AeroTime Flight Test: Grob Able motor glider

Ben Griffiths

As a pilot of fixed-wing aeroplanes, you are taught, from very early on in your training, what to do if the engine stops: immediately adopt the attitude to give the best glide speed for your machine and start looking for somewhere to put down safely, generally a suitable field.

So, when renowned display pilot Guy Westgate casually leaned over and switched off the engine in the Grob 109B we were throwing around above the English countryside, the hairs on my neck stood on end, the training kicked in, I pitched the nose forward and reached towards the control panel to begin restart drills. Meanwhile, Guy giggled mischievously, folded his arms, and looked positively relaxed.

Thankfully we were sharing the cockpit of an incredible motor glider and cutting the power is par for the course. I’d never been gliding before or attempted to pilot an plane in which one might consider flying without an engine. And yet, once my brain registered that the long-winged Grob is designed to stay aloft for a long time without needing to burn any fossil fuels, my nervous grimace relaxed into a smile, soon followed by a broad grin which lasted for hours after we’d landed. This is a super-fun and modern flying machine that brings a lot of enjoyment to every aerial adventure.

The story of the Grob 109 is one of a phoenix rising from the ashes. Britain’s Royal Air Force had operated a fleet of them with their Volunteer Gliding Squadrons, where the aircraft had been known as the Vigilant T1 since being introduced in 1991. Thousands of cadets got their first taste of life in the skies in them before the Vigilants were grounded following the discovery of paperwork irregularities and uncertainties about their fatigue life. At that point, it was a safe assumption the aircraft would never fly again. Enter stage left Mike Miller-Smith, the indomitable chief executive of flying charity Aerobility, whose remit is to offer disabled people — “without exception” — the opportunity to get aloft.

By March 2020, Aerobility had acquired 63 of the Vigilants, formulating a plan to have them recertified, refurbished and re-engined with new 100hp Rotax powerplants paired with a two-blade, constant speed and fully feathering propeller. Aerobility hopes to retain and operate up to eight of these, which it has labelled the G109 Able, while the rest will be gradually sold to finance the charity and its work.

Miller-Smith was eager for me to try out the Able for myself and see what it can do. So, air display pilot and instructor Guy Westgate, who is a long-term flyer of Grob motor gliders, was tasked with demonstrating the plane. I couldn’t have been in better hands.

So, what is the Able like to fly? The first thing to note is that the aircraft’s wings are simply massive, which does focus the mind when taxiing but can also set up some interesting wobbles and oscillations if mishandled. Best advice, according to Guy, is simply to come to a halt, let things settle and have another go.

The walkaround is fairly standard for a single engine piston aircraft, with various checks of fluids, control surfaces and undercarriage – the tailwheel is fixed and semi-steerable with differential braking.

Climbing into the cockpit was my next challenge. Guy advised me to back up to the wing-leading edge aside the cockpit and use my arms to lever myself into a sitting position on the wing. You then swing your feet inside the footwells and raise your backside over the canopy sill to plop down into the seat. Guy, of course, is well practiced at this and made it look easy. I ended up with one leg in, one outside and had to drag my left leg in after me.

When I was finally settled in, the next strange sight was the blue plastic handle of what looked like a ski pole alongside the left cockpit wall. This turned out to be the air brake. With no flaps and a very efficient wing, the Grob Able needs assistance to slow down to landing speed and the barn door-like airbrake which pops up out of the wings is the control you need for this. It’s unusual the first time you deploy it but is something you soon get used to.

A scan around the instrument panel makes it clear that a level of refurbishment has taken place. This looks and feels like a brand-new machine instead of a rebuild. An electronic engine flight information screen with temperatures, pressures and voltages leaps out alongside more traditional-looking gauges and chunky switches used to start up and manage various systems.

The thing I enjoyed most about the cockpit was the superb visibility thanks to a liberal use of clear Perspex, even down at my feet where the view of the ground was sensational. Ready to go and after Guy guided me through the start-up procedure and taxi to the active runway, we were soon on our way with a very short takeoff and were climbing away from climbing away from the runway at Lasham, nestled in the English countryside west of London and home of the largest gliding club in Europe.

Like any first flight, it’s a good exercise to try some progressively steeper turns, and it was interesting to find out for myself how the Able responds to control inputs in various configurations. Increase the speed and the ailerons feel very stiff, making rapid changes in direction challenging. But slow down a bit and those turns become easier and feel much lighter. As I became used to the feel, I enjoyed rapid roll reversals and pulling on some G as we sped around the turns. All great fun.

As a taildragger pilot I’m well used to using my feet on the rudder pedals, and the Able certainly demands that you keep in balance. This is particularly pronounced when it comes to stalling. We tried this with the throttle closed to start with. Sure enough, I didn’t push quite enough rudder to keep the wings up and we dipped into the start of an incipient spin before recovering and restoring us to straight and level flight. Next, we tried a stall with full power on. The nose high attitude was somewhat comical as we wallowed around at low speed, me pedaling furiously to try to hold the wings straight and avoid the spin.

All too soon we were heading back to Lasham airfield’s circuit and my first motor glider landing. Of course, Guy had to cut the engine again to demonstrate a glider approach. We followed this around until a short final, opting to go around and make a normal powered approach. With no flaps, those airbrakes came into their own and the Able coasted down, requiring a hint of a flare and hold off until the wheels settled onto the grass thanks to a very forgiving undercarriage.

I’d certainly recommend the Able for some fun and pure flying. Guy explains that he happily amasses many miles in his motor gliders, with fuel economy being a particular benefit as well as the ability to shift between power flight and soaring as the mood (and weather) takes you. Incredibly, they can stay aloft for more than seven hours. Working with Grob, Aerobility has hit on an excellent initiative to breathe some new life into these much-loved machines. Hopefully they will see many years of service ahead in their post-military careers.

If you’d like to find out more, including how to buy one of these machines, check out

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