Steel-tube struts in GlaStar Wing Brace Kit

Overview

Although every GlaStar retains the ability to have its wings folded thanks to the way its wings are attached to the fuselage, a GlaStar Wing Brace Kit must be installed before the wing-fold function can be used. While most components of the GlaStar Wing Brace Kit were built into N9103D during construction, several parts remain to be installed before N9103D is capable of folding its wings.

Wing-fold procedure

The first step in folding a GlaStar’s wings is to remove the two fiberglass hatches above the baggage compartment. When the hatches have been removed, part of the wings have room to swing into the back of the cabin as the wings fold.

When you fold the wings on a GlaStar, the wingtips will lower, which puts the fuel tank vent outlets below the top of the fuel tanks. In this situation, fuel may flow out the fuel vents, creating an expensive puddle of flammable liquid under the airplane. One answer to this problem is to plug the fuel tank vent outlet at the bottom of each wing, while being sure not to forget to remove the plugs prior to next flight. A better answer is to install a one-way Andair CK375-M check valve in each wingtip.

With hatches removed and fuel vents plugged, one of the two support struts (which are much longer than the remaining two struts) is connected to a permanently installed AN42B-C4A eyebolt located on the wing near the wing root. The other end of the support strut is then connected to a permanently installed strut lug where the base of the strut joins the fuselage.

This operation is repeated on the opposite side of the aircraft: The remaining long support strut is attached to the eyebolt located on the other wing near the root, and the bottom end of the strut is connected to the corresponding strut lug at the base of the strut. 

These two support struts serve to relieve the load on the two forward spar pins in the cabin, thus enabling the spar pins to be removed. The support struts also hold each wing in proper alignment so that the spar and the wing attach clevis in the cage line up again when the wing is folded back into flight position. The support struts are adjustable at one end to accommodate minor dimensional variations on each side of the aircraft.

Following attachment of the support struts, the two short steel-tube struts are connected to eyebolts which have been permanently attached to the aft spar of the wings. The eye bolts are located on the lower surface of the wings directly aft of the outermost inspection holes, close to the trailing edge of the wings.

The two short struts do not support a vertical load. Instead, they serve to hold the wings in their fully folded position close to the rudder, so they don't swing away and risk being damaged.

At this point, with long and short struts attached, one of the spar pins can be removed at the wing root inside the cabin. The wing is then free to swing back toward the tail; during this operation cable tension on flaps and ailerons will be relieved and their control surfaces will droop.

When the wing has been swung close to the vertical fin, the wing is secured to the tail by attaching the free end of the strut dangling from the eye bolt to another AN42B-C4A eyebolt permanently attached to the vertical fin. Once secured, the remaining wing can be swung and secured to the vertical fin with its strut.

Note that the action of swinging the wings backward moves the center of gravity aft, causing the tail of the aircraft to move to the ground if the tail is not supported.

Steps remaining to complete Wing Brace Kit installation in N9103D

Of the four main tasks involved in installing the GlaStar Wing Brace Kit, namely,

1. Installing the two leading-edge clevis eyebolts and strut lugs
2. Adjusting the two leading-edge support struts
3. Installing the two clevis eyebolts on the vertical fin
4. Installing the two trailing-edge clevis eyebolts on the wings

…these steps have been performed:

1. The two leading-edge clevis eyebolts and strut lugs have been installed.
2. Adjusting the two leading-edge support struts has been completed.
3. The two clevis eyebolts on the vertical fin have been installed.

However, the two clevis strut eyebolts on the trailing edge of each wing have not been installed.

The clevis eye bolts (P/N AN42B-C4A), nylon self-locking nuts (P/N AN364-1032A), and thin aluminum washers (P/N AN960D10L) needed to complete installation of the GlaStar Wing Brace Kit are available from Glasair Aviation USA and Aircraft Spruce.