DOT/FAA/AM-03/9

Van Gowdy

Rick DeWeese

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

May 2003

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, VA 22161.

Human Factors Associated

With the Certification of

Airplane Passenger Seats:

Life Preserver Retrieval

Office 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-03/9 

4. Title and Subtitle 5. Report Date 

Human Factors Associated With the Certification of Airplane Passenger May 2003 

Seats: Life Preserver Retrieval 

6. Performing Organization Code 

 

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

Gowdy V and DeWeese R 

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 14. Sponsoring Agency Code 

800 Independence Ave., S.W. 

Washington, DC 20591 

15. Supplemental Notes 

16. Abstract 

A series of human subject tests were conducted by the Biodynamics Research Team at the FAA’s Civil 

Aerospace Medical Institute (CAMI) to investigate human factors associated with the “easy reach” requirement 

in FAA regulations for under-seat mounted life preservers. The protocol was designed to observe and measure 

the effects of human physical attributes and life preserver installation features relevant to the retrieval of life 

preservers. A mockup of a 30-inch pitch, economy class transport passenger seat installation was used to evaluate 

4 configurations of life preserver installations. The position of the pull-strap, used to open the life preserver 

container, was the independent variable. 

One hundred thirty-two adult subjects were tested. Each subject was seated, restrained by the seat’s lap belts, 

instructed to reach beneath the seat, open the lifer preserver container, and extract the packaged life preserver. 

The time for retrieval of the life vest was measured from videotapes of each test. The videotapes were also 

reviewed independently by 11 outside raters, who rated the difficulty for each subject on a scale of 1 (easy) to 7 

(very difficult). 

There was significant agreement (Cronbach’s alpha = 0.978) in the “ease” ratings. In comparing the ease 

ratings and retrieval times, an average ease rating < 3 corresponded to a retrieval time < 10 seconds. An 

“EASY10” benchmark, derived from these results, indicates that a life preserver retrieval time < 10 seconds 

should be considered easy. Two of the configurations had average ratings < 3. The installation features that 

distinguish the two configurations that passed the EASY10 benchmark, compared with the two that failed, were 

the position of the pull-strap, the pull-angle on the strap necessary to effect a quick opening of the life preserver 

container, and the position of the stowed life preserver relative to the front frame of the seat. 

The results indicate that the “easy reach” criteria should be satisfied if: 1) the pull-strap and life preserver 

container are no more than 3-inches aft of the seat frame, and 2) the pull-angle to quickly open the container is 

in the range: -50° < θ < -10°.

17. Key Words 18. Distribution Statement 

Life Preserver, Transport Airplanes Document is available to the public through the 

National Technical Information Service, 

Springfield, Virginia 22161 

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

Unclassified Unclassified 16 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 
1

HUMAN FACTORS ASSOCIATED WITH THE CERTIFICATION OF AIRPLANE

PASSENGER SEATS: LIFE PRESERVER RETRIEVAL

INTRODUCTION

Compliance with FAA regulations for personal

floatation devices, e.g. inflatable life preservers, installed on transport airplane passenger seats includes

three important factors. First, the design and functional performance of the life preserver is specified in

TSO C13 (1). Second, the physical containment and

mounting of the life preserver, commonly on the

underside of the seat pan, is the responsibility of the

seat manufacturer to ensure that the life preserver and

container are properly attached to the seat. The third

factor is the access to the life preserver, evaluation of

which is usually performed during final inspection of

the cabin interior prior to approval for delivery of the

airplane into service.

The FAA regulation addressing life preserver installations specifies: “Each life preserver must be within easy

reach of each seated occupant” (2). There are no published FAA guidance or policy documents to define the

term “easy reach” in this regulation. Nor is there any

implication regarding the range of occupants (e.g. body

size) that should be able to reach the life preserver easily.

Thus, the pass/fail assessment of life preserver installation, based on the judgement of the approving official,

is subjective and potentially inconsistent.

A previous study (3) of systematic human performance related to airplane passenger life preservers

focused on retrieval time, donning time, and donning

errors for different types of life preservers installed at

two different locations on a passenger seat. A comparison of preserver retrieval times for two different

stowage locations, beneath the seat versus the seatback, was reported in this earlier study (beneath seat:

mean = 17.0 seconds, SD = 10.7; seat-back: mean =

13.6 seconds, SD = 6.2). The differences in retrieval

times were not statistically significant. Although retrieval time can be an indicator for ease-of-effort,

other factors, including human anthropometry and

the physical design/installation of the seat and preserver container, may affect the ease of retrieval.

A series of human subject tests were conducted by

the Biodynamics Research Team at FAA’s Civil Aerospace Medical Institute (CAMI) to investigate the

human factors affecting the “easy reach” requirement

for under-seat mounted life preservers. The protocol,

which included a mockup of a passenger seat installed

in an economy class transport cabin configuration,

was designed to allow observation and measurement

of the effects of human physical attributes and life

preserver installation features associated with the ease

of retrieval. The data and observations acquired from

this effort were analyzed to evaluate the key features

that influence the ease of retrieval of an under-seat life

preserver. Examined were the relationships between

subjects’ physical measurements, container/preserver

location, time to retrieve a preserver, and a subjective

ranking of “ease-of-retrieval.”

DESCRIPTION OF LIFE

PRESERVER RETRIEVAL TESTS

Test Setup. As shown in Figure 1, two

typical economy class passenger seats were

installed on a test fixture to represent the

geometry of a 30-inch seat-pitch installation. The seat-to-seat dimensions are illustrated in Figure 2. The 30-inch seat-pitch,

which is in the narrow range for contemporary US domestic carriers, was considered

conservative for assessing installation effects

on preserver retrieval. The rear seat was

offset to the right by one seating position, as

Figure 1. Test Setup
2

shown in the overview of the test setup (Figure 3).

This lateral offset between the forward and rear seats

provided ample video camera coverage of the motion

of the subjects seated in the aft seat during life preserver retrieval, and it prevented the subject from

leaning forward into the “aisle space” left of the

forward row seat. Seat-back breakover features on the

seats were locked to inhibit forward motion of the

seat-backs, and the armrests on the subject-occupied

rear seat were placed in the down position.

Video Coverage and Instrumentation. Two NTSC

video cameras were positioned on the side of the test

setup to cover the subject’s motion. As illustrated in

Figure 3, one video camera view was framed to record

the overall test setup, and the other camera focused on

a close-up view of the underside of the subject-occupied seat. Two red light-emitting diodes (LEDs), one

mounted on the top of the seat-back in front of the

subject and one mounted in the rear base frame tube

of the forward row seat, served as “start test” indicators and for synchronization between the cameras.

The seat-back LED provided the start stimulus for the

test subject, and the base frame LED was recorded in

the views of both cameras. The test conductor initiated each test by pressing a switch that simultaneously

illuminated the two LEDs, signaling the subject to

retrieve the life preserver.

Retrieval time was measured using the under seat

close-up video tape by counting the number of video

frames (recorded at 30/sec.) between the start LED

illumination and the first video frame showing complete removal of the life preserver from the container

by the subject. The close-up under-seat video was also

used to estimate (± 5°) the pull angle on the release

strap, which provided the means to open the front flap on

the container and gain access to the packaged life preserver as the subjects attempted to open the container.

A device to measure each subject’s sitting height and

under-seat reach distance was mounted behind the rear

seat. Subject weight, standing height, and waist girth

measurements were recorded prior to the tests, along

with gender, age, and education information. These data

were included in the analysis of the results.

Life Preserver Container Configurations. The

primary variable for the life preserver installation was

the location of the release strap. There were four

configurations of release strap position, as illustrated

in Figure 4. The position of the release strap varied

relative to the front edge of the main lateral tube on

front of the seat frame. Although these four configurations do not encompass the entire range of designs

and installations used on contemporary passenger

seats, the key parameters related to the location of the

release strap on the container were typical of those

installed on current seat models.

30.0

Approx. 2 in.

Belt Anchor

CRP

Approx. 27 in

Life vest pouch

Sitting Height of 50th Subject

 (approx. 35 in)

Datum Line for Reach Distance

Reach Distance

Approx. 9.5 in

Pull 

Strap

All Dimensions in inches

Seat Pitch

Figure 2. Setup Dimensions
3

View from above

Occupied seat

Camera 1

(Close up under seat view)

Camera 2

(Over all view)

Fwd row

Aft row

Seat in view of subject, providing visual

example of life vest strap hanging 

beneath seat pan.

Approx. 15 ft. from 

occupied seat.

Figure 3. Overview of Test Setup, Viewed From Above

LEDs (On = Start)

Vest container sewn to 

fabric seat pan diaphragm

Configuration 2

Snap Position A

Configuration 1

Configuration 4

Elastic Band

Configuration 3

Snap Position B

Pull-strap opens

vest containter

Vest Pkg

5.5 in.

3.5 in.

Figure 4. The Four Life Preserver /Container Configurations
4

The following summarizes the installation features

for each of the four configurations, along with general

observations made during tests:

Configuration 1. (Figure 5)

• The release strap snaps to a mating stud on the

nylon container.

• When the container is closed, the release strap

hangs vertically approximately 3.5 inches behind the

front edge of the seat frame (formed by a lateral

tubular beam).

Configuration 2. (Figure 6)

• The release strap snaps to a mating stud located

near the top (11 0’clock) on the forward side of the

front tubular beam. The mating snap stud is attached

to the front flap of the nylon seat pan diaphragm,

which wraps around the front tubular beam.

• When the container is closed, the release strap

drapes over the front beam and hangs vertically,

tangent to the front tubular beam. The seat cushion

bears on the release strap snap.

Configuration 3. (Figure 7)

• This installation is similar to that of Configuration 2, except the release snap mating stud is located

towards the bottom (8 0’clock) on the forward side of

the front tubular beam.

• When the container is closed, the release strap

hangs vertically from the lower front side of the

tubular beam. The seat cushion does not bear on the

release strap snap.

Configuration 4. (Figure 8)

• This configuration was the same as Configuration 1, except a rubber band was wrapped around the

nylon container and release strap to move the release

strap rearward. When the container flap was closed,

the release strap was approximately 5.5 inches behind

the front edge of the seat frame.

• In this configuration, the plastic bag containing

the life preserver was purposefully shoved to the rear

of the container. This increased the distance a subject

had to reach to grasp and remove the life preserver.

Figure 5. Configuration 1 Figure 6. Configuration 2

Figure 7. Configuration 3 Figure 8. Configuration 4
5

 The measured pull force to extract the plastic

package containing the life preserver from the nylon

container in all four configurations was 4 to 5 pounds.

Subject Selection. The human subjects for this

study were participating in a concurrent research

activity at CAMI related to emergency egress. The

subjects for the life preserver retrieval study, comprised of 132 healthy adults between the ages of 18

and 65 years, were selected from the pool of subjects

in the egress research project. In addition to “average”

size subjects selected randomly from the pool, small

females and large males were deliberately picked from

the groups of people arriving for the egress study. The

rational for selection of specific small female and large

male subjects in the life preserver retrieval study was

based on assumptions that data from subjects in these

two physical ranges would likely bound the performance characteristics of the general population.

Physical data for the subjects in this study are

summarized in Table 1. There was no attempt to

categorize anthropomorphic percentile ranges for the

subjects. The average weight for the male subjects,

231 lbs., is a consequence of deliberate selection of

large males from the subject pool. Figure 9 depicts the

weight and stature for all male and female subjects in

this study compared with the ranges in the general

population used to define anthropometric characteristics for regulated test dummies (4). Figure 9 shows

that the average weight of the male subjects participating in these tests is greater than the average weight of

the normal US male population.

Protocol. Each subject was directed to sit in the aft

row test seat and buckle the lap belts as if in preparation for take-off or landing. Next, a verbal description

Table 1. Subjects’ Physical Data

 Weight (lbs) Stature (in) Waist (in) * Sitting

 Height (in)

**Under-Seat

Grasp (in)

N Mean SD Mean SD Mean SD Mean SD Mean SD

Males 70 231 51 (72.2) 3.1 42 6.8 34.4 1.5 5.2 (3.1)

Females 64 170 47 (64.9) 2.7 35 6.1 31.6 1.4 5.9 (3.1)

Note: All measurements were made with the subjects fully clothed and wearing shoes, which added to the weight,

stature, and waist measurements.

* Sitting height measured vertically from the top of subject’s head to horizontal plane through the seat cushion

reference point

** Under-Seat Grasp estimated as 2 inches less than the maximum under seat reach of extended finger tips.

of the purpose of the test and the instructions for

performing the test were read to the subject. The

instructions were as follows:

The purpose of this experiment is to evaluate the ease or

difficulty passengers traveling in an airplane may have with

the retrieval of the life vest underneath their seat.

In this experiment, we ask you to perform the following actions: With your seat belt buckled and your arms

resting on your lap, observe this small red light on the

seat in front of you. When you see the light turn on, lean

forward without removing your lap belt, reach under the

seat you are sitting in, and pull on the strap hanging

down under your seat to open the life vest pouch.

(At this point of the instructions, the test conductor

directs the subject’s attention to a passenger seat in the

view of the subject, approximately 12 feet away. The test

conductor tells the subject there is a strap under his/her

seat similar to the one in view on the other seat.)

All Subjects

Stature vs Weight

50

60

70

80

50 100 150 200 250 300 350 400

Weight (lbs)

Stature (inches)

Males Females

95% Male

5% Female

Figure 9. All Subjects’ Physical Size
6

Reach into the open pouch and pull out the life vest,

which is in a plastic package. Then, sit upright in your

seat with the life vest in your lap. Do not open or try to

put on the life vest. This is not a timed event, so you do

not have to be in a big hurry.

Thus, when the light turns on, keep your seat belt

buckled, reach beneath your seat, pull the strap hanging

down under the seat, retrieve the life vest, and then sit

upright with the vest in your lap. Remember that you do

not have to be in a hurry to get the vest.

Each subject was tested once. The motions of a

subject attempting to retrieve the preserver were recorded by the video cameras (described above). Measurements of sitting height and under-seat reach

distance were made after each test (see Table 1). Note

that the sitting height reported in Table 1 is the

vertical distance from a horizontal plane through the

seat cushion reference point (CRP) to the top of a

subject’s head. This dimension is illustrated in Figure 2.

ANALYSIS METHODS

The independent variable for these tests was the

container/life preserver location beneath the seat pan.

The analysis method included subjective assessments,

described below, by a group of 11 raters who evaluated

each test subject’s efforts to retrieve the life preserver.

The ratings were examined to determine relationship

between each test subject’s efforts and the installation

features of the four configurations. The objective of

this method was to determine: 1) if there was a general

consensus of the reviewers’ opinions on the ease/

difficulty of preserver retrieval, 2) the features of the

container/life preserver locations that were associated

with easy or difficult retrieval efforts, and 3) the

effects of physical anthropometry on retrieval of the

life preserver.

Subjective Assessment. Videotapes of all the tests

were provided to the 11 raters, who were asked to

independently rank the degree of difficulty each of the

test subjects experienced retrieving the life vest. The

raters included four engineers from airplane seat manufacturers, an interiors engineer from a large airplane

manufacturer, a flight attendant, three engineers from

FAA aircraft certification offices, and two office secretaries. No rater participated in the conduct of the

tests, and the instructions provided to them did not

include details describing the installation configurations for specific tests or specific information about

the subjects. The ranking method involved assigning

a score from 1 (very easy) to 7 (very difficult) for each

subject’s efforts as viewed on the videotape.

Figure 10 presents the guidelines included in the

scoring instructions.The ranked assessment scores

were statistically analyzed to determine the degree of

consensus among all of the reviewers. Cronbach’s

Alpha, a reliability analysis, was used to measure the

consistency in the reviewers’ scores. The computed

result (11 reviewers, 132 test scores, alpha = 0.978)

indicated there was significant agreement in the ratings, and no single reviewer’s scoring of the tests

differed significantly from the others.

SCORE ASSESSMENT EXAMPLE OBSERVATIONS

1 Very Easy Subject quickly and easily reached pull-tab, then removed vest in one

continuous motion. No delays or difficulties observed.

2

3 Easy, with

minor difficulty

Subject successfully reached pull-tab AND removed vest after first

attempt. Slight difficulty was observed, such as more than one tug on

the pull-tab or more than one attempt to remove the vest package.

4

5 Difficult, but

successful

After repeated attempts and/or using different methods to open

pouch and/or retrieve vest, the vest was extracted. The subject

adjusted his/her “lean-over-posture” or reach path during the test.

6

7 Very Difficult

Subject had great difficulty in reaching pull-tab, OR opening the

pouch, OR it took too long to retrieve vest, OR the vest was not

retrieved.

Figure 10. Subjective Assessment Ranked Scoring Instructions
7

RESULTS

The EASY10 Criteria. Figures 11 to 22

and Table 2 present the results of these

tests. Although retrieval time was not explicitly identified as a benchmark for scoring the tests by the reviewers, a relationship

between the average ranked scores for each

life preserver installation configuration and

the measured retrieval time was apparent,

as shown in Figure 23. A rational (albeit

subjective) choice of an “ease assessment”

rating of 3 was selected as the demarcation

between easy and difficult. This benchmark would place Configurations 1 and 3

in the “easy” range (score < 3). Configurations 2 and 4 would be considered “difficult” (scores > 3). Referring to Figure 23,

a score of 3 relates to a retrieval time of

approximately 10 seconds. For the purpose of discussing these results, this relationship is identified herein as the EASY10

criteria, which suggests an ease assessment

score <3 satisfies the “easy reach” requirement in the regulation. Included in Figures 11, 14, 17, and 20 are cumulative

percentage results, which show the percentage of subject tests in each of the four

configurations that would satisfy this criteria (score < 3). These results are also

listed in Table 2.

Installation Effects. Although only four

configurations were evaluated in this program, the “easy vs. difficult” outcomes

from the EASY10 criteria can be applied to

specific characteristics that are common

to many life preservers installed under the

seat-pan. Three characteristics identified in

this study are discussed in the following:

1. Container Location. The most obvious factor affecting the retrieval of an

under-seat life preserver is the ability of

the seated occupant to reach under the

seat, grasp the release strap, and remove

the packaged preserver. The “grasp distance” was determined empirically as two

inches less than the measured reach distance, which was defined as the distance

 Retrieval Time - All Subjects

Preserver/Container Config. #1

0

2

4

6

8

10

12

14

048

1216202428

More

Retrieval Time (sec)

Number of Subjects

0%

20%

40%

60%

80%

100%

Cumulative Percentage

Figure 11. Configuration 1 - Retrieval Time

Figure 12. Configuration 1 – Ease Assessment Scores vs

Retrieval Time

Ease Assessment Scores vs. Retrieval Times

for All Subjects (Configuration 1) 

R2 = 0.45

1

2

3

4

5

6

7

0 5 10 15 20 25 30

Retrieval Time (seconds)

Ease Assessment Score

Avg. Assessment Score

 and Retrieval Time

 Pull Angle 

 on Container Strap

0

2

4

6

8

10

-60 -50 -40 -30 -20 -10 0 10 More

Pull Angle (degrees)

Number of Subjects

 Configuration 1

Avg. = -20 deg

Figure 13. Configuration 1 – Pull Angle on Release Strap
8

 All Subjects Retrieval Time

Preserver/Container Config. #2

0

1

2

3

4

5

6

7

0 4 8 12 16 20 24 28 More

Retrieval Time (sec)

Number of Subjects

0%

20%

40%

60%

80%

100%

Cumulative Percentage

Figure 14. Configuration 2 - Retrieval Time

 Pull Angle 

on Container Strap

0

2

4

6

8

10

-100 -80 -60 -40 -20 0 20 40 60

Pull Angle (degrees)

Number of Subjects

Configuration 2

Avg. = =10 deg

Figure 16. Configuration 2. – Pull Angle on Release Strap

Ease Assessment Scores vs. Retrieval Times 

for All Subjects (Configuration 2) 

R2 = 0.85

1

2

3

4

5

6

7

0 5 10 15 20 25 30

Retrieval Time (seconds)

Ease Assessment Score

Avg. Assessment Score

 and Retrieval Time

Figure 15. Configuration 2. – Ease Assessment Scores vs.

Retrieval Time
9

All Subjects Retrieval Time

Vest Config. #3

0

1

2

3

4

5

6

7

8

9

10

048

1216202428

More

Retrieval Time (sec)

Number of 

Subjects

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cumulative Percentage

Figure 17. Configuration 3 - Retrieval Time

Pull Angle 

on Container Strap

0

1

2

3

4

5

6

7

-100 -80 -70 -60 -50 -40 -30 -20 -10 0 10 More

Pull Angle (degrees)

Number of Subjects

Configuration 3

Figure 19. Configuration 3. – Pull Angle on Release Strap

Ease Assessment Scores vs. Retrieval Times for All 

Subjects (Configuration 3)

R2 = 0.79

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 5 10 15 20 25 30

Retrieval Time (seconds)

Ease Assessment Score

Avg. Assessment Score

 and Retrieval Time

Figure 18. Configuration 3. – Ease Assessment Scores vs.

Retrieval Time
10

All Subjects Retrieval Time

Vest Config. #4

0

1

2

3

4

5

6

048

1216202428

More

Retrieval Time (sec)

Number of Subjects

0%

20%

40%

60%

80%

100%

Cumulative Percentage

Figure 20. Configuration 4 - Retrieval Time

Figure 21. Configuration 4 - Ease Assessment Scores vs.

Retrieval Time

Ease Assessment Scores vs Retrieval Times 

for All Subjects (Configuration 4) 

R2 = 0.88

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 5 10 15 20 25 30

Retrieval Time (seconds)

Ease Assessment Score

Avg. Assessment Score

 and Retrieval Time

Pull Angle 

on Container Strap

0

1

2

3

4

5

6

7

8

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 More

Pull Angle (degrees)

Number of Subjects

Configuration 4

Avg. = -25 dg

Figure 22. Configuration 4 - Pull Angle on Release Strap
11

Table 2. Summary Results 

 

 

 Ease Retrieval Container 

 Assessment Avg. Time Strap Avg. Retrieval 

Container Avg. Score (sec.) Pull Angle Time [ 10 sec 

Config. Subjects Mean SD Mean SD Mean SD % Subjects 

1 21 ♂, 17 ♀ 2.8 1.6 8.5 5.8 -22° 15° 77% 

2 17 ♂, 18 ♀ 4.1 1.9 15.3 10.2 +9° 36° 36% 

3 18 ♂, 11 ♀ 2.4 1.4 7.4 4.0 -30° 25° 76% 

4 13 ♂, 17 ♀ 3.4 1.5 13.3 11.0 -23° 20° 48% 

Figure 23 Ease Assessment vs. Retrieval Time

Ease Assessment vs. Retrieval Time

All Configurations

R2 = 0.95

1

2

3

4

5

6

7

0 2 4 6 8 10 12 14 16

Averaged Retrieval Time (sec)

Averaged Ease Scorre

3

1

4

2

(Configurations 1, 2, 3, and 4)

Figure 24 Under-Seat Grasp Distance Distribution

Under-Seat Grasp Distance

All Subjects

0

10

20

30

40

50

0 2 4 6 8 10 12 14 16 18 20 More

Under-Seat Grasp Distance (inches)

Number of Subjects

0%

20%

40%

60%

80%

100%

n = 132

Avg = 5.3

from the front of the seat frame to the tip of the

subject’s extended fingers when the subject was directed to reach beneath the seat pan as far as possible.

The two-inch difference between reach and grasp

distance was estimated from measurements of five

subjects. The statistical distribution of the under-seat

grasp distance for the subjects is shown in Figure 24.

Analysis of these data indicates that approximately

25% of the test subjects had a maximum under-seat

grasp distance of 3 inches or less.

The under-seat grasp distance was supported by the

results of the tests. In Configuration 4, which failed

the EASY10 criteria, the difficulty to extract the

stowed life preserver package for many test subjects

can be attributed to the aft location of the container.

A number of test subjects were able to unsnap the

release strap, but were unable to grasp and extract the

stowed life preserver package. The release strap locations for the two configurations that passed the

EASY10 criteria (1 and 3) were within 3.5 inches of

the front of the seat pan.

2. Container Strap Snap Release Angle. In Configuration 2, the snap was located near the top of the

front tubular beam of the seat frame. In this location,

the initial tendency of subjects to pull the release strap

in a horizontal-forward or slightly downward direction resulted in multiple attempts to unsnap the strap

(Figure 16). This occurred because a near-horizontal

pull placed the snap in shear and prevented release of

the snap. Most test subjects were able to unsnap the

strap by pulling upward. The effort needed to unsnap

the strap was also increased by the weight of the

subject’s thighs, which caused the seat cushion to bear

on the snaps.

In the two configurations (1 and 3) that passed the

EASY10 criteria, the release strap snaps were on the

underside of the seat frame or on the nylon container

beneath the seat pan. This allowed the test subjects to

pull in a downward direction, as shown in Figures 13 and

19. Approximately 85% of the subjects in Configuration

1 tests and 75% of the subjects in Configuration 3 tests

pulled on the release strap at an angle θ , -50° < θ < -10°.
12

3. Occupant Size Effects. Based on the EASY10

scores and observations made during the tests, the larger

subjects (weight > 250 lbs.) had significantly greater

difficulty in retrieving the life preservers than the physically smaller subjects (weight <130 lbs.) In Configurations 1 and 4, where the life preserver container was

located under the seat pan, the average score for large

subjects was 4.8 (n = 16). The combined average scores

for Configurations 1 and 4 for smaller subjects was

1.6 (n = 6). Figures 25 and 26 illustrate the relative

ease a smaller occupant has in retrieving the preserver,

as compared with a large occupant. Thus, the concern

for ease of retrieval should focus primarily on larger

size passengers.

CONCLUSIONS

The four life preserver installation configurations

tested in this study can be divided into two types. Type

1 has the release strap stud snap mounted on the rigid seat

frame, as in Configurations 2 and 3. Type 2 has the stud

snap attached to the flexible fabric container, as in

Configurations 1 and 4. Based on the results and analysis, the installation features that provided positive results

(e.g., easy retrieval) are summarized in Figure 27.

The key feature of the Type 1 installation is the

location of the stud snap on the seat frame. In Configuration 2 tests, the subjects tended to pull the

release strap in a forward-horizontal direction when

the snap was mounted near the top of the frame. This

resulted in a shear force on the snaps, which would not

open the snaps. The seat cushion bearing on the snaps

also made opening the snaps more difficult.

As shown in Figure 27, the mounting position of

the stud snap should be on the forward lower quadrant of the seat frame’s tubular beam. The figure also

indicates that the release strap and the stowed life

preserver package should be within 3 inches of the

front of the seat frame.

COMMENTS

Although this study included only four variations of

life preserver configurations, the results should be applicable to a wide variety of current passenger seat life

preserver installations. The 30-inch seat pitch used in

this study should be considered as a conservative factor.

Wider pitch installations would likely present less difficulty in retrieving the life preserver, especially for larger

occupants. Premium class seats, which often have life

preservers located in center consoles or endbays, must be

assessed by different methods than those described for

this study.

The intent of this study was NOT to define or

recommend a method to conduct human subject tests to

assess life preserver retrieval. Rather, the purpose was to

identify installation features that affect the ease or difficulty of retrieving an under-seat life preserver on a

passenger seat. No inference should be made that the

conclusions described above define precise limits for the

Figure 26. Large Male: 246 lbs. weight, 72 inches stature

Figure 25. Small Female: 107 lbs. weight, 58 1⁄2 inches stature
13

installation of a life preserver. Rational and reasonable

engineering judgement must still be a part of the approval process.

The methods employed in this study involved

subjective assessment of the degree of difficulty, since

this is the approach used to approve seat installations

on transport airplanes. Analysis of the subjective ratings showed a strong consensus among reviewers from

varied backgrounds. Anecdotal reports of inconsistent approval decisions during cabin interior inspections of life preserver installations may be due to

varied personal opinions on how to assess ease of

retrieval. A lack of guidance information or pass-fail

criteria may also contribute to inconsistencies in approval decisions.

Data and analysis presented herein provide some

general guidance to assist in evaluating the life preserver

installation features associated with the “easy reach”

requirements in FAA regulations. The installation features described in this report that affected positive (easy

reach) outcomes for a wide range of occupant size can be

easily verified on most passenger seats. Incorporation of

these features by seat designers may also alleviate inconsistency in the installation approval decisions.

Figure 27. Easy Retrieval Installation Features

10

50

3 inches

3 inches

10

50

Snap Release Angle 

Range: -10° < θ < -50°

Release Snap on Seat Frame

Snap Mounted on Fwd Lower

Quadrant of Seat Frame

Stowed Life Preserver 

Pkg Within 3 inches of 

Front Seat Frame

Snap Mounted on Fabric Container

Stowed Life Preserver 

Pkg Within 3 inches of 

Front Seat Frame

Snap Release Angle 

Range: -10° < θ < -50°

Type 1 Installations

Type 2 Installations

REFERENCES

1. FAA Technical Standard Order C-13f, “Life Preservers,” September 24, 1992.

2. US Code of Federal Regulations, 14 CFR 25.1411.

3. Rasmussen, P.G., Steen, J.A., “Retrieval and Donning of Inflatable Life Preservers,” FAA Civil Aeromedical Institute Memorandum Report AAC-119-

83-5, July 1983.

4. Schneider, L.W., Robbins, D.H., Pflug, M.A.,

Snyder, R.G., “Development of Anthropometrically Based Design Specifications for an

Advanced Adult Anthropomorphic Dummy Family,” Vol. 1, University of Michigan Transportation Research Institute, UMTRI Report 83-53-1,

December 1983.