This paper deals with the study and comparison of the dynamic response of aircraft with passive and active landing gears due to runway irregularities while the aircraft is taxying. This paper develops a detailed full aircraft mathematical vibration model to describe an active landing gear system. The derived dynamic equations are used to analyze the active landing gear system using proportional integral derivative (PID) controllers. The performance of this system is compared with the passive landing gear system by numerical simulations. The active landing gear system is able to increase the ride comfort and good track holding by reducing the fuselage acceleration, vertical fuselage displacement caused by landing and runway excitations.

In this article, random vibration analysis of full aircraft with passive and active landing gears has been done by numerical simulations on random runway profile. The mathematical model of full aircraft with active landing gears and modelling of runway profiles have been developed for analysing the aircraft bounce, pitch, roll accelerations, displacement and shock strut travel while taxiing on random runways. The results show that vibration levels of the aircraft by the active landing gear system is less than the conventional landing gear system while taxiing on different grades of random runways. Comparison results also show that the active system improves the ride comfort and easiness of pilot handling and thus, increases the fatigue life of the aircraft. NOMENCLATURE MAircraft fuselage mass m 1Nose landing gear tire mass m 2 Rear left landing gear tire mass m 3 Rear right landing gear tire mass ks 1 Nose gear shock strut stiffness ks 2 Rear left gear shock strut stiffness ks 3 Rear right gear shock strut stiffness cs 1 Nose gear shock strut damping coefficient cs 2 Rear left gear shock strut damping coefficient cs 3 Rear right gear shock strut damping coefficient kt 1 Nose gear tire stiffness kt 2 Rear left gear tire stiffness kt 3 Rear right gear tire stiffness ct 1 Nose gear tire damping coefficient ct 2 Rear left gear tire damping coefficient ct 3 Rear right gear tire damping coefficient [M] Mass matrix [C] Damping INTRODUCTIONLanding gear is a critical component of the aircraft which transmits the ground loads to the aircraft structure. It provides ride comfort to the passengers during taxiing on the runways. It also improves the pilot's efficiency to control the aircraft and to read the instruments in the glass cockpits during ground manoeuvres. The landing gear fitted in the aircraft is not able to adjust the damping characteristics in real-time runway conditions. The focus on active landing gear system is essential to overcome the difficulties of passive landing gear. presented a PID controller tuned with Ziegler-Nichols rules for both robustness and vibration suppression performance aspects. The application of proportional controller to active vibration control incorporated with a passive vibration isolator to suppress the resonant oscillation at its natural frequency was studied by Liu [13]. The present study analysed random vibration of full aircraft model with active landing gears under normal landing condition and dynamic response on different grades of random runways. The designed PID controller generates the control force to reduce bounce, pitch, roll displacement and accelerations of fuselage body considerably. This article does not analyse the bank angle response by PID controller during flight. The PID controller requires the bank angle reference command to tackle the unknown banking for turn coordination. However, the bank angle reference is required by the PID controller during crosswind taxiing conditions. Runway roughness affects both the landing gear and the airframe. Nowada...

Shock tube facility in the Propulsion and High Enthalpy laboratory, Aerospace Engineering Department, has been extensively used to study the ignition characteristics of fuels by measuring the ignition delay times for various hydrocarbon fuels at high temperatures. Initially a systematic method has been followed to calibrate the shock tube for ignition delay time measurements by measuring the delay times of C2H6 - O2 gas mixture diluted with argon. The results show good agreement with earlier reported works of Ethane ignition. Ignition times of low molecular weight liquefied petroleum gas, a fuel used in many industrial and household applications has been studied in the temperature range of 1250-1880 K and in the pressure range of 6-11 atm at equivalence ratios (Φ = 0.5 & 1). The ignition delay was measured in the reflected shock region by recording the ignition-induced pressure rise and emission from CH radical simultaneously. From the present study it is noted that the ignition delay time for liquefied petroleum gas reduces with increase in temperature and its activation energy lies in the range of 40 kcal/mol.

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