MAPICA - Avion Caudron Luciole

FLIGHT TEST by Raymond Delaunay and Marc Daoudi. Interviewed by Michel Bénichou, this article appeared in "Le Fana de l'Aviation" September 1992. ( Reproduced here by kind permission of the author. This article is published in full and is protected by the Laws of Copyright.)

L'Aviation Populaire , a vast movement started in the 30's which allowed a large number of young people without great financial means to become pilots, and whic h was in fact a breeding ground for the Air Forces. The flight test for this aircraft lets us understand the methods of piloting a modern aircraft, roughly 20 years after the real beginning of aviation. Only one Luciole (a) is currently in flying state in France :- F-AZCT. It belongs to the Association "La Luciole" Ailes Anciennes de La Baule of which one of the members is Raymond Delaunay. Let us leave him to tell us about the aircraft.

"The Luciole was an aircraft simple and inexpensive although modern in the middle of the 30's. Personally speaking, the aircraft is 'pure' with a strict minimum of equipment. It is for the pilot to make it fly correctly. Today's aircraft fly almost by themselves, without a lot of input from the pilot. However, the Luciole i s not difficult. Simply, the pilot must not leave the aircraft to it's own devices. Our Caudron C275 is a bit "long legged" compared to previous versions. To climb in, you must avoid grabbing just anywhere, so as not to tear off a piece of plywood surroun ding the cockpit. Once installed the pilot is comfortable with the controls to hand. Despite having your head in the open air you feel well protected. It's only default on the ground : - zero forward visibility.

Before starting, because the engine is inverted, you must turn it over to ensure all accumulated oil in the cylinders is evacuated. Then before climbing in, you must open the fuel tap situated below the port upper wing. The starter is a compressed air Vie t. You must have a minimum of 22 kilos of pres sure, and the bottle will empty itself in 90 to 120 minutes. If there is insufficient air in the bottle, then the engine must be hand swung. The contacts are cut. The mechanic opens the engine cowling to action one or the other of the two fuel pumps, in o rder to bring the pressure up to 200 grams at least.( The manometer is in the cockpit ). At the same time that the mechanic swings the prop, the pilot gives two or three injections with the throttle lever, which he then leaves in the rear position. He clo ses the choke by pulling on the choke cable. The mechanic continues to swing the prop until fuel flows from the breather under the cowling. The pilot opens the choke, puts the magneto N\'b0 1 to 'contact' ( an impulse magneto for starting ), and opens the thro ttle to a quarter or a third. The mechanic swings the prop. It works pretty well, but if you miss the procedure... it doesn't work at all ! If we can use the starter, the procedure is not all that much simplified. The procedure is the same up till the con ta ct. At that moment the pilot must hold the stick back with his leg, with his left hand pull the security on the starter, keep it open then with his right hand, put his left hand on the throttle to move it to a quarter, then bring it back to pull the plung er on the starter.

The effect is fairly violent, much more so than an electric starter, but if the engine does not start, you must go back to the previous paragraph because the compressed air bottle will be empty ! The engine must be allowed to warm up till the oil temperature indicates 25\'b0 minimum. With older types of oil, you had to wait for 40\'b0 , in the winter it took a long time ! For a contact check, you need almost full throttle at 1.600 rpm, with the chocks in place as there is no parking brake, plus someone leaning on the rear of the fuselage.

Taxying also requires a certain finesse. The Luciole is now fitted with a tail wheel and differential braking, bur care is still needed. We tried fitting a tail wheel without the differential braking but this wa s an experience best forgotten, the aircraft would do any figure except a straight line. We went back to the tail skid until we adapted the differential brakes. Turns on the ground are done by use of both tail fin and very gentle braking. Stick always to the outside of the turn. The C275 is mounted on an undercarriage designed on the principle of deformable triangles, each extremity of the six legs has a vertical or horizontal pin, the assembly is very supple, and while taxying the aircraft can lean to th e extent where the wing tips can brush the grass. The Luciole was destined for airfields where there was little taxying and where take-off was into wind.

We will see that the Luciole is difficult to control in even a very mild cross-wind. Once lined up facing the wind, the pilot carries out his checks, without going above 1.200 rpm, above that the aircraft starts to roll.

At take-off, a steady advance of the throttle is needed, at the same time bringing the stick to the neutral position. Almost immediately th e tail lifts and the aircraft starts to vibrate on its main wheels. You must not try to make it lift off. Towards 70 km/h, it will take off all by itself. Do not allow it to climb. Level flight up to 90 km/h. At this speed it climbs well, following the pr op turning at 1.600 rpm. Do not try for more, things will finish badly: at 60 it flies ...yes but it will not climb. Slowly but surely you will climb to altitude. On leveling off the Luciole arrives very quickly at 110 km/h and you can reduce to 1.400 rp m. We have a coarse pitch prop, with a fine pitch prop the revs are increased by 200 rpm and the aircraft takes off even more rapidly. The level flight after take-of must be done really quickly in order to accelerate.

You do not feel the acceleration. You know that the speed is increasing because of the increase in wind noise, and the countryside goes by just a fraction more quickly. As for the effects of torque and secondary effects of rudder - I have nothing to say - nothing happens.

In flight the controls remain light without requiring any more effort than when on the ground, that is to say almost nothing. The rudder and tail plane are sensitive but precise, with a certain amplitude on the controls.

The ailerons are slow but precise with even more amplitude on the stick. The Luciole is in no way a dangerous aircraft, but if you do not co-ordinate you movements correctly, then the aircraft tends to waver, as though it has not understood what you are a sking it to do.

To accomplish a neat turn in the Luciole, stick and ruder are needed, well co-ordinated because the inverse effect is very pronounced (2). In the turn you leave rudder 'on' and progressively incline the stick to the outside of the turn, because induced roll is very strong. In this way the Luciole will turn on a pocket handkerchief (3). Coming out of the turn, a small stick forward is welcome to put the aircraft back on the step. It is soon off again without losing altitude.

The Luciole cruises at 110-115 km/h. If you push it higher it will not go a bove 120-130 km/h and will protest by emitting a kind of screaming through the flying wires. In other words.....it doesn't like these high speeds.

In level flight in a straight line, no question of allowing the Luciole fly all by itself. The controls are in continual movement, even in calm air, without your really noticing it. In the Luciole you learn very quickly to fly by the seat of your pants, b y instinct. It is the sound of the wind in the flying wires which indicates if the flight is symmetrical, if t he speed is correct. As it is very lively in even the slightest turbulence, it moves a lot, and gives a sense of the air to it's pilot. As in a glider, you need to know the movement of the air mass, to react as soon as any movement is felt.

In it's time there was no ball to show the symmetry of the flight. We have added one to the rear panel. The student learned by the noise of the wind, the vibrations and the turbulence. In any case in any wind above 20 to 25 km/h, the aircraft did not fly, the Luciole is also a fragile aircraft. In the 30's it was hardly ever used for anything other than circuits and very limited cross-country navigation, with a flight envelope much more limited than today's aircraft. At best you might be able to do a loop or a lazy eight - very lazy eights ! In general you need not be afraid of giving large control inputs in order to fly the aircraft. But the movements must be gentle. If you are violent, nothing happens as you intended. This aircraft flies at it's own rhythm, and each ti me you make a control input, it loses speed. You must not hesitate therefore in relaxing the control to enable it to regain some of the lost speed. It does not fly fast enough to lose much altitude. The stall is just like the rest of the flight characterist ics. The upper wing is set at 0\'b0, the lower wing at 2,5\'b0. When the lower wing stalls, the upper wing is still flying and the aircraft simply wallows without dipping the nose.

We land today with power on the engine, quite simply to save unnecessary wear by e nsuring that the engine does not cool down too quickly. Before, you landed engine fully throttled back as early as base leg. You reduced the trajectory by a PTS(5) or by side-slipping, something that the Luciole does very well.

So, you reduce to 1.300 rpm and wait for 90 km/h, and you descend at this speed. If you need to increase power, this must be done progressively, if not the engine could flood. In hot weather, the Renault has a tendency to flooding very easily ( here we ne ed to admit that the carburettor is not as young as it used to be )

On short finals you cut the throttle as you pass the threshold at 75 km/h and the aircraft will land at about 60 km/h with a pronounced ground effect. Attention ! at 75 km/h the Luciole will not land. You must be careful at the flare, because the aircraft has a tendency to drop suddenly just as the forward view disappears. You need to take a reference point well in front before flaring. If you are too high and you feel the aircraft dropping too soon, a TINY amount of t hrottle will re-establish the correct control.

Too much throttle and the aircraft will climb. It is a very fine line. The Luciole reacts readily to differences of 50 to 100 rpm ! And there is only 300 to 400 rpm between cruise power and approach power, instead of the 1.000 rpm on today's engines of t he same power. The throttle is gradual and precise, with the engine very supple. As there is no torque effect, you can control the descent trajectory easily with just the throttle, without moving the stick. \par It happened to me once, flying alone, through a mechanical problem, having to land the aircraft without any tailplane control, the only control I had was the throttle. On short finals, I remember saying to myself "It's up to you now !" As I crosed the thres hold I cut all the contacts and the Luciole landed all by itself.

Briefly, the Luciole is not a viscious aircraft...except on the ground, because it is highly sensitive to a cross wind. With 5 to 7 kts of cross-wind, on landing in the last few metere of la nding roll, you can do nothing. The Luciole will stop and gently weathercock into wind.

( PTS, prise de terrain en S ) Final approch with a course like S)

(1) Stick back facing the wind, stick neutral or forward with wind behind.

(2) Stick to the left, the aircraft inclines to the left wheras the nose goes to the right, and inversely. Stick and rudder at the same time in the right quantities and the aircraft inclines and turns, symmetrical flight without slipping or skidding

(3) Induced rolling is the inclining of the aircraft provoked, without any control input f rom the stick, by the skidding of the fuselage. Rudder to the right, the nose orientates to the right, the left wing is therefore travelling slightly faster than the right wing, it's lift therefore increases. As the aircrat is skidding, the right wing is slightly masked by the fuselage and it's lift diminishes even more ; thus the aircraft inclines more and turns. When the aircraft is in a turn, the higher wing ( on the outside of the turn ) is moving faster than the lower wing ( on the inside of the tur n ) because it covers a greater distance in the same time. As the radius of the turn is short and the aircraft is not flying very fast, the difference in speed between the two wings is relatively important. The higher wing therefore lifts more and more, the lower wing less and less : induced rolling again ! The aircraft inclines more and more, if no correction input is made, the aircraft will soon slip and lose altitude before falling like a stone

(4) The lazy eight consists of alternating two turns at high inclination, both started in the climb and finishing in a descent. Ed.

(5) Base leg. Part of the circuit which perpendicular to the runway, leads towards the "last turn" and finals.

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