Feasibility Investigation on Reduced-Power Take-off of MA600

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Feasibility Investigation on Reduced-Power Take-off of MA600 Ao liangzhong 1, a, Miao Yang 2, b 1 Civil Aviation Flight University of China, Sichuan Guanghan , China 2 Civil Aviation Flight University of China, Sichuan Guanghan , China a aolz@aemtc.com, b @qq.com Keywords: MA600 aircraft; reduce-power take-off; assumed temperature; necessary conditions Abstract: This paper investigates the feasibility of MA600 reduced-power take-off by finding the necessary conditions which reduced-power take-off must satisfy based on the performance characteristics and actual flight data of MA600 turboprop aircraft. Finally, we come to the conclusion that reduced-power take-off of MA600 aircraft can be achieved. Introduction MA600 aircraft is a twin turboprop regional aircraft developed by the Xi'an Aircraft Industry Company in In most situations, take-off weight is far less than the maximum take-off weight. So considered from the aircraft performance and the security, MA600 aircraft has spaces to take off with reduced-power. MA600 aircraft use PW12J engines. This engine include two-stage compressor, two-stage turbines and gas generator, driving four-blade propeller by free turbine, concentric shaft and deceleration gearbox. The Characteristic parameters of this kind of engine are torque and rotational velocity. In these two parameters, the most important parameter for setting engine power is torque. MA600 aircraft controls the output power by adjusting the value of torque. When take off normally, engine uses the maximum take-off power. But if take-off weight is less than the maximum takeoff weight, it will waste lots of power. At home and abroad nothing had been done about reduced-power take-off of turboprop, so it is very significant to do some research about reduced-power take-off of MA600 aircraft. Currently, Turbofan engines have a mature way to achieve reduced-power take-off by the method of assumed temperature. We can apply it to the turboprop aircraft with according modification. Turbofan engines use assumed temperature with two necessary conditions: 1. The actual take-off weight is less than the maximum take-off weight of an aircraft. 2. Assumed temperature determined by the actual takeoff weight is higher than the reference temperature [1]. Thus, we can assume that to achieve reduced-power take-off of MA600 aircraft, we must find two similar conditions. If these two conditions can be found out, it will prove that it is feasible to achieve reduced-power take-off of MA600 aircraft. Organization of the Text Maximum Take-off Weight. The maximum take-off weight of the aircraft is an important factor affecting the economy of flight transportation and one of the main factors that affect flight safety. The greater the take-off weight of the same aircraft is, the better the economy of flight transportation is. While in actual flight, a lot of factors affect the maximum take-off weight. The All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-19/09/16,11:16:31)

2 Advanced Materials Research Vols maximum take-off weight of aircraft has some restrictions, such as Course Road conditions, the take-off performance, braking energy, tires speed and ability over the barriers. It is for sure that at any time take-off weight can not exceed the limit of the maximum weight without fuel and maximum take-off weight due to aircraft structural strength. When flying on short routes, the maximum take-off weight may also be subject to the restriction of the maximum landing weight. When fly over the mountain, the maximum take-off weight may also be subject to a ceiling limit of the aircraft with single-power. Therefore, the maximum take-off weight of an aircraft is the maximum take-off weight which satisfies the restrictions of aircraft take-off security in certain airport conditions and atmospheric conditions. The maximum take-off weight of an aircraft is the minimum value which satisfies the restrictions of all the safety factors above [2]. By analysing the aircraft performance, we can find that maximum take-off weight of turboprop is an important factor which affects take-off performance just like turbofan. Factors affecting the maximum take-off weight of turboprop are also the same as turbofan. The maximum take-off weight of aircraft varies form different airports and atmospheric conditions. MA600 aircraft is a turboprop aircraft and self-made wholly by china, it has its own particularities. From MA600 Aircraft Flight Manual, factors that affect the maximum take-off weight of MA600 aircraft include the maximum design take-off weight(g1), the second segment take-off climbing gradient restrictions(g2), runway restrictions(g3), obstacle height restrictions(g4), obstacle height restrictions with single-engine(g5), approaching climbing gradient restrictions(g6) and runway restrictions during landing(g7), but not include the first segment take-off climbing gradient restrictions, the last segment take-off climbing gradient restrictions, the tires speed, brake energy and minimum unstick speed limit. MA600 take the minimum weight which satisfies all those factors as maximum take-off weight (G) [3]. G=min(G 1,G 2,G 3,G 4,G 5,G 6,G 7 ) (1) MA600 route analysis software can work out maximum take-off weight based on the actual conditions of the aircraft and airport. This weight also can be figured out by referring to related charts of MA600 manual. Combined with the usually take-off data, it satisfies the first necessary condition of reduced-power take-off when actual take-off weight is less than the maximum take-off weight. The usually take-off weight of MA600 aircraft is about 18t. It can be seen from Table 1, the maximum take-off weight is more than the daily take-off weight, so it has spaces to take off with reduced-power. Table 1. The maximum take-off weight limited by aircraft structure and take-off climbing restrictions Temperature [ C] Maximum take-off weight[kg] Flat Rat Temperature. The maximum take-off weight at a certain pressure altitude can be found from MA600 manual when the runway is in a good condition and no obstacle on the route, shown as Table 1. The characteristic curve of maximum take-off weight with temperature is plotted based

3 488 Materials, Transportation and Environmental Engineering on the values from Table 1, shown as Fig. 1 Wherein the temperature is a standard atmospheric temperature. According to the manual data, we can find that aircraft has similar characteristics at different pressure height. Fig. 1.The characteristic curve of maximum take-off weight with temperature Fig. 1 shows the law that maximum take-off weight varies with the temperature. From Fig. 1, we can find that actual take-off weight of the aircraft has a corresponding assumed temperature when actual take-off weight of the aircraft is less than the maximum take-off weight. And this assumed temperature must be greater than the actual temperature. The maximum take-off weight at assumed temperature is equal to the actual take-off weight at actual temperature. Thrust flat rat temperature of turbofan engine is determined according to temperature characteristics of the turbofan engine. So to figure out whether MA600 aircraft has a flat rat temperature, the most important data is the temperature characteristics of the turboprop engine. For turbofan engine, as the temperature increases engine thrust remains unchanged before the thrust flat rat temperature of the engine. When the temperature exceeds the flat rat temperature, engine thrust begins to decrease as the temperature increases. In actual flight, it is hard to determine the thrust of turboprop engine. While the most important parameter characterizing the turboprop is torque. MA600 manuals give the torque data which is used to set power. Form these datum, we can find the take-off torque is frozen at 90% as the temperature increases for a certain airport, when temperature reaches a certain corner point, the torque of the turboprop engine begins to decline as the external temperature increases. Draw the characteristic curve of take-off torque with temperature at sea level, shown as Fig. 2 Wherein the temperature is a standard atmospheric temperature, flat rat temperature of the torque can be found from this figure. The actual take-off weight of the aircraft is corresponding to an assumed temperature, when this assumed temperature is higher than flat rat temperature, reduced-power take-off will be implemented. Therefore, the second necessary condition of reduced-power take-off is that the assumed temperature determined by the actual take-off weight is higher than the torque flat rat temperature of an engine.

4 Advanced Materials Research Vols Fig. 2. The characteristic curve of take-off torque with temperature Fig. 3. Curve of flat rat temperature with altitude The torque flat rat temperature of MA600 aircraft is shown as Fig. 3 The different altitude has a different flat rat temperature. As the altitude increases, the flat rat temperature decreases. When the pressure altitude is higher than 10000ft, the flat rat temperature is less than -40 C [4]. The Meaning of Assumed Temperature. The difference between the reduced-power take-off of the MA600 and the reduced-thrust take-off of the high bypass ratio turbofan engine is that the two types of engine achieve reduced-power take-off by controlling the different value. Turbofan engine controls the value of N1 to adjust thrust, while turboprop engine controls the torque directly. Similar with high bypass ratio turbofan engine, the meaning of the assumed temperature in this paper is shown as follows:

5 490 Materials, Transportation and Environmental Engineering Fig. 4. The relationship between the various parameters As shown from Fig. 4, atmospheric temperature t1 is according to a maximum take-off weight Wmax1 and a take-off torque T1. The actual take-off weight is Wsj when then temperature is t C. There is a temperature point considered as assumed temperature t js, at that point the maximum take-off weight is equal to Wsj. The take-off torque is T3 when the temperature is t js. As shown in the Fig. 4, t js >TRFF and T3<T1 (T2). The torque that satisfies the need of the take-off performance security is equal to T3, which is the take-off torque when the temperature is t js, so T3 is the reduced-power take-off torque. The torque reduces T1 ( T1=T1-T3) when the temperature is t1, the torque reduces T2 ( T2=T2-T3) when the temperature is t2. Therefore, assumed temperature is the equivalent ambient air temperature determined by the actual take-off weight of an aircraft. Summary From the analysis above, we can conclude the two necessary conditions of MA600 reduced-power take-off as follows: 1. The actual takeoff weight is less than the maximum takeoff weight of an aircraft. 2. Assumed temperature determined by the actual takeoff weight is higher than engine torque flat rat temperature. After getting the torque at assumed temperature, we can get the targeted torque under the reduced-power take-off by using the analogical conditions of the turboprop to convert the torque at assumed temperature into the corresponding torque at actual temperature. So we can get the conclusion that the reduced-power take-off of the MA600 aircraft is feasible when the two necessary conditions are satisfied. References [1] Liu Xiaoming, Zhao Tingyu. Reduced-Thrust Takeoff Technique Applied to Passenger Airplanes, J. Flight Mechanics, ( ) [2] Chen Zhihuai. Aircraft Performance Engineering. Beijing, Science Press, [3] Wang Dong, Chen Hongying. Analysis on MA60 Aircraft Takeoff Performance, J. Journal of Civil Aviation Flight University of China, ( ) [4] MA600 Aircraft Flight Manual and Flight Crew Operating Manual. Xi an, Xi an Aircraft Industry Company Ltd. (2000)