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Long Climbs, With or Without Flaps?

Lawn Dart

Lawn Dart

Registered User
Las Vegas, Nv
Where I live and fly (my field is about 7000 msl) everything is down hill from here. Lately I?ve been playing with the flaps to see what gives me the best climb from the flatlander airports (about 3000 ft msl) back up to my field.

Normally, I climb at about 50 to 55 indicated with one notch of flaps from 3000ft to 9500ft. Now what I?m doing is retracting the flaps after about 500 AGL and climbing at about 65 to 70 indicated and it seems to me that I?m arriving at the same altitude (9500 ft) at about the same place as I did with one notch of flaps, albeit a lot sooner and a little cooler.

Has anybody done any ?real world? trials to see what the best long climb speed and configuration is for a SuperCub?

I know what the difference is between Vx and Vy, but has anybody really tried it on long climbs?

Jerry Burr?can you read me?

And?I see pics where the altimeter is reading like 800ft, can you guys really breath down there??? Personally, I?ve never seen an altimeter read that low.
 
Field elevation at 78fl here in Florida is 54ft. we breathe just fine.

Tim
 
Climb

I shouldn't say this but have had salt water above the axles on 36" tires . What
elevation would that be???
Used to hall sheep hunters from sealevel to about 5000 and the best for me in
the cub was about 60 mph. That would change a little with the prop you have. Fun to climb steep but hard on the eng. Wayne
 
Cavy,

The best answer to your question is largely dependant on ambient temperatures, as well as density altitude.

I've always liked to climb at about 70 mph in Cubs to give the engine more cooling. I almost never use flaps in a climb, once I'm clear of obstacles.

At slow speeds with flaps, you must be cooking your engine pretty hard, at least in spots. Remember that CHT is only determined at one point, and often on only one cylinder, and the hottest cylinder may change with attitude and speed.

I believe that 70 mph and no flaps will get you there faster in a long climb, with more engine life over time, than slower speeds or flaps.

Also, remember that fuel is used for several purposes in these engines, one of which is cooling. If you pull the throttle back some in climb, you may bring it back past the "auto-rich" function, where the carb is throwing extra fuel at the engine for cooling. Don't know what the "official" name of this feature is, but it's definitely there in these Marvel carbs.

Mike V
 
Uhhhh auto-rich function. I got to admit tech school was a long time ago but uh could you give a bit more detail on this. I know that full power will give you best cooling for the cylinders but I don't remember the extra gas
J.C.
. :bang
 
Heat

Know of a 100 hp cont. on a cub and if you back off on the throttle a little during the
climb out the temp. comes right up. Leave it wide open and run fairly cool. Wayne
 
I have a graph provided by Lycoming, which shows the fuel burn versus rpm on a Lycoming o360/ or O320. This graph is pretty much a straight line till you get to about 2500 or 2550 rpm, when the fuel flow bumps up considerably with just a small increase in RPM. This, I was told by Lycoming rep, is designed to provide additional fuel for cooling during high power operation, ie: a climb.

As Wayne says, go out and climb your cub, pull the power back a bit at a time, and at some point around 2500 rpm, you'll note an increase in cylinder head temp.

If I were smart, I'd be able to figure out how to scan and link this dang chart, but.....

MTV
 
This month's "Light Plane Maintenance" has a decent article about carbs. One of the items it discusses is the "enrichment ciruit." At full throttle, it dumps fuel, not only to cool, but to prevent detonation. Wasn't everybody taught to depart with full throttle?
SB
 
Anonymous said:
Are you saying that everytime you climb you should use full throttle?
Click to expand...
That?s exactly what I would recommend. Gas is needed for cooling. I often climb from 2000 to 12 000 feet always full throttle but starting leaning at 3500, speed at 70 Mph all the time.

Fore sure clean on flaps gives you the best rate of climb. Some plane may reach their best angel of climb by using the first stage of the flaps. I am sure for the Maule M7 but not for Super Cub.

Hans
 
Rich or not Rich.

Hi Swisspilot. Let me see if I understand you correctly. You climb always at full throttle so as to take advantage of the additional cooling of auto rich. But you start leaning to defeat the effects of auto rich at 3500 feet. What's wrong with this picture? :-? Jerry.
 
Most airplanes with fixed pitch props will show the same rate if not better at higher climb speeds because the engine turns up more. If the RPM is higher you are higher on the HP Curve.

Kelly
 
Kelly,
Did you used to work at Hood? Maybe own a red and black C180?
SB
 
SB,

Yes, that is me. Unless ofcourse you are with a part of the federal government that hasn't found me yet, HA!

My 170 has a fixed pitch prop and will show 700-750 fpm at 70 or 100 mph.

My old swift would show 800 fpm at 80 or 110 mph.

I believe in good cooling.

Kelly
 
Kelly,
I saw the old Culhane plane on the Priest River strip last year. I remember when you bought it. What a small world.
SB
 
TJ, There is an enrichment valve. It is a cylider looking thing with a phillips slot in the end on the front of the carb. I had one that the spring went bad and allowed fuel thru the circuit all the time causing it to bellow black smoke even when on the ground. I will try and post a drawing of the circuit tommorrow. The Precision Carb book doesn't have the nice colored schematic like my Stomberg manual.
 
cllimbing with flaps out

Climbing with flaps extended is one of my favorite subjects. As I understand it, climbing is best done with minimum drag, all other factors being equal. Those of you who fly jets will remember that flaps are coming up as soon as speed permits, especially on an engine out procedure. The cub is a lot simpler to figure out, since flaps up climb speed is darn near the same as flaps down climb speed. I use 40mph for best angle, and 58 for best rate. I don't know what I'd use for flaps extended, since to me the physics is clear. Flaps on takeoff are only appropriate for short fields with no obstacles, or soft fields (like water). The guru on this stuff is Dr. Lowry, who writes for Northern Pilot. Look him up if you need the math, or physics, to convince yourself.
 
i believe in most carbs what you are refering to is called a power valve and used in most modern carbs . what you call it is no matter they all do same thing
 
TJ, You are correct. I coulbn't remember how that thing worked. Slept to many times since I messed with it last. So there really is no enrichment system in these carbs. :oops:
 
I climb around 75 in a long climb and what ever throttle setting it takes to turn 2500 and I lean the engine.
 
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