After four what I would call "textbook" flights on my B-24, flight #5 ended with #1 engine coming to a stop in flight. I had made a couple low passes across the field, reclimbed to altitude and turned downwind, parallel with the runway, when about halfway through the downwind flight the plane suddenly went out of trim, with a significant "left yaw". It was easily stopped with a little right aileron, but when I let off it immediately went back left. (I have rudder coupling mixed with ailerons) My first thought was that I had lost an engine, but I expected a more violent reaction from the plane. In any event, I dropped the gear and made an uneventful landing, during which I didn't even notice if the prop was stopped or not. One of the members was video taping the thing, and I had him run the tape back and sure enough, the prop was stopped when I crossed the threshold.

2nd flight: After checking everything I could think of, re-adjust the engine, do another vertical test, etc., I decided to do another flight. After take off, I began a turn away from the runway while climbing. About the time I had completed a 180Ëš, the airplane started a very pronounced left roll. I managed to get it stopped, but was still trying to maintain altitude or even gain some. Problem this time was that I was low on airspeed and climbing when the engine quit.
Short story, I struggled, but managed to get it back to the field in one piece, much to the surprise of some others who were watching the entire thing!

Question is, why 4 near perfect flights and this crops up. Best thing I can come up with is fuel foaming in the tank. The tanks are in the outboard nacelles, and there is so little room I didn't think at the time I could get any foam in around the tank, for having to cut deeper into the wing. The tanks for the inboard engines are in the fuselage, and have foam all around them.
Going back over things, it seemed to me that on the first flight, one engine seemed to be awful rich, leaving a lot of smoke. When I mentioned it, my son said he also noticed it. I can't recall which engine it was, but probably was #1.
I am presently working on putting foam around the tank. Does anyone have any other suggestions while I'm into it?? I'm mostly baffled as to how I got 4 good flights before this showed up.
Randy

What engines are you using? When you 'checked everything' did you check for garbage in the needle valve of the problem engine? As it takes only a small amount of crud to block things up a small particle may be floating around causing some grief. Do you use fuel filters? I use Sullivan 'Crap Traps' just before the needles on my B-29. If I have to adjust them more than a couple of clicks each way the first think I look for is crud in the needle valves. - John

Need more info. I fly the C130 and have had engine out 2 times in 30 flights. But they were bad fuel and fuel starvation.

The bad fuel caused an engine to drop out at random until I switched to a different gallon of fuel. (Both gal's were the same brand and bought at the same time). I called the mfg and they were more than helpful. Email me privately and I will tell you who's fuel.

The other flame out was due to the fuel tank cap being loose,, (some dummy who built it forgot to tighten the screw ) After landing and repair the tank it has not flamed out. I fly the saito .30 and us OS F plug with a 10x6 prop. Fuel currently used is Omega Cool power 15 % all synthetic. I have had no flame outs since I corrected my fuel issues.

So to be helpful we need"

Engine type
Prop
Fuel
Tank
Plug
and method of setting needles. Jim

Here's what I've done:
1. Cut out more area inside the nacelles so I could get at least some foam around the tank. I did both outboard nacelles the same.
2. No crud in the needle valve or lines.
3. I have always filtered the fuel before it goes in the plane.
4. All four engines (O.S. .25FX) have/had the same fuel, don't think that is a problem. I run 10%/16% oil Wildcat.
5. I am going to switch, at least for now, from the Graupner 10 x 6 3 blade back to MS 9 x 5 two blade props like I'm running on the C-130. When I was running up the throttles, I noticed a slight vibation of the prop nut when going through a certain rpm range, but all 4 engines were doing this-strange.
6. I also checked the klunk, fuel lines, etc for wear and tear or any signs of leakage.
I guess we'll see on the next outing what happens. That will be a couple weeks away, heading west next week for a bit.
Thanks for the suggestions,
Randy

Randy:

Sounds like at least a part of your problem might be overheating with the 10x6 3b props. That's a whale of a load for those dinky little 0.25 engines. Try going down to 8" diameter for the 3b props. My two 0.25 engines, an MDS and a Magnum, are quite happy with the 8x6 3b props on them. The 10x6 3b is what I run on the Magnum XL 46 edngines.

Bill.

...............with the 10x6 3b props. That's a whale of a load for those dinky little 0.25 engines....
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DUH!! Must be the weather! I am running 8 x 6 and not 10 x 6 like I posted. Wasn't thinking.
One thing I was a little concerned with, is that the hole in the Graupner prop was just ever so slightly bigger than the prop shaft on the .25. I wasn't sure how much effect that would have on vibration. In any event, I'm going to try the 9 x 5 two blades next time to see if I can tell any difference. They should have more thrust, but want to compare them to the 3-baldes. Of course, if they do produce more thrust, i guess the effect if one quits might be more pronounced than with 3-blades.
I did find out that even with the left outboard out, you get bad reactions when turning into the "Dead" engine on that side. You get a whole lot of help from the right side!!
After the second landing Saturday, which was pretty hairy, my son said, "I don't know how you got that back to the field, but after that last turn, I was ready to go get a bag for it!"
Randy

8 x 6 2 bladers sound too small for a 25, 9 x 6 at least. Are all the engines mounted sideways? I had severe vibration at certain RPM's and I solved this by rubber mounting the engines via backplate mounts. Filtering the fuel before it goes in the plane - not good enough IMHO, fuel filters directly before the needle and not those 2 piece aluminium things which leak air - Sullivan Crap trap 2 stage jobbies. If you have the height throttle back before you turn & then slowly apply more power when you have it straight again, also put in RUDDER trim, easy to say when your not sweating and your knees shakin! Don't run your engines too lean, lean them out till they just break into clean 2 stroke running & no more. Don't worry about synchronization, if one stops they won't be very synchronized! - John

oomer:

It seems you missed the 3b after the 8x6 - we're talking about three bladed props. Only the 9x6 mentioned was a two blade. The 8x6 3b is a good load for the 25 engines. Works very well.

Bill.

Hi!
It's no good to have the hole inthe props bigger than the axle on the engine.
That's a problem with using metric size props and using inch size axle.
To prevent this from happening I always turn my own aluminum spinner nuts, with a flange that goes inte the prop to center it corectly.
I also recommend that you use the Tettra line of "bubbleless" fueltanks that the pylon guys are using. These tanks can't have the fuel foaming at all. Dave Shadel of Performace specialties in Nevada (US YS importer)sells them.
As for props, a 8x6 3blader seems a bit small for a 4.0 cc engine (.25), you must get around 13000-14000rpm using one of those? And that is a bit too much. I would try a 9x6 APC 3-blade prop and if this is to much (my MVVS .28 engine using the ultra quiet MVVS silencer has no problem spinning one of those) I would file away on the prop, either lessen the diameter or reducing blade area by filing away some at the trailing edge.
For a 2-blade prop I would try a APC 10x5 or a 10,5x 4,5 APC
Regards!
Jan K
Sweden

if this is the stafford b-24 the 9/5 will be fine you will find for scale flight you will be at 1/2 to 3/4 throttle.i have the old os 25's pre schnurle on 9/5 props at 13.5 pounds flies fine off of grass after 20 years.my tanks are all mounted right behind the firewall,4 oz per the plans with no problems using fai fuel,no nitro.sound to me with the 3b prop you were getting a vibration problem,specially if you could see the prop hub move,either due to the large hole in the prop,my guess ,or out of balanceprops.prop should fit on the shat without any side play at all.if there is vibration will occur as you cannot tighten the prop centered.

............sound to me with the 3b prop you were getting a vibration problem,specially if you could see the prop hub move,............
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The prop hub vibration only occurs when throttling up through a specific rpm. Once it goes past that point, about 1/4-1/3 throttle, the vibration stops. It is also doing it on all 4 engines just the same. I'm hoping that the 9x5 two blades will cure that. Either the 3 blades are slightly out of balance, or the slightly larger prop hole is causing the problem. How that is leading to an engine out I don't know, but it will eventually cause problems in any event. The actual dfference in the hole and prop shaft is very small. I don't even think I could get a shim in it.
It is the Stafford B-24. I didn't put the tanks in behind the firewall like the plans showed. The tanks for the two inboard engines are in the fuselage, fuel lines routed out through the wing. The outboard nacelles had enough room underneath to get a Slimline 4oz tank in-BARELY! I have hatch accesses in the bottom of all 4 nacelles to access throttle servos, etc., and the tanks on the outboard engines.
The catch 22 to all this it that I had 4 near perfect flights on it with no engine problems. I'm still leaning toward the fuel foaming thing due to how tight the #1 tank was installed. I guess the next flight will tell.
Won't get a chance to check it tomorrow, also got some work to do on the retracts.
Randy

have you changed or inspected the plug?I have had bad plugs that glowed but would cause the engine to die,either from the coil deforming or from a clear deposit on the element itself that would not alloww the catlytitac action between the platnium and the alchohol cause compustion.i misse if this was the same engine dying each time or different,if the same this could be a simple solution.

...................have you changed or inspected the plug?
==========
No, haven't changed the plug. In fact, I hadn't even considered it till you mentioned it, but should have. Fact is, glow plug trouble has been so rare for me that it just slipped my mind. Sure would be a cheap fix anyway. I currently have 16 O.S. engines in 7 different planes, and I can't remembr the last time I changed a glow plug! The first failure occured about 3 minutes into the flight and 3/4 throttle, and the second one ocurred within about 10 seconds after lift off at full throttle.
As far as pre-flight testing, I start each engine individually, perform the vertical test, shut it down and do the same for the other 3. I don't even put a tach on them, but listen. Then I start up all four, vertical test again to see if they sound OK, and fly. On subsequent flights, I usually just start all 4 and do a vertical test. I don't go so much for trying to get them all running together as much as having them all running at a setting each one is happy with. The plane has plenty of power as it is, and there is little point in trying to get the last ounce of power out of the engine by leaning it out.
Randy
P.S. I'll be offline for the next 6 days due to vacation. (isn't hot enough here at 90Ëš+ today, we're going to Vegas!!)
Randy

I found that OS engines run well on the #8 plug. Also make sure the lower cowl has a large enough air exit hole. Have fun in Vegas,, Jim

Cranked the engines on the flight table and sat the airplane on the ground yesterday. Just as the wheels touched the ground a barely perceptible change was heard in one of the engines. Put the airplane on the table and retuned the engine. The engine shut down during the next flight.

Removed the needle holder and under very close inspection a floater smaller than a human hair was found. I missed finding the floater during the last eight troublesome flights.

I don’t change glow plugs either but recently solved a problem with a very difficult to tune engine by going to a hotter plug. I had been working on the engine almost daily since May 15. Could have overhauled my car engine two times over. Very embarrassing.

Bill