مطالب علمی

 

Glider inspections

 

Your wing, like any aircraft, should be technically checked to ensure proper airworthiness. Regular checks will ensure that your wing remains in a good condition and in the correct trim. This will not only make flying safer but it will also give you peace of mind. If you sell your glider, you should give to the buyer an inspection certificate to prove its airworthiness.

Your wing should be checked for the first time after 24 months and every 12 months thereafter. If you are a frequent flyer (more than 80 hours per year), or perform acrobatics or you use a lightweight wing then we recommend that you get your glider checked after every flying season. If your glider is used professionally for training purposes or for tandem flights then a complete maintenance check must be carried out every 12 months. Without this periodical maintenance check, the airworthiness of the glider cannot be guaranteed and it may not conform to the EN/LTF standard that the glider was manufactured to.

We recommend that the maintenance check up is carried out by a qualified professional. You are responsible for your flying kit and your safety depends on it. Take care of it and regularly inspect all of its components. Changes in a wings launching and/or flying characteristics indicates the aging of the glider, if you notice any changes you should have the wing checked before flying again.

Glider Maintenance Inspection

Visual inspection of the canopy

A full visual check should be carried out, preferably using a light table to highlight any defections. This will also help identify any damage to the coating of the cloth. All the components of the wing should be checked: panels; stitching; ribs; diagonals; line attachment points; tabs etc.
Check for any tears, holes or damaged/loose stitching and repair accordingly. Large areas of damage will need replacement panels. Complex or large scale damage, especially to the ribs or in structurally important areas may need a factory repair. Please consult Ozone if you are unsure.

Porosity

The canopy should be measured for porosity values in several different areas of the top and bottom surface. We recommend 5 measurements on the top surface and 3 on the undersurface. The measurements should be made approximately 20 -30 cms inboard from the leading edge in the approximate positions indicated in the diagram below using a porosity meter; this measures the time taken for a certain volume of air to pass through the material. The lowest accepted average value for top and bottom surface is 10 seconds as recorded by a JDC porosity meter.

<10 secs average (JDC) = Unacceptable. Glider should be deemed un-airworthy

Cloth strength

The tearing resistance of the cloth is measured using a Betsometer (B.M.A.A. Approved Patent No. GB 2270768 Clive Betts Sails)
Puncture the cloth in the middle of a panel from the middle of the top surface and increase the load until 600g is achieved. If the material tears more than 5mm before this value is reached then the cloth is deemed too weak and the glider is un-airworthy. Repeat on a panel of the undersurface.

600g with a tear of < 5mm is the lowest accepted value.

Lines

The sail and the lines do not age in the same way; it is possible that you will have to change part or all of the line set during the normal life of the wing.
Visually check all lines for any signs of external damage, check the brake handle knots and the brake lines for any excessive wearing.

Line Strength

To check the strength of the line set; an upper, middle and lower A line, along with a lower B and a lower C (and lower D if applicable) line should be tested to the breaking point and the value recorded. The minimum value is 8 G for all lower A+B lines and 6 G for all lower remaining lines, calculated from the maximum certified flying weight of the glider. The added minimum strength for the mid lines and for the top lines should be the same.
If the breaking strength is too close to the minimum value calculated, the professional should investigate with more lines and give a period after which the strength of the lines must be tested again (normally 6/12 months).

  • The lowest accepted value for the A and B lines is the result of the following calculation : [(PTV Max x 8 ) / (number of lines A + B, without stabilo)].
  • The lowest accepted value for the C and D lines is the result of the following calculation : [(PTV Max x 6 ) / (number of lines C + D)].
  • For the upper lines the lowest accepted value is 30kg.

Where PTV Max is the all up maximum weight for the type of glider, e.g. for a Rush2 the max all up weight is 135 kg (max weight for the XL ) and there are 6 A lines and 6 B lines so the lowest accepted value for an A line would be (135 x 8 ) /12 = 90kg.
This is the standard EN/LTF calculation for line strength tests.

Line Lengths

The overall length (riser lines + mid lines + upper lines) has to be checked under exactly 5DaN of tension. The difference between the measured length and the original length should not exceed +/- 10mm. The length of the line connection tabs is also be included in the measurement. Contact Ozone for the correct line length charts for the particular wing. Any significant changes to the overall line lengths will take the wing out of the certified trim configuration and will possibly make the wing more dangerous to fly. The consequences of any changes can include a slower trim speed, difficult inflation, parachutal tendencies etc.

  • 10mm tolerance (overall line length with 5kg tension)

Risers and Hardware

Check lengths and check that the risers are in visually good condition with no abrasion damage, pay particular attention to the maillon hang loops and the main suspension loop. Ensure that all maillons are undamaged and are done up correctly. Replace any missing rubber O rings.

Test Flight/Inflation

Finally a flight test confirms that the wing behaves normally.

IMPORTANT: Take care of your glider and make sure you have it checked according to the above schedule by a qualified and experienced technician: This will ensure you hours of safe flying.

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