GHI informational letter UH1-98-11 dated 10-7-98 - Inspection of Upper Left Hand tailboom attachment
Originally published 6/26/2014
This Letter from 1998 was submitted in relation to other posts on the blog regarding the Upper Left Hand Tailboom Attachment Fitting.
GARLICK HELICOPTERS, INC. 132 Skalkaho Hwy. Hamilton, MT 59840 INFORMATION LETTER UH1-98-11 Dated 10-7-98
All Owners/Operators of Model UH-1H, UH-1B UH-1E, UH-1L, UH-
UH-1F, UH-1P, TH-1L, TH-1F, or HH-1 Aircraft Certificated
Under Garlick Helicopters, Inc. Restricted Category Type Certificate H13WE, H3NM, H5NM or H12NM
SUBJECT: Inspection of Upper Left Hand Tailboom Attachment fittings in the
tailboom for cracking.
Garlick Helicopters, Inc. has received two field reports of failed upper left-hand attachment fittings. In both cases, the pilot heard a loud bang and safely landed the aircraft. Inspections revealed the attach fittings had separated in half and the tailboom was pulled away from the fuselage bulkhead slightly at the upper left attachment. Some deformation of the forward tailboom bulkhead in the same area was noted.
Currently GHI is attempting to procure the subject fittings for laboratory analysis to determine the origin and cause of the failures. It is recommended that operators pay particular attention to these fittings during daily and pre-flight inspections. Both failed fittings should have exhibited cracks during visual inspection prior to failure since the failed area was not covered by the longeron material. However, it is not known at this time how quickly the cracks may have progressed to the point of failure.
Although all four attach fittings in the tailboom as well as the fuselage tailboom attach fittings may be subject to fatigue cracking, upper left hand fitting part numbers 205-031-821-001, 204-031-851-001 and 204-031-074-003 are subjected to higher loads and may be more susceptible to fatigue. Upon completion of further analysis, GHI will address this issue with an appropriate safety bulletin if necessary.
GHI urges operators to adhere to all required re-torque procedures in the applicable maintenance manual and recommends that operators adopt a company policy of periodic re-torque inspections of the tailboom attach bolts , especially during repeated high lift or high cycle external load operations. This would include attach bolts, especially during repeated high lift or high cycle eternal load operations. This would include attach bolts on the extension plug if STC SR00026DE is incorporated on Model UH-1B.