Carenado Piper Seminole Cruise

The “range” field on the aircraft select screen says it can go about 1,000 nm, but my last flight with it came nowhere close, even doing most of the flight in accordance with the supplied performance chart. Does anyone know what cruise parameters (altitude, manifold pressure, prop rpm, mixture percentage) could possibly yield such a range?

What were winds like at the altitude you were traveling? Were you traveling east or west?

Going east. Winds coming from the west between 0 and 2 knots. Clear Skies preset.

Wow, they have winds at 2 knots at altitude in the clear skies preset? That seems pretty wrong. What altitude were you at?

17,000. The winds on Clear Skies have been like that since release. Sometimes I delete the wind layer when the flight loads, other times I just leave it.

Throttle full, 2400rpm, mixture levers at about 50% (but with automixture on, so it could have been a lot leaner than that).

  1. How did you get to 17,000 ft in the Seminole? The performance charts end at 14,000, which I think is supposed to be the max altitude of the plane per specs?
  2. Typically, max range would be at 55% power. So I would say that’s part of the issue right there.
  3. The performance charts show a max range of ~750 NM

Wikipedia does say max altitude is 17K ft

The performance charts are in the …\OneStore\carenado-aircraft-pa44-seminole\SimObjects\Airplanes\Carenado_PA44_Seminole\Documentation

Here’s a POH for a '79/'80 model http://www.rebay.at/fliegen/manuals/pa44_manual.pdf

The POH only goes to 14,000 ft in its charts as well, but, you’re right, max throttle would be 55% power at that height.

I just noticed these charts are at pressure altitude as well, which would be what you would have in the clear skies preset. The 1000 NM range is with no reserves.

the trim doesn’t have enough control authority to induce a stall, so you can just set the vertical speed in the autopilot for maximum. With full throttle and prop speed it’ll continue climbing until it plateaus around…I’m guessing 20,000 feet. But ATC will yell at you if you try to set a cruise altitude that high because your climb rate will dip under 300ft/min well before then, so I haven’t actually attempted that.

I was under the impression that the “rated power” in the performance charts is the power the engine will produce at the specified altitude, manifold pressure, and prop speed. As in, if you’re at 14K and you set throttles to full and prop rpm to 2400 (as suggested in the chart) you’ll generate about 99bhp, which is 55% of the rated power (standard conditions, sea level). Power decreases with altitude, does it not?

I think the performance chart you’re looking at is for performance cruise. There’s another chart for economy cruise, which is what I’m doing (I think).

You think maybe descending to a 14,000 ft cruise will improve range?

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I’m not sure the plane flies quite right for the handbook and uses more fuel at standard mixture than it should.

So when I took mine up to Canada I flew it about 12Kft and cheated slightly by using Little NavMap to check the Fuel Consumption and estimated range and used that to guide how to set the mixture.

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Yes, I realized a little bit ago I was looking at performance cruise as well.

I assume you also filled up to 100% fuel. Dumb question, but just making sure since default is 50%.

Is there a gauge that shows gph? I forget. Chart says it should be 9.3 gph at 55% power.

It looks like you’d actually be at somewhere between 35% and 45% power at 17K ft. But, that’s the best you’ll see as you’ve got max throttle going. Did you notice what your rpm was at 14,000 ft with max throttle and rpm? Chart says it should be 2400 rpm? Were you still getting that at 17K?

It looks like at 14K you should have had MAP=17.2? What was it at 17K? (Nice of them not to give units, but I assume that’s inHg?)

It’s hard to say. Extrapolating the charts says it keeps on increasing. But there’s no way to really know because power is clearly increasingly decreasing quite a bit above 14K. So, given we have no data for comparison, I’d say the best altitude for comparison to actual range would be at 14K. I’d also look at the gallons/hour. POH says you should be at about 9.3 gph at 55% power. I imagine it should be less than that at 17K? It’s possible range starts decreasing above 14K ft as power is decreasing. But drag is less and fuel consumption should be less (thinner air), so, I don’t know, range could still keep increasing, too.

100% fuel, no gph gauge unforutnately. Just pressure in psi i believe.

I was indeed getting 2400 at 17K, maybe even a little more. Not sure what the manifold pressure is, I haven’t flown it in over a week.

I’ll play around with it, hopefully some experimentation will yield some answers.

Worst case you can calculate the gallons per hour. As you’re flying, you can check to see how many gallons you have left.

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Ok I’m doing another flight now. With my recommended economy cruise settings at 14,000 and got about 17.1 in manifold pressure, and I figured I was just a hair shy of a 1,000nm range. I turned automixture off and cruised at max EGT, which ended up being ~20% mixture. I’ve just completed a climb to 17,000 and got about 15.5 in manifold pressure with throttles to the firewall, and the mix a little leaner at around 18%. Both settings at 2400 rpm.

Considering that before I was cruising with automixture on (not really knowing how mixture worked) and set the levers to about 50%, that may explain some of the shortfall in range.

Update: Ended up about 80 miles short. An improvement, but I can’t help but wonder whether it’s some kind of simulation error or if I’m just not adjusting the airplane correctly.

I guess you simply expect too much accuracy from a simple 20-30$ Aircraft. Chances are too high the simulated aircraft does not have the same fuel flow at all power settings like the real one. Another point could be, that you just focus to much on your cruise. If you climb with max power, you already wasting fuel. So to see if you can save fuel, you should tell us your climb power setting and speed too. To be economic i would suggest to you, that very early after the take off you reduce power to 75% and climb with speeds around 105 kts, like the POH states.

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I don’t think I’m expecting an insane amount of realism, just for the aircraft’s capabilities to match what’s given in the basic information you see when selecting the aircraft in the flight planner. Speed, endurance, range, and max altitude should all be attainable. Either that or the figures should be revised. I can fly the stated range of Carenado’s Ovation and T182T comfortably, so I don’t see a reason this should be a whole lot different.

But maybe you’re right about my focus being in the wrong place, I’ll fiddle around with climb speed/power as well, starting with the 75%/105KIAS figure given in the POH. That may end up being the difference. If nothing else I’ll end up a better pilot for it, which is really what this is all about, right?

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If you’re worried about an 80 mile distance, and you have zero idea how these numbers were developed, yeah, that’s an insane expectation. A small difference in climb and descent settings and mixture settings could easily make up that difference.

How many times did you try to do this and how did you vary your settings?

But, in the end, I would never expect the numbers to follow that exactly anyway. Even a change in drag on the aircraft could make up that difference over a 1000 mile trip. That’s a less than 10% difference. And then you get to real life and add in winds…

I didn´t intend to offend you^^. Please let us know if you crack the 1.000 NM finally. Best regards

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