by Robert Sumwalt

Even something as routine as taxiing poses its own set of potential safety-related problems. They aren't just limited to dented wing tips and excursions through the grass, either. Some taxi-related problems are quite serious. Of the seventy-five ASRS taxi reports reviewed by this author, most involved unauthorized runway transgressions. In this article we hope to offer a few practical suggestions towards eliminating future taxi-related problems.

Runway Transgressions

Runway transgressions can be deadly. In fact, the worst accident in aviation history occurred due to a runway transgression at Tenerife, Canary Islands. Five hundred and eighty-three souls perished in that 1977 accident.

Fortunately not all runway transgressions involve accidents, but the potential for a catastrophe accompanies each and every one of them. While a national effort is underway to reduce runway transgressions, FAA figures reveal that the percentage of pilot-caused runway transgressions has increased since 1988. According to the FAA's Office of Safety Analysis, of the two hundred twenty-four runway transgressions reported in 1991, forty-one percent were pilot-caused. What can be done as an operator or flight crew to decrease the threat of runway transgressions?

Before Departing the Ramp

ASRS reports reveal that some precautions can be taken before leaving the ramp. For instance, several runway transgressions in this data set occurred because crews became disoriented while taxiing. Several others reported that the lack of conspicuous taxiway markings and signs contributed to a runway transgression. No doubt these problems could be minimized if crews would place the airport diagram chart where it could be easily referred to during taxi. Reported one pilot:

• "Had I not violated one of my own rules [of] having the airport diagram out in plain view, I don't believe this incident would have happened."

And in another incident, an air carrier First Officer stated:

• "I asked the Captain if he had any idea where [taxiway] 'G' was. He replied that he had no idea, but would continue taxiing ... until he saw a sign. I told him that I'd have a look at the airfield diagram. He replied, 'Don't bother with that,' and continued taxiing. While I was heads down digging out and figuring out the airfield diagram, we taxied across ... an active runway."

To be really effective the airport diagram should be located where it can be referenced without looking away from the taxiway. Some aircraft are equipped with chart holder "clipboards" on the side window frames. This is an ideal place to put the airport diagram. For aircraft that aren't so equipped, a piece of masking tape in the window frame works fine.

A few ASRS reports indicate that a runway transgression occurred because the Captain did not hear the clearance to hold short of a particular runway or taxiway. Reported one Captain:

• "I understood that we were to taxi to Runway 25 but I did not hear the 'hold short of Runway 34' restriction."

There are several reasons why the Captain may not hear or comprehend "hold short" clearances. These include distractions, blocked radio transmissions, a mindset to taxi to a particular runway when another runway may be in use, and rushing. One noted problem is that sometimes the First Officer calls for the taxi clearance while the Captain is still off-frequency talking to the pushback crew on the interphone. One ASRS report revealed:

• "Contributing factors: a rushed atmosphere in the cockpit.... This resulted in distractions and work overload, i.e., calling for taxi while starting engines....Captain and Flight Engineer were not monitoring [radios] as a backup to the First Officer."

Here are a few suggestions that can help combat these traps. First, the initial call to Ground Control or Ramp Control for taxi clearance should not be initiated until the Captain and First Officer are both monitoring that frequency. This ensures redundancy while critical taxi instructions are being issued.

Next, whenever a "hold short" clearance is issued, the Captain and First Officer should repeat the hold short clearance to each other. If a pilot fails to verbalize the clearance, the other pilot must then challenge him/her to be sure that the clearance was understood.

Finally, it's suggested that the First Officer write down the taxi clearance and holding instructions.

Distractions, Distractions

Several pilots complained that cockpit distractions contributed to their runway transgression. Examples include distractions caused by completing checklists, obtaining weight and balance information, and loading flight management computers. ASRS narratives include statements such as:

• "I was busy running checklists and not looking outside."
  
  
• "The First Officer was preoccupied with paperwork and not monitoring the taxi progress until after crossing the active runway."
  
  
• "My attention was diverted inside the cockpit as new weight and balance information was received from company via ACARS."
  
  
• "I changed frequency (per company procedure) to get takeoff closeout data. At this time, the Captain taxied [without clearance] onto Runway 11."
  
  
• "My First Officer was busy receiving our weight and balance data via ACARS and loading it into the computer. Had he been more in the loop he might have had time to review his taxi chart and point out that I was going the wrong way."

Another air carrier pilot reported that he became distracted when a Flight Attendant entered the cockpit to give the passenger count.

• "[We] took off, and to this moment, I do not remember being cleared for takeoff. This had the potential for a 'Canary Islands' takeoff accident. Company procedure for flight attendant cockpit visit while taxiing contributed...."

Air carriers are urged to review their policies and procedures to look for and eliminate practices that could contribute to taxi distractions. Paraphrasing FAR 121.542:

"No certificate holder shall require, nor may any flight crewmember perform, any duties during a critical phase of flight except those duties required for the safe operation of the aircraft.... Critical phase of flight includes all ground operations involving taxi...."

Can weight and balance information be delivered at the gate instead of during taxi-out? Can checklists be rewritten to minimize distractions during taxi-out? And is it really necessary to require pilots to call station operations to report "on the ground" after landing? Reported one crew:

• "After landing ... I called ops on company radio for gate [assignment] and got distracted with a short conversation about service requirements. I then realized that we had just crossed Runway 27L [without authorization]."

Careful on Inactive Runways

A few runway transgressions occurred when pilots were instructed to taxi on inactive runways. Because runway surfaces are designed for takeoffs and landings, they are not marked for taxiing. Therefore the usual cues such as holding lines for intersecting runways probably will not be present. Following a runway transgression one ASRS reporter offered:

• "If taxi operations are to be conducted on runways crossing [other] runways, then having yellow hold short lines on the runways could help. Maybe that one additional visual cue might have done the trick [in preventing my runway transgression]."

Because of the lack of these markings pilots should be particularly alert when taxiing on runways.

Runway Holding Lines: Back to Basics

Sometimes to resolve complex problems it may be necessary to go back to basics. And as basic as it may seem, a few ASRS reports indicate that some pilots have difficulty distinguishing the "holding side" of runway holding lines from the "non-holding side."

Recall that holding lines lie perpendicular to the taxiway and consist of two continuous and two dashed lines, each spaced six inches apart.

According to the Airmen's Information Manual:

"When approaching the holding lines from the side with the continuous lines a pilot should not cross the holding line without ATC clearance at a controlled airport, or without making sure of adequate separation from other aircraft at uncontrolled airports."

Caution After Landing

ASRS reports also indicate that problems can arise when pilots turn off onto another runway after landing. Reports a Controller:

• "[A medium large transport] landed on Runway 22 and turned onto Runway 28. [Another aircraft] was on Runway 28 in position ready for departure."

A pilot reported:

• "After landing, Captain cleared onto Runway 13. I noticed that the Tower had an aircraft in position on Runway 13."

Another stated:

• " ... we exited Runway 3 [onto Runway 33]. After our turnoff was completed we observed an aircraft on final for Runway 33 ... The aircraft on final was instructed to go around...."

It's important to understand that the Airmen's Information Manual states that when clearing a runway after landing, pilots should not turn onto another runway without authorization from the tower. Perhaps a study of the airport diagram prior to landing would help here by increasing situational awareness.

Hazards to Equipment and Personnel

A couple of ASRS reports illustrate hazards associated with beginning taxi without obtaining the "all clear" salute from the ground crew. A jump seat rider observed:

• "The Captain pushed up the power and released the parking brakes even though he had not received the required salute and release from [the pushback ground crew]. When the Copilot looked up he found the [widebody aircraft] moving between 5-10 m.p.h. Knowing that we had no clearance from the ground crew, and unable to see the ground crew under the nose, he slammed on the brakes to stop the aircraft. Three Flight Attendants were slammed into the bulkheads and injured, one seriously."

The reporter surmised:

"This incident occurred, I believe, because the Captain did not know the significance of our company SOP, which [states] that a taxi clearance is not to be requested until the salute and release from [the ground crew] is received. As an observer, I got the feeling that this Captain was mostly interested in minimizing ground time. The risk involved in the pushback procedure apparently had a lower priority to him than a fast getaway.... He seemed unconcerned with the possibility of running over and possibly killing the tug driver."

Another crew reported that they struck a deicing truck after beginning a premature taxi. The reporter explains that rushing and "the lack of coordination between the cockpit and ground personnel" contributed to the incident. "After deicing [was] started and the [deicing] truck moved rearward no ground personnel were [visible to] the cockpit [crewmembers]. [This led] to the assumption by the Captain that deicing had been completed." Be careful with assumptions.

May All Your Taxiways be Smooth

Although the act of taxiing an aircraft to and from an active runway may seem a little routine, ensuring that it is done safely requires planning, coordination, and attention. And more than just one set of eyeballs on a swivel is also necessary.

Let's review some of the things which can help flight crews make that taxi operation safer:

1. Ensure that all members of the flight deck crew review the airport diagram before beginning the taxi-out;
   
   
2. Locate the airport chart where it is readily available for reference and is in plain view at all times;
   
   
3. Write down those taxi instructions and any hold-short clearances;
   
   
4. Don't start your taxi from the gate until you have received the all clear from the ground crew. Make sure that Captain and First Officer are watching for obstacles--remember that when aircraft hit stationary objects, it is usually in close proximity to the gate;
   
   
5. Reduce distractions. Take your tasks in sequence, and don't let a trivial duty interfere with more important matters;
   
   
6. Use caution when taxiing on inactive runways, especially when they cross an active runway -- they lack the usual taxiway marking such as hold short lines;
   
   
7. While on taxiways, watch carefully for taxiway/runway hold lines -- do not cross them unless all flight crew members agree that clearance to enter a runway has been received. Confirm your right to cross with ATC if there is any doubt;
   
   
8. Review the airport chart before landing too. Use special care where a turnoff taxiway crosses another runway, be it active or inactive;
   
   
9. Use the same caution during the taxi-in to the gate as you did leaving it. Don't allow fatigue or get-home-itis to get in the way. Remember, just five more minutes or so of alertness will see you safely home.

Any pilot knows the danger of a midair collision. But stop and consider this: the likelihood of a collision with another aircraft, vehicle, pedestrian, or other object while taxiing is about three times greater than the chance of striking another aircraft in flight. Now then, is taxiing as routine as you may have thought it was?