Engineering News

General aviation experiences a rebirth

Seal Beach, CA--Like Lazarus awaking from the dead, America's general aviation industry is back. Nearly exterminated in the 1980's due to stratospheric liability costs, light-airplane manufacturers received resuscitation in the form of the General Aviation Revitalization Act of 1994. Limiting liability to 18 years from production, the bill has spurred a flurry of aircraft-design activity.

The life signs appeared not a day too soon. Pummeled by skyrocketing litigation and insurance costs--the industry paid $210 million in claims in 1986--production of general aviation (GA) aircraft plummeted 95% in the past two decades, from 17,811 in 1978 to just 928 last year. More than 100,000 people lost their jobs.

Cessna Aircraft ceased making piston-powered airplanes in 1986; Piper Aircraft slipped into Chapter 11 in 1991; Beech Aircraft spent an average of $530,000 defending itself in 203 accident cases in which the NTSB concluded that the aircraft's design and manufacture were not a factor.

"The average age of the GA fleet is 27 years," says Ed Stimpson, president of the General Aviation Manufacturers Association (GAMA). "We were getting sued on 30-, 40-, and 50-year-old airplanes." He jests that, prior to the legislation, had a pilot crashed the original Wright Flyer he could have sued the Wright Brothers for design defects--92 years after the aircraft was built.

When the liability law passed, manufacturers responded enthusiastically. Cessna is restarting production of its 172, 182, and 206 aircraft; Piper emerged from bankruptcy this past July; Mooney Aircraft announced a 40% boost in production; and numerous suppliers launched new designs for everything from avionics to fuel systems, electronic ignitions to cabin-pressure systems.

"GAMA companies are reporting expenditures of 15% for R&D for 1995," says Stimpson. "That's up from zero being spent on piston airplanes for the past four or five years."

One of the hottest new designs is the Jetcruzer 450 made by Advanced Aerodynamics and Structures (AASI) in Long Beach, CA. It combines a graphite composite fuselage with an aluminum wing. This hybrid approach saves weight in the body, but makes the aircraft easier to certify since the FAA takes a cautious approach toward composite wings. A Pratt & Whitney (West Palm Beach, FL) PT6A-42 engine driving a pusher prop, propels the six-seat Jetcruzer 1400 nm at 352 mph. Those are jet-like numbers for $1.2 million, 40% less than anything approaching its performance.

In June 1994, Jetcruzer received certification as the world's first spin-resistant aircraft. Pilots from both the FAA and AASI attempted 450 spin entries, all without success. "I've tried to spin it many times myself, and it's impossible," claims Gene Comfort, the company's senior vice president.

The aircraft's secret lies in its canard configuration. Engineers designed the small, forward airfoil with a greater angle of attack than the main wing. It stalls before the wing and keeps the airplane in control. The stall itself occurs at a benign 58 kts--3 kts under the required maximum--without flaps.

Supplier benefits. Aircraft manufacturers aren't the only ones enjoying an upswing in business. Unison Industries (Jacksonville, FL) recently introduced LASAR™ (Limited Authority Spark Advance Regulator), an electronic ignition system. It builds on technology developed in the 1980's that was shelved due to the litigious atmosphere. The only FAA-certified electronic ignition system for piston aircraft, LASAR improves fuel consumption by 8-14%.

Uniquely, it integrates the electronics with the mechanical dual-magneto system found on virtually every piston-engined aircraft. The reason: safety. "It's fundamentally a microprocessor-controlled electronic ignition," says Norm MacLeod, chief engineer on the project. "But if there's a problem, the engine reverts back to standard magnetos."

The heart is a 16-bit Intel microcontroller. It processes signals gathered by manifold-pressure and crankshaft-position sensors and selects the optimum timing and spark energy from a three-dimensional lookup table. Special dual-mode magnetos respond to commands from the controller or function normally in the event of a system failure. To guard against undetected failure of the CPU, a watchdog circuit continuously monitors its condition.

Though cars have been puttering around for a decade with electronic ignitions, designing one for aircraft is much more than technology transfer. LASAR varies spark output up to 300%--something no auto ignition does. It's also fail-safe and designed to withstand EMI, radar, multiple-g accelerations, altitude, and even near-miss lightning strikes.

Available on the aftermarket, LASAR has also been selected by Lycoming for the engine in Cessna's 172. Designed to work well with future engine-management packages, the system can also control the fuel-mixture or propeller pitch. "This is the biggest development in aircraft piston engines in the last 30 years," claims Brad Mottier, Unison's senior vice president.

Another Cessna beneficiary may be Dukes, Inc., Northridge, CA. An original supplier of pumps, valves, and actuators for the 172, the company hopes to add $6 million in new GA business by 1998. Chet Huffman, the company's vice president, thinks it's about time. "We went from (GA) sales of $6 million in 1979--and that's in 1979 dollars--to $300,000 today," he says. "We used to do 2,000 (fuel) pumps a month, now we do 100."

Huffman sees the biggest potential in a cabin-pressure control system engineers have been redesigning for two years. Originally targeted towards kit planes, it would be perfect for OEMs that want to build pressurized piston aircraft, he says.

An industry microcosm, Dukes recently hired a GA chief engineer for the first time in a decade. And if it gets the expected business, the company will hire 60 more employees, increasing its size by 50%. "The industry is definitely hiring again," concurs Stimpson at GAMA. "Cessna plans to add 1000 people at their new single-engine plant."

Government's role. Wanting to re-emphasize the "aeronautics" in NASA, the agency launched the Advanced General Aviation Transportation Experiments (AGATE) in 1994. It matches $63 million in seed money from NASA over six years with 61 industry and academic members. The goal: Revitalize general aviation by completely re-thinking light-aircraft design and, ultimately, create a new GA transportation system.

To that end, engineering members are looking to advance every aspect of aircraft design including aerodynamics, avionics, flight controls, engine design, emissions, and others. They see the ideal general aviation aircraft as one that starts like a car; is easy to fly in nearly all weather; provides intuitive, computerized avionics; and appeals to a broader range of users. Companies involved in AGATE include:

* Cirrus Design (Baraboo, WI): more aerodynamic de-icing system.

* Seagull Technology (Sunnyvale, CA): advanced GPS and displays for cockpits.

* Vision Micro Systems (Bellingham, WA): engine-failure warning system.

* DAR Corp. (Lawrence, KS): PC-based, preliminary airplane design software.

* BAR Inc. & Miami NDT Inc. (Miami, FL) with NASA Langley: New method of detecting corrosion in aircraft skins.

--Mark A. Gottschalk, Western Technical Editor

PDM cuts drawing search time at Draper

Cambridge, MA--Draper Laboratory has just completed the first phase of a major pilot test to see if product data management software can help engineers and managers find engineering drawings and other records.

The software, Matrix, from Adra Systems, passed the test, says Draper Information Services Manager Sheldon Buck. Draper had been testing the software in three departments, and will now install it in seven departments.

Draper engineers had been struggling with a problem common to many companies that have undergone reorganization: the loss of staff responsible for maintaining and storing drawings. "We were relying on word of mouth to find documents, and even at that you had to know the full UNIX path and the person who created the document," Buck says. He adds that using Matrix, engineers have reduced document search to minutes, "or seconds."

Buck says Matrix's encapsulation capabilities allow engineers to run most of their other engineering software packages, including CADRA 2-D, AutoCAD, Pro/ENGINEER, ANSYS, MSC/-NASTRAN, Abaqus, and Adams, without leaving Matrix. "They can double-click on the appropriate icon within Matrix and the application launches itself," he says.

Device checks conditions when astronauts take a walk

Houston--Astronauts' fingers and toes can encounter frostbite while doing Extravehicular Activity (EVA). This makes it important to measure temperatures outside the space shuttle and immediately surrounding the spacesuits. A Thermal Instrumentation Package (TIP) developed by United Technologies Hamilton Standard Management Services, Inc., does just that.

The TIPs consist of five Data Recording Devices (DRDs) and a battery pack. Each DRD uses an encapsulated circuit board with exposed leads for power connections, thermistor wires, and reading collected data once the mission returns to Earth. The thermistors range in length from a few inches to several feet. Each DRD has one thermistor that extends to a designated position on an Extra Vehicular Mobility Unit (EMU).

The battery pack contains an added circuit board, 10 power leads, a grenade-style activation pull pin, and one AA lithium thionyl chloride battery supplied by Tadiran Electronic Industries, Inc., Port Washington, NY.

One set of the DRDs and a battery pack are located on the side of the astronauts' Primary Life-Support Subsystem, covered with Thermal Micrometeroid Garment (TMG) material. Thermistors also are located across the rear surface of the life support subsystem.

Before an astronaut goes EVA, another crew member pulls the battery pack activation pin to release power from the battery to begin data collection by the five DRDs. The battery pack power is alternated from one DRD to another for each temperature reading. This allows the unit to conserve power so that the single battery can accommodate many DRDs during an EVA.

Custom cable helps land copters

Ontario, Canada--When you're landing helicopters on ships at night or during rough seas, you want a reliable docking and handling system. Indal Technologies' ASIST (Aircraft Ship, Integrated Secure and Traverse) system positions a deck-mounted securing device under a descending helicopter, snags and aligns the copter, and then maneuvers it into the hangar.

However, ASIST's weak link was the 250-ft electrical cable that runs down the deck track. The cable supplies control inputs and sends helicopter-position information to the system operator. The problem was twofold: First, the MHOF-30 Mil-C-915 cable's jacket couldn't stand up to being repeatedly dragged back and forth on the deck's steel surface. Second, the cable's conductors were susceptible to "Z" kinking because of the 90ø and 180ø turns the cable made through the tension controller and the cable's high speed of 5 ft/sec.

"The original cable failed rather severely--the conductors kinked and popped through the outer cable coating, and the jacketing eroded and also abraded," says David Cramton, Indal program manager.

Indal approached Olflex Wire & Cable Inc., Fairfield, NJ, to design a cable that could withstand these conditions. The custom Olflex design uses 3 16-AWG and 27 20-AWG conductors instead of the original cable's 30 16-AWG conductors. Olflex also added built-in tension members and changed the lay of the cable. "Rather than have it all wound in one direction, the conductors are counter-wrapped," says Cramton. As the cable is subjected to tension, rather than the conductors trying to twist, the forces tend to balance.

The new, tougher jacketing withstands sea water, aircraft fuel, hydraulic fluids, lubricating oils, and temperatures between 30 and 150F, say Olflex officials. The system with the new cable is currently in testing.

ASIST uses an electro-optic tracking system that automatically positions a securing device under the helicopter while providing the pilot with visual landing cues. Upon touchdown, the system secures the helicopter's probe, and the operator aligns the aircraft and guides it into the hangar. The electrical cable provides control signals and power.

Contamination detector senses ice on wings

Burnsville, MN--A new sensing system from Rosemount Aerospace claims to be the first capable of detecting ice or contamination over a broad area of an aircraft's wing. Called HALO, it can sense ice as thin 0.0006 in., but is expected to be limited to no more than 0.002 in. to prevent false alarms.

HALO uses a waveguide technique to send ultrasonic acoustic energy along a path either on the surface of the skin or in an overlay on top of the skin. Pairs of transducers and receivers--possibly as many as four sets per wing--play "pitch and catch" with the sound waves. The system is based on frequency, not amplitude. And it exploits the fact that each type of contaminant--glycol, water, snow, or ice--attenuates different frequencies different amounts.

"One of the biggest breakthroughs is the ability to tell if something is adhering to the surface or not," says Mike Peterson, design engineering manager on the project. HALO does this by sweeping over a range of frequencies and looking for a subset that only changes with bonded ice.

Under development for two years, a prototype system is currently installed on an MD-80 being evaluated by McDonnell Douglas and Northwest Airlines. Intended for ground use only, it could potentially not only improve detection, but also eliminate the pilot's reliance on visual inspection.

Peterson believes the system may also be instrumental in helping the FAA set a threshold for acceptable contamination, rather than the overly-cautious "zero" used now. This could reduce the environmental impact of glycol de-icing fluid used unnecessarily.

Computers speed baggage check-in

Dallas--Computer technology to let airline passengers bypass the check-in counter: Now that's the ticket!

Southwest Airlines, Dallas, TX, recently began testing the use of wireless handheld computers by their skycaps at curbside to speed baggage check-in and confirm reservations at the same time. The eventual goal: ticketless travel, to cut costs in the extremely competitive air-travel market.

The devices would enable skycaps to access customers' Ticketless Travel reservations with queries by name, confirmation number, flight number, or indicator. The handheld computers were designed by Telxon Corp., Akron, OH.

Called the Telxon 1134®, these 486-based pin/touch Windows computers include 20 Mbytes of storage and 8 Mbytes RAM. They also boast a range of approximately 2,000 feet.

The PCs communicate with the ticket counter via a radio from Telxon's Aironet™ Division. It is integrated into the computer and offers spread-spectrum radio data communication with a frequency range of 900 MHz. The computers measure 8.4 x 5.4 inches and weigh 35.2 ounces.

The PC can print out a copy of the passenger's itinerary, which can then be used as a receipt. Passengers then take the receipt to the gate, where they are issued a plastic boarding pass. The pass is turned in once aboard the aircraft. These procedures can save about 15 steps of ticket handling.

According to Charles Zug, Southwest Airlines director of marketing automation and business development, early test results for the curbside check-in system at Dallas look very promising. "We are optimistic that the new technology will greatly assist us with providing our customers greater convenience and also make travel as hassle-free as possible."

Zug predicts that future computer applications could employ scanners for baggage check-in (similar to bar coding), or allow passengers to use a card-reader for either frequent-flier information or as a form of payment.

Device eases linking microprocessors to avionics bus

Bohemia, NY--Engineers are still using the ARINC 429 avionics data bus, which has been around since the late 1970s and shows no signs of going away. However, linking the 32-bit unidirectional bus to today's microprocessors is not a trivial endeavor. It usually requires lots of discrete logic components and a complex design.

In response to the need for a flexible, intelligent interface between the bus and today's microprocessors, ILC Data Device Corp. (DDC) designed the DD-42900 ARINC 429 transceiver. "The part is much more friendly to a microprocessor bus architecture--where you have an address bus, data bus, and read and write strobe lines--than discrete logic components," says DDC Design Engineer Todd Decker.

Features include a data-match processor, data-store processor, two transmit channels, four receive channels, 128 wordsx32 bits of shared RAM, and fault-detection and self-test capabilities. On-chip intelligence lets the receiver channels decode and sort ARINC 429 label and destination bits. The two transmit channels have wrap-around data-verification circuitry. All six channels have 32-bitx32-word FIFO buffers.

"What this part brings to the table is the ability to queue up outgoing messages, and retrieve and store data without the microprocessor's help," says Decker. "This frees up the microprocessor to perform more avionics functions as opposed to data-management functions."

"There hasn't been a part before that integrated all these functions," says Rockwell-Collins Design Engineer John Persick, who was one of the customers polled by DDC before the company designed the interface. "It will make the design engineer's job much easier."

 Passengers help select 21^st century aircraft's interior

Long Beach, CA--Using results from airline passengers, McDonnell Douglas has selected a futuristic design for the interior of the MD-95, its proposed next-generation twinengine jet. The company is offering the aircraft to airlines as a new 100-passenger model built for short- to medium-range routes.

More than 500 people, including airline passengers, flight attendants, and airline executives, evaluated three full-scale mockups of the MD-95 interior provided by three suppliers. Participants were asked to base their evaluations on appearance, styling, and appeal. Evaluators came from Brazil, Canada, Colombia, Finland, Italy, Japan, Korea, Mexico, New Zealand, the People's Republic of China, the Philippines, Singapore, Spain, the UK, the U.S., and Vietnam. Fischer Advanced Composite Components, Reid, Austria, produced the interior.

"We wanted to complement the MD-95's state-of-the-art technology with stylish, yet functional, interior features that passengers of the 21^st century will expect," explains Jerry Newkirk, project manager of the 95's interior design. "Therefore, we developed an evaluation process to identify the cabin features passengers and airlines desire the most."

Participants spent about 50 minutes providing in-depth evaluations of the mockups and responding to the written survey. Their evaluations gave McDonnell Douglas the opportunity to get feedback before getting too deep into the design.

As a result of the survey, the cabin will feature wider and deeper overhead baggage bins. An ergonomically designed, full-grip handrail will be available throughout the cabin. Optional video monitors that drop down from passenger service units will be located on both sides of the cabin at every third row. The widely preferred five-across seating found on Douglas' narrowbody predecessors also will be used.

Search technology aids rescue workers

Park Ridge, IL--When survivors slithered to safety after the collapse of a five-story department store in Seoul, Korea last July, the tragedy once again proved that people sometimes survive even when seemingly buried alive. In Seoul, two dozen survivors were found, greased with vegetable oil, then pulled through a narrow 130-foot-long tunnel to safety.

To make such dramatic rescues, however, workers must first find the victims. Recent disasters in Los Angeles, Japan, Oklahoma City, and Korea have helped advance the state-of-the-art in new rescue technology. "These tragedies are testing us," notes Michael Tamillow, battalion chief for the Fairfax County Fire and Rescue team in Virginia. "We make advances every time we go to these sites."

Rescue teams are aided by the emergence of new listening devices, search cameras, and thermal sensing equipment. One such device, known as the Search Cam, was purchased by the Seoul Fire Department only four months before the department-store collapse. Used at the site, it reportedly helped confirm the presence of survivors.

Designed and built by Search Systems, Bakersfield, CA, the Search Cam consists of a sensor package on a rigid, telescoping probe. A 1.75-inch-diameter head contains a camera, microphone, speaker, and lights, enabling workers to see, hear, and communicate with survivors. Rescue workers wear the unit's video monitor on their chests, so they can view the scene while extending the probe. A gearmotor, made by Maxon Precision Motors Inc., Burlingame, CA, mounts inside the unit's head and enables workers to swing the camera 180 degrees.

The 12-foot telescopic probe is long enough to enable workers to search past pancaked piles of concrete flooring measuring 10 feet thick. "It extends the eyes and ears of the rescue team into the void of the collapsed building," says Scott Park, founder of Search Systems and designer of the device. The unit, which costs about $10,000, has become standard inventory for all of the Federal Emergency Management Association's 26 Search and Rescue teams.

Listening for life. Engineers also are designing sensor packages that "listen" for life in collapsed buildings. One approach, available from Mistral Inc., Bethesda, MD, employs acoustic and seismic sensors in a 3-inch-high cylindrical unit that is lowered into a site. Known as the TPL-310, it was developed by Elpam Electronics Ltd. of Tel Aviv, Israel, to cope with the results of terrorist activities. The system employs one acoustic sensor for communication and four seismic sensors to check for the vibration caused by tapping and scratching of trapped victims.

Similarly, Delsar, Inc., Chapel Hill, offers the Life Detector, which uses a single sensor to cover seismic and acoustic frequencies. The sensors are designed to detect vibrations down to 1 Hz. Noise is suppressed with filters, allowing rescue workers to pinpoint the location of victims.

New lifesaving technology also has spread to the realm of the rescue worker, as well as the victim. Delsar's AC Hot Stick provides workers with an early warning of the presence of high-voltage AC wires. It uses a high-sensitivity AC amplifier to aid in detection and provides an audible and visual alarm when users near downed AC lines. The AC Hot Stick has been used in building collapses and in the aftermath of wind and ice storms.

Rescue workers say the most important new technologies are the ones that save time. And in the race to find survivors, minutes saved by sensors can spell the difference between life and death. "Nothing we do ever seems fast enough," notes Tamillow. "We need the assistance of technology to help locate victims faster."

--Charles J. Murray, Midwest Editor

Passenger truck packs 'em in

Newton, MA--Take the 1995 GMC four-door Yukon out for a tail- gate party and you'll have no trouble finding a gang to join in the fun. Maximum cargo capacity is 122.5 cu ft for the Yukon, versus 81.6 cu ft in the Ford Explorer four-door, and 79.3 cu ft in the Jeep Grand Cherokee, leaving plenty of room for friends, coolers, grills, and lawn chairs.

Positioned between the GMC Jimmy and the GMC Suburban, this passenger truck combines a fuel-injected 5.6-l, V-8 engine with electronic four-speed automatic transmission, four-wheel anti-lock brakes, driver's-side airbag, and air conditioning. A ride on the highway is a treat, but the real joy comes from steering through city traffic--the truck is light on its wheels. But, don't let it fool you. Properly equipped, the GMC Yukon four-door can tow trailers up to 7,000-lbs in weight.

Everyone, even tall people in the back seat, has plenty of headroom. Leg room isn't quite as ample, but certainly adequate. Several passenger-seat riders complained that the optional leather bucket seat they occupied was a better seat for drivers than for relaxing on the ride, a bit uncomfortable apparently.

But, if you're in the market for a passenger truck, don't miss this one. Some useful options to consider include remote keyless entry, and running boards to help with the high step into the vehicle.

--Gail M. Considine, Staff Editor

Hydrogen to power research aircraft

Hamburg, GER--Engineers at Daimler-Benz Aerospace Airbus and partner companies are developing an aircraft powered by cryogenic fuels. Their goal: design an aircraft that does not emit CO₂ or rely on non-renewable fuels for power.

The "Cryoplane" demonstrator will be based on the Daimler-Benz A310 passenger aircraft. Instead of conventional kerosene fuel, its modified Airbus engine will use liquid hydrogen (LH₂).

Engineers selected liquid hydrogen for its mass-to-energy ratio and safety characteristics. To reduce storage volume, the gas will be supercooled to a liquid. Four pressurized, insulated tanks above the fuselage will maintain the fuel at -253C and approximately 1.5 atmospheres.

Although the overall engine configuration won't change, engineers will redesign the combustion chamber to minimize nitrous-oxide emissions. The shortened combustion chamber will incorporate a heat exchanger to vaporize the liquid hydrogen prior to injection.

The aircraft's tanks, pumps, pipes, and valves will require extensive design work, project engineers predict. The largest engineering hurdles involve structural materials, insulation, and the thermodynamics of filled tanks. Partner firms include Pratt & Whitney Canada, AlliedSignal, Russian airframe maker Tupolev, and Russian engine firm TRUD. If the demonstrator vehicle succeeds, a production model could enter service in 2010, say Daimler-Benz engineers.

Boeing design peaks with PEEK

Seattle, WA--For the design of two engine components on Model 757 and 737-300 aircraft, Boeing turned to PEEK (polyetheretherketone) for its inherent flame retardance, heat, and chemical resistance properties.

A fluid barrier that attaches to the engine frames consists of specialty compounded RTP 2299X PEEK from RTP Co., Winona, MN. The 38-inch part, one of the largest injection-molded PEEK parts in the world, protects engine components in the event of fuel leaks.

When the engines for the 737-300 are started, the starter air discharge ducts provide a critical role in preventing air build-up in the engine compartment.