I’ve received and evaluated two entries so far, thanks for the submissions! The results are, so far, quite fascinating; both aircraft/powerplant combinations have very different performance characteristics, to say the least…
I’m interested to see how you are going to judge these. This has been very fascinating so far.
I sent in my entry. Based as usual on an engine I already had.
You won’t believe what I sent.
An updated 1954…
Oh yeah, baby!
A bad boy 1290cc inline-4, cast iron block, alu cylinders, DOHC 2v!
This seems interesting, shame that considering how hectic my life is I would only have time to properly read the rules, let alone build something, on the weekend.
On that note, here’s a tip that someone taught me regarding forum challenges. Always put the deadline on sunday evenings or mondays, in that case the people who are busy during the week and only sit down to play and look at leisure websites on weekends can have the time they need to come up with something. That also goes in tune with the massive spike in entries I got during the weekends on the challenges I ran.
I’m not beholden to the Friday deadline…I can extend it to Sunday night if you like
EDIT: I have extended the deadline to 2359 GMT on Monday the 5th (7:59 PM Eastern Time, 0059 CET on the 6th), seeing as it is a long weekend here in North America coming up.
Alright, just a friendly reminder that the deadline for Round 1 closes in just a little more than 19 hours from this post, at 2359 GMT Tomorrow Night (7:59 PM Eastern Time, 0059 CET Tuesday morning).
So far I have entries from the following:
If you’re still interested, get your entries in before the deadline tomorrow night!
On another topic, I have yet to decide whether or not to put my own entry into this…I haven’t plugged it into the aircraft simulation yet so I have absolutely no clue if it will be competitive or not. Maybe I will do one set of results with it, and one without…
i’m pretty sure i just made a diesel.
i don’t think a diesel is right for a plane though.
#Excerpt from Fly Magazine, September 2016 Issue:
##AAI Skyleaper Light Sport - Reliable Runabout
“In the end, we realised that the single biggest issue with modern aviation is cost, and in the end we chose a powerplant combination that will make the Skyleaper cheaper and more accessible to more people than the alternatives.”
I was sitting in Automation Aviation Industries CEO Chips McCloud’s spacious office overlooking Wichita National Airport (KICT), staring out to the ramp and contemplating the clean, crisp lines of their new Skyleaper LSA. McCloud had just finished demonstrating this new aircraft to your correspondent a short while ago, when he made the most salient point I had heard yet about LSAs - it wasn’t necessarily about having the best performance that would make or break an aircraft in this market; rather, it was about making sure the aircraft had enough performance while being as frugal and reliable as possible. In this case, it was due in no small part to the highly unorthodox choice of the 20MDI powerplant.
McCloud and I climbed into the Skyleaper and immediately I was struck by the surprisingly spacious cabin, with more than enough room for two large males to be comfortable…your father’s Cessna 150 this is not. The instrumentation was clean and simple, with a Farmin display taking the place of the attitude indicator and the horizontal situation indicator, along with the companion Farmin radio stack and ADS-B ready transponder. The low glareshield and wide windows combined with the clean, strutless high-mount wing set well back from the pilot’e eyeline.
Start-up was simple, as the 20MDI offering uses direct fuel injection, long a staple of the automotive industry and electronic control to make engine operation a single-lever affair. Power is flat-rated to a respectable 94 horsepower, but with the engine itself capable of producing upward of 110 horsepower, this gives the Skyleaper excellent altitude and cruise performance, even if it is at the expense of other more traditional performance metrics. We taxied out quickly to Runway 01 Right, where the controllers quickly and efficiently slotted us in between the midday airliner traffic at this busy international airport.
Running the engine up to its 4900 RPM redline, we switched between the two redundant electronic control systems to verify their operation and that was it for the run-up; the liquid-cooled engine needing hardly any time to reach its operating temperature. After a short delay at the threshold, we lined up on the runway and departed, the Skyleaper bounding enthusiastically into the air after about 770 feet of ground roll, and holding a climb rate of at least 1000 feet per minute. Not stunning performance by any measure in comparison to its rivals, but on the other hand the generous flat-rating of the engine means it can hold that climb rate well beyond any of its rivals, and carry on up to a service ceiling of 16,100 feet.
###Forgiving and Simple Handling
Levelling off at 7000 feet, we accelerated to the Skyleaper’s cruise speed, showing just a little under 109 knots true airspeed at 75 percent power, burning 4.7 US gallons of fuel per hour at that speed. With 25 gallons of useable fuel onboard, AAI quotes a range of 485 nautical miles for the Skyleaper, a highly competitive number that only improves at lower power settings. Climb to 11000 feet and pull back to 55 percent power and the Skyleaper will return about 105 knots and 3.5 gallons per hour, good for 640 nautical miles and just under seven hours of endurance. However, since an oxygen system is not a standard fitment for the Skyleaper, it is doubtful many owners will take full advantage of this aircraft’s stunning altitude performance more than briefly.
Satisfied with the Skyleaper’s cruise performance, we did a number of maneuvers to test the handling characteristics of the little aircraft. Steep turns and reversals were despatched cleanly and easily through the aircraft’s centrally-mounted control sticks, with all control forces comfortable at all speeds. The stall characteristics of the Skyleaper are benign, with the stall speeds of 48 knots clean and 43 knots with simple split flaps fully ddwn. Power-on stalls are done with minimum wing drop, and more aggressive maneuvers like chandelles, lazy-eights and wingovers a joy to accomplish.
Returning to the airport, we found the Skyleaper to be a joy in the pattern, the good visibility and easy handling making the aircraft a cinch to land, with the rollout taking something less than 800 feet to a dead stop. Short and soft-field landings are equally easy, with no hang-ups or unpleasantly.
“We chose the 20MDI powerplant for one reason; it offered reasonably good performance in a tremendously reliable package,” says McCloud, “and while it is a simple, uncomplicated and compact pushrod layout, it’s excellent fuel economy combined with a low cost and an industry-leading time between overhaul makes this engine an ideal complement to our rugged and reliable airframe.” Displacing a respectable 1995 cubic centimetres (or just under 122 cubic inches), this 8-valve, pushrod water-cooled inline-4 weighs a surprisingly light 218 pounds as a complete unit with propeller and reduction gearbox, giving a typically equipped empty weight of 722 pounds. With the tanks brimmed, the Skyleaper has 448 pounds of payload remaining, which is more than adequate for the pilot, passenger and some baggage.
Additionally, the low cost of the powerplant makes the Skyleaper downright affordable; it will be listing for sale at all AAI authorised dealers starting at $81,073 later this year. Place your order soon though; as of this writing, AAI has booked almost six hundred pre-orders for the Skyleaper, including large orders from several very large flight schools all over the world.
By going against the grain of aviation and forsaking some performance for affordability, AAI has truly found a winning combination of engine and airframe that is poised to dominate the LSA market for years to come. Exciting times are ahead for AAI indeed.
so anyway. congrats to @riso.
and also, since, i think, most of us went into this challenge pretty blind. could you also provide feedback and advice on our powerplant setup?
and i’m first on point, what is the other aspect that isn’t ‘scored’ that is also being considered?
Oooh shit…how did I not see that! Chalk it up to long hours at work messing with my head. Yes, you actually won koolkei…it’s been fixed now. Please accept my sincere apologies for this Steve Harvey-esque gaffe!
And yes, I will break down everyone’s powerplants when I get the chance and provide some feedback.
Slight mistake: my engine does 80.7 hp at 5200 rpm.
Anyway, I am going to get you next time @koolkei!
Edit: Why does he have bigger range despite higher fuel burn?
I built so many engines for this, I wish I could test them all to see how they would do. After seeing the results I have a better idea which engine would have been better for this challenge. This was interesting.
I think I still have much to learn, so yeah, feedbackw would be excellet
Thanks for the kind words, guys - I do appreciate it!
Now, I’ve had a bit of downtime and I’ve taken the opportunity to hammer out some feedback for everyone’s entries for this challenge. First of all, some general comments:
As I had hoped when I was designing this challenge, larger, slower-turning engines performed better than small, high-revving engines. While the engine block itself will be larger, it does have some very serious benefits; first, the lower revs means you can use cheaper cast parts in the rotating assembly, and it also means you can use a smaller and cheaper cylinder head design, in addition to a smaller, cheaper and lighter reduction gearbox. With the exception of Riso’s engine, the top powerplants, if you notice, almost all used MOHV cylinder heads. In future challenges with multi-engine aircraft, the compact size of an OHV motor will give a substantial advantage in terms of the frontal area of your engine nacelle, which is calculated largely from the width and height of your engine.
The other huge, huge thing in this challenge was fuel consumption; since there is only a fixed amount of fuel aboard, every last drop counts, so your aim should be to build an engine with the absolute lowest specific fuel consumption you can manage and still produce the power you need, even if that means making the engine larger than you think is necessary.
Additionally, it seemed in this challenge as though flat-rating a more powerful engine to a lower power level outweighs the drawbacks of having a larger engine in the first place…it will be an aberration, I believe, because the next challenges will be a lot more free in terms of power and speed. Instead of a fixed speed limit, subsequent challenges will have a range of speeds that their real-world equivalents are capable of reaching. Bear in mind that the laws of aerodynamics will come into play here as well; to double your speed, you will need roughly eight times the power, which does not make sense from a fuel economy standpoint. Another note on flat-rating; if your engine has poor specific fuel consumption, it can dramatically improve your cruise fuel burn and therefore your range performance!
Now for some individual feedback:
@8bs Overall your engine was quite good; lightweight, compact and with a very good propeller choice, though the addition of variable valve timing was perhaps not entirely necessary and added to your already higher-than-average cost. Your takeoff and climb performance was excellent, but the relatively high propeller RPM (2850) meant that in order to absorb the power you produced, your propeller pitch was quite fine (a small blade angle), which hurt your cruise performance somewhat. Also, your specific fuel consumption was on the high side, which didn’t help much either. All in all though, not bad!
@AirJordan Your engine was one of two V6s, which made things a bit more complicated in terms of cost; that said, your choice of a pushrod head helped get your engine more in line with the rest of the group. Power output was good, and your (relatively) coarse-pitch propeller was more oriented towards cruise performance than takeoff and climb, and it showed - your aircraft was among the fastest in nearly every metric, but it also had a lower than average climb rate and service ceiling as well as a longer than average takeoff run. A very interesting effort to say the least!
@DeusExMackia Your engine was reasonably good in most aspects, and apart from the two entries who took advantage of a foolishly (on my part) ignored calculation loophole, had the highest Time Between Overhaul rating. However, your engine was the heaviest and most complicated, which made your payload and overall cost suffer dramatically. The small, fine-pitch propeller selection did not help a whole lot either, as your cruise speed was a little below average. That said, your engine had an excellent specific fuel consumption, so that does help!
@Kilonum Your engine was perhaps a bit on the small side, and while it gave you by far the best payload of any aircraft in the challenge, it did mean you had to work your engine very, very hard to make the power needed. As such, your fuel economy was, ummm, not good - 57.8 pounds per hour is about what I would expect an aircraft with double the power to burn - and your TBO was on the low side of things. I will also say that I think your chose the best overall propeller of all the aircraft - your takeoff, climb and cruise performance was excellent overall otherwise!
@koolkei What can I say, you won! And you could have won a bit bigger if you chose a bigger, slower turning propeller to get a bit more out of the aircraft overall, and had you opted to spend a bit more money and went with a composite-bladed prop, the weight savings would have boosted your lowest category - payload. Other than that, fantastic job!
@MrChips Don’t screw up the unveil next time! Biggest thing I could improve would be my specific fuel consumption, which I could have helped by building a slightly larger engine. My propeller was one step too far in terms of cruise performance as well, I think.
@one85db Your engine was very small and had to work very hard to make the power it needed, plus the use of a V6 AND overhead cams meant that your engine was extremely expensive - almost $10,000 more than the lowest scoring engine. On the other hand, your compact engine gave you an excellent payload number, and your high power output combined with a good, coarse-pitch cruise propeller gave your aircraft truly excellent altitude and by far the best maximum and cruise speeds of all the entries. Well done in that area!
@Riso Your engine proved that you don’t need all the horsepower or complicated, fancy engines to be very, very competitive. By choosing to flat-rate to the bottom end of the suggested horsepower range, you gave up a fair bit of takeoff and climb performance, but you also gained a tremendous advantage in TBO, fuel burn and altitude performance. Having said that, a larger, finer-pitched propeller would have improved your takeoff and climb performance to the point that you could have won the competition hands-down.
All in all, I am very satisfied with the result of this challenge, and I hope to see all of you and more back for Round Two, which will be chosen from my list of possible challenges by none other than our winner, @koolkei. I’m going to need a bit of time to iron out a couple of very minor quality-of-life issues with the simulation, and finish tweaking the revised Powerplant Calculator - no longer will it be possible to get insane and unrealistic TBO values from a big flat-rate, propeller weight is now calculated based on hub and blade characteristics (instead of just a simple algebraic length function), and I have added a couple of other things to help you guys out as well!
goddammit. i set it up using composite for days. up until the last minute when i said fuck it, it’s expensive. because i thought i already went pretty expensive with the engine
let’s not destroy my table
That poor table! What did it ever do to you?! Wait, I have some wood glue I’ll sell you real cheap like.
Thanks @MrChips for very interesting challenge and feedback.
I went V6 since it’s the most compact for displacement and quite light.
For consumption, do you take the value from .lua file at certain rpm or is it based on in game value?
I wasn’t really aware of propeller pitch but hey, I’m wiser now for next challenge
Does flat-rating add any additional weight and cost?
I don’t know anything about aero so the arcane arts of propeller design, w/e.
I’d still like to know why koolkei has larger range with higher fuel burn. How does that work?
i’d say. because it’s not purely of fuel burn per time. but also fuel burn per distance.
for example i may consume like 10% more fuel within an hour compared to yours. but within that hour, i also travel like 15-20% further, which means i cover more distance per fuel burn. unlike cars, pure engine efficiency doesn’t matter as much as overall plane efficiency.
TL;DR fuel burn per distance > fuel burn per time
now that i see it again. i do have the longest range don’t i? i didn’t noticed that
WOOT!! Proof that KSP actually teaches you something
and this competition timing is perfect. because while it’s open. i was also running in a KSP competition related to plane fuel efficiency over long distances i got plenty of videos of it on my youtube