Category: My Fleet

Continued the investigation tonight.  Set the body in my trusty PVC holders on workbench #1 and started examining from the front.  Pulled the cowl and found a couple minor issues… One cowl screw insert coming loose, ignition box moving a bit, but no smoking gun under the cowl.  Even pulled the plug and examined.  It actually looks like I have heard it should.  Sort of uniform dark grey.  Gap looks fine and no carbon buildup obvious.  Top of the piston still nice and shiny as well.  All linkage and tubing plus the telemetry sensors and wiring looked OK.  I then decided to skip an actual ignition spark test for the moment and moved on back into the wing saddle area.  Again nothing obvious so I turned on the plane and started looking to see if (as I thought) the ignition voltage sensing is beyond the kill.  The plane died quickly like that occurred but the telemetry didn’t show the ignition voltage loss.  This all worked as expected but it brought to mind the idea that maybe I had a throttle curve that brought the throttle below idle or some sort of misconfiguration of a mix that would cause that.  Looking at the radio yielded nothing but when I moved the throttle back and forth I saw some odd movement and looking more closely I found the culprit.  Here is the problem:

With this screw backed out this far the adjustable arm can end up extending enough to cause the throttle to bottom out and shut down the engine.  As you can guess, I will be coming up with a different type of connection.  I know, some folks will say this type of connection in a big gasser is just stupid to start with, but with so little force required to move the throttle I was not worried about torque causing slippage or the arm bending or any of that.  What I obviously should have been concerned about was vibration loosening the screw!  I will probably replace this linkage with a standard threaded clevis (once I solder on a threaded coupler) and a standard servo arm… non-adjustable this time…  A drop of something to keep the screw in place might be used as well.  Perhaps nail polish or the like.  I don’t think thread lock works on nylon!

Obviously its hard to be happy about a crash but the good news is the damage seems to be limited to my pride and the wing.  My pride will recover… its a nasty bruise but they heal.  The wing is not that difficult to replace, and not very expensive in the grand scheme of things.  The better news is that I now know what caused the crash and it is easily rectified.  I was hating the thought of fixing all the damage and not being able to figure out a cause.  That would really make me paranoid and give me no confidence to fly the plane again.  Now I’m back to looking forward to it!

Pulled the landing gear and servos out of the wing this evening.  Port side gear bay and main spar and ribs took the brunt of the damage.  Cracks and buckling apparent.  Would be difficult to fix.  Would need to re-manufacture at least one rib and remove and re-web the main spar.  I imagine parts of it are cracked or broken as well.  The other side the top sheeting and some of one rib is crushed.  I am fairly sure I will just order a new wing this fall and reconstruct over the winter.

Both retracts had some flexing/bending of the mounting ears.  The starboard side was bent worse as you can see here.

Some hammering against the anvil/vise seems to have straightened those out pretty well.  I don’t expect the retracts are actually hurt at all.  They seem to operate smoothly and the struts compress as before.  Best I can tell everything is pretty straight again now.

I need to carefully inspect the fuselage but on first inspection it looks unhurt.

First look through the telemetry data has nothing significant to help pin down a cause.  Both the pack voltage and ignition voltage stayed in range both before and after the engine quit.  Overlaying the altitude and RPM graphs it is pretty easy to see when the engine plummeted in RPMs over a few seconds, ending at zero!  I will have to carefully examine the wiring beyond the sensor, check the ignition itself as well as the plug, the hall sensor and of course the fuel system to see if I can determine a cause.  The log showed no signs of problems and even if it had gone to failsafe the throttle would have simply gone to idle.  I will confirm that too but don’t believe it would have quit if I took a hit and it doesn’t appear I did anyway.  There was plenty of fuel in the tank when it quit so will be sure to check the plumbing as well.  Still a mystery for today.

Due to a flame out at a very bad time the P51 made a landing in the bean field 20 feet off the end of the runway.  Analysis is underway to try to determine a cause and assess damages.  Quick guess is the wing will need to be replaced due to landing gear attachment point damage.  More to follow when I have time to work on it. Will be looking at telemetry data as well for info leading to reasons behind the failure.

Three more flights today on the P-51 today.  I think they were number 10-12 on this bird.  She flies well with adequate power from the DA-50 and with full flaps the landings are getting to be smoother all the time.  No appreciable bounces today and 2 landings that were totally greased in.  I may have to start saving to modify the retracts to electric power and consider installing them if I keep this up!  The Top Flite is a really nice flying model.  Once you get the flaps dialed in with a little up elevator mix on deployment it isn’t too bad to land.

On the skydiver front, George had a bad day.  After a successful early jump, the next two were ugly.  First, the release mechanism didn’t and he stayed firmly attached and then on the next attempt he did a “hanger” and simply drug along behind all tangled up and just to add injury to insult his arm busted off when I landed… 🙁

He has already been repaired and is ready for the next attempt.  Also had a scare with misplacing his “static line” that attaches to the plane and allows his parachute to open upon his exiting the airplane.  I eventually found it but it has inspired me to build a second one as a spare.  If I can find a little cheap metal spring hook I think I will be in business.  The rest is easy… just a release pin in the middle and small patch of hook and loop on the end and I’m in business.

Put up 3 more flights today… about 7 minutes each.  Total battery usage was around 480mah so the average looks like ~25mah per minute of flight.  Even less than last time but probably less “on-time” between flights etc… so more typical of actual flight times.

Finally got my flap mix to elevator about right I think and all three landings were good.  1  bounce or less and no really anxious moments.  Just greased’em in!  One flight I got a reported 96mph so I think maybe 100 is going to be the top speed if I get in a nice long full throttle dive unless I make some changes.  I can’t complain about that.  It seems reasonable enough.  I’m not seeing any excessive temps… around 230 I think is about normal peak which seems on the cool side so I’m not going to complain.  Flight pack voltage is very steady with the two A123 packs supplying a nice and fairly steady 6.5 or so volts if I recall correctly and the IBEC is locked in at 5.2V.

Did some nice, slightly high, photo pass/knife edge passes and some sub 30 foot high speed passes along with a few Immelmans, Split-S, loops and plenty of rolls and combinations.  Stall turns are fairly easy and I am having few problems with orientation.  All in all, its shaping up nicely.

After the 3rd flight I sat and made a few adjustments in the radio.  As is my usual method, I started with dual or triple rates configured for each of the main flight surfaces and once I narrow down throws and expo settings I like the rates go away and all are set to the same settings so there is no chance of problems due to improper switch settings.  Ailerons are pretty much dialed in and rudder is comfortable though I may need to fine tune a bit.  Elevator is nice for landing but the plane can snap if I pull too hard.

I’ll have to decide if a bit less elevator is still good enough for landing but other than that I’m getting pretty comfortable with the Red Tail.

My Red tail P-51 Mustang started out life in late 2004 as a standard Top Flite Giant Scale P51 D purchased by Mr. Tim Mills.  Tim bought pretty much everything needed to get this bird flying during a 1 week period.  Everything from engine to scale exhaust, servos and retracts, as well as the ARF itself and more.  When it arrived he started to convert it to a B model by stripping the body and adding the turtle deck aft of the cockpit using a Top Flite conversion kit.  The structure got finished and the body glassed and prepped for painting.  Tim wanted his P51 to “represent” the Tuskegee airman as he was one of the few black men involved in the RC flying hobby… at least in the greater Indianapolis area.  Tim had done some reading on the subject and found that the Tuskegee had first been issued B model mustangs so he had to convert his.

For some reason, at that point the project stalled.  I don’t know exactly why it stalled.  Likely Tim got involved helping out friends who needed some assistance with anything from Airplane setup to health issues.  Tim was the guy everyone called when they needed a ride somewhere, a helping hand with a home project, advice on flying and setting up RC planes and just about anything and everything else.  Tim had built and driven drag bikes as well as running a race circuit earlier in life, been an owner/driver of a semi-truck and maintained and rented out properties.  He was a Jack-of-all-trades and always generous with his time.  He was also a big talker and loved just hanging out with the guys at the flying field.  He helped me learn the basics of IMAC style flying and we traveled to a few events together in the last 4 or 5 years of his life.  With Tim in attendance, it was always a good time for me.  He also spent a good amount of time working on RC projects with me, both his and mine, out in my work shop.  I learned a lot during those sessions and like to think I taught him one or two things as well.

In any case, somehow the Mustang languished for almost 7 years and everyone had a good time asking Tim when the Red tail was going to be ready to fly.  This continued until Tim passed away in February, 2011.  I had personally benefited from flying and traveling and just becoming friends with Tim and I wanted to finish the Mustang in a way that Tim would have enjoyed so I contacted his nephew and bought as many of the parts Tim had acquired for the Red tail as I could.  I hadn’t planned on this project but I scraped up as much as I could and bought the Airplane, motor and Keleo scale exhaust at a very reasonable price.

By spring of 2012 I had the plane ready to fly and besides adding the distinctive red tail and other markings unique to the Tuskegee airmen, I added a few special touches toward making it a bit more of a memorial to Tim.  These include a pilot figure (black of course) who is clothed in appropriate attire and can salute on command from the transmitter; graphics on the cowl proclaiming the airplane name to be “Drag Racer II”; and adding the pilot name to the side of the cockpit area.  The call sign “Smooth” was chosen because not only did Tim enjoy Jazz music but many folks described his flying style with that word.  Here’s a picture of the cockpit area.

There are a few other nice touches I’ve added to the bird to make it unique but I’ll save those for some future posts.  I’m still working on learning to fly this plane sufficiently well to be comfortable and trying to keep it looking good in the process.  I’d hate to lose it in an accident and that is the reason it hasn’t flown much yet.  Recently though I’ve decided I just can’t let it become a hangar queen as I can easily imagine Tim’s reaction to that.  I can hear his voice in my head right now saying “Just fly it, man!”.

As I do just that, I’ll post some more information and pictures on the Red tail.  I hope Tim would approve.

Though I’ve flown the Top Flite giant scale Mustang a half dozen or so flights in the past, yesterday was the first time since I swapped in the Power safe receiver and moved it over to the DX-18 that I’ve had it in the air.  It was a sort of second maiden flight.

All in all, the weather was just about perfect once a rain storm cleared.  The wind was almost zero and the temps were in the high 70s.  The plane seemed to fly well with only the landing being a bit tricky because my flap mix resulted in a marked nose down pitch.  This meant that I could land without flaps… something I don’t recommend as the plane requires a fair amount of airspeed to fly… or with flaps while constantly holding in some up elevator to compensate.  I chose the “with flaps” option and managed to get it down with only a minor bounce or two.

I decreased the flap mix a bit after the first flight and tried again, this time getting in some knife edge flight and some high speed, relatively low passes with good results.  It appears I could use some more rudder throw and it was programmed for triple rates but I was unsure of my switchology and this was not the time to start flipping to find it so I will try some higher rates on the next flight once I am confident of which switch does the trick.  When it came time to land I found the same issue as before, though not as bad.  I will reset the mix to put in some up elevator for the next flight and see how that works out.  I guess this plane requires up elevator mixing with the application of the flaps instead of the expected down trim to prevent ballooning.  Looks like the drag wins out over the increased lift in this case.  Again the landing was at least “not damaging” but the rain was threatening so we packed it in for the day.

Today, upon recharging the flight packs I found they took 183 and 249 to top off the starboard and port packs.  Between the two flights this was about 12 minutes of flight time so it seems to take about 35mah per minute of flight.  With two 2300 LiFes on board and an average 10 minute flight…. well I don’t think I’ll worry much about charging between flights if I come with full packs!  I can monitor the idle and in flight voltages via the Telemetry system but will eventually likely need to rig a way to monitor the flight packs “at rest” at some point in the future.

Telemetry tells me I hit almost 4 Gs positive and 1 negative during these flights with a max airspeed of about 85 mph.  Temperatures on the motor stayed in the range of about 200-230 degrees (F) once it was warmed up, which seems to be a fairly normal range from what I’ve seen so far.  Static RPMs hit almost 6000 with the 22×10 Xoar but showed over 10,000 in the air.  I can’t really believe that is occurring… must be some sort of telemetry glitch.  I’ll eventually have to look into that to see if I can figure out a way to refute that and fix or at least explain that odd readings.  I plan on flying the Mustang again soon in preparation for our club Airshow coming up on July 28th.  I’ll try to post more as I get some more time on the airframe.