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Protective effect of helmet gentex hgo-56/p on hearing loss among military helicopter pilots
Aviation noise represents an important hazard for hearing loss among military pilots as they are continuously exposed to excessive noise during flight operations. Modern military aircraft, due to their maneuverability and tactical capabilities, require increasing engine power, while noise protection is limited only to the personal protective equipment which protects to a limited extent. Previous generations of helicopter pilots in the Croatian Air Force (CAF) used GSSH-A-18 headphones, whereas Gentex HGU-56/P helmets have been in use in CAF since 2004, primarily as mechanical protection for the head and secondarily to protect hearing. A study on hearing threshold measurements was performed on multi-purpose transport helicopter pilots who used headphones and helmets, respectively. The population of pilots who used GSSH-A-18 headphones had significantly higher hearing loss at higher frequencies, in the left ear, and in the speech area compared to the group using Gentex HGU-56/P helmets. The results of this study confirm the benefit of using of the Gentex HGU-56/P helmet to preserve the pilots’ hearing.
Zrakoplovna buka predstavlja važnu opasnost za gubitak sluha među vojnim pilotima, budući da su kontinuirano izloženi prekomjernoj buci tijekom letačkih operacija. Moderno vojno zrakoplovstvo zbog svojih manevarskih sposobnosti i taktičkih mogućnosti zahtjeva povećanje snage motora, dok je zaštita od buke ograničena na osobnu zaštitnu opremu koja štiti do određene granice. Prijašnje generacije pilota helikoptera u Hrvatskom ratnom zrakoplovstvu (HRZ) koristile su GSSH-A-18 slušalice, dok su Gentex HGU-56/P kacige u upotrebi u HRZ-u od 2004. godine; primarno kao mehanička zaštita za glavu te sekundarno kao zaštita sluha. Studija o mjerenju praga sluha provedena je kod pilota višenamjenskih transportnih helikoptera, koji su koristili slušalice, odnosno kacige. Populacija pilota koja je koristila GSSH-A-18 slušalice imala je znatno viši gubitak sluha na visokim frekvencijama u lijevom uhu i u govornom području, u usporedbi s grupom koja je koristila kacige Gentex HGU-56/P. Rezultati ovog istraživanja potvrđuju korist korištenja kacige Gentex HGU-56/P pri očuvanju sluha pilota.
Journal Article
Military helicopters
\"Simple text and full-color photographs describe various military helicopters\"--Provided by publisher.
Book
Differences in physical workload between military helicopter pilots and cabin crew
Purpose
The 1-year prevalence of regular or continuous neck pain in military helicopter pilots of the Dutch Defense Helicopter Command (DHC) is 20 %, and physical work exposures have been suggested as risk factors. Pilots and cabin crew perform different tasks when flying helicopters. The aims of the current study were to compare the exposures to physical work factors between these occupations and to estimate the 1-year prevalence of neck pain in military helicopter cabin crew members.
Methods
A survey was completed by almost all available helicopter pilots (
n
= 113) and cabin crew members (
n
= 61) of the DHC. The outcome measures were self-reported neck pain and exposures to nine physical work factors. Differences in the proportions of helicopter pilots and cabin crew members reporting being often exposed to the particular physical factor were assessed with the
χ
2
test.
Results
The 1-year prevalence of regular or continuous neck pain among cabin crew was 28 %. Significantly more cabin crew members than pilots reported being often exposed to manual material handling, performing dynamic movements with their torsos, working in prolonged bent or twisted postures with their torsos and their necks, working with their arms raised and working in awkward postures. Often exposure to prolonged sitting and dynamic movements with the neck were equally reported by almost all the pilots and cabin crew members.
Conclusion
Flight-related neck pain is prevalent in both military helicopter pilots and cabin crew members. The exposures to neck pain-related physical work factors differ between occupations, with the cabin crew members subjected to more factors. These results have implications for preventative strategies for flight-related neck pain.
Journal Article
How military helicopters work
\"Learn about the history of military helicopters, their parts, and helicopters in action in this informative look at a military machine.\"--Provided by publisher.
Book
Special Rotordynamics: Simulation of Contact Rotor System
The paper discusses four contact models used in the dynamic analysis of rotor systems. A mathematical imperfection of two models by a real example is shown. It consists in a significant overstatement of the calculated whirl-whip speed in case of the rotor slipping on the stator.
Journal Article
Béléstestek készítésének technikai lehetőségei alacsony sűrűségű anyagból
A kumulatív töltetek béléstestei alacsony suruségu anyagokból is készülhetnek. Ezek a típusok a hagyományosaktól eltéro hatékonysággal rendelkeznek. Azonban van egy kifejezetten nagy elonyük. 3D nyomtató segítségével viszonylag egyszeruen elkészíthetok, és tervezésük sem igényel kiemelkedo technikai szaktudást. Tanulmányunkban megvizsgáljuk néhány változat méretezésének és kialakításának lehetoségeit. A félgömb és a kúp alakzat alkalmazása bevett gyakorlat a kumulatív töltetekben béléstestként, ezért mi is ezeket választottuk ki. Célunk, hogy könnyen kivitelezheto módszert találjunk az ipari és katonai felhasználóknak egyaránt ezek elkészítésére.
Journal Article
American military aircraft : a century of innovation
During the dark days of World War II, American military air power was forged into the mightiest war machine the world has ever seen. In the space of five years, the United States progressed from the biplane era to an immensely complex bomber the sleek Boeing B-29 capable of delivering the atomic bomb. After World War II, the US Air Force, Navy and Marine Corps retained their technological superiority through the dangerous years of the Cold War. The next generation of aircraft and weapons, with the emphasis on flexibility and affordability, have proven their worth in the recent conflicts in Afghanistan, Bosnia and Iraq. American Military Aircraft is a comprehensive guide to more than 200 combat aircraft and helicopters that have kept the US at the cutting edge of aviation technology. Each aircraft is covered in detail, with feature boxes outlining its development, technical specifications, performance data, and variants. Unique graphics allow the reader to compare specific features like firepower, troop-carrying capacity, and bombload to those of other aircraft of the same type.
Book
Combination resonances of a dual-rotor system with inter-shaft bearing
This paper focuses on the combination resonances of a dual-rotor system with inter-shaft bearing. The motion equations of the dual-rotor system are formulated by the Lagrange equation, in which the unbalanced excitations of the two rotors and the clearance of the inter-shaft bearing are taken into consideration. The HB-AFT method (harmonic balance-alternating frequency/time domain method) is employed to obtain all the periodic solutions including the unstable solutions of the system. The combination resonance characteristics of the system are analyzed in detail by using the frequency response curves and separated frequency responses of the dual-rotor system. Besides the two primary resonance peaks, three more combination resonance regions in the frequency response curves of the system are found, in which the jump and bi-stable phenomena are observed. The primary resonance is mainly dominated by the excitation frequency
ω
1
and
ω
2
, the combination resonance of the system is mainly dominated by the combined frequency component of
2
ω
2
-
ω
1
,
4
ω
2
-
3
ω
1
,
3
ω
2
-
2
ω
1
and is almost independent of other frequency components. Furthermore, the effect of inter-shaft bearing clearance on the combination resonance regions is obtained, it is indicated that increasing the inter-shaft bearing clearance will not only affect the response amplitudes of the combination resonance and change the “softening and hardening characteristic” of the frequency response curves, but also show a certain “stiffness weakening effect” on the rotor system. The study in this paper is of great significance to select the parameters of the dual-rotor system reasonably so as to avoid harmful combination resonance.
Journal Article