This research investigates the impact of changing weather conditions on the crew members who sit in a side-by-side cockpit, which is unusual for attack helicopters. Extensive review conducted by the authors fails to locate similar studies; hence a helicopter simulator is developed in order to conduct the experiments. The simulator represents the realistic flight characteristics as well as the digital cockpit instruments that contain the advanced mission equipment. During the experiments, a camcorder is used to record the pilots to accurately analyze the task completion time and the physical motions of both pilots. NASA-TLX is also used to collect the workload data to assess the impact of task assignments among the pilots. The analytical findings from this study will be instrumental in improving the cockpit design for enhanced mission effectiveness.
Modern day attack helicopter is an indispensable asset in military operation. Several wars conducted over the last decades vindicate the lethal effects of this weapons platform. Equipped with high-tech surveillance, targeting, navigation, defense and offense systems, an attack helicopter acts as an eye-in-the-sky, ready to deliver a precision ordnance to enemy positions. The unique abilities, such as hovering, masking under the ground features, high speed cruise at low altitude, and flying under the radar (NOE: nap-of-the-earth flight), represent the flexibility, resilience, and lethality in the battlefield [
The side-by-side helicopter enables the pilot, who normally sits in the right, and the gunner, who occupies the left seat, to share the same working area and the flight instruments, thus allowing them to coordinate their tasks as situations demand. In theory, a pilot can perform the complete task without the aid from a gunner. However, the increased workload burdens the pilot, and distracts the pilot from performing other critical tasks, such as operating a defensive system and staying vigilant for possible threats. Especially, the target identification and enemy engagement require a full concentration. Therefore, in normal conditions, the pilot and gunner are assigned with separate tasks. This in turn enhances the chance of mission success and survival of the crew members [
Pilot | Gunner | Common |
---|---|---|
-Departure & return flight -NOE (nap of the earth flight) -Hovering, masking, unmasking -Operate unguided rockets and a 20 mm gun | -Operate guided missiles -Operate guided and unguided rockets -Operate a 20 mm gun -Target sight control | -Evasion flight -Operation of chaff and flare -Scan of the surroundings for possible enemy threats -Radio communications |
The flight instruments can be configured to display any information that the pilots need. The targeting sight (TS) is enabled with a night-time capability, built with zoom-in and out features for target identification. Weapons control allows the pilot to choose precision anti-armor missiles, guided and unguided rockets, and a 20mm gun. When enemy radar tracks the helicopter, the caution and alarm signs are set off with the direction to the enemy radar displayed. We applied randomization and conducted 5 repetitions for each weather condition, thus performing a total of 20 flights. The data of the workload of the pilot was gathered by surveying with NASA- TLX, and the total amount of time spent for each task according to the work breakdown was recorded with a camcorder. The video clips from the camcorder were also subdivided with the interval of 5 seconds. The types of experiments are shown in
Setting the confidence level at 95% and using the ANOVA, we applied the principle of time and motion study as to the recorded video clips. The mission is categorized into eight major tasks, according to the time and motion. Then, if possible, each major task is further divided into segments that indicate the important activities. Overall, the pilot has a total of 20 segments identified, while the gunner has 16 segments. Among the task breakdown, we identified a total of ten segments that are very difficult to differentiate between the experiments in terms of significance. Those segments are the routines that are performed consistently for all experiments. The code numbers include P_A1, P_B2, P_D1, P_E3, P_F3, P_G3, G_A1, G_D1, G_E4, and G_G2. The average completion time for each task and segment is represented in
Any significant difference among the experiment settings is identified, and the p-values are illustrated. For the pilot, the Pop-up and Hovering show two different patterns. When the gunner operates guided weapons, the pilot time shows no significant variations among the experiments. However, when the gunner operates non-guided rockets, the pilot time fluctuates widely and becomes significant. This is due to the fact that the hit accuracy of non-guided weapons is dependent on the stable hovering. It requires a heavy concentration from the pilot to steadily maintain the attitude of the helicopter. For the pilot, the NOE flight time appears not significant for C1
Setting | Characteristic | Cockpit View |
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Day | -Operation starts at 12:00 hr/All clear weather -Flight speed limit 130 kts/Visibility unrestricted | |
Night | -Operation starts at 24:00 hr/All clear weather -Flight speed limit 100 kts/Use of night vision | |
Bad Weather | -Operation starts at 12:00 hr/Light to medium rains with scattered fog -Visibility less than 2 - 3 miles/Flight speed limit 100 kts | |
Solo Flight | Same as the day experiment |
Task | Pilot | Mission Code | Daytime | Bad Weather | Nighttime | Solo Flight | P-value | Significance |
---|---|---|---|---|---|---|---|---|
Flight to operation area | Check aircraft condition | P_A1 | 30 | 30 | 30 | 30 | N/A | N/A |
Take-off/Contour Flight | P_A2 | 58 | 67 | 77 | 55 | 0.00 | Yes | |
Radio communication with command post | ||||||||
NOE Flight | P_A3 | 107 | 125 | 134 | 105 | 0 | Yes | |
Capture reconnaissance point target acquisition | Radio communication with command post | P_B1 | 37 | 63 | 51 | 33 | 0.02 | Yes |
Pop-Up & Hovering, Target acquisition | ||||||||
Masking & Hovering | P_B2 | 10 | 10 | 10 | 10 | N/A | N/A | |
Attack with guided missile | NOE Flight & Capture attack point | P_C1 | 102 | 105 | 97 | 95 | 0.94 | No |
Radio communication with command post | P_C2 | 37 | 43 | 50 | 41 | 0.12 | No | |
Pop-Up/Hovering | ||||||||
Evasion flight | Threat recognition/Evasion flight | P_D1 | 10 | 10 | 10 | 10 | N/A | N/A |
Radio communication with command post | ||||||||
Attack with guided rocket | NOE Flight & Capture 1st attack point | P_E1 | 121 | 138 | 139 | 118 | 0.03 | Yes |
Radio communication with command post | ||||||||
Pop-Up/Hovering | P_E2 | 39 | 46 | 42 | 42 | 0.80 | No | |
Masking | P_E3 | 10 | 10 | 10 | 10 | N/A | N/A | |
Attack with non-guided rocket | NOE Flight & Capture 3rd attack point | P_F1 | 75 | 97 | 114 | 61 | 0.00 | Yes |
Radio communication with command post | P_F2 | 27 | 40 | 35 | 38 | 0.01 | Yes | |
Pop-Up/Target acquisition & Stand-by/Fire | ||||||||
Masking | P_F3 | 10 | 10 | 10 | 10 | N/A | N/A | |
Attack with auto-cannon | NOE Flight & Capture 4th attack point | P_G1 | 111 | 127 | 135 | 105 | 0 | Yes |
Radio communication with command post/Pop-Up/Hovering | P_G2 | 33 | 34 | 40 | 33 | 0.21 | No | |
Masking | P_G3 | 10 | 10 | 10 | 10 | N/A | N/A | |
Return to base | Radio communication with command post | P_H1 | 39 | 47 | 49 | 36 | 0.01 | Yes |
NOE flight | ||||||||
Contour flight | P_H2 | 137 | 156 | 174 | 145 | 0.00 | Yes | |
Total | P_T | 1003 | 1168 | 1217 | 987 | 0.00 | Yes |
and C2 segments, while other NOE times are all significant. It can be reasoned that operating the guided missiles puts very little pressure on pilot performance. This is the same for the E2 segment for guided rockets, and the G2 segment for gun operation with TS. The total mission completion time for the pilot increases from (1) solo flight, (2) daytime, (3) bad weather, to (4) nighttime flying. It appears that the nighttime flying restricts the
Task | Gunner | Mission code | Daytime | Bad weather | Nighttime | P-value | Significance |
---|---|---|---|---|---|---|---|
Flight to operation area | Scout & guide route | G_A2 | 185 | 222 | 231 | 0.00 | Yes |
Capture reconnaissance point and target acquisition | Radio communication with command post | ||||||
Target acquisition with TS | G_B1 | 17 | 33 | 29 | 0.15 | No | |
Radio communication with command post | |||||||
Set the order of target priority | G_C1 | 112 | 115 | 107 | 0.92 | No | |
Attack with guided missile | Scout & guide route | ||||||
Radio communication with command post | |||||||
Stand-by and ready for firing | G_C2 | 27 | 29 | 38 | 0.11 | No | |
Fire & guide missile with TS | G_C3 | 10 | 14 | 12 | 0.13 | No | |
Radio communication with command post | |||||||
Attack with guided rocket | Scout & guide route | G_E1 | 121 | 138 | 139 | 0.10 | No |
Target acquisition with TS | G_E2 | 27 | 36 | 32 | 0.45 | No | |
Stand-by and ready for firing | |||||||
Fire & guide missile with TS | G_E3 | 10 | 10 | 10 | 0.40 | No | |
Attack with non-guided rocket | Scout & guide route | G_F1 | 228 | 279 | 299 | 0.00 | Yes |
Radio communication with command post | |||||||
Attack with auto-cannon | Scout & guide route | ||||||
Target acquisition with TS | G_G1 | 18 | 19 | 25 | 0.16 | No | |
Stand-by and ready for firing | |||||||
Return to base | Scout & guide route | G_H1 | 186 | 213 | 233 | 0.00 | Yes |
Total | G_T | 1003 | 1168 | 1215 | 0.00 | Yes |
pilot field of view, hence makes it more difficult to carry out the tasks at night. Since the pilot is very familiar with the simulator, the solo mission even becomes the shortest in terms of time. This suggests that the pilot is solely focused on the mission, while the crew coordination and communication becomes non-existent. Such situation may shorten the overall mission completion time, yet the actual workload becomes the highest. Solo mission likely causes the excessive fatigue to pilot, which in turn reduces the survivability and the mission success rate. It becomes obvious that a solo flight should not be recommended for attack helicopter pilots.
In
To examined the changes in the workload according to the external environmental factors, the ANOVA test was conducted with a confidence level of 95%. The workload was measured using the NASA-TLX, right after each mission is completed. Except the Physical Demand category of the gunner, all other areas show that the pilot and gunner workload is significantly affected by the external environmental factors. According to the TLX data, the pilot workload increases from (1) daytime, (2) bad weather, (3) nighttime, to (4) solo flight. For gunner, the order of increasing workload is (1) daytime, (2) nighttime, and (3) bad weather flight. For the solo flight, even though the weather condition is the best, the pilot workload appears to be the highest. This is quite reasonable, because the pilot must conduct every required task during the entire duration of the flight. It can be conjectured that the attack mission should be carried out with two pilots, in order to be more effective and survivable. For mental demand, the gunner load is at the highest in bad weather, while the pilot shows the high workload in nighttime flight. It is because that, for the gunner, the target finding, identification, and aiming can be more difficult under the rain and fog, rather than under a clear night sky. In nighttime flight, both pilot and gunner have a narrow field of view through the night vision screen (see
Through the experiments, both pilots turn out to be significantly affected by the environmental factors. Due to the fact that the TS is one of the most essential equipment for night flying, target acquisition, and weapons aiming, there is a need to put the TS in an attack helicopter and do more research about the enhancement of its functionality. This includes the integration of enemy target database with the images acquired through the TS. Situated over several kilometers away, the identification of enemy assets can be quite difficult, just by looking at the images projected by the TS. The moving map display also helped the pilots to improve their situational awareness, by integrating critical mission and flight information. The moving map display should be a part of the battlefield network system in order to exchange combat information in real-time. This will substantially
Category | Increasing Order | |
---|---|---|
Mission Completion Time | Pilot | (1) Solo << (2) Day << (3) Bad Weather << (4) Night |
Gunner | (1) Day << (2) Bad Weather << (3) Night | |
Workload | Pilot TLX | (1) Day << (2) Bad Weather << (3) Night << (4) Solo |
Gunner TLX | (1) Day << (2) Night << (3) Bad Weather |
increase the mission capability of attack helicopters. Considering the fact that the NOE flight is mandatory for attack helicopters, it is better to install the auto-pilot and automated flight systems to relieve the pilot from difficult terrain following tasks. The automatic hovering function can be especially beneficial, when the weather is windy and the pilot must maintain a steady attitude of his helicopter. The pilot can simply switch on the auto hovering and focus on the mission profile, instead of holding on to the control sticks. It is also recommended to install a weather penetrating radar (SAR) to overcome the limitations of optical targeting system. If the SAR is prohibited for every helicopter, a scout helicopter can be equipped with the radar and transmit the image data to the ensuing attack helicopters.
This work was supported by the Agency for Defense Development (ADD) under the Contract No. UD140066CD. The authors wish to express sincere gratitude for the financial support.
Eunghyun Lee,Suhwan Kim,Yongjin Kwon, (2015) Analysis of Mission Task Loading Based on the External Disturbance. Journal of Computer and Communications,03,92-98. doi: 10.4236/jcc.2015.311015