TT50 flameout

[wnor]

My TT50 in a Raptor 50v2 (purchased 2 months ago) quit without warning during an inverted hover (miraculously, an inverted auto into long, damp grass did no damage). Sundry facts are as follows. Have I missed anything?

Total number of flights: 46
Fuel: Red Max 10% Heli bought from factory 3 weeks ago
Glowplug: Enya 3; 10 flights on this plug; plug was seated in head (not loose)
Low, mid, and high mixtures all seem fine – engine was singing a nice, steady song with normal smoke in a prolonged inverted hover immediately before stopping
All fuel tubing including clunk line replaced 3 weeks and 10 flights ago (Pink Prather; Aerotrend blue on clunk)
Main tank was half empty, header tank was full
Fuel filter just upstream of engine is clear of debris
No visible debris in carb after removing main needle
Tear down of engine shows no damage and a nice, normal light tan color on the piston's top
Engine bearings seem fine
Muffler seal is intact, and tank pressurization line is not occluded
Carb is well seated on the body of the engine; o-ring is intact
Throttle linkage is intact; throttle servo functions fine; no glitching observed (PCM radio with fail-safe set to drop throttle back to a fast idle); noone else at the field at the time
Transmitter and receiver voltages normal

A very close inspection of the element in the glow plug shows that it is intact. The element shows normal wear except that a fair amount of caramelized material has accumulated at the junction of the element and the body of the plug. Almost all of the flying I have done lately has been in a hover (learning inverted hovering) – no full-throttle stuff at all.

I plan to replace the engine bearings even though they look fine. I also plan to try an OS8 plug rather than another Enya 3. Should I switch fuels? Any other suggestions?

[DavidH]

Sounds to me that Murphy paid you a visit is all that happened.
Murphy is well known for visiting helicopters when least expected.

As for the fuel, 10% nitro is a little low for heli fuel. But don't think the fuel is what caused your flame out. Thou most pilots I am around do refer to it as Rust Max.

David

[flyinfool]

The only things that I can think of off hand are;

Did it go into battery failsafe which should drop the throttle?
Do you have Battery failsafe set or is it default?
Did you check RX voltage under load?
Air leaks in the fuel filter and or line from clunk to engine (even though fairly new).

[R-4-L]

if there's an air leak i would think the engine would lean out and will be screaming.. just a thought i don't know

[wnor]

Yesterday I bench tested the engine discussed in the first post of this thread. As always, this was an interesting exercise, and some day I will learn to do it with every new or rebuilt engine. Conditions were:

TT50 engine, 71 flights, stock carburetor with no needle modifications
Byron 15% nitro Premium Sport Traditional fuel, 20% total oil, castor and synthetic blend
(the switch from Red Max to Byron fuel resulted in totally different, infinitely better engine behavior)
32 degrees F, dewpoint 5 degrees F, sealevel
New Enya #3 plug
Top Flight Power Point 11x7 prop
Stock muffler

The engine ran very well across an rpm range from dead slow to pulling like a horse (sorry, I do not have rpm measurements). Final optimal needle setting: High-speed: 2 7/8 turns open, Low-speed: 4 3/4 turns open from completely closed throttle. The really interesting part was the behavior of the engine lean of peak: RPM peaked at 2 3/4 turns open, sagged very slightly over the next few clicks, then abruptly died at 2 5/8 turns open. Prior to dying, the engine gave very little warning of a lean run. What I learned from this is to be very careful when exploring the lean side of things with this engine - unless I want to do some more practice with full-down inverted autorotations.

[SteveL]

That Castor will make a real mess of your heli and engine. I know I am the second one comenting on your fuel. Anyway it is just an FYI.