Dr. Karen Jackson, Aerospace Engineer, Landing and Impact Research (LandIR) Facility
- Tuesday, 03 April 2007
Page 3 of 3
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.