by Mike Smiley

Recently an incident was reported to ASRS that emphasizes the need for flight crews flying advanced technology aircraft to back up the computer-generated route and navigation database with "old fashioned" navigation charts. Let's examine this incident through the eyes of the reporting flight crew:

• "We were in the approach portion of the flight, among scattered cumulus clouds and thunderstorms, on autopi lot with LNAV and VNAV engaged. We had been told to expect no delays. Approach Control gave traffic ahead holding instructions at [intersection A] with right turns instead of the published left turns because of a thunderstorm. We verified the cell on our radar and received holding instructions, also at [intersection A] with right turns. When we were about 20 miles from [intersection A], Approach Control issued clearance for us to hold at [intersection B] because of weather. We tried to enter [intersection B] as a waypoint but the computer rejected it as 'not in NAV DATA BASE.' By the time we located the distance from the VOR to [intersection B] on our charts and switched to VOR mode we were past the intersection. The controller asked us if we knew we were 5 miles past [intersection B] and issued a heading. We complied and shortly after were vectored inbound."

A rare occurrence? An isolated event? Not at all! You can find related incidents in the ASRS database spanning many years and involving virtually every phase of flight.

Phase of Flight

Departure Phase

• "After receiving clearance, a departure route was programmed into the FMS. Ground Control asked if we would accept Runway 01, but we declined due to crosswind and requested Runway 28. I changed the runway in the FMS but in the process of programming, I did not activate the revised departure route. The result was that no course line was displayed from the runway to the first fix. Confusion and lack of communication between the captain and myself led to our lack of 'a last minute' verification of charts and specific departure procedures. After takeoff, the Captain initiated what he thought was the correct turn. Departure Control soon asked us if we were flying the revised departure route. We replied 'Negative.' "

The flight crew sums it up--"Problems of this type can only be avoided through greater vigilance and a commitment to use whatever caution necessary to avoid such errors; one must avoid undue dependency on computer generated flight paths."

Enroute Phase

The enroute phase is the phase of flight where technology has supposedly all but eliminated workload. Or has it?

• "The controller instructed us to hold at [intersection B] on the airway, left turns, 10 mile legs. I inadvertently started to hold at [intersection A] and ATC told us to turn right immediately to a 090 degree heading. He then cleared us direct to [intersection B] to hold on the airway...." The crew suggests complicating factors, among them "relying on the database without maps available."

Descent Phase

Descent and crossing fixes add their share to the dilemma:

• "We were issued clearance to cross 50 [miles] north of the VOR at [FL] 270. I punched it into the FMS using a new waypoint I thought was 47 north of the VOR. However the aircraft had not begun descent when ATC asked us how far north of the VOR we showed. As the VOR receivers tune automatically, it took a few moments to find a chart and obtain the VOR frequency--whereupon we discovered we had just passed the 50 mile fix."

Approach Phase

Even the approach phase is not immune from track errors, although this is usually where the crew is very alert:

• "The FMC was working slowly and incorrectly. We set up the computer for the ILS approach and received vectors from ATC. I thought the vectors were for the ILS but they were really for the VOR approach to a visual. Tower then said we were too high, and, if the field was in sight that we were cleared for a visual approach."

ATC Involvement

Sometimes re-programming woes appear to be caused by a combination of ATC not understanding flight crew workload, and the flight crew not being ready for changes. ATC clearance amendments that are not on the FMC route of flight can pose significant workload increases for flight crews flying advanced technology aircraft, even when the flight crew is able to comply. If the clearance change is received when the workload is already high, such as immediately prior to takeoff, the result can be even more dramatic:

• "Tower said '...cleared for takeoff, maintain 2000 feet, at [VOR] 154 degree radial turn left heading 220 degrees.' We had to sit on the runway, pull out different maps, install the 154 degree radial, locate the [VOR] identifier and reset clearance altitude."

Conclusions

As we all know, today's ATC environment is getting more congested and complex. Advanced technology aircraft systems, though reliable, are not perfect and will occasionally malfunction. A sure defense against this condition is to have all appropriate charts available. Additionally, if any difficulty is encountered in programming or utilizing automated flight management systems, don't hesitate to take manual control of the aircraft and fly it where you are supposed to go. Implement these two simple rules and you will avoid, "...at least I thought I was there."