7178 at a glance
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Designation
| Item | Value |
|---|---|
| Designation | 7178 |
| Class | Aluminum |
| Type | wrought aluminum alloy |
Composition
| Element | Limit |
|---|---|
| Si | 0.40 |
| Fe | 0.50 |
| Cu | 1.6–2.4 |
| Mn | 0.30 |
| Mg | 2.4–3.1 |
| Cr | 0.18–0.28 |
| Zn | 6.3–7.3 |
| Ti | 0.20 |
| Al | Remainder |
A single number is a maximum. Other elements: 0.05 each, 0.15 total, except where the Teal Sheets say otherwise. Source: Aluminum Association Teal Sheets (Aug 2018).
Properties
| Property | Value | Source |
|---|---|---|
| Density | 0.102 lb/in³ (2.83 g/cm³) | Teal Sheets |
| Allowables | None in Section 3.7 | MIL-HDBK-5J Table 3.1.1 |
| Named in | Comparison with 7050 T76 in stress corrosion | MIL-HDBK-5J 3.7.4.0 |
| Bend radius, 7178-O | See table below | FAA-H-8083-31B Chart 204 |
| Replacement | 7178-T6 and clad are in a substitution figure | FAA-H-8083-31B Figure 4-168 |
No strength value is given here because none of the sources used by this site prints one.
Minimum bend radius, inches (AMT Handbook Chart 204)
| Alloy and temper | 0.020" | 0.032" | 0.040" | 0.063" | 0.125" | 0.190" |
|---|---|---|---|---|---|---|
| 7178-O, 2024-O, 5052-H34, 6061-T4, 7075-O | .03 | .03 | .06 | .09 | .25 | .38 |
Selected thicknesses from FAA-H-8083-31B Chart 204, p. 4-61. Chart 204 and AC Table 4-6 do not agree everywhere: where they differ, use the larger radius or the SRM.
Notes from the guide
- Not a source of design allowables. Values are for reference. MMPDS and the SRM govern a repair.
- Not a substitution approval. A different alloy or temper needs approved data.
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Sources
- FAA-H-8083-31B, AMT Handbook — Airframe, Volume 1, Chapter 4 — Chart 204, p. 4-61; Figure 4-168, p. 4-87.
- MIL-HDBK-5J (31 Jan 2003), Chapter 3 — Table 3.1.1; Section 3.7.4.0. Cancelled and superseded by MMPDS: check current MMPDS before design use.
- Aluminum Association, International Alloy Designations (Teal Sheets), rev. Aug 2018 — chemical composition limits and nominal densities.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables. A repair substantiation cites MMPDS or the SRM, not a website.
Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.