Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal Failure analysis of a broken support strut of an aircraft landing gear Asad Hameed ⁎ , Ossama Zubair, Taimur Ali Shams, Zahid Mehmood, Ali Javed, Zahid Mehmood College of Aeronautical Engineering, National University of Sciences and Technology, Islamabad, Pakistan ARTICLE INFO Keywords: Aircraft landing gear failure Overload failure Finite element analysis Landing impact loads Fractography ABSTRACT This study contains the analysis of a nose landing gear support strut of an aircraft that failed during landing within 2 s after nose wheel touchdown. Visual inspection revealed that threaded portion of an eye-end bolt of the support strut was fractured. Furthermore, on the upper portion of the strut, one of the two retaining pins connecting it with aircraft structure was found dis- lodged from housing inficting damage to the adjacent brackets. During detailed fractography, no indication of progressive failure was observed; on the contrary, clear signatures of overload failure were found. Compositional analysis revealed the fractured eye-end bolt to be AISI 4130 steel. Metallography revealed no nonconformities in the microstructure whereas the hardness was found to be as per desired values. Finite element method was used to fnd the (overload failure) stress in the eye-end bolt during landing. The landing impact forces were calculated using multibody dynamic tool MSC ADAMS® and subsequently applied to the support strut model in ANSYS®. Numerical stress simulations were performed for diferent cases and the stresses at the eye-end were analysed. The stress at the fractured region was within yield limit for all cases of normal operation. However, the stress rose to well beyond UTS when one pin connection was dislodged from the housing, owing to a likely improper installation. 1. Introduction An aircraft contains several complex systems and among those fight controls, landing gears and engines are considered the most critical to fight safety. It is well known that 55% of aviation-related failures occur during the take-of and landing phases [1]. During these phases, landing gears are subjected to high impact and inertial loads, and any failure at the instant can be catastrophic. This makes both designing as well as maintenance of the landing gear systems a crucial part of aerospace engineering activities. Despite the best eforts of engineers and technicians, the failures still occur which need to be investigated thoroughly to ascertain the root cause and to avoid recurrences [2]. This has been meticulously practised in the aviation industry over the past sixty years which has rendered air travel to be amongst the safest of all modern modes of travel [3,4]. A literature study into landing gear failures reveals that most of these are caused due to problems related to (i) material, (ii) human error, (iii) component design and/or processing. In material related problems fatigue and environmental efects (such as stress corrosion cracking) are the most common [5,6]. In human error category, heavy impact landing [7], machining errors resulting in stress concentration sites [8] or overlooking necessary inspection such as missing a fatigue retardation process [9] are relevant examples. Inadequacy in design could involve the presence of stress concentration sites [1,6], whereas faulty processing may include https://doi.org/10.1016/j.engfailanal.2020.104847 Received 26 June 2020; Received in revised form 7 August 2020; Accepted 10 August 2020 ⁎ Corresponding author. E-mail addresses: asadhameed@cae.nust.edu.pk (A. Hameed), Zahid@cae.nust.edu.pk (Z. Mehmood), Zahid_mehmood@cae.nust.edu.pk (Z. Mehmood). Engineering Failure Analysis 117 (2020) 104847 Available online 13 August 2020 1350-6307/ © 2020 Elsevier Ltd. All rights reserved. T