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The Aircraft

Grob 109b - Vigilant T1

645 VGS use the two seater Vigilant, the military variant of the German glass-fibre Grob 109b motor glider (first introduced to VGS's in 1990).


The Grob 109B motor glider, known by the RAF as the Vigilant T1, is used by the Air Cadet Organization to give basic flying and gliding training to air cadets. The aircraft is built in Germany, but it has been modified to meet the RAF’s training requirements by the inclusion of an additional throttle in the cockpit and an increase in the maximum take-off weight. The Vigilant is currently used by 16 Volunteer Gliding Squadrons (VGSs), located at various sites around the UK. Their role is to train air cadets in basic flying techniques and to enable them to reach a standard where they are able to fly solo. Courses available to the air cadets are the gliding induction course, the gliding scholarship course and the advanced gliding training course. The Vigilant T1 aircraft is also used at the Air Cadet Central Gliding School, at Syerston, in Nottinghamshire, where it is used to train the VGS instructors.

The aircraft is powered by a Grob 2500E1 horizontally opposed, four-cylinder, air-cooled engine, which provides a direct drive to a Hoffman Ho- V62 R/L160BT variable-pitch, two-bladed propeller. The conventional landing gear, which is non-retractable, comprises two main wheels with fairings, and a tailwheel, which is steered through the rudder pedals. A retrofitted throttle is provided for use by the left-hand seat, giving the student the familiar military configuration of right-hand stick and left-hand throttle arrangement.

The Vigilant TMk1 is a cost-effective, modern aircraft. Its docile handling characteristics, combined with good fuel economy, make it an excellent training aircraft for cadets and instructors alike.

The Grob 109B is a high performance self launching motor glider capable of operating up to 8,000 feet at speeds in excess of 130 knots. Training in the Vigilant is carried out at up to 8,000 feet typically between 60 and 70 knots.


 The Vigilant can taxi, take off and climb under its own power to a height selected by the commander. It can be flown as a conventional glider by allowing the engine to idle or, for some advanced exercises switching the engine off altogether. It can even soar in thermals given reasonable conditions. The engine is not powerful enough for rapid climbing, taking some 5 minutes or so to reach 2,000 feet. However the ground handling time is reduced and manpower requirements are less than that of the Viking conventional glider.


The Vigilant is used for Air Experienced Gliding (AEG), Gliding Induction Courses (GIC), Gliding Scholarships (GS) and Advanced Gldier Training (AGT) and, unlike the Viking where you may experience a number of launches lasting on average 5-6 minutes, in order to achieve training objectives, Vigilant sorties typically last for about 20-30 minutes for a GIC and 45 – 60 minutes for a GS exercise.




Technical Data

Span: 17.4m (57.1ft)
Length: 8.1m (26.6ft)
Height: 1.7m (5.6ft)
Aspect Ratio: 16:1
Wing Area: 19m² (204.5ft²)
Max. Flying Weight: 908kg (2002lbs)
Max. Wing Loading: 47.8kg/m² (9.8lbs/ft²)
Engine: Grob 2500 horizontally opposed 4 cylinder air cooled

Maximum Speeds:

Never exceed speed in calm air: 130kts (below 6500ft up to 850kg)
Normal operations in calm air: 117lts (up to 850kg
Max. speed in turbulence/maneuvering: 83kts (up to 850kg)

Flight Performance Envelope:

Acceleration limits: +3.5/0g (up to 850kg)
Best angle of climb: 49kts
Best rate of climb: 60 kts (fine pitch) 75kts (coarse pitch)
Best glide angle: 1:28
Cruise fuel consumption: 12-15 liters per hour (100ltr tank)

Mass and Balance:

Max all up mass for take-off/landing: 908kg
Max baggage: 17kg
Max fuel mass: 72kg
Max crew mass for solo flight: 110kg
Max crew mass for dual flight: 220kg
CG limits: 271mm forward to 427mm aft of datum

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