Thursday, August 27, 2009

Further Thoughts on the Mid-Air Over the Hudson

Back on August 8th, as you'll recall, a tour helicopter and a Piper Saratoga collided in mid-air in the Hudson River VFR Corridor. All nine persons aboard the two aircraft perished. I offered a few thoughts on the incident in this post.

This afternoon the National Transportation Safety Board (NTSB), whose investigation of the accident is on-going, sent a Safety Recommendation Letter to the Administrator of the FAA based on the Board's preliminary findings. Let's take a look at the recommendations (which I think are, for the most part, quite sensible). (Note: In what follows, "VFR Corridor" and "Class B exclusion area" are equivalent.)

In my earlier post on this incident I observed that:

"The Hudson River VFR Corridor is intended to provide an alerted see-and-avoid environment. The means of alerting is a combination of rules-of-the-road ("Keep Right!") and self-announced position reports on the Common Traffic Advisory Frequency (CTAF) of 123.05 MHz. The Piper Saratoga that was involved in the mid-air was, regrettably, not communicating on the CTAF. Its pilot was talking to the Teterboro (KTEB) tower and may have just been switching (as directed and acknowledged) to the Newark (KEWR) tower frequency. It is unknowable whether the collision might have been averted if the Piper pilot had been on the CTAF and able to hear the helicopter's position reports."

The NTSB "gets it". In today's letter, the Board makes the following observations:

"Effective communication on the CTAF is a fundamental component of the safety procedures established for VFR operations in the Hudson River class B exclusion area. ...ATC facilities must account for the importance of CTAF communications and ensure that aircraft operating near the Hudson River class B exclusion area are either cleared into class B airspace before reaching the Hudson River class B exclusion area or are directed to switch to the CTAF in time to engage in effective communications with other pilots operating in the Hudson River class B exclusion area. Further, if circumstances require that an aircraft in communication with ATC enter the Hudson River class B exclusion area, controllers should place a high priority on providing the pilot with timely traffic advisories and safety alerts..."

The Board goes on to issue Safety Recommendation A-09-82:

"Revise standard operating procedures for all air traffic control (ATC) facilities, including those at Teterboro airport, LaGuardia airport, and Newark Liberty International airport, adjoining the Hudson River class B exclusion area in the following ways:
  1. establish procedures for coordination among ATC facilities so that aircraft operating under visual flight rules and requesting a route that would require entry into class B airspace receive ATC clearance to enter the airspace as soon as traffic permits,
  2. require controllers to instruct pilots with whom they are communicating and whose flight will operate in the Hudson River class B exclusion area to switch from ATC communications to the common traffic advisory frequency (CTAF) and to self-announce before entering the area,
  3. add an advisory to the Automatic Terminal Information Service broadcast, reminding pilots of the need to use the CTAF while operating in the Hudson River class B exclusion area and to self-announce before entering the area, and
  4. in any situation where, despite the above procedures, controllers are in contact with an aircraft operating within or approaching the Hudson River class B exclusion area, ensure that the pilot is provided with traffic advisories and safety alerts at least until exiting the area."

The Board's Recommendation A-09-83 is a reaction to the performance of ATC personal at the time of the accident. I hope you'll read the parts of the Letter pertinent to this...I have nothing to add.

Moving on, in my earlier post I offered the following observations and a suggestion:

"Would the Piper pilot, who was a transient visiting from outside the New York City area, have been able to effectively process the position information from the reports of potentially conflicting aircraft even if he had been on CTAF? This is not in any way a disparagement of that pilot's skill, expertise or competence. But how many of us, hearing 'Helicopter 405 climbing mid-river to 1100 abeam the Holland Tunnel Towers' will know just where to look...at a time when seconds count?...

...[C]onsider as a model the on-line course that is required for pilots flying VFR within 60 miles of the Washington ADIZ. A similar course could be designed, and successful completion required (yes, I said required) for pilots wishing to transit the Hudson VFR Corridor. Such a course would cover altitudes, landmarks and proper position reporting."

Once again, the Board "gets it". They offer the following:

"It is critical that all pilots operating within the Hudson River class B exclusion area share a common understanding of applicable operating practices, airspace boundaries, traffic flows, position reporting points, and reporting procedures used within the area.
The NTSB is concerned that the voluntary measures ...currently in use to educate pilots on safe operations within the area may not be sufficient to achieve this objective. The NTSB notes that, in other situations where enhanced pilot awareness and compliance with special procedures has been necessary for safety...the FAA has implemented special flight rules areas (SFRA)... The FAA has also required that pilots who fly in some of these SFRAs complete training in those SFRAs’ operational procedures. The NTSB believes that similar action regarding the Hudson River class B exclusion area would improve safety of flight operations in the corridor...The NTSB notes that the SFRA training developed by the FAA for pilots operating near Washington, DC, may be a suitable model."

Safety Recommendation A-09-84 speaks to this need, calling on the FAA to:

"Amend 14 Code of Federal Regulations Part 93 to establish an special flight rules area (SFRA) including the Hudson River class B exclusion area, the East River class B exclusion area, and the area surrounding Ellis Island and the Statue of Liberty; define operational procedures for use within the SFRA; and require that pilots complete specific training on the SFRA requirements before flight within the area."

The Board also looks at the possible influence on this accident of the disparity in aircraft performance between the helicopter and the airplane, saying:

"[A]t the time of the accident, the accident airplane was in level flight at about 1,100 feet, at a groundspeed of approximately 150 knots. The accident helicopter was climbing almost all the way to the point of impact, and the helicopter's groundspeed was approximately 93 knots when the collision occurred. Preliminary review of the radar data and witness statements indicate that the accident helicopter was overtaken and struck from behind by the accident airplane. The nearly 60-knot speed difference between the aircraft, as well as climb and descent rate differences, differing flight profiles, and other performance differences, may have reduced the time available for the accident airplane pilot to visually acquire the accident helicopter ahead and avert the collision. The NTSB concludes that segregation of helicopters from airplanes in the Hudson River class B exclusion area may provide an additional margin of safety by limiting the number of encounters between aircraft with significant performance differences."

Based on this analysis, the Board goes on to offer Safety Recommendation A-09-85, calling on the FAA to:

"As part of the special flight rules area procedures requested in Safety Recommendation A-09-84, require vertical separation between helicopters and airplanes by requiring that helicopters operate at a lower altitude than airplanes do, thus minimizing the effect of performance differences between helicopters and airplanes on the ability of pilots to see and avoid other traffic."

This is the only one of the Board's recommendations with which I do not unreservedly agree. The theory is sound, but I'm concerned that if the vertical extent of the VFR Corridor remains from surface to 1,100 feet there may be too little space for a safe vertical division. Let's say, for example, that helicopters are to be restricted to the space from the surface to 800 feet and fixed wing aircraft are to be restricted to the airspace from 801 feet to 1,100 feet. I would be worried that the large number of helicopter operations, characterized by a large number of altitude excursions, would be compressed into an inadequate amount of space with the unintended consequence of an increased number of conflicts. I suspect that the fixed-wing traffic would be just fine.

If the FAA was willing to give up a little of the Class B Airspace, so that the helicopters could operate from the surface to 1,000 feet and the fixed-wing traffic had available the airspace from 1,001 to 1,500 feet, then I believe the Board's recommendation would be fully supportable.

The last recommendation in the Board's letter, A-09-86, is a "housekeeping" item asking that the FAA review all Class B airspace to identify areas where similar measures may be appropriate.

I think that the NTSB has done a remarkable job, remarkably quickly and I hope that the General Aviation community can be unified in supporting the recommendations that the Board issued today.

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