Purpose: The purpose of this study guide is to assist the aviator in preparing for the APART evaluation and in maintaining currency and proficiency in the volumes of information required of today's 'information age' aviator. ATM's vary in their approach, sequences, and sometimes even in their task descriptions. Obviously, the most specific information is contained in the latest edition of your aircraft's' ATM. This study guide attempts to find common ground and integrate all ATMs. To the greatest extent possible, and for easy reference, this study guide attempts to follow the evaluation guidelines oral examination outline as described in your ATM.

Standards: Evaluations are conducted to determine your ability to perform assigned duties. Orally, you must demonstrate a working knowledge and understanding of the subject areas listed in your ATM. These include:

1. Regulations and Publications: You must be familiar with the airspace classification system, recognize chart depiction of the various classes of airspace, and know when and how you can operate in the different classes; to include weather, equipment, and communication requirements. Also be familiar with your unit SOP as it pertains to your flying duties, your individual (CTL) training requirements, weight and balance requirements, ALSE, inadvertent IMC procedures, flight restrictions due to exogenous factors, and interpretation of FLIP material.

2. Operating Limits: You must know the safe operating limitations of your aircraft (Chapter 5 of the -10). You must also know what to do if limitations are exceeded. This area covers not only systems limitations, but flight envelope and environmental limitations and interpretation of performance charts as well.

3. Emergency Procedures: You must know how to properly deal with emergency procedures (Chapter 9 of the -10). UNDERLINED PROCEDURES MUST BE COMMITTED TO MEMORY. Be prepared to discuss all procedures with emphasis on understanding the aircraft systems and flight characteristics during an emergency. Other areas of interest here include interpretation of Caution/Warning lights, after emergency actions, emergency equipment and emergency exits.

4. Aeromedical Factors: Be familiar with the various physiological hazards to flight. Be prepared to discuss contributing factors, symptoms, alleviation and avoidance, and regulatory restrictions.

5. Aerodynamics: Have a good working knowledge of aerodynamics and how it affects performance, flight characteristics, flight envelope and maneuvering limitations.

6. Mission Tasks: Be prepared to discuss and/or perform any and all of your CTL-designated mission tasks, as well as all base tasks listed in your ATM. consideration should be given to terrain flight safety and terrain flight mission planning.

7. Night Operations: Night operations require more in-depth planning and preparation as well as special knowledge and techniques. Discuss unaided and aided night vision, visual problems, illusions, dark adaption, distance estimation, and operational considerations.

The flight evaluation consists of briefing, preflight, start and run-up procedures, flight tasks, and after-landing tasks. The briefing should cover, as a minimum, those items listed under Task #1000 [and, for '58 pilots, those items listed in para 8-3c(l)]. You will be evaluated on your use of the checklist for preflight, start and run-up, and shutdown. Also during preflight, you will be asked to identify at least two aircraft components and discuss their functions. The flight itself will consist of evaluation of, as a minimum, those tasks listed in Ch. 5 and on the CTL as being mandatory for the evaluation being given. Please note that TC 1-210 states that the -10 test is part of the standardization eval and should be done before the flight. Please obtain a copy before your scheduled ride and bring it in completed.

Changes to this study guide since the date of last publication are indicated by a vertical line in the left margin beside the change.

Major areas outlined for oral examination in the ATM include:

(1) REGULATIONS AND PUBLICATIONS (AR 95-1, AR 95-3, TC 1-210, NGR 95-1, NGR 95-210, FLR 95-1, local Guard pubs, etc., ad nauseum.)

(a) ATP requirements. Refers to your Commanders' Task List. Be familiar with your flying hour and task iteration requirements, evaluation requirements, and, if applicable, RL progression requirements.

(b) SOP requirements. Be prepared to discuss your unit SOP, particularly as it pertains to your flight duties. AASF and GAAF SOP's also.

(c) DOD FLIP and maps. Be familiar with chart symbology, be able to interpret information in supplements. DA Pam 738-751 requires that the following be aboard the aircraft: -10 CL w/ changes, -10 cl changes, current 365-4 weight & balance, log book binder w/ HIT log, PMD checklist, 2408-4, -12, -13, -13-1, -13-2, -14, and -18, DD Form 1896 (Identaplate), and appropriate FLIP for the flight.

(d) VFR minimums and procedures. Aviators should recognize the various classes of airspace and the associated weather, equipment, and communications requirements. AR 95-1 states that before beginning a flight, aircrews will acquaint themselves with mission, procedures, and rules. A 20-minute fuel reserve is required for VFR flights, and, above 3000', semi-circular cruising altitudes apply. Minimum enroute altitude is 500' AGL (1000' over any congested area). Over-the-top flights (VFR) may not exceed 30 minutes duration unless the aircraft and crew are fully IFR legal and equipped. When converging, right-of-way rules give the right-of-way to the aircraft on the right. If approaching head-on, both aircraft should alter course to the right. If overtaking, you should pass to the right and remain well clear (the aircraft being overtaken has the right-of-way). When operating in the vicinity of an airport, helicopter pilots should avoid the flow of fixed-wing traffic.

1. Uncontrolled Airspace (Class G): This airspace generally extends from the surface to 1200' AGL (or 700' in transition areas shaded in magenta on sectional charts). It could extend as high as 14,500' in some areas. The FAA says a helicopter may be operated clear of clouds in Class G airspace (below 1200' AGL) as long as the helicopter is "operated at a speed that allows the pilot adequate opportunity to see any air traffic or obstructions in time to avoid collisions." Above 1200', helicopter operation requires I mile visibility day (3 at night) and cloud clearance of 500' below any cloud, 1000' above, and 2000' horizontally. Local SOP requires a minimum of 500' ceiling and 1 mile visibility for all VFR operations. So, when operating in Class G airspace, a Washington National Guard aviator requires a 500' ceiling, 1 mile visibility and, if above 1200' AGL, basic cloud clearance and 1 or 3 miles visibility for day and night, respectively.

2. Controlled Airspace. The FAA governs the weather minimums we have in controlled airspace. To maintain VFR in controlled airspace (Class C, D, and E), we must have minimum cloud clearances of 500' below, 1000' above, and 2000' horizontal. In Class B airspace, remain clear of clouds. In all cases, visibility minimum is 3 miles (Visibility and cloud clearance requirements increase above 10,000'). VFR is not permitted in Class A airspace. (See accompanying chart showing U.S. airspace classification). Except when operating special VFR, you may not operate VFR beneath a ceiling within the lateral boundaries of controlled airspace (B, C, D, or E) designated for an airport when the ceiling is less than 1000'. Aviators may file flight plans to a destination within Class B, C, D and E airspace when weather conditions are forecast to be equal to or greater than known special VFR minima for that airspace at ETA through 1 hour after ETA. (AR 95-1). SVFR at Gray is 300 and 1/2 day, 500 and 1 night/NVG, at FCT 500 and 1/2 day, 1000 and 1 night/NVG. Aviators will comply with the weather minimums established for the airspace in which they're operating; however, they must maintain at least the 500' ceiling and 1 mile visibility requirements for Washington National Guard aviators.

(aa) Class A Airspace: All airspace above 18,000' MSL. VFR is not permitted.

(bb) Class B Airspace: 'Upside down wedding cake', as depicted on charts. Mode C required within 30 miles of primary airport. Specific clearance to enter is required. Note that cloud clearance requirements have been reduced to clear of clouds.

(cc) Class C Airspace: As depicted on charts, generally a 10-mile ring around airports with towers and approach controls, from the surface to 4000' above the airport. Two-way communication and Mode-C transponder are required for operation within Class C airspace. Mode C is also required for operations above Class C airspace.

(dd) Class D Airspace: Depicted as a segmented blue line on charts, generally a 5 statute mile circle around airports with operational control towers, with vertical limits shown in hundreds of feet. Radio communication is required for all aircraft operating within Class D airspace, regardless of destination. VFR minimum weather in Class D airspace is 3 miles visibility, cloud clearance of 500' below clouds, 1000' above, and 2000' horizontal.

(ee) Class E Airspace: 'Other' controlled airspace, to include non-tower instrument airfields, 700' and 1200' transition areas, federal airways, and airspace above 14,500' MSL. Basic VFR visibility and cloud clearance requirements apply, but there are no specific communications requirements. Mode C is required above 10,000' MSL. Non-tower instrument airfields are depicted by a segmented magenta line indicating controlled airspace starts at the surface. Arrival extensions for Class D airports may also be indicated in magenta, indicating that controlled airspace starts at the surface, but there are no communications requirements until penetrating the segmented-blue-line Class D airspace.

(ff) Prohibited Area: No flight permitted.

(gg) Restricted Area: Flight into Restricted Areas, while not wholly prohibited, may be extremely hazardous. Know why the restriction applies and/or who to contact. An example: R6703 is active during artillery firing at Ft. Lewis. We can safely operate within the restricted area as long as we remain clear of gun-target lines. Military pilots operating within restricted areas should adjust their transponders to code 4000.

(hh) Warning Area: Similar to Restricted Area, established in international airspace.

(ii) Military Operations Area (MOA): Areas in which low-level, high-speed, acrobatic flight is permitted by military aircraft (NOT OUR HELICOPTERS, GENTLEMEN). Pilots operating VFR in a MOA should exercise extreme caution.

3. Local Airspace Usage.

(aa) Rotary-wing flight over congested areas of a city, town, or settlement will be at 2000 feet AGL, except under emergency conditions or when weather conditions or mission requirements dictate a lower altitude. Low level flights over post schools, housing areas and troop barracks are to be avoided.

(bb) Practice helicopter approaches will not be conducted at the Olympia Airport between 2200 and 0730 local. Practice instrument approaches to the Tacoma Narrows Airport are prohibited.

(cc) All active drop zones include a 1 NM buffer zone measured from the edge depicted on Fort Lewis specials. No flight is permitted within the buffer zone of active DZ's without permission.

4. Local Operational Procedures

(aa) GAAF is contained in a Class D surface area, defined as a 4.3 NM radius area extending from the surface up to and including 2800' exclusive of that area which coincides with McChord Class D airspace. That area above 2000' has been released to Seattle Approach. When the tower is closed, the airspace reverts to a Class E surface area and Seattle Approach is the controlling agency.

(bb) Normal VFR arrival/departure routes are via Eastgate, Burlington, Nisqually, and Ketron Island. Special VFR routing will be via Nisqually or Hamilton Lake to Burlington. NVG routing is a one-way pattern out to Nisqually at 750', 1200' along the river to 'little' Nisqually bridge, counter-clockwise along the corridor at 750' to Burlington, then 1300' inbound to enter downwind for runway 15. Entry to areas X, Y, and Z from the corridor will be at specified points only. Aircraft operating in the NVG corridor must have an operational UHF radio tuned to 393.3 for traffic advisories, and aircraft operating in the individual training areas must have an operational VHF radio tuned to the appropriate frequency for traffic advisories within the training area. NVG training altitudes within the areas must not exceed 200' AHO. Day or night, aircraft should contact Bullseye Radio prior to operating in the training area. The current version of the Fort Lewis Special with all hazards posted must be on board all aircraft operating in reservation airspace. Prior to proceeding north of grid line 1000, radio contact with McChord Tower will be established and approval obtained. When McChord is VFR, Army helicopters are authorized to operate in that portion of McChord airspace south of grid 1000 below 1000' without contacting the tower. When weather is less than VFR, you must contact McChord Tower prior to proceeding north of grid line 0900.

NVG aircraft will use the callsign "Goggle" followed by the last three digits of the tail number when communicating with GAAF tower, ground, or Bullseye Radio. Maximum airspeed at night within the GAAF service area is 90 KIAS for helicopters.

(cc) Aircraft experiencing lost commo will enter traffic via normal routing and maintain traffic pattern altitude until alternate instructions are received from the tower by light gun-signal.

(e) IFR Minimums and Procedures. See Instrument Study Guide.

(f) Aviation-Life Support Equipment.

AR 95-3 states that PICs will ensure that Life Support Equipment commensurate with the mission and the operational environment is available on the aircraft and that crewmembers and passengers are briefed on its location and use. 95-3 further states that safety equipment (breakout knives, fire axes, etc.) will be installed per the requirements of the appropriate operator's manual. Each crewmember will wear a survival radio. Each crewmember will wear a survival vest with components. Please be prepared to discuss the contents, location, and use of components of your survival vest. All persons aboard Army aircraft flown beyond gliding distance to land will wear life preservers. The following U.S. Army approved clothing and equipment will be worn by all crewmembers when performing crew duties. * Leather boots * Flight helmet * Flight suit * Flight gloves *Cotton, wool, or Nomex underwear (No synthetics)

AR 670-1 states, in part, "All military personnel will wear ID tags when riding in military aircraft."

(g) Weight and Balance Requirements.

AR 95-1 states that the PIC will ensure that the aircraft is within weight and cg limits for the duration of the flight, that computations on the 365-4 are accurate, and that sufficient 365-4s are aboard the aircraft to verify weight and cg will remain within limits. A single form for specific loading conditions may be used, or several forms covering the range of loading conditions may substitute. In the latter case, the actual loading must clearly be within the extremes of loading used on the forms. AR 95-3 states all Form 365-4s will be checked for accuracy every 90 days. Small differences may exist between the 365-4 and DD Form 365-3 (Basic Weight and Balance Record), provided the differences do not exceed +/- 3/10 of 1% of basic weight or .3 inches cg. Temporary equipment changes may be noted on either the -13 or -14 as "not entered on DD Form 365-3". These changes will be accounted for on the 365-4, either by using the corrections section, or, as stated above, by verifying new weight and cg fall within range of previously computed loading configurations. These logbook entries should state the weight and arm of the equipment installed or removed and may not be carried for longer than 90 days.

(h) Flight Plan Preparation and Filing.

All flight plans (except locals) will be filed at Gray Base Ops, in person or by fax through Guard Ops. Local flight plans may be filed at Base Ops or Guard Ops. Local flight plans are authorized for VFR flights within the local flying area which originate and terminate at either Gray AAF or YTC (Yakima Training Center). Local flight plans will not exceed 8 hours. Flights to McChord or Navy Whidbey are not authorized on local flight plans. IFR flights will be filed not later than one hour prior to the proposed departure time. All flights will be approved and briefed. Flight plans will be cancelled if aircraft has not departed within 30 minutes of ETD for IFR.or 2 hours for VFR. Flight plans may be extended either by contacting Base Ops directly, or through Guard Ops, Bullseye, or any Flight Service Station. Note: IFR and VFR flight plans are forwarded to FSS, local flight plans are not. Practice safe flight following, either by maintaining contact with Guard Ops or Bullseye or FSS or Seattle TRACON.

1. Approval Authority/Briefing Officer. PICS, when operating from AASF during non-duty hours, or when operating away from the AASF, may act as their own approval authority, when conducting missions directed by the commander. All flights originating from the AASF during normal duty hours or drill/AT will be approved by a designated Briefing Officer. Regardless of approval authority, all missions must be briefed by a designated Briefing Officer.

2. Weather Briefing Requirements. A weather briefing from a qualified weather forecaster must be obtained for all flights. IFR flights require a 175-1 (enter briefing # in weather block). Briefings may be obtained telephonically or in person from GAAF Base Ops. GAAF weather forecaster duty hours are from 0600-1900 Monday through Friday. Other times, weather may be obtained from the forecaster at McChord AFB, or through the FAA's Seattle FSS.

3. Pilots Information File. AR 95-1 and TC 1-210 requires current information to be posted as received and to periodically be read by all aviators (at least quarterly). AASF policy is to read and initial the daily reading file prior to each flight, and to read and initial the general reading file quarterly. For NVG crews, a separate NVG reading file must be read prior to NVG flight.

(i) Flight Restrictions Due to Exogenous Factors.

Flight safety requires that medical treatment of all aircrew members be under the supervision of a flight surgeon who is aware of the exogenous factors affecting flying and the appropriate preventive measures. Aircrew members will inform their flight surgeon when they have participated in-activities or received treatment following which flying restrictions may be appropriate. Factors to consider and appropriate medical restrictions to flying activities are:

1. Administration of Drugs. All drugs and medications will be dispensed by or with the knowledge of a flight surgeon. Individuals receiving the following drugs or types of drugs will be restricted from flying duties as indicated:

(aa) Alcohol - 12 hours after last drink consumed and until no residual effects remain.

(bb) Antihistamines or barbiturates - for the period taken and for 24 after discontinued or after any lingering effects, whichever is longer.

(cc) Mood ameliorating, tranquilizing, or ataraxics - for the period they are used and for 4 weeks after the drug has been discontinued.

(dd) Immunizations - minimum of 12 hours following all immunizations except smallpox and for the duration of any systemic or severe local reaction.

2. Blood Donations. Aircrew members will not be regular blood donors. Following donation of 200cc or more, aircrew members will be restricted from flying for 72 hours.

3. Diving. Aircrew members will not fly within 24 hours following SCUBA diving.

4. Tobacco Smoking. See Aeromedical factors, below.

5. Contact Lenses. Aircrew members will not wear contact lenses at any time.

(2) OPERATING LINITATIONS

(See Chapter 5 and 8 in appropriate -10).

(3) EMERGENCY PROCEDURES

(See Chapter 9 in appropriate -10, underlined procedures must be committed to memory).

(4) AEROMEDICAL FACTORS (FM 1-301, AR 40-8)

* Here, we deviate slightly from the outline of the ATM. Because fatigue is a result of stress, we'll first talk about stress.

(a) Stresssss. Stress results from a perceived imbalance between a demand and the ability to meet that demand. Stress affects individuals differently and causes them to vary daily in states of fitness. Everyone, however, has a breaking point. Because of this fact, it is important for aircrew members to recognize some of the causes of stress, as well as possible symptoms and alleviation. While stress can come from many sources, it can generally be considered to be either acute or chronic.

1. Acute Stress. Acute stress has the most immediate impact. It is-usually very intense in nature and occurs within a relatively short period of time. Immediate fear of failure, fear of physical harm, physical discomfort, or work load can contribute to acute stress.

2. Chronic Stress. Chronic stress differs substantially from acute stress. It is not as intense in nature and can last months or years. Duty assignments, physiological environment and illness contribute to chronic stress. Over a period of time, it can become more debilitating than acute stress, and can lead to physical illnesses such as ulcers and migraine headaches.

(b) Stress Sources. Two types of stress associated with aviation are aviation-related stress and self-imposed stress. Both types are cumulative and can lead to debilitating fatigue.

1. Aviation-Related Stress. Although aircrew members may have no control over some aviation-related stresses, they need to know the sources and understand the effects of this type of stress. Some of these sources are:

(aa) Altitude. Stress caused by altitude changes is most evident at altitudes below 5000 feet, where the greatest atmospheric changes occur. Also, even common colds can cause ear and sinus problems on descent from altitude.

(bb) Speed. Speed is stressful because it requires increased alertness and optimal response level.

(cc) Hot or Cold Environment. Extreme heat or cold causes temperature stress.

(dd) Aircraft Design. Lighting, cockpit design, and cabin environment can all divert attention and contribute to stress. Such factors as instrument location, accessibility of switches and controls, seat comfort, heating and ventilating systems, lighting, visibility, and noise levels all directly affect pilot performance.

(ee) Aircraft Characteristics. The inherent instability of helicopters require constant pilot attention and contributes to both acute and chronic stress.

(ff) Weather. Both IFR and VFR flights in poor weather bring a perceived need for greater vigilance and accuracy in reading, following, and monitoring flight instruments and navigation publications. Stress of night flight is similar to stress of flying in poor weather. Decreased awareness of color, visual acuity, and depth perception all increase aviation stress levels.

2. Self-Imposed Stress. As opposed to aviation-related stress, over which the aviator has little or no control, they can exert significant control over self-imposed stress. These stresses can be remembered by the acronym "DEATH", which stands for Drugs, Exhaustion, Alcohol, Tobacco, and Hypoglycemia.

(aa) Drugs. Many drugs are incompatible with safe flying and must never be used without medical supervision. Most drugs are designed to either cure a medical problem or alleviate symptoms. In either case, they almost always have side effects, both predictable and unpredictable, which include allergic reactions and individual idiosyncrasies. Unpredictable synergistic effects can also arise either by combining drugs or taking even prescribed drugs under stressful situations. SELF MEDICATION SHOULD NEVER BE ATTEMPTED BY AIR CREWMEMBERS.

(bb) Exhaustion. Lack of rest or sleep, whether due to environment, work requirements, emotional stress, or changes in time zone adversely affect performance. Sleeping difficulties should be discussed with the flight surgeon. (Note: See Fatigue below, paragraph (c)).

(cc) Alcohol. Alcohol acts as a depressant. Even small amounts have detrimental effects on judgment, perception, reaction time, and coordination. Alcohol reduces the brain cells' ability to use oxygen and increases the physiological altitude. Taking cold showers, drinking coffee, or breathing loot oxygen does not speed up the body's metabolism of alcohol. After consuming alcohol, an aviator should wait AT LEAST 12 hours before flying. The period should be extended beyond 12 hours whenever side effects exist.

(dd) Tobacco. One by-product of smoking is carbon monoxide. Carbon monoxide attaches to hemoglobin molecules 200-300 times more readily than does oxygen. Thus, the presence of carbon monoxide robs the body of oxygen, causing hypoxia (see paragraph (e), below). The average smoker's physiological altitude is 50001 when he is at sea level (Because of less oxygen available, the average nonsmoker loses some night vision beginning at 40001). Thus, smoking reduces night vision capabilities. Apart from this, the chronic irritation of the lining of the nose and lungs increases the likelihood of infection and illness. To aviators, this affects the ability to cope with effects of pressure changes in the ears and sinuses.

(ee) Hypoglycemia. Because of mission requirements, aviation crew members often disrupt their regular eating habits and skip meals. This can lead to the problem of hypoglycemia. Hypoglycemia is a low blood sugar level resulting in a rundown feeling. If the aviator tries an immediate "fix" such as a candy bar, hyperglycemia usually results. Hyperglycemia is an unusually high level of blood sugar. The body's reaction is to secrete insulin, which decreases the blood sugar level, compounding the original problem. The best solution is to-maintain a nutritious, well balanced diet and avoid high sugar "fixes".

(c) Fatigue. Fatigue is caused by stress. It can encompass not only problems with motor skills but also those associated with mental processes. As with stress, fatigue can be thought of as acute or chronic.

1. Acute Fatigue. End-of-the-day tiredness that results in loss of both coordination and awareness of errors. Acute fatigue is characterized by inattention, distractibility, errors in timing, neglect of secondary tasks, and need for greater stimuli.

2. Chronic Fatigue. Far more serious than acute fatigue, chronic fatigue occurs over a longer period of time. Chronic fatigue is often characterized by insomnia, depression, weight loss, irritability, poor judgment, loss of appetite, and slowed reaction times.

(d) Reduction of Fatigue. Physical and mental well-being are essential to carrying out complex, skilled tasks. Proper stress management and fatigue reduction enable the aviator to successfully complete his mission. Some management and reduction techniques are:

1. Good general physical fitness

2. Limitation of self-imposed stress

3. Good living conditions with adequate food and rest

4. Improved working conditions

5. Adequate recreation

6. Local crew rest policies based on Table 3-1, AR 95-3

7. Consult with a flight surgeon if problems exist

(e) Hypoxia. In simple terms, hypoxia is the result of insufficient oxygen in the body. There is a tendency to associate hypoxia only with flight at higher altitudes. There are, however, many other conditions or situations which can and do interfere with the blood's ability to carry oxygen. Alcohol, many drugs, and heavy smoking can either diminish the blood's ability to absorb oxygen or diminish the ability of the body to. tolerate hypoxia. There are four major classes of hypoxia: hypoxic, hypemic, stagnant, and histotoxic. Classification is made according to the cause of lack of oxygen.

1. Hypoxic Hypoxia. Hypoxic hypoxia occurs when there is not enough 02 in the air breathed or when conditions prevent the diffusion of 02 from the lungs to the bloodstream. This type of hypoxia is the one likely to be encountered at altitude. It is due to the reduction of the partial pressure of 02 occurring with altitude.

2. Hypemic Hypoxia. Hypemic (or anemic) hypoxia is caused by a reduction in the capacity of the blood to carry a sufficient amount of 02. Anemia and blood loss are the most common causes of this hypoxia. Carbon monoxide nitrates, sulfa drugs, and so on, can also cause this hypoxia by forming compounds with the blood hemoglobin. The amount of hemoglobin available to combine with 02 is thus reduced.-

3. Stagnant Hypoxia. This type of hypoxia, like hypemic hypoxia, is due to a malfunction of the circulatory system, but differs in certain respects. While the 02 carrying capacity of the blood is adequate, there is an inadequate circulation of the blood. Such conditions as heart failure, arterial spasm, occlusion of a blood vessel, and the venous pooling encountered during high G maneuvers would predispose the individual to stagnant hypoxia.

4. Histotoxic Hypoxia. This type of hypoxia results when the use of 02 by body tissue is interfered with. Alcohol, narcotics, and certain poisons, such as cyanide, interfere with the capacity of the cells to make use of the 02 available to them even though the supply of 02 is normal in all respects.

(f) Stages of Hypoxia. There are four stages of hypoxia; indifferent, compensatory, disturbance, and critical. The stages may vary according to altitude, stress loads, and individual tolerances.

1. Indifferent stage. The only consistent effect of mild hypoxia existing in this stage is the deterioration of night vision which becomes significant at about 4,000 ft. Pilots and crewmembers who fly above 4,000 ft. at night should be well aware that there is a significant loss of visual acuity.

2. Compensatory stage. The circulatory system and, to a lesser degree the respiratory system provide some defense against hypoxia at this stage. The pulse rate, the systolic blood pressure, the rate of circulation, and the cardiac output increase. Respiration increases in depth and sometimes in rate. At 12,000 to 15,000 feet, however, the effects of hypoxia on the nervous system become increasingly apparent; after 10-15 minutes, impaired efficiency is obvious. The individual may become drowsy and make frequent errors in judgment. He may also have difficulty with simple tasks requiring mental alertness or moderate muscular coordination. The most crucial thing about hypoxia at this stage is that it can be easily overlooked when performing other tasks.

3. Disturbance stage. In this stage, the physiological responses can no longer compensate for the oxygen deficiency. Occasionally, there are no subjective symptoms of hypoxia until the time of unconsciousness. More often, symptoms such as fatigue, sleepiness, dizziness, headache, breathlessness, and euphoria are reported. The objective symptoms are:

(aa) Senses. Peripheral vision and central vision are impaired and visual acuity is diminished. There is weakness and loss of muscular coordination. Touch and pain are diminished or lost. Hearing is one of the last senses to be lost.

(bb) Mental processes. Intellectual impairment is an early sign which often prevents the individual from recognizing his disability. Thinking is slow and calculation are unreliable. Short-term memory is poor and judgment and reaction time are also affected.

(cc) Personality traits. There may be a release of basic personality traits and emotions as with alcoholic intoxication. This sometimes results in euphoria, aggressiveness, overconfidence or depression.

(dd) Psychomotor functions. Muscular coordination is decreased and delicate or fine muscular movements may be impossible. Stammering, illegible handwriting, and poor coordination are typical of this stage of hypoxia impairment.

(ee) Cyanosis. The skin becomes bluish in color. This is due to the failure of an oxygen molecule to attach to the hemoglobin molecule.

4. Critical stage. Within 3 to 5 minutes, judgment and coordination deteriorate and subsequent mental confusion, dizziness, incapacitation, and unconsciousness result.

(g) Spatial Disorientation - exists when an individual does not correctly perceive his position, attitude, and motion relative to the center of the earth. Sensory illusions may lead to spatial disorientation in flight. When this occurs, the pilot is unable to see, believe, process, or rely on information provided by his flight instruments and relies instead on false information received by his bodily senses. Prevention of spatial disorientation includes never flying without visual reference points, either the horizon or artificial horizon provided by instruments. Trust your instruments. Never stare at lights. Establish a good degree of night visual adaptation prior to takeoff on any night instrument or VFR flight. Avoid fatigue, smoking, hypoglycemia, hypoxia and anxiety.

(h) Carbon Monoxide - effects are subtle and deadly. It is colorless, odorless, and slightly lighter than air. The affinity of human hemoglobin for carbon monoxide is from 200 to 300 times its affinity for oxygen. Sources are many, i.e., exhaust gasses, hydraulic fluid vapors, engine lubricants, etc.

1. Symptoms of Carbon Monoxide Poisoning include: headache, weakness, nervousness, muscular twitching, joint pain, tremors, muscular cramps, impairment of speech and hearing, and hoarseness.

2. Treatment includes: artificial respiration, administration of 100% oxygen, and application of warmth.

(i) Middle Bar Discomfort or Pain caused by inability to equalize middle ear and ambient pressure. Usually associated with rapid descents from altitude. This condition is aggravated by upper respiratory infections such as colds, etc., which cause the Eustachian tubes to become partially blocked and inflamed, blocking the passage of air into the middle ear. As this occurs, the eardrum becomes distended inward causing pain or discomfort. The only relief for this condition is to equalize the pressure by returning to altitude, or by performing the valsalva maneuver. Don't fly with acute upper respiratory infections and avoid rapid descents from altitude. Also take care passengers are comfortable with changes in pressure and are aware of the valsalva maneuver.

(5) AERODYNAMIC FACTORS (FM 1-203)

(a) Gyroscopic precession: a phenomenon in rotating systems that makes all forces react with a movement 90 degrees from the point of force in the direction of rotation.

(b) Total aerodynamic Force: As air flows around an airfoil, a pressure differential develops between the upper and lower surfaces. The differential, combined with the resistance of the air, creates a force on the airfoil. This force, known as total aerodynamic force, acts through the center of pressure of the airfoil and includes airfoil lift, induced drag, and parasite or profile drag.

(c) Relative Wind: is the apparent motion of air in relation to a body, whether the air moves about the body or the body moves . through the air. The rotation of rotor blades as they turn about the mast produces rotational relative wind. Rotational relative wind flows opposite the path of the rotor blades, parallel to the plane of rotation. Velocity is highest at the blade tips, decreasing to zero at the mast. induced flow is the component of air flowing vertically through the rotor system. It results from the production of lift. The resultant relative wind (at a hover) is the rotational relative wind as modified by the induced flow.

(d) Airflow During a Hover: At a hover, blade-tip vortices reduce the effectiveness of the outer blade portions. A helicopter hovering out-of-ground effect also creates high velocity induced flow, which reaches its maximum approximately one rotor disk below the plane of rotation. The result is high blade pitch angles and high power settings during OGE hovering. Increased blade efficiency during in-ground-effect hovering is due to two phenomena: reduction of induced flow and, as the flow pattern is deflected outward, reduction of rotor-tip vortices. Rotor efficiency is increased by ground effect up to a height of about one rotor diameter. Maximum ground effect occurs when over smooth, flat surfaces. See diagrams following text.

Out of Ground Effect In Ground Effect

(e) Airflow in Forward Flight: Airflow across the rotor system in forward flight varies somewhat from airflow at a hover. Relative wind now becomes the result of rotational relative wind, induced flow, and translational flight. Relative airflow direction and speed are constantly changing as the blades rotate through the moving air mass. As the rotor system moves from a hover into forward flight, turbulence and vortices are left behind, and main and tail rotors both become more efficient. Improved rotor efficiency resulting from directional. flight is called translational lift. At about 16 to 24 knots, the rotor system completely outruns the recirculation of vortices, allowing the entire rotor system to operate in relatively undisturbed air. This point is referred to as effective translational lift (ETL). Directional flight also results in the rotor system having an advancing and retreating side, resulting in dissymetry of lift (See next paragraph). Below ETL, pronounced blowback results from this dissymetry and, coupled with gyroscopic precession ' causes the rotor system to tilt back. Pilots must overcome this blowback by moving the cyclic forward to maintain the desired disk attitude. Transverse flow also occurs below ETL. Transverse flow is a condition of increased drag and decreased lift in the aft portion of the rotor disk caused by the air having a greater induced flow in the aft portion. It is characterized by the disk tilting to the right (again, because of the lag of gyroscopic precession). At higher speeds, dissymetry of lift causes other problems and, ultimately, limits the maximum speed of the helicopter and effects controllability.

(f) Dissymetry of Lift is a transitory difference in lift produced by the advancing and retreating halves of the rotor system. Because the directional movement of the helicopter is added to the rotational velocities on the advancing half of the rotor disk and subtracted from rotational velocities on the retreating half, a speed differential exists and several distinct 'no-lift, airflow regions are created on the retreating side. Near the hub, air actually flows backwards over the blade, creating the 'reverse flow' area. At some point along the span of the blade, rotational velocities exceed translational velocities, and airflow moves from leading edge to trailing edge. Induced flow, however, causes the relative wind to strike the blade from above, creating successive areas of negative stall and negative lift (lift vectors actually point down). As we move span-wise out along the blade, flapping moments and increasing rotational velocities finally succeed in creating a positive lift area, but near the tip of the blade a positive stall area is created and grows toward the blade root as aircraft velocities increase. Thus an ever-shrinking area on the retreating blade is required to produce the same amount of lift as the entire advancing blade. A brief look at the lift formula groan) reveals what a daunting task this is. The formula (L = C L ½ P S V2) shows that lift increases exponentially as speed increases. The factors of air density and blade area (P and S) are the same for both halves of the rotor disk, leaving only the coefficient of lift (CL) to compensate for the speed differential. The coefficient of lift is determined by airfoil shape and angle of attack; thus increased angles of attack allow the retreating blade to produce equal lift (but also lead to retreating blade stall). Blade flapping alone (by increasing angle of attack on the retreating blade and decreasing it on the advancing blade) compensates for dissymetry of lift, but would cause the rotor disk to tilt aft.

Cyclic feathering allows the pilot to keep the rotor disk tilted forward and, as it changes the angle of incidence on both the advancing and retreating sides, it also helps to compensate for dissymetry of lift. (On 'delta-hinge' tail rotors, the angle between the trunnion journals and the pitch change links actually cause the blades to feather as they flap). Up to the point of retreating blade stall, flapping and feathering equalize the lift and there is no difference in total lift being produced (the "dissymetry" being more in how the lift is produced). Thus the 'transitory' nature of dissymetry of lift.

(g) Retreating Blade Stall: As helicopter speeds increase, less and less of the span of the retreating blade actually produces positive lift. Increased flapping angles are required to compensate, but lead to higher angles of attack and, ultimately, retreating blade stall. Stalls begin at the tip of the retreating blade (where flapping moments are greatest) and spread inward as helicopter speeds increase. Along with high forward speeds,, high gross weights, low rotor RPM, high density altitude, steep or abrupt turns, and turbulent air all contribute to the onset of retreating blade stall. In single-rotor helicopters, the first sign of impending stall is generally a noticeable vibration, which may be followed by a left roll and pitch up (this may not be significant in pendular semi-rigid systems) and, finally, loss of control. In tandem rotor helicopters, the pitch up is insignificant. Blade stall is indicated by increased vibration. Blade stall will often occur on the aft rotor first because it operates in the wake of the forward rotor. If stall is suspected, the pilot should reduce power, reduce airspeed, reduce maneuvering, increase rotor RPM (within limits), and check pedal trim.

(h) Settling with-Power: Also referred to as the vortex ring state, this is a condition in which the helicopter settles in its own downwash. Conditions conducive to settling with power are a vertical or near-vertical descent of at least 300 feet per minute and low forward speed. The rotor system must also be using 20 percent or more of available power with insufficient power available to retard the sink rate. These conditions can occur during downwind approaches, NOE flight, formation takeoffs or approaches,, steep approaches, masking and unmasking, and OGE hovering. Generally, settling with power can be avoided by descending on flight paths shallower than approximately 30 degrees (at any airspeed). If encountered,, recovery can be made by increasing translational velocities (forward, lateral, or rearward airspeed) and/or decreasing collective pitch. In tandem rotors, recovery should be attempted using lateral cyclic inputs (fore and aft inputs could aggravate the situation).

Induced-flow velocity during hovering flight

Induced-flow velocity before vortex ring state

Vortex Ring State

(i) Translating Tendency: During hovering flight, thrust of the tail rotor is used to compensate for main rotor torque effects and maintain heading control. The horizontal thrust of the tail rotor tends to cause the helicopter to drift laterally to the right. The aviator may prevent this lateral drift by tilting the main rotor disk in the opposite direction. This lateral tilt results in a main rotor force opposite the tail rotor thrust. Helicopter design usually includes at least one feature that helps compensate for translating tendency. This may include flight control rigging that tilts the rotor when the cyclic is centered or increases tilt as collective is increased, or the main transmission may be mounted so that the mast is tilted slightly.

(j) Dynamic Rollover: A helicopter is susceptible to a lateral rolling tendency called dynamic rollover. It can occur on level ground but is more likely to occur and is more hazardous during slope or crosswind takeoff or landing maneuvers. When a helicopter lands on a slope, the mast is perpendicular to the inclined surface but the plane of the rotor disk must parallel the true horizon (or even tilt slightly upslope). Normally, rotor control is limited by cyclic control stops, static stops, mast bumping, or other mechanical limits. These limits are reached much sooner in down-slope wind conditions. When the helicopter hangs one side low and is landing with the low side upslope, there is also less control travel. Each helicopter has a critical rollover angle beyond which recovery is impossible. If the critical angle is exceeded, the helicopter will rollover regardless of cyclic input. The rate of roll is also critical. As the rolling rate increases, the critical angle is reduced. The critical angle is constantly changing based on such variables as which skid is on the ground, crosswind component, lateral CG offsets, and left pedal inputs. With one skid on the ground, lateral cyclic control is sluggish. The skid may become a pivot point for a variety of reasons, including being caught on protruding objects or in a soft surface, or through improper handling techniques which can 'force' a skid into the ground. A smooth, moderate collective pitch change may be the most effective way to stop a rolling motion. Sudden reduction of collective could start a roll about the downhill skid once it makes contact, and sudden increase will increase the rolling moment should the skid remain fixed; and, even if it breaks free, could result in a pendulum action of the fuselage which could become uncontrollable.

(k) Flight Characteristics. Be prepared to discuss low G Maneuvers, mast bumping, spike knock, differential collective pitch, tandem rotor attitude and heading control, pylon whirl, LTE, collective bounce, etc., applicable to your particular aircraft.

(6) TACTICAL AND MISSION TASKS (TC 1-201; FMs 17-35, 17-40, 17-50, 17-95, 1-204, aircraft ATMs)

Refer to Evaluation Guidelines in ATM for list of subjects to be covered. Your individual Commander's Task List identifies specific tasks for which you are responsible. Refer to Chapter 6 in ATM for task conditions, standards, and descriptions.

(a) Hazards to Terrain Flight Terrain Flight. Hazards include physical, weather, and human factors. Wires, dead trees, other aircraft, wires, birds, and wires all present hazards. Crewmen should keep visors down and keep their attention focused outside. To facilitate this, navigators should use rally terms (turn left, ten o'clock, through that saddle) rather than using compass points. Rain, snow, fog, haze, smoke, dust, and the setting sun all make detection nearly impossible at times. Airspeeds should be adjusted accordingly. Winds, turbulence, and high density altitudes all can affect aircraft performance. Fatigue and other human factors can affect a crewmembers ability to safely perform the mission.

(b) Vertical Helicopter IFR Recovery Procedures (AR 95-2, 95-3, FL 95-1). A VHIRP is a non-standard operating procedure that has been fully coordinated with and approved by the FAA. It is a contingency plan to be executed as a last resort after exhausting all efforts to remain VMC, to include landing as soon as possible. VHIRP is designed to permit the safe recovery of ARMY helicopters that may encounter IMC while conducting tactical terrain flight. There is no authorized VHIRP at Ft. Lewis. In the event of inadvertently entering IMC, control the aircraft (attitude indicator, heading indicator, torque, and airspeed), accept the situation, declare an emergency, and request vectors to VMC or a precision approach. All other procedures are subordinate to Aircraft Control.

(c) Crew Coordination. Crew coordination has become an integral part of Army Aviation. Its incorporation reflects the philosophy that no task is an individual accomplishment - each can be more effectively and safely accomplished by the coordinated efforts of the entire crew. Crew coordination is best enhanced by use of Positive Communication, communication is positive when the sender directs/announces/requests/ offers, the receiver acknowledges, and the sender confirms that the message was received. Crew members should be constantly aware of the potential for misunderstanding and make positive communications a habit. Crewmembers should request assistance in manipulating controls, operating systems, communicating, clearing aircraft, navigating, etc., whenever assistance is necessary and not readily, immediately apparent to other crewmembers. Crewmembers should pre-announce intended actions which may affect others perceptions or abilities to perform their duties (i.e. turning left, switching frequency, turning off landing light, etc.). Crewmembers should offer assistance whenever they perceive a need, and never assume others recognize a possible hazard or the need for assistance. Common phraseology should be used to avoid ambiguity (words like right, X have it, or back up can be easily misunderstood). ATMs contain lists of standard words and phrases which all crewmembers should understand. The Army's concept of crew coordination builds on 13 basic qualities: Leadership and crew climate established and maintained; pre-mission planning and rehearsal; appropriate decision-making techniques used; prioritize actions and distribute workloads; unexpected event management; communication is clear, timely, relevant, complete and verified; situational awareness maintained; decisions and actions are communicated and acknowledged; support is sought; actions are cross-monitored; support is offered; advocacy and assertion are practiced; crew-level after-action reviews are conducted.

(7) NIGHT FLIGHT (FM 1-204 and FM 1-300)

(a) Eye Anatomy and Physiology

The eye is similar to a camera. The cornea, lens, and iris gather and control the amount of light allowed to enter the eye. The image is then focused on the retina. The visual receptive apparatus (retina) has two types of cells, cones and rods. Vision is possible because of chemical reactions within these cells.

1. Cones. Cone cells are used primarily for day or high-intensity light vision. The concentration of cones in the central retina (fovea centralism permits high visual acuity in high illumination. The chemical iodopsin is always present in the cone cells. Regardless of the ambient light condition, this chemical is readily available so that the cones can immediately respond to visual stimulation.

2. Rods. The rods are used for night or low-intensity light vision. The peripheral retina is almost exclusively associated with rods. Peripheral vision is less precise than central vision because rods perceive only shades of gray and vague form or shape. Rhodopsin, commonly referred to as visual purple, is the photochemical found in rods. As the light level decreases, the amount of rhodopsin in the rods builds and the rods become more sensitive. When illumination decreases to about the level of full moonlight, the rods take over from the cones. The highest light sensitivity is usually achieved after 30 to 45 minutes in a dark environment. The rod cells, nominally 1000 times more sensitive to light than cones, may become up to 10,000 times more sensitive when fully dark adapted.

(b) Types of Vision

1. Photopic - experienced when high levels of light exist. Cones concentrated in the fovea centralis are primarily responsible for vision in bright light. Because of the high light level, rhodopsin is bleached out and rod cells become less effective. Sharp image interpretation and color vision are characteristic of photopic vision.

2. Mesopic - experienced at dawn, dusk, and during periods of mid-light levels. Vision is achieved by a combination of both rods and cones. Visual acuity steadily decreases as the available light decreases. A reduction in color vision occurs as the light level decreases and the cones become less effective. Due to gradual loss of cone sensitivity, greater emphasis should be placed upon off-center vision and scanning for detection of objects.

3. Scotopic - Experienced when low-level light conditions exist. Cone cells become ineffective causing poor resolution of detail. Visual acuity decreases to 20/200 or less and total loss of color perception occurs. A central blind spot occurs due to the loss of cone sensitivity. Viewing objects must be accomplished by off-center viewing and scanning. The natural reflex of looking directly at an object must be reoriented by night vision training. A characteristic of this type of vision is that a din image may fade away if your eyes are held stationary for more than a few seconds.

4. Day vs. Night vision - differences between day and night vision involve color, detail, and retinal sensitivity. Color vision is lost under low illumination due to the rods' inability to distinguish distinct colors. Although rods may be as much as 10,000 times more sensitive to levels of light, they are insensitive to color. In order for color to be perceived at night, the intensity of the light must be above the threshold for cone vision. Because of the physiology and mechanics of the eye, perception of fine detail is impossible at night. Rods are less-densely concentrated than are cones, and the pupil is wide open, allowing greater dispersion of incoming light. Therefore, objects must be large or nearby to be seen at night. Identification of objects is based on perceiving shapes and outlines, not on distinguishing features. Also, because of the threshold of perception of the cone cells and the concentration of cones in the fovea centralis, a 5" to 100 night blind spot develops. objects viewed directly may not be detected. In order to perceive objects at night, you must use off-center vision and proper scanning techniques.

5. Visual Problems

(aa) Presbyopia is a condition in which loss of elasticity of the lens causes defective accommodation and inability to focus sharply for near vision. It usually becomes apparent at about age 40, and, due to the refractive qualities of light, may be compounded under conditions where red light is used for illumination.

(bb) Night Myopia - myopia is a condition in which images come to a focus in front of the retina resulting especially in defective vision of distant objects. Again because of the refractive qualities of light and the predominance of blue wavelengths at night, what might be a mild condition during the day may become unacceptably blurred at night. Both presbyopia and myopia can be compensated for using corrective glasses.

(cc) Astigmatism is an irregularity of the shape of the cornea that may cause an out-of-focus or distorted image.

(c) Dark Adaptation and Protection of Night Vision

1. Dark Adaptation - is the process by which eyes increase sensitivity to low-levels of illumination. Rhodopsin (visual purple) is the substance in the rods responsible for light sensitivity. The degree of dark adaptation increases as the amount of visual purple in the rods increases through biochemical reactions. Maximum dark adaptation is reached in about 30 to 45 minutes under minimal lighting conditions. If the dark-adapted eye is exposed to a bright light, the sensitivity of that eye is temporarily impaired. The amount of impairment depends on the intensity and duration of the exposure. Brief flashes from a white (Xenon) strobe light commonly found on aircraft have minimal effect upon night vision because the pulses of energy are of such short duration. On the other hand, exposure to a flare, a searchlight beam, or lightning may seriously impair your night vision. The recovery of a previous maximum level of dark adaptation could take from 5 to 45 minutes in continued darkness. Night vision goggles affect dark adaptation. If you dark-adapt before donning the goggles and remove them in a darkened environment, you can expect to regain full dark adaptation in about two minutes.

2. Protection of Night Vision. Repeated exposure to bright sunlight has an increasingly adverse effect on dark adaption. This effect is intensified by reflective surfaces such as sand or snow. Exposure to intense sunlight for two to five hours decreases scotopic sensitivity for as long as five hours. Also, a decrease occurs in the rate of dark adaption and degree of adaptive capacity. These effects are cumulative and may persist for several days. If night flight is anticipated, crewmembers should wear neutral density sunglasses when exposed to bright sunlight. Dark adaption and retinal sensitivity are directly related to oxygen levels. Remember that one of the first symptoms of hypoxia is loss of night vision, which occurs at pressure altitudes of around 4,000 ft. After dark adaption, crewmembers should protect their night vision by avoiding areas of high illumination, and, if unavoidable, cover or close one eye to preserve night vision in that eye. Crews should also avoid self-imposed stresses as much as possible, as they can affect the ability of the body to dark adapt or the stamina and discipline required to employ night vision techniques.

(d) Night Vision Techniques. As ambient light levels are reduced, the human eye has some serious problems which limits a crewmembers visual abilities. Dark adaption is only the first step toward increasing the ability to see at night. Loss of color perception, acuity degradation and the night blind spot all make normal daylight viewing techniques unproductive. Thus techniques for night vision viewing must be used to overcome some of the problems associated with night vision. Because central vision is such an ingrained reflex, these techniques require considerable practice and concerted effort.

1. Off-Center Vision. Viewing an object using central vision during daylight poses no limitations; however, if the same technique is used at night, the object may not be seen. This is due to the night blind spot that exists during periods of low illumination . To compensate for this limitation, "off-center vision" must be used. This technique requires that an object be viewed by looking 10 degrees above, below, or to either side, rather than directly at the object. This allows the peripheral vision of the eyes to maintain visual contact with an object. Even using off-center vision, an object viewed for a period of time in excess of 2 to 3 seconds will tend to bleach out and become one solid tone. As a result, the object can no longer be seen. To overcome this limitation of night vision, the crew member must be aware of the phenomenon and avoid viewing an object longer than 2 to 3 seconds before shifting the eyes from one off-center point to another.

2. Scanning. Scanning techniques are important in identifying objects at night. To scan effectively, scan from right to left or left to right. Begin scanning at the greatest distance an object can be perceived (top) and move inward toward you position (bottom). Due to the inability of the light-sensitive elements of the retina to perceive images while in motion, use a stop-turn-stop-turn type motion. For each time you stop, scan an area approximately 30 degrees in width. This viewing angle will include an area approximately 250 meters wide at a distance of 500 meters. The duration of each stop is based on the degree of detail that is required, but should be no longer than 2 to 3 seconds. When moving from one viewing point to the next, overlap the previous field of view by 10 degrees.

3. Shapes or Silhouettes. Visual acuity will be significantly reduced at night. Because of this limitation, objects must be identified by their shape or silhouettes. The crew member's ability to recognize objects using this technique will be determined by his familiarity with the architectural design of the structures which are common to the area in which the mission is being flown. A silhouette of a building with a high roof and a steeple can be easily recognized as a church in America; however, churches in other parts of the world may have a low-pitched roof with no distinguishing features. Man-made features depicted on the map will also assist in recognition of silhouettes observed while in flight.

(e) Distance Estimation and Depth Perception.

The cues to distance estimation and depth perception are easily recognizable using central vision during good illumination. As the light level decreases, the crew member's ability to accurately judge distance is degraded and his eyes are more subject to seeing illusions. A knowledge of the mechanisms and cues to distance estimation and depth perception will assist the aviator in making better judgment of distance at night. While flying at altitude, most of the distances outside the cockpit are so great that the binocular cues are of little,, if any, value. In addition, these cues operate on a more subconscious level than the monocular ones. Therefore, they are not as capable of being improved by study and training and will not be discussed here. Monocular cues used to aid in distance estimation and depth perception are geometric perspective, retinal image size, aerial perspective, and motion parallax (GRAM).

1. Geometric Perspective. An object may have many different apparent shapes, depending on the distance and angle from which it is being viewed. Types of geometric perspective are:

(aa) Linear Perspective. Parallel lines such as runway lights tend to converge as distance from the observer increases.

(bb) Apparent foreshortening. The true shape of an object or terrain feature may be indiscernible because of the angle of view. Thus a circular confined area appears elliptical when viewed from a distance and not directly overhead.

(cc) Vertical Position in the field. objects or terrain features which are farther away from the observer appear higher on the horizon than objects or terrain features that are closer to the observer. This does not work for elevated or airborne objects. A light on an elevated structure or on a low-level aircraft may be mistaken for more distant ground objects.

2. Retinal image size. The size of an image focused on the retina is perceived by the brain to be of a given size. Factors that are used to determine distance using the retina image are,.

(aa) Known size of objects. The nearer an object is to the observer, the larger is its retinal image. By experience, the brain learns to estimate the distance of familiar objects from the size of their retinal image. To use this cue, the observer must know the actual size of object and have prior visual experience with it. If no experience exists, an object's distance would be determined primarily by motion parallax.

(bb) Increasing and decreasing size of objects. If the retina image size of an object increases, it is approaching or moving nearer the observer. Whereas, if the size is constant, the object is at a fixed distance.

(cc) Terrestrial Associations. Comparison of an object, such as a confined area, with an object of known size, such as a tank, will help to determine the relative size and apparent distance of the object from the observer.

(dd) Overlapping of contours or interposition of objects. When one object is seen to overlap another, the object which is being overlapped is farther away. Stated another way, any object which is partly concealed by another object is determined to be behind the object being seen clearly. Disappearing or flickering landing area lights may indicate barriers between your aircraft and the area.

3. Aerial Perspective. The clarity of an object and the shadow cast by the object are perceived by the brain and used as cues for estimating distance. Factors used to determine distance using these aerial perspectives are:

(aa) Variation in Color or Shade. Even in daylight, color and shading fade with distance. Also, subtle variations which exist are discernible close-up but as distance increases these distinctions blur.

(bb) Loss of detail or texture. As you get farther from an object, discrete details become less apparent. For example, a cornfield becomes a solid color, the leaves and branches of a tree become a solid mass, and the object is judged to be at a great distance.

(cc) Light and Shadows. Every object will cast a shadow if there is a source of light. The direction the shadow is cast depends on the position of the light source. If a shadow of an object is toward the observer, the object is closer to the observer than the light source. (No duh!)

4. Motion parallax. This cue to depth perception is often considered the most important. Motion parallax refers to the apparent relative notion of stationary objects as viewed by an observer moving across the landscape. The rate of apparent movement depends on the distance the observer is from the object. Objects near the aircraft move rapidly, while distant objects appear to be almost stationary. Thus objects that appear to be moving rapidly are judged to be near while those moving slowly are judged to be at a greater distance. For example, when flying low-level,, objects near the aircraft appear to rush past while more distant objects may appear stationary. As you fly over a power line that extends to the horizon, that part of the power line that is near the aircraft appears to be moving swiftly, opposite the path of notion. Toward the horizon, the same power line will appear fixed.

(f) Visual Illusions. As visual information decreases, the probability of spatial disorientation increases. Reduced visual references also create illusions that can induce spatial disorientation. There are several visual illusions which occur in the aviation environment.

1. Autokinesis. When a person stares at a static light in the dark, the light will appear to move. This phenomenon can be readily demonstrated by staring at a lighted cigarette in a dark room. Apparent movement will b4tgin after about 8 to 10 seconds. Although the cause is not known, it appears to be related to the loss of surrounding references which normally serve to stabilize your visual perceptions. This illusion can be eliminated or reduced by visual scanning, by increasing the number of lights, or by varying the intensity of the light. The most important of the three solutions is the visual scanning technique. You should not stare at a light or lights for longer than 10 seconds. An awareness of this illusion and how to cope with it are essential to ensure safe operations at night.

2. Ground Light Misinterpretation. A common occurrence is to mistake ground lights for stars. When this happens, the aviator unknowingly positions the aircraft in an unusual attitude to keep the lights above him. For example, some aviators have misinterpreted the lights along a seashore for the horizon and have maneuvered their aircraft dangerously close to the sea while under the impression of flying straight and level. Cross-check your instruments to avoid this problem.

3. Relative Motion. Relative motion is perceiving the motion of another aircraft as your own, or vice versa. If a pilot is at a stationary hover and another helicopter hovers by, as the other aircraft is picked up in the pilot's peripheral vision he may sense movement in the opposite direction. You may also experience this illusion during formation flying. You may interpret notion by the wingman or leader as movement of your aircraft. The only way you can correct for this illusion is to understand that such illusions do occur and that you should not react to them on the controls. Using proper scanning techniques can help prevent this illusion.

4. Reversible perspective Illusion. An aircraft may appear to be retreating when it is in fact approaching your position. This illusion is often experienced when aircraft are on converging (or is it diverging) paths. Perceiving only the silhouette of an object compounds the problem, as a quartering-tail view closely resembles a quartering-head view. Watching position lights may help. If the intensity of the lights increases, the aircraft is approaching your position. If the lights become dim, the aircraft is retreating. The 'red-right-returning' rule may not help discern between converging and diverging traffic.

5. False Horizons. The illusion of false horizons is experienced when something other than the actual horizon is identified as being parallel to the horizon. For example, an aviator flying his aircraft between two cloud banks may position the aircraft in relation to the lower cloud bank because it seems to be parallel to the horizon. Cross-checking your instruments can help prevent this situation.

6. Altered Reference Planes. Approaching a line of mountains or clouds alters your plane of reference. You may feel that you need to climb even though your altitude is adequate. Additionally, when flying parallel to a line of clouds, you may have a tendency to tilt away from the clouds.

7. Height perception Illusion. Flying over desert, snow, or water causes an illusion of having more altitude than you actually have. This is because of a lack of visual reference. To overcome this problem, it may be necessary to drop an object (such as a chemical stick or flare) on the ground before landing. Flight when visibility is restricted by haze, smoke, or fog produces the same illusion of height perception.

8. Flicker Vertigo. A light flickering at a rate of 4 to 20 cycles per second can produce unpleasant and dangerous reactions. Such conditions as nausea, vomiting, vertigo, and on rare occasions, convulsions and unconsciousness may occur. Fatigue, frustration, and boredom tend to intensify these reactions. Most common cause for a helicopter crewmember would be any light source viewed through or reflecting off of the rotor system (A semi-rigid rotor system rotating at 354 RPM flickers at 11.8 cycles per second, 324 RPM at 10.8).

9. Fascination (Fixation). This illusion occurs when a pilot ignores orientation cues and fixes his attention elsewhere. This is especially dangerous at night. Aircraft ground closure rates are difficult to determine because of the reduction or absence of normal daylight peripheral movement. Increased scanning by the pilot will help prevent this illusion.

10. Structural Illusion. Structural illusions are caused by heat waves,, rain, snow, sleet, or other factors which obscure vision. For example, a straight line may appear to be curved when seen through a desert heat wave, or a wing tip light may appear to be double or move when viewed during a rain shower.

11. Size-Distance Illusion. This illusion results from viewing a source of light that is increasing or decreasing in brightness. You may interpret the light as approaching or retreating. For example, if the position lights on a nearby aircraft are switched from dim to bright, the aircraft may appear to jump toward you.

(g) Unaided Night Flight and Use of Lights. The design of some Army aircraft will degrade your ability to see outside the cockpit. To minimize the loss of night vision because of aircraft shortcomings, you must properly prepare the aircraft for night flight. Windscreens can reduce your ability to see outside the aircraft. To minimize the effect of windscreens on night vision, they must be kept clean. Remove dirt, grease, bugs, and scratches from the windscreen before each night flight. Aircraft instruments are easier to read under high levels of instrument illumination. However, the level of light needed for optimum reading interferes with maximum dark adaptation needed for seeing dim objects outside the aircraft. Interior lights also interfere with dark adaptation. They reflect off the windscreen, reduce outside visibility, and are subject to detection by the enemy.

To-minimize these effects, turn off all nonessential lights and keep the intensity of essential lights to the lowest usable level. Fort Lewis 95-1 requires that position lights be on bright and anti-collision lights be on. UH-60's and CH-47's may have the lower anti-collision light off. In formation, all aircraft other than trail will have anti-collision lights out. Whenever possible, preflight should be accomplished in daylight. If the preflight must be performed at night, use a flashlight with an unfiltered lens. If they don't interfere with mission or safety considerations, landing lights should be pre-positioned (remember, they may degrade the effectiveness of the WSPS in OH-58s). Increased scanning during hover and hover power checks will help reduce spatial disorientation. For takeoff, if sufficient illumination does not exist to view obstacles, an 'altitude-over-airspeed' type takeoff should be accomplished. Crewmembers not on the controls should make all internal checks. During approach, altitude, apparent ground speed and rate of closure may be difficult to estimate. To avoid abrupt changes in attitude, rate of descent should be slightly lower than during the day. After beginning the descent, airspeed may be reduced to 40-45 knots until apparent ground speed and rate of closure appear to be increasing. Rate of descent at touchdown should not exceed 300 fpm.

(h) Crew Night and NVD Requirements. Every NVG RL 1 aviator in an NVG-designated position must fly a minimum of 9 hours NVG each semiannual period. This also applies to NVG PC's, whether or not they occupy an NVG-designated position. These hours may not be reprogrammed. A maximum of 3 hours in a compatible visual flight simulator may be substituted for aircraft flight time each semi-annual period. To be considered NVG current, an aviator must fly a one-hour flight in the aircraft or a compatible visual simulator once every 45 days. At least once every 90 days, the one-hour flight must be in the aircraft. An aviator whose currency has lapsed must complete a one-hour NVG proficiency evaluation prior to resuming NVG flight duties. An annual NVG evaluation must be accomplished by all crew members who maintain NVG currency. The evaluation must be performed at night in the aircraft.

(i) NVD Limitations, Techniques, and Operational Considerations. NVGs are an invaluable tool for enhancing night operations, but they must be handled properly and used correctly to maximize their effectiveness. Special care should be exercised to protect NVGs from adverse environmental conditions such as saltwater, sand and dust ' or rain. Goggles should be inspected and thoroughly cleaned after exposure. NVGs are sensitive (and expensive) electro-optical devices. To protect the lenses from damage, keep caps on when not in use. The intensifier tubes contain toxic material. If a tube breaks, avoid contact with the chalky, white phosphor material. NVGs are sensitive to light intensity, and may become grainy or unusable in extremely low light levels and may 'shutdown' in higher light levels, also rendering them unusable. You may hear the terms civil, nautical, and astronomical twilight. These refer to the center of the solar disk being 6, 12, and 18 degrees below the horizon, respectively. Light levels when the sun is higher than 12 degrees below the horizon (nautical twilight) are not compatible with NVG use. Times vary with season and latitude, but on average, the sun travels at 15 degrees per hour. This means that, on average, NVG flight should not be attempted prior to 48 minutes after sunset. ANVIS are monochromatic light amplifying devices which have an electrical gain of 25,000 to 1; resulting in light intensification of 2000-3500 times. An 'Automatic Brightness Control' adjusts gain to keep output intensity within a preset range. This 'ABC' feature is what causes the NVG to 'shutdown' when exposed to high-level light sources. (The 'shutdown' can often be overcome either by shielding the NVGs from the light source or by use of the pink light.) ANVIS wavelength sensitivity extends well into the near-IR range and they have a 'minus blue' filter which makes them insensitive to cockpit lights. They have a focal range of approximately 10 inches to infinity, a 40 degree field of view, and best-case visual acuity of 20/40. -Depth perception and distance estimation both suffer with NVGS. Ambient light, degree of contrast, and use of monocular cues affect both. NVGs do not magnify images and, while they can compensate for certain refractive errors, they are not as accurate at doing so as are spectacles and should not be used to make such corrections. Aviators with refractive errors must wear spectacles during NVG flight. After extended NVG use, you may experience a tint or discoloration of objects viewed with the naked eye. This is the normal physiological phenomenon known as monochromatic adaption, which is not harmful and disappears after a few minutes.

When preparing for use, NVGs should be pre-flighted IAW the -10. Certain operational defects may be detected which render the goggles unacceptable for use. These include:

1. Shading. Caused by defective vacuum seal in the intensifier, shading results in image being less than fully circular. Shading is a sign of impending tube failure. NOTE: Shading may be confused with a blurred condition caused by improper interpupillary, tilt, or vertical adjustments.

2. Edge Glow. Caused by a defective phosphor screen allowing light feedback, edge glow is a bright or sparkling area at the edge of the viewing area which remains visible even with all incoming light blocked.

3. Flashing, Flickering, or Intermittent Operation. May occur in either or both tubes. Check for loose connections.

Cosmetic blemishes which may be deemed acceptable provided they do not interfere with mission accomplishment include bright spots, emission points (pinpoints of light similar to edge glow), black spots, 'chicken wire' and fixed-pattern noise, image disparity (difference in tube brightness), output brightness variation (varying brightness in or across the image area), and image distortion (the -10 says that distortion does not change throughout the life of the tube, and each tube is screened for distortion before first use.).

When setting the eyepiece focus, it is possible to achieve a clear image in each eye separately and yet have a blurred image when viewing with both eyes. Over-accommodation and/or focal imbalance between the eyes can cause eyestrain and periodic blurred vision. It is important, when adjusting the lenses for individual acuity, that both eyes remain open. The following is the latest thinking on proper adjustment techniques.

Set the diopter adjustment to zero and turn objective lens focus ring fully counter-clockwise. Turn the goggles on and look at a high-contrast target 100-200 feet away. cover one objective lens (be careful not to touch the lens) and slowly turn the opposite objective focus ring clockwise until the image is it's sharpest. Turn the eyepiece focus ring counter-clockwise until the image blurs slightly. Now turn it slowly back clockwise until you first obtain a clear image. Stop. Try not to 'over-minus'. Repeat for other tube. Now, viewing through both tubes, place one slightly out of focus with the objective lens ring and fine tune the other with the eyepiece focus ring. Repeat for the other tube.

A recommended starting weight of 12 oz. should be used when fitting a counterweight for the NVGs. The weight can be adjusted up or down from there, but should never exceed 22 oz. maximum.

A low battery voltage condition is indicated by a steady or blinking LED which illuminates when voltage drops below 2.4 volts.

For NVG operations, there are several altitude/airspeed restrictions. NOE flight (for NVGs) is defined as wheels or skids above the trees to an altitude of 25 feet - 40 KIAS is the maximum airspeed allowed. Contour flight is between 25 and 80 feet - 70 KIAS is the maximum airspeed allowed. Low-level flight is above 80 feet up to 200 feet. Aircraft may fly at whatever airspeed operational requirements dictate. In all cases, adjust airspeed to avoid overflying the field of view when conditions of possible reduction or loss of vision exist.