Register to reply

L/d ratio

by kevjcarvalho
Tags: l or d, ratio
Share this thread:
kevjcarvalho
#1
Jun6-10, 12:35 AM
P: 42
hey,
I was reading Aircraft Design: A Conceptual Approach by Raymer and i came across the following line.
' The aerodynamic efficiency of an aircraft, expressed as the lift to drag ratio is greatly reduced during low level, high speed flight as well is its engine efficiency. '
Can someone tell me why. Thanks.
Phys.Org News Partner Science news on Phys.org
Physical constant is constant even in strong gravitational fields
Montreal VR headset team turns to crowdfunding for Totem
Researchers study vital 'on/off switches' that control when bacteria turn deadly
abhi88
#2
Jun7-10, 05:54 AM
P: 3
Search for the reason Airliners fly at 30,000ft during cruise.
and, as far as speed is related, you must be aware of the 'wave drag' and 'critical mach number'.
kevjcarvalho
#3
Jun7-10, 08:27 AM
P: 42
Thanks.

dtango
#4
Jun7-10, 10:42 AM
P: 43
L/d ratio

Here's a bit more explanation: 1) drag increases with the square of airspeed 2) drag also increases with increasing air density. Air density is the highest near sea level and then decreases the higher you go. So at low altitudes and high speeds, that's the worst possible combination from a drag perspective because it maximizes drag in level flight. We could further expound on all this but that's a basic explanation to Raymer's statement.


Register to reply

Related Discussions
Mass Ratio to Mole Ratio Biology, Chemistry & Other Homework 3
Ratio simplification using ratio series. Calculus & Beyond Homework 7
Ratio Mu/Ru General Physics 2
E/m ratio? Special & General Relativity 13
Help with ratios Precalculus Mathematics Homework 6