Flight Test: Bell 47
PUBLISHED: 10:26 12 December 2013 | UPDATED: 10:26 12 December 2013
© Neil Harrison
So brightly shines the M*A*S*H helicopter star, they're putting it back into production
There’s a brand new helicopter coming to market and it’s called the Bell 47. It’ll be made of the most modern composites, it’ll have a turbine engine and state-of-the-art avionics, but it’ll still be the Bell 47 we know and love – star of Whirlybirds and M*A*S*H, the first ever helicopter to be certified for commercial use, way back in 1946. It will be as though someone decided to re-engineer the Ford Popular and offer it as tomorrow’s family saloon, and not just as a gimmick: the new Bell 47’s makers say it will stand up against any small helicopter on cost, capability and safety. And it’s probably true, because rarely can any manufacturer have got everything so right first time as they did with the Bell 47. Today, 67 years after certification and forty years after the model went out of production there are hundreds of original Bell 47s still flying. The machine has its idiosyncrasies, and it’s quite slow and expensive by modern standards but it has a fanatically loyal following, and having had the privilege of flying it for a brief hour I can tell you why. It’s more than a piece of aviation history, a work of pioneering genius and an engineering marvel – it’s quite the most engaging feelgood aircraft I’ve ever sat in, and I want some more.
The Bell 47 is dead easy to fly and any helicopter pilot could teach himself to operate it in twenty minutes. But that’s like saying anyone can hack out a tune on a Stradivarius; true, but it doesn’t tell the whole story. After I’d booted the poor contraption about the skies for a while, I was treated to a display of the skills that you develop when you’ve done 2,500 hours of crop-spraying in a Bell 47. The pilot was Sean Anderson Brown, Managing Director of HeliAir, and I could only sit back and laugh inside as we wheeled and soared and swung with easy grace between six inches and sixty feet above Wellesbourne aerodrome. You see, you’re absolutely at one with the controls in a Bell 47 − every twitch and squeeze communicates itself to the swirling air.
Apart from a negligible cam in the collective run, no device interposes itself between pilot and rotors; you might as well touch your fingertips to the pitch links and your toes to the tail rotor. A spray run is an aerial ballet where the orchestra of throttle and collective, cyclic and pedals responds in harmony to the baton of the conductor-pilot, who need only raise an eyebrow to lift into a wingover at the hedge and fall in a sideslip back into his furrow, his forty-foot boom just out of the crop, his wrist, hands and feet conjuring up pianissimo and forte with no quaver wasted. Maybe in another 2,500 hours I’ll be able to fly like that.
The Bell 47 must be one of the few machines to have been designed and built by a philosopher-poet. By rights it ought to be called the Young 47; Larry Bell’s contribution was to recognise genius when he saw it, fund and encourage the work, deploy his own special talents as a salesman and not meddle too much. Designer Arthur Young was first and foremost an artist and an aesthete, and in
his youth he expressed a desire to reconcile science, mathematics and philosophy. Born in Paris of parents who’d made a good living in the 19th century from their art, young Arthur turned to the
problems of vertical flight as a way, he said, of creating “a synthesis of science and fundamental philosophy”. And you thought it was just a machine!
In the year Lindbergh crossed the Atlantic Young, liberated from drudgery by a modest inheritance, began building model helicopters. He’d had no engineering training and was unencumbered by prevailing orthodoxies, approaching his experiments from first principles. He didn’t work in complete isolation; he sat in on the Rotating Wing Aircraft Meetings in Philadelphia and New York where the first-rank helicopter pioneers of the day, including Frank Piasecki, Lawrence LePage, Haviland Platt and Igor Sikorsky met to exchange ideas. In the pre-war years Young regularly abandoned everything he’d worked on and started again from scratch, which must have been daunting for him. But his was an impressive learning curve. It’s not quite true to say there’s no device between the pilot’s fingertips and the rotor: Young’s attempts to inject stability into erratic main blades led to the introduction of the famous Bell ‘fly-bar’, the piece of genius which lies at the heart of the Bell 47’s success. Set at ninety degrees to the two-bladed main rotor, this tip-weighted bar is connected to the blades in such a way that it can affect their pitch. Under gyroscopic forces the hydraulically-damped bar retains its plane of rotation long enough after the main blades have been disturbed to dampen their movement, or adds about a third of a second’s lag to smooth out control-induced vibration. The improvement in stability was dramatic, and at the final Rotating Wing meeting in 1941 Igor Sikorsky congratulated Young on having trumped them all.
Bell’s idea of a ‘flying car’
With America working flat out on war production, private investment for helicopters was hard to find, but Bell Aircraft was looking to the post-war era and its founder Larry Bell was labouring
under the misapprehension that in the new world, everyone would have a flying car. He hired Young and built a small team around him, exiling him to a satellite factory so production of Airacobras and B-29s under licence would not be affected. Arthur was left alone to crash and modify his babies until by 1944 he had the basics.
Larry Bell’s insistence that the helicopter had to be car-like in every regard hampered progress. He never came to terms with the fact that the helicopter would never look like a car, and
particularly detested the open steel-tube tailboom; “I don’t want to see the sun set through that damned thing one more day!” he instructed. But Young stuck to his guns. The Bell 47 rolled out in
December 1945 and was granted a type certificate in May 1946, the first helicopter to get one. The mass market for aerial cars never materialised and the company’s huge investment looked like going sour until the Korean War came along in 1950 to save the day. By war’s end helicopters had evacuated 20,000 wounded men from the field of battle, and more than 85 per cent of them were carried in Bell 47s. Helicopters were credited with lowering the combat death rate to two per cent, less than half the World War Two level. The 1,000th Bell 47 was delivered in April 1953, a month before the unveiling of the best and most successful version, the Bell 47G. Powered by a 200hp Franklin engine, it had fundamental rotor blade and control system improvements and two twenty-gallon fuel tanks. The G had a top speed of 90mph and a cruise speed of 77mph, and was again upgraded in 1954 as the G-1 with the addition of a monocoque tailcone. Despite Larry Bell’s predilections, the G-1 and subsequent ‘car-styled’ models, the H and the J, failed to capture the public’s imagination. The girder-tail 47G continued to sell briskly, especially after 1955 when the G-2 was fitted with a more powerful and reliable 260hp Lycoming VO-435 engine. Hydraulic controls followed soon afterwards. Hollywood did the type a huge service with the TV series Whirlybirds − and if you can’t hum the
theme tune you can’t be in my gang.
Work of art — or just a machine?
Arthur Young must have thought his philosophies vindicated when in 1984 a Bell 47D-1 was acquired by the Museum of Modern Art in New York, where it is suspended above the entrance to the
Architecture and Design Wing. The tag says: ‘Its designer, Young, who was also a poet and a painter, consciously juxtaposed its transparent plastic bubble with the open structure of its tail boom to create an object whose delicate beauty is inseparable from its efficiency.’ And you thought it was just a machine!
What Sean has at Wellesbourne is G-CHOP, a Bell 47G-3B1 (modified) dating from 1966, built under licence by Agusta in Italy and for sale at £87,000. It has the Lycoming VO-435, but the ‘(modified)’ refers to the fact that the toilet-bowl-sized turbocharger installed for hot and high work in the Italian Alps has been removed. This is good because it added nothing but weight low down, needed a five-minute warm-down and was a swine to rig. If you aren’t familiar with the Bell 47 you’ve probably picked up Pilot by mistake in place of Needlework Today, but I’ll jog your memory. Big Perspex bubble squatting like a sumo wrestler on a strong, wide tubular undercarriage. Flat six mounted vertically abaft the bubble, the shaft running directly into a main gearbox from which a tail rotor drive runs along the top of a crane-jib tailboom. Massive (37 feet) high-inertia main rotor overhead, with stabiliser bar at right angles. Two peanut-shaped shoulder tanks close to the C of G. Below and behind the engine block, everything you need to make it go, air intake, carb, oil cooler and so forth, right out where the pilot can check them and the engineers can get at them. Wires to the tail running across little pulley wheels inside the tailboom − two sets, one for tail rotor pitch, the second connecting the cyclic to the horizontal stabiliser, which pitches down as the cyclic goes forward, keeping the fuselage relatively level at higher speeds so you don’t get the hanging-by-the-straps feeling you get with the Hiller 12, among others.
Everything on view
On the walk-round you can see and touch absolutely everything, to check that all the nipples have been greased, the turnbuckles are tight and there are no weld cracks anywhere. The tail rotor drive shaft takes a few degrees of kink at a flex coupling just above the ventral fin, then cranks more seriously up to the ninety-degree gearbox at a universal joint. There’s a big lead counterweight at the extremity of the tailboom (as Sean points out, he is a well-built chap). The tail rotor on G-CHOP is JetRanger style, tapered and with a twist, larger and more powerful than the original and begetter of ample tail rotor effectiveness. It’s surrounded by a curved tube known as the harp, which will contact the ground before the rotor does and stops you walking into the blades. Back in the middle the fully-gimballed head looks clean, with just a toadstool of shims for balance and a pair of bob weights − the ‘bunny ears’, which act as droop stops.
Setting up a 47 head is a black art, I’m told. First you balance the head, then you balance each blade, then you balance them as a pair, then you do the tracking − all of which also involves tampering with the tie bar; but if you get it right the helicopter is remarkably free of vibration, as we shall find when we go flying.
The fuel tanks are held by straps in fixed bathtubs, the theory being that when you crash, the straps will break and the tanks will roll away. Sean had occasion to test this, and it didn’t work. He suffered a dead cut just as he was climbing with full fuel and 100 gallons of chemicals and went in hard. Fuel leaked over the engine and went up; Sean climbed out of the broken bubble and had to run through burning fuel to get away. “I was in hospital for a month with ninety per cent burns on my legs and it wasn’t nice,” he says. “The day I got out I was driving home and a guy pulled right out in front of me. I T-boned him and rolled over in a field, and when the ambulance came I was standing in a pool of my own blood trying to explain that I’d been unhurt in the car accident, but the injuries from my helicopter crash had opened up − and straight back to hospital I went. Next time they let me out, I went flying again the same day.”
Vast cockpit, stupendous view
G-CHOP has no accident history, but the bubble has a couple of drilled and taped cracks and Sean is looking for a replacement. The doors are small, and squeezing in entails a little pot-holing as you hoick your leg around the stick, but the vastness of the cockpit is enhanced by the stupendous view; nothing but a yellow plimsoll line and a thin door frame, well below the pilot’s eye-line, gets in the way. Flown from the left, the 47 has two further seats for passengers: two-up it feels spacious − I suspect with three fat blokes in there it could get a little clubby. The binnacle looks exactly as it would have done to Chuck and P T (Whirlybirds, of course) with the addition of a Garmin 250 and transponder on top, and a small panel on the left with ADF, horizon and VOR.
This is the only Bell 47 in the country that can be used for ab initio PPL training because the engine is only one year old: you cannot train for a PPL on an engine that’s more than twelve years old. Sean’s also had an underslung load hook added, and he has a full set of spray gear.
On the left of the binnacle you’ve got mixture and carb heat levers in a quadrant. Mixture you set rich and never touch, carb heat you never leave alone − to the 47 pilot, it’s the fifth control. There’s a carb heat gauge next to the lever and it pays to give it regular attention. Below it, battery and generator switches, then RPM and ASI above MAP and altimeter, oil temp, oil pressure and cylinder head temp, fuel gauge and some lights and circuit breakers. The magnetic compass is over on the left door pillar.
There’s a pair of fans, much-needed in such a greenhouse. There are useful ventilation panels in the doors, and you also need a baseball cap because there’s no paint on top of the bubble. Once you’re strapped into your four-point harness the controls feel quite far away, especially if you’re used to the R22. The chunky pedals have an inspired adjustment you can flick with the toe of your shoe. The throttle has a friction collar at the end that I initially mistook for the throttle itself, leading to a puzzling lack of response and an intervention from the other side. While the
ship is remarkably tolerant of notchy wristwork and will happily fly while the rotor revs flounder up and down, it really does reward accuracy, and keeping Nr (rotor speed) at the optimum value takes work. Collective friction is a knob under the seat, while the cyclic has a friction collar halfway up and is bare but for an R/T button; there are bumps and holes in it for spray gear controls, and there’s a redundant yellow lever by the collective for the same work. Down there you’ll also find the fuel valve.
Pleasing, throaty rumble
Starting is simple; mixture richand battery on, mags both, collective fully up, half a dozen twists of the throttle to prime, lever down, throttle cracked and push the start button on the end of the collective. The Lycoming fired first time with a pleasing, throaty rumble and Sean settled the engine revs at 1,700 for the warm-up. The centrifugal clutch shifted the rotor in seconds, and there was some lumpy padding while it put on speed. Within a minute the cylinder head temperature had gone to fifty degrees and we took her up to 2,200 engine rpm, passing through a small avoid arc on the tacho where resonance affects the stabiliser bar. Now you’re waiting for the engine and transmission temps to come up. They share a gauge, and there’s a toggle switch to choose
between them − one of those old knob-ended metal switches they used to fit. Interestingly, the MAP gauge has a button which, when pressed, raises the needle to ambient − if it doesn’t you’ve got a
blockage, which you fix by the high-tech expedient of getting out and blowing in the tube.
When you’ve done your mag check with that lovely old rotating switch − less than fifty rpm drop − you wind the throttle up to 2,800, the bottom mark on the tacho, check all round and go flying. Raising the lever calls for quite a lot of left foot but very little throttle movement. We were heavy − I’m no featherweight either, and we had full fuel − but we came off very quickly. I was
surprised at just how sensitive the controls are, especially the pedals. I’d expected more inertia, but every breath and heartbeat goes straight into the mix. There was remarkably little vibration from the head; you’d never think it was a two-bladed rotor.
At close to the 2,850lb maximum weight we sat in the hover at 25in MAP and 2,800 rpm, with the CHT going to 150 degrees. There was a little bit of lever creep, cured by a dab of friction, and as I nudged the stick forward I found I had to come a long way off the left pedal to keep straight. The vertical stabiliser introduced on the G model is helpful in keeping straight in the cruise and makes tail rotor failure less dramatic, I’m told. There’s no VSI, but at 45 knots I reckon we were climbing at about 600fpm, and levelling off into the cruise I came so far off the left pedal that
the right was to the fore.
Finding the cruise attitude takes a minute because there’s no ready mark on the bubble: for training, Sean says they draw a couple of chinagraph lines for sixty and eighty knots. It reinforces the fact that this helicopter is flown very much by feel, and some say it makes a better pilot than the Robinson, where you can pin your attitude down by reference to the level of the E2B compass. Seventy knots is an adequate cruise, with remarkably little vibration – fuel consumption is about fourteen gallons per hour at this stage. Vne is 91 knots, so this is not a long-distance tourer, although it’s so stable that you can let go the cyclic for several seconds before she starts to depart. Add carb heat, drop the lever with a tweak of throttle and sixty knots gives you a descent of around 500fpm. Coming to the hover is undramatic, especially if you get the throttle right.
As we climbed for an autorotation Sean explained that the yellow line around the bubble effectively demarcates your autorotation options − you can land on anything under the line, you’d be pushing
it beyond that. With the inertia of the -23 model blades and their nine-pound tip weights, the entry is smooth and unhurried, the descent at sixty knots bringing up about 1,700 fpm, and the flare stress-free − very different from the crash-bang-wallop engine-offs of the low-inertia world. The helicopter tolerates 45 to 60 knots in an autorotative descent, while the rotor rev brackets are
quite wide: 322 to 370, according to the book. The ‘avoid curve’ starts at only 400 feet and falls to 50 knots at 150 feet. My first attempt to a power recovery (the ground was very wet) floated a long way across the field because I let it get too low and was wary of tightening the flare, but Sean demonstrated that if you’re ahead of the helicopter, an engine-off landing is a non-event. Simulating engine failure in the hover led the aircraft to nod to the left, a movement I over-cancelled with pedal, and we settled to the ground without fuss.
On the next approach Sean flicked off the hydraulics, and the result would not be challenging even for a tired old lady. I found that the 47 performs particularly well on sloping ground thanks to those wide skids and the fact that there’s fifteen degrees of lateral authority in the cyclic. A limited power takeoff, replicating the often-overloaded conditions of crop-spraying, bore us aloft after a fifteen-metre ground run at 21 inches MAP. And despite keeping busy throughout the flight, I didn’t neglect to look out of the bubble at the unmatched panorama of the earth that the Bell 47 affords, which will be my abiding memory of this day.
When we finished messing about we ‘warmed down’ at 2,200 revs, and after a 25 degree CHT drop Sean reduced the revs to 1,500 and turned off the mags. There’s no rotor brake. As the blades wound down I sat reflecting on an hour of no-numbers flying − seat of the pants aviation, helicoptering by ear and by feel. There are no caution lights or warning horns. The Bell 47 rewards acute senses, a soft touch and an accurate hand and foot, and it becomes an extension of your body once you learn to guide it like a sensitive horse. You hear the engine, the airflow, the blades flapping and bending. Anyone could fly this puppy with half an hour’s practice, but it would take hundreds of hours to fly it really well. For Sean, it’s “like putting on an old pair of shoes”. For me the shoes pinch, but they would soften in time, and I’d be proud to wear them. If I had £87,000 under the mattress I’d have flown it home.
Costs that make sense today
So why was the 47 superseded? The R22 did for it, really. Originally the Robinson cost £70,000 and used eight gallons an hour, with £25 an hour for maintenance. The 47 was £90,000, with twice the fuel consumption and about £100 an hour into the fund, so training schools migrated to the 22 overnight. Today, things have changed; an R22 Beta is almost £200,000 with all the toys and uses nine gph, while Bell 47 prices haven’t shifted that much. You can bank £150 an hour for depreciation and maintenance, and the insurance will cost you maybe £3,500 a year. Unlike the Robinson, it doesn’t lose much value if you don’t use it. So Scott’s-Bell 47, the company that bought the type certificate in 2010, has decided to begin manufacturing Bell 47s from scratch, conforming to the original design but using modern materials and a jet engine. The Scott’s-Bell 47-GT6 will be powered by the same Rolls-Royce RR300 that’s in the R66 and at $820,000 it sounds like an attractive proposition. Get your name down now for delivery in 2016, no less than seventy years after Arthur Young’s remarkable icon first flew.