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The Push-Pull Effect refers to a potential aircraft maneuver that can set up a pilot for G-induced loss of consciousness. The Push-Pull Effect is characterized by ______________

Decreased + Gz tolerance when preceded by 0 Gz or - Gz exposure. Increased baroreceptor pressure due to increase blood volume in the neck triggers reduced blood pressure during the 0 or - Gz exposure. the subsequent + Gz exposure catches the pilot with (1) reduced eye level blood pressure and (2) dilated blood vessels.


Of the 304 F-16 Class A mishaps in the US Air Force from 1975 to 2003, the three PRIMARY causes were:______________

Engine failure, collision with ground, and midair collision account for the majority of the primary causes of Class A mishaps.


G-induced loss of consciousness is best defined as:

A state of altered perception wherein (one's) awareness of reality is absent as a result of sudden, critical reduction of cerebral blood circulation caused by increased G force.


The pilot of a high performance aircraft turns in his seat to "check six" just prior to pulling + 9 Gz. Which answer best describes what could happen next to the pilot:

The pilot is no more likely to GLOC while checking six than when facing forward and pulling 9 Gz.


The following statements concerning the use of positive pressure breathing for G-protection are true except:
1) PBG can aggravate arm pain in some seat configurations
2) PBG can approximately double the duration of G-exposure that a pilot can tolerate.
3) PBG is effective in preventing G-LOC when used without anti-G trousers.
4) Chest counter pressure increase pilot comfort and allow for the use of higher levels of PPB.

3) the use of PBG without anti-G trousers leads to blood pooling in the extremities and loss of consciousness. It does not prevent G-LOC under these circumstances.


The following statements concerning the physiologic and medical consequences of + Gz acceleration are true except:
a) Ultrasound studies have demonstrated cardiac abnormalities, such as right ventricular enlargement, resulting from chronic exposure.
b) Cervical spine injuries have been reported in high performance pilots.
c) G-induced loss of consciousness can be preceded by loss of vision (greyout or blackout).
d) A pilot can experience G-LOC and not remember it.
e) None of the above.

A. Ultrasound studies have NOT found significant cardiac abnormalities in pilots exposed to + Gz acceleration.


The following factors are associated with increased tolerance to + Gz acceleration EXCEPT:
a) Reclined seat back angle greater than 45 degrees from vertical.
b) Sex (males have a greater tolerance for + Gz).
c) Short stature
d) A properly performed anti-G straining maneuver.
e) A recent exposure (within the past two weeks) to the high-G environment.

b). There is no evidence of a difference in G tolerance between the sexes.


Angular acceleration is defined as:
a) the centripetal acceleration acting along the radius of a circle during curvilinear motion.
b) the rate of change of angular velocity, which in turn is the rate of change of angular position.
c) the rate of change of linear velocity acting tangentially during curvilinear motion.
d) 32.2 ft/sec2 or 980 cm/sec2
e) radians/sec or degrees/sec

b. Angular acceleration is the rate of change of angular velocity, which in turn is the rate of change of angular position. In aviation, angular accelerations occurs as a change of pitch, roll, or yaw velocity.


Systems (or studies) that have been used to improve + Gz tolerance include:
a) water immersion
b) anti-G suit/valve
c) tilt back seat
d) vasoactive drugs
e) all of the above

e. All of the above. Any technique that increases venous return, increases cardiac output, increases arterial blood pressure, or that counters the gravitational effect will increase + Gz tolerance. All of the above systems or studies have been used to try and improve pilot G tolerance.


Studies of miniature swine exposed acutely to G stress up to levels of + 9 Gz for 45 seconds have consistently revealed subendocardial hemorrhage and cardiomyopathy. The cardiomyopathies include myofibrillar degeneration, translocation and clumping of mitochondria and necrosis of cardiac myocytes. It is believed that these same cardiomyopathies occur in humans who are exposed to similar G forces. True or False.

False. Although the swine studies revealed these pathologies at operational G levels, a follow on study in humans using all available clinical monitoring techniques did not reveal similar conditions.


Loss of vision or blackout during + Gz acceleration ensues when the retinal artery pressure falls below the intraocular pressure. The intraocular pressure is approximately:

The arterial pressure drop at eye level is linearly related to the increased G level, ie- it falls about 24 mmHg per G. It was noted that vision was affected as retinal systolic pressure fell below 50 mmHg and a complete loss of vision occurred when retinal systolic pressure fell below 20 mmHg which is intraocular pressure.


During - Gz acceleration the following symptoms may occur EXCEPT:
a) rapid heart rate
b) severe facial congestion, throbbing headache
c) subconjunctival hemorrhage
d) an increase in arrhythmic heart beats

a) Rapid heart rate is incorrect. The increase in preload and vagal stimulation would actually decrease the heart rate. The increase in arrhythmia is due to an increase in vagal tone as a result of increased pressure in the neck, precipitating carotid sinus syndrome. This would cause a decrease rather than an increase in heart rate.


Methods or techniques other than anti-G suit and straining used to increase + Gz tolerance include all of the following EXCEPT:
a) tilting the pilot back from the vertical, ie- up to 65 degrees.
b) positive pressure breathing
c) pre-breathing 5% CO2
d) running

D) Running.
Numerous studies have looked at tilt, decreasing the vertical distance between the heart and eye to increase vision during Gz. From 45 degrees to 75 degrees an improvement in vision, heart rate, and muscular straining decreases. Positive pressure breathing reflexly leads to an increase in systemic arterial blood pressure, hence + Gz tolerance. Prebreathing gaseous mixtures with 5% CO and 95% oxygen causes peripheral vasoconstriction and cerebral vasodilation hence increasing tolerance. Aerobic exercise (running) has not been shown to increase tolerance.


The Acceleration Atelectasis Syndrome requires the combination of three factors acting on the pilot during flight. Which one is NOT a factor?
a) the inflation of the anti-G suit
b) the performance of a vigorous M-1 or L-1 straining maneuver
c) exposure to + Gz acceleration
d) breathing 100% oxygen

B) M-1 or L-1 Straining Maneuver
Several studies have investigated this syndrome. In the USAF, cases were found in a group of fighter pilots, 31 of whom had difficulty in taking a deep breath. The symptoms were attributed to absorption atelectasis but was considered that the creation of edema in the lower lung played an important role. Studies in the RAF showed that pilots with G suit inflation and breathing 100% oxygen while pulling G's were susceptible. M-1 and L-1 straining maneauvers do not appear to be implicated.


Premature ventricular contractions (PVC's) of the heart have been observed in human subjects during high sustained + Gz exposure (+ 6.0 Gz for 15 secs). Possible contributing factors include all of the following EXCEPT:
a) effects of sympathetic nervous system stimulation and increased catecholamine levels.
b) changes in cardiac filling.
c) changes in position and mechanical stresses on the heart.
d) inadequate coronary blood flow.
e) lean body mass of the subject.

e) Lean body mass has not been shown to be a contributing factor. Numerous studies, including Shubrooks (+ 9Gz for 45 seconds) showed impacts due to cardiac filling, catecholamine levels, and coronary blood flow, but lean body mass showed no impact.


What is the current USAF approved Anti-G Straining Maneuver (AGSM)?

The L-1 maneuver. It combines a regular, 3 second strain against a closed glottis, interrupted with a rapid exhalation and inhalation, with tensing of all major muscle groups of the abdomen, arms, and legs.


What is the difference between the M-1 and L-1 and Hook Straining maneuver?

The M-1 is done against a partially open glottis while grunting. However, studies showed that it had a lower intrathoracic pressure when compared to the L-1 (closed glottis) and therefore is no longer recommended. The "Hook" is the Navy version of the L-1 where the pilot says "hook" as they begin to strain to close the glottis.


Factors that determine + Gz tolerance (inertial force acting in a head to foot direction) include all of the following EXCEPT:
a) duration at G
b) magnitude of G
c) restraint system
d) rate of onset of G
e) direction of G

C) Restraint system. The direction of the G, rate of onset of G, magnitude of G and duration of G all have an impact on G tolerance. The restraint system has no impact on G tolerance.


From a cardiovascular standpoint, the M-1, L-1 and Valsalva maneuvers are the same and offer equal + G protection when performed by a fighter pilot during high G maneuvering. True or False?

False. The M-1 maneuver is against a partially closed glottis (audible grunting). This has been shown to be less effective than the L-1. The Valsalva consists of forced exhalation against a closed glottis, but without simultaneously tensing the muscles. Thus it is also inferior to the L-1.


What is the Frenzel maneuver?

The Frenzel maneuver was taught to WWII German fighter pilots to help them clear their ears. It is placing the tongue on the roof of the mouth far forward, moving the closed jaw forward to open the eustacian tubes and allowing air to equalize. It is used by scuba divers as well. It does not have anything to do with G tolerance (like M-1, L-1) but rather pressure equalization in the ears.


Positive Gz forces (ie- the inertial force acting from head to foot) causes cerebral hypoxia by decreasing blood flow to the head. However, arterial hypoxemia occurs because + Gz:___________
a) increase the pulmonary ventilation-perfusion inequalities normally present.
b) increases the distance that arterial blood must travel to the cerebral cortex.
c) decreases the time that mixed venous blood is present in the pulmonary capillaries.
d) decreases the time that arterialized blood remains in the retinal capillaries.

a) increase the pulmonary ventilation perfusion inequalities. With increasing Gz, the amount of blood forced into the lower lung fields increases, which increases the VQ mismatch causing a right to left shunt in the alveoli. At + 5 Gz, the mismatch equals about 50% and oxygen saturation to below 85%.


Acceleration tolerance is an important factor in the design of new aircraft. What type of acceleration is best tolerated by the human body?
a) positive acceleration
b) negative acceleration
c) alternating positive and negative acceleration
d) transverse acceleration

d) Transverse acceleration. Human studies have shown that the body can tolerate up to + 20 Gx acceleration (think space capsules).


Which of the following statements concerning the Valsalva maneuver is INCORRECT?
a) it is safer than the Frenzel maneuver for use in the flying population.
b) Use may cause a temporary reduction in blood pressure.
c) Cardiac arrhythmias may accomany its use.
d) the technique may be difficult for some people to learn.

a) The Frenzel maneuver is safer. It does not cause a change in blood pressure or arrhythmia. The valsalva maneuver may cause a temporary reduction in blood pressure due to pressure in the neck causing vasovagal tone and a decrease in heart rate. The Frenzel maneuver is simply moving the jaw and tongue forward to open the eustacian tube for equalizing ear pressure. It has no vagal or cardiac components.


The mean time of incapacitation resulting from + Gz-induced loss of consciousness on a human centrifuge is:
a) 2 sec
b) 5 sec
c) 10 sec
d) 15 sec
e) 30 sec

d) 15 seconds


All catapult launches typically expose the pilot to 2 to 4 seconds of inertial force that peaks at +3 to + 5 Gx. What is the appropriate velocity of an aircraft immediately after having been catapulted at a constant 4-G acceleration for 2 seconds? (1 nm= 6080 ft).
a) 130 knots
b) 140 knots
c) 150 knots
d) 160 knots
e) 170 knots

C. 150 knots.

Velocity = acceleration x time
= 4 g (32 ft sec2)/g x 2 sec
= 256 ft sec2
= 256 ft sec (1nm/6080 ft) (3600 sec)/hour
= 152 nm/hr or knots


All catapult launches typically expose the pilot to 2 to 4 seconds of inertial force that peaks at +3 to + 5Gx. What is the appropriate velocity of an aircraft immediately after having been catapulted at a constant 4-G acceleration for 2 seconds? (1 nm= 6080 ft).
a) 130 knots
b) 140 knots
c) 150 knots
d) 160 knots
e) 170 knots

c) 150 knots
Velocity = acceleration x time
= 4 g (32 ft sec2)/g x 2 sec
= 256 ft sec2
= 256 ft sec (1nm/6080 ft) (3600 sec)/hour
= 152 nm/hr or knots


Relaxed G tolerance is most closely correlated positively with which of the following parameters?
a) The component of the aorta-to-eye distance that is in line with the net G forces (they hydrostatic column, h).
b) The reciprocal of h (1/h)
c) The size of the angle between the seat back and the vertical.
d) The size of the angle between the seat back and the net G force.
e) The cosine of the angle between the seatback and the net G force.

b) Relaxed G tolerance is the reciprocal of h (1/h).


A pilot notices during sustained high + Gz stress, which has been applied rapidly, that there is a certain delay before the onset of tunnel vision, greyout and/or blackout. How long after the necessary hemodynamic compromise (reverse flow or cessation of flow at the eye level) do the visual symptoms appear?
a) Within 0.5 seconds
b) 0.5 to 2 seconds
c) 2 to 10 seconds
d) 10 to 20 seconds

2 to 10 seconds.


Which factor is the least likely consideration to avoid G-LOC during maneuvering aircraft?
a) magnitude, direction, duration and onset rate of G's
b) Low visibility (IMC- Instrument Meteorological Conditions)
c) Anti-G Straining Maneuver (AGSM)
d) Push-Pull Maneuvers

B Low Visibility and Meteorological conditions may increase susceptibility to spatial disorientation, but it not a causal factor in G-LOC.


The purpose of the anti-G straining maneuver (AGSM) such as the M-1 or the L-1 is to:
a) Keep the venous blood in the extremities
b) Keep the venous blood in vital organs like the brain
c) Increase the pulse rate, thus raising cardiac output
d) Increase intra-thoracic pressure to maintain blood flow to the brain

d) AGMS increases intrathoracic pressure and this increased pressure forces blood flow in the heart to the brain.