Characteristics in the Atmosphene of Long-Range Transport Aircraft ...

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Characteristics in the Atmosphene of
Long-Range Transport Aircraft Cabins
Vretu.eFOrro, H., P. Fovarr, and R . AorrFanr_ Characteristics
in the atmosphere of tong-range transport aircraft cabins . Aviat.
Space Environ . Med. 48(6):503-507, t977.
F_' In the long run, the fatigue In aircrews performing frequent,
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long-range flights is linked to factors connected to the sireraft,
such as noise, temperature, cabin pressme, atmosphere quality,
and flight characteristics. These are the factors Inherent to the
aircraft which we have investigated duriug six loag-range flights
without time mne changes -in DC-8 and DC-10 aircraft of the
U.T.A. Cie. TLe results show that none of the pollutants researched
reach doses considered hazardous by FAR 25 or by
French legislation. This fact is due to the effective ventilation in
the cabins . In flight, thermal comfort is limited by a too-low
hygrometry RH - 12%. Even In a modem aircraft, the noise
( level remains high, in .t acoustical energy is spread over the
i less detrimental frequencies .
T HE CAUSES OF FATIGUE experienced by crewmembers
in long-range transport aircraft appear to
be due to several factors_ Some are due to aircraft
characteristics : ease of handling, noise level, vibration,
cabin environment. Others are a result of flight conditions
: abrupt climatic changes, time variations, loss of
regular food habit .
Fatigue, indeed, is an important problem of aeronautical
ergonomy, affecting all long-distance air transports .
Much work has been done to study the factors affecting
the human operators. More scarce are those studies
which attempted to take a quantitative approach to the
physico-chemical characteristics determining the cabin
environment during long-duration flights, and which
identify therein the causes of fatigue .
The present study treats this area, and was carried out
during six flights between Paris and Central Africa to
observe and eliminate the effects of time zone changes .
Three flights were made in a DC-8 and three others
in a DC-10 .
MATERIALS AND METHODS
For each flight, we have measured a number of parameters
deemed to be representative of the cabin atmosphere
and the deviation from normal which generates
a detrimental effect for crews on duty as well as for
passenger comfort .
The measure of selected parameters should not raise
too many metrological problems during a normal commercial
flight .
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STORAGE
H. VIEILLEFOND, P . FovaN, and R . AuFFREr
Medical Department of f1 .T .A . and Laboratoire de Medecine
Aerospatiale-Centre d'Essais en Vol 91220, Bretigny-Air,
France
Atmosphere quality was estimated through its gaseous
components . Indeed, numerous pollutant gases may contaminate
the aircraft cabin atmosphere .
These pollutants may come from the exterior and are
often encountered during stop-overs and in terminals .
Most are exhaust gases from power and air conditioning
trolleys, hydrocarbide vapors from refueling, etc.
Otherwise, they may originate from the cabin itself,
galley and toilet odors, smoke fumes, or biological
pollutants. -
Finally, they may be gases encountered at high altitude,
such as ozone .
Based on this, we measured the CO (carbon oxyde),
COY (carbon dioxyde), fuel vapors, nitrite vapors,
mercaptans, sulfuric hydrogen, ammonia, and ozone .
These various dosages were effected by use .of Dr£ger
reactive devices, with a relative error of 10-15%, taking
into account the scale of the tube used . .
In addition, the partial pressure of oxygen was measured
with a Biomarine type OM 300 sensor .
Likewise, we measured the following physical values :
-Ambient temperature up to 0.1 °C.
-Relative humidity, computed from the specific humidity
value as given by a Drager CFI 234 pump .
-Noise level with a Bruel and Kjaer 2203 "sonometer"
fitted with one octave filter. We used a 1-in .
microphone equipped with a random incidence corrector
. Noise measurements were carried out in an
endeavour to follow the ISO 1996 Standard, that is,
by placing the microphone between 1 .2 and 1 .5 m
above the cabin floor and 1 .5 m away from any
sidewall . Such conditions are often difficult to obtain
in some aircraft types or at certain crew positions,
such as pilot seats, rear galleys .
These various parameters were measured on the parking
ramp, before takeoff, in flight, and at the beginning
and end of the trip, so that it was possible to follow their
evolution throughout .
RESULTS
We shall successively consider the ambient gaseous
quality in the cabin on the ground and then during
flight, and finally the noise level for both aircraft types .
On the ground, the qualities of the atmosphere obviously
depend upon the climatic condition and aircraft
air-conditioning possibilities .
Aviatioa. Space, arrd Environmenta! Medicine - June, 1977 503

TRANSPORT CABIN ATMOSPHERE-VIELLEFOND ET AL .
In winter, these are always satisfactory on the parking
ramp at Roissy, but not so good at the African stations
of Niamey, Ouagadougou, or Lagos, where cabin temperatures
of 32°C were recorded, as well as a relative
humidity of 60% . Fortunately, these uncomfortable conditions
last only a few minutes .
The most significant point is that of fuel (kerosene)
odors which penetrate into the cabin during refueling
at the African stations . The high temperature causes fuel
vapors in the cabin to'reach concentrations up to 0 .08-
0.1% in volunte .
Such concentrations, fortunately transient, are very
uncomfortable however. From the toxicological point of
view, there is not yet in France any norm which limits
the maximum acceptable concentration .
However, Evrard (2) points out that for a permanent
exposure, the limit could be fixed between 0 .03 and
0.1 %u . For safety purposes, it may be stated that concentrations
of 0.1 % volume are 7 to 10 times lower than the
flash point for the aviation fuel . Therefore, during refueling,
there appears no risk of spontaneous fire or
intoxication .
In flight at cruise altitude, no matter which type of
aircraft, ambient temperature remains constant. It stays
quite homogeneous along thee length of the cabin and
during the preparations of meals, it increases only by
0.3°C in the galleys .
In the type 3/63 DC-8, the cabin temperature varies
from 21 .5-23°C and 21-22°C in the DC-l0_
Such temperatures appear quite satisfactory as they
correspond to those in our homes or offices . In fact,
taking into account hygrometry, they are not always sufficient.
At the flight altitude of the DC-S or DC-10, approximately
9100 m, outside temperature is extremely low, on
the order of -44°C, so that the absolute humidity of air
is very poor and not over 125 mg/ms . As this very dry
air is used for conditioning the aircraft, it is not surprising
to find in the cabin some specific hygrometries varying
from 1 .5 to 5 mg/m', which correspond, considering
the cabin temperature, to a relative humidity between 8
and 16%, with an average of 12% . In fact, at cruising
level the cabin hygrometry is essentially constituted by
breathing out water vapor ; this, in turn, is a function of
the number of occupants .
If we indicate on a diagram (Fig . I) these data of wet
temperature against dry ambient temperature, determining
isohygrometric lines, it can be seen that they fix the
boundaries of an area crossed by the thermal comfort
zone, described by Fanger (3), for an individual doing
physical work, such that his metabolism at rest is increased
by 50 W . The feeling of discomfort is still
further increased by the fact that heat loss is greater at
altitude than on the ground, given that the aircraft flies
with cabin pressures corresponding to 1220-m to 1520m
altitudes . Such climatic data perfectly explain the
currently observed fact that the lightweight blankets at
the disposal of the passengers are mostly used during
sleep, or that a short walk between the rear rows improves
the feeling of thermal comfort .
In air intake, the oxygen partial pressure depends on
504 Avialion, Space, and Enrironmenlal Medicine - June, 1977
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75 20 25 Y
Ory ~emyerowr .
Fig. t . Dry temperature, wet temperature, and straight hygrometry.
The dotted curves define the comfort zones at rest and
during increasing power of muscular exercise (3) . The area
shown in a parallelogram corresponds to ambient conditions on
board .
the cabin pressurization . This is a characteristic of the
aircraft. On a DC-8, the maximum P is 8 .77 psi and on
the DC-10 its value is 8.6 psi only
. During our measurements, we found in the cabin some
oxygen partial pressures varying between 2.56 and 2.63psi
when the aircraft had reached level 330 .
These pressures correspond to a cabin altitude of 1310-1520 m
. In such a case, there is no constraint for
hemoglobin saturation, even for aged persons or-those=_-"~ _
having minor cardiac or pulmonary trouble .
In the cabin, the COY ratio is essentially of respiia= . ° . '
tory origin. This means that the number of passengers is
a major factor in its increase during the course of the •
flight . In fact, after 5 h flying on a DC-10, the COz
concentration never exceeds 0.06% volume, and never
0.1 % volume after 7 h of flight on a DC-8 . Although
much .higher than those commonly measured in ambient- -""
air at ground level, such concentrations are very far
from the maximum acceptable concentration, set at
0.5% by . INRS in 1974, for a permanent exposure of 8 h .
As to the CO, we obtained the maximum value of 5
ppm at the end of the longest day flights when a largee
number of smokers were on board . Most of the time,
and particularly at night, the presence of CO was not
noticeable . It may be noted that in France the maximum
acceptable dose is set at 50 ppm .
We never detected any presence of ozone in the cabin
atmosphere. Our analyzer was only sensitive to concentrations
over 0 .05 ppm and it could be estimated that, in
the cabin, the ozone concentration was not very different
from that on the ground, i.e . nearly 0 .01 ppm from
Guerin (5) .
The absence of this gas in the cabin is easily explained
by the flight level of commercial transport aircraft,
which remains considerably lower than the level of the
atmospheric layers rich in ozone, and also by high temperatures
to which air conditioning is brought in the
compressors. .
Finally, wee could never prove pollutants were at
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TRANSPORT CABIN ATMOSPHERE-VIELLEFOND ET AL .
TABLE r . TABLE OF NOISE LEVELS RECORDED AT VARIOUS LOCATIONS
IN DC 8 AND DC 10. THESE ARE GLOBAL ACOUSTIC VALUES IN LINEAR
dB, AFTER A PONDERATION AND SPEECH INTERFERENCE LEVEL {SIL) .
LOCATION
pilots' compart.
front cabin
front galley
rear cabin
rear galley
biological origin, even at the termination of the longest
trips, and when pollution of human origin was suspected .
Also, we never noticed any toxic vapors generated by
the galleys.
As for the ambient noise level, we made two kinds of
measurements. The first consisted of measuring the
global noise energy at various cabin stations, with and
without ponderation .
The second was a spectral analysis of this energy by
octave band . The results are tabulated in Table I for
both types of aircraft investigated . They are related to
measurements carried out at cruising altitude of the aircraft,
at the different stations shown on Fig. 2 and 3 .
The noise level is given in linear dB ; after using a
ponderation filter A ; and finally the speech interference
level (SIL), computed from the arithmetic average of
acoustic pressures at three prevailing frequencies of
speech: 1000, 2000, and 4000 Hz .
It can be seen that noise levels are high and correspond
roughly to intense automobile traffic or to a machine
shop in the Wissner scale (10), or to a "cocktail
party" according to Guignard (6) . For this author, conversation
is only possible by raising the voice . However,
the values of SIL corresponding to such noise levels permit
normal voice level speech (9) up to 1 .8 m, at least
for the DC-10 .
Approximately the same values are quoted in the BIT
(Geneva) recommendations .
For comparison with another modem, long-range aircraft,
note that in a Boeing 707, cruising at Mach 0 .82
and 12200 m, 78 dBA were noted in the pilot's compartment,
80 dBA in the first-class front cabin, and 78
dBA at the rearmost seats of the rear cabin .
cz,
B
Tf lrl 0
U
DC 8
Fig. 2. Noise level measurement points for assessment of the
acoustic frequency spectrum on a DC-8 aircraft .
112 0 3 070 n
5
iT----- D -
Q t n n _
DC 10
Fig. 3 . Noise level measurement points for assessment of the
acoustic frequency spectrum on a fK-10 aircraft .
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DC 8 DC 10
LINEAR A-POND SIL LINEAR A-POND SIL
87 76 70 93 71 60
86 72 56 82 71 55
95 78 68 90 70 62
87 78 60 88 73 54
89 78 62 95 84 66
6
5
As can be seen, these results are very similar .
The same measurements were recorded during takeoff
at the location of the stewards' seats near the rear doors .
We obtained the following results :
on DC-8 : 96 dBA with 66 dB SIL, and
on DC-10 : 86 dBA with 58 dB SIL.
These are very high noise levels for which normal
voice is only intelligible within 60 cm .
In an attempt to state these results more precisely, we
established the frequency spectrum of these noises by
octave band, the center frequencies of which are displayed
from 31 .5 to 16000 Hz .
In fact, we found but a few frequencies over 8000 Hz
in the pilots' compartment and reargalley of the DC-10.
At 16000 Hz, acoustic pressure was quite low, not
even reaching 35 dB. The results of this frequentiall
analysis are shown graphically in Fig. 4 for a DC-8 and
in Fig. 5 for a DC-10.
In order not to overload graphs already difficult to
read, we recorded the spectrum for two or three stations
only.
. For a DC-8 (Fig. 4) these stations are the pilots'
compartment (Curve I) and the rear galley (Curve 3) ;
for a DC-10 (Fig. 5) again the pilots' compartment
(Curve I), the first-class lounge (Curve 3), and the
tourist-class rear cabin (Curve 4) . These graphs show,
on the left ordinate, the global acoustic pressure level in
dB . On the right ordinate are drawn the curves of NR 85
ratio, or `Noise Rating' in accordance with I .S.O. R 1996
recommendation . On the abscissa is the central frequency
of octaves measured between 31 .5 and 8000 Hz . The
survey of these spectra evidences the great interest of
frequency analysis for fighting against noise . Obviously
the global noise strength level is, with a fluctuation of 5
dB, almost identical on both types of aircraft .
It is not the same for energy distribution as a function
of frequency. From an ergonomy point of view, if we
take the example of the pilots' compartment, we note
that in the DC-8 the maximum energy is distributed between
125 and 2,000 Hz, whereas in the DC-30 there is
a maximum energy between 31 .5 and 250 Hz (Fig. 4,
5) .
This partly explains that the SIL measured at the
pilots' compartment of the DC-10 is 10 dB lower than
that on the DC-8, thereby increasing the comfort for
crews .
As for passenger comfort, there is very little difference
in the frequency spectrum of the tourist-class cabins of
both aircraft . The main point of energy is set from 31 .5
to 1000 Hz, and over 2000 Hz ; the acoustic pressure
Aviarion, Space, and Environmental Medicine • lune, 1977 505
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TRANSPORT CABIN ATMOSPHERE-VIELLEFOND ET AL,
®
m
dB
120
100
80
60
40
20
0
31,5 125
_DC 8-
500 2000
dB
120
110
100
90
70
60
so
40
30
20
10
8000 Hz
Fig. 4 . Establishment of the spectrum frequency of noise
measured in a DGB. On the ordinate, noise strength in dB ; on
the abscissa, octave frequency between 31 .5 and 8000 Hz
level does not exceed 60 dB, which corresponds to a
medium quiet atmosphere, according to the Furrer (4)
scale. For comparison, it is to be noted that in this scale,
a home (flat) is considered as "quiet" with a noise level
of 40 dB .
DISCUSSION
Although our measuring instruments allowed a relative
error of about 10 to 15%, we found no chemical
pollution in the cabin atmosphere of aircraft flying over
long distances, but the CO and COz ratios are found to
increase slowly by the end of the trip, when the load of
the aircraft is very high. No doubt such features are due
to the considerable values of air flows ventilated through
the cabin . The 284 m3 of fuselage air in a DC-8-3/63 is
completely renewed every 4 min . Under such conditions,
an occasional pollutant cannot reach important concentrations
and our measurements show that the regulations
enforced by the FAR 25831 standard are fully met .
506 Avtation, Space, and Env :ronmenfat Medicine • June, 1977
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4
d8
120
100
80
40
20
X
;
-DC10-
- ---- - -,
. ._,
0
1 0
31,5 125 500 2000 8000 Hz
Fig. 5. Establishment of the spectrum frequency of noise
measured in a DGIO. On the ordinate, noise strength in dB; on '
the abscissa, octave frequency between 31 .5 and 8000 Hz
The cabin altitude of the DC-8 not exceeding 6700 ft .
and that of the DC-10, 2319 m, partial oxygen intake
pressure is never inferior to 2 .29 psi . If on the ground
this pressure is found to be around 3 .03 psi, such a reduction
cannot seriously trouble passengers, even those
not in perfect condition, nor decrease the psychomotor
performances of healthy crewmembers . This is very far
from the threshold of hypoxia trouble as described by
Strughold (7,8) . The only problem still not solved is the
dryness of air at altitude . It causes a decrease in the
thermal comfort feeling and a relatively constant thirst .
Unfortunately, remedies are obtainable only through
delicate technology and entail an unfavorable weight
estimate.
Studies showing detrimental effects of noise on workshop
productivity, on intellectual output and on decrease
of human performances are now too numerous to be contested
. For passengers, it is essentially a problem of
comfort and, in our opinion, no pathologic incidence is
to be expected for several reasons .
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TRANSPORT CABIN ATMOSPHERE-VIELLEFOND ET AL .
First, it is an occasional aggression, the intensity of
which does not exceed that of some offices in the center
of a large city.
On the other hand, the fact that the noise is- continuous
and, in the passengers' minds, is linked to the
smooth functioning of the motors thereby providing a
feeling of security, makes the nuisance factor generally
well accepted by the passengers and does not prevent
them from falling asleep .
Finally, in modern aircraft such as a DC-l0, the
distribution of sound energy towards low frequencies is a
favourable element, as it is now well established that
high frequencies are deemed more unpleasant and constraining
than low frequencies .
During repeated long-range fligbts, the noise problem
concerns the prevention of auditory injuries and the
maintenance, at its best level, of the psychomotor potential
of the crew. It is thus a problem for the "Medecine
du Travail," (workmen's compensation) or ergonomy .
Still, it should not be exaggerated since a study conducted
on this subject by Broadbent (1) shows that noise
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interferes with such psychomotor performance only at
very high levels, on the order of 90 dB .
REFERENCES
1 . Broadbent, D . E . 1957. Ergonomics 1 :21 .
2. Evrard, E. 1975. Prfcis de MEdecine Afronautique et SpaN
ale. Maloine Ed . Paris .
3. Fanger, P . O . 1970 . Thermal comfort . Analysis and applications
in environmental engineering . Dan. Tech . Press.
Copenhagen.
4. Fhrrer, W. 1962 . Raum und Banakustik Liirmabwehr Birkhauser-Verlage
Bale .
5. Guerin, H . 1952. TraitE de manipulation etd'analyse de gaz
Masson Ed. Paris.
6. Guignard, J. C. 1965. Noise In : A Textbook of Aviation
Physiology. Gillies, J. A . Ed. Pergamon Press . Oxfort.
7 . Strughold, H . 1938 . Lufrfahrtmedizin 2 :210 .
8 . Strughold, H . 1941 . Laftfahrrmedizin 5 :66.
9 . Von Gierke, H . I?, and C . W. Nixon . 1971 . Noise effects
and speech communication in aerospace environments .
. In : Aerospace Medicine. H. W. Randel Ed. Williams and
Wilkins Co . Baltimore .
10. Wisner, A . H . in DesoiBe, J . Schetrrer, R . Truhaut. 1975 .
PrEds de MEdecine du Travail . Masson Ed . Paris.
Serum lipid levels: a function of weight,
not diet
Serum cholesterol and triglyceride levels among Americans are much more de- .
pendent on the degree of adiposity in each person than on his or her consumption
of fat, sugar, starch, or alcohol . Therefore, weight reduction should be the first step
in control of hyperlipidemia .
This finding is based on a prospective dietary survey of 4,057 adults in Tecumseh,
Michigan, done by Dr. Allen B . Nichols and associates of the University of
Michigan. The frequency of consumption of 110 different foods was determined for
each participant, and the average weeklyeonsumption rates of foods high in fat,
sugar, starch, and alcohol were compared with serum cholesterol and triglyceride
levels in each person . Lipid levels were also compared with individual adiposity
indexes, which included measurements of skinfold thickness .
Younger men and women in the study consumed high-fat food items more often
than older men and women, and men consumed high-fat foods slightly more often
than women did. Ingestion of foods high in sugar was nearly identical for both men
and women and for all age groups . Young men consumed foods . high in starch
considerably more often than older men or women did . Alcohol consumption was
almost identical for men and women in all age groups, although more men and
women in the older age groups were total abstainers .
Serum cholesterol and triglyceride values were not correlated with the frequency
of consumption of dietary constituents . However, serum cholesterol and triglyceride
concentrations were positively and significantly correlated with the adiposity index
in both men and women . The apparent independence of dietary habits and serum
lipid levels does not mean that diet and lipid levels are unrelated, said Dr . Nichols .
But the degree of adiposity in this population was a more obvious determinant of 'i
serum lipid levels than the particular nutritional composition of the diet, he ex- tJ1
plained . Most patients in this study were considerably overweight by compariso ~n
with ideal weights. i
ALLEN B. NICHOLS, MD, CATHERINE RAVENSCROFT, MNS, .DONALD E. LAMP-
HIEAR, MA, and LEON D. OSTRANDER; JR, MD, University of Michigan, Ann Arbor .
Independence of serum lipid levels and dietary habits . JAMA 236:1948-7953, 1976
. Reprinted from Modern Medicine Q 1977 by Harcourt Brace Jovanovich, Inc .
Aviation, Space, and Environmental Medicine • June, 1977 507