Thursday, October 26, 2017

Emergency Locator Transmitter – Yep, It Works! “Eyes In The Sky” Found Me

Not long ago I read a few posts on the forums indicating there have been instances where the ACK E-04 Emergency Locator Transmitter was accidentally triggered while cleaning the aircraft. Apparently, the static charge generated by cleaning cloths or dusters next to the antenna have triggered the ELT to transmit. After contacting ACK about the anomaly, the builders were instructed by ACK to install a static suppressor in line with the antenna's coax cable. The Van’s assembly instructions for the RV-12 do not show or mention the use of the static suppressor. As I understand it, early shipments of the ACK E-04 may not have included the static suppressor … so this may explain why the suppressor is not shown or mentioned in Van’s drawings even though a static suppressor is now included in the ACK E-04 ELT box. Anyway, did not install the static suppressor during the build because it was not mentioned in the instructions or shown on the drawing. However, after reading the reports of others accidentally triggering the ELT while cleaning and ACK suggesting instillation of the static suppressor, decided it can’t hurt to install the static suppressor while performing the condition inspection … after all, the suppressor was included in the box from ACK.

One thing that has bothered me is the way the RV-12 assembly instructions show wrapping the excess antenna coax cable for the ACK E-04 ELT in a loop and using wire ties to flatten out the loop and secure the excess coax to the side of the ELT. This is done because the antenna cable from ACK is 5' long and the antenna is within inches of the ELT. Seriously, this is NOT the way a coax cable feeding an antenna should be treated.
Van’s assembly instructions direct the builder to coil the ACK E-04 ELT’s excess black coax antenna cable as shown here. This is not a good practice for coax cable being run to a transmitting antenna.

Decided since the ELT needs to be removed from it's mounting tray to comply with the requirement of testing the internal G switch annually, this would be the perfect time to do something about all the excess coax cable. Referring to the ACK E-04 instillation manual, ACK states the coax antenna cable can be as short as 2' … perfect, so headed over to the local avionics shop on the field and had them fabricate a 2' cable made from higher quality double shielded coax cable.

After removing the ELT from the mounting tray and completing the test procedure for testing the G switch (all successful), the ELT unit was placed back in the mounting tray and the new 2' antenna cable and static suppressor was installed. The new shorter coax cable was routed around the back of the ELT’s mounting tray, down under the ELT and back up to the ELT’s antenna. This will eliminate the coiled mess shown in the photo above.  The static suppressor was installed on the base of the ELT antenna between the antenna and the coax cable coming from the ELT, as can be seen in one of the photos below. So far so good.
The new 2' ELT coax antenna cable (copper looking) is routed behind the ELT’s mounting tray and loops under the ELT and up to the ELT’s antenna. I feel this a much better instillation as opposed to coiling the excess coax and using wire ties to secure 4 1/2' of coiled coax cable to the side of the ELT.
The static suppressor supplied in the box with the ACK E-04 ELT can be seen on the top right … it is the silver cylinder attached to the base of the ELT's antenna. The shorter copper looking coax antenna cable from the ELT is attached to the static suppressor.

I can assure readers the 2' coax cable connected to the static suppressor works great! How do I know? Well, I accidentally activated the ELT after performing the required testing of the G switch. The main reason for this admission of guilt is to reinforce the fact one should not  perform tasks on an aircraft when in a hurry. During construction of the DOG Aviation RV-12, extra effort was made to insure work sessions were not hurried or rushed so complete attention could be given to the task at hand. Being pressed for time and rushing is a recipe for errors, especially if the work environment throws in mitigating factors as I’m about to share with you.

Admittedly, I was somewhat in a hurry to finish up working on the ELT as to not be late for an appointment. After testing, the ELT was placed back in the mounting tray and wire ties were used to secure the audio alert indicator and associated wiring to the side of the ELT. This where it all went downhill, the mistake(s) made were threefold … instead of flipping the toggle switch on the ELT to the “ARM” position, the toggle switch was inadvertently flipped to “ON” … mistake one. When the ELT audio alert indicator began beeping, I quickly reached across the cockpit to slap the remote panel indicator mounted on the instrument panel. Thinking I pressed the reset button when in fact I must have slapped the “EMERGENCY ON” button … mistake two. At this point, I quickly walked away to make a log book entry documenting the testing and changing of the antenna cable ... mistake three. Next the environmental contributors came into play as it was raining moderately outside so the noise level inside the hangar was high. ( For those who have never been inside an all metal hangar during a rain .... light rain is noisy, moderate rain is very loud and a heavy rain is literally defining to the point ear protection is needed).  Between the music playing in the hangar at the time and the increased noise level caused by a steady rain hitting the all metal roof, it created a very noisy environment … so much so, I did not hear the occasional beeps coming from the ELT until between songs when the beeping finally caught my attention as the rain eased up a bit … OH CRAP!!!!  I quickly raced over and flipped the toggle switch on the ELT to OFF … and just then noticed I had initially flipped the toggle to “ON” by mistake. DUH!

As a side note for those readers not familiar with how the new dual frequency ELT’s work … when first activated, the ELT transmits on the FAA’s emergency frequency of 121.5 MHz. Typically, the 121.5 MHz  frequency is monitored with a handheld or aircraft radio during testing the ELT’s functionality. The testing should be performed between on the hour to 5 minutes after the hour ... this is so brief transmissions seen during this timeframe can be ignored as testing . Once activated for testing or accidentally, the ACK E-04 ELT needs to be reset immediately within 30 seconds or so … if the ELT has not been reset or powered off before 50 seconds has passed, the ACK E-04 ELT will begin transmitting on a second frequency of 406 MHz to the COSPOS/SARSAT satellites high overhead. The 406 MHz transmission to the satellites also includes the last GPS coordinates received by the ACK E-04 ELT from the aircraft’s avionics.

Apparently, I did not power off the ELT in time ... because 5 minutes or so later, I received a call from home where Jan said she just received a call from a government agency and they needed to talk to me. Of course, I called the monitoring agency back immediately and apologized profusely for setting off a false alarm for them to chase down. The woman I spoke with was very kind and said it happens all the time … nice to hear, but it did not make me feel any less of a dumb ass! We had a chat about how extremely sensitive the satellites really are because I was truly astonished that the satellite had picked up the signal and that they knew my exact location … given it was raining outside and I was in a totally enclosed all metal hangar with both hangar and access doors closed due to the rain. We joked about now knowing the ELT really works and actually transmits accurate GPS coordinates … still did not make me feel any less of a dumb ass!!! By the way, if desired, there is a form that can be submitted to the SAR agency in advance for scheduling an actual test of the ability of the E-04 ELT to transmit on the 406 MHz frequency.

Already have plans for the 5' of coax cable removed from the ELT antenna. The plan is to keep the coax cable in the map box as an emergency insurance policy. Should the Garmin GTR 200 radio ever fail in flight, my plan is to connect the coax cable to the handheld radio I always carry. The rubber duck antenna on the handheld radio will be removed and the 5' coax will be used to temporarily connect the handheld radio to the ELT’s antenna. The BNC connector on the ELT's antenna is within easy reach and should significantly extend the communication range of the handheld. Of course, this assumes there no other issues with the aircraft, just a broken radio. I’m not condoning this practice … but if the radio fails …there is a com antenna within easy reach … just sayin'.

Tuesday, October 24, 2017

The First Condition Inspection – Tips For Builders

Have procrastinated a little getting this post written but the good news is, the first condition inspection has revealed no significant issues with the DOG Aviation RV-12. However, I did run across a couple of speed bumps that created delays. One time consuming task was looking up the torque values for all the hardware on the airplane. I’m not referring to the standard torque values for AN3 or AN4 bolts which builders have well memorized by the time the airplane is completed … no, I’m talking about the myriad of parts that have unique torques such as Matco brake hardware, the Rotax engine hardware, propeller bolts, etc. Plus, there is the time spent sifting through the documentation for additional information such as tire pressures, stabilator cable tensions, nose gear breakout forces, etc.

Tip for builders: My suggestion is while assembling the RV-12 each time you run across a nonstandard torque value, breakout force, gap measurement or pressure reading document it on a list that can later be tailored to suit your needs via a word processor or spreadsheet. Having a list that shows torque values, clearances, breakout forces, spark plug gaps, etc. will make the first condition inspection on your RV-12 or any kit aircraft move along so much faster and all inspections thereafter. In fact, I would also suggest taking things one step further by making a complete list or spreadsheet of inspection due dates for items such as testing of the transponder and the required quarterly ELT test … in addition, include expiration/replacement dates for items such as the batteries in the ACK E-04 (I did record the main battery for the ELT in the avionics log but did not record the battery dates for the associated remote panel indicator or audio alert indicator) along with dates for firewall forward items such as fuel pump replacement, rubber hoses, brake fluid, coolant, etc. Wish I had thought about creating those lists during the construction process. Moving forward, assembling a meaningful list related to inspection items along with perhaps keeping a white board in the hangar will make future inspections much less time consuming. I spotted a white board in the hangar across from me and thought it was a good idea so took a photo of it to use as a guideline for making my own white board.
Photo of a whiteboard spotted in a hangar across from me. There seems to be merit in creating a white board for keeping a visual on major inspection due dates and time related items such as oil changes.

Decided to begin the condition inspection at the nose of the aircraft and move aft. Van’s documentation suggests checking the torque of the propeller hub after the first six hours … I went beyond that knowing the annual was nearing. For the benefit of non-aviation readers of the Blog, the two Sensenish propeller blades are captured between two half hubs … the one called the mount hub is bolted to a mounting flange attached to the propeller shaft coming out of the gear reduction unit on the front of the Rotax 912ULS engine and the other is called a clamp hub which captures the two propeller blades and is bolted to the mount hub. Unfortunately, to check the mounting bolt torque on the mount hub, it requires removing the clamp hub and both propeller blades. It would be nice if the bolt heads sat in a recess or up against a stop so the bolts would not rotate allowing the bolt torque to be checked without removing the blades … but sadly, that is not the case so the clamp hub and blades need to be removed to gain access to the mount hub bolt heads. As it turns out, the nuts on two of the six bolts moved slightly when the torque was checked … the required torque is 18-20 foot pounds so I was shooting for 19.5 lbs. to allow for a little drag in the locknut.
These are the nuts and bolts that attach the mount hub onto the mounting flange. Unfortunately, to properly check the bolt torque it requires the removal of clamp hub and propeller blades to gain access to the heads of the bolts.

Avid readers of the DOG Aviation blog may recall when the propeller blades were first installed they were pitched wrong and after posting photos of the work session, I received an Email from a fellow builder who caught the error (thanks again Nick). This required loosening the clamp hub bolts a couple of extra times while readjusting the blades. Unfortunately, Nord-Lock washers self-destruct a little each time a bolt is loosened, so they are only effective for a few cycles because the capturing ridges on the washers get worn down easily. Knowing this, I figured the Nord-Lock washers should be replaced since they had been exercised a few times already… so prior to beginning the condition inspection, I purchased new Nord-Lock washers at a local bolt & nut supply. Well, much to my surprise, when about to use the new Nord-Lock washers, I discovered they were a much smaller outer diameter than the Nord-Lock washers supplied by Sensenich with the propeller kit. This resulted in a parts delay because I needed to order new Nord-Lock washers directly from Sensenich. So my tip to fellow RV-12 builders is to plan ahead and have some spare Nord-Lock washers on hand when planning to remove the prop mounting bolts … just make sure the Nord-Lock washers are the larger diameter ones.
On the left is a used Nord-Lock washer removed from the propeller hub and split in half to reveal the worn ridges on the washer. On the right is a new Nord-Lock washer split in half so the locking ridges can be seen.  Also note the outside diameter of the standard Nord-Lock washer on the right that was procured locally has a much smaller outside diameter than the Nord-Lock washers supplied by Sensenich on the left.

The new Nord-Lock washers received from Sensenich were placed in the digital caliper and measured in at 21/32". So fellow builders attempting to locally source Nord-Lock washers for the propeller bolts, make sure you purchase washers that have an outside diameter of 21/32" … otherwise you will need to place an order through Sensenich.
The Nord-Lock washers that Sensenich supplies for the RV-12 propeller utilizes a washer with an outside dimeter of 21/32" which is a larger OD than typical for a 5/16" diameter bolt.

After replacing the Nord-Lock washers that hold the clamp hub in place, the propeller blades were pitched with a digital level to 71.4° using the method in Van’s plans along with the Van’s pitch tool. Got the pitch even better than the first time around … now both blades are within .05° of one another. For those not familiar with the process of adjusting the RV-12’s propeller blades, the following is a link to a post that covers that procedure:
Link to the procedure for adjusting the Sensenich propeller blade pitch on the RV-12.

About the only item I found that NEEDED correcting was the temperature thermostat for the Reiff heating system … it had popped off the oil tank. Frankly, I was not surprised to see this because when installing the Reiff heating system I began by scuffing up the aluminum on the bottom of the engine and cleaning with Acetone then mixing the epoxy and attaching the heating pad to the bottom of the engine. Then without thinking I slathered the thermostat for the oil tank with epoxy and affixed it to the side of the oil tank …. only to realize, darn (not the word I used at the time) I had not yet scuffed the oil tank and cleaned it with Acetone before applying the epoxy. Figured it was too late to do much of anything, so the thermostat would either stick, or not … which ended up being the case. To correct the problem all the old epoxy was cut off the thermostat and the oil tank with a razor and both the oil tank and thermostat were roughed up with sandpaper and a jewelers file. Reiff suggests using JB Weld as a substitute for the epoxy they supply with the heater kit, so that is what was used for the repair. The JB Weld was applied in two applications. The first application was to the bottom and sides of the thermostat so a piece of safety wire could be placed around the oil tank and tightened to keep the thermostat pressed against the oil tank while the epoxy cured. After the epoxy cured, the safety wire was removed and a second application of epoxy was used to cover the top and sides of thermostat. Hopefully this will no longer be an issue … but moving forward, this will be an area I will be keeping an eye on especially now that winter is coming and I’ll be using the heater.
My finger is pointing to the oil tank thermostat for the Rieff heating system  that was epoxied back onto the oil tank using JB Weld epoxy. This time both the thermostat and oil tank received a good scuffing and cleaning with Acetone … hopefully the thermostat it will stay affixed to the oil tank.

Friday, October 13, 2017

Switching To “Newest” & “Improved” Carburetor Floats

For a large portion of time during the construction of the DOG Aviation RV-12 there have been some issues with the Rotax 912 ULS engine’s carburetor floats. The root of the problem revolves around some carburetor floats absorbing fuel and sinking in the float bowls. Apparently, the material the floats were made from (looks to me like some sort of special foam plastic with a hard outer coating or sealant) tend to adsorb fuel which causes them to get heaver so they begin sinking in the carburetor bowls. The sinking floats allow more fuel into the carburetor bowls than desirable … which begins to create a rich mixture as the engine becomes flooded with excess fuel.

A few years back when this began to become problematic, Rotax changed the manufacturing process and tested the floats. The newer tested floats were given dimples for identification so they can be distinguished from the older non-dimpled floats and were supposed to be “the fix” for the fuel absorption issue. Rotax issued a service bulletin suggesting that all non-dimpled floats should be replaced with ones that are dimpled as pictured below. And, if not replaced, the non-dimpled floats required being checked at regular intervals (25 hours or 60 days) by using one of two methods …. either remove the floats and weigh each pair (the pair must weigh less than 7 grams) or pass a displacement test where a measured amount of fuel is injected into the carb with a syringe while looking at the overflow orifice until fuel flows out of it. Depending on the amount of fuel it takes to see fuel exiting the overflow orifice, one can determine if the floats are soaked with fuel or not. Either way, it is a pain in the butt.
Going back a few years, per a Rotax service bulletin, older non-dimpled carburetor floats in Rotax 912 engines are to be replaced with floats that are dimpled such as the ones shown in these photos.

However, as time went on, it was realized that even the newer “dimpled” replacement floats were developing the same problem of adsorbing fuel and sinking in the carburetor bowls … it just did not occur as often. Now Rotax has changed the floats yet again and given them yet another new part number of 861-188. It is my understanding Rotax has also changed the material the floats are made from and is now making the floats from a denser material. The “newest” floats can be identified by what appears to be the loss of the brass sleeve or bushing that passes through the float. In fact, there is still a brass bushing but it is much shorter and centered in the hole making it difficult to see. This next statement is purely a guess on my part: I suspect because the material the newest floats are made from is denser, it is very likely also heaver … so to keep the measured weight for each float the same as the old floats, the amount of brass used for the bushing was reduced.
The old style float is on the left and the “newest” style 861-188 float is on the right. The maximum weight remains the same … both floats weighed together must weigh less than 7 grams. (They typically weigh slightly under 3 grams each out of the box).

Admittedly, I was not currently experiencing issues with the floats in the DOG Aviation RV-12 but decided to make a preemptive strike and just replace the floats with the “newest” 861-188 floats now that they are available. When ordering the newest floats, the DOG Aviation procurement department also purchased a float bracket gauge (part number 877-730) so the float arms could be accurately adjusted to parallel. To use the float bracket gauge the main jet is removed and the gauge is screwed to the base of the carburetor in place of the main jet.  Glad the gauge was purchased because the float bracket arms were adjusted by sight the last time the carb floats were changed … but the gauge reveled that although close (think it was around .024"), the float bracket was out of spec which is listed between .016" to .020" measured between the gauge and the float bracket arm using a feeler gauge. With the 877-730 gauge in place, the float bracket arms were adjusted to .018" which is the sweet spot per the maintenance manual.
The Rotax 877-730 float bracket arm gauge in position after removing the main jet. The float bracket arms are tweaked so the gap between the float bracket arm and the gauge is .016" - .020" … I chose to adjust the arms to .018" as can be seen here.

Hopefully, by switching to the newest style 861-188 carburetor floats at this time, it will eliminate the likelihood of carburetor float issues in the future.

Wednesday, October 11, 2017

Condition Inspection - Rotax 912ULS Differential Pressure Check

One of the tasks I wanted to perform during the condition inspection was a check of the differential pressure of the Rotax 912ULS engine. According to the maintenance manual, this could have been delayed until the engine has 200 hours but thought creating a baseline now would be a good idea.  The differential cylinder pressure test involves a special testing apparatus called a Differential Cylinder Pressure Tester. The test apparatus consists of a built in pressure regulator and two matched pressure gauges. The pressure gauges are connected together via an orifice and valve. The size of the orifice will change depending on the displacement of the engine … typically, engines with a cylinder bore smaller than 5" will need a tester utilizing a .040" orifice and, of course, the Rotax 912ULS engine falls into this category. (A tester for larger bore engines typically utilize a .060" orifice).
The ETC Model E2A differential cylinder pressure tester with 12mm adapter hose.

To accommodate various spark plug hole and thread sizes, the ETC Model E2A differential cylinder pressure tester pictured above can be ordered with various hoses that have the proper threads for the spark plug holes on the engine being tested. The correct adapter hose for the Rotax 912ULS engine requires a 12 mm thread to screw into the engine’s spark plug holes.

A differential cylinder pressure tester IS NOT a compression tester in that it does not read the actual compression value for a cylinder as one would with the typical compression testing gauge. Instead, the differential cylinder pressure tester gives an overall indication of how well the piston rings and valves are sealing. This is accomplished by connecting the tester to an air compressor then adjusting the regulator on the tester so the left gauge displays 80 psi … this becomes the reference pressure. The test reading is obtained by placing the cylinder under test to top dead center and slowly opening the valve to allow the pressure to enter the cylinder under test. While making sure the left reference gauge still displays 80 psi (adjust regulator if necessary) the reading on the right gauge is recorded. The difference between the left reference gauge and the reading on the right gauge establishes the differential which can be represented as a percentage. According to the Rotax maintenance manual, the maximum permissible differential is 25% so that would be a reading as low as 60 psi on the right gauge.
With the valve off (facing down) and the ETC Model E2A differential cylinder pressure tester connected to an air compressor, the regulator knob on the tester is adjusted until the left reference gauge displays 80 psi.

Caution: One can become seriously hurt while performing this test if not very careful. The instructions caution the user of potential dangers and suggest the testing be performed while a helper holds the propeller when opening the valve to apply air pressure to the cylinder under test. This is truly good advice especially if new to using a differential pressure tester because if the cylinder is not at a perfect top dead center, there will be a tremendous amount of rotational force applied to the propeller. I have helped perform this test in the past and was well versed in what can happen if not careful. It can be done by yourself, but it is tricky. After the left gauge is adjusted to 80 psi place a finger in the spark plug hole of the cylinder being tested and turn the propeller until you begin to feel the compression stroke pushing air out of the cylinder then screw in the 12 mm adapter hose into the spark plug hole. While tightly holding the propeller, very SLOWLY open the valve just enough to allow a little air to pressurize the cylinder enough to feel some torque being applied to the propeller. Next slowly move the prop back and forth a little while watching the right gauge … the object is to move the propeller to the position where a peak reading is obtained. The peak reading will occur when the piston is at or very near top dead center. At this point, while holding onto the propeller really tightly continue SLOWLY opening the valve further until it is full open and record the reading on the right gauge … then close the valve and wait a little for the air to bleed out of the cylinder. If done correctly, it is very easy to hold the prop at top dead center with one hand …. however, if you are off a little it takes both hands to prevent the prop from moving.

Unfortunately, because of the inherent danger of performing the differential pressure testing by myself, I felt it was not safe to try fiddling with a camera to obtain photos showing pressure readings on the right gauge. All the cylinders showed approximately a 1% drop which is about what I would expect from a virtually new engine since there is always a small amount of air that gets past the rings even on new engines.