a300 vertical tail structural evaluation design flaw in lower rear spar by xavier j. maumus

A300 VERTICAL TAIL STRUCTURAL EVALUATION

DESIGN FLAW IN LOWER REAR SPARDESIGN FLAW IN LOWER REAR SPAR

ByBy

Xavier J. MaumusXavier J. Maumus


DESIGN FLAW IN LOWER REAR SPARDESIGN FLAW IN LOWER REAR SPAR

PART 1—DESIGN FLAW DETAILSPART 1—DESIGN FLAW DETAILS

PART 2--FAILSAFE CRITERIAPART 2--FAILSAFE CRITERIA

PART 3--ULTIMATE CRITERIAPART 3--ULTIMATE CRITERIA

PART 4—FAILURE SCENARIOPART 4—FAILURE SCENARIO


PART 1—DESIGN FLAW DETAILSPART 1—DESIGN FLAW DETAILS

Spar Design Susceptible to Lateral Spar Design Susceptible to Lateral DeflectionDeflectionSpar and Yoke Reaction System Designed Primarily to React Spar and Yoke Reaction System Designed Primarily to React Lateral Load. Relieves Lateral Shear and Bending in the Main Lateral Load. Relieves Lateral Shear and Bending in the Main Lugs. Lugs.

Geometry makes Yoke Design Very Efficient in Resisting Geometry makes Yoke Design Very Efficient in Resisting Lateral Deflection.Lateral Deflection.

Poor in Resisting Vertical Deflection.Poor in Resisting Vertical Deflection.

. .

CRITICAL DESIGN FEATURERear Reaction System

NTSB Docket No. 168606, Factual Report 02-077, pg 9 of 63, NTSB Docket No. 168606, Factual Report 02-077, pg 9 of 63, Section 2.2.2Section 2.2.2

Suspected Description of a Bearing Failure in LHS Rear Suspected Description of a Bearing Failure in LHS Rear Transverse Spar Lug Located at the Upper/Outboard Edge of Transverse Spar Lug Located at the Upper/Outboard Edge of the Lug Bore. This Failure Produced Substantial Compression the Lug Bore. This Failure Produced Substantial Compression in the LH Yoke which is Inconsistent with the FEM Boundary in the LH Yoke which is Inconsistent with the FEM Boundary Loads. Loads.

Working Model Demonstrates that the Lower Rear Spar moves Working Model Demonstrates that the Lower Rear Spar moves to the Right which is necessary to Produce Compression Load to the Right which is necessary to Produce Compression Load in the LH Yoke. in the LH Yoke.

DISCOVERY OF FLAW

MECHANICAL LEVERLever Bar

Main Lug Reaction

Py

0Yoke

Reaction

Rotation of Lever Rotation of Lever Bar Develops Bar Develops Resistance PsResistance Ps

Vertical Tail

Geometry of Lower Rear Spar Design Produces a Geometry of Lower Rear Spar Design Produces a Mechanical Mechanical Lever (ML) in the Spar Lever (ML) in the Spar Reaction SystemReaction System..

As Aft Portion of the VT Deflects, its Lower As Aft Portion of the VT Deflects, its Lower SparSpar Rotates and Rotates and Produces Lateral Deflection at Spar Attachment to the Yokes.Produces Lateral Deflection at Spar Attachment to the Yokes.

Spar Reaction System is Very Efficient in Developing Lateral Spar Reaction System is Very Efficient in Developing Lateral Resistance. Resistance.

Yokes Resist and Develop Large Internal Loads in VT Reaction Yokes Resist and Develop Large Internal Loads in VT Reaction System.System.

Loads are Reacted at the Main Lugs (Shear and Out-of Plane Loads are Reacted at the Main Lugs (Shear and Out-of Plane Bending) and Additive to the VT Loads.Bending) and Additive to the VT Loads.

DESIGN FLAWDESIGN FLAW

REAR REACTION SYSTEMFAILSAFE CONFIGURATION

.480 in.Deflection of Lug

ROTATION OF NO 1 RIB AND REAR SPAR

Py

Rotation of Spar Produces Large Deflections at YokesRotation of Spar Produces Large Deflections at Yokes

Fulcrum

S

P

LOAD DEVELOPMENT IN LEVER MECHANISM

Spar Rotates and Produces Lateral Deflections at Spar Rotates and Produces Lateral Deflections at its Lug Attachment to the Yokesits Lug Attachment to the Yokes

Yokes Resist Lateral Deflection and Develop Large Yokes Resist Lateral Deflection and Develop Large Internal Loads in Reaction SystemInternal Loads in Reaction System

Large Shear and Bending Loads are Reacted at the Large Shear and Bending Loads are Reacted at the Rear Main LugsRear Main Lugs

MECHANICAL LEVERAGE

Failed RHS Main LugVertical Movement of

Fulcrum—Located near Rib No. 1 in Skin Transition Area above LHS Lug

Transverse Spar Rotates Counterclockwise about Fulcrum

Resistance to Spar Deflection Develop Large Loads in Yokes

.480 in

0 Additional Side Load Reacted at LHS Main Lug

FAILSAFE CONFIGURATION

EVIDENCE OF DESIGN FLAWFor Failsafe Criteria with the RHS Rear Main Lug For Failsafe Criteria with the RHS Rear Main Lug Disconnected, the FEM shows the RHS Lug moves to the Right Disconnected, the FEM shows the RHS Lug moves to the Right and Up. and Up.

Deflections Consistent with the Mechanical Leverage Model, Deflections Consistent with the Mechanical Leverage Model, Shows Rotation of Spar. Shows Rotation of Spar.

Most Significant is the Deflection to the Right which Verifies Most Significant is the Deflection to the Right which Verifies the Spar’s tendency to move Laterally. This Lateral Movement the Spar’s tendency to move Laterally. This Lateral Movement is what Produces the Interference Resistance Between the Spar is what Produces the Interference Resistance Between the Spar and Yoke.and Yoke.

Working Model Demonstrates the Flaw.Working Model Demonstrates the Flaw.

Loads and Deflection Analysis Results are Consistent when Loads and Deflection Analysis Results are Consistent when Mechanical Leveraging is Consisted. Mechanical Leveraging is Consisted.

FREEBODY OF LUGAdditional Load on Lug Bore

MXX

P

S

3.70

Lateral Resistance in Yokes Produce Additional Shear and Bending in Lug

SIGNIFICANCE OF MLMechanical Leveraging makes the Design Susceptible to small Mechanical Leveraging makes the Design Susceptible to small Deflections in the Lower Spar Structure. Deflections in the Lower Spar Structure.

Large Internal Loads are Produced in all members of the VT Large Internal Loads are Produced in all members of the VT Reaction Systems, Main Lugs are especially Susceptible.Reaction Systems, Main Lugs are especially Susceptible.

Airbus FEMAirbus FEM does not Account for Mechanical Leverage in the does not Account for Mechanical Leverage in the Loads Analysis.Loads Analysis. FEM Deflections are Correct. FEM Deflections are Correct.

Mechanical Leverage supports a Pre-mature Failure in the Mechanical Leverage supports a Pre-mature Failure in the RHS Rear Main Lug below UltimateRHS Rear Main Lug below Ultimate

Renders Failsafe Capability IneffectiveRenders Failsafe Capability Ineffective

TEST TO PROVE DESIGN FLAWFull Scale TestFull Scale Test

Failsafe CriteriaFailsafe CriteriaRHS Rear Main Lug ReleasedRHS Rear Main Lug Released

Apply Load25% Limit BI

17

Vertical Tail and Rudder mounted on Aircraft

TEST CASE VS. AIRBUS FEMCONDITION Rear Transverse Yokes

LHS RHS

AIRBUS 8185 3747

TEST CASE -1276 13203

Note the large load in the RHS Yoke for Test Case

TEST TO PROVE DESIGN FLAWFull Scale TestFull Scale Test

Ultimate CriteriaUltimate Criteria

Apply Load25% Limit BI

17

Vertical Tail and Rudder mounted on Aircraft

TEST CASE VS. AIRBUS FEMCONDITION Rear Transverse Yokes

LHS RHS

AIRBUS 2373 -2363TEST CASE -1457 1457

Note the difference in sign between the two load cases

TEST TO PROVE DESIGN FLAW Perform Full Scale Calibration Test of Vertical Tail Perform Full Scale Calibration Test of Vertical Tail

on A300 Aircrafton A300 Aircraft Disconnect Fairings, Control Rods and Systems to Disconnect Fairings, Control Rods and Systems to

Avoid Damage to A/CAvoid Damage to A/C Mount Cameras to Record Movement of Rear SparMount Cameras to Record Movement of Rear Spar Strain Gauge and Calibrate Aft YokesStrain Gauge and Calibrate Aft Yokes Apply Side Load (12,000 lb about 25% Limit Load) to Apply Side Load (12,000 lb about 25% Limit Load) to

VT about 157 Inches Above Attachment VT about 157 Inches Above Attachment Read Gauges and Measure Rotational Deflection of Read Gauges and Measure Rotational Deflection of

Rear SparRear Spar Disconnect RHS Rear Main Lug and Repeat TestDisconnect RHS Rear Main Lug and Repeat Test

QuestionsQuestions

The Effectiveness of the Mechanical Lever is Dependent on the Location of the Fulcrum, how was this Point Located?

In the Failsafe Analysis, the Fulcrum is located near the Intersection of the LH Skin and N0. 1 Rib. The Fulcrum location is a Function of the Stiffness of Two Primary Structural Members. One is the VT Box that is very Stiff and whose Lower Side is Bound by the No. 1 Rib. The other being the LH Main Lug Area whose Stiffness is a Function of its Moment of Inertia and Fixity at the Lug Attachment. These Stiffness Parameters Produce a Natural Inflection Point 2.83 inches above the Main Lug Bore.

In the Ultimate Criteria Analysis, no Fulcrum Location is Determined. A .0125 inch Lateral Displacement is Assumed since no FEM Defection Data is Available for Ultimate.

PHYSICAL EVIDENCE Supports Mechanical Leverage Bearing Failure in LHS Aft Transverse Spar Lug Bearing Failure in LHS Aft Transverse Spar Lug

Located at the Upper/Outboard Edge of the Lug Bore. Located at the Upper/Outboard Edge of the Lug Bore. NTSB Docket No. 168606, Factual Report 02-077, pg 9 NTSB Docket No. 168606, Factual Report 02-077, pg 9 of 63, Section 2.2.2.of 63, Section 2.2.2.

The Bearing Failure indicates that the Lower Spar The Bearing Failure indicates that the Lower Spar moved to the right to Produce this Failure.moved to the right to Produce this Failure.

Deformation of Left Transverse Yoke Sleeve. NTSB Deformation of Left Transverse Yoke Sleeve. NTSB Docket No. 168606, page 5 of 63. Docket No. 168606, page 5 of 63.


PART 2--FAILSAFE CRITERIAPART 2--FAILSAFE CRITERIA

DESIGN FLAW IN TRANSVERSE DESIGN FLAW IN TRANSVERSE SPARSPAR

FAILSAFE CRITERIA

Requires That Vertical Tail Structure Requires That Vertical Tail Structure Sustain Limit Load With One Major Sustain Limit Load With One Major Structural Member FailedStructural Member Failed

AIRBUS FAILSAFE PHILOSOHY When one of the Main Lugs Fail, the Loads of that When one of the Main Lugs Fail, the Loads of that

Lug are Redistributed, Primarily to an Adjacent Lug are Redistributed, Primarily to an Adjacent Main LugMain Lug

In the Case of a Failure in the RHS Rear Main In the Case of a Failure in the RHS Rear Main Lug, 90% of the Load goes Forward and only 10% Lug, 90% of the Load goes Forward and only 10% is Resisted by the Yokesis Resisted by the Yokes

In Order for this Redistribution to Occur the In Order for this Redistribution to Occur the Design must Allow the Failed Lug to DeflectDesign must Allow the Failed Lug to Deflect

AIRBUS FAILSAFE ANALYSIS Assumes RHS Rear Main Lug Fails

Results Based on Non-Linear FEM Results Based on Non-Linear FEM Analysis—Set for Strain SolutionAnalysis—Set for Strain Solution

Design Certification Lateral Gust Design Certification Lateral Gust Condition at Limit LoadCondition at Limit Load

LHS Spar Lug CriticalLHS Spar Lug Critical Max Deflection of the Right Rear Main Max Deflection of the Right Rear Main

Lug in A/C Coordinates is:Lug in A/C Coordinates is:

x = .004 in., y = .037 in and z = .480 in.x = .004 in., y = .037 in and z = .480 in.

AIRBUS FEM RESULTSNon-Linear Analysis

FAILURE ANALYSIS—RHS REAR MAIN LUGFAILURE ANALYSIS—RHS REAR MAIN LUG

FAILSAFE—BI17 LIMIT LOAD (LB)FAILSAFE—BI17 LIMIT LOAD (LB)

Rear Transverse Yokes

LHS RHS

Fx -3890 -1781

Fy 31963 -14633

Fz -5936 -2718

Fres 32742 14990

AIRBUS DETAIL ANALYSIS LHS SPAR LUG CRITICAL

Load Capacity of Lug = 40,271 lb. Ulti.Load Capacity of Lug = 40,271 lb. Ulti. Margin of Safety = + .23 LimitMargin of Safety = + .23 Limit

Critical for Shear Tear OutCritical for Shear Tear Out

1.547

3.54 1.224

DIA.

3.54

1.224 Dia.

1.574PLUG = 32,742 lb. LHS

MECHANICAL LEVERAGE FAILSAFE ANALYSIS Assumes Right Rear Main Lug Fails Results Based on Deflection Analysis Results Based on Deflection Analysis

(Virtual Work) (Virtual Work) Considers Mechanical Leverage in Considers Mechanical Leverage in

Lower SparLower Spar Design Certification Lateral Gust Design Certification Lateral Gust

Condition at Limit LoadCondition at Limit Load Deflection of the Right Rear Main Lug Deflection of the Right Rear Main Lug

in A/C Coordinates is:in A/C Coordinates is: y = .037 z = .480 in.y = .037 z = .480 in.

REAR REACTION SYSTEMFAILSAFE CONFIGURATION

.480 in.Deflection of Lug

ROTATION OF NO 1 RIB AND REAR SPAR

Py

Rotation of Spar Produces Large Deflections at YokesRotation of Spar Produces Large Deflections at Yokes

Fulcrum

S

P

LOADS ANALYSISAnalysis Considers Mechanical Leverage

FAILURE ANALYSIS—RHS REAR MAIN LUGFAILURE ANALYSIS—RHS REAR MAIN LUG

FAILSAFE—BI17 LIMIT LOADFAILSAFE—BI17 LIMIT LOAD

Rear Transverse Yokes Transition Area

LHS RHS LHS

Fx 607 -6275Fy -4984 -51556 79724Fz 926 -9575

Fres -5105 52811

DETAIL STRESS ANALYSIS RHS SPAR LUG CRITICAL

Load Capacity of Lug = 40,271 lb. Ulti.Load Capacity of Lug = 40,271 lb. Ulti. Margin of Safety = - .24 LimitMargin of Safety = - .24 Limit

Critical for Shear Tear OutCritical for Shear Tear Out

1.547

3.541.224

DIA.

3.54

1.224 Dia.

1.574PLUG = 52,811 lb. RHS

TRANSITION AREAINTER-LAMINA SHEAR CRITICAL

Inter-lamina Shear Capacity = 50,215 lb. Ulti.Inter-lamina Shear Capacity = 50,215 lb. Ulti. Margin of Safety = - .37 LimitMargin of Safety = - .37 Limit

A

SECTION A-A

20.00

1.17

A

PINTER-LAMINA SHEAR = 79724 lb.

LHS REAR MAIN LUG

UP

FWD LOOKING INB’D

CONCLUSIONSBased on Analysis Considering

Mechanical Leverage

RHS Rear Spar Lug will Fail at 76% of Limit RHS Rear Spar Lug will Fail at 76% of Limit LoadLoad

LHS Rear Main Lug will Fail at 63% of Limit LHS Rear Main Lug will Fail at 63% of Limit Load Load

Vertical Tail does not Meet Failsafe Criteria when Vertical Tail does not Meet Failsafe Criteria when Considering Mechanical LeverageConsidering Mechanical Leverage

QuestionQuestion

The Component Tests were Used to Support Failsafe Certification. Why didn’t this Flaw Show Up During those Tests?

To my Knowledge none of the Spar Component Tests Included Yokes attached to the Spar, so the Additional Internal Loads from Mechanical Leverage wasn’t Allowed to Develop.

Additionally, Component Testing never Examined a Failsafe Condition in which a Main Lug was disconnected.

The Boundary Loads used in all Component Tests were Controlled by the FEM Loads Analysis that did not Account for Mechanical Leverage.


PART 3--ULTIMATE CRITERIAPART 3--ULTIMATE CRITERIA

ANALYSIS IS INCOMPLETEANALYSIS IS INCOMPLETE

NEED DEFLECTION DATA OF REAR SPARNEED DEFLECTION DATA OF REAR SPAR

ULTIMATE CRITERIA

Requires That Vertical Tail Structure Requires That Vertical Tail Structure Sustain 1.5 Times Limit Load Without Sustain 1.5 Times Limit Load Without Failure of any Major Structural MemberFailure of any Major Structural Member

AIRBUS ANALYSIS--ULTIMATE

Results Based on Non-Linear FEM AnalysisResults Based on Non-Linear FEM Analysis—Set for Strain Solution—Set for Strain Solution

Design Certification Lateral Gust Condition Design Certification Lateral Gust Condition at Ultimate Loadat Ultimate Load

RHS Rear Main Lug CriticalRHS Rear Main Lug Critical

AIRBUS FEM RESULTSNon-linear Analysis

BI17 LOAD CASE—ULT. BI17 LOAD CASE—ULT.

S = 3,100 LB

P = 160,319 LB

MXX = 41,109 IN-LB

Margin of Safety = +.18

Critical for Shear Tear OutMXX

P

RHS LugView looking Aft

S

REAR REACTION SYSTEMNORMAL CONFIGURATION

Rotation of Spar Produces Deflections at YokesRotation of Spar Produces Deflections at Yokes

Py

Fulcrum

Py

0S S

Pc Pt

Additional Side Load Reacted at RHS Main Lug

MECHANICAL LEVERAGE

Fulcrum—Located near Rib No. 1

Rear Spar Rotates Counterclockwise Produces Deflection at Lugs

Resistance to Spar Lateral Deflection at Lugs are Developed in Yokes

Mechanical Leverage Influences the Distribution of Internal Load in Rear Reaction System

Additional Side Load Reacted at LHS Main Lug

0

DETAIL ANALYSIS RESULTS Considers Mechanical Leverage

BI17 LOAD CASE—ULT.BI17 LOAD CASE—ULT.NO DEFLECTION DATA AVAILABLE, ASSUMES NO DEFLECTION DATA AVAILABLE, ASSUMES

LATERAL INTERFERENCE IN YOKES = .0125 LATERAL INTERFERENCE IN YOKES = .0125 IN.IN.

(.030 Vertical Deflection of Rear Spar)(.030 Vertical Deflection of Rear Spar)

S = 26,075 LB

P = 160,319 LB

MXX = 74,376 IN-LB

Margin of Safety = - .13

Critical for Shear Tear Out

MXX

P

S

RHS LugView Looking Aft

CONCLUSIONSBased on Analysis Considering ML

Assume Lateral Deflection of .0125 in. in Rear Spar Assume Lateral Deflection of .0125 in. in Rear Spar --Need Deflection Data----Need Deflection Data--

Rear Main Lugs will Fail at 87% of Ultimate Load Rear Main Lugs will Fail at 87% of Ultimate Load

Must be Substantiated by FEM Analysis and Full Scale Must be Substantiated by FEM Analysis and Full Scale Static Test on AircraftStatic Test on Aircraft

Vertical Tail may not Meet Ultimate Criteria Vertical Tail may not Meet Ultimate Criteria

QuestionsQuestions

The Full Scale Static Test was Used to Support Ultimate Certification. The Test Article Failed at 126 % of Ultimate. Why didn’t this Flaw Show Up During this Test?

The Full Scale Static Test didn’t Include Yokes, so the Additional Internal Bending Load in the Rear Main Lugs from Mechanical Leverage wasn’t Allowed to Develop.

The Boundary Loads of the Static Test were a Duplication of the FEM Loads Analysis that did not Account for Mechanical Leverage.

.

RECOMMENDATIONFEM ANALYSIS

Current Airbus FEM Internal Loads Current Airbus FEM Internal Loads Analysis needs Modification to Account for Analysis needs Modification to Account for Mechanical Leverage of Rear SparMechanical Leverage of Rear Spar

FEM should be run on Non-linear set for FEM should be run on Non-linear set for Geometry SolutionGeometry Solution

RECOMMENDATIONNTSB

Perform Proof TestPerform Proof Test

Full Scale Tests to Failure should be Full Scale Tests to Failure should be Preformed for both Failsafe and Ultimate Preformed for both Failsafe and Ultimate CriteriaCriteria


PART 4—FAILURE SCENARIOPART 4—FAILURE SCENARIO

QUESTIONSQUESTIONS

FAILURE SCENARIO

The RHS Rear Main Lug Failed First at below Limit and Initiated a Series of Failures in the Rear Attachment System.

RHS Rear Main Lug Weakened by Overload Event 7 Years RHS Rear Main Lug Weakened by Overload Event 7 Years Earlier--Second Wake EncounterEarlier--Second Wake Encounter

LHS Rear Main Lug--Thump LHS Rear Main Lug--Thump Rear Transverse Spar Lugs, RHS then LHS --Two ThumpsRear Transverse Spar Lugs, RHS then LHS --Two Thumps Rib No. 1 between Middle and Rear Spar– Snap and Loud Rib No. 1 between Middle and Rear Spar– Snap and Loud

ThumpThump Fwd and Middle Main Lugs and Yokes Instantaneously– Fwd and Middle Main Lugs and Yokes Instantaneously–

Loud BangLoud Bang

QuestionsQuestions

What Caused the RHS Rear Main Lug to Fail?

There is no way of knowing the exact Strength of the failed RHS Main Lug, but in Part 3 of this Presentation, Ultimate Analysis shows that the Lug might not meet Design Strength Requirements when Mechanical Leverage is Considered.

The Lug had been Weakened by an Overload Event that Occurred Seven Years Earlier. During this Event the Lug came very Close to Failure and Caused Delamination around the Lug Bore.

Increase Stress from the Mechanical Leverage Phenomena caused further Delamination and Weakening of the Damaged Lug Continued Until Failure.

QUESTIONS

How does Mechanical Leverage support Pre-mature Failure of the RHS Rear Main Lug?

Bending Loads in the Lug are reacted at the Lug Bore and Bending Loads in the Lug are reacted at the Lug Bore and Produce Strain in the Critical Outer Fibers of the Lug. Produce Strain in the Critical Outer Fibers of the Lug.

Mechanical Leverage Increases these Bending Strains making Mechanical Leverage Increases these Bending Strains making the Lug even more Susceptible to Delamination. the Lug even more Susceptible to Delamination.

If the Lug has been Damaged from a Previous Overload Event, If the Lug has been Damaged from a Previous Overload Event, it is even more Susceptible to further Delamination. it is even more Susceptible to further Delamination.

As the Lug Continues to Weaken from Delamination, the As the Lug Continues to Weaken from Delamination, the Bending Strains in its Outer Fibers are Driven to Larger Bending Strains in its Outer Fibers are Driven to Larger Levers Promoting Delamination Growth. Levers Promoting Delamination Growth.

QuestionsQuestions

Why do you believe the RHS Rear Lug Failed below Limit?

My Analysis supports a Failure Scenario in which the RHS Rear Main Lug may have been severely damaged from the Overload Event that the Aircraft Experienced Seven Years earlier. The Mechanical Leverage Effect Develops larger than expected Bending Loads in the Lug that caused further Delamination Growth.

Over the Years, the Lug continuously Weakens until it Pre-maturely Fails (below Limit Load) when Exposed to the Loads of the Second Jet Wake Encounter about 17 Seconds before Separation.

QuestionsQuestionsWhat Proof Exist to Support a Failure of the RHS Rear Main Lug below Limit?

No Direct Evidence Exist to show that the Lug Failed below Limit.

Failure Scenario Assumes that the Lug Ruptured at Second Wake Encounter. Wake Encounter Load seems Less than Limit.

Need Analysis supported by Testing.

(Yes, you can say that Failsafe did not work but remember that Airbus will say that it was a load beyond Limit that caused the VT to go at once. You need some evidence that there was no overload or that the intact system is not capable of carrying the load.)

QuestionsQuestionsWhat Evidence Exist to Support a Zipper Type Failure of the VT?

This Presentation provides Physical Evidence and Failsafe Analysis that Supports a Series of Failures (below Limit) in the Rear Attachment System that may have Lasted a number of seconds.

The Physical Evidence suggests a Series of Component Failures that is Consistent with a Zipper Type Failure and takes some Time to Develop because the Loading is not Overwhelming.

The Mechanical Leverage Design Flaw and Delamination Damage of the other AA Aircraft proves a problem exist with the Design.

Cockpit Voice Recording suggest that something was happening to the Aircraft 17 seconds before the VT Departure.

QuestionsQuestions

What does the Voice Recording Suggest to you?

Its an indication that the Vertical Tail may have been coming Its an indication that the Vertical Tail may have been coming apart at least 17 seconds before separation from the aircraft.apart at least 17 seconds before separation from the aircraft.

During the time between 0915:51.8 and 0915:58.5, there are During the time between 0915:51.8 and 0915:58.5, there are recorded the sounds of three thumps, one snap, one loud recorded the sounds of three thumps, one snap, one loud thump and one loud bang. These sounds were probably the thump and one loud bang. These sounds were probably the sounds of the VT's aft reaction system failing and No. 1 Rib sounds of the VT's aft reaction system failing and No. 1 Rib breaking apart with the last 'loud bang' at 0915:58.5 being the breaking apart with the last 'loud bang' at 0915:58.5 being the sound of the simultaneous failure of the fwd and middle sound of the simultaneous failure of the fwd and middle structure. structure.

Questions Why do you believe the LHS Rear Main Lug Failed before the Why do you believe the LHS Rear Main Lug Failed before the

Rear Spar Lugs?Rear Spar Lugs?

Failsafe Analysis in this Presentation shows the LHS Main Lug to be more Critical than the Spar Lugs.

The Physical Evidence:Two Large Areas of Delamination in the Lower Aft Transverse Spar above both Lug Bores, NTSB Public Docket No. 168624, Factual Report 02-078 App. A, page 9 of 52, Figure 06. These Failures Result from Bending Produced by Out-Of-Plane Loading on the Rear Spar.

These Delaminations Indicate that the Lower Spar moved Substantially before Failure. In Order for the Lower Spar to Move that much Meant that the LHS Rear Main Lug had to be Disconnected.

PHYSICAL EVIDENCE Supports Failure Scenario Witness Marks on Forward LHS Aft Transverse Spar Witness Marks on Forward LHS Aft Transverse Spar

Upper/Outboard Area between the Lug Bore and Rib No. 1. Upper/Outboard Area between the Lug Bore and Rib No. 1. Roll No. 15-08-M.jpg. Roll No. 15-08-M.jpg.

Marks Result from Contact with the Outboard Edge of the LH Marks Result from Contact with the Outboard Edge of the LH Yoke. Indicates that the Lower Spar moved Substantially Yoke. Indicates that the Lower Spar moved Substantially Downward and to the Right.Downward and to the Right.

The Photo also shows the Bearing Failure at the Edge of the The Photo also shows the Bearing Failure at the Edge of the Lug Bore of the Previous Slide. Failure located at the 1 o'clock Lug Bore of the Previous Slide. Failure located at the 1 o'clock position. position.

PHYSICAL EVIDENCE Supports Failure Scenario Two Large Areas of Delamination in the Lower Aft Two Large Areas of Delamination in the Lower Aft

Transverse Spar above both Lug Bores, NTSB Public Transverse Spar above both Lug Bores, NTSB Public Docket No. 168624, Factual Report 02-078 App. A, page 9 Docket No. 168624, Factual Report 02-078 App. A, page 9 of 52, Figure 06. These Failures Result from Bending of 52, Figure 06. These Failures Result from Bending Produced by Out-Of-Plane Loading on the Rear Spar.Produced by Out-Of-Plane Loading on the Rear Spar.

Because the RHS and LHS Rear Main Lugs were Failed, Because the RHS and LHS Rear Main Lugs were Failed, the Aft Structure of the VT was free to Twist. As this the Aft Structure of the VT was free to Twist. As this occurred, Resistance Developed in the Yokes . The Canted occurred, Resistance Developed in the Yokes . The Canted Transverse Spar rotated in a Vertical Plane about the A/C Transverse Spar rotated in a Vertical Plane about the A/C Longitudinal Axis. Longitudinal Axis.

This Twisting of the aft structure could only occur while This Twisting of the aft structure could only occur while the Fwd Structure remained Attached. the Fwd Structure remained Attached.

PHYSICAL EVIDENCE Supports Failure Scenario

Witness Mark on the RHS Rear Main Lug. Witness Mark on the RHS Rear Main Lug. Impact Damage to the Fracture Surface of the Impact Damage to the Fracture Surface of the Fwd Outboard Leg of the Lug may have come Fwd Outboard Leg of the Lug may have come from the VT moving to the right after failure of from the VT moving to the right after failure of the two Rear Main Lugs. The damage was the two Rear Main Lugs. The damage was caused by contact with a piece of No. 1 Rib. Roll caused by contact with a piece of No. 1 Rib. Roll No. 13-03-M.jpg No. 13-03-M.jpg

QuestionsQuestions

What was the Configuration of the VT at the Instant of Departure?

Analysis supports a Failure Scenario in which the VT was Supported only by the Fwd and Middle Attachment Systems at Departure.

Ultimate Analysis shows that the RHS Rear Lug may be Under Strength and Failsafe Analysis shows that the remaining Rear Attachment System, LHS Main Lug and Yokes and the No. 1 Rib is not Capable of Sustaining Limit Load.


In order for the No. 1 Rib between the Aft and In order for the No. 1 Rib between the Aft and Middle Spars to become Overloaded means that Middle Spars to become Overloaded means that the Rib became a Primary Load Member. The the Rib became a Primary Load Member. The Rib acted as a Cantilevered Beam and Attempted Rib acted as a Cantilevered Beam and Attempted to Restrain Movement of the Aft VT, and in to Restrain Movement of the Aft VT, and in doing so, Provides effective Evidence that the doing so, Provides effective Evidence that the Forward Structure of the VT remained Intact Forward Structure of the VT remained Intact and Attached for some time after the Failure of and Attached for some time after the Failure of the Aft Reaction System.the Aft Reaction System.

QuestionsQuestions

What Load was on the VT at Time of VT Departure?

Consistent with Failure Scenario, at the Time of Complete Failure and Departure of the VT only the Fwd and Middle Reaction Systems were Attached.

Failure Load was Equal to the Strength of the LHS or RHS Middle Main Lug and probably Less than Airbus’s Predicted Load (192 % of Limit).


Lack of Witness MarksLack of Witness MarksNTSB Public Docket No. 168624, Factual Report 02-078 NTSB Public Docket No. 168624, Factual Report 02-078 App. A, page 9 of 52, Figure 05. Middle Transverse App. A, page 9 of 52, Figure 05. Middle Transverse Spar shows no Out-of-plane Delamination Damage or Spar shows no Out-of-plane Delamination Damage or Bearing Failure in the LHS Lug Bore. Bearing Failure in the LHS Lug Bore.

The two Forward and Middle Main Lugs Failed The two Forward and Middle Main Lugs Failed Instantaneous and resulted in no Out-of-plane Instantaneous and resulted in no Out-of-plane Delamination in the Middle Spar. As the VT departed, Delamination in the Middle Spar. As the VT departed, the VT Structure was free to move aft and vertically in the VT Structure was free to move aft and vertically in the plane of the Canted Spar, and hence, no Out-of-plane the plane of the Canted Spar, and hence, no Out-of-plane Resistance produced by the Yokes.Resistance produced by the Yokes.

NTSB Public Docket No. 168606, page 5 of 63. Both NTSB Public Docket No. 168606, page 5 of 63. Both Forward and Middle Yokes were free to rotate on their Forward and Middle Yokes were free to rotate on their Lower Attach bolts.Lower Attach bolts.

QuestionsQuestionsHow do you Explain Airbus’s Prediction of a Failing Load of 192% of Limit?

Airbus’s Load Prediction is Based on a Fully Effective Rudder and Fin Completely Supported by the Fwd, Middle and Rear Attachment Systems.

In Failure Scenario at the Time of Departure, the VT was only Supported by the Fwd and Middle Attachment Systems and Missing the Aft Section of No. 1 Rib. This Configuration Reduced the Effectiveness of both the Rudder and Fin which in turn, Restricted Load Development on the VT System.

a300 vertical tail structural evaluation design flaw in lower rear spar by xavier j. maumus

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