1 ABS Spar Web Investigation Report to Wichita ACO/ FAA Small Airplane Directorate Wichita, Kansas July 23, ABS-ASF Proprietary Data 7/23/2009

Mandatory Service Bulletins MSB 2269 issued August 1989 –Barons (except 58P and 58TC) –Travel Airs MSB 2360 issued November 1990 –Bonanzas H35 and later –All Model 33 Debonairs/Bonanzas –All Model 36 Bonanzas Required inspection and repairs 2ABS-ASF Proprietary Data 7/23/2009

Airworthiness Directives AD –Incorporates MSB 2269 (multiengine) AD –Incorporates MSB 2360 (singe engine) –One time inspection –Required reporting to Beech No record of any data AD –Repetitive inspections –No reporting 3ABS-ASF Proprietary Data 7/23/2009

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Current AD Inspection Initial No cracks: every 500 hours thereafter Small cracks: every 200 hours thereafter 5ABS-ASF Proprietary Data 7/23/2009

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SurveyReported% ModelResponsesCracksCracked Notes 35 (O/IO- 470) % Short body, <3300 MGW 35 (IO-520) % Short body, 3300 MGW or greater 33 (IO-470) % Short body, <3300 MGW 33 (IO-520) % Short body, 3300 MGW or greater % Long body, MGW 3600 lbs A % Long body, MGW 3600 lbs (3650 lbs 1984 and later) A36TC2100.0% Long body, MGW 3600 lbs B36TC % Long body, MGW 3850 lbs Baron 55/ % Short body, twin-engine Baron % Long body, twin engine % Short body, twin-engine ABS Member Survey 7ABS-ASF Proprietary Data 7/23/2009

Location of Cracks 8ABS-ASF Proprietary Data 7/23/2009

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FAA No-Crack Policy The Old Policy –For cracks found in structural components some ADs have allowed continued operational flight if the cracks are smaller than a certain size. –Inspection requirements will be more stringent for known cracks. The New Policy –Continued operational flight with known cracks in primary structural components should not be allowed. –Small Airplane Directorate will adhere to this basic policy. 10ABS-ASF Proprietary Data 7/23/2009

ABS Position Known issue for two decades Current inspection process has ensured ongoing safety No history of in- flight failure ABS asked FAA for time to investigate 11ABS-ASF Proprietary Data 7/23/2009

Summary of Analysis Data Presented Nov 2008 Preliminary fail-safe analysis –Demonstrated >limit load capability with one web completely failed Preliminary FEA of “medium hard” braking condition –Showed peak web bending stress of ~36 ksi at Huck bolt collars –Sufficient to cause early cracking with repeated applications 12ABS-ASF Proprietary Data 7/23/2009

13ABS-ASF Proprietary Data 7/23/2009

3 PT. BRAKED ROLL µ = 0.30 PRINCIPAL STRESS – AFT SIDE OF FORWARD WEB 14ABS-ASF Proprietary Data 7/23/2009

Completion of Investigation Focus: Ultimate load capability with cracks Most likely initial cracking causes Post-cracking web bending stress alleviation Substantiation that existing AD requirements adequately maintain safety 15ABS-ASF Proprietary Data 7/23/2009

The Critical Issue Is the existing AD sufficient to ensure continued safe operation? Need credible substantiation –Evidence from two decades of safe fleet experience Impressive, but qualitative –Detailed engineering analysis Will provide quantitative data 16ABS-ASF Proprietary Data 7/23/2009

Analytical Substantiation Dependent on four quantitative elements: 1.That ultimate load is sustainable with cracks equal to or greater than the existing AD limits 2.That, in the event of complete failure of one web, the remaining structure can sustain at least limit load 17ABS-ASF Proprietary Data 7/23/2009

Analytical Substantiation Dependent on four quantitative elements: 3.A credible post-cracking crack growth assessment to validate the fleet-observed crack-limiting behavior 4.Confirmation that the existing inspection program will ensure timely detection of any significant crack growth (regardless of likelihood) 18ABS-ASF Proprietary Data 7/23/2009

Analytical Substantiation Items 1 & 2 are essentially unaffected by the cause and mechanism of cracks Items 3 & 4 require rational insight into likely causes, pre-crack stresses and post-cracking behavior 19ABS-ASF Proprietary Data 7/23/2009

Post-Cracking Strength Lower front spar carry-thru with failed web Critical ultimate condition –6.6g positive maneuver –71% wing bending carried by front spar –Net wing moment/side = 429,298 in-lb –Couple upper & lower spar caps = 39,027 lb –Effective lower cap area ~1.45 sq in F t Ultimate = 26,915 psi F tu = 54,000 psi MS >1.0 20ABS-ASF Proprietary Data 7/23/2009

Post-Cracking Strength One web failed between upper & lower spar caps Critical ultimate condition –6.6g positive maneuver –Net F/spar shear/side transferred to skin = 4557 lb –Critical element, 13 AD4 rivets –Load/rivet = lb –Shear critical at 375 lb –Minimum MS = ABS-ASF Proprietary Data 7/23/2009

Summary: Post- Cracking Strength The analysis substantiates ultimate load capability for cracks ranging from existing AD limiting sizes through complete failure of one web Obviously satisfies fail-safe limit load requirements Existing requirements for repair if cracks exist in both webs on one side should continue in force 22ABS-ASF Proprietary Data 7/23/2009

Likely Causal Conditions Primary mechanism producing web bending High fore/aft load transferred from wing lower attach fitting to belly skin Web bending tendency increases with belly in tension from fuselage bending Decreases as belly loading changes to compression Unless local belly compression is high, web bending almost totally a function of the fore/aft load transfer 23ABS-ASF Proprietary Data 7/23/2009

Lower Fitting Load Transfer Schematic P – Load transferred from wing fitting LBT – Local belly tension due to fuselage bending ABS-ASF Report to FAA 7/23/ ABS-ASF Proprietary Data 7/23/2009

Likely Causal Conditions Normal operating spectrum investigated as a possible cause Potential random conditions more severe than typically encountered –No individual known history –Arbitrary but reasonable selection To provide insight into post-cracking behavior 25ABS-ASF Proprietary Data 7/23/2009

Normal Operating Spectrum Analysis Conditions within normal operating flight spectrum unlikely to cause cracking Most conservative negative gust/maneuver condition investigated to confirm this –Selected -0.6g condition with cruise thrust –Frequency: Once per 1500 flights Web bending stresses are low & unlikely to cause early cracking 26ABS-ASF Proprietary Data 7/23/2009

-0.6g Up Gust Condition 27ABS-ASF Proprietary Data 7/23/2009 Net Lwr Ftg. Load: 63 lb

-0.60 G GUST CONDITION FEA RESULTS WEB BENDING STRESSES 28ABS-ASF Report to FAA 7/23/ ABS-ASF Proprietary Data 7/23/ ksi 7.4 ksi

Investigation of Off-Normal Conditions Considered several possible relatively severe conditions to study forward and aft web bending environments –Arbitrary but rational Forward web cracking –3-point braked roll, mu = 0.30 –Engine run-up, 350 lb thrust –300 lb forward towing load reacted at main gear 29ABS-ASF Proprietary Data 7/23/2009

Investigation of Off-Normal Conditions Aft web cracking –Tied down airplane in 50 kt crosswind –25 fps gust at 1g cruise –300 lb reverse towing condition 30ABS-ASF Proprietary Data 7/23/2009

Investigation of Off-Normal Conditions Approach: For each condition, the fore/aft wing fitting load is calculated, together with the local fuselage belly loading The 3pt braked roll condition is analyzed by the FEA model to develop peak web bending stresses at the crack locations 31ABS-ASF Proprietary Data 7/23/2009

Investigation of Off-Normal Conditions Approach: Using the relative F/A wing fitting loads the bending stresses for the other conditions are estimated Those conditions yielding high stresses are considered to be the most likely to initiate early cracking 32ABS-ASF Proprietary Data 7/23/2009

Stresses, Forward Side, Forward Web 3-pt Braked Roll condition, mu=0.3 Peak Web Bending Stresses Huck bolt collars Web face Flange of web Stress 14,174 psi at flange radius 33ABS-ASF Proprietary Data 7/23/2009

Principal Stresses, aft Side of Forward Web Huck bolt collars Web face Flange of web Plate element Stress 33,240 psi Detail A 3-pt Braked Roll condition, mu=0.3 Peak Web Bending Stresses 34ABS-ASF Proprietary Data 7/23/2009

3 Point Braked Roll, mu=0.30 Fatigue Assessment Peak web bending stress = ksi (assumes no hard turns) For ksi, predicted fatigue life = 2400 cycles (typically 1560 hours) Potentially 3 or more hard baking events/landing Assuming frequency of 1 event in 4 landings, 2400 cycle life reached in 3200 landings (~2000 hours) 35ABS-ASF Proprietary Data 7/23/2009

Off-Normal Conditions: Comparative Results 36ABS-ASF Proprietary Data 7/23/2009 Fwd orFwd AttachPeak WebEst. Fatigue ConditionAft WebFitting Load (lb)Bending StressLife (Cycles) Neg. 0.6g gust/Fwd637.4>500,000 maneuver 3 PBR, mu=0.3Fwd lb thrustFwd engine run-up 300 lb fwd towingFwd Tied downAft ,000 w 50kt crosswind 25 fps fin gustAft678.9>500, lb reverseAft towing

Off-Normal Conditions: Conclusions Flight conditions appear non-critical Ground conditions all demonstrate significant web bending stresses, potentially sufficient to initiate early cracking Estimated cycles to failure range from 2400 to 14,000 cycles Results consistent with fleet observed cracking at hours and greater incidence of forward web cracking (4:1) 37ABS-ASF Proprietary Data 7/23/2009

Web face pre-crackWeb face post-crack 15,089 psi post-crack Huck bolt “B” Huck bolt “B” 33,240 psi pre-crack Post-cracking Stress Alleviation, 3pt Braked Roll Condition, mu=0.3 38ABS-ASF Proprietary Data 7/23/2009

Post-Crack Damage Growth With AD allowable crack lengths –Post-crack web bending stresses reduced >50% –Normal operating conditions generate negligible web bending (pre- or post-cracked) –Worst-case (3 PT Braked Roll), peak stress – 15.1 ksi & estimated life to significant crack growth is ~50,000 cycles Even assuming frequent repeated aggressive operation, anticipated crack extension rate will be very slow –As evidenced by fleet experience 39ABS-ASF Proprietary Data 7/23/2009

Investigation Findings Ultimate loads sustainable with cracks beyond AD limits—up to complete failure of one web Web bending stresses are low for all normal operating spectrum loads Several aggressive ground operating conditions generate high stresses –Potential for early cracking 40ABS-ASF Proprietary Data 7/23/2009

Investigation Findings Post-cracking stresses reduced by >50% –Any subsequent crack growth will be very slow These findings are consistent with 20 years of safe fleet experience 41ABS-ASF Proprietary Data 7/23/2009

Conclusions Cracks up to and beyond existing AD limits pose no threat to continued safe operation Existing inspection requirements will continue to adequately monitor/maintain on-going safety 42ABS-ASF Proprietary Data 7/23/2009

Recommendations Continue with existing AD requirements Additional emphasis to operators on avoidance of aggressive ground operations 43ABS-ASF Proprietary Data 7/23/2009

44 Questions? ABS-ASF Proprietary Data 7/23/2009