This weekend marked a major milestone for the new Boeing 787 Dreamliner -- the flight-test aircraft was cleared to fly throughout its performance range for the first time. It is a critical step for Boeing in the company's effort to receive Type Inspection Authorization from the Federal Aviation Administration for the long-awaited new composite airliner.
Wired.com was in Boeing's telemetry room on Friday during the final flutter-test flight as teams of engineers diligently worked with test pilots Mike Carriker and Regis Hancock aboard 787 ZA001. As the test pilots executed test after test after test, the engineers on the ground quietly studied computer monitors and, yes, paper strip charts to ensure oscillations introduced to the flight controls were effectively damped and the composite aircraft was ready to fly safely throughout its flight envelope.
Flutter testing is critical to any aircraft development program. The tests ensure that small oscillations that may develop at the natural frequency of the flight surfaces and flight controls do not increase to a point where they can be destructive or cause structural failure.
Engineers design an aircraft so that these oscillations are damped without external input from the pilot. There are numerous examples of flutter causing problems throughout the history of aviation, including some crashes. But with the modern, thorough flight testing implemented today, the problem is extremely rare in airliners.
Boeing vice president Randy Tinseth said on his blog Friday, "The technical team has made an initial assessment of the data and we couldn't be more pleased with the performance of the 787. The damping was as predicted and the pilots report that the airplane responded as expected."
ZA001 departed Boeing Field, just south of downtown Seattle, at 10:15 on Friday morning. After watching the now iconic arcuate flexed wings of the 787 disappear into the distance, we watched much of the final flutter-test flight from inside Boeing's telemetry room located just east of the runway.
The telemetry room (everyone in the flight-test group calls it the "TM room") is a room without windows. Despite this shortcoming, it has the best view anywhere for watching the Boeing flight-test program -- except for perhaps the cockpit, though there is a lot more information available on the ground.
"Confirm that we're at 921 Echo."
The voice from ZA001 is calm and assured as it comes in over the headsets in the TM room. The voice from the cockpit along with those of the engineers on the ground would soon become as regular as the reminder not to leave your bags unattended at the airport.
"Good config" says an engineer carefully monitoring his screen and communicating with flight test director Scott Peterson who is sitting close by.
"Good config for 921 Echo, start sweep" relays Peterson who is the only one in regular direct communication with the cockpit.
Carriker and Hancock are currently flying eastbound at just over 15,000 feet in the vicinity of Wilbur, Washington, 150 miles east of Seattle. They will fly a series of long, east-west laps across northern Washington for more than three hours.
"Start sweep, 3-2-1 start."
With this, the pilots begin one of many test conditions being performed from a test plan that is several pages thick and sitting in front of every engineer in the room.
"Good start" confirms the engineer.
The TM room is used by Boeing primarily during the early stages of flight test for a new aircraft. The aircraft itself is equipped with numerous instruments and recording devices, but during initial air-worthiness testing, which was completed in January, as well as flutter testing, only the pilots are on board the aircraft.
So, in order to monitor the tests, the information from the numerous sensors, accelerometers and other devices must be sent down to the engineers on the ground. This is accomplished through a direct line of sight to the TM van, which looks like a cross between a TV satellite truck and a motor home.
The TM van was parked in central Washington near Moses Lake during Friday's flight. From there it can maintain contact with the airplane for most of the flight track, only losing contact briefly during a few of the turns at either end of the track.
Walking into the TM room Friday, it was clear what the primary business has been for the past several weeks. A simple sign on the door seemed almost unnecessary for a company eager to deliver its latest airliner to customers.
"Room Reserved, ZA001 Flutter Testing, February 13 - March 20, 2010." The team finished a day early.
In fact the sign is necessary because the 787 isn't the only new airplane the Boeing flight test team is working with right now. The new 747-8 is also undergoing flight test and needs the use of a TM room, as well.
To avoid those classic office squabbles over who gets to use the fancy equipment, Boeing installed a second TM room just down the hall. They even managed to find enough of the Astro-Med strip chart printers to fully equip the room, even though the somewhat antiquated devices have been out of production for years.
"We're old school for some of this" says Byron Billingsley.
For more than 30 years, Billingsley has been working in the flight-test group at Boeing. He says the strip charts give them the opportunity to quickly read the history of various parameters in a way you cannot get on a computer screen. During Friday's flight, engineers were constantly reaching over and tapping the paper as it came off the Astro-Med machines to help the several feet of paper properly fold on the desk.
"Okay folks, he's rolling out of the turn, so get ready" Scott Peterson says preparing the TM room for the next test.
ZA001 is at the east end of its track near Spokane. It's made the turn back to the west and Carriker and Hancock are about to start the next condition on the test card.
"And your configuration is confirmed, start pulse."
"Start pulse, 3-2-1 start" comes the reply from the cockpit.
"Complete."
"Arm/disarm."
"Flight controls, good pulse."
"Flutter good damping, clear to the next condition."
And repeat.
Billingsley points to a table in the middle of the room, "those are all structural dynamics people." The group is sitting beneath a pair of widescreen TVs with graphs of diminishing oscillations scrolling by. "They're looking at time history for a number of parameters as well as frequency domain" Billingsley says.
The engineers at the table are carefully monitoring the data as it flows in at a rate of 15 megabits per second. They calculate damping coefficients making sure they are ready for the next condition.
Everybody in the room has a function: There are people validating the airspeed/altitude and performance. Others check that the airplane is configured properly to make sure they get the correct data. During Friday's test everybody in the room monitors tasks specific to flutter tests. During other testing, propulsion for instance, the group would be different.
The TM room is a very quiet and reserved place. There isn't a sense of excitement or danger. In fact, though it can be fascinating to see all the data flowing in and listen in on the conversation with the cockpit, it could be seen as dull by all but the aviation faithful.
"Our intent is to make it boring," Billingsley says with a certain amount of pride. "It's not quite our motto" he adds, "but we get paid to watch paint dry a lot of the time. Sometimes literally."
"And Boeing 001, good pulse, clear to configure for tango ..."
We'll have more from about the TM room tomorrow, including how test pilots view the extra eyes, ears and brains on the ground. We'll also take a closer look at flutter testing, how it's done, and a look at what can happen when flutter becomes a four letter word.
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Photos: Jason Paur/Wired.com*
