FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1914
1914 - 0713.PDF
JULY 3, 1914. THE FLYING MACHINE FROM AN ENGINEERING STANDPOINT. By FREDERICK WILLIAM LANCHESTER, M.InstX.E. (Continued from page 692.) 12. Landing Gear. 8. The question of alighting mechanism the intention being to take care of the relative motion of the ground detail next claims our attention ; this is necessarily of two distinct when alighting across the wind* ; experience appears to show that types depending upon whether the machine is designed for land or with reasonably careful handling this provision is unnecessary. Two for marine usage. Taking first the land or military type of machine, types of suspension are illustrated in Figs. 31 (R.A.F.) and 32 the essential features comprise ordinarily a pair of pneumatic-shod (Bleriot); it will be noted that in both cases the medium employed wheels (in some cases two pairs) arranged on a common axis some- to absorb the shock is rubber ; this is preferable to steel (as »hat forward of the centre of gravity of the machine, and supplied universally employed on road vehicles) for two reasons : firstly, the Fig. 31. Figs. 34 and 35. proper a sufficient height above the ground to provide clearance for the propeller, aerofoil, &c. ; unless careful design and workmanship is put into the landing chassis its " spidery " proportions necessary to give clearance may, on the one hand, constitute a source of weakness, or, on the other, give rise to excessive resistance. Owing to the liability of the landing chassis to injury it is clearly desirable that its structure should be complete within itself, yet this is very difficult of achievement in actual design ; more often than not there are members in common to the landing chassis and the aerofoil structure or the juselage. This must be considered a weak point in any design, since it involves the risk that some essential flight organ may on landing be strained or otherwise injured or at least-stressed beyond the limit for which it has been designed. In spite of all that has been done up to the present the landing chassis is only able to take a very moderate " bump " with safety, a 1 foot free fall on to a hard surface is as much as can be deemed safe in the best of existing machines, a free fall of 4 or 5 feet would lead to almost certain failure. This requires that, in landing, a machine should never under any circumstances be allowed to take the ground with a greater vertical velocity component than 8 feet per second. Assuming a gliding angle of i, this means that a machine, flying at 38 miles per hour (56 feet per second or ft./sec.) could be allowed to take the ground (presuming the latter horizontal), without intervention of the pilot, but for any higher velocity of flight its course must be eased or flattened ; in actual practice it is, of course, part of the art of flying to avoid all shock when alighting, no pilot would think of taking the ground without at least making his best effort to flatten his angle of descent. There is probably a future for some form of hydraulic-pneumatic device ; already several attempts have been made in that direction. Passing now to the marine type, we find in the earlier examples a * Messrs. Voisin Brothers, in the days of tbeir pioneer work, attached great importance to this point. They attributed the early success of Farman (on his Voisin machine)largely to the fact that this feature was embodied in his machine. l/tiGHT] with a rudimentary elastic suspension of some form, in addition to runners or skids to take the " bump" in emergency, and the .provision of some kind of temporary tail support, consisting either Fig. 32. • of a castor-pivoted wheel, or (as more generally the case) of a simple spring-controlled skid. It was at one time believed to be essential ithat the alighting wheels should be all castor-pivoted or orientable, 713
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
