Swinging it
Joined: Jul 2010
Posts: 2,807
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From: Ansião (PT)
FWIW: before cold starting a Rotax 4-stroker, I was taught to check the oil level by opening the reservoir, then rotating the prop by hand until hearing from the reservoir a noise like flushing the loo, then apply the dipstick. But other pupils started the engine for a minute, then stopped it to check. Not sure which is best, likely it is the most troublesome...
When hand-turning the prop, it has to be done counterclockwise (as one looks at it) otherwise air might be sucked into the oil circuit. That's to say, if my dusty memory is to be trusted.
When hand-turning the prop, it has to be done counterclockwise (as one looks at it) otherwise air might be sucked into the oil circuit. That's to say, if my dusty memory is to be trusted.
Joined: Jan 2004
Posts: 5,658
Likes: 501
From: Canada
As was stated above, unless the engine has a starter with a slipping clutch all radials must be pulled through to ensure that there is no oil in the lower cylinders which would cause a hydraulic lock. When doing this by hand one should always go gently and stop at the first sign of resistance. On the smaller radials like the YAK's MP14, you can exert enough force to damage a hydraulically locked engine, especially if you are pulling on the end of the blade and therefore have lots of leverage.
Another occasion for pulling through an engine is if the starter is very weak. Pulling through will limber the engine making the starter's job a bit easier especially if its cold. You can also hasten the start by prestart priming. For example on a simple carburated 4 cylinder (cold), give it a 1/2 shot of prime turn the prop 1/2 a rev, and repeat 3 more times add one last 1/2 shot and hit the starter, the engine will immediately start everytime. Obviously you will have the mags off when pulling through, but you still consider the prop hot and take appropariate precautions.
Another occasion for pulling through an engine is if the starter is very weak. Pulling through will limber the engine making the starter's job a bit easier especially if its cold. You can also hasten the start by prestart priming. For example on a simple carburated 4 cylinder (cold), give it a 1/2 shot of prime turn the prop 1/2 a rev, and repeat 3 more times add one last 1/2 shot and hit the starter, the engine will immediately start everytime. Obviously you will have the mags off when pulling through, but you still consider the prop hot and take appropariate precautions.
Fleet Manager
Joined: Aug 2006
Aviation Qualifications: CPL
Posts: 7,089
Likes: 2,952
From: Ontario, Canada
Obviously you will have the mags off when pulling through, but you still consider the prop hot and take appropariate precautions.
With all of the chatter here about the need, or at least benefit, of pulling the engine through proir to start, lets not overlook a very real hazard. The only time I have ever damaged an aircraft was during an unexpected start during pulling through. Unsafe and embarrassing!
On another occaion (different plane) I was hand starting for a trusted friend. I called "mags off", he called "mags off". I pulled the prop through. The engine started, and ran. I glared at him through the running propeller, so as to convey my unhappiness about his error in ignition selection. To convince me he had not made an error, he held up the keys, which I saw through the windshield, and turning propeller. Failed key switch.
EVERY time you put your hand on the prop, you should be ready for the engine to start, both in propeller clearance, and aircraft restraint. If you have ANY doubt about swinging a prop safely, don't do it!
That said, during winter starts, and particularly when a preheat is not possible, I very certainly "limber up" and prime an engine by hand - as long as the aircraft is restrained, and I have satisfied myself with a prior live mag check.
Joined: Nov 2002
Posts: 52
Likes: 0
From: Darkest Midlands
So how did they check / clear hydraulic locks on Stirlings, Sunderlands et al? Just interested.....
IN CASES OF EMERGENCY, DC3 ENGINES CAN BE ‘ROPE STARTED’, SHOULD THE
STARTER MOTOR BE INOPERATIVE. IN CARRYING OUT THIS OPERATION, IT IS
ESSENTIAL TO PAY PARTICULAR ATTENTION TO SAFETY AND PROCEDURE AND ALWAYS
START THE ENGINE TO BE ROPE STARTED, FIRST. IN ADDITION, A CHECK SHOULD
BE MADE THROUGH THE OPERATIONS OFFICE TO ENSURE THAT NO OPERATIONAL
ALTERNATIVE IS POSSIBLE.
PROCEDURE:- WITH THE APPROVED ROPE SLING ON HAND, PROCEED AS FOLLOWS:--
A) CHECK THAT IGNITION SWITCHES ARE 'OFF' AND MIXTURE CONTROL IN IDLE
CUT-OFF,
B) THE ENGINE TO BE STARTED SHOULD BE TURNED OVER BY HAND, FOR FOUR AND
A HALF COMPLETE TURNS (14 BLADES), TO CHECK FOR HYDRAULICING
C) PRIME ENGINE.
1) IGNITION OFF (2) MIXTURE IDLE CUT-OFF
3) THROTTLE SET (1/2 INCH ON GATE) (4) BOOSTER PUMP ON
5) WHILE THE ENGINE IS BEING TURNED BY HAND, GIVE PRIMING IN ONE SECOND
BURSTS (FOUR FOR HOT AND UP TO, PERHAPS, FOURTEEN FOR COLD ENGINE)
6) BOOSTER PUMP OFF.
D) FIT ROPE SLING. PLACE END BOOT OVER ONE BLADE TIP AND ROTATE ENGINE
BACK WARDS UNTIL THE FOLLOWING BLADE IS AT THE EIGHT O'CLOCK POSITION
AND THEN PLACE SECOND BOOT OVER THE TIP ENSURING THAT :-
A) BOOTS CENTRALLY POSITIONED AROUND BLADE TIPS.
B) ROPES PARALLELED (NO TWISTS)
c) RUBBER SLEEVE (1) LOCATED FIRMLY AGAINST TRAILING EDGE
OF BLADE (B)
D) RUBBER SLEEVE (2) LOCATED ABOUT 2 FT. FROM LEADING EDGE
OF BLADE (B)
LAY OUT REST OF ROPE IN STRAIGHT LINE TOWARDS THE PORT OF THE AIRCRAFT.
YOU ARE NOW READY TO START, TO CHECK 'All CLEAR' DOOR SHUT, STEPS AWAY
ETC.
WITH THE PILOT IN THE COCKPIT, MAN THE ROPE WITH, PERHAPS, THREE PEOPLE
PLACED
COMFORTABLY HOLDING THE ROPE WITH A SLIGHT SAG IN THE MIDDLE,
THE PILOT NOW SWITCHES IGNITION 'ON', BOOSTER PUMP 'ON' AND, AT A GIVEN
SIGNAL THE ROPE 15 PULLED THROUGH WITH A JERK AND, IMMEDIATELY THE
ENGINE FIRES THE PILOT OPENS THE MIXTURE CONTROL AND FLICKS THE PRIMING
SWITCH IF NECESSARY.
SHOULD THE ENGINE NOT START ON FIRST PULL, REPEAT PROCEDURES FROM D)
ENSURING THE IGNITION SWITCHES ARE 'OFF' WHILE THE PROPELLER IS BEING
HANDLED.
CAUTION:- To AVOID POSSIBLE FLOODING ETC.; RETURN MIXTURE CONTROL TO
‘IDLE CUT-OFF’ AND SWITCH OFF BOOSTER, AS SOON AS IT IS REALIZED THAT
THE ENGINE HAS NOT STARTED.
Joined: Feb 2007
Posts: 4,598
Likes: 0
From: Amsterdam
FWIW: before cold starting a Rotax 4-stroker, I was taught to check the oil level by opening the reservoir, then rotating the prop by hand until hearing from the reservoir a noise like flushing the loo, then apply the dipstick. But other pupils started the engine for a minute, then stopped it to check. Not sure which is best, likely it is the most troublesome...
When hand-turning the prop, it has to be done counterclockwise (as one looks at it) otherwise air might be sucked into the oil circuit. That's to say, if my dusty memory is to be trusted.
When hand-turning the prop, it has to be done counterclockwise (as one looks at it) otherwise air might be sucked into the oil circuit. That's to say, if my dusty memory is to be trusted.
On the Rotax 4-stroke (912/914) there's a separate oil reservoir but there's no pump between the sump and this reservoir. Instead, blow-by from the cylinder gases past the piston rings provide pressure in the crankcase to push the oil into the reservoir.
To ensure that all oil has returned to the reservoir, so that you can take an accurate measurement of the oil level in there, you hand-turn the prop slowly (with the ignition off, obviously). The hissing sound is the piston blow-by, and the burbling sound means that all oil has been pushed back. What you're hearing is the crankcase air burbling in the oil reservoir.
Starting the engine for a few seconds would work too, but only if you are absolutely sure that there's oil in the engine/reservoir to begin with. And that was the purpose of the pre-flight wasn't it?
Joined: Aug 2007
Posts: 74
Likes: 0
From: Southern England
Joined: Oct 2009
Posts: 50
Likes: 0
From: Northamptonshire
As well as checking for hydraulic lock and then for sucking in fuel it has the added benifit of priming the engine with oil if it has not been run for a while, also it give's you the chance to manually asess what the compression's feel like and if they are fairly even.
Austerwobbler
" no starter, suck in fuel by hand every time by hand"
Austerwobbler
" no starter, suck in fuel by hand every time by hand"
