|HU-16B/D/E Wing Life Limit Information|
(c) 2019 by Ray Wolfe. Not to be reproduced without prior permission. Additional copies of this and other charts are available by contacting Grumman Albatross Research at firstname.lastname@example.org or by phone at 561-430-7804 or fax at 775-546-6029.
As part of the development of the Type Certificate A33SO for the long wing Albatrosses, the FAA mandated a life limit on those aircraft due to the construction of the wing and the results of testing conducted by the US Navy. This testing was conducted in by the US Naval Air Development Center Johnville in Warminster, PA after the discovery of corrosion damage in the spar caps of several aircraft. The results of the testing were published 30 June 1970 as Report # NADC-ST-7007 "Determination of the Life Remaining in the Model HU-16E Airplane Wing" which has become commonly referred to as "The Philadelphia Report". As part of the Long Wing conversion process all 4 spar caps had steel reinforcing doublers installed which appears to have precipitated the corrosion that prompted the fatigue test. Additionally 2 rivet holes were plugged during the conversion and this is the spot where the cracks in the spar caps originated.
During the test a USCG HU-16E (USCG 1264 - G150) wing with 7,216 service hours was subjected to a total of 12,500 test hours. The right wing failed at 8,200 test hours at which point a Grumman designed steel doubler plate was installed on the left wing in the area of the jack pad holes. The failure originated in the Main Beam Lower spar cap in the area of the jack pad holes. The test was continued and the left wing accumulated an additional 4,000 test hours before catastrophic failure. It was determined that the presence of exfoliation corrosion was a definite factor in the origination of the fatigue cracks but the the amount of corrosion was not relevant (the wing with less corrosion failed first in the test)
The report recommended that all Long wing airplane spar caps be immediately inspected using eddy current NDI procedures and that the Grumman designed doubler be installed on all Long Wing airplanes followed by repetitive eddy current inspections every 200 hours or less. The recommendation was also made that all USCG aircraft be retired at 12,500 flight hours and all USAF, USN and Canadian aircraft be retired at 9,500 flight hours.
Based on the data I have accumulated, the USCG established a life limit of 11,000 flight hours for their aircraft. The vast majority of retired USCG HU-16E models were retired with somewhere between 10,500 and 10,999 hours. USAF airplanes generally seem to have been retired in the 7,000-8,000 hour range. Because of their shorter time in service before retirement, USN HU-16D's were generally retired with roughly 4,000-5,000 flight hours.
The specific life limit for each airframe as determined by the FAA is listed in the Type Certificate Data Sheet. The life limits under TCDS A33SO range from 7,371 hours to 9,855 hours. These limits do NOT apply to the short wing Albatross.
As part of the civilian G-111 conversion, the wing spars on 12 of the 13 G-111's were rebuilt with new titanium spar caps which eliminated the life limit on those aircraft. (1 of the 13 aircraft that was converted to a G-111 did not receive the spar cap replacement and thus retains a life limit. See the Type Certificate for more details)
|MIN-1705 - NADC-ST-7007 - Philadelphia Report||Determination of the Life Remaining in the Model HU-16E Airplane Wing
||Airframe Type Certificates
||TCDS #||Owner||Revision||Revision Date||Applicable Models||Comments
Air Transport Inc
|Original||20 Jun 1978||HU-16B - 1||Single Pilot
||A20NM||Viking Air||Original||3 Oct 1986||HU-16D - 1||_
||A22SO||Amphibian Aircraft Technologies, LLC||Revision 10||1 May 2016||G-111 - 13||_
||A23NM||Dennis Buehn||Revision 4||10 Sep 1998||HU-16C - 55|
TU-16C - 5
||A33SO||Amphibian Aircraft Technologies, LLC||Revision 10||23 Jan 1995||HU-16A - 12|
HU-16B - 12
HU-16C - 16
HU-16D - 8
HU-16E - 6
||T00003LA||Reid Dennis||Original||3 Dec 1998||HU-16RD - 1||_