Beechcraft Model 18 Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! ===Spar problems=== The [[wing spar]] of the Model 18 was fabricated by welding an assembly of tubular steel. The configuration of the tubes in combination with drilled holes from aftermarket [[Supplemental Type Certificate|STC]] modifications on some of these aircraft have allowed the spar to become susceptible to corrosion and cracking while in service.<ref>Ramey, Taigh. [http://www.twinbeech.com/beech18sparconcerns.htm "Spar concerns."] Twinbeech.com. Retrieved: December 17, 2014.</ref> This prompted the FAA to issue an [[Airworthiness Directive]] in 1975, mandating the fitting of a spar strap to some Model 18s. This led, in turn, to the retirement of a large number of STC-modified Model 18s when owners determined the aircraft were worth less than the cost of the modifications. The corrosion on unmodified spars was not a problem; it occurred due to the additional exposed surface area created through the STC hole-drilling process. Further requirements have been mandated by the FAA and other national airworthiness authorities, including regular removal of the spar strap to allow the strap to be checked for cracks and corrosion and the spar to be [[Industrial radiography|X-rayed]]. In Australia, the airworthiness authority has placed a life limit on the airframe, beyond which aircraft are not allowed to fly.<ref>Ramey, Taigh. [http://www.twinbeech.com/considerations_when_buying_a_twi.htm "Vintage Aircraft: Things to Consider when Buying a Twin Beech Project."] ''Twinbeech.com'', Stockton, California. Retrieved: August 24, 2008.</ref><ref>[http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/0EA4F6AC8BB1222986256A46004B8A4E?OpenDocument "FAA Airworthiness Directive No. AD 75-27-09."] ''Federal Aviation Administration''. Retrieved: August 24, 2008</ref><ref>[http://www.casa.gov.au/airworth/airwd/ADfiles/under/beech18/BEECH18-017.pdf "CASA Airworthiness Directive No. AD/BEECH 18/17."] {{webarchive|url=https://web.archive.org/web/20080801104732/http://www.casa.gov.au/airworth/airwd/ADfiles/under/beech18/BEECH18-017.pdf |date=2008-08-01 }} ''CASA.'' Retrieved: August 24, 2008.</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page