What do the experts do to assure a good needle setting on the first morning flight at a contest? Let’s say we have had a 25 degree temperature drop and 30 % RH shift – in either direction -- from the previous afternoon practice flight. To make it easy, assume the previous day’s practice was at the contest location, not at your home field. (The question is for unpiped engines)
   Launch RPMs, I’ve found, don’t seem to be as reliable on the first flight of the day as following flights the same day. Needling on the line while the clock is running seems like amateur hour, and risky (under-run) to boot.

I’ve found that running an engine in the pits (other than burping a prime) doesn’t endear you to your fellow competitors. Besides, you have to either have a helper or some sort of tie-down. It is usually difficult to find the space so the prop blast isn’t directed towards other planes.

What is your “first flight of the day” routine at a contest? Taking an attempt just to get a setting is one rude (unacceptable) answer, and also risky.

Edit: add unpiped

Larry Fulwider

What do the experts do to assure a good needle setting on the first morning flight at a contest? Let’s say we have had a 25 degree temperature drop and 30 % RH shift – in either direction -- from the previous afternoon practice flight. To make it easy, assume the previous day’s practice was at the contest location, not at your home field. (The question is for unpiped engines)
   Launch RPMs, I’ve found, don’t seem to be as reliable on the first flight of the day as following flights the same day. Needling on the line while the clock is running seems like amateur hour, and risky (under-run) to boot.

     For muffler engines (and bear in mind I haven't done it in >20 years) I always tried to do a needle flight or even two. It was just too variable from flight to flight, and if it was off even the tiniest bit from ideal, you were sunk. For example, I never flew a Fox in PAMPA classes, but I know from extensive practice that even one click off in either direction and it was too fast, or didn't have enough.  Failing that, I would run it for about a minute off to the side.    I do that in some conditions even with piped engines, although they are a lot more predictable, and don't have to be perfect to get an acceptable run.

   Of course, never run the engine in the pits - take it off to the side. I do it before I hook up the lines, and the time it takes will let it cool off to normal start conditions. AAC/ABC engines like to start hot, or at ambient, but sometimes are tricky of they are in an intermediate state.

    The only muffled engine I run anymore in contests is the Skyray, and in that case I have so much margin for the performance I don't spend a lot of time worrying about the needle. I don't even remember what the rpm might be, it's about peaked out minus about 6-8 clicks.

     I have absolutely no compunction about needling when on the clock. If it's wrong, fix it.  Of course, you can get burned and if you have to move the needle more than a little bit either way, you should cut it off and try again later. And you can get misled over blacktop, if it's extremely hot, you can end up having to lean it out to hit an RPM, and then when it takes off and gets in cooler air, it's too fast. That's a classic misuse of the tach to just hit the number -  even with it, you have to use a little "Kentucky Windage" to vary it based on conditions. It's a good measuring tool, but it's not a substitute for good sense.

       With piped engines, the bite of the prop seems more significant than the engine setting per se - hot, and it slows down, even at the same in-flight revs. The engine is probably always pretty close to the same.

     Brett

p.s. had  a chance to try it out this morning. First 20FP flight in about 3 years, very cold (39 degrees on the car thermometer when I pulled up). First flight, I primed it through the venturi, flipped a few times until it felt loose, bingo, first flip. But it took 3 flights to home in on the right setting. I had basically forgotten anything about, so give it a couple of flights to remember. If I had been flying it every weekend, I might have gotten it on the first try, but that's unlikely. I would just assume that you need a needle flight.

   Another off-topic but interesting point. Flite Streak ARF+25LA+9-4 APC= very good combination. This was a rear-needle engine, and despite their reputation, it was bulletproof and dead steady in the air. That's what I had found on my previous attempts with rear needles on the Fox and the 15FP, too. The only problem that it seemed to have was getting it started. The FP fired right off even at 40 degrees, but it was a real problem getting the 25LA-RN going, hot or cold. One it got going, it might have been as steady as the 20FP with very similar performance. For whatever reason, although it has the same muffler, it was noticeably louder. The airplane flew *great* with just one trim adjustment. It didn't turn as nicely as the Skyray but round maneuvers were like falling off a log. That's generally true of elevator-only airplanes, but this one stood out.

. . .
 
p.s. had  a chance to try it out this morning. First 20FP flight in about 3 years, very cold (39 degrees on the car thermometer when I pulled up). First flight, I primed it through the venturi, flipped a few times until it felt loose, bingo, first flip. But it took 3 flights to home in on the right setting. I had basically forgotten anything about, so give it a couple of flights to remember. If I had been flying it every weekend, I might have gotten it on the first try, but that's unlikely. I would just assume that you need a needle flight.  . . .

Your original post was a great summary. The follow-up filled in a lot. Thanks for taking the time, as the KOI is this weekend, and the "first run" can be a particularly thorny issue there. Well, with three events Sat, doubt that I can get a needle flight in all three, but that is a goal.

       Larry Fulwider

I don't really have problem either. Just push the start button and go!