Is it worth sacrificing 20 lbs of weight and lose another passenger at full weight to gain 80 pounds of thrust?
OK, so a Few Questions from someone wanting to give this a Try:
the Calibrated speed for the Planned Speed box, would that be Max IAS (Indicated Air Speed), or would it be a Little Different? as it is currently, I Have it set to 145.22 kts for 250 kts TAS at 10K ft (So it Don’t break the Speed Limit of 250 KIAS below 10K ft)
Can we Put anything in for Reduction Ratio? I’m Not sure what’s sensible or not for that, Currently have it set to 4.6, with a Max Engine RPM of 6300 & 92" Props I’m Getting 0.489 Prop tip Mach & 85.45 for Noise Level with Constant Speed 3 Blade Props
Does Economy Matter? If Not, then maybe it could in the Future, Could possibly effect Range based on Tank size.
For Climb Gradient, As Long as it’s Positive/Green it’s good Correct? currently have 1040 ft/nm for General Performance results & 95 ft/nm for Engine Out at 5K ft, engine is a 7.86L V6 that makes 774hp at 6300RPM Redline & 709 ft-lb of Torque at 3500 RPM
in regards of Torque, Maybe that could affect something also, maybe the Prop? More Torque=Bigger/Heavier Prop could be used or something?
That’s a question you need to ask yourself. And, having seen only my own entry so far, I can’t honestly tell you if that’s the right thing to do or not. We’re in uncharted territory here if I’m honest.
- The planned speed is the maximum calibrated airspeed you intend the aircraft to fly at. As the aircraft climbs, it will still be able to reach that calibrated airspeed, but the true airspeed will potentially be a lot higher.
As an aside, the limit (in the US and a few other countries only) is 250 knots indicated airspeed below 10,000 feet, not true airspeed It’s also something we will not concern ourselves with either in this or any other Aero Challenge round.
You can put anything you like for a reduction gearbox, but bear in mind that as the reduction ratio goes up, the weight and cost of the gearbox does too. For the size of the propellers in this round, I would imagine most of the entries will be fairly close to the real-world aircraft examples, with maximum propeller RPM in the 1800-2200 range.
Economy DOES matter - in fact, it matters more than just about anything!
Yes, as long as the climb gradient is in the green, it’s fine. Even if it isn’t in the green, it’s fine - the question being would you be willing to potentially lose a lot of points in the evaluation if it isn’t?
Since horsepower is already a major part of the evaluation of each entry, and also since horsepower is a function of torque, it’s already in the challenge!
Ok, Thanks. I’ve flown in Microsoft Flight simulator before but wasn’t aware of Calibrated Air Speed before, I’m More Familiar with Indicated Air Speed.
Thanks for the Tip, Didn’t See Prop RPM on the Calc Sheet till I had another Look.
10-4, Never seen anything on the Calc Sheet where we enter anything about Economy so I Wasn’t sure if it played a factor or not.
10-4, Knew Green was good, was mainly referring to the Rates I Had, It’s green but I’m thinking it might be a little on the shallow side, then again I’m Thinking of ft/min while it’s ft/nm that’s used for the challenge.
10-4, was wondering due to Torque being less than HP in some cases, but only HP is to be listed on the Calc Sheet.
I’m having a bit of trouble making a prop effective enough to absorb all the power of the engines while also maintaining a lower noise limit and keeping the props in the correct size range. Any tips?
If noise is yellow you’re probably fine. Try going more fine grained with the gearbox, fit a muffler on the engine and/or revise it to use less rpm.
If static thrust increases why does takeoff roll not decrease?
The static thrust calculation is tied to propeller RPM, propeller diameter and number of blades; it is at best an approximation in its current form (and, frankly, is more useful for challenges where fixed-pitch propellers are used). I have some plans to revise it, but to make the calculation more accurate would be heinously complicated, and with the changes I’ve made on my end to the simulation model, probably doesn’t even need to be in there.
Just a friendly reminder to everyone; the deadline for the challenge is only a few short days away; please have your entries submitted no later than 2359 GMT on Monday, May 15th!
what affects climb gradient?
i’m at red with 51feet/nm which seems really bad. and can’t do anything to change it
i don’t think you can handle MOAR POWAHHHH
I don’t know then. I’ve got less power at higher rpm but a better gradient.
it’s my flatrating… apparently flat rating 10% of my available power cuts it sooooo deep
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This was a fun one, and is great for automation, all the IRL planes in this class are turbine powered and have been for 30-40 years, we are venturing into the unknown world of gasoline piston powered everything which is automation’s strong suit. No idea where we should be for price point but my entry is sent in, looking forward to seeing the results.
You know you went too far evaluating engines when you create
Because I had to do this by hand, the engine I actually used isn’t pictured.
That’s super light nice job, I went way more executive with mine, bigger, quieter, and more efficient. But damn you can fit another passenger per engine than mine, we’ll see if quality or quantity wins out, but with such a high rpm your gearbox must be pricey.
good luck with your economy and TBO
@nialloftara how big is big? he’s using a 4.6 OHV i6.
i’m on a 5 valve DOHC 6870cc i6
OK, entries are now closed for Round Four. I have received entries from:
Expect the results in the next couple of days; hopefully tomorrow!