Ntsb Investigation Into Twa Flight 800 Aging Systems

NTSB INVESTIGATION INTO TWA FLIGHT 800 AGING SYSTEMS

Robert L. Swaim Systems Group Chairman

LINT & DEBRIS ON L-1011 GENERATOR CABLES. TWA 800 Accident The primary function of the Safety Board is to promote safety in transportation. 49CFR 800.2(a)

Cause-RelatedCause-Related SafetySafety IssueIssue FindingsFindings FindingsFindings Why did the fuel tank explode? WHAT HAS BEEN FOUND? NTSB WIRE INSPECTIONS Total Time Since New (TTSN) 120000 B-747 B-747 102712 102709 100000 B-747 93303 92141 B-747 86552 B-747 B-747 83477 B-747 80787 B-747 80758.8

80000 B-747 76775.7

60000 B-747 55218

40000 TOTAL TIME (HOURS) TIME TOTAL TWA 800 TWA B-767 B-757 24743 24225.5

20000 Accident Airplane MD-90 B-737 B-737 1488.46 B-747-400 3.56 3.85 7.76 0 8 5 21 6 3 4 10 1 2 7 18 22 15 12 13 14 AIRPLANE NTSB TRANSPORT AIRPLANE WIRE SURVEY http://www.ntsb.gov/events/twa800/exhibit.htm 2 INCHES OF LINT HYDRAULIC ON CABLES “B-NUT” PLASTIC NUTPLATE WRAPPER

FOIL WRAPPER IN GEN. CABLES

PAPER LOOSE HOSE CLAMP CTSB / NTSB L-1011 FINDINGS OF MARCH 17, 1991 SHORTSHORT CIRCUITCIRCUIT EFFECTSEFFECTS :: Ignition of flammable surroundings, such as lint. Destroyed or interrupted system functions. Unintended system operation. Misleading flight crew displays.

INSERT PHOTO OF Lint bridging Paper A300 crkt brkrs. Rivet Tails

Lint A300B4 WIREWIRE EXTERNAL AGING CONTAMINATION, SUCH AS WITH DRILL SHAVINGS MECHANICAL DAMAGE USAGE FORCES THERMAL CYCLES STRESS, SUCH AS REPETITIVE FLEX AGE-RELATEDAGE-RELATED LEAKAGELEAKAGE DUCT LEAKS HEAT TANK & NEARBY MATERIALS O-RINGS LEAK FUEL INSIDE TANKS MATERIALMATERIAL DEGRADATIONDEGRADATION MAINTENANCEMAINTENANCE CONSUMPTION COLLATERAL DAMAGE AGING AIRCRAFT SYSTEM FINDINGS

DDEESSIIGGN

E G A E G A (Usage & Chemical)

THE GROUP SAW THE GROUP PHENOMENON OF:

3 LEGGED STOOL

E E

C C

E E

N N I I A A M M SHAVINGS AND CONTAMINANTS 747 FLOOR STRUCTURE REPAIR

OVER WIRE BUNDLES WITH SHAVINGS

REPAIRS ABOVE WIRES WITH DRILL SHAVINGS PLACEHOLDER FOR :

Boeing Standard Wiring Practices manual has no directions for how to clean wire. HOLE WORN THROUGH WOVEN SLEEVE AND WIRE INSULATION INSERT PHOTO OF NASA 757 WORN WIRES DENTS

757 CWT COMPENSATOR 747 CWT FUEL PROBE & WIRE ABRASIONS & COMPENSATOR CWT COMPENSATORS INSERT CHART FROM E-4B THAT SHOWS THERMAL CYCLES UNDAMAGED AREAS OF AGED POLY-X DID NOT PASS MANUFACTURER SPECIFICATIONS, BUT :

“WOULD BE EXPECTED TO PERFORM ADEQUATELY IN THE SHORT TERM, PROVIDED THERE IS NO ADDED STRESS BEYOND WHAT IT HAS EXPERIENCED.”

TESTING OF DAMAGED AREAS WITH WATER, FLUID REACHED THE CONDUCTOR IN ABOUT 1 OUT OF 5 DAMAGED AREAS.

POLY-X FAILED MORE TESTS THAN OTHER TYPES (FOUND IN 1970s to AGE 7X FASTER THAN KAPTON).

(SAMPLE WIRES FROM PROTECTED FUSELAGE AREAS.) RESULTSRESULTS OFOF TESTINGTESTING AGEDAGED WIRESWIRES (RAYTHEON) BOEING SL 747-SL-20-048

DEGRADED MATERIALS Residue visible on surface - high concentrations of silver, copper, and sulfur DAMAGE BETWEEN TERM. BLOCK WIRES

Compression damage to PTFE insulation where wires were in tight contact

B-747 N93105

0.06 inch ACCIDENT AIRPLANE, N93119, WING TANK Teflon Wrap

Fiberglass Lacing Braid

025i h NTSB FQIS IN-TANK FINDINGS B-747 N93105

PTFE insulation thinned and split through to the conductor

0.0415 inch B-747 N93105

Cross-sectional view of compression damage. This 0.016 inch Section was taken where black film can be seen on the insulation surface in Figure 42 WIRE DAMAGE AND SULFIDATION TIMELINE: 1969 – 1980 1991 1995 1998 – January 1998 – July 1999 Maintenance damage.

Wear (example - Pump conduits)

Parts not approved by design (example - clamps)

Chafes on thin wall fuel tubes.

Lightning (bonding) straps degrade & separate.

Electrically isolated metal components. MISC FUEL TANK FINDINGS BOEING SL 747-SL-20-048

OPEN AND OVERFILLED CLAMPS OVERHEATED WIRE AT PLUG BOEING 747-SL-20-048

CHEMICAL DAMAGE STRETCHED WIRES

TORN THERMAL INSULATION BLANKET

THERMAL BLANKET FAILURE DATA FROM LECTROMECHANICAL DESIGN CO SHOWN FOR MIL-W-81381 (KAPTON)

OURS 60,000 H

R EL . H UM ID IT RE Y TU RA PE TEM SAMPLE WIRE DEGRADATION CURVE DATA BY LECTROMECHANICAL DESIGN CO. DESIGN LECTROMECHANICAL BY DATA

MIL-W-81381 (KAPTON) WIRE DEGRADATION Boeing production illustration shows bundle separation

Boeing SWPM requires 1/4 inch separation

WIRE SAGS AND CHAFES Results of B-767 Wire Fire, LHR, January 9, 1998

SH OR T C IRC UIT

REMOTE SECONDARY DAMAGE TO THRUST REVERSER INDICATION CIRCUIT CARD

EXAMPLE OF HIDDEN DAMAGE FROM SHORT CIRCUIT PLACEHOLDER FOR ATE