Flare Canister Restoration Begins:
While Pioneer Aero has rightly focused on rebuilding the SBD's major structural items, they have also made time to work on some of the aircraft's smaller components. Recently, this effort involved working on the parachute flare canisters which sit in the lefthand rear fuselage just behind the gunner's compartment, as the above image illustrates quite effectively.
Naval Parachute Flares:
During the 1930s, the U.S. Navy equipped many of its combat aircraft with the ability to drop parachute flares. These flares, theoretically, allowed pilots to illuminate a target at night, or a runway if necessary, and their use formed a staple in pre-war training regimens. However, it does not appear that the Navy actually employed them for that purpose during WWII. Even so, the SBD Dauntless (developed from the Northrop BT-1 of 1935) came equipped with a pair of parachute flare canisters of an identical design to those which featured in the earlier Northrop aircraft.
What is in a Parachute Flare Canister?
Each tube could hold a 27” long 4.75” diameter illumination device such as the Navy Flare Mk.5. These flares, actuated individually from separate controls on the left wall of the pilot’s cockpit, fell vertically from their housing with the arming plate remaining fixed to the airframe. A lanyard spools out and then actuates the ignition timing mechanism (which both deploys the parachute and the illuminant) once the flare has fallen a sufficient distance. It was also possible to adjust the flare ignition delay time (prior to loading) so that the device would light up at the appropriate distance from the ground. A Dauntless pilot could deploy these flares from between 2,500’ and 15,000’ altitude. The parachute, naturally, allowed them to linger in the air above the target area; they burned for roughly 3 minutes, with a peak illumination of up to 750,000 candle power.
Assessment:
The following images offer a detailed view of the flare canisters prior to their disassembly. It is worth noting the generally excellent condition of the tubes and their supporting structure.
A topside view of the flare canister assembly showing the two flare loading doors. The access panel for loading the flares lies in the base of the machine gun trough behind the rear cockpit. Note how one of the Dzus fasteners securing one of the doors is undamaged while the other is completely eaten away. (image via Pioneer Aero Ltd.)
A view of the canister doors in the open position. Note the lower doors (not fitted) would be closed during loading and stay that way until a flare was deployed in flight. (image via Pioneer Aero Ltd.)
The lower end of the flare canisters with their associated mounting structure. The curved ribs attach the canisters to the lower left side of the fuselage behind the life raft tube. The lower doors (not fitted here) match the curve of the ribs; they fit to the steel hinge brackets on the bottom end on the flares tubes. (image via Pioneer Aero Ltd.)
Disassembly & Refurbishing:
Martin Hedley began the restoration process by disassembling the canisters and their associated mounted structure into their component parts. He then assessed each item as to its potential future airworthiness, media-blasting those items which held promise. Thankfully, most of the structure proved reusable, so Hedley began refurbishing these parts, while remanufacturing those beyond redemption or salvaging substitutes from the donor airframe. The following images show this process as it unfolded.
The forward face of the aft rib which helps attach the flare tubes to the fuselage. The part has just been removed from the rest of the structure and is awaiting bead blasting and the removal of the short angle seen riveted to the narrow end of the component. (image via Pioneer Aero Ltd.)
The forward faces of the three ribs which mount the flare canisters to the fuselage. The aftmost rib is at image left while the forward element is on the right. The latter two ribs have no need for repairs, and only await primer-painting before they are ready for reuse. The middle rib awaits bead blasting and the removal of the short angle section at its narrow end. (image via Pioneer Aero Ltd.)
A closeup of the bottom end of the flare canisters during disassembly. The lower doors mount to the steel hinge brackets on the bottom end on the flares tubes. The aft hinge (right in photo) and collars beneath it are visibly corroded and proved unrestorable following assessment. The forward hinge is also not airworthy, obviously, however its collars were indeed salvageable. (image via Pioneer Aero Ltd.)
The upper collars and mount for the flare canisters awaiting assessment and bead blasting. While corrosion on the upper mount (top) and aft, outboard collar (center right) proved to be beyond airworthy limits, the other three components exhibited only minor issues and were easily refurbished. (image via Pioneer Aero Ltd.)
The handful of flare canister components which corrosion damage rendered unsalvageable. Deep corrosion in the upper mount (top) was discovered during bead blasting, stopped part way through as a result. Corrosion in one door (middle right) proved deeper than expected during mechanical removal. While the upper door, mount and three collars must be refabricated, a donor aircraft will supply the other replacement parts. (image via Pioneer Aero Ltd.)
The flare tube lower collar replacements part way through their refabrication. This blank was made from 2024-T0 aluminum sheet which, due to its softened state, allowed the required curve to be formed without cracking. The two parts were then cut to the required shapes using using the lines inked onto the flat surface. Once fully-formed, the new collars will be heat treated to 2024-T3 condition, and drilled to match the attachment holes on the original flare tubes. (image via Pioneer Aero Ltd.)
The original flare tube upper mount (top) had too much corrosion to be airworthy, so its replacement (just below) was fabricated using the two MDF forming blocks at the bottom of the image. The new part was made from 2024-T0 aluminum sheet, which permitted the sharp curves to be formed. The next step will see the new mount undergo heat treating to 2024-T3 condition and then drilled to match the flare tubes. (image via Pioneer Aero Ltd.)