CG 1705 Mid-Air, Where was the Squawk?

The Coast Guard investigation of this mid-air collision found that ” No single factor or individual act or omission caused this mishap. It was the product of a tragic confluence of events, missed opportunities, and procedure/policy issues in an airspace where most aircraft fly under a “see-and-avoid” regime (i.e. where individual aircraft de-conflict themselves).”

The Coast Guard investigation does, however, contain considerable criticism of the action or in-action of FACSFAC San Diego, the agency that oversees this area, as does the Navy’s own investigation.

Mentioned, but receiving far less attention, under action, page 10, para 2.c., of the CG investigation, is a recommendation that the FAA consider review of regulations to more precisely define formation flight… such as requiring, “all formation aircraft squawk a discrete code unless otherwise directed.”

I would like to point out why this is critically important, why there is no reason this should not have been standard procedure, and why this single action might have made all the difference, even if FACSFAC SD had done nothing differently.

This collision involved a CG C-130 actively engaged in a SAR case that required it to repeatedly enter an airspace Warning Area, W-291, and a Marine AH-1W, Cobra gunship, call sign Vengence (V) 38, that was one of a flight of four helicopters that were “flying in formation.”

When the collision occurred, the C-130, CG 1705, was maintaining an established altitude, 1000 feet, all it’s collision avoidance lighting was on, and its transponder was activated.

The four Marine helicopters, two CH-53Es and two AH-1Ws, were practicing night combat conditions using Night Vision Devices. Only one, a AH-1 call sign V-39, in trail and to one side, was displaying full anti-collision lighting. The others were generally displaying only their position lights and they were dimmed. Their anti-collision strobe lights were not activated. Only one helo, CH-53E call sign Warhourse (WH) 53, not involved in the collision, had an active transponder, and it was never keyed to its assigned unique code. At the time of the collision it was still set to 1200, the default for aircraft in operating under visual flight rules, VFR.

Three aircraft in the flight of four were flying without their anti-collision lighting and three were flying without active transponders because they were “flying in formation” which would allow the aircraft to be treated as a single aircraft by air traffic control, for purposes of navigation and position reporting. While all four helos were supposed to be operating in close proximity, and moving as a single aircraft, in fact they were not. They was substantial separation laterally, longitudinally, and in altitude. Even as planned this flight of four was not a standard formation, and no attempt was made to clarify that the formation was non-standard. This point seems to have been missed or glossed over by the investigations.

“A standard formation is one in which a proximity of no more than 1 mile laterally or longitudinally and within 100 feet vertically from the flight leader is maintained by each wingman.” (“formation flight,” Aeronautical Information Manual–Pilot/Controller Glossary) As planned the CH-53s and the AH-1s were to have maintained a 300 ft vertical separation, meaning that this was not a standard formation, even if executed as planned, and should not have been reported as a single unit unless Air Traffic Controller had acknowledged and agreed. The planned lateral and longitudinal separation was to have been 500 feet between aircraft. I fact it was much more.

At the time of impact, the flight of four was heading 276 at 109 knots with WH53 at 900′ and V38 at 1000′. CG 1705 was heading 226 at 184 knots and 1000′. WH53 was 0.766 nautical miles directly in front of CG 1705. V39 was 1.005 nautical miles at approximately the 9 o’clock position from CG 1705. With approximately 1.3 miles separating WH53 and V38 the flight of four no longer met the definition for a standard formation in terms of proximity either.

Converging on a bearing of approximately 190 from CG1705 to the Cobra, the two aircraft covered the 5.5 miles in less than four minutes with CG1705 overtaking the darkened Cobra, with it’s low visibility paint scheme, from its starboard quarter as it climbed into the flight path of the C-130. The closing rate was approximately 82.5 knots.

The most commonly understood function of the transponder is to provide information to air traffic controllers. It is capable of enhancing the radar presentation, providing a unique code used to identify the aircraft, and in all but the least sophisticated versions, providing altitude information. But it can also provide information directly to other aircraft, if they are equipped with a Traffic Collision Avoidance System (TCAS). This system can alert other aircraft in the area of their relative bearing, proximity, relative altitude, and can recognize and provide alerts when there is a risk of collision and in some cases even provide recommendations for evasive action. The C-130 was equipped with a TCAS and it was functioning. Just seconds before the collision, the TCAS detected a danger of collision and issued a warning, apparently with regard to the only Marine helo with an active transponder, CH-53 WH53, still more than three quarter of a mile a head. CG1705’s pilot initiated a climb, apparently based on this warning, just before impact. I saw no indication if the Marine helicopters were equipped with TCAS, although if it were civilian aircraft, Their maximum takeoff weight would have required installation of one. If the mishap AH-1 had had a TCAS and it was in operation, presumably it would have alerted the pilot of the impending collision.

I understand the need to secure lights and transponders in combat. I can understand the need to practice night flying in darkened condition with lights dimmed or even off, since bright lights would adversely effect night vision devices, but I cannot understand the need to secure transponders for this exercise since presumably, it would have no impact on the execution of the mission. In prep for the mission, turn the transponder off to get in the habit, because that  is what you would do “going into combat,” but then make a conscious decision to turn it back on, because you are in a training environment.

The see-and-avoid concept works on the presumption that aircraft will want to be seen and will have lights on at night. Helicopters without lights and with paint schemes intended to minimize visual detection work against the basic presumptions. Recognizing this, the Marine helos should have made every effort, that would not have interfered with their training, to enhance detection of their aircraft. There is already provision for this, “If necessary for separation between a nonstandard formation and other aircraft assign an appropriate beacon code to each aircraft in the formation or to the first and last aircraft in trail.” (FAA JO 7110.65S)

This tragedy, as COMPACFLT noted, was entirely preventable.

3 thoughts on “CG 1705 Mid-Air, Where was the Squawk?

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