Controlled Impact Demonstration
Under the name Controlled Impact Demonstration (English for demonstration of a controlled charge), short CID, the U.S. aviation authorities FAA and NASA conducted in 1984 by a crash test with a remote-controlled passenger aircraft. Thus, a novel fuel additive should be tested in the first place; at the same time wanted to collect various data on the safety of the occupants in a crash. As the subject of a disused four-engine Boeing 720 was selected.
After more than four years of preparation, those responsible could crash on the grounds of Edwards Air Force Base, the fully fueled machine on 1 December 1984. The impact caused a spectacular fireball, the wreck burned for over an hour. The test shall be a failure in terms of the experimental fuel additive, but led to other proposals to improve aviation safety.
The Boeing 720 was the largest used aircraft that flew by remote control ever.
- 6.1 perception in the media
- 6.2 Reactions of the parties
Objective
In a typical accident occurs from fuel from damaged tanks or pipes in the air and forms a fine, flammable mist that catches fire. This reduces the chances of survival of the occupants of the aircraft considerably: The FAA estimated that around a third of the victims succumbed to an accident in the takeoff or landing phase of the fire exposure. Also as on March 27, 1977 on the runway of the airport in Tenerife two jumbo jets collided and so triggered the worst accident to date of civil aviation, many passengers did not die immediately from the impact, but only by the consequences beaten fuel.
One of Imperial Chemical Industries (ICI ) newly developed fuel additive, a long-chain polymer with the designation FM -9 should reduce the formation of such fuel clouds and their flammability. The so blended kerosene was antimisting kerosene ( German as: non- fog forming kerosene ' ), short AMK called. It had the desired properties in model tests and crash tests with decommissioned Navy aircraft type SP -2 Neptune already shown and should now put under realistic conditions to prove this. To this end, they wanted to crash remotely a typical passenger jet for the time controlled.
The plans for this experiment, it quickly became clear that a design of this magnitude could be used for a variety of other experiments. In the foreground, the behavior of the AMK was in a fire after a collision. Addition was intended to examine new developments to increase the probability of survival in a crash, including redesigned seats and restraint systems, refractory materials in the cabin and fire-proof window. Also innovations in the flight recorders were involved in the experiments. Moreover, the forces to be measured which act on the aircraft on impact, in particular the structural loads of the aircraft fuselage, and the wing of the cabin floor. It was planned with the results of the sensor data to check, among other things, the prediction accuracy of computer models.
Participant
The U.S. Federal Aviation Administration Federal Aviation Administration ( FAA), among others, responsible for safety regulations and guidelines ( FARs ) for air traffic in the U.S., teamed up for this experiment, together with the National Aeronautics and Space Administration (NASA). On the part of NASA primarily research centers Ames, Langley and Dryden on the CID program involved. Besides attended institutions of the U.S. military, British and French institutions and a number of business enterprises; the latter were primarily attributable to the aviation industry, such as General Electric, Lockheed and Boeing.
The management of the program was to the FAA, which also was responsible for most of the experiments and ready made 8.1 million dollars for the financing of the project. For the remaining costs in the amount of 3.7 million U.S. dollars, NASA came up. She was primarily responsible for the remote control of the test aircraft and the development of a system for data acquisition, in addition, they placed experimental seats on the plane and took over part of the evaluation.
Preparations
The preparations for the actual experiment lasted a total of four years. They included the exact specifications of the program objectives, structural changes to the experimental aircraft, the preparation of the planned crash site and 14 test flights, the flight that ended with the crash of experiment, not one of them.
Planning of the experimental procedure
The plans for the Controlled Impact Demonstration began in July 1980. Attempting should adjust an accident in the survival of all occupants of the aircraft was typically possible, such as after a go-around or a take-off. Thus, the AMK was able to prove its effectiveness, had conditions are simulated under which normal kerosene would in all likelihood become inflamed. FAA and NASA sighted in cooperation with the major aircraft manufacturers, the data of nearly one thousand aircraft accidents that occurred 1959-1979 worldwide, and developed it into a corresponding scenario. Also, the predictions of analytical computational models and findings from other experiments were included with.
The test aircraft was up to an altitude of about 2300 feet ( 700 m ) [note 1] rise above the ground, and then to fly with the planned flight parameters (speed, rate of descent, etc.) along a predetermined glide path the target area. Up to a height of 400 feet ( about 125 m) was able to determine the termination of each conductor of an experiment, if his equipment pointed out critical errors. Between 400 and 150 feet, the time specified for that flight decision height, the decision on the continuation of approach was exclusively the pilot. Below 150 feet ( 45 meters ) of the controlled crash in any case had to be done, discontinuation was considered too risky and could have ended in an uncontrolled crash. In the target area the aircraft should put a full gas tank with AMK, with retracted landing gear and flap setting of 30 degrees. Immediately after charge was planned that the wings would be damaged by special devices so that fuel flow out of the tanks therein and could ignite, while the trunk remained intact. The aircraft should slip on a gravel road about 300 to 350 meters and then come to a standstill.
Preparation of the crash site
As a testing ground Rogers Dry Lake was selected in the Salt Flat in the Mojave Desert. Here the Edwards Air Force Base has, among other things, several runways for experimental purposes. At the proposed crash site an area of approximately 90 by 350 meters was covered with gravel and provided with reference marks. The plan was that the aircraft would touch down just before this runway and arrive there after a short slide to a stop. As optical assist the pilots marked a big X-shaped cross the point at which the aircraft was expected to open.
Between the impact point and the beginning of the runway eight metal, around 180 per kilogram and nearly 2.5 meters high devices were cemented into the desert floor. If that were the front wing edge on one of these equipments, their lower half turned up, cuts into the lower wing part and cracks so the fuel tanks located there. Therefore, these instruments were as wing opener ( German: , Flügelöffner ' ) or wing cutter ( German: , wing cutter ') respectively. Previously, a fence made of easily breakable material was built up, which should also help the pilot to control the crash site. The extended center line of the runway was marked on the fence by an orange bar.
About 90 meters behind the point of impact of a lighting system was built of two rows, each with six posts, as they are used to the approach lights of runway. They were each approximately 30 meters behind the other with a lateral distance of about 23 meters, which was thus clearly less than the span of the test plane of approximately 40 meters. Each of these posts was about 3 feet high, consisted of lightweight fiberglass tubes with predetermined breaking points and contributed five lamps of 300 watts. In a collision with the aircraft they would cancel and serve as a realistic source of ignition for spilled fuel. As an alternative, it was envisaged that the fuel would ignite the spark of the gravel road or destroyed aircraft parts.
To document the impact nationwide, around one hundred synchronized with each other photo and video cameras have been installed around the crash site around, including high-speed and thermal imaging cameras. The system was supplemented by cameras in two near the crash site floating Bell UH -1 helicopters and in an accompanying aircraft type Lockheed P-3 on the test aircraft.
Demolition and failure procedure
For a landing after a controlled demolition of the crash experiment, the runway was 25 provided south of the planned impact point. As an additional safety measure in the event of failure of the remote control, a boundary was defined at the edge of the experimental area. Had the aircraft reaches this without being under control of the ground station, a signal would be an additional radio link has been sent to the aircraft that would have introduced a method of self-destruction. The thrusters would be stopped and the control surfaces have been moved to a position through which the aircraft would be spirally flown to the ground.
Changes to the test aircraft
As an experimental aircraft, a Boeing 720 was selected. This pattern represented with respect to cell drive and features the cross section of the aircraft used at that time for the airlines. The test aircraft was bought in 1960 by the FAA for the training of their staff and had claimed more than 20,000 flight hours and more than 54,000 takeoffs and landings, the end of its useful life achieved.
In June 1981, it was transferred to prepare for the CID program for Ames - Dryden Flight Research Facility. In the summer of 1983, the actual technical re- started. First, parts of the interior were removed to make room for the necessary adjustments. Seats and restraint systems were replaced by testing device. Selected areas, for example parts of the cargo compartment, was left deliberately in original condition. The aircraft should, in principle the rules and regulations of the FAA and by the manufacturer. As of October 1983, the cabling for measuring instruments, sensors, and additional power supply was installed. In December 1983, the integration of systems for data acquisition and high-speed cameras began, the cockpit has been adapted in terms of instrumentation and restructured for the proposed remote control. The autopilot of the Boeing 720 has been modified so that through him the flight control could be performed by remote control. Unused autopilot functions have been disabled to exclude them as a possible source of error.
The fuel and propulsion system was prepared for operation with AMK. This can not be introduced directly into a gas turbine, since this could lead to various technical problems, such as clogging of the filter of the engine. AMK must therefore be chemically degraded, until the normal Jet-A fuel so similar that it can be processed by the aircraft engines. To this end, General Electric installed at each of the four Pratt & Whitney JT3C -7 engines of the aircraft attempt a degrader mentioned apparatus, which was preparing the fuel for the engine. To grow the degrader, the turbo-compressors of air conditioning and cabin pressurisation system were removed from the engines.
A first comprehensive system test was carried out on 29 February 1984. Installation and testing of the AMK system began on April 4, 1984. Here first the degrader was checked, mounted to an engine ground and subjected to a test run. After correcting interferences as the first run of an engine with Degrader took place on 11 April 1984.
Another focus was on the accident behavior, ie the ability of the airframe and the restraint systems to protect the lives of passengers and crew in a typical landing or accident. Technicians installed including new seating systems, which should in the event of a crash to absorb energy directed against the direction of flight seats and a special restraint system for children. In general, the innovations were located right next to a conventional seat system, so that a direct comparison could be made. On the seats in the passenger cabin and cockpit crash test dummies were placed and acceleration sensors installed at different parts of the aircraft. Thus, the forces should be measured, which acted upon impact on the occupants, luggage compartments and the facilities of the galley.
In the passenger cabin and cockpit eleven high-speed cameras were installed to monitor the dummies and the cabin interior can. More high-speed cameras were in the nose of the aircraft ( in addition to the camera, the images were transferred to the pilot for the remote control ) and attached to the vertical stabilizer. This deformation could be detected more easily painted one uniform vertical stripes on the fuselage.
Other changes were the testing of newly developed fire protection measures. About half of the passenger seats equipped with fireproof textiles. At the sitting on the floor emergency lighting was installed, the passengers should point the way to the nearest emergency exits in a real accident when smoke worsens the view on the plane. Furthermore, several windows were replaced by fireproof new developments. In previous tests it took about 60 seconds longer in comparison with conventional windows until they were blown.
The aircraft was also equipped with four different flight recorders. Three of them corresponded to guys who were at that time in passenger aircraft in use, the fourth system was in development. Storage space in the galley was filled with dangerous goods packaging, so that they could prove their resilience in practice.
Test flights
Beginning on March 7, 1984 have been made in order to test the various new systems with the Boeing 720 a total of 14 test flights. The AMK concentration in the tanks and engines was increased gradually and monitors the performance of the systems. With the flights data were collected for the further development of mathematical models for simulations, determines the aerodynamic performance of the machine near the ground and checked the hardware and software of the remote control. They also provided an opportunity to become familiar with the flight characteristics and systems, and to practice the approach to the subsequent crash site.
During the test flights, the Boeing was manned, but was already largely flown by remote control. These directed NASA test pilot Fitzhugh L. Fulton of the Department of remotely operated vehicles (Remotely Controlled Vehicle Facility) in Dryden, the experimental aircraft from a control station on the ground. This was equipped with various instruments and two screens, were transferred to the power absorbed by the nose of the aircraft from video images. The controls were essentially those from the cockpit of the Boeing 720, the pilot and the copilot on board were able to disable the remote control and then take control of the aircraft. Overall, the crew completed 14 test flights with a total flight time of about 30 hours. More than half of this time was directed the aircraft via remote control to the remote-controlled maneuvers include 9 -offs, landings 13 and 69 CID profiles with hints on the planned crash site until at altitudes between 150 and 200 feet.
The Boeing 720 was the largest aircraft ever to be flown by remote control.
As a result of the test flights the AMK - degrader and the systems have been revised for remote control. They also led to the realization that the task was a heavy workload for the pilot on the ground. Therefore, the devices have been improved, which should help the pilot to reach the goal. Among other things, the fence was erected as a target help on the wing cutters. The success of all attempts to make crash site more noticeable, however, was diminished in the control booth by the low resolution of the video transmission from the aircraft. In addition, the specified requirements have been eased by the tolerances for descent rate, forward velocity, pitch angle and the accuracy of the contact point were increased.
Expiration
On the morning of December 1, 1984, the experimental aircraft lifted fully fueled from the 15th and last flight of the CID program of runway 17 at Edwards Air Force Base. Pilot Fulton drew the machine by remote control over the intended flight path to the target area. He could take the parameters for the final approach initially as planned, but flew later in some cases significantly too low and too far to the right of the center of the runway. The workload has increased constantly, so there were further discrepancies by corrections.
In deciding the level of the pilot was expected that he would get the deviations until impact in the tolerance range. He continued the approach. His control inputs, however, led to a pilot induced oscillation: The plane began to swing its longitudinal axis. As a result, it hit 90 meters from the finish with a bank angle of about 13 ° to the left. These values were significantly out of tolerance.
Less than nine minutes after takeoff, the aircraft touched because of the left bank of the left outer engine (No. 1) the ground first. It was shifted to the right from the center axis of the runway, its nose was directed to the left. The forward speed was 150 knots ( about 275 km / h), [note 1] the rate of descent at 18 feet per second (about 5.50 m / s), both in line with the nominal values. The machine turned upon further slides about 40 ° around the yaw axis and met with a residual speed of around 120 knots ( 220 km / h) on the wrong wing cutter.
Here, first the inner right engine (No. 3) was taken. A wing cutter came from the right in the engine nacelle and stopped the rotation of the turbine within about one third of a turn. A tenth of a second later, inflamed left of the engine fuel to the heat of the destroyed engine. The wing- cutter- cutting also hit fuel and oil lines and sat lubricants, hydraulic fluid and AMK free. Then broke the wing cutter off and turned up into the main fuel tank of engine No. 3 At the same time penetrated with the destruction of the engine No. 3 two wing cutter between this engine and the fuselage into the wing one, of which up to the fuselage on average. Burning fuel got into the inside of the hull and caused a fire in the cargo hold, which continued up to the cabin.
The flame that had been created in engine number 3 hit on the fuselage while the aircraft slid further and turned more and more about the yaw axis. The cut-through right wing broke off, which leaked more fuel to the breaking point. Eleven seconds after engine had no one touches the ground, the plane came to a halt, and the fire decreased significantly. Overall, it had the hull shrouded nine seconds long. As the flames went back, the exterior of the hull had not been visibly damaged by fire. Internal half minutes began a unit of the airport fire brigade to fight the fire. Until it was completely extinguished, went over an hour.
- Video recordings of the controlled crash
The crash from various internal and external perspectives
The impact from the perspective of the vertical stabilizer at the rear
Results
By crooked Einrutschen of the aircraft in the wing cutter, the actual sequence of the experiment substantially deviated from the plans. Consequently, most individual experiments were impaired.
The main experiment to burn suppressing effect of AMK developed completely differently than planned. The destroyed engine was not foreseen heat source, which significantly influenced further events. Actually, aircraft engines are designed so that they fall in a crash of the plane before they catch fire. Engine No. 3, however, was stuck by the peculiarities of the wing cutter burning on the wing. The kerosene ignited the engine had already passed through the degrader, so again more resembled the normal Jet-A fuel and could not unfold the special properties of AMK. Lubricants and hydraulic fluid provided additional fire material. In addition, the remains of the engine and other parts taken shielded from the fuel before the oncoming air, so that he could remain longer on the ignition source as provided in the experimental design.
The experimental setups for crashworthiness of aircraft structures and restraint systems were made partially unusable by various factors. Since the aircraft first came up with the wing, his rate of descent changed to the relevant measurements for the impact of the aircraft fuselage. The rear fuselage section, in which there were the special testing seats, would first have to set up. For the experiment, a rate of descent had been provided of at least 15 feet per second, the end of the fuselage struck, however, only about 6 feet per second ( about 1.80 m / s), and so with much less force than planned. Even more devastating was that the damage had affected by a wing on the trunk opener and the fire inside the cab, the deformation of the fuselage. For the same reasons, a good part of the measuring equipment was lost. For example, of the total 27 seats equipped with sensors two directly affected by the wing- cutter- strike, ten more were destroyed by fire. The remaining 15 did not show any structural deformation, which can be attributed to the low rate of descent. The camera shots from the passenger compartment led to the assumption that both the standard seats and the modified systems have endured the G-forces of impact. The measurement data obtained flowed among other things, in the development of databases and the improvement of computer models of the FAA and NASA for the simulation of a flight accident behavior of new designs.
The experiments for fire protection developed by the unplanned fire in the cabin differently than expected. However, the modern seat covers fared consistently better than the conventional ones. As the fire burned primarily through the floor in the cabin, the CID experiment brought no reliable evidence of differences between the new and the ordinary windows. Camera evaluations showed that the smoke had spread so strong within 5 seconds in the front and 20 seconds in the rear cabin section that the view was completely restricted. Starting from the time that is necessary in order to achieve the emergency exits and to use the escape slide, the FAA under for 33 seconds for the complete evacuation. In its final report, it is estimated that in a crowded airplane around a quarter of the 113 passengers would have survived the crash. The report's authors assessed these assessments, however, even as highly speculative.
The three common types of flight recorder functioned as expected, and in particular resisted the heat. The sampling of some signals were too low, even though they were in line with the guidelines of the FAA. A new recorder showed, however, only partially the expected benefits. The tested dangerous goods packaging intact. Also, the system for data collection, including the photographic surveillance work as desired.
Review and Follow
The CID program is with respect to its main purpose - to demonstrate that an effective fire prevention is possible by using AMK - mainly classified as a failure. The remaining experiments are viewed partly as a failure, partly successful.
Perception in the media
The experiment took place under the public eye. The media interest was so great in advance that the FAA had been led crash test dummies with black and white color, which were successively delivered and accordingly placed behind each other in the passenger compartment, subsequently implement in order to avoid associations with times of racial segregation. For the actual crash test an area had been set up for members of the press not far from the crash site. By telerecording million viewers could see how the plane disappeared in a fireball.
Already in the days after the experiment reported news papers like the New York Times, Newsweek, LA Times, the magazines or the science magazine New Scientist of the Controlled Impact Demonstration. Although the FAA had let announce at the press conference immediately after the experiment, the AMK had worked. However, the timely reporting of completed fire unanimously as a sign of a failure of the AMK and for the failure of the main experiment.
Reactions of the participants
For the parties to the extent of the fire was a surprise. Flames had indeed been expected, but only on a smaller scale, so that the airplane would slip away and would remain a significantly longer time for the evacuation of passengers. As a first cause a failure of the AMK was suspected. Only by evaluating the photo and video documentation was clear that not had a fog of AMK formed and ignited but that lubricants, hydraulic fluid, and already degraded fuel for the fire could be held responsible. The FAA undertook following the CID program a number of other tests that should clarify how the fuel could ignite. Although they came to the conclusion that AMK had not the ability to avoid the spread of fire under all circumstances. Nevertheless, she represented consistent with the FM -9- developers ICI believes that the AMK works and had prevented an even bigger fire. The FAA ruled on, the Controlled Impact Demonstration was comparable because of their special features with no previously occurred in practice accident.
In the spring of 1985 decided a subcommittee of the Congress, the use of AMK for the time being not to prescribe. In the end, the FAA gave this project entirely, and the development of fire suppressing fuel additives has been set. For ICI, this meant the fruitless end of 17 years of research. The ICI managers David Lane did not result in the setting to a failure of the AMK back, but on the visibility of the spectacular fire. Thereby was in politics and the public created the impression that the additive does not work. In fact, the AMK attempt was a success.
As far as the other individual experiments brought useful results, they are considered successful. Several experiments were from the outset only the review of regulations already adopted. Thus, the FAA had set new standards for the fire resistance of seat covers and for emergency lighting on the ground a week before the test. Other well-established guidelines needed to be revised as a result of these findings, for example regarding the sampling rates of the black box. Overall, the FAA in the addition experiments sees the source of much useful information.
NASA concluded that the crash landing, which was carried out for the CID program, have shown an unusually high workload for the pilot. Through better technical support, these could have been reduced. Because of the variety of insights that have been gained from the collected data and were reflected in measures to improve aviation safety, NASA rated the failed experiment in the core in the sum as a success.