Bringing Cardinal Owners Together
for safety, savings and fun
Welcome Guest ()
Join or Log In
  Home |  Prepurchase |  Ops |  Community |  Members |  Mods |  Tech |  Data
Tech Index
CFO Search Page

Alphabetic Index

A
ADs
Aileron Trim Tab
Aileron Bellcrank
Air Box Repair
Air Duct/Spar
Air filter Gasket
Air filter mods
Airfoil story
Alternate Parts sources
Alternate Air Door
Alternator
  Bracket
  '68 CB
  Circuit Breaker
  Circuit Breaker kit
  Debug
  Troubleshoot
  Whine and noises
  OV switch
  Standby
Ammeter blip
Amsafe Install
Antenna Mount
Annual Inspection
Autopilot
  300AP transistors
  300AP hints
  Bellcrank
Avionics Air Scoop

B
Back seat removal
Baffle Mods
Baffle Rebuild
'68 Baffle Mods
Baggage door seal
Baggage latch spring
Baggage Bulkhead
BAS seat belt
Battery lid mod
Bellcrank, Aileron
Belly Cleaning
Bike Rack
Brackett Air Filter
Brake hose FG
Brake master FG
Brake master rebuild
Brake hose RG
Brake Swivel (RG)
'Braly Mod'
Boroscopes
Bulkhead repair ('68)
Bungee (Steering)
Bus Bar repair

C
Camera Windows
Carb Data
Carbon Monoxide
Case mods
CAT tubing replace
Charging Debug
Chart desk/table
Compass leaks
Concorde Lid Mod
Console Repair
Connector options
Console: add-on
Cntrl Column Bearings
Cntrl Column Bushings
Cooling Cylinders
Cooling in Climb
Cover review
Cowl
  '71 mods
  Baffle
  Bumper
  Bumper 2
  Camloc Fasteners
  Camloc Issues
  Camloc Evolution
  Chafing Mods
  Eyelets
  Flap cable replace
  Flap exit ramp
  Flap fences
  Flap bumpers
  Flap Exit
  Flap Effectiveness
  Grommets
  Rubs on Spinner
  Southco fasteners
  Screws
  Custom Inlets
  Inlet Fences
Cylinder Cooling
Cylinder cooling details
Cylinder "doghouse"
Cylinder inspection

D
Data Plate
Dash cover fab
Defroster fan
D Engine Swap
  FG details
  RG details
  IO390 install
  Governor modifications
Display repair
Door
  Fuse damage
  Handles - inside
  Handles - outside
  Handle spring
  Hinge reinforcement
  Hinge repairs
  Latch Clutch
  Lubrication
  Locks
  Pin alignment
  Seal replacement
  Seal source
  Spring replacement
  Tightening
Doubler repairs
Drilled yoke
Dual Speaker (overhead)
Dual Mag install
Dukes Fuel Pump

E
Elevator: see Stabilator
Electrical Noise
Electrical Parts
Electrical Connectors
Elevator Trim Rod clearance
Engine baffle mods
Engine Cables
Engine Gages
Engine mount
Engine swap (D)
Engine Upgrade '68
  180 HP O-360
  IO-360 RG engine
Exhaust fairings

F
FG Gear Adjust
FG fuel pump rebuild
FG Strut Rebuild
FG Strut Rebuild 2
Firewall Forward mod
FG Jacking
FG Fuel Flow
Flap:
  Adjustment
  Adjust Problems
  Follow-up cable
  Follow-up cable Options
  Motor source
  Noise
  Operations
  Rigging
  Rigging hints
  Slow
Flood light
Fuel Caps
  Flush Cap rebuild
  Monarch thoughts
  Monarch Install story
  Replacement Options
  Types
  Umbrella dissection
Fuel
  Aux Tanks
  Dipstick
  Drain valve
  Dukes Pump(RG)
  Dukes Pump Option
  Feeding unevenly
  Flow FG
  Gage info
  Header Tank leak
  Hose replacement
  Indicator repair
  Pump (Weldon)(RG)
  Pump rebuild (FG)
  Quick Drain (FG)
  Shutoff issues
  Shutoff rebuild (FG)
  RG Selector Valve rebuild
  FG Selector Valve rebuild
  Tip Vent
  Vent leak (crossover)
  Weldon Fuel Pump (RG)
'68 Fuse Repair

G
Gages
Gap Seals
Garmin 500 install
Gear Indicator lights
Gear Leg Adjust (FG)
Gear Light Secrets
Gear Magnets
Gear Mirror
Gear pump brushes
Gear pump Diagnosis
Gear pump 'bumps'
Gear Pump Light
Gear pump rebuild '78
Gear wobble (FG)
Governor bracket mods
Governer control lube
Governer plate
Gov plate: One Mech's View
Governer Surge
Grab Handle Clip
Green Goo

H
Handicapped passengers
Handle Clip
Headrests
Headlights
Headlight Replacement
Headliner R & R
Heater improvements
  Exhaust fan
  Bulkhead seal
  Aux heat tube
  Tailcone mods (RG)
  Flow Improvement
  Underseat fans
Heavy Wing
Hoisting
Horton STOL
Hose Standoffs
HP Plus Mod
Hydraulic Hoses (RG)

I
Ignition: Lasar
Injection system
Injector Clamps
Intake Manifold Seal
Intake Manifold Drain
Intercom noise
Interior parts
Interior Rework

J
Jacking the FG
Jacking the RG
Jack options
Jack buying
Jack building
Jacks: my design
Jon's Workbench

K
King display repair
Kinzie presentation
Kinzie install


L
Landing Gear (FG)
Landing Lights
Landing Light Replacement
Lasar Ignition
LED Lights
 Courtesy lights
 Dimming filter
 Gear indicators
 Tail Beacon
 Wing tips
Light (flood)
Lighting troubleshoot

M
Magnets (gear)
Mag Install (dual
Magneto points
Manifold Pressure gauge
Manuals
Master cylinder rebuild
Mixture cable (Cablecraft)
Mixture Cable Attach
Monarch Fuel Cap Install
Muffler
  Bracket Removal
  Clamp (RG)
  Cracks

N
Nav Light Indicator
Nose Gear
  Actuator rebuild
  Arm pad
  Drag link cracks (RG)
  Door Hinge (RG)
  Door wear
  NG Door Grommets
  Door Grommet option
  Door Bumper
  Scissor bolt shearing
  Shimmy
  Strut Rebuild (RG)
  Strut Rebuild (FG)
  Strut Rebuild 2 (FG)
  Swinging
  Door Triming
  Uplock Roller (RG)

O
Oil Canister issues
Oil Cooler Baffle (RG)
Oil Cooler Info
Oil Cooler Hoses
Oil Cooler gap (RG)
Oil Cooler upgrade (RG)
Oil Draining tricks
Oil Filter (D) Adapter
Oil Filter Cutting
Oil leaks
Oil line: prop
Oil Paths
Oil Pump
Oil Separator
Oil Screen (FG)
Oil Screen (RG)
Omni antenna
Overhaul
Overhead Console Repair
Over Voltage Sensor
O/V switch wiring
Owner Maintenance

P
Panel forming
Panel Project
Panel Tilt
Paint
  Colin's Paint Story
  Hints and Tips from Guy
  RG Colors
  FG Colors
  Painting templates
Pitot-Static Troubleshooting
Placards
Plane Power VR
Preflight Inspection
Prop control lube
Prop oil line
Prop oil line fitting
Prop Surge
Prop Torque
PTT options
PTT in Yoke
PWM filter
Pump rebuild: gear

Q

R
Radio noises
Rain leaks
FG gear adjust
Retractable Gear (RG)
  (Also see 'Gear')
  Alternate Air Door
  Ammeter blip
  Brake Swivel
  Configuration (by year)
  Downlock rebuild
  Early switches
  Gear Leg removal tool
  Gear Lights
  Gear Magnets
  Gear Mirror
  Gear Selector Rebuild
  Gear pump 'bumps'
  Gear pump diag/light
  History
  Hoisting
  Internal Leak
  Jacking
  Leg pin removal tool
  Lock Valve rebuild
  Light design
  Light socket
  Main Gear Pin
  Main Rod End
  Main Rod End Sources
  Manifold
  Mechanical switches
  MG up-bumper
  MG Saddle Replace
  MG Saddle Repair
  MG actuator bracket
  NG Door wear
  NG drag link
  NG Hoses
  NG Swinging
  NG Switch wire
  NG arm pad
  NG Door Trim
  Parts (by year)
  Pressure Switch
  Pump brushes
  Pump Bump
  '78 Pump bypass leak
  Pump Internals
  '71-3 Pump Manifold
  Pump rebuild '78
  Pump Shuttle Valve
  Reed switch
  Reed switch rebuild
  Rod End
  Rod End sources
  Schematics
  Selector Rebuild
  Service Bulletins
  Speaker (gear warn)
  Squat switch wire
  Shuttle Valve
  Switch rebuild
  Throttle switch arm
  Throttle switch example
  Troubleshoot
  Uplock Roller (RG)
  Warning cam
  Warning horn
Rear seat removal
RG stall switch repair
Rigging
Rope trick
Rosen Sun visors
Royalite Replacements
Rudder shimmy
Rudder trim

S
SCAT tubing installation
Screw Removal
Seats, rear
Seat belts for 2
Seat pivot
Seat rails
Serial numbers
Service Bulletins
Shimmy dampener
  RG rebuild
  FG issues
  Solutions
  More FG
  FG solution
Shimmy
Shoulder harness
Sniffle Valve
Sill seal installation
Sound Proofing
Sound Insulation
Southco fasteners
Spar
  AD inspection
  Cap inspection
  Cap cracks (177)
  Cap cracks (210)
  Carrythrough
  Carrythrough AMOC
  Carry-thru Bottom inspection
  Attach Pins
  Carry-thru Repair
  Repair avoidance
  Replacement
  '68 Bracket Crack
  Servicability
Speaker (overhead)
Speed mods
Spinner Baffle
Spinner Issues
  '68 Spinner
  Paul's Spinner
  Chuck's Spinner
  Rubs on Cowl
Stall switch rebuild
STD Temp
Sticking Valve
Stinger Screw Map
Steering Bungee
Squat Switch
Springs
  Wing Tiedown Ring
  Door holdopen
Squat Switch
Stabilator
  Balance
  Bracket cracks
  Bracket inspection
  Bracket rework
  Bracket fasteners
  Bushings
  Bushing fabrication
  Creaking noises
  More Brackets
  Trim Rod clearance
  Trimming
  Wobble
  '68 Stab attach
Stall switch
Standby Alternator
Standoffs
Starter Troubleshooting
Static System Troubleshooting
S-Tec autopilot
STCs
Step removal
STOL kit
Strobes, adding
Strut rebuild (RG)
Strut Rebuild (FG)

T
Tach cable
Tailcone Bird cover
Tailcone Screw Map
Throttle cable
Throttle cam
Tiedown Ring spring
Tilt in Panel
Turbocharging
  Air Foil Bearings
   Primer
  Checklist
  Heat Exchanger
  Install Info
  FG Virtual tour
  RG Virtual tour
  Paul's pics
  Parts List
  Performance
  Power Setting
  System Overview
  Operations Manual
  Vacuum Seal
  Vince's pics
  Keith's pics
Type Cert Data

U
Uplock Actuator (RG)
  Umbrella fuel cap
Uneven Fuel Feed

V
Vacuum Seal
Valve sticking
Vent Hoses
Vent window crank
 Vent Example
Vernatherm Details
Vernatherm Theory
Vernatherm Tool
Vernatherm Fix
Voltage Drop: starter
Voltage Regulator
Voltage low on bus
Vortex Generators
VG Installation

W
Water leaks
Wheelchairs
Wheelchair lift
Wheel Pant Upgrade
Wheel hub cracks
Whisker antenna
Windshield leaks
Window replacement
Window crank, vent
Wing Air Inlets
Wing Pins
Wing removal
Wing Rigging
Wing smoothing
Wing Tiedown Ring
Wing tip mods
Wing Vent hoses
Wing wiring plug
Wire Standoffs

X

Y
Yoke Drilling
Yoke Bearings
Yoke Bushings

Z
  

Spar Carrythrough Corrosion

and Air Ducting

UPDATE 2/2023: As our spar carry-through has gotten more scrutiny in recent years, the issue described below has become less of a concern.

Those of us with engineering training have always considered these slight material losses in the middle of the spar flange to be inconsequential. After all, Cessna drilled a 4 inch hole through the spar web, so it doesn't seem like critical material. And the simplest stress analysis tells us that this area is not critical.

Indeed, once the FAA and others looked at the spar, the focus turned to the bottom flange, which is where the tension is consentrated, and as such is the properly place to focus. Subsequent inspection requirements do not require inspection of the area described below.

It is still good to keep your spar clean and unmarred, so this tech page will remain, partly as a history document to share the concerns we were looking at around the year 2000.


Jan Hovat, a CFO member from Norway, first brought the issue of spar carrythrough corrosion to our attention. We were able to get his problem resolved without replacing the spar, but since then we have heard of a couple airplanes where the spar carrythrough twas replaced and a few others others that were close to having a problem.

While the issue is far from common in the Cardinal fleet, it is well work checking before purchase and a few moments of time for each owner to make sure their spar is not at risk for future damange.

Several mechanics have shared that this issue also exists on the Cessna 210 Centurian, so there may be some useful knowledge to leverage across the fleet.

Click here to read Tom Connor's discussionof how he redid his air ducts to avoid such issues in the future.

If it's too late for you, see Peter Staeuble's spar replacement story.

This issue should be high on the list of details that should be looked into at your next annual. If you find corrosion on your spar carrythrough, you should review this page for information on the specifications for servicability.

Here is Jan's story:

From: "Jan Hovet" (hovetco@online.no)

Subject: C177 Severe corrosion detected in wing spar

My mechanic found some corrosion on the wing carrythrough spar today, by the holes where the air vent hoses go. Our guess is that the thin steel wires in this hose has been rubbing against the aluminium. It is so bad that the aircraft is no longer considered airworthy. Stricken by panic, I suddenly foresee that the whole spar must be replaced, and that the cost will be too high for the aircraft.

Does anyone know approximately what cost I should typically be looking at, or what can be done in such a situation?

What Jan had found was that the spar had substantial corrosion in the area near the hole where the air vent hoses passed through it. The hoses on the right side of the airplane can be seen in the above picture.

Then came a later note from Jan..

From: "Jan Hovet"
Subject: Wing carrythrough spar corrosion

About a week ago, I reported severe corrosion on my wing carrythrough spar. Cessna has authorized scraping away the corrosion on the worst places, but my mechanic feels that there are too many of them, and that only changing the spar will really fix the problem in the long run. There is also some starting corrosion the side of the spar, where you cannot scrape it away without taking off the wing. And according to Cessna, these spars are no longer available, although previously made to order. Does anybody know where I could obtain a new or overhauled (or "experienced" as they call "used") unit?

As the second picture shows, there are more tubes on the left side of the airplane that also pass through the spar.

The problem with these tubes is that they are the lowest grade of tubing of this type, called CAT tubing. They are not impervious to moisture, so when the rain comes in it tends to soak the hoses and create a point of corrosion between the steel spiral wire and the aluminum spar carrythrough structure.

The picture to the right shows a place where the Cat tubing is actually tied up to the spar, causing a potential wear and corrosion point. In this installation there is a pad between the parts, but other owners have reported no such pad and in some cases substantial corrosion.

The solution that most Cardinal Flyers have gone to was the replacement of the Cat tubing with Scat tubing, a version with a much better resistance to moisture. With some improvements in the attachment methods and better padding between aluminum and tubing they felt confident that their spar would not suffer any problems.

There are a couple of key locations which are the most likely to have problems. You can find them by looking at the locations where the CAT tubing touches the spar. With experience one can know where that usually happens and check even if the CAT has been replaced.

This inspection can be done while looking through the flap cable access panel in the back seat ceiling, although proper cameras are a lot better than the mirror that many mechanics use for inspection.

Here's a followup from another reader who checked his recently:


From: Rick Wayne (fewayne@facstaff.wisc.edu)
Subject: redbird's annual

Finished up my part of our 1975 177B's annual last night, I wound up taking four days off work to do it but it was worth it, as usual. I took the list's recommendation to drop the headliner in order to get a good, unobstructed look at the spar carrythrough and such, and was very glad that I had. Turned out there was a tiny bit of surface corrosion on the spar CT; not enough to worry anyone, but definitely enough to clean off and treat. Probably saved us BIG bucks a few years down the line.

For information on replacement of the duct tubing, so as to avoid this problem, check out this page.


These pages are a collection of the ideas and impressions of the Cardinal pilots who frequent this site. This information is anecdotal, informal and may not be completely accurate. The Cardinal Flyers are not certified mechanics and do not guarantee the accuracy of the contents of these pages. Please research and confirm anything that is referenced on these pages with the experts appropriate to your situation.

As always, the Cessna maintenance, operations and flight manuals, and the advice of a certified mechanic and flight instructor, should be your primary sources of information regarding safe maintenance and operation of your aircraft.



Copyright Cardinal Flyers Online LLC 1997-2024