On March 17, 1971, Chief Warrant Officer 2 Michael J. DePaul climbed aboard a United States Army AH-1G Cobra at Can Tho Airfield in South Vietnam. The aircraft, tail number 67-15676, belonged to C Troop (Air), 16th Cavalry, 1st Aviation Brigade, and operated under the call sign “Darkhorse 32.” It was not scheduled to be a combat mission. There would be no enemy fire, no rockets rising from the jungle and no desperate call for assistance from soldiers pinned down somewhere in the Mekong Delta. DePaul and Captain Robert Carrell Green were conducting a check flight in the traffic pattern around the airfield.

That distinction is important. A check ride was not simply a casual flight or an opportunity to accumulate more time in the aircraft. It was a formal evaluation of an aviator’s ability to control the helicopter, follow procedures and respond properly to simulated emergencies. DePaul was serving as the instructor pilot and evaluator, while Green was undergoing an aircraft commander check ride. Available accounts indicate that approximately eight-tenths of an hour had passed since the evaluation began.

DePaul’s experience was not limited to the narrow, heavily armed Cobra. He had also flown the UH-1 Huey, the aircraft that became almost inseparable from the American experience in Vietnam. The Huey carried troops, ammunition, food and wounded men. It landed in confined clearings, hovered over dangerous landing zones and became a lifeline between isolated soldiers and the outside world. Flying the Huey and flying the Cobra demanded different instincts. The Huey was a versatile working aircraft, capable of transporting people and supplies or serving as a gunship. The AH-1G Cobra was built around speed, firepower and a slim profile. Its tandem cockpit placed one aviator ahead of the other, and its narrow fuselage made it much more difficult for an enemy gunner to hit than the broader-bodied Huey. For an aviator like DePaul, experience in both aircraft represented a wide range of Army aviation skills.

The Cobra assigned to DePaul and Green that day was working inside the Can Tho traffic pattern, practicing approaches and emergency procedures. One of those procedures was an autorotation, a maneuver in which the helicopter descends without normal engine power while airflow keeps the rotor turning. Pilots practiced autorotations so that an actual engine failure would not leave them without a way to control the aircraft. Although the engine is normally reduced to idle during training rather than completely shut down, the maneuver still requires precision. The pilot must maintain the proper airspeed and rotor revolutions, judge the descent and flare at exactly the right moment. There is little room for hesitation.

While Darkhorse 32 maneuvered near the airfield, another aircraft was approaching Can Tho from the west. It was an Air America Pilatus PC-6 Porter using the call sign 93R.

Air America occupied an unusual place in the history of the Vietnam War. It was a civilian airline, but it was closely associated with American intelligence operations and provided aviation support throughout Southeast Asia. Its aircraft operated in South Vietnam, Laos, Thailand and Cambodia, moving passengers and cargo into locations that were difficult, dangerous or politically sensitive. Its crews flew into places where conventional airlines could not operate. They delivered food, medicine, ammunition and equipment. They transported military personnel, government officials, refugees and members of irregular forces. Air America aircraft also supported reconnaissance, communications and search-and-rescue operations, sometimes entering areas where enemy activity, mountain weather and primitive landing strips made every flight hazardous.

The Pilatus PC-6 Porter was particularly well suited to that work. Designed in Switzerland, it was a high-wing, single-engine utility aircraft with exceptional short takeoff and landing capabilities. Its large wing, strong landing gear and relatively low operating speed allowed it to use rough airstrips carved into mountainsides or cleared from remote valleys. Air America frequently depended upon rugged aircraft such as the Porter to reach isolated landing grounds known as Lima Sites, especially in Laos. The Porter was not fast or glamorous. Its value came from what it could carry and where it could land. A skilled pilot could bring one into a strip that appeared impossibly short, unload passengers or supplies and depart again with very little runway. In the hands of Air America crews, the aircraft became a workhorse of the covert and unconventional air war.

That versatility came with danger. Mountain ridges, changing weather, heavily loaded aircraft, enemy fire and inadequate navigational facilities made many missions unforgiving. The crews often operated far from conventional maintenance facilities and emergency services. Their civilian status did not protect them from the risks of war. The Porter approaching Can Tho on March 17 was flown by Captain Kenneth A. Houp, an Air America pilot whose name appears among the company personnel lost during its operations in Southeast Asia.

Unlike the remote mountain strips for which the Porter had become famous, Can Tho was a major military airfield. It served as an important center of American and South Vietnamese aviation activity in the Mekong Delta. Helicopters, observation aircraft, transports and civilian contract aircraft moved through its airspace. That variety of traffic required constant coordination. On this day, that coordination began to break down.

The Porter contacted Can Tho tower while approximately six miles west of the airfield. It was using a VHF radio frequency. The controller instructed the aircraft to make a straight-in approach to Runway 08 and report when it reached two miles from the field. Darkhorse 32, meanwhile, was communicating with the same control tower on a UHF frequency. The significance of that difference cannot be overstated. Both crews could communicate with the tower, but they could not hear one another. DePaul and Green could not hear the Porter’s position reports. Houp could not hear the Cobra’s transmissions or know precisely what maneuver the helicopter had been cleared to perform. Each crew was receiving instructions from the same controller while operating inside separate radio conversations.

Darkhorse 32 reported from the downwind portion of the traffic pattern and requested an autorotation to the active runway. The Cobra was cleared as the second aircraft in the landing sequence. An OH-58 observation helicopter ahead of it was already touching down near a helipad area. DePaul entered the autorotation and turned toward the runway. At nearly the same time, the controller saw a fixed-wing aircraft approaching on final and asked for its identification. The reply came back from the Porter: “93R, one mile out here.” The aircraft were now converging.

The tower instructed the Porter to slow its approach. Evidence from the wreckage indicated that an intermediate flap setting had been selected, reducing the Porter’s speed to somewhere around 70 to 80 knots. Darkhorse 32, descending in the autorotation, was reportedly moving at approximately 60 to 70 knots. The difference in speed was small enough that the Porter was slowly overtaking the Cobra from behind. The Cobra’s narrow fuselage would have been difficult to see beneath and ahead of the Porter. At the same time, the Porter was approaching from a position that would have been largely hidden behind and above the helicopter. Neither cockpit offered the crews an unrestricted view of the other aircraft.

The controller suddenly recognized the danger. Darkhorse 32 was urgently instructed to go around, and Michael DePaul acknowledged the command. Seconds later, the tower asked the Porter pilot whether he had the Cobra in sight. “Negative.” The controller began another warning, but he never finished the sentence.

The Pilatus Porter overtook Darkhorse 32 from above and behind. Its landing gear and lower fuselage entered the rotating arc of the Cobra’s main rotor. In an instant, two aircraft that had been under control became tangled wreckage. The impact shattered the Cobra’s rotor system and inflicted catastrophic damage on both machines. Darkhorse 32 fell beside the runway, killing Chief Warrant Officer 2 Michael J. DePaul and Captain Robert C. Green. The Porter also crashed, killing Captain Kenneth A. Houp and the other people aboard the aircraft.

Publicly available summaries differ on the precise number of occupants carried by the Porter, with some accounts reporting six people aboard and others reporting seven fatalities in the aircraft. What is consistent is that there were no survivors from either aircraft. There was no time for either crew to understand fully what was happening. DePaul had only moments between the tower’s go-around instruction and the collision. Houp had only enough time to answer that he did not see the helicopter.

The tragedy unfolded not over enemy territory but directly beside an American-operated airfield. There were no hostile weapons involved. There was no mechanical failure that had developed over several minutes. The Cobra and the Porter were both operating normally until the final seconds. Each crew believed it was following the instructions provided by the tower. Their paths simply came together.

Michael Joseph DePaul served as an attack helicopter pilot with C Troop, 16th Cavalry. His role as an instructor pilot reflected more than flight time. Instructor pilots were entrusted with evaluating other aviators and ensuring that they could safely handle demanding aircraft under combat conditions. The Vietnam War placed enormous responsibility on young Army aviators. Many were in their early twenties, yet they were expected to command aircraft, make decisions under fire and carry the lives of other men in their hands. An instructor pilot carried an additional burden. He had to judge whether another aviator was prepared to assume that responsibility.

The check ride aboard Darkhorse 32 was part of that process. DePaul was not merely accompanying Captain Green. He was watching his control movements, monitoring the aircraft, evaluating his judgment and preparing to intervene if necessary. Green, in turn, was demonstrating his ability to perform the maneuvers expected of an aircraft commander. The autorotation they were practicing was itself an exercise in survival. It existed to prepare a pilot for the moment when an engine failed and only training, judgment and rotor energy stood between the crew and the ground. There is a painful irony in that detail. DePaul and Green were practicing how to survive one type of emergency when another arrived from a direction neither man could see.

Both men are recorded as casualties of the Vietnam War even though their deaths were classified as non-hostile. That administrative distinction may explain how they died, but it does not diminish the fact that they were serving in a combat theater, flying military aircraft and carrying out duties essential to the war. They died in service.

Captain Kenneth A. Houp belonged to another aviation community, one that operated outside the traditional structure of the United States military but often shared the same dangers. Air America pilots developed a reputation for flying into locations that other crews avoided. Their missions required confidence, improvisation and an intimate understanding of their aircraft. A Porter pilot had to judge mountain winds, short strips, rising terrain and aircraft weight with great precision.

Many Air America personnel worked without the public recognition normally associated with military service. Because some missions supported classified or politically sensitive operations, the details of their work remained obscure for years. Families sometimes knew little about where their loved ones had flown or what missions they had performed. Houp’s final flight was not into a secret mountain base. It was an approach to an established airfield. Yet the risk became just as real. His last recorded response was a simple statement that he did not have the Cobra in sight. That answer says everything about the final moments. He was being warned about an aircraft that was already dangerously close but remained hidden below and ahead of him.

What remains so haunting about this tragedy is its proximity to safety. Darkhorse 32 was almost at the runway. The Porter was preparing to land. The tower was watching both aircraft. The men were surrounded by an established airfield, maintenance facilities, fellow aviators and emergency crews. They had returned from whatever hazards the day had carried, and yet they were not safe.

A runway can create the feeling that a mission is already over. For aircrews, however, the flight does not end when the airfield comes into view. The approach and landing remain among the most demanding portions of any flight, especially at a busy military installation where helicopters and fixed-wing aircraft may use overlapping traffic patterns. The collision at Can Tho illustrates how quickly several individually understandable circumstances can combine into disaster. The aircraft were on separate frequencies. Their speeds were similar. The Porter approached from above and behind. The Cobra was descending during a training autorotation. Neither crew could hear the other. By the time the controller recognized how closely their paths had converged, only seconds remained.

No single dramatic act defined the tragedy. There was only a series of ordinary transmissions, clearances and acknowledgments ending in a warning that was never completed. Sometimes fate gives you only seconds.

Chief Warrant Officer 2 Michael J. DePaul, Captain Robert C. Green and Captain Kenneth A. Houp came from two different aviation organizations. DePaul and Green wore United States Army uniforms and flew an armed helicopter. Houp flew a civilian-marked aircraft for Air America. Their duties were different, but their lives ended in the same sky.

DePaul was an instructor pilot, a Cobra aviator and a Huey pilot helping prepare another officer for the responsibilities of aircraft command. Green was demonstrating the skills required to take that next step. Houp was bringing a rugged utility aircraft home to Can Tho. All three were doing what aviators had done thousands of times before them. They were preparing to land.

Today, we remember Chief Warrant Officer 2 Michael J. DePaul, Captain Robert Carrell Green, Captain Kenneth A. Houp and everyone aboard the Air America Porter. We remember not only the collision, but also the service that brought each of them to Can Tho. They were soldiers, aviators and crew members carrying out the daily work of a war that extended far beyond the battlefield. They are not forgotten.

This historical photograph has been digitally restored and enhanced by Ghosts of the Battlefield to help preserve the memory of the American serviceman pictured. No historical details have been altered.

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