Fascinating! This group needs more "in person" tales like this, and like Wiltons. Gerry
Rich Thomas wrote: > So back when I was in kawledge I had summer internships at NASA > Langley. One summer I was in the Flight Research Division, having > worked the previous summer in the Flight Simulation Division, wherein > the aircraft being simulated I was then working on in the real world. > The primary aircraft was a 737 called the Terminal Configured Vehicle, > which had a replica flight deck in the back cabin, from which the > airplane could be flown "by wire" with the safety pilots up front being > able to manually override the pilots in the back. We did all kinds of > tweaking of the software to allow the plane to take off, fly, and land, > all either automatic or by the "wire" inputs to the flight computer. I > "flew" the simulator quite a bit while we were tweaking things, we would > do a simulation of something then my colleagues would twiddle with the > software (running on CDC Cyber computers, which were about the size of > my 30 cuft refrigerator) and then we would see what happened. If stuff > worked OK then it would be uploaded to the airplane, probably on tapes > or something, I never saw that process. > > As far as I know this airplane and the software was the precursor to > pretty much all the FBW stuff in all the planes today, so it is kinda > fun to think back on that and whatever small role I might have had in > that "progress." > > One day while I was in the Flight Research group someone came to me and > said there was some problem in the autoland algorithms, pull the flight > data and go over to my previous group and see what we could figure out. > The problem was that when the plane was landing on one particular > runway, it would pound in hard. The safety pilots would think it was > descending too rapidly and then try to correct and the result was a hard > landing. Of course the pilots, whose man-equipage needed its own seat, > were never to blame for this. > > So I printed off all the data, made plots, looked at all the control > loops, we put it all in the simulator and "flew" the same landings with > no problems. I spent a lot of time trying to figure out the problem. > One day I was driving to lunch on the other side of the airfield and > noticed there was this big drainage ditch off the end of that runway, > and the runway was 10 or 12 ft above the ditch. HMMMM I am thinking, > remembering some radar altimeter data. (Langley sits on the marsh on a > backwater of the Chesapeake, and is about 2ft above sea level, pretty > much like my place is now) > > So I get back and look at all that, and sure enough you could see a big > "altitude" jump right before landing, where the altimeter was sensing > that ditch and commanding the aircraft to go down a bit to compensate. > But in the simulator, once it crossed the threshold and got over the > runway, it would pitch up a bit to maintain proper descent to landing. > At that point it was maybe 30ft above the runway, the ditch made it > think it was like 40+ ft. So I look at the simulator, and quite clearly > the flight computer caught this, and the airplane was responsive enough > to the computer, that it would land properly and smoothly, no drama. > But when the pilots got in the loop, they were of course much slower to > react and command the aircraft, so it would not pitch up to compensate > and would pound in, sooner than the touchdown point the computer would > land it. The pilots basically were the problem. > > So a few days later we had a meeting to go over what was going on, and > my older colleagues say, "Rich how about you go over what you found." > So I do that, we took the data, ran the simulations, no problems, then > hey look at when the pilots took over because they thought it was going > to land short or hard, then BANG it lands short and hard." If you had > let the system do its job, no problems. > > So, the pilots then had a shitfit and start in on me, > whothehellisthiskidwhatdoesheknowblahblah, and I see the guys smirking > at me, they had set me up to deliver the news and catch the flak from > the guys with the big.... egos. > > So then a coupla days later one of the pilots comes charging in our > space and walks over to me and says, "THOMAS YOU'RE COMING WITH US!" I > of course about evacuated, but followed him and he goes to the airplane, > tells me I am going, and they are going to fly the profile a few times > and see what happens. So I take a seat back behind the aft flight deck > where I can watch what's happening, and after 3 or 4 touch and gos we > come back, nothing is said. So we get back to the office and a couple > of the other guys who were on the plane are all laughing at me and > saying "those guys were pretty damn quiet, huh, looks like you were > right!" So, shonuff, the computer landed the plane fine, the pilots > tried it and pounded it in. Vindication! Of course the pilots never > admitted it but they treated me a bit nicer for the rest of the summer. > > Here's a blurb about the research fleet, the bottom pictures of NASA 515 > show the airplane. My office was in that hangar to the left in that > picture, it was full of mice and cockroaches we would launch paper clips > at with rubber band slingshots. > https://books.google.com/books?id=wyJCIhtknPcC&pg=PA91&lpg=PA91&dq=NASA+TCV&source=bl&ots=fDj3VbqLZU&sig=VogQvNb-twMlFeWtAOAktmy4iKQ&hl=en&sa=X&ei=jVAYVfLFEoGDgwT02YGoBw&ved=0CEYQ6AEwBg#v=onepage&q=NASA%20TCV&f=false > > > Here's a paper by one of the crazy guys I worked with > http://www.researchgate.net/publication/23819008_Verification_and_validation_of_the_NASA_Terminal_Configured_Vehicle%27s_TCV_Wind_Analysis_program_using_real-time_digital_simulation > --R > G Mann wrote: > > Gentle crash landing... for an Airbus. > > > > Since Airbus uses computer controls for landing approach and touchdown, I > > would want to replay the last 6 minutes prior to contact with the runway, > > and the full replay of all control imputs made after contact. > > > > It is pretty apparent from the chosen parking spot that the landing > > envelope was exceeded. _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
