CFI - Power Off 180s - Cherokee 140

[bluerooster]

No carb heat, (unless conditions indicate it's need) By the time I get slowed to 80, while holding altitude, I'm far enough away from the TDZ that I feel it prudent to u-turn, and be a bit high, than risk being a bit low, and coming up short. High, I can add flaps, slip, slow down some. Low, I'm screwed.

 

[CC268]

Went out today for some more power off 180s. Tried out the technique people recommended here and had much better results.

 

[Salty]

Yes, save your flaps for when they are needed. If you feel you are too low, slowly add a notch or two. you will notice a "balloon" effect.
Not as prominent as in the 172, but it's there.

Do you believe adding flaps will stretch your glide further?

 

[dtuuri]

Ok, my 2¢.

You don't ever need to slip or manipulate flaps. You can hit your spot every time no matter whether you use no flaps or full flaps, within reason. All you need to do is use the PC between your ears. It's unbelievably fast if you use it right. It can tell in an instant if you are trending better or worse than the last time it evaluated your glide. So, you make a small correction without slipping or fumbling with flaps, then immediately assess the change. Then correct again, over and over and over, continuously. No waiting. Make a guess and make a change if you can't tell whether you're better or worse off--you'll see in a second or two which it is, then correct back.

Now, about those "corrections"... How many ways can you adjust your glide path other than with slips and flaps? You can steer in closer or out farther, slightly. You can change your airspeed to a more efficient or less efficient speed wrt L/D. You can S-turn on final or overshoot or undershoot the turn, slightly. Doing all these things in a coordinated way, numerous times, an observer will not be able to even tell you did anything at all! But you have to do SOMETHING every few seconds (with practice you get the hang of how soon), right or wrong, to keep track of the changes in your glide's trend.

And aim for 1/3 the way down the runway until you have made the field for sure, then tweak toward the beginning of the runway.

You heard it here first.

 

[bluerooster]

Do you believe adding flaps will stretch your glide further?

With slow application of flaps, while holding constant attitude, you will get a "ballooning" effect, as air is directed downward, by the extension of the flaps. newtons law. (action, reaction and all that)
Then the drag will come into effect, but not untill after altitude has been gained, thus extending the glide.
Not saying that you can get another mile or two, but it most certianly can mean the difference between making the runway, or landing in the rough.

 

[Salty]

With slow application of flaps, while holding constant attitude, you will get a "ballooning" effect, as air is directed downward, by the extension of the flaps. newtons law. (action, reaction and all that)
Then the drag will come into effect, but not untill after altitude has been gained, thus extending the glide.
Not saying that you can get another mile or two, but it most certianly can mean the difference between making the runway, or landing in the rough.

Thanks for adding the context. I’m smelling a controversial subject here I don’t want to instigate so I’ll leave it at that.

 

[CC268]

Thanks for adding the context. I’m smelling a controversial subject here I don’t want to instigate so I’ll leave it at that.

LOL...like just about every subject on PoA

 

[jsstevens]

With slow application of flaps, while holding constant attitude, you will get a "ballooning" effect, as air is directed downward, by the extension of the flaps. newtons law. (action, reaction and all that)
Then the drag will come into effect, but not untill after altitude has been gained, thus extending the glide.
Not saying that you can get another mile or two, but it most certianly can mean the difference between making the runway, or landing in the rough.

You're trading kinetic energy (airspeed) for potential energy (altitude). It would be interesting to test, but pure physics says TNSTAAFL (There's No Such Thing As A Free Lunch) and you won't glide further. In fact, I'd guess you'd glide shorter.

 

[kgruber]

1. You can't get something for nothing.
2. You can't break even.
3. will end up at zero.

 

[jsstevens]

1. You can't get something for nothing.
2. You can't break even.
3. will end up at zero.

Ah! The three laws of Thermodynamics! You can't win. You cant break even. You can't get out of the game.

 

[dell30rb]

Ok, my 2¢.

You don't ever need to slip or manipulate flaps. You can hit your spot every time no matter whether you use no flaps or full flaps, within reason. All you need to do is use the PC between your ears. It's unbelievably fast if you use it right. It can tell in an instant if you are trending better or worse than the last time it evaluated your glide. So, you make a small correction without slipping or fumbling with flaps, then immediately assess the change. Then correct again, over and over and over, continuously. No waiting. Make a guess and make a change if you can't tell whether you're better or worse off--you'll see in a second or two which it is, then correct back.

Could not have said it better myself!

When doing this maneuver, I pull the power abeam and begin a gentle turn toward the runway. If I feel I am trending short, i'll roll in a bit more bank to cut the distance i'll have to fly to get to my touchdown point. If i'm trending long, decrease bank or roll wings level for a second. Works very well.

At any point in your glide, you have a window of correction available to you, to fix an under or overshoot condition. Constant evaluation of your position and making small corrections is the key to staying within this window.

 

[dell30rb]

One problem I had with this technique in an Arrow is that rolling in more bank reduces the vertical component of lift and increasing the sink rate even more. There's a fine line between enough bank and too much which caused me much aggravation and the instructor much amusement.

If you keep the bank <30 degrees you don't lose all that much vertical component, the correction will very much "extend" your glide.

If you pulled the power and instantly began a 30 degree bank turn directly to your touchdown point, you'd fly over it at 400 feet.

 

[kgruber]

The human brain is good at solving simultaneous multiple differential equations in real time. Don't screw up!

 

[dtuuri]

One problem I had with this technique in an Arrow is that rolling in more bank reduces the vertical component of lift and increasing the sink rate even more. There's a fine line between enough bank and too much which caused me much aggravation and the instructor much amusement.

If your intended pattern isn't going to glide you all the way to the field, you need to revise it and head for the runway, now! Then, the second you see the bank is too steep--shallow out a touch and check again. Any time you can't tell if you'll be either too high or too low, pick one, adjust accordingly and voila! It'll become highly obvious. Then make the right correction.

 

[TRocket]

Power Off 180 you have to hit your spot with 200 feet - I always go for the aiming point markers.

That is what I used to to aim for too. Did my commercial ride last month in a Cherokee 140. I don't care what anyone says, a cherokee does not glide anything like a 172. Best advice, be patient and don't be too quick to the flaps, Cherokee does NOT mean "Airplane Glides Far". On my check ride I left it (a little too) high just to be safe, then I had to slip like an SOB and aim her right at the earth...

Starting to fly my Cherokee 140 from the right seat to prepare for the CFI checkride. I did my Commercial in the 172, which glides forever when doing the Power Off 180 - my Cherokee is quite the opposite. My first few times I was way short - I kept the pattern tighter and kept the downwind shorter which helped. 10 degrees of flaps at the key position on base.

Do you guys have any tips for the Power Off 180 in a Cherokee? I will obviously go through this when I get with an instructor, but wanted to get some preliminary feedback in the meantime.

Thanks.

When it comes to flaps one word...patience.