Instead of PM ing you, I figured others could learn from some of your wisdom. Like the title says I’m building a Pitts S1D. I don’t plan on doing air shows or competing in unlimited. I’m building it because I’ve always wanted a Pitts and I just want something fun to fly for 30 minutes and putter around with.
Here are some of the specs:
D wings with plywood leading edges
Short fuse but with tilted seat back and turtleneck
Larger T rudder
Pin hinges but considering modifying the elevator horns to accept the KP4 bearings and adding the bronze half’s to make them strap hinges.
I still don’t have an engine or prop but I’ve been keeping an eye out in case a decent one comes along. I plan on keeping the Pitts light. No alternator. Just a lightweight earth x battery and starter. Handheld radio or a lightweight Trig. Wood/carbon prop. I have a stock canopy that’s cracked, but the rails are still good. Don’t know if I’ll build it open cockpit or not to save some weight.
I’m considering a 160 hp O-320 instead of an 0-360 but if a decent one comes along I’d jump on it. Most 320’s you find aren’t fuel injected so I’d be looking at adding a Airflow Performance system or Silver Hawk system. Any thoughts?
Would you stay away from an engine that had a prop strike even if the crank dialed within limits? Obviously it would have to be disassembled and inspected. Places like Wentworth take a little bit of the prop strike risk out of the equation because they guarantee the crank, case and cam will pass inspection.
Would you stay away from Superior?
Any other tips, things to look/watch out for?
Thanks for your time.
Re: Engine for Pitts S1D
Posted: Mon May 23, 2022 1:45 am
by Colonel
Sorry about the delay responding ... lots of questions!
S-1D is a neat little airplane. Never got the hype of the S-1S because of the flat-bottom wing
but remember when you are pulling +ve G (99% of the time) you're ahead with the S-1D :^)
Keeping it light is a really good idea. Get a Lithium battery and a lightweight starter. No alternator,
just plug it in after every flight! An external antenna with a minature radio will work fine. Most important
thing is an ANR headset or those earplug guys (Clarity Aloft) because a Pitts is crazy loud. Ask Neil!
For a prop, consider a fixed-pitch (don't go C/S) 3-blade, either from MT or Catto.
Catto makes a superb prop for the Pitts S-1 - DanM is a hoot. Or phone Gerd at MT.
Engine: either 320 or 360 parallel-valve, whatever you can get.
You probably want high-compression pistons (most people do) unless you have to run 94UL (SCC) and
then suddenly stock starts to look good. A lot of people change out the camshaft (I think for the helicopter,
LW-13356) and run the RPM's much higher than stock. When I flew Neil's, I think I saw 3300 RPM?
Neighbors might not like that, but sure a lot of fun. Carefully choose your prop pitch to match your RPM
redline and Vne. Prop diameter is also a function of desired RPM. You actually want mach 0.9 at the
tips ...
I have lots of experience with the stock Bendix RS-5A fuel injection, but it's expensive. The Ellison
throttle body worked well (inverted) on the R-985 Stearman. Do some searching of websites to see
what people think is the current hot setup that doesn't break the bank and works inverted.
Speaking of inverted ... you will need a Christen 801 inverted oil system. Pricey. A lot of the RV guys
that aren't doing a lot of -ve G get the "half-Raven" system which is much cheaper. Again, do some
reading and figure out what gives you the best bang for the buck for your flying. Realistically you're
probably not going to be doing outside loops, so if it doesn't puke oil when it's momentarily inverted
that might do it.
There are prop strikes, and there are prop strikes. As long as the engine is inspected, I would be
ok with it. For example, this looks bad (and it is, for the prop) but I would be very happy with this
engine. It will be undamaged because the prop was sacrificially turned into toothpicks (I'll bet
the hub is perfect):
Note that the above (not mine) was caused by a lack of competent tailwheel training. Another topic.
Try not to be "that guy". Notice this guy was on grass which is FAR easier to keep straight with
tailwheel, but the catch is that you can't tell what direction you are going without color contrast at
the runway edges (Geneseo is like that - all green, all the time):
Remember that a dry, paved or concrete runway is the worst possible surface for a taildragger - you
land with even a tiny bit of crab, you better have brought your A-game on the rudder pedals. Me, I land with no crab, and the fucker rolls out straight every time. They taught us that in mathematics
as an undergrad - transform your equations and give yourself an easy problem to solve. You'd be
amazed how many people think that's a really stupid idea. Whatever. A zero-friction surface (ice, snow,
even wet grass) is the safest and easiest for a taildragger. You can land in a crab and roll out, in a howling crosswind!
My feet hurt, looking at the picture.
Back to your engine. Probably more important is the lightening holes on the crankshaft - they can
cause problems. Read this carefully:
If you go with a composite blade prop, the forces on the crankshaft are MUCH reduced compared
to metal blade. Depends how crazy you get with the tumbling/spinning. I remember meeting a
guy in Alabama (?) at an airshow, he beat the sh1t out of an S-1S. Angry as hell at ICAS. Turned
out having the hangar next to me here, a few years back. Cris Ferguson, that's his name! What a
small world. Jimmy Buffet says there are only 200 people in the world. He's an idiot about a lot
of things - ask him about his Stearman - but he's probably right about that.
Cylinders are very hard to get these days. I think Lycoming is backlogged a year right now?
I tend to go with factory, because I've never had a problem with them, and the other cylinders
(eg Millenium) have had a spotty history. Again, some reading is a good idea to get the best
bang for your buck right now. If you can, piggyback on the knowledge and parts supply of
the RV guys. They can be a little strange (yeah, yeah, I know, pot meet kettle) but there's
quite a pool of knowledge and parts supply there.
Lycoming cylinders, GAMI injectors and a data-logging engine monitor (takes 1 amp, replaces
your steam gauges) is a pretty good recipe. I look at the data after every flight. Anything looks
off, I get it addressed immediately. Rough running engines drive me nuts. In flight, I look at
1) oil pressure
2) fuel flow
3) EGT-D
4) CHT-H
Oil pressure/oil temp inversely correlate so anything funny on either shows up on one.
Fuel flow is how I set my mixture. Either full for takeoff or landing, or 1.25 inches out
on the ground and for cruise. I cruise at 25 squared and 15 gph because I can remember
those numbers and I get bored easily, straight and level. I have spent enough of my life
straight and level, don't need any more.
EGT-D is the difference between EGT's. The absolute value is meaningless. But the
delta should be below 100F in flight. 25F if things are working well.
CHT-H is the hottest CHT. You want your cylinders to be above 300F to scavenge lead
but below 400F for longevity. The front cylinders will run much cooler than the back,
and this will drive you nuts. Try to keep the entire band within 300-400F.
That's my kid. He doesn't lean enough on the way home, but I don't like to nag him.
NB You can read the entire flight, just from the EGT above:
I insist on fuselage overlap for the formation landing. Looks like shit when you get
strung out on the runway. No "comfort zone"! If you're not anxious, you're not flying.
Note that I touch the tailwheel FIRST in TPS, as per the S-2B POH. That's a 150 foot
wide runway (for jets) so it's easy-peesy to land two Pitts side by side. You each have
a 75 foot wide runway. The contract is to not cross the centerline. Ever. You can each
slide forward or backwards, but it looks good for the wing to hold the sight picture during
the rollout.
I remember going to Gatineau and people were impressed with a formation L39 landing -
I have video somewhere. Again, 150 foot wide runway. We each had a 75 foot wide runway,
just like at CYSH except longer. It was actually pretty easy. Weird what impresses people.
My friend Rob Holland flies some of the best formation I've ever seen. He gets in
real close and repeats to himself, "Don't hit him. Don't hit him. Don't hit him" over
and over again. I like to see that kind of anxiety in a pilot. It shows that he's trying :^)
My people. If all you ever do in aviation is fly formation aerobatics on the wing of a
Beech 18 at an airshow, you probably haven't missed much. I know, I know, there's
probably something wrong with me, but straight and level is boring as fuck.
That old fucker could FLY! The anxiety of the youngster in the right seat is hilarious.
Re: Engine for Pitts S1D
Posted: Sun May 29, 2022 10:55 am
by dumbbell daddy
Thanks for taking the time to write such a detailed response packed with Pitts information Colonel! I think formation aerobatics and formation landings are quite a ways down the road for me. I do plan on getting a thorough checkout and training though. Especially spin training. I have a chunk of tail time in “easy” taildraggers but nothing like a Pitts. Speaking of tailwheels, my project came with a Haigh tailwheel. Never flown a locking a tailwheel before. I’m wondering if I should just keep it and see if I like it. Then swap it out later with an API or something if I find it annoying. What’s your opinion?
I’ve been reading the Cherokee forum (vansairforce) the last couple years, even though I have no intention on building or buying an RV. Like you said, a lot of information and discussion on there. Some of those panels have more bloody glass then the jets I fly. Definitely going to go with a light Earth X battery and ditch the alternator like you mentioned. Any good reason to install a transponder? I’ve heard of guys just flying formation with someone that has one, if they need to.
When the time comes, I’ll check out MT or Catto. Sensenich just started making an experimental 2 blade wood/composite aerobatic prop. I’ll take a look at that when the time comes. I remember hearing about Spencer and his “lost prop”. Crazy story and a great job getting her down.
I was initially looking at a throttle body and buying a carbed 320/360 but I keep hearing that getting those Ellison throttle bodies overhauled is expensive and next to impossible. There’s only like 1 guy in the US that overhauls them and his cost is the same price of converting to an aftermarket fuel injection system. The other option is Rotec. They have a TBI. A bunch of RV guys tried to use it, but have had nothing but problems. As of right now Raven is still making inverted parts but the company has been for sale for a while……so hopefully he keeps making them.
I haven’t really started looking at engine monitors yet but I plan to put one in. I’ll probably have a bunch more questions on those down the road.
Thanks again for taking the time to drop all these knowledge bombs.
