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Abstract
When one of the engines on a multi-engine aircraft stops working the one engine inoperative (OEI) condition exists. This causes several negative effects to a number of performance variables in addition to the loss of engine thrust. The range and endurance of an aircraft are directly related to the quantity of the fuel available and the fuel consumption rate.
This thesis was conducted to investigate range and endurance performance of a twin-engine jet aircraft of the Boeing 737 class, with One Engine Inoperative (OEI). The aims of the thesis also include analysis on All Engine Operating (AEO) performance including range and endurance performance, and turning flight performance. The modelling was mainly based on methods available in Jan Roskam textbooks and USAF DATCOM.
The model used Thrust and Specific Fuel Consumption data presented in Jenkinson, L.R., Simpkin, P., and Rhodes, D., "Civil Jet Aircraft Design," and detailed aircraft geometry properties given in Jane's All the World Aircraft as well as materials made available in references.
Required control surface deflections (ailerons and rudder) to maintain a moment balance in a given flight condition were determined. The increment in total drag (trim drag) on the aircraft due to these control surface deflections as well as the drag from wind milling inoperative engine were then added to the steady state drag. The total drag in One Engine Inoperative (OEI) condition was calculated to be increased by 30% at optimum range speed at 12,000 ft.
The range and endurance were calculated using the Breguet Range and Endurance equations and then compared with numerical integration methods to verify the reliability of the equations. It was observed that sensitivity of weights in determining range performance was not significant with numerical integration methods yielding favourable results.
It was found that the range performance with one engine inoperative (OEI) is approximately 2 to 5% superior while the endurance performance is about 11 to 14% superior to those with all engine operative (AEO) condition at flight levels where single engine flight is possible. The maximum one engine inoperative (OEI) altitude capability for the aircraft was estimated to be 12,000 feet. Speed reduction of about 15-20% of optimum range and endurance speeds with AEO is required to achieve optimum range and endurance performance in OEI condition for the aircraft.
Validation of the results predicted for AEO and OEI conditions for the aircraft with performance data in Boeing 737-300 flight planning manual revealed that difference fell within 11% for both conditions for range.
Finally, a further investigation into asymmetric thrust was conducted: turning performance (left turn vs. right turn) in a level coordinated flight condition with right OEI was analysed with turning on operative engine side (left turn with right OEI) proving a better option.