1893 Airport Rd, Kalispell, MT 59901

Piper Apache Modifications


Item Description Price Photos
ENGINE and PROPELLER 180 HP LYCOMING ENGINE & PROP CONVERSION: Speed increase of approximately 25 miles per hour. Higher twin and single engine ceiling, shorter take-off and increased useful load. Lighter weight props with dynafocal engine mounts reduces noise and vibration which results in lower operating costs, more comfort and increased performance. Optional Q-Tip Props reduce sound levels by five DB and slightly increase climb speed. The down time is about one month. Please Call For Prices (no photo)
FIBERGLASS NACELLES Low drag fiberglass engine cowling incorporates major improvements to the engine cooling system, engine accessibility and aircraft appearance.

Engine Cowling and Turtleback - All new components.
Air Induction System - All new components up to carburetor.
Engine Cooling System - All new components.
Oil Cooling System - All new components up to the oil cooler.

Streamlined in design, the cowling increases airspeed approximately 12 mph and markedly enhances the aircraft's appearance and resale value. Camloc fasteners allow engine cowling to be completely removed from both engines in less than five minutes with installation in like time. Engine baffling has been completely replaced with a new, simpler and more efficient design to sharply reduce failure and maintenance requirements. Approved for standard Piper PA23 or PA23-160 with the Geronimo 180 HP conversion. Price does not include painting. Down time - fifteen days plus painting time
EXTENDED NOSE with FULL NOSE WHEEL WELL DOORS The nose is 31 inches longer than standard with a baggage compartment. Nose wheel well doors fully enclose wheel in streamlined aerodynamic bubble. This modification does more for performance and aesthetics than any other mod except the 180 HP engine conversion. Airspeed is increased by ten to twelve mph. Rate of climb, single engine performance, CG stability and cabin ventilation are substantially increased. Modifications are made of impact resistant fiberglass. This combination of modifications goes far towards making the Apache perform and look like a modern day light twin. Relocation of antennas are extra. Down time three weeks. $ 15,995 INSTALLED
Full Main Wheel Gear Door Ki Main wheel full clamshell door kit includes complete streamlined door housing/fairings for both sides, and all necessary gear door actuator components and hardware. Adds about 5 Mph to cruise, and very noticeable increase in climb performance $3,900 $ 5,195
EXTENDED SHORT NOSE The nose is 16 inches longer than standard with a baggage compartment $ 5,195 $ 5,195
WING TIPS Improves lateral stability, stall characteristics and appearance. Increases speed approximately four mph, decreases take-off distance and lowers the stall speed. The wing span is reduced by 22 inches $2,495
WING TIP TANKS Same aerodynamic advantages as the regular wing tips plus an increase of 48 gallons of fuel capacity. Call for price  
DORSAL FIN Reduces single engine control speed and yaw tendency in turbulence. Greatly improves single engine performance $1295
SQUARE TAIL KIT Greatly improves the appearance and single engine performance of the aircraft. Includes fiberglass horizontal stabilizer fairings (both sides) for a slightly increased airspeed $1495
TAIL CONE Increases speed & directional control, and is more streamlined in appearance $595
FLAP GAP SEAL KIT Flap gap seals lower the stalling speed and increases the rate of climb, cruise and top speeds, especially when heavy or at high altitudes. $849
ONE PIECE SPEED SLOPE WINDSHIELD KIT Quarter-inch thick, distortion free plexiglass. Much more streamlined than the standard one piece windshield. Increases airspeed up to four mph. Tremendous improvement in appearance and style. Includes new fiberglass cowler and hardware. Available in green tint or solar gray for additional $60. $1495
ENGINE NACELLE & WING ROOT FAIRING KIT Improves airflow for reduced drag, a slight increase in airspeed and an enhanced appearance. $1295  
FIBERGLASS ENGINE NOSE BOWLS Replace the original with impact resistant fiberglass. Eliminates problems of metal fatigue, cracking, splitting and repairs. $1400  
GROSS WEIGHT INCREASE A computer assisted engineering study has culminated in an STC allowing Diamond Aire to increase the maximum gross weight of the Piper PA23 (150 HP Apache) Geronimos, from 3684 pounds to 4000 pounds. Down time 2 weeks. $3500 Installed  
INFLATABLE DOOR SEAL KIT Greatly improved sealing for your protection. Considerably lower cabin noise and lasts longer than other door seals. Available with either electric or manual pump. Call with specific application. This enhancement also approved for Aztecs. $595 - $949  
FIBERGLASS WINDOW MOLDINGS Available in several different options. Call for details. $450- $950  
INSTRUMENT PANEL STC KIT Approved for Aztec, Apache & Geronimo aircraft, this one-piece design eliminates cockpit display clutter and is shock-mounted to isolate full panel. Several panel styles include back-lighting or post-lighting, engine instrumentation and radio configuration options. Dual centerstack design with option for copilot instruments. Kit price consists of STC paperwork, eight Lord mounts and complete installation plans only. Swing-down buss/ switch panel optional. Custom cut panels and pre-fabricated PMA bracket sets available. This STC affords the owner/installer great latitude in customizing panel to fit individual avionics & instrumentation needs without the need for a field approval. Installation available, call for details. We also offer a new fiberglass glareshield in two styles for $389. Note: PMA approved, 2-1/4 inch round, dual backlit engine instrumentation/fuel gauges available soon! $1195
REAR BAGGAGE COMPARTMENT KIT Aluminum construction, measures 33 inches deep, 36 inches high. Extends cabin & baggage area to create a more modern interior appearance. $1295  
THIRD WINDOW KIT Aztec Style available in several different options. Improves passenger comfort, styling and appearance. Call for details. $2295  
DUAL BRAKE KIT Includes upgrading system to dual Cleveland brake calipers. Holds aircraft during application of full power engine run-up and shortens landing roll. Especially useful with gross weight increase STC. $1995  
HIGH DENSITY SOUNDPROOFING KIT Reduces noise level to a point of normal conversation. Improves passenger comfort and is an effective barrier against heat transfer. Can be installed with or without the purchase of a new interior. $1295  
MAJOR AIRFRAME INSPECTION and OVERHAUL This inspection far surpasses a 1000 hour inspection and brings the airframe back to factory new tolerances. Price will vary greatly with condition of airframe. Call for details Call for price  


Purchasing a combination of the above modifications will qualify you for a discount. Discounts also available for AOPA members, FBO’s and Piper Owners Society members.

****Coming Soon!****

Rams-horn style control yokes. We currently have this STC but our supply has back-ordered. A new manufacturer is in the process of designing an updated style yoke similar to the Aztec F yoke. It will include push-to-talk switches on both yokes, provisions for autopilot cut-off switches on both yokes, and electric trim switch-mounting provision on pilot yoke. Price will be about $1,295 per pair.

Rochester engine instrumentation.   We are currently working with Rochester Gauges of Texas to introduce new 2-1/4″ dual-needle STC’d backlit gauges. All gauges will be electronic with analog movements. They will include: Fuel quantity with new sending units, oil temp, oil pressure, fuel pressure, CHT & EGT. These gauges will eliminate the inaccuracy and availability problems associated with the old AC and Stewart Warner obsolete OEM units installed at the factory. These will be available for injected, carburated and turbo-charged models. A 3-1/8″ dual electric STC’d tachometer will also be available. This unit will pick-up signals from the magnetos, thus eliminating the need for noisy, heavy tach cables or expensive tach generators. Other advantages of these new gauges includes reduced weight, modern appearance and no oil or fuel lines running into the cabin. All gauges will be switchable for 14v or 28v operation.

Co-pilot brakes. We have been working with a firm in Wisconsin to add co-pilot brake pedals and hydraulics similar to the OEM design found on some E and most F model Aztecs. These will become available for all Aztec and Apache/Geronimo models in the near future.


  • All prices subject to change without notice.
  • The state of Montana has no sales tax.
  • Kit prices do not include crating or shipping charges.
  • All fully STC’d modifications include PMA-approved parts.
  • Some modifications approved for PA23-250 (Aztec).
  • Speed figures established by exhaustive testing, and are relative to particular airframes and other installed modifications. They are accurate to within 2%

Diamond Aire Kalispell Piper Apache Aztec Geronimo Upgrades Kits Modifications Panels

Montana Diamond Aire Inc.
Apache Modification Aircraft Corp

Call: 406-752-5092
Fax 406-752-5082

1893 Airport Road
Kalispell, MT. 59901