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Flight Design MC flight test

PUBLISHED: 17:10 29 February 2012 | UPDATED: 14:11 10 October 2012

Flight Design MC flight test

Flight Design MC flight test

A change in direction, as the leading LSA and European ultralight manufacturer introduces an all-metal model to its established line of composite aircraft

Words Dave Unwin     Photos Keith Wilson
When it comes to aeroplanes, you can argue the case for composite construction or against metal manufacture ad nauseum. I’ve also flown many fine flying machines made mostly from wood, while the Editor might present a compelling case for rag ‘n’ tube aircraft. There is no right or wrong way; all have their advantages and disadvantages. Typically, most manufacturers stick with what they know. This is why the 2011 Cessna 162 is built using essentially the same methods and materials as the 1951 195, and also explains why Diamond has only ever built composite aircraft. Flight Design stands out in having a product line that includes both metal and composite machines. So, when Pilot first heard that P&M Aviation had taken delivery of the first MC (Metal Concept) to come into the UK on an EASA Permit to Fly, we were particularly keen to get our hands on it. We had already enjoyed something of a preview: I was the first journalist to fly the type in Florida last year, logging several hours on the prototype S/N 002. The MC’s lineage is obvious, even though it is made predominantly of metal while Flight Design’s best selling CT-SW (Short Wing) and LS (Light Sport) are primarily of composite construction. Even at first glance I could see that this machine was different from the prototype in many ways. For example, G-CGOM is fitted with a three-blade variable pitch Kaspar composite propeller spun by a 100hp Rotax 912S, whereas the prototype had a fixed-pitch prop. The next difference I spotted was that the LED landing light in the cowling had been relocated. On the prototype it was centrally mounted immediately below the spinner, while on ‘Oscar Mike’ it is lower and slightly offset to port. Other new items include the transverse rod through the nosewheel strut for the tow bar, and the cut-out in the nosewheel spat. The exhaust also looks slightly shorter. There is a hatch on top of the cowling for checking the oil and coolant levels, while for a more thorough inspection of the engine bay the top half of the cowling can be removed quickly. Even removing the bottom half is quite easy. Unlike many Light Sport Aircraft, the MC looks quite robust. The fuselage and strut-braced wings are made mostly from conventional steel and aluminium, using solid rivets and traditional construction techniques, while the cockpit structure is a welded steel-tube cage. The constant-chord wings use a semi-symmetrical aerofoil designed by FD. The all-composite LS uses the same section, but – unlike the MC – its wings are fitted with stall strips. I remember from flying the prototype that the rivet heads cause the laminar flow to separate earlier. This produces adequate aerodynamic pre-stall buffet, but only when positive flap is selected. The single-slotted electrically-actuated flaps cover about two-thirds of the wing’s trailing edge. They have five settings and move through an arc of +35° to -12°. Unlike the prototype I flew, Oscar Mike has small fences between the fuselage and flaps. Although (in conjunction with the large winglets) they constrain span-wise airflow, the fences’ primary purpose is drag reduction, as when the flaps are negative they close the gap between flaps and fuselage. The winglets look very sophisticated, and are fitted with LED position lights. I don’t like the design of the fuel tank vents – they’re mounted on top of the wing, and look like an afterthought. All the fuel is carried in a pair of fifty-litre tanks, one in each wing. Only the last six litres are unusable. The tricycle undercarriage consists of slightly forward-swept fully-faired main undercarriage legs made from composite material, while the nosewheel leg features urethane polymer shock absorbers. All three wheels are the same size, have snug-fitting spats and carry hydraulic brakes with drilled discs. The rear fuselage tapers sharply towards the tail, which consists of a large fixed tailplane and separate horn-balanced elevator, swept-back fin, broad-chord rudder and a surprisingly large ventral fin. Pitch trim is provided by a large tab on the trailing edge of the elevator. Access to the cockpit is excellent. Gas struts hold the big gull wing doors open, the sills are low and the wing struts sit aft of the openings. There are, however, no external handles – you have to reach through the DV panels to unlatch the doors. On the plus side, each has three widely-spaced locking pins. Although the rudder pedals are fixed, the seats adjust longitudinally and vertically, and also incorporate pneumatic lumbar supports. They’re very comfortable, and I approve of the four-point harnesses. (Quite a few modern aircraft only have a three-point system – and I’ve not yet found one that I liked. The only restraint system that’s better than a four-point harness is a five-point harness.)
Confusion in the cockpit I was both impressed and irritated by the MC’s cockpit. At first glance, the sticks and throttle seem fine. However, the throttle handle is blue and the prop control’s black, and it should be the other way around. The stick tops carry red PTT buttons that look all too much like disconnects for the optional autopilot. When I flew the prototype last year I grumbled about the identical carburettor heat and cabin heat knobs, mounted close together at the top of the panel. Flight Design has replaced the round carburettor heat knob with a square one, but its centre is round so it still looks too similar. I would say the carb heat ought to have a square silver centre and black outer, and the cabin heater should be exactly the opposite. All of the instruments and avionics are mounted in a large central binnacle, and there are several different options. Oscar Mike has the flight and navigation data presented digitally via a Dynon 60 EFIS and Garmin GPS496, with standby analogue ASI and metric altimeter beneath the EFIS. Garmin also supply the SL40 radio and GTX330 transponder. The panel could be improved by moving the EFIS higher up and placing the numerous placards lower down, and using smaller standby instruments located in a column to the left of the EFIS. As the fuel quantity on Oscar Mike can only be ascertained via the sight tubes in the wingroots, a panel mounted ‘Low Fuel’ light that illuminates when you’ve got 30 minutes left might be a good idea. The analogue engine instrumentation is rather basic – there really should be a manifold pressure gauge. The single warning light is misleadingly labelled Generator, when I’m sure it’s an alternator. The alternator’s CB is similarly mislabelled. A centre console extends down to the floor from the base of the binnacle and continues aft between the seats. The vertical section carries rocker switches for the various lights, a 12V power outlet and the audio input socket and intercom. The flap-shaped flap selector is mounted in the centre, with a digital position indicator just above. This display shows the flap angle in degrees: I’m not sure if I really need to know that Flap 2 equates to +30º: it would be better to use the display to show the limiting speed for each setting, if for no other reason that even Flap 0 has a limiting speed (making the MC unique in my experience) To prevent the flaps from being inadvertently deployed at high airspeeds, the flap servo incorporates a load-limiting device. Its operation is signified by the flap position indicator flashing. This stops when the pilot reduces speed to the limiting value, at which point the flaps will go to the position selected. This is why the flap CB is not in the main busbar, but is located next to the flap selector. The key-operated magneto/starter switch and fuel shut-off handle are arranged so that it is difficult to insert the key until the fuel is turned on – an excellent safety feature. At the console’s base are the circuit breakers for the battery and alternator, and a knob for the instrument lighting’s rheostat. The horizontal section of the console carries a rocker switch for the electric pitch trim and a co-located LED strip position indicator, plus levers for the choke, throttle, prop and wheel brake. I’d prefer the throttle and prop levers to be next to each other and be the correct colours, with the trim position indicator adjacent to the EFIS and electric pitch trim switch. I’d also like to see a bicycle-type lever for the brakes mounted on the stick – or, even better, some separate toe brakes. An increasing number of LSAs have hand-operated brakes. There are obviously advantages to the manufacturer, as a hand-operated units are lighter and simpler to both design and produce. However, from a pilot’s perspective they are less attractive. As an aviator of the old school, I prefer to be able to keep one hand on the throttle and the other on the stick or yoke during ground operations. Further aft is the parking brake, held on by a simple, non-return-valve, and a shallow tray. The red T-handle for the BRS is mounted at the very back. Immediately behind the seats is a large baggage bay and parcel shelf. Up to 50kg can be carried back here, and it is accessible in flight. The location of the headset sockets is, however, poorly designed. They are mounted vertically between, and just aft of the seats – which means that when you move anything in or out of the baggage bay you risk damaging the jack plugs. This isn’t an issue with the SW and LS, however, as they have baggage bay doors located on either side of the fuselage. Despite all those niggles, the cockpit really does have some excellent features, the most impressive of which is its size. At its broadest point it’s 1.31m across – considerably wider than some four-seaters. It really is big, and feels even bigger as the doors are roughly fifty percent Perspex, the windscreen is vast, there’s a skylight, and there are windows in the aft fuselage.
Fired up in an instant The engine started instantly and with Oliver Achurch – Commercial Director of British Flight Design partner company P&M – in the other seat, I followed the Chipmunk cameraship towards the runway. Despite my inherent dislike of hand-operated brakes, the MC’s work well. The nosewheel steers through the rudder pedals. Setting Flap 1 (15°) I lined up on the opposite side of the centreline to the Chipmunk, counted three seconds after it started to roll and then smoothly opened the throttle. Oliver and I are fairly well-rounded individuals, and with approximately 75 litres of fuel on board we were 10kg below the 600kg maximum all-up weight. The variable-pitch prop gives Oscar Mike better acceleration than the prototype’s fixed-pitch propeller, and a smooth rotation at 50kts had the MC airborne within 200m. The MC copes well with short runways – indeed, Oliver operates this particular aircraft from a 300m strip. Once we are at a sensible altitude, retracting the flaps through zero to the negative setting seems to make the aircraft ‘settle’ slightly – but no height is lost. With the flaps at -1 and the prop lever pulled back to the fourth of its five detents (it goes fully fine if the operating lever fails) the MC flies – and feels – like a much heavier aircraft. The huge cockpit makes you think you’re piloting a much larger machine, while the all-round view is (for a high-wing aircraft) excellent and the ride is solid and stable. As we moved into formation with the Chipmunk I set the flaps to zero and pushed the prop lever forward one notch to fine off the pitch and conjure up more revs. It was quite bumpy below the clouds, so we climbed above them for smoother air. Handles very nicely The general handling is good, with light ailerons, an effective elevator and a powerful rudder. Pushrods drive the elevator and ailerons, while the rudder is cable actuated. Control harmony is fine, with minimal ‘stiction’ and low breakout forces. There’s a degree of adverse yaw, which requires some rudder for coordinated flight – a good feature in a trainer. With regard to its stick-free stability, the aircraft is neutral laterally, positive directionally and strongly positive longitudinally – even the long-wavelength, low-amplitude phugoid produced by a 20kt displacement from a trimmed speed of 80kt damped out after only two oscillations. Behaviour at the low-speed end of the envelope was interesting: flaps up, there is very little aerodynamic pre-stall buffet – although there is plenty with the flaps extended – and the ailerons continue to work (albeit rather sluggishly) even after the mainplane has exceeded its critical alpha. This is shown by coloured chevrons on the AoA display within the EFIS, driven by a sensor inside the pitot. The stalls were so benign that I even tried a few with negative flap and power, but could never provoke the MC to do anything even remotely unpleasant – it just stalled some 8-10kt faster. For the transit back to Conington, I set the flaps back to -1 and put the prop back to fully coarse pitch, once again being reminded of the shortcomings of the engine instrumentation: with any sort of adjustable prop you really do need a manifold pressure gauge, and the tachometer should show prop, and not engine rpm. You don’t need a degree in aerodynamics to know that the plethora of rivets and wing struts all add up to a considerable ‘built-in headwind’, and it came as no surprise that speed is one area where the MC’s composite cousins are clearly superior. It’s fair to say that for any given power setting the MC is about ten knots slower. Nevertheless, it cruises quite comfortably at 100kt IAS, and 112 is achievable at the max continuous power setting of 5,500rpm – albeit with a considerable increase in fuel consumption. No need to worry about the CHTs Approaching Conington, I reminded myself to keep the flaps at -1 until the speed had dipped below 90. The limiting speeds for the various settings could certainly be higher, although fining the prop off and pulling the throttle back soon slows things down, and at least the Rotax’s liquid-cooled cylinders mean that the CHTs don’t go bananas. While flying circuits I experimented with different speeds and flap settings in the climb. Sixty knots with the flaps at zero gave the best rate (about 950fpm), while Flap 1 and 50kt produced an impressively steep angle. As for landing, Flap 2 is plenty for most situations. The combination of low inertia and full flap (35º) means that if the throttle is closed and the aircraft flared simultaneously, it bleeds energy very rapidly. On the last landing I did exactly that and also gave the composite main undercarriage a ‘functionality check’ by thumping it on slightly more firmly than usual. It coped well. Aircraft in this class usually fulfil one of two functions: they’re either trainers or tourers. So how does the MC rate? As a personal tourer, good. It has a fair useful load, reasonable cruise speed, range and endurance, plus a comfortable cockpit. It’s also a fine trainer, and the handling, stability, performance and operating costs would appeal to any flight school. I’d still prefer toe brakes, though – if only to help students transition onto a C172 or PA-28. In fact, if you piped the noise of a Lycoming O-235 through the intercom, increased the fuel consumption and reduced the cockpit width, the MC would be just like a ‘traditional’ American trainer!

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