The BGA require that the normal weighing interval for Gliders is 8 years unless the aircraft has been recovered, repainted or substantially repaired or whenever the weighing information is believed to be inaccurate. In which case it must be done on completion of any work. They also require that Metric or Imperial units as previously used for the subject aeroplane be used again to prevent confusion. Ref TNS 02/02

It is important that the maximum All Up Weight (AUW) is not exceeded as the aeroplane can be overstressed and possibly suffer structural damage. The AUW is specified in the Flight Manual (FM) and can also be found in the data sheets on the BGA web site for most current and common types. Note that where a concession has been granted for a greater AUW there may also be limitations imposed, for example, aerobatics may be prohibited or limited. It is also important that the aeroplane is operated within the specified Centre of Gravity (CofG) range and that the Specified Maximum Seat Load is not exceeded. Again see the FM or the data sheets.

To operate outside of these limits can affect the handling of the aeroplane and reduce the control authority, perhaps making it difficult to recover from a spin or to effect a proper round out on the approach to land. Operation outside the permitted limitations not only jeopardizes your safety but the safety of the pilots who fly after you, as damage to the aeroplane can be cumulative.

The mechanics of weighing the aeroplane and calculating its C of G is Secondary School General Science stuff (so why did I not learn this till the age of 23?? Ed) but it needs to be authorised by a BGA Approved Inspector. The BGA Airworthiness and Maintenance Procedures Manual (AMP) tells all. The availability of suitable weighing equipment that is accurate and whose calibration has been checked is important. Data applicable to the aeroplane being weighed, such as attitude and recommended datums, is also required. Several approaches are available, we can either take our gliders to an organisation that is authorised to do the work or we can employ someone to bring their weighing gear on site. The first option will cost up to £120 plus transport. The second will be cheaper, perhaps £60 plus travelling expenses for a single aeroplane and less if several are weighed at the same time. Perhaps the best approach is to do what Clubs like ours do best and employ the skills and time of the Members.

We are fortunate that we have on loan, at the Club, a set of digital scales, a chain hoist and webbing slings that allow the aeroplane to be suspended from the hangar roof. Simple bathroom scales, suitably calibrated can be used to support the tail wheel/skid. With the addition of a spirit level to set up the correct attitude, a pair of plumb-bobs and a tape measure we have the tools to do the job. Several willing pairs of hands to help with the positioning are also required. All additional equipment such as batteries, radios and loggers must be installed as for flight.

The sum of the weights indicated by the scales, less any supporting gear, represents the AUW of the glider. The CofG is calculated from measurements from and between the points of weighing and the aircraft datum. Where additional ballast is utilised the exercise is repeated with the ballast in position. From the results a Weight and Balance Report is compiled for submission to the BGA and inclusion in the aircraft logbook. Pro-formers are available from the BGA or simple computer programmes are available to produce the report. The results are summerised in the tables of limitations displayed in the cockpit(s).

If your glider need weighing we might be able to help although we will suggest a contribution to the NVGC Social Fund.

Only you or your Instructor can properly brief you on this bit but as we mend 'em and even sometimes fly in them; we will take the liberty of expressing a Mechanics view. It may not be enough when running through your pre-flight ballast checks to simply say "We/I have flown before in this aeroplane type." Different areoplanes of the same type may have different load limitations, the limitations may have even changed since you last flew. Your weight may have changed! Check that the maximum payload is not exceeded. If the flight is to include aerobatics or cloud flying your total weight might prohibit certain maneuvers. Weight distribution will affect the CofG, check the limitations placard. Check that the maximum permitted seat loading is not exceeded. Remember that cumulative damage might hurt some one who has not yet been born.

Reposted 15th January 2007