Carry through spar bolt replacement

1 month 1 week ago #3136 by STEVE ELLS
Replied by STEVE ELLS on topic Carry through spar bolt replacement
Hi Henke;
I found this information in the 1996 and new Single engine Structural Repair manual:
A. Standard solid shank MS rivets are those generally used in airplane construction. They are
fabricated in the following head types: roundhead, flathead, countersunk head, and universal
head. Flathead rivets are generally used in the airplane interior, where head clearance is required.
MS20426 countersunk head rivets are used on the exterior surfaces of the airplane to minimize
turbulent airflow. MS20470 universal head rivets are used on the exterior surfaces of the airplane
where strength requirements necessitate a stronger rivet head than that of the countersunk head
rivet. Hi-Shear rivets are special, patented rivets having a high shear strength equivalent to that of
standard NAS bolts. They are used in special cases in locations where high shear loads are present,
such as in spars, wings, and in heavy bulkhead ribs. This rivet consists of a cadmium plated pin of
alloy steel. Some have a collar of aluminum alloy. Some of these rivets can be readily identified by
the presence of the attached collar in place of the formed head on standard rivets. Blind rivets are
used, where strength requirements permit, where one side of the structure is inaccessible, making it
impossible or impractical to drive standard solid shank rivets.
3. Replacement Of Hi-Shear Rivets
A. Replacement of Hi-Shear rivets with close tolerance bolts or other commercial fasteners of equivalent
strength properties is permissible.
(1) The hardware used for the Hi-Shear rivets is determined according to the size of the holes and
the grip lengths required.
(2) Bolt grip length should be chosen so that no threads remain in the bearing area.
(3) Holes must not be elongated, and the Hi-Shear substituted must be a smooth, push-fit.
B. Field replacement of main landing gear forgings on bulkheads may be accomplished by using the
following hardware:
(1) NAS464P, NAS436P, and either: NAS1103 through NAS1120, NAS1303 through NAS623 or
NAS6203 through NAS6220 bolt, and either:
(a) MS21042 nut and AN960/NAS1149 washers in place of Hi-Shear rivets for forgings with
machined flat surfaces around the attachment holes.
(b) ESNA2935 mating base washer and ESNA RM52LH2935 self-aligning nut with forgings
(with a draft angle of up to a maximum of eight degrees) without machined flat surfaces
around the attachment holes."

This may help,

Let me know if I can help further.

PS If anyone has more detailed information, please post it in reply to Henke's request.


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1 month 1 week ago #3135 by Henke Beyers
Carry through spar bolt replacement was created by Henke Beyers
Good day

I need some help regarding the replacement bolt/ hi-lock specs on the front and rear spars of a C-185. The manual calls for Huckbolts R3104T6-5 in the front and R3104T6-3 in the rear spar. What is the correct replacement in either NAS or Hi-locks for this application?


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