All LGC aircraft are fitted with 180HP Lycoming O-360 engines.
Glider towing is very hard on engines due to the alternate use of high and low power settings. Cylinder head cracking can happen when rapid changes (temperature ‘shocks’) or differential changes in temperature occur in an engine. More detailed information can be found under Operations – General Information and Robin Ground Operations.
Use pre-take-off scan to ensure the aircraft is ready for flight.
As above, the take-off is a critical time for the engine. It is therefore important that opening the throttle at the start of the ground run should be gradual and take at least 3 seconds. On reaching full throttle check the RPM. This is very important and will give the first clue on engine problems. If RPM is low, check the carb heat is OFF before considering rejecting the take-off. Once at 20-30 knots, look in the mirror to ensure the gliders air-brakes are closed. See the ‘Emergencies’ page for actions in the event of a rejected take off.
On commencement of the take-off run the stick should be held well back. Lift off at or just below 50 knots. Hold the aircraft in the normal climbing attitude, the speed will increase rapidly to 60 knots which should be maintained to at least 300 feet. Retract the flaps and climb in the normal climb attitude and speed thereafter. Should the normal climb speed be achieved, by perhaps a strong wind gradient, then hold on to the speed, don’t try and reduce to initial climb speed. You may also choose to gain the normal climb speed early if there is significant turbulence.
Each tug’s climb speed may vary due to type or ASI error. For the most up to date information on speeds to fly see the ‘Climb/Descent Summary’ page.
At glider release, stop the climb, acknowledge release with a short turn to the right, reduce power VERY SLOWLY to 2100 rpm [DR300 2000 rpm], whilst accelerating to 100 knots [DR300 110 knots]. This is the most critical part of engine operation and it is very important that the power reduction is achieved in NOT LESS THAN 30 SECONDS. (Any adaptions to these figures are detailed on the ‘Climb/Descent Summary’ page).
In the DR400 fly 100 knots and 2100 rpm in the descent, this will give a 1000 fpm descent rate.
In the DR300 fly 110 knots and 2000 rpm in the descent, this will give a 1000 fpm descent rate.
These parameters should be maintained to 500 feet, when pilots should slowly reduce power and allow the aircraft to decelerate in level flight, in order to enter the base leg at 70 knots or so, before continuing descent on the final approach profile. Take-off flap should be selected soon after levelling at 500′ and once the speed has reduced below 90kts. Approach scan should be completed around this time. Typical speed is 60-65 knots on finals. Landing flap should be used for landing and should be selected at a suitable point to achieve a low power approach into the landing area. Carb heat should be operated in mid-descent if you are suspicious of carb icing and in any case during the approach scan. Carb heat should always be returned to cold after the check. Full details on carb icing can be found in the Aircraft section.
The higher speed of the DR300 will require a longer decent distance and this should be allowed for. Also the level deceleration phase is significantly longer and about 3/4 mile is required compared with the 1/4 mile with the DR400. Good circuit planning is essential to accommodate these characteristics, whilst maintaining the necessary power settings.
The DR400s are currently fitted with a four bladed propeller. The advantage of this is that high rpm at full throttle minimises the ground run and produces an efficient climb profile. The downside is that it operates very close to the 2700 rpm red line limit which will be reached at full power at just over 80 knots and very quickly after the glider releases if the correct power reduction technique is not applied. It is also possible during strong convection or heavy turbulence to see surges towards the red line, it is usually sufficient to just slow down, however, reducing the throttle setting may be needed.
Landings should be fully held off and the stick should be kept back during the decelerating ground run to keep as light a load as possible on the nose wheel. Brakes should be used cautiously.
The tug should be stopped and brakes applied. Allow the engine to idle at 1000 rpm for a short time to allow it to adequately cool, check carb heat during this phase.
Switch ALL electrics off, including the fuel pump, anti-collision light, radio and transponder.
Shut down by closing the throttle and pulling the mixture control to cut-off.
After the engine stops, switch the magnetos OFF and remove the key. Turn the master switch OFF (or pull the lever in the DR300).
If leaving the tug, you should also lower the flaps.
It is possible to operate the Robin in very strong winds, up to 40 knots. This strength of wind, however, is unlikely to be suitable for a safe aero-tow operation. The terrain around Dunstable creates extreme and unexpected turbulence. Consideration must also be given to the type of glider and the glider pilot’s experience. It is important to remember that it is the tug pilot’s decision to aero-tow or not, if you are uncertain DON’T.
Maximum permissible crosswind is 22 knots.