Helicopter Group Research Articles

The Effects of Chronic Exposure to Aircraft Noise on the Prevalence of Hypertension

Exposure to environmental noise has been suggested to increase the prevalence of hypertension. The present study investigated whether or not chronic exposure to military aircraft noise is related to an increased prevalence of hypertension. The study population consisted of 137 subjects (mean age 60+/-14 years) who lived within 5 km of a helicopter airbase and 486 subjects (58+/-16 years) living within 5 km of a fighter-jet airbase. A control group consisted of 252 subjects (58+/-16 years) not exposed to aircraft noise. Overall, the subjects exposed to military aircraft noise had a higher prevalence of hypertension than those in the control group (p=0.037). However, whereas those exposed to helicopter noise had a higher prevalence than the control group (p=0.020), those exposed to fighter-jet noise did not (p=0.094). The prevalence of known hypertension in the helicopter group was higher than in the control group (p=0.024). The prevalence odds ratio for hypertension adjusted for age, gender, body mass index, current smoking, alcohol intake, diabetes, and regular exercise was 1.62 (95% confidence interval [95% CI], 1.02-2.59) for the subjects exposed to helicopter noise, and 1.23 (95% CI, 0.87-1.74) for those exposed to fighter-jet noise. In conclusion, the results of the present study suggest that chronic exposure to military aircraft noise may be associated with hypertension. The difference in the effects between helicopter and fighter-jet noise implies that different kinds of noise will have different influences on the prevalence of hypertension.

Full formation control for autonomous helicopter groups

SUMMARYThis paper reports the design of sliding-mode control laws for controlling multiple small-sized autonomous helicopters in arbitrary formations. Two control schemes, which are required for defining arbitrary three-dimensional formation meshes, are discussed. In the presented leader–follower formation control schemes, each helicopter only needs to receive motion information from at most two neighboring helicopters. A nonlinear six-degree-of-freedom dynamic model has been used for each helicopter. Four control inputs, the main and the tail rotor thrusts, and the roll and pitch moments, are assumed. Parameter uncertainty in the dynamic model and wind disturbance are considered in designing the controllers. The effectiveness and robustness of these control laws in the presence of parameter uncertainty in the dynamic model and wind disturbances are demonstrated by computer simulations.

Helicopter transportation of burn patients

Analysis of 437 consecutive acute burn patients transported to our burn center revealed 339 transported by ground and 98 by helicopter. There were 18 air transport patients from within a 25-mile-radius, and 80 flown further than 25 miles. Mean age was the same in all groups ( P>0.05). Percent total body surface area (TBSA) burned was 8.26% in ground transport patients, significantly less than the 20.35% (within 25 miles) and 21.40% (greater than 25 miles) seen in helicopter transports ( P<0.0001). Three percent of ground transport patients and 28% of helicopter patients had inhalation injury ( P<0.0001). There was no difference in incidence of inhalation injury among helicopter groups (28 vs. 29%, P=0.8). In patients with coexistent inhalation injury, the mean TBSA burned was significantly larger when compared with the TBSA of burns without inhalation injury ( P<0.001). Air transported groups contained patients whose status was not critical based upon lack of inhalation injury and small burn size, and who could have been transported by ground. Non clinical factors such as insurance status, desire to keep ground ambulances in their community, and competing helicopter services reluctant to refuse to transport a patient appears to be factors in choosing air ambulance transportation. Regional single helicopter services and regional cooperative ground ambulance services should reduce use of helicopter transport of burn patients when it is not clinically indicated.

Effect of Helicopter Transport of Trauma Victims on Survival in an Urban Trauma Center

This paper reports a retrospective analysis of patients with serious yet substantially survivable injuries represented by ISS scores from 20 to 39 and whether or not survival was influenced by the use of helicopters. A review of 606 of these patients with blunt trauma was performed for the period from 1983 through 1986. When the group was evaluated there were 451 patients in the ISS cohort of 20-29 and 155 in the 30-39 group. The mean age was 30.5 years and 76% were males. A total of 259 patients were transported by ambulance and 347 by helicopter. Characteristics of the two groups were similar. The mean TS was 12.7 for ambulance and 12.1 for helicopter patients. Mean GCS was 10.4 in the ambulance group and 9.6 for helicopter patients. Overall the mortality for ambulance transported patients was 13% compared to 18% for the helicopter group. We conclude that there is no survival advantage in the helicopter transported group in an urban area with a sophisticated prehospital care system. Patients of rural origin deserve further study.

Effect of Helicopter Transport of Trauma Victims on Survival in an Urban Trauma Center

This paper reports a retrospective analysis of patients with serious yet substantially survivable injuries represented by ISS scores from 20 to 39 and whether or not survival was influenced by the use of helicopters. A review of 606 of these patients with blunt trauma was performed for the period from 1983 through 1986. When the group was evaluated there were 451 patients in the ISS cohort of 20-29 and 155 in the 30-39 group. The mean age was 30.5 years and 76% were males. A total of 259 patients were transported by ambulance and 347 by helicopter. Characteristics of the two groups were similar. The mean TS was 12.7 for ambulance and 12.1 for helicopter patients. Mean GCS was 10.4 in the ambulance group and 9.6 for helicopter patients. Overall the mortality for ambulance transported patients was 13% compared to 18% for the helicopter group. We conclude that there is no survival advantage in the helicopter transported group in an urban area with a sophisticated prehospital care system. Patients of rural origin deserve further study.

Noise environment of a typical school classroom due to the operation of utility helicopters

Municipal governments and other agencies are using light utility-type helicopters for police operations and other activities. These activities require that the machines be operated over populated areas at relatively low altitudes and low speeds for extended periods of time. Concern has been voiced as to the effects of these operations on the interior noise environment of institutional facilities such as schools, hospitals, public buildings, etc. Noise measurements under controlled conditions have been made inside and outside of a school building during flyover and orbit operations of four different helicopters. The helicopters utilized for this series of tests were the Bell 204, 206, and 47G2A and the Hughes 269A. This group of helicopters included both turbine- and reciprocating-engine-powered aircraft. The helicopters were operated at conditions considered typical for the police patrol mission. Flyovers were made at altitudes of 1000 and 500 ft, at 45 miles per hour. During these operations, the acoustic measurements were made inside and outside of the school building with the windows closed and then open. For the windows closed ease, the noise levels due to the operation of the helicopters ranged from 53 to 60 dBA with the normal ambient being approximately 45 dBA.