Hello, and Merry Christmas!

OK... we're going to 'take the long way home' here. As mentioned before, Piper built (14) normally aspirated standard Navajos from 1967 through 1969, interspersed with their turbo brethren. They are the PA-31-300 models, but there was a long controversy in the infancy of Navajos, and some PA-31-310 turbo Navajos got listed as a -300. So for awhile, Piper decided to just name them all PA-31. Later, the remainder of that series were just listed as PA-31-310. Both engines turn clockwise on all of these models. The gross weight of the PA-31-310 without V/G's is 6,500#. There is no V/G mod for the PA-31-300 normally aspirated aircraft, and their gross weight is 6,200#.

An old friend of mine is a master at working on and rebuilding wrecked Beech 18s. He was once the DOM for one of the largest Twin Beech operators in the country -- Buckeye Air Freight -- and his name is Bruce Bullock. Later in the 1970's and throughout the '80's and much of the '90's, Bruce had his own company at Cleveland-Hopkins, OH, Called Electroair, Inc., and was contacted by none other than Carl Millard (Millard Air Canada fame - Toronto), to try and duplicate the earlier normally aspirated version of the Navajo for some contract flying they were doing in Canada. Everyone knows the weak spot of up-and-down flying in those aircraft is primarily the turbos. If you don't need them for mountain flying purposes or the gross weight, they can be a significant headache and unnecessary cost center. The other weak area can be the heater, but there's now a fix for that... thanks to Bruce Bullock (and Bruce McSwiggan [former Academy Airlines] -- who now holds that STC and can furnish kits.)

During this time, I was developing a small commuter airline out of Jonesboro, Arkansas, called Air Mid-South, to reconnect all the smaller towns that lost service several years after deregulation. Bruce had mentioned what he was doing for Carl at Millardair, and we decided it would be the perfect plane to start this commuter with. During this time, we started petitioning the FAA to allow IFR single pilot commuter ops with a single-engine Cessna Caravan, but that was a growth aircraft in the distance, and no single-engine planes were yet approved for IFR commercial pax ops. That's a whole other story. By the way, the "Canada-Mod Heater" for Navajos, is really not from Canada. It was done in conjunction with Carl Millard, but was designed, built and certified by Bruce Bullock, in Cleveland... as were the cargo mods done to the 90, 100 and 200 series King Airs.

Bruce ended up converting (6) planes from turbos to normal aspiration. Because the Piper aircraft were PA-31-300's (signifying the horsepower of one normally aspirated engine), he ended up calling his the "Navajo 600" (the total horsepower of both engines). The engines are Lycoming IO-540-M1A5's. Some were the earlier models and some were later models with the extended nacelle baggage. None of the factory normally aspirated aircraft had the extended nacelle wing lockers, as Piper was done with that experiment by then. What was discovered during the testing, was that the single-engine characteristics of these aircraft with the long nacelles and lower powered normally aspirated engines, was borderline abysmal at gross weight. Apparently, the longer nacelle on the critical (left) engine blocked too much airflow to the tail in single engine situations, and at heavy weights, that coupled with angle of attack wouldn't give you enough control with the rudder. I was steered away from the ones with the wing-lockers. We did not follow through with our commuter plans after the marketing research had concluded, as we ended up moving to Texas to be involved in something else.

Fast forward to 2007, in another fit of insanity, we moved to the Puget Sound of the Pacific NW to begin an air tour operation, that could also someday be morphed into a small commuter to serve the uncovered territories of that region. Once again, we sought to find some normally aspirated Navajos after a futile attempt to begin this operation trying to keep some passenger Beech 18's in commercial operation. That's yet another story. I got in touch with the principals involved in the Navajo 600 ordeal, as I had decided to try to buy the STC to do the conversions ourselves. Finding any of these normally aspirated aircraft at that point was becoming elusive. What we discovered, was that Bruce had such a great reputation with the Cleveland FSDO through all his other work over the decades, that they let him convert ALL of those Navajos under Field Approvals, so no STC was ever issued. You'd now have to set precedent with a factory normally aspirated aircraft, and work with a DER on the certifications for an STC yourself by replicating. During the planning process of our company in 2003, I actually visited with Mr. Joe Soloy, of Soloy Aviation Modifications, in Olympia, WA, and he was interested in helping us modify and receive an STC for this Navajo conversion, but unfortunately, he passed away the year after that and Soloy changed hands. I also discussed a follow-on aircraft that I drew up and called a "Super Chieftain". I wanted to hang 400 hp normally aspirated, direct-drive 8-cylinder, Lycoming IO-720's on the Chieftain. You'd eliminate the turbos, free up that cowling space for cooling and have plenty of room for the extra two cylinders. With the precedent already set by Excalibur on the Twin Bonanza, Queen Air and the Mr. PRM Aero Commanders, this mod was not much of a stretch in engineering. It is not impossible to do these things, just not very cost-effective anymore. Unless you were converting an entire fleet of turbo-Navajos, the numbers just wouldn't work after it was all said and done. You're better off financially just overhauling turbos every 600 hours if you do a lot of up-and-down flying. That's what we have concluded. The now limited fleet, and its' age, will no longer financially justify this kind of capital investment.

We almost bought that recently advertised normally aspirated Navajo on Controller. Tried hard. That aircraft, C-GMLJ (31-228) was in fact the FIRST factory delivered normally-aspirated Navajo, and was the actual aircraft originally used by Bruce and Carl to develop the conversion. It was the plane they replicated to begin with. It had been sitting for years (with another later serial number converted Navajo 600 -- C-GAFF) in Millardair's big hangar following the demise of the company and the ensuing troubles of the Millard family. In the end, the price to be paid for it was too great for what existed. The aircraft was sold to a fellow in the Caribbean, who - let's just say - has had a colorful past in aviation.

Sorry it's not what you probably wanted to hear, but hope this helps explain some things anyway. ~~ Mark

Thanks for posting it here Mark, I really appreciate it.

KW

This place is certainly unique in its reach.

During the first six months of 2015, there were two normally aspirated Navajos for sale on Controller. One factory built 1969 PA-31-300, the other one a converted Navajo 600. Both of them sold by June. There are a lot of turbo Navajos for sale, and they don't sell as fast. I am more concerned that I might not be able to convert one, as it seems like there is no STC for this conversion. Check out Mark's reply above.

KW

I did look at the B55. Gorgeous airplane. Then I thought that if I go up a little bit from the B55's 260 hp engines to say 300 hp per side, I am in the Navajo territory, where I get cabin class cabin, six seats, a bar/galley, and a toilet, a mini airliner.

KW

I'd like to hear more about the story of starting an air tour business in 2007 using Twin Beeches. Sounds very interesting, could you tell some of that story?

This forum is like a spicket of knowledge. Just ask the question, turn the knob, and the knowledge you seek will flow from it. I love BT.

We have the same thing at our Saturday morning airport coffee group, Liars & Flyers... Lotsa Knowledge, not so much Wisdom....

Hi Gerry,

Here are the actual performance numbers straight out of the manuals, on a standard day, at maximum gross weight of 6200 lbs. for the Normally Aspirated Navajo, and 6500 lbs. for the Turbo Navajo.

Normal Navajo 75% cruise, best power, 6500', 185 kts., 31.3 gph.
Turbo Navajo 75% cruise, best power, 6500', 186 kts., 38.6 gph.

Normal Navajo sea level two engine rate of climb 1670 fpm, at 10000 feet 700 fpm.
Turbo Navajo sea level two engine rate of climb 1480 fpm, at 10000 feet 1260 fpm.

Normal Navajo sea level single engine rate of climb 315 fpm.
Turbo Navajo sea level single engine rate of climb 245 fpm.

Above ten thousand feet, and into the teens and twenties the Turbo Navajo will naturally pull ahead of the Normally Aspirated Navajo, and realize better fuel economy, where say at 22000 feet you will true out 213 kts. on the same fuel flow, but you have to use oxygen. I plan on tooling around in this airplane below 10000 feet.

KW

I have heard the term 'lead sled' used for those.
The PA31 got the turbo to achieve the required performance, not for high altitude ops or pressurization. Spending 100k+ to reduce performance and make the plane a one-of would seem an unusual step. Putting the 350hp chieftain engines on the 'short' navajo seems to be a popular mod.

Krzysztof,

I think you make several legitimate points. One solution may be a Twin commander. You could get a cabin class interior with NA engines. A normally aspirated twin would be a great airplane. I have done the same mental game myself. With a baron, you gain 10-15 knots but lose the cabin class. Just be careful with losing an engine at a high density altitude. Then again look up the single engine climb of a Cessna 421 at a high density altitude. Not pretty.

Hi Ryan,

I am still looking at twins ranging from the Twin Comanche up to the Mojave and Chancellor, but I think that the last two are just too heavy, too complex, too much of an airplane for my purposes. I sort of like the Twin Commanders also, but there is a big issue with the wing spar. 24 inflight breakups due to failure of a spar. I guess this issue has been addressed properly, and there is some sort of an AD/mod. Due to it's relatively light weight, simplicity, and efficiency, the Normally Aspirated Navajo is my favored airplane. It will climb on one engine at 200 fpm on the hottest of days, up to a density altitude of about 2800 feet, at maximum take-off weight of 6200 lbs. At higher altitudes you would have to reduce your weight, to guarantee take-off engine-out performance. At 6000 foot density altitude, to guarantee a 200 fpm climb, the take-off weight would have to be reduced to 5400 lbs. Still not bad, workable, though you very likely will not meet climb gradients, and so if you wanted to take-off IFR it would be a no-go. During a VFR departure you could maneuver for a return to the departure airport, while slowly climbing, or visually proceed to another airport, considering engine-out escape routes, for which we should plan before every departure.

KW

Krzysztof,

You're welcome about the repost. Was going to fix all my grammatical errors when reposting, but ran into time constraints, so just added a little more info instead. The 'correct' name for the IO-720 Aero Commander mod, is called Mr. "RPM". I won't bore you with the other mistakes.

Just to set the record straight. The Normally Aspirated PA-31-300, or the Navajo 600 in its' converted form, is a phenomenal aircraft... as long as you get one with the original short engine nacelles. It is about as useful, dependable and economic as you are going to find in a medium-sized, twin-engine general aviation aircraft. Contrary to what's been said by others already, I can tell you that it is VERY difficult to get ahold of one of these aircraft. I have skipped buying a few, only because the owners wanted so much for them, that it was just unreasonable. The ONLY reason I didn't get one beforehand from the Millard's, is because Wayne would not part with the two they had left. He said, "All things being equal, Mark, I will die before those planes leave this family. They are great." Well, he did end up dying do to suspect reasons, so those two planes (C-GMLJ & C-GAFF) were caught up in an estate mess for several years, and finally recently released by his mother. These things are very elusive. If you're not flying in too much mountainous terrain, they're darn close to perfect. They are a cabin-class aircraft with two very reliable engines, burn 25 gph TOTAL in cruise, have a mod to deal with any heating concerns [ground or air], and now have a mod to remove the pesky inboard main landing gear doors [think: Piper Seneca or Boeing 737]. At 6,200# gross weight, versus the 6,500# in a standard turbo Navajo, or 6,773# for one with V/G's, you're already lighter, so it'll do fine on one engine. If you normally fly it with a 6,000# max weight in mind, performance is not an issue. We fly all Travel Airs at a max weight of 4,000# (the early model max), versus the 4,200# or +, for the V/G models, and it helps a lot during climb or in the unlikely event of an engine failure. Flying an airplane around at the MAX weight all the time, is like always flying one around at sea level with the throttles pushed all the way up to the firewall. You're asking a lot out of it continually, and sooner or later, there could be a problem. Remember the old slogan the FAA used to publish in their multi-engine propaganda... "Always Leave Yourself An Out."

The only problem with these Navajos, is getting one... specifically, getting one for a reasonable price for what's there. You might have to pry it out of the owner's hands, or show up with a wad of cash. You might have to get one with the wing lockers and convert it back to short nacelles, but there weren't that many converted with the lockers (after figuring out it wasn't the optimum situation). There have been a few that had run-out engines, where the owners wanted as much as a turbo-Navajo with low to mid-time engines. Navajo engines are not cheap, so we've had to stick with the turbo'd planes this time around -- plus, what we do is primarily go up and around big mountains. I wanted the normally-aspirated versions again for a possible commuter airline start-up that generally flies in the valleys and over water, but our MEA's out west are really too high for that -- even over the low parts, for some reason. Flying IFR commercially with peeps, twins have to meet very strict single-engine performance criteria, particularly in regions of mountainous terrain.

Anyway, if you get really serious about finding one to purchase and are ready to go, I'll help you find one. PM me when you're ready. I know where most of the remaining airframes are, although I might have to do some digging in my archives to find a few of them. A few have wrecked hauling cargo, a few have been parted out and a couple have been modified to the 'Panther' conversion. This is out of a total population of (20), including the '600's. I have one that I can get for you that is an almost complete airframe, but needs to be totally restored. It has the long wing lockers, but can be modified back. It is sitting on gear in one piece, but will need to be trucked to where it'll be brought back to life. It is rough, and a major back-of-the-hangar project for us, but mostly all there. We haven't brought it home yet, but the guy that has it is ready for us to. It was a late factory original normally-aspirated plane that had the wing lockers installed later.

As for Kevin Fruehwirth, that wanted to know more about flying tours in Beech 18's... what would you like to know? It is a long, protracted story and journey that I'd be more than happy to share, but doubt too many folks on this message board want it cluttering up the space. Shoot me a few simple questions here, or PM me if you want to hear more in depth.

Alrighty... I've blabbed enough here and now I'm running late again. Please excuse any more grammatical flubs. Hope this helps!

~~ Mark

Hi Gerry,

Here are the actual performance numbers straight out of the manuals, on a standard day, at maximum gross weight of 6200 lbs. for the Normally Aspirated Navajo, and 6500 lbs. for the Turbo Navajo.

Normal Navajo 75% cruise, best power, 6500', 185 kts., 31.3 gph.
Turbo Navajo 75% cruise, best power, 6500', 186 kts., 38.6 gph.

Normal Navajo sea level two engine rate of climb 1670 fpm, at 10000 feet 700 fpm.
Turbo Navajo sea level two engine rate of climb 1480 fpm, at 10000 feet 1260 fpm.

Normal Navajo sea level single engine rate of climb 315 fpm.
Turbo Navajo sea level single engine rate of climb 245 fpm.

Above ten thousand feet, and into the teens and twenties the Turbo Navajo will naturally pull ahead of the Normally Aspirated Navajo, and realize better fuel economy, where say at 22000 feet you will true out 213 kts. on the same fuel flow, but you have to use oxygen. I plan on tooling around in this airplane below 10000 feet.

KW

You are comparing planes at different weights.

Further up, someone involved in the attempt to develop the STC is telling you that the 300s performance was 'marginal at best'. For the application they were talking about, requiring lots of short hops with a regulatory requirement (at the time) for a second engine, eliminating the turbos may have been a worthwhile project. Unless you have a really unusual usage pattern for a private aircraft, I just dont see that there is any payback on removing the turbos.

If you want to spend money, hire a DER and follow Dougs recommendation above to hang a 330hp IO580 on a Navajo. For that project, dont start out with the 310 but a 325 and get it certified on a known icing airframe. There are several thousand Navajos out there, you may even be able to sell a couple of copies of that STC.

By the time you are done hanging different engines on a Navajo, you would probably be better off buying a high-time Caravan.