P-51 Redtail – Electric Retract mistake… no good deed goes unpunished!

A while back, Kelly brought his P40 over to complete final piece of the install for his electric retracts into his Top Flite Giant Scale P-40.  The tail wheel.  We had the main gear already installed in the wing and tested and had just the tail left to complete the job.  We were well into the job and ready for some testing when we realized that we needed to cycle the gear to finish up… but a problem presented itself.  Kelly had not thought to bring the wing for the P-40 and attached to that wing was the control unit!  There is no way to cycle this gear without a control unit, but luckily (not as lucky as I thought at the time) I have a very similar control unit in my Mustang so I just walked across the shop and pulled it out.  That is where the trouble began…  You see, for some reason over the course of the last 6 months, Robart has decided to switch the connector type from a standard servo type plug to a 2 wire… I’m not sure what it is so let’s just call it a “Robart connector”!  They also decided to change from using type 1 and type 2 to using type A and B… but more on that later.

OK, so this connector issue is “no hill for a climber”, right!?  First, cut out the plastic around the opening on my control board and plug in the P-40 tail wheel there, then create a female to female servo lead to hook the control box to the receiver… my lead is tied down in the Mustang… and wallah!!  That taken care of we can now cycle the tail gear.  Yahoo!  With a bit of custom fitting (Dremel tools are great, aren’t they?) the P-40 tail wheel is all good.  That all accomplished, just stick the control board back in the Mustang and reconnect it… careful of polarity… that would be expensive!!  All good and the Mustang can retire back to it’s corner for a few weeks….  All good… I thought.

So a few weeks pass and it’s time for the club picnic.  Great fun, good food, excellent weather… sounds like a good time to show off the Mustang for the members and especially the families that rarely make it out to the field any other time.  Low 110+ MPH, nice slow (for a Mustang) photo passes, big loops and stall turns… and then have the pilot salute the crowd after a perfect main wheels only landing… The perfect recipe for a nice day at the field.  At least that’s the plan…

Upon arriving at the field, we (it takes a village) got the Mustang assembled and did a quick cycle of the landing gear and, yep it all works but… wait a minute.  One of the mains goes up when the other goes down!??  That’s weird.  Power down and back up with the wing opened up… try unplugging and replugging the two main retracts to get them in sync… still no joy.  How strange…  As I’m standing there cycling them one more time (bordering on insanity now… repeating the same actions waiting for something different to happen) and get a whiff of something hot/stinky.  Thinking the engine that someone is running 20 feet down the flightline must be getting hot or maybe something got against the hot engine down there.  Back to my problem and now the tail gear has quit moving… just staying down.  When I decide to check that connection it suddenly becomes obvious… the tail gear is plugged into a main gear slot on the Robart controller!  That must be what’s wrong, the two are reversed.  Swap those two and now the main gear works great.  But wait, the tail gear still isn’t working…

OH CRAP!!!  Now the full impact of what I’ve done hits.  The tail retract is what Robart calls a type 2.  The difference is that a Type 2 takes less voltage than a type 1.  And in case you’re wondering I can attest that plugging a type 2 into a slot that is set for a type 1 will release the smoke that is part of the “smoke and magic” formula that makes these things work.  At least it will after several cycles…  I haven’t even flown yet and I suspect this trip to the field just cost me $50-100.  That burning smell I detected earlier was something getting hot alright… but it was a lot closer than I thought!

If there is a silver lining… that tail gear was fully down and not likely to go anywhere so since I’d already paid the price I went ahead and got some flights in.  The last one for the day was a pretty close approximation to the one I’d dreamed of, complete with a 115 MPH high speed pass and a sweet landing that elicited some envious comments from fellow warbird pilots.  “You know you make us look bad when you do that, right?”  and “Mine doesn’t do that!” were among the shouts from the spectator area.

Once home I sent some email to Robart asking about a replacement and they promptly replied with the appropriate part number and instruction on how to get a unit that would drop in and fit my control board.  When it arrived, one more little detour came up.  The new unit arrived and was marked with a “Type A” tag.  Huh?  I only have Type 1 or Type 2 options on my controller??  OK, so type 1 would be A and 2 is B, right?  Wrong!!  My old unit was a type 2 and Kelly’s tail wheel worked when set to type 2 on my controller… Plus it’s still a lower voltage unit (checked the instructions and confirmed, main gear is Type B and tail is Type A) so not only did the nomenclature change but it didn’t follow what you might think of as the logical choice either!

After reading everything over 2 or 3 times to confirm that things are as I think they are, got the new unit plugged in and tested and it seems to be working fine… no sign of smoke or heat.  Nice smooth cycles up and down.  So, the moral of the story is…. “Quit being nice to your buddies!”   Wait that can’t be right!?  Maybe, “Be a bit more careful when plugging and unplugging all those wires in your complicated and expensive airplanes!”  That one sounds better!  For sure this one applies: “No good deed goes unpunished.”

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