pulled against the screen, and small items can be pulled through the screen. This results in thousands of dollars of damage to the engine. Exhaust Area Hazards Jet engine exhaust also creates hazards. Tests show that while the carbon monoxide content of jet exhaust is low, other gases are present that irritate the eyes. Less noticeable, but as important, is the respiratory irritation that may be caused by exhaust fumes. The two major hazards of jet engine exhaust are the high temperature and high velocity of the exhaust gases from the tailpipe. High temperatures are found up to several hundred feet from the tailpipe, depending on wind conditions. Closer to the aircraft, temperatures are high enough to damage asphalt pavement. The blast from the exhaust is strong enough to knock a person down at close distances and can even blow a body off of the flight deck overboard. Do not take the signs lightly. BEWARE OF JET BLAST. When a jet engine is started, excess fuel accumulates in the tailpipe. When the fuel ignites, long flames can be blown out of the tailpipe. All flight line personnel should be aware of this hazard, and all flammable materials should be kept clear of the danger area. During maximum power settings, the high velocity of the exhaust gases may pick up and blow loose dirt, sizable rocks, sand, and debris several hundred feet. This is an eye and FOD hazard. Therefore, you should use caution when parking an aircraft for run-up. The general information section of the applicable MIM contains information concerning the exhaust area hazards. These instructions should be strictly followed. No one should foolishly experiment with the specified safety margins. After engine operation, no work should be done to the exhaust section for AT LEAST ONE-HALF HOUR (preferably longer). If work is necessary immediately, you must wear leather gloves. Engine Noise Jet engines produce noise capable of causing temporary as well as permanent loss of high-frequency hearing. When working around jet engines, you should take the following precautions to protect your hearing: Wear the proper ear protection (ear plugs or sound attenuators and sometimes both). Do not exceed the time limits on exposure to the various sound intensities. Have periodic checks on your hearing ability. Engine noise is broadcast from the aircraft in patterns, which vary in direction, distance, and intensity with engine speed. The most intense sound areas are in the shape of two lobes extending out and aft from the aircraft center line. However, dangerous intensities are also present to the side and forward of the aircraft. (See fig. 5-13) This information is found in the applicable Naval Air Training and Operating Procedures Standardization (NATOPS) manual. Damage to hearing occurs when the ear is exposed to high sound intensities for excessive periods. The higher the sound intensity, the shorter the period of exposure that will produce damage. Above 140 decibel (dB) sound intensity, any exposure without ear protection can cause damage. NOTE: Sound intensity is measured in decibels (dB). A dB is a number that relates a given sound intensity to the smallest intensity that the average person can hear. By wearing regulation earplugs or sound attenuators, you can raise the limits of time exposure. Personnel working within danger areas should be familiar with calculated noise dB levels (as specified in the applicable MIM), and should wear the necessary protective equipment. Q24. Q25. Q26. Q27. Q28. According to many insurance companies, what is considered the most dangerous environment in the world? When you work around aircraft with propellers, when is it safe to walk through or stand in the prop arc? Does a protective screen over the inlet of an operating aircraft engine eliminate the possibility of serious injury? What are the two major hazards of jet engine exhaust? Any exposure, without ear protection, can cause hearing damage above what decibel (dB) level? Movable Surface Hazards Moveable surfaces, such as flight control surfaces, speed brakes, power-operated canopies, and landing gear doors, are a major hazard to flight line personnel. These units are normally operated during ground 5-18