21-08-2013, 04:28 PM
Vertical Drop Test of a Beechcraft 1900C Airliner
Vertical Drop Test.pdf (Size: 3.68 MB / Downloads: 38)
INTRODUCTION
This report presents the results of a dynamic airplane vertical impact test conducted at the
William J. Hughes Technical Center, Atlantic City International Airport, New Jersey. The
purpose of the test was to determine the impact response of the fuselage, cabin floor, cabin
furnishings (including standard and modified seats), and anthropomorphic test dummies. The
test was conducted to simulate the vertical velocity component of a severe but survivable crash
impact. A low-wing Beechcraft 1900C 19-passenger commuter airliner fuselage was dropped
from a height of 11' 2" resulting in a vertical impact velocity of 26.8 ft/sec. The airframe was
configured to simulate a typical flight condition, including seats, simulated occupants, and cargo.
The data collected in the test and future tests will supplement the existing basis for improved seat
and restraint systems for commuter category 14 Code of Federal Regulation (CFR) Part 23
airplanes.
BACKGROUND
This vertical impact test is one of a series of fuselage section and full-scale airplane tests
conducted in support of the Federal Aviation Administration's (FAA) ongoing Aircraft Safety
Research Plan [1]. The FAA has proposed seat dynamic performance standards for 14 CFR
Part 23 commuter category airplanes. Those standards were established empirically using the
results of prior airplane crash impact test programs. In development of those standards, it was
noted that the full-scale airplane impact test database did not include airplanes representative in
size of the commuter category airplanes. To provide data for those size airplanes, the FAA
initiated a full-scale vertical impact test program of 14 CFR Part 23 commuter category
airplanes. A test of a Metro in aircraft was conducted in April 1992 [2]. The tests were
structured to assess the impact response characteristics of airframe structures, seats, and the
potential for occupant impact injury.
DESCRIPTION OF TEST FACILITY AND TEST ARTICLE
TEST FACILITY.
The Technical Center drop test facility, shown in figure 1, is comprised of two 50-foot vertical
steel towers connected at the tops by a horizontal platform. An electrically powered winch,
mounted on the horizontal platform, is used to raise or lower the test article and is controlled
from the base of one of the tower legs. The current lifting capacity of the winch is 13,600
pounds. Attached to the winch is a reeved hoisting cable which is used to raise the test article. A
sheave block assembly hanging from the free end of the reeved cable is engaged to a solenoid
operated release hook. The release hook is connected to the airframe by a cable/turnbuckle
assembly with hooks bolted to the fuselage section at four locations. Located below the winch
cable assembly and between the tower legs is a 15- by 36-foot wooden platform which rests upon
I-beams and is supported by 12 independent load cells.
DATA ACQUISITION SYSTEM.
The NEFF 490 data acquisition system is a high-speed data acquisition system which has the
capability to sample and record data at sampling rates up to 1 MHz. The system consists of 92
channels. Each channel includes a 12 bit analog-to-digital converter with an accuracy of 0.1% of
programmable full scale, a 6-pole Bessel low-pass filter with four programmable cutoff
frequencies which cover a range from 100 Hz to 200 kHz, and a differential input amplifier with
12 programmable gain steps. Input signals range from ±5 mV dc to ±10.24 V dc full scale.
For the test, the system was set to sample and record 79 channels of data simultaneously at
10,000 samples per second per channel. All data channels were prefiltered at a cutoff frequency
of 1 kHz and temporarily stored in the NEFF 256K word DRAM memory during the test. Test
data were then transferred to an IBM compatible computer by an IEEE-488 interface for further
analysis. The full-scale value for a channel was chosen based on an estimate of the maximum
output of the sensor on the channel. Full-scale values for each sensor as well as engineering unit
conversion and measured sensitivity are shown in table 3.
PLATFORM.
The platform data are presented in appendix A, figures A-52 to A-65. The platform accelerations
were recorded by two accelerometers mounted underneath the center of the platform.
Figure A-64 shows that the impact and rebound accelerations of the platform were about 50 and
52 g's, respectively. The impact load was measured by the 12 load cells that supported the
platform. Posttest observation clearly showed that two rows of platform load cells had bottomed
out. This might cause the total measured impact load to be less than the actual impact load. The
total measured impact load is presented in figure 9.
CONCLUDING REMARKS
1. The Beechcraft 1900C test article was dropped from a height of 11' 2" with an impact
velocity of 26.8 ft/sec.
2. The fuselage experienced an impact in the range of 140-160 g's, with an impact pulse
duration of 9-10 ms.
3. The simulated occupants experienced g levels in the range of 32-45 g's with a pulse
duration of 44-61 ms. This is considered to be a severe but definitely survivable impact.
4. The fuselage structure maintained a habitable environment during and after the impact.
5. The seat tracks remained attached to the floor along the entire length of the fuselage.
This applied to both the side wall and floor track on both sides of the airplane.
6. All standard seats (i.e., Beechcraft seats and PTC Aerospace seats) remained in the seat
tracks in their preimpact locations.