Are We (Really) Cleared to Cross?

January 26, 2023

The recent near-disaster at JFK on January 13th involving a Delta 737 and an American 777 illustrates the continuing problem of runway incursions.  Imagine two airlines, one accelerating for liftoff and the other taxiing out for departure, suddenly trying to share the same runway.

Here’s what we know so far.  The Delta 737 was cleared for takeoff from runway 4L bound.  The American was cleared to taxi to runway 4L for departure.  

Instead for remaining clear of the active runway 4L, the American 777 crossed 4L without a clearance directly into the path of the departing Delta 737 which was now accelerating down the runway a high speed.  Fortunately, a very alert air traffic controller noticed the American 777’s potentially fatal error and quickly cancelled the Delta 737’s takeoff clearance, forcing the 737’s pilots to perform a high-speed abort. 

The Delta 737 rejected its takeoff roll at approximately 150 knots, a huge problem in and of itself.  Rejecting a takeoff beyond V1, the maximum speed at which a rejected takeoff can be initiated without going off of the runway, presents a huge accident risk.  The Delta jet reportedly stopped within 1000 feet of the American 777, a very close call indeed.

Many will recall the Tenerife runway incursion in 1977 that resulted in 583 fatalities and is considered to be the deadliest aircraft accident in aviation history.  The recent JFK incident clearly shows that we are still struggling with the same pervasive problem nearly 50 years later.

What is a runway incursion? 

Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and takeoff of aircraft.

— International Civil Aviation Organization (ICAO), PANS-OPS Doc 4444, Ch.1

Runway incursions continue to be one of the greatest hazards in aviation.  The FAA’s statistics show that there were 1574 incursions in 2021 and 1732 in 2022, with no sign of abating. 

Taxiing an aircraft seems like it should be fairly simple.  In reality, it is a very complex task that becomes even more complex at busy airports.  Throw in fatigue, limited visibility, darkness, congested frequencies, time pressure, and a seemingly endless variety of distractions, and we have now turned what would seem to be a basic maneuver into a recipe for disaster.

The FAA investigation will likely take some time.  In the meantime, we should ask the following questions:

·       Was the crew adequately rested?  Its no secret; fatigued pilots make mistakes.

·       Did the crew follow good operating practices? 

·       Were sterile-cockpit procedures followed, which limit cockpit conversation to essential communications only below 10,000 feet?

·       Was the crew task saturated or distracted?  Were they running checklists, programming the computer, starting engines, or otherwise “heads-down”?

·       Was there expectation bias?  Did they “expect” to depart from runway 31L?

I firmly believe in one procedure that might have prevented this incident, one that I have used in my airline pilot career.  That would be to require a specific crossing clearance to cross any runway, a procedure that is not required today.  Had the American 777 simply requested a clearance to cross runway 4L as it approached that runway, the controller would have surely denied it, providing a much-needed error check in a situation where the result of human error is unthinkable.

TCAS in TA-ONLY? Mode  No way!

January 13, 2023

The massive failure of the FAA’s NOTAM system on January 11, 2023 dramatically exposed the potentially serious consequences of human error in aviation.  The FAA has disclosed that the probably cause of this massive system failure was human error by system programmers involving a failure to follow established procedures.  Fortunately, in this event there were no lives lost or people injured, just a lot of frayed nerves.

Whether or not the failure was accidental or intentional is a concern yet to be determined.  However, the most important takeaway from this unprecedented event is that human errors will occur in a system that relies on human behavior.

Why do I bring this to your attention?  There is a continuing effort in the airline industry to require pilots to modify existing procedures used in TCAS.  TCAS is the onboard Traffic Collision Avoidance System that was fielded in the 1980’s and mandated worldwide for most airliners, that is designed to help prevent midair collisions.  TCAS is an onboard technology, a black box, that quietly sits in the cockpit constantly surveilling nearby aircraft.  Its primary purpose is to warn pilots of potential threats.  In the most critical situations, in TA-RA mode, it directs pilots with escape maneuvers to help prevent a midair collision.  Pilots are required to follow TA-RA escape-maneuver commands.

The airline industry, in its never-ending attempt to cut costs by increasing system capacity, is lobbying to require pilots to switch the TCAS to a downgraded mode called TA ONLY.  TA ONLY is an advisory-only mode where pilots are only advised about potential threats.  The industry’s solution is to direct the pilots to go to TA ONLY mode in which collision avoidance escape-maneuver commands are suppressed.   There is no evasive maneuver guidance provided in TA ONLY mode.  Pilots are specifically trained not to maneuver based on TA ONLY advisories.

Here is what is driving this effort.  Some airports were designed with runways that are too close together.  San Francisco is one of those airports with runway centerlines only 748 feet apart.  TCAS doesn’t like two large airliners operating at around 200 knots or greater, sometimes with wingspans over 200 feet, operating that close together.  When the planes get that close together, the TCAS in TA-RA mode sometimes issues commands to the pilot to avoid the threat, just as it was designed to do.  Can you argue against that?  I cannot. 

Have you ever been a passenger landing at SFO and looked out your window just to see another large airliner right next to yours filling the view?  Did it cause you concern?  TCAS doesn’t like it either, especially if there is closure rate.

These design constraints cost the industry a lot of money in delays and even more money in lost potential revenue.  Accordingly, they want pilots to degrade the collision avoidance system so that they can operate airliners side-by-side in very close proximity.  The capacity problem would be greatly alleviated if controllers would simply stagger the aircraft but the controllers say no to that due to their increased workload.

We should note that this goes against TCAS basic design and operating principles which directed that the operation of TCAS should not be altered to accommodate the system but rather vice versa.

We have recently seen the effects of human error in the failure of the NOTAM system.  If the airline industry is truly committed to safety as their primary goal, why would they want to take away one of the most, if not the most, valuable and proven collision tool on the aircraft to accommodate more airspace capacity?

Let’s face it…we are talking about a human system and humans make mistakes.  We have a proven and effective collision avoidance technology that has been around for decades.  It sits quietly in the background waiting for a pilot, controller, or system error to present a potentially disastrous threat to the flight.  When the unthinkable happens, TCAS leaps into action and pulls the airplane and all of its occupants out of harm’s way. 

Let’s leave TCAS alone, fully functional, and able to perform its intended job as designed and without artificial limitations in an attempt to increase system capacity and lower operating costs.  There are better ways to do that without jeopardizing flight safety.  To do otherwise would not be fulfilling our responsibility to the traveling public.

Captain Ross Sagun

Sagun Aviation Consulting