• About IPRR
  • Origin
  • Description
  • Forums
  • Contributors
  • Archives
  • Visitor Log
• Theory
  • Introduction
  • Theory Papers
  • Evaluations
• Research
  • Projects
  • Wish List
  • Problems
• Library
  • Introduction
  • Books
  • Papers
  • Presentations
  • Standards
• Tools
  • Introduction
  • Manuals
  • Guides
  • Tutorials
  • Software
• Reviews
  • Introduction
  • Projects
  • Books
  • Papers
  • Tools
  • Articles
• Opinions
  • Editorials
  • Musings
  • Commentaries

Launched Aug 26 1996.

Office of the Chairman

National Transportation Safety Board Washington, D.C. 20594  June 8 2000

Air Line Pilots Association, International, Petitioner
Aircraft AccidentBlock Island, Rhode Island
December 28, 1991
File No. 2121, Accident No. NYC92FAO53
 
 

 In accordance with 49 Code of Federal Regulations, Section 84541, the National Transportation Safety Board has reviewed the June 25, 1997, petition for reconsideration and modification its findings and probable cause in the aviation accident near Block Island, Rhode Island. on December 28, 1991, involving a Beechcraft I900C, N811BE, operated by Business Express, Inc. On the basis of this review, the Safety Board hereby denies the petition in its entirety. However, the Board modifies findings 5 and 9 in the original report to more accurately reflect the facts of the accident.

 Background

The purpose of the flight was to prepare two Business Express first officers for a captain upgrade flight. A flight plan was not filed, nor was one required; the exact departure time is unknown. According to the cockpit voice recorder (CVR), during the accident flight, the instructor pilot (IP) disabled the captain-trainee's attitude indicator, after which the trainee had difficulty maintaining airplane control. About 6 minutes later, the instructor simulated an engine failure. As the trainee maneuvered the airplane to align it for a very high frequency omnidirectional radio uncontrolled ascent and crashed into the ocean. The three pilots were presumed dead, although their bodies were never recovered. The airplane was destroyed on impact.

The probable cause of the accident adopted on April 27, 1993, was the following:
 

altitude too low for recovery; and company management's lack of involvement in and oversight of its Beechcraft 1900 flight training program. Contributing to the accident was the instructor pilot's exercise of poor judgment in establishing a flight situation and [an] airplane configuration conducive to spatial disorientation that afforded the pilots little or no margin for error.:

2. There was no evidence of airframe or powerplant failures prior to impact with the water,

3. There were no airplane system malfunctions or failures before impact with the water except when electrical power to the captain-trainee's attitude indicator was deliberately removed.

5. The IP disabled the captain-trainee's attitude indicator, and about 6 minutes later, he simulated a failure right engine by retarding the power level to the flight idle position which, in effect, introduced multiple emergencies contrary to the provisions of the company's BE 1900 operating manual.

6. The IP used poor judgment by encouraging the captain-trainee to fly the airplane with his altitude indicator disabled and uncovered, followed about 6 minutes later by a simulated failure of the right engine under simulated instrument conditions on a dark night

7. The IP failed to recognize in a timely manner that the captain-trainee was spatially disoriented when the captain-trainee asked the IP to take control of the airplane [by saying] "Your aircraft?"); instead, the IP attempted to coach the captain-trainee into a recovery from an unusual attitude.

 

8. The attempted recovery from an unusual attitude was not successful, apparently because the IP lost awareness of the airplane's altitude and rate of descent and may have become spatially disoriented at an altitude too low for recovery.

9. The airplane probably crashed into the ocean in a near-inverted attitude with the outboard section of the left wing striking the water first and with the longitudinal axis at substantial angle with respect to the surface of the ocean.

The petitioner's primary contention is that the accident was caused by a catastrophic in-flight breakup at 1,900 feet, which was triggered by a preexisting structural fault in the right engine truss tube assembly. The petitioner further asserts that this scenario is supported by (1) analysis of the wreckage (2) analysis of the CVR tape, and (3) a lack of evidence supporting the Safety Board's scenario. The petitioner also argues that the IP exercised good judgment and did not violate any company policies or procedures.

According to the petitioner, irrefutable evidence exists that a failure of the right engine truss tube assembly resulted in a whirl flutter[1] event in the right engine and propeller, which subsequently resulted in the separation of the right engine from the airplane. The petitioner alleges that the right engine subsequently struck and removed the right horizontal stabilizer, which caused the CVR to shut off and also resulted in a total lass of control of the airplane and the in-flight separation of most of the right wing and the outboard portion of the left wing.

Analysis of the Wreckage

The petitioner has submitted documentation of the wreckage (on the basis of its own examination of the wreckage after the Safety Board's investigation was complete) that it believes shows evidence of an in-flight breakup of the airplane before it collided with the water. Specifically, the petitioner refers extensively to a metallurgical study of the wreckage prepared by Packer Engineering, Inc., under contract to AIG-Business Express, Inc, The Board has not reexamined the accident airplane's wreckage since the conclusion of its Investigation[2] but, as further discussed below, has reviewed the petitioner's submission and does not believe that the petitioner has presented any evidence to justify a finding that the airplane experienced an in-flight breakup.

The Safety Board's visual examination of fractures on the airplane's wreckage during the initial investigation revealed features typical of overstress separations. The airplane fuselage, empennage, and internal structure exhibited no preexisting cracking or corrosion degradation A Board senior metallurgist from its Materials Laboratory Division reviewed the Packer Engineering report and determined that it contained no evidence of preexisting damage in any of the components that could have caused an in-flight breakup. The Packer Engineering report indicated that a small section of the right wing (the rear spar cap) showed a' defect-related fracture that the report attributed to intergranular attack. However, both the fractography and the microsection through this area were representative of an overstress fracture. The Board notes that the Packer Engineering report concluded that
 

Only a small part of one fracture of the right wing components was considered to be from prior, before accident, damage. Neither the size of this 'prior damage' nor the extent of its coverage was sufficient to satisfy fracture toughness requirements for fast fracture. Only two other structural pieces from the right wing were recovered and examined and both show tensile overload failure. Assuming aerodynamic loading prior to the crash produced acceptable stresses, we conclude, on the basis of this evidence (three fractures) alone, that defects or prior damage were not sufficient in size or magnitude to cause in-flight loss of the right wing. (Emphasis in original) 

A map of the underwater wreckage debris field that was created during the original investigation also refutes the petitioner's theory. The debris field was approximately 600 feet long and 300 feet wide and was oriented on a magnetic heading of approximately 20¡. The underwater map shows that many airframe parts were found close to components that the petitioner alleges separated from the airplane in flight For example, It shows that the right engine power section, labeled "power sect 1/2" was found within approximately 100 feet of cabin seats, a cabin emergency exit door, a wing flap section, and a first aid kit. The right engine gas generator, labeled "engine back 1/2, " was found within approximately 100 feet of the copilot's seat, the cockpit section, a condenser blower motor, and the entire left engine labeled "eng." The empennage section, labeled "tail section,"was found very close to the right elevator section and within 100 feet of a set of headphones, a main landing gear, and the CVR. The fact that all of the airplane's wreckage was found in the debris field except for the outboard section of the right wing[3] and the forward airstrip door, which were found floating in the ocean the morning after the accident, is not consistent with the petitioner's in-flight breakup scenario. An underwater video survey of the wreckage debris, conducted by American Underwater Search and Survey, Ltd. during the Safety Board's initial investigation, also provides evidence refuting the petitioner's in-flight breakup scenario. Raytheon Aircraft Company personnel reviewed the video survey and subsequently identified and catalogued the various components of the accident airplane that appeared in the survey. The accident airplane was equipped with a single air conditioner condenser blower, which was mounted in the right wing between the fuselage and the engine. This blower was found near the right engine gas generator and near the left engine/propeller With both the right gas generator and left engine propeller located in close proximity to the condenser blower, the Board concluded that the right and left engine components were in proximity to one another, The clearly visible and undisturbed close relative location of the right engine half to the left engine refutes the petitioner's assertion that the entire right engine. propeller, and nacelle separated from the airplane while in flight. The underwater video survey also showed pieces of cabin interior trim entwined with the right engine power section. This intermingling of the right engine power section with interior components from the cabin is consistent with water impact with the right engine still attached to the airplane. if the engine had separated in flight, no cabin pieces would have been found in the engine wreckage, 

To further examine the possibility of an in-flight engine separation, the Safety Board conducted flight path and engine path studies (enclosed). Radar data indicated that the accident airplane was executing a procedure turn to runway 28 at the Block Island Airport. The airplane was in a right turn toward the in-bound final approach course when radar contact was lost. The airplane's indicated airspeed and heading were derived from radar data. At the time of the disappearance, the airspeed was greater than 160 knots, and the heading was approximately 200¡

The Safety Board modified a computer program to calculate the airplane motion of a BE-1900. Initial conditions of position, altitude, airspeed, ground track, flight path angle, and upper air winds were defined to be consistent with recorded radar data and other data. The roll angle and G-load time histories were defined to produce a flight path from the last recorded radar return of the accident flight to the impact area. The time of calculated impact coincided with the end of the CVR recording. A second study was conducted to show a typical trajectory if the wing had separated at the time of the final radar return. If the airplane had progressed without a wing from the time of the final radar return to the end of the CVR recording, the airplane would have continued to move to the southwest and would have impacted the water about 1 mile south of the crash site. Therefore, the flight path study shows that the wing did not likely separate from the airplane at the time of the last radar return, as postulated by the petitioner.

The enginepath study examined the possible motion of the right engine if it had separated from the wing, moved back relative to the airplane, and struck the horizontal tail. The Safety Board modified a computer program to calculate trajectories of the BE-1900 engine and propeller. An initial airspeed of 160 knots was assumed, as were a total frontal area of 11 square feet and a weight of 700 pounds. The Board determined that the engine would move about 33 feet aft of its mounts in approximately 1.2 seconds. However, the petitioner's scenario appears to require that the right engine tore off moved back relative to the airplane, and struck the horizontal tail in about _1/4 second (the 0.263 second between the first and second CVR spikes). Therefore, the engine path study shows that the right engine did not separate from the airplane as postulated by the petitioner.

Finally, the petitioner asserts that the exact attitude of the airplane at the time of impact with the ocean is unknown. As noted above, the petitioner asserts that a major portion of the right wing, the right engine and nacelle, the right horizontal stabilizer, and the outboard portion of the left wing were no longer attached to the airframe upon water impact, having separated about 1,900 feet mean sea level (msl). The petitioner believes, based on documentation by the Safety Board as well as its own work, that the remainder of the airplane impacted the water nose and left wing root first, in a nearly vertical attitude. Although the Board concurs with the petitioner that the airplane's attitude at impact cannot be definitively determined, the Board believes that the airplane was intact when it hit the water. Therefore, the Board agrees to modify finding 9 to read as follows: "The airplane's exact attitude at impact could not be determined from the available data."

Analysis of the CVR Tape

hi response to the petitioner's contention that a CVR spectroanalysis shows that an engine separated in flight, the Safety Board analyzed the last 15 seconds of all of the CVR channels to determine if any sounds were recorded that could be associated with the engines and/or the propellers. Two of the CVR channels contained identifiable engine sounds: the area microphone channel and the unused third crewmember's radio channel. The airplane engine sounds were most identifiable on the unused CVR channel.

The Safety Board's sound spectrum analysis concluded that no sounds were recorded on any channel of the CVR that could be associated with a whirl flutter event or any structural] or component failure. If the engine truss mounts had broken and whirl mode had been initiated, sounds unique to such an event would likely have been recorded on the CVR. Further, if the engine had separated and subsequently struck the tail, the CVR would have recorded the sound of the engine tearing loose, the sound of the propeller changing angles and slowing down, and I second or more later, the sound of the engine striking the tail, resulting in structural damage, No such sounds were recorded.:

The petitioner presents the results of sound spectrum studies of the accident flight's CVR tape, which were conducted by two private laboratories.[5] These studies analyzed a constant clicking or snapping sound that can be heard on the unused CVR channel. The petitioner asserts that the sources of these sounds originated from an electroacoustic or triboelectric effect[6] acting on the accident airplane's wiring bundle. The petitioner assumes that some unknown wire or wires were subjected to mechanical movement consistent with a broken truss tube end impacting on the tube joint and that the induced voltage or current was introduced into the CVR recording system. Although the triboelectric effect is widely known and can be easily demonstrated in the laboratory, the voltage produced as a result of the physical bending of a wire is on the order of several thousandths of' a volt. If given the right physical movement and an instrumentation recorder with sufficient sensitivity to record the small voltages that are produced, this phenomenon in theory could be an indication of mechanical stress on the wiring. However, any triboelectric-induced voltages or spikes would have to be uncharacteristically large to be electrically coupled from the engine wiring to the CVR wiring because the CVR system wiring installed on the BE- 1900 consists of only four or five individual wires that connect the front systems to the CVR recorder located in the tail of the airplane. No CVR wires run in the wing structure or near either of the airplane's engines or engine mounts.

During the Safety Board's initial investigation, it was noted that when the recorded waveforms of these clicking sounds were examined, each waveform consisted of one complete wave cycle. This cycle rhythmically alternated, starting either in the positive or negative direction. The approximate period of the larger clicks was I .18 seconds (0.84 hertz [Hz]). The waveforms also contained other (smaller in amplitude) waveforms, or spikes, identical to the louder (larger in amplitude) waveforms. These sounds had a shorter period of approximately 0.58 second (1.73 Hz). This second spike set was approximately half' the period of the larger first set. In some areas of the recording, several more sets of' spikes were identified. Each multiple set of spikes had approximately half of the period of the preceding set.

Further, the accident airplane was equipped with anticollision strobe lights which can produce or dissipate large amounts of electrical energy. The signatures of' the clicking sounds recorded on the CVR channels, especially the unused channel, can be classified as very noticeable during the low background noise areas of the recording. The voltages and the energy associated with the strobe light system are of sufficient levels to cause interference in the airplane's wiring. The chance of Interference increases if a defect or bad ground path exists in one of the high-energy lines. After conducting Its own sound spectrum study of the CVR tape, the Safety Board concludes that the most likely source of the constant clicking or snapping sound on the unused CVR channel is discharge sounds from the airplane's strobe light system.

Finally, the Safety Board notes that the petitioner's scenario assumes that the CVR recording ended about the time of the last radar return at 1,900 feet.[7] However, the Board's analysis concluded that the CVR recording ended at the time the airplane impacted the water, about 26 seconds after the last radar return.[8] Based on that timing, the flight path study indicated that a sharp turn was required to maneuver the airplane back toward the crash site. A loss of altitude would have occurred as a result of banking and activated the altitude alert warning at about 1 ,700 feet msl. Thus, during the last 26 seconds of the flight, while the airplane was banking to the right on a southwest heading, the transponder antenna was blocked by the airplane's body from transmitting to the radar site to the north.[9]On the basis of its review of the evidence from the original investigation and after conducting additional analysis in response to this petition, the Safety Board concludes that no CVR evidence exists showing that a catastrophic in-flight structural failure occurred causing the disruption and failure of all airplane systems before its impact with the water. Therefore, the petitioner's request to modify findings 2 and 3 in the original Accident Report is denied.

Alleged Lack of Evidence Support the Safety Board's Scenario

Instructor Pilot's Performance

The petitioner contends that no evidence exists that the IP was ever "spatially disoriented"during the flight or that he lost awareness of the attitude and altitude of the airplane. The petitioner further asserts that although bank angle might have been excessive during the last few seconds of controlled flight, no evidence exists that the trainee was ever in an "unusual attitude" and that the comment, "Your airplane?"may in fact have been a query as to who should be or actually was flying the airplane, not a request for the IP to take over control.

A review of the intracockpit communications revealed that, at 2144:08, the captain-trainee started the procedure to turn outbound on the VOR approach and, at 2144:28, confirmed a simulated right engine failure. At 2145:04, the IP states, "Okay there's a minute,"The captain-trainee replies, "Okay and in a right turn"At 2145:30, the captain-trainee states, "And just confirm what altitude I'm still good to ah down to now." The IP replies "Ah two thousand still." At 2146:27, the captain-trainee states, "What altitude am I good down to?' The IP states, "Ah once your established inbound right you're good to what?"At 2146:34, the captain-trainee states, "Oh #," followed by the sound of an altitude alert chime. At 2146:35, the IP states, "Stop one thing at a time. You're in a bad situation so correct one thing first,"followed by "nope." At 2146:40, the captain-trainee states, "whoa,"followed by "your aircraft?" at 2146:42. The IP replies. "No take it, get the bank. Power to idle." A sound of the landing gear warning horn starts and continues until the end of the recording. At 2146:47, the IP states, "All right." The recording ends at 2146:49. 

After thorough reanalysis of the CVR recording, the Safety Board concludes that the IP exhibited a lack of situational awareness immediately before the crash. Particularly, the 1P exhibited a lack of situational awareness regarding the captain-trainee's degree of confusion and disorientation. The IP also exhibited a lack of situational awareness regarding the airplane's altitude and the limited time available for the captain-trainee to recover from his disorientation and regain positive control of the airplane. The IP's lack of situational awareness was demonstrated when he continued to "coach"the captain-trainee throughout the maneuver rather than taking control of the airplane. During this time, the IP made no comments indicating that he was aware that the airplane had descended well below published minimums for that segment of the approach, which further suggests that he had lost situational awareness. Therefore, the petitioner's request to modify findings 7 and 8 in the original Accident Report is denied.

The petitioner contends that neither the IP nor the trainees violated any company operations specifications or policies or procedures. The petitioner also asserts that the IP simulated the failure of the right engine by reducing the power to zero thrust only, not to flight idle, and that the IP had a valid reason for simulating those particular system failures during this training flight. The Business Express BE-1900 company operating manual (COM) in effect at the time of the accident stated, "During training, no multiple emergencies, in the event of an actual emergency, the simulated emergency will be restored to normal, if possible before correcting the actual emergency." The COM, in the section, "Simulated Single Engine Flight" stated that "Engine failure can be simulated by reducing torque pressure to 200 psi, being approximately equivalent to zero thrust like a feathered propeller." The Safety Board's evidence indicated that these guidelines were not followed by the IP. A review of the accident flight's intracockpit communications revealed that, at 2138:46, the captain-trainee stated, "Have a failure on the attitude indicator." At 2144:28, the captain-trainee stated, "Confirm right engine failure." At 2144:35, the IP stated, "Right prop lever confirmed." At 2144:38, the captain-trainee stated, ".. .ah flight idle,"and the IP confirmed, "idle,"

Although disabling the attitude indicator did not technically constitute an emergency as defined in the pilot's operating handbook because there was another operational attitude indicator for backup, when the IP dimmed the light rheostat for his flight instruments, he thereby eliminated thus attitude indicator as a backup,[10]Therefore, the Safety Board modifies finding 5 to read as follows: "The IP disabled the captain-trainee's attitude indicator and dimmed the light rheostat on  his own flight instruments, which eliminated the availability of a backup attitude Indicator. About 6 minutes later, he simulated a failure of the right engine by retarding the power level to the flight idle position, which, In effect, introduced multiple emergencies contrary to the provisions of the company's BE-l900 operating manual."  

The petitioner also alleges that the CVR documented that the IP demonstrated technical and professional competence during all training maneuvers. To support this contention, the petitioner states that

It is evident that the instructor detects basic weaknesses in the performance of the student, particularly in the areas of 'partial panel' instrument flying, single engine work and instrument approach procedures. There arc numerous discussions regarding these particular maneuvers recorded on the CVR, and in fact, [the IP] has the student repeat these procedures several times in order to strengthen the trainee's abilities. [The IP] does load the student up with a lot of work, but on all occasions he gives the trainee ample time to stabilize one situation (i.e., partial panel) before introducing another (engine failure). (The captain-trainee] is a 'captain' candidate, and as such, has to be able to handle difficult situations such as those presented to him by his instructor. 

In response to ALPA's petition for reconsideration, the Raytheon Aircraft Company cited the sworn deposition testimony of Dr. Richard D. Gilson (a Certified Professional Ergonomist and aviation human factors expert with court experience, research publications, certifications, patents, and commercial products in aviation designs and training) regarding the facts and circumstances of the accident flight. In his sworn deposition, Dr. Gilson stated thatThe instructor pilot provided inadequate instruction and evaluation for this trainee and became, at best imprudent, even reckless in his position of EP, when he chose to progressively lower the margins of safety in this circumstance. The development of a situation that cascaded beyond the capacity of the trainee to handle was entirely at the direction and control of the instructor pilot. The Instructor pilot configured the airplane to create, in combination, the challenging tasks (emergencies) that had given the trainee the most difficulty (i.e., essentially a single-pilot single-engine non-precision instrument approach, with a failed yet uncovered artificial horizon and no visual access to real horizon or to the other attitude indicator). For whatever reason, the IP pressured (stressed) this trainee to maximum capacity and beyond. It is not surprising then, with this background that the final scenario set up the crash sequence, however unintended it was. The trainee repeated the control problems that he had evidenced before, entered an unusual attitude, and was being 'coached' without a 'takeover' by the instructor pilot right up to the end of the CVR... The instructor pilot had the obligation to take over when the situation was going beyond the trainee's control. Also, since he was acting as a second pilot while training for a two pilot operation with crew coordination, the IP had the duty to fly at the request of the captain-trainee, or even to suggest to do so. The Safety Board concurs with Dr. Gilson's observations regarding the IP's conduct during the accident flight; therefore, the petitioner's request to amend finding 6 in the original Accident Report is denied.