ACRO E-mail Archive Thread: [Acro] Re: Pitts S-1S questions - Here are the ...
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Thread: [Acro] Re: Pitts S-1S questions - Here are the ...
Message: [Acro] Re: Pitts S-1S questions - Here are the REPLIES!
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From: "David Magaw" <dmagaw at att.net>
Date: Wed, 17 Oct 2001 02:54:27 UTC
Thank you. This is very good info for us pitts wanabes. Dave ----- Original Message ----- From: <Klusmanp at aol.com> To: <acro at gf24.de> Sent: Tuesday, October 16, 2001 7:15 PM Subject: [Acro] Pitts S-1S questions - Here are the REPLIES! > 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> ...as 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 > engine.>> > > <<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 > pistons.>> > > <<High compression pistons make if extremely difficult to hand prop a hot > engine!>> > > << (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 > bolt > 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 > aircraft.>> > > <<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 www.musclebiplane.org 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 > stab).>> > > > 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.>> > > <<Paul, > 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 <musclebiplane.org>. > >> > > <> > > <<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 > ignorant. > > 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.>> > > <> > > <> > >