DVE through NVG Scintillation
NAME WITHHELD BY REQUEST The mission
As a California Army National Guard aviator, we often have the opportunity to support a number of units conducting training rotations at the National Training Center at Fort Irwin. During one rotation, a Special Forces unit requested aircraft support. The request was nothing out of the ordinary and involved dropping off some gear, food and passengers in three different locations within the training area. Since the passengers and cargo were part of the Special Forces group conducting training, it was requested that the mission take place at night under the cover of darkness and minimum lighting to conceal their drop-off. The planning
Once the crew was selected, the planning began. A prior permission required (PPR) was requested, maps were gathered and updated, Fort Irwin’s Aviation Procedures Guide and other documents were reviewed, weather was evaluated, and the flight was briefed and approved. The risk level for the mission was MODERATE due to the moon angle being slightly above the horizon and only 11% illumination. As a crew, we discussed the challenges of flying in low-light conditions and agreed to use aircraft lighting to mitigate the risks. The execution
The night of the mission, we loaded the gear and passengers and departed Barstow-Daggett Airport en route to the designated landing zones (LZ). After entering Fort Irwin and passing the cantonment area, we proceeded northeast toward our first LZ. Although we expected low ambient light levels, we did not anticipate how dark a desert gets when there is little to no moonlight. The lack of illumination became apparent as soon as the contrast in the goggles dropped and scintillation increased.
The pilot (PI) was on the controls and planned to land at the first LZ. Although young, he was a confident and competent aviator, so as the pilot in command (PC), I had no concerns with him flying the mission. As we approached, we set up for landing and turned on the infrared (IR) lights. However, the IR search light did very little to improve the contrast or reduce the amount of scintillation present in the goggles. The PI stated he could not see anything and was not comfortable with the landing and transferred the flight controls. We conducted a go-around and proceeded to come back and attempt the landing. This time we planned on landing on a dirt road because, due to the lack excessive scintillation and contrast, we could not confidently rule out hazards such as large rocks or other protruding objects on the ground. (We could only see dark spots on the ground up until about 10 feet.) Only light dust kicked up as we landed.
After the PI landed at the second LZ, which was closer to the cantonment area and had better visibility, he said he felt comfortable flying to the next LZ. The third LZ was on the other side of a range and completely dark. Once again, with the absence of ambient light, scintillation became prevalent in the googles — this time at a level I had never experienced before (and I have flown over Iraqi desert). The rate of decent and the rate of closure were perfect and allowed for a go-around or a continued decent with minimum forward airspeed.
We proceeded to land, maintaining the same rate of closure; however, the lack of contrast, the excessive scintillation in the googles and the dust accumulation caused the PI to prematurely dump the collective. The aircraft landed a little harder than we anticipated, scaring the entire crew. After dropping off the gear, we flew back to base, where we conducted a very thorough post-flight and called it “mission complete.” Later that night we talked about the mission and discussed how we could have done things differently. The lesson
Although we could have done many things differently that night, I believe the biggest issue was not understanding how much degradation the NVG experience under low light levels. The sudden reduction in contrast and increase in scintillation should have been indicators that we might need additional lighting. Additionally, the PI’s experience with low-level light operation was very limited. The degraded visual environment (DVE) increased stress for the entire crew. The PI stated he wasn’t comfortable with the lack of contrast, so when it came to landing, he “just wanted to get the aircraft on the ground.” He also said that he had trouble judging the rate of closure and how far the aircraft was off the ground.
As the PC, one option I should have explored was doing all the landings myself, but I also had issues with contrast and scintillation. Another — and probably the best — option would have been to adjust the mission to fly during a period of better lighting. While I have operated under DVE conditions due to dust and snow, this was the first time I have experienced DVE due to NVG degradations under low-level light operations. I recommend pilots anticipate the possibility of NVG degradation under these conditions and be prepared to operate in a DVE. Treat it with the same respect as any other operation conducted under DVE.