How the Scheme Works


Perhaps we should start by trying to dispel a few “myths”

Firstly the Over 20kg Scheme is “owned” by the Civil Aviation Authority and the United Kingdom Large Model Association, with the support of the British Model Flying Association so please DO NOT contact the CAA (Civil Aviation Authority) directly. The LMA are “accredited” by the CAA to administer and control the procedures of the scheme. Many people ask why the scheme is there in the first place and there is a very simple answer.

Any model aircraft that weighs more than 20kg is regarded under the ANO (Air Navigation Order) as a full size aircraft but it is recognised by the CAA that an aircraft of this type cannot comply with all the ANO rules of a full size aircraft. To overcome this issue the CAA issue an “Exemption to Fly” to any model that has been successfully put through the procedures of the scheme. This also applies to “pure gliders”.

Secondly, there is a “myth” that because some members of the LMA operate large models in this category  then the LMA is an “elitist” group. We are not “elitist” but are considered to be specialist in the same way that the various specialised interests of the BMFA get together to enjoy the hobby.

Sometimes it is difficult to explain to some modellers that the LMA has only 60/70 registered aircraft over 20kg in any given year and those aircraft are owned by about 30/40 members. As the LMA has now reached a membership of over 1000 it becomes patently obvious that this aspect of the LMA is very much a minority – there are hundreds of models in the LMA which operate from the 7kg level (WW1 ¼ scale for instance) up to 20kg. Now we do accept that sometimes the egos of modellers can be equated to the size of their model but that is applicable to any speciality – have you noticed how defensive (notice that I didn’t say elitist) some of the top people in the BMFA specialisms can be about this issue!

The LMA do not have competitions but they do like to draw the attention of the general public about our hobby by displaying them at public events.


So how does the Over 20kg Scheme work ?

If you plan to build and fly a model in the UK which weighs over 20kg then it is mandatory (a requirement of the Air Navigation Order) that the aircraft is built, inspected and flight proven using the scheme operated by the LMA on behalf of the CAA. Therefore, if you are planning to build or fly an aircraft over 20kg, you must contact the LMA CAA Liaison Officer. Please do this BEFORE you begin building. Registration of a project can be made using this form .  The principal aim of the LMA is to help you complete a successful project that will be a safe aeroplane to fly. Note that if you are considering building a model that weighs over 150kg you will have to put the model through a FULL airworthiness certification and this can only conducted through the full CAA regulations which relate to Ultralight aircraft. As part of the LMA’s relationship with the CAA , there is a an annual meeting to discuss topics of interest which is also attended by the BMFA and the SAA.

The first part, the inspection process, starts with an appointed inspector overseeing the construction of the model and final approval so that a Certificate of Design and Construction can be issued by the LMA’s CAA Liaison Officer. The owner will be issued with a form to apply direct to the CAA for an Exemption to Test Fly and will also be given a copy of the Certificate of Design and Construction to accompany the application. This exemption will be an Exemption To Test Fly and will only permit the model to be flown in private for test purposes in the presence of an appointed LMA witness. Please note that if the owner wishes the first test flights to be carried out by another person they will also have to be named on the Exemption. There are procedures however where the test flying may also be carried out by a small number of LMA Approved Examiners. The exemption will be valid for three years and it is expected that during that time the named pilot will complete a Flight Test Log in accordance with the guidance given below.

An Exemption (Test only) will not permit test flying a model where the general public are in attendance – club events, fly ins etc are not considered to be public fee paying flying events. Only when the pilot has a Full Exemption to Operate will the named pilot be permitted to fly the model without an LMA Examiner or other approved LMA witness  being present. If another pilot is to be added at a later date, that pilot can apply to the LMA CAA Liaison Officer for  a Flight Test Log which will give approval for the other pilot to start test flying, which when completed, will enable the second pilot to be added to the Full Exemption.


Flight Test Log

The approved LMA witness will be required to complete a flight test log for every pilot that is to be named on the Exemption to Operate. As mentioned previously all flights must be witnessed by an approved LMA witness. The pilot should check with the approved list before commencing any flights. The flying site must also be able to comply with the rules regarding the operation of Over 20kg aircraft and any doubt about this should be clarified . No pilot is  permitted to carry out any flights whilst operating under an Exemption (Test only) without the presence of an approved  LMA witness. This clause is incorporated on the Exemption to Test Fly. All flights must be recorded on the log and must total a minimum of one hour flying time with the individual specified manoeuvres completed over the period of the test flying. The flying time must be completed in not less than six flights totalling one hour and each flight should include start-up and shut-down of the engines and radio. There are specific minimums in relation to jets and  Over 80kg aircraft and this is covered later. It should be stressed that one hour is an absolute minimum and it is likely that it will take longer than this to satisfactorily complete the test program.  Any modifications to the model that are identified during the test program, or any repairs that are needed, should be carried out with the involvement of the original build inspector(s) and recorded on the build log, and this may mean further testing is required. It is expected that for unusual, complex, or types of model new to the pilot, that the test program will be extended to ensure that both the model and pilot are competent.

The individual manoeuvres listed on the log are designed to demonstrate the integrity of the model and the ability of the pilot to control the model under more “extreme” conditions that it would see in normal use. Special care should be taken to ensure that the pilot is competent to carry out crosswind take-off and landings and knows the models limitations in this respect. The pilot should also be able to demonstrate take-offs without having to stand behind the model. The show routine box is there to confirm that the pilot is capable of positioning the model safely in relation to a crowd-line. It is not meant as a method of judging how good an aerobatic or low flying display the pilot can put on, but it should include any types of manoeuvres that the pilot would wish to normally fly. Sometimes it may be necessary to complete the test flying over a period of time and not in one day. Witnesses should be sure that the pilot is capable of operating the model in a variety of weather conditions and not only on a “nice” day.

On satisfactory completion of the Flight Test Log it should be returned to the LMA CAA Liaison Officer who will then provide the owner of the model with an  application form requesting a Full Exemption to Operate which is to be completed, signed and sent to the CAA. The CAA will then issue the Full Exemption. Once the named pilot has a Full Exemption to Operate the model can be flown without an LMA witness being present noting that the model must be operated within the requirements as laid down on the Exemption.



Witnesses are approved by the LMA Committee and are appointed depending on their geographic location to the project, they are provided with Guidance Notes about the test flying procedures. In certain circumstance a witness may be chosen by the owner of a project but then must first be approved by the committee. An inspector or proficiency scheme examiner may be used as a witness and a list may be found here. The witness of any flight test programme takes on a big responsibility for the subsequent safe operation of the model. Witnesses should be sure that all of the requirements of the Flight Test Log are fully completed in accordance with the above guidance and also any specific requirements or guidance attached to the model before completing the log. Brief notes should be included in each box commenting on the performance of the model and pilot and the comments section on page one should also be completed with any relevant information relating to the testing. If the witness considers that additional flights should be completed prior to the issue of a Full Exemption to Operate, this should be recorded. By signing the log the witness is confirming that the pilot is safe to fly the subject model at the place and in the weather conditions noted.

In the exercise of these responsibilities the witness should take great care to make sure that this part of the process is carried out accurately and without fear or favour. It should be understood that the test programme is not only to test the model, but also test the pilot’s ability to operate the model in a safe manner – especially in relation to flying at public events.


In association with CAA the LMA Committee have established the following guidelines to enhance the ‘Over 20kg Scheme’;-


Movels Over 20Kg But Under 80Kg

One Inspector will be appointed who will record ‘progress’ inspections on the Progress sheet and complete a Final Inspection for the issue of a Certificate of Design & Construction. The ‘Exemption to Test Fly’ issued by the CAA will also allow an LMA designated Examiner to do the test flying in addition to any named pilot(s) on the Exemption. This enables the builder or owner to delegate this responsibility if they so wish. All pilots wishing to fly in public with the aircraft will have to complete the minimal requirements of 6 flights totalling 1 hour.

The minimum requirement for gas turbine powered models is-
-over 20kg but under 30 kg no less than 6 flights totalling at least 1 hour
-over 30kg but under 80 kg no less than 12 flights totalling at least 2 hours


Models Over 80Kg But Under 150Kg

One Inspector will be appointed who will record the “progress” inspections and liaise where necessary with an LMA Senior Inspector who will then attend the Final Inspection for the issue of a Certificate of Design & Construction. Some test flights in this category must be witnessed by an LMA Senior Inspector who was not involved in the build inspection process  together with an approved LMA witness. The test flying must consist of a minimum of twelve flights totalling two hours. All pilots will be required to meet this criteria before being allowed to fly the aircraft in public.


LMA Statement on the Airborne Systems in Over 20kg Models

Since the introduction of the LMA Over 20kg Scheme 25 years ago there have been tremendous developments in the technology of R/C model activity. This has, more recently, been accelerated by the approval of 2.4Ghz for model aircraft and has challenged our concept of what is, and what is not, acceptable. The LMA Safety Panel have discussed this issue and also sought technical advice.

For many years the LMA have operated a policy of addressing “single point” failure in airborne systems and wherever possible system installations have been given approval using that concept. However it is felt that in order to deal with enhanced technology our emphasis in the future should be based on a “minimum risk” approach and we are asking Inspectors to use this criteria. The LMA recognise that irrespective of the airborne installation system that failure will probably result in a crash – this is why we and other model organisations use the criteria defined in CAP 658 regarding safety distances at public events and also in the “club flying” environment.

Specific attention has been given to systems which have the facility to plug in one or more aerials (called satellite receivers). We have come to the conclusion that as these are only attached to a single decoder when they are so connected they comprise of only a single receiver. This system would need to be duplicated to meet the LMA criteria because they represent a greater risk. As a result of these discussions we feel we are in a position to recommend the following scenarios which present the “minimum risk”:

  1. The traditional system of 2 batteries, 2 Rx’s, and “crossed” controls.
  2. A Powerbox (or any other similar manufacturers system) which provides for the fitting of 2 Rx’s and 2 batteries – these Rx’s can be Futaba, JR, Spectrum, or any other proven product. In this system it is expected that all controls surfaces would still be operative in the event of most recognised failures.
  3. The Weatronics (or any other similar manufacturers system) which has dual receiver systems on either 35Mhz or 2.4 Ghz. This system would emulate the operation in No 2 above.

We must emphasise that the success of the Over 20kg Scheme has been largely achieved by the relationship between the builder and the appointed Inspector. Anyone contemplating building a model that will come close to, or exceed the Over 20kg limit should register it and then liaise with the appointed Inspector before proceeding. This is particularly important when purchasing radio equipment which is intended for use in the model.

The LMA Safety Panel, in conjunction with the Civil Aviation Authority will continue an “on going” re-appraisal of new systems and technology in the future.


Some Frequently asked Questions

Q      Can some else test fly my new project

A      Yes – the CAA have approved some pilots in the LMA to carry out test flying. You can obtain that information from me. Alternatively you can also nominate a pilot (or several pilots) on the application form which you use to apply for an Exemption to Test fly.

Please remember that any pilot who flies your aircraft in public must have completed the mandatory test flying programme in accordance with Test Flight Log procedures.


Q     What happens if unintentionally, my project creeps over 20kg and I have not registered it.

A     Houston, we have a problem!  We will try our best to resolve the situation but if the wings have been sheeted etc then there may be some hacking about to do.

 Far better to register the project in the first place and if it comes in Under 20kg ,as some do , then nothing is lost except the expense of the Inspectors cups of tea!! If you are an LMA member then the LMA pick up the travelling costs.


Q     What do you do about ARTF models  

A     Obviously, quite a few of  these are composite , and  our Inspectors are usually able to look at the build quality. If you have any doubts contact us first.


Q    What do I do if someone builds the model for me

A     You can register the project in your name but the builder must ensure that the appointed Inspector can carry out Progress checks and perform the Final Inspection.


Q     What do I do if I buy a second hand large model.

A     Get in touch with me first before you part with any money. E bay bargains may look good at face value but quite a few aircraft have “been round the block” a few times and have failed Inspections. Even if the aircraft has had an Exemption or even has a current one please remember that when it is registered in your name it has to be re-inspected – you cannot go on flying it with the previous registered owners Exemption. The motto in this scenario is “buyer beware”. Having said that there are some good reputable large models for sale. If they are advertised on our LMA website then the owner is obviously not too concerned about the rest of the LMA knowing about it.!


Q    What do I do if I want to have additional pilots after getting the Full Exemption.

A     The CAA now allow us to approve test flights for additional pilots on aircraft that hold a Full Exemption. Until recently you would have needed to apply for another Exemption to Test Fly for your new pilot. You can use the form found “here” to arrange additional pilot test flying. When the flights are completed in accordance with the Test Flight Log procedures I process it and inform the CAA who will send you another Full Exemption with the existing and new pilots names on it.


Q     What do I need to do if I damage the aircraft, change the engine, alter the flying surface area, change the radio installation i.e from 35Mhz to 2.4Ghz.

A     All these changes affect the Certificate of Design and Construction and thereby the Full Exemption. Any of these aspects should be reported to me so that I can appoint an Inspector to view the changes and he will provide me with an audit trail of the work involved. Strangely enough, either I, or the Chairman  usually get to know a large model has crashed about 2 minutes after the incident!! 


“Well I hope that covers everything – I am sure some people will come up with a few more questions. I cannot emphasise strongly enough – if in doubt ring me, text me, E-mail do anything rather than nothing – we are here to help not hinder. We just want to help you to stay legal!”


Tony Hooper MBE

UK Large Model Association CAA Liaison officer

(Information last checked and updated 14th October 2015)

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