FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1961
1961 - 1880.PDF
994 FLIGHT, 28 December 1961 Mechanized Air Dropping: DETAILS OF THE BLACKBURN DELIVERY SYSTEM IN theory, bombing and supply-dropping are identical pursuits—except for the important fact that parachuted stores are in-tended to remain intact. The actual moment of arrival, there- fore, marks the point at which the two operations should begin todiffer. Up to the moment of arrival, the procedures have this common purpose: to collect stores at a base and deliver them to aremote point with speed and accuracy, irrespective of whether the stores are bombs or bloaters. One might reasonably expect thetechniques employed to be similar in detail; but, until very recently, most of the world's supply-dropping has been done using tech-niques that fall far short of the science of bombing. Object of the Blackburn Air Delivery System is to eliminatedelays, inaccuracies and risks inherent in manual handling and despatch. Its most significant contribution is an automatic despatch-ing gear, which has at last permitted the development of a dropping technique comparable to bombing. One of the most important requirements of supply dropping isthat all the material dropped shall reach the recipient for whom it is intended. Waste of precious equipment is bad enough, but making apresent of it to an enemy is even more unacceptable, and this has happened often enough to emphasize the need for accurate droppingand tight grouping of the loads. Manual release of a succession of individual loads not only increases dispersion, but also inevitablyexposes the despatcher to some risk. By contrast, the Blackburn equipment permits close spacing of dropped loads and entireabsence of risk, because a succession of loads can be dropped in a "stick " at the pull of a lever, and there is no despatcher. From themoment that the supply-dropping officer operates his selector lever, the process is fully automatic. The complete system is made up from three main constituents :roller tracks, side guidance rails and an automatic release mechan- ism for each load. The roller tracks allow rapid loading of the air-craft, and form a low-friction floor for dropping. The side guidance rails ensure that the loads leave the aircraft freely, and at the sametime form part of the load-restraining system. The automatic release mechanism is the kernel of the whole process of sequentialdespatch. Installing the System Installation in an aircraft is remarkably simple. First, sets ofshort transverse members are mounted on the freight floor. These are secured by quick-release attachments, and locate the rollertracks and guidance rails. The roller tracks are divided into 5ft lengths, each carrying fixed pegs at one end and sprung pegs at theother, so that it can be fitted between the transverse members in a second or two. The track sections do not depend upon the rollermountings for structural rigidity, but are braced by tubular struts. This allows the roller ball-races to be mounted in simple trunnions,so that a damaged roller can be removed and replaced without dismantling its section of track. The guidance rails are also made in sections. These dove-tailtogether and are fixed to the same transverse members by quick- release pins; several rails can remain locked together and be handledas a unit. The transverse members, to which track sections and guidance rails are fitted, have two rows of locating holes to enablethe system to cater for a wide variation of load widths. Aft-facing hooks on the guidance rails engage with spigots on theload platforms and prevent forward or upward movement of the latter. Each hook is controlled by a pair of ad justing levers mountedon the outboard side of the rail, which move the hooks horizontally and vertically so that they can grip the spigots tightly even if theplatform has been slightly distorted. When the platform moves aft, its spigots strike the backs of any hooks in their path anddepress them into slots in the guidance rails, where they are auto- matically retained by pawls. The rails are thus left unobstructed forsubsequent releases and for loading-up, and adjustment of the hooks during loading takes less than Imin for each platform. The guidancerails are also fitted with retractable spigots, which can be made to engage with holes in the sides of freight pallets which are not to beair-dropped. The automatic release mechanism (upper picture) is also illustrated in a drawing opposite. On the right is a close-up of the guidance rails, hooks and adjusting levers described in the text above Since the clearance between a load platform and the guidancerails is only about 0.25in, the latter not only ensure a clean exit from the aircraft, but also provide restraint against sideways move-ment in flight. The rails prevent the load from moving upwards, forwards or sideways. Movement aft is prevented by links betweenthe floor and the automatic release mechanisms mounted centrally on the aft faces of the load platforms. Each link consists of ashort rod, one end of which is attached by trunnion to a channel- section member on the cargo floor and the other end is formed intoa lin ball which is grasped by the release mechanism. When the connection has been made, the guidance-rail hooks are so adjustedas to leave no fore-and-aft play. Once the platforms have been loaded and secured, the necessary cables are attached to the releaseunits and the loads are then ready. The air-drop sequence may be described by starting at the rear of the aircraft and assuming thatonly two loaded platforms are to be dropped. Two extractor parachutes are mounted at the extreme aft end ofthe cargo hold, one to port, and the other to starboard; in the case of the Blackburn Beverley they are on the vertical face of the cargo-floor sill. It is standard practice for the port parachute to control the first (i.e., rearmost) load to be dropped. These extractorparachutes are released by two selector levers under the control of the dropping officer, who occupies a position near the nose of theaircraft from which he has a clear view of the approach to the dropping zone. To release the starboard parachute (forward load) with theaft load still in the aircraft would be a painfully unprofitable procedure against which the aircraft and its crew must beprotected. The two selector levers are therefore mechanically inter-
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
