The northern border of South Korea roughly along the 38th parallel is the demilitarized zone or DMZ. On each side of the border between the Koreas, roughly 2 kilometers away is a second border fence creating a buffer zone between the countries. Extending south of these southern border fence is a No-Fly zone that was established to prevent accidental overflight of the border with North Korea. There are specific corridors, each 1.5 kilometers wide established in the no-fly zone, to allow for specific mission needs in the area. You have to be certified to fly these zones by an already corridor qualified pilot and all flights in the No-Fly Zone had to be completed between 10 AM and 4 PM and never continue after dark. All of this information was part of the regional training for a US Army pilot in South Korea in 1990 (It may have changed since I left, I don’t know.) The “Rock Haul” was a mission exception to even those restrictions.
The South Koreans were building an observation post (OP) 400 meters south of the southern border fence on top of a mountain ridge that was 7500 ft. Mean Sea Level (MSL). This OP was in the vicinity of the Peace Dam on the Bukhan River. The Peace Dam was built to stave off possible catastrophic flooding should the upstream Imnam Dam in North Korea. South Korea found the Imnam Dam worrisome because if it ever failed it could be disastrous for areas of South Korea downstream. This OP was being built at a point where the Imnam Dam could be observed. This construction was why hauling gravel to the top of the mountain was requested. Due to the remote location and the lack of road infrastructure, a single load of gravel via truck to the site required a 24 hour or more journey in a dump truck. This made the cost of using a Chinook ($7500.00 per hour was the price I was quoted, the Koreans were providing the fuel) economically feasible.
The mission came down to our unit and I was assigned as co-pilot for the mission. Our orders were pretty simple. We were to pick up a South Korean border qualified pilot to ride in our jump seat (Between and behind the pilots) and verify our navigation. (Flight out of the specific parameters of our flight plan could result in our being shot down by South Korean air defense.) He also guided us to a pickup zone near the quarry where South Korean army troops prepared and hooked up the loads. From there we flew 15 kilometers to the top of the ridge and set down our loads on the ridge landing zone (LZ) then returned to the pickup zone for the next load. Every fourth trip we did a pinnacle landing (Rear wheels only on the ridge, front of aircraft at a hover) and recovered the slings used in the previous loads. Refueling and lunch were provided at a South Korean base in the No-Fly Zone about 20 kilometers south of the area we were working.
Pre-flight and our mission brief were completed and we took off from Camp Humphreys just after 9 AM so that we would arrive at the corridor at 10 AM. We landed at the corridor airfield and picked up our passenger and headed to the pickup zone (PZ). The PZ was a large field near the river and I assume there was a quarry nearby although I never saw it. When we arrived, there were two loads already rigged each with two Republic of Korean Army (ROK) privates as hookup men standing on each load and a ROK Army sergeant with a bamboo cane supervising them.
We came to a 10-foot hover about 50 feet behind the loads and we started moving forward. My flight engineer was in the hole calling us forward to hook up the load: “Forward forty, forward thirty, forward twenty, forward ten, Forward hook is hooked, Aft hook is hooked, hookup men are clear.” In real time, this took say thirty seconds or so and we commented that these hookup men were pretty aggressive. (Aggressive = Good) The flight engineer mentioned that one soldier was holding the clevis for the load and it appeared that the soldier supporting him was throwing him at the hook. It appeared they didn’t want to make their sergeant angry and he his demeanor appear "unfriendly" from the cockpit.
With the loads hooked, we brought the helicopter up and the slings came tight, the loads came off the ground at 98% torque and we estimated the loads at slightly over 20,000 lbs. We completed the before takeoff checks and nosed the bird over a bit and accelerated through effective translational lift (ETL) to where we were flying in undisturbed air and began our climb up the mountain. Max climb airspeed was 70 knots and we were climbing over 1500 feet per minute so it took four to five minutes to climb to altitude. We then we turned north heading toward the DMZ. About 400 meters south of the fence we turned west and made our approach to the pinnacle.
Pinnacle approaches with a heavy load are tricky as you have to come to an out of ground effect (OGE) hover then set the load on a very precise spot. You couldn't dither around too long either because you could get into a vortex ring state (where you lose lift due to your own downdraft recirculating and creating an increasingly fast downward airflow to the point where you don’t have enough power available to counteract the flow.) and that is when bad things happen. I tried hard to avoid bad things while flying as they tend to be very unforgiving.
With care and precision, but not wasting any time either, I made the approach and came to a hover over the ridge. We relied on the Flight Engineer (FE) over the intercom because from our location 30 feet forward, all I could see looking down was the side of the mountain about 300 feet below. Once the load was on the ground, I released the slings and nosed the helo over and headed down the mountain and toward the PZ. Descending the mountain was also done at 70 knots but you could descend much faster than we climbed and I was nearly in an auto-rotation as we were descending over 2000 feet per minute.
When we arrived at the PZ the next load was already in position, rigged and our ROK hookup men were again leaning forward wanting to get up hooked up as fast as humanly possible. Their sergeant still had a scowl on his face. The second load was exactly like the first, except we came to a hover again at 98% torque. Since we’d burnt off 900 lbs. of fuel the first trip the meant the second load was about 21,000 lbs. These guys were good, they even accounted for our fuel burn on the trip.
I took turns with the Pilot-in Command (CW4 Bob Johnson) and we made four circuits up and down the mountain before we had to go for fuel. We flew to the ROK airfield in the corridor about 15 kilometers to the south and shutdown while they were fueled the bird. Our guide (Captain Park) took us to the mess hall couple hundred yards away and we had a quick lunch. Our enlisted crew showed up a few minutes later after refuel was complete and we enjoyed a nice meal with our ROK comrades, then it was back to work.
During each approach to the pinnacle, we were painted by North Korean radar and we could see the end of the Imnam Dam in the valley north of the DMZ. This was the most nerve wracking point in the mission because we all had heard stories of North Korea incursions in the DMZ and stories of border skirmishes with both ground troops and aircraft. (My Godfather told me of taking fire at a South Korean observation point in the 1970s and calling in a F4 to bomb the location that was engaging them.) This was the closest I’d ever been to real hostile forces and I was uneasy at best about the proximity of the enemy. Lucky for us, nothing happened, but I didn’t relax until we’d exited the No-Fly zone
We continued with the cycle of four loads up the mountain then back haul the nets and slings until about 3:30 PM. After that last load was placed on the DZ, we hovered over to the pinnacle and landed to recover the slings and nets and they rapidly unloaded the last two nets while I hovered on the pinnacle. Apparently, there the ROK soldiers on the pinnacle had a twin to the PZ ROK sergeant. they took maybe a minute to drag empty the nets and drag them on to the aircraft. We took the express elevator back down the mountain one last time, returned the slings and our guide at the ROK airfield in the corridor before flying out of the No-Fly Zone at about 3:50 PM, mission complete. The flight back to Camp Humphreys was uneventful.
In a little less than six hours we made 14 trips up and down that mountain and carried 331,000 lbs. of cargo. Not a bad day’s work. Not bad at all.
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