Piper Aztec with 300 Horsepower

[Tony Jestis]

So here's what I'm thinking. The Piper Aztec was fitted with 2540 horsepower engines at 2575 RPM. This means a few things:

First, reliability! The IO-540 making 250 Hp lives a long time. Second, Big propeller. Because it's turning relatively slow, I can swing a long prop. Third, Fuel burn, compared to its bigger horsepower cousins, it burns less fuel.

That all being said, how do I have 300, 310, or 350 horsepower engines on a Piper Aztec? I have read the "alphabet soup" of Lycoming model numbers and I can see where it might be done. And, I know, I would need to mate a propeller to the engine, to the airframe, etc.

Why do it? Why not! If it's never been done, that's reason enough for me.

Anyone have any ideas?

Yes, it's nuts! But what the heck? You only live once!

 

[champ driver]

With that big fat Cub airfoil it ain't gonna go no faster.

 

[Tony Jestis]

With that big fat Cub airfoil it ain't gonna go no faster.

Possibly. I was thinking of maybe gaining a few knots, a little more weight carrying, but a whole lot of cool factor!

 

[Ted]

I looked at this when I had an Aztec. It will gain speed but you’ll have a couple issues.

1) Certification on the aircraft side. Have fun with that.

2) Angle valve heads won’t fit under the stock cowls so you’ll need to change those. I forget how much but I think fairly significantly.

3) While it will go faster, you’re still talking about a plane that’ll top out at maybe 180-185 knots.

An Aerostar 600A has 300 HP naturally aspirated Lycomings already and a much slicker wing. The cert effort on the aircraft alone would be monumental in today’s environment. 40 years ago it would’ve been different.

 

[Tarheelpilot]

Possibly. I was thinking of maybe gaining a few knots, a little more weight carrying, but a whole lot of cool factor!

Having a 100k in your bank account is really cool too. The engine swap would be very expensive for very little benefit.

 

[GRG55]

Possibly. I was thinking of maybe gaining a few knots, a little more weight carrying, but a whole lot of cool factor!

I am certain you are the only person that has ever used the description "cool" in any context related to a Piper Aztec.

So here's what I'm thinking. The Piper Aztec was fitted with 2540 horsepower engines at 2575 RPM. This means a few things:

I wish my Aztec had 2540 hp on each wing.

First, reliability! The IO-540 making 250 Hp lives a long time. Second, Big propeller. Because it's turning relatively slow, I can swing a long prop. Third, Fuel burn, compared to its bigger horsepower cousins, it burns less fuel.

That all being said, how do I have 300, 310, or 350 horsepower engines on a Piper Aztec? I have read the "alphabet soup" of Lycoming model numbers and I can see where it might be done. And, I know, I would need to mate a propeller to the engine, to the airframe, etc.

Why do it? Why not! If it's never been done, that's reason enough for me.

Anyone have any ideas?

Yes, it's nuts! But what the heck? You only live once!

The Aztec has been around a looong time. Through the entire heyday of 1960s/70s light GA, when just about every airplane out there was being modified to make it faster and "better". Maybe the reason it's never been done is because the Aztec is one of the few airplanes that didn't need to be "improved" - Piper pretty well got it right out of the box by the 'C' model in the mid-1960s.

As I have posted before, the Aztec is an under-rated, largely unloved airplane these days. It's biggest fans are those that know it best - people who have owned them and/or flown them (including @Ted DuPuis @Kristin and John Talmage at DiamondAire in Montana) . It doesn't excel at any one thing, but it also does everything expected of it reasonably well, with no bad habits or hidden gotchas. And for an aging piston twin, it has a remarkably small number of recurring ADs, a testament to how robust the airframe really is (I'll put my 'truk up against any Beechcraft, any day, in that respect). Could be that's why nobody ever thought it needed a raft of STCs to "fix" it?

 

[Pilawt]

Around 1969 Piper toyed with an experimental Aztec with 260 hp on each side, bigger baggage compartments and a 5400 lb MGW. There was no significant improvement in performance, so the project was abandoned.

Even earlier there were sketches of a proposed Aztec derivative with 390 hp per side, lengthened fuselage, tapered wings, left-hand door and club seating in the rear. It never left the drawing board.

 

[Ted]

So @GRG55 when are we going flying? I’ve been missing me some PA23-250 time.

 

[GRG55]

So @GRG55 when are we going flying? I’ve been missing me some PA23-250 time.

That's something we've been needing to line up since I first joined this forum!
I expect I will learn a ton about how to fly it more proficiently from watching you in the left seat.

In phases through this winter and early spring the 'truk just came out of a major maintenance cycle; addressed a raft of age related matters including new hydraulic hoses, new engine hose kits, new Lord engine mounts, refurbished the exhaust systems (cracks and blisters), rebuilt all the oleos, and so forth. The usual story, you start with the intention of repainting one bedroom and pretty soon you have an out of control bathroom and kitchen renovation underway.

I was thinking about starting a thread like the one @Mtns2Skies did for his 180, to see if I could get anyone to commiserate ...but looking for sympathy from the PoA crowd is probably lousy odds.

I'm still fiddling around with a few things, but she's in presentable enough condition she might even pass your inspection standards now.
All I have to do is figure out an excuse and enough time to get down to your neck of the woods now.
You got time in between bulldozing Cobras and whatever else you're doing down there?

 

[Tony Jestis]

I looked at this when I had an Aztec. It will gain speed but you’ll have a couple issues.

1) Certification on the aircraft side. Have fun with that.

2) Angle valve heads won’t fit under the stock cowls so you’ll need to change those. I forget how much but I think fairly significantly.

3) While it will go faster, you’re still talking about a plane that’ll top out at maybe 180-185 knots.

An Aerostar 600A has 300 HP naturally aspirated Lycomings already and a much slicker wing. The cert effort on the aircraft alone would be monumental in today’s environment. 40 years ago it would’ve been different.

Okay. What a discussion! As far as certifying, I am thinking 337 or painting "Experimental" (Big letters MENTAL, lol).

Cowling? Hmm, didn't think of that. Is it the width? Or do the heads make it bump the cowling? Just trying to get a handle on the problem. Perhaps, adapting the Aerostar cowling? Just thinking out loud.

What about spinning the engine faster and using a smaller prop? That would cut reliability, but may make 300 hp.

Hey at least I didn't say, "Let's mount a pair of 720's" Now there's a discussion!

 

[Ted]

That's something we've been needing to line up since I first joined this forum!
I expect I will learn a ton about how to fly it more proficiently from watching you in the left seat.

In phases through this winter and early spring the 'truk just came out of a major maintenance cycle; addressed a raft of age related matters including new hydraulic hoses, new engine hose kits, new Lord engine mounts, refurbished the exhaust systems (cracks and blisters), rebuilt all the oleos, and so forth. The usual story, you start with the intention of repainting one bedroom and pretty soon you have an out of control bathroom and kitchen renovation underway.

I was thinking about starting a thread like the one @Mtns2Skies did for his 180, to see if I could get anyone to commiserate ...but looking for sympathy from the PoA crowd is probably lousy odds.

I'm still fiddling around with a few things, but she's in presentable enough condition she might even pass your inspection standards now.
All I have to do is figure out an excuse and enough time to get down to your neck of the woods now.
You got time in between bulldozing Cobras and whatever else you're doing down there?

Oh, I’d find time to fly in an Aztec.

Yours sounds like it’s much nicer than mine ever was. Mine was a working girl and she looked it. But I loved her.

Okay. What a discussion! As far as certifying, I am thinking 337 or painting "Experimental" (Big letters MENTAL, lol).

Cowling? Hmm, didn't think of that. Is it the width? Or do the heads make it bump the cowling? Just trying to get a handle on the problem. Perhaps, adapting the Aerostar cowling? Just thinking out loud.

What about spinning the engine faster and using a smaller prop? That would cut reliability, but may make 300 hp.

Hey at least I didn't say, "Let's mount a pair of 720's" Now there's a discussion!

It’s been a long time and I can’t remember the details, but when I lived in PA and was more “in the know” we looked at the details in greater detail.

If you want to go faster just buy an Aerostar.

 

[GRG55]

Around 1969 Piper toyed with an experimental Aztec with 260 hp on each side, bigger baggage compartments and a 5400 lb MGW. There was no significant improvement in performance, so the project was abandoned.

Even earlier there were sketches of a proposed Aztec derivative with 390 hp per side, lengthened fuselage, tapered wings, left-hand door and club seating in the rear. It never left the drawing board.

I wonder how much the 1972 flood killed a lot of Piper's product development plans, and forced it to focus almost exclusively on derivatives of the Vero Beach located Cherokee?

Despite its LH rear door, the underpowered Seneca never had the useful load to invade the charter market the Aztec satisfied. And by the time the later model Aztecs were ready to be replaced the single turbine was the logical successor to high octane swilling piston twins. I don't think its a complete coincidence Aztec production stopped right about the time Cessna was certifying the Caravan.

 

[Ted]

The flood is what killed the real Piper.

They couldn’t get approval to fly the bunch of Navajos etc literally 100 feet to US-220, and so they got angry and left.

 

[Pilawt]

1972 was the worst flood, but not the only flood that affected the Lock Haven plant. There were also May 1946 (13 aircraft repaired or rebuilt); November 1950 (108 aircraft scrapped or repaired); February 1961, March 1964, February 1975 and February 1977 (no aircraft damaged). There just wasn't a future there.

They couldn’t get approval to fly the bunch of Navajos etc literally 100 feet to US-220, and so they got angry and left.

Roger Peperell's Piper Aircraft: The development and history of Piper designs has a photo of a line-up of Navajos and P-Navajos on the not-yet-opened Highway 220, "flown there to escape the rising waters of the Susquehanna River in February 1977."

 

[denverpilot]

As someone who started flying in the early 90s, stories abounded of cargo folk having their asses saved by having been in AzTrucks in more ice than most cocktail places keep behind the bar, turbulence that should have ripped wings off, and all sorts of bad things other than direct thunderstorm penetrations. Also rock solid IMC platforms.

Everyone who flew them hard for a living loved them other than how slow they were, back then. But that’s the thing, they’re ultimately slow, and lots more HP won’t help much because they’re also fat.

Had a solid reputation as an honest workhorse airplane compared to a number of much more fussy twins back then. People loved them.

 

[skier]

With that big fat Cub airfoil it ain't gonna go no faster.

The USA-35b isn’t that fat. It’s max thickness is only 11.6%. The NACA 4412 (Citabria) and 2412 (Cessna 172) are both 12% thick. The

The Cessna 414, Aerostar, Citations, etc. all also have airfoils thicker than the Cub and Aztec.
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[Kenny Phillips]

Your main gain from more horsepower is going to be rate of climb, followed by takeoff distance. A distant third will be increased airspeed. Negatives may be higher powerplant weight (and thus decreased useful load) and increased fuel burn. Of course, I think AzTrucks have a 10-15% margin in gross weight, depending on the mood of the pilot.

 

[Ted]

Other benefit is better altitude performance since you’ll make horsepower further up high.

You’ll never turn an Aztec into a Lear, but more horsepower would make it faster, just like a 310 with 520s is faster than a 310 with 470s.

I’d just argue the certification burden will make it a futile exercise.