Modifications, Maintenance & Repairs
Note- all bold print items represent modifications from the original aircraft configuration
Mods, Repairs, and Maintenance to Twin Comanche N8121Y
Careful inspection of logbooks prior to my purchase of aircraft revealed that both engines were top-overhauled at 684 tach time in May 1979 and both prop blades on both engines were replaced in 1971 per Hartzell service bulletin. All other maintenance appeared regular and routine. Very careful inspection of this aircraft revealed no damage history or signs of repair.
Note---engine oil and oil filters are always replaced at each annual inspection and on many occasions in between.
July 19, 1989
Purchased Twin Comanche N8121Y
Tach Time and Total Time on Airframe: 789 hours
August 1989
Engine starters both rebuilt
Permanently removed 5th and 6th seats and associated seat belts for insurance purposes.
October 1989
We did a major rebuild of avionics panel as well as a general refurbishing of airplane:
We kept the King KNS-80 RNAV and KT-76A transponder, the Narco AR-500 encoder, and the KMA 20 audio panel, but almost everything else was changed out:
We added:
KR-87 ADF with KI 229 slaved ADF readout
KX-155 NAV-COM with KI 209 glide slope indicating head
KY 97A COM radio
KCS 55A HSI
S-TEC 60-2 Autopilot with altitude pre-select and new turn & bank
Astrotec clock/timer
WX 10A Stormscoope
Apollo Model 618 Loran
PS Engineering intercom dual type with rear seat isolation
Davtron pressure altitude readout
Davtron DVOR
PTT on both yokes
Westbend timer on pilot yoke
Electric trim on yoke
New 1/4 inch aluminum instrument-avionics panel (one piece)
Dual master avionics switches
Dual tachometer replaces two separate ones
Handheld radio jack in panel
Input jack for cassette player
Avionics cooling fan
Replaced flap indicator
Replaced VSI and Manifold Pressure Gauge
All 4 fuel bladders reconditioned
Rebuilt R Bendix fuel servo
Both fuel selector valves reconditioned
New copper cables from battery to starters and aux power plug to replace aluminum
Installed strobes on wingtips
Re-sealed both aux fuel pumps
Replaced one fuel level transmitter
New oil and fuel line hoses in both engine compartments
New floor insulation
New door locks- Ace tubular key type
Replaced door seal around cabin door
Airplane weighed with new wt and bal
Installed new Rosen type sunvisors
New fuel selector decals
New fuel door latch
Replaced L cowl flap cable, adjusted R one
Replaced all engine compartment hoses both engines made by Aviall
Installed loran to autopilot coupling
Installed external airswitch to Hobbs meter
Rebuilt "whiskey" compass with new gaskets
New Airspeed indicator
Rebuilt prop governor in L engine
April 1990:
Dynamic prop balance at Byam Propeller shop
New battery
Replaced mirror on L engine cowling
Replaced Southco fasteners on nose cowling with nutplates
May 1990:
Annual Inspection
Replaced generator brushes both sides
Replaced brake discs and pads
Replaced sparkplugs all 8 cylinders
Replaced Timken bearings in nose gear wheel
Replaced air filters both engines
Replaced L main gear brake line
" L main gear door hinge
" Oil and filters both sides
" scat tubing L generator
" R Lord engine mounts
Rotated L engine mounts
Cleaned and gapped plugs
Timed magnetos
Replaced Zerc fitting in nose gear (grease nipple)
Replaced L landing light bulb
November 1990
Replaced carpet, sidewalls, curtains, and upholstery of seats
Removed Apollo 618 Loran and installed Northstar M1A Loran
March 1991
Replaced generators both engines with Interav alternators, regulators, and over-voltage relays in addition to circuit breakers
Repaired (welded) exhaust stack on R engine
June 1991
Annual Inspection
Installed new fuel selector decals
Replaced ELT battery
Replaced push rod tube O rings and seals, oil return line hoses, rocker box cover silicone gaskets,
Replace fuel door latches
Replaced brake O rings
Installed Hobbs meter on Janitrol Heater
Heater AD inspection
Replaced brake discs with Flite Life black stainless discs and organic pads
Replaced nose wheel shimmy dampener with new rebuildable model made by Parker-Hannafin
Overhauled landing gear transmission
Repaired (welded) alternate air box R engine and installed new bell crank kit
Repaired (welded) exhaust stack #4 cylinder Left engine
Replaced nose gear tire
January 1992
Annual Inspection
Installed new exhaust hanger hoses
Installed new bungee cords both main landing gear
Replaced nose gear canvas tent
Replaced various bolts and bushings in landing gear per inspection for AD
Replaced boot on nose wheel steering rod
Installed Piper Kit 761-082 on nose gear
Replaced both main gear tires
Replace cylinder head temp probe on L engine
May 1992
Replaced Davtron 903 Unit with model 903 ID-Z s/n 2796
Replaced Davtron Model 630 with Model M655 s/n 3972
Purchased Kennon Heat Shields for aircraft
August 1992
Replaced all 4 magnetos with New Slick Model 4373 Magnetos and wiring harnesses
Replaced engine driven fuel pumps both engines Lycoming LW15473
Replaced all spark plugs both engines with Champion REM40E type plugs
Replaced bushing in R starter housing MZ298 bushing
March 1993
Annual Inspection
Replaced prop governor oil lines and installed steel fittings, c/o AD 90-04-06
Replaced both front crankshaft seals, prop O rings and alternator belts
Replaced air filters both engines
Replaced battery
Replaced Lord engine mounts L engine
Replaced brake pads both main gear Cleveland 66-105 pads
Installed Strike Finder Weather avoidance system and removed StormScope
Installed Northstar M2 Loran/GPS Unit, removed Northstar M1A
IFR certification for altimeter and transponder
April-May 1994
Annual Inspection
Replace Vacuum Pump R Engine
Repaired R exhaust manifold with installation of ball joint modification by A/C Exhaust Systems in W.Va
Replaced diaphragms in both fuel manifold blocks
June 1994
Replaced display in KNS 80
April 1995
Annual Inspection
Replaced R starter Bendix
Repaired Air Filter Box R Engine
Repaired Alternate Air Box L Engine
Replaced both air filters
Replaced ELT battery
Replaced L over-voltage relay
Added two standoff steel brackets for fuel injection lines per AD 93-02-05 (two per engine)
June 1995
IFR certification of altimeter and transponder
August 1995
Heater decay test to comply with AD
April 1996
Annual Inspection
Replaced Luggage Door Strut with new design by Knots 2 U
Complied with SB 518 Lycoming thermostatic valve inspection
Replaced bungee cords on both main landing gear
Replaced cushion material in pilot seat
May 1996
Overhauled Attitude Indicator
Replace existing ELT with installed Ameri-King model 450 in same location using same antenna and cable
March 1997
Replaced battery in remote Northstar GPS unit
April 1997
Annual Inspection
Replaced Vacuum Pump L Engine
Replaced EGT gauge with Alcor dual EGT gauge model 46125
October 1997
Replaced battery with new Gill G-35 Battery
December 1997
Heater decay test to comply with AD
May 1998
Annual Inspection
Re-swung “whiskey” compass
May 1999
Annual Inspection
Rebuilt Nose wheel strut with new O rings, etc.
Replaced R and L Main gear tires with 6.00X6 6 ply rated Custom Goodyear Tires
Installed new brake pads both main gear 66-10 organic Cleveland pads
Installed remote ELT switch in panel
Replaced landing gear bungee cords both main gear
Overhaul L prop due to oil leak
Replaced Vacuum pump L engine
Replace Fuel lines both engines
Replaced L alternator belt
December 1999
Update on Y2K issues with Northstar GPS
February 2000
IFR certification of transponder and static system
June 2000
Heater decay test per AD at Brodie’s Aircraft in Fort Worth
July 1, 2000
Annual Inspection
Replaced Schraeder Valve in nose gear oleo strut
Replaced EGT probe on L engine
Replaced Air Filters both engines WIX 42040
Replaced vacuum regulator filter L engine
Replaced Lord engine mounts R engine
August 1, 2000
Repaired #4 cylinder L engine, new exhaust valve, seat, guides, piston, rings. Note- on return trip from Colorado, it was noted that the compression was low on that cylinder while hand-turning the prop to circulate oil. Exhaust valve stem was noted to be corroded and tolerance was very loose in the guides. All other cylinders had good compression.
August 10, 2000
Installed exhaust extensions on both engines
Replaced internal battery in Navigator M2 Loran
August 20, 2000
Replaced #3 cylinder R engine with re-built chrome cylinder assembly in Louisville, KY after noting engine running rough on landing. The plane was then flown back to Grand Prairie, TX.
August 31, 2000
On disassembling cylinder, it was found that exhaust valve had broken off and had been ingested by cylinder, damaging the piston and cylinder head. Therefore it was elected to replace/repair the remaining cylinders on both engines. All cylinders were removed and inspected. Three cylinders were found to be in good condition and therefore those 3 were put on the L engine after replacing the rings, exhaust valves, seats, and guides.
Replaced all cylinders on R engine with rebuilt chrome cylinder assemblies
Replaced L EGT probe
October 10, 2000
Overhauled both fuel injection controller servos
June 20, 2001
Repaired left engine exhaust manifold with ball joint by A/C Exhaust Systems of Jumping Branch, W.Va.
Weld repair of left engine cowling crack which occurred when exhaust manifold broke and hit inside of cowling.
August 31, 2001
Annual Inspection- packed wheel bearings, serviced brakes, new Janitrol heater AD complied with
Repaired broken field wire to R alternator
Replaced brush block on R alternator
Replaced panel gear indicator lights with press-to-test type lights
September 5, 2002
Annual Inspection
Replaced Gill G-35 Battery
Replaced both bungee cords
Replaced both starter drives
Replaced ELT batteries (6 D cells expire March 2008)
Replaced brake pads, O rings in slave cylinders, both sides
Rebuilt brake master cylinders with new O rings, etc., both sides
Cleaned fuel strainers, replaced gaskets, and O rings in sump drains
Cleaned finger screens in fuel injector servos
Replaced Garlok seal in vacuum pump drive
Adjusted idle mixture in Left engine
Repaired both air filter box covers
Cleaned and gapped spark plugs
Repacked wheel bearings
Placarded Heater controls inoperative to avoid AD inspection (had very mild winter)
Repaired hinge on "clam shell" of right engine cowling.
October 1, 2003
Annual Inspection
Replaced all engine hoses, including flexible fuel and oil hoses.
500 hour inspection of all 4 magnetos, including lubrication, and re-setting internal timing
Flushed and pressure tested left oil cooler due to left engine running hotter than right
Replaced all cowling screws with stainless steel screw kit
Replaced both induction air filters
Replaced all spark plugs on both engines.
Rebuilt right brake master cylinder with new O rings.
Repaired another hinge on "clam shell" of right engine cowling.
Changed oil and replaced oil filters both engines.
Adjusted idle and idle mixture on left fuel injector servo.
Cleaned belly of plane and under wings behind engines with industrial grade detergent.
November 14, 2003
Replaced roll servo in S-Tec autopilot with factory rebuilt servo at Tomlinson Avionics, Gainesville, TX.
November 1, 2004
Annual Inspection
Drained and replaced engine oil and oil filters both engines.
Rebuilit left main gear brake master cylinder.
Replaced O rings in left fuel drain sump.
December 15, 2005
Annual Inspection
Changed oil and replaced oil filters both engines.
Changed bungee cords on landing gear.
Inserted spacer washers between engine and lower Lord mounts on right engine to raise engine
slightly. Recommended by Maurice Taylor to raise engine even after new Lord mounts will
not raise engine to proper position in cowling due to age of engine mounts, etc.
Replaced Garlock seal and both gaskets on vacuum pump on right engine.
Replaced no-blow gasket on left engine #2 cylinder.
Replaced O rings in both main gear slave cylinders and rebuilt left master cylinder.
Replaced brake pads on both main gear.
November 1, 2006
Annual Inspection
Due to a rough running right engine, found #4 exhaust valve stuck. Subsequently checked all valve guide
clearances and reamed three exhaust valve guides.
Replaced landing gear side brace stud (AN26-25) and main side brace stud bushing on left main gear.
Replaced both main gear tires and tubes.
Cleaned battery box and painted inside with acid resistant paint.
Removed prop governor on left engine and replaced with overhauled unit from Quality A/C Accessory in Tulsa.
Installed new cabin door hinge pins.
Installed new lug on P lead to right magneto on right engine.
Changed oil and replaced oil filters both engines.
Cleaned belly of plane and under wings behind engines with industrial grade detergent.
Replaced one spark plug on #4 cylinder on right engine which failed pressure testing.
Feb 12, 2007
Static and Transponder Check for IFR flight
March 31, 2007 Removed #3 cylinder on Right Engine for overhaul due to low compression
May 12, 2008
Annual Inspection
Changed oil and replaced oil filters both engines.
Installed new lug on right magneto of Right Engine.
Replaced D cell batteries in ELT. Next replacement due 2011.
March 12, 2010
Annual Inspection
Performed Landing Gear AD 77-13-21 totally disassembled landing gear, measured all bolts and bushings, drag link ends and bearing rod ends. Installed new AN 178-40 and AN 6-26 bolts on left side of nose gear linkage. Fabricated new steering arm roller bushings. Installed new bungees on both main gear. Performed retraction load test with torque tube adaptor and torque wrench. Found less than 95 pounds required which is well within tolerance. Greased all Zirc fittings on landing gear after reassembly. Inserted new hinge pins in main landing gear doors. Stop-drilled three small cracks in left main gear door near hinge. Fabricated and installed a 3 nut plate aluminum strip on each side to replace the three #10 nuts which attach the main gear doors to the wing. Had both nose gear doors repainted at GLO A/C Paint at Northwest Regional Airport. Performed AD 97-01-01-R1: removed both main gear side brace studs and had both magnaflux and dye tested for cracks at Apex Lab in Addison, TX. No cracks found. Repaired and reinstalled nose gear blanket.
Repainted battery box with acid resistant paint on inside and flat black enamel on the outside. Stripped and treated nose section fore of the wheel well with Alodine and painted with primer. Replaced all battery drain hoses. Removed, repaired, and reinstalled battery drain assy. Installed new Gill G-35 battery.
Installed new Rapco brake disks on both main gear, P/N RA 164-02201. Replaced brake pads and both flexible brake lines. Bled brakes.
Replaced landing gear wiring harnesses and switches. Weight and balance not affected.
Rebuilt both fuel strainers using new gaskets, O-rings, and drain hoses.
Per AD 96-09-10, on both engines, removed all accessories and rear accessory case and replaced oil pump housing assy P/N 00SL78528, gear kit P/N 00AEL18109-S, and oil pump drive shaft P/N 00AEL61174. Reinstalled all accessories with new gaskets.. Compression check Right engine: (1) 78/80 (2) 75/80 (3) 79/80 (4) 78/80. Left engine: check (1) 79/80 (2) 77/80 (3) 76/80 (4) 78/80. Replaced engine driven fuel pump on left engine P/N LW 15473 and gasket. Timing reset to 25 degrees BTC on both mags on both engines.
Heater reconnected and determined to be in airworthy condition. Performed Heater Pressure Decay Test per AD 04-21-05. Heater passed test.
ELT battery exp date 2011.