Fairing panels were fabricated to evaluate the fabrication characteristics and flight service performance of PRD-49 (Kevlar-49) a composite reinforcing material and to compare it with the fiberglass which is currently in use. Panel configurations were selected to evaluate the PRD-49 with two resin matrix materials in sandwich and solid laminate construction. Left and right hand versions of these configurations were installed on L-1011's which will accumulate approximately 3000 flight hours per year per aircraft. The direct substitution of PRD-49 for fiberglass produced a twenty-six percent weight reduction on the panel configurations. Examination of these panels revealed that there was no visible difference between the PRD-49 and adjacent fiberglass panels

Wooley, J. H.

English

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NASA CR-132647
LR-26580
JULY 1974
iff
FLIGHT SERVICE EVALUATION
OF PRD-49/EPDXY COMPOSITE PANELS
IN WIDE-BODIED COMMERCIAL TRANSPORT AIRCRAFT
1
FIRST ANNUAL
FLIGHT SERVICE EVALUATION REPORT
BY
JOHN H. WOOLEY
Prepared under Contract No. NAS1-11621
for
Langley Research Center
National Aeronautic, ­ nd Space Administration-.-
Hampton,	 rginia 23365	 f^ .	 '7,7 t
G N
by
^^	 1
Lockheed-California Company
Burbank, California
A Divi6lon of Lockheed Aircraft Corporation
(NASA -Ci- 132647)	 FLIGHT SE L VI17h FV'+1.1JAr10N	 N75 - 24719
OF PRD-49/EPDXY COM"OSlr!, PANELS IN
WIDE-BODIED CGM.1F:FCIAL TRANSPORT F.I^:iAFT
Annual Flight, Service Evaluation 4ePI)rt 	 unclas
(Lockheed-California Co.)	 14 p HC $3.25	 G3 /05 X4171
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LR-26580
FOREWORD
This is the first annual flight service evaluation report
on the condition of PRD-49 fairing panels installed on three
Lockheed L-1011's as a part of Contract No. NAS1-11621, "Flight
Service Evaluation of PRD-49 Composite Panels in Wide-Bodied
Commercial Transport Aircraft". The manufacture and installa-
tion of these panels was completed in February 1973 and was
reported in NASA CR-112250, dated March 1973. Annual reports
describing the service performance of these panels will be
prepared and submitted for the next four years.
This program has been administered by the Langley Research
Center, National Aeronautics and Space Administration with
Mr. Benson Dexter of the Materials Division being the Project
Engineer.
The program is being performed by the Lockheed-California
Company under the direction of John H. Wooley. Special
assistance in the flight service evaluation was provided by
N. L. Seeley, R. S. Beck, D. H. Horadam and B. Woods of the
Product Support Branch.
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LR-26580
CONTENTS
Page
SUMMARY	 1
INSPECTION RESULTS	 4
Air Canada Aircraft 4
Wing-to-Body Fairing Panel 4
Wing Body Fillet Panel 5
Center Engine Fairing Panel 5
Eastern Airlines Aircraft 6
Trans World Airlines Aircraft 6
Wing-to-Body Fairing Panel 7
Wing-to-Body Fil?.et Panel 7
Center Engine Fairing Panel 7
LR-26580
SUMMARY
Eighteen PRD-49 (Kevlar-49)* L-1011 fairing panels were
fabricated to evaluate the fabrication characteristics and
flight service performance of this new composite reinforcing
material and to compare it with the fiberglass which is
currently used in these parts. Three panel configurations
were selected to evaluate the PRD-49 with two resin matrix
materials [344°K (160°F) and 422°K (300°F) maximum operating
environments] in sandwich and solid laminate construction.
Left and right hand versions of these three configurations
were installed on three L-1011's which will accumulate
approximately 3000 flight hours per year per aircraft.
Eastern, TWA and Air Canada L-1011's were selected to provide
eastern seaboard, trans-continental and cold northern route
structures. A summary of the program tasks is presented in
Figure I.
The direct substitution of PRD-49 for fiberglass pro-
duced a twenty-six percent weight reduction on the three
panel configurations being evalt •red. Other results of the
fabrication and instal ation phases of the program are pre-
sented in NASA report u: ,1,12250, dated March 1973.
* Du Pont has designated the PRD-49 fiber, Kevlar-49
1
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L:, 2t)580
After approximately one year of operation, Eastern Airlines
has accumulated 3539 hours and 1722 flights; TWA 2404 hours and
1037 flights and Air Canada 2360 hours and 1470 flights on their
aircraft. Examination of these panels revealed that there was
no visible difference between the PRD-49 and adjacent fiberglac„
panels. There were some minor nicks, indentations and elonga-
tion of holes in the panels, but similar damage was also evident
on the fiberglass panels.
All three panel configurations are continuously exposed to
phost',ate ester hydraulic fluid, such as Skydrol or Aerosafe
2300, This fluid will attack many organic materials and acts
as an excellent paint stripper on certain paints, but it had no
apparent effect on the PRD-49 panels. The extensive exposure
to this fluid was not anticipated as one of the environments
that would be encountered; however, prior accelerated tests
have demonstrated that both the resin matrix and PRD-49 fiber
are resistant to these fluids.
As the result of a fire in the TWA aircraft in April 1974,
the subject panels were removed and will be installed on a new
TWA L-1011 to be delivered in December 1974.'
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LR-26580
INSPECTION RESULTS
The flight service evaluation of this program consists of
annual inspections of the PRD-49 fairings. This will normally
be accomplished during a major inspection of each of the three
aircraft. The participating airlines and Lockheed Product
Support personnel have also been instructed to report any
damage and repair that might occur in the interim.
Detail observations on each of the panels during the first
annual inspection are described below. On all three aircraft,
each of the panels was covered with a film of phosphate ester
hydraulic oil, but there was no evidence of any deterioration
from the fluid.
Air Canada Aircraft No. CF-TNB-50 2
Inspection of the Air Canada. aircraft was conducted in
April 1974, !chile it was at the Lockheed Burbank plant for
modification. There had been 2360 flight hours and 1470 flights
accumulated on the aircraft at the time.
Wing-to-Body Fairing Panel
There were some minor indentations on the exterior surface
of the panels, but similar damage was also observed on adjacent
fiberglass panels. In one instance there was a 2.54 centimeter
(one inch) crack in the exterior skin of the left panel as shown
in Figure II. Minor repair will be required to cover the hole.
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4
LR-26580
The panel on the left side was removed for closer examina-
tion. Thorough tapping of both the interior and exterior sur-
faces produced no evidence of delamination and there was no
damage to the fastener holes. A weight check showed no dis-
cernible change in the panel weight after the year of operation.
Wing-Body Fillet Panel
A few attachments were removed from the panels and the
fastener holes that were observed were in good condition.
Figure III shows the right nand panel installed on the aircraft.
Center Engine Fairing Panel
Some paint had been removed from the exterior surface of
E"	 the right hand panel as shown in Figure IV. Therefore, it was
i!
decided to remove the panel for closer examination. The paint
topcoat and primer were not adhering to the flame sprayed
aluminum surface. A few fiberglass panels also have had paint
ti
	 adhesion problems which have been traced to inadequate release
agent removal. Since these panels contained the elevated tem-
perature resistant resin, they had to be cured at a higher
temperature which creates some difficulty in getting the flame
spray coating to release from the tool. However, this problem
has been resolved on subsequent production lots, All loose
paint was removed and the panel was repainted prior to re-
installation.
5
LR-26580
It was also observed that a single ply of fabric had been
bonied to both ends of the panel as shown in Figure V. However,
there is no record of this rework at either the Lockheed or Air
Canada facilities. The repair material used and the time of its
application are still unknown.
Some elongation of the holes was observed in a few areas on
the panel, but the condition was not serious enough to warrant
repair.
4
Eastern Airlines Aircraft No. D1314EA
The PPD-49 panels were examined on the aircraft by Lockheed
and Eastern personnel during a regular scheduled inspection at
Eastern Airlines' Miami facility. After one year and four
months of operation, the aircraft had accumulated 3539 flight
hours and 1722 flights. There was no indication of any damage
or any difference between the PRD-49 and fiberglass panels.
Trans World Airlines Aircraft No. N31-007
As the result of a fire in this aircraft in April 1974,
the panels were removed and returned to the Lockheed-California
Company for re-i.stallation on a new TWA L-101.1 to be delivered
in December 1974. There was nci damage to the panels from the
fire; however, other minor damage was found as described below.
The panels experienced 2404 flight hours and 1037 flights
during the first year.
6
dWing-to-Body Fairing
sThese panels were in excellent condition when received at
Lockheed with the exception of a very small indentation and
a crack in the right hand panel. The crack in the exterior
surface is being repaired by covering it with two plies
of glass cloth impregnated with an epoxy resin consisting
of Epon* 812, Epon* 828, Versamid** 115 and Versamid** 125.
This resin cures for one hour at 355°K (180°F) or , 12 hours at
294°K (700F).
x
Wing-Body Fillet Panel
S
The only damage to the fillets was some elongation of the
holes in the right hand panel as shown in Figures VI and VII.
These holes will be repaired by sanding down the frayed fibers,
solvent cleaning and completely filling the holes with the
M abovementioned resin system containing five percent glass
a
fibers. Elongation of fastener holes in any of these panel
configurations is not peculiar to PRD-49. More severe hole
damage has been witnessed on other fiberglass fillet panels.
Center Engine Fairing Panel
The panel on the righ t_ side had one ply of the fabric
delaminated along the edge as shown in Figure VIII. On close
k
1	 examination it can be seen that a fillet of sealing compoundi
f	 was still adhering to the edge of the panel along the delami-
nated areas.
* Shell Chemical Company
** General Mills Inc.
7
I,R-26580
3i
Evidently the adhesion of the sealing compound to the laminate
and metal substructure placed it peeling force on the resin
matrix causing it to peel back as the panel was removed.
The delaminated ply will be bonded back together with a
resin capable of withstanding the 422°K (300° p) service en-
vironment.
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Figure IV Center Fn,vine Fairing;
Figure V Center Engine Fairing; with Wde.l 'laterial at Fndti(fit p^^L pAV^	 ,.
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Figure VI h;ing-Body Fillet with I-Iongated holes
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Figure VII Clow-up oE' wing-Body Fillet with Flongatea Boleti
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Figure VI I I	 De I am inar ion on Center Engine Fairing;
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Flight service evaluation of PRD-49/epoxy composite panels in wide-bodied commercial transport aircraft

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