Hi All,

I have a bit of a strange question for anyone with AG aircraft experience, specifically behind a round motor. I am trying to find out how high you can fly one, specially the AT-301 and AG-Cat. I believe they are certified to around 14K, but if lightly loaded could it easily reach 20K (by lightly loaded I mean rip all the AG stuff off the aircraft).

Again, I know this is a strange questions but I have a business idea I just cant shake.

Thanks.

I have a buddy that took a 301 to 13,500 crossing the Rockies. He was dragging a spreader and said that’s all it would do. Spreaders create a huge amount of drag, so you could definitely go higher without, but 20k would probably be pushing it. I’ve taken my Ag Cat w/ a R985 to 5k and it was kind of a pain, just not a great climber.

I’m curious what the business is?

Hi,
I don't know about the 301 but the production AT-802 was placarded to 12,000 and not below 0* in visible moisture. Once properly modified we routinely operated to FL 180 and up to FL250 at times. (1750SHP PT-6A-67F engine) Hey, you said round engine

Engine performance aside, I imagine the 301 would fly fine up in the high teens.

Turbocharged round engines went high just fine. But, WWI pilots got to 20,000. The higher pilot was generally the one to survive, according to the WWI fighter pilot I knew. Dirty airplanes don't get up easily, or forward easily. Pulling air limits airplanes, but helps get onto the surface slow where we want.

It looks like that bird is well equipped for pest control.

Steve

Thanks for the reply's,

Hmmmmmmm I love the AT-801, and yes it is technically a round engine . It is also more than technically not in my budget.

Would it be safe to assume that the AT-301 would be able to fly higher than the AG-Cat because its a cleaner air frame. Or does the greater wing area of the AG-Cat win out.

Another question: aren’t the engines on both those airplanes supercharged (Roots type blower)?

If so, power shouldn’t be that limiting, at least to the middle teens???

MTV

Yes the P&W on both of the aircraft has a engine driven supercharger on it.

Yes the P&W on both of the aircraft has a engine driven supercharger on it.

mtv wrote:If so, power shouldn’t be that limiting, at least to the middle teens???

MTV

But it is. Field elevation for me is 2700 ft. red line on the R-1340 is 36in. @ 2250RPM. I only see 34in on takeoff and I think the gauge is pretty close because it says 27 static which is where the other read on the field static. The one time I went to 7500 on a 100 mi. ferry I could only get 29 inches manifold pressure and then when I slowed the prop down to 1850RPM the manifold pressure drops too because it is engine driven.

In my opinion they are no better than a normally aspirated engine at altitude. I think Pratt & Whitney build a 12:1 blower option for those engines. All the AG engines I've been around have the 10:1 blower.

Thanks for the reply,

I was wondering about the MP drop with altitude because the supercharger is engine driven. It sounds like the P&W crop duster will get up into the low to mid teens, but probably not all the way to 20K? I was looking into the beech Stagger Wing and it has a P&W 985 in front and is certified to 25K. So it looks like the motor will operate in the high altitudes but the air frame of the crop dusters might be a bit draggy to get to 20K?

What about the M18B Dromader? 21,000ft service ceiling.

I get a nose bleed at more than 1000 ago, must need a higher drive ratio on my blower.

I wonder what the supercharger ratio is on the Stag....

And, P&W made two speed super chargers on some larger engines, like the R 2800. Dunno if they ever equipped smaller Pratt’s with something like that.

MTV

cfimechanic wrote:I was wondering about the MP drop with altitude because the supercharger is engine driven. It sounds like the P&W crop duster will get up into the low to mid teens, but probably not all the way to 20K? I was looking into the beech Stagger Wing and it has a P&W 985 in front and is certified to 25K. So it looks like the motor will operate in the high altitudes but the air frame of the crop dusters might be a bit draggy to get to 20K?

The air frame I am experienced with is the Snow S2D. I would guess the poor altitude performance is as much the air frame on the AG aircraft as anything. I've never flown one stripped down and cleaned up either, that would help.

Fuel capacity is usually limited on AG aircraft as well. The S2D only holds 100 gallons (2.5 hours), I think the 301's are 125.