Hand Propping a Rotax 912

Capt. Geoffrey Thorpe

Capt. Geoffrey Thorpe

Touchdown! Greaser!
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Jun 7, 2008
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Light and Sporty Guy
Dan Thomas said:
Because the only commonality between the 503 and 912 is the name on the engine. The 912 is a four-stroke, the 503 a two-stroke.
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So, I'll put this in a new thread.

CT4ME said:
Capt. Geoff...
Your posting is just about the only thing I've found that said it can be done. Do you have a 100HP? Please set the record straight and post a video. Quite frankly, I WANT to see it can be done, as the thought of being stranded on a small dirt 'strip on the Baja has always haunted me.
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OK, I said it would be a couple weeks, but after I got home I decided I was having a "**** it, I'm going to the airport" day.

So, here it is. Hand propping a Rotax 912 UL - 80 hp, no slipper clutch. If anyone has a 100 HP with the clutch, bring it by.

 
Bravo! Now for that 100 horse! Thanks for setting the record straight...
 
Pilots know only what they know. They have no idea what they don't know. We see this over and over again.

Thank you Geoffrey.
 
:rofl::rofl::rofl:

I like the chocks. Do you use a tow hook for your tail tiedown?
 
I think his video is proof positive why a 912 should NOT be hand propped. ;)
 
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bbchien said:
Pilots know only what they know. They have no idea what they don't know. We see this over and over again.

Thank you Geoffrey.
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What I do know is Rotax, the manufacturer of the engine advises NOT to hand prop any 912.

When a drug manufacturer tell you as a DR that 12cc of their drug in a 200 pound adult is a lethal dose do you give them 12cc and hope for the best? :dunno:

Manufacturers have recommendations for using their product safely. This video demonstrates why it should not be ignored.

Upon starting the engine (according to the manufacturer) a Rotax 912 should be immediately given enough throttle run smoothly to avoid the clunking sound heard in this video. What you are hearing it the gear box clattering ( no slipper clutch) due to prop inertia, gear box drag, and low rpm.

Capt. Ron when was the last time you have the gear box inspected? For your engine I believe it is every 100 hours ( no slipper clutch)
 
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jnmeade said:
Rotax documentation citation, please?
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So based on your vast experience in flying, maintaining, and operating Rotax engines you are recommending hand starting a Rotax engine as described in the video and will defend any law suit resulting from injury or damage to the engine, or damage to the aircraft, or damage to surround hangars, planes or people?

Look up the operating instructions yourself, nothing about hand propping. :no:
 
Geico,
I think you missed the point....this started as a discussion on WHETHER a 912 COULD be hand propped. I, like most everybody, thought it couldn't, and repeated it as a fact. Geoff only set the record straight. I haven't seen anywhere where he has advocated anyone do this as a matter of normal operation. In fact, the video gives some great safety points and reminds us how potentially dangerous hand propping can be...
It's odd that there is so little, if any, legitimate information about this topic. What's out there seems to be mostly lore.
 
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Henning said:
:rofl::rofl::rofl:

I like the chocks. Do you use a tow hook for your tail tiedown?
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No need. I normally just use the starter.

But I can run a line through a handle welded to a longeron and tie it to the strut so I can get in before I untie anything.
 
Geico266 said:
So based on your vast experience in flying, maintaining, and operating Rotax engines you are recommending hand starting a Rotax engine as described in the video and will defend any law suit resulting from injury or damage to the engine, or damage to the aircraft, or damage to surround hangars, planes or people?

Look up the operating instructions yourself, nothing about hand propping. :no:
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Seems to me to be quite a leap to say that the manufacturer says "don't handprop" based only on the absence of handpropping instructions in a POH. Either ROTAX specifically prohibits (or recommends against) handpropping or it doesn't. Which is it?
 
Capt. Geoffrey Thorpe said:
You win.
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If we used the plane much I would have built a trebuchet starter for it.:D As it was it only got used in rushes. Wasn't too bad if you set it out in the sun or point heat on it to get warm, warm oil is a good thing when hand propping, 180* cylinders fire very well too. Sit there and prime the hell out of it with the wobble pump, can't put too much fuel in it. You,ll never flood the top cylinders and they will fire and carry it through to fire, just keep on pumping like crazy till all 9 are firing and the engine pump can do the job.:rofl: You want to pull through 6 blades with the mags cold to get some fuel distributed around and it would usually fire on the first pull with the mags hot. Same technique as with a starter really, you just don't have a guy out there turning it so you don't have the luxury of doing it all over again because you A: didn't prime enough, or B: didn't keep pumping hard enough to keep the top cylinders running. They are big engines and need a lot of fuel to start. If you can't work the pump right, the guy working the prop ain't gonna be pleased...:no::lol:
 
Geico266 said:
So based on your vast experience in flying, maintaining, and operating Rotax engines you are recommending hand starting a Rotax engine as described in the video and will defend any law suit resulting from injury or damage to the engine, or damage to the aircraft, or damage to surround hangars, planes or people?

Look up the operating instructions yourself, nothing about hand propping. :no:
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I don't understand what my experience flying, maintaining or operating Rotax engines has to do with this discussion. BTW, you missed schools covering Rotax.

I looked up the Rotax Operating Instructions and found no mention of hand propping before I politely asked you for the citation upon which you based your statements.

As you point out, I found no mention of hand propping. I take it that your failure to find a Rotax position on hand propping constitutes the basis for your assertion that it is unsafe and unapproved by Rotax. Thanks for clarifying your position.
 
What is the max potential cost to overhaul and or replace if you find it bad? Is the unit on the 914 more or less onerous?
 
Getting off topic... but... Re: Gear Box inspection... 600 Hour inspection for No clutch or if it has run mostly 100LL, otherwise it's 1,000 hours. Inspection runs $200-$600, but depends on: removed from plane or not, 80HP/100HP, Clutch/No.Clutch, 100LL use, shims/washer/seals needed. Clutch work requires it be sent to one of three service centers.
My Rotax guy says my 912ULS will cost about $3-400 max with parts, when done as part of Annual, when it's time.
 
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Henning said:
What is the max potential cost to overhaul and or replace if you find it bad? Is the unit on the 914 more or less onerous?
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The gear box can generally, always be rebuilt. What wears is the spring "conical" washers. There needs to be a certain amount of spring tension "pre loading" to minimize the effects of propeller inertia.

Cost to remove and replace, inspect and replace the washers as needed is around $300.

Capt. Ron, you are correct about the 600 hours. When I started flying 912's 15 years ago we had a 200 hour inspection time on engines without slipper clutches. :eek: I got pretty good taking the gear box off. :D
 
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I'd like a Kitfox on amphibs with a 914, although 100hp 912 for now...?
 
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