Fatality and Injury Rates 

for Two Types of Rotorcraft 

Accidents

David Palmerton

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

October 2005

Final Report

DOT/FAA/AM-05/17

Offi ce of Aerospace Medicine

Washington, DC 20591
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page 

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 

DOT/FAA/AM-05/17 

4. Title and Subtitle 5. Report Date 

Fatality and Injury Rates for Two Types of Rotorcraft Accidents October 2005 

6. Performing Organization Code 

 

7. Author(s) 8. Performing Organization Report No. 

Palmerton D 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

FAA Civil Aerospace Medical Institute 

P.O. Box 25082 11. Contract or Grant No. 

Oklahoma City, OK 73125 

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered 

Office of Aerospace Medicine 

Federal Aviation Administration 

800 Independence Ave., S.W. 

Washington, DC 20591 14. Sponsoring Agency Code 

15. Supplemental Notes 

 

16. Abstract 

An analysis of the frequency of four different types of rotorcraft accidents was conducted to determine if the 

number of fatalities and injuries between accident conditions was different. Accidents involving rollover, no 

rollover, fire, and no fire were studied to determine if accidents with a rollover or fire might be creating 

evacuation delays that contribute to the fatality and injury rates.

A search of the FAA Accident Incident Data System from January1986 to March 1997 produced 2704 accident 

records for this analysis. A Chi-Square test for independence was used to determine the difference between the 

rollover and no rollover and fire and no fire accident categories. Further analysis were performed on 

combinations of the two main categories to determine if an event such as a rollover and fire produced more 

fatalities or injuries than a rollover without a fire.

There were more fatalities in the no rollover category (P=.0001) and more injuries in the rollover group 

(P=.001). Accidents with a fire produced more fatalities than accidents without a fire, (P=.0001). Rollover 

accidents without a fire produced more fatalities (P=.0001) than no rollovers without a fire, and more injuries 

were produced in the rollover no fire group (P=.0001) than the no rollover no fire category. The group of 

accidents where the rotorcraft rolled and caught fire lead to more fatalities (P=.0001), and the no rollover group 

with fire generated more fatalities (P=.0001). 

Rollover accidents injure more pople, and accidents with no rollover kill more occupants. It appears as if the no 

rollover condition produces greater impact forces, preventing the rotorcraft from bouncing and rolling; 

consequently, the higher fatality rate. Fires produce more fatalities but not more injuries. Autopsy data might 

explain this, but smoke inhallation during the evacuation and the speed of the evacuation warrent more 

attention, since it may be a contributing factor in the number of fatalities.

 

17. Key Words 18. Distribution Statement 

 

 

Accident Incident Data System, Rollover, Fire, Rotorcraft, 

Evacuation, Chi Square, CFR Title 14 Part 29.807, Injury, 

Fatality

Document is available to the public through the 

Defense Technical Information Center, Ft. Belvior, VA 

22060; and the National Technical Information 

Service, Springfield, VA 22161 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 9 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 

1

FATALITY AND INJURY RATES FOR TWO TYPES OF ROTORCRAFT ACCIDENTS

INTRODUCTION

Rotorcraft Operations are not routinely associated with 

high passenger loads, but it is an area that accounts for a 

signifi cant part of general aviation activity. Statistics show 

rotorcraft generally transport fewer than four passengers 

(2), thus, rotorcraft accidents do not generally get the 

kind of attention afforded large commercial aircraft where 

the potential for a large number of injuries and fatalities 

is greater. Ensuring that all rotorcraft occupants have a 

rapid means of escape is, however, of importance. 

Airworthiness standards for normal and transport 

category rotorcraft operations are governed by the Code 

of Federal Regulations (CFR), Title 14, Aeronautics and 

Space, Parts 27 and 29, respectively. Normal category 

rotorcraft have a maximum weight of 7,000 lbs with 9 

or less passenger seats and must have at least 1 emergency 

exit on the opposite side of the cabin from the main 

door. This emergency exit must consist of a movable 

window, panel, or additional external door, to provide an 

unobstructed opening that will accept a 19-by-26 inch 

ellipse, be readily accessible, require no exceptional agility of the person using it, and be located so as to allow 

ready use without crowding in any probable attitude that 

may result from a crash (3). Transport category rotorcraft 

have a maximum weight greater than 20,000 lbs with 10 

or more passenger seats. The number of emergency exits 

located on the opposite side of the main door is based on 

seating capacity; however, CFR Title 14 Part 29.807(c) 

specifi es a requirement for exits on the top, bottom, or 

ends of the rotorcraft. Specifi cally, there must be enough 

exit openings in the top, bottom, or ends of the fuselage 

to allow evacuation with the rotorcraft on its side, or the 

probability of the rotorcraft coming to rest on its side in 

a crash landing must be extremely remote (4). The intent 

of these regulations is to provide occupants with a viable 

means of escape in any type of rotorcraft accident.

With the large number of passengers traveling on commercial fi xed wing aircraft, it is imperative that evacuations 

are effi cient, expeditious, and can be executed without 

injury. CFR Title 14 Part 29.803 requires manufacturers 

of transport category rotorcraft to demonstrate that a 

full load of passengers can exit the aircraft in 90 seconds 

or less, in darkness, using half the emergency exits, and 

with only emergency lights illuminating the cabin (1). 

Requiring these evacuations to be completed within 90 

seconds has signifi cantly reduced the effects of post-crash 

fi res and toxic smoke on evacuating passengers. Although 

commercial aviation accidents are capable of producing the highest number of fatalities per accident in the 

aviation industry and warrant strict regulatory oversight, 

general aviation accidents also produce post-crash fi res 

that may exacerbate the injuries and increase the number 

of fatalities. 

The large volume of highly combustible fuel carried 

by commercial and general aviation aircraft increases the 

threat of an in-fl ight or post-crash fi re in a survivable accident. The National Transportation Safety Board (NTSB) 

defi nes a survivable accident as one in which the fuselage 

remains basically intact, the impact forces are within human tolerance limits, and the seat belts restrain the passengers during impact. Using this defi nition, fatalities in 

survivable accidents are caused by events that occur after 

the initial impact. That is, the crash impact forces do 

not kill the occupants, but rather the post-crash fi re and 

toxic smoke routinely cited in the autopsy reports are the 

primary cause of death. For this reason, government and 

industry have continually sought ways to not only prevent 

the threat of aircraft fi res but to expedite the evacuation 

of the occupants once a fi re has developed. 

This study analyzes the frequency of rotorcraft accidents involving fatalities and injuries to determine if 

certain types of accidents are inherently more dangerous 

in relation to rapid evacuation capability. Four categories 

of accidents were analyzed: those involving a fi re, those 

without a fi re, those in which the rotorcraft rolled over, 

and those without a rollover. It was hypothesized that 

rollover accidents create evacuation delays that produce 

more fatalities, particularly in situations involving a 

rollover and post-crash fi re, where evacuation delays 

may expose occupants to toxic fumes longer than they 

would be if the rotorcraft remained upright and the 

evacuation only required occupants to quickly step out 

of the rotorcraft. 

DATA SOURCE

The Federal Aviation Administration (FAA) maintains 

a database of every accident investigated over the last 25 

years. This database (approximately 140,000 accidents 

dating back to 1973), the Accident Incident Data System (AIDS), has become the comprehensive source of 
2

i nformation for all accidents investigated by the FAA. 

Aircraft make and model, phase of fl ight, weather 

conditions, accident location, date of the accident, 

primary and secondary causes, a narrative describing 

the accident, and the number of fatalities and injuries 

comprise a small portion of the information collected 

from each event. In this study, the narratives for each 

accident were analyzed to identify accidents where a 

rotorcraft rolled over and/or caught fi re. Statistical 

analysis of the data was then conducted to show if one 

type of accident consistently produced more fatalities 

or injuries than another. 

METHODS

There are 181 fi elds used to describe an accident or 

incident in the AIDS database. Most of these fi elds are 

coded with letters or numbers specifying a particular 

condition, action, or consequence associated with the 

event. Even though the database contains a large amount 

of information, unique questions concerning the cause of 

injuries and fatalities associated with fi res and rollovers 

are not easily answered. 

The two factors in rotorcraft accidents thought to be 

the most likely reasons occupants are not able to rapidly 

egress a rotorcraft are rollover and fi re. However, no fi elds 

in the database specifi cally allow accidents to be identifi ed by rollover and fi re. Descriptions (e.g. in-fl ight fi re, 

engine fi re, post-crash fi re, and cockpit fi re) are routinely 

used to explain the primary or contributing cause(s) of an 

accident. Consequently, multiple searches must be used 

to identify those situations where a fi re has occurred. In 

addition to the coded fi elds in the database, a narrative 

text fi eld is available that briefl y describes the accident. 

By conducting word searches on this narrative fi eld, it is 

possible to categorize accidents by rollover and fi re. 

A search of the AIDS database for accidents occurring 

between January 1, 1986, and March 4, 1997, showed 

there were 2870 rotorcraft accidents or incidents reported. 

Screening of these accidents revealed 166 that did not 

accurately report the number of injuries or fatalities 

and were excluded from the population sample. The 

remaining 2704 records became the dataset on which 

all other queries were based. Using the fi re codes: infl ight fi re, post crash fi re, and engine fi re, as well as word 

searches for rollover, a total of 148 accidents involving 

fi re, and 365 accidents involving rollover, were identifi ed. 

A comparison of the accidents by rollover and fi re status 

is shown in Figure 1.

In addition to the descriptive accident information in 

the database, a count of the number of injuries and fatalities associated with each event is available. Two statistical 

tests were used to compare the number of fatalities and 

injuries for each accident type to determine if one type 

of accident signifi cantly produced more fatalities or injuries than another. The fi rst test analyzed the frequency 

of fatality and injury accidents for the different groups, 

while the second test compared the fatality and injury 

rates of the subsets of accidents that had at least one 

fatality or injury. 

The Chi Square (χ2) Test of Independence for Frequencies is used when data are arranged in categories. 

Comparisons are made between the observed and expected 

frequency to determine dependence or independence 

(5). Accidents involving rollovers and fi res make up the 

different categories of information, while the number 

of accidents with fatalities and injuries represents the 

frequency of occurrence in each category. The analysis 

focused on the difference between rollovers/non-rollovers and fi re/no-fi re accidents. Further analysis was 

also performed on combinations of these two categories 

to determine if an event such as a rollover with fi re produced more fatalities or injuries than a rollover without 

fi re. Table 1 shows the four main categories, as well as 

the combinations of these categories that were analyzed 

using the χ2 statistic. 

Figure 1. A Comparison of Accidents by Rollover and Fire 

Status. 

Total Number (2704) 

of Helicopter 

Accidents (1986 – 97)

Rollover Accidents 365 (14%) 

(Includes Fire & Non Fire 

Accidents) 

Non Rollover Accidents 2339 (86%)

(Includes Fire and Non Fire 

Accidents) 

Fire Accidents 148 (5%) 

(Includes Rollovers and Non 

Rollovers) 

Non Fire Accidents 2556 (95%) 

(Includes Rollovers and Non 

Rollovers) 

Total Number (2704) 

of Helicopter 

Accidents (1986 – 97)

Table 1. Analytical Design for Each Accident Category 

Fire No Fire 

Rollover Rollover & Fire Rollover & No Fire 

No Rollover No Rollover & Fire No Rollover & No Fire 
3

The second statistical test performed on the data 

compared the fatality and injury rates for the different 

accident groups. The mean number of fatalities and 

injuries were calculated and a comparison of means was 

performed using the t statistic (6).

RESULTS

Figure 2 shows the total number of accidents, 

accidents with fatalities, and accidents with injuries 

for each category. 

The χ2 analysis for accidents with fatalities and accidents with injuries was initially run on the two main 

categories: rollover vs. non-rollover and fi re vs. no-fi re. 

These were then divided into the subcategories shown 

in Figure 3. Using the data in Table 2, separate χ2 values 

were also calculated on the number of fatal and injury 

accidents in each of the remaining four categories. 

Table 2 shows the number of fatality and injury 

 accidents for all categories. 

The χ2results for the rollover and fi re categories are 

listed in Tables 3 and 5, respectively. 

Comparisons of accidents involving rollovers versus 

those without rollover showed a signifi cant difference 

between the two groups; fatal accidents occurred more 

often without rollover while injury accidents occurred 

more often with rollover (Table 3). 

The χ2 values for the rollover accidents with fi re vs

rollover accidents with no fi re showed there was a greater 

number of fatal accidents in the rollover with fi re category. 

In contrast, no difference was found in the number of 

injury accidents in these groups. A greater number of 

fatal accidents with fi re but not rollover was found relative to those with neither fi re nor rollover; again, there 

was no difference in the number of injury accidents for 

the two (Table 4). 

Figure 2. Total Number of Accidents, Accidents With Fatalities, and Accidents With 

Injuries for Each Category. 

Total Number of 

Helicopter Accidents

2704 Accidents

662 Injury Accidents

320 Fatal Accidents

No Rollover

2339 Accidents

546 Injury Accidents

299 Fatal Accidents

Rollover

365 Accidents

116 Injury Accidents

21 Fatal Accidents

No Rollover

No Fire

2214 Accidents

509 Injury Accidents

247 Fatal Accidents

No Rollover

Fire

125 Accidents

37 Injury Accidents

52 Fatal Accidents

Rollover

No Fire

342 Accidents

108 Injury Accidents

13 Fatal Accidents

Rollover

Fire

23 Accidents

8 Injury Accidents

8 Fatal Accidents

(1)

Rollover

vs

No Rollover

(2)

Rollover & Fire

vs

Rollover & No Fire

(4)

Fire

vs

No Fire

(6)

No Fire & Rollover

vs

No Fire & No Rollover

(3)

No Rollover & Fire

vs

No Rollover & No Fire

(5)

Fire & Rollover

vs

Fire & No Rollover

Figure 3. Subcategories of Accidents. 
4

Table 2. The Number of Fatality and Injury Rates for All Categories. 

Accidents 

with no 

Fatalities 

Accidents 

with at 

Least 1 

Fatality 

Accidents 

with no 

Injuries 

Accidents 

with at 

Least 1 

Injury 

Rollover (365) 344 (94%) 21 (6%) 249 (68%) 116 (32%) 

No Rollover (2339) 2038(87%) 299 (13%) 1791(77%) 546 (23%) 

Fire (148) 88 (59%) 60 (41%) 103 (70%) 45 (30%) 

No Fire (2556) 2294(90%) 260 (10%) 1939(76%) 617 (24%) 

Rollover Fire (23) 15 (65%) 8 (35%) 15 (65%) 8 (35%) 

Rollover No Fire 

(342) 

329 (96%) 13 (4%) 234 (68%) 108 (32%) 

No Rollover Fire 

(125) 

73 (58%) 52 (42%) 88 (70%) 37 (30%) 

No Rollover No 

Fire (2214) 

1965(89%) 247 (11%) 1703(77%) 509 (23%) 

Table 3. χ2 Results for the Rollover Category.

Accident Type Fatal Accidents Injury Accidents 

Rollover (1) χ2 (1, N =2702)=14.98, p = .0001* χ2 (1, N =2702)=12.09, p = .001* 

No Rollover 

Table 4. Results of the Rollover and Fire Categories.

Accident Type Fatal Accidents Injury Accidents 

Rollover Fire (2)

Rollover No Fire

χ2 (1, N=365)=38.15, p < .0001* χ2 (1, N=365)=0.10, p=.749 

No Rollover Fire (3)

No Rollover No Fire

χ2 (1, N=2337)=98.22, p < .0001* χ2 (1, N=2337)=2.87, p = .09 

Table 5. F Results for the Fire Category.

Accident Type Fatal Accidents Injury Accidents 

Fire (4)

No Fire

F (1, N =2702)=123.5, p < .0001* F (1, N =2702)=2.95, p = .086 

*

 Signifi cance greater than or equal to .001
5

The χ2results for the fi re category are listed in Table 5.

Comparison of the accidents with fi re versus those 

without fi re showed there were more fatality accidents 

involving fi re than without. There was no difference in 

the number of injury accidents based on fi re condition 

(Table 5). 

Comparing accidents with fi re and rollover with accidents 

with fi re but not rollover revealed no difference for either 

the fatality or injury groups. Accidents with rollover but 

not fi re, and accidents with neither, produced χ2values 

for fatalities and injuries that were consistent with the 

main rollover categories (Table 6). 

Determining a difference among various accident 

types does not mean there is an analogous difference in 

the total number of fatalities or injuries. For example, 

an equal number of fi re versus non-fi re fatal accidents 

does not mean the total number of fatalities for the two 

categories will be the same. Since the objective was to 

look at the difference between the total number of fatalities and injuries for the different accident types, we 

decided to analyze accidents involving at least 1 fatality 

Table 6. Comparison of Accidents With Fire Versus Those Without Fire.

Accident Type Fatality Accidents Injury Accidents 

Fire Rollover(5)

Fire No Rollover

χ2 (1, N=148)=.38, p = .54 χ2 (1, N=148)=.25, p = .62 

No Fire Rollover

(6) No Fire No Rollover

χ2 (1, N=2554)=17.57, p < .0001* χ2 (1, N=2554)=11.87 p = .001*

Table 7. Breakdown of Accidents, Fatalities, and Injuries. 

Accidents 

1 or More 

Fatalities

Total

Number 

Fatal Mean 

Accidents 

1 or More 

Injury 

Total

Number 

Injured Mean 

Rollover 21 26 1.238 116 178 1.534 

No Rollover 299 527 1.763 546 927 1.698 

Fire 60 109 1.817 45 72 1.600 

No Fire 260 444 1.708 617 1033 1.674 

Rollover Fire 8 12 1.500 8 9 1.125 

Rollover No Fire 13 14 1.077 108 169 1.565 

No Rollover Fire 52 97 1.865 37 63 1.703 

No Rollover No Fire 247 430 1.741 509 864 1.697 

or injury. A comparison of the mean number of fatalities and injuries for the subsets of accidents with at least 

1 fatality or injury made it possible to determine if one 

accident type, on average, produced more fatalities or 

injuries than another. (See Table 7 for a breakdown of 

accidents, fatalities, and injuries.) 

Toward this end, a comparison of the means was run 

using a t test (5). The results are listed in Table 8.

In most cases, the τ statistic showed little difference 

in the average number of fatalities or injuries for the 

different accident categories. The results in Table 8 did 

reveal, however, that accidents without rollover produced 

more fatalities than those with rollover. This indicates 

that not only is the frequency of fatal accidents in the 

non-rollover group higher, but more people on average 

are killed in accidents when the rotorcraft does not roll 

over. There also were more injuries in the rollover no-fi re

group than the rollover fi re category. Among accidents 

with a fi re, it was the non-rollover category that produced 

the most injuries.
6

DISCUSSION

The effects on passenger evacuation related to rollover 

and fi re generally met expectations. For example, there 

were more injury accidents with rollover than without, as 

would be expected when considering the crash dynamics 

related to occupants being thrown around the cabin during 

rollover. In contrast, there were unexpected results, such 

as the greater number of fatal accidents attributable to 

the non-rollover condition. A likely explanation for this 

circumstance could be that the impact forces that cause 

a rotorcraft to roll are less severe than those encountered 

in a non-rollover situation, where the rotorcraft hits the 

ground with such direct force that it embeds fi rmly. These 

extreme forces would also explain the relatively greater 

number of fatalities in accidents that do not involve rollover. Comparison of these two situations suggests that 

the impact, and not the rollover, is the more important 

consideration for passenger evacuation. 

Evaluation of the effects of fi re in rotorcraft accidents 

also produced mixed results. There were more fatal accidents with fi re than without; however, there was no 

difference in the number of injury accidents for the two 

conditions. The reason fi re produced more fatalities, 

but not injuries, is not immediately obvious, although 

a likely explanation would be that the impact/rollover 

forces primarily injured occupants, while accidents 

involving post-crash fi res included the effects of both 

crash dynamics and the heat/toxic byproducts produced 

by the fi re. This would also explain the larger proportion 

of injuries in rollover accidents without fi re, as compared 

with those having fi re; i.e., the presence of fi re makes 

the relative number of injuries appear lower, since many 

initially injured passengers may be killed by smoke or 

fi re. The inaccessibility of autopsy data precludes the 

ability to draw appropriate conclusions regarding such a 

speculation, although the combination of crash and fi re 

effects would disable occupants more than would the 

crash alone, exacerbating diffi culties with evacuation and 

increasing the likelihood that passengers would succumb 

to the worsening environment. Thus, the effects of rotorcraft fi re on passenger evacuation warrants particular 

attention, especially in situations in which the rotorcraft 

has rolled over. 

CONCLUSION

Of the 2,704 crashed rotorcraft included in the analysis, approximately 14% rolled over and 5% caught fi re. 

These percentages, while small, are not insignifi cant; that 

is to say, there is more than a remote possibility that a 

rotorcraft will roll over and/or catch fi re in an accident. 

The demonstrated results of these crash factors makes 

the provision of emergency exits in appropriate numbers 

and locations a necessity. 

REFERENCES

1. Title 14, United States Code of Federal Regulations, 

Part 25, Section 803, 1997.

2. Federal Aviation Administration Accident Incident 

Data System, 1998.

3. Title 14, United States Code of Federal Regulations, 

Part 27, Section 807, 1997.

4. Title 14, United States Code of Federal Regulations, 

Part 29, Section 807c, 1997.

5. Havlicek, L.L., Crain, R.D., “Practical Statistics for 

the Physical Sciences,” 1988, pp. 194.

6. Havlicek, L.L., Crain, R.D., “Practical Statistics for 

the Physical Sciences,” 1988, pp. 169.

Table 8. Results of t-test of Means Comparison. 

Fatal Injured 

(1) Roll vs No Roll t (34) = 3.36 p = 0.002* t (187) = 1.5 p = 0.135 

(2) Fire vs No Fire t (66) = 0.41 p = 0.687 t (50) = 0.40 p = 0.689 

(3) Roll Fire vs Roll No Fire t (8) = 1.26 p = 0.245 t (19) = 2.73 p = 0.013* 

(4) No Roll Fire vs No Roll No Fire t (56) = 0.41 p = 0.684 t (41) = 0.02 p = 0.981 

(5) Roll Fire vs No Roll Fire t (21) = 0.83 p = 0.418 t (40) = 2.35 p = 0.024* 

(6) Roll No Fire vs No Roll No Fire t (37) = 6.47 p < 0.001* t (170) = 1.15 p = 0.251 

*

 Signifi cance greater than .05