337 - Aztec Comparison
 

Hi All,
Please no tomatoes.

We have been in discussions of late on several issue relating to Aircraft for Purchase.
We are basically looking at two craft or three I guess really. These are the 337 P, O2-A or poss B and Piper Aztec.
To be honest I have leaned towards the O2-A for the War birds and fun side but my Partner has been swayed towards the Aztec. Does any one have any comments re these two aircraft and comparisons?

Any help would be greatly appreciated as we cannot afford two planes as yet!

Thanks agin.

Guess it just depends on how proficient you are when that one engine quits!

Thanks Jim,

This is the sort of thing we are after.
If you refer to how good at check and feather I assume the Skymaster is a little more 'forgiving' for lack of a better description?

Although we all know what assume stands for shall I assume they are very similar in most aspects except when you have an engine failure?

I have read several differing accounts of the Skymaster climb rates with engine failure and most state neg rate when fully laden. I have been told, but not read that the Aztec has pos rate even when fully laden during engine failure?

Please help to convince my purchasing partner that a 337 is for us!

Regards
Hamish

I Also just noted you stated one engine? Aztec here in NZ Has twins.... Is this different to US Spec?

The Aztex
 

The Aztec has a number of drawbacks... first off, it's is a gas guzzler compared to any of the Skymaster models, and for sure, the second mill on the Aztex will definitely take you to the scene of the accident. Do you EVER want to play the game of 'assymetrical thrust'? While the advertised single-engine climb rate on the Aztex is something like 225 FPM, I seriously doubt that you'd stay airborne at full gross... and if you lost one on takeoff, well, where do you want the flowers sent?

How do you like climbing up on a wing at night with it pouring down rain... plus all the PAX seat gets soaked when you open the door to get in, or out. Not good. Skymaster affords a little better protection in this area, plus, you can stand under the wing for shelter. Makes good for camping too. Gee, there's something really awkward about the Aztex design overall... it just doesn't look like an airplane... more like a Tuna boat with twin counter-rotating oars. They do counter rotate, don't they?

Hey, it's an ugly boat!

SkyKing

PS
 

Oh, forgot to mention... get rid of the rear gear clamshell doors and you won't have a negative rate down + makes for quicker gear retraction and less junk to go wrong. Our P-model has the R.T. Aerospace no-doors kit and there's no worrying about suck-down.

On the Skymasters, you could always add-on the Horton or Roberstson S/STOL... and that makes quite a performer out of already great wing design.

Well, what'd you expect coming to a Skymaster board for advice on an Aztex?

SkyKing

Hamish,

I haven't seen any GA recripricating engine aircraft that have a GOOD positive rate of climb when one engine fails. The skymaster is not an exception to this.

The really, really nice thing is that when you lose one in a skymaster, the airplane doesn't try to turn over on you because of asymetrical thrust. The skymaster is pretty docile on one engine.

Proficiency also counts in the skymaster. The sooner you identify and clean up the faulty engine, the sooner you have maximum performance.

For those of us who are not on the cutting edge of proficiency, the skymaster is kind enough to remain under control until we get things cleaned up.

Yes, our Aztecs are twins too.

I had a rear jug blow on rotation on our 67 337.
Two on board, light on fuel, sea level , temp 65 degrees.3000 ft runway with mud flats at end No problem . I continued the take off on runway 12 called the tower told them I had a problem they clear me to land back on 07. Landed had the jug repaired and flew the plane home. In an aztec I would have had a lot more to deal with. I vote for the skymaster.

Frank

Thanks Skyking, Stackj and Frank.
This is helping for sure. I would be keen to look into the gear door upgrades as this sounds pretty good. Does it cut economy ?

It does not affect economy. All it does is to reduce enormously the drag of the gear when it is in transition. See www.rtaerospace.com

Ernie

Gear doors
 

I had my large main gear doors removed and the airspeed is the same at cruise. Only now I can get the gear up if no runway left in front, at 10 feet off ground. So I can climb cleaner and that is usually 1500 feet/minute. If I loose a engine I only have to feather and keep flying and get higher to go down wind for a safe landing. I had a instructor pull the front engine to idle with 3 on board, 85 degree day and near full tanks. I was just 200 feet high but gained another 90 feet down wind. I know I could gain more if the prop wasn't windmilling causing drag. No problem, even a single engine pilot could do it. Try that in a Aztec. You would have your hands full and probably mess your pants, if you didn't hit the ground first.

So the gear doors sounds like a good mod then!
Thanks guys.

I don't know if you plan on doing a lot IFR down in Kiwi land, but you'll be much happier in a Skymaster, one engine or two. I just completed IFR training and can tell you that if I lost an engine IMC in an Aztec, it would be a prescription for disaster. I have a conventional ME licence, prior to buying the Skymaster and knew that engine out in IMC in a conventional light twin would be too much for the average 200 Hr a year pilot. Engine loss in IMC in a Skymaster is much easier. I was actually able to accomplish missed approaches, single engine in the Skymaster without too much fuss. It was sufficiently challenging however, even not having to deal with the asymetrical thrust. I would not want to try that in an Aztec.
If you are a glass is half empty guy and make your decisions on what could go wrong, the Skymaster is the bird. As another example, I know you fly over a lot of water down there like I do here in the Caribbean. God forbid you have to ditch, but I think the Skymaster configuration with the high wing will be easier to land in water. If you can slow it up prior to touchdown, it really helps. I have installed Micro VG's with stall speed 1 knot slower than Robertson conversion ( according to MD stats) so you have a much better chance of surviving ditch in Skymaster with wings above waves, reducing the flip possibility. ( maybe that's why I like the Skymaster; it makes a better boat than other twins....)
Also on positive safety side is that is has (arguably) the best cockpit visibility of any GA aircraft. Helpful in busy airspace.
On the fun side ( I know you Kiwis are world champions at this) it is a much better bird to just go sightseeing. Not much fun in an Aztec. However, if you want to haul dead people, the Aztec is the bird. We have two of them here modified to do that.
Just my two cents.

Hi Nick,
Thanks for that most invaluable 2 cents worth!
The short answer is that yes, we here in Kiwi land will be logging IFR. Other wise we might not get to fly with the weather the way it has been! More like England.
Very good point on the water landings as we had not taken that into account to be honest. We fly over a lot of liquid and plan to "Jump the Ditch" over the Tasman sea on regular occasions to Australia.

Thanks again.

Hamish

Wow, what time is it where you are?!!
Another couple thoughts.. Skymaster is not the station wagon the Aztec is, but adding a cargo pod is definately my next purchase. A friend here added one and noted only about a 2 knot speed differential. Big enough to stow surf boards. also if you land gear up, can save your props, or so I've heard. Will also help if you have to ditch as it should provide higher touchdown and better floatation once stopped (provided it stays on which i don't know about...)
Another addition I might consider if you will do a lot of long range flying is Gami jectors, to assure LOP operation. From everything I've been able to read on the variopus websites I am running about 4-5 GPH less than a Skymaster running ROP without gamis. (Recently, ran at 17GPH 150ktsTAS, 7000 ft Compare that to Aztec economy)) If fuel costs are high and you are flying a lot of hours, long trips at cruise settings, the economics begin to work.

Hi Nick, It's 2.29 PM here lovely afternoon at 28 Deg C and Blue Skies. I’m working in front of a computer.... Go figure.
Hey all great points there. I hope I don’t have to worry about the belly box floating us in the ditch situation! My father in-law has had one of his 337s ditched coming across to here (NZ) from the US and was not a nice story. Pilot did survive though to ditch another aircraft last year on the same run!! He should retire!

We also learned later he was running a little pocket money run on top of the delivery and trying to carry some Mustang P51 parts in with him! Bad maths.

Cheers

Hamish

climb rate
 

I have a P337G 1975 model with TSIO-360-CB engines, turbo charged and inter-cooled. Single engine climb rate at sea level is 360 fpm. Yes, it will do it.

Jerry
N34EC:D

WOW,
Thanks Jerry. Who did these mods or were they an option?

mods
 

TSIO=360-CB engines with turbo chargers are standard on the 1975 P337G.

Inter-coolers are Riley. Also, the plane has the main gear doors removal kit.

When you look at Skymasters, the model year and if the plane is normal asp. or turbo charged is important on performance. Let's talk some book numbers.

I had a 1972 337F normal asp. aircraft. Loved that plane, could carry a load. According to the POH, with single engine with the front engine operating, it will hold about 5,000 feet. Single engine with the rear engine operating, it will hold 7,200 feet.

Front engine operating single engine climb was about 260 FPM however, when gear is being tucked away, climb becomes slightly negative. With rear engine operating in single engine configuration, climb rate was slightly postive.

The POH on my 1975 P337G dipicts either engine climb is 360 FPM and either engine will hold 18,500 feet. The book says that,--not sure if plane will actual do it. I have however done the 360 Plus climb in single engine training.

BTW, in that training, flying below blue line speed, 100 MPH, loss an engine and you can't climb. Have to put plane in nose down configuation to gain air speed above blue line so you can enter climb phase.

Jerry

Re: single engine service ceiling in a P model

I have tested it, it will do it. Was as a result of another thread on this board, I went out to find out, because someone said they could not maintain 13,000. With properly maintained turbo/exhaust system, and a tight cabin, it will maintain 18K on one engine.

Kevin

One engine alt.
 

Thanks Kevin, It's good to know that the book numbers are okay.
I've lost engines before and flew on one engine but in those cases I was below 9,000 feet.
Cheers
Jerry

It just occurred to me that the only real failure I have ever had was at 15,000 with just me and 1/2 fuel. I secured the engine and motored on to my destination (about 150 miles over mountains, no suitable field in between) with no undue effort.

Kevin

Among ALLl common pressurized twins (including the p-baron, duke, 340, 414, 421), the P-Skymaster has the best published single engine rate of climb, and comes in at 2nd place on single engine service ceiling.

I recently did some engine out work in the skymaster. Instructor pulled the rear engine just after takeoff. Climbed at about 200 FPM with the gear hanging out, and improved after I cleaned things up. A little scary to be climbing so slowly that close to the trees, but I can only imagine what it would have been like if I had been sinking instead of climbing!

Also, did a single engine-go around while practicing. No problem.

My p-model is stock. I am tempted by the gear-door mod, but haven't done it yet.

Door removal
 

Hi Kyle, I have the gear door removal mod on my P337G. Lots of good reasons to have it but one big reason not to have it. Depends on what's important to you. The only thing I don't like about it is that every single drop of oil that comes off the front engine seems to find it's way into the wheel well. Real pain at times. Great thing about them, I no long fuss with door adjustments and less work for the hydraulic unit.


Jerry
N34EC