On the Design of Flight-Deck Procedures - Intelligent Systems ...

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3. THE FOURTH P: PRACTICES3.1. AN EXTENSION OF THE THREE P'sAs we began this study we focused on the macro-ergonomics aspects of flight operations: thephilosophy, policies, and procedures. As we progressed, it appeared to us that something was missing.We discovered that the macro-ergonomics approach had led us astray from the focal point of any humanmachinesystem -- the human operator. We neglected the ultimate consumer of the procedure -- the flightcrew, whose decisions and actions determine the “system outcome.”To correct this, we have added an additional component -- practices. The term “practice” encompassesevery activity conducted on the flight deck: correct execution of a procedure, deviation from a procedure,omission of a procedure, the use of a technique, or any other action. While a procedure may bemandatory, it is the pilot who will either conform to it or deviate from it. The procedure is specified bymanagement -- the practice is conducted by the crew. Ideally procedures and practices should be thesame. The high prevalence of the “pilot deviation from SOP” classification mentioned earlier indicatesthat no one can assume that pilots will always follow any given procedure dictated by management 4 .The goal of flight management is to promote “good” practices by specifying coherent procedures. Butwe must also recognize that this is not always the case: procedures may be poorly designed. The crewcan either conform to a procedure or deviate from it. The deviation may be trivial (e.g., superimposingsome non-standard language on a procedural callout), or it may be significant (e.g., not setting the autobrakesaccording to the takeoff procedures). The alternatives of conformity versus deviation can bevisualized as a switch (Figure 3). This may be somewhat of an over-simplification, but it expresses thechoice that the crew member must make: to conform to the company's SOP, or to deviate. For example,we once observed a captain who, in response to the first officer's question regarding the conduct of amandatory taxi procedure, replied “I just don't do that procedure.” That captain, unequivocally, placedthe switch in the deviate position.CrewConformDeviatePracticesFigure 3. The deviate versus conform “switch”4 Assuming, of course, that the procedure is clear to the crew. We recognize, however, that this is not always the case andsome SOPs can be ambiguous and lead to deviations by a well meaning pilot.8
We envision a term “∆” -- delta, or the degree of difference between procedures and practices (Figure 4).This “∆,” not to be taken as a quantitative value by any means, expresses symbolically the amount ofdeviation from a specified procedure. This term has two components: (1) the magnitude of deviationfrom the procedure, and (2) the frequency of such deviations during actual line operations. The goal offlight management is to minimize “∆.” When “∆” is large (flight crews constantly deviate from SOPand/or deviate in a gross manner), there is a problem. This “∆” may be due to a crew's deviation and/ora problem in using this procedure.ProceduresCrewPractices"∆" = | Practices - Procedures |Figure 4. The quantity “∆” - deviation from procedures.The human operator in this situation is analogous to a filter. From the above, standards and trainingdepartments dictate and teach the way procedures should be performed. However, in daily lineoperations (and not under the watchful eye of a check-airman), the individual pilot may adjust the gaugeof the filter. This gauge will determine the degree to which the SOPs actually will be observed,modified, misused, or completely ignored. The purpose of standardization is to bias the filter towardprevention of deviations.The consequences of the failure to conform to a procedure can be seen in the following report fromNASA's Aviation Safety Reporting System (ASRS) 5 :Our flight departed late PM local time for the 4:30 plus flight to SFO. F/O was PF. En-route discussednecessity to request lower altitudes with both OAK Center and Bay Approach when approaching SFO due totendency to be “caught high" on arrival in this aircraft type. Area arrival progressed smoothly and we werecleared for the QUIET BRIDGE visual to 28R. Good speed control and vertical descent planning until vicinityof BRIJJ LOM. When changing radio frequency from approach to tower (head down), F/O selected "opendescent" to 400 feet MSL. Autopilot was off, both flight directors were engaged, and autothrust was on. Whilecontacting SFO tower I became aware that we were below the glideslope, that airspeed was decaying, and that wewere in an "open descent." Instructed the F/O to engage the “vertical speed” mode in order to stop our descent,restore the speed mode for the autothrust, and continue the approach visually once above the 28R ILSglideslope. Company procedures explicitly prohibit selecting an altitude below 1500 feet AGL for an opendescent, since this places the aircraft close to the ground with engines at idle. (ASRS Report No. 149672)5ASRS reports are quoted here verbatim.9
Page 2 and 3: TABLE OF CONTENTSSUMMARY ..........
Page 4 and 5: 1. INTRODUCTIONWhen we try to pick
Page 6 and 7: Hendrick (1987) states that human f
Page 8 and 9: influenced by the individual philos
Page 12 and 13: To summarize, the ultimate factor t
Page 14 and 15: Humor. Humor is closely related to
Page 16 and 17: technical deficiencies, induce work
Page 18 and 19: operations and the philosophy of th
Page 20 and 21: 5.3 MERGERS AND ACQUISITIONSMergers
Page 22 and 23: Figure 7. A Boeing B-757 checklist
Page 24 and 25: e made. Consider, also, the followi
Page 26 and 27: flight operations, the philosophy m
Page 28 and 29: 5.7.3 Technique and PoliciesAny giv
Page 30 and 31: For example, one company constantly
Page 32 and 33: 6. ISSUES IN PROCEDURE DESIGN6.1 CO
Page 34 and 35: solution involves “anchoring” a
Page 36 and 37: On August 19, 1980, a Saudi Arabian
Page 38 and 39: 3. The procedures allow the other a
Page 40 and 41: coordination of tasks between agent
Page 42 and 43: Similarly, it has been a common pra
Page 44 and 45: 7.1.3 Structure of ProceduresAs men
Page 46 and 47: mission simulation (see Wiener et a
Page 48 and 49: felt that this is an efficient tech
Page 50 and 51: esponse. The PF, therefore, can con
Page 52 and 53: 7.5.1 Cross-fleet StandardizationCr
Page 54 and 55: 1. Training department (for both pi
Page 56 and 57: REFERENCESAviation Week and Space T
Page 58 and 59: Perrow, C. (1986). Complex organiza
Page 60 and 61:
APPENDICESAppendix 1 - Guidelines f
Page 62 and 63:
14. In managing automated cockpits,
Page 64 and 65:
APPENDIX 3 - QUESTIONS ASKED OF FLI
Page 66 and 67:
APPENDIX 5 - QUESTIONS ASKED DURING
Page 68 and 69:
8. Change in operational environmen
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