AD 67-26-04 Westin Garwin Carruth Altimeters
September 16, 1967
This AD applied to the “G” Model 150, and a whole list of other airplanes that were equipped with the Westin Garwin Carruth model 22-374 altimeter. If the altimeter was modified, you were good to go. If not, you could fly VFR only, but only after you checked that it indicated within 100 feet of the field elevation, and then monitored inflight for erratic movement. If it was outside either of those limits the airplane was grounded.
Today the odds of having one of these altimeters in your airplane are slim to none. However, if your current altimeter doesn’t pass the simple checks listed in this AD, then the limits of this AD should apply.
BTW, Garwin, Inc has been involved in aircraft instrumentation since the early 50s. Today they are a part of Sigma-Tek.
67-26-04 WESTON GARWIN CARRUTH: Amdt. 39-479, Part 39, Federal Register September 16, 1967. Applies to Aircraft Equipped with Model 22-374 Series Altimeters, except those Altimeters which have been Modified and Marked with a White : “M-1” on the Back of the Instrument. The Unmodified Model 22-374 Series Altimeters are known to have been installed in Cessna Model 150G, 172H, 180H, 182J, 182K, 185E, 188, A188, P206A, P206B, TP206A, TP206B, TU206A, U206A, U206B, TU206B, 210F, 210G, T210F, T210G, 337B, T337B, Serial Nos. 310L-0018 through Serial No. 310L-0182, Serial Nos. 320E-0055 through Serial No. 320E-0276, Serial Nos. 320F-0001 through Serial No. 320F-0016, Serial Nos. 401-0014 through Serial No. 401-0022, Serial Nos. 402-0032 through Serial No. 402-0122, Serial Nos. 411-0240, 411-0241, 411-0243, 411-0246, Serial Nos. 411A-0255 through Serial No. 411A-0276 Aircraft, Reference Cessna Service Letter 67-52 dated September 23, 1967. Beech Model H-18 Serial Nos. BA743 through BA750, A23-A Serial Nos. M992 through M1064, A23-19 Serial Nos. MB154 through MB272 except MB266 and MB268, A23-24 Serial Nos. MB125 through MB272, V35 Serial Nos. D8250 through D8567 and D8571 except 35-C33 Serial Nos. CD1045 through CD1114, 35-C33A Serial Nos. CE80 through CE174, 56TC Serial Nos. TG1 through TG5, TG8 through TG10, A65 Serial Nos. LC257 through LC268, 65-B80 Serial Nos. LD332 through LD348, LD351 and LD352, 65-88 Serial Nos. LP43 through LP45, 65-A90 Serial Nos. LJ237 thru LJ304, 65-A90-1 Serial Nos. LM2 through LM37, LM39, LM41 and LM42, 95-C55 Serial Nos. TE186 through TE433, D95A Serial Nos. TD665 through TD687, and TD689 through TD704 Aircraft, Beech Model 95-B55, Serial Nos. TC-1005 through TC-1039 Aircraft, Mooney Model M20C, Serial Nos. 670001 through 670149, M20E, Serial Nos. 1177, 1199, 1217, 1268, 1273, 1277, 1281, 1283, 1286 through 1288, 1290, 1292, 1293, 1295 through 1308, 670001 through 670062, M20F, Serial Nos. 660001 through 660004, 670001 through 670486, Model M22, Serial Nos. 670001 through 670003 Aircraft. Aero Commander Model 500B, 500U, 680FL, 680FLP, 680T Aircraft, Bell Model 47G-2A, 47G-2A1, 47G-3B-1, 47G-4, 47G-4A, 47G-5, 206A Helicopters. The unmodified Model 22-374 Series Altimeter may have also been installed in other Aircraft as a replacement part since June 1, 1966.
Compliance required as indicated.
To prevent loss of reliable altitude information, accomplish the following:
(a) Unless already accomplished, within 12 months after the effective date of this AD:
(1) Modify altimeter by replacing balance arm assembly with an assembly identified by an M-1 stamped on the brass portion thereof available from Weston Instruments, Inc., Weston-Garwin Carruth Division in accordance with Weston Instrument, Inc., Weston-Garwin Carruth Division Service Bulletin 600-0002 or equivalent approved by the Chief, Engineering and Manufacturing Branch, Central Region, FAA or
(2) Replace the altimeter with an altimeter known to be airworthy.
(b) Until the altimeter is modified or replaced in accordance with paragraph (a) of this AD, for those aircraft equipped with only one operative unmodified Weston-Garwin Carruth Model 22-374 Series Altimeter,
(1) on and after the effective date of this AD, flight is limited to those conditions in which flight is maintained with visual reference to the ground and when flight visibility is 3 miles or better, and
(2) within 10 hours flight time after the effective date of this AD a placard must be installed on the instrument panel in plain view of the pilot which states “This aircraft is limited to operations in those conditions in which flight is maintained with visual reference to the found and when flight visibility is 3 miles or better.”
(c) On and after the effective date of this AD, for those aircraft equipped with unmodified Weston-Garwin Carruth Model 22-374 Series Altimeter(s) the pilot shall accomplish the following in order to determine if the altimeter(s) is operative:
(1) Prior to the commencement of flight, check the altimeter reading(s) against the known field elevation at the appropriate altimeter setting(s). If a deviation of more than 100 feet is observed in the altimeter reading and the aircraft is equipped with only one altimeter, further flight is prohibited until the altimeter is replaced with an altimeter known to be airworthy. If such a deviation is observed in one altimeter on an aircraft equipped with two unmodified Weston-Garwin Carruth Model 22-374 Series Altimeters, flight may only be accomplished in accordance with paragraph (b) of this AD.
(2) During flight, check the altimeter(s) for erroneous or erratic reading(s). If such reading(s) are observed and the aircraft is equipped with only one altimeter, flight may be continued in accordance with subdivision (1) of paragraph (b) of this AD to the next point of intended landing. Flight beyond that point may be conducted only in accordance with FAR 21.197 to a base where repairs can be accomplished. If such reading(s) are observed in only one altimeter on an aircraft equipped with two unmodified Weston-Garwin Carruth Model 22-374 Series Altimeters, and the other altimeter is operative, flight may only be accomplished in accordance with paragraph (b) in this AD.
This amendment effective September 18, 1967.
Revised October 27, 1967.