FLYING THE FOX MOTH
The Fox Moth presents some interesting challenges to the pilot, but overall it is a very pleasant airplane to fly, quite controllable on grass surfaces if the crosswind is kept below 8 kts [less than 5 on pavement until the brakes are deemed reliable], with a surprising turn of speed. It’s handling is consistent with other De Havilland 1930’s-era aircraft, and for someone qualified in Tiger Moths, the Fox will not likely prove too difficult a transition.
Pre Flight
Some aspects of the Fox Moth require particular care before flight. The wing-folding mechanism must be closely examined. There are 4 pins, 2 lower and 2 upper. The lower pins are easily checked; the inner ends of the upper are hidden in the wing. If the wings were folded for storage and the aircraft is being prepared for flight, it is recommended that the pilot be present to ensure that the upper pins are properly inserted. In any case, a forward and aft flexion of the wings, from a position at the wingtips, should be included in the walkaround.
The fuel tank configuration (wing and fuselage tanks) can result in an out-of-limits aft C of G situation. A weight-and balance must be calculated, but this is simple in the case of C-FYPM – a calculator and scratch pad is mounted in the aircraft manual, and the calculation takes only a minute.
The engine can only be primed while the port cowl is open. This involves the standard DH pull-the-ring-and-tickle-the-fuel-pump, which may result in a puddle of fuel on the ramp. This may require moving the aircraft to reduce fire risk.
The priming must result in fuel trickling out the overflow. No-fuel must be investigated: either the priming has not happened for some reason, or the intake manifold drain tube has been blocked, and the manifold contains too much fuel. In this latter case, it is possible for fuel to enter the rear cylinder through the intake valve, which could cause a “hydraulic lock”.
Other than that, the walk-around reveals no surprises for those familiar with open cockpit biplanes. The cabin must be made secure, and any items placed on the baggage shelf should be removed – the pilot will find it useful to look through the instrument panel window later, along this shelf, to see out the passenger side windows while taxiing.
The cockpit is very cramped, a result of the elegantly streamlined fuselage. There are toeholds to aid in climbing up, but one must grasp a cabane strut and slide-in from above. The seat is uncomfortable and lumbar support needs to be added, but all the controls are well-positioned and easy to reach. The “Spitfire” grip on the stick is a nice touch. Space is very limited. To extend an arm outside the cockpit requires a complicated manipulation. My shoulders – admittedly remarkably wide, now that I’ve flown a Fox Moth! – touch both sides of the opening. Fortunately the canopy is not too low, and there is sufficient room to move one’s head, but I doubt there’s room for a hard helmet. (Not that I’d wear such an anachronism in an aircraft of this type.)
Start
The aircraft has a starter. Normally a Gipsy engine propeller is turned 4 or 5 blades after priming to bring the fuel into the cylinders, but enough time seems to pass in this aircraft between priming and starting, so that the engine catches within a blade or two with no sucking-in at all. Turning the engine over seems to be quite a load for the battery/starter, but if unsuccessful, the Gipsy is easily hand-started – assuming a qualified person can be found. (There is also an external power cable in a pan under the pilot’s seat, which plugs into a fitting on the starboard side.) The start is accomplished on the right, impulse mag, and the other selected on as soon as there is ignition. In this case 2 volunteers were positioned at the tail to hold the airplane during start to augment the limited parking brake. In future, chocks with lines attached may be required, to be removed when ready for taxi.
The Gipsy 1C on C-FYPM idles with exceptional smoothness. Another feature is the very low RPM. The throttle appears to have a stop at about 700 rpm, but if it is pulled very firmly aft, the rpm will drop to about 450 rpm, which is convenient for an airplane with limited brakes. The oil pressure comes up quickly to 30 psi. There is no oil temperature gauge. At this point the ammeter shows a discharge of course, because the generator is wind-propelled.
Taxiing C-FYPM on pavement in its initial condition, with practically no brakes, was impossible. A wing-walker was required. Later, the brakes were adjusted so that the aircraft could taxi across a 5 kt wind on pavement – very cautiously, very slowly, but with adequate control. It was particularly useful to be able to throttle back to 450 rpm to keep the speed back. The aircraft radio, though occasionally generating much static, is adequate. The transponder works.
Once on the grass, maneuvering is simple if one adopts the techniques of a tailskid aircraft, such as the DH 82A. This involves planning ahead, not getting into any corners, and never approach obstacles head on – only from a gentle angle. The small, “hockey-puck” tail wheel produces substantial drag. This allows the pilot to taxi using bursts of throttle. Each burst directs a strong flow over the rudder, which aids indirectional control. If a turn-around is required in limited space, the maneuver must be planned ahead. The turn should be made away from obstacles and ditches in case it takes more space than anticipated.
The actual minimum-radius turn-around is interesting. It’s accomplished by setting up a ground loop that runs out of energy at the 180-degree point. The aircraft is taxied to the edge of the area and then stopped. Then about half-throttle is applied, full rudder, and substantial forward stick. The radius of the turn is inversely related to forward stick pressure. The power is brought to idle about halfway around, and the airplane continues around, uncontrollable, but with idle thrust it stops (with practice) when facing the desired new direction. It’s a startling maneuver at first, but in time becomes second nature.
Visibility during taxi is very poor. On the grass this is no problem, because the airplane can be easily S-turned, but on pavement the pilot is quite blind. Some advantage can be gained by peering through the pass-through hole in the instrument panel (which is a brass-rimmed porthole!), and then through the forward cabin side-windows, but one feels a bit like Lindbergh in the Spirit of St. Louis, wishing for a good periscope. Unless there are adequate brakes, a wing-walker is required. (This is amusing. Remember the old adage about taxiing at a jogging-pace? Well, in this case it’s easy to judge, just glance sideways at the person by the wingtip and estimate his gait!)
The volunteer was required for a run-up, holding the tail while facing aft. Mag drop at 1500 rpm was 50R 75L. Normal test rpm is 1700, but pity was exercised.
After exploring the ground-handling qualities of the aircraft, and finding them conventional for a brake-less aircraft of 1932, we taxied for departure. The pre-take-off check is simple and quickly accomplished. The slats were left unlocked, but during the initial part of the run they were checked to ensure they were both deployed.
Take-off
The power was advanced smoothly and with no great hurry. Yaw was minimal. The static power was a surprise – only 1850 rpm, when 2100+ was expected. Yet the engine was smooth and acceleration was adequate, so the takeoff was continued. After the throttle was against the forward stop, steadily increasing forward pressure was applied to the stick, and the tail came up – more pressure was required than with a Tiger. Visibility was still not great but there was enough peripheral to keep straight. She flew herself off at about 55 mph indicated. There were no unusual control inputs required, indicating a well-rigged aircraft.
There is no rate-of-climb gauge, but the climb was quite brisk and the airspeed tended to rise. Altogether the performance was better than with the Tiger, even though the rpm was less. Oil pressure was 45 psi.
Cruise
A pleasant surprise was the airspeed rise at cruise. A Tiger makes about 85 indicated, on a good day. The Fox accelerated to 105 ias, at 1850 rpm. (No wonder it once won the King’s Cup!) Obviously the fuselage streamlining overcomes the straight wings and exposed control wires. Also, perhaps the Fairey-Reed metal propeller is pitched for cruise. At cruise the ailerons stiffen up noticeably, but control is adequate. It reacts to turbulence yaw-inputs with more “wallowing” than a Tiger, probably due to the fact that the empennage is no larger than a Tiger combined with a wider fuselage, but again control is adequate. The trim mechanism is a spring applied to the elevator cable, not a tab on the surface. It isn’t very powerful, but was adequate during climb. At cruise it took full nose-down, but once a load is in the cabin the trim position will probably come back off the stop.
The takeoff was performed with the canopy back. The turtleback design results in a strong blast against the pilot’s neck, but visibility once flying is excellent. When brought forward, the canopy forms a tight seal and eliminates most drafts, but one of the toehold doors lacks a proper spring, and a strong flow chills the pilot’s left arm. Visibility is still quite good even with the hood closed. There is no firm latch for the canopy, but it doesn’t move around on its own. Cabin heat was exercised, and works, somewhat.
At a safe altitude the speed was reduced, with the goal of exploring the slat deployment. They emerged at 60 ias, but not evenly. Strangely, it didn’t seem to make much difference. Only a minor correction was needed. Due to traffic considerations no stalls were attempted. (Spins are prohibited.) Slow flight down to 55 ias in smooth air presented no difficulties. Sideslips with reduced power were quite controllable.
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Approach
Returning to the circuit, a low-approach and go-around was planned, to explore the landing environment. Base and final were flown at 70 ias. Visibility is good until lined-up for the runway, then the nose of the aircraft obscures forward vision. A slight sideslip restores adequate visibility. A curving, fighter-style approach, keeping the runway in site ahead and to one side until near-touchdown, is probably more appropriate, but Sunday traffic at the field precluded that.
I believe that executing a planned go-around on one’s first approach to land is a very useful exercise. It teaches the pilot a great deal about the way the aircraft handles in the landing environment without the risk of touchdown. It also evaluates the winds at that location of the airfield. The pilot’s landing references are firmly established. Thus the aircraft was brought down to about 10 feet and then the power was brought gently up to full. At speeds down to 65 ias there was good control and adequate peripheral visual reference. The slats stayed retracted. I was able to wave to my wing-walker as I went by. The aircraft seemed less reactive in lift to the light gusts and wind variations than the Tiger – more stable, less “poppy”.
Landing
On the next circuit the aircraft was set up for a tail-low wheel landing, approaching at 70 ias with a gentle and progressive round-out. The touchdown was smooth, and the roll-out was straight. There was no difficulty estimating height – always good for the ego! The tail was held up until the stick was approaching it’s forward stop, then lowered gently and the stick brought hard-back. The roll-out was quite simple to keep straight – the small tail wheel in the grass generates substantial drag, which tends to straighten-out the run. The surface itself was a bit rough, though dry, but this generated no ill effects, other than demonstrating a need to keep taxi speeds low.
Another 5 circuits were flown, all to a similar pattern: wheel landings on the grass, the last 3 touch-and-go’s. Though it was a busy Sunday, there was no difficulty spotting transient aircraft, or hearing the radio. All approaches were flown with the canopy back. Side-slips were flown with progressively more aggressiveness, encountering no adverse effects. After the last, the wing-walker was recovered – fine airshow! he said – and the aircraft taxied back.
Again, maneuvering on the ramp is not a good idea due to the poor visibility from the cockpit. A better idea is to shut down early and push the airplane into place.
The engine is shut off with the mags, and the throttle is smoothly opened as the rpm winds-down, to prevent back-running. The large, identical, well-mounted electrical switches make shutdown easy and obvious.
All in all, the aircraft is a delight to fly. The sensation is that one is flying a small airliner, more than a large Tiger. There is a wonderful feeling of time-warp in the Fox Moth. Every sight that meets the eye, every flowing curve, distinguishes it from all other aircraft in my experience. It exudes the atmosphere of Stag Lane, De Havilland’s airfield in the early days of commercial flight, when designers were challenged to meet performance goals, yet accomplished it with style and innovation and low-horsepower engines. There is a grace that flows from its every movement in the air. One gets the feeling it is willing and able to do it’s best for the pilot, to haul heavy loads in and out of small rough strips, and offer no tricks.
It was a privilege to be the pilot returning a Fox Moth to the air, after a long break, in Canada, and having the chance to connect with such a unique and successful past.
Later in the afternoon another flight was undertaken, this time with a passenger. Mike Potter sat in the King’s Seat. I believe he’d rather have been in the pilot’s seat, but as we toured a section of the north shore of the Ottawa River, on a glorious spring day, I looked through the brass porthole into the red leather of the cabin, and observed that he looked well-pleased.