A commercial flight is planned with a turbojet aeroplane to an aerodrome with a landing distance available of 2400 m The aeroplane mass must be such ?
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At the destination aerodrome the landing distance available is 3000m The appropriate weather forecast indicates that the runway at the estimated time of arrival will be wet For a commercial flight ?
With zero wind the angle of attack for maximum range for an aeroplane with turbojet engines is ?
Two identical turbojet aeroplane whose specific fuel consumptions are considered to be equal are at holding speed at same altitude the mass of first aircraft 130 000 kg and its hourly fuel consumption 4300 kg/h the mass of second aircraft 115 000 kg and its hourly fuel consumption 38 4 kg/h, 3578 kg/h, 3365 kg/h, 4 44 kg/h. (115/130)x4300 = 3803 kg/h. 
A jet aeroplane equipped with old engines has a specific fuel consumption of 0 06 kg per newton of thrust and per hour and in a given flying condition a fuel mileage of 14 kg per nautical mile in same flying conditions same aeroplane equipped with modern engines with a specific fuel consumption of 0 035 kg per newton of thrust and per hour has a fuel mileage of 8. 7 kg/nm,.7 kg/nm,.7 kg/nm,4 kg/nm. 14 x 0.035/0.06 = 8.1666 kg/nm. 
The determination of maximum mass on brake release of a certified turbojet aeroplane with 5° 15° and 25° flaps angles on take off leads to following values with wind flap angle 5° 15° 25°flltom kg 66 000 69 500 71 500cltom 72 200 69 000 61 800wind correction head wind +120kg/kt tail wind 360kg/kt given that tail wind component equal to 5 kt maximum mass on brake release and corresponding flap angle will be 677 kg /5°, 69kg /5°, 722 kg / 5°, 697 kg / 25°. cltom climb limited take off mass flltom field length limited take off mass the climb limited take off mass based on still air, so wind correction only applied to runway limitation. tailwind component 5 kt, correction is 360 x 5 = 1800 kg field length limited take off mass runway limit flap 5° = 66000 1800 = 64200 kg. runway limit flap 15° = 69500 1800 = 67700 kg. runway limit flap 25° = 71500 1800 = 69700 kg. the climb limited take off mass remain unchanged so maximum take off mass 67700 kg flap 15°. 
During certification test flights a turbojet aeroplane actual measured take off runs from brake release to a point equidistant between point at which vlof reached and point at which aeroplane 35 feet above take off surface are 1747 m all engines operating 1950 m with critical engine failure recognized at v1 other factors remaining unchanged considering both possibilities to determine take off r tor the certificated value of take off r is 29 m,95m, 2 96 m, 2243 m. the certificated value of take off run the greater of the 'all engine distance x 1.15' or 'engine out distance'. all engine distance x 1.15 = 1747 x 1.15 = 2009 m. engine out distance = 1950 m. Question CS-25 Performance Class A - theory 81 Answer 8
For a twin engine turbojet aeroplane two take off flap settings 5° and 15° are certified given field length avalaible= 2400 moutside air temperature= 10°cairport pressure altitude= 7000 ftthe maximum allowed take off mass 2105 56 kg, 53 kg, 52 kg, 7kg. we'll gonna perform a flap 15° take off you have to be very precise when you are drawing line, otherwise you will always find something closer to 55 000kg than 56 000 kg. Question CS-25 Performance Class A - theory 81 Answer 9
The lowest take off safety speed v2 min. 3 vsr two three engine turbo propeller turbojet aeroplanes,.2vsr all aeroplanes,. 5 vsr all turbojet turbo propeller aeroplanes,.2vsr all turbo propeller aeroplanes. Cs25 v2min, in terms of calibrated airspeed, may not be less than (1) 1.13 vsr for (i) two engined threeengined turbo propeller powered aeroplanes and (ii) turbojet powered aeroplanes without provisions obtaining a significant reduction in one engine inoperative power on stall speed (2) 1.08 vsr for (i) turbo propeller powered aeroplanes with more than three engines and (ii) turbojet powered aeroplanes with provisions obtaining a significant reduction in one engine inoperative power on stall speed and (3) 1.10 times vmc established under cs 25.149. vsr reference stall speed. Question CS-25 Performance Class A - theory 81 Answer 10
Which of following three speeds of a jet aeroplane are basically identical the speeds Holding, maximum climb angle minimum glide angle, maximum drag, maximum endurance maximum climb angle, maximum range, minimum drag minimum glide angle, maximum climb angle, minimum glide angle maximum range. holding speed a jet at vmd speed ((vmd means velocity minimum drag, this the speed minimum fuel consumption). for a jet aeroplane, maximum climb angle achieved at a speed corresponding to maximum cl/cd ratio, which vmd (where gap between power required power available greatest). minimum glide angle speed permits to fly longest ground distance without wind, it achieved at a speed corresponding to maximum cl/cd ratio, which vmd. Question CS-25 Performance Class A - theory 81 Answer 11
The lift coefficient decreases during a glide with constant mach number mainly because Ias increases, aircraft mass decreases, tas decreases, glide angle increases. tas ias increase during a descent at constant mach number, thus we must decrease our angle of attack otherwise lift will increase (lift = 1/2 rho s v² cl) the descent may be stopped. so, it the increase in tas ias which lead to decreasing lift coefficient. Question CS-25 Performance Class A - theory 81 Answer 12
During a descent at constant mach number margin to low speed buffet will Increase, because lift coefficient decreases, remain constant, because mach number remains constant, increase, because lift coefficient increases, decrease, because lift coefficient decreases. during a descent at constant mach number, your tas increases. with increasing tas, ias increasing, thus, from lift formula, lift coefficient decreases. the gap between your speed the stall speed increases. the margin to low speed buffet will increase, because lift coefficient decreases. Question CS-25 Performance Class A - theory 81 Answer 13
A jet aeroplane climbing at a constant ias and maximum climb thrust how will climb angle / pitch angle change Reduce / decrease, reduce / remain constant, remain constant / decrease, remain constant / become larger. to maintain a constant ias while climbing, you have to reduce climb angle power available decreasing with an increase of altitude. and a reduction of climb angle done reducing pitch angle. Question CS-25 Performance Class A - theory 81 Answer 14
A jet aeroplane flying long range cruise how does specific range / fuel flow change Increase / decrease, increase / increase, decrease / increase, decrease / decrease. jjansen isn't it 'decrease/increase' ? long range cruise = 1% less range (specific range decrease), 4% faster (fuel flow increase). the question doesn't compare long range cruise maximum range cruise. specific range given as 'distance covered per unit of fue as you are flying, aircraft mass decreases, the same long range cruise speed, fuel flow decreases. thus, specific range increases along flight since a same distance covered your fuel consumption decreased. Question CS-25 Performance Class A - theory 81 Answer 15
During a glide at constant mach number pitch angle of aeroplane will Decrease, increase, increase at first decrease later on, remain constant. during a glide aircraft descending. descent + constant mach number => tas increase see ertm diagram the mach line vertical because question states a glide at constant mach number. if tas increase => pitch angle decrease to remain at constant mach. Question CS-25 Performance Class A - theory 81 Answer 16
During a cruise flight of a jet aeroplane at constant flight level and at maximum range speed ias / drag will Decrease / decrease, increase / decrease, increase / increase, decrease / increase. To maintain flight at max range speed, which the tangent to drag curve 1.32 vmd, we must reduce speed as mass decreases to maintain 1.32 vmd. the mass reduction as a consequence of fuel burn means less induced drag. the total drag curve moves down left takes 1.32 vmd with it. Question CS-25 Performance Class A - theory 81 Answer 17
An aeroplane descends from fl 410 to fl 270 at its cruise mach number and from fl 270 to fl 100 at ias achieved at fl 270 assuming idle thrust a clean configuration and ignoring compressibility effects how does angle of descent change i in first and ii in second part of descent (i) increases (ii) remains constant, (i) increases (ii) decreases, (i) remains constant (ii) decreases, (i) decreases (ii) increases. Descending at constant mach, ias tas will increase. total drag proportional to v², drag will increase while descending, in order to maintain a constant mach number, you must increased descent angle (at idle thrust). at fl270, now we perform descent with a constant ias. tas will decrease density will increase drag will stay constant. our angle of descent will also stay contant. Question CS-25 Performance Class A - theory 81 Answer 18
With a jet aeroplane maximum climb angle can be flown at approximately The maximum cl/cd ratio,.vs, the maximum cl/cd² ratio,.2 vs. for a jet aeroplane, maximum climb angle achieved at a speed corresponding to maximum cl/cd ratio, which vmd (where gap between power required power available greatest). Question CS-25 Performance Class A - theory 81 Answer 19
What happens to drag of a jet aeroplane if during initial climb after take off constant ias maintained assume a constant mass The drag remains almost constant, the drag increases considerably, the drag decreases, the drag increases initially decreases thereafter. during initial climb, if ias maintained constant, tas increases (see ertm graph below) density decreases. you can maintain a constant angle of attack to produce same lift, if lift does not change, drag remains almost constant. the eas/ias line vertical because question states constant ias maintained. Question CS-25 Performance Class A - theory 81 Answer 20
Which of following sequences of speed a jet aeroplane correct from low to high speeds Vs, maximum angle climb speed, maximum range speed, vs, maximum range speed, maximum angle climb speed, maximum endurance speed, maximum range speed, maximum angle of climb speed, maximum endurance speed, long range speed, maximum range speed. Question CS-25 Performance Class A - theory 81 Answer 21
If a flight performed with a higher 'cost index' at a given mass which of following will occur A higher cruise mach number, a lower cruise mach number, an increased maximum range, an increased long range performance. Cost index the ratio of time related costs (crew salaries, maintenance, etc.) to fuel cost as one of independent variables in speed schedule computation cost index (ci) = flight time related cost/fuel cost the cost index allows airlines to weight time fuel costs based on their daily operations. a higher 'cost index' will result in a higher cruising speed. jomargra but at a higher cruise mach number aircraft will burn more fuel the ci will reduce... no, we are talking about fuel cost, not quantity. cost index a made up figure, which when input into fmc used to calculate econ speed. the higher cost index number, faster aircraft flies. basically, company decides on cost of keeping aircraft in air, includes all sorts of costs such as crew, aircraft operating costs, fuel etc... they then decide whether they want aircraft to fly faster or slower adjust cost index as needed. Question CS-25 Performance Class A - theory 81 Answer 22
For a jet transport aeroplane which of following the reason the use of 'maximum range spee Minimum specific fuel consumption, minimum fuel flow, longest flight duration, minimum drag. specific fuel consumption is weight of fuel consumed per unit power per unit time. the reason the use of 'maximum range spee because you want to go far as possible. usually, a commercial airplane fly at 'long range spee which 4% faster than 'maximum range spee. you will lose only 1% of maximum specific range, but you will save time thus, you will reduce whole costs (atc fees, engines hourly costs, leasing costs, crew costs,...). if you are looking the longest flight duration, you will fly at minimum fuel flow consumption. Question CS-25 Performance Class A - theory 81 Answer 23
What happens when an aeroplane climbs at a constant mach number The lift coefficient increases, the '.3g' altitude exceeded, so mach buffet will start immediately, the tas continues to increase, which may lead to structural problems, ias stays constant so there will be no problems. lift = cl x 1/2 rho v² x s cl = lift coefficient rho = density v = tas (in m/s) s = surface for a standard commercial aircraft, climb first carried out at constant ias, after crossover altitude at constant mach number. if you look at ertm diagram a climb at constant ias we can see that tas increases when altitude increases. now if you look at ertm diagram a climb at constant mach number we can see that tas decreases when altitude increases. since rho decreases in both case, tas decreases when we climb at constant mach number, to maintain lift we must increase our angle of attack (which means an increase in lift coefficient). Question CS-25 Performance Class A - theory 81 Answer 24
Which of following a reason to operate an aeroplane at 'long range spee It efficient to fly slightly faster than with maximum range speed, in order to achieve speed stability, the aircraft can be operated close to buffet onset speed, in order to prevent loss of speed stability tuck under. jomargra is not more efficient to fly at maximum range speed? with a 1% less of specific range speed can be increased to 4% more...the nordian book states 'it also gives aeroplane better handling qualitie. long range speed 4% faster than maximum range speed. you will lose only 1% of maximum specific range. you will save time thus, you will reduce whole costs (atc fees, engines hourly costs, leasing costs, crew costs,...). maximum range speed a certified 'safe spee (you are stable you do not risk a loss of control). Question CS-25 Performance Class A - theory 81 Answer 25
If value of balanced v1 found to be lower than vmcg which of following correct Vmust be increased to at least value of vmcg, the one engine out take off distance will become greater than asdr, the vmcg will be lowered to v , the asdr will become greater than one engine out take off distance. vmcg the minimum speed at which it possible to maintain control following failure of critical engine during take off run. if failure occurs before vmcg then aircraft will go out of control run off side of runway. for this reason v1 must never be less than vmcg. if pre take off performance calculations reveal that v1 less than vmcg, then v1 must be increased to equal vmcg. Question CS-25 Performance Class A - theory 81 Answer 26
Reduced take off thrust should normally not be used when Windshear reported on take off path, it dark, runway dry, runway wet. apstudent46 reduced thrust take off used engine life, it not permitted slippery runway contamined runway antiskid unserviceable reverse thrust unserviceable nadp (the noise abatment departure procedure) should not be used under one following conditions runway surface condition adversly affected horizontal visibility < 1nm crosswind > 15kt tailwnd > 5kt windshear reported or forecast thunderstorm expected to affect approche or departure windshear a condition to avoid nadp, not the reduced thrust. the correct answer (regarding jeppesen book) the wet runway. reduced thrust not permitted with icy or slippery runways. a wet runway defined in air law as being dark in colour has no effect on braking coefficient... a wet runway not dangerous. reduced thrust should not be used when anti skid unserviceable. reduced thrust should not be used when windshear reported on take off path. Question CS-25 Performance Class A - theory 81 Answer 27
Reduced take off thrust should normally not be used when The runway contaminated, it dark, runway wet, obstacles are present close to end of runway. apstudent46 in jeppesen book obstacles aren't condition 'reduced take off thrust' to be used. these 4 conditions are runway slippery runway contamined antiskid unserviceable reverse thrust unserviceable Question CS-25 Performance Class A - theory 81 Answer 28
The use of reduced take off thrust permitted only if The actual take off mass (tom) lower than field length limited tom, the take off distance available lower than take off distance required one engine out at v , the actual take off mass (tom) including a margin greater than performance limited tom, the actual take off mass (tom) greater than climb limited tom. a reduced thrust take off a take off that accomplished utilizing less thrust than engines are capable of producing under existing conditions of temperature pressure altitude. it not necessary to use maximum takeoff thrust when you are not at maximum takeoff weight (performance limited take off mass). Question CS-25 Performance Class A - theory 81 Answer 29
Which combination of circumstances or conditions would most likely lead to a tyre speed limited take off A high runway elevation tail wind, a low runway elevation a cross wind, a high runway elevation a head wind, a low runway elevation a head wind. conditions would most likely lead to a tyre speed limited take off are high tas, high groundspeeds, high temperatures, tailwinds high pressure altitudes. you need to increase take off speed since density reducing, to gain your lift. Question CS-25 Performance Class A - theory 81 Answer 30
The drift down requirements are based on The obstacle clearance during a descent to new cruising altitude if an engine has failed, actual engine thrust output at altitude of engine failure, maximum flight path gradient during descent, landing mass limit at alternate. in a multi engine aircraft, losing power from one or more engines may require a descent due to aircraft weight atmospheric conditions. if a descent required, most fuel efficient method a driftdown. this would be done first, setting engines to a prescribed power setting (usually set to max continuous thrust (mct) on remaining engine(s) ). then achieving a computed 'driftdown' airspeed, begin a descent to best altitude the aircraft on engines that are remaining. the goal to stay longest time at high altitude (to remain clear of obstacles) to burn less fuel as possible, having maximum chances to reach a suitable airport. Question CS-25 Performance Class A - theory 81 Answer 31
Which of following statements concerning obstacle limited take off mass performance class a aeroplane correct It should be determined on basis of a 35 ft obstacle clearance with respect to 'net take off flight path', it should not be corrected 3 ° bank turns in take off path, it should be calculated in such a way that there a margin of 5ft with respect to 'net take off flight path', it cannot be lower than corresponding climb limited take off mass. Question CS-25 Performance Class A - theory 81 Answer 32
The 'maximum tyre spee limits Vlof in terms of ground speed, vin kt tas, vr, or vmu if this lower than vr, vin kt ground speed. vlof lift off speed. the speed at which main wheels lift from ground. this speed marks an important point the end of rolling part of takeoff, also called end of 'ground rol. vmax tyre maximum ground speed of tyres. the highest speed that tires can handle without becoming damaged. it possible to drive so fast that tread actually flies of tires. if you drive fast enough centrifugal forces become so great that tire falls apart. that must be avoided therefore there a maximum rolling speed a tyre. that speed printed on side of tyre near size, usually a number in miles per hour. vlof &le vmax tyre in terms of ground speed. Question CS-25 Performance Class A - theory 81 Answer 33
Which of following factors determines maximum flight altitude in 'buffet onset boundary' graph Aerodynamics, theoretical ceiling, service ceiling, economy. anytime that too great a lift demand made on wing, whether from too fast an airspeed or from too high an angle of attack near mmo, 'high speed buffet' will occur. mach buffet occurs as a result of supersonic airflow on wing. stall buffet occurs at angles of attack that produce airflow disturbances (burbling) over upper surface of wing which decreases lift. as density altitude increases, angle of attack that required to produce an airflow disturbance over top of wing reduced until density altitude reached where mach buffet stall buffet converge (coffin corner). when this phenomenon encountered, serious consequences may result causing loss of airplane control. this purely aerodynamics factors which define 'buffet onset boundary' graph. Question CS-25 Performance Class A - theory 81 Answer 34
Which data can be extracted from buffet onset boundary chart The values of mach number at which low speed mach buffet occur at various masses altitudes, the value of maximum operating mach number (mmo) at various masses power settings, the value of critical mach number at various masses altitudes, the value of mach number at which low speed shockstall occur at various masses altitudes. anytime that too great a lift demand made on wing, whether from too fast an airspeed or from too high an angle of attack near mmo, 'high speed buffet' will occur. 'buffet onset boundary' graph. mach buffet occurs as a result of supersonic airflow on wing. stall buffet occurs at angles of attack that produce airflow disturbances (burbling) over upper surface of wing which decreases lift. as density altitude increases, angle of attack that required to produce an airflow disturbance over top of wing reduced until density altitude reached where mach buffet stall buffet converge (coffin corner). Question CS-25 Performance Class A - theory 81 Answer 35
Why should temperature of wheel brakes be checked prior to take off Because overheated brakes will not perform adequately in event of a rejected take off, to ensure that brake wear not excessive, to ensure that wheels have warmed up evenly, to ensure that thermal blow out plugs are not melted. Question CS-25 Performance Class A - theory 81 Answer 36
A jet aeroplane climbing with constant ias which operational speed limit most likely to be reached The maximum operating mach number, the stalling speed, the minimum control speed air, the mach limit the mach trim system. mach number increasing with altitude at constant ias, you may reached mmo (maximum operating mach number). vmca (minimum control speed air) stalling speed refer to ias. the question states 'climbing with constant ia so there no risk. Question CS-25 Performance Class A - theory 81 Answer 37
A jet aeroplane descends with constant mach number which speed limit will be exceeded Maximum operating speed, never exceed speed, high speed buffet limit, maximum operating mach number. vmo/mmo defined as maximum operating limit speed. vmo expressed in knots calibrated airspeed (kcas), while mmo expressed in mach number. the vmo limit usually associated with operations at lower altitudes deals with structural loads flutter. the mmo limit associated with operations at higher altitudes is usually more concerned with compressibility effects flutter. at lower altitudes, structural loads flutter are of concern at higher altitudes, compressibility effects flutter are of concern. the operational limit that may be exceeded during a descends with constant mach number vmo (maximum operating speed). Question CS-25 Performance Class A - theory 81 Answer 38
Which of following statements regarding reduced thrust take off technique correct Reduced thrust can be used when actual take off mass less than performance limited take off mass, the reduced thrust take off technique does not preserve engine life, reduced thrust used in order to save fuel, the maximum reduction of thrust permitted the mrjt using a reduced thrust take off, 2 %. a reduced thrust take off a take off that accomplished utilizing less thrust than engines are capable of producing under existing conditions of temperature pressure altitude. it not necessary to use maximum takeoff thrust when you are not at maximum takeoff weight (performance limited take off mass). Question CS-25 Performance Class A - theory 81 Answer 39
Which statement in relation to climb limited take off mass of a jet aeroplane correct The climb limited take off mass decreases with increasing oat, the climb limited take off mass determined at speed best rate of climb, 5 % of a head wind taken into account when determining climb limited take off mass, on high elevation airports equipped with long runways aeroplane will always be climb limited. the climb limited take off mass reduced because density (rho) decreases when air warmer. the take off climb path has a fixed value, to be able to deal with this value, we must reduce our maximum take off mass. the climb limited take off mass the highest takeoff mass that meets all of following regulatory requirements minimum one engine inoperative climb gradient ?first segment. ?second segment. ?final segment. jomargra why answer 50% of a headwind taken into account when determining climb limited take off mass wrong? there are several performance criteria to comply with take off but they can be broadly split into two groups 1 runway performance 2 climb performance for 'runway performance', you would include things like field length limits, brake energy limits, tyre speed limits obstacle limits. for all these you take into account runway length, wet/dry, slope, qnh, wind (50% or 150%), altitude (field elevation) temperature. 'climb performance' has nothing to do with runways or obstacles. it simply a regulatory requirement to achieve a minimum gradient of climb in various configurations at various engine settings (and numbers of engines) different climb segments. Question CS-25 Performance Class A - theory 81 Answer 40
What the advantage of a balanced field length condition A balanced field length gives minimum required field length in event of an engine failure, a balanced take off provides lowest elevator input force requirement rotation, for a balanced field length required take off runway length always equals available runway length, a balanced field length provides greatest margin between 'net' 'gros take off flight paths. a balanced field where toda = asda. toda take off distance available. asda acceleration stop distance available. if you have an engine failure at v1 you continue take off, you will just make screen height of 35ft v2 at end of toda. but if you stop, you will just stop within asda. this then must be minimum required field length.
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