On a Swivel

On a Swivel

On a Swivel

Recently, two aboard a Cessna 150 died when the trainer collided with a Cessna 525 Citation jet on the runway at Marion Municipal Airport in Marion, Indiana. The C150 was attempting to take off to the southeast on Runway 15 when it struck the tail of the Citation, which had just landed from the north on Runway 22. The tail of the jet was torn off while the C150 crashed and caught fire. Five people were on board the jet and escaped unhurt. The airport, about 50 miles north of Indianapolis, has no control tower and pilots coordinate via CTAF (Common Traffic Advisory Frequency). 

What are the odds the two airplanes arrived at the intersection of the runways at the precise, simultaneous time? I can’t imagine them doing it on purpose without significant planning and practice, and active communication between airplanes during the attempt. Yet, they did collide. The timing was exactly wrong. 

This makes me wonder: since actually arriving at the same point at the same time is challenging at best when attempted intentionally, and completely random at any other time, how many times is more than one airplane using conflicting runway and traffic pattern space, but a collision does not occur solely because the timing was not wrong? In other words, how often does the unsafe condition of traffic pattern and runway conflict at non-towered airports occur, but we never hear about it because the aircraft do not collide? 

It’s not all or nothing, a collision or five miles of separation. Scary thought, huh? At the same time, every time a pilot holds short or goes around because he or she detects a possible conflict, the system worked. It’s obvious, however, that we need to remain vigilant.

Top-of-Mind

The FAA and industry were con–cerned about collision avoidance at non-towered airports even before this collision. Two recent publications address collision avoidance at non-towered airports:

NBAA: The National Business Aviation Association (NBAA) has published, “Operating into a Non-Towered Airport?” The document is aimed primarily on the issue of closing contract control towers, turning Class D airspace into Class E and often Class G close to the surface. The guide states:

When approaching the airport, crews should also make a point to keep their eyes outside the cockpit in order to see and avoid other traffic and monitor the radio to help ascertain the positions of other aircraft in the vicinity. Pilots should also communicate their position and cooperate with other pilots in the area to establish the safest approach to the field, with the least potential for conflict with other traffic. 

This is fairly basic guidance, and is prefaced by this statement: 

…pilots operating under an IFR flight plan to a newly non-towered field will need to be prepared for the transition from the positive control environment of instrument flight when approaching their destination. These are skills that all business aircraft pilots should be familiar with, but now will have to be applied at locations with newly closed control towers….

Well, yes, business pilots not only should, but must follow the rules of visual flight in non-towered and uncontrolled airspace. See and avoid is the first and last defense, regardless of the aircraft type or performance. The NBAA guide does not specifically address the issue of non-towered operations at airports with intersecting runways.

FAA: In March 2018, the FAA issued Advisory Circular 90-66B, “Non-towered Airport Flight Operations.” Also basic in its guidance, it states:

The pilot in command’s (PIC) primary responsibility is to see and avoid other aircraft and to help them see and avoid his or her aircraft. Keep lights and strobes on. The use of any traffic pattern procedure does not alter the responsibility of each pilot to see and avoid other aircraft. Pilots are encouraged to participate in “Operation Lights On,” a voluntary pilot safety program described in the AIM, paragraph 4-3-23, that is designed to improve the “see – and – avoid” capabilities. 

Pilots should clearly communicate on the CTAF and coordinate maneu–vering for and execution of the landing with other traffic so as not to disrupt the flow of other aircraft. Therefore, pilots operating in the traffic pattern should be alert at all times to aircraft executing straight-in landings….Instrument approaches should be par–ticularly alert for other aircraft in the pattern so as to avoid interrupting the flow of traffic, and should bear in mind they do not have priority over other VFR traffic. Pilots are reminded that circling approaches require left-hand turns unless the approach procedure explicitly states otherwise. This has been upheld by prior FAA legal interpretations of § 91.126(b).

The AC goes on to describe radio communications and traffic pattern entries in detail. But it doesn’t provide any specific guidance for non-towered operations with inter–secting runways. In fact, even the Aeronautical Information Manual fails to mention this directly.

Technological Aids

There are several technological aids to collision avoidance, but they have their limitations. The first and by far most common aid is radio communication. The NTSB’s preliminary report, while subject to additional findings before it becomes final, states:

There were three witnesses to the accident, located in the airport lounge, within hearing distance of the UNICOM radio. Each witness reported seeing the Cessna 150 just airborne when it struck the empennage of the Cessna 525. Two of the witnesses stated that they heard the Cessna 150 pilot on runway 15 UNICOM frequency. The pilot of the Cessna 525 stated that he did not see the departing Cessna 150 while he was on a straight-in approach to runway 22, nor did he see the 150 during the landing roll. He stated that he did not recall making a radio call on UNICOM….

Landing at a non-towered airport under Instrument Flight Rules can be a high-workload event, even if weather is VMC and you are flying a visual approach. It’s easy to let vital tasks like making position and altitude calls on the CTAF when you are on Center or Approach and need to cancel your IFR flight plan. All too often, instrument pilots ignore these vital CTAF calls – making it less likely other pilots will see and avoid their aircraft. Of course, in most cases there is no requirement for aircraft at non-towered airports to have a radio at all, so looking outside is still the primary means of collision avoidance.  

Most turbine aircraft have an onboard Traffic Collision Avoidance System (TCAS). TCAS calls out the relative location of aircraft on a possible collision course and in some cases, suggests an avoidance strategy. According to the NTSB, the pilot of the Citation stated that while he did not make a radio call on CTAF, he did utilize his on-board Traffic Collision Avoidance System (TCAS) system while on approach. He stated that the TCAS did not show any traffic on the airport.

Unfortunately, this statement suggests a lack of familiarity about how TCAS works. TCAS relies upon receiving transponder information from other aircraft. Here’s why we can’t rely upon TCAS while landing at a non-towered airport:

  1. Not all aircraft are transponder-equipped. There is not requirement for an airplane like a Cessna 150 to have a transponder at all. 
  2. Transponders emit replies to in–terrogations triggers when the transponder receiver is hit by an Air Traffic Control radar beam. An aircraft close to the ground, such as the Cessna 150 during its takeoff roll, is almost certainly too low to be in radar contact with ATC. Even if the aircraft had a transponder, the transponder would not have been emitting a signal to be picked up by the Citation’s TCAS.
  3. Unless an aircraft has a TCAS or lower-technology TCAD (Traffic
    Collision Alerting Device, which warns of nearby aircraft but may not provide relative position information and does not give specific instructions for collision avoidance), transponder antennas are mounted on the bottom of the aircraft. This makes sense, because transponders rely on line-of-sight transmission, and they are designed to communicate with stations on the ground. Because transponder antennas are on the belly of the aircraft, however, that aircraft’s fuselage and wings blank out the transponder signal to nearby aircraft that are higher up. Even if a departing aircraft had a transponder and was somehow being interrogated by ATC radar, it’s almost certain that a nearby landing aircraft would not receive its transponder transmission, and the departing aircraft would not appear on the landing aircraft’s TCAS.

What about ADS-B? Even after the January 1, 2020 installation deadline, ADS-B probably would not have made a difference. The Cessna 150 almost certainly operates in airspace where ADS-B will not be required. If the C150’s operation does require ADS-B, its owner may well elect to equip with ADS-B Out only. The Citation pilot might have “seen” the C150 on ADS-B, but the C150’s occupants would not have seen an ADS-B plot on the jet. Even if both aircraft had in-cockpit traffic display, and both crews could see the other aircraft on their screens, one or both pilots would have to act to avoid the collision before it was too late. 

Shared Responsibility

This article may seem to focus on what the crew of the Citation did or did not do. But the pilot of the Cessna 150 was just as responsible for seeing and avoiding the landing jet. The reported weather at the time of the accident was VMC with four miles of visibility due to haze. The NTSB notes that at the departure and arrival ends of runway 15/33 (the C150 was using Runway 15) there is a sign stating, “Traffic Using Runway 4/22 Cannot Be Seen, Monitor Unicom 122.7.” There are similar signs at the ends of runways 4 and 22. Although monitoring the CTAF would not have helped if the Citation crew in fact did not report its position, and there’s no reason to believe the Cessna pilot was not listening to the CTAF, seeing such a sign should also alert a pilot to very carefully scan the approaches to the crossing runway just prior to (and if possible, even during) the landing roll. 

Whether departing or arriving at a non-towered airport, especially one with multiple runways:

  1.  Report your position and inten-tions on the CTAF.
  2. Monitor CTAF for the reports of others
  3. Use, but do not rely solely upon, collision avoidance technologies.
  4. Know how collision technologies work, and the limitations of their operation.
  5. Look all around the airport before you begin your takeoff roll, and also as you’re coming in to land. 

As the old fighter pilots said, keep your eyes out the windows and your head on a swivel. See and avoid is the first and last means of collision avoidance.

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