The History of the Cricri
The CRICRI story is already fairly old. It started back in the 60's when it's future designer, Michel Colomban, then a student pilot was constantly being surprised by airplane dimensions finding them over-generous and even disproportionate to the load they carried. As much through technical curiosity as by his desire to create something tiny and economical (even then...) , Colomban, an engineer in aerodynamics and ex-model aircraft fan, decided on a relatively simple research program. His aim was to find a minimal construction capable of excellent performances and flying characteristics using a light 20HP engine and 10Kg of fuel which would carry a 78Kg pilot He undertook a series of parametrical calculations He determined the principle performances (take-off, rate of climb, max and min speeds) by studying wing area parameters such as surface and aspect ratios naturally accounting for associated tail units and corresponding masses. The resulting graph showed that a single seat aircraft having a 4 m2 wing area and a 180Kg gross weight was perfectly feasible. Although this took place in 1957, construction could not take place at this time.
Twelve years later, conditions finally came favourable and the first construction test components were realised. In the mean time the original project had under gone some changes.
* Metal, although heavier, took the place of wood; its clean flying surfaces taking full advantage of low-drag airfoils.
* To simplify things, standard 1m x 2m sheet metal was used as wing skin reducing wing area to 3.1m2.
* Two light 9 Hp chain saw engines took the place of the inexistent 20 Hp one dividing the power also improved propeller efficiency at high speeds.
* The fuselage was designed as a simple rectangular box with a stream lined panoramic canopy on top.
* The horizontal tail was perched on top of the fin firstly in order to avoid obstacles on the ground and also to improve its aerodynamic qualities and make construction and positioning in its trailer easier. The result of all this was the MC10 which at the time its masses and performances and especially its propeller speed and its efficiency had been announced and brought many a complacent smile; only proving that you're wrong when you are right too soon!
Because of the innovation of the structure technique, a large number of tests of all sorts were conducted before the actual construction began. In particular, they dealt with the bonded joints and their resistance to cold, heat, humidity and in relation to surface preparation conditions. The was probably tested most extensively going from the classically resistance to tearing, crushing and shearing to the more specific resistance to humidity, thermal cycles, freezing, fatigue, aging.... etc
Numerous structural test were also performed on everything from simple structural components to the whole wing tested at full limit load. Successful static and fatigue tests on the glass fibber laminated main gear leg (100,000 cycles at 1 m/s impacts followed by 60,000 cycles at 1.5 m/s impacts showing no signs of failure). The engine mount was then tested (78,000 cycles before fatigue failure).
The CRICRI prototype first came out on June 23rd 1973 in Guyancourt. At that time, the MC10 weighed only 63Kg. After taking it on its maiden flight in Guyancourt on July 19th 1973, Robert BUISSON, 69, ex-fighter pilot with 12,000 hrs on 150 different airplanes under his belt and ironically very strongly in favour of high power airplanes had to admit; a page in the history of light aviation has just been turned. Shortly afterwards the first memorable public presentations took place in 1973 in Montargis at the National Amateur Constructors Meeting, followed by the National Meetings of 1974 and 1975 and finally by the famous landing on the Ferte-Alais woods, caused by an obstruction in the air vent of the fuel tank, in which the CRICRI prototype finished its career by giving living proof of its great strength. Since that incident, plans and manuals have been executed and some premature but convinced amateurs went on with the construction of their CRICRI's. Thanks to the problems they met up with and the solutions which were found, the building and operating instructions has been amended and perfected. The time was also used to advantage especially to find good engines which was the CRICRI's main, if not only problem. On the whole, tuning and adjusting the power plant presented some serious problems (out of proportion to the installed power). However, Michel COLOMBAN would not rest until he had them completely under control before issuing the building and operating instructions: Safety first.
We can say today, that very good results have been reached in the domain of carburetion as well as in the domain of working reliability, sound level and particularly vibration level. Adopting the excellent JPX engines, especially designed for the CRICRI, added largely to over come these problems. However, it took nearly ten more years to achieve the result of all this, namely the CRICRI MC 15.