Ready, willing and Able…

Once upon a time there was an aircraft called the Vigilant T1. A derivative of the Grob 109 motor glider, it was introduced into service with the RAF’s Volunteer Gliding Squadrons in 1991. A fleet of some 60 Vigilants provided thousands of cadets with their first taste of flight, but rather than living happily ever after, there was trouble ahead for the Vigilant when airworthiness paperwork concerns were raised. A QinetiQ engineering report pointed out that due to multiple training flights being logged as one it was impossible to determine the fatigue life of each airframe, while other irregularities in maintenance records made it impossible to be completely certain of the status of any individual airframe. The Vigilants were never considered to be unsafe, but their fate provided evidence to support the theory that flight has nothing to do with Newton or Bernoulli, and everything to do with paperwork and money. The much-loved Vigilant fleet was grounded and withdrawn from service in May 2018. To many, it looked like the aircraft would never fly again.

“The naysayers hadn’t figured on Aerobility’s CEO Mike Miller-Smith MBE, on his eternal optimism, nor on his boundless energy.”

The naysayers hadn’t figured on Aerobility’s CEO Mike Miller-Smith MBE, on his eternal optimism, nor on his boundless energy. In March 2020 Aerobility purchased 63 (count ’em!) Vigilant airframes, with a plan to put them back in the air after a full refurbishment and re-certification project. In addition to airframe work, the aircraft will be re-engined with the 100hp Rotax 912iS mated with an MT constant speed prop and fitted with Garmin’s G3X as an option. Grob itself, a partner in Aerobility’s bid to acquire the aircraft, will refurbish 10 airframes and after that, the work for the remaining fleet will transfer to Southern Sailplanes in the UK. The resulting model will be known as the Grob 109 Able, with Aerobility planning to fly and operate up to eight aeroplanes, some of which will be converted to hand-control by Tim Dews of Airborne Composites. Profit from further sales will help to support Aerobility and its work. With a bit of luck, a bit of a win, win, win situation.

Clearly Covid didn’t do anything to make things quicker or smoother, but nonetheless (and undoubtedly in no small part thanks to Mike’s persistence), Aerobility persuaded Grob to let them borrow its development and certification aeroplane (see Brexit complexities). Not long after, Mike invited FLYER to the charity’s HQ at Blackbushe to learn a bit more about the project, and to fly the aeroplane.

Yes, you’d expect a TMG to have a decent wingspan, but at over 57ft (17.4m) the 109 has that – and then some. They’re bloody huge, and unlike the super slender wings of a top competition sailplane they have a decent chord (wing area is 19 square metres) – I’m told each wing weighs in the region of 100kg, something we’ll come back to shortly.

The aeroplanes are normally powered by the Grob 2500 E1 engine which develops 95hp, although if you mention that number to most people who know Grobs, you either get a look of derision or hearty laughter. Let’s just say that nobody has accused a Grob 109 of having too much power.

Where the Grob engine sat under a normal-sized cowl, the Able sports a front end that’s considerably longer, presumably to keep the CofG in a sensible position given the lighter weight of the fuel injected Rotax. The long vertically split cowl is adorned with various growths to support air intake, exit cooling and lights. It’s a fine piece of composite work, but perhaps not the most beautiful cowl to ever grace the skies.

The cockpit clearly has a developmental past, but sports Garmin’s G3X along with a transponder, GTN650 plus the usual collection of steam gauges and a bunch of electrical switches to help with the running of the Rotax’s engine management system (there’s a back-up battery, that covers alternator failure, but no electrical power = no engine power). Unusually for a 109 there’s a hydraulic prop control (traditionally the prop had three positions: feathered, fine and course, which were set via a mechanical handle coming out of the dash), and unusually for SEP pilots at least, there’s a blue handle on the cabin side that operates the airbrakes which are recessed into the top surface of that big wing.

After walking around the aircraft with Guy Westgate, (Aerobility supporter and display pilot) I sat on the wing, swung my legs into the cockpit and half lifted, half lowered myself into the seat. I had spoken to Mike earlier about cockpit access for disabled pilots, and he’d explained that with the top-hinged doors and sturdy wing it was one of the easier aircraft to get in and out of, a big plus given one of the charities main aims of offering disable people, without exception, the opportunity to fly an aeroplane.

There’s plenty of space inside, the seats have adjustable rake and the rudder pedals can be adjusted forward and aft, so after a little faffing, something comfortable and functional can be found for pretty much anyone. Guy ran through the start sequence for the injected Rotax, this involved bringing alternators online and tying in various electrical supplies before checking the dual lane engine management system. I guess it’s something you’d get used to quickly, but it’s more complex than it surely needs to be?

If you take a look at the pictures you’ll see that at the end of a fairly long moment arm there’s a large tail and rudder. This will give plenty of control authority while also acting as a nice big sail should you be operating on the ground in any kind of crosswind. For people like me who have only really flown relatively short-wing aeroplanes, there’s a bunch to learn. The tailwheel is steerable (but can, and will ‘jump out’ of its steering collar to become fully casting just when you don’t need it), and remember my earlier mention of 100kg wings? Well, there’s some potential momentum just waiting to nip you should you taxi too fast or too enthusiastically. I managed to weave my way to the runway without hitting anything, but operating away from gliding sites and at airfields where you might have a bunch of parked aircraft you need to take even more care than usual.

There are no flaps to worry about (we’ll get to the airbrake in a bit), so after the checks I line up, apply power, keep things straight, and when there’s enough speed, raise the tail a bit. Just as I was thinking about rotating, the Grob levitated off the runway and we climbed away at over 600fpm at 60kt, reducing power a bit in the climb. Visibility is great (including through the quirky perspex windows by your feet), but once again those long, long swings make their presence felt and the Grob is ready to offer lessons in adverse yaw to anyone who forgets about using the rudder and balanced turns.

“Guy mentioned that ‘this is now the aeroplane it always should have been’ more than once”

Cruising along…

According to Guy the power of the Rotax combined with the hydraulic MT prop transforms the aeroplane’s performance when compared to Grob powered examples, in fact Guy mentioned that ‘this is now the aeroplane it always should have been’ more than once, and given that we had no trouble cruising along a little north of 100kt, I can see what he means.

Trying to get used to those wings I flew a few steep turns which are great (remember your feet) before climbing to the west for some stalls. With power off there was a break and slight wing drop somewhere around 46kt. A power on stall gave a bonkers pitch attitude, I would have needed a bit more time on type not to mention altitude to explore any more.

Being a TMG there may be times when you’d want to soar rather than power your way along. I’m told that for most people the heavy Grob with its 1:26.5 glide ratio needs the kind of thermals you find in Spain for this to generate significant height gain, but it’s fun to try. So Guy shut down the engine and feathered the prop. There were a few bumps around, but the best we did was to reduce the sink rate to a couple of hundred feet a minute, but it reminded me of both the peaceful nature and frustrating challenge of soaring. Guy restarted the engine and we headed back to Blackbushe in order to explore another significant difference between a motor glider and SEP.

The combination of no flaps, low drag and a soaring wing means that trying to land the Grob without airbrakes is likely to end in a long float all the way to whatever obstruction action is waiting for you at the end of the runway. To avoid this embarrassing, expensive and painful experience you choose to fly the aeroplane as a glider or as an SEP, and first up we looked at the glider option…

A normal circuit is flown until you are well within gliding range and then some. The airbrakes are powerful, and Guy had me remain high enough that I was beginning to wonder if we’d get in. Throttle to idle (where it stays), right hand on the stick and left on the airbrake. Taking full airbrake dumps lift, adds drag and shows how easy it would be to undershoot, while putting all of the airbrake away shows how easy it would be to overshoot, all from the same approach. Going around from this involves closing (and locking) the airbrake with your left hand, swapping hands on the stick and then using your now liberated right hand to add full power and assume the attitude.

Now for the SEP landing option. Recessed into the side panel by the airbrake is a nylon block. A small lever moves that out into the path of the airbrake, and you can set the airbrake in a machined panel so that it is basically half deployed. You then leave the airbrake alone, and manage the approach and landing with the (for SEP pilots) traditional pitch and power. Although going around in this configuration ideally involves putting the airbrakes back in, the aeroplane will climb with them half out.

The flare gave a higher nose attitude than I was expecting, but we were down and stopped in a little over 200m, at which point the whole focus once again became those long wings and accurate steering.

So how does it stack up? It’s an interesting and entertaining set of compromises. If you want to enjoy some fun economical cruising, you can waft along at 90kt (you can go faster but I always think a Rotax is a bit more relaxed at lower rpm) and the 100 litres of fuel will get sipped at about 12 to 14lph (although if this is your thing, you will want to add some extra padding to the fairly firm seats). If you want to try your hand at a bit of soaring you can do that, although I’m told that gets easier the further south you go in Europe. If you are a gliding club, then you could use this for both towing and training. A basic refurbed version would set you back £155,000, to which you can add lots and lots if a full suite of glass panel avionics is your thing.

Mike Miller-Smith is one of the smartest aviation people I know, and if anyone can make this work he can, and on that basis, there’s every chance that this particular story will have a fairy-tale ending.