# What is “Carson cruise” and can I determine it myself?

Mike Y. just posted an answer containing the following:

With today’s fuel costs, the Carson cruise angle of attack, which represents the most efficient way to fly fast with the least increase in fuel consumption, is of significant interest.

Being an outstanding human, Mike also added a reference to the document that it came from:

"Low-Cost Accurate Angle-of-Attack System", Borja Martos and David F. Rogers, Journal of Aircraft 2018 55:2, 660-665

But for those of us who don't have access to that journal or can't be bothered to go find it, what is Carson cruise? What exactly are the benefits and how is it determined? Finally, can I determine it myself for my airplane without an AOA indicator?

From this highly reliable web page http://www.eaa1000.av.org

The maximum range airspeed may be the most economical way to fly, but it's quite slow... Hence, we may consider the speed for which the ratio fuel flow/knot of airspeed reaches a minimum. That speed, marked by the point where a line from the origin is tangent to the thrust required curve, is called 'Carson's speed'.

In s/l flight, drag = thrust. Hence, the lower graph shows the 'thrust required' curve. There is a fixed ratio (1,316) between the maximum endurance speed, maximum range speed and Carson's speed, so that:

Maximum range speed = 1,316 x Maximum endurance speed

Carson's speed = 1,316 x Maximum range speed

That's a simple way to find Carson's speed for your plane. You can get the value of the Max. range speed from the POH

• Can you summarize the page in your answer? Images aren't searchable and it's too small to read easily on mobile. – Pondlife May 3 '19 at 21:05
• @Pondlife Done... – xxavier May 3 '19 at 21:19
• Isn’t TAS/FF the specific range? So wouldn’t Carson cruise simply maximise specific range? In a jet, that’d be max range speed, right? What am I missing? – Cpt Reynolds May 3 '19 at 22:19
• @CptReynolds I believe you are correct, but I have seen the use of Carson's speed most commonly in general aviation where pilots want to fly faster than max range speed for a propeller airplane, for which this 'Carson's speed' is the best compromise. – Mike Apr 16 '20 at 21:32