Normal for a 'bo to dump fuel during startup?

Jim K

Jim K

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Second leg pilot I met at osu this afternoon flies an F33A Bonanza. I watched him start it up, and it made all the familiar noises I hear in @Martin Pauly 's videos. I was a bit alarmed though when it starting puking fuel out the bottom of the cowl. It stopped when he (I assume) shut the boost pump off. It then spit out some more while he was cranking, but stopped when the engine took off. Is this normal behavior, or should I call and alert him to an issue? Seems a bit dangerous to leave a puddle of fuel right near the exhaust.

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NealRomeoGolf said:
Overprime?
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That's kind what I thought, but man it'd take a lot of gas to dump that much overboard. I wouldn't think you'd ever get it started. It did take a while to catch, and the engine went to pretty high rpm, so maybe it was just a massive overprime and then he had to open the throttle to get it to start.
 
WAY overprimed. The high-boost pump in the prime power setting from the POH shoves 16-18gph or so into the big engine contis, and it only takes a second or two. I've heard knuckleheads running that thing for 5, 6, more seconds, and I just cringe a bit. The sound of "pouring some 100LL out for my fallen vtail homies" follows a few seconds later, as depicted in your photo. :)
 
Likely overpriming that resulted in fuel running from the manifold drain line. That is a tube that runs from a low spot in the intake manifold, through a check valve, and down to the bottom of the cowl.
 
Interesting. I prime my io540 for 5s when cold, but the flow meter only shows like 3-4gpm. Of course I also don't get out and look. I knew lyco and conti used different fuel injection systems, but I wouldn't have expected that much of a difference in operation.

The guy said he's been flying that plane for 11 years I'm surprised he hasn't caught on yet. I think I'll text him and play dumb and ask about the fuel, and maybe he'll figure it out.
 
Jim K said:
Second leg pilot I met at osu this afternoon flies an F33A Bonanza. I watched him start it up, and it made all the familiar noises I hear in @Martin Pauly 's videos. I was a bit alarmed though when it starting puking fuel out the bottom of the cowl. It stopped when he (I assume) shut the boost pump off. It then spit out some more while he was cranking, but stopped when the engine took off. Is this normal behavior, or should I call and alert him to an issue? Seems a bit dangerous to leave a puddle of fuel right near the exhaust.

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Looks a lot like the 172SP (fuel injected) I saw a couple summers ago where the pilot was trying to hot start on a warm day.
 
The CSOBeech hot start guide says to run the fuel pump for 45+ seconds with the mixture at cut off. It looks like someone tried that and either didn’t have the mixture at cut off or has a problem with the mixture that is allowing fuel to flow at cut off.
 
Jim K said:
The guy said he's been flying that plane for 11 years I'm surprised he hasn't caught on yet. I think I'll text him and play dumb and ask about the fuel, and maybe he'll figure it out.
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Not everyone is mechanically minded and cares to understand what is happening and how to adjust their starting techniques. This even includes a fair amount of aircraft mechanics, who in my opinion should know better. If you’ve ever wondered why you see 100 responses with 100 different “techniques” on how to do a hot start, well you’ve seen why that happens now.
 
my tsio360 gives times for priming based on outside temps -but I followed that today and still saw fuel spilling out the overflow vent. Started it like a flooded start and all well- used a bit less prime on the other engine and started fine.
 
Some people do all big Continental starts as flooded starts.

You over prime, then throttle Full, Mixture ICO, crank until it fires, then do the hand dance to get the throttle back and the mixture to full rich. When I was flying my friend's IO-550 T-34, we did all starts that way. And doing formation clinics before Oshkosh and Sun n Fun, we would fly 6 - 8 flights a day, so lots of hot starts, and this worked every time.

But I would say that much fuel is a more than needed.
 
I use the flooded start thing on my IO-550 any time I suspect we're in the "hot start" regime. That's defined as the engine has been run and then has sat for medium amount of time (the time it takes to put gas in the plane is prime territory). It gives enough time for the fuel to vaporize in the lines. Some of the Navion guys open up their cowling doors while fueling to try to avoid that. If the engine is cold, I'll just run the boost pump up until I have pressure. If it's a very quick shutdown, I'll just crank and go.

One thing is for sure on the IO-5xx, is you don't use that HIGH BOOST except with great care. Seen engines fail because some fool tried to fly with that running.
 
flyingron said:
I use the flooded start thing on my IO-550 any time I suspect we're in the "hot start" regime. That's defined as the engine has been run and then has sat for medium amount of time (the time it takes to put gas in the plane is prime territory). It gives enough time for the fuel to vaporize in the lines. Some of the Navion guys open up their cowling doors while fueling to try to avoid that. If the engine is cold, I'll just run the boost pump up until I have pressure. If it's a very quick shutdown, I'll just crank and go.

One thing is for sure on the IO-5xx, is you don't use that HIGH BOOST except with great care. Seen engines fail because some fool tried to fly with that running.
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They will run on HIGH BOOST, but you need to pull the mixture back some when you hit the switch, else it insta-floods. I've ran high boost in the climb on a 550 more than once when "full rich" just wasn't "rich enough".

Anyhow. This guy could have avoided all of this if he would have just: Primed as normal. Throttle 100%. Start cranking. Smoothly pull throttle back while cranking until engine starts. Go flying.
 
I don’t have a Bonanza, but seen another small Beechcraft have a similar problem of “fuel spitting out into the ground when priming”. Incase it helps anyone else: the problem was a bad fuel pump (electric fuel pump, in this case for IO360 engine the pump was only used for priming not used in flight)
The pump was bypassing/dumping fuel onto the ground (at a startlingly fast rate) whenever it was run for priming before engine start. Rebuilding or replacing the electric fuel pump fixed the problem.
 
Checkout_my_Six said:
How many seconds was that pump running?o_O
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Good question. I would guess 5s or so, but I didn't start counting when I heard the pump start, so it's just a guess.
 
Pictures like this make me feel better about being me compared to everyone else here who HAS NEVER had an issue hot starting and has a perfect landing every time.
 
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Continentals have a manifold drain. Lycomings use a sniffel valve. They have to let excess fuel drain when the manifold isn’t pulling vacuum. Once a guy sees it (usually on video) he’ll usually change his priming routine.
 
I texted the gentleman and sent him that picture, and he thanked me for letting him know and that he'd talk to his mechanic about it. Hopefully that'll help help him sort out his priming assuming that's what it was. If we ever hook up on a flight together again I'll be interested to see if he has changed his procedure.
 
Jim K said:
It stopped when he (I assume) shut the boost pump off. It then spit out some more while he was cranking, but stopped when the engine took off. Is this normal behavior, or should I call and alert him to an issue?
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During the course of the annual, my mechanic just informed me that one of the boost fuel pumps on my twin was leaking. I had no idea. I never noticed unusual fuel usage on the one side so I assume it was only leaking when the pump was active? In any event the leaking boost fuel pump is being sent out for a rebuild. Timeframe is 3~4 weeks. Unfortunate but it is what it is.

@Jim K - Nice that you noticed the fuel on the ground and informed him. This way he can decide what he wants to do.
 
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Mongoose Aviator said:
During the course of the annual, my mechanic just informed me that my boost fuel pump on my twin was leaking. I had no idea. I never noticed unusual fuel usage on the one side so I assume it was only leaking when the pump was active? In any event it is being sent out for a rebuild. Timeframe is 3~4 weeks. Unfortunate but it is what it is.

@Jim K - Nice that you notice and informed him. This way he can decide what he wants to do.
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That drain from the pump on this aircraft is near the belly sump drain (probably not what we are seeing)....this was either from the sniffle valve (the drain for the intake) or the spider (fuel distribution connection on top of the engine).
 
Checkout_my_Six said:
Was there a back fire when he started?
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No, there wasn't. I was standing there thinking about going to get my fire extinguisher in case it lit off when the engine started. I suppose that as long as the engine kept running, there wouldn't have been enough fuel there to cause a hazard with the prop wash blowing it backward. My fear was a backfire like you mention lighting it off, and then the engine not starting, and the flames getting up into the cowl. It would've been tough evacuating 3 unfamiliar passengers, including a disabled little girl from the back seat.
 
Let's just say....I've seen the fire and it does burn out fairly quickly. :D
 
If you see me starting an engine over a puddle of gas, please do let me know. There are some embarrassing lessons we can figure out from the cockpit (e.g. forgot to pull chocks) but many that we will never learn if nobody tells us.
 
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