Archive of Weekly Updates
April - June, 2004
2004-06-28
- Photos of Scimitar Propeller Testing (click on image for larger photo):
Inspecting Prop
|
Testing Prop
|
Note Pitch Arm
|
- Stiffening the pitch control linkages appears to have corrected the blade weave problem in the scimitar propeller.
- The propeller failed during testing on Wednesday. The failure occurred at 403 hp, 5080 engine rpm and a thrust of 1581 lbs. The weight arm, which counters the moment produced by the blade weight as it trys to pitch the blade to the plane of rotation, initially failed in compression and came off. A contributing factor to this compression failure was the use of a new resin system with higher temperature properties, which due to its high viscosity, did not wet out well and caused some of the carbon filaments to be dry. Once the pitch arm failed, the 1.25 lb. brass weight then hit the bottom side of the following blade, cut through the skin and hit the blade spar at the point where the spar bonds to the skins (~3/4 radius). At this point the blade appeared to explode, however the entire leading edge spar and metal abrasion strip were intact. When the blade "exploded," the prop was so out of balance that the drive shaft moved out and was cut into by a retaining plate. The shaft and prop hub deflected so far that it caused both blade spars to bend in the flatwise direction until they broke.
- While we obtained some performance data, no attempt has been made to optimize the pitch and rpm for any given hp. Still at one test point, 268 hp and 5000 rpm on the engine, the prop thrust was 1458 lbs. This is very good even without the prop spinner and with turbulent flow off the test stand.
- Since we have all the tooling made, we could be back testing a new prop with appropriate design modifications in 3-4 weeks. The prop drive shaft and blade pitch horns will also have to be rebuilt, but it appears those are the only metal parts.
2004-06-21
- We apologize for the delay in posting a weekly update. Our co-webmaster in charge of the updates has been out of the office.
- Finished the test stand data collection system so we could start the prop test.
- Ran the prop up to a full throttle engine rpm of 3500. To load up the engine to full throttle at this rpm, the prop pitch had to be higher than optimum. Still, at 280 HP, prop thrust was slightly over 1400 lbs. - more thrust than the previous propeller could achieve at 400 HP (it was only designed for 300 HP).
- We hit a natural frequency at about 3800 engine rpm. This lower first natural frequency was caused by the drive train being different than that used before, and the propeller having a higher moment of inertia than the previous design. We decided to use the actual drive train hardware out of the aircraft, which corrected the problem in the test stand. If we lose the prop, we can make the drive repairs while the prop failure is analyzed, and a new prop is redesigned and built.
- The prop abrasion strip came off one blade. It was not bonded on with the proper adhesive. The out of balance was not enough that we immediately noticed it. No damage was done and the abrasion strips on both blades were rebonded with the proper adhesive.
- At around 4500 engine rpm, we experienced what looked like a prop blade weave. We believe that it was due to the control linkages not being stiff enough. We have modified the controls to make them stiffer. We have also installed a microwave transmitter (no slip rings required) to monitor the pitch link loads and hopefully have time to shut down before a failure could occur, should we hit another natural frequency.
- The engine efficiency is so good at this new 12.5 compression ratio, that at full throttle, 3500 rpm, 280 hp, the exhaust temperatures were about 1400ºF at optimum fuel air ratio. With the previous compression ratio we would have already reached our max temperature of 1650ºF, and would have had to enrichen the fuel mixture.
- Finished the prop spinner, except for final balancing.
- Finished repairs to the fuselage.
- Have begun work to replace the current gas tank with a larger capacity tank, including making a new rear shelf and installing new mounting brackets in the aircraft.
2004-05-31
- Replaced fire damaged section of fuselage.
- Laid up main portion of new prop thrust and support beam.
- Continued work on test stand and data collection system, including running wires for sensors and installing gauges in cockpit. All mechanical work was completed.
- Ran engine for short period to check out systems.
- Laid up the scimitar propeller spinner.
2004-05-24
- Cut out fire damaged sections of fuselage and performed a general clean up of the undamaged fuselage and aircraft parts.
- Cleaned and checked out the aircraft fire extinguisher system and refilled.
- Rerouted several air lines in preparation of replacing mechanical air compressor with 2 electric ones.
- Made a new sensor to measure rotor flapping.
- Disassembled engine and inspected. Increased compression ratio from 10 to 12.5.
- Modified test stand for longer propeller drive shaft and installed reworked aircraft engine to test new scimitar propeller.
- Built an intercom for the test stand and started reworking the test stand data collection system to be compatible with the aircraft data collection system.
- Completed the molds (2 parts) for the scimitar propeller spinner.
2004-05-17
- Last Wednesday, the CarterCopter experienced an in flight fire, caused by an exhaust leak which ignited the cowling. The aircraft landed safely, and the pilots were not injured in any way. There was slight damage to the aircraft, though the propeller and spinner were destroyed. The repairs to the fuselage will take about 3 weeks, but it will take about 5-6 weeks to complete the test stand testing of the new scimitar prop, reassemble the components in the aircraft, recalibrate and have the aircraft ready to fly. More information and photos are available in the Progress Update.
- Began repair work on the aircraft- Removed engine and other components from engine compartment to examine the components and clean the engine compartment; Cut out damaged section of fuselage to be replaced.
- Painted the scimitar propeller and extreme mu rotor.
- Began making the plug for the spinner for the scimitar propeller.
- New progress update showing the results of the fire. Also added the four press releases from Sun 'n Fun.
2004-05-10
- UPDATE 2004-05-14 The CarterCopter experienced an in flight fire on Wednesday, 5/12. The aircraft landed safely, and the pilots were completely unharmed. There was slight damage to the aircraft, though the propeller and spinner were destroyed. The repairs to the fuselage will take about 3 weeks, but it will take about 5-6 weeks to complete the test stand testing of the new scimitar prop, reassemble the components in the aircraft, recalibrate and have the aircraft ready to fly. More information and photos are available in the Progress Update.
- Continued flight testing in Olney. It looks like we've finally got the engine temperature problems under control. The side scoops improved the cooling, and we use a water spray on the ground and during climb out until the aircraft gets up to a speed sufficient to keep the oil and coolant temperatures low enough.
- There was a problem with airspeed not being calculated correctly, due to electromagnetic interference in the signal wires causing noise. We rerouted the signal wires and some power wires to correct this.
- On the ground, prior to one of the flights, the engine quit. Exhaust had leaked out of a slip joint on the copilot side, blew past the insulation and into the engine compartment. It melted the insulation around wires for the engine crank position sensor, shorting the signal. The slip joint has been modified with a stainless steel sleeve to keep a similar problem from occuring again, and the entire engine wiring harness has been redone to relocate the wires away from the exhaust.
- Completed prefinish work on the scimitar propeller and extreme mu rotor.
2004-05-03
- We took the aircraft to Olney for flight testing. We are having problems with water and oil temperatures running too high. We think the problem is related to the turbo installation, by the extra heat that the turbo adds to the engine compartment, by the restrictions to cooling air flow caused by the ducting needed for the turbo, and by the extra heat produced by the engine when making 400 HP instead of 325. To correct this, we have added intake scoops to the sides of the aircraft, to bring in more cooling air downstream of the restrictions. We have also better sealed several areas where air could leak out of the engine compartment without having to go through the radiators.
- The final bonding operation of the scimitar propeller has been completed. Without paint, the leading edge abrasion strips, or the pitch horns, the propeller weighs 27 lbs. The completed propeller should weigh only 32 lbs.
- Carter had an exhibit at the Oklahoma Small Aircraft Transportation System (SATS) Expo on Friday and Saturday. SATS is a nationwide program funded by NASA, whose aim is to utilize the 5,000 existing small airports in the U.S. to relieve safety and congestion problems, both on our nation's highways and its airways.
2004-04-26
- We finally got the new engine fuel/air controller working satisfactorily. We can still probably improve on it, but at the present it works better than anything we have been able to do in the past. This new controller uses feedback to maintain the engine at its peak efficiency at any rpm and power setting, so we will no longer have problems associated with the operating conditions being different from those when the engine was tuned.
- We ran tests on several different hardeners at several temperatures to determine which one was best suited for our propeller. We found the best one, and have continued construction. All of the parts have been made. Remaining work includes the final bonding of the blades, affixing the leading edge abrasion strips, prefinish and painting, and final assembly including the prop pitch mechanism.
- Built or modified several parts for the propeller test stand, including lengthening the drive shaft and propeller pitch shaft, fabricating a new engine coolant cooler, and working on the electronics for the propeller controller.
2004-04-19
- Company president, Jay Carter, traveled to Washington, D.C. on Monday to visit with several military personnel. Over the weekend, he traveled to Lakeland, Florida for the Sun 'n Fun EAA Fly-In. Carter had an exhibit at the fly-in in the NASA section the entire week.
- Bonded the spar in place on the scimitar propeller. We used a high temperature resin that we had not used before, and found cracks in the resin around the spar. We did not know it before, but this resin is not intended as a potting resin. We were able to salvage the spar and the skins, but will need to remake the shear webs and ribs. This week, we are running tests on several resins at several temperatures to determine which one to use for our propeller.
- Began work on the exhaust manifold for the engine for the propeller test stand. This is the same exhaust manifold that will be used in the Next Generation CarterCopter (NxCC).
- Continued work on the new engine fuel/air controller. On Friday, we ran the engine with new hardware to control the left half of the engine, with the right half still running stock. It appears that our method is finally working. We are now building the hardware to control the right half as well, and will continue testing this week.
2004-04-12
- Look for Carter at this year's Sun 'n Fun EAA Fly-In (website), which will run through this weekend. NASA has given us space to put up our exhibit in their section.
- Laid up shear webs and ribs for the the scimitar propeller intended for testing.
- Continued work on the new engine fuel/air controller. The method still appears very promising, but it requires additional refinement.
2004-04-05
- Laid up shear webs and ribs for the first test layup blade of the scimitar propeller, and completed the bonding procedure. Weight of one blade and half of the spar was 13.5 lbs. Estimated weight of finished prop with pitch horns is 30 lbs. The prop will be 8 ft. in diameter and rated for 600 HP.
(See Photo)
- Completed the upper and lower skins for both blades of the scimitar propeller intended for testing.
- Tested a new engine fuel/air controller. The tests were very promising, but the method needs some additional refinement, including new hardware and software.
|
Home
