 Some aircraft in Germany have been fitted with a turbocharged engine, and with structural strengthening of the fuselage have been adapted to aero-tow gliders.The Vigilant T1 is the designation of the adapted Grob 109B used by the Royal Air Force (RAF) for use on Volunteer Gliding Squadrons.Modifications to the Vigilant T1 include a landing light, a higher maximum all up mass (AUM) of 908 kg and a throttle for use in the left hand seat.