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ADs / MSBs / 2360 Carry-Thru Spar Web Cracks

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Presentation on theme: "ADs / MSBs / 2360 Carry-Thru Spar Web Cracks"— Presentation transcript:

1 ADs 90-08-04 / 95-04-03 MSBs 53-2269 / 2360 Carry-Thru Spar Web Cracks
American Bonanza Society/ ABS Air Safety Foundation Spar Web brief 09/05

2 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 Carry-thru spar web cracks were first noticed in Barons used in an European airline training environment in the late 1980s. On further investigation similar cracks were found in non-training Barons. Beech Service Bulletin 2269 was issued in August 1989 to provide a means of inspecting and, if necessary, repairing cracks found in Baron and Travel Air carry-thru webs. 58P and 58TC Barons were exempt from the inspection because the spar web material in these airplanes is significantly thicker, and thought to be immune to these cracks. Soon afterward similar cracks were found in some Bonanzas. Beech Service Bulletin 2360, released in November 1990, applied the same inspection and repair requirements to H35 and later Bonanzas, and all Debonairs. Beech’s current spar web repair kit appears to be a factory adoption of a field repair applied to the first Barons that were found to have cracked. To the best of our knowledge there has been no independent engineering of this repair kit. Spar Web brief 09/05

3 Airworthiness Directives
AD Incorporates MSB 2269 (multiengine) AD Incorporates MSB 2360 (singe engine) To date there have been NO reports of aircraft mishap or in-flight failure resulting from cracks in wing carry-through spar web structure. The FAA followed up by making the inspections and repairs mandatory. AD , applicable to Travel Airs and Barons (except the 58P and 58TC), adopted the requirements of Beech SB 2269. A 1992 AD provided for a one-time inspection of Bonanza and Debonair carry-thru webs along the lines of Service Bulletin This AD required owners to report the results of spar web inspections to Beechcraft, which would maintain the data. ABS has requested this data from Beech, only to learn that no such data exists. It’s thought this lack of data come from noncompliance with the AD reporting requirement by inspectors in the field. The 1992 AD was later revised into AD , codifying repetitive inspections identical to those required for the multiengine airplanes. AD does not contain any inspections results reporting requirement. Beech felt it addressed the problem internally by installing heavier-material webs in production airplanes beginning in 1985, before the ADs were issued. Airplanes built after the introduction of heavier webs are exempt from the AD requirement, although the Shop Manual calls for visual inspection of the affected area for cracking in ALL Beech airplanes. These ADs remain unchanged to this date. It’s important to note, that to date there have been NO reports of aircraft mishap or in-flight failure resulting from cracks in the wing carry-thru spar web structure. The inspection-and-repair-as-necessary ADs appear to be doing the job of preventing mishaps. Spar Web brief 09/05

4 Carry-through spars For illustration, the carry-thru spars are depicted on this drawing. This issue concerns the forward carry-thru spar web. Spar Web brief 09/05

5 The forward carry-through itself looks like this, looking aft
The forward carry-through itself looks like this, looking aft. The structure is a box beam with the top and bottom spar caps held in position by a forward and rear web, thus making up the box. Tension and compression loads of the spar are carried by the spar caps. The purpose of the web is to hold the spar caps in place. Spar web fasteners at the lower, outboard corners of the web are called Huck bolts. The Huck bolt area is one region of concern, and where at least half of the reported spar web cracks have been found. The flange of the web is the rounded area that creates a former to which the fuselage skin attaches. A number of cracks have been found in the “radius of the web,” or the rounded corner. The flange of the web material in the carry-thru becomes a bulkhead that actually attaches the wing to the fuselage. Structure in this area, while not necessarily carrying wing spar loads, is carrying all the loads between the fuselage and the wing. It’s generally considered benign for small cracks to exist around the Huck bolts or in the radius of the flange, so long as the cracks remain small and are confined to the lower part of the web material. Larger cracks, or cracks propagating to the upper parts of the spar web may present a more potentially hazardous situation as they may affect the load-carrying capability of the carry-thru section. Spar Web brief 09/05

6 Tie Plates Carry loads between ends of carry-thru in Huck bolt area
Potential damage to tie plates and internal C-channels make stop drilling hazardous in this area ABS’ contract engineers feel there are techniques to get around this problem Tie plates carry the loads between the spar caps at the ends of the carry-thru in the Huckbolt area. Not all Bonanza-derivative airplanes have tie plates as part of the carry-thru. Potential damage to tie plates as well as the “C” channels underneath that make up the spar caps make stop drilling difficult and currently unacceptable. Our engineers suggest that techniques could be worked out to alleviate this problem. Spar Web brief 09/05

7 Tie Plates Tie plates may carry the load
Lower material may not carry carry-thru loads Tie plates differ in different models Need to further investigate the design Because the tie plates, when installed, are made of very heavy material, they may carry the web structural loads and the relatively light weight sheet metal visible in the picture may in fact not be serving the function of the spar web. Cracks in this material therefore may not be in a primary load bearing structure. That portion of thinner material that extends below the lower spar cap does not meet the definition of a “spar web”. The importance of this distinction is yet to be determined. Tie plate design differs by model of the Bonanza and Baron, and they are not universal to all versions. This is another example of the need to more thoroughly investigate the function and stresses of the carry-thru. Spar Web brief 09/05

8 Current AD Inspection Initial inspection @1500TT
No cracks: every 500 hours thereafter Under current rules the ADs call for dye penetrant inspection of the indicated areas on the front and aft sides of the forward carry-thru, beginning at 1500 total hours and, if no cracks are found, at every 500 airframe hours thereafter. There are currently no approved alternatives to the dye penetrant check. At least one shop earned approval to substitute an eddy current check some time ago, but that approval is no longer active. It’s important to note that to be done properly the dye penetrant inspection requires the area be stripped of all paint, cleaned scrupulously before and after the inspection and repainted. Our suspicion is that this is often not done. Spar Web brief 09/05

9 Current AD Inspection (continued)
If cracks in web near/through huck bolts: <1.0 inch: reinspect at annual/every 200 hours >1.0 inch or connecting two huck bolt holes or cracks on forward and aft side of web on same side of aircraft: Install Beech doubler repair kit Cannot stop drill through web: damage beneath Under current AD rules, unchanged since 1990 and 1995, respectively, small cracks affecting no more than one Huck bolt location can be monitored with dye penetrant inspections at every 200 airframe hours. Stop drilling the cracks is specifically prohibited because of the possibility of damaging structure beneath the spar webs. Larger cracks, and those affecting more than one Huck bolt, require installation of the Beech doubler repair kit. Kit installation is required also if cracks appear on the front and aft side of the carry-thru on the same side, regardless of crack size. Spar Web brief 09/05

10 Current AD Inspection (continued)
Cracks in the flange radius: <2.25 inch: Stop drill crack Reinspect every 200 hours thereafter 2.25 – 4.0 inch Install Beech doubler repair kit within 100 hours >4.0 inch Install Beech doubler repair kit prior to flight Cracks of up to 2 ¼ inch in the flange radius can be monitored with 200-hour dye penetrant checks. These cracks should be stop drilled to prevent growth, as there is no danger of damaging interior structure by stop-drilling these areas. Larger cracks require installation of the doubler repair kit, in some cases prior to further flight. Spar Web brief 09/05

11 Doubler Installation (Show doubler installation) Spar Web brief 09/05

12 RAC Communiqué 103 Issued October 2003:
“The FAA no longer allows aircraft operation with known cracks….” RAC “is in the process of revising both service bulletins to remove any reference to continued flight with cracks in the spar web.  The revised service bulletins…will require repair of any crack found during inspection of the spar web regardless of size." Inspections and AD requirements were deemed appropriate by Beech/Raytheon and the FAA, and acceptable to ABS members and aircraft owners, for nearly two decades. Without fanfare Beech issued Communique 103 in November 2003, stating that “the FAA no longer allows aircraft operation with known cracks” and advising that Raytheon was “in the process of revising (Service Bulletins 2269 and 2360) to remove any reference to continued flight with cracks in the spar web.” Justification of this release was later traced to a 1996 internal FAA memo that adopts a “no cracks” philosophy unless engineering definitively shows that the airplane continues to meet its certified load-carrying capability with the specific size and orientation of crack found. Spar Web brief 09/05

13 MSB Revisions June 2004 “At the request of the FAA….”
Eliminates option of continued flight with identified spar web cracks (and accelerated inspections) Not “mandatory,” but may be required under Part 135 and for some foreign-registered airplanes ABS Comparison sheet Raytheon followed this up with release of revised Mandatory Service Bulletins , for Barons and Travel Airs, and for Bonanzas and Debonairs, in early June, These Bulletins contain an unusual preamble that states the Bulletins were revised “at the request of the FAA”—usually the process is reversed, with the manufacturer issuing a bulletin and then the FAA becoming involved. The revised Service Bulletins, as expected, removed the option of the 200-hour repetitive inspection for minor cracks. Any crack discovered, under the revised Bulletins, would require installation of the Beech doubler kit. ABS has published on its website a comparison of pre- and post June 2004 serviced bulletins, showing the changes. Nonetheless the ADs themselves have not been revised. Hence the “no cracks” Bulletins are not mandatory except in the case of commercial operators who have written Mandatory Service Bulletin requirements into their Ops Specs, and for some foreign-registered airplanes. Part 91 operators are still covered by the Airworthiness Directives, which (as they have not been changed) continue to permit 200-hour dye penetrant inspection of “minor” spar web cracks. This has generated some confusion in the field. A shop that diligently updates its Service Bulletin guidance no longer has the original Service Bulletins 2269 and 2360, which the Airworthiness Directives reference for inspection and compliance. Some ABS members have reported shops wanting to install the Beech doubler for “minor” cracks because they have no bulletin describing a 200-hour inspection cycle. ABS has posted both the original and revised Service Bulletins on its website, so members (and their mechanics) can reference the older Bulletins that are still the method of compliance with the Airworthiness Directives. Spar Web brief 09/05

14 ABS Investigation Initial contact with FAA and RAC to confirm moving toward “no cracks” in “primary load-bearing structure” January 2004: Dick Wilson calls ABS with opposing view Engineering study grew from an independent “peer review” of Wilson ABS began investigating the possible impact of the emerging “no cracks” philosophy as soon as Beech Communique 103 was issued. Later clarifications from the FAA state that they no longer wish to allow operation with known cracks IN A PRIMARY LOAD-BEARING STRUCTURE. This is an important distinction, and points to the need to determine the precise stresses being carried by the spar webs, i.e., what actually constitutes the “spar web,” and are the spar webs “primary load-bearing structure?” In January 2004 ABS member and retired engineer Dick Wilson approached ABS with a dissenting viewpoint. He feels the cracks emanate from the stretching of the lower spar cap under lifting stress. We asked Wilson to write up his ideas for ABS to discuss with the FAA. He instead began a personal website and his own correspondence with the FAA, which includes a view that the ADs and MSBs are not only unnecessary, but destructive and should be withdrawn. Needless to say, his demands have been rejected by the FAA. The next step for ABS was to contract with two highly qualified engineers to perform a peer review on Wilson’s work. We engaged Peter Harradine, retired chief of structures engineering for the Boeing company, and Joe Dwerlkotte, a practicing FAA-DER fatigue and structures engineer who worked in Beech engineering in the 1950s and 60s. The engineers’ full resumes, and their reports, are posted on the ABS website. ABS gave the engineers a mandate to review the ADs and Dick Wilson’s opinions, to evaluate the current Beech repair, and to list recommendations for possible courses of action. Spar Web brief 09/05

15 Probable cause of spar web cracking
Engineering Reports Probable cause of spar web cracking Low-intensity, frequently repeated loads from normal operation Primarily driven by nose gear loads during landing and ground handling Longitudinal stresses directed around the fuselage skin wing spar cutouts The engineers concur that the probable cause of spar web cracks is repeated, low-intensity stress caused primarily from nose gear loads during normal landing and ground handling. Specifically, the engineers theorize that longitudinal stresses are concentrated in the carry-thru as a result of fuselage skin cutouts where the wing spars pass into the cabin. Spar Web brief 09/05

16 (point out the forward attach points and their fuselage skin cutouts)
Spar Web brief 09/05

17 J Stringer (example of crack, V35A)
Longitudinal stresses flex the web material. Most cracking on the web faces occurs around or through the outermost, lower Huck bolt hole. Spar Web brief 09/05

18 Longitudinal flexing (example of crack, A36)
Here it’s perhaps easier to visualize the flexing force imposed on the web as stresses from the stringer impact the carry-thru. Spar Web brief 09/05

19 (example of crack, A36) Here’s another image showing a Huck bolt area crack in the lower, outboard hole, near a stringer that transfers longitudinal stresses to the vertical web Spar Web brief 09/05

20 (example of crack, Baron 58) The green lines indicate the ends of the crack, and are perpendicular to the crack itself. And yet another image of this familiar Huck bolt crack pattern Spar Web brief 09/05

21 (example of crack, Baron 58)
Many cracks also occur in the radius of the flange, as in this photo. There appears to be a small Huck bolt-area crack as well Spar Web brief 09/05

22 Engineering Reports (continued)
Probable cause of spar web cracking Initial Huck bolt-area cracks allow flexing that develops to bend radius cracks The engineers “doubt the validity” of Wilson’s work and “cannot agree with his conclusion that the cracking will not potentially cause safety problems.” The engineers suggest that the sequence of cracking begins with stress cracks near the Huck bolts. This permits web flexing that later leads to cracks in the flange area as well. The engineers conclude that they “doubt the validity” of Dick Wilson’s views, and “cannot agree with his conclusion that the cracking will not potentially cause safety problems.” The orientation and pattern of reported cracking, according to the engineers, proves the related stresses are longitudinal and not related to wing lifting, which further defeats Wilson’s arguments. Spar Web brief 09/05

23 Engineering Reports (continued)
Current MSB effectiveness Kit repairs cracks locally but does “very little for the fore and aft loads that are the cause of cracks seen to date.” Kit increases stiffness and therefore increases web stresses Kit in conjunction with “a robust external doubler to the fuselage skin should cause no harm.” ABS asked the engineers to comment on the Beech repair doubler as well. The engineers feel that the doubler may cover cracks locally, but they do “very little for the fore and aft loads that are the cause of cracks….” They feel the doubler stiffens the web structure and therefore increases web stresses. Harradine proposes that, in addition to a doubler to repair existing cracks, a “robust external doubler to the fuselage skin” should re-route stresses from the fuselage skin cutouts, and “cause no harm” to the structure. Dwerlkotte advises: “We do not see that the (Beech) kits provide a permanent repair unless a set of doublers are installed on the outside of the fuselage skin to redirect the fore/aft loads around the (bathtub fitting) cutouts..” At this point all these learned opinions are still just that, opinion, and the effect of spar web cracks on safety is uncertain. Taken together, however, they are a call for a detailed engineering study to arrive at a definitive answer in the interest of safety and the sustained, long-term airworthiness of the fleet. Spar Web brief 09/05

24 Engineering Reports (continued)
Engineers’ recommendations It is vital to obtain all available information A Finite Element Analysis is “essential to…validate any proposed repair….” Perhaps the most notable observation by the engineers is that we have a very long way to go to fully understand the dynamics of spar web cracking, and possible long-term effects of installing the Beech doubler. They call for a Finite Element Analysis, or computer stress simulation, as “essential to…validate any proposed repair….” Such an analysis requires access to original Beech engineering data, or else a complex and costly reverse-engineering process. Results would have to be validated through in-flight testing and/or ground-based testing on airframe components. Despite ABS’ best efforts, just last week Beech ruled that it will not release any of its engineering data on the carry-through structure or the repair kit. Hence it’s up to us to investigate the issue by developing engineering data from scratch. Spar Web brief 09/05

25 Other ABS Actions Regular FAA and Raytheon contacts
Airworthiness Concern Sheet, September 2004 AOPA meeting November 4, 2004 GAMI meeting November 8, 2004 National Institute for Aviation Research T-34, Twin Cessna, Twin Beech, T-6 issues From the very beginning ABS has kept in close contact with the FAA’s Small Aircraft Directorate and Wichita Aircraft Certification Office, which are responsible for this issue ABS has also repeatedly spoken with Raytheon officials up to and including Beech president Randy Groom A September 2004 Airworthiness Concern Sheet, published by the FAA and seen as a precursor to a Notice of Proposed Rulemaking to change the spar web ADs, resulted in an FAA commitment to postpone any change in rulemaking until ABS can more fully investigate the spar web issue ABS representatives traveled to AOPA headquarters and briefed AOPA President Phil Boyer and his Government Affairs staff, resulting in a financial gift from AOPA that partially offset the cost of the Harradine and Dwerlkotte reports ABS also sent advance copies of the reports to GAMI, and took our engineers to their facility in Ada, Oklahoma to discuss their findings. GAMI’s engineer reported essentially identical opinions as a result of a parallel and independent investigation. Subsequently every member of ABS’ Technical Committee and several other Board members have visited Ada and seen GAMI’s plans for a test set-up. GAMI is working on an Alternate Means of Compliance and ABS is enthusiastic about the work they are doing. Many of their inspection and repair techniques may become useful on our airplanes even though some are being developed to address other problems. Looking farther into the future, ABS has also visited the National Institute for Aviation Research’s Aging Aircraft laboratory, at Wichita State University. NIAR conducts much of the engineering work contracted by the FAA, and has experience developing airframe longevity programs to detect and repair the effects of fatigue The FAA has repeatedly told us, by the way, that they do not see the T-34 AD issues carrying over into other Beech airplanes. Significant design differences, including the lack of a fuselage door cutout in T-34s and the additional upper longerons in those airplanes, may create substantially different stress patterns. In addition, the use of those airplanes, particularly those that have had in-flight failures, is unique and drastically different than our fleet. However, we are keenly interested in what the T-34 investigations will yield in the way of a better understanding of the structure. GAMI engineer George Braly will be discussing lessons from his work for the T-34 Association in a separate session Saturday. Other, much more serious fatigue issues face owners of T-34s, Cessna twins, the Twin Beech, and T-6/SNJs. ABS has been in contact with officers of the T-34 Association since their issue resurfaced last December. We attended the FAA’s public meeting on the T-34 in February 2005, taking engineer Dwerlkotte as an advisor. We have also keep in close touch with the Cessna Pilots Association’s Twin Cessna technical consultant regarding their wing spar AD. Closely monitoring other type clubs’ experiences with aging aircraft-related regulation helps ABS better plan for any work we’re called upon to do in this arena. Beginning in late 2004 the FAA’s Small Aircraft Directorate has been overwhelmed with these investigations, putting our spar web issue on hold until further notice. This provides ABS a wonderful opportunity to learn as much as we can about spar web cracks before the FAA’s attention returns to our airplanes. It also gives us the opportunity to learn more about Bonanza/Baron structures, and what (if any) lessons from the T-34 may apply directly to our airplanes. ABS continues to be in contact with the FAA approximately every two weeks for a status update on the spar web issue. Spar Web brief 09/05

26 ABS Member Survey 1770 responses 110 aircraft (5.9%) MSB-defined crack
32% of ABS members with affected airplanes estimated ~14% of remaining affected fleet 110 aircraft (5.9%) MSB-defined crack 52 aircraft (2.9%) require doubler under existing rules 60 aircraft (3.3%) cracked but do not currently require doubler To date we have received 1770 responses to our spar web survey. This represents about 32% of the ABS members with affected airplanes. We estimate about 14% of the total affected, U.S.-registered fleet has responded, but it’s likely that the actual number of airworthy airplanes is far fewer than the registrations number suggests. About 6% of the respondents report spar web cracks. This percentage has hovered within a tenth of a percent since the time about 80 airplanes were reported—suggesting that this may be a fairly accurate figure. It’s quite possible, however, that owners with cracks are more likely to have responded to the survey that those without, and this percentage therefore may be artificially high. ABS actively encourages ALL owners of affected airplanes to report, to develop the most correct information. Of those reporting cracks, only slightly more do not require doubler installation under current rules than those for which the doubler is mandatory. Spar Web brief 09/05

27 ABS Member Survey (continued)
H35 – K reports M35 – P report S35 – V35B 15 reports 33 (IO-470) 4 reports 33A/C 7 reports reports Here are the numbers of spar web crack reports broken down by model of Bonanza and Debonair. It’s suggested that the longer moment arm between the nose gear and the forward carry-thru on Model 36 Bonanzas may contribute to the higher rate of web cracks in these airplanes Unfortunately, the relatively low number of responses we’ve received, and the very small number of pictures and sketches of cracks that have been given ABS, severely limits the effectiveness of any conclusions we might draw from these numbers. Spar Web brief 09/05

28 ABS Member Survey (continued)
Travel Air 1 report 55/56TC 29 reports reports Here are the figures for Travel Airs and Barons. The number of Baron 58s reporting cracks is lower than other Barons most likely because a larger percentage of Model 58 Barons are in commercial or corporate use, and their owners are more frequently not members of ABS. It’s possible that additional forces contribute to the higher rate of cracking in Barons. On touchdown the engines, hung ahead of the forward spar, will naturally flex downward. This in turn may flex the wing spar and impart a twisting force to the carry-thrus. Again, the small volume of data sent by members hampers our investigation. Spar Web brief 09/05

29 ABS Member Survey (continued)
Best information is that this limited response is indicative of fleet as a whole Still does not account for RAC’s report it has sold 2000 spar repair kits Post-AD airplanes Information on cracks that have propagated into upper web We’re working to learn whether our survey response is statistically valid, or if we need to do yet more to encourage reporting. The best information we have to date, however, is that our results are indicative of the fleet as a whole. This does not account for Raytheon’s report that it has sold over 2000 spar repair kits Two disturbing trends have emerged—first, we’re getting limited reports that airplanes with thicker spar webs, those not current affected by the Airworthiness Directives, are developing spar web cracks as well. These reports come from very high-time airplanes, in excess of 17,000 hours, operated in training environments—similar to the Barons that first reported spar web cracks in the 1980s. Secondly, in a few isolated cases we have reports of cracks that have begun to grow after years of no observed growth, and cracks that have propagated into the upper spar web, which the engineers feel may have more serious implications. Spar Web brief 09/05

30 ABS Position Given that:
Beechcraft spar web cracking has been a “known problem” for well over a decade; In that time there has been no aircraft failure or mishap attributed to spar web cracking; Current AD procedures have prevented mishaps ABS stated position, delivered to the FAA and Raytheon in November 2004, is, given that: The Beechcraft spar web cracking has been a “known problem” for well over a decade; In that time there has been no aircraft failure or mishap attributed to spar web cracking; and Service histories suggest, at least to date, current AD requirements are satisfactorily detecting and addressing cracks, and preventing virtually all growth and/or recurrence of spar web cracking except in very few, unusual cases; Spar Web brief 09/05

31 ABS Position (continued)
ABS therefore requests that: Current Airworthiness Directive procedures should not be revised until such time as additional, detailed analysis determines the true nature of stresses and spar web crack development; ABS therefore requests of the FAA that current Airworthiness Directive procedures should not be revised until such time as additional, detailed analysis determines the true nature of stresses and spar web crack development. We also ask that operators required to maintain their airplanes in accordance with factory bulletins be allowed to use pre-June 2004 procedures pending the results of such study. Spar Web brief 09/05

32 Aging Aircraft Beyond the basic spar web issue, investigation of T-34s has shown long-term fatigue issues that may be “leading indicators” of what we’ll see in Bonanzas, Barons, Debonairs and Travel Airs in the future. To date there’s no evidence that specific T-34 fatigue patterns also exist in “our” airplanes. The FAA does feel, however, that longevity issues faced by the T-34, twin Cessnas, T-6s and Twin Beeches, along with our less critical spar web ADs, point to a pattern that, in the FAA’s view, calls for proactive type club and private industry efforts to identify problems and develop means of ensuring continued airworthiness. Spar Web brief 09/05

33 Safety by Retirement (SBR) From FAA T-34 Public Meeting slide, February 2005
“Run and retire” Pre-emptive replacement/modification at an established time regardless of condition Typical approach for small airplanes, rotorcraft and engines Success depends on retiring/modifying all parts early enough to address even those of lower fatigue quality One disturbing stance mentioned by the FAA at the T-34 public meeting is the concept of “Safety by Retirement”—that a possible option taken by the FAA at some point in the future is simply to ground whole fleets of airplanes when a pattern of airworthiness issues appears. (Review FAA’s bullet points) Spar Web brief 09/05

34 Safety by Retirement (SBR) From FAA T-34 Public Meeting slide, February 2005
Vast majority of parts will be retired/modified with life remaining May be used whether or not cracks are detectable before they become critical (Review FAA’s bullet points). The FAA’s concept of unilateral “Safety By Retirement” provides yet another reason that makes proactive longevity studies by ABS imperative. Spar Web brief 09/05

35 Aging Aircraft Beyond the basic spar web issue, investigation of T-34s has shown long-term fatigue issues that may be “leading indicators” of what we’ll see in Bonanzas, Barons, Debonairs and Travel Airs in the future. To date there’s no evidence that specific T-34 fatigue patterns also exist in “our” airplanes. The FAA does feel, however, that longevity issues faced by the T-34, twin Cessnas, T-6s and Twin Beeches, along with our less critical spar web ADs, point to a pattern that, in the FAA’s view, calls for proactive type club and private industry efforts to identify problems and develop means of ensuring continued airworthiness. One possible option for the Society may be to work with the National Institute for Aviation Research’s Aging Aircraft Laboratory, located on the Beech factory airfield in Wichita. (Introduce Dr. Dale Cope of NIAR for his presentation on their types of aging aircraft longevity programs) Spar Web brief 09/05

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