No. The certified T3 systems (ABI-51343 and ABI-51525) have no new or additional airworthiness limitations beyond what is required under FAR 43.16 and 91.403.
No. The spring is a heat-treated and stress-relieved component. Drilling or reaming oversized holes in the spring is not acceptable. If the spring bolt holes are worn, the saddle and spring assembly must be replaced.
Yes. Weight and balance must be updated after installation and appropriate logbook and maintenance record entries are required.
Yes. The STC is SA02573AK, which covers both the titanium and steel tailspring part numbers. STC paperwork is available separately under part number SA02573AK.
No. The tailwheel assembly is not included and must be retained from the removed OEM assembly. If the existing tailwheel head is not compatible with a 1-1/8" diameter tail spring, a new tailwheel head capable of accommodating the 1-1/8" spring will be required.
No new airworthiness limitations are added. At each 100-hour or annual inspection, inspect and service per the T3 ICA (ABI-DST3-ICA). The T3 requires no routine lubrication.
Yes. The OEM Husky rear tail spring bracket (P/N 37800-001) is replaced with the ABI bracket (P/N ABI-37800-001). The ABI bracket is installed with points up so it grips the spring correctly.
Yes, for certified aircraft. The STC is SA02573AK. STC paperwork is available separately under part number SA02573AK if you already have the spring installed and only need the documentation.
Yes. All T3 systems are designed as bolt-on replacements using the existing factory attachment points. No airframe modifications are required.
No. Titanium's natural corrosion resistance eliminates the need for paint. However, it can be painted if preferred.
Possibly. Because the titanium tailspring is thinner than a traditional steel tailspring, shorter AN bolts may be required for both the tailwheel-to-spring attachment and the spring-to-fuselage attachment. Always use a new locknut and verify at least 2 threads are visible above the locknut after torquing.
No. Both settings are factory-set to the optimal position and are not intended to be changed. Pilots should verify the settings are maintained at each preflight inspection.
The ABI spring features an increased spring angle (from 14.5 to 16.5 degrees) and increased end diameter on older model aircraft. These changes allow installation of a heavier-duty spring and are specifically designed to reduce the incidence of tailwheel shimmy. Otherwise, installation is identical to OEM and no maintenance manual changes are required.
The T3 replaces the OEM leaf spring with dual coil springs and oil shocks working in tandem. This significantly reduces fuselage stress on landing, minimizes bounce and rebound, and improves pilot control during landing rollout, takeoff, and taxi. For aircraft operated regularly at or near gross weight, or frequently in rough backcountry conditions, the T3 dual shock system is recommended over single-spring options.
The ABI-76082-00 three-leaf spring weighs 5 lbs 13 oz (approximately 5.8 lbs). The OEM Husky 4-leaf spring (37319-001) weighs 5.8 lbs and the 5-leaf spring (37319-011) weighs 7.5 lbs, making the ABI spring comparable to or lighter than both OEM options.
Both replace the OEM tailspring and absorb landing energy, but the titanium version (ABI-51599 series) is significantly lighter and offers superior shock absorption and elasticity. The steel spring (ABI-PA18-1/2) is the more cost-effective option. The T3 dual shock system (ABI-51343) provides the highest energy absorption and rebound control for heavy use or backcountry operations.
Inspect the bushings in the side plates at the pivot points. If the inner diameter has worn more than 0.010" above the nominal bolt diameter for that attach point, ABI recommends replacing the bushing.
Move the tail side to side and inspect visually for movement between the fuselage and the tail gear. If play is present, check the torque on the saddle bolts and tailwheel attach bolts first. If play remains after verifying torque, remove the assembly and inspect the saddle, tailwheel, and spring bolt holes for wear. Replace worn components with new ABI parts.
Refer to the T3 Approved Model List (ABI-DST3-AML) for certified aircraft applications. For experimental aircraft, select based on your aircraft make and model, gross weight, and whether you need FAA STC approval. Contact Airframes Alaska directly if your aircraft is not listed.
Turn the rebound knob all the way to "Slow." Lift the tail of the empty aircraft to waist height and drop it. The system should compress and return to static position within 1 to 2 oscillations. More than 2 oscillations means the shock should be replaced.
Typical installation time is under one hour.
Typical installation time is under one hour.
The steering springs should be just slack after reattaching to the rudder steering horns. They should not be tight.
SA02573AK is the STC paperwork only. The spring hardware must be purchased separately under the applicable part number (ABI-PA18-1, ABI-PA18-2, ABI-51599-1, or ABI-51599).
Yes. STC paperwork only is available under part number SA02299SE for owners who need the documentation separately from the hardware.
Yes. The ABI-4000 is FAA-PMA approved.
Yes. STC paperwork only for SA00417BO is available under part number SA00417BO for owners who need the documentation separately.
No. When reinstalling the tailwheel assembly with the ABI-4000 spring, the Scott 1.5" spring spacer (P/N 3241-15 or ABI-3241-3S) is not reinstalled.
Inspect the original attach bolts carefully. Any worn bolts must be replaced with new hardware before installation.
ABI-51526 is designed for the Glasair Sportsman and ABI-51551 is designed for the GlaStar. Both are for experimental use only.
The ABI-4000 is designed for Maule conventional geared aircraft. Always consult the current revision of the Maule Aerospace Technology Inc. maintenance manual for the specific model being serviced.
The ABI-51215 is designed for experimental PA-18 aircraft and direct PA-18 copies. It is for experimental use only and is not FAA STC approved for certified aircraft.
The ABI-51343 is FAA STC approved (SA00417BO) for certified Piper PA-18 Super Cubs. It is also compatible with experimental Piper and SQ model aircraft.
The ABI-51376 is designed for experimental Kitfox aircraft. It is for experimental use only.
The ABI-76082-00 is a three-leaf replacement tailspring designed for Aviat Husky aircraft. It is FAA-PMA approved.
The ABI-PA18-1 and ABI-PA18-2 tailsprings are designed for certified Piper PA-18 Super Cub aircraft. The installation is FAA STC approved under SA02573AK.
The ABI-51599 and ABI-51599-1 titanium tailsprings are designed for certified Piper PA-18 Super Cub aircraft, FAA STC approved under SA02573AK.
The ABI-51215 measures 16" x 2" and weighs 5.2 lbs.
The ABI-51376 measures 15" x 2" and weighs 5.0 lbs, making it the lightest T3 suspension in the lineup.
Both units measure 18" x 5" and weigh 6.8 lbs.
Torque the NAS6205-31 saddle bolts to 160 in/lbs. Torque the attachment bolts per the Cessna 100 Series Service Manual.
Torque the front attach bolt (AN6-23) to 160-190 in/lbs. Torque the rear spring attach bolt (AN4-16A) to 50-70 in/lbs. Torque the tailwheel attach bolt (AN7-21) to 450-500 in/lbs. Torque values are per AC 43.13-1B, Table 7-1.
Torque the AN7 bolt(s) securing the tailwheel assembly to the spring to 40 ft/lbs. For the three fuselage attachment bolts, torque the AN7 bolt to 40 ft/lbs and the AN4 bolts to 5 ft/lbs. Use new locknuts and confirm at least 2 threads protrude above each nut.
The ABI-0742152 is approved for Cessna 180 (all variants 180 through 180K) and Cessna 185 (185 through 185E, A185E, and A185F). It is FAA-PMA and STC approved under SA02299SE.
The complete assembly includes: ABI-0742152-2 tail gear spring, ABI-0742150-2 saddle tube, ABI-0742146-10 saddle assembly, ABI-0742151-1 spring stopper, 2x ABI-0742112 angled bushings, ABI-0742100-6 washers, ABI-0742179-1 black washers, NAS6205-31 bolts, AN960-516L washers, MS20392-1C33 clevis pins, cotter pins, and all-metal lock nuts. STC documentation is included.
The kit includes all components required for a complete installation: ABI-4004, ABI-4005, and ABI-4006 springs, the ABI-4003 spring attach bracket, and all required mounting bolts, nuts, and washers. No additional hardware is needed.
The ABI-4000 replaces the original Maule 1.5" spring (P/N 4004/5/6) and the original spring attach bracket (P/N 4003).
The ABI-51343 weighs 6.6 lbs and measures 16" x 3".
The kit includes spring leaves ABI-76082-01, ABI-76082-02, and ABI-76082-03, the replacement tail spring bracket ABI-37800-001, and all required bolts, nuts, and washers.
The ABI-PA18-1 and ABI-PA18-2 tailsprings weigh 5.6 lbs each.
First verify the rebound setting is correct per the factory spec. If the setting is correct and damping is still absent, replace the shock(s).
After lowering the aircraft, perform a low-speed taxi test including a straight taxi and a full 360-degree turn in both directions. Also verify the tailwheel has no excessive side-to-side movement and swivels freely to full deflection in both directions.
Visually inspect before each flight for corrosion, cracks, or damage. Perform a full inspection per the ICA at each 100-hour and annual inspection. There are no additional airworthiness limitations associated with this assembly.
With the tail unloaded (not resting on the ground), tighten the lower spring perch nut to its initial contact with the spring, then add one full additional turn. At each preflight, grab the coil spring and check for any free play between the spring and the spring perches — any looseness means the nut may have backed off.
Turn the adjustment knob all the way to "Slow" (the negative/minus direction), then back off one click toward "Fast." This is the factory preset and should be verified at each preflight.
ABI-51599 is the 2-bolt configuration and ABI-51599-1 is the 1-bolt configuration. Both are machined from the same 6AL-4V titanium and share identical performance characteristics. Choose based on your airframe's tailwheel attachment configuration.
ABI-PA18-1 is the 1-bolt configuration and ABI-PA18-2 is the 2-bolt configuration. Both are three-leaf steel tailsprings with identical performance specs. Choose based on your airframe's tailwheel attachment configuration.
The ABI-PA18-1 and ABI-PA18-2 are drop-test rated to 5.7 G.
The installed weight is 11.13 lbs. To calculate the net weight change, subtract the weight of the removed OEM assembly from 11.13 lbs, then revise weight and balance accordingly.
Both ABI-51526 and ABI-51551 are rated for a maximum gross weight of 2,350 lbs.
The ABI-51215 provides 1,500 lbs/in of compression and is rated for a maximum gross weight of 2,000 lbs.
The ABI-51376 provides 1,000 lbs/in of compression and is rated for a maximum gross weight of 1,550 lbs.
The ABI-51526 and ABI-51551 provide a total spring compression of 2,400 lbs/in, making them the heaviest-duty T3 option in the lineup and suited to the higher weight of Glasair aircraft.
The T3 dual shock system provides a total spring and shock compression rating of 2,000 lbs. It is approved for certified PA-18 aircraft with a gross weight up to 2,500 lbs.
The T3 is a coil-over style tail suspension system that replaces the OEM leaf spring with one or two coil springs and an oil shock working together. The coil springs absorb the initial landing impact while the shock controls rebound, reducing bounce and fuselage stress. The result is improved pilot control during landing rollout, takeoff, and taxi across all surface types.
It is machined from 6AL-4V titanium, the same alloy used widely in aerospace and high-performance structural applications. It is heat-treated for maximum strength and durability.
SA02573AK covers the ABI-PA18-1, ABI-PA18-2 (steel tailsprings) and ABI-51599-1, ABI-51599 (titanium tailsprings) for certified Piper PA-18 aircraft.
Lubricate the unpainted end of the tail spring with rust preventative oil or grease before installing the tailwheel assembly. This prevents corrosion and galling of the aluminum during and after installation.
Check that the spring preload is set correctly. If preload is correct, inspect the springs for damage or breakage and replace as needed.
The ABI-51215 is compatible with Scott or ABI 3200 single-bolt tailwheel setups.
The ABI-51343 is compatible with the ABI 3200 Series single-bolt tailwheel.
Compatible with Scott or ABI 3200 single-bolt tailwheel setups.
Both ABI-51526 and ABI-51551 are compatible with Scott or ABI 3200 single-bolt tailwheels, or a Matco setup.
The ABI-51215 single shock T3 is suited to experimental PA-18 aircraft operating within a 2,000 lb gross weight. For aircraft regularly operated at or near gross weight, or frequently flown in rough backcountry conditions, the dual shock T3 (ABI-51343) is recommended. Note that the ABI-51343 is the only STC-approved option for certified PA-18 aircraft.
Contact Airframes Alaska / ABI LLC directly. Phone: 907-331-4480. Website: www.airframesalaska.com. Address: 81 E. Commercial Drive, Palmer, AK 99645.
The titanium tailspring is significantly lighter than the steel version, which improves aircraft performance and reduces empty weight. It also provides superior shock absorption and elasticity for smoother landings across a wider range of conditions. Titanium's natural corrosion resistance means no paint is required, reducing long-term maintenance costs, though it can be painted if desired.