Damaging an engine by turning the prop backwards

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Panama Jack
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Re: Damaging an engine by turning the prop backwards

Post by Panama Jack »

With a lot of small aircraft now being powered by Rotax 9 series engines (912, 914, 915), I think it is important to point out that the manufacturer specifically states that its engines should not turned opposite direction.
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corethatthermal
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Re: Damaging an engine by turning the prop backwards

Post by corethatthermal »

I pull my prop through in the forward direction. I also do mag checks, so I know I won't have a live mag
Yesterday. I swore the mag check worked, today im in the hospital LOL I always treat the engine as live and do prop starts from behind!
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pelmet
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Re: Damaging an engine by turning the prop backwards

Post by pelmet »

Panama Jack wrote: Thu Jun 13, 2019 7:52 am With a lot of small aircraft now being powered by Rotax 9 series engines (912, 914, 915), I think it is important to point out that the manufacturer specifically states that its engines should not turned opposite direction.
Thanks. From the point of view of preventing an accidental start, it won't happen anyways when pulling it through in the forward direction at normal or even more than normal speed(unless you really pull it through super fast). Thank goodness as this is standard for every pre-flight when 'burping' the engine. The worst one I had to deal with require more than a hundred pulls to get a gurgle. Not fun on a hot day and a bit embarrassing too with restaurant people wondering what you are doing.
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AirFrame
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Re: Damaging an engine by turning the prop backwards

Post by AirFrame »

Jungle Jim wrote: Thu Jun 13, 2019 6:09 amMy logic in this is that it is better to have the oil pump gears pushing oil into the engine in the normal direction as opposed to having the oil sucked out, like it would if the prop were turned backwards.
You can't generate enough suction in your oil pump, turning it a few blades in either direction by hand, to move a noticeable amount of oil.
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trey kule
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Re: Damaging an engine by turning the prop backwards

Post by trey kule »

Free turbines spin the prop the wrong way all the time on windy day.....
There is no lubrication going on at that point. As someone else mentioned it is not a good thing.

When you typically start a free turbine, you will almost immediately get oil pressure...before introducing fuel and starting...it is why we check to see we are getting oil pressure before moving the condition lever to low.

It is also why there are prop locks ( the stringy kind) that stop the windmilling. As used regularly by professional pilots.
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goingnowherefast
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Re: Damaging an engine by turning the prop backwards

Post by goingnowherefast »

How do you stop the prop from wind milling between removing the tie and hitting the starter? Wind milling (backwards) for 5 or 10 minutes while boarding won't hurt a PT6 or PW100 series. 15 hours of day long neglect isn't good.
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Re: Damaging an engine by turning the prop backwards

Post by trey kule »

Gosh...seems to me , if wind is an issue, you could take them off right after the pax are on board while they are getting seated . It is not a common problem.
I even seem to recall some crews doing this.
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goingnowherefast
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Re: Damaging an engine by turning the prop backwards

Post by goingnowherefast »

I'll let the Encore crew know next time I see them at the airport on a windy day and #2 is wind milling for 15 minutes.

Point being, don't get your knickers in a knot for short durations, it'll be fine.
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Rowdy
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Re: Damaging an engine by turning the prop backwards

Post by Rowdy »

How come we only tie the left prop on the Dash and Q400?.. One word and it starts with P.

There is enough oil sitting in the gearbox for ample lubrication of everything while it slowly turns at a couple of revolutions per minute if left untied.

Interesting how a question posted about piston engines being turned backwards turns into a rant about PT6's and PW's. The joys of Avcanada I guess...
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Re: Damaging an engine by turning the prop backwards

Post by Panama Jack »

pelmet wrote: Fri Jun 21, 2019 6:20 am
Panama Jack wrote: Thu Jun 13, 2019 7:52 am With a lot of small aircraft now being powered by Rotax 9 series engines (912, 914, 915), I think it is important to point out that the manufacturer specifically states that its engines should not turned opposite direction.
Thanks. From the point of view of preventing an accidental start, it won't happen anyways when pulling it through in the forward direction at normal or even more than normal speed(unless you really pull it through super fast). Thank goodness as this is standard for every pre-flight when 'burping' the engine. The worst one I had to deal with require more than a hundred pulls to get a gurgle. Not fun on a hot day and a bit embarrassing too with restaurant people wondering what you are doing.

Thanks Pelmet. Recently viewed this interesting video which debunked something I had heard earlier about it not being possible to prop a Rotax 912.

https://youtu.be/-JUBrHYsh4E


He makes it clear that the 912 mags don’t have impulse coupling like your garden variety Continentals and Lycomings and from a safety aspect that is probably a good thing, especially since burping the engine is a standard procedure for checking the oil level.
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pelmet
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Re: Damaging an engine by turning the prop backwards

Post by pelmet »

Panama Jack wrote: Sat Sep 07, 2019 12:30 am
pelmet wrote: Fri Jun 21, 2019 6:20 am
Panama Jack wrote: Thu Jun 13, 2019 7:52 am With a lot of small aircraft now being powered by Rotax 9 series engines (912, 914, 915), I think it is important to point out that the manufacturer specifically states that its engines should not turned opposite direction.
Thanks. From the point of view of preventing an accidental start, it won't happen anyways when pulling it through in the forward direction at normal or even more than normal speed(unless you really pull it through super fast). Thank goodness as this is standard for every pre-flight when 'burping' the engine. The worst one I had to deal with require more than a hundred pulls to get a gurgle. Not fun on a hot day and a bit embarrassing too with restaurant people wondering what you are doing.

Thanks Pelmet. Recently viewed this interesting video which debunked something I had heard earlier about it not being possible to prop a Rotax 912.

https://youtu.be/-JUBrHYsh4E


He makes it clear that the 912 mags don’t have impulse coupling like your garden variety Continentals and Lycomings and from a safety aspect that is probably a good thing, especially since burping the engine is a standard procedure for checking the oil level.
They are interesting engines and quite different so I made extensive personal notes for myself taking bits of information from a variety of websites.
You mention about mags but it is important to understand that the Rotax 4 stroke mags are different than the mags we are used to.....

From my notes(and therefore subject to possible error)….

"Most ignition systems used in piston aircraft are inductive discharge ignition (IDI) systems. IDI systems rely solely on the electric inductance at the coil to produce high-voltage electricity to the spark plugs as the magnetic field collapses when the current to the primary coil winding is disconnected (a disruptive discharge). This is the traditional magneto.

The Rotax 912 engine has a dual electronic ignition manufactured by Ducati which is a contactless solid-state capacitor discharge ignition system. While these ignition systems are referred to as magnetos, they are different than the traditional magneto. In a CDI(Capacitor Discharge Ignition) system, a charging circuit charges a high voltage capacitor, and at the instant of ignition the system stops charging the capacitor, allowing the capacitor to discharge its output to the ignition coil before reaching the spark plug.

Each of the two ignition systems is powered by independent, stationary charging(or generating) coils located on the ignition housing at the back of the engine. Magnets are rotated on a wheel on the crankshaft and induce current in two coils on the perimeter on left and right sides of the rear of the engine. These induced currents are fed to two capacitors that increase the potential and discharge a high voltage through the sparking plugs. The crankshaft-mounted flywheel rotates around the ignition housing. The permanent magnets mounted in the flywheel rotate about the 8 fixed generating coils(one for each spark plug). As they pass the coils, each magnet induces a voltage in the coil as its magnetic field cuts through the coil.

Aside from the flywheel, which is mounted directly to the crankshaft, there are no moving parts to wear out in this ignition system: no gears, belts, seals, or bearings. The lack of moving parts is far more reliable and efficient. "
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co-joe
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Re: Damaging an engine by turning the prop backwards

Post by co-joe »

Rowdy wrote: Sat Jun 22, 2019 7:12 pm How come we only tie the left prop on the Dash and Q400?.. One word and it starts with P.

...
Piss Poor Performance? :lol:

Couldn't resist.

I was told by an AMA that the issue with turning the prop the wrong way on PT6's, was on the old style prop heat, the brushes could be damaged, but that with the newer style there's no problem.
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Rowdy
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Re: Damaging an engine by turning the prop backwards

Post by Rowdy »

co-joe wrote: Mon Sep 09, 2019 8:37 am
Rowdy wrote: Sat Jun 22, 2019 7:12 pm How come we only tie the left prop on the Dash and Q400?.. One word and it starts with P.

...
Piss Poor Performance? :lol:

Couldn't resist.

I was told by an AMA that the issue with turning the prop the wrong way on PT6's, was on the old style prop heat, the brushes could be damaged, but that with the newer style there's no problem.
:lol: Passengers!
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co-joe
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Re: Damaging an engine by turning the prop backwards

Post by co-joe »

Oh those? Yeah I forgot about them. :lol:
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