19.1 Almost Ready to Fly Models
(a) ARTFs are very popular and usually offer very good value for money but you should be aware that some airframes you may buy could have manufacturing or design defects. Close scrutiny of even a pre-covered airframe may pay big dividends if you can prevent a future failure.
(b) All visible glue joints within the fuselage should be checked, especially the engine bulkhead, fuselage bulkheads, wing mounting plates or wing dowels, undercarriage mountings and servo mountings. If you have any concerns then the reinforcement of many of these joints using scrap balsa stripwood will significantly increase the strength and durability of the airframe for very little weight increase.
(c) Take particular care when gluing wing panels together. Follow the manufacturers instructions and when adding such things as dihedral braces make sure that the whole joint is wetted out by the glue.
(d) Check pre-fitted pushrods, snakes and clevises for suitability. Most will be fine but some have been seen that were inadequate for the job expected of them, either being to thin or too weak. The rule of thumb should be ‘if I was fitting this, would I fit this’.
(e) Always check flying surfaces for warps – don’t assume that a wing will be straight because it was built for you. Minor warps can sometimes be removed by gently heating the covering, twisting the surface in opposition to the warp and holding until cool. Major warps are a reason for returning to where you bought the model.
(f) The ONLY acceptable (and beneficial) warp on an R/C model is matched wash-out. That is, looking from the rear the trailing edge at each wingtip is twisted upwards a little compared to the root of the wing. If this is present then it MUST be even on both wings or it’s just another warp.
(g) On i/c powered models, have a good look at the fuel proofing around the engine and fuel tank bay. If you are looking towards something more than a throw away airframe then an extra coat of fuel proofer in and around the nose will certainly be worth while.
(h) Extra care should be taken with second hand airframes as you will usually have no idea of their history. Close scrutiny of the whole airframe and any necessary repairs and strengthening are essential before you fly the model.
19.2 Ultralight R/C Models
(a) There are numerous electric powered ‘Slow Fly’ or ‘Park Fly’ models on the market that may be classed as ‘Ultralight’ and this is encouraging the flying of R/C models in places that have never seen model flying or which have been out of bounds to flying for many years.
(b) Although virtually all of these models are lightly loaded, great care must be taken when flying them as you can be led into situations that you would not face on a club field.
(c) Read the Safety Codes contained in this handbook carefully as virtually all of them still apply to this type of flying, especially those concerned directly with radio control.
(d) Be very careful to avoid flying near to existing model flying sites if you are using 35 MHz equipment. Find out where models are being flown in your area and check on a local map that your chosen flying area is far enough away to be safe.
(e) Take special care to avoid putting members of the public at risk. Your activities, with quiet slow models will almost certainly draw the attention of passers by – they could appear from anywhere.
(f) Park flyers have the possibility of introducing model flying to great numbers of the general public who may never have seen our sport close up before. Your behaviour and safety awareness could result in there being many new model flyers in the future.
(g) Be aware that some Local Authorities have by-laws banning the flying of powered models from their open spaces. Check carefully to avoid trouble.
(h) You may, however, find yourself in a situation where you are flying sensibly, safely and not causing a nuisance and are approached by someone who says he represents the Local Authority or some other official body and who tells you that you are not allowed to fly. You are within your legal rights to ask to see a copy of the by-law that bans flying on the area you are using.
(a) It cannot be stressed enough that a model helicopter must have a higher degree of safety built into it than perhaps any other flying model. Because the BMFA feels so strongly about this the following comprehensive guide is set out below. This is in addition to the regular R/C safety code.
It is VITAL that you never fly or run up your helicopter in or near the pits area or near spectators.
Rotor blades must always be carefully balanced and you should always remember that vibration in helicopters can be very destructive.
(b) Electric Model Setup
An electric model can start up with full power and torque immediately. Therefore when setting up an electric model it is imperative that the electric motor is disengaged from the transmission. This can be done by disconnecting the motor, disconnecting the pinion or disengaging the gears. This procedure should also be followed when any changes are made to the ESC.
(c) For I/C Powered Helicopters
When starting the model in the pits, hold the rotor head firmly. When the engine is running carry the model a sensible distance from other people before running up or flying. Do not release the rotor of the model until you are sure that it is safe to do so and NEVER FORGET the amount of energy there is in a spinning rotor.
Never hold the model overhead to run up the engine or run the engine with no rotor blades fitted.
(d) For Electric Powered Helicopters
Electric helicopters should be carried out from the pits area with the flight battery disconnected and it should only be connected in a safe area. The model MUST be considered to be live as soon as this is done and great care is needed during this procedure.
(e) A MODEL HELICOPTER MUST NEVER, UNDER ANY CIRCUMSTANCES, BE FLOWN OR RUN UP:
(i) IN OR NEAR the pits area or close to any spectators.
(ii) Directly towards the pits area or any spectators.
(iii) With knife sharp leading edges on main or tail rotors.
(iv) With damaged or out of balance rotor blades. Note that blades, especially wooden ones, should be reinforced at the root with hardwood, glass-fibre or some other suitable material.
(vi) With radio equipment unproofed against shock and vibration.
(vi) In the presence of spectators or at a competition or fly-in until properly tested and proved airworthy.
(vii) Until thorough maintenance checks are carried out as set out in (A) and (B) below.
(viii) Note that all helicopters weighing more than 7 kg without fuel are subject to the ANO regulations concerning models over this weight and must comply with those conditions when flown. In particular, you must have permission to fly from the appropriate Air Traffic Control Unit if you are flying in controlled airspace. If you don’t have such permission, your flight is illegal.
(f) Checks Before Daily Flying Session
(i) Check all ball links for slop and change as necessary.
(ii) Check that all rotor blades have no damage apart, perhaps from minor tip damage.
(iii) Check for loose or missing nuts and bolts.
(iv) Check that there is no backlash in the drive system apart from gear backlash which should not be excessive.
(v) Check that servos are secure and free from oil.
(vi) Check that the fuel tank and all piping is secure.
(vii) Check that the receiver aerial is secure and in good condition with no chafing or damage.
(viii) A range check involving a 360 degree rotation of the model to check for any receiver aerial shielding. This is especially important on 2.4Ghz systems where the aerials are easily shielded by carbon and metal
(g) Checks Before Each Flight
(i) If a helicopter suffers damage or a heavy landing, recheck all of (A) above.
(ii) Check all controls before starting especially for binding of links or slowing of servos.
(iii) Re-check controls at high rotor rpm just before lift-off.
(iv) Check for vibration and eliminate before flight.
(v) Check main rotor blades for true tracking in hovering flight.
(vi) Check that the receiver aerial cannot become entangled with any moving or rotating part.
(vii) Double check that all switches are in their correct positions before EVERY flight.
(viii) Check that the gyro systems are responding in the correct direction (tail rotor and swashplate for flybarless models).
(ix) Check receiver and transmitter batteries have sufficient capacity for the flight plus a safety margin.
For more information on the Association of Helicopter Aerosports, contact the BMFA’s Leicester office.
(h) Helicopter Rotor Blade Safety
Rotor blade failures have five basic causes:
(i) Most design and manufacturing faults seen are centred around the rotor fixing hole. Typical faults are the hole being drilled on the junction between two wood laminations and incorrect wood selection leading to the hole being drilled in a soft lamination.
Blades with this type of fault should not be used. Even root reinforcement may not stop a failure.
(ii) Incorrect user assembly is commonly found in root reinforcements and in blades which have to have tip weight of some description added. In all cases you should take the greatest care that any components added are fitted correctly and with suitable adhesive. Incorrect glue joints and badly applied reinforcing components are probably the biggest single cause of blade failure so it is very important that you take the greatest care with any assembly work you have to carry out.
(iii) Do not be tempted to undertake any repairs to damaged rotor blades.
(iv) Any ground strike or boom strike will almost certainly cause damage to rotor blades and in many cases this may go unnoticed under the blade covering. If in doubt, have no hesitation in stripping off the covering for inspection. Re-covering and re-balancing the blades is a small price to pay for peace of mind.
(v) Ageing of glue joints in wooden structures is common and the high stresses inherent in rotor blade operation mean that you should keep a close eye open for delamination in wooden blades. A problem sometimes seen in composite blades is heat damage. Blades left in a car on a hot day can suffer from softening of the resin and this, combined with an expansion of the foam filler, can make the blades unsafe. To summarise, keep a close eye on your rotor blades and do not hesitate to discard them if you are at all concerned over their condition.
(i) Metal Rotor Blades
The BMFA has negotiated a dispensation from the CAA concerning the use of metal rotor blades. These may now be used under certain restrictions on non-aerobatic models over 7 kg and strictly subject to a written permission from the CAA.
The CAA will only grant such dispensation for a model following an application from the BMFA. All applications will be subject to scrutiny of blade manufacturer, material specifications, method of manufacture etc and there will be ongoing monitoring by both the AHA and the BMFA.
Advances in modern electronics has lead to the development of a wide variety of multi-rotor aircraft of various shapes and sizes, with varying levels of autonomous abilities. However, it must be stressed that a pilot should not simply rely entirely on electronic autonomy alone for flight. If using autonomous modes, the pilot MUST be able to take back manual control of the aircraft at any time. It is VITAL that the pilot of any multi-rotor is aware of the abilities of their aircraft and knows what flight functions are available, how they affect the aircraft and how to operate them. The pilot MUST also be able to identify what mode the aircraft is in at any given time. This may be done by a visual indicator on the aircraft such as a beacon LED or via the transmitter switch positions or screen. Please remember that multi-rotors may not be flown in excess of 400ft above ground level at the launch point.
(a) Electric multirotors should be carried out from the pits area with the flight battery disconnected and it should only be connected in a safe area. The model MUST be considered to be live as soon as the battery is connected. As the position of multiple propellers is generally facing straight up at the pilot during arming, great care is needed during this procedure. It is worth remembering that electric models have the potential to go to full power the moment they are armed.
(b) Propeller orientation and motor direction is VITAL for multirotors and special care should be taken to ensure that everything is correct prior to attempting any flight. While adjusting the settings on a multirotor or during programming, propellers MUST be removed to prevent any accidental losses of control.
(c) Unlike fixed wing aircraft or helicopters that can glide or auto rotate after a power failure, a multi-rotor that loses a propeller, or suffers motor or esc failure in flight can become dramatically unstable with a total loss of control. Aircraft with six or more propellers may have an increased level of redundancy against total loss failures.
(d) Compared to most other model aircraft, where the electronics are enclosed within an airframe, multi-rotors tend to have exposed components. Therefore care should be taken to ensure they are kept free of debris and that all wiring is securely routed and not in a position to be damaged by or entangled with any moving parts.
(e) Multi-rotors require 3-axis gyros for stabilisation to enable flight and these are sensitive to vibration, so care should be taken to ensure all propellers are balanced and that correct anti-vibration materials are used where necessary.
(f) If you are intending to use your multi-rotor for FPV flying, then the relevant section of this guidebook MUST also be given careful review. Importantly, attention should be paid to the frequency that the pilot intends to use for their FPV equipment. The pilot must comply with any local video frequency control system, where applicable. In addition they should understand that switching their FPV equipment on while other pilots are flying FPV could result in a pilot losing video signal, so they should check that the frequency/channel they intend to use is clear before switching on.
(g) If you are intending to use your multi-rotor to carry a camera, then it is VITAL to understand the additional CAA regulations from article 95 (formerly article 167) of the Air Navigation Order.
(h) Many modern cameras have wireless connection options such as WIFI or Bluetooth, this may need to be switched off to avoid potential interference with the radio control signal.
(i) If using GPS on a multi-rotor it is VITAL that the system be given time to accurately locate the aircraft’s position before attempting to fly, taking off before a full GPS lock is achieved may result in an uncontrolled fly away. Where appropriate, a pilot MUST also understand when and how to calibrate the aircraft’s compass in line with the manufacturer’s guidelines in order to ensure accurate control of the aircraft is maintained.
(j) Intelligent Failsafes – In order to use intelligent fail safe modes, the aircraft will need, as a minimum, to be fitted with a control board capable of self levelling, with the more advanced options also requiring GPS to be fitted. If the aircraft is not capable of intelligent fail-safe, then the fail-safe mode should be set to reduce throttle idle/off as a minimum.
(i) Loiter – In this mode the aircraft will attempt to stay in a fixed position and maintain altitude upon loss of radio signal. It is intended that the pilot will then have the chance to get closer to the aircraft to in order to regain control. It is not advisable to use this mode without GPS, as the aircraft can drift away with the wind.
(ii) Controlled descent – Aircraft that can self-level may have the option to set the throttle to a soft point, such as to induce a smooth controlled descent on loss of signal.
(iii) Return to home – Aircraft capable of storing a take off point while using GPS may be set to return to their take off point and land autonomously upon loss of signal. It is important to note that in this mode the aircraft will typically fly a straight line from its current location to the take off point, so careful consideration should be given when flying near obstacles such as trees or buildings, which potentially may obstruct the return path. It is often possible to set the aircraft to climb to a ‘safe’ height, before returning. If ‘return to home’ is to be used, careful consideration should also be given to the location for the take off point, as the GPS modules may only be as accurate as 5 -10m from the original take off point.
- Checks before daily flying session:
(i) Check the propellers for damage and correct orientation, as well as ensuring that they are securely fixed to the motors or blade grips. This check should also include a careful examination of the propeller for any signs of stress, which is typically indicated by a ‘whitening’ of the plastic. This often occurs close to the hub and propellers showing any such damage should be discarded.
(ii) Check for loose or missing nuts and bolts
(iii) Check the motors for any signs of damage or debris
(iv) Check the airframe for any damage and ensure all components are secure.
(v) Check that the rotor arms are secure, especially in the case of collapsible/folding airframes.
(vi) Check all wiring is secure and routed safely to avoid snagging on any moving components.
(vii) Check that any gyro or flight controller is secure and that all aerials (including GPS) are secure and orientated correctly.
(viii) Check that the battery is secure and capable of supplying enough power for the duration of any autonomous flight stages planned.
(ix) Check that all aerials are securely attached, free from any damage or chafing and are orientated correctly.
(x) Ensure all transmitter switches are in the correct position for flight prior to initial arming.
(xi) Confirm the integrity/reliability of any FPV link, if appropriate.
(xii) If appropriate, check there is no backlash in the drive system apart from gear backlash, which should not be excessive.
(l) Checks before and after each flight.
(i) If the multi-rotor suffers damage or a heavy landing, recheck all of (k) above.
(ii) Check all controls before starting especially for binding of links or slowing of servos.
(iii) Check for vibration and eliminate before flight.
(iv) Check that all wiring is secure and cannot become entangled with any moving or rotating part, especially the receiver aerial.
(v) Before starting insure all switches are in the correct position for takeoff and the correct flight mode selected before EVERY flight.
(vi) If planning to use GPS at any point during the flight, confirm that you have a suitable lock before taking off. (Method for this will vary from unit to unit, but is typically by way of a flashing indication LED)
(vii) Check receiver and transmitter batteries have sufficient capacity for the flight plus a safety margin before the flight.
(m) Flight Modes
(i) Manual – The simplest of modes, the aircraft is still stabilised by the gyros, but only to enable flight. The aircraft will not self-level or fly autonomously in any way and can be rolled inverted.
(ii) Self levelling – More a feature than a full mode and can be used in conjunction with manual mode. The aircraft may still be manually inverted by rolling for example, however releasing the sticks will result in the aircraft automatically returning to an upright level position.
(iii) Atti – Sometimes referred to as ‘stabilised’. In this mode the aircraft cannot be rolled inverted, instead a full push and hold of the aileron or elevator stick will only result in the craft tilting to a set angle of approximately 30 degrees. Releasing the sticks to centre will see the aircraft self level to horizontal, however it will drift with the wind. This is often mistaken for manual mode, which it is not.
(iv) GPS – Sometimes called ‘position hold’. In this mode a GPS module is connected to the main controller and allows for additional autonomous aircraft control functions, such as ‘way point programming’ or ‘return to home’. Typically an aircraft flying in GPS mode will behave the same as one in ‘Atti mode’, however when the sticks are released the aircraft will no longer drift with the wind, but attempt to stay in one location.
(v) Geo-Fencing – Appearing in more and more controllers, geo-fencing is designed to prevent an aircraft flying in restricted areas, such as near a major airport. Pilots may find their aircraft either won’t take off at all, or will stop in the air as if it has reached an invisible wall.
(vi) IOC – ‘Intelligent orientation control’ (IOC) has a few different modes, such as ‘point of interest’ or ‘compass heading’. In these modes the basic controls of the aircraft can be changed at the flick of a switch to accomplish specific tasks, such as flying a perfect circle around a fixed point. A pilot should fully understand the different modes available via their chosen control board, how each mode will effect the controls of their craft and how to deactivate them quickly in case of an emergency. On some aircraft these modes cannot be used if the aircraft is within a set distance of the take off location.
19.5 Silent Flight – General
R/C silent flight models generally operate with low wing loading and low drag. Consequently, landing approaches may cover a lot of ground at low level. Check your landing approach path before you launch. Check again before you enter the landing circuit. Remember that people will not hear your model coming so take no chances.
When strong thermal or slope lift is encountered, beware of flying too high. At altitude, lift is often very strong and turbulent. Models fitted with spoilers or ‘crow’ brakes should have little trouble leaving such lift but do not try to dive out of strong lift if these are not fitted. Fly away from the lift and try to find sinking air. In an emergency, full up elevator and full rudder may give the safest descent.
Design considerations mean that many silent flight models are built light. Be sure that the design, construction and materials are adequate for the job.
Silent flight models are often flown at considerable distances from their pilots, therefore make sure that the failsafe is working properly before each session and a high visibility colour scheme can be a great safety factor. Be extra careful when flying at distance and/or height and beware of flying across the sun.
Remember also that both thermal and slope soaring flights can last for exceptionally long times. It is imperative that you ensure that both your receiver and transmitter batteries have sufficient capacity for the flight plus a safety margin.
19.6 Thermal Soaring
(a) When using a towline, bungee or power winch, locate yourself and your equipment well away from car parking areas and ensure that there is no possibility of launching lines falling on buildings, persons, roads or where they might distress wild, domestic or farm animals. Stay well clear of overhead power lines.
(b) Launch stresses can be severe. Be sure that wing joiners/attachments are strong enough to cope with the high loads imposed. The use of a ‘weak link’ of known breaking strain in launch lines is a measure that may safeguard model wing structures and should be considered.
(c) Bungee (Hi-Start) anchorages must be very secure. Use a screw-in type of fixing and do NOT peg the end down with devices such as old screwdrivers. Consider using guy lines on the stake for extra security and always do so if the stake is in soft earth.
(d) Electric winches should have an obvious, clearly marked master on/off switch accessible to anyone in an emergency. Shrouded plugs and sockets should always be used and the motor switching should be indirect, i.e. by relay.
(e) Turn-round pulleys must be very securely staked and braced with guy lines. Remember that the load at the pulley is double that on the line and pulley carrier geometry may produce even more load at the stakes.
(f) Whether you use winch, bungee or hand tow, make sure that spectators cannot be endangered if the model veers to one side on launch.
(g) Soaring pilots may tend not to stand together when flying. If this happens on your site then avoid overflying other transmitters at any distance from your own. It is your model that will suffer from interference and it could easily be damaged.
(h) Aerotowing requires careful handling of both the tug and the glider. Remember that to fly any model over 7 kg above 400 feet requires a permission. Your local club may already have such a permission as they may have taken advantage of the CAA scheme which allows site permission to be granted, but check before you fly. In controlled airspace contact the appropriate Air Traffic Control Organisation. Never tow to any height without making sure that you are legal.
19.7 Slope Soaring
(a) Slope sites are often used by many people other than model flyers. Always ensure that flying is permitted on your selected site. Note that an increasing number of slope sites are being used on an exclusive basis by clubs who may be paying considerable fees for the privilege. Keep away from paths used by ramblers and climbers and make sure that you do not frighten or disturb any animals.
(b) If the site is regularly used or overflown by full size gliders or hang gliders, then you should attempt to contact them and arrange shared use of airspace and land. We all have airsports participation in common and discussion is better than confrontation. Advice is available from the Association’s Leicester office along with details of an agreed code of practice for shared sites.
(c) If a frequency control system is operating on the site, you MUST use it. If no control is operating you must not switch on your radio until you have checked that it is safe to do so.
(d) To avoid possible interference, pilots should attempt to keep reasonably close together. If this is not possible (i.e. if a pilot does a cross-country flight) then everyone on the slope should be made aware of the fact.
(e) Be aware of the turbulence immediately behind the apex of the slope. With high wind conditions and/or steep slopes this can be severe. If necessary, land either slightly down-slope or well back in the lee of the hill.
(f) Specific guidelines for the flying of slope combat, covering models, flying sites and legal requirements, are available from the BMFA Leicester office. These contain important advice and information for the slope combat flyer and should be considered essential reading if you fly this type of model. Be aware, though, that this is a legal activity if carried out on suitable sites and with care taken to avoid the endangering of other people on the slope.
(a) The first and most important principle of electric flight ground safety is to understand that the instant you start to plug in the flight battery, the model you are holding may transform itself from a dead airframe into one with its motor running at full revs and all controls moving. No matter how good your other safety checks, you must be prepared for this to happen every single time you start to connect the flight battery.
(b) Since plugging the flight battery in is nearly always a two handed job you must give serious thought to how your model will be restrained BEFORE it does something you don’t expect. When plugging in the flight battery, positive restraint, either by a helper holding the model or by some other method, and staying completely clear of the propeller must always be part of your regular routine.
(c) Electric motors have very different power and torque characteristics to normal i/c model engines. You must take very great care when setting up their control systems and handling them as an accident, such as the propeller hitting your hand, which would stall a glow engine might just make an electric motor turn harder.
(d) Developing technology has made it much more acceptable to use battery eliminator systems (BECs) to save the weight of a receiver battery, especially in lightweight installations using two or three small servos. You should not use BEC in an installation where servo battery drain may be high or prolonged, for instance with four or more servos or with standard servos in a thermalling electric glider. Also, many older BEC systems are not as reliable as the modern equipment and in all these cases the use of a separate battery is still considered to be the safer choice. The decision is yours but if you have any doubts then you should use a separate battery. It should be noted that the use of BECs will not invalidate your insurance.
(e) Always check that motor operation does not interfere with the R/C equipment in the model. Range checks with the motor off and with it on will highlight any problems. Suppression of a brushed motor is a simple task and you should seek the advice of an experienced flyer on the subject.
(f) All connectors and cables should be robust enough to carry safely the current for the motor/s used. Wiring used for small motors will reduce the power of larger motors and may run dangerously hot. If you change a motor, check that the wiring is adequate for the new one.
(g) Batteries:- Ni-Cd or Ni-Mh fast charge cells and larger Li-Po packs can be discharged at very high currents (up to 100 amps and more). Short circuits, faulty wire insulation or loose contacts can result in very considerable heat generation and may cause fires.
(h) The standard two pin polarised connectors supplied with many ‘buggy’ type battery packs are only suitable for small to medium current draw as they can offer significant resistance at times and have been known to overheat badly. There are other specialist connectors, especially the readily available gold plated ‘bullet’ connectors (available in various sizes from 2mm upwards), which are much better as they offer very low resistance and are designed to carry high currents.
(i) Always ensure that flight batteries are securely fixed and that they cannot move in flight.
(j) Many speed controllers have a specific ‘arming’ sequence, which is a pre-programmed sequence of actions that have to be followed before the motor will respond to throttle stick movements. For instance, after switching on the transmitter and receiver and then plugging in the main flight battery, one type of controller requires that you move the throttle stick from low to full throttle and then back to low before the motor is ‘armed’ and ready for flight. You must be fully familiar with the system fitted to your model.
(k) You must pay particular attention to the ‘throttle to low – transmitter on – receiver on’ sequence and be aware that the model you are holding will be ‘live’ as soon as you start to plug in the flight battery, no matter what controller arming sequence you may then have to go through.
(l) The setting of the failsafe to, as a minimum, reduce the engine(s) speed to idle, obviously applies to all electric models too. However, given the ability to re-start the motor(s) at will, it makes sense to have the failsafe cut the motor(s) completely. This will give you the desired ‘minimum power’ situation and will avoid you having to decide on what idle speed you might need to set.
19.9 Control Line
(a) Always use steel lines of sufficient strength for the type of model you are flying. Where possible, stranded lines should be used when flying over grass or when the model is going to be manoeuvred.
(b) If swivels are used between the control handle and the lines they must be of substantial construction. Do not use the thin bent wire type.
(c) Before each flying session and after any heavy landing, the model should be subjected to a pull test of at least 10 times the model’s weight.
(d) Before every flight check the lines and linkages thoroughly. If any damage is found, DO NOT FLY until it has been rectified and re-tested to your satisfaction.
(e) Ensure that there are no spectators near to the circle before you release the model.
(f) Do not fly near ANY overhead cables. Even the low level distribution cables on wooden posts carry lethal voltages which can ‘jump’ many metres to your control lines. KEEP WELL AWAY.
(g) Control lines make good lightning conductors. Do not fly in thundery weather.
(h) Whenever high pulls are expected, use a safety strap connecting the handle to your wrist.
(i) Never release the control handle when the model is flying.
(j) Encourage spectators to stand upwind of the circle.
(k) Always mark a centre spot for your circle, ensuring that adjacent circles are not too close to each other.
(l) Always stay on the centre spot when flying.
(m) If someone strays into the circle whilst you are flying, fly high to avoid them and stay high until the circle has been cleared.
19.10 Free Flight
(a) A model should not normally be launched from an area such that it would overfly houses, major roads, railways or similar hazards in its expected flight pattern.
(b) Always launch models, particularly powered ones, well away from and downwind of any spectators or vehicles.
(c) When a fuse type dethermaliser is used, always use a snuffer tube.
(d) Check flying surface alignment and, if your model employs them, the dethermaliser and any automatic systems fitted thoroughly before launching.
(e) All glider launches should be undertaken with the towline detached from the hand winch.
(f) The use of radio dethermalisers i(RDT) in free flight models is positively encouraged. Having control of when the model is DT’d provides the benefits of bringing the model down away from trees, buildings and other hazards. It also helps to keep the model within the confines of the flying site.
19.11 Indoor Free flight
(a) Take care when launching that no one is standing in the flight path of the model.
(b) If your model hangs up at height, take great care when retrieving. If you have to climb to get the model, use ladders and get someone to hold them steady. Do not over-reach, take foolish risks or take on tasks that are beyond your ability.
19.12 Indoor Radio Control
(a) Most of the precautions for outdoor R/C club flying will apply to indoor events.
(b) It is not advisable, except under exceptional circumstances, to have free flight and radio control flying at the same time.
(c) Active transmitter control should be in operation throughout the meeting and at larger events a transmitter pound should be used.
(d) You should take note that some indoor specification receivers may not have the performance of standard receivers and should be prepared to limit the available frequencies to 20 kHz spacing for some sets.
(e) The pits area should usually be situated along the shorter wall next to the door and you should, if possible, use netting to isolate the pits area from the flying. Pilots should stand together in front of the nets.
(f) A ‘duty pilot’ should always be on duty to act a flight marshal. This may not be the same person for the whole event but, whoever it is, they must have the authority to ground any persistently unsafe pilots.
(g) The duty pilot should decide on the number of aircraft to have safely in the air and which direction the circuit to be flown should be.
(h) A written event briefing sheet should be given to all pilots if staggered arrivals make a pilots briefing impractical.
(i) The size of the venue will limit the size of model allowed to fly but as a general rule for a larger hall you might consider a maximum weight of 200 grams and a maximum wing loading of 15 grams per square decimetre (just over 7 ounces and 4.5 ounces per square foot).
19.13 Models Between 7 kg and 20 kg – General (Large Models)
(a) Any model aircraft (that is, either power fixed-wing, glider or helicopter) weighing between 7 kg and 20 kg without fuel is subject to regulation by the Air Navigation Order, over and above Articles 240 and 241. Full details are included in the section ‘Legal Controls over Model Flying.
Pilots of models between 7 and 20 kg should take great care to comply with these regulations as their wilful or negligent breaking could result in their flights being illegal under the terms of the ANO and they may be liable to criminal prosecution.
The address of the CAA is listed at the back of this handbook and you can contact them or download a copy of CAP 658 from the BMFA web site. In addition, BMFA will supply news of all the latest CAA conditions on request. Contact the Leicester office for more details.
One of the most important clauses in the ANO regulations for these larger models is Article 94 (2) which says ‘The person in charge of a small unmanned aircraft may only fly the aircraft if reasonably satisfied that the flight can safely be made.’
This puts a legal requirement on the pilot to consider all aspects of safety before a flight is made. Pilots should take great care not to underestimate the importance of this clause.
(b) Large models may not be flown in any full-size air traffic control zone or special rules zone without the specific permission of the appropriate ATC authority. For information on such zones, contact your nearest airfield or airport air traffic control. They will be able to give you the permission you require if your flying site falls within such an area. If you have any problems with this process you should contact the Leicester office for advice.
(c) Pilots of large radio control models should be aware that such models may have different operating characteristics to smaller models, several of which may not be initially apparent.
The greater mass and inertia of the large model, its generally more robust (less compliant) structure and the differences in aerodynamic efficiency of larger flight surfaces can mean handling characteristics nearer to full size aircraft than to models. You may be caught out if you are not aware of this.
You may also have visual perception problems caused by the size of the model. This usually takes the form of the aircraft being much further away than you think and can cause positioning problems in flight and danger on landing due to the large ‘swept’ area on the approach. Be aware of this problem, especially when flying at low level.
(d) When constructing the model ensure that all parts have adequate strength for the task they perform. Pay special attention to the way in which wing load stresses are transferred between the wing structure and the fuselage. Tailplane members, if detachable, should have a positive lock to their mounting so that they cannot be shed in flight.
(e) Never use long unsupported control rods to the control surfaces or plastic clevis connectors as control forces will be high. Wherever possible each aileron should have its own servo and the elevator should preferably have two independent servos with either (a) mechanical interconnection so that either can drive the control surface (with reduced movement) should the other fail or (b) each servo should drive one half of the elevator through separate pushrods.
(f) Pay particular attention to the state of the battery and the switch harness. Ensure that the batteries in both the model and the transmitter have adequate capacity for the flight to be undertaken and are fully charged for each flying session. Don’t expect a standard receiver battery pack to cope with the demands of high power servos and large control forces. Loss of battery power is the most frequent cause of system failure. There are commercial battery back-up systems available and circuits have been published for similar systems. These should be seriously considered if overall servo current drain is likely to be very high.
(g) As required by the CAA, a radio fail-safe device must be fitted and operational to all models over 7 kg. Remember that the purpose of the device is not to land the model but to prevent it from flying away in the event of radio failure. You should test it regularly as part of your pre-flight checks.
(h) It is recommended that all ‘large model’ pilots should hold the BMFA ‘B’ certificate or a similar qualification (e.g. SAA Silver Wings, LMA Certificate of Competence), and should ensure that both adequate third party insurance is operational and that all flights made comply with CAA regulations.
(i) Do not operate large models at a site which allows public access to the take-off or landing area unless that access can be marshalled during the duration of the flight. Although you may be aware of the potential dangers, the general public, especially children, will not know these of hazards.
19.14 Large Power Fixed Wing
(a) The fail-safe device fitted must, as a minimum, bring the engine to idle speed.
(b) Pay particular attention to vibration proofing the airframe. Larger engines may produce high amplitude low frequency vibration unlike that normally associated with model aircraft engines. Ground test the airframe under full power until you are satisfied that nothing will loosen in flight.
(c) Take No Chances With a Running Engine. The greatest care should be taken when running the engine of a large model. Full-size aviation standards of safety and awareness must be exercised whenever you start, run and adjust the settings of the engine.
19.15 Large Helicopters
(a) The fail-safe device fitted must, as a minimum, bring the engine to idle speed.
(b) The greatest attention must be paid to the effects of vibration on the airframe and radio installation. Linkages must be regularly checked and any that are suspect must be renewed.
(c) Because of the high airframe density and lifting power of modern helicopters, it is very easy to be operating a model weighing over 7 kg without being aware of the fact. Pilots are recommended to weigh all helicopters powered by ‘40’ sized engines and above and to make certain that you are complying with any current CAA regulations if necessary.
19.16 Large Gliders – Slope and Thermal
(a) Considering that the purpose of the fail-safe device fitted is to avoid a flyaway, it is recommended that it should be set with that in mind. Activation of spoilers, crow brakes or even the elevator to full up and the rudder to full left (or right) would be appropriate.
(b) Many large gliders have scale ‘bolt on’ wing fixings. Pay strict attention to how the wing load stresses are passed from the wing skins and spars through any such fixings to the fuselage.
(c) When flying from the slope be sure that you give audible warning to spectators, assistants and other pilots when about to launch or land. Agree a flight pattern to be used along the slope with other pilots or follow local rules. Always turn away from the hill at the end of each pass.
(d) Do not operate large gliders in the same airspace as other users, e.g. full-size gliders, aircraft, hang gliders etc. (see the earlier section on ‘mixed sites’).
(e) Always perform aerobatics well away (not less than 50 metres) from people or property and never, under any circumstances, overhead.
19.17 Flying Sites For Models Between 7 kg And 20 kg
Models between 7 kg and 20 kg are directly regulated by the Air Navigation Order and two of the main legal requirements are that they are not flown in controlled airspace or in aerodrome traffic zones (ATZ) without Air Traffic Control (ATC) permission and that they are not flown at more than 400 ft agl without the permission of the relevant authority. Within controlled airspace this is the appropriate ATC unit and outside controlled airspace it is the CAA itself.
CAP 658 says;
Models between 7 and 20 kg must not be flown above 400 ft agl unless with ATC permission, and should be flown well clear of any congested area of city, town or settlement; 150 metres is suggested. (note that the CAA definition of ‘congested area’ includes playing fields that are actually in use, i.e. if a football match is in progress – Ed). Arranging to fly on a site already cleared for model flying could save you some problems.
Long term permission can be arranged for sites within controlled airspace and ATZs and you should liaise with your local ATC to arrange this. Such permission should be in writing and will probably be for one year. This type of long term permission is endorsed by the CAA and BMFA and if your local ATC is not willing to give it in what you consider to be reasonable circumstances then you should contact the BMFA Leicester office. An arbitration procedure has been agreed with the CAA and the matter will be taken further on your behalf by the BMFA.
19.18 Models Over 20 kg
Models over 20 kg are subject to the issue of a CAA ‘Permission to Test’ exemption certificate before they may be flown. This certificate lasts for twelve months.
The CAA will not issue such a certificate unless the construction of the model has been monitored and ‘signed off’. A UK wide building inspection system which is available to all who need it has been set up and details can be obtained from the BMFA office.
A full exemption certificate will then only be issued by the CAA on the completion of a witnessed test flight schedule. Only pilots named on the exemption certificate may fly the aircraft in public and each named pilot is required to complete the flight test schedule on the aircraft separately.
It is extremely important that anyone building or thinking of building a model that may exceed 20 kg should use the inspection service and test flight monitoring service. If you don’t then an exemption certificate will not be issued by the CAA. Flying the model will then be illegal (in the strict definition of the word) and you will be liable to prosecution if you do fly it.
19.19 Flying Sites For Models Over 20 kg.
Such models are subject to the issue of a CAA exemption certificate before they may be flown. The certificate will set out any conditions required but you can certainly expect any restrictions to be at least based on those noted above for models between 7 and 20 kg and it is extremely unlikely that they will be less strict.
19.20 Space Models – CAP 658 Says
NOTE: Article 240 of the ANO 2016 (Endangering Safety of an Aircraft) applies to all rockets: the operator of a model rocket must ensure that it does not endanger a real aircraft.
(a) General – Only fly on sites that are clear and open with adequate open space downwind of the launch point and in good visibility. No person shall launch a rocket unless he has reasonably satisfied himself that:
(i) the flight can be safely made; and
(ii) the airspace within which the flight will take place is, and will throughout the flight remain, clear of any obstructions including any aircraft in flight. Models should be constructed of lightweight materials capable of meeting the minimal structural loads expected during flight. The use of metal components should be limited to the absolute minimum necessary to ensure the integrity of the rocket during flight and recovery.
(iii) Models should, for the most part, use commercially available factory-produced motors, otherwise non-commercial motors must follow the United Kingdom Rocket Association (UKRA) approved safety code. Only motors that are compliant with all relevant UK legal requirements shall be used. For further information contact either the BMFA or the UKRA.
(iv) Models should be equipped with a suitable recovery system to ensure a safely retarded descent.
(v) Motors should be ignited electrically in such a way that the operator is at least five metres from the launch point.
(b) Rockets between 160 newton.seconds (‘G’ Rating) and 10,240 newton.seconds (‘M’ Rating).
In addition to the above, article 96 of the ANO 2016 (Rockets) applies to all rockets with motive power exceeding 160 newton.seconds (‘G’ Rating) and the requirements of the article are summarised below.
No person shall launch a rocket with a motive power that exceeds 160 newton.seconds (‘G’ rating) unless he has reasonably satisfied himself that:
(i) the flight can be safely made; and
(ii) the airspace within which the flight will take place is, and will throughout the flight remain, clear of any obstructions including any aircraft in flight;
(iii) for a flight within controlled airspace, he has obtained the permission of the appropriate air traffic control unit for aircraft flying in that airspace;
(iv) for a flight within an aerodrome traffic zone he has obtained the permission of the air traffic control unit, the aerodrome flight information service unit at the aerodrome or the air/ground communications service unit as appropriate; and
(v) for a flight for aerial work purposes the flight is carried out under and in accordance with a permission granted by the CAA.
(c) Rockets over 10,240 newton.seconds (‘M’ Rating)
Large rockets exceeding 10,240 newton.seconds must not be launched unless in accordance with a permission granted by the CAA. Further details can be obtained from the Airspace Utilisation Section of the CAA (Contact the BMFA for contact details).
BMFA Notes In addition:
(i) Models must be launched from a stable platform equipped as a minimum with a launch rod for initial guidance and must not be launched at an angle of more than 30º from the vertical.
(ii) A clearly audible countdown of at least 5 seconds must be given by the launch supervisor. In the event of a misfire, do not approach the model until it is certain that ignition will not occur.
(iii) Where spectators are present, a Range Safety Officer should be appointed to take responsibility for all flying activity.
(d) Large Scale Rockets, ‘H’ to ‘M’ Motors.
Details of the operating and safety procedures for large scale high powered rockets are naturally more extensive and involved than for the lower powered ones.
A comprehensive safety code has been written by UKRA to cover such operations and is published by the BMFA. It is required reading if you are interested in large scale rocketry.
(e) Space Modelling Specialist Bodies
The BMFA Specialist Bodies covering space models are Federation Aeronautique Internationale Rocketry (FAIR) and the United Kingdom Rocketry Association (UKRA). These bodies can be contacted via the BMFA’s Leicester office.
19.21 Gas Turbines
A ‘Code of Practise for the Operation of Gas Turbines’ has been prepared by the Gas Turbine Builders’ Association and the Jet Modellers’ Association. Anyone intending to build and fly a gas turbine model should obtain and read this document before proceeding, as it covers all the essential safety procedures and additional legal liabilities concerned with this type of model. It is available for download from the BMFA web site (www.bmfa.org) or directly from the Leicester Office.
(i) The operation of gas turbines requires special care and the manufacturer’s operating instructions must be understood and closely followed. All pilots and helpers must be fully briefed on the operation of the engine before any starts are attempted.
(ii) Never run an engine in excess of the manufacturer’s recommended power rating. Always follow the manufacturer’s recommendations on pipework and fittings, especially with regard to periodic renewal.
(iii) Take extra care during the engine’s initial operating period. Until the unit is proven, do not operate it near people.
(iv) Pressurised gas fuels, such as Propane, require care in handling; spill dispersal rates can be slow and the gas can ‘pool’ in hollows or in void areas in fuselages. The liquid can also cause frostbite, if allowed to come into contact with skin.
(v) Ensure that all fuel is stored in labelled containers fit for the purpose. These containers should be no larger than necessary.
(vi) Model jet turbine installations may produce significant amounts of RF interference. In particular, fuel pumps, if they use brushed motors, and the turbines themselves, which have been known to produce significant static interference, especially if ceramic bearings have been incorporated. Make sure that you do not install receivers or servos or run aerials near to the engine installation.
(vii) All gas turbine models are required by the CAA to be fitted with a failsafe. This must, as a minimum, bring the engine to idle in the event of radio interference or failure. The fuel system must be capable of manual shut off via a fuel valve or fuel pump switch.
(b) Before Starting
(i) Smoking or naked flames must not be allowed near the engine and the fuelling area.
(ii) A suitable fire extinguisher (CO2 or dry powder but not water) should always be present at Start Up and for any period during which the engine is running.
(iii) The Start Up area should be kept clean and free from any loose items that may get sucked into the fan or turbine.
(iv) Ideally, the Start Up area should be on a paved surface, but if this is not possible the grass should be short and clear of all loose material.
(v) Check the integrity of any compressed air hoses, clips etc, prior to turning on the air. Manufacturer’s instructions should always be followed, particularly those relating to safety.
(vi) Gas fuelled models must never be left in the pits area fuelled up. Once fuelled up they should be moved directly to the designated start-up area.
(i) The engine should normally be started facing into wind but make sure that it is not pointed at people or the pits area. The effect of the jet blast must always be kept to the absolute minimum.
(ii) Beware of ‘wet’ starts with liquid fuels.
(iii) After starting the engine always check the oil flow to the bearings. It is also advisable to check the exhaust gas temperature each day and you should keep a constant watch for any new noises or vibration. Any deviation from normal could indicate trouble. Do not run the engine if you are not sure.
(iv) Whenever possible a reliable helper should assist with the start. The helper should be close by and fully briefed on the operation of the engine. The helper should ensure that you are not distracted during the start sequence.
(v) Models must be physically restrained during start up. The use of wheel brakes alone is not sufficient.
After every flight ensure that the engine is fully shut down, the fuel shut-off has been operated and that any hatches are opened to assist engine cooling.
(e) Turbine Model Flight Safety Information:
(i) Adverse runway conditions can have an adverse effect on the aircraft’s performance on take-off. E.g. wet or long grass will significantly increase take-off distance.
(ii) The rate of climb at take-off weight may be significantly less than that of a propeller driven model aircraft. Care must be exercised to ensure safe clearance of any obstacles immediately after take-off.
(iii) The lack of “prop wash” over the control surfaces of a jet propelled model aircraft will result in less control surface effect particularly at low speed.
19.22 First Person View R/C
FPV R/C is a legitimate activity but there are limitations that you must observe to be both legal and insured.
NOTE: The Air Navigation (Amendment) Order 2018 limits FPV flight to less than 400ft, however an exemption (in addition to the Exemption overleaf) has been granted by the CAA for SUAs less than 3.5kg in weight including batteries or fuel allowing flights up to 1000ft. This excludes multi-rotors and any SUA with automatic or autonomous flight capability unless it is for flight stabilisation purposes.
CAP 658 Says
(a) What is First Person R/C? – Also known as First Person View, is a system whereby a radio control model aircraft is piloted, not through direct line of sight, but by using a live video downlink from an on-board camera allowing the pilot to experience a ‘cockpit view’ and to control the aircraft from the visual perspective of that camera. The live video is normally displayed to the pilot through ‘video goggles’ worn on the pilot’s head or through a stand-alone monitor.
(b) Legal Position – The law requires that the person in charge of a model aircraft must maintain direct unaided visual contact with the aircraft sufficient to monitor its flight path so that collisions may be avoided. This is obviously not possible if the person in charge is wearing goggles. Therefore there needs to be a way to facilitate this and to address other safety concerns.
(c) Safety Concerns – Images captured by a camera and displayed on a flat screen afford the pilot little by way of depth perception and no peripheral vision. This can make it difficult for the pilot to accurately judge speed and distance and to maintain sufficient awareness of the area surrounding the aircraft to effectively ‘see and avoid’ obstacles and other aircraft. The ability to control the aircraft and avoid collisions is also greatly affected by the quality of the video being displayed. Furthermore, in the event of a loss of the video data stream, which can easily occur if the aircraft is flown beyond the range of the transmitter, the pilot is likely to experience difficulty in locating the aircraft relative to his own position and visually acquiring it before loss of control occurs.
(d) Control Measures – There are two mechanisms to address the safety concerns depending on the all up weight (auw) of the model.
(i) For models less than 3.5 kg auw an exemption (ORSA 1226) which permits the person in charge to wear the headset provided a spotter is employed. Please see section 19.23 following for full details.
(ii) For models in excess of 3.5 kg the buddy box system will need to be employed and then the person in charge will have the master transmitter and also direct line of sight to the model whilst another person flies the model by reference to the live video feed.
(iii) Remember that the operating conditions in both these cases clearly places the legal responsibility for the safety of the flight on the person in charge.
(e) In addition to the guidance already given above, consideration should also be given to the following:
(i) Pre-flight Checks – Ensure that the additional transmitters (data/video) are switched on whilst conducting the range check.
(ii) Battery Charge Status – FPV can involve several more batteries than normal R/C flight. All batteries should be checked for full charge before each flight.
(iii) Training – FPV flying means that the pilot controls the aircraft by reference to the horizon – just as with full size aviation. Before attempting a first flight it is a good idea for a novice FPV pilot to wear the goggles and view the video feed as a ‘passenger’ whilst another pilot flies the aircraft.
(iv) Positional Awareness – FPV flying differs from line-of-fight flying in that the pilot sees a completely different perspective and, during his first flights, it is easy to lose track of where the aircraft is relative to the flying field – especially when directly above it.
19.23 FPV Pilot Exemption for Lightweight Models
The CAA have issued an exemption (Official Record Series 4 No 1226 – General Exemption E4457) which allows the solo flying of lightweight FPV models, subject to the following conditions:
(a) The Civil Aviation Authority, in exercise of its powers under article 266 of the Air Navigation Order 2016 (‘the Order’), exempts any person in charge of a Small Unmanned Aircraft (SUA) from the requirement at article 94(3) of the Order to ensure that direct unaided visual contact is maintained with the aircraft sufficient to monitor its flight path in relation to other aircraft, persons, vehicles and structures for the purposes of avoiding collisions.
(b) This exemption only applies if the conditions at paras. (c) to (g) below are met.
(i) The person in charge is the person piloting the SUA.
Note: The person in charge remains responsible for the safety of the operation and may only fly the SUA if reasonably satisfied that the flight can safely be made.
(ii) The person in charge is accompanied by a competent observer who maintains direct unaided visual contact with the SUA sufficient to monitor its flight path in relation to other aircraft, persons, vehicles, vessels and structures for the purpose of avoiding collisions and advises the person in charge accordingly.
(iii) The maximum take-off mass of the SUA does not exceed 3.5 kg, including any batteries or fuel.
(d) The person in charge must not fly the SUA:
(i) In class A,C,D or E airspace unless permission of the appropriate air traffic control unit has been obtained;
(ii) within an aerodrome traffic zone during the notified hours of watch of the air traffic control unit (if any) at that aerodrome unless permission of any such air traffic control unit has been obtained;
(iii) at a height of more than 1000 feet above the surface (provided the competent observer can maintain visual contact with the SUA throughout the flight);
(iv) over or within 150 metres of any congested area;
(v) over or within 150 metres of an organised open-air assembly of more than 1000 persons;
(vi) within 50 metres of any vessel, vehicle or structure which is not under the control of the person in charge of the SUA;
(vii) within 50 metres of any other person, apart from the competent observer, except when taking off or landing in accordance with para. (viii);
(viii) within 30 metres of any other person, apart from the competent observer, other adjacent model operators, or any model flying club members, during take-off or landing
(e) For the purposes of this exemption, a ‘competent observer’ means someone whom the person in charge has designated as the competent observer.
(f) Before designating someone as the competent observer, the person in charge of the SUA must be satisfied that he or she:
(i) has been briefed in accordance with paragraph. (g);
(ii) is competent to perform the tasks which he or she may be called upon to perform in accordance with paragraph (g); and
(iii) is competent by direct unaided visual observation of the SUA, to assist and advise the person in charge with the safe conduct of the flight.
(g) The person in charge must ensure that;
(i) the competent observer is fully briefed on the planned flight and what is expected of him/her taking into account the prevailing conditions;
(ii) the competent observer understands that he/she must stay directly adjacent to the person in charge and maintain direct unaided visual contact with the SUA at all times, to visually and aurally monitor the airspace for other aircraft and the take-off and landing area for any persons;
(iii) the competent observer has been instructed on the actions to take in the event of another aircraft being spotted and a risk of collision is assessed; and
(iv) the competent observer understands that he/she must advise if the SUA is proceeding beyond the point at which he/she is able to monitor its flight path sufficiently to identify a risk of collision.
(h) This exemption supersedes Official Record Series 4 No. 1168, which is revoked.
(i) This exemption has effect from the date it is signed until varied, suspended or revoked.
BMFA NOTE – The conditions that you must comply with to use this exemption are almost identical to those applied to models over 7 kg. In particular, you MUST take note of the requirement not to fly in any controlled airspace without the permission of the relevant Air Traffic Control Authority. Considering that controlled airspace down to ground is applied to many urban and semi-urban areas, you should check very carefully to avoid flying illegally and negating the exemption.
Next Section 20. MODEL FLYING DISPLAYS