By Boran Pivčić
Of course, Cessna is not the only one to have a couple of oddballs in its lineup. Piper ranks high up there as well, with a number of significant or interesting aircraft that had the misfortune of being unjustly forgotten. To make things more interesting, Piper also has a tendency to cram a lot of power into some versions of their popular models, creating fascinating hot ships that are today both very rare and highly prized.
The three aircraft I’ve chosen – again after extensive digging through the Airliners.net database these past few years – represent a mix of singles and twins, both piston and turbine, all variations of some of Piper’s most famous aircraft: the Comanche 400, Pressurised Navajo and the monstrous Cheyenne 400 (I had thought of including the PA-60 Aerostar as well, but that plane is a story in itself 🙂 ).
1. Piper PA-24-400 Comanche 400:
Years produced: 1964
Piper PA-24-400 at Airliners.net
Another PA-24-400 at A.net
Often called the “Queen of the Comanches”, the 400 was Piper’s attempt at making a high-speed single engine tourer. The subtle clean aerodynamics approach of today’s Lancairs was obviously frowned upon, because the 400 – as it’s name says – sports an incredible 400 HP! The power comes from an engine as unique as the aircraft itself, the eight cylinder Lycoming IO-720. That’s 720 cubic inches of capacity, or an impressive 11.8 liters. Those of you with experience in GA may have already seen that a 400 HP IO-720 nicely divides into two 200 HP IO-360s – one of the most popular four cyl engines of modern times – and you’re right: the IO-720 is basically two IO-360s stuck together at the crankshaft :). Ingeniously simple – though there were some problems with cooling the rear cylinders in flight (unlike other 6+ cylinder non-radial engines which are water cooled, the IO-720 remained air cooled).
To control the extra power, the Comanche 400 was fitted with a strengthened rear fuselage and completely new rear control surfaces taken off the Aztec and Twin Comanche. Fuel tanks were also increased to cater for the thirstier engine and thicker wing skins were provided, but otherwise the rest of aircraft is generally identical to the standard Comanches.
However, the Comanche 400 was not without its problems… it wouldn’t be in this post otherwise. A cruise speed of only 185 knots, when leveled against a fuel consumption of 23 gallons per hour at high cruise power, isn’t all that impressive, which made the aircraft quite expensive to operate even back in its day (though it was the fastest normally aspirated single back then). The aforementioned modern Lancairs have significantly higher cruise speeds (by up to 30-40 knots) with 20-25% less power – and fixed landing gear to boot – which makes them far simpler and cheaper to fly and maintain. But on subjective terms, a 60s tourer with four Cessna 150s under the hood still keeps its charm, and the survivors of the 148 built are in high demand today.
Specs (Plane & Pilot Magazine): http://www.planeandpilotmag.com/aircraft/specifications/piper/1964-piper-comanche-400.html
2. Piper PA-31P-425 Pressurized Navajo:
Years produced: 1970-1984
PA-31P-425 at Airliners.net
Another flying at Airliners.net
PA-31P-425 cockpit shot (with rare, old avionics) at Airliners.net
Another interesting (to me fascinating) and rare aircraft to come from the Piper works is the PA-31P-425, a unique Navajo modification that is the only Piper pressurised piston twin. You’ve probably noticed by now it’s striking resemblance to the turboprop Cheyenne I and II – though they’re not directly related. Same problems warrant same solutions, hence two aircraft that look almost the same. In reality, they were developed almost concurrently from the basic PA-31-350, sharing components to add a pressurisation system, the needed fuselage changes and various structural and landing gear updates to handle the increased weight.
As the pressurisation system saps quite a lot of engine power, the haul itself at a respectable speed the Pressurised Navajo was equipped with massive TGIO-541-E1A engines – turbocharged, geared and fuel injected – producing 425 HP. With all of this power – 850 HP in total – you’d believe the P-Navajo could touch Mach 1, but as mentioned, most of the excess power was spent on spinning the massive turbocharger, which needed to be large enough to both charge the engine and pressurise the cabin with bleed air. But, like the Beech 60 Duke that had a similar system, this led to a highly complex engine (the Duke – which was labelled as very maintenance intensive – didn’t even have geared engines), which consequently kicked the operating price up.
All of this – combined with a production run of only 259 aircraft – make the P-Navajo a prized aircraft with a unique character, pretty much the case as with the Comanche 400. Sadly, if the Airliners.net database is anything to go by, few appear to be flying nowadays.
Specs (Airliners.net): http://www.airliners.net/aircraft-data/stats.main?id=311
3. Piper PA-42-1000 Cheyenne 400:
Years produced: 1984-1993
PA-42-1000 at Airliners.net
Another 400 at Airliners.net
And another from the same source
What better way to finish this post than with the awesome Cheyenne 400 – in a nutshell, the biggest, fastest and most powerful aircraft that Piper has ever built. A modification of the standard PT6-powered PA-42-720 Cheyenne III, the 400 sports two 1,000 HP Garrett TPE331 turboprops, driving imposing four-blade composite propellers, which together give it a cruise speed of an impressive 335 knots – almost 60 knots faster than the equivalently-sized (and far more expensive) Beech King Air 200. At maximum cruise, the 400 can outrun even the Big Brother King Air, the 350, by a comfortable 20 knots.
With almost 30% more power – but only 6% more weight and the same dimensions – than the Cheyenne III, the 400 (originally designated the Cheyenne IV and 400LS) was designed to compete with smaller bizjets such as the Cessna Citation I and II. In the event, only 43 were ever made, making it one of the rarest and unique production aircraft in the world today.
Specs (Rising Up Aviation): http://www.risingup.com/planespecs/info/airplane363.shtml
Achtung, Skyhawk! 
I would like to point out that in the case of the Comanche 400, several small speed modifications including gap seals, more modern, efficient wing tips and Knots2U gear lobes will enable the aircraft to cruise at 200 knots. A Lancair or similar has turbo charging and achieves it’s incredible speed at altitude and with a very small cabin. The Comanche 400 has a prodigious bladder busting range and will carry four people in comfort, is very strong and a true ‘muscle car with wings’. If fitted with a new MT lighter composite propeller will climb at 2500 feet minute.
Actually, there are piston Lancairs that are normally aspirated and work best at low altitudes, between 7,000 and 10,000 ft. The two-seat Legacy for example, cruises at around 200 knots indicated – which, at its most efficient cruise altitude of 8,000 ft, translates into roughly 230 knots TAS – and can maintain that speed for six hours on end. Performance is similar in the climb, with 2,000+ ft seen even at MTOW. The cabin too doesn’t lag behind established aircraft, with a width of 43.5″ – just 0.5 less than the Comanche.
In the four-seat category, the now-discontinued ES also has an impressive set of numbers – achieved too on a run-of-the-mill normally aspirated engine. At the same 8,000 ft as the Legacy, it can cruise 195 knots, giving roughly the same six hour endurance – and roughly the same climb performance of around 2000+ fpm when loaded. The cabin is, if anything, roomier than on the Comanche, with a width of 46″ (vs. the Comanche’s 44) and height of 48 (vs. 46″).
EDIT: it’s also not that Lancairs have achieved these numbers by sacrificing carrying capacity. Even though the nominal useful load of the ES is nearly 300 pounds less than that of the Comanche, the ES’s lower fuel consumption does give it the edge in most situations. For example, at 75% cruise, the ES can touch 1150 NM (reserves included); the Comanche, at the same power power setting and nearly the same cruise speed, can barely make it to 730 (reserves included again). If your target is say 700 NM away, the Comanche has 700 leftover pounds for self-loading cargo after the tanks have been topped. The ES however, needs only 400 or so pounds of fuel to reach that distance (including a 45 minute reserve); and on a 1350 pound payload, that works out to 950 pounds available for passengers and baggage :).
Thanks for your comments, my Comanche will cruise at 190 knots on 20.5 gal/ hour and carries 130 gallons of fuel. 1500 lb useful load. Most of the early problems have been addressed and it truly is a rare aircraft with abundant power reserves. It still makes 215HP at 16,500 feet. The range you speak of is with standard tanks, most have the additional auxiliary fuel. And on take off that IO 720 with the MT propeller has a real snarl!
The big difference, I suppose, is that the Lancair is an experimental aircraft, while the Comanche 400 is a certified aircraft. Imagine the performance numbers obtainable if you put a Comanche 400 into an experimental status. I’m thinking of serious weight reduction, drag reduction, ram air, exhaust modifications, compression increase and/or turbo charging with intercoolers. That Lancair might be eating the Comanche 400’s dust.
While all that may be true, for the Comanche to outrun the ES – with its clean aerodynamics – would involve serious modification and customization, as well as a host of STCs… and the attendant costs. The ES is made up of off-the-shelf components; the engine is entirely stock and there’s very little on it that departs from OEM specs. That’s its secret – it was designed to go fast at ease from the outset; it doesn’t have to be forced to do so by being modified beyond recognition :).
EDIT: to add, the Lancair could well be a certified aircraft, but isn’t for two reasons: first, being experimental allows the owner to customize the interior and avionics without the constraints of STCs; and secondly, if certified, it would become much more expensive due to certification fees and administrative dues – costs that contribute nothing to safety and quality.
Experimental aircraft don’t need STC’s. Hence, all of the upgrades I spoke about can be done by the owner, just as they can be done on the Lancair. The ES cruises, as you point out, at 195 knots. The top speed of the Comanche 400 is 194 knots (look it up). The 185 knot cruise speed you mention as published by Piper is at 65% power and at gross weight of 3600 pounds. Now, even things up a bit by limiting the gross weight of the Comanche 400 to that of the ES, then certify the ES, then design it in 1963 using slide rulers and paper and pencil. I think you’d be suprised at just how much better the Comanche 400 is than the experimental Lancair ES. I have pictures of a true airspeed of 202 knots in my stock Comanche 400 as does at least 2 other Comanche 400 owners as well.
However, the Comanche is not an experimental aircraft – and transferring it to the experimental register and then modifying it is too much of a hassle and expense for the average owner who just wants a fast piston single (plus you lose the most valuable element of the aircraft – its certification). If he/she needs it for personal use, why bother with buying, re-registering and modifying an old and quite rare design, when for much less work and money you can get a modern, top-spec aircraft that needs little additional work (if already completed by someone else)? 🙂 The 400 may have an “old school” charm, but getting it to consistently perform as well as an ES – and at the same time retain its reliability – makes little sense for the average owner.
There is no doubt however that Piper’s Comanche 400 has one of the best thrust to weight ratios of any light aircraft. Certainly better than the ES Lancair and on par with a P 51 Mustang or P 40! Just sayin! You have never experienced ‘smooth’ running until you have flown behind a balanced 8 cylinder stove, it purrs like a kitten too!
I have roughly over 1,000 hour of time in the P-Navajo as I liked to call it. It was a solid 190 knot airplane. Thie biggest thing was throttle contro. When descending,1 inch for every 3 minutes. 40 gals a hour and very comfortable. You just had to plan ahead. Yes the engines are expensive. But beats the Hell out of a Duke.
The information above indicating the P-Navajo is the only pressurized Piper reciprocating twin is incorrect. The 1985 Piper Mojave was the more refined version of the P-Nav and only produced one year.
Scott Miller
Scott, thanks! Had forgotten about it… will soon change the article hopefully.
I was fortunate to have worked on and flowen in all three magnificent aircrafts