Frequency of the "push-pull effect" in U.S. Air Force fighter operations.

BACKGROUND: Recent investigation into the push-pull effect (PPE), the reduction of +Gz tolerance when preceded by less than +1 Gz, has focused on centrifuge studies to demonstrate the presence of adverse cardiovascular responses. Maneuvers found to cause the Push-Pull Effect (PPEM) have not been studied previously in U.S. Air Force (USAF) fighter aircraft. The frequency of and extent to which PPEMs are performed in fighter aircraft are unknown. METHODS: Head-up display (HUD) videotapes from F-15 and F-16 air combat training missions were reviewed for the presence of PPEMs. The frequency of engagements containing PPEMs and the magnitude of the Gz profiles were noted. RESULTS: PPEMs were found in 11 to 67%, of engagements reviewed, depending on the nature of the training mission, with an overall average of 32%. The PPEMs that were observed contained segments of less than +1 Gz, ranging on average from 0.0 to 0.5 Gz for an average of 3.5 to 5 s duration. CONCLUSIONS: PPEMs are present in air combat training missions performed by today's USAF fighter aircraft and represent an operationally significant source of risk for accidents. These findings support continued research into the physiologic response to PPE and the development of countermeasures.

The "push-pull effect" and G-induced loss of consciousness accidents in the U.S. Air Force.

BACKGROUND: A recent Canadian Forces CF-18 Hornet aircraft accident has focused interest on the push-pull effect (PPE). PPE has not previously been identified in U.S. Air Force (USAF) G-Induced Loss of Consciousness (G-LOC) Accidents. The presence of maneuvers known to cause the push-pull effect (PPEMs) that lead to G-LOC accidents suggests that PPE is operationally significant and is a potential cause of G-LOC accidents. METHODS: USAF accident reports where G-LOC was found to be causal were reviewed for indications of a PPEM immediately prior to the G-LOC. Terminology in the narratives was used to indicate a PPEM in the accident sequences. RESULTS: In 3 of 24 mishaps, the presence of a PPEM was highly probable, while another 4 mishaps were found to have a probable association with PPEMs. The probable presence of PPEMs represents a significant percentage (12.5-29%) of USAF G-LOC accidents. CONCLUSION: USAF G-LOC accident reports contained descriptions that indicated the presence of PPEMs in accident sequences. This finding suggests that the PPE is an operationally significant source of risk for accidents in USAF high-performance aircraft.

Assessment of the anti-G straining maneuver (AGSM) skill performance and reinforcement program.

Initial high-G centrifuge training of USAF fast jet pilots was instituted in 1985. Also, since the mid-1980's, pilot awareness of G-induced loss of consciousness (G-LOC) has been enhanced by briefings, videotapes, and safety articles. Aircraft accidents caused by an improperly performed anti-G straining maneuver (AGSM), however, continue to occur. Deficiencies in the AGSM of pilots in flight have not been systematically studied. A test program to reinforce the proper performance of the AGSM in flight was initiated in the United States Air Forces Europe (USAFE) in 1993. Head-up display videotapes (HUD tapes) were recorded during flight and critiqued during debrief by flight leads for AGSM technique and continuity. Questionnaires were completed by F-16, F-15C, and F-15E pilots assigned to USAFE: 78 surveys were completed out of 110 distributed (71%). There were 57 pilots (73%) who reported one or more problems with their AGSM: 33 noted that the timing of their breathing was too quick (< 2 s cycle), 11 that their breathing was too slow (> 4 s), 9 that inhalation was too long, 18 occasionally did not "get the jump on the Gs," and 34 frequently or occasionally talked during +Gz exposures. Of the 105 reported deficiencies, 67 (64%) were mostly or completely corrected: 30/33 (91%) if the timing of breathing was too quick, 8/11 (73%) if too slow, 5/9 (56%) if inhalation too long, 12/18 (67%) "jump on the Gs," and 12/34 (35%) if they talked. This program was most successful in remediating timing problems with the AGSM.

Chronic glomerulonephritis: medical and aeromedical disposition.

A case of presumptive IgA nephropathy (IgAN) in an aircrew member is presented IgAN is a common form of glomerulonephritis associated with IgA deposits in the mesangium of the kidney. Although in the past progression of IgAN was thought to be infrequent, it is now known to lead to end-stage renal disease in 30-35% of patients. In most cases, the presence of IgAN does not represent a risk of sudden incapacitation to aviators. Nevertheless, the significant risk of eventual progression requires adequate follow-up for the patient's welfare as well as the maintenance of aeromedical fitness. Although as a flight surgeon it is often tempting to focus on the question of flight status when evaluating a specific condition, the primary responsibility of any physician is to his or her patient's well-being.