Best angle proceedure

[BC12D-4-85]

Back in 1987 with a new to me Cub I stuck one of these to my left window. Just to see of before and after VG's made any difference in level flight. They did but don't recall how much, or flaps used. But still have the gauge in my toolbox, plane's gone. Edit: That had no bearing on Vx.

Gary

 

[supercub83a]

I was thinking I would try the same thing this spring. Maybe try my cub with slats and a friends to determine the differences between them and for each plane flaps up vs down climb. My thoughts were to first go do a full flap and no flap Vx flight test to make sure my Vx speeds are accurate. Then figure out exactly where the plane departs the ground with full flaps and no flaps. From that unstick point I would like to measure altitude very accurately at several distances, say 500, 1000, and 1500ft. My hope is to figure out what the climb gradient is under each and at what distance one configuration might/should begin to outperform the other. I havent thought of a good way to accurately and consistently measure the altitude at exactly the same spots. Was thinking maybe a range finder from a person standing on the runway at those points, that should work as long as the rangefinder will show the angle.


Sent from my iPhone using SuperCub.Org

 

[supercub83a]

That link to the spreadsheet for determining Vx and Vy a few posts back should be helpful for determining your actual climb speed and a little math you can calculate the actual angle too. Thats the method given in AC90-89 as well.


Sent from my iPhone using SuperCub.Org

 

[bob turner]

I am just going to do it at altitude - no longer have the courage to do this on takeoff. My recollection is that at full power full flaps and two big guys the thing is still going up pretty good just before the stall. I really don't know the angle of attack at full flap stall. I will try to measure it in a level flight stall.

Really serious measuring does require better equipment than most of us have. Maybe a good GPS unit and an observer who can write down distances and altitudes? Runway roll is easy here with the markings we have - I can get that within about ten feet.

 

[hotrod180]

Actually, you can have a significant deck angle and not really going up much. I’m not sure deck angle means much when trying to climb over an obstacle. MTV

"If you want to go up, pull back on the stick.
If you want to go down, pull back more."

I would think deck angle is irrelevant, for determining any V speeds.
I'd say check the altitude gained over:
1) a given distance, for Vx,
2) a given amount of time, for Vy.

 

[FatCub300]

I don't mean to sound taciturn, but...I think the question as to speed to use also mentioned P Stol flaps and slats. I don't have P stol, but what Hotrod said above is really the case...with slats, when you pull back, you go up. And you can go up, at least in my case, with 300hp snarling away, at an absolute stupid deck angle. BUT...at some point, gravity does in fact kick in and you start coming down. There is no real stall and I have no idea what the indicated speed is, but exactly like flying the Helio Courier, once the drag overcomes the thrust, then gravity starts winning. You can end up going almost straight down, like a 2:1 angle, with the nose way up high and the engine bellowing away.

So, I maintain that any test Bob would do in his ship, would be irrelevant for anyone other than one in his same configuration, which did not sound like the question being asked way back at the top.

What I don't get...is why any of this matters at all?? Go fly the profile that makes sense to you and fly that profile often.

A recipe for killing yourself, is to go train yourself to do something stupid and then do that stupid thing alot and count on getting away with it and see what happens...

Guys like Greg Miller and Lonnie, who put in a ton of effort to knowing their own ships like the back of their hand, successfully use those skills and attributes to their level of skill and stituational awareness.

My bet is that they are still operating quite conservatively and far from absolute performance capabilities. Those capabilities are what we always want in the bank...EVERY single time.

My opinion, is that mistakes happen more than we'd like and I am glad to have a bit more performance than I counted on or trained to, every now and then.

One of the single biggest mistakes I see, when flying with different pilots is how easy it is, to get fixated on a plan and lose all sense of options. Missing an elk, is pretty easy in the big picture...you might have to lift a wing a couple feet, or skid a turn 10 degrees, or pop up over and then float a few seconds accelerating away in ground effect. The options are endless...unless you have completely boxed yourself into something truly dumb and on that day....you're gonna pay.

That should be our sole focus. Options. Contingency planning. An analysis that begins before each flight that in our head says:
WARNING....I AM AN AIRPLANE...DISRESPECT ME AND I WILL KILL YOU!!!

After you soak that in a sec...maybe you start to realize that we are money in the bank to keep our wits about us, operate to mitigate risks, rather than become the next youtube star and ask ourselves whether we really need to know the answer to questions that should never be asked, if the goal is safety and staying alive.

But that's me.


Steve.

 

[skywagon8a]

I am just going to do it at altitude - no longer have the courage to do this on takeoff. My recollection is that at full power full flaps and two big guys the thing is still going up pretty good just before the stall. I really don't know the angle of attack at full flap stall. I will try to measure it in a level flight stall.

Really serious measuring does require better equipment than most of us have. Maybe a good GPS unit and an observer who can write down distances and altitudes? Runway roll is easy here with the markings we have - I can get that within about ten feet.

Bob, My Cub has double length flaps, some extra span and is on floats. Floats do lower the stall speed as they provide lift at higher angles of attack. The stall angle of attack is about 18 degrees with the AoA probe.

 

[bob turner]

Thanks. 14 clean vs 18 full flap - that gives me some numbers that are useful.

I will try to get steady state vertical speed - I will take the 496 with me. Writing this stuff down while watching for traffic and avoiding the Class B floor will be a challenge.