By Rohit Jaggi
As I look out for spring rainclouds above the lush British Cotswolds, it occurs to me that the French-built aircraft I am flying removes many of the concerns that pilots of little two-seat helicopters have drummed into them.
Many of those pilots’ concerns are mechanical. In some ultralight aircraft, the single bolt that holds the fabric-and-tube wing on to the fuselage is known as the “Jesus bolt”. In helicopters it is the rotor head that plays a similar vital role, acting as the mount for the blades of the main rotor and taking the weight of the rest of the helicopter suspended beneath it.
The £250,000 Cabri, though, has three rotor blades set in a hub as sophisticated as that on bigger helicopters costing millions of pounds. This means the potentially weak point is extremely strong – and the Cabri can be thrown around the sky with what, for most light helicopter pilots, is an unprecedented degree of abandon.
Despite the exhortations of Steve Dean, a Cabri instructor for UK importer Cotswold Helicopters who is seated beside me, I’m only scratching the surface of that potential.
Even so, the safety advantages are reassuring. The Cabri is the first light helicopter to be certified under stringent European regulations.
Its passenger cabin and shock-absorbing seats are designed for a descent rate of 2,000 feet per minute. That is the rate seen in autorotation, or gliding – when air passing through the rotor disc spins the blades and provides lift. Or, as Dean puts it, if the engine fails and you do nothing else but lower the collective control to alter the pitch of the rotor blades and enter autorotation, you will survive the un-avoidable collision with the ground.
Although simulated engine failure is a key part of helicopter training, in the Robinson R22 – the little two-seat machine that is the workhorse of the training and personal flying market – the low-inertia twin-blade rotor’s speed can decay so quickly that unless the pilot lowers the collective within a few seconds of the engine stopping, there is no chance of the rotor speeding up enough to provide sufficient lift.
Other safety aspects are more of a mixed bag. The anti-torque rotor – the one at the rear that stops a helicopter from vividly illustrating Newton’s third law of motion and spinning in the opposite direction to the main rotor – is embedded in the vertical tail surface. That cuts the risk of people walking into it and of it hitting objects such as trees in tight landing spots.
But, ironically for a helicopter that sells itself so hard on its safety aspects, my flight in the Cabri was delayed because the Cotswold Helicopters machine was involved in a “hard landing” when it started spinning uncontrollably.
Drawing lessons from that, I make sure to keep the rotation speed down and use all the travel in the pedals – and have no problem. At least the hard landing demonstrated the strength of the machine.
Its monocoque body is made from a carbon-fibre honeycomb, like that used in Formula One cars. That is extremely light, at just 20kg, allowing for a hefty payload. Admittedly, neither Dean nor myself are particularly heavy, but we could have brimmed the 170 litre fuel tank, giving up to six hours’ flying time.
As I cruise at a relaxed, vibration-free 90 knots (about 104mph), a big electronic readout on the instrument panel of the sophisticated and comfortable interior displays all the relevant parameters – from rotor speed to engine oil temperature and a precise readout of fuel left in both quantity and remaining running time.
With efficient systems and controls taking care of so much – there are similar aids for engine management – flying the Cabri is made more enjoyable. The cyclic in my right hand, which controls the angle of the main rotor disc and therefore whether the aircraft flies forwards, backwards or sideways, has the weight of much heavier machines. But its effect is direct and lag-free, which means it is easy to settle into moving it enough but not too much – “overcontrolling” is too easy in many helicopters and makes any flight a series of wobbles rather than soaring through the sky.
Where the Robinson two-seater wins is on price. At about £167,000 its base price, before taxes, is significantly lower than that of the Cabri. But the Robinson requires a £100,000 complete rebuild every 12 years or 2,200 hours.
Another way to look at it is that the Cabri’s price is close to that of the Ferrari 458 Italia I was driving a few days before I flew the Cabri. The mid-engined, two-seat car is a fine machine. But between that and the – also mid-engined – French two-seat helicopter, it is the flying machine that would give me more pleasure. Slower on paper but quicker in the real world, the helicopter would also actually get more use.
Source: http://www.ft.com
Many of those pilots’ concerns are mechanical. In some ultralight aircraft, the single bolt that holds the fabric-and-tube wing on to the fuselage is known as the “Jesus bolt”. In helicopters it is the rotor head that plays a similar vital role, acting as the mount for the blades of the main rotor and taking the weight of the rest of the helicopter suspended beneath it.
The £250,000 Cabri, though, has three rotor blades set in a hub as sophisticated as that on bigger helicopters costing millions of pounds. This means the potentially weak point is extremely strong – and the Cabri can be thrown around the sky with what, for most light helicopter pilots, is an unprecedented degree of abandon.Despite the exhortations of Steve Dean, a Cabri instructor for UK importer Cotswold Helicopters who is seated beside me, I’m only scratching the surface of that potential.
Even so, the safety advantages are reassuring. The Cabri is the first light helicopter to be certified under stringent European regulations.
Its passenger cabin and shock-absorbing seats are designed for a descent rate of 2,000 feet per minute. That is the rate seen in autorotation, or gliding – when air passing through the rotor disc spins the blades and provides lift. Or, as Dean puts it, if the engine fails and you do nothing else but lower the collective control to alter the pitch of the rotor blades and enter autorotation, you will survive the un-avoidable collision with the ground.
Although simulated engine failure is a key part of helicopter training, in the Robinson R22 – the little two-seat machine that is the workhorse of the training and personal flying market – the low-inertia twin-blade rotor’s speed can decay so quickly that unless the pilot lowers the collective within a few seconds of the engine stopping, there is no chance of the rotor speeding up enough to provide sufficient lift.
Other safety aspects are more of a mixed bag. The anti-torque rotor – the one at the rear that stops a helicopter from vividly illustrating Newton’s third law of motion and spinning in the opposite direction to the main rotor – is embedded in the vertical tail surface. That cuts the risk of people walking into it and of it hitting objects such as trees in tight landing spots.
But, ironically for a helicopter that sells itself so hard on its safety aspects, my flight in the Cabri was delayed because the Cotswold Helicopters machine was involved in a “hard landing” when it started spinning uncontrollably.
Drawing lessons from that, I make sure to keep the rotation speed down and use all the travel in the pedals – and have no problem. At least the hard landing demonstrated the strength of the machine.
Its monocoque body is made from a carbon-fibre honeycomb, like that used in Formula One cars. That is extremely light, at just 20kg, allowing for a hefty payload. Admittedly, neither Dean nor myself are particularly heavy, but we could have brimmed the 170 litre fuel tank, giving up to six hours’ flying time.
As I cruise at a relaxed, vibration-free 90 knots (about 104mph), a big electronic readout on the instrument panel of the sophisticated and comfortable interior displays all the relevant parameters – from rotor speed to engine oil temperature and a precise readout of fuel left in both quantity and remaining running time.
With efficient systems and controls taking care of so much – there are similar aids for engine management – flying the Cabri is made more enjoyable. The cyclic in my right hand, which controls the angle of the main rotor disc and therefore whether the aircraft flies forwards, backwards or sideways, has the weight of much heavier machines. But its effect is direct and lag-free, which means it is easy to settle into moving it enough but not too much – “overcontrolling” is too easy in many helicopters and makes any flight a series of wobbles rather than soaring through the sky.
Where the Robinson two-seater wins is on price. At about £167,000 its base price, before taxes, is significantly lower than that of the Cabri. But the Robinson requires a £100,000 complete rebuild every 12 years or 2,200 hours.
Another way to look at it is that the Cabri’s price is close to that of the Ferrari 458 Italia I was driving a few days before I flew the Cabri. The mid-engined, two-seat car is a fine machine. But between that and the – also mid-engined – French two-seat helicopter, it is the flying machine that would give me more pleasure. Slower on paper but quicker in the real world, the helicopter would also actually get more use.
Source: http://www.ft.com
No comments:
Post a Comment