control tests.
Pitch/ -- Wind-up turn or symmetric pull-up/push-over Longitudinal -- Slow-down-turn at fixed g or on AOA or g-limiter -- Stall or AOA-limiter approach -- Push-pull off trim speed
Roll -- Rapid bank-to-bank roll
Yaw -- Sudden heading change -- Constant heading sideslip
Operational -- Pitch/roll upset recover -- Emergency descent -- Climbing/diving turn -- Takeoff/land windshear escape maneuver -- Go around/power application from low speed -- Arrest of high sink rate, at touchdown or level-off altitude -- Collision avoidance roll/pull -- Takeoff and landing flare with abuse or high crosswind
C. CLOSED-LOOP PRECISION REGULATION OF FLIGHT PATH Generally, these are tightly-bounded, pilot closed-loop tasks performed in routine commercial flight. These controlling tasks are almost exclusively associated with the NORMAL FLIGHT ENVELOPE, or certainly not far outside the NFE boundary.
ILS and precision touchdown, various atmospheric disturbance and initial offset Formation flying (as simulator for maneuver tracking)
Appendix 6 A6-13
SPD/ALT/HDG tracking, in various atmospheric disturbance and cockpit display status, for:
- - T a k e o f f
- - C l i m b
- - C r u i s e
- - D e s c e n t
- - H o l d -- Configuration changes/power changes -- Transition between aforementioned
Figure 12. Minimum HQ Requirements
ATMOSPHERIC DISTURBANCE (Xa)
FLIGHT LIGHT MODERATE SEVERE CONDITION FLIGHT ENVELOPE (Xe) (Xc+Xem) NFE OFE LFE NFE OFE LFE NFE OFE LFE
PROBABLE
CONDITION
S
S
A
A
C
C
C
C
C
IMPROBABLE
CONDITION
A
A
C
C
C
C
S=SATISFACTORY A=ADEQUATE C=CONTROLLABLE
Appendix 7 A7-1
Appendix 7
Rudder Pedal Force-Limited Air Minimum Control Speed
The following analysis presents one method of addressing rudder pedal force limited air minimum control speed. This method is applicable to either jet or propeller driven airplanes.
The effect of banking into the operating engine is accounted for, and the method will work with either fixed pitch or constant speed propellers, including the effects of windmilling drag. For rudder deflection limited VMCA, see Appendix 3.
Given the static lateral/directional equations of motion for straight line, unaccelerated flight:
Fy = 0 Cy + C yaa + Cyrr = CL · sin
Mx 0 Cl + Claa Cl r r = 0
Mz = 0 Cn + Cnaa Cnrr = Cna
For a reversible control system, rudder force versus deflection is:
F R = GR · q · SR · cR · Ch R · R
and R = kR · FV Re 2
Substituting for R in equations (1) through (3), and solving, results in an identity of the form:
F R = A·Fna - B·Wsin
All the airspeed terms cancel, indicating that the engine-out rudder force required for straight flight is not a function of airspeed, but only of asymmetric thrust, weight, and bank angle. If asymmetric thrust did not vary with airspeed, it would be possible to stabilize at any airspeed with the same rudder force. At higher speeds, less rudder deflection would be required (varies inversely with Ve2), but the same force would be required (varies directly with Ve2). When a force limited VMCA is determined during flight test, the variation in rudder force with airspeed results solely from the change in net thrust with speed, and if an airspeed (thrust) is reached at which the rudder force is 150 lbs, there is no way to correct this force limited VMCA to any other thrust level. Therefore, if VMCA is rudder pedal force limited, takeoff thrust at all flight conditions should be limited to the test value of asymmetric thrust.
Appendix 7 A7-2
In some cases, it is possible to achieve full rudder deflection at the test altitude without reaching a pedal force limit, but with the higher thrust at standard conditions, a force limit would exist.
To preclude missing this crossover effect, the following analysis should be performed whenever test day rudder pedal forces are greater than 90 percent of the CFR limit (i.e., 135 lbs after amendment 25-42; 162 lbs prior to amendment 25-42).
1. At any convenient airspeed (typically 1.13 VSR with minimum takeoff flaps), shut down the critical engine, and leave it windmilling (propeller feathered if autofeather is required), apply maximum available power/thrust to the operating engine, and while maintaining constant heading, vary the bank angle from 10° to less than 5° in approximately 2°-3° increments, noting the rudder force at each stabilized bank angle.
2. Plot the rudder force vs Wsin for each of the test points.
3. Calculate Wssin 5°, where Ws is either the average test weight, or the lightest weight scheduled in the AFM, and define standard day rudder force (FRs) as the intersection of this value of Wsin and the curve from step (2). For example:
Fnat = 2600 lbs V = 1.13 V SR W s = 9000 lbs FR=166 lbs Wsin = 784 lbs -50 0 50 100 150 200 250 400 800 1200 1600 Wsinlbs Rudder Pedal Force (FR) - lbs
Appendix 7 A7-3
4. Determine the maximum allowable asymmetric thrust from the relationship:
FFna namax t 150FRs * *( 180FRs prior to amendment 25-42)
Assuming a 180 lb force limit: 1661802600F maxna 2820 lbs
5. Plot maximum scheduled AFM thrust vs airspeed, and determine V MCA at the intersection of this curve and Fnamax :
80.5 KEAS 2820 lbs 2600 2650 2700 2750 2800 2850 2900 2950 3000 60 80 100 120 140 160 Ve - kts.
Fna - lbs.
If the force limited VMCA value is high enough to impact adversely the takeoff speed schedule, it can be reduced to an acceptable value by derating takeoff thrust. For example, if the standard day rudder force (FRs) was 140 lbs on an amendment 25-42 airplane, the maximum allowable asymmetric takeoff thrust would be:
F 2600 150140namax 2686 lbs
Using the same maximum asymmetric thrust available vs airspeed as before: