777-200LR Flight Test Journal: Archives

31 August 2005

The Cave

Noel Lucero, Lead, Aerodynamics Performance Certification, Takeoff Team

Fred Krueger, Lead, Flight Test Aero Analysis Engineering Team

Flight tests of the 777-200LR, or any other airplane model, produce an enormous amount of data. All of that information needs to be carefully analyzed to make sure our tests tell us what we need to know: Is the airplane performing to Boeing standards and FAA certification requirements?

That's a lot of what our teams do. We determine the conditions or specific performance characteristics that need testing. Then, we make sure the airplane gets the necessary instrumentation required for us to gather the data we need. During testing, our groups run software tools that calculate real-time and post condition data. This information allows us to evaluate condition quality and pilot techniques.

We give the pilots a "bug card." This card tells them the parameters we're targeting for the next test condition. Our teams have created very nice software tools that generate the bug card onboard the airplane. It includes the takeoff field lengths and the target engine failure speed, rotation speed, climb-out speed and pitch angle, and the power setting to hit the target thrust-to-weight ratio at liftoff.

Then we go through and conduct the targeted condition. As soon as they call "condition off" and we're turning around to come back and land, we're busy processing the data.

We also give the pilots feedback about how they flew the condition - such as how they hit the target speeds, pitch rates and pitch angles, or if they used too much wheel during an engine-out condition and raised some spoilers. If the condition targets were missed, we work with the pilots to determine what techniques they could use to get the kind of performance we're looking for.

We work together to see if the last condition was good or bad, based on how the condition met predicted performance and if the atmospheric conditions were within tolerances, and if we need to fly it again or can move on to the next test condition. For some programs there isn't much turnaround time between conditions, maybe five or 10 minutes, so we have to turn data around very quickly. Even though we have the tools to do a lot of the data analysis onboard the airplane, after the test day is over we still go back to "The Cave."

If you've talked to anybody who has been on a remote at Edwards Air Force Base in California, you've probably heard about "The Cave." It is just a hotel room or conference room, but it has a colorful history. It's where we keep the equipment that allows us to analyze flight test data with a fine-toothed comb, on-site. The first hotel room that served this purpose was a bit of a dump - dark and dingy, which is the genesis of the name, "The Cave."

There are sometimes different groups that have to be in this tiny room together for long hours. So we set up some rules, which make it fun. For instance, you can't be in the cave barefoot. Imagine what it would be like in this tiny room with everyone's bare feet on top of the table that we're all working on! It's amazing how well we manage to work together and get our jobs done.

The Cave is also like our own little network. We take our laptops, a router and a server and we're in constant communication with Seattle to supply testing updates. We take everything into The Cave in case we need to make changes on the fly. The airplane performance is what it is. You can't change it. We have to see if it was flown correctly within the parameters we're looking for and if the atmospheric conditions were good enough to get consistent data.

Flight testing the -200LR at Edwards went pretty well, especially compared to its predecessor, the -300ER. For the earlier model we ended up waiting for 45 days to do five days worth of testing, mostly because the winds were blowing like crazy. We need calm winds, which means testing at the crack of dawn. We were onboard the airplane at 4:45 for a 5:39 taxi down the runway, which makes for a long day. We do more before 9 a.m. than the Air Force does the rest of the day!