The following is a message from the BGA (March 2022) regarding tailwheel operations:
Here are a few tailwheel tips. In all cases, the Aircraft Flight Manual should be referred to paying particular attention to any wind and cross-wind limitations.
The dynamics of a nose-over
Aircraft with a tailwheel have nothing to stop them nosing over except the propeller. The C of G of a tug aircraft is somewhere above and behind the mainwheels. As the tail rises (eg at the start of a nose-over), the C of G is rotated forwards towards the axle line and the natural tendency for the aircraft to sit on its tail (gravity) quickly reduces. Once the tail starts to rise, the force which is causing it to rise has a progressively easier job and it will accelerate into a nose-over resulting in a bent prop and a shock loaded engine.
The following factors contribute to a nose-over
Using power against brakes. The thrust line is above the axle line. Any power against one or both brakes may try to pitch the aircraft forward over the wheels. The same effect can occur on soft ground.
Elevator control position. The elevator is an effective control on the ground. With all 3 points in contact with the ground, the stick should be held fully back. With any wind or slipstream blowing over the tailplane, this stick position provides a powerful download on the tail in addition to gravity. Landing roll outs and taxiing into wind without full back stick may lend themselves to nose-over. Taxiing with a tailwind component should be carried out with the elevator neutral or down. That way the tailwind will provide a little more download on the top surface of the tailplane/elevator. In aircraft with a trim tab, the trim tab can be positioned to add to the effect.
The elevator trim position needs care. In some aircraft, elevator loads on the ground vary with trim setting and can result in less actual control authority than perceived by the pilot.
Aileron control position. With the wind on the nose from any angle, the ailerons should of course be used conventionally to help to maintain wings level. Once any crosswind also becomes a tailwind, the upwind aileron should be lowered. That way the tailwind will provide a little more download on the top surface of the aileron to help to offset any upload.
Propeller effects. Power-on torque drives the propeller in one direction and tries to roll the fuselage the opposite way. This pushes one wheel hard into the ground, ground friction is increased (especially on soft ground) and the aircraft yaws towards that wheel. The propeller’s gyroscopic and aerodynamic forces can complicate the process further.
Taxiing. Great care must be taken when taxiing in strong winds, particularly when operating off grass when more power is needed to taxi. If the aircraft will not turn with the brakes correctly set, it can be tempting to keep adding power to force the aircraft to turn. A safer option is to use a wing holder/walker to assist. This minimises the use of power against a braking force, which features in almost all tailwheel nose-over incidents. Other extra weight, eg a fixed ballast weight on the back seat of a tandem aircraft can help to increase the tail load.
Changing conditions. Staying aware of the evolving situation is important. If the wind becomes very strong or very gusty and as a result taxiing is difficult, shut down with the aircraft pointing into wind and manhandle the aircraft back to the launch point or retrieve it with its tow rope. In both cases, keep the aircraft's nose pointing as near to the wind as possible and keep the pilot in the cockpit. Restart only when pointing into wind. Only continue towing if satisfied it is safe to do so. Consider moving the launch point forward if safe to do so.
Training. Any tug pilot - experienced or otherwise - who would like more training in operating tailwheel aircraft is encouraged to approach a suitably qualified and experienced Flight Instructor or Class Rating Instructor.
Please note that guidance on all aspects of towing is available here.