Unique aircraft testing videos.
January 22, 2007 2:24 AM   Subscribe

Load testing a Boeing 777 wing. To failure! Also, engine testing, and maximum rejected takeoff.
posted by loquacious (26 comments total) 15 users marked this as a favorite

 
Okay, I thought the wing break was spectacular. Then I saw the birds going through a Pratt & Whitney 4084 Engine in slow motion. Great links loquacious.

It's no wonder flying is the safest way to travel.

Also, $750,000 for a set of wheels?
posted by kisch mokusch at 2:52 AM on January 22, 2007


I find these videos very reassuring. The next time I fly, I resolve to focus on the strengths of these machines, rather than my usual practice of mentally running that scene from Final Destination over and over until we reach cruising altitude.
posted by Optamystic at 3:08 AM on January 22, 2007


I'm not sure I want to sit thru Final Destination to find out: What happens? Crash on takeoff?
posted by pax digita at 4:09 AM on January 22, 2007


If Optamystic is referring to the scene I'm thinking of, it's easily one of the most terrifying aircraft scenes every filmed, ever.

Mainly because it preys upon a very reliable set of common phobias, not so much because it's actually air travel related. It's got heaping scads of claustrophobia, agoraphobia and acrophobia, with lots of "inside the plane" shots looking down the length of the plane as the airframe twists and warps and the bulkheads and luggage holds are popping and shaking themselves to pieces.

Repeat with ramping intensity over something like (if I recall correctly) 15-20 minutes of ever-increasing and improbably intense air turbulence. It's basically a film plot designed to stretch the drama of a commercial aircraft crash over the length of a feature film.

So, yeah, you could say "crash on takeoff". Or perhaps even "crash on box office release".
posted by loquacious at 4:26 AM on January 22, 2007


The next time I fly, I resolve to focus on the strengths of these machines

If only pilots were as thoroughly designed as the machines they fly.
posted by three blind mice at 5:05 AM on January 22, 2007


Mesmerizing videos (though I could have done with less of the "suspense-building" narration while we watch nothing happening—guess I've been spoiled by this fast-paced age we live in); great post!
posted by languagehat at 6:01 AM on January 22, 2007


Also, $750,000 for a set of wheels?

Wheels, as in "Wheel Assembly." They'd have to replace the tires, the brake pads, the disks, the brake pistons, the wheel bearings, and the wheel rims themselves. The load bearing frame survived, but after that -- max breaking force, minimum allowed brake material, and soaking in that heat for five minutes, everything replaceable needed to be. And there are 12 of them on the main gear -- I don't think they put brakes on the nose gear of the large commercial aircraft.

A/C tires aren't cheap, either -- they're very large, and they deal with extreme heat (friction on landing spinup and braking) and extreme cold (flight at cruise altitiude.) as well as the pressure changes.

Note that you'd almost never encounter this level of sustain braking in real life. But to tell you why, GEEK MODE ON (bzap!)

After analyzing a bunch of takeoff crashes, the NTSB and others realized a common problem was trying to take off when you couldn't, but there was a gray area where you might be able to take off -- but if you try to stop, you'll run out of runway and die. The solution to this problem is to make sure the pilots know exactly where they can try to stop safely (and encourage them to do so, if needed.) If you take the uncertainty out of it, it becomes easy, so the pilot-not flying calls out certain speeds, and the pilot flying knows if he can stop (and thus *will* if there are problems) or if she can't (and thus, will get the plane in the air and work the problem there.)

So, V1. Part of the preflight is you figure out the mass of the aircraft, and do some math (or, in a modern airplane like the 777, you let the computer do some math for you.) You tell it how much runway you have, what power you are using1, and it tells you a few speeds. The ones you care about are V1, Vr and V2. Many airlines also have a lower speed (80kts is common) that they'll call out as well. What they are.

< 80kts -- if any warning happens, you stop. you can usually stop at these speed without hitting a brake temp warning, which means if you can fix the problem, you can try again. 80kts> V1 -- Engine Fire, Hydraulic Warning, multiple electrical, you stop. Otherwise, you take off. These are the speeds that are really hard on the brakes.

V1 -- Takeoff Decision Speed. You take off. Period. You can't stop on the runway you have left.

VR -- Rotate. At this speed, you can lift the nose off the ground (but not the whole plane.)

V2 -- Takeoff Safety Speed -- Liftoff speed plus 5kts. You can take off and climb (slowly.) Ideally, you don't lift off until you hit V2.

Note that for this test, they have a very long runway. Those signs on the side are distance to the end in thousands of feet. When you're looking at the nose, though, you're seeing distance to the end the plane started on. He hits the brakes at 13, so it took 13,000 feet to get to the test speed. He then has several thousand feet to stop the plane.

No commercial runway has 19,000 feet of runway. The longest two in the US that I know are at DEN (16,000) and JFK (just over 14,000)

So. No 777 pilot in service is going to have a V1 of 210 knots. He wouldn't be able to get to that speed and safely stop without running out of runway. So V1 will be much lower, the stopping distance will be shorter (and, of course, you'll get to V1 in less distance as well.)

So, the plane ships with more brakes than you'll ever need. If you're in the worst case -- dual engine failure at V1 on a very long runway with MTOW aboard and brakes just short of replacement, you *won't* need to use as much braking force as this test did.

Thus, your wheels will probably be okay. You will, however, have to get another plane. Aborted takeoffs like this means the plane goes for a maintenance check. (the worst are landings above MLW, those earn a mandatory D check -- take the whole plane apart, check everything, and put it back together. Expensive, normally happens about every ten years on a commercial aircraft, and there's been more than one parked to avoid paying for the D check.

1) Modern plane with electronic engine controls can look at a problem like "I'm in a 757-200 -- a rather overpowered aircraft, flying to STL from ORD, less than 300 miles, and I'm half full of pax and not much cargo. I can take off in 3000 feet of runway, but I'm assigned to takeoff from 32R at T-9, which gives me over 9000 feet. So, I'll use 70% thrust, which is much easier on the engines, and take off in 6000 feet."

When you see a narrowbody plane take all of a long runway to do this (and the runway is dry, the procedure isn't approved otherwise) that's why -- they're saving the engine by using the runway.

When you see a widebody like a 747 or an A340 doing this, it's probably because they're loaded very close to MTOW, and they want every inch of runway they can. At ORD, if you see a plane using the full length of 32R in the day, they're doing so because they need it. Usually, this means they're going across the Pacific.

Late in the evening, the 777s going to London will often use 32R and partial thrust. The load is light -- AA flies the same plane to Tokyo from Chicago, London is easy -- so they save the engines.

The problem with 32R is that it crosses the east-west runways, which are almost always in use for landings. Getting the gap you need on both of them to take off a heavy plane (and wait for the turbulence to die down) is not trivial, and the few that ask for it and only it usually will wait for at least 30 minutes for ATC to get the gap open.

After 8PM, arrivals drop dramatically, and getting 32R is easy. This is when the cargo planes tend to head out, they want all the runway they can get.
posted by eriko at 6:04 AM on January 22, 2007 [33 favorites]


Well, I think we can all agree that that question's been successfully dealt with.
posted by kisch mokusch at 6:13 AM on January 22, 2007


yes, and fascinatingly so. thank you eriko.
posted by infini at 6:31 AM on January 22, 2007


Fascinating.
posted by odinsdream at 7:07 AM on January 22, 2007


Coolness. As an engineer that has done some aircraft work, this stuff is just as dramatic in real life as it is on the Discovery channel.

And when I was going for a job interview at Pratt & Whitney Aircraft Engines in Florida, we actually had an engine failure on the Airbus I was on, about an hour before landing at DFW Airport for our scheduled layover. (Pretty sure it was an engine out- loud BANG and severe airframe shudder, followed by pronounced loss of altitide and slight yawing. The high lift surfaces normally used at landing came out, the remaining engine sped up and finally the high lift surfaces retracted... we made it to DFW uneventfully after that, except we landed early and had to be pulled by a tractor to the gate.)

On the return trip, the plane did an aborted takeoff- just as you would expect rotation to begin, we all were thrown forward against our seatbelts for the fastest stop I've ever experienced. The pilot explained that "one of the engines just wasn't actining right" so he aborted the takeoff.

25 years of flying, and the two most exciting events happened on the same trip. Go figure.
posted by Doohickie at 7:24 AM on January 22, 2007


check out landing number 4 and 5!
posted by phaedon at 7:54 AM on January 22, 2007 [1 favorite]


I can see it now. It will happen someday. I'll get settled in and just be dozing off when the steward pipes up through the intercom "Welcome to flight ONE FIFTY FOUR..."

and I shit my pants.
posted by hal9k at 8:03 AM on January 22, 2007


Re: flock o' fowl shot into the engine test. A neighbor worked for GE in some kind of huge turbine facility, marketing to beef producers. I didn't get the specifics and I really don't want to know, but the engine for the semi-size meat grinder he sold was calculated at cph or "cows per hour".
posted by hal9k at 8:16 AM on January 22, 2007


Phaedon - holy shit!
posted by notsnot at 8:27 AM on January 22, 2007


Awesome, and a great comment from eriko.
posted by OmieWise at 9:56 AM on January 22, 2007


About halfway through that wing test video, I was ready to shut it off. The narrator keeps telling you about how they're bending the wings, but they don't actually show you the wings bending until the end — at which point the video becomes very cool.
posted by cribcage at 10:45 AM on January 22, 2007


The second to last landing in the clip posted by Phaedon is from the old Kai Tak airport in Hong Kong. There's a write-up of Kai Tak landings on Airliners.net and there's also a quicktime clip (money shot is at about 1:25).
posted by nathan_teske at 10:51 AM on January 22, 2007


Friends were at the 777 wing test; although they were kept on the other side of the enormous building they still said it was a fairly scary event.

I've been watching the building of the test harness for a new airplane. This is the gantry that will be used for a new wing-to-failure test sometime later this year. What I find amazing is how much effort goes into testing these things, and how much gets measured.
posted by printdevil at 10:56 AM on January 22, 2007


I remember my first landing at Kai Tak.

Thankfully there was no crosswind, but it was still hairy.

Nothing like looking out the window and seeing into people's flats.

While crosswinds and other wind phenomena are worse at Chek Lap Kok, at least there's little chance of clipping a high-rise.
posted by bwg at 4:31 PM on January 22, 2007


I discovered Kai Tak a few years ago and have always been fascinated with the videos of the landings there. I'm pretty sure only the craziest pilots and passengers miss that airport.

I've seen a cockpit video and have read some detailed descriptions of the landing and it's enough to set off bursts of adrenaline, and I like this kind of stuff. Heck, I enjoy turblence. I pay damn good money for negative Gs.
posted by loquacious at 4:54 PM on January 22, 2007


Kai Tak was just wrong.

The approach. Fly an ILS approach right at a mountain. When the middle marker alert goes off, look hard right. If you see a runway, *turn* hard right and land. If you don't, turn hard right and climb, because you are flying RIGHT AT A MOUNTAIN.

To help you see the mountain, there was a big orange and white checkerboard. At the middle marker, you were 1.8 nm from the threshold of the runway. At 150kts -- not an uncommon approach speed for the 747 -- you'd cover that distance in about 50 seconds.

Worst was the attitude of Cathy Pacific and JAL pilots about not going around, so they'd swing that big plane around, and be way off the runway, then they'd start trying to sideslip the plane in and still get the plane lined up with the runway. JAL smacked at least a dozen engines into the runway before the company had a long heart-to-heart with the pilots about how go around were expensive, but engines were much more so, and the next Captain to leave one on the Kai Tak runway would replace the broken engine on the flight home.

A good page on the technical aspects is here, complete with the Instrument Approach Plate Of Doom.
posted by eriko at 5:05 PM on January 22, 2007 [2 favorites]


A fascinating post! There was a time when I had difficulty flying, but I've since come to look forward to it. Planes are such engineering marvels . . .

A side note: erico, in his fantastic comment (flagged as such) mentioned the intersecting runways at O'Hare. They've caused complications for pilots and delays for everyone flying. Hence the current plan to expand the airport with parallel runways such that long haul flights don't have to dodge incoming and outgoing traffic.

I've come to realize that this is a really important project, even though it will undoubtedly result in Chicago-style graft, corruption, cost overruns and the forced displacement of lots of homes and small businesses. Conveniently, I suspect Da Mare will get it all sorted out in time for the 2016 Olympics.
posted by aladfar at 6:56 PM on January 22, 2007


For a different kind of aircraft testing, consider the Chicken Gun. Sorry, I don't have a video, but I saw it demonstrated once on a hot June day in 1993. Since they don't clean up the test area very often, the smell is intense. The chickens come pre-euthanized, refrigerated, in silk bags, from the farm/factory down the road.
posted by Araucaria at 8:53 PM on January 22, 2007


a mate of mine who worked on A380 was present at their failed wing ultimate load test a year ago - souveniring of wing fragments was apparently rife. "I have a piece of wing that will be retrospectively defined to be strong enough"...

eriko: At the middle marker, you were 1.8 nm from the threshold of the runway

I originally parsed that as nanometers, and assumed it was hyperbole... that's what I get for dropping out of Aero Eng back in the day...
posted by russm at 2:39 AM on January 23, 2007


A side note: erico, in his fantastic comment (flagged as such) mentioned the intersecting runways at O'Hare.

(s/ico/iko)

Yeah. ORD is the perfect two runway airport -- you'd never with more than a 45 degree crosswind, and never with a headwind.

Alas, ORD needs three runways, because they need to take 100 arrivals an hour.

even though it will undoubtedly result in Chicago-style graft,

Which is just a simpler form of taxation. See, the crooks in Chicago understand that if you kill the city, they go broke too.

The trick is you skim a couple of percent, and then get the job done. Daley keeps getting reelected, because he remember the lessons that Bilandic taught. Honesty is one thing, not plowing the streets is another. Skim a couple points, pick up the trash, get the job done, nobody cares. Skim 20%, fuck up the job, and the Feds come into city board meeting and arrest everyone.

I doubt, to be honest, the whole plan will be built, because I think air travel is going to drop quite a bit over the next ten years. However, they're building the north runway now, once that's finished, ORD will be able to handle 120 arrivals an hour 85% of the time, which is vastly better than what we have now (which is 100/hr about 60% of the time.)

The real problem with ORD is regional jets. Replace lots of little with fewer bigger, and we get the same number of passengers in with less arrivals. UA and AA, the two big tenants at ORD, agreed, and cut arrivals voluntarily to help the hub. Everyone else then packed flights in, and AA & UA told the FAA "Sorry. We tried to work it out, and we got screwed."

So. If the runways get wet, the arrival rates drop. So far this year, I've had one on time, two late, and two cancelled to ORD,
posted by eriko at 5:39 AM on January 23, 2007


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