Catastrophic Accident Adverse UNACCEPTABLE Effects on Occupants Airplane Damage Consequences of Consequences of Failure Condition Failure Condition Emergency Procedures Abnormal Procedures ACCEPTABLE Nuisance Normal Probable Improbable Extremely Improbable *From AC 25.1309-1A Probability of Failure Condition Probability of Failure Condition (Sys. Design & Anal.)
Figure 2: Probability vs. Consequence Graph*
Certification Program Need:
A320 1988/89 MD-11 1989/90 B777 1995/96 Informal Contacts NASA Dryden AFFTC AFWAL Society/Industry Documents Cooper-Harper Rating Method Existing FAA Contract Research
MIL SPEC/STD Rating Methods & Elements
FAA HANDLING QUALITIES RATING METHOD (Current Special Conditions, Issue Papers, & Certification Review Items Figure 3: Development of FAA HQRM Criteria ADAPTED HQ REG’S AND ADVISORY MATERIAL
OBJECTIVES AND APPLICABILITY
FAILURE
CONDITIONS FLIGHT
ENVELOPES
ATMOSPHERIC
DISTURBANCE
COMBINATION
METHODOLOGY TASKS
HQ RATING
CATEGORIES
FIND COMPLIANCE Figure 4: Major Elements of Task Oriented Handling Qualities Rating Method
PROBABILITY
RELATIONSHIPS
Figure 5 PROBABILITY GUIDELINES FOR
COMBINED OCCURRENCE FLIGHT CONDITIONS
HQR METHOD ELEMENT ISOLATED PROBABILITY
OF OCCURRENCE (at limit boundary) A. FLIGHT ENVELOPE Normal Generally associated with 10° NFE Flight practical, routine operation and/or Envelope: prescribed conditions, whether all-engine or engine inoperative.
Operational Generally associated with warning 10-3 OFE Flight onset; outside the normal flight Envelope: envelope.
Limit The most outside flight envelope, 10-5 LFE Flight generally associated with Envelope: airplane design limits or EFCS protection limits.
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° 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 to 25 kts.
Figure 5 (CONT’D)
HOR METHOD ELEMENT ISOLATED PROBABILITY
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: 10º Probable Failures: 10º - 10-5 Improbable Failures: 10-5 - 10-9 D. COMBINATION GUIDELINES The above occurrence probability guidelines apply in isolation and should be modified when interrelationships exist according to the design or intended or expected operation of the airplane. For example, a severe windshear event may generate on Operational Flight Envelope or Limit Flight Envelope escape task at 10 º 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 the OFE task probability would be 10 º. not 10-3 in the limit. this probability adjustment concept would apply to EFCS failure cases where, for example, loss of warnings or exposure to reduced airplane stability might contribute to excursions outside the 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 (se e 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 occurr ences 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" (10 º - 10-5) or "Improbable Flight Condition" (10-5 - 10-9).
(4) Select or develop appropriate task(s) from FIGURE 11.
(5) Using this task(s), determine the minimum applicable HQ Rating s hown in FIGURE 12 with the given Flight Envelope and Atmospheric Disturbance, plus "Flight Condition" determined from step (3).
NFE OFE LFE NFE LFE OFE Normal Flight Envelope Operational Flight Envelope Limit Flight Envelope Rudder appropriate task/operation/or rudder lock eval VVVV VV V V V DFCMOS LOWEST SELECT FTO SW LIM STDY V LIM DYN CL MAX
1.3 OR OR OR MMM DFCMO LIM LIM OR
- 15 O +30 0 OR LIM +
- 67 0 OR NFE ENG INOP PITCH V AOA ROLL N Z
ALTITUDE PITCH V BUFFET N Z BETA * * * * LIM LIM LIM
1.3
1.6
2.5
0.8
0.0
- 1.0 IB DET +- 50 0 +- 40 0 +- 40 0 LIM DYN CL MAX SW LIM STDY OR OR Figure 6: Flaps UP Flight Envelopes
NFE OFE LFE NFE LFE OFE Normal Flight Envelope Operational Flight Envelope Limit Flight Envelope Rudder appropriate to task/operation/or rudder lock eval V V V SW LIM STDY V LIM DYN CL MAX OR OR LIM LIM OR -15 O +30 0 OR LIM +
- 67 0 OR NFE ENG INOP PITCH V AOA ROLL N Z
ALTITUDE PITCH V BUFFET N Z BETA * * * * * LIM
1.3
1.6
0.8 IB DET +- 50 0 +- 40 0 LIM DYN CL MAX SW LIM STDY OR OR Figure 7: Flaps DOWN Flight Envelopes +- 30 0 TO +- 40 0 LAND
2.0
0.5
0.0 TO & L +3000 TO & L +3000 V FE V FE + V FE + V REF V 2 V 2 + XX
FIGURE 8: Pilot Ratings FAA HQ RATING
FAA DEFINITION
COMPARISON
MIL STANDARD
LEVEL QUAL CH SAT ADQ CON Full performance criteria met with routine pilot effort and attention.
1-3.5
3.5-6.5
6.5-8.0 SAT ACCEPT CON Adequate for continued safe flight and landing; full or specified reduced performance met, but with 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.
1 2 3 heightened pilot effort and attention.
* Note: * Cooper-Harper 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 airworthines) · Assume Envelope Probabilities ( Xe) and Atmospheric Probabilities ( Xa) for Scenario · Modify the Envelope Prob ability (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
DISTURBANCE FAA RATING
- Flight Test
- Simulator (high risk and specific atmospheric conditions) FIGURE 9. PROBABILITY COMBINATION LEADING TO HQ RATING
FIGURE 10 : Probability Guidelines to determine HQ Requirements
NFE OFE LFE
MOD SEVERE FLIGHT
ENVELOPE
ATMOSPHERIC
DISTURBANCE 3 5 8 14 20 fps 10 18 25 33 45 kts SHEAR XWIND
SMALL RAMP INCR & JFK DEN MSY DFW (TO & L) LIGHT GUST**ug Xc 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 0 -1 -2 -3 -4 -5 -6 -7 -8 -9
PROBABLE FAIL IMPROBABLE FAIL Xc = EFCS FAILURE RATE ~10 EFCS
FLIGHT ENVELOPE &
ATMOSPHERIC DISTURBANCE with altitude and between u, v, w axes Xe Xc Xa *Based on (Xe+Xc) **Gust intensity variations may be expected PROB ABILI TY ~10 X IM PR O B FL T C O PR O B FL T C O N
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/ o Wind-up turn or symmetric pull-up/push-over Longitudinal o Slow-down-turn at fixed g or on AOA or g-limiter o Stall or AOA-limiter approach o Push/pull off trim speed * Roll o Rapid bank-to-bank roll * Yaw o Sudden heading change o Constant heading sideslip * Operational o Pitch/roll upset recover o Emergency descent o Climbing/diving turn o Takeoff/land windshear escape maneuver o Go around/power application from low speed o Arrest of high sink rate, at touchdown or level-off altitude o Collision avoidance roll/pull o 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) * SPD/ALT/HDG tracking, in various atmospheric disturbance and cockpit display status, for: o Takeoff o Climb o Cruise o Descent o Hold o Configuration changes/power changes o Transition between aforementioned Figure 11: General HQ Task Categories
(Xe) (Xa)
FIGURE 12: Minimum HQ Requirements
ATMOSPHERIC DISTURBANCE
LIGHT MODERATE SEVERE
FLIGHT ENVELOPE
PROBABLE
CONDITION
IMPROBABLE
CONDITION FLIGHT
CONDITION
NFE OFE LFE NFE OFE LFE NFE OFE LFE S A C S A
A A C C C C C C C C S = SATISFACTORY A = ADEQUATE C = CONTROLLABLE (Xc + Xem)