Energy management (Waco)

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ebetancourt

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Ernie
Well, maybe I won't compete anytime soon. I have some real doubts about being able to fly the sequence anytime soon. It isn't really a power to weight issue, it is a power to drag issue. First, the Jake redlines at 2200 and power reduction with the fixed pitch prop is a requirement much above 130. I have previously just noted level flight on my way to a loop for example. But that requirement for a brief bit of level flight is a speed killer. I went up today to try to work on the half cuban, and saw that I need a lot more skill to routinely be able to start anywhere near the 150mph recommended for a loop. Dive to 160, pull hard, level off for about 2 seconds(!) and watch the airspeed droop through 130. That was carrying redline RPM down, through the pullup and then full power when able (starting up). From experience I know that 140 at the moment of level flight does a nice loop, and today I did one from 130. From 130 the top of lift is from inertia, not lift. I glanced at the airspeed and was at or a little below 40 across the top. 60 is stall from level flight. I was pushing on the stick and hanging a little.

Did I mention I need more skill? Next time I will try 180 or more on the down line and see what happens.
 
Well after sleeping on this, I think the mistake is pulling hard at the bottom. Better to plan it and keep building speed in a smooth easy pull. I will try that later this morning.
 
Ernie, so if I understand correctly, you feel the main issue is with maintaining energy after the half cuban for a decent round loop? What sort of G are you pulling into the loop? The less you pull, the larger your loop diameter will be, meaning it takes more speed/energy over the top to round it out. These types of high drag, lightly loaded airplanes need to do fairly small diameter loops to be round. They are just too dirty to do low G, large round loops...unless maybe you had a 450 in it. :) It may take around a 5G pull to get it round. Many folks starting out tend to pull no more than around 3.5G, which isn't enough in many cases to draw round looping segments. Are you entering the loop with full power, or adding it as soon as possible on the way up as your RPM redline allows?

ebetancourt said:
Well after sleeping on this, I think the mistake is pulling hard at the bottom. Better to plan it and keep building speed in a smooth easy pull.
Click to expand...

I assume you're talking about the pullout from the half cuban? I would recommend against a soft easy pull out from the 45 downline. Doing this can make it hard for the judges to determine exactly when you have broken your 45 downline for the pullout. Remember line lengths should be equal before and after the roll, and if you pull very softly out of the figure, it may appear to the judges that you are "long after" the roll.

If you're simply trying to maintain speed, I think it would be better to build more speed on the 45 downline than try to make up speed on a soft pullout. Fly up to Vne if needed, and make a nice assertive pullout from the 45 downline. Due to the drag, I imagine you would gain little if any additional speed during the pullout if done firmly enough.

Eric
 
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No actually talking about the pull out from the spin. If can enter the half cuban with enough energy, say 150 or even a little more, I am comfortable I can get the loop and the 180. I can exit a loop with pretty close to the same speed I enter it with, ought to be able to do that with the half cuban.

Remember, my simple goal is to fly the entire sequence and not zero anything.

Again thanks for the suggestions. I am, as of now, thinking an exit/reentry is the solution for the roll as you have suggested.

If the winds die down, I will try this this afternoon. And I now have a video camera attached to a DC headset, so maybe I can see what I did wrong through my practice sessions. I hate flying with a headset, but I couldn't figure out how to attach it to my QT Halo. :) Camera only weighs one ounce!
 
Also, how much fuel are you carrying? I used to fly with full fuel till I was told not to... When I started with half tanks it was easier for me to pull hard enough for the loops. Actually, I had to be careful to not pull 5.5 Gs
 
Jeanie said:
Also, how much fuel are you carrying? I used to fly with full fuel till I was told not to... When I started with half tanks it was easier for me to pull hard enough for the loops. Actually, I had to be careful to not pull 5.5 Gs
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No, I fly with 20 above the minimum recommended for T/O. (I burn 25/hr in a climb.) Yesterday, I got through the energy management issues out of the spins.

Now all I need is skill. This is all harder than I remember. :D
 
Ernie,

Speeds like 150-180 seem awful high for a biplane. I know a stock Stearman is apples to oranges, but I dive to 130 (mph) for a loop and make a brisk pull for about 4.5Gs and come over the top at about 55mph for a 0-G loop.

On any of the dives, I pull the power back to keep it just under redline (2,300rpm) and advance to full throttle just prior to pulling through the horizon.

You're correct, you're fighting drag and it's quick to take over. It's almost like racing the clock in big biplanes as you have to pull hard and execute the maneuvers quickly before drag takes over. (i.e. small loops). The figures may look graceful and slow from the ground, but you have to work your *ss off at the stick to make them look that way.

Sammy Mason Jr. does a great aerobatic routine in a 275 Jake powered Stearman and he uses 130mph for loops.

I also use no more than a 1/4 tank of fuel.

Mike-
 
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stearmann4 said:
Ernie,

Speeds like 150-180 seem awful high for a biplane. I know a stock Stearman is apples to oranges, but I dive to 130 (mph) for a loop and make a brisk pull for about 4.5Gs and come over the top at about 55mph for a 0-G loop.

On any of the doves, I just pull the power back to keep it just under redline (2,300rpm) and advance to full throttle just prior to pulling through the horizon.

You're correct, you're fighting drag and it's quick to take over. It's almost like racing the clock in big biplanes as you have to pull hard and execute the maneuvers quickly before rag takes over. (i.e. small loops). The figures may look graceful and slow from the ground, but you hae to work your *ss off at the stick to make them look that way.

Sammy mason Jr. does a great aerobatic routine in a 275 Jake powered Stearman and he uses 130mph for loops.

I also use no more than a 1/4 tank of fuel.

Mike-
Click to expand...

Thanks for the info/ideas. The book recommends 150, I have normally used 140 and as mentioned, I have successfully done one from 130. You're right, it was zero G across the top. The YMF-5C has a VNE of 214, so at least I am not worrying about that. I'l have to try pulling harder initially and starting slower. I've been pulling about the same as I do in the Citabria (it has a G meter, the Waco doesn't) or about 3 1/2 to 4.

Ernie
 
I believe the Mystery Ship is your only option :wink2:
osh03_061.jpg
 
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