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
On 3/29/15 1:53 PM, 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.
On Sun, Mar 29, 2015 at 8:31 AM, Andrew Strasfogel <astrasfo...@gmail.com>
wrote:
It'll buff right out.
On Sun, Mar 29, 2015 at 10:55 AM, Curly McLain <126die...@gmail.com>
wrote:
Air Canada plane 'exits' Halifax runway while landing
2 passengers seriously injured. Plane severely damaged.
http://www.bbc.com/news/world-us-canada-32103971
________
Read again GMann's position on flying in airbus...
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