Basic aerobatic questions (pitts)

[digits]

Hi all,

After having worked up the courage of taking the pitts up for her first aerobatic flights, I noticed some things that I want to research a bit further.

1) On the downward path of the loop the plane picks up speed (obviously). I noticed that, when I try to correct my heading a bit with the ailerons, they are ineffective and feel as if they are stalling (a bit of flutter it seems). This happens when the plane goes through the 80 - 100mph speed range. As the plane accelerates through it, everything starts to work again. Note that the ailerons are effective below 80mph. It happened consistently so I could experiment a bit. The elevator and rudder still work fine through that speed range. I was vertical at that time as well, so I doubt the plane could have been actually stalled. It didn't feel or look as a spin either, as the plane was keeping it's heading.

It also wasn't a scary experience or antyhing, no excessive altitude loss or violent movements or anything like that. Just curious as to what this could be.

2) Inverted, I see some fuel evaporate/leak from the gas cap vent. Is this normal/acceptable?

3) What is a normal g-load on touch down for a pitts s1? Just to have some sort of feedback on what is a "good" landing.

Thank you all!

[Colonel]

1) weird.  Never seen that.  Any slop in the ailerons if you
wiggle them on the ground?  Do you have two or four?
Symmetrical or not?  Have you tried gap seals?  How
big is the cove gap?  The S-2C is so tight they rub.  3M
bookbinding tape is the "hot tip".  What I do, is go to
Canadian Tire, and get a roll of red "tuck tape".  Great
for temporary patches on blown paint, too.  Anyways,
cut two lengths of tuck tape, just slightly shorter than
the length of the aileron gap.  Stick the two lengths of
tape together lengthwise, facing opposite directions,
sticky sides together,  with an inch or so of overlap. 

You now have a ghetto aileron gap seal.  Stick one side
to the aileron, the other to the cove.  You will notice an
improvement, although it may whistle a little weirdly to
people on the ground.  Feel free to do the same trick on
the elevator and rudder.


2) No.  Get a new cap.  They wear out.  BTW, it oughta
be pretty tight.  Crank it up.

[url=https://www.aircraftspruce.com/catalog/ ... hermos.php]https://www.aircraftspruce.com/catalog/ ... hermos.php[/url]

Note that these "aerobatic caps" have NO HOLES. 


3) Doesn't matter.  Just keep the fucker straight is the
most important thing.  If you bounce or flare too high,
throttle all the way in.  If you don't like an approach
or flare or touchdown or rollout, left arm goes straight.

A "good" Pitts landing is when you touch down precisely
aligned with your direction of travel, and you don't have
to get on the rudder pedals.  No wiggle as you slow down.

Flare to land, squat to pee.  They can put it on my tombstone.

[Colonel]

Here is a pretty good demonstration of a Pitts
landing. 

[youtube][/youtube]

Throttle to idle abeam the threshold on downwind,
and it is not touched again during base/final.

Note that I use a continuous descending-U from
downwind, to a slant final.  Budd Davisson teaches
to never be within 10 degrees of the extended
runway centerline - he calls it the "black zone".

Another way to approach is to stay level on base
and then turn final, still at downwind altitude.
Ridiculously high.  You slideslip all the way down
on the extended runway centerline.  Gerry Younger
and Rich Perkins are fans of this technique.

The other way to fly a final approach on the extended
runway centerline is even weirder, and requires a
constant speed prop.  Prop completely changes
airplane (fixed pitch, c/s, metal, composite).

Favoured by Sean Tucker, Skip Stewart and Freddy
Cabanas, you descend with the throttle all the
way in.  At least 200 mph.  On very short final
the throttle comes suddenly all the way back to
idle, the three constant speed blades go flat and
your shoulders are thrown forward into the straps
by the deceleration and if you time it right, you
touch down on the mains on the runway numbers
at 120 mph and roar down the runway with full
forward stick and your tail up as high as possible.

Note that these are jet speeds, so you need a runway
suitable for jet lengths - 4000 feet is tight, 5000
or 6000 feet is nice, because after the tail comes
down, you have no forward visibility and you have
no idea if you are about to run off the end of the
runway.

Get your local TC Inspector to demonstrate all three
techniques to you, in a two-seat. 

[digits]

Hi,

thanks!

[quote author=Colonel Sanders link=topic=5424.msg13989#msg13989 date=1484709932]
1) weird.  Never seen that.  Any slop in the ailerons if you
wiggle them on the ground?  Do you have two or four?
Symmetrical or not?  Have you tried gap seals?
[/quote]
4 ailerons, no slack that I could see, all felt nice and tight to me. The same thing did not happen during the downline of my hammerhead by the way.

[quote]
2) No.  Get a new cap.  They wear out.  BTW, it oughta
be pretty tight.  Crank it up.

[url=https://www.aircraftspruce.com/catalog/ ... hermos.php]https://www.aircraftspruce.com/catalog/ ... hermos.php[/url]

Note that these "aerobatic caps" have NO HOLES. 

[/quote]
Interesting. I have seen these caps on an S2, but I have a C172 style gas cap... So I doubt these aerobatic ones will fit :(


[quote]

3) Doesn't matter.  Just keep the fucker straight is the
most important thing.  If you bounce or flare too high,
throttle all the way in.  If you don't like an approach
or flare or touchdown or rollout, left arm goes straight.

A "good" Pitts landing is when you touch down precisely
aligned with your direction of travel, and you don't have
to get on the rudder pedals.  No wiggle as you slow down.

[/quote]

I have some work to do then  O0

[Colonel]

There is no "right way" to approach in a Pitts.  I try to
show people the most common techniques, and generally
they pick and choose elements that work for them.

Touching down perfectly aligned with the direction of
travel is the prime directive of a tailwheel landing. 

Beware that if you have a metal blade prop with any
significant gyroscopic pitch-yaw coupling, a sudden
flare will generally result in a yaw to the right, and
a crabbed touchdown.  Don't do that.

[cgzro]

1- how much aileron are you using? Push humpties sometimes run out of aileron and you feel like its reversing when really its torque that you can no longer override. You can try pumping them or carry a bit more speed, or precompensate before you get that slow. Certainly I have never seen them stall like an RV or Harvard at full deflection.


2- no gas leaks from cap are not norml. Get a new proper sealed cap and replace every 5 years or so.


3- let me know when you figure it out. a greaser in a Pitts is mostly luck and as Andy points out unnecessary and counter productive anyway. My favorite is a good solid into wind wheel touch before putting the other down.  three pointers always drop from 6 inches with a solid arrival unless i flair a bit late  end up flying into a three point and skipping slightly.

[digits]

[quote author=cgzro link=topic=5424.msg14009#msg14009 date=1484761842]
1- how much aileron are you using? Push humpties sometimes run out of aileron and you feel like its reversing when really its torque that you can no longer override. You can try pumping them or carry a bit more speed, or precompensate before you get that slow. Certainly I have never seen them stall like an RV or Harvard at full deflection.


[/quote]

I thought it was almost nothing as I intended to make small corrections. Definitely not full deflection. Might be worth to mention my ailerons are one rib bay wider than "standard" (if there is such a thing in a pitts ;-) ) I will try again next week and try to pinpoint the problem a bit more. The torque thing you mentioned is something I experienced at the top of the loop before, this felt different. It was also not a reversal, it just felt buffety/stalled but in the aileron direction of movement, not the elevator one. There was no response to the aileron input either way.

[cgzro]

The extra inward bay is to give you better roll control from slipstream when dead stopped or nearly. You may be feeling the prop slipstream which is not very smooth at low speeds.


As an experiment try power off stalls upright and inverted and see how the ailerons behave at different speeds without the engine adding to the mix. obviously watch out for spin entry due to adverse yaw.


Not sure how much spin training you have but you should get the full treatment from somebody like Andy first.

[praveen4143]

[quote author=Colonel Sanders link=topic=5424.msg13990#msg13990 date=1484711506]
Get your local TC Inspector to demonstrate all three
techniques to you, in a two-seat.
[/quote]


Sorry but I'm probably not adding a lot of value to this thread, but wanted to mention that I got quite the chuckle after reading this part.  :))

[Colonel]

I know.  I am not a good person.
But in a better world, they would be capable of this.

We forget that your taxes pay their salaries, and
wouldn't it be nice if they helped instead of attacking.