|LongEZ - N961EZ on the tarmac in Alamogordo, New Mexico|
I FLY EZ
31 Jan 2007. Testing for jammed wheel results in Emergency Blow Down Test (ops)
QUESTION: "What happens if the strut extends inside the wheel well"? Under normal circumstances, this is a very unlikely event. BUT lets say a Strut Line hose blows after the gear is retracted: When the strut pressure drops, the pilot will have a warning, as the UP pump will be cycling (or running continously) in an attempt to maintain 1,100 psi in the strut line and hold the struts compressed. NOTE: If you use the original strut switches instead of a pressure switch, make sure the switches are adjusted so they can detect it if the strut moves this short distance. SETTING UP THE TEST: To set up for this test, I would retract the gear normally. I would shut off power, then, using a combination of the Emergency Down valve to bleed off the UP pressure, and a jumper wire to activate the Strut valve to relieve strut pressure, I would get the struts to extend inside the wheel wells, and relieve the UP pressure. The gear would now be jammed inside the wheel well. OBSERVATION:Most of the time, the gear would come out normally as if nothing happened. BUT, If I took extra time and made sure there was ZERO pressure in the strut line (disconnect the hose), the gear would not come out of the wheel well using normal DOWN pressure. The pump will run forever, building pressure in the DOWN line. The strut valve does NOT open, because it should sequence only after the gear is down and locked (overcentered). ANSWER: I tried this on both sides, left and right, using Normal down pressure and also with no down pressure. If I gave the gear a light tug, I would estimate 25 lb force at the axel, the gear would slide out, every time. As the gear came out of the well, the strut would extend a couple inches as the pressures inside the strut equalized. In flight, this "light tug" would be induced by a 2 or 3 G bumping or pullup. I think normal turbulance or even a little dutch roll motion would do the trick. It didn't take a lot to free it up! After the tug, if the DOWN line was open to atmosphere, the gear would freefall into position. After the tug, if there was any pressure in the DOWN line, the gear would freefall into position. After the tug, if there was no pressure in the DOWN line, but the line was intact, the gear would fall to some random position and stop. Pressure from the DOWN pump (or CO2) is then needed to push it the rest of the way into position. NOTE: If this condition exist. (strut extended inside wheel well) Placing the GEAR SWITCH in the UP position immediately repressurizes the strut line to 1,100 psi and retracts the strut, The UP pressure is then built up to 600psi. This is the normal design of the controller. IMPROMPTU EMERGENCY BLOW DOWN TEST OK, we got that out of the way! As I was cracking open the Emergency Valve to bleed off the UP pressure. Well, I cracked it open to far and popped the CO2 bottle. How do you say "@#$%^&*()!+-|?%*&^ OK, No big deal, I was going to do this anyway, I just didn't plan on doing it tonight! start taking notes, quick. As the contents of the CO2 bottle emptied itself into the down line, the gear came down smoothly, just about the same speed as with the pump. There was no jerkiness or slamming. The gear went over center and locked in the down position. The strut was still retracted. When the gear was down and overcenter, the DOWN pressure was sitting right at 600psi. I had to stop and review what had just happened, as this caught me by surprise! Recovery and cleanup from this event was messy (this time). When the CO2 mixes with the Hydraulic fluid, its like taking a 2 liter bottle of Coke, shaking it up real good, then popping the top. (JD warns about this in the manual) When I tried to cycle the gear, the fizzing hydraulic fluid shot out the Pump Reservoir Vent and dumped all around the nose area. The next time this happen (I hope never) Leave all the switches and valves in their current position. Hook up the "Folgers reservoir" to the Pump Reservoir Vent to capture the mess. Then start cycling the gear for short one second bursts. Wait for the bubbling to stop before doing the next short burst. It takes about 20 minutes to clear out most of the CO2.
BIG NOTE: It only takes about 2 turns of the Emergency Valve handle to puncture the CO2 bottle.
Oh, Before all this excitement, I replaced the faulty Gear circuit breaker, updated the electrical drawings, and corrected the wiring for the strut bypass switch.
CONCLUSIONS: This was a very productive night. I took a lot of data (some I hadn't planned on) and answered for myself one of the most common questions regarding the Infinity Gear. I'm happy with the answers and more importantly, I've seen it for myself, and no longer rely on hearsay.
30 Jan 2007. Landing Gear - Cleaning Up
I made a couple changes to the Waiters Landing Gear Controller software. I added a short hysterysis to the Strut Pressure (0.1 sec) and UP Pressure sensors (0.3 sec). This keeps the pumps from shutting off, then immediately restarting if the pressure dips for just a fraction of a second. I removed the Kneel function. Although this was a really neat idea, it can't safely be done using the current hardware configuration. If anyone is interested, Kneel can easily be done by adding another strut valve, but connected to the DOWN line. The struts could then be compressed (Kneel function) using the DOWN pressure, instead of the UP pressure. The normal strut valve in the UP line would serve to compress the strut for the normal gear retraction.
I removed my temporary "Folgers reservoir" (big coffee can with AN4 hose coming out the bottom) and reconnected the Vent Hose and Breather plug. I cleaned up fluid from the leaks I had on Sunday. I cycled the gear 30 or 40 times.
The only outstanding issue I have regarding the basic system is; The left tire just barely touches the forward edge of the wheel well when retracting or extending. I knew this was going to happen as I made a series of adjustments to the gear back in March and April of 2005. To make a long story short, back in 2005, I machine the top surface of the half fork to correct for the tire rubbing the aft edge of the wheel well. Several weeks later, I found a slight alignment problem with the left main trunion. When I fixed the trunion alignment problem, this would have corrected the "tire rubbing" problem, BUT, to late. Now I need to remachine the half fork back to its original dimensions. You can get a better idea of this if you look at the 24 APR 2005 and the 22 MAR 2005 entries; Other than this minor problem, I am very pleased with the system and its performance. When I finished in the shop on Sunday night, I left the gear in the UP position. When I checked the UP pressure today (48 hours later), it was exactly the same, 600psi. NO "UP" LEAKS. I still have a long way to go in this project, but getting the gear operational is a MAJOR, MAJOR milestone. I want to thank JD from Infinity Aerospace, and Jack from EZNose Lift, They both have an excellent quality product, workmanship, and their support has been exceptional.
Thanks JD and JACK
28 Jan 2007. Landing Gear - IT WORKS
I spent the morning hooking up the hoses to the actuator cylinders, then sorting out a couple problems. When I energized the UP pump, I could see pressure on the UP pressure guage, but the gear would go down. The big question, did I mislabel the actuator feed lines, or are there other plumbing problems?? Using jumper wires, I troubleshot the system by energizing the Strut Solenoid, and at the same time, energized the UP pump. The strut acted like it was retracting, as its supposed to. However, when I de-energized the strut solenoid, the DOWN actuator was pressurized. I plumbed the actuators backwards (URGH). Obviously, I mis-identified the connections in the wheel well when I originally laid out the hose routing during the initial installation. Ordinarily, this would be a simple fix, just swap the connections. However, because of the tight fit inside the wheel well, hoses are custom made to correct lengths. These lengths are to short to allow a "swap". After a period of cussing, bending, and tweaking, I came to the conclusion that if I modified the original hose connectors, I could successfully reroute the hoses to correct for the plumbing error. So, a do or die attempt was made. If this didn't work, I'd have to wait until Monday and have four new hoses made (bummer). I placed the hose fitting in a press, and was able to rebend the 45 degree fitting to a full 90 degrees, without collapsing or kinking the connection tube. YES!!! After reinstalling the hoses, I liked this new routing better then my original. It places less stress on the connections and the actuators.
The original routing is shown on the left, the new routing is shown on the right. If you look carefully at the hoses where they connect to the wheel well bulkhead, you can see the original hose connection made a 45 degree turn, the new hose conection makes a 90 degree turn.
I'm happy with the original software on "Waiters Landing Gear Controller", it worked great. The only change I made was extend the Strut timer from 5 seconds to 10 seconds to allow the strut to fully extend after a down sequence. I may need to add some hysterious into the signal that tells the pump to shut off. I noticed a couple times it would shutoff, then turn right back on again as the gear reached its full up position. A 1/2 or 3/4 second delay would solve this. I also adjusted the UP pressure sensor. It was causing the pump to cut off before the gear was fully in the well. I raised it by 50 psi. (600psi). This solved the UP problem. Down pressure works OK at the factory setting of 450psi. NOTE: The original Infinity Aerospace design used microswitches mounted on the gear legs to sense when the struts were compressed. I changed this early on to incorporate a pressure sensor in the Strut line. The sensor is set at approximately 1,100 psi. This signals that the struts are fully compressed and the gear can now be retracted into the wheel well. This pressure sensor can be purchased from Velocity Aircraft. They use it on their landing gear. The video runs 1 minute and 17 seconds (2 meg). It shows the complete UP/DOWN retract sequence.
NOTE: These times were based on a battery voltage of 11.8 to 12.4 Vdc. The times may be a little faster (10% ?) with an operational voltage of 14.5 vdc.
10.9 Sec > Strut Compression 6.0 Sec > Main Gear Retract 16.9 Sec > MAIN TOTAL Retract Time 17.5 Sec > NOSE GEAR Retract time
5.4 sec > Main Gear Extend 9.4 Sec > Strut Extend 14.8 Sec > MAIN TOTAL Extend Time 18.0 Sec > NOSE GEAR Extend Time
27 Jan 2007. Landing Gear Hydraulic system
1) The throttle cables are all installed, these are the standard ACS cables that are 10 ft long.
2 & 3) I made up a couple hoses to use for purging and bleeding. The container is a milk jug, but it had a small hole in it, so I rescued a coffee can and used it instead. I used clear plastic hose as its easy to see air bubbles and flow. These hoses aren't under any pressure. The Oversize reservoir (coffee can) is temporarely plumbed into the hydraulic pumps air vent. The lines are purged, and the minor leaks that showed up are now fixed (tighten fittings). The BIG LEAK I had dumped a quart of hydraulic fluid into the front seat before I caught it. On the Emergency Down Valve, the fitting where the CO2 bottle screws into is open to the hydraulic DOWN port. So, when I ran the pump "DOWN" without the CO2 bottle installed, it dumped fluid out the CO2 fitting. How do you say *&^$#@)!?. THREE NOTES:
1) The CO2 bottle must be installed prior to running pump! 2) Double check wheel well connections for proper labeling! 3) Have a 12 pack of paper towels, and a bag of Kitty Litter on hand!
27 Jan 2007. HAPPY ANNIVERSARY
Waiter and Goldfish celebrate their 34th wedding anniversary today. We have two daughters and four grand children! :-)
21 Jan 2007. Landing Gear Hydraulic system
A lot of little jobs. Got the new battery hooked up. Its identical to the old one, an Odessy 930. The original battery is over ten years old, I think I finally killed it by letting it sit for a long period without being charged.
I touched up the paint on the left pilot console. Before installing the hydraulic gauges, I placarded them for UP, DOWN, and their correct pressures.
I also installed the bolts in the emergency blow down valve, and reinstalled the Electrical DOWN bypass switch.
I serviced both main struts. 8 oz of Dexron III Automatic Transmission fluid and then pressurized the struts to 100psi.
Since I am going to use Dexron III in the Landing Gear System, I would also like to use it in the brake system. I put an O-Ring to soak in regular brake fluid, and Dexron III.
Does anyone know why I shouldn't use Dexron III instead of 5606 in the brakes???
14 Jan 2007. LongEZ Left armrest console
1) The front cockpit left armrest cover is cleaned up and ready to flox in place. This won't happen until almost the end.
The hydraulic guages will have a removable cover (4 ply BID) over them. Probably held in place by two small strips of Valcro. The Oval shapped cutout provides access to the Landing Gear Emergency CO2 bottle and service access to the push/pull cables. The square cutout behind the Aircraft Spruce throttle quadrant will have a small removable cover installed. This cutout provides access to the Landing Gear Emergency CO2 valve and the Landing Gear Electrical Override switch. This switch provides another emergency means of electrically lowering the Nose gear and the Infinity main landing directly, bypassing the landing gear controller module. The smaller round cutout below the Aircraft Spruce throttle quadrant provides access to the push/pull cables.
One important feature of the side armrest consoles is their load bearing capability. When getting into and out of the airplane, you normally lift yourself up by placing your hands on the consoles (just about where the hydraulic guages are) and lifting your body. Needless to say, the consoles must be able to support the weight of the pilot.
2) I marked the hydraulic guages with their normal and Red Line pressures. These guages will be used during testing and/or gear troubleshooting. They will normall be covered, with a cover that can be easily removed during flight. Normal UP pressure (pressure required to hold the gear in the UP position is 400psi. The down pressure is normally 550 psi. The down pressure is not needed to hold down and locked, but certianly desired.
13 Jan 2007. LongEZ Cowling, Clean up plenium intakes
The Pleniums were laid up in two steps, the plenium box that goes over the cylinders, then after that cured, the duct was added to the front of it. In these views, the duct openings are now cut out and the insides of the duct are cleaned up.
I still need to post cure this entire assembly to a full 350 or 400 Deg F.
9 Jan 2007. Cowls, Final Thoughts
I looked at the cowl shells last night. I'm very pleased with how they turned out. They are symetrical with only minor imperfections. I didn't do anything special to get them symetrical, I just eyeballed the forms from all angles as I was carving. I'm by no means an "artist", but I'm impressed with this creation that I made with my bare hands! Although I hand carved several major components on my EZ, i.e. the nose, Wheel pant mounts. This is the first time I did something of this magnatude without having firm instructions, templates, or plans. So, here are a couple observations:
The new shape is drive by several factors, downdraft cooling, integral duct work, and smoother upward slope of the bottom cowl.
I've looked and read about many different cowl shapes that would minimize drag. Most of these design shapes apply to the bottom cowl. My original "Sport Flight" cowl had a nice gentle upward slope. Through real time airflow testing (I always had a minor oil leak that would drip on the lower cowl) I never seen any airflow seperation on the lower cowl. SO, I decided that my new cowl would resemble the original, but the upward slope would be even more gental. (Basically, a refinement of the original cowl)
Unlike several versions of downdraft cooling, my upper cowl is not part of the high pressure side of the cooling plemium. The cooling intakes are part of the fuselage. The pleniums themselves are a one piece shell that surrounds the cylinders and aren't connected to the cowl in any way. The cooling intake area is approximately 11 sq inches per side, a total of 22 sq inches on the high pressure side. The exit area , low pressure side, is approximately 40 sq inches, This is the two squared areas that also serve to exit the exhaust, plus a 1 inch clearance around the circumference of the prop spinner.
The lower cowl incorporates intake scoops and ductwork for engine combustion air and the oil cooler. The intakes are approximately 6 sq inches each. The left intake is ducted (integral part of lower cowl) so when the cowl is in place, the intake duct fits up against the bottom of the oil cooler (mounted on the back of the centerspar). The top of the oil cooler is ducted to a selection valve on the firewall. The valve selects the oil coolers hot air to either be dumped overboard, or routed to the carburator in the form of "Carb Heat". To vent overboard, ducting installed in the bottom of the lower cowl (integral part of lower cowl), fits up against this valve. The ducting runs along the bottom left of the cowl and forms an exit (shaped like a 1/4 moon) under the propellor spinner. This exit area for the oil cooler air is approximately 10 sq inches.
In a similiar fashion, the right intake is ducted (integral part of lower cowl) along the bottom of the cowl to a valve that selects "FILTER or DIRECT". The filter assembly is also an integral part on the bottom of the cowl. The output of the "FILTER or DIRECT" valve is ducted (integral part of lower cowl) along the bottom right side and fits up against the "Carb Heat" valve.
As you can see, most of the oil cooler and combustion air ducting is actually mounted to and an integral part of the lower cowling shell.
The cost in materials alone comes close to the cost of a pre-made cowl. 10 gallons of 2 part foam ($200), Epoxy ($100), Glass ($100), Sheetrock Mud ($20), Lacquer ($15), Mold Release ($15), Gloves, mixing cups, plastic sheet, trash bags, etc ($20). OH YAH, I'm not done yet, I still need to add duct work , glass the mounting lips, install mounting nutplates, then finish and paint the inside and out.
The bottom line, I'll have about $550 in my cowl, Plus, I would guess about 80 hours of labor, (priceless). The main reason for building vs buying is of course, there simply isn't a cowl available that will do what I need it to do.
THINGS I WOULD DO DIFFERENT
1) Make the forms (cardboard box) a little better fit. I wasted a lot of foam because the box forms were to big. 2) Use only two part foam. I ran out of foam, and decided to use the spray foam for the last little bit. This stuff caused me all kinds of problems. 3) Use less dense foam. I used 4 lb (15x), If I had used 3lb (20x) I would not have run out of foam. 4) I painted two coats of Lacquer. This allowed for a good release, but I would probably paint at least 4 next time.
NOTE: When I get finished with the cowl, I'll move this short piece from here and place it under "HOW TOs"
7 Jan 2007. When the Cows come home!
It seems my neighbors cows decided to take advantage of a break in the fence and explore the roads, barns, and nearby fields. Bud (the cows owner) was probably in church and wasn't aware of his livestock's escapades. The Police tried to corral the animals, but they spook easily and would tromp off whenever the boys in blue got to close.
I got a frantic call from a neighbor and a visit from the local Magistrate to see if I could do anything. The cows know me and I occasionally give them a snack when I'm working out at my wood pile. I figured the instigator of this impromptu field trip was probably "Burt" (shown in photo), the other cows will usually follow him around. I walked out to the field with a make shift lasso and just started to holler "Burt". With in a couple minutes, I had Burt tied up and we were walking down the road with a small herd and a police escort.
OK, Back to work, the cows did come home.
7 Jan 2007. LongEZ Cowling shells now finished
1) In order to get the cowlings to pop off the mold, I had to dig some of the foam out. I removed the fake wings, and dug out most of the foam until I hit the engine. I was then able to pull, pry, and twist (Gently of course) until I got both the top and the bottom cowl shells came free.
2 and 3) Both top and bottom shells are off and look very good.
X-RAY vision - NOT
While cleaning the foam off the engine, I stepped back and said; "Now that would make a neat picture". You can see the basic engine components, starter, flywheel, cylinders, etc. almost embeddeed in the two part foam.
6 Jan 2007. LongEZ Cowling, Glass top cowling
The top cowl is now glassed. I put up 4 layers of BID on the main cowl. I also laid up 2 layers of 3 inch BID tapes across the back, and along the sides. The intake ramps have three layers of BID.
I'll knife trim it later this afternoon.
4 Jan 2007. LongEZ Cowling, Lacquer Coat
Lacquer is painted on the form. Lacquer seals the form and allows the painting of mold release. The mold release keeps the fiberglass layups from bonding to it
2 Jan 2007. LongEZ Cowling, Continued
SAND AND FILL - Sanded top cowl. One more layer of mud. Looks good.
1 Jan 2007. LongEZ Cowling, Continued
1) This is the stuff I refer to as "mud". When you mix it, you got about 20 minutes and it starts getting gummy.
2 and 3) Because of the rubberiness of the foam I used (spray can to fill in some holes) I wasn't able to get as good a shape as I wanted with the foam.
Instead, I'll need to do a "sand and Fill" with the mud to get the shape correct. Its kind of like everything on this project, the better job you do on the foam cores, the less sand and fill that needs to be done later.
HAPPY NEW YEAR - 2007
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