Aspects of Aircraft Design and Control ... The flow around the wing is extremely
complex – no ... A lift-producing wing generates more downwash than upwash.
Aspects of Aircraft Design and Control Olivier Cleynen – February 2014 – v1.3
Lecture 3 Runway Performance
The school of hard knocks is an accelerated curriculum Menander, 300BC
~ foreword ~ ●
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The present notes serve as a support for in-class work, not the opposite! Refer to the introductory course notes for explanations. These notes are used as a succinct introduction to selected topics. They are purposefully incomplete and must not be used for real-life applications.
Feedback is always appreciated: olivier.cleynen ariadacapo.net
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Some photos and illustrations have their author and specific license indicated on the bottom of the page. All other content is © 2011-2013 CC by-sa Olivier Cleynen. You are encouraged to copy, modify, and re-use this content under specific conditions: http://creativecommons.org/licenses/by-sa/3.0/
3.1 Notation and conventions
3.1.1 Forces on aircraft
Cruise flight (ideal case)
CC-0 Olivier Cleynen
Low-speed flight (ideal case)
CC-0 Olivier Cleynen
Low-speed flight: thrust angle
CC-0 Olivier Cleynen
Cruise flight: general case
CC-0 Olivier Cleynen
Cruise flight: general case
CC-0 Olivier Cleynen
Aircraft forces: the most general case
CC-0 Olivier Cleynen
© Glenn Alderton
3.1.1 Upwash and Downwash
Upwash & Downwash ●
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The flow around the wing is extremely complex – no simple explanation will do! A lift-producing wing generates more downwash than upwash All angles are measured (or calculated) relative to freestream velocity – far ahead of the wing
CC by-sa Marina Lystseva
3.2 A take-off ~Jacques Darolles FTW~
CC by-sa WCU:Mandeep
CC by-sa Matthieu Marquer
Taxi
“ordinary extraordinary”
CC by-sa F:Ack_Ook
Thrust levers forward
Minimum control, ground
V mc , g Aircraft can maintain heading Will shift no more than 9 meters sideways Leave nosewheel control for yoke
CC by-sa Superjet International
Stall speed
VS
Minimum flight speed in take-off configuration (attitude may not be attainable on ground)
Rotation speed
VR V R ≡ 1,1 V S Rotation may be initiated
Incorrect VR calculation or reading: risk of tail strike
CC by-sa Ercan Karakaş
Minimum Unstick speed
V MU
Speed is sufficient to generate lift out of ground effect, at maximum ground attitude [tail strike]
Decision speed
V1 Decide whether to proceed or not Either maximum breaking, or continuing take-off with one engine inoperative, would necessitate the same runway length From there on, there is no stopping!
Lift-off speed
V LO
Speed reached during rotation time (1 – 3s) Usually VLO = VR
Safety speed
V2 V 2 ≡ 1,2 V S Aircraft can maintain heading with one engine inoperative Has to be reached at (or before) a height of 10,4 m , with positive gradient, with one engine inoperative Concludes take-off
CC by-sa F:BriYYZ
thrust = max. continuous power
Two cases for take-off
The Balanced Field Length
Shortest distance at which an aircraft may safely take-off with one engine inoperative
Determining Balanced Field Length: minimum runway length for a safe take-off ●
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“Safe” means the aircraft clears a 10,4 m obstacle at runway end; One engine provides no thrust (“N-1”); That inoperative engine is shut down as late as possible (at the point where maximum braking would bring aircraft to a halt in front of the obstacle).
CC by-sa Vincent Edlinger
GPL W:ILA-boy
MD-11 brake
CC by-sa Jean-Patrick Donzey
the Balanced Field Length ●
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Is the minimum required take-off runway length for which the aircraft is certified Will vary with aircraft weight, flap settings, air density, and runway conditions (wet, dry...) Is usually the critical certification performance criteria for twin jets
CC by-sa Vincent Edlinger
Project 2: Calculating a take-off distance
CC by-sa Laurent Errera
CC by-sa Pedro Aragão
CC by-sa Laurent Errera
CC by-sa Laurent Errera
CC by-sa Laurent Errera
CC by-sa Laurent Errera
Project 2 ●
Your employer is developing a twin-jet wide-body airliner
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Aircraft weight and thrust have just been set
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What is the minimum runway length at MTOW?
Question 1 ●
A short, in-class thinking exercise
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No numbers
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What runway length does an arbitrary aircraft need to reach an arbitrary speed?
Question 2 ●
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What will the “normal” take-off distance of the new aircraft be? How does speed vary along the runway?
Project 2 ●
You may (will?) have to simplify things – state your assumptions
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Get “working” results, then refine your calculations
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Have fun!
