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  #11  
Old 10-04-2017, 09:06 PM
AeroDog AeroDog is offline
 
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Originally Posted by RFSchaller View Post
I agree with the folks who talked about low drag. That was the biggest surprise coming from a Cherokee. There is also a distinct pitch change down when the flaps are applied (opposite from what my Cherokee does) and the flaps donít act as air brakes like on the Cherokee. If you are fast pull the power off. Small power reductions donít slow the plane down expeditiously.
I've flown many of the various flavors of Cherokee and Arrow and they all pitched down with flap extension. I'm surprised that your plane is the opposite.

Jerre
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  #12  
Old 10-04-2017, 09:51 PM
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DonFromTX DonFromTX is offline
 
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Originally Posted by AeroDog View Post
I've flown many of the various flavors of Cherokee and Arrow and they all pitched down with flap extension. I'm surprised that your plane is the opposite.

Jerre
My Cherokee pitched down as well, must have been something hooked up backwards
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  #13  
Old 10-05-2017, 07:18 AM
Fast Eddie B Fast Eddie B is offline
 
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Thanks to all for the valuable feedback!

A few comments…

1) I appreciate the head’s up about low drag in ground effect, and speed being critical. I’ve flown several low-wing planes with similar characteristics, including the aforementioned Grummans, but also Mooneys and Cirrus’. If RV12JT is correct and the RV12 flies pretty much like my old Tiger, I should be in pretty good shape there.

2) I think some have the impression that a “full stall” landing involves dropping the plane in from a height. What I mean is to hold the plane off as long as possible - if timed just so, the stick or yoke hits the aft stop just as the mains touch down, at the lowest possible airspeed. A couple good examples of what I aim for are shown here: https://youtu.be/hDCb9dMFlB4. Fast-forward to about 2:15 for perhaps the best example at my home base of Copperhill, TN. If you watch the airspeed indicator on the left side of the panel, you can see the plane touches down right about at my 40kias stall speed. My point is, there should be nothing inherent in the technique that would cause any problem with the gear, if done right.

3) I’ll be alert for the tendency of the nose to aggressively drop on rollout. Other planes I’ve flown (Piper twins and some t-tails, C210, etc.) also had that tendency. Though I don’t favor keeping power in on landing except in isolated cases, there are times when it helps.

4) I really meant to ask in my OP, “Given that I like to make full stall landings, is there anything weird or quirky about the RV12 I should be aware of?” I did not mean to begin a discussion on landing technique in general, but would be happy to do so. I’ll attempt to articulate my reasoning in a subsequent post to this thread.

5) Pretty much all GA planes should pitch down slightly with flap extension, unless there is some sort of interconnect. Why? The flaps cause the center-of-lift to move aft. Since the cg remains constant, the lift is operating at a longer arm and with more leverage should cause the nose to pitch down.

Again, thanks for the input, and I'm really looking forward to getting familiar with the RV12.
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  #14  
Old 10-05-2017, 08:18 AM
AeroDog AeroDog is offline
 
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Quote:
Originally Posted by Fast Eddie B View Post
Thanks to all for the valuable feedback!

A few commentsÖ

....snip...

5) Pretty much all GA planes should pitch down slightly with flap extension, unless there is some sort of interconnect. Why? The flaps cause the center-of-lift to move aft. Since the cg remains constant, the lift is operating at a longer arm and with more leverage should cause the nose to pitch down.

Again, thanks for the input, and I'm really looking forward to getting familiar with the RV12.
I've flown some Cessnas that pitch up with flap extension.
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  #15  
Old 10-05-2017, 08:51 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Fast Eddie B View Post
Thanks to all for the valuable feedback!

A few comments…

1) I appreciate the head’s up about low drag in ground effect, and speed being critical. I’ve flown several low-wing planes with similar characteristics, including the aforementioned Grummans, but also Mooneys and Cirrus’. If RV12JT is correct and the RV12 flies pretty much like my old Tiger, I should be in pretty good shape there.

2) I think some have the impression that a “full stall” landing involves dropping the plane in from a height. What I mean is to hold the plane off as long as possible - if timed just so, the stick or yoke hits the aft stop just as the mains touch down, at the lowest possible airspeed. A couple good examples of what I aim for are shown here: https://youtu.be/hDCb9dMFlB4. Fast-forward to about 2:15 for perhaps the best example at my home base of Copperhill, TN. If you watch the airspeed indicator on the left side of the panel, you can see the plane touches down right about at my 40kias stall speed. My point is, there should be nothing inherent in the technique that would cause any problem with the gear, if done right.

3) I’ll be alert for the tendency of the nose to aggressively drop on rollout. Other planes I’ve flown (Piper twins and some t-tails, C210, etc.) also had that tendency. Though I don’t favor keeping power in on landing except in isolated cases, there are times when it helps.

4) I really meant to ask in my OP, “Given that I like to make full stall landings, is there anything weird or quirky about the RV12 I should be aware of?” I did not mean to begin a discussion on landing technique in general, but would be happy to do so. I’ll attempt to articulate my reasoning in a subsequent post to this thread.

5) Pretty much all GA planes should pitch down slightly with flap extension, unless there is some sort of interconnect. Why? The flaps cause the center-of-lift to move aft. Since the cg remains constant, the lift is operating at a longer arm and with more leverage should cause the nose to pitch down.

Again, thanks for the input, and I'm really looking forward to getting familiar with the RV12.
An example of a (nearly) full stall landing in an RV-12 can be seen https://www.youtube.com/watch?v=haqgyE25YbI starting at about 1:30. So to answer your clarified question... no there was nothing weird or quirky that had to be dealt with in making this landing.

The only time the nose is likely to aggressively drop on an RV-12 is if you make a full stall landing with the C.G. near the aft limit and keep the nose up real high until the stabilator runs out of effectiveness and then the nose drops.
Best technique for all landings is to hold the nose off as long as possible but ease it down softly before totally loosing elevator effectiveness.

As mentioned, Cessnas typically pitch nose up with flap application because the high position of the flaps causes an airflow change on the horizontal tail, but you are correct, the RV-12 acts just like most low wing airplanes with a slight pitch down with flap deployment.
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Last edited by rvbuilder2002 : 10-05-2017 at 08:59 AM.
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  #16  
Old 10-05-2017, 10:14 AM
Fast Eddie B Fast Eddie B is offline
 
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Nice landing! Lots of tail clearance, which was one concern.

As an aside, in a Cirrus the POH calls for all landings to be made with full flaps. With less than full flaps if you try for a full stall landing a tail strike is possible.



Thanks for the correction/clarification on Cessna flaps and their affect on pitch. It sounds familiar - pretty sure I used to know that and forgot!
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  #17  
Old 10-05-2017, 12:00 PM
RFSchaller RFSchaller is offline
 
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I read an article years ago that seemed to explain the pitch up with flaps. It claimed that in addition to increasing the angle of attack the flaps can cause an increased downwash on the tail. I always thought that explained it. Interesting that other Cherokee pilots experience the opposite.

FWIW mine is a 1973 Cherokee 180, but I doubt the model matters.

Rich
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  #18  
Old 10-05-2017, 06:14 PM
Fast Eddie B Fast Eddie B is offline
 
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Allow me to take this opportunity to pitch my case for slow landings.

Let me stipulate that if the average pilot touches down at 5, or even 10kts over stall speed, he or she can likely do it for their entire career and never have an issue. But the Law of Large Numbers being what it is, every year we will read accident reports where excess speed was a contributing cause in landing accidents*. I see it across the board, in all varieties of GA aircraft.

Let's say an RV12, with proper technique, can land at about its stall speed of 41kts. Let's further say some pilots are more comfortable "flying it on", and routinely touch down 5kts fast, at maybe 46kt. Does not sound like much worth worrying about.

But energy increases as the square of the increase in velocity. I even made a little Excel spreadsheet to do the math for me:



That silly little 5 kt difference results in 26% more energy at touchdown. Most landings it matters not a whit, and who cares? Maybe a little more tire and/or brake wear, so what? But should something go wrong - a broken axle, a locked or failed brake, a flat tire, T-boning an elk, whatever - that 26% extra energy could be the difference between no injury and a bruise, or between a bruise and a broken bone, or even between a serous injury and death.

And how many pilots routinely land at 10 kts over stall? Check this out:



That 55% more energy has to be dissipated somehow should an accident occur, often with predictable results.

Anyway, not every plane nor every condition will be conducive to a full stall landing. But I still hold its an admirable goal most of the time in most GA planes. For those who land faster because its "easier", there's nothing inherently "hard" about holding the plane off for another few seconds as the speed bleeds off - all it takes is practice.


*Admittedly, getting too slow at the wrong time or at the wrong height in the landing process can also lead to problems, but I think far less often than the problems caused by excessive speed.
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Last edited by Fast Eddie B : 10-05-2017 at 06:17 PM.
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  #19  
Old 10-05-2017, 06:33 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by Fast Eddie B View Post
Allow me to take this opportunity to pitch my case for slow landings.

Let me stipulate that if the average pilot touches down at 5, or even 10kts over stall speed, he or she can likely do it for their entire career and never have an issue. But the Law of Large Numbers being what it is, every year we will read accident reports where excess speed was a contributing cause in landing accidents*. I see it across the board, in all varieties of GA aircraft.

Let's say an RV12, with proper technique, can land at about its stall speed of 41kts. Let's further say some pilots are more comfortable "flying it on", and routinely touch down 5kts fast, at maybe 46kt. Does not sound like much worth worrying about.

But energy increases as the square of the increase in velocity. I even made a little Excel spreadsheet to do the math for me:



That silly little 5 kt difference results in 26% more energy at touchdown. Most landings it matters not a whit, and who cares? Maybe a little more tire and/or brake wear, so what? But should something go wrong - a broken axle, a locked or failed brake, a flat tire, T-boning an elk, whatever - that 26% extra energy could be the difference between no injury and a bruise, or between a bruise and a broken bone, or even between a serous injury and death.

And how many pilots routinely land at 10 kts over stall? Check this out:



That 55% more energy has to be dissipated somehow should an accident occur, often with predictable results.

Anyway, not every plane nor every condition will be conducive to a full stall landing. But I still hold its an admirable goal most of the time in most GA planes. For those who land faster because its "easier", there's nothing inherently "hard" about holding the plane off for another few seconds as the speed bleeds off - all it takes is practice.


*Admittedly, getting too slow at the wrong time or at the wrong height in the landing process can also lead to problems, but I think far less often than the problems caused by excessive speed.
Eddie,

You make your point about touch down @ higher than stall speed, and I understand the need for a pilot to be able to demonstrate the ability to execute near full stall landing on the numbers. When there is ample runway..to do a round out @ stall plus 5-10 knots, then hold off till stall (near 41 knots) which ends in a very smooth touch down (which gives me more time to sample cross winds etc.)....you will have to do way more convincing to change my approach.
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  #20  
Old 10-05-2017, 06:40 PM
Fast Eddie B Fast Eddie B is offline
 
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Originally Posted by Phantom30 View Post
When there is ample runway..to do a round out @ stall plus 5-10 knots, then hold off till stall (near 41 knots) which ends in a very smooth touch down (which gives me more time to sample cross winds etc.)....you will have to do way more convincing to change my approach.
Your approach is my approach. When I refer to "landing" I'm talking about the moment of touchdown. As long as that is at or near stall speed, what came before is of little consequence, given your "ample runway".

Watching my videos, I usually seem to hold about 55kts until about a wingspan over the ground, then round out to a few knots over stall speed as I enter ground effect, then "hold off" as long as I can. That's what results in a "full stall' landing in my book.

Sorry if I failed to communicate clearly - I do my best!
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