Wichita Falls, Texas: Tuesday, 3 July 2001

Edited by Carl Hawkins and Paul Smith, GAA

MILITARY-STYLE PROGRAM PAYS DIVIDENDS: ADDITIONAL 11 ½ DAYS OF PROGRESS

Efforts by CarterCopter (CC) and Golden Arm Associates (GAA) to restructure the CC flight-test program to more closely follow military flight-test procedures have begun to pay dividends. The large amounts of test data collected without incident during the two recent flight-test series (9 days + 2 ½ days) show that the system is working.

Unfavorable weather continues to create problems. At least one full day and numerous afternoons were lost due to high-gusting winds, high ambient temperatures and widespread thermal activity (including T-cells). Rusty Nance, CC chief test pilot, flew left seat as pilot-in-command (PIC). Larry Neal of Popular Rotorcraft Association (PRA) fame joined CC as test pilot / flight-test engineer (FTE) and flew right seat.

Except for delays caused by weather, the program progressed smoothly with few exceptions. R&D programs for new types of aircraft like the CarterCopter Technology Demonstrator (CCTD) regularly take two steps forward and one step backward. The CCTD followed this pattern until the 4-day flight-test series that began May 25th. Since then, efforts have produced mostly positive results and the flight-test program continues to accelerate. The CCTD established new records for range and altitude - flying outside normal airport patterns for the first time. Each new flight now includes the possibility of extending the CCTD flight envelope even further. Flight-times are more often determined by flight-test objectives than by problems with the aircraft.

THE WEATHER PLAYS IMPORTANT ROLE IN FLIGHT-TESTS

Weather conditions during flight-testing are crucial for several reasons. Gusting and high crosswind components that exceed a pre-determined safety limit keep the CCTD grounded. Once the CCTD is airborne, wind gusts and thermal activities make it difficult for the pilot to fly the pre-assigned headings, altitudes and speeds required for good test data to be collected by the ground-based telemetry (TM) system. Good flight-test data is (by definition) repeatable. If good data cannot be collected -- there is no reason for the CCTD to fly. Bumpy flight conditions are also physically and mentally stressful for the flight crew.

High ambient temperatures cause additional problems. The CCTD has no air-conditioning system. Cockpit temperatures above 100°F are exhausting and distracting to the flight crew. High temperatures can prevent takeoffs - especially following long periods of idling and/or taxiing. Heat buildup degrades engine performance - which during prerotation can prevent the rotor from reaching the minimum 325 RPM specified for the CCTD to take off.

BRIEF USE OF NON-RETRACTABLE NOSE GEAR

The CCTD flew well during the previous flight-test series (May 25-28), but had not been returned to the flight configuration used prior to the accident on 16 December 2000. The landing gear was still non-retractable, ailerons were not connected and the horizontal stabilator set to 7.5° trailing edge down (TED) with respect to the rotor spindle. The goal was to slowly return the CCTD to the prior configuration so that high speed, high altitude flights could resume. Small, progressive steps are necessary to determine the effects of each change. The flight-test community calls this the "build-up" approach. The pilot (essentially) trains himself as he goes.

The 9 day flight-test period (June 8 - 16) began with the CCTD still using the long (non-retractable) nose gear. The main landing gear was pressurized to make it fully extended and firm. The combination provided the CCTD a fairly level pitch-attitude that makes takeoffs and landings a little easier. The pilot made four runway flights to ensure the takeoff procedure he developed during the previous flight-testing was both repeatable and robust. Prerotations were to 325 RPM. The flights were to 75 MPH and approximately 75 ft altitude.

The pilot next worked on refining his landings. The rudders were toed-in to increase rudder control at low airspeeds (angled more into the prop blast). Adjustable cyclic dampening was also added. The ailerons remained disconnected and were set at neutral. Aerodynamic braking was used exclusively when landing - which saves the brakes and makes for shorter rollouts. To do so, the pilot pulls the cyclic back into his lap and slowly raises the collective so that the rotor acts as a huge air brake.

RETRACTABLE NOSE GEAR REINSTALLED

When the pilot felt ready, the shorter (retractable) nose gear was reinstalled. Air pressure on the main gear was reduced. This softened the landing gear and served to keep the pitch attitude the same as before. Weights were added to the rotor's stabilizer bar to reduce cyclic stick-shake. A little stick-shake is good - and the pilot was happy with the feel after the modification. The rudders were toed back to neutral to increase rudder effectiveness at higher airspeeds. The needle valves on the main gear were adjusted to reduce the extension rate on the gear during takeoff. Prerotations were done at 350 RPM instead of the previous 325.

Once takeoffs were comfortable, the pilot continued work on shortening his landing rolls. Short rollouts are a safety requirement for longer flights in case an emergency off-field landing is necessary. A few configuration tweaks were made including changing the horizontal tail trailing edge down (TED) setting to fix a problem with pitch changes that occurred with throttle changes. Eleven runway flights were made at speeds up to 80 MPH and at altitudes up to approximately 150 ft. Climb-outs gradually became more aggressive and landing rolls shorter. On Wednesday, 13 June, the CC flew the traffic pattern at 800 ft. AGL with everything happening as planned. The last pattern flight had been in November 1999.

The following morning, stops on the rotor were set with 2½° of collective as a safeguard for upcoming flight-tests designed to determine if a previous problem with vertical oscillations had been resolved. One normal traffic pattern and one double pattern were flown. Weather related problems caused the flight-test program to shut down early.

AILERONS CONNECTED

The flight-tests schedule for Friday, 15 June, included test points to determine best climb speed, power and RPM setting. To improve lateral control at higher speeds, the ailerons were reconnected the night before. They were previously disconnected to reduce lateral control forces caused by friction.

The morning weather was beautiful. The pilot flew the airport pattern and reported the CCTD was well balanced in roll. It was decided that roll trim would be added in the near future. On request of the pilot, the pitch trim had been temporarily disconnected. This was now reconnected. During the following flight, the rate of climb at full throttle was approximately 300 fpm at 80 mph. It was determined that the rotor was producing too much lift and (consequently) unnecessary drag. The stabilator was adjusted to 3 degrees TED to unload the wing more. This returned the CCTD to a less stable takeoff configuration and the pilot made several short runway flights to ensure that his takeoff technique was still suitable.

RESOLVING TELEMETRY PROBLEMS

Telemetry (TM) data stream reception has been marginal at times and occasionally lost for short periods. With much longer flights planned for the near future, an effort was made to diagnose possible problem areas. It was found that the TM receiving antenna on the roof of the building used for CC ground control operations had been mounted halfway up a metal pole -- reflected signals from this pole and a nearby antenna reduced its effectiveness. The antenna was remounted to the top of a separate pole, which improved reception.

Analysis of the TM transmitting antenna location revealed that the CCTD engine firewall and the carbon wings were probably blocking much of the transmitted power. Moving the TM transmitting antenna from inside the cockpit to the outside front of the rotor mast appears to have solved this problem.

NINE-DAY SESSION ENDS ON HIGH NOTE

The morning weather on Saturday, 16 June, was again beautiful. Tests were planned to collect flight data on the engine at specified increments from 4700 - 5400 RPM while flying first at 80 and then 100 MPH. The second part of the flight was to see how retracting the landing gear affected airspeed.

The pilot took off and climbed the CCTD under full power. Once clear of the airport pattern, he held the climb at 80 mph and varied the engine RPM (5400, 5100, 4900 & 4700) for brief periods to establish data points. The data points were then repeated at 100 mph for each of the previous engine RPM settings. Several times during the flight the pilots had difficulty hearing ground control above the ambient cockpit noise.

Next, the CCTD was trimmed in level flight and the landing gear raised in the following order; nose gear first -- then mains. This procedure was designed to isolate any pitch instabilities caused by reduction in drag and to provide the pilot with a simple way to abort the gear test if problems were encountered. Raising the nose gear increased airspeed (approximately) 7 mph while raising the main gear increased airspeed (approximately) 5 mph. As the nose gear retracted The CCTD pitched upward slightly. It pitched up even less as the main gear retracted. The gear was lowered again shortly after retraction. The pilot then made an uneventful power-off landing to provide data on power-off glide performance. This flight went to a maximum altitude of 1500-ft AGL and lasted 19 minutes - the highest and longest flight to date. It was only the second time since flight-testing began in September 1998 that the landing gear had been retracted in flight. Maximum airspeed was 112 mph.

The second flight was designed to determine if a vertical oscillation problem previously encountered at 125 mph had been resolved. Following takeoff, the CCTD climb rate increased from 100 fpm to 300 fpm and then failed to improve much thereafter. Gear was raised shortly after takeoff and the data matched that from the previous flight. After climbing to pattern altitude, the FTE changed the engine controller from manual to auto as part of an engine test. This caused a strange vibration. The pilot elected to shorten the pattern and land. (NOTE: a software problem was later discovered in the prop controller and fixed).

SECOND FLIGHT-TEST SERIES (23 - 25 JUNE)

CCTD flight-testing at Olney resumed again on Saturday afternoon - seven days after completion of the first series. The test objective was to determine if interim efforts to reduce drag had been successful. Efforts had been directed towards reducing the drag from the open rotor hub, the engine cowling flap (beneath the prop spinner) and the training wheels on the tail booms. The communication difficulties between ground control and the pilots were also addressed.

During pre-taxi system checks, an unusual noise in the engine area caused the planned flight to be canceled. Because the noise refused to readily repeat itself, the diagnosis took until noon on Sunday. The test crew was finally able to determine that the drive belt to the prop was occasionally slipping due to unwanted slack in the system. Corrective action was taken to prevent reoccurrence.

On the subsequent takeoff attempt the CCTD suddenly developed rotor blade-weave and the flight was aborted. Jay determined that the new rotor hub enclosure was too large. Relative wind that struck the disk when the rotor blades were side-to-side - acted to move the center of rotor lift forward. The center of lift then centered again when the blades were fore and aft. This caused a pulse that was exaggerated by the soft rotor-mast system. The enclosure was removed for the remaining flights. A smaller rotor disk cover and mounting system will be designed.

Three airport pattern flights were made on Monday morning, 25 June. Data showed that the CCTD rate of climb improved as the rotor slowed. Climb increased to 500 fpm by slowing the rotor from 250 to 230 RPM. The observation was not pursued further during the flight-test period because of a perceived flapping problem.

Data analysis showed that rotor flapping was being reported approximately 2-1/2 degrees higher than calculations predicted (i.e. six degrees rather than 3-1/2 degrees). This greatly limited flight-testing due to established safety limits. It now appears that the erroneous data was caused by the soft rotor-mast system. The pilot suggested we measure the force on the spindle that causes spindle deflection. A software change was made to incorporate this more direct measurement of rotor stability, and it appears to have solved the problem. Flapping indications are now close to Jay's calculations.

CREATOR OF X-PLANE HELPS CC BUILD FLIGHT SIMULATOR

Austin Meyer, creator of X-Plane (see www.x-plane.com) visited CC for 4 days earlier this month. He worked with Jay and Rusty to fine-tune the computer model of the CCTD he created for X-Plane. Purchasers of X-Plane software can download the CCTD model at www.x-plane.com/order.html. When version 6.0 is released later this summer, the CCTD will be one of the aircraft that purchasers will have available to fly.

Austin is assembling an X-Plane based 3-D CCTD flight simulator that will be displayed at AirVenture 2001 this summer. Hardware for the 3-D flight simulator will include a cyclic with the same grip and switches used on the CCTD, a collective with throttle grip, a CCTD seat, rudder peddles with toe brakes - and a large flat screen monitor for viewing the dashboard and outside view. Later this summer we hope to enclose the hardware in a replica of the CCTD cockpit with a co-pilot seat and dual flight controls. Eventually the flight simulator cockpit will be mounted on a full motion platform and include an interactive instrument panel. An advanced projection system will replace the flat screen monitor for outside views.

CCTD AT AIRVENTURE 2001

The next flight-test period (June 29 - July 4) will determine if the CCTD will fly to AirVenture this July. If the decision is made not to go, the CCTD will continue flight-testing at Olney during this time period.

Regardless of the outcome of the flight-test program, CC will provide an exhibit at AirVenture we hope you will enjoy. Numerous videos of the CCTD in flight will be shown. These include video from the lipstick camera on top of the right rudder (facing forward), from inside the cockpit, from the chase plane and from the runway chase vehicle. The X-Plane based flight simulator will demonstrate the piloting techniques used to fly the aircraft.

We will also highlight the CC Heliplane Transport (CCH-T) design. The display will include a 1:72 scale model of the CCH-T and the Popular Mechanics' Design and Engineering Award 2000, presented to CC last December. Professionally rendered video animation will help visitors understand the impact this huge rotorcraft will make on the aviation world.

"AL" RIVERA JOINS CC AS ELECTRICAL TECHNICIAN

Al Rivera joins CC with over 24 years of electronic experience and 5 years of computer networking experience. Much of his experience came from 21 years as an avionics tech in the US Air Force -- working on the F-15 fighter and B-1 bomber. His experience includes electronic warfare, radio, automatic test stations, flight controls, and satellite communications.

He is a certified occupational instructor, a command acquisition specialist and a command circuit-card repair technician. Al has job experience in creating schematics and updating obsolete boards with modern components. He is certified by COMPIA as an A+ certified computer technician.