DA 85 cost me a QQ Yak 54 101

[swatman260]

After a two week build, I was able to maiden my brand new QQ Yak 54 101 this past weekend. I used my DA 85 for this plane. This engine is about 7 months old and has probably 5-6 gallons of fuel through it.
The first flight lasted about 10 minutes, and was a perfect flight. The plane flew awesome and required only a few clicks of aileron to fly hands off. After the initial shake-down flight, I landed and checked over everything. All seemed to be good, so I re-fueled, let the engine cool down, and then flew again. About 3 minutes into this flight, the engine quit. I didn't have enough altitude or airspeed for a safe recovery and the plane pancaked into the ground. My brand new plane was pretty much destroyed.
Enough grumbling...Here is my question. This was a well broken-in engine that was properly tuned. I have had several other gas engines, so I'm pretty confident that tuning wasn't an issue. It was pretty early in the flight, and I had not been taxing the engine hard, so I don't feel that it was overheating. The fuel lines were still connected after the crash, and didn't have any blockage. Prior to the engine quitting, I was simply flying at about mid-throttle. There had been no significant changes in the throttle position. The motor had not been burbling (in fact, it had been running pretty smoothly), and did not lean out prior to quitting. It sounded as if it just shut off in mid flight. All flight batteries were checked post-crash and had full charges. Does anyone have any ideas as to why this engine would just quit running? I'm sending it back to DA to be checked out, but I'm gonna have a hard time feeling confident with this motor in the future. I don't think that I've ever had one just quit like this with no warning and no carb input. Any suggestion that you guys may have will be appreciated. I'm not trying to bash DA here, just find a solution to my problem.

[Thomas_W]

was the ignition system working after the crash? I've had a few pickup sensors call it quits while flying, but its fairly rare.

[JoeAirPort]

Well if it was tuned that smooth....with no burbling at all....it could have been too lean and hence a flame out. You need some burbling there or that can happen. Also if it's too lean your acceleration will suffer. Not sure that was it but it can happen from too lean of a low needle. It's happened to me in a low and slow knife edge. Thanks to the huge rudder and full deflection of the 87" EF Yak, I was able to turn it around and still land it on the field. It was close though. If I had been a little less lucky I would have had a pile o' sticks to take home.

[swatman260]

Yeah, I wound up with that pile of sticks.
I've not been able to check the ignition since the crash. I'm not ruling that out as a cause yet, but DA should be able to verify that one way or the other.
I guess it could have been too lean, but it just didn't act like it at all. Transition was great all the way through, and acceleration was good. Again, I've been running this engine for several months, so I would think that I'd have noticed if something was too far out of the norm.

[bodywerks]

Do you have a choke servo? do you have an optical ignition kill with the receiver failsafe set for either of these to kill your engine? have you thoroughly checked everything else pertaining to the powerplant before assuming that it was the engine's fault? I'm not saying that it definitely wasn't something pertaining to the actual engine or ignition, but I'd definitely rule out 100% everything else before making a post with a title that pretty much blatently says that you don't have a plane anymore and it's Desert Aircraft's fault. any number of things could have happened - a failsafe that cut your engine off (due to interference from the ignition - which you can still get even if you are on 2.4), a bad battery, battery connection in the pack or wire connector, internally broken wire in the battery or switch lead, a faulty ignition kill unit (if you have one), fauty switch, a bad choke servo (if you have one)that went to full choke after failing, bad throttle servo, fouled plug, dirty spark plug cap, too lean, too rich, bad fuel - the list goes on and on. Just showing that it could be a huge number of things besides the engine itself.
I can understand that you are rather upset. I lost a 75cc extra after only 10 flights because the engine quite in a bad spot (pushing into a hover from an inverted harrier that started at like 3 feet off the deck). I sent (well, drove) the engine to DA, and besides needing the hub mod (which had not affected the engine at the time of the crash) they found nothing.
Bottom line is that $h!t happens, and I just wrote the crash off to me having too much fun and getting too comfortable with a plane that had a new engine in it that wasn't even broken in and probably not properly tuned yet.
Even if DA does find something that would obviously have caused your engine to die, chances are that it will ultimately not point to a manufacturing defect (which usually show their ugly faces early in the engine's life), and in the unlikely event that it does, its still not going to get you your plane back.
Lick your wounds, send the engine in for a check-up, get it back and buy another plane.

[Wild Thang]

Dude that sucks.

Sorry to hear about that.

[Flatlandman]

on mine the carb bolts came lose and caused the same crash but mine had less damage thaN YOU DESCRIBE YOURS HAD. Mine pancaked and dug the f1 former into the ground cracking it and the gear plate plusthe momentum of the wings pulled the fuse apart. Not to bad a fixer. Other thaN the carb bolt being loose the engine ran like a sowing machine. I did have a seal leak but da assured me it would run fine with it untill i could recieve some seals and it did i had 8 or 10 gallons on the leak with out issues and they sent me some seals so i didnt have to spen any cash sending in the engine for such an aesy fix.

[Vic3D]

Wow that's horrible. Sorry for your loss.

[alan anderson]

Things do happen but there must be a reason for the engine quiting, I just had a dead stick on a upline
found that the fuel pickup had stuck in the front end of tank, in corecting that problum I found the fuel tank plug was detearing and had pices of the plug in the carb screen and in the needel valve.
Most of the time you should be able to find the caus of the dead stick. fuel ?, battery switch, connector to ingnition,possable engine it's self. check everything when you build next plane.

[Wild Thang]

	Quote: Originally Posted by alan anderson
	Things do happen but there must be a reason for the engine quiting, I just had a dead stick on a upline found that the fuel pickup had stuck in the front end of tank, in corecting that problum I found the fuel tank plug was detearing and had pices of the plug in the carb screen and in the needel valve. Most of the time you should be able to find the caus of the dead stick. fuel ?, battery switch, connector to ingnition,possable engine it's self. check everything when you build next plane.

eehhh... yeah... kinda i guess

Single cylinder DA's do seem to deadstick quite often. Nothing against DA, I have a DA-85. It's the truth though. And yes, sometimes it's user error. Like not being tuned right or somthing. The big-uns are spot on .

[Rolling Thunder]

Did you check the fuel tank to make sure the clunk line didn't fall off.

[MikeC3D]

	Quote: Originally Posted by Wild Thang
	eehhh... Single cylinder DA's do seem to deadstick quite often. Nothing against DA, I have a DA-85. It's the truth though. And yes, sometimes it's user error. Like not being tuned right or somthing. The big-uns are spot on .

I know what you mean, I had a 50cc once that died on me twice in flight, resulting in major damage, The damn things just dont run on fumes........My 100cc died on me many times after months of flawless flights, and it turned out to be a bad battery solder connection on a Fromeco battery,The damn thing just dont run without a spark.....I put my 1600mah fuel tank battery on and engine ran good again, ALTHOUGH....when I installed the new Fromeco battery, I soon learned that the DA ignition handled 8volts and never failed in 6 flights that day, until another deadstick resulted in a completly dead ign. battery...WHAT??? what happened to my regulator????? I forgot to put it on......... Hello Kurt, I need another battery, thanks.........
My reason for the story is just to remind you that just because you THOUGHT youwere doing everything right, doesnt mean you didnt miss something, we all make mistakes and alot of times it takes 3-4 people to figure out what happened. And nothing last forever, things just go bad, (kinda like a car battery leaving you stranded on the ferry boat at 2:00 a.m.) I have a 170cc now and so far it has been flawless, with the exception of 1 reed valve breaking, and DA's first class Customer Service hooked me up in 2 days....good luck buddy.

[DATech]

Sorry to hear about the crash. Without inspecting the motor, I would only be guessing as to what happened. It could be a problem with the motor it's self, or something else. Get the motor and ignition here and we'll go through it thoroughly. You can also include any ignition regulators, switches, battery, or optical isolators. We can test run it with your system.
We'll let you know what we find as soon as possible.

[decoy26]

That is awesome customer service right there!

[swatman260]

That absolutely is great customer service, and I'll be shipping everything back today. I realize that I vented a bit, but I did say in the post that I was not knocking DA, just this particular engine. I recognize that a host of things could have occurred. I'm running a Smart-Fly system with an optical kill, that was still working after the crash. Both the throttle and choke servos worked prior to, and after the crash. The fail-safe points on both were set to hold position, so I don't think it was a hit (I'm on 2.4, but I don't count that out). I also checked the fuel tank, and everything was connected after the crash. While I recognize that it could have been an error on my part, I don't THINK that it was (not ruling it out). I think it may have been a bad ignition, but I'm not certain. Hopefully the guys at DA will at least be able to pinpoint a cause so that I can lower the chances of it happening again.