On 30 September 1964 Piper flew the prototype of a new twin-engine executive aircraft which was then the largest built by the company. Identified at first as the Piper PA-31 Inca, the aircraft had been redesignated as the PA-31 Navajo when deliveries began on 17 April 1967.

Piper PA-31 Navajo / Chieftain Article

A six/eight-seat corporate/ commuter transport of cantilever low-wing monoplane configuration with retractable tricycle landing gear, it was powered by two 224kW Avco Lycoming IO-540-K flat-six engines, and was available in optional Standard, Commuter and Executive versions with differing interior layouts.

The internal cabin is 15 ft 10in long and 51.5in high and a nose baggage compartment has 14 cu.ft for 150 lb of luggage, and the aft compartment has 16 cu.ft for 200 lb.

The Standard version has accommodation for six passengers, rear baggage compartment, wardrobe and optional seating arrangements for seven or eight, plus a toilet.

The Executive and VIP version accommodates six passengers, with a pilot/passenger divider, curtained off area, refreshment unit, foldaway tables and a toilet, plus the optional seventh or eighth seat.

The Commuter version accommodates eight passengers, with a curtain divider, foldaway tables, refreshment unit, magazine racks, fasten seatbelts and no smoking signs, plus a luggage capacity of 350 lb.

Piper PA31 Navajo Owner’s Handbook

Made available at the same time was the optional PA-31T Turbo Navajo, which differed only by having two 310 hp /231kW TIO-540-A turbocharged engines.

In 1974 an additional model of the Turbo Navajo was made available, the PA-31-325 Turbo Navajo C/R, which introduced a 242kW version of the counter-rotating engines installed in the Chieftain.

The Turbo Navajo B, cruising at 251 mph at 24,000 feet (404 km/h at 7000 meters); 223 mph at 12,000 feet (359 km/h at 3600 meters), featured new nacelle compartments increased luggage space 42 percent – 62 cubic feet (1.76 cu.m) and hold an additional 300 pounds (136 kg) total 650 pounds (295kg.), seating for up to nine people.

Production of the PA-31 Navajo ended and at the same time the company introduced for 1973 the PA-31-350 Navajo Chieftain which had the fuselage lengthened by 0.61m so an extra pair of seats could be fitted to the cabin, and was powered by two 350 hp / 261kW TIO-540-J2BD turbocharged engines driving counter-rotating propellers.

Piper expanded their 1976 medium twin line by offering the Navajo C/R. This airplane has 325 hp engines that eliminate the critical engine characteristics that stem from both propellers rotating in the same direction; the Navajo C/R’s left propeller turns in the conventional clockwise direction, but the right prop rotates counter-clockwise. The Navajo CR had wing lockers.

The basic model remained in production until 1983 by which time 1785 were built. Included in this total were the higher powered (325 hp) models which featured contra-rotating engines.

The engine variations provide the main performance difference among the models. The plain Navajo is a 3500 gross, 2,174 useful airplane, with a 310 hp turbo¬charged but otherwise unfettered TIO 540. The Navajo CR is the same airplane, with the same engine for that matter, except that the horsepower rating has risen to 325, magnetos are pressurized, and the right hand engine turns its propeller inboard, which the left one does anyway. The benefits of counter-rotation are minutely improved single engine performance and speeds, largely theoretical improvement from the neutralization of slipstream and prop wash effects, and the minimization of P factor. Gross weight remains the same, while useful weight drops a tad as a result of the CR’s capacious wing lockers.

The range was extended in 1970 by introduction of the PA-PA-31P Pressurized Navajo (First flying in March 1968) with a fail-safe fuselage structure in the pressurised section and two 317kW Avco Lycoming TIGO-541-E1A engines. The pressurised PA31P seated six was marketed for business high-fliers: 259 were built from 1970 till 1977.

The Chieftain is 24 inches longer than the CR, has a 7,000 gross and a 350 pound greater useful and the same engine. But horsepower has now been boosted to 350 with a tuned induction system and a slightly larger compressor.

One hundred and sixty seven Navajo Chieftains were licence built in Brazil by Embraer circa 1981, as the EMB-820.

Fifty Embraer EMB-820C Navajos were converted to turboprop configuration with Pratt & Whitney Canada PT6A-27 engines flat-rated to 550shp, being named Neiva NE-821 Caraja. The Carajá’s MTOW of 8,003 pounds (3,630 kg) was 1,000 pounds (454 kg) more than that of the Chieftain.

In 1984 a piston-engined version of the turbine Cheyenne I known as the PA31P-350 Mojave was intro-duced but production ceased that same year after only 50 had been completed. It incorporated the Chieftain II wings, pressurised Cheyenne I fuselage, and a Chieftain tail, with the powerplant of the PA-315-350 Chieftain. With increased wingspan and fuel capacity, plus airstairs, production of the PA-31P Pressurized Navajo ended during 1977, at which time a total of 248 had been built.

Schafer Aircraft Modifications Inc was founded 1977, and from 1979 developed modifications for other aircraft. Included were installing turboprop engines to Piper Navajo as the Schafer Comanchero, turboprop engines to Piper Chieftain as the Comanchero 500.

Chincul SACAIFI manufactured aircraft under license from Piper Aircraft Corporation. The company was a wholly owned subsidiary of “La Macarena S.A.”, Piper’s Argentine agent. Production included Piper PA-31 Navajo.

Production of the PA-31 Navajo started in 1973 and, after 1825 were built, ceased in 1983.

Gallery

Certification:

FAA A20SO
PA-31
31-1 to 31-659
31-661 to 31-711
31-752 to 31-7612110
31-7712001 to 31-7912124
31-8012001 to 31-8312019

FAA A20SO
PA-31-325
31-7300932 to 31-7612110
31-7712001 to 31-7912124

FAA A20SO
PA-31-350
31-5000 to 31-7652176
31-7752001 to 31-7952250

FAA A8EA
PA-31P
31P-1 to 31-7630019

FAA A8EA
PA-31P-350
31P-8414001 to 8414050

Specifications:

PA31-300 Navajo
Engine: 2 x Lycoming IO-470-M, 300 hp

PA31-310 Navajo
First built: 1967
Engine: 2 x Lycoming TIO-540-A2C, 310 hp
TBO: 1800 hrs
Fuel; 100/100LL
Prop: Hartzell 3 blade, constant speed 80 in
Seats: 6/8
Length: 32.6 ft
Height: 13 ft
Wingspan: 40.7 ft
Wing area: 229 sq.ft
Wing aspect ratio: 7.2
Max ramp wt: 6536 lbs
Max take off wt: 6500 lbs
Standard empty wt: 4003 lbs
Equipped Weight; 4529 lbs
Max useful load: 2533 lbs
Max landing wt: 6500 lbs
Payload full std Fuel; 1650 lbs
Baggage Capacity; 350 lbs
Wing loading: 28.4 lbs/sq.ft
Power loading: 10.5 lbs/hp
Fuel Capacity; 192 US gals
Usable Fuel; 187.3 US Gals / 1124 lb
Climb rate: 1300 fpm @ 94 kt
Climb gradient: 830 ft/nm
Rate of climb @ 8000 ft: 1220 fpm
Best Angle of Climb; 80 mph
Absolute Ceiling; 27,300 ft
Certificated ceiling; 24,000 ft
SE rate of climb: 245 fpm @ 94 kt
SE climb gradient: 157 ft/nm
SE ceiling: 15,200 ft
Max speed: 227 mph
Never exceed ; 236 mph
Cruise @ 65% power @ 8,000ft: 176 kts
Cruise @ 65% pwr @ 18,000 ft: 192 kts
Cruise 75% 22,000 ft Best Power: 213 mph
Cruise 75% 22,000 ft Best Economy: 208 mph
Cruise 65% 24,000 ft Best Power: 202 mph
Cruise 65% 24,000 ft Best Economy: 196 mph
Cruise 55% 24,000 ft Best Power: 182 mph
Cruise 55% 24,000 ft Best Economy: 171 mph
Max Range (with res) 75% 22,000 ft Best Power: 870nm
Max Range (with res) 75% 22,000 ft Best Economy: 1005 nm
Max Range (with res) 65% 24,000 ft Best Power: 910 nm
Max Range (with res) 65% 24,000 ft Best Economy: 1052 nm
Max Range (with res) 55% 24,000 ft Best Power: 922 nm
Max Range (with res) 55% 24,000 ft Best Economy: 1068 nm
Fuel Consumption 75% Best Power: 37.5 US gph
Fuel Consumption 75% Best Economy: 29.7 US gph
Fuel Consumption 65% Best Power: 33.0 US gph
Fuel Consumption 65% Best Economy: 26.0 US gph
Fuel Consumption 55% Best Power: 28.7 US gph
Fuel Consumption 55% Best Economy: 22.7 US gph
Fuel flow @ 65% power @ 18,000ft: 172 pph
Endurance @ 65% power @ 18,000ft: 6.3 hr
Stalling speed clean: 78 kt
Stall speed gear/flaps down: 74 kt
Turbulent air penetration speed: 159 kt
Retractable undercarriage
Trims; Elevator, Rudder, Aileron
Min Control (Vmc); 74 mph
Take-off Ground Run; 1720 ft
Take-off 50ft; 2290 ft
Landing 50 ft; 1521 ft
Accelerate/stop; 2450 ft

PA31-325 Navajo C/R
First built: 1975
Engine: 2 x Lycoming TIO-540-F2BD, 325 hp
TBO: 1600 hr
Prop: Hartzell 3 blade, constant speed 80 in
Seats: 6/8
Length: 32.6 ft
Height: 13 ft
Wingspan: 40.7 ft
Wing area: 229 sq.ft
Wing aspect ratio: 7.2
Max ramp wt: 6540 lb
Max take off wt: 6500 lb
Standard empty wt: 4099 lb
Max useful load: 2441 lb
Max landing wt: 6500 lb
Wing loading: 28.4 lbs/sq.ft
Power loading: 10 lbs/hp
Max useable fuel: 1425 lb
Climb rate: 1220 fpm @ 100 kt
Climb gradient: 720 ft/nm
Rate of climb @ 8000 ft: 1100 fpm
Certificated ceiling; 24,000 ft
SE rate of climb: 255 fpm @ 97 kt
SE climb gradient: 157 ft/nm
SE ceiling: 15,300 ft
Max speed: 228 kts
Cruise @ 65% power @ 8,000ft: 180 kt
Cruise @ 65% pwr @ 18,000 ft: 196 kt
Fuel flow @ 65% power @ 18,000ft: 195 pph
Endurance @ 65% power @ 18,000ft: 7.1 hr
Stalling speed clean: 72 kt
Stall speed gear/flaps down: 70 kt
Turbulent air penetration speed: 159 kt
Retractable undercarriage and counter-rotating prop

PA31-350 Navajo Chieftain
Engine: 2 x Lycoming TIO-540-J2BD, 350 hp
TBO: 1600 hr
Prop: Hartzell 3 blade, constant speed 80 in
Seats: 6/10
Length: 34.6 ft
Height: 13 ft / 3.96 m
Wingspan: 41 ft 8 in / 12.4 m
Wing area: 229 sq.ft / 21.27 sq.m
Wing aspect ratio: 7.2
Max ramp wt: 7045 lb
Max take off wt: 7000 lb / 3175 kg
Standard empty wt: 4421 lb
Max useful load: 2824 lb
Max landing wt: 7000 lb
Wing loading: 30.6 lbs/sq.ft
Power loading: 10 lbs/hp
Max useable fuel: 1416 lb
Climb rate: 1120 fpm @ 101 kt
Climb gradient: 665 ft/nm
Rate of climb @ 8000 ft: 980 fpm
Certificated ceiling; 24,000 ft / 7315 m
SE rate of climb: 230 fpm @ 106 kt
SE climb gradient: 130 ft/nm
SE ceiling: 13,700 ft
Max speed: 231 kt / 428 km/h / 266 mph
Cruise @ 65% power @ 8,000ft: 181 kt
Cruise @ 65% pwr @ 18,000 ft: 197 kt
Fuel flow @ 65% power @ 18,000ft: 185 pph
Endurance @ 65% power @ 18,000ft: 7.4 hr
Stalling speed clean: 77 kts
Stall speed gear/flaps down: 74 kts
Turbulent air penetration speed: 162 kt
Retractable undercarriage

PA31P
Engines Lycoming TIGO-541 ElA, 425 hp
TBO 1,200 hr
Propellers Hartzell three blade, constant speed, full feathering, 93 in. dia
Length 34 ft. 6 in
Height 13 ft. 3 in
Wingspan 40 ft. 8 in
Wing loading 34.1 lbs./sq.ft
Seats 6/8
Empty weight 5,611 lb
Useful load 2,189 lb
Payload with full fuel 773 lb
Gross weight 7,800 lb
Power loading 9.18 lbs./hp
Fuel capacity, equipped 236 USG/1,416 lb
Baggage area 42 cu. Ft
Minimum runway requirement 2,700 ft
Rate of climb 1,740 fpm
Single engine rate of climb 240 fpm
Single engine service ceiling 12,100 ft
Maximum speed 280 mph/243 kt
Endurance, maximum cruise (incl. allowance for climb) 4 hr
Normal cruise (@ 24,000 ft.) 244 mph/212 knots
Endurance, normal cruise (incl. allowance for climb) 5 hr
Long range cruise (@) 24,000 ft.) 222 mph / 193 kt
Endurance, long range cruise (incl. allowance for climb) 6.3 hrs
Stall speed (clean) 92 mph/80 knots
Stall speed (gear, flaps down) 83 mph/72 knots

PA31P-350 Mojave
Engines: 2 x Lycoming TIO-540-V2AD, 350 hp
Props: Hartzell 3 blade CS 6ft 8in
Wingspan: 44 ft 6 in
Length: 34 ft 6 in
Height: 13 ft 0 in
Wing area: 237 sq.ft
Max speed: 278 mph
Cruise eco: 224 mph
Cruise norm: 270 mph
Stall: 83 mph
ROC: 1220 fpm
Service ceiling: 30,400 ft
SE service ceiling: 14,300 ft
TO run: 1625 ft
TO to 50ft: 2469 ft
Ldg from 50 ft: 2300 ft
Ldg run: 1390 ft
Range loaded: 679 mi
Range normal: 1280 mi
Range econ: 1405 mi
Pressure differential: 5.2 lb
Empty weight: 5065 lb
Loaded weight: 7200 lb
Useful load: 2516 lb
Fuel capacity: 243 USG
Cabin: 14 ft 5.75 in x 50 in x 51.5 in high
Left rear cabin door: 46in x 28in
Cabin baggage: 22 cu.ft
Nose baggage: 22.5 cuf.t
Nacelle lockers: 18 cu.ft
Seats: 7

EMB-820C Navajo Chieftain

The Twin Comanche was a derivative of the single engine Comanche and was introduced in 1963 as a replacement for the Apache H. Little was done to the original Comanche fuselage when it was adapted for use in the Twin Comanche in order to simplify tooling and assembly operations. A cantilver low-wing monoplane with retractable tricycle landing gear and powered by two 160 hp / 119kW Avco Lycoming IO-320-B engines.

First flown in 7 November 1962, then production form flew on 3 May 1963, the PA-30 was superseded in 1965 by an improved four/six-seat PA-30B-160 Twin Comanche, and made available also at the same time was the PA-30B Turbo Twin Comanche with Rayjay-turbocharged IO-320-C1A engines.

In total 2,001 were built.

Delivering the first Twin Comanche to Europe in September 1963, Max Conrad spanned the 2100 miles from Gander to Shannon in 9 hr 21 min averaging 206 mph, at 50% power, burning 11 USG/hr. The co-pilot was Winston S. Churchill, 22 year old grandson of Sir Winston Churchill.

The PA-30 was offered in four models: Standard, Custom, Sportsman, and Turbo. The latter differed in engine power, and the rest contained different interior appointments, electronics, and instrumentation.

Both were replaced in 1970 by generally similar versions which introduced a powerplant with counter-rotating propellers. Designated PA-39 Twin Comanche C/R and PA-39 Turbo Twin Comanche C/R, manufacture of these two models ended in 1972, when total production of all versions amounted to 2,142. Piper announced the end of PA-30 production in 1970 and introduced a new PA-39 line.

Certification was under FAA A1EA.

One of these aircraft was used by Max Conrad to establish a new world class distance record when he flew non-stop from Cape Town, South Africa, to St Petersburg, Florida, during 24-26 December 1964. The distance of 12,678.83km remained a record in its class in 1993.

Its responsive handling earned it an airworthiness directive that raised Vmc from 70 to 78 knots.

The Super Twin Comanche was “Kind of a nice little bomb,” Pug muses, recalling the time he put two 300 hp Lycomings on the little Twin Comanche, almost doubling its horsepower. Even Piper, however, seriously questioned whether an airframe originally developed to hold a single four cylinder, 180 hp engine was quite ready for 12 jugs and 600 horses.

Piper PA-30 1964 Twin Comanche
Engine: Lycoming IO-320-B1A, 160 hp
TBO: 2000 hr
Fuel type: 100LL
Propeller: Hartzell two-blade CS
Landing gear type: Tri/Retr.
Max ramp weight: 3600 lb
Max gross weight: 3600 lb
Max takeoff weight: 3600 lb
Empty weight: 2160 lb
Max landing weight: 3600 lb
Useful load, std: 1390 lb
Payload, full std. fuel: 900 lb
Usable fuel, std: 86 USgal
Wingspan: 36 ft. 0 in
Overall length: 25 ft. 2 in
Height: 8 ft. 3 in
Wing area:178 sq. ft
Wing loading: 19.56 lbs./sq. ft
Power loading: 11.25 lbs./hp
Wheel base: 7 ft. 4 in
Wheel track: 9 ft. 10 in
Wheel size, mains: 6.00 x 6
Wheel size, nose: 6.00 x 6
Seating capacity: 4
Cabin doors: 1
Cabin width: 44 in
Cabin height: 46 in
Baggage capacity: 200-250 lb
Cruise speed 75% power @ 8,000 ft: 168
Cruise speed 65% power @ 12,000 ft: 161 kt
Cruise speed 55% power @ 14,000 ft: 148 kt
Max range (w/ res) 75% power @ 8,000 ft.: 823 nm
Max range (w/ res) 65% power @ 12,000 ft.: 890 nm
Max range (w/ res) 55% power @ 14,000 ft.: 970 nm
Fuel consumption 75% power: 17.2 USgph
Fuel consumption 65% power: 15.2 USgph
Fuel consumption 55% power: 13.4 USgph
Stall speed (gear, flaps down, power off): 66 kt
Stall speed (gear, flaps down, power on): 60 kt
Best rate of climb: 1460 fpm
Service ceiling: 18,600 ft
Takeoff ground roll: 950 ft
Takeoff over 50-ft. obstacle: 1530 ft
Landing ground roll: 1215 ft
Landing over 50-ft. obstacle: 1875 ft
Service ceiling: 18,600 ft
Single-engine service ceiling: 6600 ft
Takeoff ground roll: 950 ft
Takeoff over 50-ft. obstacle: 1570 ft
Landing ground roll: 700 ft
Landing over 50-ft. obstacle: 1875 ft

PA-30B Twin Comanche B
1965
Engines: 2 x160hp Lycoming IO-320-B
Wingspan: 36’0″
Length: 25’2″
Useful load: 1440 lb
Max speed: 205 mph
Cruise: 194 mph
Stall: 65 mph
Range: 948-1200 mi
Seats: 5

PA-30C Twin Comanche C
1968
Engines: 2 x 160hp TSIO-320-C1A

1966 PA-30B Turbo Twin Comanche
Engine: Lycoming IO-320-CIA, 160 hp
TBO: 1800 hr
Propeller: Const. spd.
Landing gear: Tri/Retr.
Gross weight: 3725 lb
Empty weight, std: 2408 lb
Useful load, std: 1317 lb
Fuel: 120 USgal
Wingspan: 36 ft
Overall length: 25 ft. 2 in
Height: 8 ft. 2 in
Wing area: 178 sq. ft
Seating capacity: 4
Cabin width: 44 in
Cabin height: 46 in
Baggage capacity: 250 lb
Cruise speed 75% power: 194 kt
Cruise speed 65% power: 179 kt
Max range (w/ res) 75% power: 812 nm
Max range (w/ res) 65% power: 948 nm
Fuel consumption 75% power: 17.2 USG
Fuel consumption 65% power: 14.9 USG
Stall speed (gear, flaps down): 60 kt
Best rate of climb: 1460 fpm
Service ceiling: 30,000 ft
Takeoff ground roll: 950 ft
Landing ground roll: 1700 ft

1969 Piper Twin Comanche
Engine: Lycoming IO-320-B1A, 160 hp @2700 rpm
TBO: 2000 hr
Fuel type: 100/100LL
Propeller: CS
Landing gear: Tri/Retr.
Max ramp weight: 3600 lb
Gross weight: 3600 lb
Landing weight: 3600 lb
Empty weight, std: 2210 lb
Useful load, std: 1390 lb
Payload, full std. fuel: 850 lb
Usable fuel: 90 USG
Optional fuel – std. (tip tanks): 120 USG
Oil capacity: 8 qt
Wingspan: 36 ft
Overall length: 25 ft. 2 in
Height: 8 ft. 3 in
Wing area: 178 sq. ft
Wing loading: 20.2 lbs./sq. ft
Power loading: 11.3 lbs./hp
Wheel base: 7 ft. 3 in
Wheel track: 9 ft. 10 in
Wheel size: 6.00 x 6
Seating capacity: 4-6
Cabin doors: 1
Cabin width: 44 in
Cabin height: 46 in
Baggage capacity: 250 lb
Cruise speed 75% power @ 8,000 ft: 169 kt
Cruise speed 65% power @ 12,000 ft: 162 kt
Cruise speed 55% power @ 10,000 ft: 144 kt
Max range (w/100 nm reserve) 75% power: 724 nm
Max range (w/100 nm reserve) 65% power: 791 nm
Fuel consumption (@ .42 lbs./hp/hr. sfc) 75% power: 16.8 USgph
Fuel consumption (@ .42 lbs./hp/hr. sfc) 65% power: 14.6 USgph
Fuel consumption (@ .42 lbs./hp/hr. sfc) 55% power: 12.3 Usgph
Vs: 66 kt
Vso: 60 kt
Best rate of climb (SL): 1460 fpm

PA-30C Turbo Twin Comanche C
Engines: 2 x IO-320-C1A

Miller Twin Commanche 200 / Piper Twin Commanche
Engines: 2 x Lycoming IO-360-C1C, 200 hp
Seats: 6
Wing loading: 20.2 lb/sq.ft
Pwr loading: 9.5 lb/hp
Max TO wt: 3780 lb
Empty wt: 2366 lb
Equipped useful load: 1315 lb
Payload max fuel: 403 lb
Range max fuel 75% cruise: 1353 nm/7.1 hr
Range max fuel / 55% cruise: 1455 nm/ 8 hr
Service ceiling: 21,000 ft
Max cruise: 191 kt
55% cruise: 183 kt
Vmc: 72 kt
Stall: 60-66 kt
1.3 Vso: 78 kt
ROC: 1900 fpm
SE ROC: 500 fpm @ 91 kt
SE ceiling: 11,500 ft
Min field length: 1875 ft
Fuel cap: 504/912 lb

Miller Turbo Twin Commanche 200
Engines: 2 x Lycoming IO-360-C1F, 200 hp
Seats: 6
Wing loading: 20.2 lb/sq.ft
Pwr loading: 9.5 lb/hp
Max TO wt: 3780 lb
Empty wt: 2406 lb
Equipped useful load: 1275 lb
Payload max fuel: 363 lb
Range max fuel/ 75% cruise: 1332 nm/5.9 hr
Range max fuel / 55% cruise: 1587 nm/ 7.5 hr
Service ceiling: 30,000 ft. 75% cruise: 226 kt
55% cruise: 213 kt
Vmc: 72 kt
Stall: 60-66 kt
1.3 Vso: 78 kt
ROC: 1900 fpm
SE ROC: 500 fpm @ 105 kt
SE ceiling: 22,000 ft
Min field length: 1875 ft
Fuel cap: 504/912 lb