G-A YDY is fitted with an Aeronca JAP engine, which one was interested to hear was once the property of Latimer-Needham himself.
For starting, the ignition advance/retard is set halfway forward, and the throttle lever set to match it. The starboard magneto only "ON" for swinging. As soon as the engine fires, the port mag. is placed "ON" and the throttle slightly closed, and the engine warmed up at 1000 rpm, taking something like five minutes for the well cooled oil to reach a temperature at which the engine can be run up. In fact, during the whole flight the oil temperature never rose beyond 55 degrees C and that after a series of climbs at full throttle and low speeds. Run up on the chocks gave 2150 rpm, with only little mag. drop, although until the engine was well warmed the mag. drop on the starboard side tended to be higher than was expected.
G-AYDY has a tailskid and no wheel brakes. Nevertheless taxying in a light wind (about 7 Kts.) was without problems, and any pilot who can handle a Tiger Moth on the ground is unlikely to experience any problems with a Luton Minor. The rather hard suspension was noticeable however, and a healthy reminder not to taxy too fast.
G-ASEA on the other hand has a remarkably effective pair of heel-operated brakes on the main wheels, and a tailwheel. The heel pedals are well placed, and the arrangement confers a degree of controllability on the ground, which is superior to G-AYDY, especially when proceeding across or down wind. Take off is straightforward with no significant tendency to Swing from the straight-ahead course. Rudder and elevator are effective immediately, and the long line of the nose makes it easy to judge correct attitude.
One does not expect a high wing aircraft to benefit from ground effect but there is no doubt that the take off run is remarkably short, even with the 1ow powered Aeronca JAP; ground run into the 7 knots wind was estimated at something of the order of one hundred yards on smooth grass, though no precise measurements were taken. The aircraft takes a few moments to attain its recommended best climbing speed of 42 knots (IAS) but as it accelerates it becomes "alive" in the way that a thoroughbred will, and one would be little troubled in flying the Luton Minor reasonably accurately without instruments, and relying only on feel. It is that sort of aeroplane.
In level flight, G-AYDY settled comfortably at 2150 rpm giving 47 knots IAS (interesting how often rpm on the chocks turns out to be the nicest cruise speed), and the general handling was explored. The first surprise was the almost entire absence of aileron drag. The remarkable lack of friction in the aileron control circuit of G-AYDY was especially noted, and is not only a tribute to the excellence of Bill Goldfinch’s construction, but also contributes much to the pleasant handling and responsiveness of the aircraft.
Turns in either direction are possible without touching the rudder, though it is beneficial to use a touch of rudder when entering a turn and in turns of over 30 degrees, proper co-ordination of all three controls is essential if a sloppy turn is to be avoided. The aircraft is directionally stable, and can be flown straight and level feet off indefinitely. The high wing also confers a good degree of lateral stability. There is, however, no fore and aft trim, so that it is not possible, unless weights and loadings are so arranged beforehand, to fly hands off.
This brings me to a point of personal preference, which I consider important. The design of G-AYDY is cleaned up by enclosing the elevator cables within the fin fairing: but as a result, there is only a single elevator control circuit, with no back up system. One has only once to experience the failure of an elevator control circuit to feel very strongly for evermore that ever aircraft, however light, must have either a duplicate elevator control circuit: as the Tiger Moth: or a pilot controlled elevator trim tab which is enough to get you home in an emergency. In addition, the latter confers the benefit of making it possible to fly an otherwise nicely trimmed aircraft like G-AYDY hands off whenever desired. One can do without rudder or ailerons if necessary but not elevator control. Controls are nicely harmonized, and whilst light throughout the speed range, as one would expect in such an aircraft, always have plenty of feel to tell the pilot just what the aircraft is doing.
Popular Flying quotes the stalling speed of the Luton Minor with JAP engine as 25 kts. The stall with the stick fully back on the stops was off the 20 kt clock on G-AYDY. The reading looked like about 17-18 knots, which, if the PF figures are correct, suggests the not unlikely position error of 7-9 knots at this attitude. From entering the straight level engine off stall to full recovery to normal flight without any particular haste lost only two hundred feet. There was a slight tendency each time for the port wing to drop at the stall, but so slight as to suggest that it might have been due to no more than the pilot leaning that way in the cockpit. The stall on each occasion was gentle and without vice, though there was no prior buffet or similar warning.
Two timed climbs gave a rate of 260 ft/min. and 300 ft/min. an average rate of 280 feet per minute at 42 knots IAS. This agrees with the figures given by the owner, though the times r obtained varied slightly, since there was some sort of thermal activity present and the air not completely still. This is quite a good figure for the low powered engine, and since the forward speed is low, represents quite a reasonable ANGLE of climb, with consequent obstacle clearance after take off much better than the rate of climb might at first lead one to suspect.
All out level speed at 1900 ft. ASL using 2340 rpm gave a reading of 60 kts IAS which computed in the conditions of the day to a true speed of 62 kts, assuming the likely condition of nil position error in this attitude. At all speeds the Aeronca JAP was notably smooth, especially so flat out, and there was less vibration than one normally finds even than with the best of VW engines.
The figures obtained during a shorter flight in G-ASEA were certainly affected by the fine pitch of the propellor fitted, if not by anything else. Run up on chocks at sea level, and OA T similar to that obtained during the flights on G-AYDY (but barometric pressure regrettably not compared) resulted in 2250 rpm. A number of timed climbs were done all in smooth air off the sea and gave the following results:At 42 kts IAS - 2500 rpm, climb negligible; At 38 kts IAS - 24OO rpm, of the order of 180 ft/min: At 34 kts IAS - 2350 rpm. 200 ft/min.
Because of the high rpm obtained even at 42 kts whilst climbing, no high speed measurements were attempted: in other respects the handling conformed to the type and was not significantly different from that of G-AYDY. The JAP engine was delightfully smooth and responsive at all speeds and suggests that with the proper propeller fitted performance should not differ markedly from the superior figures recorded for G-AYDY. As will be gathered from the figures just quoted, the Luton Minor is a relatively high drag aircraft and in consequence the gliding angle engine off is fairly steep.
Recommended approach speed is 45 kts IAS throughout, though if this is increased a little, say to 50 knots, no harm results and there is still no tiresome float. It is advisable in the circuit to arrange one’s turn into a piece of sky which one has previously searched, for in a turn the high wing conceals the sky in the direction of the turn. For this reason, a well-organised square circuit pattern has advantages.
On the other hand, the high wing when one is not turning, gives the pilot uninterrupted vision of his intended point of touch down and this is very pleasant. Being highly maneuverable, the circuit can be kept small and point of touchdown gauged with the sort of accuracy one is accustomed to in light gliders.
Final approach at 45 knots is recommended as the normal speed but this of course can be adjusted as conditions demand and in still air speed over the hedge could be less. The angle of flare required is not great and during the approach and round out the touchdown point remains clearly visible at all times over the nose.
The aeroplane seems to tell its pilot just about the moment for that final movement of the stick fully back into the stomach, and when down remains nicely put, though the hard springing makes it fairly difficult to produce that absolute greaser landing which is the desire of every (right thinking) pilot! Again, a good point for the Luton Minor, for although it is easy and forgiving it is likely to make its fans work hard to achieve absolute perfection.