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

5.7.3 Technique and PoliciesAny given technique may indeed conform to the written procedure, and thus not add to “∆,” but couldstill entail an unnecessary risk or inefficiency. Consider the example mentioned earlier (Section 3.2.1) ofleveling off at FL 250 during a climb to a higher cruise altitude for the sake of avoiding the use of theoxygen mask. If this technique is evaluated from a procedural stand point, there is no “∆.” Thetechnique is in full conformity with the FAR and company procedures. Yet, if the companypolicy/philosophy includes a statement about efficiency of operations, then it is non-conformity.Therefore, it is not enough for the technique to conform to the procedure; it must also be consistent withthe policies.In some cases there is no procedure for a given task and related procedures do not help in solving theproblem. At this point policies are the only guidance to the crew on how they may use a technique. It ishere where the structure of policies and philosophy pays off. Figure 9 depicts this relationship betweenthe technique and the policy.PoliciesProcedureTechniqueSub-TasksSub-TasksFigure 9. Framework of technique and policy.For example, one of the many auto-leveloff techniques we observed involved placing a 300-knotairspeed in the autothrottle while climbing in vertical speed mode below 10,000 feet. The purpose wasto provide a smoother acceleration to an intermediate speed when leveling at or above 10,000 feet.During the leveloff the pilot would switch to airspeed mode and the aircraft would smoothly accelerate asit leveled. The potential hazard is that it would not be difficult to switch inadvertently to airspeed modebelow 10,000 feet and thus violate the speed restriction.Properly applied, the technique should work well, provide a smoother flight for the passengers, andremain in conformity with the 250 knots restriction. And although “∆” is not increased, time after timewhen the technique is employed, the seeds of a latent error may have been planted. The following ASRSreport illustrates a similar technique for the same task and the potential for an error:Our departure clearance of out Atlanta included instructions to maintain 10,000 feet. On this flight the captaindecided to delete the 250 knots restriction from the FMS climb page in order to eliminate the throttle burstassociated with leveling off at 10,000. He planned to follow the flight director pitch bar up to 300 AGL [duringtakeoff] and then decrease pitch to allow the aircraft to accelerate to 250 knots Once at 250 knots his plan was26