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1、4-1 Preparation for the arrival and approach begins long before the descent from the en route phase of flight. Planning early, while there are fewer demands on your attention, leaves you free to concentrate on precise control of the aircraft and better equipped to deal with problems that might arise
2、 during the last segment of the flight. TRANSITION FROM EN ROUTE This chapter focuses on the current procedures pilots and air traffic control (ATC) use for instru- ment flight rule (IFR) arrivals in the National Airspace System (NAS). The objective is to provide pilots with an understanding of ATC
3、arrival proce- dures and pilot responsibilities as they relate to the transition between the en route and approach phases of flight. This chapter emphasizes standard terminal arrival routes (STARs), descent clearances, descent planning, and ATC procedures, while the scope of coverage focuses on tran
4、sitioning from the en route phase of flight, typically the origination point of a STAR to the STAR termination fix. This chapter also differentiates between area navigation (RNAV) STARs and STARs based on conventional naviga- tional aids (NAVAIDs). Optimum IFR arrival options include flying directly
5、 from the en route structure to an approach gate or initial approach fix (IAF), a visual arrival, STARs, and radar vectors. Within controlled airspace, ATC routinely uses radar vectors for separation purposes, noise abatement considerations, when it is an operational advantage, or when requested by
6、pilots. Vectors outside of con- trolled airspace are provided only on pilot request. The controller tells you the purpose of the vector when the vector is controller-initiated and takes the aircraft off a previously assigned nonradar route. Typically, when operating on RNAV routes, you are allowed t
7、o remain on your own navigation. TOP OF DESCENT Planning the descent from cruise is important because of the need to dissipate altitude and airspeed in order to arrive at the approach gate properly configured. Descending early results in more flight at low altitudes with increased fuel consumption,
8、and starting down late results in problems controlling both airspeed and descent rates on the approach. Top of descent (TOD) from the en route phase of flight for high performance airplanes is often used in this process and is calculated manually or automatically through a flight management system (
9、FMS) Figure 4-1, based upon the altitude of Figure 4-1.Top of Descent and FMS Display. PROGRESS 2 / 3 SPD / ALT CMD VSTOD 240 / 3000 2400 TOC FUEL QTY 151 . 5NM / 00 + 23 20000 TOD GROSS WT 1022NM / 02 + 17 62850 AIR DATA FLT SUM Top of Descent 4-2 the approach gate. The approach gate is an imaginar
10、y point used by ATC to vector aircraft to the final approach course. The approach gate is established along the final approach course 1 nautical mile (NM) from the final approach fix (FAF) on the side away from the airport and is located no closer than 5 NM from the landing threshold. The altitude o
11、f the approach gate or initial approach fix is subtracted from the cruise altitude, and then the target rate of descent and groundspeed is applied, resulting in a time and distance for TOD, as depicted in Figure 4-1 on page 4-1. Achieving an optimum stabilized, constant rate descent during the arriv
12、al phase requires different procedures for turbine-powered and reciprocating-engine air- planes. Controlling the airspeed and rate of descent is important for a stabilized arrival and approach, and it also results in minimum time and fuel consumption. Reciprocating-engine airplanes require engine pe
13、rform- ance and temperature management for maximum engine longevity, especially for turbocharged engines. Pilots of turbine-powered airplanes must not exceed the airplanes maximum operating limit speed above 10,000 feet, or exceed the 250-knot limit below 10,000 feet. Also, consideration must be giv
14、en to turbulence that may be encountered at lower altitudes that may necessitate slowing to the turbulence penetration speed. If necessary, speed brakes should be used. DESCENT PLANNING Prior to flight, calculate the fuel, time, and distance required to descend from your cruising altitude to the app
15、roach gate altitude for the specific instrument approach of your destination airport. In order to plan your descent, you need to know your cruise altitude, approach gate altitude or initial approach fix altitude, descent groundspeed, and descent rate. Update this information while in flight for chan
16、ges in altitude, weather, and wind. Your flight manual or operating handbook may also contain a fuel, time, and distance to descend chart that contains the same information. The calculations should be made before the flight and “rules of thumb” updates should be applied in flight. For exam- ple, fro
17、m the charted STAR you might plan a descent based on an expected clearance to “cross 40 DME West of Brown VOR at 6,000” and then apply rules of thumb for slowing down from 250 knots. These might include planning your airspeed at 25 NM from the runway threshold to be 250 knots, 200 knots at 20 NM, an
18、d 150 knots at 15 NM until gear and flap speeds are reached, never to fall below approach speed. The need to plan the IFR descent into the approach gate and airport environment during the preflight planning stage of flight is particularly important for turbojet pow- ered airplanes. A general rule of
19、 thumb for initial IFR descent planning in jets is the 3 to 1 formula. This means that it takes 3 NM to descend 1,000 feet. If an airplane is at flight level (FL) 310 and the approach gate or initial approach fix is at 6,000 feet, the initial descent require- ment equals 25,000 feet (31,000 - 6,000)
20、. Multiplying 25 times 3 equals 75; therefore begin descent 75 NM from the approach gate, based on a normal jet airplane, idle thrust, speed Mach 0.74 to 0.78, and vertical speed of 1,800 - 2,200 feet per minute. For a tailwind adjust- ment, add 2 NM for each 10 knots of tailwind. For a headwind adj
21、ustment, subtract 2 NM for each 10 knots of headwind. During the descent planning stage, try to determine which runway is in use at the destination air- port, either by reading the latest aviation routine weather report (METAR) or checking the automatic terminal information service (ATIS) informatio
22、n. There can be big differences in distances depending on the active run- way and STAR. The objective is to determine the most economical point for descent. An example of a typical jet descent-planning chart is depicted in Figure 4-2. Item 1 is the pressure altitude from which the descent begins; it
23、em 2 is the time required for the descent in minutes; item 3 is the amount of fuel consumed in pounds during descent to sea level; and item 4 is the distance covered in NM. Item 5 shows that the chart is based on a Mach .80 airspeed until 280 knots indicated airspeed (KIAS) is obtained. The 250- kno
24、t airspeed limitation below 10,000 feet mean sea level (MSL) is not included on the chart, since its effect is minimal. Also, the effect of temperature or weight variation is negligible and is therefore omitted. Due to the increased cockpit workload, you want to get as much done ahead of time as pos
25、sible. As with the Note: Subtract 30 lb. of fuel and 36 seconds for each 1,000 feet that the destination airport is above sea level. .80/280 Press Alt - 1000 Ft Time - Min Fuel - Lbs Dist - NAM 39 37 35 33 31 29 27 25 23 21 19 17 15 10 5 20 19 18 17 16 15 14 13 12 11 10 10 9 6 3 850 800 700 650 600
26、600 550 550 500 500 450 450 400 300 150 124 112 101 92 86 80 74 68 63 58 52 46 41 26 13 is is fo or a or ea t a ote:e: S S 5 5 10 12 1 2 6 60 0 0 6 650 0060 50 0 0 12 2 NAMA AMM t - Figure 4-2.Typical Air Carrier Descent Planning Chart 4-3 climb and cruise phases of flight, you should consult the pr
27、oper performance charts to compute your fuel require- ments as well as the time and distance needed for your descent. Figure 4-3 is an example of a descent-planning chart. If you are descending from 17,000 feet to a final (approach gate) altitude of 5,650, your time to descend is 11 minutes and dist
28、ance to descend is 40 NM. During the cruise and descent phases of flight, you need to monitor and manage the airplane according to the appropriate manufacturers recommendations. The flight manuals and operating handbooks contain cruise and descent checklists, performance charts for specific cruise c
29、onfigurations, and descent charts that provide information regarding the fuel, time, and distance required to descend. Review this information prior to the departure of every flight so you have an understand- ing of how your airplane is supposed to perform at cruise and during descent. A stabilized
30、descent constitutes a pre-planned maneuver in which the power is properly set, and minimum control input is required to maintain the appropriate descent path. Excessive corrections or control inputs indicate the descent was improperly planned. Plan your IFR descent from cruising altitude so you arri
31、ve at the approach gate altitude or initial approach fix altitude prior to beginning the instrument approach. Figure 4-4 on page 4-4 Descending from cruise altitude and entering the approach environment can be a busy time during the flight. You are talking on the radio, changing radio fre- quencies,
32、 pulling out different charts, adjusting controls, Figure 4-3. Descent Planning Chart. Altitude Loss Required Approach Gate Altitude Determine the required altitude loss by subtracting the approach gate altitude from the cruise altitude. Calculate the descent time by dividing the total altitude loss
33、 by the descent rate. This provides you with the total time in minutes that it will take to descend. Using a flight computer, determine the distance required for descent by finding the distance traveled in the total time found using the known groundspeed. The resulting figure is the distance from th
34、e destination airport approach gate at which you need to begin your descent. 4-4 reading checklists, all of which can be distracting. By planning your descent in advance, you reduce the work- load required during this phase of flight, which is smart workload management. Pilots often stay as high as
35、they can as long as they can, so planning the descent prior to arriving at the approach gate is necessary to achieve a stabilized descent, and increases situational awareness. Using the information given, calculate the distance needed to descend to the approach gate. Cruise Altitude:17,000 feet MSL
36、Approach Gate Altitude:2,100 feet MSL Descent Rate:1,500 feet per minute Descent Groundspeed:155 knots Subtract 2,100 feet from 17,000 feet, which equals 14,900 feet. Divide this number by 1,500 feet per minute, which equals 9.9 minutes, round this off to 10 minutes. Using your flight computer, find
37、 the distance required for the descent by using the time of 10 minutes and the groundspeed of 155 knots. This gives you a dis- tance of 25.8 NM. You need to begin your descent approximately 26 NM prior to arriving at your destina- tion airport approach gate. CRUISE CLEARANCE The term “cruise“ may be
38、 used instead of “maintain“ to assign a block of airspace to an aircraft. The block extends from the minimum IFR altitude up to and including the altitude that is specified in the cruise clearance. On a cruise clearance, you may level off at any intermediate altitude within this block of airspace. Y
39、ou are allowed to climb or descend within the block at your own discretion. However, once you start descent and verbally report leaving an altitude in the block to ATC, you may not return to that altitude without an additional ATC clearance. A cruise clearance also authorizes you to execute an appro
40、ach at the destination airport. When operating in uncontrolled airspace on a cruise clearance, you are responsible for determining the minimum IFR altitude. In addition, your descent and landing at an airport in uncontrolled airspace are governed by the applicable visual flight rules (VFR) and/or Op
41、erations Specifications (OpsSpecs), i.e., CFR, 91.126, 91.155, 91.175, 91.179, etc. HOLDING PATTERNS If you reach a clearance limit before receiving a further clearance from ATC, a holding pattern is required at your last assigned altitude. Controllers assign holds for a variety of reasons, includin
42、g deteriorating weather or high traffic volume. Holding might also be required fol- lowing a missed approach. Since flying outside the area set aside for a holding pattern could lead to an encounter with terrain or other aircraft, you need to understand the size of the protected airspace that a hold
43、ing pattern pro- vides. Each holding pattern has a fix, a direction to hold from the fix, and an airway, bearing, course, radial, or route on which the aircraft is to hold. These elements, along with the direction of the turns, define the holding pattern. Since the speed of the aircraft affects the
44、size of a hold- ing pattern, maximum holding airspeeds have been Figure 4-4. Descent Preflight Planning 4-5 designated to limit the amount of airspace that must be protected. The three airspeed limits are shown in Figure 3-31 in Chapter 3 of this book. Some holding patterns have additional airspeed
45、restrictions to keep faster airplanes from flying out of the protected area. These are depicted on charts by using an icon and the limiting airspeed. Distance-measuring equipment (DME) and IFR-certi- fied global positioning system (GPS) equipment offer some additional options for holding. Rather tha
46、n being based on time, the leg lengths for DME/GPS holding patterns are based on distances in nautical miles. These patterns use the same entry and holding procedures as conventional holding patterns. The controller or the instrument approach procedure chart will specify the length of the outbound l
47、eg. The end of the outbound leg is determined by the DME or the along track dis- tance (ATD) readout. The holding fix on conventional procedures, or controller-defined holding based on a conventional navigation aid with DME, is a specified course or radial and distances are from the DME sta- tion fo
48、r both the inbound and outbound ends of the holding pattern. When flying published GPS overlay or standalone procedures with distance specified, the holding fix is a waypoint in the database and the end of the outbound leg is determined by the ATD. Instead of using the end of the outbound leg, some
49、FMSs are pro- grammed to cue the inbound turn so that the inbound leg length will match the charted outbound leg length. Normally, the difference is negligible, but in high winds, this can enlarge the size of the holding pattern. Be sure you understand your aircrafts FMS holding program to ensure that the holding entry procedures and leg lengths match the holding pattern. Some situa- tions may require pilot intervention in order to stay within protected airspace. Figure 4-5 DESCENDING FROM THE EN R