Piper PA-31 & PA-31T, Embraer EMB820 & Neiva NE821
Pipers entry in the ‘cabin class’ piston twins was the Piper PA‑31 Navajo. Later it evolved into the Chieftain, Mojave and PA‑31T Cheyenne. Like the similar Cessna 400 series and Beech Queen Air it has low mounted straight wings with engines in the leading edge. The horizontal stabilisers are attached to the fuselage and the gears have single wheels. The main gear retracts sideways in the wings. Key recognition point of the PA‑31 are the large rectangular cabin windows with rounded corners.
Some versions of the aircraft were built under license by Embraer and Neiva in Brazil.
The different versions of the Piper PA-31 series can be distinguished by:
- the length of the fuselage
- the number and size of the cabin windows
- the shape of the cockpit windows
- the presence of tip tanks
- the presence of winglets
- the shape of the engine nacelles
- the number of propeller blades
- the turning direction of the props
- the shape of the nose
- the wing span
The original version of the PA-31 has four cabin windows on each side, of which the last one is a triangular one (although the prototype at first only had two cabin windows). Furthermore, all these Navajos have short engine nacelles, two blade propellers, no cockpit doors and no wider entrance door (there is till a triangular cabin window there). There were two engine options, one with 300 hp (designated PA-31-300) and one with 310 hp (designated just PA-31).
PA-31 Navajo B & Navajo C
The improved version has turbocharged engines, although this cannot be seen from the outside. The Navajo B has an option for two or three-bladed props, so with the first option it is hard to distinguish from the original Navajo. The Navajo C has slightly different engines with three blade propellers only.
Both versions optionally have a pilot entry door, baggage lockers at the end of engine nacelles (extending beyond the trailing edge) and an additional cabin door that can be opened to have a wider entrance. In case this is on the aircraft, there is no triangular last cabin window.
PA-31-325 Navajo C/R
The Navajo C/R is generally the same as the PA-31 Navajo C, but has counter rotating props and engine nacelles stretching beyond the wing trailing edge as standard. Therefore you may need to see the props to recognise it. The props move towards the fuselage at their highest point.
PA-31-350 (Navajo) Chieftain, PA-31-350 T-1020 & Embraer EMB820C
The PA-31-350 Navajo Chieftain (from 1980 on just Chieftain) is a Navajo C/R with a two feet longer fuselage, making room for a fourth rectangular cabin window on each side. This is immediately after the cockpit side window, and a bit less wide than the three subsequent cabin windows. Like the Navajo C it comes with an optional additional cabin door next to the regular cabin door, in which case there is no triangular last cabin window on the left side.
Developed as a small commuter aircraft the T-1020 version is supposed to have no main landing gear doors, except the ones along the strut, but we have found no evidence so far. At least some seem to have doors like the Chieftain. Other improvements to make it more hardened for its new task are not externally visible.
Embraer built the Piper PA-31-350 in license under the designation EMB820. Is not different from the Piper-built aircraft.
PA-31-351 & PA-31-352 Chieftain
These are PA-31-350s with one foot and three wing extensions respectively. This is difficult to notice though, except maybe when you see the models side by side.
PA-31-353 Chieftain II
Another attempt to revive the Chieftain sales resulted in a PA-31-350 with four feet wing extensions. The props counter rotating away from the fuselage (at their tops) are a better visible feature though. It also has the horizontal tail of the PA-31T3 (T-1040).
PA-31P Pressurized Navajo
While similar in appearance as the non-pressurised version, the PA-31P has significantly smaller windows (but still rounded rectangular ones) and a longer nose than the previous Navajos. It has two cabin windows left, and three on the right side. The Pressurized Navajo has has short nacelles, ending before the trailing edge, and three blade props. The first production series had low cockpit windows, of similar height as the cabin windows, but from the 1977 model on the height was increased, like on the Cheyenne (see below).
Piper converted one PA-31P with a T-tail, similar to the original one for the PA-42 Cheyenne III. Another development was a PA-31P with 450 hp engines driving four blade, counter rotating propellers. Both were single aircraft conversions.
The Piper Mojave shares the Cheyenne I fuselage with the wings of the PA-31-353 and the Chieftain tail. Is also powered by counter rotating piston engines in long nacelles, unlike the Pressurized Navajo. Another way to differentiate it from the PA-31P is by looking at the cockpit side window: the window of the PA-31P is wider than it is high; that of the Mojave is higher. This only works for early model PA-31Ps though.
PA-31T Cheyenne/Cheyenne II & PA-31T1 Cheyenne I/IA & Schafer Comanchero 750
The first turboprop version of the PA-31 was developed from the PA-31P, although Piper made a PA-31 Navajo with turboprop engines as a proof of concept. Apart from turboprop engines the PA-31T Cheyenne also has wing tip tanks. The earliest models have “eyebrow” cockpit windows. From 1977 onward the Cheyennes lost the eyebrow windows and had the higher, Mojave style cockpit side windows. However, the main cockpit windows remained the same, so the main windows are less high than the side windows. After a few years, from the 1980 model on, the main cockpit windows became the same height as the side windows. It was later called Cheyenne II, after the Cheyenne I saw daylight.
The PA-31T1 Cheyenne I features lower rated PT6A engines, but is otherwise the same as the Cheyenne II. Only in the beginning it had no tip tanks, but (nearly) all we later retrofitted with them. Older models still feature the low cockpit main windows of the second generation Cheyenne IIs. Compared to the original PA-31T1 the Cheyenne IA has different engine cowlings. However, this difference is probably internal, as we could not spot it on the outside. Other changes include a lower panel glare shield and improved interior.
Piper offered the longer air intakes like that of the PA-31T3 as a retrofit for both the Cheyenne I and II. The intake starts closer to the propeller.
The Schafer Comanchero 750 conversion is a Cheyenne II with more powerful 750 hp PT6A engines. The conversion has not lead to a different external appearance, unfortunately.
The PA-31T1 Cheyenne I is externally not different from the similar PA-31T Cheyenne II. This particular one is equipped with longer air intakes, that are closer to the props (compare with the 1977 model PA-31T).
PA-31T2 Cheyenne IIXL
The extra large (XL) version is indeed 24 inches longer than the Cheyenne II, meaning room for an additional, square cabin window, a third left and a fourth right. It is placed immediately after the cockpit side window and a bit smaller than the other cabin windows.
To have a better product for the commuter market Piper mated the fuselage of the Chieftain to the wings, engines, nose and tail of the Cheyenne II. So the PA-31T3, marketed as T-1040, has more and larger cabin windows than the Cheyennes. Tip tanks are optional. The PA-31T3 has the air intakes close to the propeller, closer than on the similar Neiva NE821.
The PA-31T4 was a development aircraft of the PA-31T fitted with TCM TP-500 engines. These engines have smaller air intakes than the PT6As and no exhausts at the side of the nacelles. The project was cancelled however after one aircraft had been converted.
PA-31T5 Cheyenne IIXLa
As another aircraft developed for the commuter market, the PA-31T2 received extra long nacelles with baggage lockers and modified cowlings.
Colemill Enterprises has developed performance improving modifications for the Navajo series. Most apparent are the winglets, but the engines, driving four-bladed props, are also different. The Panthers (or Panther Navajos) are converted PA-31s and PA-31-325s, so with three rectangular cabin windows. Note that some modified aircraft have only winglets and no different engines, while it can be the other way around as well.
Colemill Panther II & III
Panther II and Panther III are modified PA-31-350s with the same external changes: different coller intakes at the front of the nacelle, four blade propellers and winglets (in most cases). On the Panther III, the winglets are supposed to be standard, but we don't know if that is the only difference. In any case Panther IIs may have wingelst as well.
Schafer fitted PA-31Ps with PT6A turboprops and named this aircraft Comanchero. It looks much like the PA-31T Cheyenne I, but has no tip tanks! Additionally, it has long nacelles, extending beyond the wing trailing edge.
Schafer Comanchero 500A/B & Neiva NE821 Carajá
Schafer also fitted PA-31-350s with PT6A-20 or -27 turboprops and named this aircraft Comanchero 500A respectively 500B. They can be recognised from the PA-31T3 by the engine nacelle. The air intake is closer to the props on the PA-31T3 than on the Comachero.
Neiva used this conversion on the EMB820 to create the NE821. This is an EMB820 with turboprops, very similar to the Schafer Comanchero 500A/B conversion. Hence there are no external differences.
Soloy TCM conversion
Soloy converted one Chieftain with TCM TP-500 turboprops, which has different engine cowlings than the Comanchero conversion. They are specially wide near the front, narrowing down to the original nacelle about halfway. The exhausts are not at the side but at the back(?) of the nacelles.
Confusion possible with
Cessna's 400 series twins with rectangular cabin windows, especially the 402C and 404 with no tip tanks, are the main source for a mix-up with the PA-31. The Piper has larger rectangular cabin windows, with rounded corners. Another clearly visible difference is in the main gear doors.
This could be mistaken for a Piper Cheyenne, in particular due to the cabin windows. These are smaller though on the Cessna. Furthermore the Cessna 441 has horizontal stabilisers with significant dihedral and an exhaust at the back of the nacelles.
The Beech Queen Air is comparable in size to the PA-31 family, but has square cabin windows and different cockpit windows. Also the main gear retracts forward in the nacelles.
Considering the general shape and windows configuration, the Aerostar comes close to a possible mix-up with the PA-31. However, the PA-31 is a low wing aircraft and lacks the curved leading edge of the vertical stabiliser.
The Swearingen Merlin IIA has similar cabin windows and nacelles as the Cheyenne, also a single wheel gear and the same basic configuration. However, the Merlin IIA has a forward retracting main gear and no tip tanks.
The Cessna 400 series twins with oval cabin windows can be considered as a less likely source for confusion: the oval cabin windows are a clear recognition point. For the rest they have the same configuration.