Lesson 3 B LR Specifications/Limitations

Transcription

1 Copyright Avfacts ATPL B727 Flight Planning Limits page 1. Lesson 3 B LR Specifications/Limitations Specifications The B727 aircraft is a 3 engined airliner with all engines mounted in the tail section. (refer fig 1-1). The engines are Pratt and Whitney JT8D-15 low bypass turbofans. The LR denotes the long range version with extra fuel capacity. Seating capacity is variable, but typically 144 passengers can be carried. An under-floor area provides storage for freight and passenger baggage. The wings feature positive dihedral (ie: higher at the tips than at the wing root), and are swept rearwards approximately 35 degrees. A flight crew of 3 is required, 2 pilots and one flight engineer. Fig FP1-1. B tri-jet aircraft. Maximum taxi weight Limitations This describes the maximum weight at which the aircraft can leave the terminal building and is 89, 700 kg. It is a structural limitation. Maximum brake release weight Refer B727 manual pages 1-1 to 1-5. Abbreviated as Max BRW, this describes the maximum structural weight limitation at which the aircraft can begin it s takeoff roll, and is 89, 350 kg at airports below 3, 000 ft pressure altitude. If taking off at airports at or above 3, 000 ft pressure altitude, the max BRW is reduced by 50 kg per 1, 000 ft. (eg: at a 3, 000 ft pressure altitude airport max BRW is limited to 89, 300 kg. At a 4, 000 ft pressure altitude airport the max BRW is 89, 250 kg, and so on). In low lying countries such as Australia the reduction in the takeoff limit is not of concern, as no airport is high enough to achieve a 3, 000 pressure altitude.so for Australia and the like the max structural BRW remains at 89, 350 kg. Note well: As the standard taxi fuel allowance is 150 kg from the terminal building (ramp) to the takeoff point, the heaviest weight that the aircraft will leave the ramp is 89, 500 kg (ie: 89, 350 kg kg). In countries such as America and in Europe there are often 10 or 20 aircraft waiting to takeoff, in which case the standard allowance to taxi from terminal to takeoff point will be approximately 350 kg, meaning a ramp departure weight of 89, 700 kg is possible.

2 Copyright Avfacts ATPL B727 Flight Planning Limits page 2. There are only three elements which make up the total weight of any aircraft. They are basic operating gross weight (Basic Op GW ), fuel on board (FOB), and payload carried (ie: passengers/freight). Basic Operating Gross Weight The fleet average is 47, 000 kg, but varies from B727 to B727 dependant on the equipment carried. For example a B727 used on overwater operations such as between islands in the Pacific will have life rafts on board, which a B727 used exclusively for over land operations will not be required by law to carry. Typically in exams a particular Basic Op GW will be specified in the question. If not you will be expected to assume and know the fleet average of 47, 000 kg. Basic Op GW includes all crew members, lubricating oil, fuel trapped in the tanks due to tank design (called unusable fuel ), food etc. It does NOT include usable fuel, passengers or freight. Max Zero Fuel Weight (MZFW) All B727 s are limited to a maximum zero fuel weight of 63, 500 kg. This is effectively a wing spar load limit. It is made up of the aircraft basic operating GW and the weight of passengers/freight (ie: payload). It represents the maximum weight which a B727 can be loaded, after which any addition weight must be fuel. Exceeding the MZFW will over-stress the wing spar, especially in turbulent conditions and during steep turns. Fig FP 1-2. Fuel in wings relieves spar stress. The actual aircraft ZFW, and ZFW centre of gravity position must be checked and recorded on the aircraft load sheet. Fuel loaded in the wings assists in relieving the upward force generated by the wings when they create lift (refer fig 1-2). The ZFW is only of consequence during flight when the wings create lift, and so it is assessed at the takeoff point (ie: brake release weight). Payload This is always the difference between the aircraft actual zero fuel weight and the aircraft basic op GW. For example the aircraft may have a BRW of 80, 000 kg, and a FOB of 20, 000 kg, so the ZFW will be 60, 000 kg (ie: 80, 000kg - 60, 000 kg). If the aircraft basic operating GW is 47, 100 kg, then the payload of passengers and freight that can be carried is 13, 100 kg (ie: ZFW of 60, 000 kg - 47, 100 kg). Maximum payload is simply the difference between the maximum ZFW of 63, 500 kg, and the aircraft Basic Op GW. Airspeed upper limits The maximum operating speeds are shown in the B727 manual at the bottom of page 1-1. The airspeed indicator (ASI) has a red and white striped needle called the VMO/ MMO needle often referred to as the barbers pole (refer to fig 1-3). Thisgraphically represents the upper airspeed limits to the pilots. At low altitudes below approximately 26, 600 ft the aircraft is limited by an indicated airspeed (IAS) value, whereas above this level it is limited by a Mach number of Mach If the aircraft is operated above these speeds a loud clacking overspeed warning will activate in the cockpit. It can not be inhibited (silenced) except by lowering the speed below the VMO/MMO limit speed. VMO/MMO limit pointer (barbers pole) Airspeed indicator needle Fig FP 1-3 Airspeed indicator barbers pole.

3 Copyright Avfacts Limits page 3. ATPL B727 Flight Planning Centre of gravity This is covered in the Performance and Loading texts, not in Flight Planning! 73, 000 kg - flap 30 set 72, 600 kg Maximum Structural Landing Weight 30 degrees flap This flap setting is that normally used unless the runway length is short. Most B727 s landing at capital city airports will lower 30 degrees of flap. The maximum aircraft GW weight at which 30 flap can be used is 72, 600 kg. The maximum aircraft gross weight at which 30 flap can be lowered is 73, 000 kg. 5 nm Fig FP Flap landing. Runway Landing flap is normally selected at about 5 nm from the runway threshold. Approximately 400 kg of fuel is burnt over the last 5 nm of the approach, meaning the aircraft will land at the 72, 600 kg maximum. (Refer fig FP 1-4) Max Structural Landing Weight 40 degrees Flap 65, 100 kg - flap 40 set This is 64, 650 kg. The maximum GW at which the pilot can select 40 flap in flight is 65,100 kg. The 450 kg between this weight and the maximum landing weight represents that fuel which is burnt during the last stages of the approach. Boeing provided 40 flap to allow jet operations into airports previously restricted to slow propeller driven aircraft due to the short runway lengths (refer fig 1-5). 5 nm 64, 650 kg During testing the B727 prototype was flown to La Paz, Bolivia, in South America. La Paz airport had previously been restricted to commercial propeller operations due to the high 13, 000 ft elevation of it s airport. Fig FP Flap landing. The world aviation press, plus several airline representatives were invited to witness the historic landing of the first commercial jet at La Paz - something some thought impossible. The B727 landed, easily pulling up with runway to spare. After the usual photo opportunities whilst being loaded with a large load of freight, the airliner began it s takeoff and climbout which was uneventful. Just to underline the incredible performance of the B727, the flight crew failed one of the engines at V1, the aircraft easily climbing with smoke only visible from the two operating engines. Needless to say the airlines and press were very impressed, and airlines lined up to purchase this amazing aircraft. In the early 1980 s the B727 was replaced on the production line by the B757 twin jet. There are approximately 1, 000 B727 s still in service. Mach 0.83 Maximum Landing Gear Operating speeds -VLO/MLO (refer fig FP 1-6) This represents the maximum speed expressed as either indicated airspeed (IAS) or as a Mach number, at which the landing gear can be lowered. VLO is 270 KIAS from sea level up to 37, 000 ft. Above 37, 000 ft the limit is expressed as a Mach number (Mach 0.83). 37, 000 ft 270 KIAS Fig FP 1-6. VLO/MLO limits. Landing gear retraction should be achieved before 200 KIAS. The aircraft typically becomes airborne at 150 KIAS. Landing gear is retracted once clear of the ground, and a positive rate of climb is recorded.

4 Copyright Avfacts ATPL B727 Flight Planning Limits page 4. Maximum speed with landing gear extended (VLE/MLE) VLE is 320 KIAS up to 29, 500 ft. MLE is Mach 0.83 above 29, 500 ft. (Refer fig FP 1-7). (Note: 320 KIAS = Mach 0.85 at 29, 500 ft) These figures assume that most of the gear doors are closed. If the gear doors fail to close and the landing gear does not retract, this limit is reduced to 270 KIAS/Mach 0.8. Mach , 500 ft 320 KIAS Fig 1-7. VLE/MLE limit speeds. Maximum Flap Speeds (refer B727 manual, page 1-2) These denote the maximum IAS at which the flap can be lowered, or remain lowered after takeoff. There is no limiting Mach number quoted. Maximum IAS if only the leading edge devices (slats and Kreuger flaps) lowered is 245 KIAS. Flaps are NOT to be lowered above 20, 000 ft pressure altitude (ie: FL200) for three primary reasons. Stickshaker/stickpusher operation which warns of proximity to the low speed stall may be compromised. Flap actuators and guide fatigue life is based on using flaps during takeoff and initial climbout, and in the last few minutes of the approach. Use at other times will compromise design fatigue life. The level of proof strength is less when the flaps are lowered (ie: less G force can be accepted, such as in turbulence). Altitude Mach 0.80 limit Turbulent Air Penetration speed (refer fig FP 1-8) This is 280 KIAS/Mach 0.80 irrespective of the degree of turbulence (light, moderate or severe). Below FL335 turb penetration speed is 280 KIAS. Above this level turbulent air penetration speed is referenced to Mach 0.8 instead. (Note: 280 KIAS = Mach 0.8 at FL335). SL FL KIAS 280 KIAS KIAS Fig FP 1-8. Turbulent Air Penetration speed. Operation Limits Takeoff/Landing: The B727 is NOT to use airports with a pressure altitude greater than 8, 300 ft amsl. This does not impose any limits in the Australia/Pacific area. Runway Slope: The runway longitudinal slope measured between the runway thresholds is not to exceed 2% up or down (refer fig FP 1-9). Threshold Maximum slope 2% Runway Threshold Fig FP 1-9. Maximum longitudinal slope.

5 Copyright Avfacts ATPL B727 Flight Planning Limits page 5. Maximum tailwind component: This is a legal limit of 10 knots. You will notice that no aircraft takeoff or landing performance graphs incorporate any more than 10 kt tailwind for this reason. Taking off or landing with any tailwind component significanly increases the runway length required. Maximum operating altitude: The aircraft is certificated to 42, 000 ft. B727 cruise altitudes are normally limited by engine thrust limits to a bracket between FL290 to FL370, so this limit will not affect us. (refer fig FP 1-10) FL370 FL330 FL350 FL310 Yaw Damper limits FL290 Swept wing aircraft such as the B727 can suffer a condition called Dutch Roll, which is a directional stability problem most pronounced at high altitudes/high speeds. During Dutch roll the aircraft yaws and rolls, this normally being brought on by encounters with turbulence at high altitude. EAST WEST Fig Normal operational cruise levels IFR. To counter Dutch roll, you as a pilot could apply just the right amount of rudder at just the right time to kick the aircraft straight. A Yaw Damper system will do a better job, and do it automatically the instant that the first hint of yaw becomes apparent. The B727 has two yaw damper hydraulic channels for redundancy (fail safe) reasons. Failure of either or both yaw dampers mean that the aircraft will be limited to certain speed/altitude limits as shown on page 1-3 in the B727 manual. Dutch roll is not such a problem if you are operating within these limits. Dutch roll, and yaw damper operation is covered in detail in the AGK texts.

6 Copyright Avfacts ATPL B727 Flight Planning Limits page 6. The maximum altitude if you are to fly EAST IFR is FL290, and at that level the maximum speed is 280 KIAS (Mach 0.73). FL300 The maximum altitude if you are to fly WEST IFR is FL280, and at that level the maximum speed is 290 KIAS (Mach 0.74). FL290/280 KIAS Note: FL300 is NOT an IFR hemispherical level, and the ATPL examination will most likely require you to plan an IFR level with one or both yaw dampers inoperative. (refer fig FP 1-12) FL280/290 KIAS FL270/300 KIAS Flight Manoeuvre Load Limits Describes the amount of G force which the aircraft is capable of withstanding. It is greater if the flaps are up rather than down. FL260/310 KIAS Flaps UP +2.5G/ -1.0G Flaps Down +2.0G/ -0.0G FL250/350 KIAS EAST WEST Fig FP Yaw Damper limit envelope. Crosswind Limits This depends on runway surface condition, and aircraft system status. Dry runway: Max crosswind component 29 kt. Significant water on runway: Meaning 6mm or more depth of water and/or puddles. It is only 15 kt due to the high chance of hydroplaning in these conditions. Slick runway: Runway is contaminated with deposits of rubber from other aircraft landing and is only 17 kt. This can cause viscous hydroplaning, with associated control difficulties. Wet runway (not slick or puddled): This means that the runway is merely damp and is 26 kt. Runway traction is quite good with reduced chance of hydroplaning. One hydraulic system inoperative: Means that only one of the two hydraulic lines that power the rudder is operating. As during flare in crosswind will place high demands on this hydraulic system, the reaction time could be sluggish, hence the maximum of crosswind component of 19 kt. Rudder load limit light illuminated: In this case the max crosswind is reduced to only 19 kt. Leading edge slat, flap failure: Max crosswind is 19 kt. Manual reversion: If both hydraulic systems that power the primary control surfaces fail, you will be left with the rudder powered by the standby hydraulic channel, but the elevator and ailerons will revert to manual reversion. In this case movement of the elevator and ailerons is by conventional mechanical means (cables and bellcranks and the like). Control wheel movement moves the aileron and elevator trimming surfaces, which in turn moves the aileron or elevator in the opposite direction through action/reaction. Moving the primary surfaces would demand unusually high strength on the part of the pilots. The reaction to control wheel demands is slow, hence the reduction in maximum crosswind to only 15 kt.

7 Copyright Avfacts ATPL B727 Flight Planning Limits page 7. Maximum tyre speed limits: This is 182 KIAS, by which time the aircraft should be airborne. Tyre failure may occur if the aircraft is still on the runway above this speed. Maximum brake energy limits: This is covered in the AGK texts under Landing Gear and Braking Systems. Please refer to those texts. Fuel system quantities/management: This is on page 1-4 in the B727 manual, but is covered in the weight and balance texts (not flight planning texts), and the Performance and Load paper of the CASA exam. Engine EGT limits: Read if you like, though it is unlikely to be assessed in the CASA exam. Know where to find them just in case. For additional guidance on EGT limits, refer to the Basic Gas Turbine texts. Normal Operations max cruise EPR limits The normal ops in-flight cruise data pages 3-73 to specify the maximum EPR thrust limits for the engines at the various altitudes and total air temperatures (TAT). The table is at the bottom of the page, and is the same for all cruise mach numbers. As an example, if you were cruising at FL300, and the TAT was -20 degrees C, then the maximum EPR that can be set is 2.13 for engines 1 and 3 (the side engines), and 2.17 for the centre engine. Refer fig Above these thrust settings, you run the risk of over-temping the turbines. Normally, bleed air for air conditioning/pressurisation is taken from the side engines, not from the centre engine. The EPR values shown in the main box represent this standard configuration. Max EPR in standard bleed air configuration. Non-standard configuration corrections. Fig FP1-13. Max cruise EPR values. If for example the bleed air for the air conditioner was being drawn from the centre engine, not say the left (No.1) engine as is normal, then you would have to consult the corrections box to arrive at the maximum EPR in that configuration. Using the case outlined above, engine No.1 EPR maximum can be increased by 0.06, from 2.13 to This is because compressor air is not being bled off, and subsequently more air is delivered to the combustion chambers meaning more fuel can be added to keep the primary fuel/air ratio at the optimum value of 15 air to 1 of fuel. More fuel means more thrust (higher EPR). By contrast, the EPR demanded of engine No.2 will have to be reduced to avoid over-temping it s turbine, due to the reduction in the amount of air being delivered to the combustion chamber. No.2 EPR value will have to be reduced by 0.06 from 2.17 to Engine No3 (right side engine) will have bleed air taken from it normally, so it s maximum EPR value remains at 2.13.

8 Copyright Avfacts ATPL B727 Flight Planning Limits page 8. Similar corrections to the maximum EPR values need to be applied if the airframe, and/or engine inlet anti-ice system is selected on. In the last example, No.1 and 3 engine EPR values would need to be reduced by 0.08 for engine anti-ice only, and 0.16 if wing and engine anti-ice is selected on. Engine No.2 would have it s maximum EPR values lowered by 0.11 and 0.11 respectively. For more information on compressor bleed air extraction, and turbine temperature limits, refer to the BGT texts. A different set of maximum EPR tables is published in the abnormal ops section of the B727 manual, which feature higher allowable turbine limit temperatures, and hence higher maximum EPR values. These tables will be covered in discussions about abnormal operations. End of B727 limits texts. Now attempt the assignment Normal Ops Limits.