The PA-60 Aerostar

TFaudree_ERAU

TFaudree_ERAU

Mashin' dem buttons
Was just reading a thread in the CFI forum that discussed prop wash over the stall warning tab on the wing of a PA-44. It made me think of a question I had a while back about the PA-60. There was a 700P model that frequented our little 2270 x 45 strip in my hometown in Virginia. Talk about a nail biter.

Anyway, I know the Aerostar wasn't a true Piper design, but actually one of Ted Smith. I noticed one day that this aircraft has 2 critical engines. Instead of either a counter-rotating setup like you see on a Seminole or similar trainer, or the conventional left engine critical design, both of the PA-60-700P's props have the descending blade on the outside.

Were the 600 series built this way? And why on earth would Mr. Smith design the airplane with 2 critical engines? Does it have something to do with the airflow over the ailerons on it's short and stubby wing?
 
The P-38 was the same way, and I have often wondered why. This is all I could find:
"The XP-38 had been powered by two liquid cooled, Allison V-1710 engines turning 11 1/2 foot Curtiss Electric, inward turning, counter-rotating propellers. With the YP-38s and all subsequent Lightings, the propellers rotated outward negating torque when both engines were operating (A batch ordered by Britain did not have counter-rotating propellers.) "

It is rather interesting that other than the initial prototype that had conventional handed engines, subsequent P-38's had outward turning props like the Aerostar.

It was noted that the British P-38 models without the counter-rotating engines had crappy handling characteristics.

The reason you came up with is logical. Who knows?
 
TFaudree_ERAU said:
Were the 600 series built this way? And why on earth would Mr. Smith design the airplane with 2 critical engines? Does it have something to do with the airflow over the ailerons on it's short and stubby wing?
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It depends on how you look at it.....you could say it has no critical engine.......lol.

I do know the Aerostar is a very stable airplane with the counter-rotating props outward.
 
B767Driver said:
Is it true Ted Smith originally put jet engines on the Aerostar?
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Here is what I found out about the 700. It is not contra-rotating, its counter rotating like most more modern twins. It was slated to be a Jet Airplane originally and then was made to be a piston twin. It is the fastest piston twin made. Since it was slated to be a jet first, that explains the speed. Not much drag on that airframe.
 
I understand the definition of critical engine being "the engine that, if failed, most adversely effects aircraft performance". However, I think it safe to say that, while technically not accurate, if EITHER engine on the Aerostar quit, it would have the same factor of performance degredation as losing the left (critical) engine on a conventional twin. Thats the reason I said "2 critical engines" in my originial post
 
Alright, this is what I found out from Jim Christy, one of the owner of Aerostar Aircraft. Not all Aerostars have counter-rotating props, and only a few of these had engines where the blades descend outboard. When Aerostar purchased the rights to the aircraft from Butler, I belive, they focused their business on modifying, restoring, maintaining and supporting Aerostars. Piper was also doing the same thing for a while. One modification that came about was a counter weight system on the yoke to help improve pitch stability, Piper was working the same issues and they tried having the props descending outboard. It did not affect stability to the extent needed by was quieter in the cabin, so they left it alone. Now, you will see most Aerostars with both engines rotating the same direction, this helps reduce mx costs, and there is not a significant change in single engine performance. All Aerostars modified or overhauled by Aerostar end up with this setup.

Also, Jim showed my a new version of the jet powered aerostar. Looks pretty good too.


It felt really nice to sit in the comfy leather seat at the controls, now if I can get Jim to let me take it out.

Let me know if anyone has a question, I can run it past Jim.
 
Berkut said:
That certainly is an interesting way of looking at it.
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Which is why I was joking that you could have two critical engines, or no critical engine, depending on if you're a cup half full or half empty kind of person.
 
Yup, even jets have critical engines but not in the same light as a prop.
 
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