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Spin. Engine quits. Why?

Marabou

Member
I tried long spin in my 7A recently. After 3 or 4 turns at idle RPM slowly drops and approximately at seventh turn engine quits. My impression that spin at idle and lost engine are different. At least delay with recovery is much longer when prop stopped. I tried 4 times with the same result. I wonder why engine quits in a first place. I keep Mogas in one tank and Avgas in other. Both filled less than half for aerobatics. First I thought Mogas is to blame. I switched to Avgas with exactly same outcome. Next idea was that centrifugal force pushes gas out of intake. Once right at the moment when the engine was just about to stop I pushed throttle a little bit forward. I did not expect any reaction but it worked like in straight and level flight. I finished my 10 turns with engine running.
Next I tried to enter spin at 1000 RPM rather than at idle. I liked it. Engine kept 1000 RPM thru entire 10 turns. Recovery is faster and more predictable that at idle. So there are two important questions: why engine quits and is there any danger to enter spin at RPM a bit higher that idle? Engine is injected 360M1B.
Thanks in advance for help.
Sorry for poor English. I am from third world. We don?t waist too much money for stupid and useless things like education))
Here is a link to stopped engine: https://www.youtube.com/watch?v=FIOWtnijlSA
 
Zdravstvuyte Ruslan!

Your problem is obviously a fuel starvation issue and my first thought as I was reading your post, was that you had a carbureted engine. You mention towards the end of the post that the engine is fuel injected though.

One thought might be your fuel pickup tube or flop tube. Vans put out several service bulletins in the past concerning these coming loose inside the fuel tank. You might look into weather those SBs were complied with, not knowing of course how old your airplane is or if you built it or not.

Then, possibly a problem somewhere in your fuel injection system, where you're not able to maintain adequate fuel pressure through the injectors at very low rpm.
 
A nose down attitude and the centrifugal (yeah, I know) force from the spin may be moving fuel away from the pickups. The lower the fuel level, the bigger impact these factors would have.
 
Anybody else doing 7-10 turns? (!) Video pretty dramatic even without the engine stopping.
 
By adding power, even 1000 RPM's, you raise the nose slightly. This may be enough to keep from unporting the fuel puckups.

Just a guess.
 
By adding power, even 1000 RPM's, you raise the nose slightly. This may be enough to keep from unporting the fuel puckups.

Just a guess.

Nah, adding power only raises the nose when spinning left. Spinning right, it's a nose down effect. In any case, flattening the spin reduces the roll component of the spin and increases the yaw component. The yaw component is what's driving fuel outboard away from the fuel pickups.

And regarding an earlier post, carbs are are not impacted by spins. It's all about the G load for them. Upright spins are always positive G load, so the carb will keep feeding fuel.
 
I did the same thing once (ONCE) in a Citabria. (upper wings & gravity feed).
I voted for the centripetal force keeping the fuel mixture going up the Lycoming vertical induction. Added just a bit more RPM on the next one, and worked fine.

BTW, DONT dive down after going dead stick to get the prop turning. Doesnt work, and lose that valuable altitude.
 
Restart

I did the same thing once (ONCE) in a Citabria. (upper wings & gravity feed).
I voted for the centripetal force keeping the fuel mixture going up the Lycoming vertical induction. Added just a bit more RPM on the next one, and worked fine.

BTW, DONT dive down after going dead stick to get the prop turning. Doesnt work, and lose that valuable altitude.
Depends on the airplane compression ratio and prop. Cassutt with a wood prop restarts at around warp factor 8.
 
Restart

Thanks to all for answers. About restart. It restarts just well at about 110 knots. Of cource if remaining altitude allows.
 
Here is a video of a 47 turn (I think ...) spin:

http://www.spatscheck.com/oliver/Spin.mp4

the engine quits because fuel gets pushed to the outside of the tank so the engine starves. Prop stops turning couple of turns later because there is little airflow over the fuselage (in the correct direction that is).

Starts right back up after the prop starts spinning again. I was a bit surprised though how fast I had to get for the prop to start spinning on it's own. Didn't feel like using the starter as I wasn't sure it wouldn't damage something if I used it in flight at high speed and I had plenty of altitude to work with... .

Oliver
 
Wow Oliver...that made me dizzy just watching that.

Let's see....what did I do with that big zip lock bag....ugh! :eek:
 
Spin

For the first video the spin is significantly flatter than I would expect. Note a little outspin aileron at the start increasing slightly as the spin develops. Any significant outspin aileron(left stick in this case) will flatten the spin.
I think the disrupted induction airflow is the likely cause of engine stoppage.
 
I have a similar spin characteristics in my Giles G-200: the combination of a flattish spin and a lightweight prop may cause engine stoppage. I just add a tad of power after it breaks and this solves the mystery. It has nothing to do with the fuel starvation or a particular nose-down attitude. I've heard Extra-200 has similar behavior
 
Marabou,

What altitude are you doing your spins at and where is your mixture set? In the beginning my engine was quitting also. When doing spins from 5000? or higher, I finally figured out that my mixture was too rich at altitude when I pulled the throttle to idle. After doing a full throttle climb with the mixture full rich, I began to lean the mixture after pulling the throttle to idle. The engine stopped quitting after adopting this technique.

Also, in competition aerobatics, a commonly used technique is to go to full throttle before rotation stops to increase airflow over the vertical stabilizer and rudder. This helps stop the spin on an exact heading.

Good luck!
 
Marabou,

What altitude are you doing your spins at and where is your mixture set? In the beginning my engine was quitting also. When doing spins from 5000? or higher, I finally figured out that my mixture was too rich at altitude when I pulled the throttle to idle. After doing a full throttle climb with the mixture full rich, I began to lean the mixture after pulling the throttle to idle. The engine stopped quitting after adopting this technique.

Also, in competition aerobatics, a commonly used technique is to go to full throttle before rotation stops to increase airflow over the vertical stabilizer and rudder. This helps stop the spin on an exact heading.

Good luck!

I start at about 6000. 10 turns later I still have at least 3500. And I always lean even at lower altitudes and even while climbing if CHT allows.

My main question is regarding your advice to go to full throttle before rotation stops. I?ve got some flat spin training with three different instructors in other ?a bit more aerobatic? aircraft then RV. One way to enter flat spin I learned is just go to full throttle right after you entered regular spin. Plane immediately raises the nose and here you are. I tried it in RV but did not succeed. Actually I couldn?t induce flat spin at all using any technique. Possibility of flat in RV had been discussed here earlier. My guess it is nearly impossible at least very difficult due to nose heavy nature of RV. A few hundreds of pounds behind the back will definitely help but go flat is not the goal. It just would be nice to know how safe it is to apply full throttle at recovery.
 
I have a similar spin characteristics in my Giles G-200: the combination of a flattish spin and a lightweight prop may cause engine stoppage. I just add a tad of power after it breaks and this solves the mystery. It has nothing to do with the fuel starvation or a particular nose-down attitude. I've heard Extra-200 has similar behavior

Now you got me intrigued. I was pretty sure it was fuel going to the outside as I can reproduce the same effect if I do 6-8 rolls in a row (compared to the airplanes you mention I don't have inverted fuel). Guess I have to go flying again and try this ... .

Oliver
 
Here is a video of a 47 turn (I think ...) spin:

http://www.spatscheck.com/oliver/Spin.mp4

the engine quits because fuel gets pushed to the outside of the tank so the engine starves. Prop stops turning couple of turns later because there is little airflow over the fuselage (in the correct direction that is).

Starts right back up after the prop starts spinning again. I was a bit surprised though how fast I had to get for the prop to start spinning on it's own. Didn't feel like using the starter as I wasn't sure it wouldn't damage something if I used it in flight at high speed and I had plenty of altitude to work with... .

Oliver
Nice video Oliver! Haven?t seen it before. You rotate to the left. I carefully measured rate of rotation to the left and to the right. In my case it is 1,7 seconds to the right and almost 2 seconds to the left. And altitude loss is higher spinning to the left than to the right for the same quantity of turns. But I measured it with prop still spinning. May be there is no difference once prop had stopped.
 
Nice video Oliver! Haven?t seen it before. You rotate to the left. I carefully measured rate of rotation to the left and to the right. In my case it is 1,7 seconds to the right and almost 2 seconds to the left. And altitude loss is higher spinning to the left than to the right for the same quantity of turns. But I measured it with prop still spinning. May be there is no difference once prop had stopped.

Good question. I never measured it that precisely. It does seem that spin entry to the right is quit a bit slower but I never timed that precisely either.

Oliver
 
... I was pretty sure it was fuel going to the outside ... .
Oliver

Not likely in my case. My spins are actually slower than the rolls and I have a header tank with a fresh flop tube in it. My impression is that it's caused by a funny airflow around the prop in the spin. Tail slides are also known for making the engine stop for the same reason.
 
In Marabou's video, it is pretty remarkable how quickly a uniform, fully developed spin developed. Maybe 2-- 2.5 turns, and no nose bobbing from the spin axis being inclined.

Oh and Marabou, your english is fine.
 
My main question is regarding your advice to go to full throttle before rotation stops. I’ve got some flat spin training with three different instructors in other “a bit more aerobatic” aircraft then RV. One way to enter flat spin I learned is just go to full throttle right after you entered regular spin. Plane immediately raises the nose and here you are. I tried it in RV but did not succeed. Actually I couldn’t induce flat spin at all using any technique. Possibility of flat in RV had been discussed here earlier. My guess it is nearly impossible at least very difficult due to nose heavy nature of RV.

Yeah, full throttle applied in conjunction with the recovery rudder can help stop competition spins more crisply. No need to do this with recreational spins unless you just want to see how your plane responds.

Regarding flat spins, I assume you know they only really work when spinning left, assuming a Lycoming motor. I never tried one in my old RV-3, but I've seen video of an RV-7 doing a nice looking flat spin like any other aerobatic airplane would do. Once the left spin starts, you apply full right aileron and full power, keeping the stick back. In most aerobatic airplanes, unloading the aft stick just a little will stabilize and accelerate it slightly. Be aware that high power flat spins apply high gyroscopic stress to the crank/flange...something to be aware of if you're running a metal prop and a light and/or hollow crank and do a million of these over and over. If not, don't worry about it.

I noticed you applied left aileron a few turns before recovery. Not sure if that was inadvertent, but you can see that it accelerated the spin slightly, and may have delayed recovery a little. Not exactly "proper" technique, but you seemed to have a handle on things and plenty of altitude, so no problem.

I've gone dead stick a number of times doing spins in the Pitts. In my case it was a low idle (light Catto prop) issue rather than a fuel issue. Not so much an issue with a metal prop due to flywheel effect. I got used to blipping the throttle as needed during spins and tail slides once I was able to start counting blades. With wings tanks, you can of course unport the fuel depending on fuel level.
 
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I noticed you applied left aileron a few turns before recovery. Not sure if that was inadvertent, but you can see that it accelerated the spin slightly, and may have delayed recovery a little. Not exactly "proper" technique, but you seemed to have a handle on things and plenty of altitude, so no problem.

.

I did it unintentionally. Caught myself several times making this mistake earlier but it happens sometimes again especially at recovery. It really feels like rotation is different if some aileron deflection is involved but according to my measurement rate of turn remains the same or within measurement error.
 
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