LogbookThe 450Logbook
N7740C in 1964
N7740C in 1978
N7740C in 2004
See photos taken during the restoration here.
You have not restored a Stearman if you have not done the actual work. That is to say, that if you have funded the restoration of an airplane, it is not the same as having actually done the restoration.
A restoration differs from a rebuild. Most of the components of the Stearman can be found in new-manufactured condition. Replacing missing or old parts is not necessarily a restoration. Certainly fabricating new parts that are not the same as the old ones degrades a rebuild or restoration.
For example, if you are lucky enough to acquire a Stearman with it's documented original engine and you choose to replace that engine with another, similar engine, you have not restored the airplane. Simply put, the aim of the restorer is to capture as faithfully as possible the airplane as it was at one specific moment in time.
Where possible in this restoration I have restored the parts I have acquired. When given the choice of good origianl or new manufacture, I have used good original parts and restored them to new-condition. This project was essentially a one-man job. I feel in this way, the airplane is reflective of one particular mindeset, and develops a unique personality, something very important in an airplane.
In reality, there are very few people with the skills and equipment required to complete a full restoration on an airplane of this caliber. Even the professional shops farm out some services for a variety of reasons. In truth, the restoration process can take many forms, and does not necessarily require digging the iron ore, mining the bauxite, growing and harvesting the spruce, and so on. However the process is more than acquiring parts and blueprints and assembling.
For those considering undertaking a Stearman restoration, or wishing to compare notes, I think it's important to understand the skills and resources commonly required for such a task. If you are too reliant on outside help, your control over the final product and ownership of the process suffers. If you attempt to do too much, the same final product will likely suffer as well as the ability to complete the task in a timely fashion, which can have a major effect on the completed airplane.
There are many talented aircraft mechanics who have restored and rebuilt Stearman essentially by themselves, with a minimal amount of help during times when extra bodies are needed. It can be done. However, as a mechanic you must be honest with yourself in determining whether you can do this or not.
I have found the following skillset to be the foundation of a successful restoration:
About the only aircraft building skills you can be light on will be avionics, and extensive sheet metal skills as the Stearman has few riveted structures, and you are likely to have only basic aviation instrumentation installed.
Of course, in addition to the skills required, the restorer will have many thousands of dollars invested in tools and equipment to support the restoration, as well as the protected hangar space to store everything.
Typical items that can be farmed out in the restoration process are engine building, prop overhaul, wing building, and perhaps covering and final fabric painting.
This project began as an imcomplete collection of parts, the most important of which was the FAA Registration. This provided the history necessary to document the status of the airplane, from which a project could be started with a reasonable chance of ending up with a useable airplane.
Without registration documents, FAA airworthiness records and ownership records would not be available, and thus establishing airworthiness would be problematical.
You can see some of the parts I started with at
page 1 of the
photo page, near the top of the page.
The inventory at the beginning was:
+ Fuselage frame
At the time I purchased the project I also made a deal for an engine with
carburetor, an unused mount, a used propellor, and logbooks for the engine and prop.
Missing from the engine
assembly was the exhaust, starter, generator (or alternator), and a few other
miscellaneous items.
The only part that were usable without overhaul at the time of purchase were
the engine. The stabilizer required repairs as it had been broken at the end
of one structural tube. The fuselage frame was still in the duster configuration
with tubing having been removed for the hopper, and other duster modifications
having been made. Some tubing in the frame had to be replaced due to corrosion,
and one longeron was bent.
Altogether, this was the beginning in which I saw potential.
An evaluation of the fuselage frame showed:
Otherwise, the frame was straight and relatively corrosion free. New tubing was
cut and fitted to replace the missing and corroded, and the bent tubing was
straightened cold, using a series of clamps and a lot of patience.
One of the more difficult operations was replacing the lifting handles as they
had to be bent up for me by a fellow with a mandrel bending tool. This was one
of the very few restoration processes I had to farm out.
After repairing the frame, I took it to a sandblaster who removed all the old
paint and any remaining corrosion. A close inspection after blasting showed one
more tube section to replace.
The cleaned and repaired frame was treated with a metal cleaner and conditioner,
and sprayed with a primer specially formulated as a base for a polyurethane
topcoat. A polyurethane topcoat in medium gray was applied.
It's important to note that all paints were from one supplier, and all are
aircraft coatings, specifically made for aircraft.
The primer application was the one process that was performed in my home garage,
and not in my hangar at the airport. I did this as the blaster was nearer my home,
and once the metal was blasted it was very important to get it primed as soon
as possible to prevent any corrosion attacking the now-bare metal. My neighbors
wondered if I was building a bridge! They had no idea what the structure was
that followed my home on an auto trailer!
After the painting, I injected tube oil (linseed oil based) into the frame, and
closed the holes with rivets, and turned the frame several times to coat the
inside of the tubing.
I acquired most of the missing cockpit pieces in used condition, many in very
sorry, but restorable condition, such as the seats. Seats are always in short
supply, especially the stock items. I used a pair of seats, one from a P-51, and
the other from an AT-6, both of which required a total restoration. Fortunately,
they pose no problem in fitment as they all use standard military structures.
At the time I was constructing the frame, good replacement birdcage assemblies
(the stringers and formers that provide the fuselage shape under the covering)
were not available. I purchased the raw material for the stringers and formers,
which had been formed to the correct cross-section, with another restorer. I then
purchased new inner supports for the birdcage and the required clamps-to-fuselage,
and with the aid of the blueprints, I fabricated the birdcages on the frame.
I created a fuselage turning device from an engine stand, and supported the
tail of the frame on a sawhorse. With this, I could turn the frame to any side
I wished while building up the components and the birdcages.
After the frame was completely restored, and the formers and stringers in place,
I installed the landing gear at the front after restoring only the exterior of the
gear. I visualy inspection showed no corrosion, and the legs were full of
hydraulic oil, so I felt it unnecessary to rebuild the gear at this time. This was
a mistake I paid for at the first annual inspection after the restoration, as we
found the right gear leg to be frozen and needing overhaul.
Once the frame was completed and on landing gear, it was time to install the
electrical system and fit up the tail group. The photo page will show all the
items that had to be installed in the frame, which makes up most of the airplane's
complexity.
In addition to engineering an electrical system (the original was rudimentary, and
did not accomodate modern radios, transponders, etc.) I had to engineer the
oil tank, oil cooling system, and placement of the battery in the baggage
compartment area. All this had to be documented with engineering drawings to
be approved as airworthy.
I created the cooling duct system, hand fabricated a scoop for same, engineered
a base plate for the battery and cooler, fabricated a structure to support the
oil tank and lines coming from and going to the firewall area as well as vent lines.
I provided an outflow area for the cooling air that was introduced through
the oil cooler in the tail fairings. I also fabricated a baggage area box,
with a removeable bottom to provide access to the battery and cooler.
Other items I created was the oil drain door below the oil tank, at the left
side of the fuselage (how you going to drain the oil?), a doubler system to support
the rotating beacon and radio antenna, and custom placement of the old
fire extinguisher door to the left side to provide access to the baggage and
electrical area.
The greatest amount of time was spent in this phase of building, by far.
After reviewing other 450 Stearman, I decided to place the radio gear to the
pilot's right, rather than in a stack behind the front seat. This has turned out
to be a good idea.
The electrical system is 24 volt, and consistes of an alternator, battery,
external power receptacle, instrument power lines,
com radio, intercom, transponder and altitude reporter, ELT, ammeter, panel lights,
position lights, and appropriate switches, fuses, and circuit breakers.
I did not install a landing light due to the cost and availability of the
preferred 6 inch retractable unit. I did provide the wiring and switches should
I want to retrofit the unit at a later date.
I went with a 24 volt system to take advantage of its efficiencies in wiring and
distance capabilites. The battery was placed behind the rear cockpit in anticipation
of weight and balance considerations. As it turned out, I could have mounted it
in the original (for a standard Stearman) position, just aft of the firewall.
Throughout the electrical system, I used solder and a light crimp covering the
joint with shrink tubing at each connector. This gave a better appearance than
the colored crimp connectors, and I believe a better connection based on my years
of living with both aircraft and motorcycle crimp connectors submitted to the
vibration and oil everpresent in both. I also tried NOT to use the ubiquitous
nylon zip ties in deference to traditional tie wrapping.
Of course, I created several pages of schematics for the system, as well as
a complete load analysis document for all components in the system. These
are retained not only for the final inspection, but make up a large chunk of
the items I use during maintenance and inspections.
After the installation of the electrical system, it remained to restore and
test fit the tail group. Only the elevator required extensive restoration, as
I had to repair a spar, and replace the leading edge, as well as one rib. The
difficult part of repairing the stabilizer was maintining exact alignment of the
bearing supports for the elevators while welding up the spar using an interal
doubler, fishmouth and rosette welds to accomplish the repair.
All the tail components were cleaned of all old finish, and primed with the same
primer as the fuselage. No coating beyond the primer is required. The modern primer
is superior to the original zinc chromate coating in that it is dope-proof.
The wheel and brake assemblies were disassembled down to the smallest component.
All hardware was replaced with new. Shoes were re-lined, bearings replaced,
wheel cylinders sleeved and rebuilt, and all tubing hoses and fittings were
fabricated from new. The only item not renewed was the drums, which I postponed
to the first annual. The wheels were checked for cracks with a dye penetrant.
The master cylinders are automotive, and are new, and original to a 1953 Ford
F-100 truck application. The master cylinders are 1 1/8" bore, and the wheel
cylinders are 1" bore, which provide excellent braking results. A small amount
of fabrication (brackets, spring clamps, etc.) was required to make the master cylinders work in place of the
originals. The project while in a duster configuration was fitted with these
master cylinders and the BT-13 wheels when they were plentiful, and matched up
with the larger engine.
Overall this braking system is robust, operates correctly, and performs better than
the originals as the brake swept area is larger.
27 inch tires were at one time difficult to find, but are now more plentiful,
and work well. At the rear, I acquired a 10 1/4 " inch tailwheel, which as one
time was popular with the dusters. It rides on a straight axle, and it seems
an adequate number of tubes and tires exist, and it works just fine.
One caution I would provide to others is in the use of silicone brake fluid. It
works very well, and is much nicer to work with than standard automotive DOT 3
fluid, and aircraft red fluid is not compatible with the automotive cylinders. The
issue with the silicone fluid I found is that you must be absolutley fastidious
in keeping the fluid away from the brake linings! Any contamination of the linings
with this fluid will reduce the braking to almost zero! So, keep it clean,
especially during bleeding.
The fuel system restoration was very straightforward. Clean the tank, take out
what dents you can, and check for leaks. Paint it and set it aside. Of course,
all new lines and fittings were used.
See my article on restoring the BT-13 type fuel gage
here.
Since the engine had been swapped to a 450 Pratt & Whitney in 1968, I did not
have to fit the 1/2" studs in place of the original 7/16" items as it
was already done for me. I did however have to find the correct engine bolts
which are special manufacture, where studs could not be found of the correct size.
Otherwise, engine attachement
was pretty straightforward.
I chose to use a Broussard exhaust system, which is a twin-outlet system, in
addition to a Beech 18 cowl and intake system. I am now installing a
Beech Staggerwing exhaust instead. There's nothing wrong with the Broussard
unit at all. I just like the way the Beech exhaust fits up and exits. Look
for my article on installing this exhaust here.
The difficult part of the engine installation is fabricating the controls to work
with the different engine, and routing exhaust, while fitting the cowling
correctly. There is no single way of doing this, and much engineering must be
done on the spot such as how to accomodate guards, hoses, instrument hookups,
carburetor air, and so on.
Items I fabricated during the engine installation were:
Some tips I would offer for others installing a 450 would be:
One item that takes special care is the configuration of the fuel lines from
the tank sumps. They must be bent carefully to prevent fuel starvation while
in an unusual attitude in low-fuel conditions.
Each 450 Stearman is a little different in the way the engine and any cowling
is installed. When originally installed, the R-985 might have been un-cowled, and
may have had any one of several types of engine mounts. There is a wide latitude
in how the controls are installed, as well as many different types of exhaust
and intake installations. With such a variety of possibilities, it is important
to have many resources at hand to help in the decision making and engineering.
Some of the best resources are the 450 Stearman experienced mechanics, as well
as other 450 Stearman you can find locally.
Remember, FAA airworthiness documents are available for other airplanes. So, if
you can identify another 450 Stearman and wish to review the approvals and
available engineering notes on the approval paperwork, they are available through
the FAA. You cannot have too much information.
In order to accomplish the restoration in a reasonable time, I purchased a
wood kit for the four wing panels, and pre-cut spars for the center section.
The remaining work was substantial enough, and requires what I consider
expert joinery, and knowledge of the finest aircraft standards in woodworking
and materials.
The kit came with pre-assembled and formed ribs, tip bows, and spars. There was
considerable fitting and joinery remaining as the tip bows were not shaped, and
of course all the tip cross bracing was not cut or shaped. Considerable work with
plane, saw, sanders, and very small aircraft nails and mahogony plywood ensued.
The center section required considerable skill in wood shaping to apply the
leading and trailing edge mahogonly plywood, and to create the trailing edge
bow and grab handles.
The challenges of wing restoration are many. Among the more notable are tool
selection, material selection and specification, glue types and requirements, and
a wide variety of clamping and nailing fixtures. It is helpful to be able to
see a completed wing from time to time as well. Keep in mind that there may be
legal variations in wing structures as well. For example, the aileron bays may
be enclosed in a variety of ways differing from the blueprints, and the leading
edges may also vary in material and attachment methods, to some degree.
I used nothing but approved rescorcinol glue, and spruce and mahogony plywood
of the highest grade. I used aircraft nails, and followed all the best standards
and practices. I learned to keep all my woodworking tools sharp, read the blueprints
several times before cutting, and that many details are not on the 'prints.
Make sure when you are building your wings, to match the ribs of the upper panels
to those of the center section, and to mate the lower wings to the fuselage with
the birdcages in place to assure proper fit down the line.
I spent considerable time adjusting each wing bay and all the drag and anti-drag
wires in the wings to be square and within specified measurements. I trammelled
each wing bay to better than 1/64 of an inch of square, and overall, no dimensional
tolerance of greater than 1/16 existed. Just take your time and be patient.
To cover the airplane, I used Ceconite 101 material (the heaviest), and the
Randolph Ranthane polyurethane covering system. This covering system saved
considerable time over a dope finish, and will last longer, and is much more
durable. I followed the manufacturer's instructions to the letter.
I used pre-sewn envelopes on all the major surfaces. The tools required for
covering are a good few, but you cannot skimp. I used a common household iron,
and calibrated it temperature scale. I also had a small-foot hobby iron for tight
places. I used high quality sewing needles, and the best dacron threads. I found
the 'gloves in a bottle' cream to be indespensable for keeping the adhesive from
sticking too aggressively. Any form of gloves are totally useless in fabric work,
as you must use your fingers and feel extensively.
You will need lots of razor blades, and lots of practice. Do not be afraid to
build several practice structures to build confidence in stitching, tightening,
and overall covering skills. Even though I was was not using the Stits covering
process, I found a video tape produced for the Stits process invaluable for
teaching several skills and processes in covering.
Painting was pretty straightforward for anyone with good experience in spraying
polyurethanes. I found the best finish was achieved with good primer fill, and
color sanding for the best top coat. The final finish is brilliant and
practically indestructable.
A note here: paints can kill you. I used a fresh air respirator at all times. If
you are not in a position to be a professional painter, don't risk your life by
being cheap.
Perhaps the most rewarding part of the restoration is final assembly and rigging.
Once you have acquired to appropriate tools as outlined in the rigging manual,
the process is completely and succinctly described in the Stearman Erection
Manual, in step-by-step fashion.
I used a tensiometer available from Aircraft Spruce and a beam type torque
wrench to rig the wires, and it worked out very well. Total time to rig the
airplane was about 16 hours for one person from start to final re-check. There's
is a lot of ladder climbing involved, but one person can do it.
Assembly of the wing panels is best handled by at least a 3-man crew. You will
see a photo of a stand I made to help fit the top wings in the photo section. I
found this stand much better than using a forklift or a series of ladders.
Amost all 450 Stearman have had one or more of the leveling lugs provided from
the factory at the front fuselage bay cut off to make way for hoppers and other
duster equipment. These lugs are essential for rigging and weight and balance
operations, and it is not an option to simply guess at when the airplane is in
a level orientation. I was lucky to have 3 of the original 4 lugs present on
the frame. For the fourth lug, I referred to the blueprints and found the
dimensions and location for the lug. I then fabricate a clamp with a bendable
tab to fit in its (originally welded) place. I could then adjust the tab to
perfection with a little tapping and filing, and thus achieved perfect level
while rigging.
Prior to this restoration, the last flight
of this airplane was in February of 1978. She was involved in an
accident in that year which 'totalled' the aircraft.
First flight after the restoration was on the fourth of July, 2004. At the controls
with me in the aircraft was
Kevin Munson, an experienced Stearman pilot who gracefully consented to the task.
Prior to flight after restoration, the engine and propellor operation was checked
and verified to be correct, and the airplane had been inspected at least 3 times
by Stearman-familiar A&P mechanics.
On the day of the flight, it turned out to be an overcast day at Half Moon Bay Airport,
not entirely uncommmon for this seacoast field, and as such we agreed to perform
only low level hops, for the length of the runway, which is 5,000 feet.
After complete runup, Kevin rolled into position, and accelerated for takeoff.
For this run, Kevin just lifter the tail and got a feel for how the controls were
working. Some rubber channel on the upper wing gap seals showed some looseness,
and I fixed that from the front cockpit for the second run.
On the second run, we held the brakes until 30" MP showed, and released. This
time after the tail came up, we lifted off for about 10 feet, and everything
held together well. A few more hops like this showed no problems right away,
so we called the airplane ready for actual flight. Thank you Kevin.
Within the first few hours of flight, some small problems showed up, the
most noticeable was a problem with excessive oil porting out the
engine.
It turned out to be a poorly routed crankcase breather. I repaired this
be re-routing the main breather tube, and adding an air-oil separator.
In the first 3 hours, I added friction to the prop control, sealed a gap in
the forward left inspection door, replaced the rebuilt spark plugs with new plugs,
and added some insulation on the inner firewall to keep the forward cockpit
cooler. No other adjustments were necessary. For such an extensive rebuild, these
issues were not too significant.
The rigging was right from the beginning, as she flew straight and level when trimmed.
There is no tendency to wander nor roll of course.
The brakes are excellent in feel and power, and the tailwheel steering is
positive and very controllable.
In summary, I'd say there were no serious squawks after the restoration, and
all the design decisions seem to be working out ok. She flies straight, true,
and completely controllable in all axis. It's a very nice airplane!
Contact me if you have any questions or comments via
Stearman Email
+ Fuel tank
+ Main landing gear
+ Horizontal stabilizor
+ Main wheels and brakes
+ 2 right-hand elevators
+ Elevator torque tube
Fuselage & Frame
* Missing cross tube at station 1
* Corroded tubing between station 0 and station 1
* Bent longeron at the upper left side of the rear cockpit
* lifting handles removed
Electrical and Tail Group
Brakes, and Wheels
Fuel, Engine, and Exhaust
>> Modified Beech 18 dishpan and brackets
>> Oil temperature manifold
>> Various control bellcranks and rods for all engine and prop controls
>> Modified lower Beech 18 cowling, and other cowling support and internal items
>> Modified air box inlets to accomodate the Broussard exhaust
>> Firewall
1. Use coat hangar or welding wire to prototype the shape and bend of control rods.
2. Don't be afraid to lengthen one arm of a bellcrank to achieve correct throw
on modified controls.
3. Use only aircraft grade components, standards and practices.
4. The wrong or wrongly attached engine mount can kill you. Seek expert guidance here.
Wings and Covering
Assembly and Rigging
First Flight
At cruise power settings on warm days, the engine maintains about 190 degrees F
oil temperature, and the cylinder head temp is good too, so the cowling, oil
cooler, and various cooling outlets seem to work well.