Data pertaining to nonmotion factors affecting ride quality of transport aircraft were obtained as part of NASA in-house and sponsored research studies carried out onboard commuter-airline and research aircraft. From these data, quantitative effects on passenger discomfort of seat width, seat legroom, change in cabin pressure, and cabin noise are presented. Visual cue effects are also discussed

Conner, D. W.

English

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N76-16759
NONMOTION FACTORS WHICH CAN AFFECT RIDE QUALITY
D. William Conner
NASA Langley Research Center
SUMMARY
Data pertaining to nonmotion factors affecting ride quality of transport
aircraft have been obtained as part of NASA in-house and sponsored research
studies carried out onboard commuter-airline and research aircraft. From
these data, quantitative effects on passenger discomfort of seat width, seat
legroom, change in cabin pressure, and cabin noise are presented. Visual cu_
effects are also discussed.
INTRODUCTION
Ride quality can be defined as the impact on the passenger of all aspect|
of the carrier-vehicle physical environment that affect his acceptance of the
ride. Within this definition, environmental factors other than motion and
vibration would be included. These other factors are the subject of this
paper. Surveys of travelers using a given mode of transportation are useful
in identifying the importance of various environmental factors. Abridged re-
sults from one British survey (ref. l) are shown in figure 1. In this survey,
travelers were asked to rank in preference 18 suggested improvements for
railway coaches. The 18 improvements covered a variety of items ranging from
Extra entertainment to More luggage space. In the cumulative order of pre-
ference, four of the top five suggested improvements concerned ride quality:
Less vibration, More space, Less noise, and Better seats. These results are
typical of survey findings for other modes of transportation (refs. 2 and 3),
where various ride-quality factors rank high in importance from the traveler's
viewpoint.
Some new information pertaining to nonmotion factors affecting ride
quality of aircraft has been obtained as part of NASA in-house and sponsored
research studies carried out onboard airline and research aircraft. No attempt
was made in these studies to determine systematically the effects of varying
specific nonmotion factors on ride quality. Data which will be presented were
only incidentally obtained and therefore are of limited scope. A brief over-
view will first be given of the airline traveler surveys from which much of
the data originated to provide a proper backgz_und for subsequent discussion
of individual factors.
[
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https://ntrs.nasa.gov/search.jsp?R=19760009671 2020-03-20T01:59:49+00:00Z
AIRLINE TRAVELER SURVEYS
Small transport aircraft used by feeder lines and commuter lines can
provide much valuable ride-quality information because a significant percentage
of travelers often rate their ride as marginal at best. Lack of good ride
quality is associated with a lack (by economic constraints) of features and
characteristics common to the much larger and heavier jet transports. Four
such small commuter aircraft, shown in figure 2, were the subject of recent
ride quality studies (ref. 4) carried out by the University of Virginia under
NASA grant. The aircraft include the 19-passenger De Havilland of Canada
DHC-6 twin-engine turboprop, commonly known as the Twin Otter; the 26-passenger
Aerospatiale Nord 262 twin-engine turboprop; the 1B-passenger Beech 99 twin-
engine turboprop; and the 26-passenger Sikorsky S-61 helicopter. Each of the
aircraft was used by a different airline; hence, operating conditions differed
somewhat between aircraft. All operations took place, however, in the north-
eastern part of the United States.
Table I provides an overall summary of traveler survey information. More
than 800 travelers participated. Trip time ranged between 20 and 60 minutes
for the three fixed-wing aircraft and between 7 and l0 minutes for the heli-
copter. Near the end of the trip the passengers rated the overall trip ride
on a 7-point (undefined) descriptor scale ranging from Very uncomfortable to
Very comfortable. The ride was given some form of uncomfortable (Somewhat
uncomfortable, Uncomfortable, or Very uncomfortable) rating by slightly more
than B0 percent of the passengers riding in each of the three fixed-wing air-
craft and by 12 percent of the passengers riding in the helicopter. The
relatively low percentage of helicopter passengers who expressed discomfort
may have resulted from the relatively brief time of the trip. On the basis of
general observations of passenger reactions to riding helicopters, an increase
in trip time to B0 or 40 minutes could well result in a greater percentage
of passengers who would be uncomfortable. In addition to obtaining the
passengers' assessment of the overall trip ride quality, the investigators
obtained passengers' opinions concerning their satisfaction with various motion
and nonmotion factors believed to affect ride comfort. Some of the nonmotion
factors identified as significant are discussed in the following section. A
complete discussion of all factors is given in reference 5.
EFFECTS OF NONMOTION FACTORS
Seat Width
In small aircraft, constraints on interior volume and the economic need
to accommodate as many passengers as safety will allow limit the width of seats
to a value considerably less than that normally used in larger aircraft and
inother public transport vehicles. Figure 3 presents in bar graph form the
percentage of passengers expressing dissatisfaction with the width of the seats
for each of the four aircraft of the survey. Values range from 39 percent to
88
/67 percent. Also shown in each bar graph is the percentage of passengers that
indicated strong feelings about seat-width discomfort. Strong feelings were
expressed by less than one-fourth of those giving a discomfort rating to seat
width.
Seat width differed between types of aircraft. In the lower part of
figure 3 is presented the variation of percent passengers dissatisfied as a
function of measured seat width. The data indicate a linear relationship, which,
if extrapolated to zero dissatisfaction, indicates that seats ideally should
be about 60 cm wide. Although seat shape and firmness differed between air-
craft, questionnaire answers revealed that the great majority of passengers
considered shape and firmness characteristics of these seats to be satisfactory.
Legroom and Workspace
In addition to width, there are other factors in seating which can affect
ride comfort to some extent. In tourist-class sections of conventional-size
Jet transports, each seat row generally consists of a group of three seats
on each side of the aisle. Although seat width may be ample, a passenger sit-
ting in the center seat, when both adjacent seats are occupied, has little
freedom of movement, particularly if a task, such as eating a meal, is being
performed. Also, both reduced floor width for window-seat passengers adjacent
to an incurving fuselage shell and insufficient seat pitch (fore-and-aft
spacing) will tend to limit passenger leg movement, which in turn can adversely
affect ride comfort, particularly for long trips.
Figure 4 presents in bar graph form the percentage of passengers expressing
dissatisfaction with the amount of legroom. Values range from 63 to 73 percent
for the fixed-wing aircraft and 28 percent for the helicopter. Of those ex-
pressing discomfort, up to 20 percent indicated strong feelings. In the lower
part of figure 4 is presented the variation of percent passengers dissatisfied
as a function of legroom measured from the front edge of the seat. A nonlinear
relationship is indicated, with rapid reduction in dissatisfaction as the leg-
room is increased beyond 2h cm. Extrapolation of the results indicates that
a legroom of about 28 cm should be satisfactory to practically all passengers.
In the survey, passengers were also queried about adequacy of workspace
(which may be inferred to include both side-to-side and fore-and-aft space in
front of the passenger). Responses were very similar to those for legroom,
with values for percent uncomfortable ranging from 66 to 81 percent for the
fixed-wing aircraft and 43 percent for the helicopter.
Change In Cabin Pressure
The rate of change of cabin pressure which occurs in aircraft depends on
how the aircraft is operated and whether or not the cabin is pressurized.
Smaller transports oftentimes are not pressurized, and, except for the Nord
89
262, this is true for the four aircraft of the survey. Terminal-area maneuvers
used to minimize time and costs for short-haul operations generally involve
rates of climb and descent which change cabin altitude (pressure) at a far
greater rate than recommended. Suchwas the case for the aircraft surveyed,
as shownin figure 5. At the top of the figure is presented in bar graph form
the percent passengers dissatisfied for each aircraft. Values range from 26
to 60 percent.
Measuredrates of change of altitude or pressure are not available for
the four aircraft surveyed but are available from another study utilizing the
U. S. Air Force Total In-Flight Simulator (TIFS) research aircraft. In this
study, also reported in the present compilation (ref. 6), the effect of various
flight maneuverson ride quality was determined. During the course of the
study, written commentsincidentally offered by the test subjects for certain
maneuversoftentimes indicated discomfort due to change in cabin pressure.
Data for h23 test-subject--maneuver situations are available and have arbitra-
rily been divided into 5 groups with each group covering a specific, nonover-
lapping range of rate of change in cabin altitude. Within each group the per-
cent of passengers offering commentsof dissatisfaction was determined and
the results are presented in the lower part of figure 5 as a function of rate
of changeof cabin altitude. At rates from zero to 150 meters per minute, no
dissatisfaction was expressed. Dissatisfaction was first evidenced by a small
percentage of passengers in the range of rates between 250 and 350 meters per
minute and then increased almost linearly to more than 50 percent dissatisfied
when the rate of change of cabin altitude was between 850 and llO0 meters per
minute. Although a direct relation between these data and the airline survey
data cannot be established, the trends shownin figure 5 certainly indicate
that all four aircraft must have engagedin rather rapid rates of change of
altitude during someportion of their Journeys.
Cabin Noise
Passenger surveys indicate cabin noise to be a commonsource of discomfort
for various air, surface, and marine forms of public transportation. Even in
large jet transports the noise level can be quite low near the front of the
aircraft but can be uncomfortably high near the rear. The four commuterair-
craft of the airline survey were no exceptions, as can be seen by the bar
graphs presented in figure 6 for percent passengers expressing discomfort from
cabin noise. Discomfort levels ranged between 60 and 70 percent for all four
aircraft, with lO to 25 percent feeling strongly. The discomfort results from
a noise environment which varies during the trip as the aircraft climbs,
cruises, and descends to landing. No attempt has yet been madeto equate cabin
noise dissatisfaction from this survey with measurednoise environment.
Limited information is available, however, concerning effects of cabin
noise level on passenger comfort rating. A brief in-house flight study was
recently carried out on a Boeing 737 airplane at Langley Research Center. In
the study 13 passenger subjects rated their comfort associated with noise and
vibration during 1-minute segments of straight and level flight. A range of
vibration and noise levels was obtained by varying aircraft thrust, forward
9O
speed, and position of the landing gear and drag brakes. Figure 7 presents
the variation of average rating of comfort with cabin noise level for a constant
(vertical) vibration condition of 0.047g. Comfort rating was indicated by the
test subjects on a 5-point scale, with 1 as Comfortable and 5 as Uncomfortable.
The data showeda reasonably consistent trend, with average comfort rating
increasing from a value of 1 to h as noise level in the cabin increased by
about 15 dB(A).
The interrelated effects of noise and vibration, however, were not clearly
established during the study. This was particularly true whennoise level was
maintained constant and vibration level was allowed to vary. Muchmore research
is required to establish quantitatively the contributions of noise to passenger
discomfort in combined environment situations. Such information is needed
since likely candidate concepts of advanced transports (large civil helicopters,
powered-lift Jet aircraft, etc.) maywell have significantly high levels of
interior noise in combination _-ith other worrisome environmental inputs. In
a paper presented earlier in this compilation (ref. 7), Stephens describes the
magnitude of the problem and suggests areas for future research.
Visual Cue Effects
Another factor which can affect passenger ride comfort is the presence
or absence of visual cues from outside the vehicle. Most vehicles are equipped
with windows for various reasons, someof which are psychological (e.g., to
minimize claustrophobia). Although quantitative information regarding visual
cue effects on ride comfort is lacking, several observations madeduring recent
ride-quality investigations are worth mentioning. For random-motion ride en-
vironments, presence of a window adjacent to the seat appears to have a slightly
favorable effect on comfort as observed in preliminary checkout studies of a
helicopter to be used for ride-quality research (ref. 8). If an aircraft
carries out tight turns at a relatively low altitude, however, an unfavorable
effect can result because of the passenger's natural instinct to turn the head
simultaneously to look out the windowat the rapidly changing visual scene.
The resulting change in force vector on the vestibular organs produces a dis-
comfort sensation which can be significant if head motion is rapid. Another
unfavorable visual cue situation results from flickering light due to inter-
ruption of sunlight by the rotor blades. This situation occurred during the
helicopter checkout studies cited above. Only a small percentage (<lO pezcent)
of passengers are generally affected, but the effects can be quite severe.
Light flicker at appropriate frequencies can even lead to seizures by persons
prone to epilepsy. Fortunately, light flicker can be minimized by darkening
light-reflecting surfaces and by tinting the windows.
CONCLUDINGREMARKS
For various modesof travel by air, surface, and water, passenger surveys
have identified nonmotion factors as important contributors to ride discomfort.
91
Ride-quality information has been obtained for such factors in passenger
studies onboard four types of commuteraircraft. Considerable discomfort was
specifically identified for seat width, legroom, and workspace and was quan-
titatively related in terms of percent passengers dissatisfied as a function
of pertinent dimensions. A significant percentage of passengers were dissatis-
fied with excessive rate of change of cabin altitude (pressure). In a separate
study using a research aircraft, percent of passengers dissatisfied was quan-
titatively related to rate of change of cabin altitude. In the commuterair-
craft, a majority of passengers were also dissatisfied with the cabin noise
levels. Preliminary exploration in a Jet transport indicated that although
passenger comfort rating could generally be related to noise level, the com-
bined effects on comfort of noise, vibration, and other factors are complex,
and much research is required to better understand and quantify contributions
of individual factors to overall passenger discomfort in combined-environment
situations. Visual cue effects by passengers sitting adjacent to windows were
indicated to affect ride comfort unfavorably for two situations which could
occur in transport aircraft.
92
RE FERENCE S
1. Branton, P.: Ergonomic Research Contributions to Design of the Passenger
Environment. Passenger Environment, Railway Div., Inst. Mech. Eng. (London),
Mar. 1972, pp. 64°69.
2. Kuhlthau, A. R.; and Jacobson, I. D.: Analysis of Passenger Acceptance of
Commercial Flights Having Characteristics Similar to STOL. Canadian
Aeronaut. & Space J., vol. 19, no. 8, Oct. 1973, pp. 405-409 and M-1 - M-6.
3. Clarke, Michael J.: Reaction of Passengers to Public Service Vehicle Ride.
1975 Ride Quality Symposium, NASA TM X-3295, DOT-TSC-OST-75-40, 1975.
(Paper No. 19 of this compilation.)
4. Richards, L. G._ Kuhlthau, A. R.; and Jacobson, I. D.: Passenger Ride Quality
Determined From Commercial Airline Flights. 1975 Ride Quality Symposium,
NASA TM X-3295, DOT-TSC-OST-75-40, 1975. (Paper No. 18 of this compilation.)
5. Noskowitz, David_ and Jacobson, Ira D.: Passenger Demographics and Subjective
Response to Commuter Aircraft in the Northeast. Mem. Rep. 403219 (Grant
No. NGR 47-005-181), Univ. of Virginia, Dec. 1974. (Available as NASA
CR-142876.)
6. Schoonover, W. Elliott, Jr.: Ride Quality of Terminal-Area Flight Maneuvers.
1975 Ride Quality Symposium, NASA TM X-3295, DOT-TSC-OST-75-40, 1975.
(Paper No. 17 of this compilation.)
7. Stephens, David G.: Review of Measured Vibration and Noise Environments
Experienced by Passengers in Aircraft and in Ground Transportation Systems.
1975 Ride Quality Symposium, NASA TM X-3295, DOT-TSC-OST-75-40, 1975.
(Paper No. 4 of this compilation.)
8. Snyder, William J.; and Schlegel, Ronald G.: Vehicle for Civil Helicopter
Ride Quality Research. 1975 Ride Quality Symposium, NASA TM X-3295,
DOT-TSC-OST-75-40, 1975. (Paper No. 6 of this compilation.)
93
TABLE I.- TRAVELER SURVEY SUMMARY BY AIRCRAFT TYPE
A lRCRAFT DHC-6 N-262 B-99 S-61
TRAVELERSSURVEYED 200 156 133 339(Total Number)
AVERAGETRIP TIME 20-25 35 25-60 7-10(Minutes)
UNCOMFORTABLETRIP RIDE 33 3] 31 12
(Percent Passengers)
BRITISH TRAVELERSURVEY
RANKS
l LESS VIBRATION
1
MORE SPACE I
LESSNOISE 1
PUBLICADDRESSSYSTEM I
BETTERSEATS I
18JBETTERLIGHTINGJ
Figure it- Preferred improvements for railway coaches from
British traveler survey.
94
DE HAVILLANO DHC-6 (19 PAX) 
BEECH 99 (13 PA 
Figure 2.- Ai rcraf i  of commuter a i r l i n e  t r ave le r  survey. 
DHC-6 
N -262 
S -61 
40 
35 
0 25 , a,, 50 75 SEAT WIDTH c m  
PASSENGERS DISSATISFIED. PERCENT 
Figure 3.- Discomfort from seat width from a i r l i n e  
t r ave le r  survey. 
95 
FEELSTRONGLY
OHC-6 1
N-262 I
B_9
S_I
LEGROOMcm
20L
I I I
O 25 50
PASSENGERSDISSATISFIED, PERCENT
Figure 4.- Discomfort from seat
legroom from airline traveler
survey.
I
75
FROMAIRLINE SURVEY
DHC-6 J
N-262 I
S -61
FROMTIFS STUDY
CABIN ALTITUDE / 84
RATEOFCHANGE 500F 116
m,min I_"
0 L_-
I I I I
O 25 50 75
PASSENGERSDISSATISFIED, PERCENT
Figure _.- Discomfort from change in
cabin altitude (pressure).
60 (PAX IN GROUP)
FROMBOEING-737STUDY
FEELSTRONGLY"_
DHC-61/_ l 11
s-611 _1 I
I I I I
0 25 50 7p
PASSENGERSDI SSATISFIED, PERCENT
Figure 6.- Discomfort from cabin
interior noise from airline
traveler survey.
CABIN NOISE
LEVELdB(A) 95E °8
80
I 1 I I I
! 2 3 4 5
COMFORTABLE _ UNCOMFORTABLE _
AVERAGE RATING OF COMFORT
(13PASSENGERS)
Figure 7.- Effect of noise level on
passenger comfort rating.
96
O_G _ _


Nonmotion factors which can affect ride quality

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