Reduced fuel consumption by flying at the Carson #

[1970m20e]

http://www.aopa.org/members/files/pilot/2010/december/technique.html

I found this article on AOPA website today.  When I get back from my deployment I will be trying out this technique.  My question is, what is the VG speeds on our Mooney m20e's?  Does it vary?  And if so then I guess what would be the Carson Speed?  After purchasing the Mooney, I'm all about efficient flying.  In fact I'm planning on removing the belly strobe when I get back to help reduce the drag.

 

 

[Jeff_S]

Quote: 1970m20e

http://www.aopa.org/members/files/pilot/2010/december/technique.html

I found this article on AOPA website today.  When I get back from my deployment I will be trying out this technique.  My question is, what is the VG speeds on our Mooney m20e's?  Does it vary?  And if so then I guess what would be the Carson Speed?  After purchasing the Mooney, I'm all about efficient flying.  In fact I'm planning on removing the belly strobe when I get back to help reduce the drag.

 

 

[Hank]

For a quick answer, Vg varies slightly across the vintage fleet.

In my C, Vg = 105 mph indicated.

Max Endurance = Vg/1.316 = 80 mph indicated, way, way too slow to even think about. My charts show 1950/20" as the longest range at 10,000 msl and below [speeds are 128 sea level to 149 at 10K, still too slow . . . ]

Vopt. cruise = Vg x 1.316 = 138 mph, which is around 1950/20" in the 7-10K range.

Personally, I'll burn the extra gas and run WOT-½" or so, and 2500, for speeds in the 160-165 range. I usually descend around 20" and cruise RPM.

Why buy a Mooney if you want to fly slow????

[scottfromiowa]

True that Hank. 

[jlunseth]

Ya, thanks, that would make my Carson around 120, and my cruise speed at altitude is around 165-175.  I think I like cruise speed better.

[1970m20e]

Nothing wrong with flying fast.  I just like to fly fast and cheap.  So the Carson number is the best way to get there fast as well as save the most fuel at the same time.

[Hank]

True, flying at the Carson number is the cheapest way to go. But 138 mph = 120 knots less wind, and I've recently spent enough time flying at Skyhawk groundspeed into the wind . . .

A quick math check:  318 nm to my brother's for Christmas.

Base travel time at 165 mph = 2:16, 9 gph => 20.25 gallons.

At Carson cruise, 138 mph = 2:38, ~7.5 gph => 19.75 gallons.

So is 20 minutes worth ½ gallon or ~$2.00-$2.50? Along with not-so-crisp handling? What about a 20-knot headwind? That takes either 2:38 or 3:10, using 23.7 or 23.75 gallons, so at Carson cruise I use more fuel . . . Methinks Carson's calculations were in the pre-Mooney days, and would probably work much better for a 182 or a Piper or some other gas-hog . . . . . .

[Igor_U]

Quote: 1970m20e

Nothing wrong with flying fast.  I just like to fly fast and cheap.  So the Carson number is the best way to get there fast as well as save the most fuel at the same time.

[Awful_Charlie]

There is a good article here: http://www.db.erau.edu/research/cruise/piston.frame.html for getting the range out of fuel.  I wouldn't use it unless I needed to avoid the stop, or there wasn't one available, as although you can save some cash on the fuel, engines are still TBO at 2000 hours, and the check still comes at 100 hours.  It doesn't make any difference if you do those hours at max cruise or most economical, anything with a flight hours limitation is going to have to be replaced/serviced/reduce in value.

Your insurance company might have something to say too if you want to increase your hours by a considerable factor, and as has already been pointed out, if you're gonna go real slow, get a brand C or brand P machine, or take the car!

Ben

[Igor_U]

Ben,

Article I had in mind is this one:

http://cafefoundation.org/v2/pdf_tech/MPG.engines/AIAA.1980.1847.B.H.Carson.pdf

There is no such limitation for Part 91 flying and (my) insurance company has nothing to say. However, I normally not fly above 10-11k ft unless going far and high over mountains (14,000 MEA). That is the only time I would fly at Carson speed as it is equal to my plane’s max cruse speed.

 Having said that:

I see you fly Bravo… and dare to say you fly (or should) at or close to Carson speed if you fly high, as Bravo is meant to be flown.:>

I am not familiar to you best Glide speed but keep in mind that if you indicate 145 KT at FL200 (standard atmosphere) your True speed is 200KT and at FL250 true speed is 216KT.

I would be interested to know Vg for M20M; due to higher gross weight it should be significantly higher than 105 mph for my M20F.

 

Regards,

 

Igor

[Awful_Charlie]

Quote: Igor_U

Ben,

Article I had in mind is this one:

http://cafefoundation.org/v2/pdf_tech/MPG.engines/AIAA.1980.1847.B.H.Carson.pdf

There is no such limitation for Part 91 flying and (my) insurance company has nothing to say. However, I normally not fly above 10-11k ft unless going far and high over mountains (14,000 MEA). That is the only time I would fly at Carson speed as it is equal to my plane’s max cruse speed.

 Having said that:

I see you fly Bravo… and dare to say you fly (or should) at or close to Carson speed if you fly high, as Bravo is meant to be flown.:>

I am not familiar to you best Glide speed but keep in mind that if you indicate 145 KT at FL200 (standard atmosphere) your True speed is 200KT and at FL250 true speed is 216KT.

I would be interested to know Vg for M20M; due to higher gross weight it should be significantly higher than 105 mph for my M20F.

 

Regards,

 

Igor

[Igor_U]

Ben,

That is interesting analysis, thank you.

I used 145 KIAS as it gave me roughly max speeds advertised for Bravo at FL200 and FL250. I wasn’t aware that max gross Vg is only 91kt as that is 105 mph; the same speed for my M20F with 2740 lb max gross. That is somewhat suspect number (for me anyway:>) as Vg is higher with weight (while gliding distance is constant) but numbers must be close. Maybe slightly larger wing area on new Mooney models (wingtips) accounts for that improvement.

Anyway, my point was that flying high enough, Vcarson approaches normal cruse speed. At FL200, 120 KCAS would be 183 KTAS – quire respectable, but you burn fuel to get that high first.

 

Yes, Part 91 allows for flying engine past TBO, no 100h checks, no mandatory vacuum pump replacement, SB etc… Only AD, those are mandatory. I understand elsewhere is different and can be frustrating; I have a friend owning a flight school in South Africa and I’ve helped him buy 4 planes from USA. They have to comply too all SB, have all the yellow cards etc, and importing a plane from US gives him nightmare.

 But he can choose a better plane for a lower price…

Regards,

 

Igor