Dr. Karen Jackson

In a crash, keeping the occupants alive and uninjured is paramount. In order to study the dynamics of an impact, military and general aviation aircraft, like cars, must be tested for their ability to keep their riders safe. A part of Structural Dynamics Branch in the Research and Technology Directorate at NASA Langley, the Landing and Impact Research Facility (LandIR) tests aircraft by crashing them. Dr. Karen Jackson is part of the research team.

NASA Tech Briefs:

Explain the Landing and Impact Research Facility, and how does it fit into NASA?

Dr. Karen Jackson: The facility has had a long history. It was originally built in the early 1960s, and was used as a lunar landing research facility to allow the Apollo astronauts to practice the last 150 feet of descent onto the lunar surface. The surface underneath the gantry was cratered to look like the Moon, and the astronauts would climb up into mock-ups of the Lunar Excursion Modules, and then they would practice landing. Through a series of load-augmentation, thrusters, and what have you, they could recreate or simulate the actual landing on the Moon.

As the Apollo program was coming to a close, the facility was converted over to a full-scale test facility. As such, it was used, from 1974 to 1983, in running a cooperative research program with the FAA to look at general aviation crash-worthiness. And it just so happened that there was a flood at the Piper plant in Pennsylvania, and we were able to obtain a whole cadre of aircraft for crash testing that we didn't have to purchase — we basically got them because the FAA wouldn't certify them for air-worthiness. We got them for scrap aluminum value. We build a whole research program on that.

LandIR has a lot of different uses. We've had customers come to us and want to do a variety of different tests. We certified all the Wire Strike Protection Systems (WSPS) for eight different army helicopters, the passive blade-type devices that go on the top and bottom of the cabin. They prevent the helicopter from getting caught in wires or power cables during close-to-the-earth flight. It's prevented a lot of accidents; and that's a crossover into the commercial world as well. Most police helicopters now have that wire stripe protection capability.

Right now, the LandIR has gone back to its roots. We're evaluating landing and attenuating systems for the Crew Exploration Vehicle, the Orion. These are not for lunar impacts, but when the capsule comes back to Earth. We're looking at where to land it, on water or on land, and various attenuation systems like airbags, retrorockets, and passive energy absorbing struts. All those concepts are being evaluated now. It has been used to simulate terminal velocity impacts of a Mars Sample Return aero shell and passive energy attenuating system.

As it fits into NASA, LandIR is owned and maintained by the Structural Dynamics Branch. The Structural Dynamics Branch is in the Research and Technology Directorate here at NASA Langley. Because we support both aeronautics and aerospace research, we go "across code" at Headquarters.

NTB: Describe the layout of the facility.

Dr. Jackson: We have a gantry that is 240 feet high, and is a steel truss structure. A lot of people describe it as a Lego Erector set on steroids. It's a series of three A-frames, so there is a canted leg that goes up 240 feet, and then there is a horizontal component, and then there is another leg on the opposite side canted at the same degree down to the ground. At the top of the gantry we have crosswalks that connect all three A-frames, and at one end we have a bridge. The bridge has a winch on it that is used to pull the test article back to the drop height to release it for the test.

NTB: What are the vehicles you test?

Dr. Jackson: All sorts, but flight craft, mostly. We are affiliated with space exploration, so right now, we are testing a boilerplate, which looks like the bottom of a flying saucer. It has some weights attached to it and some instrumentation. Underneath of it, where the surface is curved, we have all the energy attenuating devices that we are considering. Right now, we're testing airbags. That's one test article.

We've tested all the general aviation aircraft. We've done a number of crash qualification tests for helicopters. The Bell and Sikorski Advanced Composite Airframe program helicopters that were tested back in 1987. We've tested both the Blackhawk and Huey helicopters to qualify external fuel tanks to increase the payload or range of those models.

We even tested a car from NASCAR. This was after the Dale Earnhardt accident in the 2001 Daytona 500. NASCAR was seriously looking at what kind of barriers they could place around the racetrack to absorb some of the energy of these crashes. We had been developing some energy-absorbing subfloors, and one of the coworkers of mine that was working on that program said we could apply this to a soft-wall design. So we approached it, NASCAR said they wanted to look at it, and we said we could do a crash test here. We placed the barrier design on the ground, and used a NASCAR racecar donated by Richard Petty. We hooked a cable that was attached to a 10,000-pound weight to the car and ran the cable up to the top of the gantry. At the time of the test, we released the weight, accelerating the car into the barrier. We didn't do the test like an airplane crash test, where we swing the article into the impact surface. But it was a successful test. It was a different kind of test we've never done before.

NTB: How is a crash test conducted?

Dr. Jackson: First, there are several weeks to a month of preparation before the actual test. We have to know what the instrumentation plan is. The center of gravity, or CG, of the aircraft must be determined, because you want to lift the aircraft through the CG. This prevents rotations or any kind of rocking motion when the aircraft is lifted and so that it hits at the impact attitude we want it to hit. There is a lot of preparation with finding the CG and attaching the lifting devices.

We also have to manufacture the cable, and there are two sets that get attached to the aircraft, the swing cable and the pullback cable. The pullback cable is used to pull the aircraft back to the drop-at position. During the test, when they say "t-0," the winch releases and the aircraft swings to the ground. There is a lot of work in instrumentation; sometimes we have as many as 200 channels of data. We typically have anthropomorphic test dummies, and these are instrumented with lumbar load cells, head accelerometers, and chest and pelvic accelerometers. We have a completely on-board data collection system, and it has to be set up and checked out. The technician has to go out with a hammer and beat on the dummy's chest to see if we are reading accelerations. We used to use an umbilical system, where all the data cables came to a single point, a long, large cable we called an umbilical, and it ran up and then back into our building. It wasn't the best method, because we often had a lot of chatter and noise in the data. It even lost channels.

On the day of the test, the aircraft is brought out, put in the actual impact position, and then all the external and on-board cameras are set up — we use high-speed film cameras and video systems — and these cameras focus on a specific thing, like an airbag. We may want to see how the dummy with the airbag reacts. We may put the camera in the nose of the aircraft and focus it on the dummy occupant just to see how he responds to the airbag.

When in comes time to do the test, there is a long checklist. All the cables have been attached at this point, the swing cables are generally placed on the western end of the gantry, and the pullback cable has been installed with the winch. All these cables that are attached have "pyro-cutters" in them, pyrotechnic cutters, because when we conduct a test, you want the craft to be in a free-flight condition. We don't want to constrain it by having cables attached. So right before impact, about three or four feet off the ground, all the cables are pyrotechnically separated from the aircraft. All that has to be set up.

During the countdown, we do a t-5 and the cameras are turned on. At t-3, the data acquisition system, or DAS, is triggered so you capture the full event — the aircraft swinging down, impact, and slide-out. At t-0, the pullback cable is released from the winch and the aircraft swings, pendulum-style, to the ground. Of course, the height of the aircraft and the length of the swing cable determine what the impact velocity is going to be. Occasionally, we will have a harness system that is attached to the cables that will allow us to get pretty much any roll, pitch, or yaw attitude at impact that we want.

After the test, there is a lot of post-test work that goes on. We have pre-test pictures, post-test pictures, and all of the data that has been collected on board has to be saved to the disk. It's quite a lot of work. There are a lot of people around here on the day of a test.

NTB: What constitutes a "successful test?"

Dr. Jackson: We learn something from everything, so there really isn't an "unsuccessful test." But in 1983, when we were still using the umbilical data system, we had a test of a GA aircraft. The umbilical cable was supposed to release a few seconds after the aircraft hits the ground, because we would have recorded all the major impact response that we wanted, and we really aren't that interested in the slide-out. And the slide-out can be several feet, so you have to plan on that amount in the length of cable.

In this test, the release mechanism of the umbilical didn't work. And so, here we had an airplane sliding out, it had this short umbilical cable, and what happened was like the phoenix rising from the ashes! It came back up and then impacted itself again, not only the initial impact, but again on the top of the vehicle.

But those things happen. We didn't learn a whole lot from that second impact, but we did collect the data for the first part. So even that test was successful, even with two impacts for the price of one.

NTB: How is crash-test information interpreted?

Dr. Jackson: Generally, the whole purpose of crash-worthiness is to lessen the loads that get transmitted to the occupants of the vehicle. If we have occupants on board, the most important thing is to assess is if the occupants survived the crash or not. So we look specifically at the occupant data and compare it to known human injury criteria and determine the level of survivability of the occupant.

We also look at seats, any crushable structure that was on board. For helicopter crashes, we look to see if the occupant's head hit the dashboard or the interior of the cabin in any way. That's a big problem with helicopters.

For the analytical model, we look at any kind of airframe, floor, and seatpan responses. The motion picture analysis, the film data, can be very helpful in determining exact impact conditions — the forward velocity, the vertical velocity, and any roll, pitch, or yaw attitude. That's all very important, especially for those of us that do modeling.

NTB: Have your tests resulted in redesigns?

Dr. Jackson: One of the most important things to come out of this cooperative program with the FAA, in which we crashed over 33 general aviation aircraft, we had a tremendous database of information on what a typical crash "pulse" for GA aircraft is. Based on that data, the FAA was able to use that information from that 10-year program to write a seat certification standard that is still in use today. That was a significant contribution.

The Wire Strike Protection System has saved numerous lives. We tested external fuel tanks that increase the range and payload of two particular helicopters. In the late 90s, we did a series of three tests of a Cobra helicopter, looking at a system called CAB, the Cockpit Airbag System, and also another system called IBAHRS, the Inflatable Body and Head Restraint System, that was where airbags were built into the seatbelts of the occupants. These tests were intended to prevent the pilot and co-pilot from hitting their heads on interior structures, including the collective stick, the interior panels — it's all very enclosed inside a helicopter and a common cause for accidents. Based on the qualification tests that we did, all Blackhawk and Kiowah helicopters have now been outfitting with CABS. These are some tests that we did that resulted in significant improvements. There's been a lot of things.

NTB: What commercial applications have resulted from LandIR tests?

Dr. Jackson: Most of the aircraft that come to us come for one specific reason or another. During NASA's AGATE Program (Advanced General Aviation Transports Experiment), we tested both a modified commercial Cirrus SR20 aircraft and Lancair aircraft. Both of these aircraft had been modified to prove crash-worthy features. For the Cirrus, there were some features included to make sure the aircraft didn't plow into the soil. Most crashes don't occur into hard, prepared surfaces; they happen on soil or marshy areas or even into water. One of the things we found from doing the test, in comparing a hard surface to soft soil, is that a lot of aircraft "stick" into the soil like a lawn dart. The ideal situation would be to have these aircraft plow through the soil, making the impact event last longer so not as much energy is put into the event because it is so short a time. This particular aircraft had been modified to have features like "mass shedding." The wings fall off, the engines fall off, and the mass of the craft is lessened, which is a good thing.

One of the last crash tests that we've done was with the modified Lancair, and it had a number of crash-worthy feature factors. It was the highest velocity crash test we've done at LandIR since I've been here: 90 feet per second. And the people doing the test claim that crash is completely survivable, which was amazing.

We have also conducted tests to evaluate an externally deployed energy absorber manufactured using a composite honeycomb design. It is structurally efficient, stores flat if not needed, and is a near-perfect energy absorber. It could be used in place of external air bags for both crash and landing attenuation of space applications.

We sponsored a parachute system for general aviation aircraft, so that when the aircraft got into trouble, liking loosing one or both engines, the aircraft could be brought back down to earth using parachutes. I've seen some reports that say over 200 lives have been saved by this parachute technology for GA aircraft.

For more information, contact Dr. Karen E. Jackson at This email address is being protected from spambots. You need JavaScript enabled to view it. .