Photo by John King, 1000ft, very close formation

WB's   CRICRI Construction over 6 yrs

In flight comfortable cruise, but high rate of fuel consumption at this setting







Selected Images

       

Photo by John King, 1000 ft, off the coast of Taranaki - shot July 11th 2010 


View any of  8 cricri videos at this site

Current Progress:  August Update:

Just back from a fantastic week at Oshkosh where Cricri were mostly abscent except for one mounted from the roof in the wearhouse store. Forums on electric powered flight were extremely popular, and many questions asked about the carbon fibre electric cricri being build by Airbus Industries as their "green" project. At present battery energy density the maximun flight time for an electric cricri is - by my calculations, 20 minutes, When the batteries store 350 watts/ Kg I will have an electric conversion on my drawing board.

Another short seamless flight today. I am slowly learning the intriguing flight characteristics of this little craft.

 Just recently aviation photographer guru (John King) arrived  to take some in flight photos of CRI for a forthcoming magazine publication. I have contributed a short piece on "building light". The photo shoot was just after dawn on a frosty morning from a Cessna 172 with the door off. He froze. I froze - but the in flight photos are supurb +++. To keep you checking this site I'll feed them in as the lead image - a fresh one every few weeks. You will not see better in flight photos of a Cricri. To see more - follow the 'Photos' tab above to 'John Kings Professional Photos'.

Latest edition on New Zealand Sport Flying.
For info, contact the editor (and Photographer) - John King via SAA web site.

Those that are sharp will notice the myriad of small changes on CRI over past six months - wheel pants converted to one piece, radio aerial underneath fuselage, props painted white, unpainted spinners, new turtledeck mid brace, and pilot wearing A grade ear muffs instead of a standard aviation headset (over the clarity aloft earpiece)
Wayne
July 11th






Typical Flight:  To outline a typical flight, after the aircraft is fueled to around 18 litres ( of 23 for a full tank) the aircraft is gentled pushed out of the hanger onto to grass berm. This gives a AUW of 370 lbs - close to MAUW of 375 lbs.

Preflight, I pay particular attention to tyre pressures, all visible fasteners, security of nose cone, and double check of wing pins and aileron attachments. I carefully check the canopy attachments, seat attachments and seat belt attachments. All these items are as light as could be - and any of these could fail with catastrophic consequences.

The fuel tank is then pressurised with a small sphygnomanometer bulb - to about 4 PSI. The carbs are tickled with my unpatented lever which opens the fuel valve, and pressurised fuel flows directly into the carburettor throat - for 7 seconds.
 
Ignition on - RH engine first. It is started from the front and turns counterintuitively. This is, of course, after brakes have been secured (velcro wrap around brake lever). Two flicks usually suffices. Then the same treatment to the right turning LH engine, but I start this engine from behind - to be well clear of the other prop.

With both engines idling at 1700RPM I climb in - easily performed single handed -  5 point harness secured, clarity aloft headset in place and earmuffs over top of them. Radio on and tune to ATIS as I taxi to the holding point for run up and take off checks.

Lined up, takeoff approved, full throttle. The response is very brisk and within 7 seconds and 250 ft CRI has departed the ground, climbing at 1200 ft/ min at 70 kts. The flap handle can be relocated into the "flaps up" detent with the little finger.
Throttle back to 4800 to continue a gentle climb and conserve fuel.
With 3W engines it has been possible to go through 15 litres/ hr with lots of full power climb (at 1300 ft/min).  8 l/hr is the desired rate of fuel consumption, but achieving this economy requires conservation of power.
The noise level is high and the out of synch thrubbing can be annoying, but easily corrected with gentle nudge of the throttle. The panaromic view and responsiveness to the controls make each flight pure adrenaline surging pleasure.

For me - I wouldn't even think of aeros and high G manouvres at this early stage of flight testing. Arriving safely on the ground after each flight gives satisfaction in gobs.

More later



Flying the Cricri
So just what is the Cricri like to fly? I am a 650 hr PPL (private pilots licence) pilot with only 6 or 7 aircraft types in my log. From the first flight the aircraft has been quite stable and predictable in handling. I am accustomed to the sensitive pitch - which is common to many homebuilts - but the rapidity of roll is just stunning - and effortless.
Here are some basic performance parameters from the early hours of flying CRI

-climb out at 70 kts at 1300 ft/ min
- max speed of 115 kts
- comfortable cruise of 90 - 100 kts
- fuel consumption  8 - 15 litres/hr-  to be refined.
- single engine climb at 2500ft, 70 kts is 150 ft/min.
- stalls at book numbers - 39 kts with flap, 49 kts without.
- noise level - very high - like a sawmill
- fun - unbeatable

Stall is gentle but no warning - around 49 kts without flaps.  to Maintaining 49 kts gives a high rate of descent (600 ft/min) without the nose dropping. Pulling back further produces a  typical stall - straight ahead - no surprises. This is reassuring verification of effective washout (difference in incidence between wing roots and wing tips), where the wingtips continue to maintain lift after the wing roots have stalled.

 Little rudder is needed for balanced medium turns. The stick is sensitive so don't bump it inadvertantly with your knee while taking a photo! Orientation changes very rapidly indeed. Easy to trim for hands off flying (but only lasts a few seconds).


Modifications since first flight

1.  Pressurize the fuel tank. To achieve this I have two tubes with one way valves into the tank vent hose. One line has a blood pressure bulb attached for initially pressurizing the tank. The other line goes to a nipple bleeding pressure from the exhaust chamber.
The system works well and maintains 3 -4 psi in the tank, sufficient to maintain fuel to the carb without negative pressure in the line. Photos show the pressure bulb for pre-start pressurization, one way plastic valve, and exhaust nipple with tubing to fuel tank. Its started clear plastic, now black because of carbon particles which don't make their way to the fuel tank.
  



 

Total cost of project-  roughly US$26,000 (with trailer)

          
                                                             First fitting in trailer


Trailer
 The trailer is wide enough to fit the Cricri with installed tailplane, whereas the Colomban version is narrower than the tailplane so a flared upper piece is needed to protect the tail. The slight drawback is a larger and heavier trailer.

  Points of Interest:

Note the red self aligning electrical plug where front of wing attaches to fuselage. This is the connection for the wing tip strobes - earth and two cores. Works well. No wires to connect. The unit floats on small springs, so self centres. Available from specialist electrical stores.


Throttle Cable

With a lot of fiddling the throttles are now light and synchronous. The icing on the cake is the extra link with spring loading on the "pull to close" side. This puts the circuit in constant tension so little chance of the throttle wire disengaging from the pulley.

The Cricri

The Cricri is a remarkable single seat aerobatic ultralight aircraft aircraft designed by French aeronautical engineer Michel Colomban. Plans for construction can still be purchased from M Colomban for approx $600US, but he will not sell to residents in North America. All the information to purchase plans is on Petr Philips web site.  The saga behind the refusal to supply North Americans stems from a kit version of the aircraft that was available several decades ago with some unfortunate consequences. If interested, scroll the relevant threads of the Yahoo cricri group forum  where the issue has been well explained by the moderator. (CriCri@yahoogroups.com)

4. Instrument panel fabrication
The instrument panel is hard to flange around the outside edge. Consider a fibreglass mold with raised segment for instrument groupings. This is an idea I saw in an aviation magazine. Fabricate a female panel mold and vacuum 4 layers of fine weave cloth/epoxy. Vacuum bag as for the Cricri flying surfaces. Best with releasing agent and gelcoat which you can get from any fibreglass and epoxy supplier.

5.  Paint colour
If you don't want grey or yellow primer you can tint with pigment from other paint with similar chemistry. Experiment first. I have used Altex 2 pot epoxy primer tinted with Altex Tasman Blue Polyurethane (colour only - no hardner), and other colours. Only for surface protection - not bonded surfaces! Just makes it pretty.

6. Maintanence:
Access to rudder and noseleg bungees, fuel lines, steering cables, battery and wiring through the front fuselage is  poor in the cricri. Forget the looks - I am putting an access hole with nutplates in the front fuselage skin. Also running fuel hose and electrical wire thru automotive split conduit. This way you can replace and service the items. In my humble opinion it adds functionality without much compromise.

7. Brakes
I have seen comments about poor braking from the plans proposal for drum brakes.  So I am using Shimano Deore hydraulic bike brakes with 160mm rotors. The tricky bit is designing the rotor and caliper mounts, and machining the "t" hose splitter. Will tell you if it works - later!!

Yah - it does. Just finished bleeding and assembly tonight. Takes nearly full excursion of the lever but the assembly is smooth, light, and powerful (Sept 24th 2007). Note the filler site with cap head screw!

8. Canopy Mod
I'm 5 ft 11 inches. Had to add 50mm (2 inches) to the rear canopy to fit comfortably with headset on. As a retro change this cost approx 20 hours. Advise  consider from the start if you are over 5ft 8 - as outlined as an option by M Colomban.

 10. Bushes for wheel pant screws
Fibreglass wheel pants are extremely thin to remain light and the securing screws soon tear through. To resolve, install small shouldered washers/ bushes  (aluminium - simple to turn on the lathe - you need around 20) and epoxy into the hole so the screw is only in contact with the washer and the nutplate into which it is driven.The wheel pants can now be removed regularly - and no ovalled holes.

more later.....