Load tests and moments evaluation of aircraft pylon using refurbished test assembly

Abstract

An aircraft pylon is a suspension device under the fuselage or wing of an aircraft

used to attach and carry missiles, gun pods, propulsion units, fuel tanks etc. The

component-loaded pylon experiences considerable loads in yaw, pitch and roll

during the corresponding aircraft flight manoeuvres. It is deemed necessary to have

reliable test facility and methodology, and accurate load estimation procedure that

can establish on ground the load coefficients for a pylon useful for arriving at

various loads during the aircraft flight.

In this dissertation, a non-jettisonable pylon of F- 16 Aircraft used for carrying an

external fuel tank or store (600 gallons capacity), is studied. The pylon, which has

been the specimen of this experimental stud y, is equipped with st rain gauge bridges

to monitor the loads transferred between the fuel tank and the pylon structure. It

was ensured that the test rig, although portable, was able to facilitate 13 predefined

load cases without any distortions, lifting and deformations in any of its sections.

Some of the important details are presented. Experiments were conducted as

specified by the OEM report [4] and each strain gauge bridge response was

monitored for different levels of (20 to 100%) loading for the all 13 load conditions.

The methodology established for determining load equations and load coefficients

(s lope and probable error) in pitch, roll and yaw using the obtained strain gauge

data is explained. The strain gauge information was analysed using a MATLAB

program written for this purpose. The load coefficients thus accomplished are

specific to the pylon and the suspended load, and their trends, relationships, the

effect on them of change in strain gauge locations are discussed. Additionally, a

similar exercise is conducted using ASYS, a genera l-purpose FEA software, and

findings are compared with the test results. Other inferences and deductions drawn

from this study are deliberated. Apart from that, two different approaches for

reducing the probable error are also attempted.