distributed by: national technical information service summary page the problem from the military...

AD-AO14 423

ORIENTATION-ERROR ACCIDENTS IN REGULAR ARMY UH-1

AIRCRAFT DURING FISCAL YEAR 1971: RELATIVEINCIDENCE AND COST

W. Carroll Hixson, et al

Naval Aerospacp Medical Research Laboratory

Prepared for:

Army Aeromedical Research Laboratory

11 June 1975

DISTRIBUTED BY:

National Technical Information ServiceU. S. DEPARTMENT OF COMMERCE

------ ',-. . .. tthtLliL,,,~~.~ .

Unclassified_____

DOCUMENT CONTROL DATA. P & D

Naval Aerospace Medical Research Laboratory UnclassifiedPensacola, Florida 32512__________ ______N/A

ORIENTATION-ERROR ACCIDENTS IN REGULAR ARMY UH-1 AIRCRAFT DURING FISCALYEAR 1971: RELATIVE INCIDENCE AND COST __ _

A' ----------.----- ~ - __ ___ _ __ _ _

W. Carroll Hixson and Emil Spezia

6 *Il011, 11 0 - I.. T 01A L. f1O0 V04 PA GI (I, 5i r

I1I June 1975 __ _ _ _ _ _ _ _31 1A. ((t14 I A, N 1 l A- l t41 (( qIl. 0• i1C.1OIA to lt's ' •i t 011 NUMIPI 144SI

h 1 ....... '14.1) BuMed NAMRL- 1218MF51.524.005-7026BA1 J

,"hv 1 li II It" lo ll r 410(54 (An l)'ll /Inlla tlnbe flit Ibm l t iny h. S*ljtied

USAARL Serial No. 75-211 0 ~l S I N11lt IONl S T AIS N

SApproved for public release; distribution unlimited.

Joint report with U. S. Army AeromedicalResearch Laboratory, Fort Rucker, Alabama

This report is the fifth in a longitudinal series of reports dealing with the magnitude of thepilot disorientation/vertigo accident problem in Regular Army UH-1 helicopter operations. Inci-dence and cost data presented for fiscal year 1971 include a total of 31 major and minor orienta-tion-error accidents (15 of which were fatal), resulting in 44 fatalities, 52 nonfatal injuries, anda total UH-1 aircraft damage cost of $6,337,446.

DD POI/m 14 73 PAt' Unclassified",/l /I'4 4., / .. ..- I•. . hrH (Id..-.nlldlrf

L Unclassified

4LINK A LINKS0 LINK C

PROLIC WY ROLE WT ROLE WT

Army aviation

Aviation medicine

Aviation safety

Aircraft accidents

Pilot disorientation

Vertigo

UH-1 helicopters

CEN

D 473Ucasfe

D D POEM 147 S~BAC)) U Classified io

..... . ..

259081N4MRL-1218 USAARL

Serial No. 75-21

ORIENTATION-ERROR ACCIDENTS IN REGULAR ARMY UH-I AIRCRAFT

DURING FISCAL YEAR 1971: RELATIVE INCIDENCE AND COST

W. Cartoll HIxson and Emil Spezia

W.•

%I OF

ARMY- NAVYJoint Report

• /

June 1975

RptoPduced by

NATIONAL TECHNICAL "INFORMATION SERVICE

U S r ) p tj .n . r, f •, o rC m o c f. 1 dcngb•,l VA. 22151

ý%d for public releaw.; distribution unlimited.

NAMRL-1218 USAARLSerial No. 75-21

ýk.

ORIENTATION-ERROR ACCIDENTS IN REGULAR ARMY UH-1 AIRCRAFT

DURING FISCAL YEAR 1971: RELATIVE INCIDENCE AND COST

W. Carroll Hixson and Emil Spezia

[1.

Bureau of Medicine and SurgeryMF51.524.005-7026BA1J

U. S. Army Aeromedical Research Laboratory

11 June 1975

Approved by Released by

Ashton Graybi'I, M.D. Captain N. W. Allebach, MC, USNAssistant for Scierit-fic Programs Commanding Officer

NAVAL AEROSPACE MEDICAL RESEARCH LABORATORY

PENSACOLA, FLORIDA 32512

I' 19

SUMMARY PAGE

THE PROBLEM

From the military mission viewpoint, the amount of research effort to be expendedon the solution of a given aviation medicine problem must be keyed to the operational

cost of the problem. Therefore, a necessary first step in the development of a solutionis the assimilation of data that define the magnitude of the problem. Though orientation-error accidents involving pilot disorientation and vertigo have been long recognized toexist, little quantitative data are available , describe the actual incidence and costof such accidents in Army aviation.

FINDINGS

To initiate the action necessary to establish the magnitude of the orientation-error problem in Army cviation, an interservice research program was organized underthe joint sponsorship of the U. S. Army Aeromedical Research Laboratory, the U. S.Army Agency for Aviation Safety, and the Naval Aerospace Medical Research Laboratory.The first task was the construction of an operational definition of an orientation-erroraccident. The assimilation of data pertaining to the incidence and cause of such acci-dents and their act,)al and relative costs in terms of fatalities, injuries, and aircraftdamage was then set as the working objective of the program. Accordingly, the decisionwas mode to implement a five-year longitudinal study of all major and minor orientation-error accidents involving Regular Army flight operations beginning with fiscal year 1967.

' Findings are being summarized on a fiscal-year basis in three separate lines of reports:The first line is devoted to defir.ing the over-all magnitude of the orientation-error prob-lenm .n all aircraft types; the second line to the presentation of similar incidence andcost data for accidents involving only the UH-1 aircraft, the predominant rotary wingaircraft in the Army inventory; and the third line to the description of the various causalfactors found to be present in the major UH-1 orientation-error accidents.

This specific report is the fifth in the series dealing with the magnitude of theorientation-error problem in UH-1 aircrafk. Incidence and cost data are presented forall major and minor orientation-error accidents involving Regular Army UH-I flightoperations that were detc :ted in the search of the fiscal year 1971 accident files.

The findings in this report are not to be construed as an official Department of theArmy position, unless so designated by other authorized documents.

ii

ACKNOWLEDGMENTS

The authors wish to thank Colonel R. W. Bailey, MSC, USA, CommandingOfficer, U. S. Army Aeromedical Research Laboratory, for his direction and assist-once in the initial setup and structure of the project and for his continued support ofits research objectives. The authors wish to thank also the director of the U. S. ArmyAgency for Aviation Safety and his data processing staff for making the master acci-

2 dent files available for analysis and for compiling the all-accident and pilot-erroraccident statistics included in this specific report. NAMRL personnel whom the authorswish to acknowledge include Mr. A. N. Dennis and Mr. C. A. Lowery, both of theBioenvironmental Engineering Division, who assisted in the compilation and graphicallayout of the data, and Mr. R. C. Barrett of the Visual Aids Branch, who photographedthe report figures.

iiii

--------------------

LIST OF TABLESPage

Table 1. All Accident Types ................................................... 4

Table II. Pilot-Error Accidents Only ......... .................................... 13

Table Ill. Orientation-Error Accidents Only ....................................... 17

LIST OF FIGURES

Figure IA. Weighting Factor: Total UH-1 Flying Hours ................................ 5

Figure 18. Weighting Factor: Total UH-I Landings ................................... 5

Figure 2. All UH-1 Accident Types: Incidence of Major and Minor Accidents ............. 6

Figure 3A. All UH-I Accident Types: Total Number of Fatal .,ccidents .............. 7

Figure 38. All UH-I Accident Types: Total Number of Fatalities ..... ................... 7

Figure 3C, All UH-1 Accident Types: Total Number of Nonfatal Injuries ................... 7

Figure 3D. All UH-1 Accident Types: Total Aircraft Dollar Damage ...................... 7

SFigure 4A. All UH-1 Accident Types: Accident Rate per 100,000 Hours .................... 8

Figure 48. All UH-I Accident Types: Accident Rate per 100,000 Landings ................. 8

Figure 5. UH- I Pilot-Error Accident Types: Incidence of Major and Minor Accidents .... 10

Figure 6A. UH-1 Pilot-Error Accident Types: Total Nurrber of Fatal Accidents. .......... ... 11

Figure 68. UH-1 Pilot-Error Accident Types: Total Number of Fatalities ................... 11

Figure 6C. UH-1 Pilot-Error Accident Types: Total Number of Nonfatal Injuries ......... .... 11

Figure 6D. UH-1 Pilot-Error Accident Types: Total Aircraft Dollar Damage ............. .... 11

Figure 7A. UH-1 Pilot-Error Accident Types: Accident Rate per 100,000 Hours .......... ... 12

Figure 7B. UH-1 Pilot-Error Accident Types: Accident Rate per 100,000 Landings ........ ... 12

Figure 8. UH-1 Orientation-Error Accident Types: Incidence of Major and Minor Accidents . 14

Figure 9A, UH-I Orlentation-Error Accident Types: Total Number of Fatal Accidents ...... 15

Figure 98. UH- 1 0rientation- Error Accident Types: Total Number of Fatalities .......... .... 15

Figure 9C. UH-1 Orientation-Error Accident Types: Total Number of Nonfatal Injuries ..... .. 15

Figure 9D. UH-1 Orientation-Error Accident Types: Total Aircraft Dollar Damage ........ ... 15

Figure 10A, UH-1 Orientation-Error Accident Types: Accident Rate per 100,000 Hours ...... .. 16

Figure 10B. UH-1 Orientation-Error Accident Types: Accident Rate per 100,003 Landings .... 16Figure 11. Comparative Costs: Percent Fatal Accidents ......... ...................... 19

Figure 12. Comparative Costs: Average Number Fatalities per Fatal Accident ........... .... 20

Figure 13. Comparative Costs: Average Number NonfataI Injuries per Accident ......... .... 21

F;gure 14. Comparative Costs: Average Dollar Damage per Accident ..................... 22

Figure 15. UH-1 Orientation-Error Accidents: Parce.it Total Incidence ................... 23

Figure 16. UH-1 Orientation-..? or Accidents: Percent Total Fatal Accidents ............ ... 24

Figure 17. UH-1 0rientation-Error Accidents: Percent Toaal Fatalities .... ............... 25

Figure 18. UH-1 Orientation-Error Accidents: Percent Dollar Cost ....................... 26

iv

..I........ "T "91P P M

INTRODUCTION

To investigate the operaflonal role of pilot disorientation and vertigo in the pro-duction of orientation-error type aircraft accidents, the authors have organized an inter-service research program under the joint sponsorship of the U. S. Army AeromedicalResearch Laboratory (USAARL), the U. S. Army Agency for Aviation Safety (USAAAVS),and the Naval Aerospace Medical Research Laboratory (NAMRL). Since little quantifieddata were available to describe the actual magnitude of the orientation-error prob!em inRegular Army flight operations, the decision was made to conduct a five-year longitudi-nal study, beginning with fiscal year 1967, of all Army aircraft accidents that involvedan erroneous judgment of aircraft motion or attitude on the part of the pilot. Two sepa-

0 rate, but related, project objectives were set for the longitudinal study. The first wasto extract and assimilate data from the USAAAVS master aircraft-accident files whichdefine the actual and relative cost of orientation-error accidents to Regular Army flightoperations. These data, by defining the operational magnitude of the problem, wouldthen serve to define the extent of the research support which should be devoted to itssolution. The second working objective was to extract data on a case-history basiswhich would describe the various pilot/aircraft/mission/environment factors found to bepresent in each of the orientation-error accidents. Assimilation and analysis of thesedata over the study period would result in better knowledge of the most common opera-tional causes of orientation-error accidents and thus point out those research directionswhich offer the greatest potential toward the reduction of accident incidence.

M, The results of the longitudinal study are being summarized in three separate linesof reports, with one report in each line prepared for each fiscal year of the five-yearstudy. The first line of reports (for example, ref. 1) is devoted to defining the incidenceand cost of all major and minor orientation-error accidents involving all aircraft types,fixed wing as well as rotary wing, that occurred in Regular Army flight operations foraach fiscal year. Since the UH-1 "Huey" helicopter has been, and is, the predominantaircraft in the Army rotary wing inventory, the second line of reports (for example, ref.2) is devoted to defining the magnitude of the orientation-error accident problem in onlythis aircraft. The layout and format of this line of reports are almos. identical to thoseof the first line. The third line of reports (for example, ref. 3) deals exclusively withthe various causal factors found to be present in all of the major UH-1 orientation-erroraccidents. Typical dcta to be presented include phase of flight, time of day, type ofmission, pilot experience, physiological factors, psychological factors, facility factors,environmental factors, and the like.

This specific report is the fifth in the series dealing with the magnitude of theorientation-error problem in UH-1 aircraft. Incidence and cost data are presented forall major and minor orientation-error accidents involving Regular Army UH-1 flightoperations that were detected in the search of the fiscal year 1971 accident files. Inaddition, corresponding cost data are presented for both all accident types, regardlessof cause, and for pilot-error accident types so as to better establish the relative magni-tude of the UH-1 orientation-error accident problem.

!t I

PROCEDURE

A basic requirement for the commencement of this study was a workable definitionof the class of accidents to be defined as involving orientation error. The reader isreferred to previous reports (refs. 1-3) for a comprehensive definition and discussion ofits rationale. Briefly, orientation is considered to involve the correct determination ofthe dynamic position and attitude of an aircraft in three-dimensional space. The keyword here is dynamic, which implies that full knowledge of the motion as well as staticattitude and position is required to define its instantaneous spatial orientation. Accord-ingly, a pilot is considered to have made an orientation error whenever his perceptionof the motion and attitude of his circraft differs from the true motion or attitude; i.e.,the true orientation of the aircraft. An orientation-error accident is then defined as onethat occurs as a result of an incorrect control or power action taken by a pilot (or a cor-rect action not taken) due to his incorrect perce, fion of the true orientation of his air-craft.

With this definition of orientation-error accidents serving as a classhication refer-ence, an experienced classifier read all briefs in the USAAAVS master accident filesand selected all major and minor accidents of this type occurring during fiscal year 1971oFor redundancy, the entire accident files were also searched by sifting the coded sum-maries that USAAAVS prepares for each accident for a wide range of indicator terms.

The authors then reviewed the accident briefs independently for the purpose ofestablishing whether or not an orientation-error accident classification would result. Inaddition, the comprehensive master file on each suspect accident was obtained and re-viewed. Whenever there was serious question as to the contribution of orientation errorto the accident or where equally weighted alternative causal factors were present, thent'ie accident v/as not included in the classification. The net effect of this policy is togive a conservative estimate of the magnitude of the orientation-error accident problem.

RESULTS AND DISCUSSION

To place the operational significance of UH-1 orientation-error accidents inproper perspective, it is necessary to have at least a cursory understanding of the inci-dence and cost of UH-1 aircraft accidents in general. As with the previous UH-1 reports(reFs. 2,5,8, 11) this is accomplished as follows: The lead section below is devoted todescribing the over-all cost of all Army UH-1 aircraft accidents, regardless of type orlocation, that occurred during fiscal year 1971. In a second section, equivalent datain a nearly identical format are presented to isolate those UH-1 accidents in the firstsection that were classified by USAAAVS as involving one or more pilot-error factors.Incidence and cost statistics pertaining to UH-1 orientation-error accidents only are thenpresented in a third section. By using these three sets of data as independent references,it then becomes possible to derive some quantitative insight into the relative, as well asactual, cost of UH-1 orientation-error accidents in Army flight operations. Selectedcomparative relationships are presented in the last section of the report.

2

To facilitate the point-by-point comparison of these fiscal year 1971 UH-1 data?'. with corresponding data derived for other fiscal years of the longitudinal study, the lay-

out and numbering of all tables and figures in this report follow identically those used inthe previous UH-1 reports (refs. 2,5,8, 11).

ALL TYPES OF UH-1 AIRCRAFT ACCIDENTS

The data presented in this section describe the incidence and cost of all major andminor UH-1 helicopter accidernts involving Regular Army flight operations during fiscalyear 1971. Separate data groupings are provided for those accidents that occurred inVietnam, those accidents that occurred elsewhere, and their combinei total. Since thevast majority of the ar..idents that do not occur in Vietnam (VN) take place within thecontinental limits of the United States, the abbreviation US is arbitrarily used to denoteul• accidents that do not occur in Vietnam. It should be realized then that the US datagrouping will include a small number of accidents that may have occurred, for example,

• in Europe, Afric.:i, or elsewhere. A second point to be stressed is that the VN data per-

tain strictly to accidents, not losses due to enemy action.

In the interpretation of the accident statistics to follow, it becomes possible tocompare VN and US accident incidence only when some common measures of aircraftutilization are selected as weighting factors. A similar requirement exists for compari-son of accident incidence in one given fiscal year with incidence in other fiscal years.To establish such reference, percent aircraft inventory, total flying hours, and total air-craft landings are used as basic weighting data in this report. These data, as well as theincidence and cost statistics discussed in this section, are summarized in Table I.

The aircraft inventory data listed in Table I show that for fiscal year 1971, theaverage number of UH-1 aircraft operating out of VN was 43.59 perc.Int of the totalUH-1 inventory. However, the total flight hours and total landings data shown in Fig-ure 1 show a greater utilization in VN, i.e., a VN/US total hour ratio of 2.14 to 1and a VN/US total landings ratio of 1.87 to 1.

With these aircraft utilization data serving as background reference, it becomespossible to make a weighted interpretation of the raw accident data presented in Table I.Selected excerpts from these data are presented in Figures 2 and 3. The numericol inci-dence of all major and minor UH-1 aircraft accidents, regardless of type or causal factor,is plotted in Figure 2. The cost of these accidents, as measured by the number of fatalaccidents, number of fatalities, number of nonfatal injuries, and aircraft dollar damageis outlined in Figures 3A through 3D, respectively.

In terms of the over-all UH-1 accident problem, these data show that during fiscal

year 1971, there were a total of 299 accidents (54 of which were fatal), resulting in

180 fatalities, 398 nonfatal injuries, and a UH-1 aircraft damage cost of $47,375,401.The Vietnam contribution to this total was 250 accidents (49 of which were fatal), result-ing in 166 fatalities, 356 nonfatal injuries, and an aircraft damage cost of $40,389, 140.In all cases, the unweighted incidence and cost of accidents occurring in VN exceeded

V 3

TABLE I

FISCAL YEAR 1971 DATA

ALL ACCIDENT TYPES UH- 1 AIRCRAFT ONLY

U.S. VIETNAM ALL VN to USACCIDCNI INDEX ACCIDENTS ACciDENTS ACCIDENTS RATIO

Major Accidents 43 242 285 5.63

Minor Accidents 6 8 14 1.33

Total Accidents 49 250 299 5.10

Aircraft Inventory Percent Total 56.41 ...... 43.59 100.00) 0.77

Total_ FiHours 676,776 1,445,392 2,122,168 2.14

Total Landings ___. 2,433,753 4,552,239 6,985,992 1.87

Major Accidents per 100,000 Hours 6.35 16.74 13.4" 2M I

Minor Accidentsjer 100,000 Hours 0.89 0.55 0.66 0,63

Total Accidents peýr 0,000 Hours 7.24 17.30 14.0S 2.39

Major Accidentsper 100,.000 T, Landins 1,77 5.32 4.0 3.01

Minor Accidents per 100,000 Landings 0.25 0.18 0.2C 0.71

Total Accidents per 100,000 Landings 2.01 5.49 4.2E 2.73

Total Dollar Cost 6,986,261 40,389, 140 47,375,401 5.78

Average Dollar Cost per Accident 142 161,556.56 158,446.1 1.13

Total Fatalities 14 166 180 11.86

Aea e Fatalities per Accident 0.29 0.66 0.60 2.32

Fatal Accidents - umber . .... _5 49 54 9.80

Fatal Accidents - Percent 10,21 19.60 18.06 1.92

Average Fatalities per Fatal Accident 2.80 3.39 _3.33 1.21

Total Nonfatal Injuries _1 42 356 _ .. 398 8.48

Avr_''Nonfcita. Injuries per Accident 0-86 1.42 1.3. 1.66

4

Ilk.F " I IT' U -1 AImIcAm

3.0 WEIGHTING FACTOR1* -TOTAL FLYING HOURS-

104;

44- 0 ' * * -

U.S. ALL VIll NA14

~,k 1 A AICVS AIRCRAF? AlCI?

4;

V il Uh1 AFlylAIT

WEIGHTING FACTOR-TOTAL LANDINGS -

. ,

Q'S' ALL VIlI MUM1BAINCIA11 AIECRAfU AIIC 1AVfO

Figure 1

Total flying hours (A) and total landings (B) by location of UH-1 (Huey) helicopter aircraft flownin Regular Army flight operations during fiscal year 1971. In ]A, the right-hand bar indicatestotal hours flown in Vietnam. the left-hand bar total hours flown elsewhere (primauily in the United

States), and the central bar the direct sum of the adjacent data to either sido. The format of thetotal landing data in 1B follows identically. For that year, 2.14 times as many hours were flown in

Vietnam as were flown elsewhere. Correspondingly, 1.87 times as many landings were made inVietnam as were made elsewhere.

5

FY71 ALL ACCIDENT TYPES UH-1 AIRCRAF1

800 INCIDENCE OF MAJOR AND MINORST ACCIDENTS

600-

hA

Lai

e 400-

"C.3

U.S. ALL VIET NAM

ACCIDENTS ACCIDENTS ACCI DE NTS

Figure 2

All UH-1 Accident Types: Total number of major and minor UH-1 aircraft accidents of all typesthat occurred in Regular Army flight operations during fiscal year 1971. The right-hand bar denotesthe number of UH-1 accidents that occurred in Vietnam, while the left-hand bar denotes the numberof accidents that occurred elsewhere. This latter bar has been identified as "U. S. Accidents" forconvenience since the vast majority of the accidents that dc not occur in Vietnam (VN) take placewithin the continental lfinits of the United States (US). This convention applies throughout theremaining report figures. The central bar totcalizes the adjacent VN and US data. As d'iscribed intWe text, the VN data pertain to accidents, not losses oue to enemy action. The number of acci-donts that occurred in VN wus 5.10 t1 ines the number of accidents that occurred elsewhere.

i• , . .. . ... ..

FlTI ALL ACCI|IUT rAPED UKI ULRCRAFt ALL ACIDINT TYPlS N -I AIRCRAFTNUMBER OF FATAL

ACCIDENTS FATALITIES-

"Utoo

I ,A'lot

r' O ....* I . .....Z1L ..... ' _____!

U.S ALL Vitt NAM U.S. AiL Vlit MAN3 A ACCIDIS AIDINTI ACCINT$ 3 e UCCISC'.IS ACCIOIHT$

F- T ALL ACCI|I FI 1i1| U1*I AIRCRAFT v I ALL ACCIDiAt IYPIS 1U1 I AIICRAFI

loll COST LoT COST} NONFATAL INJURIES- -AIRCRAFT DAMAGE-

S|1t FOL

4#1 40 I--

if$ 29

L.S. AVIT NAM U.S, ALL VITT NAV' AC MI ALI I ANNI3 C UCCCCITINIS UCCASTID( ACCIAMS 3 CCINISS ACCIDENT$ ACCIICNIS

Figure 3

All UH-1 Accident Types: Total number of fatal accidents (A), total number of fatalities (B), totalnumber of nonfatal injuries (C), and total dollar cost of resulting UH-1 aircraft damage (D). In oilcases, the VN costs were greater.

7

Y" I Il A tt ACCIDENT lwI TtS UN Ia AIICAJ-• T

it .ACCIDENT NATET -PER 1~00O00 WLING HOURS -

20

All VIIt NAM4 A ACCIlI~tTU . ACCID[NIS ACCIDlIIIS

I~!ALL acc;IOlI YPI S t CVI HIAlC°IAV

4 1ACCIDENT RATE

PER 100,000 LANDINGS -

I;

I*if

4 B v rIIIo tMS ACCID T S A VItl N AI MS

Figure 4

All UH-1 Accident Types: Normalized incidence data showing the average number of LJH-1 acci-

derts per 100,000 flying hours (A) and average number of accidents per 100,000 landings (B). Theover-all rates were 14.09 accidents per 100,000 hours and 4.28 accidents per 100,000 landings.The VN rate was 2.39 times the US rate using hours as reference and 2.73 times the US rate using

landings as reference.

8

•,.7

those of accidents occurring elsewhere. That is, the VN/US total accident ratio was5. 10 to 1, the VN/US total fatal accident ratio was 9.80 to 1, the VN/US total fatal-ity ratio was 11.86 to 1, the VN,/US total nonfatal injury ratio was 8.48, and the VN/US averaoe cost per accident ratio was 1.13 to 1. In terms of total dollar damage, thecost of VN accidents was 5.78 times the cost of US accidents.

To facilitate the comparison of these fiscal year 1971 accident incidence data toaccident incidence in other fiscal years covered by the longitudinal study, the data inFigure 2 have been normalized relative to the total number of flying hours flown in each

r location and plotted in Figure 4A as the average number of accidents occurring every100,000 hours. The same normalization using tota! landings as reference was accom-plished for Figure 4B, which shows the accident rate for every 100,000 landings. Con-sidering ih. total number of UH-1 accidents, these data show that, on the average,there were 14.0)9 accidents per 100,000 hours and 4.28 accidents per 100,000 landings.The UH-1 data indicate that, even after normalization, the accident rate in VN wassubstantially greater than that elsewhere. That is, the accident rate in VN was 2.39times greater than the rate elsewhere using total houri as reference, and 2.73 timesgreater using total landings as reference.

UH-1 PILOT-ERROR ACCIDENTS

In this section, incidence and cost data are presented for all UH-1 accidents thatwere classified by USAAAVS as involving one or more pilot-error causal factors. Itshould be observed that this classification does not imply that pilot error was the only,or even the primary, accident causal factor. That is, this grouping includes all UH-1accidents involving one or more pilot erro~s even though, for example, materiel failure,maintenance shortcomings, or poor facilities may also have contributed to the accident.A further point, by definition, is that these pilot-error accidents are a subgroup of theall-accident statistics discussed in the previous section.

Incidence and cost data for these fiscal year 1971 pilot-error accidents are pre-sented in Table II and Figures 5 and 6. These data show that there were a total of 186major and minor UH-1 pilot-erro, accidents (36 of which were fatal), resulting in 109fatalities, 271 nonfatal injuries, and an aircraft damage cost of $28,888,732. As withthe all-accident data, the incidence and cost of pilot-error accidents that occurred inVietnam were considerably higher than those which occurred elsewhere. From Table IIit can be seen that the VN/US accident incidence ratio was 4.32 to 1, the VN/US fatalaccident ratio was 8.00 to 1, the VN/US fatality ratio was 8.08 to 1, the VN/US non-fatal injury ratio was 7.74 to 1, and the VN/US average cost per accident ratio was1.25 to 1. In terms of total dollar damage, the cost of VN accidents was 5.41 timesthe cost of US accidents.

In Figure 7, accident rate data are presented using the total hours and total land-ings data of Figure 1 as normalization reference. The over-all rates were 8.77 accidentsper 100,000 hours and 2.66 accidents per 100,000 landings. In VN and US, the rateswere 10.45 and 5.17 accidents, respectively, per 100,000 hours resulting in a \/N/US

9

PILOT-ERROR ACCIDENTS ONLY UH1I AIRCRAFT

400 INCIDENCE OF MAJOR AND MINORACCIDENTS

200

100

1*0 NAM

U.S. ALL VIET NAMACCIDENTS ACCIDENTS ACCIDENTS

Figure 5

UH-1 Pilot-Error Accident Types: Total number of major and minor UH-1 aircraft accidentsinvolving the presence of one or more pilot-error factors as classified by USAAAVS. The ,,umberof pilot-error accidents that occurred in VN was 4.32 times the number of accidents that occurredelsewhere.

10

IT

P5P1 1 0111 VI Bill ACIAII1S11 ONLY goI AIC V 11111 111 piti [list ACCIIINTS SILY IN-1 AISCIAN I

1:1 NUMBER OF FATAL COSTACCIDENTS " FATALITIES-

Illn

qMI 4 !

.. Fd6A 11

I S A tLLVtt III I •V llt WAN6 A iillll ACII~l CCII|$6 i~ltlT$ ACCISlKIII ACCIllITI

1`i 1111- 011111 ACCIVIIS MYl 1111.1 AINCIAFT PILOT 1111 W(il CIWI$T ONLY V11. AIICIAVT

COST COST-NONFATAL INJURIES- -AIRCRAFT DAMAGE -

ill• IS-..

l l

Its1 41

111I IA-

IIs

IAll Tiff NAN ALI W Y NAN

6 C ACCIDIS ACCIII I ICIIIil L ACCII(NIS ACCIINiS ACCIS IIS

Figure 6

UH-1 Pilot-Error Accident Types: Total number of fatal accidents (A), total number of fatalities(B), total number of nonfatal injurie. (C), and total dollar cost of resulting UH-1 aircraft damage(D). As with the all accident data, the loss wao greater in VN.

11

S~.. ..- ............

36. ACCIDENT RATEItPER 100,000 FLYING HOURS- I

is

I,

333Pilot A~lso ACCIAL1t 0613 IN I AMAIIA3

ACCIDENT RATE*PER 100,000 LANDINUS -

V $ l it A

79B ACCIDIIA3 ACCIDNItS AMCItIVNT

Figure 7

UII- 1 Pilot-Error Accident Types! Normalized incidence data showing the average number ofUJH- I pilot-error accidents per 100,000 flying ho-urs (A) and average number of accidents per100,000 landings (B). The total hours and total landings data of Figure 1 served as normaliza-tion reference. The"e rate data are intended only as a fiscal year 1971 baseline reference forcomparison with similar data for other fiscal years of the longitudinal study. The over-all rateswere 8.77 pilot-error accidents per 100,000 hours and 2.66 accidents per 100,000 landings.The VN rate was 2.02 times the US rate using hours as reference and 2.31 times the US rateusing landings as reference.

12

ratio of 2.02 to 1. With landings as reference, the VN and US rates were 3.32 and1.44 accidents, respectively, per 100,000 landings, which results in a VN/US ratio of2.31 to I.

1' UH-1 ORIENTATION-ERROR ACCIDENTSK

This section summarizes the incidence and cost of all UH-1 major and minor

orientation-error accidents detected in our review of the USAAAVS accident files forthe stated fiscal year. As detailed with selected qualifications in the procedure sectionof the first report in this series (ref. 2), this listing includes all accidents that were clas-sified as involving incorrect pilot perception of aircraft motion or attitude. The readerI, should recognize that the orisntation-error accidents discussed herein are a subgroup ofPt, pilot-error accident statistics presented in ihe previous section.

Incidence and .. ost data for these fiscal year 1971 orientation-error accidents areFresented in Table III and Figures 8 and 9. These data show that there were a total of31 major UH-1 orientation-error accidents (15 of which were fatal), resulting in 44

R fatalities, 52 nonfatal injuries, and an aircraft damage cost of $6,337,446. For thisfiscal year, there were no minor accidents. As with the all-accident and pilot-erroraccident data, the orientation-error data show a much higher acrident incidence andpersonnel cost in VN; i.e., the VN/US total accident incidence ratio was 5.20 to 1,the VN/US fatal accident ratio was 6.50 to 1, and the VN/US nonfatal injury ratio was5.50 to 1. Ir the case of the VN/US average dollar cost per accident ratio, the VN

TABLE IIFISCAL YEAR 1911 DATA

PILOT-ERR2)R ACCIDENTS ONLY UH-I AIRCRAFT ONLYU.S. V!ETNAM ALL VN to US

ACCIDENT INDEX ACCIDENTS ACCIDENTS ACCIDENTS RATIO

M ajor Accidents ... . ... .._29 145 174 5.00

Minor Accidents 6 6 12 1.00


Total Dollar Cost 4,510,056 24,378,676 28,88P,732 5.41

Average Dollar Cost per Accident 128,858.74 161,448.19 155.,315.76 1.25


Average Fataities per Accident 0.34 0.64 0.59 1.87

Fatal Accidents - Number 4 32 36 8.00

Fatal Accidents - Percent 11.43 21.19 19.36 1.86

Average Fatalities oer Fatal Accident 3.00 3.03 3.03 1.01

Total Nonfatal jnjuries __ _31 240 _ 271 7.74

A verage Nolfat~a Injuriesper Accident 0.891 1.59 1.46 1.80

13

FY71 ORIENTATION - ERROR ACCIDENTS ONLY UH-I

60, INCIDENCE OF MAJOR AND MINORACCID"NTS

40-

i 30.-

20-AI

10

0-

U.S. ALL VIET NAM

8 ACCIDENTS ACCIDENTS ACCIDENTS

Figure 8

UH-1 Orientation-Error Accident Types: Total number of major and minor UH-1 aircraft acci-dents involving orientation error that were detected in the search of the USYAAVS masteroccident files for fiscal year 1971. The VN incidence was 5.20 times the US incidence.

14

0111111I1o0 111101 ACCl~ lO ItIS OW ON I 01 III|2 AN [11loo ACCIDIEIS 00•- UK I

"NUMBER OF FATAL COST

ACCIDENTS "FATALITIES -

%! : f .0I

40. '

U S, I A U l I A

9 A "'cI0IIIs 'Ns At"a'IN 's9 .]CDET A~CIP( Mr$ ACIII MI

1 1 1 1 1. H ot.. . ......... 1 1 ItA ION k... Ac.IN...- ON IT.. . "

10o COST IQ, COSTNONFATAL INJURIES- -AIRCRAFT DAMAGE-

S!1A. .... 1 ~l '-*

U I AMAN i i U S Alt VIEI NAM

9 C ACCIOINIS ACCIDENTIS ACaIDI 9 D ACCIDElTS ACCIDENiT AC NIDINI$

'•! Figure 9

UH-T Orientation-Error Accident Types: Total number of fatal accidents (A), total number offatalities (B), total number of nonfatal injuries (C), and total dollar cost of resulting UH-T air-craft damage (D), The higher cost of VN operations is mos! obvious.

15

Ii

OBIIINlAItO•-|aia AcCCIbfIt ONLY UMN 1

ACCIDENT RATE-PER 100,000 FLYING HOURS -

II

At L -

10 A ...... . . ACCI' WiMI' S

fOiI(XiAIIOU - lM ll cCgbI~fMIt aMIV 'lt

A ACCIDENT RATE

-PER 100,000 LANDINGS-

""t

I~ ~ u AL ..... NAM ..... ,10 B k"' I E ACCIO ItS

Figure 10

UH-1 Orientation-Error Accident Types: Normalized incidence data showing the average number

of UH-1 orientation-error accidents per 100,000 flying hours (A) and average number of accidents

per 100,000 landings (B). The total hours and total landings data of Figure I served as reference.These rate data are intended only as a fiscal year 1971 baseline reference for compaiison with

similar data for other fiscal years of the longitudinal study. The over-all rates were 1.46 orientation-

error accidents per 100,000 hours and 0.44 accidents per 100,000 landings. The VN rate was 2,44

times the US rate using hours as reference and 2.78 times the US rate using landings as reference.

16

TABLE IIISFISCAL YEAR 1971 DATA

ORIENTATION-ERROR ACCIDENTS ONLY UH-I AIRCRAFT ONLYU.S VIETNAM ALL 'VN to US

ACCIDENT INDEX ACCIDENTS ACCIDENTS ACCIDENTS RATIOMo'Maor Accidents 5 26 31 5.20

Minor Accidents 0 0 0 ---


Tota! Dollar C,.,t 888,296 5,449, 150 6,337,446 6.14

Average Dollar Cost per Accident 177,659.20 209,582.69 204,433.74 1.18


Average Fatalities per Accident 1.20 1.46 1.42 1.22

Fatal Accicents - Number 2 • 13 15 6.50

Fatal Accidents - Percent 40.00 50.00 48.39 1.25

i Average Fatalities per Fatal Accident 3.00 2.92 2.93 0.98

STotal Nonfatal Inj uries 18 44 152 5.501

Average. N.or.fatal Infu.ries per Accident 1.60 . 1.691 1.6B ] 1.0,6

cost was higher by 1.18 to 1. With regard to total dollar damage, the cost of orientation-error accidents that occurred in VN was 6. ',4 times greater than the cost of US accidents.

The accident rate data of Figure 10, derived from the total hours (A) ar:d totallandings (B) dat of Figure 1, indicate that there was an over-all average of 1.46 and0.44 orientation-error accidents per 100,000 hours and per 100,000 landings, respec-tively, for fiscal year 1971. These rates are lower than the corresponding rates for allfour preceding fiscal years. As with the all-accident and pilot-error accident data, theorientation-error accident rate was greater in VN. Based on equal flying hours, the VNrate was 2.44 times the US rate; with equal landings as reference, the VN rate was 2.78times the US rate.

COMPARATIVE INCIDENCE AND COST OF UH-1 ORIENTATION-ERROR ACCIDENTS

The arrangement of the data presented in the preceding sections was selected todifferentiate between the actual incidence and cost of all UH-1 accidents, pilot-errortype UH-1 accidents, and orientation-error type UH-1 accidents. In this section, selec-ted incidence and cost data are expressed in percentage figures, with the objective ofgaining some insight into the relutive contribution of orientation-error accidents to theover-all accident problem.

17

In FiGure 11, the total number of fc~tal accidents occurring within each of thethree accident classifications is expressed as the percentage of the total number of ucci-dents occurring within the given classification. For the combined total of VN and USaccidents, 18.06 percent of all accidents were fatal, 19.36 percent of all pilot-erroraccidents were fatal, and 48.39 percent of all orientation-error accidents were fatal.The probability of a fatal accident was highest when orientation error was present. How-ever, as indicated in Figure 12, when a fatal accident did occur, the average numberof fatalities that resulted wus about the same for all types, pilot-error, and orientation-error accidenrs in fiscal year 1971. In terms of the average number of nonfatal injuriesresulting from an accident, as indicated in Figure 13, t. e cost was only slightly higherfor orientation-error accidents and lower for pilot-errcr accidents. The average dollarcost of an accident, as shown in Figure 14, was also higher for the orientation-errorclass of accidents. The relative magn;tude of this damage can be assessed on the basisof the replacement cost of a UH-1 which then was slightly greater than $250,000.

In Figures 15 through 18, orientation-error accident statistics are expressed astheir pe,-cent contribution to both the a!l-accident and pilot-error accident statistics.Thus in Figure 15, the total number of orientation-error accidents is expressed as thepercent incidence of the total numLtr of all accidents and percent incidence of the totalnumber of pilot-error accidents. For fiscal year 1971, orientatior,-error accidents ac-counted for 10.37 percent of all accidents and 16.67 percent of all pilot-error accidents.

As shown in Figure 16, the contribution of orientation-arror fatal accidents to theover-all fatal accident problem was =onsiderably greater than its contribution to thetotal accident incidence. Of the total number of fatal accidents of all types, orienta-tion-error accidents accounted for 27.78 percent. Of fatal pilot-error accidents, 41.67percent were due to orientation error. The same trend follows for total fatalities as indi-cated in Figure 17. Fatalities due to orientation-error accidents accounted for 24.45percent of all fatalities, 3nd 40.37 percent of all pilot-error fatalities. In terms of theaircraft dollar cost of orio;ntation-error accidents, they contributed 13.38 percent of thetotal cost of dll accidents, and 21.94 percent of the total cost of all pilot-error acci-dents (Figure 18).

As with the previous UH-1 incidence and cost reports (refs. 2,5,8,11), a relatedreport will be prepared to describe the various accident factors found to be present ineach of the fiscal year 1971 major UH-1 orientation-error accidents.

This report completes the compilation of accident incidence and cost data for the

fiscal years 1967 through 1971 period. A final report will be prepared to summarize theover-all findings of this five-year I igitudinal study of orientation-error accidel.ts inRegular Army operation of the UH-1 aircraft.

18

f Y11 UH-1 AIRCRAFT

!•,•!• 50. PERCENT FATAL ACCIDENTS

40-

30

20 ALL ALL VNVK

10 usus

ALL PILOT-ERROR ORIENT. ERROR11 ACCIDENTS ACCIDENTS ACCIDENTS

Figure 11

Comparative incidence of fatal accidents expressed as the percent of the total number of accidents

within the "All Accident Type, ' "Pilot-Error Accident Type, " and "Orienration-Error AccdentType" classifications that resulted in one or more fatalities, Orientation-error accidents had the

greatest percent incidence of fatal accidents.

19

FY71 UH-1 AIRCRAFT

8.0- AVERAGE FATALITIESPER FATAL ACCIDENT

6.0

4.0-AAL

ALL

VN ALLALus VN US N

2.0

ALL PILOT-ERROR ORIENT. ERRORACCIDENTS ACCIDENTS ACCIDENTS

Figure 12

Average number of fatalities per fatal accident for each of the three basic accident type classifications.

20

FY'1 UH-I AIRCRAFT

4.0 AVERAGE NONFATAL INJURIES

PER ACCIDENT

3.0

- -

z

S"iALALL

ALL VN usVIN

n .!us us

"' .11 I

ALL PILOT-ERROR ORIENT. ERROR13 ACCIDENTS ACCIDENTS ACCIDENTS

Figure 13

Average number of nonfatal injuries per accident for each of the three basic accident type classifications.

21

F Y 71 UH-1 AIRCRAFT

250. AVERAGE $ COSTPER ACCIDENT

ALL--- VN

200

usALL ALL

VN VN150 V

-J US

IdI

us

S100

ALL ,LOT -ER ROR ORIENT. ERROR14ACCIDENTS ACCIDENTS ACCIDENTS

1,14

Figqure 14

Average d~llaf cost of ahiacfot damage per accident for each of the three basic accident classifi-

cation%. C )ttike damagce to a UH•-1 aircraft appioximates $2.50,000.) The average cost of

orientaition-errof occide:nt, .,ligjhtly exceeds the cost of the other two accident classifications.

22+

250

.•~~~~~~~~~~~~ ... .. .... •.••• •.4•.• •,•- . -.. .

F Y71 UH-I AIRCRAFT

20 r ORIENTATION-ERROR ACCIDENTS- PERCENT INCIDENCE -

' "AALLVN

{J

15-

us

ALL10 us VN

ALL PILOT-ERROR

15ACCIDENTS ACCIDENTS

Figure 15

Percent contribution of all I.1H-1 orientation-error accidents to the total number of UH-1 accidents

occ-uning within the "All Accident Type" and "Pilot-Error Accidert Type" classifications. Orienta-

tio',-eiror o•-.ccdents accounted for 10.37 percent of all accidents and 16.67 percent of all pilot-error aiccidents.

23

FY71 UH-1 AIRCRAFT

ORIENTATION--ERROR FATAL ACCIDENTS- PERCENT INCIDENCE -

100.

860"

C.)

60

SUS ALL

S40 ,-US VN

ALL

VN

ALL PILOT-ERROR16 ACCIDENTS ACCIDENTS

Figure 16

Percent ontribution of fatal UH-1 orientation-error accidents to the total number of fatal accidentsoccutring within the "All Accident Type" and "Pilot-Error Accident Type" classifications, Fatal

orientation-error accidents accounted for 27.78 percent of all fatal accidents and 41 .67 percent ofall fatal pilot-erof accidents.

24

"F Y7I UH-1 AIRCRAFT

ORIENTATION-ERROR ACCIDENT FATALITIES-PERCENT TOTAL FATALITIES -

•. 80.

(- 60.ic

us', • ALL

40' us A

ALL

20 VN

1174

ALL PILOT-ERROR

17 ACCIDENTS ACCIDENTS

Figure 17

Percent contribution of all UH-1 orientation-error accident fatalities to the total number of fatal-ities occurring within the "All Accident Type" and "Pilot-Error Accident Type" classifications.Fatalities due to orientation-error accidents accounted for 24.45 percent of the total number ofaccident fatalities and 40.37 percent of Oie pilot-error accident fatalities.

25

FY71 UH-1 AIRCRAFT

50 ORIENTATION- ERROR ACCIDENT COST-PERCENT TOTAL COST-

40

30,

ALLVI'

20 us

ALL

us10

ALL PILOT-ERROR18 ACCIDENTS ACCIDENTS

Figure 18

Pewcent contributicn of the total dollar cost of all UH-1 orientation-error accidents to the totaldMlar cost of all accidents occurring within the "All Accident Type" and "Pilot-Error AccidentType" classifications. The dollar cost of orientation-error accidents accounted for 13.38 percentof the total cost of all accidents and 21.94 percent of the total cost of all pilot-error accidents.

26

.% .......

REFERENCES

I. Hixson, W. C., Niven, J. I., and Spezia, E., Orientation-error accidents inRegular Army aircraft during fiscal year 1967: Relative incidence and cost.NAMRL-1 107 and USAARL Serial No. 70-14. Pensacola, FL: Naval AerospaceMedical Research Laboratory, June 1970.

2. Hixson, W. C., Niven, J. I., and Spe-ia, E., Orientation-error accidents inRegular Army UH-1 aircraft during fiscal year 1967: Relative incidence andcost. NAMRL-1108and USAARL Serial No. 71-1. Pensacola, FL: NavalAerospace Medical Research Laboratory, August 1970.

3. Hixson, W. C., Niven, J. I., and Spezia, E., Major orientation-error accidentsin Regular Army UH-1 aircraft during fiscal year 1967: Accident factors.NAMRL-1109 and USAARL Serial No. 71-2. Pensacola, FL: Naval AerospaceMedical Research Laboratory, October 1970.

4. Niven, J. I., Hixson, W. C., and Spezia, E., Orientation-error accidents inRegular Army aircraft during fiscal year 1968: Relative incidence and cost.NAMRL-1143 and USAARL Serial No. 72-4. Pensacola, FL: Naval AerospaceMedical Research Laboratory, September 1971.

5. Niven, J. I., Hixson, W. C., and Spezia, E., Orientation-error accidents inRegular Army UH-1 aircraft during fiscal year 1968: Relative incidence and cost.NAMRL-1145 and USAARL Serial No. 72-5. Pensacola, FL: Naval AerospaceMedical Research Laboratory, October 1971.

6. Hixson, W. C., Niven, J. I., and Speza, E., Major orientation-error accidentsin Regular Army UH-1 aircraft during fiscal year 1968: Accident factors.NAMRL-1147 and USAARL Serial No. 72-6. Pensacola, FL: Naval AerospaceMedical Research Labcratory, October 1971.

7. Hixson, W. C., Niven, J. I., and Spezia, E., Orientation-error accidents in4 Regular Army aircraft during fiscal year 1969: Relative incidence and cost.

NAMRL-1161 and LSAARL Serial No. 72-13. Pensacola, FL: Naval AerospaceMedical Research Laboratory, April 1972.

8. Hixsrn, W. C., Niven, J. I., and Spezia, E., Orientation-error accidents inRegular Army UH-I aircraft during fiscal year 1969: Relative incidence and cost.NAMRL-1163 and USAARL Serial No. 73-1. Pensacola, FL: Naval AerospaceMedical Research Laboratory, August 1972.

9. Hixson, W. C., Niven, J. I., and Spezia, E., Major orientation- :-ror accidentsin Regular Aimy UH-1 aircraft during fiscal year 1969: Accident factors.NAMRL-1169 and USAARL Serial No. 73-2. Pensacola, FL: Naval AerospaceMedical Research Laboratory, October 1972.

27

...... .....

10. Niven, J. I., Hixson, W. C., and Spezia, E., Orientation-error accidents inRegular Army aircraft during fiscal year 1970: Relative inciden,:e and cost.NAMRL-1188 and USAARL Serial No. 74-3. Pensacola, FL: Naval AerospaceMedical Research Laboratory, August 1973.

11. Niven, J. I., Hixson, W. C., and Spezia, E., Orientation-error accidents inRegular Army UH-1 aircraft during fiscal year 1970: Relative incidence andcost. NAMRL-1192 and USAARL Serial No. 74-5. Pensacola, FL: Naval

Aerospace Medical Research Laboratory, September '973.

12. Hixson, W. C., Niven, J. I., and Spezia, E., Major orientation-error accidentsin Regular Army UH-1 aircraft during fiscal year 1970: Accident factors.

NAMRL-1202 and USAARL Serial No.74-12. Pensacola, FL: Naval AerospaceMedical Research Laboratory, June 1974.

13. Hixson, W. C., Niven, J. I., and Spezia, E., Orientation-error accidents inRegular Army aircraft during fiscal year 1971: Relative incidence and cost.NAMRL-1 209 and USAARL Serial No. 75-6 . Pensacola, FL: Naval AerospaceMedical Research Laboratory, November 1974.

vi•

J

28

distributed by: national technical information service summary page the problem from the military...

Documents