The results of an investigation to determine the pressures in the open cockpit of a Vought VE-7 airplane are given. The observed values are small and the effect upon instruments is inconsiderable

Carroll, Thomas

Mcavoy, Wm H

English

NASA Technical Reports Server

No. 300
THE VARIATION IH P.ZESSURESIN THE COCKPIT
OF AX AIWLAiiT?iIN FLIGHT
v
By Thomas Carroll and ‘5311iam H. lJcAvcy
Langley Wmcmial Aeronautical Laboratory
FVLE CX3FW’
T8+Hw#w! te
the tlltx of the Langley
Memerial Aeronautical
Laboratory
.- .
https://ntrs.nasa.gov/search.jsp?R=19930081072 2020-03-17T04:22:35+00:00Z
NATIONAL ADVISORY COMKCTTEE FOR AERONAUTICS.
TECXNICA.LNOTZ NO. 300.
— ,. —
.
THE VARIATION IN PP3WJJRES IN THE COCKPIT
OF Al?AIRPLANE IN FLIGHT.
.
By Thomas Carroll and William H. ~cA’Voy.
Summmy
The results of an investigation
in the open cockpit of a Vought VE-7
,
.
to determine the pressures
airplane are given. The
—
information has been, considered valuable on account of its pos–
sible effect upon the operation of instruments, particulmly
altimeters, due to a variation from the true static pressure
which is induced by the passa&e” of the airplane through the air.
The observed values are in general small and the effect upon
instruments is inconsiderable.
.
This investigation has been undertaken in order to provide
information as to the variation in pressure within the fuselage
l
of an airplane which might produce erroneous indication by in–
—
struments with particular regard to altimeters.
The airplane which was used was a Vought VE-7 airplane,
.
which is of the open cockpit type with normal windfihields in-
stalled on each of the two cockpits. A standard N.A.C.A. pres-
sure reccrding instrument (Reference 1) wa,sused in conjunction
*
3.A.C.A. Technical Hote Eo. 300 . 2
with a swiveling static head mounted upon a forward outer bay
strut in the usual position. To the other side of the instru–
:lent a special hand held static head ~~as coar.ected. The differ-
ences in pressure thus observed are shown in Tables I and II.
*
AS a check on the value md constancy of the pressure at the
swiveling static head, it was compared in all conditions of
flight with a true static pressure provided by a trailing 3ead
suspended 30 feet below the airplane in flight. The difference
observed Was an increase of pressure at the-swiveling static
head of 0.16 inch of water which was constant thro~hout the
..
range of speeds from 60 to 120 ‘ti.P.H. It Was’therefore consid-
ered that the static pressure provided by the swiveling static
head was sufficiently true and constant for comparison wit::the
.
pressures observed in the various positions within the fuselage.
Several positions were investigated in ‘ooththe front and
rear cockpit and axe indicated in Figure 1 on the cross section
of the fusel~~e. A number of other positions were investigated
which might be occupied by instruments and t’heresults were
..
found to be in general conformity with the tabulated information.
The airplane was flown through a series of speeds of from
60 to 120 Z.P.H. in the condition of level flight’and of climb.
The results are given in Table I.
The min’imum observed depression in the cockpit was found to
be .39 inch of H20 at 60 M.P.Hq gliding.
N.A.C.A. Technical Note No. 300 3
A greater depression was induced within the fuselage with.
increase of speed and the maximum depression observed occurred
at 120 d.P.H. in the climbing attitude, the ~depression being
1.74 in. of H20. “
To determine the effect of altitude upon the cockpit Pres-
sures, observations were made in corresponding flights at alti–
tudes of 1000 ft. and at 10,000 ft. ; the observed pressures are
given in Table II and the differences are observed to be small.
It is therefore observed that the maximum difference between
the true static ad the pressure in the cockpit of this type of
airplane is only about l+ in. of water. This would induce a
maximum error in an altimeter of 115 ft. which may be expected
due to the cockpit depression and its effect upon the instrument.
Greater or less divergence nay be expected in cabin types
or possibly in other open cockpit types of different conforma-
tion from the VE-7, but it need not be expected that its effect
may be great upon
instruments which
in the cockpits.
the information provided by altimeters or other
wculd be affected by the static pressure with–
If a greater precision than this is required, “~” ,i,
it is easily obtained by sealing the instrument and connecting ,
the static side with the static side of the pitot-static air
speed head, preferably of the swiveling type. .’
Langley Xemorial Aeronautical Laboratory,
National Advisory Committee for Aeronautics,
Langley Field, Vs., June 20, 1928.
IT.A.C.A. Technical Note No. 300
Reference
1. Norton, F. H. : N.A.C.A. Recording Air Speed Meter.
N.A.C.A. Teclxaical Xote Xo. 64. (1921)
.
.
.
I
,’-—
.
.,. .
:
!I!K8LEI.
Front Cockpit at 1000 Feet
Pressures are given in inches of H20
Air speed
60 M.P.H.
100 M.P.H. I 120 M.P.H.
mi.ml
.88
.90
.90
.90
.90
.90
Ilides
.40
.44
.39
.’39
.39
.39
Level
.88
.78
.74
.74
.76
.76
;lides elm
ups
I
Glides
1.72
Climb Turns
Level !
I
flight clm
l52 .58
.52 .58
.46 .53
.48 .63
.44 .53
.44 .53
Pos.
Ho.
1
2
3
4
5
6
rurm
.87
.89
.32
.78
.78
.82
Level
1.34
1.34
1.26
1.26
1.26
1.26
Glidef
.1.03
1.06
1.06
1.06
9.6
9.6
——
.52
.52
.52
.52
.52
.52
.68-
.68
.68
.69
.69
.68
L34
1.34
1.34
1.34
1.34
1.34
1.34
1.34
1.24
1.24
1.24
1.24
1.14 1.64
1.14 1.66
1.72
1.74
l.’l%!1.14 1.64
1.14 1.64 1.72
*
1.’74
I
—
u-l
..
pos .
No.
1
?
3
Pos .
No.
1
7’
3
“,
TABIJ3 II.
Re&r Cockpit at 1000 Teet.
Pressures are given in inches of H20.
Air speed 120 M.P.H.
60 M.P.H.
Level
.56
.49
.49
I
Climb Level Climb
Air speed
60 K.P.EI.
T
Level Cltml
.39 .54
.39 I
.45 .49
Rear Co&pit at 10,000 I’eet
.
120 M.P.H.
—~
Level
+
1.94
1.62
1.62 1.94
m
N.A.C.A. Technical Note No.300
1 2
5 6
4 3
7
Fig.1
Fig.1
f


The variation in pressures in the cockpit fan airplane in flight

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server