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5. climb
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- 2. CLIMB Engine ratings Climb analysis Climb speeds • Maximum angle • Maximum rate of climb • Constant IAS • Constant IAS/MACH • Optimum climb speed Factors affecting climb Operative ceilings Step climb
- 3. ENGINE RATINGS Engines arecertified to deliver standard thrusts depending upon atmospheric conditions: Maximum Takeoff Thrust: This is the maximum thrust that the engine can deliver for 5 minutes at standard sea level atmosphere. MCT - Maximum Continuous Thrust: This is the maximum thrust that the engine can deliver with no time limit. MCL - Maximum Climb Thrust: This is the maximum thrust certified for en-route climb; sometimes it is the same as MCT. (not certified) MCR - Maximum Cruise Thrust: This is the thrust allowable for unlimited flight duration at the design altitude. (not certified)
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- 5. CLIMB ANALYSIS From theprevious graph it can be deduced that: sin φ = (T – D) / W In addition, the rate of climb (R/C) is the vertical component of the True Airspeed of the aircraft, so it is affected by the climb angle: R/C = TAS · sin φ φ R/C TAS
- 6. CLIMB ANALYSIS Combining thetwo previous formulas we obtain: Therefore, the rate of climb will increase then with: a higher TAS, a higher excess of thrust and with a lower weight. W D-T ·TASR/C =
- 7. CLIMB ANALYSIS TAS R/C Vx: Best angle speed Vy : Best R/C speed VyVx
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- 10. CLIMB ANALYSIS In generalterms, it can be concluded that: Vy is always greater than Vx. As the altitude increases, Vx increases and Vy decreases (IAS). A higher flap setting will decrease both speeds. Vx (piston) is close to Vs, while Vx (jet) is close to the L/DMAX speed. Therefore, Vx is greater in jet aircraft than in piston- powered aircraft. Vy (jet) is also greater than Vy (piston).
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- 12. CLIMB SPEEDS CLIMB ATMAXIMUM ANGLE SPEED Climbing at maximum angle speed (Vx) enables a given altitude to be reached over the SHORTEST DISTANCE. CLIMB AT MAXIMUM R/C SPEED Climbing at maximum R/C speed (Vy) enables a given altitude to be reached within the SHORTEST TIME.
- 13. CLIMB SPEEDS CLIMB ATCONSTANT IAS Climbing at a constant IAS would simplify the operation, but it have some disadvantages. As the aircraft climbs TAS increases, drag increases (due to compressibility effects) and therefore R/C decreases. This results in a long and inefficient climb. % Climb capability FL330 IAS FL290 FL250 FL200 100 90 80 70 60 50
- 14. CLIMB SPEEDS CLIMB ATCONSTANT IAS/MACH Since it is impractical to climb at decreasing IAS speeds, the constant IAS/M climb is usually performed, simplifying the operation: The climb is performed at a constant IAS until a certain MACH is reached. Then the climb is continued keeping this MACH number. For instance, a climb profile for an A320 is: 250kt / 300kt / M.78 Below FL100 (due to ATC) Above FL100 until reaching M.78 (crossover altitude) Until the end of climb
- 15. CLIMB SPEEDS In thefirst part of the climb (constant IAS), TAS is increased as the aircraft climbs. In the second part of the climb (constant MACH), TAS is decreased as the aircraft climbs. TAS Theoretical R/C TROPOPAUSE 25% 9% 30% R/C PA PA Real R/C
- 16. CLIMB SPEEDS OPTIMUM CLIMBSPEED The optimum climb speed is the result of taking into account all the factors that affect climb in terms of efficiency and operative costs. It is usually higher than the best R/C speed (Vy). Factors that affect this speed: Weight: Optimum climb speed increases with more weight. Wind: It barely affects optimum climb speed (+5 kt / 100 kt HW). Fuel price: If it increases the optimum climb speed will decrease. Maintenance and crew costs: If they increase the optimum climb speed will also increase. OAT and final cruise level do not affect the optimum climb speed.
- 17. SOME FACTORS AFFECTINGCLIMB Climb gradient ↓ PRESSURE ALTITUDE ↑ Rate of climb ↓ Climb gradient ↓ TEMPERATURE ↑ Rate of climb ↓ Climb gradient ↓ WEIGHT ↑ Rate of climb ↓
- 18. OPERATIVE CEILINGS ABSOLUTE ORAERODYNAMIC CEILING The aircraft cannot climb beyond the aerodynamic ceiling, which is determined by the aerodynamic properties of the aircraft. This situation of R/C = 0 fpm (impractical) could only be established at one speed (Vx equals Vy at this point). In this case, the aircraft reaches a situation in which a higher speed would produce a high-speed stall, and a lower speed would produce a low-speed stall. This situation is known as “coffin corner”. PROPULSION CEILING Is that altitude that the available thrust provided by the engines permits to reach. It is usually lower than the aerodynamic ceiling.
- 19. OPERATIVE CEILINGS SERVICE CEILING Sincereaching the absolute ceiling is impossible in practice, the service ceiling is considered. At this altitude the aircraft has a maximum rate of climb of 100 fpm. DESIGN CEILING It is the maximum altitude that the aircraft can reach taking into account the structural limits (maximum differential pressure, etc).
- 20. OPERATIVE CEILINGS OTHER CEILINGS Otherceilings have been established as a reference. To sum up, we have four ceilings based upon the maximum rate of climb: Absolute ceiling: R/CMAX = 0 fpm Service ceiling: R/CMAX = 100 fpm Cruise ceiling: R/CMAX = 300 fpm Combat ceiling: R/CMAX = 500 fpm
- 21. STEP CLIMB The optimumcruise altitude is increased as the aircraft loses weight (due to fuel consumption). Since it is impractical to perform a continuous and slow climb during the cruise phase, a solution known as step climb has been established. Step climb is only used in long haul flights, and consists of climbing from time to time at a higher level in order to keep the aircraft close to the optimum altitude. Optimum altitude