777-200LR Flight Test Journal: Archives

28 September 2005

Running the wind station

Daniel Downey, radio services technical staff, wind station operator

Robert Snyder, radio services technical staff, wind station operator

Roger Klinger, data systems and support lead

The wind station collects and reports all kinds of weather data during testing - wind speed and direction, temperature, barometric pressure and humidity. It's pretty straightforward: We set up the station next to a runway where the airplane is testing systems or conditions like auto-lands, runway work, ground effects penetration, crosswind-landing and tailwind takeoff.

We don't forecast the weather, we report it. The flight test crew works with the meteorologist to determine where they need to go. Once they decide, we go along to prove they met the target conditions. Engineering will say the airplane can meet certain Boeing specifications, we prove that it does.

Generally, we look for two things: limits and specific wind conditions. Limits refer to the maximum amount of wind you can have. For example, initial airworthiness runway testing needs something like a five-knot wind or a ten-know wind limit.

For other tests we need specific winds, like for crosswind landings or tailwind takeoffs that need a more precise amount of wind. We may look for a 23-knot crosswind. The wind station proves the crew got the wind it needed to certify the airplane under those conditions. We literally can go to the ends of the earth to find the right wind conditions for flight tests, like to Iceland, Newfoundland and Australia.

Our team supplies other critical weather data, too. The engine guys need to know humidity and temperature, which affect engine performance. In brake testing, they need to know the direction and speed of the wind, which get figured into the calculations for brake energy. Obviously, a tailwind makes the airplane go faster and a headwind slows it down.

On remote flight test, like at Edwards Air Force Base, we also install radios, supply the frequencies and get base stations set up. Everybody wants a radio in their vehicle. We put them in temporarily so our crews can communicate with the base station, airplane and ground control if they're going to be out driving around the airport.

We're actually in the process of upgrading the wind station. The one we currently use is the crème of 1960s technology, developed in the 1940s. We have photographs from 1963 certifying the original 727 using our wind station. It's not a technical marvel, but it's simple and it works.

We debuted the new wind station on the 777-200LR. It's laptop driven, with electronic sensors and no moving parts. The new system is accurate within 2 percent of a reading, much better than the old one. It's amazing technology. The data loads onto an Excel spreadsheet. If the test director calls and asks about winds at condition, a display shows you the direction, speed, crosswinds and the exact time is synchronized to GPS. It's all recorded at between one and 10 samples per second.

We will carry two of the new stations; one and a spare. It doesn't do you a lot of good to get to Iceland and discover your one wind station doesn't work.