What is ANC-18 and how does it relate to wood structures in Very Light Aeroplanes (CS-VLA)?

ANC-18 is the ANC Bulletin 'Design of wood aircraft structures', issued June 1944 by the Army-Navy-Civil Committee on Aircraft Design Criteria (USA). For wood materials, allowable normal stress levels of maximum limit load should be according to ANC-18.

What should be done if stress levels are higher than the allowable levels for Very Light Aeroplanes (CS-VLA)?

Higher stress levels need further fatigue investigation using either a fatigue test based on a realistic operating spectrum or a fatigue calculation using strength values which have been proved to be sufficient by fatigue tests of specimens or components.

How is the allowable normal stress level determined for aluminium and steel alloys in Very Light Aeroplanes (CS-VLA)?

For Aluminium Alloy and Steel Alloy, the allowable normal stress level is half of rupture tensile strength.

What stress levels are considered sufficient evidence for structural items in Very Light Aeroplanes (CS-VLA)?

The use of specific stress levels, in conjunction with good design practices to eliminate stress concentrations, may be taken as sufficient evidence that structural items have adequate safe lives. Examples include 25 daN/mm2 for glass rovings in epoxy resin and 40 daN/mm2 for carbon fibre rovings in epoxy resin.

AMC VLA 572(b) Parts of structure critical to safety (Interpretative Material and Acceptable Means of Compliance)

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ED Decision 2003/18/RM

1 The use of the following stress levels may be taken as sufficient evidence, in conjunction with good design practices to eliminate stress concentrations, that structural items have adequate safe lives:

Material used	Allowable normal stress level of maximum limit load
– Glass rovings in epoxy resin	25 daN/mm²
– Carbon fibre rovings in epoxy resin	40 daN/mm²
– Wood	According to ANC-18*
– Aluminium Alloy	Half of rupture tensile strength
– Steel Alloy	Half of rupture tensile strength

2 Higher stress levels need further fatigue investigation using one or a combination of the following methods:

a. By a fatigue test, based on a realistic operating spectrum.

b. By a fatigue calculation using strength values which have been proved to be sufficient by fatigue tests of specimens or components.

*ANC-18 is the ANC Bulletin 'Design of wood aircraft structures'; issued June 1944 by the Army-Navy-Civil Committee on Aircraft Design Criteria (USA).

Details

Source-Title: AMC VLA 572(b) Parts of structure critical to safety (Interpretative Material and Acceptable Means of Compliance) View latest amendments

Erulesid: ERULES-1963177438-7894 Compare versions

Domain: Initial airworthiness

Amendedby: Initial issue

Applicabilitydate: 14 November, 2003

Entryintoforcedate: 14 November, 2003

Regulatorysource: ED Decision 2003/18/RM Navigate

Regulatorysubject: CS-VLA

Typeofcontent: AMC to CS (Acceptable means of compliance to certification specification)

Origin: EASA

Category: EAR