©M. S. Ramaiah University of Applied Sciences 1 Faculty of Engineering & Technology Session Speaker M. Sivapragasam M. Sivapragasam Session 04 Aircraft.

©M. S. Ramaiah University of Applied Sciences 1 Faculty of Engineering & Technology Session Speaker M. Sivapragasam M. Sivapragasam Session 04 Aircraft Accelerated Flight – 2

©M. S. Ramaiah University of Applied Sciences 2 Faculty of Engineering & Technology Session Objectives At the end of this session, student will be able to: Differentiate take off and landing requirements of different types of aircraft Calculate the take off performance of an aircraft Explain balanced field length requirements for aircraft take off Calculate the landing performance of an aircraft Calculate the climb performance of an aircraft

©M. S. Ramaiah University of Applied Sciences 3 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 3 Conventional Short Super short Extremely short Vertical Rocket assisted Types of TO/L

©M. S. Ramaiah University of Applied Sciences 4 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 4 Take off using a conventional runway Ground roll distance is determined by the requirement to clear a 50ft (35ft for commercial) obstacle Land on a conventional runway and decelerate after clearing a 50ft obstacle Flare is a deceleration maneuver to reduce airspeed and altitude Conventional TO/L

©M. S. Ramaiah University of Applied Sciences 5 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 5 Take off and clear 50 foot obstacle in between 1000 and 1500 ft Land and stop between 1000-1500 ft after clearing 50 foot obstacle Aerostar 600 Cessna 182 De Havilland Canada Dash 7 Short TO/L

©M. S. Ramaiah University of Applied Sciences 6 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 6 Take off and clear 50 foot obstacle in between 500 and 1000 ft Land and stop between 500-1000 ft after clearing 50 foot obstacle SSTOL concept from Advanced Composites Anronov AN- 28 Great Lakes Sport Trainer Super Short TO/L

©M. S. Ramaiah University of Applied Sciences 7 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 7 Take off and clear 50 foot obstacle in under 500 ft Land and stop under 500 ft after clearing 50 foot obstacle ESTOL Aeronca Champion Sherpha K650T Canaero Toucan Extremely Short TO/L

©M. S. Ramaiah University of Applied Sciences 8 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 8 No need for runway or obstacle avoidance requirement Aircraft can take off and land without the need for a runway F35 The Harrier and V-22 Osprey Vertical Takeoff Vehicles Vertical TO/L

©M. S. Ramaiah University of Applied Sciences 9 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 9 The use of rockets (usually solid rockets) to shorten takeoff distance C130 To decrease landing distance use rockets opposed to direction of flight to fall out of the sky. Rocket-assisted TO/L

©M. S. Ramaiah University of Applied Sciences 10 Faculty of Engineering & Technology Take-off and Landing Take-off Field Length The take-off field length is generally split into three sections: – Take-off Distance: The ground distance required from brakes release at the start of the runway, accelerating from rest until the aircraft reaches a 'screen' height above the runway. – Take-off Run: The ground distance required from brakes release at the start of the runway, accelerating from rest until the aircraft reaches a point between lift-off and a 'screen' height above the runway. This point can vary between different airworthiness requirements.

©M. S. Ramaiah University of Applied Sciences 11 Faculty of Engineering & Technology Take off Field Length Accelerate-Stop Distance: The ground distance required from brakes release till the aircraft reaches a decision speed and then the brakes are applied until the aircraft comes to a complete stop.

©M. S. Ramaiah University of Applied Sciences 12 Faculty of Engineering & Technology Take off Distance Components The take-off distance can be split into four different phases: – Ground acceleration – Rotation phase – Transition phase – Initial climb out to screen Typically, the aircraft take-off manoeuvres corresponding to the take-off distance phases listed above can be split as seen in figure

©M. S. Ramaiah University of Applied Sciences 13 Faculty of Engineering & Technology Take off Distance Components 1.Ground acceleration until lift-off speed 2.Air acceleration until climb safety speed 3.Transition to climb 4.Climb to required altitude SpeedJAR25 Decision speed (V 1 )V 1 > V EF > V mcg Rotation speed (V R ) V R > V 1 V R > 1.05V mca Minimum take-off safety speed (V 2 ) V 2 > 1.2V s V 2 > 1.1V mca

©M. S. Ramaiah University of Applied Sciences 14 Faculty of Engineering & Technology Take off Distance Components Before the aircraft becomes airborne – the aircraft is accelerating along the ground until rotation at the rotation speed (VR) – transition to lift-off speed (VLOF) – and climb out to achieve take-off safety speed (V2) at the screen, usually 35 ft.

©M. S. Ramaiah University of Applied Sciences 15 Faculty of Engineering & Technology Takeoff : Ground Run To calculate the ground roll, we need to write the equations of motion for the vehicle as it moves down the runway. – See figure below

©M. S. Ramaiah University of Applied Sciences 16 Faculty of Engineering & Technology Takeoff : Ground Run The forces that act on it are the aerodynamic forces of – Lift and Drag (L and D), the thrust force (T), – The ground normal force (R) and the ground friction force (μR), where μ is the coefficient of rolling friction. We can now write the equations of motion along the runway and perpendicular to it.

©M. S. Ramaiah University of Applied Sciences 17 Faculty of Engineering & Technology Takeoff : Ground Run

©M. S. Ramaiah University of Applied Sciences 18 Faculty of Engineering & Technology Friction Coefficients (μ) Runway Surface Friction Coefficients (μ) CONCRETE wet dry 0.03 - 0.035 0.04 - 0.05 Grass wet dry 0.07 - 0.1 0.09 - 0.13 Hard Snow-0.05 - 0.055 Dry Soft Groundsand0.2 - 0.3

©M. S. Ramaiah University of Applied Sciences 19 Faculty of Engineering & Technology Takeoff : Ground Run Re-arranging we have During takeoff, high lift devices like Flaps, Slats etc are deployed and the landing gear is also exposed. Here C Lg and C Dg refer to lift and drag coefficients of the aircraft in such a configuration. Obviously both the coefficients are large

©M. S. Ramaiah University of Applied Sciences 20 Faculty of Engineering & Technology Takeoff : Ground Run In order to be able to integrate the above equations, we need some functional relationships. We assume that Thrust T depends on V as follows Substituting the above assumption into the equations derived earlier and collecting terms of V 2

©M. S. Ramaiah University of Applied Sciences 21 Faculty of Engineering & Technology Takeoff : Ground Run Here, A and B are defined as:

©M. S. Ramaiah University of Applied Sciences 22 Faculty of Engineering & Technology Takeoff : Ground Run Dividing both sides by V and realising V = (ds/dt) and rearranging we have In the previous slide we had shown Here if we assume A and B to be constant as a first approximation, The above equation for “ds” can be integrated between V1 and V2

©M. S. Ramaiah University of Applied Sciences 23 Faculty of Engineering & Technology Takeoff : Ground Run Here we consider the case of staring from rest then the above equation simplifies to Where, A and B are defined as:

©M. S. Ramaiah University of Applied Sciences 24 Faculty of Engineering & Technology Takeoff : Ground Run As before we want to find the condition when S is minimum This happens when we have – Maximum value for A which depends on Thrust/weight ratio and friction coefficient μ – Minimum value for B, here we have control only over C Lg and C Dg Reduce this by cleaner aircraft

©M. S. Ramaiah University of Applied Sciences 25 Faculty of Engineering & Technology Takeoff : Ground Run Improve C L g by better high lift devices and also higher angle of a/c during ground run – Simply making the front landing gear taller achieves this !! We can find the optimum value by differentiating and equating to zero

©M. S. Ramaiah University of Applied Sciences 26 Faculty of Engineering & Technology Takeoff : Ground Effect When an aircraft is flying near the ground it’s efficiency improves – Because of interference between the horse-shoe vortex and ground One of the methods for correcting for ground effect is to modify value of K h = height of the wing above the ground b = wingspan e = Oswald efficiency factor

©M. S. Ramaiah University of Applied Sciences 27 Faculty of Engineering & Technology Landing Run The opposite of the takeoff procedure is the landing procedure. Just as in the takeoff, the landing maneuver consists of two parts: – The terminal glide over a 50 ft obstacle to touchdown – The landing ground run Some calculations include a flare from the landing glide to the touchdown. However, for a maximum performance landing (short field landing procedure), very little flare is used.

©M. S. Ramaiah University of Applied Sciences 28 Faculty of Engineering & Technology Landing Run Here we will neglect the flare portion of landing and assume the aircraft touches down at slightly higher speed than it would after flaring. The equations of motion governing the landing ground run are the same as those for takeoff. However, the constants A and B can be quite different. – Thrust can be zero or even negative (reverse thrust) – The runway rolling friction can be much larger due to braking.

©M. S. Ramaiah University of Applied Sciences 29 Faculty of Engineering & Technology Landing Run The boundary conditions are different – At the beginning of the ground roll the velocity is that at touchdown, V TD – At the end of the ground run, the velocity is V2, usually zero Differential equation of motion for the landing run is the same as that for takeoff: – Results are different For V 2 = 0, we have

©M. S. Ramaiah University of Applied Sciences 30 Faculty of Engineering & Technology Balance Field Length In order for a multi-engine commercial aircraft to takeoff from a runway, the runway must at least be as long as the Balanced Field Length (BFL). BFL is determined by considering two options available to the pilot if an engine fails. – continue the takeoff on the remaining engines to clear the 50 ft (15m) obstacle and establish a takeoff distance – apply the brakes as soon as possible after the engine failure and to bring the aircraft to a halt in some distance. – If the two distances are the same, that distance is called the BFL

©M. S. Ramaiah University of Applied Sciences 31 Faculty of Engineering & Technology Balanced Field Length 1.Assuming a speed (and distance along the runway) when that the engine failure occurs. 2.Continue the takeoff on the remaining engines and compute the additional distance for the vehicle to clear a 50 ft obstacle, determining the takeoff distance 3.Starting with the speed assumed in (1), assume two additional seconds go by and then the engines are shut down, brakes applied and the ground roll to stop calculated.

©M. S. Ramaiah University of Applied Sciences 32 Faculty of Engineering & Technology 4.Compare the distance in (2) with that in (3). If the distance to stop is shorter than the distance to fly over the 50 ft obstacle, increase the guess in step (1). If the distance to stop is shorter than that required to clear the 50 ft obstacle, then decrease the failure airspeed in step (1). Continue this procedure until the total takeoff distance and the total distance to stop are the same. This distance will be the balance field length, and the associated velocity found is called the critical engine failure speed Balanced Field Length

©M. S. Ramaiah University of Applied Sciences 33 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 33 All TO/L data recorded throughout entire flight test program Tests devoted to TO/L done at: – Various gross weights – Clean and several “dirty” configurations – Standard to contaminated runway conditions Must rely on statistical average of as many tests as possible – Greatly affected by factors that cannot be measured and properly accounted for Typically delayed in flight test program b/c of amount of support and time required Flight Test – Basics

©M. S. Ramaiah University of Applied Sciences 34 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 34 Conducted prior to any TO/L tests due to: – Always present possibility of a refused takeoff in those tests – Needed to determine parameters used in TO/L tests Parameters: – Thrust transients – Drag – Rolling C f – Ground Handling 787 High Speed Taxi Test: Reached 100 knots first test, V R actually about 150 knots High-Speed Taxi Test

©M. S. Ramaiah University of Applied Sciences 35 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 35 V mc = minimum control speed (OEI) V 1 = critical engine failure recognition speed V R = rotate speed V lo = liftoff speed V 2 = cleared obstacle speed Takeoff Critical Locations

©M. S. Ramaiah University of Applied Sciences 36 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 36 Rejected Takeoff Distance: The distance required for the vehicle to stop from full throttle at V1 speed for a specified altitude, weight, and configuration. Also known as aborted or refusal takeoff Rejected Takeoff Test

©M. S. Ramaiah University of Applied Sciences 37 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 37 To reduce risk to multi-million dollar aircraft, brakes are first tested individually in a simulated environment. Rejected Takeoff Test

©M. S. Ramaiah University of Applied Sciences 38 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 38 Full scale aircraft test - Aircraft is accelerated to V1 at max throttle - A 3 second delay given to simulate pilot time to recognize situation - Engines are set to max reverse and brakes are applied Rejected Takeoff Test

©M. S. Ramaiah University of Applied Sciences 39 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 39 Aircraft Steady Gliding Flight

©M. S. Ramaiah University of Applied Sciences 40 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 40 Aircraft Steady Level Flight

©M. S. Ramaiah University of Applied Sciences 41 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 41 Steady Climbing Flight

©M. S. Ramaiah University of Applied Sciences 42 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 42 Steady Climbing, Descending Turn

©M. S. Ramaiah University of Applied Sciences 43 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 43 Climbing Flight ε is angle between T and Centre line

©M. S. Ramaiah University of Applied Sciences 44 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 44 Climbing Flight small angle approximation

©M. S. Ramaiah University of Applied Sciences 45 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 45 Climbing Flight

©M. S. Ramaiah University of Applied Sciences 46 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 46 Climbing Flight Max Angle of climb

©M. S. Ramaiah University of Applied Sciences 47 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 47 Climbing Flight Max Angle of climb

©M. S. Ramaiah University of Applied Sciences 48 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 48 Climbing Flight R/C

©M. S. Ramaiah University of Applied Sciences 49 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 49 Climbing Flight R/C For our idealized jet airplane, best rate of climb does not occur at minimum power required – Maximum rate of climb occurs at the velocity where excess power is greatest The velocity for maximum rate of climb is determined for any aircraft as follows : – Plot power required and available versus true airspeed – Choose the velocity where the distance between the two curves is greatest.

©M. S. Ramaiah University of Applied Sciences 50 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 50 Climbing Flight

©M. S. Ramaiah University of Applied Sciences 51 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 51 Climbing Flight Max R\C

©M. S. Ramaiah University of Applied Sciences 52 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 52 Climbing Flight Effect of altitude

©M. S. Ramaiah University of Applied Sciences 53 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 53 Climbing Flight Effect of altitude Typical Thrust and Power change with altitude Power required reduces as density drops hence Drag reduces with altitude However, Power available drops faster, hence R/C decreases with altitude

©M. S. Ramaiah University of Applied Sciences 54 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 54 Climbing Flight Propeller aircraft

©M. S. Ramaiah University of Applied Sciences 55 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 55 Climbing Flight Jet Aircraft

©M. S. Ramaiah University of Applied Sciences 56 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 56 Ceiling The ceiling is the altitude at which R/C has reached some minimum value Absolute ceiling Is defined as the altitude at which the R/C = 0 Is dictated when PA is just tangent to the PR curve Service ceiling is defined as that altitude where R/Cmax = 100 ft/min, is the practical upper limit for steady, level flight

©M. S. Ramaiah University of Applied Sciences 57 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 57 Procedure calculate values of R/Cmax for different altitudes, plot R/Cmax versus altitude extrapolate this latter curve to 100 fpm and 0 fpm to get the the service and absolute ceilings Ceiling

©M. S. Ramaiah University of Applied Sciences 58 Faculty of Engineering & Technology©M. S. Ramaiah University of Applied Sciences 58 Time to Height

©M. S. Ramaiah University of Applied Sciences 59 Faculty of Engineering & Technology Example: F-15 K Weapon launched from an F-15 fighter by a small two stage rocket, carries a heat-seeking Miniature Homing Vehicle (MHV) which destroys target by direct impact at high speed (kinetic energy weapon) F-15 can bring ALMV under the ground track of its target, as opposed to a ground-based system, which must wait for a target satellite to overfly its launch site.

©M. S. Ramaiah University of Applied Sciences 68 Faculty of Engineering & Technology Example: High aspect ratio glider To maximize range, smallest q occurs at (L/D) max A modern sailplane may have a glide ratio as high as 60:1 So q = tan -1 (1/60) ~ 1° 

©M. S. Ramaiah University of Applied Sciences 69 Faculty of Engineering & Technology R/C Example Use the vehicle characteristics for the very large capacity transport aircraft A380 Estimate the rate of climb for this aircraft at two distinct points in the climb profile: – 600 meters (2,000 feet) and 210 knots - IAS – 8,000 meters (26,200 feet) and 290 knots - IAS Estimate the thrust produced by the engines under both conditions Find the Lift to Drag ratio for both conditions – Assume the International Standard Atmosphere applies to both aircraft states

©M. S. Ramaiah University of Applied Sciences 70 Faculty of Engineering & Technology R/C Example An aircraft similar in size and performance as the Airbus A380 – Four turbofan engines each developing 34,400 kg (338,000 N) at sea level – Maximum takeoff mass is 540,000 kg. (1.188 million pounds)

©M. S. Ramaiah University of Applied Sciences 71 Faculty of Engineering & Technology R/C Example Visualize the scene and sketch a free body diagram of the system – For this analysis we will ignore the second term in the Right Hand Side (RHS) of the differential equation (acceleration term) – The pilot is interested in climbing as fast as possible – using all the engine thrust to climb

©M. S. Ramaiah University of Applied Sciences 72 Faculty of Engineering & Technology R/C Example Aircraft is treated a point mass for this calculation – And we treat both start and end points 600 m

©M. S. Ramaiah University of Applied Sciences 73 Faculty of Engineering & Technology R/C Example Step 1: Estimate true airspeed using atmospheric model Step 2: Estimate the lift coefficient needed to sustain flight using the basic lift equation Step 3: Estimate drag coefficient Step 4: Estimate total drag (D) Step 5: Estimate the thrust produced by the engines at altitude (T) Step 6: Find the rate of climb (dh/dt)

©M. S. Ramaiah University of Applied Sciences 74 Faculty of Engineering & Technology R/C Example Using the standard expression to estimate the true mach number of the aircraft at altitude, – The true mach number is 0.3267, the speed of sound at 600 meters is 337.96 m/s and the density of air is 1.156 k / m 3. – The true airspeed (TAS) is 110.41 m/s or 214.6 knots – Use the fundamental lift equation to estimate the lift coefficient under the known flight condition

©M. S. Ramaiah University of Applied Sciences 75 Faculty of Engineering & Technology R/C Example The lift coefficient need for flight is calculated The Drag coefficient is computed using the Drag polar CD0 is interpolated from values

©M. S. Ramaiah University of Applied Sciences 76 Faculty of Engineering & Technology R/C Example Thrust is always given with dependencies on Mach number and Altitude – Sea level and static thrust is the highest

©M. S. Ramaiah University of Applied Sciences 84 Faculty of Engineering & Technology R/C Observations R/C is highest at sea level and low Mach number – maximum thrust is available Reduces non-linearly with increasing altitude – depends on density drop – tapers of to zero as it nears the service altitude R/C is also affected by aircraft Weight and Climb speed. Next slide shows the effect of weight on R/C

©M. S. Ramaiah University of Applied Sciences 87 Faculty of Engineering & Technology Summary In this session following topics were discussed: Take off and landing requirements of different types of aircraft Take off performance of an aircraft Balanced field length requirements for aircraft take off Landing performance of an aircraft Climb performance of an aircraft

©M. S. Ramaiah University of Applied Sciences 1 Faculty of Engineering & Technology Session Speaker M. Sivapragasam M. Sivapragasam Session 04 Aircraft.

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©M. S. Ramaiah University of Applied Sciences 1 Faculty of Engineering & Technology Session Speaker M. Sivapragasam M. Sivapragasam Session 04 Aircraft.

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Presentation on theme: "©M. S. Ramaiah University of Applied Sciences 1 Faculty of Engineering & Technology Session Speaker M. Sivapragasam M. Sivapragasam Session 04 Aircraft."— Presentation transcript:

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