Flight, September 1938

FOR the C.A.G.
The Chrislea Monoplane Described

   SINCE the announcement of the Civil Air Guard scheme many problems have faced the clubs, chief among them being that of providing suitable training aircraft. It almost seems that the designer of the Chrislea Airguard might have had this very point in mind when he first drafted out his ideas many months before any hint of C.A.G. was even whispered in the dovecotes of Kingsway, for from many viewpoints the Airguard is a most suitable aeroplane for the purpose.
   From the outset, Messrs. R. C. Christoforides and B. V. Leak manfully attacked the problem of evolving a small-engined machine which should be simple and accessible, while at the same time having the comfort and robustness of an aeroplane with double the engine capacity - all this to be achieved without noticeable sacrifice of performance. The result now waits at Heston, where it is practically ready for the Farnborough and Martlesham tests.
   As a prototype the Airguard is most interesting. Briefly, it is a side-by-side low-wing cantilever cabin monoplane, powered by a Walter Mikron II 62 h.p. four-in-line inverted engine. The fuselage is of torsion-box construction from the tail to the rear of the cockpit. It has four spruce longerons, the whole being ply-covered, with vertical spruce stiffeners. For the cockpit the two top longerons are carried on and “broken” to drop several inches, so that the view out of the cabin is considerably enhanced. The decking of the fuselage is a separate component, and may be regarded as a fairing for the cockpit. It is of light ply construction.
   The cabin gives ample accommodation for two people and provides an excellent view both forward and downwards. The two side windows are so placed that it is a simple matter to look not only out but also back without having to crane one’s neck, while a “skylight” is also provided. Behind the seats is a locker for baggage up to 40 lb.
   Controls are simple. A central stick is fitted, with a low-geared tail trimmer. The rudder is operated by dual pedals, one pair of which is detachable. The control system is operated by cable and rod, with no pulleys in either the aileron or elevator controls.
   The wing is assembled in three sections or, to be more accurate, five, if the detachable wing tips are regarded as individual units. The centre-section is built up round two parallel spruce box spars, which rest on top of the bottom longerons and are cleated to the vertical members of the cockpit walls. High-tensile steel plates with dural bolts provide a basis for the attachment of the wings and also the mounting for the undercarriage. In future models a universal joint will be fitted on the rear spar roots so that the wings can be pulled back and turned vertically before swinging them back to rest on the tailplane.

The Wings

   The wings are of Clark Y section and have box spars with stiffening diaphragms at frequent intervals. The spars taper both in plan and thickness to the tips. Ply-wood ribs with light vertical stiffeners are used, and the whole wing is ply-covered. Two plates with two bolts apiece secure each wing tip to the main spars.
   Simple three-position manually operated flaps are fitted on each side of the fuselage and extend out to the ailerons.
   The tail consists of two solid spruce spars, ribbed as in the wing and ply-covered. The tailplane is built in two halves and linked by two dural plates which extend down the bulkhead of the fuselage. The elevators are inter connected with a steel torque tube with central lever. A steel quadropod, of tubular construction and bolted to the top longerons, forms the base for the tail fin.
   The undercarriage is of the simple half-fork type, employing eight rubber buffers under compression. The rebound is taken on one buffer, with a split fibre bush bearing on a conical shoulder to serve as a check. The leg, attached to the piston, is keyed in two places. An interesting feature of the undercarriage is that one leg can be detached from the main spar and replaced in less than thirty minutes, by the removal and subsequent re-insertion of two spar bolts.
   Finally, the Walter Mikron engine is carried on a fully braced mounting which obviates crankcase stresses.
   On its initial tests, it is stated, the Airguard attained a service ceiling of 15,000ft., fully loaded. Its maximum cruising speed was 110 m.p.h., with a safe range of 375 miles. The span is 36ft., the overall length 21ft. 6in., and the height, 6ft. 3m. With flaps, it is claimed, the Chrislea can be landed at 40 m.p.h. The price of the machine, delivered at the Chrislea Aircraft Co., Ltd., Heston, is £550.

Flight, October 1938

British Sport and Training types

CHRISLEA

   A NEW type to be considered as being particularly suited to C.A.G. requirements is the Chrislea, which is a side-by-side two-seater cabin low-wing monoplane. It was, however, designed, and the work of building the prototype had been started, before the details of the cheaper flying scheme had become public property.
   Although, with the excellent view provided for both occupants and the normal flying characteristics which the initial test flights have shown, the Chrislea should make a good trainer, it was designed primarily to interest those private owners who require a good performance, comfort and reasonable roominess at economical first and later costs. The engine is a Walter Mikron II and this, it is expected, will be shortly put into production by an associated company.
   The machine, which is known as the Airguard, has a number of interesting structural features. One of these invokes an ingenious wing-folding arrangement in which a universal joint is fitted to the rear spar roots so that the wings can be pulled back and turned vertically before they are swung against the fuselage. In order to provide a good all-round view, the two top longerons of the box-type fuselage are dropped several inches at the rear of the cabin to give a low waistline where this is most necessary. The result, is that the occupants appear to sit very high up behind a deep screen, and even on the ground it is possible for either occupant to see out on both sides. Manually operated three-position flaps are fitted on each side of the fuselage and extend out to the ailerons. The undercarriage is of the simple half-fork-type, compression being taken by eight rubber buffers, and it is claimed that either of these legs can be detached from the main spar and replaced in less than half an hour. There are dual rudder pedals and a centrally disposed control column.
   Complete load and performance figures are not yet available, but the machine is to be sold for /550.
   Makers:- Chrislea Aircraft Co., Ltd., Heston Airport, Middlesex. (Hounslow 2345.)

Flight, November 1939

Britain's Civil Aircraft

CHRISLEA

   THE Chrislea light monoplane is a side-by-side two seater which, with a Walter Mikron engine, has a top speed of 118 m.p.h., a cruising speed of 105 m.p.h. and a range of 350 miles.

Chrislea Aircraft, Ltd., Heston Airport. Middx.