在起飞性能分析中,如果起飞方向上有一个无法越过的障碍物,你就需要考虑转弯.
如果转弯半径确定了,那么速度的最大值就确定了，这个速度称为V2maxnV= ( R * g * tan(坡度) ) ^ (1/2)
比如半径为2266米，坡度15度
V= sqrt( 2266 * 9.8 * tan(15) ) = 77.2 m/s = 150kt 这个速度是IAS，转换成TAS后就是最大的V2
如果速度太小也不行，如果你的速度已经接近失速速度，转弯时就可能失速。
通常审核的性能数据是在V2时能完成30度的坡度角（15度的坡度角加上15度的overshoot）时不会抖杆。这个抖杆速度可以在性能工程师手册里查表得到。比如查表得抖杆速度Vss为125kt，今天的V2是140kt。
cos(坡度) = ( Vss / V2 ) ^ 2 = ( 125 / 140 ) ^ 2n坡度 = 37.1度。因此这个V2可以做20度的坡度，还留有17度的overshoot余度。OK
昨天在看RJBB的通告，有老长一段：
A1504/09
RJBB
B) 0905061500 C)UFN
E) OPERATIONAL TRIAL FOR CONTINUOUS DESCENT ARRIVALS(CDA) AT KANSAI INTERNATIONAL AIRPORT (RJBB) IS UNDERWAY. FOLLOWING PROCEDURES ARE APPLIED. 1. PARTICIPATING ACFT: FMS EQUIPPED ACFT WHICH IS OPERATED BY JAPANESE AIRLINES WITH ETA RJBB BTN 1400UTC AND 2200UTC. 2. AIRSPACE WHERE OPERATIONAL TRIAL FOR CDA IS OPERATED: KANSAI APCH CTL AREA AND CTL AREA. 3. ROUTES APPLICABLE TO OPERATIONAL TRIAL FOR CDA: THOSE ARRIVAL ROUTES FOR RJBB VIA KARIN, KAZRA OR EVERT AND JOIN TOMO ARRIVAL,MARIO ARRIVAL OR PEACH ARRIVAL. 4. CONDITIONS ON OPERATIONAL TRIAL FOR CDA: RADAR MUST BE IN OPERATIVE AT RELEVANT ACC AND KANSAI RADAR APCH CTL FACILITY. 5. REQUEST AND CLEARANCE FOR CDA: CDA ROUTES FOLLOWING ARE USED WHEN PILOT REQUESTS CDA AND WHEN ATC CLEARS CDA. THERE ARE ALT RESTRICTIONS ON CDA ROUTES. ATC MAY ADD ALT RESTRICTIONS WHEN NECESSARY DUE TO TRAFFIC CONDITIONS. CDA MAY NOT BE CLEARED DUE TO TRAFFIC CONDITIONS. 6. TIMING FOR REQUESTING CDA: PILOT SHOULD REQUEST CDA NOT LATER THAN 10 MINUTES BEFORE REACHING TOP OF DESCEND(TOD) WITH POSITION OF TOD AND EST TIME OVER KARIN,KAZRA OR EVERT. 7. REPORT OF BEGINNING DESCEND: ONCE CDA IS CLEARED BY ATC, PILOT SHOULD REPORT ATC OF BEGINNING DESCEND. 8. SUSPENSION OR CANCELLATION OF CDA: ATC MAY SUSPEND OR CANCEL CDA DUE TO TRAFFIC CONDITIONS EVEN AFTER CDA IS CLEARED. ALTERNATE INSTRUCTIONS WILL BE ISSUED WHEN CDA IS SUSPENDED OR CANCELLED. TO BE CONTINUED
查了一下wiki，CDA就是“Continuous Descent Arrivals”或者“Continuous Descent Approach”，就是从TOD点或指定高度之后，飞机一直保持大约3度的角度（应该是下降梯度的意思吧），直到截获ILS落地。油门始终保持在慢车位。这种下降方法也称为Optimized Profile Descent (OPD)。这种运行方法的目的是为了减少耗油和减少噪音。过去，人们认为CDA在繁忙机场是很能实现的。现在随着导航技术和飞机性能的提高，国际上几大机场已经开始使用了，比如London Heathrow Airport、Los Angeles International Airport。通告上看5月6日之后大阪就开始试运行了。我个人觉得这种给管制部门找麻烦、航空公司得好处的事情在中国很能推行。
就收到的通告看，CDA要求飞机装有FMS，有特定的空域和进场程序，必须有雷达引导，机组需要在下降前10分钟提出申请，机组需要向管制报告下降开始，管制可以取消或者暂停CDA。不知道以后大阪开始全面实行CDA后，对非CDA的航班会不会有影响。
据说这是中国国内航空公司的第一次。汗～～，幸亏最近和台巴子们关系好。哈哈，竟然不用批复就飞跃了。以后遇到这种临时改航路的事情，一定要慎之又慎！