Tuesday, August 29, 2006

Cleared for ...

The recent accident involving a Comair regional jet emphasizes the importance of situational awareness - knowing where you are and the implications to your phase of flight. Situational awareness is most often emphasized while airborne, particularly on instrument approaches and departures, but it can be just as critical on the ground. Several people have asked me how the Comair accident could have happened and all I can tell them is that taking off or landing on the wrong runway (sometimes at the wrong airport) by mistake is not that uncommon.

The Aeronautical Information Manual provides a section on ground operations, but it's not in the chapter on Air Traffic Procedures. Instead, ground operations are covered in the previous chapter, buried between information about radio phraseology and a section on ATC clearances and separation. I'm not suggesting that the layout of the AIM is what creates confusion on the ground, but it does make one wonder if, historically, ground operations have been given their due during training.

For many years, runway incursions have been a problem, with the majority (but not all) of incursions involving GA aircraft. A runway incursion is when an aircraft, vehicle, person, or object creates a collision hazard or loss of separation for an aircraft taking off, landing, or intending to land. A surface incident is an unauthorized movement of an aircraft, vehicle, or person on either a taxiway or runway that affects, or could affect, the safety of flight. The distinction between incursion and incident is important. If you taxi across a runway without a clearance and cause a loss of separation for a landing aircraft (an incursion), you can expect to be given a phone number to call. Surface incidents usually result in a just stern scolding on the frequency.

When you've taxied from the same spot for takeoff on the same runway hundreds of times, it's easy to get complacent, casual, maybe even sloppy. You may even think the controller told you what you expected to hear, what's known as a hear back error, and not hear what the controller really said. For taxi, it's critical that your read back all runway assignments and any hold short instructions. Saying "roger" or clicking the mic switch twice is not good enough. In fact, it's dangerous. Clear, concise, and standardized phraseology when talking to a ground or tower controller can go a long way toward preventing confusion during ground operations.

There are some GPS products that purport to display an aircraft's position on an airport taxiway diagram in a moving-map fashion. My experience is that these products can be useful, but they have limitations. Both the CMax system in the Cirrus and the new Garmin 496 suffer from the same problem: They aren't terribly accurate. I've seen both show my aircraft being between a runway and a taxiway, even though I was right on the centerline of the taxiway. They do show your general location and the direction you are headed, but you'll need to rely on you eyes, too. Even pilots whose budget doesn't allow sophisticated equipment can have the taxiway diagram for the airport out and ready to reference during taxi operations. Even if you have one of these GPS systems, I recommend having a airport taxiway diagram out so you can refer to it should the ground controller ask you to do something out of the ordinary. Have it out even if you think you know the airport like the back of your hand.

GA pilots usually operate with just one required crewmember, but we can still use some simple Cockpit Resource Management techniques when another person is on board. If I'm instructing a pilot or have another pilot flying with me, I always verify ATC clearances with that person. After the pilot-in-command has been given a taxi clearance and read it back, I'll make an observation like "I heard 'taxi runway 19 right'" and wait for the pilot in command to verify. The same goes for landing clearances- "I heard 'cleared for the option 29 left.'" If we don't agree on what we heard, the PIC asks the controller to repeat the clearance. If we are both unsure of a controller's instructions or intent, we'll ask the controller to clarify, not just repeat, the clearance.

Being in a rush to beat incoming weather, or make a release time, or for any other reason creates a dangerous distraction that can cloud your judgement and affect your perception. When I get in a hurry, I start thinking ahead and anticipating what will happen next in hopes I can make things go more quickly. This is precisely what can lead a pilot to think they heard what they wanted to hear instead of what the controller actually said. I've seen controllers affected in a similar way, telling an aircraft to do something out of habit without realizing they gave the wrong instructions. Many a time I've heard a controller accept an incorrect read-back from a pilot without correcting the pilot, probably because the controller was distracted or in a hurry.

Pilots, controllers and mechanics are only human and unfortunately, humans make mistakes. As a friend who files for a major airline observed: Professional pilots make mistakes every day, but they usually catch their mistakes before they become a danger to the flight. Some interesting reading on these topics is available in the Callback newsletter published by the Aviation Safety Reporting System, administered by NASA. ASRS allows pilots, controllers, and mechanics to anonymously describe incidents, to provide insight into the factors that contributed to the problem, and to offer ways to prevent the situation from happening again. Here's one example:
... BEFORE LEAVING THE GATE, THE CAPT BRIEFED ME TO BE SURE AND ASSIST HIM WITH THE TAXI DIRECTIONS. DUE TO A SHORT TAXI, THE 'BEFORE TKOF CHKLIST (ABOVE THE LINE)' WAS NOT QUITE COMPLETE AS WE APCHED THE END OF THE TXWY. WE WERE STILL ROLLING WHEN THE TWR CTLR QUERIED IF WE WERE READY. THE CAPT INDICATED HE WAS, SO I REPLIED 'AFFIRMATIVE' AND WE WERE CLRED FOR TKOF. THE CAPT THEN CALLED FOR THE 'BEFORE TKOF CHKLIST (BELOW THE LINE)' AND BEGAN TURNING AS I CONTINUED WITH THE REMAINDER OF THE CHKLIST. AS I WAS COMPLETING THE CHKLIST THE CAPT STATED THAT WE MUST BE ON THE TXWY PORTION OF THE DISPLACED THRESHOLD. UNBEKNOWNST TO US, WE HAD JUST TURNED ONTO A PARALLEL TXWY INSTEAD OF THE RWY. NOT YET LOOKING UP, I COMPLETED THE LAST 2 ITEMS ON THE CHKLIST AS THE CAPT BEGAN A SLOW ACCELERATION EXPECTING TO SEE THE THRESHOLD. I LOOKED UP AND SAW ONLY TXWY LIGHTS. THE CAPT THEN BROUGHT THE THRUST LEVERS UP EVEN HIGHER TO ALMOST THE TKOF THRUST SETTING AND I STATED, 'WE'RE ON A TXWY, WE ARE NOT ON THE RWY, ABORT, ABORT, THIS IS A TXWY!' THE CAPT IMMEDIATELY BROUGHT THE THRUST LEVERS TO IDLE AND BEGAN SLOWING. I ADVISED THE TWR THAT WE WERE ABORTING THE TKOF AND THEY INQUIRED IF WE NEEDED ASSISTANCE. I SAID NEGATIVE AND WE WOULD LIKE TO TAXI BACK FOR DEP. THE TWR CTLR ASKED WHAT THE REASON FOR THE ABORT WAS AND THE CAPT ANSWERED THAT WE WERE ON THE TXWY AND NOT THE RWY. ...
So if you're thinking this sort of thing can't happen to you, think again.

2 comments:

Anonymous said...

Appreciate your many excellent posts John. Signed up for the ASRS Callback and passed the link to some other pilot friends too. Aviation is an unforgiving endeavor. I know an experienced, competent, and professional biz jet pilot who shared with me that several years ago he also turned onto 26 instead of 22 at LEX. It was daytime and he did recognize the mistake and then radioed the tower who redirected him. Apparently, even before the current taxiway construction, it was prone to misperception. As I read on Dave's blog at Flight Level 390 (http://flightlevel390.blogspot.com/) There, but for the grace of God, go I . . .

Anonymous said...

my $.02...

Somewhere along the line I've seen this "call back error" referred to as "expectancy".