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ACRO E-mail Archive Thread: [Acro] Pitts S-1S questions - Here are the REP ...


Thread: [Acro] Pitts S-1S questions - Here are the REP ...

Message: [Acro] Pitts S-1S questions - Here are the REPLIES!

Follow-Up To: ACRO Email list (for List Members only)

From: Klusmanp at

Date: Wed, 17 Oct 2001 02:22:13 UTC


  As I have received no less than six requests from other members of the Acro 
list to fwd replies to my Pitts S-1S questions, I have condensed the many 
replies I have received and now offer them to all on the mailing list.

My apologies to anyone who replied to me in private and did not intend for 
their comments to be made public on the list. In the spirit of privacy I will 
not include names with the comments.

My thanks again for the almost overwhelming response to my questions! I 
receive mailings from another aircraft list and an automotive list. This acro 
list is by far the most friendly and responsive list of the three.

Below are my original questions and responses from one or more people.

1) A sport aviation article mentions that "Sparcraft" wings don't fly quite 
as well as true "Pitts" wings. How significant is this? Is there an 
appreciable weight or strength difference?
<<As far as Sparcraft wings I have not heard mention them flying differently 
but there is a factor of strength. Sparcraft wings have a routed plywood 
rib as opposed to truss style built ribs in the pitts wings. There have 
been some problems with the Sparcraft ribs breaking. A good source of 
information for this would be the IAC technical tips manuals available 
through EAA. How hard the aircraft has been flown and how hard you plan on 
flying will play a factor in this also.>>

<<<<All I do is aerobatic aircraft maintenance...  <snip>   ...sparcraft 
wings are o.k. , the spars are built the same as the factory , but the ribs 
are 1/4 " routed out plywood instead of build up ribs , roll rate is a little 
slower on  a sparcraft wing due to the freese ailerons and the large gaps in 
the aileron wells>>

<<Although many folks fly the Spartcraft wings they haven't always been as 
stout as the Pitts style wings.  Although all of them have pull block 
problems from time to time. >>

<<Same airfoil as the Pitts S-1 but heavier because the ribs are solid. 
Weight is bad but if this is your first Pitts,  not the end of the world.>>

<<Unless you buy a factor Pitts, you have a slim chance
you will be getting Pitts wings. Most are sparcraft.
They are good wings, but however, are slightly heavier
(so I am told. At out levels, it will not be
noticable. Later on you can build you own set.>>

<<Sparcraft wings are OK, not as light, but not many
floks will know the difference.>>

2) Many planes have a flat pitched prop for good climb. These props have the 
potential to over-rev the engine at full throttle. What is a good 
conservative TBO for an engine that has seen a lot of 3,000+ rpm operation?

<<With a fixed pitch prop you will over rev the engine. I have a 74-56 so it 
runs about 3500 RPM max in the box. You may get varying responses on this but 
the bottom line is that the RPM isnt as bad for the motor as high EGT or CHT 
temps. You can burn a cylinder very quick at 2000 RPM if the CHT is too high. 
My motor has over 700 hrs of Advanced acro and the compressions are all over 
78 and the oil analysis is better than my Aeronca. If you fly often enough 
the high RPMs shouldnt affect it too much but obviously bearings and some 
other rotating parts will wear out sooner than the 2000 hr TBO. I would think 
my motor will go 1000-1100 hrs but Sportsman  type acro would yield 1400-1500 
hrs. Its a different story if the airplane sits for a long time between 
flights as the corrosion that builds up acts like sandpaper. If you fly once 
a week or more often that would be ideal>>

<<<<All I do is aerobatic aircraft maintenance... <snip> for the prop a 
60" pitch works the best with a 180hp and your rpm's will still be 2900 
straight and level. all aerobatic engines should make it 1200hr.s even with 
high compression pistions.>>

<<800 hours is a common time to do a major overhaul on an over -revved 

<<You cant have it all. If you want climb performance, you have to have a 
climb prop  and the engine will be operated above red line at times. My 
Pitts, at full power in level flight  will indicate 3300 rpm. >>

<<Many people wind the Lycomings up to 3500 RPM without any apparent damage 
to the engines or significant loss between overhauls.  That 800 or so RPM 
represents almost a 30% boost in horsepower which is nice to carry into a 
vertical.  High pitch, hi revving props are noisy and slow crosscounty but 
they do help while doing figures.>>


<<3000 rpm will not hurt a TBO is the engine is/has
been taken care of properly.>>

3) Do high-compression pistons reduce TBO?
<<The high compression pistons will do a lot more to reduce TBO than high 
RPM. The increase in CHT and Oil Temps will reduce TBO due to cylinder wear. 
I dont run them in my airplane but I wouldnt hesitate to throw them in. Just 
understand the TBO may go down a couple of hundred hours as a result>>

<<  Reaching TBO, you will probably get allot of different replies on this 
one. I have seen both sides of the story here. I know San Burges had a 
engine with countless overspeeds that went to TBO, but have also heard not 
to expect an acro engine to get past halfway to TBO. The two large 
variables here how hard the aircraft has been flown and how well it has 
been maintained. I would suggest contacting some of the better known acro 
engine builders,Lycon, Barret, Demars and get there opinion. They should 
also be able to give you some insight into the question of high compression 

<<High compression pistons make if extremely difficult to hand prop a hot 

<< (Do high-compression pistons reduce TBO?) Not that I know of. Some 
certified engines (Lyc 0-320-D2A) are high compression engines and the TBO is 
2000 hours.  Heavy aerobatics will reduce TBO.>>

<<(Do high-compression pistons reduce TBO?) Quite
simply, yes.>>

<<The higher compression the engine is, usually the
lower the TBO is.>>

4) Any items of airframe stress and wear I should look for?

<<The weakest part of my airplane is the fabric. Due to the propwash and g 
forces the tapes on the inside portions of the wings tend to come loose. Many 
people never glued down their tapes and just doped them on. This is bad. 
After mine came loose I reglued them and switched to 3" from 2" wide and no 
more problems. There is nothing worse than having to do fabric repair on a 
shiny new Pitts

If you plan to only fly Sportsman or rec acro I wouldnt worry too much about 
anything else. Once you start flying Advanced engine mounts, tapes, and drag 
wires will start to go. They are generally very strong airplanes>>

<<  Be sure to check wing attach brackets for cracks and any signs of the 
hole being enlarged by movement. If the aircraft has spring type gear 
inspect the longerons around the gear attach VERY WELL. As I am sure you 
are discovering most S1S's being home builts there are endless variables to 
deal with. I would suggest getting some with pitts knowledge to inspect the 

<<There are some stress points on the S-1S you should be aware of. The lower 
wing, rear attach fitting and the upper longeron just forward of the 
instrument panel are 2 areas. Check the AD's or factory support. >>

<<Some of the things that are likely to bite you and cost money are:

Fabric and paint. If the fabric and paint are not in good shape walk away
because it costs more to recover and paint than it does to put a new motor
on AND it takes 6 months.

Motor. Obviously you want to check the heck out of it, I'd want to get an
oil sample, have a look at the oil screen, compression test etc. etc.
nothing out of the ordinary for a good mechanic.

Tubes etc. make sure there is close to zero rust. Once it starts to rust its
hard to control it. Note that rust on some of the fittings is no big deal,
just change them but if the tubes in the back start to go its gonna be
expensive. There are rear spar attach AD's that require inspection every 50
hours but I've never heard of an S1 with a cracked rear spar attachment. It
happened on an S-2B and the entire line got the AD.

The fuel tank in the S-1's is subject to cracking. Check the front and rear
of the tank to make sure there are no cracks. If it is cracked and has been
putty repaired it will cost many thousands of dollars to repair properly. (I
found this in my pre-purchase). 

The S-1s were modified early on to stiffen up the tail feathers. In
particular they added under stab diagonal cross braces. Make sure your plane
has these as it's a rather important mod. 

The S-1's were also prone to tail wheel breakage. The tab at the bottom of
the rudder post would come unwelded and let the tail wheel leaf springs go
left or right for a run ride. The SB calls for a small triangular tang to be
welded behind the tab. Mine broke on my 5th landing. No problem but a pain
to get fixed and on a narrow runway it could have been costly.

Check the dates on all the rubber parts in the plane. All the hoses etc. and
especially the flop tube in the gas tank. If its more than say 8 years old
that rubber is getting hard and probably needs changing. A complete hose
change in a Pitts is many thousands of dollars because of the inverted oil
system which adds a bunch more hoses to the system.>>

<<First, check out the service bulletins.
One major one you will hear alot about is the rear
attach point. Also, go to and
then to the maintainence area. Excellent photographs
and suggestions for stuff to look at. If you are going
to get into tailslides later on, you will be advised
to get the rear tail struts. Ckeck the motor mounts.
Also, find out if has EVER been ground looped or even
just "dragged a wing (common)". Even though it may be
just cosmetic dammage, there is a signifigat moment
out there and it puts alot of stress on the wind atach
points AND the upper cabine attach points. Check
carefully.Also, check the cut out area around the
bungees. Sometimes they will start to wear the
protction around the bungees and will lead to an
earily replacement.>>

<<Check the longerons, especially by the landing gear.
If you are able to, check the H-tube (by the horizontal

5) I've encountered many different engine types: Ellison pressure carb, fuel 
injected, and some carburated engines converted by adding a Bendix fuel 
injection system. Is there a big operational difference between pressure 
carb. and fuel injected?

<<Stay away from the Ellisson TBI lke the plague. I have it on my airplane 
and its the worst. Already been overhauled twice in 500 hrs at a total cost 
of $1500. 

Do whatever you can to find a fuel injected airplane but if not the pressure 
carb is good>>

<<All I do is aerobatic aircraft maintenance... <snip> ...Ellision throttle 
bodies suck , allways a probelm , as the same for pressure carbs . Fuel 
injection is the only way to go>>

<<Bendix or AirPower fuel injection systems are now the most popular.  
Pressure carbs are expensive, difficult to keep repaired and designed for 
much larger engines so they give problems.  Some folks have had no problems 
with the throttle body Ellisons.  Others have had trouble.  It may do with 
cleanliness.  I don't know.  The only throttle body that has ever had any 
success in aerobatic circles is the Ellison.  Overall it is hard to beat the 
Bendix or its successor fuel injection.>>

<<The Bendix pressure carb is excellent if it is well cared for. If you find 
a Pitts with one, make sure it has been recently overhauled and the NEW 
gaskets installed. If you have the replace the OLD gaskets  the bill is $1400 
dollars. The overhaul of a PS-5C with the NEW gaskets already installed in 
about $150. Experience talking>>


<<On the carb vs FI,   the only pressure carb is the PS5C.  It performs OK, 
but is quite expensive to have OH'd.
I have one on a O320 pitts.    Not many know how to work on that carb so its 
important to find a shop that can work on them.   Bendix FI is probably best, 
but it is not cheap to OH either.
 The Ellison  TBI is the lowest cost to buy and to OH, but it can be very 
frustrating to get it working properly as it is VERY sensitive to the air box 
and airflow into the TBI.>>

<<A fuel injected engine is better overall, whether it
is from the factory or from Airflow Performance.>>

6) Do I need to look for a specific aerobatic crankshaft on the engine?

<<As far as the crank that depends on what kind of acro you will be doing. 
With a metal prop regardless of wether you have an acro crank or regular you 
will break a crank when you do a lot of snaps. I run a composite prop on my 
std crank and no problems and I do 20-30 snaps a flight. My buddy cracked a 
crank on his S-2B after 300 hrs with a metal prop>>

<<Be certain you have the aerobatic crankshaft or else don't ever do snap 
rolls, tail-slides, flat spins and gyroscopics.  You might "toss your prop".>>

<<If possible, make sure it has the solid flange
crankshaft.If not you will be doing frequent
inspections and will always have the worries
accompaning it. If you can get an wooden OR composit
prop, it will be less wear on the flange.>>

<<On the crank, best is to have the aerobatic crank. These don't have holes 
in the flange. If you have a CS with holes in the flange, then you must 
inspect it each 25 hours per   AD and/or Lyc SB if you are flying any acro.>>

7) What inspection interval does the prop need?

<<A  fixed pitch prop is good for only 800 hours or so according to 
Sensenich. Don't get one that has been re-pitched or damaged -ever.>>

8) How much is a composite prop and where do I get one?

<<A commposite prop is nominally an advantage if you plan to do a lot of 
gyroscopic maneuvers such as tumbles, agressive snaps etc.  It reduces the 
precession forces on the crankshaft.  Otherwise it may not be worth the 
considerable extra price over a fixed pitch.  One advantage of a fixed pitch 
is that you can wind up the engine considerably over the 2700 rpm that is 
imposed by a controlled pitch prop.>>

<<Composite - Performance Propeller
Wood - Sensenich>>

9) Other comments:

<<What made you decide on an S rather than a T?
While the S is a good aircraft the T will outperform the S.  
Now that I've said that you will understand my bias when I tell you I have a 
S1t that I'm selling.  Its a factory built aircraft with the AEIO 360.  About 
600hrs on the engine and 930 TTAF.  Was built in 1986 and and recovered about 
94.  With out the log books in front of me not real sure of exact numbers.>>

<<You do want to get a good pre buy from someone that knows Pitts though as 
many builder problems will cause headaches later on>>

<<Hi Paul and welcome to the world of aerobatics. As a former owner of a 
Pitts S1S I can recommend a very reliable source for all of your questions. 
Call Mike Mays at So. Aerobatics in West Palm Beach. He has been working on 
aerobatic airplanes (especially Pitts) for many many years. Mike likes to 
talk and he can answer all of your question. He seems to be tapped into a 
network of the Pitts market as well and can help you locate just the right 
airplane for your needs. Yes, he will make a buck on the transaction, but in 
the end, you will thank him for taking your money and steering you onto the 
right (safe) airplane.

By the way, every one of us thought when we started that we only wanted to do 
recreational aerobatics. I am sure that some people do stick to that level of 
the game, but most who I have known have gotten totally involved. It is a 
real head rush to compete.>>

<<Don't look at anything. Find the best Pitts machanic in the area and pay 
him to find you a good Pitts. Then plan on spending $3000 to $5000 more to do 
what needs to be done. You haven't got a clue on what to look for and you 
might get hurt if you try. I have owned a few aerobatic airplanes and worked 
on many more. I have seen things flying that you would say could not fly. 
Most Pitts ' with sparcraft wings are not S1Ss. Thye are S1Cs made to look 
like S1Ss but there is much more to it then that. Just don't buy one. That is 
why they are so cheap. $30,000 to $35,000 is a good price for an S1S. You 
won't get 1000 hours out of any aerobatic airplane. Find a good machanic.>>

    I do not claim to be an expert but hopefully I can give you some 
information that will be helpful. First of all how much tail wheel time do 
you have. I you do not have allot I would strongly suggest getting tail 
wheel proficient in a another type of aircraft, cub,champ,citabria ect. 
Then practice flying a citabria or decathlon from the back set. When 
comfortable with this the transitioning to a pitts is not a big deal.
    Another good source for information is the Muscle Biplane web site, I 
think the address is <>.


<<All I do is aerobatic aircraft maintenance , and the best advise I can give 
you is get a good prepurchase from someone who knows the wear points on an 
aerobatic plane . Whatever area you are looking at one , there should be 
someone around who can check it out for you. <snip>    MAKE sure you are 
buying a S-1-S and not an S-1-C , the S has a longer fuselage and more inside 
room. <snip>     get one with 180hp or better.>>

<<Get some complete spin training before you start fooling around in your 
Pitts.  there are many places you can get this training.  Since I don't know 
where you live I will give you a few names of reliable sources.  I may 
overlook a few.  That doesn't mean I don't approve, just forgot or am 

Bill Finagin (Annapolis MD)
H-R Aviation (LaPorte, TX)
John  Walkup  (Chandler, AZ)
Michael Church (Sunrise Aviation at Orange Co. Airport)
Don Hart (Hart-Aire at Long Beach, CA)
Ken Erickson  (Sean Tucker's School at Salinas, CA.)
Dick Rihn (Attitude Aviation at Livermore, CA.)

The Pitts is a pussycat when you know how to fly it.  It is a tiger until 
then.  Get trained by experts.  It will be money well spent.>>

<<Find an A&P with Pitts experience and have him/her go over the plane IN 
GREAT DETAIL. Dont get overly concerned about HP. At your stage there is 
little to be gained by having an 0-360 instead of an 0-320>>

<<My mechanic has been Ray Williams near Nashville TN. He is w/o a doubt the 
best Pitts mechanic anywhere. Ask some of the aerobatic people and they will 
know of his rep.>>

<<Paul, I sent a similar email out to this group a couple of years ago and the
advice I got was invaluable. I purchased a Pitts S-1T about 2 years ago in
Florida and my use of a very good knowledgeable Pitts mechanic saved me 10's
of thousands of dollars.>>




© Dr. Günther Eichhorn
Email Guenther Eichhorn