TUG-PILOTS NOTES

These notes are intended as an introduction to towing at Booker.  They will not be updated once issued, and therefore as time goes by they may become inaccurate as operating procedures are refined.  If there is any discrepancy between what is written here and what is taught by the tug-pilot trainers, then consider their methods correct.  If there is any doubt the Chief tug-pilot will deliver the definitive answer.

The notes are divided into sections, the first part being general advice on engine/airframe management, climbouts, etc., and the second part contains type-specific information on specific directions.

GENERAL ADVICE

BGC is dependent upon a reliable, efficient launch system.  The club member tyg-pilots are a useful adjunct to the full-time tuggies and staff members, but only so long as they maintain this high level of efficiency.

What this amounts to is launching gliders to the most advantageous position whilst keeping cost and noise nuisance to a minimum and maintaining a good launch rate.  It requires the application of a fair degree of ability and judgement in order to balance these, to some extent, mutually exclusive goals  this is what makes towing interesting.  If you get bored after half a dozen tows you are not trying hard enough.

It must be emphasised that the tugs are extremely expensive to run and maintain and that the way they are flown has a great influence on this cost.  It would be impossible to make every member a tug-pilot, even if they all had licences, and so it is incumbent upon everybody fortunate enough to fly the tugs to operate to the utmost of their ability, in order to keep everyones flying bill as low as possible.

Engine Handling

This is where the biggest gains or losses can be made.  The types of engine used in our aircraft are big (6 litre), heavy, slow-turning, low technology machines.  They use a large quantity of relatively thick oil for lubrication and are air-cooled, thus they ar sensitive to poorly managed cooling techniques.

Because the oil takes some time to reach operating temperature these engines should not be operated in a manner which entails them being started and stopped unnecessarily, since they are adequately lubricated until the oil is warm.

In quiet periods, do not be in too much of a hurry to start up an extra tug.  On an unsoarable day there is no point in starting a tug because there are three or four gliders In the queue if there are already tugs flying.  It will only result in doing one or two tows and then shutting down again  this is very poor engine management and also contributes to the premature failure of the starter.  When it is not soarable it does no harm for the gliders to wait a few minutes for a launch (providing the onset of darkness isnt imminent).

The minimum warm-up times are as follows:

            For a cold engine:

            Before taxi or exceeding 1200 RPM                   50' CHT

            Before power checks                                      100 CHT

            Before take-off                                                150' or 4 minutes

 

            For a warm engine:

 

            As above but take-off may be after 2 minutes

 

Being air-cooled they experience much bigger and more rapid changes in temperature than a liquid-cooled engine with a proper cooling system.  This aspect of their operation is the most critical.  It is essential at the end of a climb, when the engine is very hot owing to a high power setting and low cooling airflow, that the descent is not made with a lower power setting and high speed (= high cooling).  If this is allowed to happen, the aluminium cylinder head shrinks at a much greater rate than the steel cylinder barrel and valve seats, resulting ion thermal stresses which will break the cylinder head.  Even if this does not cause the complete failure of the engine it will result in the scrapping of the cylinder at a cost of about £1000.  The solution is the careful management of the descent to keep the rate of CHT reduction to a minimum.

The type-specific sections contain a full explanation of the required techniques.

The oil also performs an important cooling function.  Don't let the oil level drop below 6 quarts, especially in Summer, but remember that if the engine has just been shut down there will be about ½ qt. distributed around the engine.

Make all throttle movements smooth and gradual.  When taxiing try to set an RPM which gives a slow, steady taxiing pace without needing to constantly open and close the throttle.  On take-off take at least five seconds to set full power.  Be conscientious abut checking the T's & P's both befre take-off and when fly8ing.  Get to know what the readings should be, and if there is any discrepancy find out what is causing it - it may be an early warning of impending failure.

Airframe handling

Looking after the airframe is largely a matter of common sense combined with a little mechanical empathy.

The first step is a thorough D.I. to discover any incipient damage before it becomes too serious (full notes are given in the type-specific sections).  This is only possible if the airframe is kept clean enough o spot any signs of damage.  The aircraft should be cleaned in the morning if they were not cleaned before being put in the hangar; cleaning equipment is kept in the main hangar, in the blister hangar and by the hose at the Flightworks end of the trailer rack.  Canopy cleaning kit is also kept in each tug.  If you find any of this kit missing please tell a staff member so it can be replaced.

When cleaning the tugs it is necessary to clean those areas of the aircraft which are difficult to get to as well as those where accessibility is straightforward, e.g. the underside of the aircraft (in particular the Robin's wing), the underside of the tailplane, the Robin eleos, the Cubs- strobes, etc.

In addition to the normal daily cleaning routine, the propeller requires to be kept free of contamination by bugs or mud, since this has a significant effect on its efficiency.  If there is a build up of bugs on the leading edge or blade face it is time to clean the prop-, this may need to be done more than once a day - check the prop each time you shut down.  The blade face is the back of the propeller i.e. the black side.  This is the bit it is most important to keep clean, since it does most of the work.  It is also the part which is more rarely cleaned.

It is unacceptable to fly at Booker with a dirty canopy.  Clean it whenever it is dirty, preferably each time you shut down at the end of a session of tows; there should be canopy cleaner in the tug.  Never use a brush or broom to clean perspex.

The part of the airframe which suffers most from towing is the undercarriage since it is subjected to so many take-offs and landings, generally off rough ground.  It is inevitable that the undercarriage of our tugs will take a pounding, but a few simple habits can make a lot of difference:

            *Always carry out fully held-off landings.

*Keep braking to a minimum.  Try to stop at the launch point without using the brakes  this will mean using the lowest safe approach speed.  Aircraft brakes, like everything else to do with the tugs, are ridiculously expensive  at the moment it costs between 20p and 40p per launch to maintain the brakes.

*Avoid tight turns when taxiing wherever possible - it places a surprisingly high load on the undercarriage, and the Robin in particular suffers damage from tight turns and turning a too high a speed.

*Don' taxi too fast.  Again, the Robin undercarriage in particular suffers if it is taxied across grass surfaces at excessive speed.  After landing reduce speed to a brisk walking pace before turning, and do no subsequently exceed this speed.

When ground-handling, the same basic rules as gliders apply.  Never push on trailing edges or tailplanes and ensure that you can see exactly what is going on If you are manhandling in a confined spaced, e.g. the hangar.

Additionally, when handling a propeller extra cautions need to be observed.  The propeller should always be treated as 'live'.  If other people are helping make certain that they understand the hazards.  Ensure the mags re switched off, throttle closed and mixture set to idle cut-off before handling a prop.  Only push or pull from close to the hub i.e. As near to the spinner as possible.  Do not push on the spinner itself as the backplate is of a brittle material and will fail as a consequence of mishandling.

If pulling/pushing on the struts of the Cub, handle as near to the attachment points of the strut as is practical.

Noise abatement

It is vital for the future of Booker, like all other airfields, that we keep the level of noise nuisance to our neighbours to a minimum.  Other airfields have suffered sever restriction of their activities as a result of the actions of well-funded and powerful anti-noise lobbies.

At Booker there is a group which contains representatives of all airfield operators and local committees of residents.  This meets occasionally to discuss any problems and, predictably enough, the resulting recommendations are a compromise made by all parties.  The crux of the matter is that the residents of the surrounding area will never be entirely happy with the agreed operating policies, and are therefore extremely sensitive to what they consider to be transgressions.  Unfortunately, past experience has shown that they have vastly more support for their arguments that we aviators and it is thus extremely important to minimise, and be seen to minimise, noise nuisance.

There is a map of noise sensitive areas published within these notes, and sent out with the periodic tug-pilots' newsletter.  You must know the position of the noise sensitive areas and avoid them.

When towing, vary your climb out path as much as possible in order to spread the noise around.  Avid climbing out over buildings, especially when low.  Circuits should be at a low power setting, ending in a glide approach.

Do not assume that because you are at height you may fly in the prohibited areas.  In noise tests carried out a couple of years ago the passage of a tug overhead at 1500' was one of the most irritating phases of flight from the noise perspective.

More comprehensive notes on recommended climb-out directions are given in the section dealing with runway-specific information.

Climb

Immediately after take-off the priority is to place the combination in a position which maximises the chances of a successful forced landing for both the tug and the glider in the event of a rope-break or engine failure.

Choose a path which puts a reasonable number of fields in front of you until you are at a height where you could consider turning if the engine failed.

In windy conditions be aware of the effect the wind gradient will have on your flightpath.  If you simply climb at yur selected airspeed you will find that your initial rate of climb will be very high as you climb through the wind gradient.  As you reach the top of the wind gradient at a few hundred feet you will suffer a sudden drop in airspeed and rate of climb, and will need to lower the nose to regain speed.  The glider, however, will probably have been left behind by the abnormal climb rate.  As you fall out of the wind gradient it will still be climbing through the same gradient to catch up and it will probably therefore zoom above the tug as you stop climbing.  By the time the glider has got its nose down and is getting back down in position you will have regained speed and be climbing once more, thus leaving the glider behind again.

The cure for this undesirable manoeuvre is to fly by attitude.  After lift-off, set the tug in its normal climbing attitude and accept the fact that the speed will be a few knots high for the first couple of hundred feet ' it I much easier for the glider to cope with this than the phugoids which result from chasing the ASI.

Once you have reached a few hundred feet it is time to concentrate on where you are going to take the glider.  Tow it through all available lift (whilst observing the noise abatement procedures) but bear in mind that different pilots want different things.

A high performance single seater will probably pull off in the first good lift above 800', maybe lower.  A K-13 will probably go to 2000', especially if it is a trial lesson, but will still want to soar.  Try to arrange the tow such that you reach 2000' in or near lift, and in a position where the glider can climb.  It is pointless to drop someone in a thermal at 2000' under the airspace.  An early solo pilot will probably want the same sort of tow as the K-13 described above.

Whatever the glider, spend as much of the climb as you can in lift since this will greatly reduce the turn-round time.  Do not, however, tow through a thermal where several gliders are circling ' it is better to fly abeam the gaggle and let the glider pilot decide where he wishes to release and join it.

AT ALL TIMES MAINTAIN A VERY GOOD LOOKOUT

Descent

The type -specific sections contain full information on enginer handling in the descent, and the runway-specific sections give more detailed guidance on choosing descent paths and circuit patterns.

After the glider has released, first check that it really has pulled off.  The vital action is to go down once the glider has gone.  It doesn't matter if, or which way, you turn so long as you go down.  Likewise the glider may turn either way or not at all, but it must climb.  This guarantees separation.

As previously mentioned, the most important aspect of the descent is to manage it in such a way as to minimise the rate of cooling of the engine.

As the glider releases make a mental note of the height for the log, and the CHT, since this will be required to judge your descent.

Whilst descending in accordance with the technique applicable to the type you are flying, maintain a very good lookout --there is a lot of traffic in the vicinity of the field, and a lot of it will be keeping a poor or minimal lookout.

Your descent path should be planned to fly outside the noise abatement areas and away from other aircraft.  It should also be outside areas of lift - in fact, if you plan your descent to keep in the sink you should automatically avoid most of the glider traffic.  Remember that gliders have right of way.

Your circuit should end in a glide approach, and a fully held-off landing.  Do not let the rope hit the hedge.

Don't forget you are trailing 180' of rope; don't commit yourself to landing in a small area where the rope will cause a hazard to people and aircraft on the ground, and if you have to go-around from low-level remember the rope.  (You always have the option of dropping it.)

REMEMBER  IT IS ALWAYS MUCH CHEAPER TO SPEND MORE TIME AND BURN MORE PETROL IN THE DESCENT THAN TO CRACK A CYLINDER IN A RAPID DESCENT.

Signals

There are three signals you need to know.  The first is the wave-off, this is employed to tell the glider to release.  Rock the wings several times, make the movements large and obvious ' at least 30 degrees of bank each way.  If the glider does not release after a couple of waggles then release it.  In a dire emergency where time was critical you would probably dump the glider without giving the signal.

This signal is to be used only if you need the glider to release, it must not be used to indicate you think the glider should release because it is in lift, etc.

If the glider has its airbrakes open there is a specific signal (try the radio first).  Assuming the combination is flying at a safe airspeed and is climbing adequately waggle the rudder.  Again, make the movements obvious, and obviously deliberate.

It is vital that this signal is not given unless the tug is flying at a safe speed, and well clear of the ground.  If you are struggling to climb and maintain airspeed and ground contact is likely then dump the glider.

Lastly, if the glider finds it cannot release the rope it will fly out to the left and waggle its wings.  In this case release the rope, but first check you are not too far from the field since the performance of the glider is greatly degraded by the dangling rope.  If necessary tow back towards the field before you release the glider, bearing in mind that it will need to make a steeper than usual circuit and approach.

RT Procedures

The RT procedures at Booker are very straightforward and are in place to protect three areas; the active runway, the taxiway to the 25 threshold and the parallel helicopter taxi lane.

The relevant frequencies are:             TOWER                     126.55

                                                            GROUND                   121.77

                                                            LAUNCHPOINT            129.97

At times of flight when it is not necessary to be tuned to the tower frequencies monitor 129.97, this frequency will be used on the ground to pass details of pilot's name etc., and in the air for glider to tug comms.  Normally we speak to Wycombe Tower (126.55) but at busy periods you may be instructed to call Wycombe Ground (121.77).

The procedures are as follows:

Runway 35 & 17

The gliding operation is non-radio on these runways, therefore monitor 129.97 full-time.  The only time you need to speak to ATC is when requesting clearance to cross the  power runway.

Runway 25

It is necessary to call ATC prior t landing in order to ensure the taxiways are clear.  The phraseology is to call 'Wycombe Tower, tug &.. late downwind'.  ATC will reply 'Tug &.. taxiway secure' or '&..taxiway obstructed'.  This is not a clearance to land or otherwise - in either case you may continue the approach at your discretion.  Should you decide to land behind an aircraft on the taxiway having ben advised the taxiway is obstructed, extreme caution should be exercised in case there is another aircraft following, or a helicopter hover-taxiing in parallel.

Runway 07

On 07, call ATC before take-off.  Once the rope is attached to the glider call tug &. ready for departure.  Once again, the reply will be either taxiway secure or obstructed, and again it is to your discretion whether or not you take off.  If you decide to go having been informed the taxiway is obstructed have a very good look for helicopters, they can be very difficult to spot against the buildings.

Wycombe ATC are generally quite relaxed about the need for calling for start and taxi as far as the tugs are concerned.  In general there is no need to call for start or taxi clearance provided you keep out of the way; you should, however, monitor ATCs frequency when in the vicinity of the apron or pumps since they do occasionally call the tugs.

SUPER CUB

General

The Piper flight manual is available for study in the office.  See a staff instructor or the chief tug-pilot if you wish to borrow it.

Engine -

            Lycoming 0-360 A1A, 180hp at 2700RPM

            Oil capacity 8qts.  Minimum for towing 6qts.

            Max. RPM 2700, max. continuous 2700

            Max. CHT ' full power climb 265'C, otherwise 235C

Airframe -

            Piper PA18-150M

            Empty weight approx 950lb

            MTOW 1750lb

            Vne 153 mph

            Vno 121 mph

            Vf 85 mph

            Vso 45 mph approx

            Max. load factor 3.8g (with flaps lowered 2g)

            Fuel capacity 2 x 15 imp. Galls

RPM restriction - the engine should not be operated continuously between            

                            2150 & 2350 RPM

Daily inspection / pre-flight

To be carried out before the first flight of the day and if the aeroplane has been left unattended.

The general idea is to have a good look at the airframe in order to ensure it has suffered no damage since the previous check.  Firstly, look at the aircraft as a whole - this will show up defects not obvious from a close inspection only; for example one soft undercarriage bungee resulting in a slight list.

Ensure that the master and mag. switches are off.  Mixture should be set to idle cut-off and park brakes set if the prop. will be turned by hand during the inspection.  Leave the fuel on all the time.

While you are checking the cockpit, ensure the rear stick is removed and stowed, the rear straps are secured, that there is canopy cleaner, tug-logs, pen and a headset in the aeroplane and have the usual look around under the seats for pens and other junk.  This includes in the baggage area.  Check the fire extinguisher.

It is then best to circumnavigate the aircraft for the exterior inspection.  Starting at the right undercarriage particular points to note are:

The undercarriage should be checked carefully.  All the bolts should have a noticeable amount of oil on them, all the welds should be checked for cracks as should the lugs where the u/c legs attach to the fuselage.  If the u/c area is too dirty to check for cracks then clean it: it may be necessary to use petrol from the fuel drains for this if it is heavily oil contaminated.  The tyres should be checked for inflation and for creep.

Have a good look under the cowls.  As well as checking the oil level and draining the fuel strainer, make sure the baffles are in good condition and check that the hoses have not worn.  There is a high level of vibration in a 180 Cub which tends to cause hoses and leads to chafe and wear through.  Check the cowlings for cracks - these need to be stop-drilled.

The prop. should be clean, especially the leading edge and blade face (the black side).  Also ensure the protective tape on the L/E is not coming adrift.  The spinner should not be cracked, it will fail spectacularly if flown with a propagating crack.

When checking the main structure look for tell-tale wrinkles in the fabric which indicate underlying damage.  In particular check the wing ribs for slop, if they are not entirely rigid it indicates they are broken.  This normally results in irrevocable damage to the spar and should immediately be brought to the attention of the workshop.  Whilst looking at the wing, check carefully the struts and their attachment bolts for corrosion and damage.  The ailerons and flaps should be checked for play, the aileron linkages should be free of frayed cables and the flaps should be pushed down against the springs in order to look at the horns to ensure they are crack-free; this is an area of weakness.

Work along the fus. to the tail end.  The tailplane bracing wires should be tight.  There should be less than 5mm of vertical play at the leading edge of the tailplane, this is another weak point of this aircraft.  The tailwheel assembly should have no obviously broken springs, no surface rust, no lateral play (another weak point), and the hook should be clean and free of corrosion.

Dont forget to check all three fuel drains, if you do not have a proprietary fuel check available let the fuel stream for long enough to ensure that any water present has drained.  Be aware that it is difficult to distinguish between a full and an empty tank on this aircraft, if in doubt open the filler and look or feel inside.  Check the filler caps for security.

Power checks

These should be carried out facing into wind, ensuring that the propwash will not pose a hazard t people or objects behind the tug.  It is worthwhile to change tanks from the one which you have been using while taxiing, so the engine has been run on both tanks before take-off.

Having checked the CHT is 100 or greater carry out the power checks at 1800rpm.  The mag. drop should be no more than 125rpm, with a difference between mags of 75rpm or less.  If there is a large drop on one mag. accompanied by rough running of the engine it may be caused by oil build upon the plugs, particularly if the engine has been allowed to idle for a time.  This can often be cured by weakening the mixture until the rpm just begins to drop from 1800, the much higher flame temperatures in the cylinder should burn off the oil deposits.  After half a minute or so return the mixture to rich and perform the mag drop checks again, if there is no improvement consult an engineer.

If there is no mag. drop then it is likely that it is permanently live.  Shut down and consult an engineer.

Check the carb. heat.  There should be a discernible reduction in rpm, in the order of 50 -100.  If not the carb heat may not be functioning, shut down and get an engineer to check the carb heat box and controls.

Reduce to idle.  The engine should idle between 500 and 700 rpm.  Any higher than this and the landing float will be excessive, any lower and the engine will tend to stop during the approach.  Increase rpm back to 1000 -12--; idling for excessive periods will cause the spark plugs to foul with oil deposits.

Take-off

Do the pre-take-off checks.

Having established that the approach and the take-off run are clear, smoothly set full power, taking at least five seconds to do so.  When towing, the stick should be held fully back while setting take-off power in case the glider should release while the rope is under tension.

Check 2450rpm and rising, check oil pressure and temp. in the green.  If the oil is cool, the oil pressure will rise into the upper yellow band.  If it rises into the red you should abandon the take-off and wait for the oil to warm.

Once full power is et the stick can be brought forward to lift the tail.  Raising the tail too high merely results in an extended ground run and more weight on the u/c during the take-off, hence more wear.

It is important to keep the ground run straight in order to give the glider the best chance of staying in position.  Pick a feature over the nose as an aid to this.

Once airborne, quickly establish the appropriate climbing attitude and maintain this through any wind gradient or low-level turbulence.

Crosswinds - On take-off the Cub is very straightforward to control, with plenty of rudder authority.  The tension in the rope will help to keep the combination straight, but be ready to counter any swing if the glider drifts downwind.  It helps to slightly lower the upwind wing while you are holding rudder to keep straight.

Flaps - It is not necessary to lower the flaps for take-off under normal circumstances.  However half flap is excellent for muddy airfields but be careful to accelerate after lift-off before climbing away as the airspeed will be much lower than usual.  Use half flap also for vintage gliders.

Fuel management

The fuel system is gravity feed only from two wing mounted fuel tanks, each of 15 galls. Capacity and each feeding the engine via a small 'header' tank.

The 180hp conversion of the Super Cub introduced a few complications concerning the fuel system, and has resulted in some unusual placarding of the fuel gauges which will require some explanation:

The right tank is placarded 'AUX'and 'LEVEL FLIGHT ONLY'.  This is because it feeds the engine via the rear header tank, mounted above the baggage area.  It is possible, in the 180 Cub, to achieve an attitude in the climb such that this header is below the level of the carburettor float, thus interrupting the fuel supply.

The left tank is placarded 'EMPTY' when it is still half full.  This is because with less than 7.5 galls in the tank the fuel system does not deliver a maximum flow rate with a sufficient margin of excess to satisfy certification requirements.

In practise, neither of these potential problems has occurred during towing operations either at Booker or elsewhere - the climb angle is obviously much reduced when towing, and the certification fuel flow rates contain considerable safety margins.  It is therefore acceptable to operate using either tank for any phase of flight while towing and to use more than 7.5 galls from the left tank, so long as the considerations above are understood and caution is exercised when climbing very steeply with the right tank selected.

The fuel gauges, although very simple, are notoriously unreliable.  On the ground even a very small angle of bank due to uneven ground will cause large errors - the higher wing will over-read and vice-versa.  The slip ball is a useful aid to determining whether or not you are level.

One serious problem with these gauges is that if the hose to or from the gauge becomes blocked or restricted the fuel gauge may indicate a constant level of fuel, or the ball may go down but not as quickly as the contents of the tank.  In the past there have been several instance of fuel starvation due to this.  Check the tank contents each tow and if the contents do not drop as quickly as you would expect assume the gauge is over-reading.  When you refuel make a not on the tug-card, this will help the next person that gets in the tug to determine whether the gauge is stuck.

Although there are no handling problems produced by flying with one full tank and one empty tank it is better to keep the fuel reasonably in balance by alternating tanks every few tow.  In crosswind conditions it may help to keep the upwind wing a little heavier.  Change tanks just after landing, not just before take-off.

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Climbout

As described previously, the two main considerations in the early part of the climb are to deal with any wind gradient effects and to place the combination in a favourable position for dealing with an engine failure.  Once a reasonable height has been achieved you should concentrate on taking the glider to a suitable position, bearing in mind the considerations detailed in the General section of these notes.

The recommended towing speeds are as follows:

            Vintage gliders                     55mph see also section on low speed towing)

            Wooden types                     60-65mph

            Glass types                           70-75mph

On occasions, plastic gliders may wish to be towed at high speeds.  There is no need to tow faster than 80mph.

The visibility from the Cub is quite restricted, particularly laterally, and this has an impact on how you arrange the tow pattern.  Always avoid prolonged shallow turns in the Cub, since these leave you blind into the turn.  Because it is generally undesirable when towing to employ an angle of bank which enables you to look through the roof into the turn, the only option is to turn no more than about 60 degrees at a time, then level the wings to check you are still clear.  Before turning, lift the wing briefly so you can see under it to confirm the path is clear.

The attitude is not excessively nose up when towing, the nose is more or less on the horizon, but this is high enough to require an occasional turn to ensure there is clear airspace ahead.

While climbing, monitor the T's and P's, particularly the CHT.  The redline is 265', the flight manual maximum for towing is 260, but a CHT in excess of 240 is an indication of a problem.

If the CHT becomes excessive do not  throttle back - this is more likely to worsen the situation.  Instead, increase speed by at least 10mph, check mixture fully rich and carb. heat cold.  If you are at sufficient height and the CHT is in excess of 250 or is rising rapidly, wave the glider off.  Be particularly careful not to overcool the engine after glider release.

If the oil temperature is high it is normally indicative either of an indication fault or a major problem.  In this case throttling back will normally help; at a safe position wave the glider off and return to the field to investigate the problem.

Keep a good lookout and remember gliders have right of way.

In turbulence, or if the glider is out of position concentrate on maintaining a constant attitude, this makes it easier for the glider to get back into the correct position and remain there ,  This is particularly important if the glider is letting the rope go slack - if you raise the nose to prevent the speed from building it will cause the rope to tighten rapidly and may cause the weak link to break.

Towing at low IAS

The flight manual minimum speed for towing is 55mph.  At low speeds in the cub there is a marked tendency for pilot system position error to cause the ASI to under-read, therefore it is acceptable to fly at lower indicated speeds than this.  Ask a check pilot for specific speeds.

When towing at low speeds (<60 mph) set one stage of flap, this reduces the attitude and aids cooling airflow in addition to improving forward visibility.  Closely monitor the CHT, if it shows signs of becoming excessive take early action to prevent it doing so by accelerating.

Descent

When the glider releases, check that it really has gone and immediately lower the nose whilst pulling full flap and reducing power to 2100rpm.  Accelerate to 80mph, taking care not to exceed flap limit speed of 85mph.  There is a very strong nose up trim change with the selection of flap so you will need to push quite hard in order to prevent the aircraft from climbing,  it is very important that the tug does not climb after the glider has released.  It is not important which way you turn, if at all.  Make a mental note of the tow height and the CHT so you can monitor the rate of cooling.

After glider release: adopt a descent attitude, throttle back to 2150rpm and select full flap whilst accelerating to 80mph for the descent.  Note the height and CHT.  The prohibited band applies to Cubs fitted with A1A type engines and Sensenich propellers, (ie ours).  Operation within this band sets up a mode of vibration which causes the propeller to break.

Having established the descent, plan a route back towards the airfield whilst maintaining your lookout and monitoring the CHT.  The idea is to gradually reduce power during the descent in order to carry out a glide approach, the method is as follows:

During the descent gradually reduce power to 2000rpm then 1800rpm, then 1600rpm, etc.  Then idle for glide approach to land.

Carb. heat may be used as you see fit.  Bear in mind that carb. icing is related more to the humidity of the air than the temperature, and is possible at temperatures of 30'C.  If the engine runs roughly or power is reducing select carb. heat; if you wait until the engine has been stopped by carb. icing the carb. heat will have no effect.

The descent path should be clear of other aircraft, avoiding areas of lift, avoiding noise abatement areas and the shortest track distance back to the field which allows you to carry out a glide approach having properly cooed the engine.  If you fly in lift you will find it impossible to descend until you make the reduction to 1800rpm.  Monitor the VSI.

During the descent it will be necessary to manoeuvre in order to keep a look-out.  The best method is to periodically roll the aircraft, looking both above and below the wing.  When turning make the turn steep enough to see into the turn through the roof glazing but take care not to let the speed build above flap limit speed (this also has the effect of increasing the RPM into the red bank).  Although the flight manual gives a max. of 2g with the flaps down, the limit set at Booker is 1.5g.  The limit is lowered to take into account of the huge number of cycles our tugs perform and the cumulative nature of fatigue.  Take care not to exceed this limit, since excessive g causes failure of the inboard wing ribs and this rapidly leads to irreversible spar damage.

If you are getting low as you approach the airfield it is more fuel efficient to retract the flaps rather than apply extra power, ie there is no point having extra power to counter the drag from the flaps when you have the option of retracting the flaps.

Circuit and approach

Enter the circuit above the normal glider circuit, ideally starting from about 1500.  By flying above the glider circuit you get a good view of conflicting glider traffic, but dont forget that gliders may be approaching from any direction; a good lookout is critical in the circuit.

Think ahead  there is no point in carrying out an expeditious glide circuit if you have to go around because the landing area is block.  If there is likely to be a bottleneck ahead slow down early and you may avoid having to put power on to wide the circuit.  Before you get experienced going around will be necessary from time to time however, to the experienced tug pilot it is usually the result of poor awareness and planning.

In an ideal circuit you will make the final power reduction to idle power at some point along the base let and be in a position to carry out a glide approach.  Prior to the final turn, have a very good look around for gliders on a long final approach or approaching from an odd direction.  Make the final turn in such a position that you do not conflict with the extended centreline of the power runway, and monitor your airspeed during the final turn.  You will have reduced speed just prior to the final turn and although the Cub is extremely docile it will spin with the flaps lowered, and it is obviously easy to let the speed drop during the final turn when concentrating on clearing the hedge, possibly in a wind-gradient and probably out of trim.

When you are more experienced you will find that it is possible to fly your circuit inside the glider circuit, which sometimes makes it easier to fit in with other traffic.  It is necessary to be able to maintain a very high standard of handling and judgement in order to do this without conflicting with other traffic or noise sensitive areas, so wait until you have done plenty of towing before you attempt this.

After turning finals check your feet are off the brakes and carb. heat cold.  The final approach should be conducted such that there is no chance of the rope catching the hedge.  Don't forget that the rope is well behind and below the tug, and by the time the end of the rope is passing the hedge the tug will be much lower.  If at any stage of the approach it looks as though there is the possibility that the rope will catch the hedge take immediate action to recover the situation; add plenty of power to arrest the rate of descent and do it sooner rather than later.  Most of the rope strikes at Booker have been caused by people not wishing to make it obvious their approach wasnt perfectly judged - it is considerably more embarrassing to carry out a succession of marginal glide approaches culminating in a rope strike than to be seen to add power on finals.

When you first start flying the Cub use an approach speed of 60mph.  As you get used to the aeroplane you will find that you can reduce this by quite a lot  you should aim for a holding-off period after rounding out of two or three seconds rather than the eight or nine which results from too high an approach speed.

It is most important that you hold off fully in the Cub.  The undamped bungee suspension is very unforgiving and if you fly the aircraft on it will bounce spectacularly; particularly so now the field is not as smooth as it was.  Even after a fully held-off landing the cub will often bounce slightly as it traverses bumps in the ground, in either case the method of dealing a bounce is the same as any other type, ie keep the stick fully back and do not attempt to correct the bounce with a forward movement of the stick.  The Cub always feels as though it is reaching a height of several feet when it bounces; it is rarely anything like as bad as it feels, and you will only need to add power in exceptional circumstances - when it would probably be better to give up and go around.

After touchdown keep the stick hard back, leave the flaps alone until you turn off after landing.  There is no need to brake heavily in a Cub, in fact the ground roll is quite short enough without using the brakes at all.  Once speed has reduced to walking pace turn the aircraft through 90 degrees to ensure the approach is clear before you taxi to the launch point.

When you taxi back to fetch the next glider do not taxi straight up to its nose, but position the tug about 100 ft in front of it and rather than stop facing at 90 degrees to the glider, turn so you are at an angle of 30 degrees or so to the take-off run.  These steps will keep you well away from people at the launch point and will reduce the amount of time it takes to take up slack.  It should also ensure that you do not blow any canopies shut with the propwash.

Sideslipping

The Cub sideslips very well, and this is a useful manoeuvre on hot, calm days when the landing tends to be deeper into the field.  Unlike the pot type pilot system of a glider, there is very little ASI error caused by yawing a Cub, so you have a reliable indication of airspeed while slipping.

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Do not leave it tool late to remove the drift - you should aim to have the aircraft straight before you start the flare.  If the descent rate seems high in the last twenty feet or so remove the sideslip.

If you are high when you turn finals a slipping turn is very effective in removing height.  It is essential that you use top rudder (slip) rather than bottom rudder (skid).  The latter invites a sever wing drop or spin if the speed becomes too low.  If you are going to get close to the extended centreline of the power runway during the final turn bear in mind that the rate of turn is considerably reduced in a slipping turn.

Going around

If you abandon the approach and go-around, smoothly apply full power and raise the nose enough to maintain your approach speed.  Once you are climbing, slowly retract the flaps (there will be a strong nose down trim change as you do so - be ready to apply a lot of back pressure until you can re-trim).  Climb straight ahead until you are well clear of any possible traffic approaching in an odd direction, then rejoin the normal circuit.

Remember the rope - depending on what situation you are in, you may need to drop it.  (ie climbing overhead a glider at low level).

Crosswinds

As with taking off, the cub is straightforward to deal with in a crosswind.  If the tailwheel springs are slack it can be more difficult to keep straight, you will have noticed whether or not this is the case when taxiing.  (If the rudder does not steer the a/c very well the springs are probably slack.)

Take care not to apply the brakes inadvertently when using the rudder.  If possible land into wind, for example you may choose to land on 35 when we are operating from 25 in a Northerly.

At the end of the landing run exercise care when turning off if the turn is downwind - do it slowly without using the brakes.  It may be best to make a 270' turn which is initially into wind.

Shutdown

(Does the aircraft need refuelling?! - if in doubt fill it up.)

Park the aeroplane facing into wind in a sensible area, the normal parking areas are shown in the runway specific sections.  If you have only just landed allow the engine to run at 1000rpm for a short time in order to let temperatures stabilise, and ensure the radio is switched off before shutting down.  Perform a mag. drop check to ensure the mags will not remain live, then set the mixture to ICO.  After the engine has stopped shut down all the electrics, ensure the mags are off and then push the mixture back in, this prevents the mixture control from being kicked when getting in or out.

If the canopy is dirty, clean it now, before the aeroplane is needed again.  Likewise, if the airframe is dirty take it to the hose and clean it during the break in operations.  This is especially helpful in Summer when flying goes on until dark and the tugs dont get washed in the evening.

If the tanks are less than 2/3s full, fill them.  The next time the tug is started it may be needed to carry out a lot of towing.  If the tanks are filled in quiet periods it means the tugs dont have to break off from towing while there is a queue of gliders.

After parking the tug lay the rope out behind it in a series of 'S's' such that it does not encroach on too much space around the tug, this should prevent it being picked up by a car or another tug.

If it is breezy fit the control lock.

Non-normal operations

Induction fire:

If you suffer a fire in the air filter on start the actions are:

            * MIXTURE                    -            CUT-OFF

            * THROTTLE                 -            FULLY OPEN

            * STARTER                   -            KEEP CRANKING

Crank the engine until the fire is extinguished.  The actions described above should draw the fire into the induction manifold and it should extinguish once the fuel has burnt.  If there are still signs of fire after 20 seconds abandon the aircraft and use the fire extinguisher.

Induction fires are invariably caused by overpriming.

Engine fire in flight

If smoke and/or flames are seen emerging from the cowls the priority is to shut the fuel supply off.  The drill is:

            * THROTTLE                 -            CLOSE

            * MIXTURE                    -            CUT-OFF

            * FUEL SELECTOR            -            OFF

            * CABIN HEAT            -            OFF

Whether or not the fire extinguishes you need to land as soon as possible.  Declare a Mayday (if time allows), pick a field and carry out a descent at high speed (100-120mph).  Slow down to a more reasonable speed in time to carry out a circuit and approach.  Before landing switch off remaining electrics, in particular the strobe.

Rough running

If the engine begins to rough run, check:

            * CARB HEAT               -            ON

            * MAGS              -            CHECK BOTH, TRY EACH IN TURN

            * MIXTURE                    -            FULLY RICH

            * FUEL                                    -            CHANGE TANKS

Check RPM and Ts and Ps.  If they are all normal, and the roughness is not too severe, continue the tow, aiming to release the glider near the airfield.  Carry out a descent such that you can always glide in.  Try reducing the rpm.  If the engine parameters are abnormal or the roughness is sever discontinue the tow and return to the airfield.  If the roughness is sever enough to be concerned about the integrity of the airframe or propeller, shut the engine down.

Before and after start

Check the aircraft is not stood on gravel or other loose surface.  The best method to ensure you are set, if you dont use one of the popular mnemonics, is to work from left to right of the cockpit, ie:

Fuel selector  to desired tank; throttle  set; carb. heat  cold; mixture  rich; radio  off; master  on; alternator  off; nav. & strobe lights - off

For start hold the stick between your knees and put your heels on the brakes, rather than rely on the parking brakes.

Priming  This aeroplane does not have a primer, it can be primed using the carburettor accelerator pump.  From cold give the throttle 4 pumps and return the throttle to the starting position (open ½).  From warm (CHT 50 or greater) give no more than one pump.  Allow a few seconds for fuel vapour to migrate through the induction manifold.

Take care.  If you over prime using the throttle you will cause fuel to drain through the carb. into the air filter, this carries a high risk of fire when starting.

Ensure the area is clear then turn the starter.  The engine should fire almost immediately, if not then stop cranking the starter after 4-6 blades have passed by.  If the engine has not started it is normally through over priming rather than under priming -don' start pumping the throttle willy-nilly.  On the next attempt try slowly opening the throttle while cranking, but do not open the throttle more than two-thirds and be prepared to close the throttle as the engine fires.  If you still have not success after a second attempt check the fuel is switched on, there is fuel in the selected tank and that the mixture is rich.  If so, and a third attempt fails, it may be due to a failure of the impulse coupling on the magneto  ask and engineer or staff member to check.

After start if the aeroplane rolls forward do not apply the brakes, close the throttle first then gently brake to a halt.  Check rising oil pressure, switch on the alternator and check a positive reading on the ammeter, then switch on the radio.  Do not taxi or exceed 1200rpm until the CHT has reached 50.

Taxiing

Remember to keep the stick fully aft when you are taxiing with a head wind component.  Unless it is very windy the primary reason for a cub standing on its nose when taxiing downwind is more likely to be excessive taxi speed or harsh braking than just having the stick back.  This is not to say, however, that you should taxi without paying due regard to stick position, but that taxiing at the correct pace will cover a multitude of sins.  Accordingly, when taxiing downwind in addition to keeping the stick forward keep the speed down, avoid soft ground/long grass and avoid unnecessary braking.

Although the forward visibility from the Cub is good, it is still necessary to weave the nose from side to side occasionally to check the path is clear.  When turning the Cub use full rudder deflection before starting to use the brakes, it is normally quite enough to turn the machine.  Many people get into the habit of initiating the turn with brake and not bothering to try the rudder first, not only does this cause premature wear of the brakes but it also increases the chances of tipping the machine up.

Keep the taxi speed down to no more than that of a brisk walking pace.

Engine failure in flight

If the engine failure is accompanied by mechanical noises, oil from the cowls, an indication of nil oil pressure/excessive oil temp or CHT, or a rapid seizure of the engine you may assume an irreversible mechanical failure.

If none of the above symptoms are present and the engine simply runs down and windmills it is probably a case of either fuel starvation or mag. failure.  In this case 

            * ATTITUDE                   -            NOSE DOWN TO ACHIEVE GLIDE

            * THROTTLE                 -            CHECK FULLY OPEN

            * MIXTURE                    -            FULLY RICH

            * FUEL SELECTOR            -            CHANGE TANKS

            * CARB HEAT               -            ON

            * MAGS              -            CHECK BOTH TRY EACH IN TURN

If no response, or in the case of obvious mechanical failure as described, carry out checks 

            * GLIDE             -            80 MPH

            * THROTTLE                 -            CLOSE

            * MIXTURE                    -            CUT-OFF

            * FUEL                                    -            OFF

            * MAGS              -            OFF

Pick a suitable landing area, declare a Mayday.  The glide angle is improved by stopping the propeller from rotating, it will be necessary to reduce speed for a short time to achieve this.  Before landing switch off remaining electrics, in particular the strobe.

Rejected take-off

If you decide to abandon the take-off, the convention is that the tug should turn left and the glider turns right, use common sense to determine whether this is the best way to handle the situation.  The main thing is to refrain from heavy braking in order to give the glider the best chance of avoiding you.

Carb icing

If you suspect carb. icing remember that after selecting carb heat the engine will probably run more roughly for a short time while it ingests the melted ice.  It should regain normal running in less than 30 secs.  Carb icing is most often encountered when taxiing over wet grass in this a/c.  It is best to use carb heat in these conditions, despite common advice to the contrary.