phlpsfrnk

I wrote this for a newsletter article a few years back. Sorry no pictures, not that there was much left to take a picture of. Enjoy.

The model was an old Mark’s models stand off scale P-51D Mustang. I believe it was later bought-out by Dynaflight models but I haven’t seen one in years. This was a very basic kit that I’d bought at a swap-meet. It had about a 36-38” wing span with strip ailerons and called for a .25 to .30 sized engine as I recall. The only RC engines I had that came close were an old Enya .19 and an OS .46FX. The engine was to be mounted upright in the nose with the muffler hanging out the side. I figured an overpowered P-51 had to be better than underpowered P-51 and I’d just mount the radio equipment as far aft as possible to get the CG right. It was a simple and fast build and the engine was not as tight a fit as I thought it might be.
Ground handling was not good at first with a lot of nose over’s. I had to adjust the landing gear forward with the CG at its most aft point before I could even get it in the air. Most of the time it was a hand launch with a nose over landing. After a lot of trial and error with and about 1 ¾ ounces of sticky lead stuck to the tail, larger wheels for the grass, the ground handling improved and with practice the nose over landings quit. The CG was now at its farthest aft recommended location and the plane tracked in the air like it was on rails. I flew this plane for about a year and a half and really enjoyed it. The only time I used full throttle was at take off and during steep or vertical climbs. Usually all maneuvers were performed at half to ¾ throttle and that was fast enough for anything I wanted to do.
Our field has a north south runway with a dirt road and trees at the south end. About twenty feet of the southern approach grass is intentionally left to grow to about waist height. One of my favorite maneuvers is to fly down the center of the runway at about ten feet and pull up to vertical at the end and execute either a hammerhead stall or a snaproll at the top. As I was setting up for my third such pass of the day I overhead one of the new members behind me talking to another member about how fast my plane was. This little voice inside my head said “YOU WANT TO SEE FAST” as my thumb involuntarily pushed the throttle to full. (At this point the sequence of events is a little blurred in my mind but I’ll describe them as best I can recall.) At the point that I normally level off for my pass down the runway, and I think I’d started to, I heard a buzzing sound I’d never heard before. My immediate reaction was to chop the throttle and pull up. If that thought was communicated to my thumbs I’ll never know. About the same time as I’d heard the buzzing I saw part of the horizontal stab and half the elevator depart the aircraft. On my best day I could not have executed as perfect a snaproll as that plane executed on its own. (The little voice in my head must have still been flying it.) The plane immediately disappeared in the tall grass and exploded into hundreds of more pieces than what was in the original kit. I now know the true meaning of the “deafening silence” as the small peaces of balsa and shredded monokote floated down in the tall grass. The point of impact was about three feet short of the runway at about a 90 degree angle (in other words straight in). The ground was soft so the engine buried itself about six inches in the dirt. The largest piece of the aircraft left was half the horizontal stab and elevator that was found alongside the road about 20 feet from the impact point. There was no putting this one back together. Later, while inspecting the engine I discovered that the engine had ingested very little dirt so maybe I (or the little voice) had succeeded in closing the throttle before the impact.

spad

I had almost exactly the same thing happen with a small, shall we say"unusual", British sports plane of about 42" span and inherited as part of a job lot. It came with a very old and tired Irvine 20 and would unstick after about 60~70' run on very short mown grass. So I re-engined it with an OS32SX screamer. Boy did it motor then! I did about 4 flights with it in this configuration and had immense fun pulling short tight loops at immense speed and that was after pulling the throttle to idle as I pulled up into the loop! All was going swimmingly until I pulled a slightly larger loop (thereby preserving more speed than usual) and got onto the throttle a little earlier than usual. I guess the speed held in the loop and the early throttle-up was just too much for the tired old airframe. Like you, as it shot past at about 30' I heard the ominous buzz of flutter. Simultaneously I saw a bit detach itself and as my eye caught the small piece being left behind, the plane very neatly andincredibly quickly bunted over and went verticle onto the barbed wire fence that edges the strip. It very efficiently cheese wired the wing off and broke the rear needle off the backplate.
Examining the debris showed that the flutter must have been the elevator which caused the stbd tailplane to separate with a clean break at the root where the builder had, all those years ago, scored the surface grain when trimming the shrinkfilm to glue the tailplane into the fuse.
A couple of lessons learned there!
All in all it took about a second from the buzz to the impact and, no, I didn't have time to close the throttle![&:]

cheers all!
Rick

allans

My Feedback: (11)

Maybe , just maybe, was this cause by flutter in the elevator . Overspeeding the flat tail surfaces.

I wonder. After so many flights - the structure seemed capable of handling the extra power.

Allan

phlpsfrnk

Allans,
I was well aware of the possibility of flutter and had seen it happen to others. Until that little voice overruled my good sense in the interest of showing off I had always kept the speed well within Vne, the Never exceed speed of all aircraft designs (large and small). In the shallow dive I was in at the time when I'd pushed the throttle to full the speed accelerated past Vne in a heart beat. Once you hear the flutter it's usually too late.

Frank
"Takeoffs are optional, Landings are Mandatory"

allans

My Feedback: (11)

Well said. A nice life lesson for all of us, that clearly applies to thngs beyound RC.

Also well written. You have some skills.

Allan

phlpsfrnk

Thank You, and it's because for a living I write technical operations and maintenance manuals for a leading manufacturer of Military flight simulators. I've done some club newletter editing in the past but this is my first publishing to the public of anything non-technical. I've tried to upload my company E-mail signature with its animated gif. Thank you again.

Regards
Frank R. Phelps
Technical Writer
CAE USA | Military Simulation and Training

basman

I think that voice is connected to our male ego's. A light goes on and all reason is abandoned!!!!!!! I had a Dolphin that I powerded with OS 55 AX. Had just recovered it, was looking nice as this was my first recovering attempt. I knew the 40 size low wing trainer was a tad overpowered but just go steady on the throttle. Doing a pass down the flight the flight line I heard that fluuter, and watched as bits flew off. As this was my second plane and I had only been flying a couple of months my reaction was panic!!!!! [X(] I throltted down and yelled from the flight line that bits flew off my plane and was making an emergency landind. I completed a circuit and decended dirrectly from about 40ft coming in fast. I hit the strip and bounced about 10ft, then proceeded to bounce the full length of the stip. On inspection of the plane the left airilone had come off catching the rear left staberliser and elevator cutting them clean off at the side of the fuse. I still had control of the plane and if I hadn't paniced could of made a controlled decent. Long story the plane was repairable

basman

Pic's Pre flutter incident

LuftwaffeOberst

If you look at all the builds here at RCU, you always will see someone over powering a ARF. [:'(]

FlyerInOKC

My Feedback: (6)

I am a stand off Golden Era scale builder and have a tendency to slightly over power my airplanes but since I have a tendency to also slightly overbuild it evens out. I usually have a little extra power when I have one of those senior moments and can't tell left from right. etc. The nice thing is scale airplanes look all wrong when they go to fast. I have a SIG 1/5th scale Cub with an old Saito .80 on it. It's considered a .40 to .46 2 cycle or .40 to .65 4 cycle airplane. I built a custom box firewall to get the engine positioned correctly to fit the cowling and mounting the engine inverted allowed the engine to be completely enclosed except for the needle valve and the stock muffler that ended up running parallel with the bottom of the fuselage thanks to the stock pipe and the 90 degree fitting from a Saito inline twin. You can't beat those factory Saito parts! This system has none of the problems the flex pipes have.

Mr67Stang

Too many people forget(do not know) that the stick on the left is more than an "on/off" switch and ground steering control.

qldviking

I had a good laugh a while back, this clown had bought a new extra arf 46 size and jammed an os91 in it, it last 3 minutes into its maiden being flown to its max before breaking just behind the wing. His comment? I'm taking it back for a refund [X(] I couldnt help laughing when he complained the next weekend that they wouldnt refund

Woogaus

Don't we all know that feeling, LOL. I did a Falcon 2 about 36 in wingspan with a MDS .48 Pro in it. fun to fly, but a pain to land.

RVator

My Feedback: (1)

I have seen some people not only overpower but overprop as well. A 90 funtana with a 100 Saito is not overpowered but the same airplane had a 14x10 prop on it. If it ever got up to speed it would flutter.

donnyman

for your consideration

over powering a bird usually isn't wise (don't ask) especially arfs and the like.

BUT when done it would be wise to consider;

all flight surface gaps should be sealed

no sloppy control connections

If you need to ask why ........... don't overpower anything

Flutter KIllS.