- Sudden Stoppage
- Hydraulic Lock Article
- V-530 Prop Blade Install & Settings
- Centrifugal Advanced Magneto
- Introduction to the M-14P
To add our experience on the “sudden stoppage” question, I offer the following with respect to M-14P engines and V-530 props:
While we have not sold hundreds of aircraft, since 1993 we have repaired more engines than anyone in the West, including complete teardowns. We are also certified by OKBM for repair and overhaul of the M-14P.
Let’s start by defining terms. A “prop strike” alone says nothing about forces experienced by the engine. A “sudden stoppage” defines a reduction in engine RPM from some external or internal cause. The rate of deceleration is the key to how much damage may have occurred. We have seen only four sources of stoppage:
- The engine had oil in a cylinder that did not compress with the air start turning the engine. This will usually result in a bent link rod. A teardown of the power section is necessary to check crank runout (necessary) and is perhaps the easiest way to change the link rod as any other way.To add our experience on the “sudden stoppage” question, I offer the following with respect to M-14P engines and V-530 props:
- The engine had oil in a cylinder or sucked it in from the intake tube and did not compress after the engine fired. The first thing to check, if the engine will turn, is the magneto timing. This tells if the accessory shaft is twisted. Next, a teardown of the power section. We usually find the crank rear counterweight has rotated on the bearing shaft. This is a quick, cheap fix. Continued rotation, however, results in broken teeth on the cam drive gear and cam idler gear. Broken teeth on the generator drive gear and damaged accessory shaft are very possible. A new link rod and probably a new cylinder will also be needed.
- A previously bent link rod fails in flight. The prop shaft will shear. In the worst case we have seen, there were two pistons in one cylinder. The entire engine will be trash.To add our experience on the “sudden stoppage” question, I offer the following with respect to M-14P engines and V-530 props:
- The rotating prop hits something. If you taxi into something solid like a fire hydrant, the resultant damage will be the same as in #2 above, except for no damage to a link rod or cylinder. If you experience a gear up landing you have to make a decision. At landing speed, the aircraft travels 3.5 feet for each blade in contact with the ground at initial point of contact. As the engine slows, this increases. Consequently, the rearward deflection of a very thin blade exceeds the rotational shearing. Additionally, the reduction of blade length per rotation with a normal flare landing is less than a tenth of an inch. In other words, the wood fails well before any engine parts are stressed to the +400 foot/lbs of torque design load.
To add our experience on the “sudden stoppage” question, I offer the following with respect to M-14P engines and V-530 props:
We had many conversations with the Russian overhaul factory during the 90’s and with OKBM in 2001. They require a teardown under their system (labor is cheap) but no one could recall damage from a gear up landing. We have sold 20 – 30 sets of blades for replacements on gear up landings with no known subsequent problems with the engines. Having overhauled many V530 prop hubs, there is no doubt that it will fail last.
If you land gear up, you must weigh the costs, down time, damage probabilities and future consequences.
~Carl W. Hays
Bent Link Rods
Written by Carl W. Hays ~ 1995
We have had 3 M-14P engines in our shop with bent link rods. These were all liquid lock (hydrauliced) on start-up and the #5 rod was bent. To some extent, we are learning lessons in years past when radial engines were much more common. The problem is simple; the solution is much more complicated.
The compression chamber on the M-14 engine has a volume of about 4 ounces. Anytime there is as much as 3 ounces of a liquid in the chamber there is a potential problem. No, it does not have to be full to cause damage on startup. It will diesel if the compression ratio reaches about 18:1; which it can do with 3 ounces. Pulling the engine through, however, with it nearly full of liquid will not harm the engine.
As you know, if the engine is pulled through by hand before starting, the oil in the cylinders will be forced out of the exhaust valve and the cylinder will be clear enough to start without damage. This is true on the first firing but may not be true as it runs. The intakes on cylinders #4,5 & 6 can pool oil in the bend of the intake tube if the engine is tilted back, as it is on a tailwheel plane. This is why there are drains on these cylinders. We flow-tested 100 weight oil at 70 degrees (Fahrenheit) and found that the oil will be forced into the cylinder at an airflow of 25 cubic feet per minute. This is the airflow at about 15% RPM. If the oil is warmer it will flow at a lower RPM. THERE CAN BE ENOUGH OIL IN THE INTAKE TUBE TO RUIN THE ENGINE EVEN IF THE CYLINDER IS CLEARED BY HAND OR DRAINED.
Pulling the engine through backwards compounds this problem. A manifold drain for these intakes is really necessary if you have a tailwheel aircraft and do not want to pull the drain plugs every start.
WHEN you pull it through by hand is very important. Pull it through at least 3 blades just before starting. Even 5 minutes delay can mean the end of your engine if the conditions are correct. When the engine is cold it should be pulled 15-20 blades and then 3 just before start. If it is warm, then 3 blades are enough.
The lower cylinder valve rocker housings remain full of oil in this engine. Over time, the oil will run between the valve and guide and into the cylinder if the intake valve is open. One of the lower intake valves is always open. We have a drain kit to tie the manifolds together with a quick drain. Leave it open when not running and this works for the intake tubes. When we overhaul these engines, we will modify the cylinder so that it will drain like the Pratt & Whitney 985. These modifications will solve the problem of oil from the intake tubes and rocker housings. Unfortunately, there are two more sources of oil that can get into the cylinder and cause damage. When the engine shuts off, the oil in the top ylinders will drip or run down the rods into the lower cylinders. If it hits the cylinder wall it will eventually run past the rings and into the combustion chamber. If it hits the piston it will pool until it covers the oil holes on the oil ring and then run past the rings and into the combustion chamber. No matter how thoroughly this oil is drained, this oil will be present on start-up unless the spark plugs are pulled and the engine spun at starting RPM using anti-vacuum plug valves. If no other source of oil gets to the combustion chamber this oil will not cause damage but it will cause plug fouling and smoke at the start.
The unpredictable source of oil is from the oil tank and past the oil pump gears and check valve. While the engine manual does not show a check valve, there is one. It is installed in the oil pump housing. Since this valve has only a very weak spring to block oil flow if the pump is not turning it is easily held open by any small particle. It may never happen, but if it does when the engine is hot, you could flow enough oil to fill a combustion chamber in a few minutes. The oil will run into the crank and down to a lower cylinder. This is why it is so important that the prop ALWAYS be pulled through just before starting.
If you are thinking of an oil shutoff valve between the oil tank and the engine, keep thinking. This is not permitted on a standard category aircraft for a very valid safety reason. The consequences of an engine failure after takeoff due to lack of lubrication are always worse than liquid lock damage on starting. I have known several who had it happen even though they thought it was foolproof. The only way that I can see it being safe is to install a double coil, fail maintained, solenoid valve with an indicator light and the start wiring run through a limit switch on the open position.
All of this still leaves us with a solution being to drain the intakes on tailwheel aircraft and pull the engine through just before starting. Pull plugs if there is a lock. This is the way the Russians do it.
May your link rods remain straight forever!
V-530 PROP BLADE INSTALLATION AND SETTING INSTRUCTIONS
- Torque wrench
- Smart Level (digital protractor) or Protractor
- Flat-bladed screwdriver
- Safety wire twisters
- Pair of dykes
- 17 mm wrench
- Masking tape
- Safety wire
- 3 cotter pins
- Remove all of the safety wire, screws and weights on the sides of the blade nuts.
- Remove the skull cap or spinner.
- Cut the safety wire on the screw/keeper for the dome/piston assembly. Remove the screw and keeper. Rotate the dome until you can lift the assembly out of the hub. (Almost always, the piston will remain inside of the dome. It is wise to keep a bucket underneath the hub, in case it doesn’t. The dome assembly will be filled with oil.) If you have noticed oil on your gills or sprayed out on the blades, you will want to clean and inspect the dome assembly. If there is scoring on the inside of the dome, it is advisable to remove the scratches by chucking the dome up on a lathe and lightly polishing it with Scotchbrite or a fine Wet or Dry sandpaper with water, until the scratches are gone and you have a smooth surface. You will remove the anodizing in this process, but it is bathed in oil and not likely to corrode. Take a look at the surface of the seal on the piston. It may need to be replaced, if there is any metal imbedded in the seal or visible scratches in the rubber. *** If you have evidence of an oil leak at the bottom of the junction of the hub and flange serrations, you may want to remove the snap ring and lock plate on the oil delivery tube and tighten the oil delivery tube a small amount. The torque is 102 ft-lbs. There are two gaskets and a thick metal spacer underneath the oil delivery tube. This will require a (22 mm or near equivalent US) deep socket. The lock plate will align with the delivery tube in limited positions. Reinstall the lock plate and snap ring when finished.
- Begin with the hub in a horizontal position for mounting of the blades.
- Make sure the counterweights are positioned so that the blades will be against their mechanical stop in the flat position. (You may wrap a couple turns of elastic material between the counterweight ends and the hub to secure them in a full forward position.)
- The hub is assembled such that every piece is particular to side “1” or side “2” of the hub and stamped accordingly. The reason for the stampings is to account for weight variations between individual pieces of the hub. The blades may be stamped on the metal collar with a “1” or “2”. On some blades this may not be visible any longer. It is advisable to keep these pieces matched to their particular side of the hub. Mark in some manner yourself for reassembly purposes.
- The threads on the blades and the threads inside the intermediate bushing MUST BE super clean for the blades to screw in freely, so it can be accurately determined when the blade has bottomed out at initial installation.
- Lightly grease the threads. I use Lubriplate. Also, you can lube the threads lightly inside of the hub. Please note, you will see some of this grease work its way out on your blades the first few subsequent flights. It will dissipate over time. ****IMPORTANT***** While lubing the threads of the hub nuts, make sure that the alignment pins are installed for the counterweights. These are small pins that are peened into the intermediate bushings. They line up with the slot in the center of the counterweight. Another way of checking is if the counterweights swing around freely on the blade bushing, the pin is missing. In which case, you will need to make one.
- With the hub in the horizontal position, slowly begin to the thread the blade into the hub. It should go easily. If not, investigate the problem. Turn the blade all the way in until it stops. Then back it out to an approximation of where it should be for fine pitch.
- Double check that the counterweights are still against the stops in the fine pitch position. Place the Smart Level vertically across the face of the hub. Take a reading. For example, it may read something like 87.2 degrees. Your aircraft nose will be pitched higher than the tail. Your blade setting angle is 14.5 degrees. It is measured 8” in from the tip of the blade. If you have a set of factory original blades a thin, red line will be painted at this location. If you have a set of newly painted blades, use a piece of masking tape to mark the 8’ line. You will place the center of the Smart level on the edge of the tape, so make note which side of the tape is the 8” line. To obtain the reading you want to see on the Smart Level on each blade: (Example) 2 degrees tail low from vertical on the hub face: 90 degrees – 2 degrees = 88 degrees 88.0 (hub reading) – 14.5 (Blade angle setting) = 73.5 degrees (Blade reading at the 8” mark for the port blade or the left side of aircraft from the cockpit.) Or, if it is more convenient to work on the right side blade 90 degrees + 2 degrees = 92 degrees hub reading. 92.0 (Hub reading) – 14.5 = 77.5 degrees on the right side blade.
- Take the Smart Level and go to the back of the installed blade. Place the center line of the tool on the 8” line. You should also have the tool center in the chord of the blade. (You want to make sure you position it the same on the next blade.) Rotate the blade until you get the proper setting. In our case of the example: 72.7 degrees.
- Rotate the prop 180 degrees to bring the second blade socket to the same position. Recheck the hub reading. Follow the same procedure on the second blade.
- One final time, check the angles again. The factory manual allows only 20 minutes of angle difference between the left and right blades!
- Once satisfied with the settings, put a final torque of 59 ft-lbs. on the counterweight nuts and install the cotter pins. MAKE SURE THE COUNTERWEIGHT IS FLUSH AGAINST THE LIP OF THE INTERMEDIATE BLADE BUSHING ALL OF THE WAY AROUND. If not you will be sure to have some balance problems. It is very easy to misalign this when you are snugging the nut. Run your fingernail around the perimeter. You should not have a gap that you can run your nail in between. Tighten the nut so it is snug and the blade will not move.
- Reinstall the dome/piston and keeper. Safety the screw/keeper.
- Install the skull cap or spinner and safety the nut with a cotter pin.
- Test run aircraft. Many times, the match-balanced blades will allow for smooth operation and no/little vibration. However, if you have a hub that is heavy on one side, you may need to have the prop dynamically balanced after installation of the blades.
Written by: Jill Gernetzke
Centrifugal Advance Magneto Timing Procedures
- Bring engine to TDC on #4 compression stroke. Use TDC tool to ensure top dead center.
- Install pointer to align with zero on prop shaft. (See photos.)
- Hook up magneto timing tool.
- Check stamped degrees on magneto to determine magneto timing from selected chart.
- Move prop to correct setting on the prop shaft, as referenced on the chart.
- Install left magneto so that the points open at the selected degrees. If the correct magneto setting exceeds the adjustment travel, remove the magneto from the accessory case. It will be necessary to make a fine adjustment of the timing.
Fine Adjustment of Magneto Timing:
– Remove the magneto.
– Align the brass drive on the bottom of the magneto so that it is 90 degrees from rubber shock bushing in the case . (See photos.)
– Place a reference mark with a pencil or scribe on the magneto bushing to enable a reference point for the direction of turn.
– Remove cotter pin and loosen the non-slotted bolt on the brass drive, first.
– Remove cotter pin and loosen the slotted bolt. (The slotted bolt is threaded completely and is the “adjustment” bolt . The threads of this bolt turn on the threads of the worm of the bushing.) Turning the adjustment bolt clockwise normally advances the magneto timing. Turning the adjustment bolt counter-clockwise normally retards the magneto timing. One complete turn of the adjustment bolt, changes the timing approximately 2°.
– In order to ensure that the magneto points are releasing back into the same place every time, you will need to load the magneto drives. This is performed by turning the propeller backwards and advancing slowly into the timing mark on the propeller flange. Since M9 – 35M magnetos are centrifugal advance, you must rotate the rotor on the magneto clockwise till it is at a hard stop, before you bring prop shaft into timing mark. This will insure that the magneto is at its fully retarded position or “fully loaded”. If you do not carry out this important step, your magneto timing will be difficult to adjust and the readings on the magneto timing device will be inaccurate each time you check it. (See photos.)
- Once the points are opening at the correct setting, remove the magneto and tighten bolts to align cotter pin holes and install cotter pins.
- Reinstall the left magneto with mounting hardware (nut, lockwasher and washer).
- Double-check the timing using the “loading” method. Once the correct timing is achieved, tighten the 3 mounting nuts.
- Repeat process for the right magneto. NOTE: The magnetos may have different timing, as evidenced by differing degrees stamped on the magnetos.
- After magnetos are timed correctly, install the pencils, distributor caps, covers and P-Leads.
- Safety magneto covers. Remove indicator from prop shaft.
An Introduction to the M-14P for Flat-Engine Pilots
By Fred Abramson
If you learned to fly in Russia, most of what is in this article is probably second nature to you. But if you, like me, learned to fly in the good old U.S. of A., sitting behind horizontally opposed Lycomings and Continentals, the M14P may have some surprises in store for you. Expensive surprises. Maybe even scary surprises.
Now, lest anyone get the wrong impression, the M14P really is a wonderful engine. It’s strong, robust, and has a lot of character. It is, of course, basically the same kind of animal as the aforementioned flat engines. It just has a different growl, different needs, and its table manners are a little more messy. I believe that the M14P is just as reliable as our flat engines, too. It’s just a matter of knowing how to maintain and operate it.
So, how did I get my experience with this wonderful engine? Well, I purchased a Sukhoi 26 in 1993, and have put well over a thousand hours on it since then. I’ve learned lots of things from reading and talking with folks since 1993. I’ve learned some things more vividly from my direct experience. I wish people had told me about these things before I learned them. What do they say? “Experience is the thing you get the moment after you needed to have it.”
Also, it’s only fair to tell you that although I often get oil on my hands, and occasionally bust my knuckles, I’m not a mechanic. So this article is written from a pilot’s point of view. Nevertheless, a pilot who does know some things, thinks about them, and tries to learn more. The “thinking about things” part makes a difference. How many dumb things I’ve done when I really had the information in my head to do better, but just didn’t analyze the information enough. There are some common misconceptions, about hydraulic lock in particular, that I have fallen prey to, in cases where a little putting two and two together could have guided me better than conventional wisdom. Or maybe it was just the conventional wisdom of the people I had happened to talk to.
This article is not a systematic exposition on radial engines. Nor is it an operating manual for the M14P. Much of the discussion here will only make sense if you know something about radial engines already, and you have seen the innards of the M14P, or have at least seen some drawings. Serious disclaimer: If you try to operate your engine based only on what you read here, God help you.