Trust. Sometimes that’s all we have.
By Steven Athanas
It was a caution none of us had seen previously, at least not while operating the CQ-24A Unmanned K-MAX air vehicle. We were watching the operator maneuver the vehicle over Forward Operating Base Payne, which was some miles to the south of us. Because it was over the horizon, he was using the Beyond Line of Sight (BLOS) datalink. Maneuvering manually under BLOS was nonstandard, but I had directed it as a contingency in case the Payne equipment, operated by two Marines we had previously trained, became inoperative. We had the ability to deliver autonomously from far away but I thought it useful to know if we could reposition manually if asked to do so by the landing zone controllers. After all, this was a war zone.
We soon discovered that manual control of a hovering, over the horizon vehicle was difficult work. The CQ-24A BLOS installation had the same limitation as any other: system lag. Once a control input was made from our command tent, it could take up to six seconds for its signal to bounce off the satellite down to the vehicle, influence its vector, then send the resulting change in attitude, speed, and position back to the operator’s Graphic User Interface (GUI) screen.
With this lag, it was quite easy to chase the aircraft. Our eventual technique was to make a one second input on the hand controller, release, then wait until we saw the vehicle’s icon stop on the GUI screen. Repeated as necessary, it was as tedious as it was inefficient. The BLOS installation was so basic there was no guarantee a one second displacement on the hand controller would produce the same amount of vehicle movement each time. And without external cameras, the operator had to contrive his entire closed-loop feedback from the GUI screen.
Unmanned K-MAX had begun as a fancy science project years before. The brainchild of Greg Lynch, a Lockheed Martin program manager and former Air Force helicopter pilot, he first fought his own superiors then Department of Defense officials over the feasibility of an unmanned helicopter delivering supplies to remote locations. He believed the K-MAX was the perfect platform for this, already proven by hundreds of thousands of manned flight hours. It was simple for a helicopter, which meant it was reliable to the extreme. It was also quiet. Its dual intermesher configuration didn’t require a tail rotor, making its aural signature among the lowest in the world.
The Unmanned K-MAX prototype, using off-the-shelf components, began winning the hearts and minds of executives and officials alike through a series of successful demonstrations, culminating in a final test in 2011. By this time the United States had absorbed significant ground convoy casualties in its two war zones, the ground convoy being the primary method of satisfying the logistical needs of the warfighter. Due to the desire to “get off the roads”, nearly overnight the fancy science project gathered sufficient gravitas for the Marines to send it to Afghanistan, as is, with us civilians as the maintainers and as the bulk of the operators.
The GUI had been slaved to a large TV monitor inside the command tent, which allowed everyone to see the Bingo Fuel caution light now glowing in bright amber on the left side of the screen. Though it was late December, temperature in the tent rose perceptually. As the Team Lead, I wanted calm. I asked the operator, “What does the manual say?”
The system engineer at the back of the tent interjected, firm in his opinion that the vehicle depart for home base immediately. I ignored him. I wanted to keep to procedure, seeing it as a good training opportunity. Our real missions had yet to begin and it was unclear how the team would perform outside the benign and rigidly controlled flight test environment. The fact that the engineer was not a pilot also mixed into my soup, which may have been cruel in hindsight.
The CQ-24A’s operator’s manual had ten pages of advisories, cautions, and emergencies. After a few seconds of looking, the operator found the entry. “It says that fuel remaining is insufficient to complete the mission without consuming fuel reserves. Abort the mission.”
It wasn’t that simple. First, the vehicle had to ascend vertically to its preprogrammed departure altitude, in this case a previously coordinated 1,500 feet AGL to avoid other Payne traffic. The operator could have allowed the vehicle to climb autonomously but in that mode the rate was anemic. It was standard procedure to use manual mode with its higher vertical velocity limits, which is what the operator did. Due to the system lag, he overshot his 1,500 foot perch slightly, which was acceptable, but still the climb had taken nearly 90 seconds, all while the Bingo Fuel light appeared to grow brighter.
Once the vehicle stabilized, the operator announced “Depart” while simultaneously mashing the appropriate hand controller button with his thumb (in tune with the science project nature of the program, these controllers were from an X-Box, configured appropriately). We all watched the vehicle’s GUI icon skip forward and gather airspeed on-screen, slowly leaving its wind line and pointing NNE for home.
The GUI had a winds aloft indicator and as the vehicle climbed further into the Afghanistan sky, we could see a substantial headwind component developing for the vehicle. The CQ-24A’s maximum airspeed was 80 knots while loaded, a value dialed back by its not insignificant 2,500 pound external payload, which then meshed with the wind component to produce an anemic 59 knots of groundspeed. This meant the return voyage would consume nearly an hour, a long time to absorb visual bombardment by the amber words.
The vehicle had barely settled into cruise flight when the BLOS connection icon went gray, indicating the datalink was down. We would receive no further information from the vehicle nor could we give it commands until the link was reestablished. Loss of BLOS was a common occurrence since it was dependent on the randomness of the satellite constellation orbiting the earth. Some satellites were stronger and newer than others. Others were down completely. It was a heavenly crap shoot.
Though we couldn’t see it, we were confident the vehicle had settled into its autonomous return. We also knew that the Bingo Fuel situation would unlatch itself if the onboard brain determined the conditions improved sufficiently. We considered jettisoning the load, which would allow the vehicle to accelerate to its unloaded maximum speed of 100 knots TAS. I decided against it; while the vehicle may dip into its fuel reserve, it was not in danger of flame-out and the amount of adverse publicity generated by a jettisoned load could set the program back before it had even begun.
I made this decision despite not knowing precisely how much fuel the vehicle had. To save cost and time, the onboard brain did not take a direct reading from the fuel tank. Instead, the fuel was estimated by algorithm and while it had been quite accurate in flight testing, it was just another sliver of uncertainty weighing down our thoughts.
Though we were presently blind, the tone in the tent was mostly calm. The system engineer sporadically voiced his opinion regarding our courses of action, the most prominent that the vehicle be directed to land under power at the preplanned recovery point outside our base perimeter. I knew that putting the vehicle down “outside the wire” meant a high probability it would be damaged or destroyed. The base was under surveillance by the Taliban and from a previous contract I knew they had a propensity for coming out of nowhere to wreck havoc on a grounded aircraft.
We waited patiently for a fresh datalink signal. Later we’d learn to monitor the satellite constellation on a separate laptop but at the start of the deployment we had no way of knowing what was occurring high above our heads. The engineer went mute for a time. After a few minutes the datalink restored automatically, the vehicle’s icon staggering anew across the screen. The amber words remained.
“Put it down at the recovery point. It’s not going to make it home,” declared the engineer.
I had great respect for the man who was nearly young enough (or me old enough?) for him to be my son. I had come to value his opinion during flight test, even staking decisions entirely upon it. But now he was in my realm. I stepped from the back of the tent and pulled from my pocket the greatest aviation invention known to mankind, the CPU-26A/P air navigation computer, better known as the E6B Whiz Wheel.
I spun the inner scale under the black pointer until I hit the vehicle’s current ground speed, then read the estimated flight time remaining opposite the distance to be flown. I repositioning the black pointer to fuel flow in gallons per hour and matched the estimated flight time on the inner scale to gallons to be burned on the outer. The output was multiplied by 6.7 for JP-8 density, then subtracted from the fuel remaining.
As calmly as possible, I announced, “it’ll land with 200 pounds.”
Coincidentally, this was our minimum landing fuel by directive. The tent went still for good after this. When the vehicle finally came within range of our Line of Sight antennas, a spot just before the outside recovery point, I quickly revalidated my computation. All good. A few minutes later we acquired the vehicle visually, then watched it decelerate for its programmed high hover above the landing pad. The operator wasted no time first getting the load on the ground, then the vehicle itself. It throttled back to ground idle without a hiccup.
When I climbed into the cockpit to shutdown the vehicle, I went right to the fuel gauge. Its needle was dead on the 200 pound graduation.
We gathered lessons that day that served us well later. We learned that airmanship was a thing whether the pilot was in the machine or not, but mostly that we could trust our vehicle. Unmanned K-MAX blew past its planned six-month deployment and delivered 4.8 million pounds of material, mostly under the cover of darkness, over the next 2 ½ years. We used it in ways never envisioned by the original Request for Proposal or later Concept of Operations. We retrograded material with it, bringing things from the forward bases back to us. We conducted hot hook-ups to payloads from an unmanned hover. We dropped and picked on the same sortie.
Above all, we saved lives. The formula said that the 4.8 million pounds Unmanned K-MAX moved equated to 48 men and women who would have otherwise been lost on ground convoys. That is what it was all about.