CAA PAPER 2005/03

DOT/FAA/AR-04/27

A Benefit Analysis for Aircraft 16G Dynamic 

Seats Configured without Enhancements to 

Head Injury Criteria 

www.caa.co.uk

Safety Regulation Group
CAA PAPER 2005/03

DOT/FAA/AR-04/27

A Benefit Analysis for Aircraft 16G Dynamic 

Seats Configured without Enhancements to 

Head Injury Criteria 

Safety Regulation Group

October 2005
CAA Paper 2005/03 A Benefit Analysis for Aircraft 16G Dynamic Seats Configured without Enhancements to Head Injury Criteria 

© Civil Aviation Authority 2005

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ISBN 0 11790 357 4

Published October 2005

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CAA Paper 2005/03 A Benefit Analysis for Aircraft 16G Dynamic Seats Configured without Enhancements to Head Injury Criteria 

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List of Effective Pages
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List of Effective Pages iii

Executive Summary v

Introduction 1

Objectives 1

Accidents Analyzed 2

Method 4

Analysis and Results 10

Discussion 16

Conclusions 17

References 18

Definitions 18

October 2005

Contents
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Executive Summary

The objective of this analysis was to assess the number of Serious Injuries and Fatalities that

might be avoided from the use of ’16g dynamic seats configured without enhancements to

head injury criteria’ and to compare this with the assessed benefit from ’fully compliant

dynamic seats’. 

The analysis was based on twenty-five impact related accidents, occurring during the period

from 1984 to 1998, that may have involved seat related Fatal or Serious Injuries. An earlier

Benefit Analysis carried out on “fully compliant dynamic seats” used the same accidents as a

basis for predicting number of lives saved and reduction in Serious Injuries. Using the same

accidents in this analysis enabled a direct comparison between the two analytical methods. 

Each accident was analyzed in detail and a mathematical technique was used to model each

accident scenario. The analysis was based on an evaluation of the injuries sustained by the

passengers to determine the total achievable benefits. 

The prediction of benefit for ’16g dynamic seats configured without enhancements to head

injury criteria’ over the period 1984 to 1998 to U.S. registered aircraft, operating under 14 CFR

Part 121 is:

The re-evaluation of the benefit, based on currently available data, for ’fully compliant dynamic

seats’ over the period 1984 to 1998 approximates to: 

This reduction in Fatalities and Serious Injuries is to a similar level as that determined from the

earlier analysis.

The proportion of benefit attributable to the enhanced Head Injury Criteria (as defined in TSOC127a) is:

Account has been taken of the reduction in fire threat afforded to the impact survivors by the

improved fireworthiness of cabin interiors compliant with the standards defined in 14 CFR Part

25 at amendment 72. The fire threat is often severe in accidents where ’16g seats’ are likely

to reduce the number of impact Injuries and Fatalities. This is a significant factor in terms of

the ultimate benefit attained even when the recent improvements in the fireworthiness of

aircraft cabins is taken into account

Due to the extensive disruption to the floor during the impact sequence, a number of accidents

analyzed would not have any potential for lives being saved with the introduction of ’16g

seats’.

The analytical methods employed provide as accurate an assessment, as is possible with the

available data, using the mathematical tools currently in existence. However, there will still

remain an element of uncertainty associated with assessments of this kind, and this should be

borne in mind when making decisions concerning aircraft safety that are predicated on the

results of this analysis. 

Reduction in Fatalities = 28

Reduction in Serious Injuries = 22

Reduction in Fatalities = 45 

Reduction in Serious Injuries = 40

Fatalities = 39%

Serious Injuries = 46%

October 2005
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A Benefit Analysis for Aircraft 16G Dynamic Seats 

Configured without Enhancements to Head Injury Criteria 

1 Introduction

1.1 This report has been prepared on behalf of the U.S. Federal Aviation Administration

(FAA). It contains the method and results of a benefit analysis on ’16g dynamic seats

configured without enhancements to head injury criteria’. The analysis relates to

aircraft, type certificated with 30 or more passenger seats, operating to 14 CFR

Part 121 or equivalent. 

1.2 TSO-C127a prescribes the minimum performance standards for Transport Airplane

Seats. Seats that are fully compliant with this Standard are identified in this report as

’fully compliant dynamic seats’. Seats that meet this Standard but are not compliant

with the enhanced head injury criteria (HIC) are identified in this report as ’16g

dynamic seats configured without enhancements to head injury criteria’. The term

’16g seats’ is used generically to refer to both standard of seat.

1.3 An earlier analysis of past accidents determined the benefit to be derived from ’fully

compliant dynamic seats’ (Reference [1]). This analysis was carried out using the

Cabin Safety Research Technical Group Accident Database (Reference [2]) as a

means of selecting the appropriate accidents from which to assess benefit. Since the

time of this earlier analysis, further data have become available enabling a more

detailed assessment of the benefit likely to accrue. The same accidents were

analyzed in this assessment as used in the earlier analysis, thus enabling a direct

comparison between the two analytical methods.

1.4 The assessments have been carried out such that they reflect the benefit likely to

accrue to aircraft compliant with the latest standard of cabin fireworthiness as

prescribed in 14 CFR Part 25 at amendment 72.

1.5 The methodology utilized is aimed at providing an indication as to the order of benefit

likely to be achieved. Certain assumptions have been made in the analysis of data.

The more significant of these are described in paragraph 5·1.

1.6 Any analysis of this kind must involve a degree of subjective judgment and relies on

the accuracy of the data available. The analytical methods employed are intended to

provide as accurate an assessment as is possible with the available data, using the

mathematical tools currently in existence. However there will still remain an element

of uncertainty associated with assessments of this kind, and this should be borne in

mind when making decisions concerning aircraft safety that are predicated on the

results of this analysis.

1.7 Section 9 of this report contains the definition of terms used in this analysis.

2 Objectives

The objective of this analysis was to assess the number of Serious Injuries and

Fatalities that might be avoided from the use of ’16g dynamic seats configured

without enhancements to head injury criteria’ and to compare this with the assessed

benefit from ’fully compliant dynamic seats’.

October 2005
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3 Accidents Analyzed

3.1 The earlier assessment (Reference [1]) of benefit from ’fully compliant dynamic seats’

was based on an analysis of accidents occurring over the period 1984 to 1998. The

accidents analyzed to determine benefit are shown in Table 1.

Table 1 List of Accidents Analyzed in the Earlier Benefit Analysis for ’Fully 

Compliant Dynamic Seats’

Date Location Aircraft

20-Dec-95 Buga, Nr. Cali, Colombia B757-223

02-Jul-94 Charlotte Airport, Charlotte, North Carolina DC9-31

26-Apr-94 Nagoya/Komaki Airport, Nagoya, Japan A300B4-622R

21-Mar-94 Vigo Airport, Spain DC9-32

14-Sep-93 Warsaw, Poland A320-211

06-Apr-93 Nr. Shemya, Alaska, U.S.A. MD11

21-Dec-92 Faro, Portugal DC10-30CF

22-Mar-92 La Guardia, New York, U.S.A. F28-4000 a

20-Jan-92 Nr Strasbourg, (France) A320-100

01-Feb-91 Los Angeles, California, U.S.A. B737-300

03-Dec-90 Romulus, Detroit, U.S.A. DC9-14

14-Feb-90 Bangalore, India A320-231

25-Jan-90 Cove Neck, Long Island, New York, U.S.A. B707-321B

20-Sep-89 La Guardia, New York, U.S.A. B737-400

19-Jul-89 Sioux City, U.S.A. DC10-10

10-Mar-89 Dryden, Ontario, Canada F28 Mk1000

08-Jan-89 Kegworth, East Midlands Airport, U.K. B737-400

31-Aug-88 Hong Kong TRIDENT 2E

31-Aug-88 Dallas Fort Worth, U.S.A. B727-232

26-Jun-88 Habsheim A320-100

15-Apr-88 Seattle-Tacoma Intl. Airport, Seattle, U.S.A. DHC8-102

15-Nov-87 Denver Colorado U.S.A. DC9-14

16-Aug-87 Detroit DC9-82

02-Aug-85 Dallas Fort Worth, U.S.A. L1011-385-1

21-Jan-85 Reno Nevada, U.S.A. L188C

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3.2 Table 2 shows the Total Number of Fatalities and Serious Injuries to passengers and

the benefit assessment for each accident determined from this earlier benefit

analysis.

NOTE: (U/K = unknown)

Table 2 List of Accidents Identified as having Potential for Benefit from ’Fully 

Compliant Dynamic Seats’ showing the Number of Fatalities and Serious 

Injuries

Date Location Aircraft

Total No. 

of 

Fatalities

Total No. 

of Serious 

Injuries

Benefit 

Lives 

Saved

Injuries 

Saved

20-Dec-95 Buga, Cali B757 159 4 0 0

02-Jul-94 Charlotte DC9-31 37 16 3 0

26-Apr-94 Nagoya A300B4 264 7 0 0

21-Mar-94 Vigo DC9-32 0 2 0 0

14-Sep-93 Warsaw A320 2 47 0 4

06-Apr-93 Shemya MD11 2 60 0 25

21-Dec-92 Faro DC10 56 U/K 3 6

22-Mar-92 La Guardia F28-4000 27 9 4 5

20-Jan-92 Strasbourg A320 87 5 7 -5

01-Feb-91 Los Angeles B737 22 13 0 0

03-Dec-90 Romulus DC9-14 8 10 0 0

14-Feb-90 Bangalore A320 92 22 9 -5

25-Jan-90 Cove Neck B707 73 81 23 21

20-Sep-89 La Guardia B737 2 3 0 0

19-Jul-89 Sioux City DC10-10 111 47 3 1

10-Mar-89 Dryden F28 24 18 0 5

08-Jan-89 Kegworth B737 47 74 5 0

31-Aug-88 Hong Kong TRIDENT 7 4 0 0

31-Aug-88 Dallas B727-232 14 26 0 0

26-Jun-88 Habsheim A320-100 3 30 0 0

15-Apr-88 Seattle DHC8 0 4 0 2

15-Nov-87 Denver. DC9-14 28 28 4 5

16-Aug-87 Detroit DC9-82 154 1 0 0

02-Aug-85 Dallas L1011 134 15 0 2

21-Jan-85 Reno L188C 70 1 1 0

October 2005
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3.3 These accidents have been reassessed using the methodology described in Section 4

to re-evaluate the benefit from ’fully compliant dynamic seats’ and to assess the

benefit from ’16g dynamic seats configured without enhancements to head injury

criteria’.

4 Method

4.1 General Overview

4.1.1 Each accident, shown in Table 2, that exhibited a reduction in the number of Fatalities

or Injuries based on the earlier assessment for ’fully compliant dynamic seats’ was

reassessed in accord with the methodology described in the following Sections. 

4.1.2 Additional data have become available, since this earlier analysis was carried out,

pertaining to individual occupants. In many instances, the full extent of the nature and

severity of injuries sustained was available together with their age and sex. Survivor

statements often provided additional information relating to localized areas of the

cabin, including whether the seats were detached and the level of disruption of the

floor. 

4.1.3 The methodology adopted for this analysis was to consider the injuries for all of the

passengers where data were available. This assessment was carried out for both

’fully compliant dynamic seats’ and ’16g dynamic seats configured without

enhancements to head injury criteria’. This enabled a comparison to be made

between the assessed benefit likely to accrue from the two seat standards.

4.2 Accident Scenarios

4.2.1 The severity of hazard in an accident can vary markedly throughout the aircraft.

Experience has shown that considering occupant injuries on a “whole” aircraft basis

can be misleading when assessing the effects of survivability factors. It is therefore

desirable to divide the aircraft into “Scenarios”.

4.2.2 A Scenario is defined as:

“That volume of the aircraft in which the occupants are subjected to a similar level of

threat.”

4.2.3 A similar level of threat need not necessarily result in the same level of injury to

occupants. The extent of injury sustained can vary with numerous factors including

age, sex, adoption of the brace position etc. Furthermore, the threat to occupants can

vary over relatively small distances. For example, a passenger may receive Fatal

Injuries because of being impacted by flying debris, and a person in an adjacent seat

may survive uninjured. However, dividing accidents into scenarios provides a more

meaningful basis on which to analyze accidents than considering the whole aircraft

due to the marked variation in potential for survival with occupant location.

4.2.4 The flight deck and flight attendant areas are generally considered as separate

scenarios. The flight crewmembers usually have full harness restraints, and sliding

cockpit windows in the area provide a nearby method of egress. The flight attendant

areas are normally considered as a separate scenario from the passenger cabin, again

due to the significant differences in seating, restraint systems and exit availability.

4.2.5 For these reasons, where sufficient data were available, the assessments of injury

reduction were carried out for each accident scenario. 

October 2005
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4.3 Injury Reduction Assessment

4.3.1 For many of the accidents analyzed sufficient data were available to consider each

passenger separately and to assess the probability of their injuries being ameliorated

by the use of ’16g seats’. An assessment was made of the probability that:

4.3.2 For the Fatally injured, that their injuries would:

a) Remain Fatal

b) Be reduced to Serious

c) Be reduced to Minor/None

4.3.3 For the Seriously injured, that their injuries would:

a) Remain Serious

b) Be reduced to Minor/None

4.3.4 The factors taken into account in deriving these probabilities included the following:

a) The nature and extent of their injuries. Often the data was such that a

determination could be made as to whether or not the occupant sustained:

i) Injuries that might have been ameliorated by the enhanced head injury criteria

specified in TSO-C127a.

ii) Other impact related injuries that might have resulted from cabin disruption,

such that ’16g seats’ would not have changed the nature and extent of their

injuries.

iii) Injuries resulting from any existing fire threat.

b) Statements made by Survivors as to the nature of the disruption in various areas

of the cabin. This might include whether seats were detached, floors failed or local

structure crushed 

c) The age of the passenger can be an important factor in their survivability. An age

related issue, particularly relevant to this analysis, is that children would be less

likely to benefit ’from fully compliant dynamic seats’, simply because of their

stature. 

4.3.5 An example of the way in which an estimate of the resultant number of Fatalities and

Serious Injuries may be derived from the assessed probabilities is shown in Table 3.

October 2005
 Page 6

For each seat location (Seat/Ident) the following information was recorded:

• Age: of the passenger• Injury/AIS:The extent of the injuries S= Serious, F=Fatal and AIS = Abbreviated Injury Scale indic

Section 9, Definitions).

• Head: YES = the passenger sustained head injuries; NO = the passenger did not sustain head in

• Seat Detached: YES = the seat became detached; NO the seat did not become detached.

Having made the assessment of the probabilities, pertinent to each passenger, based on these data, tcategory were summed to arrive at the total number of passengers in the scenario, following the inta) Minor/No Impact Injuries (Impact M/N) 

i) 2·65 in the example for ’fully compliant dynamic seats’ (Full 16G Seat), and

ii) 2·0 in the example for ’16g dynamic seats configured without enhancements to head injury c

b) Serious Impact Injuries (Impact Serious) 

i) 4·5 in the example for ’fully compliant dynamic seats’ (Full 16G Seat), and 

ii) 5·1 in the example for ’16g dynamic seats configured without enhancements to head injury c

c) Fatal Impact Injuries (Impact Fatal) 

i) 0·85 in the example for ’fully compliant dynamic seats’ (Full 16G Seat), and 

ii) 0·9 in the example for ’16g dynamic seats configured without enhancements to head injury c

Table 3 Example of the Method for Assessing the Resultant Number of Fatalities and Serious In

SEAT/IDENT AGE

INJURY/

AIS HEAD

SEAT 

DETACHED

IMPACT 

M/N

IMPACT 

SERIOUS

IMPACT 

FATAL

2.65 4.5 0.85 

6A 39 S4 NO YES 0.5 0.5 0 7A 57 S4 NO NO 0 1 0 7C 54 S5 NO NO 0 1 0 

8E 30 S4 NO YES 0.3 0.7 0 

12F 25 S2 NO YES 0.7 0.3 0 

13A ? F6 YES YES 0.05 0.1 0.85 13C ? S2 NO YES 0.5 0.5 0 13D ? F4 YES YES 0.6 0.4 0 

FULL 16G SEAT 

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4.4 Survivability Chains

4.4.1 The assessment described in paragraph 4.3 results in a prediction of the number of

Fatally Injured, Seriously Injured and surviving passengers (Minor/No Injuries)

resulting from the impact in each accident scenario. A determination is required of the

probability of those Seriously Injured or surviving the impact with Minor or No Injuries,

succumbing to any fire threat that might also exist. Such an assessment may be

made by the use of a mathematical model, known as a Survivability Chain (see

Figure 1). This model enables an assessment to be made of the overall effect on

survivability, from improvements made to impact related survivability factors such as

’16g seats’. 

4.4.2 The following is an example of the model and the effects of improvement in Injuries

and Fatalities resulting from changes to survivability factors for a hypothetical

accident scenario.

4.4.3 In this example, of the 100 occupants in the scenario there are: 

• 45 uninjured survivors (Minor/No Injuries). 

• 25 Serious Injuries, 10 because of the impact, 10 because of the fire, and 5

seriously injured because of the impact and fire.

• 30 Fatalities, 20 because of the impact, and 10 because of the fire (5 of whom

sustained Serious injuries from the impact).

Figure 1 Example of a Survivability Chain for an Accident Scenario

45 

MINOR/NO 

INJURIES

10 SERIOUS 

FIRE 

INJURIES

60 IMPACT

MINOR/NO 

INJURIES 

20 SERIOUS 

IMPACT 

INJURIES

IMPACT

FIRE

100 OCCUPANTS 

FIRE 

20 FATALITIES 

5 FIRE 

FATALITIES

10 SERIOUS 

IMPACT 

INJURIES 

5 SERIOUS 

IMPACT/FIRE INJURIES

5 IMPACT/FIRE 

FATALITIES

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4.4.4 If improvements are made to an impact-related survivability factor, such that there are

only 12 Fatalities and 16 Seriously Injured of the 100 occupants, the survivability chain

then becomes: 

4.4.5 It is known from the accident that 5/60ths of those that survive the impact uninjured

and 5/20ths of those that sustain injuries from the impact subsequently succumb to

death because of the fire. Furthermore, 10/60ths of those that survive the impact

seriously injured are seriously injured from fire and 5/20ths of those that sustain

injuries from the impact also sustain injuries because of the fire. It is assumed that

these ratios are constant for this particular scenario.

4.4.6 On this basis an assessment of the numbers of Fatalities and Injuries may be made

as follows: 

Figure 2 Example of Survivability Chain showing Possible Improvements in 

Impact-related Survivability Factor

Figure 3 Example of Survivability Chain showing the Overall Improvements in 

Survivability

MINOR/NO 

INJURIES 

SERIOUS 

FIRE 

INJURIES

72 IMPACT

MINOR/NO 

INJURIES 

16 SERIOUS 

IMPACT 

INJURIES 

IMPACT

FIRE 

100 OCCUPANTS 

FIRE 

12 FATALITIES 

SERIOUS 

IMPACT 

INJURIES 

SERIOUS 

IMPACT/FIRE 

INJURIES

IMPACT/FIRE 

FATALITIES

FIRE 

FATALITIES

54 

UNINJURED 

MINOR/NO 

INJURIES 

12 SERIOUS 

FIRE INJURIES

72 IMPACT

MINOR/NO 

INJURIES 

16 SERIOUS 

IMPACT 

INJURIES 

IMPACT

FIRE 

100 OCCUPANTS 

FIRE 

12 FATALITIES

6 FIRE 

FATALITIES

8 SERIOUS 

IMPACT 

INJURIES 

4 SERIOUS 

IMPACT/FIRE 

INJURIES

4 IMPACT/FIRE 

FATALITIES

[(10/60) x 72 = 12] 

[(5/60) x 72 = 6] [(5/20) x 16 = 4] 

[(5/20) x 16 = 4] 

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4.4.7 Hence, the improvement to the impact related survivability factor results in: 

• 54 uninjured survivors. (Minor/No Injuries)

• 24 Serious Injuries, 8 because of the impact, 12 because of the fire, and 4 seriously

injured because of the impact and fire.

• 22 Fatalities, 12 because of the impact, and 10 because of the fire (4 of whom

sustained Serious Injuries from the impact).

4.4.8 It should be noted that the survivability factor improvement resulted in a reduction in

impact Fatalities of 8 and impact Injuries of 4. However, the overall situation is as

follows: 

4.5 Analysis of Accidents with Limited Passenger Injury Data

4.5.1 There were limited data available to assess the benefit, based on the injuries

sustained, for two of the accidents - those occurring at Bangalore and Strasbourg. It

was assessed, from the earlier benefit analysis (Reference [1]) that these accidents

would yield significant benefit. Therefore, it was assumed that the proportionate

reduction in impact Fatalities and Injuries would be similar to that experienced on

other accidents from which there was significant benefit. By reference to Table 2 it

may be seen that the total derived benefit exceeded more than one Fatality in nine

accidents. Two of these were Bangalore and Strasbourg. The remaining seven

accidents may be classified as yielding significant benefit. Six of these accidents,

Kegworth being excluded, were used to derive an assessment of the proportionate

reduction in impact Fatalities and Injuries. Kegworth was not considered since the

accident aircraft was fitted with seats that were likely to meet the 16g criteria in all

respects other than with regard to head injury protection. 

4.5.2 Therefore, the average reduction in impact Fatalities and Injuries was derived for the

accidents occurring at Sioux City, La Guardia, Cove Neck, Denver, Faro and Charlotte

in the following manner:

4.5.2.1 The total number of impact Fatalities derived from this assessment, following the

introduction of ’16g seats’, Tf1, was simply divided by the actual total number of

impact Fatalities, Tf0, experienced in these accidents. :

4.5.2.2 A similar factor, I, was derived to assess the reduction of impact Injuries likely to occur

following the introduction of ’16g seats’:

Where:

Ti1 = the total number of impact Injuries assessed for all of the accidents yielding

significant benefit following the introduction of ’16g seats’.

Ti0 = the total number of impact Injuries actually experienced in all of the accidents

yielding significant benefit following the introduction ’16g seats’.

Survivors Serious Injuries Fatalities

Prior to survivability factor improvement: 45 25 30

Post survivability factor improvement: 54 24 22

F =

Tf1

Tf0

I =

Ti1

Ti0

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4.5.2.3 The values of F and I may be derived for both ’fully compliant dynamic seats’ and ’16g

dynamic seats configured without enhancements to head injury criteria’. They could

then be applied to the actual impact Fatalities and impact Serious Injuries experienced

in the accidents at Bangalore and Strasbourg to assess the number of impact

Fatalities and impact Serious Injuries likely to occur following the introduction of ’16g

seats’. In order to make a determination of the proportion of those surviving the

impact (Serious Injuries or Minor/No Injuries) succumbing to any fire threat that might

also exist, the methodology described in paragraph 4.4 was used. In this way, the

number of lives saved and injuries saved could be made for the accidents at Bangalore

and Strasbourg.

5 Analysis and Results

5.1 Assumptions

The assumptions made in this analysis include the following:

a) If seat standards were not specifically stated in the accident report, they are

normally considered not to be ’16g seats’.

b) No disbenefit from the introduction of ’16g seats’ has been considered. For

example, ’16g seats’ might reduce the evacuation capability of occupants due to

seat backs not breaking over.

c) The accidents determined to yield zero benefit from the earlier analysis

(Reference [1]) would not show any reduction in the number of Fatalities or Injuries

if re-evaluated using the methodology described in this report.

5.2 Results 

5.2.1 Assessed Benefit From Accidents with Limited Injury Data

Since there were limited injury data available for the accidents occurring at Bangalore

and Strasbourg the methodology described in paragraph 4.5 was utilized. This

involved making a determination of the average reduction in impact Fatalities and

Injuries based on the average reduction in impact Fatalities and Injuries determined

for the accidents yielding significant benefit. Tables 4 and 5 show the Injury data

pertinent to these accidents. 

Rgwc 1707/Master Record/Imprvmnt.Impact inj Full 16g

Table 4 Injury Data for Accidents Analyzes Yielding Significant Benefit - Fully 

Compliant Dynamic Seats

ACTUAL ACCIDENT FULL 16G IMPROVEMENT

TOTALS> 157 187 224 123 159 286 0.79 0.85

ACCIDENT 

LOCATION

IMPACT 

FATAL

IMPACT 

SERIOUS 

INJURY

IMPACT 

M/N

IMPACT 

FATAL

IMPACT 

SERIOUS 

INJURY

IMPACT 

M/N

IMPACT 

FATAL

IMPACT 

SERIOUS 

INJURY

SIOUX CITY 55 23 113 51 23 117 0.9 1.0

LA GUARDIA 9 17 21 5 13 29 0.6 0.8

COVE NECK 65 80 4 48 67 34 0.7 0.8

DENVER 18 22 6 14 21 11 0.8 1.0

FARO 6 41 80 2 31 94 0.4 0.8

CHARLOTTE 4 4 0 3 4 1 0.7 1.1

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Rgwc 1707/Master Record/Imprvmnt.Impact inj 16g noHIC

NOTE: M/N = Minor/No Injury

5.2.1.1 The values in the final two columns of Tables 4 and 5 have been rounded to one

decimal place.

5.2.1.2 The values in the columns headed ’IMPACT FATAL’, ’IMPACT SERIOUS INJURY’ and

’IMPACT M/N’ have been rounded to the nearest whole number.

5.2.1.3 For certain accidents the introduction of ’16g seats’ results in an increase in the

number of Serious Injuries. This is due to the number of Fatally injured, having their

injuries reduced to Serious, being greater than the number of Serious Injuries having

their injuries reduced to Minor /None.

5.2.1.4 The column headings in Tables 4 and 5 are:

• Actual Accident: These three columns show the actual number of impact

Fatalities, impact Serious Injuries and passengers with Minor or No Injuries in the

actual accident. The TOTALS figure relates to the total number of passengers

sustaining the injuries indicated in all six accidents.

• Full 16G: These three columns in Table 4 show the assessed number of impact

Fatalities, impact Serious Injuries and passengers with Minor or No Injuries that

would result had the aircraft been configured with ’fully compliant dynamic seats’.

The TOTALS figure relates to the total number of passengers sustaining the

injuries indicated in all six accidents.

• 16G No HIC: These three columns in Table 5 show the assessed number of impact

Fatalities, impact Serious Injuries and passengers with Minor or No Injuries that

would result had the aircraft been configured with ’16g dynamic seats configured

without enhancements to head injury criteria’. The TOTALS figure relates to the

total number of passengers sustaining the injuries indicated in all six accidents.

• Improvement: These two columns, in Tables 4 and 5, show the ratio of the

resultant impact Fatalities to the actual impact Fatalities and the ratio of the

resultant impact Serious Injuries to the actual impact Serious Injuries after

configuring the aircraft with the improved seat standard in all six accidents. The

TOTALS figure relates to the ratio of the total resultant impact Fatalities to the total

actual impact Fatalities and the ratio of the total resultant impact Serious Injuries

to the total actual impact Serious Injuries after configuring the aircraft with the

improved seat standard.

Table 5 Injury Data for Accidents Analyzed Yielding Significant Benefit - 16g Seats 

Configured without Enhancements to Head Injury Criteria

TOTALS

ACTUAL ACCIDENT 16G NO HIC IMPROVEMENT

157 187 224 135 167 267 0.86 0.89

ACCIDENT 

LOCATION

IMPACT 

FATAL

IMPACT 

SERIOUS 

INJURY

IMPACT 

M/N

IMPACT 

FATAL

IMPACT 

SERIOUS 

INJURY

IMPACT 

M/N

IMPACT 

FATAL

IMPACT 

SERIOUS 

INJURY

SIOUX CITY 55 23 113 53 23 115 1.0 1.0

LA GUARDIA 9 17 21 6 15 26 0.7 0.9

COVE NECK 65 80 4 52 69 28 0.8 0.9

DENVER 18 22 6 15 25 6 0.8 1.1

FARO 6 41 80 5 31 91 0.8 0.8

CHARLOTTE 4 4 0 4 4 1 0.9 0.9

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5.2.1.5 The derived values of F and I may then be determined from the data in the tables

using the formulae in paragraph 4.5 as follows: 

a) For ’fully compliant 16g seats’:

b) For ’16g dynamic seats configured without enhancements to head injury criteria’:

5.2.1.6 These factors were applied to the number of impact Fatalities and Serious Injuries

occurring in the accident Scenarios, which had the potential to yield benefit from ’16g

seats’, for both the Bangalore and Strasbourg accidents. The survivability chains

derived for each of the pertinent Scenarios were used (see paragraph 4.4) to

determine the resultant number of Fatalities, Serious Injuries and Minor/No Injuries

following any existing fire threat. The final assessed number of lives and Serious

Injuries saved for these accidents is included in Table 6.

5.2.1.7 Table 6 shows that the benefit for these accidents is: 

a) For ’fully compliant dynamic seats’:

b) For ’16g dynamic seats configured without enhancements to head injury criteria’:

NOTE: All values are rounded to the nearest whole number.

5.2.2 Assessed Benefit from all Accidents Studied

Table 6 shows the prediction of the number of lives and Serious Injuries saved. The

column headings are:

F =

Tf1

 =

123

 = 0·79

Tf0 157

I =

Ti1

 =

159

 = 0·85

Ti0 187

F =

Tf1

 =

135

 = 0·86

Tf0 157

I =

Ti1

 =

167

 = 0·89

Ti0 187

Lives Saved = 56

Serious Injuries Saved = 49

Lives Saved = 34

Serious Injuries Saved = 27

Date: Date of Occurrence of the accident analyzed

Location: Location of the accident

Aircraft: Aircraft involved in the accident

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Operation: Whether the aircraft was operating under 14 CFR 

Part 121 or for non-US operators, or its equivalent, 

annotated as {Part 121}

Total No. of Fatalities: The total number of passenger Fatalities in the 

accident analyzed

Total No. of Serious Injuries: The total number of passenger Serious Injuries in 

the accident analyzed

A - Benefit Full 16g Seats: The benefit for ’fully compliant dynamic seats’ 

derived from the earlier assessment as described 

in Reference [1].

B - Revised Benefit Full 16g 

Seats:

The assessed benefit derived from this analysis for 

’fully compliant dynamic seats’

C - Benefit 16g Seats No HIC: The assessed benefit derived from this analysis for 

’16g dynamic seats configured without 

enhancements to head injury criteria’.

October 2005
 Page 14

Table 6 Summary of Assessed Reduction in Number of Fatalities and Serious InjuriesNOTES: 1 Assessed benefit rounded to the nearest whole number of passengers. (The total number of inju

would appear to be 52 by adding the rounded numbers for each of the accidents

2 A negative value for Serious Injuries reflects situations where the number of Fatal Injuries that 

than the number of Serious Injuries reduced to Minor or No Injuries. The net outcome is an incr

3 U/K = Unknown4 Part 121 = Accident to aircraft operating under 14 CFR Part 1215 {Part 121} = Accident to aircraft operating under equivalent rules to 14 CFR Part 121

Lives Saved Injuries Saved Lives Saved 

62 66 56 

25-Jan-90 Cove Neck B707 {Part 121} 73 81 23 21 17 14-Feb-90 Bangalore A320 {Part 121} 92 22 9 -5 3 20-Jan-92 Strasbourg A320 {Part 121} 87 5 7 -5 12 08-Jan-89 Kegworth B737 {Part 121} 47 74 5 0 5 22-Mar-92 La Guardia F28-4000 Part 121 27 9 4 5 4 15-Nov-87 Denver. DC9-14 Part 121 28 28 4 5 4 21-Dec-92 Faro DC10 {Part 121} 56 U/K 3 6 4 19-Jul-89 Sioux City DC10-10 Part 121 111 47 3 1 4 02-Jul-94 Charlotte DC9-31 Part 121 37 16 3 0 1 21-Jan-85 Reno L188C Part 121 70 1 1 0 2 06-Apr-93 Shemya MD11 {Part 121} 2 60 0 25 0 10-Mar-89 Dryden F28 {Part 121} 24 18 0 5 0 14-Sep-93 Warsaw A320 {Part 121} 1 50 0 4 0 15-Apr-88 Seattle DHC8 Part 121 0 4 0 2 0 02-Aug-85 Dallas L1011 Part 121 134 15 0 2 0 

Aircraft Operation

TOTALS >

B 

Revised Benefi

Total No. of 

Fatalities

Total No. of 

Serious 

Injuries

A 

Benefit Full 16 g Seats

Date Location

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5.2.3 Benefit Assessment for the World Fleet

5.2.3.1 The assessed number of lives saved and injuries saved shown in Table 6 are those

predicted for the accidents to the world fleet of aircraft, operating to 14 CFR Part 121

or equivalent, analyzed over the period 1984 to 1998 inclusive. To make a

determination of the benefit likely to accrue for US aircraft operating under 14 CFR

Part 121 over this period, these values must be factored to take into account the

following:

a) Other accidents where seat related injuries occurred but because there are little or

no data available, they cannot be analyzed.

b) The proportion of the world fleet of impact related accidents that occur to the US

fleet of 14 CFR Part 121 aircraft.

5.2.3.2 Two methods for deriving these factors were considered in the earlier analysis

(Reference [1]). The method considered to give the more accurate prediction, since it

was based on a larger sample size, yielded the following factors appropriate to a) and

b) above:

5·37 and 0·152 respectively

5.2.3.3 Applying these factors to the total benefit shown in Table 6 yields the predicted

number of lives and injuries to be saved for the accidents applicable to the US fleet of

14 CFR Part 121 aircraft over the period 1984 to 1998 inclusive:

a) The revised benefit for ’fully compliant dynamic seats’ becomes:

b) The revised benefit for ’16g dynamic seats configured without enhancements to

head injury criteria’ becomes:

NOTE: All total values are rounded to the nearest whole number.

5.2.4 Proportion of Benefit From Enhanced Head Injury Criteria

It may be seen from Table 6 that based on the analysis described in this report the

proportion of benefit from ’fully compliant dynamic seats’ attributable to the

enhanced Head Injury Criteria defined in TSO-C127a is:

Lives Saved = 56 x 5·37 x 0·152= 45

Serious Injuries Saved = 49 x 5·37 x 0·152= 40

Lives Saved = 34 x 5·37 x 0·152= 28

Serious Injuries Saved = 27 x 5·37 x 0·152= 22

Fatalities: =

56 - 34

= 39%

56

Serious Injuries: =

49 - 27

= 46%

49

October 2005
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6 Discussion

6.1 Accuracy of Predictions 

6.1.1 The analytical methods employed are intended to provide as accurate an assessment

as is possible with the available data, using the mathematical tools currently in

existence. However there will still remain an element of uncertainty associated with

assessments of this kind, and this should be borne in mind when making decisions

concerning aircraft safety that are predicated on the results of this analysis. Any

analysis of this kind must involve a degree of subjective judgment and relies on the

accuracy of the data available. The methodology utilized is aimed at providing an

indication as to the order of benefit likely to be achieved. Certain assumptions have

been made in the analysis of data and the more significant are described in

paragraph 5·1.

6.1.2 This analysis considered only the accidents studied in the earlier analysis

(Reference [1]). This earlier analysis utilized an early standard of the CSRTG Accident

Database (Reference [2]), which at the time had few accidents with 100% Fatalities.

It is unlikely that there are many lives to be saved from the introduction of ’16g seats’

in accidents of this severity. However, it is feasible that the benefit assessment might

increase slightly if accidents of this type were studied. 

6.1.3 The accidents yielding zero benefit in the earlier analysis were not re-evaluated as part

of this analysis (Reference [1]). It is considered unlikely that a reassessment of these

accidents would yield any significant benefit.

6.2 Factors Influencing the Determination of Benefit

6.2.1 Impact intensity is a significant factor in the accrued benefit from ’16g seats’ likely to

be achieved in an accident. It is evident that there will not be any benefit from the

introduction of ’16g seats’ when the impact intensity is beyond the level of resilience

of the seat design. Furthermore, at impact intensities below those sustainable by ’9g

seats’, there would be little benefit beyond that afforded by enhanced Head Injury

Criteria. This limits the number of ground impact related accidents that would benefit

from the introduction of ’16g seats’. 

6.2.2 It might be expected that the higher the impact intensity the greater the probability of

an intense fire. Since the accidents that would benefit from the introduction of ’16g

seats’ are at higher levels of impact intensity, it is hence more likely that there will

also be an intense fire. This secondary threat to survival is extremely significant in the

determination of lives to be saved. If passenger impact injuries are prevented with

’16g seats’, and there is an intense fire threat, then the occupants are likely to perish

even if they survive the impact uninjured. If the fire threat could be reduced, then the

enhanced impact protection afforded by ’16g seats’ may provide the occupants with

the capability of evacuating the fire-threatened area. 

6.2.3 As fire standards for transport category aircraft are improved, the potential for

increasing the live saving capability of ’16g seats’, due to the occupants reduced

exposure to the secondary fire hazard, will also improve.

6.2.4 Due to the extensive disruption to the floor during the impact sequence, a number of

accidents analyzed would not have any potential for lives being saved with the

introduction of ’16g seats’.

6.3 Methodology used for the Determination of Benefit from the Accidents

Occurring at Bangalore and Strasbourg

It was not possible to carry out an assessment of benefit based on an understanding

of the injuries sustained in the accidents occurring at Bangalore or Strasbourg due to

the unavailability of the appropriate data. The assessed total number of lives saved

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from these accidents based on the earlier analysis was 16 with an increase in the

number of Serious Injuries of 10. This current analysis suggested that the total life

saving from ’fully compliant 16g seats’ would be 15 with 0 increase in the number of

Serious Injuries (See Table 6). It may be seen that the derivation of the life saving

improvement, from the methodology used for these accidents in this analysis, is

similar to that determined from the earlier analysis, albeit with a difference in the

reduction of Serious Injuries. On this basis, it is considered that the methodology

used for these accidents is to a satisfactory level of accuracy.

6.4 Comparison of Derived Benefit with Earlier Analysis 

6.4.1 In the earlier analysis, the Benefit for ’fully compliant dynamic seats’ (derived from the

method considered the most accurate when the analysis was carried out) applicable

to the US fleet of CFR Part 121 aircraft over the period 1984 to 1998 inclusive, (see

Reference [1]) was:

Reduction in Fatalities = 51 

with a 95-percentile range from 33 to 68

Reduction in Serious Injuries = 54 

with a 95-percentile range from 28 to 79

The equivalent Benefit derived from this analysis was:

Reduction in Fatalities = 45 

Reduction in Serious Injuries = 40

6.4.2 It may be seen that the reduction in Fatalities and Serious Injuries is to a similar level

and that the values derived from this analysis are within the 95-percentile range

determined from the earlier analysis (Reference [1])

7 Conclusions

7.1 An analysis, based on the accidents studied in an earlier benefit assessment for ’fully

compliant dynamic seats’ over the period 1984 to 1998, has been carried out to

assess the potential benefit that might result from the introduction of ’16g dynamic

seats configured without enhancements to head injury criteria’. This benefit has been

derived in terms of reduction in Fatal and Serious Injuries for aircraft type certificated

with 30 or more passenger seats and operating to 14 CFR Part 121. Account has been

taken of the reduction in fire threat afforded to the impact survivors by the improved

fireworthiness of cabin interiors compliant with the standards defined in 14 CFR Part

25 at amendment 72. The prediction of benefit for ’16g dynamic seats configured

without enhancements to head injury criteria’ approximates to: 

7.2 A re-evaluation, based on the accidents studied in an earlier analysis for ’fully

compliant dynamic seats’ over the period 1984 to 1998, has been carried out to

assess the potential benefit that might result from the introduction of ’16g seats’. This

benefit has been derived in terms of reduction in Fatal and Serious Injuries for aircraft

type certificated with 30 or more passenger seats and operating to 14 CFR Part 121.

Account has been taken of the reduction in fire threat afforded to the impact survivors

by the improved fireworthiness of cabin interiors compliant with the standards

defined in 14 CFR Part 25 at amendment 72. The predicted benefit approximates to: 

Reduction in Fatalities = 28

Reduction in Serious Injuries = 22

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7.3 The proportion of benefit attributable to the enhanced Head Injury Criteria as defined

in TSO-C127a is: 

7.4 The fire threat, which is often severe in accidents where ’16g seats’ are likely to

reduce the number of impact Fatalities, is a significant factor in terms of the ultimate

benefit attained. If significant improvements to occupant protection from fire could be

made this would result in an increase in the assessed benefit from ’16g seats’.

7.5 Due to the extensive disruption to the floor during the impact sequence, a number of

accidents analyzed would not have any potential for lives being saved with the

introduction of ’16g seats’.

8 References

[1] ‘Benefit Analysis for Aircraft 16g Dynamic Seats’ 

Report No. DOT/FAA/AR-00/13 (US Department of Transportation Federal Aviation

Administration)

[2] ‘The Cabin Safety Research Technical Group (CSRTG) Accident Database’ (see

www.fire.tc.faa.gov)

[3] ‘The Abbreviated Injury Scale’ 1990 Revision

(Association for the Advancement of Automotive Medicine)

9 Definitions

Abbreviated Injury Scale (AIS) (Source: Reference [3])

“The Abbreviated Injury Scale (AIS) is a consensus derived anatomically based

system that classifies individual injuries by body region on a 6-point ordinal severity

scale ranging from AIS 1 (minor) to AIS 6 (currently untreatable)."

Accident Scenario

“That volume of the aircraft in which the occupants are subjected to a similar level of

threat.”

Fatal Injury (Source: NTSB, ICAO)

“An injury resulting in death within thirty days of the date of the accident.”

Serious Injury (Source: NTSB, ICAO Annex 13, Eighth Edition, July 1994)

“An injury, which is sustained by a person in an accident and which:

a) Requires hospitalization for more than 48 hours, commencing within seven days

from the date the injury was received; or

b) Results in a fracture of any bone (except simple fractures of fingers, toes, or nose);

or

Reduction in Fatalities = 45

Reduction in Serious Injuries = 40

Fatalities = 39%

Serious Injuries = 46%

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c) Involves lacerations which cause severe hemorrhage, nerve, muscle or tendon

damage; or

d) Involves injury to any internal organ; or

e) Involves second or third degree burns, or any burns affecting more than 5 per cent

of the body surface; or

f) Involves verified exposure to infectious substances or injurious radiation.”

Fully Compliant Dynamic Seats 

The term is used in this report to refer to seats that are fully compliant with the

minimum performance standards prescribed in TSO-C127a.

16g Dynamic Seats Configured Without Enhancements to Head Injury Criteria

The term is used in this report to refer to seats that are compliant with the minimum

performance standards prescribed in TSO-C127a other than the enhanced head injury

criteria (HIC).

16g Seats 

The term is used generically, in this report, to refer to both fully compliant dynamic

seats and 16g dynamic seats configured without enhancements to head injury

criteria.

October 2005