Rise and fall of my 40% Yak54

[warren cross]

Woody,no the throttle servo was under the motor box,and ignition was back in the box(6-8in) seperation.DKinippen,rudder servos were fine (newones) no grinding etc. I know new dont mean much, but it was my best shot. Everything will be sent in to be checked out. Thanks for the input. Keep it coming

[DKjens]

Were both mufflers still on tight? Did you use a paper gasket material or a fluid gasket material between mufflers and cylinders?

I lost my last 3.0m Extra due to a less than completely tight muffler. I had used red silicone as gasket, since no solid gaskets were available for this engine, so as soon as one muffler bolt loosens slightly you can have movement and metal to metal contact.

I had made it a point to yank at the mufflers before each flight just to prevent this, and of course I forgot on that flight. Either that or it was becasue I had just taken pictures of it to post it for sale he he. Somehow they just seem to come back and kicking you in the b@@!!s.

I took of, into a quick four point roll, the plane kept rolling, first one way, then the other, probably due to me rolling back and forth trying to save it, and the Rx going in and out of lock out probably. The plane ended up going in at probably 100 mph, inverted at a 20 degree bank or so.

[gsxr]

Was there alot of vibration from the engine? did any of your wires touch metal at all? was there a bad ignition wire?

I am sorry to hear about your loss They are awesome flying airplanes.

[Throttlestick]

Sorry for your loss!

[G limit]

I guess it's time for me to jump in here. I had the dubious honor of standing next to SEG during the Yak"s last flight.
Let me assure one and all in NO WAY did SEG have anything to do with it's demise! Contrary to what has been previously described, flight attitude was not "knife-edge". SEG was simply making a straight inverted pass at approx. 100' alt., 100' out, parallel to the runway. As the airplane approached "stage center", the rudder started to swing STOP TO STOP(low rate), with no other input. Rest of controls were UNPOWERED, not in "PCM hold". Aircraft slowly rolled to the left and arced to an ever increasing nose low attitude, impacting 300+' from us, 25deg bank(from inverted), 20deg nose low, 80% power, with the rudder continuing to drive stop to stop.
In all my years, I have never seen this scenario. A loose servo connecter can mimic what we saw the rudder do, but if that were the case, the other controls would have functioned normally, allowing a save.
Old Dawg,
Long Live Team Vegas!

[jholt]

Hey Warren,

Sorry to hear about your Yak. I can appreciate all the work you put into getting it ready for flight. I hope to have mine finished soon. See picture at left. No cowl on plane, it is in painting stage now. It has same basic scheme as Jeremy's Carden you saw at the Shootout. I hope to order motor this month. Did you ever check the weight of your Yak? Your post said a 3w157 carried the Yak without problems. Let me know your thoughts on that.

Better luck on the next one. Keep me updated.

Jerry

[paffy]

	Quote: Originally Posted by G limit
	I guess it's time for me to jump in here. I had the dubious honor of standing next to SEG during the Yak"s last flight. Let me assure one and all in NO WAY did SEG have anything to do with it's demise! Contrary to what has been previously described, flight attitude was not "knife-edge". SEG was simply making a straight inverted pass at approx. 100' alt., 100' out, parallel to the runway. As the airplane approached "stage center", the rudder started to swing STOP TO STOP(low rate), with no other input. Rest of controls were UNPOWERED, not in "PCM hold". Aircraft slowly rolled to the left and arced to an ever increasing nose low attitude, impacting 300+' from us, 25deg bank(from inverted), 20deg nose low, 80% power, with the rudder continuing to drive stop to stop. In all my years, I have never seen this scenario. A loose servo connecter can mimic what we saw the rudder do, but if that were the case, the other controls would have functioned normally, allowing a save. Old Dawg, Long Live Team Vegas!

Now that makes sense. If you lose power to all servos, ailerons and elevators won't flutter on their own at medium airspeed. Rudder will however start to oscillate at much lower airspeed (unless you added lead counter balance to it).

It sure sounds like the plane had no power when it went in. Also, not going to idle (if set to do so) is usually a clue suggesting no power.

Make sure you guys build the next one with redundancy. That way, only half of your plane would die if the same issue came up again.

Good luck with the next one !
P.

[PTS]

The loss of your plane is definitely tragic! On another note the looks of the plane has made my mind up for my next build. Do I understand correctly that Aerotech is coming out with a 118" plane? Also I may be unaware but it seems the DA-150 in this bird is underpowered.

PTS

[BOATNIK]

Yes, I think there is a build thread on this site.

[warren cross]

DK,muffs were tight,did use red gasket silicone in place of gaskets. Thanks for ur input. Paffy,hopefuly my nex Yak will be able to use the new2.4 gig stuff,I never used redundant equipment,pehaps i should have,thanks for ur input,hows that extra of urs coming?? What a great thread ur putting down, I enjoy it. JHolt,I didnt get a chance to weigh it,but 42pds would be my best bet. Hurry and get yours done !! You will love it. The 157 had a LOT of beans!! More than enough power,great choice!

[Xipp]

Warren the only thing i can think that happened was a rudder cable may have come loose and tore off the antenna, After looking through the pile of busted up balsa i seen that your antenna was tore from the receiver and that would account for the lock out that the plane went through and seeing as how every cable on your SWB servo tray were off their pullys that is all i can relate to...Once again sorry for loosing such a fine flying airplane...Now get to work on the new one

[G limit]

Let me say it again. The airplane/radio was NOT in PCM hold. If that were the case, we would have been picking up the wreckage over at the high school 3/4's of a mile away.
Instead, it acted as if the radio (receiver) just signed off...

Old Dawg