Landing Gear Forging for Commercial Aircraft: Titanium and Steel Requirements

Landing Gear Forging for Commercial Aircraft: Titanium and Steel Requirements

August 24, 2026
Landing Gear Forging for Commercial Aircraft: Titanium and Steel Requirements

Landing gear is the most highly loaded structural assembly on a commercial aircraft – it must absorb the impact of thousands of hard landings over a 25-year service life while weighing as little as possible. The main gear beam, side struts, trunnion pin, and drag brace of a widebody aircraft landing gear are forged in Ti-6Al-4V (AMS 4935 beta-processed), 300M ultra-high-strength steel, and 4340M (AMS 6415) — materials chosen for their combination of high strength-to-weight ratio, fracture toughness, and fatigue resistance. This technical blog covers the forging specifications, heat treatment, and NDT requirements for commercial aircraft landing gear components.

ComponentMaterialSpecificationKey Property




Main gear beam (widebody)		Ti-6Al-4V beta-processed
AMS 4935 STA		Fracture toughness, fatigue
Side strut (narrowbody)
300M ultra-high-strength steel		AMS 6257 Q&T150 ksi UTS minimum
Trunnion pin4340M (modified)AMS 6415 Q&THigh bending fatigue
Drag brace fittingTi-6Al-4V STAAMS 4928 STATensile + fatigue
Truck beam (widebody)300M or Ti-6Al-4VAMS 6257 / AMS 4935Impact + fatigue

Landing gear main gear beams for widebody aircraft (Boeing 777, 787, Airbus A330, A350) are among the largest and most demanding structural titanium forgings produced globally — each main gear beam forging weights 200–600 kg in the rough-forged condition before machining. These forgings are produced using beta-processed Ti-6Al-4V (AMS 4935) — where the solution treatment is performed above the beta transus (1,010–1,040°C) rather than the sub-beta-transus temperature used for standard AMS 4928 STA processing. Beta-processed microstructure provides the higher fracture toughness and damage tolerance required for landing gear primary structure, at a modest sacrifice in tensile strength compared to conventional STA.

The primary landing gear OEMs — Safran Landing Systems (formerly Messier-Bugatti-Dowty), Collins Aerospace (formerly UTC Aerospace/Goodrich), Liebherr-Aerospace, and Triumph Group — procure titanium landing gear forgings from a very small number of globally qualified manufacturers: Precision Castparts (PCC), Howmet Aerospace (Arconic), and Aubert & Duval (France). Entry into this supply chain is extremely challenging — the landing gear OEMs require extensive qualification programmes including full fatigue coupon testing, damage tolerance analysis, and multiple AS9102 FAIRs before production qualification. However, as a development or repair forging source for non-primary-structure landing gear components (trunnion pins, drag brace fittings), Indian AS9100D manufacturers with beta-processed Ti-6Al-4V capability can access the landing gear supply chain.

300M steel (UNS K44220) — a silicon-modified version of 4340 with superior fracture toughness at very high strength levels (minimum 280 ksi / 1,930 MPa tensile in the fully heat-treated condition) — is specified for narrowbody aircraft main gear side struts (Boeing 737, Airbus A320) where the weight penalty of titanium is less justified than for widebody applications. 300M forgings are produced per AMS 6257 (bar and billet specification) or AMS 6417 (forging specification), and heat treated per AMS 2759/2 (heat treatment of ultra-high-strength steel) to achieve the minimum 280 ksi tensile with adequate Charpy toughness. The combination of very high strength, high hardness (54–58 HRC), and adequate toughness in 300M requires extremely precise heat treatment — temperature control within ±3°C during austenite and within ±5°C during tempering.

Shot peening (AMS 2430) is mandatory for all landing gear structural forgings — the compressive residual stress induced by shot peening at the forging surface inhibits fatigue crack initiation at the stress concentrations of fillet radii, bore surfaces, and thread roots. The Almen intensity (the measure of shot peening energy, verified by the deflection of standard Almen strips) must be within the specified range — insufficient peening intensity fails to achieve the required compressive stress depth; excessive intensity can cause plastic flow and surface damage. For titanium landing gear forgings, the shot velocity and coverage requirements are specified in the applicable landing gear OEM’s engineering drawing, cross-referencing AMS 2430 with OEM-specific Almen intensity requirements.

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Vinir Capability

AS9100D full scope. Ti-6Al-4V beta-processed (AMS 4935) closed die forgings to 600 kg — solution treat above beta transus at 1,010–1,040°C, controlled cooling, age at 538°C. Standard Ti-6Al-4V STA (AMS 4928) for drag brace and secondary structure forgings. 300M (AMS 6257/AMS 6417) open die and closed die forgings to 500 kg — Q&T per AMS 2759/2 to 280 ksi minimum tensile. 4340M (AMS 6415) closed die forgings. Alpha case control per AMS 2801 for all titanium landing gear forgings. AMS 2154 Class AA immersion UT for beta-processed titanium. FPI to AMS 2647 Level 3. Shot peening per AMS 2430 at NABL-accredited or OEM-approved peening facility. AS9102 FAIR for all new landing gear part numbers.

Frequently Asked Questions

1.What is beta-processed Ti-6Al-4V (AMS 4935) and why is it specified for landing gear instead of standard STA (AMS 4928)?+–
Beta-processed Ti-6Al-4V (AMS 4935) is heat treated above the beta transus temperature (~995°C for Ti-6Al-4V), then slow-cooled or air-cooled to produce a lamellar (Widmanstätten) microstructure rather than the equiaxed bimodal microstructure of standard STA. This lamellar microstructure provides significantly higher fracture toughness (Kq typically 80–100 MPa√m versus 60–80 MPa√m for STA) and better fatigue crack growth resistance at the cost of slightly lower tensile strength (typically 895–930 MPa versus 930–1,000 MPa for STA). Landing gear primary structure is damage-tolerant designed — the structure must be able to sustain a detectable crack for at least one inspection interval without catastrophic failure. The higher fracture toughness and crack growth resistance of beta-processed Ti-6Al-4V extend the detectable crack size and the allowable inspection interval, making it the mandatory specification for landing gear beams and struts.
2.What is 300M steel and why is it preferred over 4340 for high-strength landing gear applications?+–
300M (UNS K44220) is a low-alloy ultra-high-strength steel — essentially a silicon-modified 4340 with approximately 1.6% silicon (versus 0.2–0.35% in standard 4340). The silicon addition delays the formation of epsilon carbide during low-temperature tempering, allowing the tempering temperature to be reduced while maintaining adequate toughness at the very high strength levels required for landing gear (280–300 ksi tensile). Standard 4340 at 280 ksi strength level has inadequate toughness — its Charpy impact energy drops below the safe threshold for landing gear applications. 300M at the same 280 ksi strength level achieves significantly better toughness than 4340 — it is the enabling material for narrowbody landing gear side struts where the thin-section geometry requires very high yield strength.
3.What NDT requirements apply to landing gear forgings for commercial aircraft qualification?+–
Landing gear forgings require the most stringent NDT in commercial aviation — they are fracture-critical (primary structure whose failure could result in aircraft loss). NDT requirements typically include: 100% immersion UT per AMS 2154 Class AA for titanium forgings (3.18mm FBH rejection threshold) and Class A for steel; 100% fluorescent penetrant inspection (FPI) per AMS 2647 Level 3 on all accessible machined surfaces; magnetic particle inspection (MPI) per AMS 2641 on steel forgings after all machining operations; and dimensional inspection per the landing gear OEM drawing (full CMM report for all critical dimensions). Some landing gear OEM programmes add eddy current inspection of specific bore surfaces where fatigue is the critical failure mode — eddy current can detect tight surface fatigue cracks not detectable by FPI.
4.What is the shot peening specification for landing gear forgings and how does Almen intensity verify compliance?+–
Shot peening for landing gear forgings is specified per AMS 2430 (Shot Peening of Metal Parts) with landing gear OEM-specific Almen intensity requirements overlaid. Almen intensity is measured using standardised spring steel strips (Almen ‘A’, ‘N’, or ‘C’ gauge depending on the intensity range) that are peened under the same conditions as the production component. After peening, the Almen strip deflects (arcs) due to the compressive stress introduced — the arc height measured on an Almen gauge is the Almen intensity. The required Almen intensity range (e.g., 0.010–0.018A for a titanium landing gear fitting) must be achieved and verified by peening at least two Almen strips per setup. Peening coverage (percentage of surface with overlapping dimple indentations) is typically specified at 98–100% minimum — verified visually under magnification by the process operator.
5.What landing gear component categories are accessible to Indian AS9100D forging manufacturers without OEM primary structure qualification?+–
The primary structure landing gear forgings (main gear beams, side struts, truck beams) require the most extensive OEM qualification and are currently dominated by PCC, Howmet, and Aubert & Duval. More accessible categories for Indian AS9100D manufacturers include: secondary structure forgings (door hinges, uplock fitting, down-lock fittings, torque link structural pins) where the failure consequence is a nuisance rather than catastrophic; MRO replacement forgings for in-service aircraft structural repair (where the OEM provides design approval and the forging manufacturer provides material and manufacturing conformance); and development/test forgings for landing gear OEM R&D programmes where production volume is low and qualification time pressure is less severe. Developing AS9100D track record in these accessible categories is the entry path to eventual primary structure qualification.