Unsafe ATC practices in US airspace (3)

I will now restate those ATC practices which I consider unsafe and what should be done about it.

1.        “See and avoid” and “visual separation” applied to airline traffic. These principles are clearly unsafe and should not be relied upon to maintain safe separation between airliners and other traffic in controlled airspace. It should only be applied between airliners in daylight and good visibility when there is no possibility of misidentification, for example in the case of airliners following each other to land or when landing on parallel runways.

2.      The US practice of clearing multiple aircraft to land pending the runway to be clear of traffic. This “US only” practice does not expedite traffic but allows the controller to “take his eyes off the ball” at a critical moment and has led to several serious incidents at US airports. A go-around at the last moment presents an increased risk and should be avoided. This is an unsafe practice which should be discontinued.

3.      Nighttime visual approaches. These entail greater risks than daytime visual approaches and for this reason are prohibited by several airlines. This is an unsafe practice for airliners and should be restricted to general aviation or when the runway in use does not have an instrument landing system. Naturally, this prohibition will reduce capacity at some major airports, especially in the northern winter months, but this is a necessary sacrifice in favor of safety.

4.      Taxi clearances which include permission to enter or to cross a runway without stopping. The danger of a clearance which includes permission to enter or to cross a runway is that it is open to misinterpretation or that the crew can mistake one runway for another or for a taxiway, which is not uncommon. A safer practice is to rule that all aircraft should always stop before entering or crossing any runway; at controlled airports a positive clearance from ATC would be required before proceeding to enter or cross a runway.

Of course, I do not pretend that these ingrained practices will be changed any time soon, much less just because I consider that they are unsafe. An adequate procedure would be for the NTSB to study them and make recommendations to the FAA. The FAA would then convene a special committee, which would ideally include pilots as well as ATC specialists, to consider if any changes should be implemented.

Unsafe ATC practices in US airspace (2)

Continuing with my call for a reappraisal of potentially unsafe practices in the US air traffic control system, I will now add the following to my list:

“Hold short of Runway X”. Evidently, this instruction, which requires a correct readback, was instituted in order to enhance safety by preventing an aircraft from entering an active runway. However, I believe that in fact it is part of an unsafe practice that allows ATC to clear an aircraft to cross one or more runways before coming to a stop. A safer practice is to rule that all aircraft should always stop before entering or crossing any runway; at controlled airports a positive clearance from ATC would be required before proceeding to enter or cross a runway.

The danger of a clearance which includes permission to enter or to cross a runway is that it is open to misinterpretation or that the crew can mistake one runway for another or for a taxiway, which is not uncommon.

For example, in the ground collision between a Japan Air Lines Airbus A350 and a Japan Coast Guard DHC-8 which occurred at Tokyo Haneda Airport on 2nd January 2024, ATC instructed the DHC-8 to “taxi to holding point C5”, but the surviving captain of this aircraft asserted just after the accident that he had been cleared for take-off. The DHC-8 proceeded to enter and line-up on the runway, where it was hit by the landing A350. Of the six crew on-board the DHC-8, only the captain survived; all 379 occupants of the A350 managed to evacuate the aircraft before it was completely destroyed by fire.

Another recent example was the near-miss at Chicago Midway International Airport (MDW) on 25th February 2025. A Bombardier Challenger 350 CL-35 was operating under General Aircraft (GA) rules as Flexjet flight 560 and was initially given a clearance to taxi to runway 22L via taxiway F and to hold short of runway 4L. When they were on taxiway F, ATC instructed them to turn left onto runway 04L, cross runway 31L and then hold short of runway 31C. The flight crew initially read back the instructions incorrectly; the ground controller immediately reissued the instructions and received a correct readback. After turning left onto the runway 04L with a width of 150 ft, the crew crossed runway 31L, mistaking it for a taxiway and then proceeded to cross runway 31C believing it was runway 31L.[1] At that moment a Boeing 737-800 operating as Southwest Airlines flight 2504 with 136 passengers and six crew, was about to land on runway 31C. The airliner was below 100 ft when the co-pilot realized that the business jet was going to cross runway 31C; he called for a go-around and the captain executed it, with the airliner reaching within 25 ft of the runway surface before climbing away. The Boeing passed with a vertical separation of 75 ft and a horizontal separation of 200 ft behind the Bombardier. In this case, the change I propose would have required the business jet to stop before entering runway 04L and before crossing runways 31L and 31C,[2] but better safe than sorry. In 2001, another business jet strayed onto the runway at Milan-Linate Airport in Italy, killing all 110 passengers and crew on an SAS airliner, four more persons on the ground as well as the four occupants of the smaller aircraft.  

[1] It is noted that runway 31L/13R has a width of just 58 ft and its runway signs and hold-short line on runway 04L can be difficult to see from an aircraft turning onto runway 04L from taxiway F because these markings are just 75 ft from the centerline of taxiway F and just where the nosewheel of the aircraft would be straightening out. Runway 31L/13R has no surface markings crossing runway 04L/22R. From the lack of tire marks on runways 13L/31R and 04L/22R, it appears that these are mostly used as taxiways.

[2] It appears that runway 31R/13L was decommissioned between 2023 and 2024; it is now a taxiway.

Visual Separation

According to FAA Order JO 7110.65AA - Air Traffic Control, paragraph 7.2.1 VISUAL SEPARATION, in a TERMINAL area visual separation can be either Tower-applied or Pilot-applied.  Pilot-applied visual separation requires the controller to:

(a)   Maintain communication with at least one of the aircraft involved and ensure there is an ability to communicate with the other aircraft.

(b)   The pilot sees another aircraft and is instructed to maintain visual separation from the aircraft as follows:

(1)   Tell the pilot about the other aircraft. Include position, direction, type, and, unless it is obvious, the other aircraft's intention.

(2)   Obtain acknowledgment from the pilot that the other aircraft is in sight.

(3)   Instruct the pilot to maintain visual separation from that aircraft.

(c)   If the pilot reports the traffic in sight and will maintain visual separation from it (the pilot must state both), the controller may “approve” the operation instead of restating the instructions.

(d)   If aircraft are on converging courses, inform the other aircraft of the traffic and that visual separation is being applied.

(e)   Advise the pilots if the targets appear likely to merge.

(f)    Control of aircraft maintaining visual separation may be transferred to an adjacent position/sector/facility. Coordination procedures must be specified in an LOA or facility directive.

Up to letter (c), the conditions were met in the case of the PAT25 helicopter and the CDA Local controller on the night of 29th January 2025; the controller was not required to inform the CRJ that there was traffic ahead and that the other aircraft would maintain visual separation; in this case, the CRJ could hear the controller’s instructions to the helicopter on another frequency but could not hear PAT25’s responses. Since the rule did not require PAT25 to read back the controller’s instructions, neither the controller nor the crew of the CRJ were aware that parts of the instructions were not heard by PAT25.

However, letters (d) and (e) contradict the notion that once visual separation has been established by the pilot of one of the two aircraft and approved by the controller, the controller is relieved of all responsibility for maintaining safe separation between the two aircraft. These rules require the controller to continue to observe the two aircraft on his screen, that he will warn the other aircraft if they are on converging courses, and that he will advise the pilots of both aircraft if the two targets appear likely to merge. Note that the rules do not mention vertical separation.

In the case of the Washington DC accident, the CRJ and PAT25 were on converging courses and finally merged on the radar screens, otherwise they would not have collided. Evidently, the controller believed that the conflict would be resolved by vertical separation but, as observed in a previous Blog, a vertical separation of less than 200 ft is not a safe separation. Had the Local controller expressly informed the CRJ that it would cross the path of a helicopter flying south along the river at 200 ft, the crew would have been made aware that a potentially dangerous situation was developing, would have been on the lookout for the helicopter and could have taken other actions, such as abandoning the approach or evasive manoeuvres if they saw the helicopter.

“Visual separation” is dependent on the “see and avoid” principle; since “see and avoid” cannot be relied upon to maintain safe separation between an airliner and a General Aviation or Military aircraft, even in daylight with good visibility, it follows that permitting a General Aviation or Military aircraft to unilaterally maintain visual separation from an airliner is not a safe practice and should be discontinued.

Where airliners are concerned, visual separation should only be permitted between two airliners following one another, in daylight in good visibility, when there is no possibility of misidentification.