Broken Plane - Lesson learned i think, need feedback

[ray copeland]

Working on moving up to Intermediate and took my favorite flyer, an arf P-40 out today. Have flown about a dozen times this winter and it flew great. Today it cranked right up and i signaled for a launch and after 2 laps went to the wingover and didn't have enough umphh to get over and i couldn't save it. My thoughts after looking back at the quick disaster is  the needle was too rich. This is an la46 with plenty of power. Is it possible the difference in 45 degree flying and 85 degree flying made that much difference in the needle setting?  I hesitated to change it before takeoff after it had been running so good before.   

[Robertc]

Yes the temp will effect your needle.  Air is less dense as the temp rises, and will cause less air in the venturi and therefore a rich run.  Same thing as you
go up in altitude.  You can either turn in the needle or go up in nitro.  One reason why people use tachs.

[Randy Cuberly]

Ray,
I would strongly advise the use of a tachometer to establish the correct needle setting.  It's not safe for even an "expert" in engine technology to always trust the "ear" after a significant layoff from flying or running engines.
That's not to mean that you must live by the tach as I see some folks do, but use it sensibly to establish the engine run in different conditions.
The temperature, humidity, and prop load all can severly affect the needle setting to maintain a certain power level and speed.  The difference in temperature between early morning flights and high noon flights can result in a quarter of a turn or more in needle valve settings on most engines.
Tower Hobbies and others sell reliable tachs for very reasonable prices (far less than the cost of a re-kit).   
 
Randy Cuberly

[Paul Taylor]

Ray,
Been there done that. Like Randy said always, always, always tach it. You might set it +or- 100 rpm but get close.
One thing I do each time I go out is short tank the first flight of the day and just punch holes in the sky. This does two things for me. Makes sure I got a good needle setting, and gets the dust off my plane, and cob webs out of my head. And takes a little bit of the edge off, kind of get over the gitters. Ok maybe does more then two things. I am not saying this is the correct way to do things, it just works for me.

Paul

[Jerry Leuty]

       

     I don't know how long you have been flying but way back in the dinosaur days with the old Fox and McCoy .35s I use to and still do set an engine by ear. Granted I need to invest in a good tach for sure. But a good rule of thumb is listen to the sound of the exhaust. If it sounds too lean on the ground then it will probably lean out even more in the air. Too rich and you will be just two feet high for a power landing. Never attempt any maneuvers with a too rich running engine. Air temps, altitude, and humidity all make a difference in a naturally aspirated fixed venturi engine. It is the one thing that we all fight in burning fuel. If you are really serious about learning and flying stunt then here is the remedy. Get good equipment and fly the wings off it. Personally I am flying Orientals for the foreseeable future. Both profile and built up fuselages. Next stay with .35 to .46 size planes. You can use the same set up, and equipment for every plane. You just cannot beat a great set up that works well and you are comfortable flying it. Now if you want to take some of the stress out of the equipment then call Eric Rule @ RSM Distributors and purchase an electric set up. Get a charger and extra battery. You will invest around $500 but the benefits are worth it if you can afford it. It is litterally hit the switch and go fly. The motor runs the same at 32 or 102 degrees.

Jerry

[Warren Leadbeatter]

Another good reason for flying Electric I think.    But seriously, get yourself a Tach and check the rpm before every launch.  Altitude, Air Temp, Humidity etc all affect the tune and  this can even change between morning and afternoon.

First thing I do after takeoff is do a quick check of my lap time, by counting 1-1000, 2-1000 etc in my head. By the time I get to the 1000 of the 5-1000 I am usually completed a lap. This is a very rough way of checking. From here I can tell if I am slow or fast. Or better still use a stopwatch.  I usually fly in the low 5 secs, ie 5.2 sec laps while others go up to 5.7 secs but mostly around 5.4.

Once you get to know your lap time for a good flight you get used to it and can feel if you're too fast or too slow. If you're a bit slow you can tell pretty quickly when you try to do a wingover that it wont make it, so the easiest thing to do is alter the flight path to fly the wingover at 45 deg or 60 deg. Then chicken out, ie dont go inverted.  Better to continue to the 6 mins rich and survive.

Cheers





 

[Scott B. Riese]

Working on moving up to Intermediate and took my favorite flyer, an arf P-40 out today. Have flown about a dozen times this winter and it flew great. Today it cranked right up and i signaled for a launch and after 2 laps went to the wingover and didn't have enough umphh to get over and i couldn't save it. My thoughts after looking back at the quick disaster is  the needle was too rich. This is an la46 with plenty of power. Is it possible the difference in 45 degree flying and 85 degree flying made that much difference in the needle setting?  I hesitated to change it before takeoff after it had been running so good before.   

Just a thought. If it's the first flight of the day you must reset the needle. I always open mine up an 1/8th of a turn then reset it.
Second. You said TWO laps then did the reverse wingover? ALWAYS practice the same as you would as for a contest and or the rule book. 5 laps min.
Here's what I think happened. When you went up to do the wing over you still had some OLD OIL RESIDUE in the engine that hadn't blown out, and it's this coagulation that reduced your power and bad things happen.

[john e. holliday]

The tach is a good thing if you like to fiddle.  I tried one and was spending more time setting needle.  Need to learn your equipment(engine) and how it works.  At VSC had two rounds in the later part of the day.  Engine run made me happy.  Third day I am number 3 on the circle.  Fired engine and it sounded good on the ground.  Launch and it still sounded good until the inside loops.  It then decided to go lean.  Needless to say an over run.  With the wind and engine run I called it quits early.  If you watch the guys that practice early in the day, will usually change the needle if they fly in the afternoon.  It takes practice and a lot of flights to get it right.

Now someone suggested going electric.  I aske Bobby Hunt about that and he stated to me, if I remember right, "I use IC engines only in Old Time and Classic,  all else is electric".  Even then it still takes practice and flying to learn the set up for the area you are flying in.  What works in Kansas may not work in California and vice versa.  Anyway, repair your plane and go to it.

[Garf]

I seem to need a different setting every time out, between the changes in temp, humidity, and barometric pressure.

[Paul Smith]

You can't do it with a tach or by counting turns of the screw.  You just need to develope a feel for when the plane has enough power to stunt and when it doesn't. 

The wind is a variable that won't show up on even the best of tachometers.

[ray copeland]

Not jumping to any far fetched ideas here ( well maybe a little), but i just got back from the flying field with my new Firecat and a new Akromaster. Had more trouble with needle settings and low power except when level than i can ever remember!  The only constant in all is the new can of fuel, starting with the p-40 the other day. I won't mention the brand cause i could be way off here, but is the same 10% nitro , 22% percent half and half i have been using, what  i did notice was no break in any of the runs. I may just be having some off days, but i can typically get decent runs. The firecat has an Enya 35 with a 3.5 oz wedge uniflow on suction and the Akromaster an La 15 3 oz. uniflow on suction, the p-40 is a la 46 6 oz uniflow on suction. I will try some of my old Omega 15% next time i fly to see if there is any difference. Thanks for all advice.

[Jim Thomerson]

I am not a needle valve fiddler.  I sometimes do notice that the first run of the day is a little different than the rest of the runs, not enough to bother, but enough to notice.  Generally, If I am putting an engine up for a while, I will squirt some Rislone through the NVA.  I think this stops the congealed castor oil in the spraybar.  Several years ago I did the same trick you did, tried a wingover with the engine running too rich.  So much for that!

I generally run Sig Champion 10% nitro, 20% oil, half and half.  I have, a couple of times, run the same mix in another brand and had to make a radical change in the needle setting. 

[Gene O'Keefe]

Just my humble opinion but I always set the plane up on my stooge (even if I have a launcher present) and run a full tank of fuel on the ground to allow engine to come up to normal operating temperature .... allows me to see if needle needs tweeking/fuel flow is normal/and tach it if neccessary.

 Geno

[Jerry Leuty]

      I buried a 10 year old Super Chipmunk today here in north Texas. It had a LA .40 up front. It seemed to be a little tail heavy as it constantly hunted for air in level flight. In the second half of the reverse wing over it just fell in with the engine running good. You know it is funny but after a crash you have all these extra parts like; an extra engine, wheels, fuel tank, etc. It was a nice looking airplane but my idea is if it is for flying stunt then it had better preform. I am tired of hanger queens. If they are too heavy then they are just an accident waiting to happen. I am going to learn to build lighter and straighter. Then go fly the thing.................Jerry

[ray copeland]

Well, i stayed up half the night repairing th p-40, internal bracing on the fuse and wing , hinges , bellcrank and a lot of gorilla glue! Took the engine apart this morning and cleaned out all the sand and dirt, and re assembled. Put everything back in the right places in the clunk tank and hurried off to the field with my friend. Got off a perfect flight, may be better than before the crash, perfect engine run with the same fuel,  kinda leaves me scratchin my head but very happy!! I am chalking up the crash to a hurried flight with a rich needle setting..

[john e. holliday]

For some reason or other in all my years it seems a rebult will fly better.  It may be just me as I guess you quit worrying about crashing it again.  Glad it is working for ya.