Hurlburt Field, FL
23 Nov 2003
~Due to size of this report it had been condensed here~
UNITED STATES AIR FORCE AIRCRAFT ACCIDENT INVESTIGATION BOARD REPORT
MH-53M, AIRCRAFT NUMBER 70-1625
20th SPECIAL OPERATIONS SQUADRON
16th SPECIAL OPERATIONS WING
HURLBURT FIELD, FLORIDA
LOCATION: N34° 56.25, E069° 26.79
NEAR BAGRAM AB, AFGHANISTAN
DATE OF ACCIDENT: 23 NOVEMBER 2003
BOARD PRESIDENT: BRIGADIER GENERAL STEVEN C. SPEER
Conducted IAW Air Force Instruction 51-503
SUMARY OF FACTS AND STATEMENT OF OPINION
MH-53M ACCIDENT 23 NOVEMBER 2003
TABLE OF CONTENTS
COMMONLY USED ACRONYMS & ABBREVIATIONS…………………………………………iii
SUMMARY OF FACTS……………………………………………………………………………..1
1. AUTHORITY, PURPOSE, AND CIRCUMSTANCES…………………………………………1
2. ACCIDENT SUMMARY……………………………………………………………………….1
4. SEQUENCE OF EVENTS……………………………………………………………………..2
f. Life Support Equipment, Egress and Survival……………………………………..6
g. Search and Rescue………………………………………………………………………7
h. Recovery of Remains …………………………………………………………………..7
STATEMENT OF OPINION………………………………………………………………………..8
MH-53M, 70-001625, 20031123
SUMMARY OF FACTS
1. AUTHORITY, PURPOSE; AND CIRCUMSTANCES
On 25 Nov 03, Lieutenant General Paul V. Hester, Commander, Air Force Special Operations Command (AFSOC), appointed Brigadier General Steven C. Speer to conduct an accident investigation of the 23 Nov 03 crash of an MH-53M aircraft, serial number 70-1625, near Bagram AB, Afghanistan (Tab Y, 1). The investigation began at Bagram AB, Afghanistan, on 27 Nov 03 and continued at Hurlburt Field, Florida, on 26 Jan 04 after the Safety Board investigation was completed. Their investigation was completed on 26 Jan 04. Technical advisors were Major David P. Charitat, Legal Advisor; Major Percy E. Dunagin, Pilot Member; Captain Michael J. Colvard, Maintenance Member; Captain Scott M. Cummis, Flight Surgeon; and Senior Airman Leanna Grard, Recorder.
This aircraft accident investigation was convened under Air Force Instruction (AFI) 51-503. The primary purpose is to gather and preserve evidence for claims, litigation, and disciplinary and administrative actions. In addition to setting forth factual information concerning the accident, the Board President is also required to state his opinion as to the cause of the accident or the existence of factors, if any that substantially contributed to the accident. This investigation is separate and apart from the safety investigation, which is conducted pursuant to AFI 91-204 for the purpose of mishap prevention. The report is available for public dissemination under the Freedom of Information Act (5 United States Code (U.S.C.) §552 and DOD 5500.7, AF Supplement).
The accident board was convened to investigate the Class A accident involving an MH-53M aircraft, SIN 70-1625, assigned to the 20th Special Operations Squadron, 16th Special Operations Wing, Hurlburt Field, Florida, which crashed on 23 Nov 2003.
2. ACCIDENT SUMMARY
Aircraft 70-1625 experienced a compressor stall in the number two engine during an Infiltration/Exfiltration mission on 23 Nov 2003 and impacted the ground approximately nine miles from Bagram AB, Afghanistan. The Pilot, Major Steven Plumhoff; a passenger, Army Sergeant Major Phillip Albert; the Right Scanner Technical Sergeant William J. Kerwood; the Left Scanner, Technical Sergeant Howard A. Walters, and the Flight Engineer, Staff Sergeant Thomas A. Walkup were killed in the mishap. The Co-pilot, First Lieutenant Christopher C. Richardson; the Tail Scanner, Senior Master Sergeant Wayne C. Lopez; and passengers Second Lieutenant William H. Waggy, Staff Sergeant Jonathan Purser, Specialist Diane C. Gilliam, Specialist Gary L. Craig, Specialist Juan C. Aguilera, and Specialist Demetrius D. Kincaid successfully egressed the aircraft post-crash and survived with injuries varying from severe to minor. The aircraft was destroyed upon impact with the loss valued at $26,000,000.00. There was some damage to a local field, which was mitigated within a week of the crash, and no civilian casualties or injuries occurred.
MH-53M, 70-001625, 20031123
The 16th Special Operations Wing, stationed at Hurlburt Field, Florida, maintains, among other aircraft, the MH-53M Pavelow for use in support of Special Operations worldwide. The Wing and its subordinate units are all components of Air Force Special Operations command. The 20th Special Operations Squadron (SOS) is a subordinate organization of the 16th Special Operations Wing. The mishap unit was a 4-ship detachment of the 20th SOS Bagram AB, Afghanistan supporting a joint task force (JTF) conducting combat operations in that theater.
Aircrews and aircraft converged in Kandahar, Afghanistan in early Nov 2003 in support of operations tasked and operationally controlled by the theater Combined Joint Special Operations Air Component Commander (CJSOAC). Three MH-53M’s were transferred by strategic airlift from another theater location and one helicopter (MA) was brought directly to Kandahar from Hurlburt Field. Aircraft were built up, test flown and forward deployed to Bagram AB, Afghanistan. Aircrews were paired based upon previous Afghanistan experience and overall crew qualification. Maintenance crews were formed into shifts and assignments given. All MH- 53M aircraft were in place on 13 Nov 2003.
The CJSOAC Commander, the JTF Air Component Commander, and the deployed Mission Commander of Pave Low operations discussed tasking and types of missions in depth during preplanning efforts and again upon arrival in theater. Operational requirements, aircraft performance, enemy operations, and environmental factors (terrain, weather, temperature) led to decisions that factored in all the above to arrive at mission sets/tasking’s that would be given to the MH-53 aircrews (Tab V 19.1-19.2). These tasks continually placed the aircrew and helicopter in the upper end of the medium risk category. Only the CJSOAC Commander had approval authority for high-risk missions (Tab V, 21.1-21.2). Additionally, he had the waiver authority from the AFSOC/DO to authorize aircraft gross weight operations above 46,000 pounds up to 50,000 pounds. This waiver is common during wartime operations because it allows maximum flexibility to support combat operation loads. In practice, the Mission Commander, had limited gross weights to 48,000 pounds as a rule of thumb, but his primary consideration was aircraft power performance, not weight (Tab V, 21.5).
The mountainous region of the Afghanistan AOR requires terminal area operations at 6-10,000 ft. MSL and enroute operations at 10-15,000 ft. MSL. Often, the MH-53 at mission gross weights does not have hover or single-engine power capability at these altitudes without both engines operating and/or reducing weight through the auxiliary fuel tank jettison system, which puts the helicopter back in the single engine envelope, enabling it to recover safely when conditions warrant. Therefore TACON decisions by the JTF Air Component Commander had the aircraft performing only missions that were within the training, scope and performance limitations of the aircraft. Specifically, terminal area operations were limited to conditions where 50-foot hover power was available. Enroute operations were limited by maximum power output from both engines, and dependent upon the ability to rapidly reduce weight in an emergency (Tab V, 21.2-3).
4. SEQUENCE OF EVENTS
The mission was tasked as a two-ship movement of special operations forces and supplies between Bagram, Afghanistan, and remote sites in the mountains of Afghanistan. The Commander, Combined Joint Special Operations Air Component, authorized the mission.
MH-53M, 70-001625, 20031123
The two crews tasked to fly this mission were on their third day of a 3-day rotation of support missions. The planning cycle was set up so that an additional crew was tasked to coordinate and plan daily missions while the flying crews were executing the current missions. Initial mission planning was conducted by the duty/planning crew, but the flight lead crew for this day had finalized the detailed planning for this mission the morning of the flight (Tab V, 6.15, 8.1). The mishap crew was the Chalk two element of all missions in this rotation. The Detachment Commander and Squadron Director of Operations, Lt Col. Slife, was fully aware of the daily operations and talked regularly to the flight lead pilots about the specifics of each mission (Tab V, 21.3). He did not always attend the mission briefings but was fully aware of each mission’s profile.
On the day of the mishap, both crews woke in the morning at approximately 0800 L and began final preparations for the mission. Capt. Mark Newell, the Aircraft Commander of the flight lead element, Beatle 11, conducted the mission briefing using the standard briefing guide. Because this was the third day of similar re-supply missions, this briefing was familiar to all the crewmembers. All of the crewmembers interviewed fully understood the mission. The mission was to be a daylight mission, with a possible brief extension into nighttime, depending on the actual flow of the re-supply. This variable was mitigated by varying the routes to shave off time in order to maximize daylight operations. The available routes to do this had been discussed and weighed by all the crews on an ongoing basis (Tab V, 8.1- 8.3). There had been some fluidity to the missions in the past two days, in that the supported team members had changed their loads from the pre-briefed loads (cargo and passenger requirements) at the last minute. Therefore, the mission crews were aware of this trend and fully expected there to be last minute changes. They had dealt with these changes with little problem and had adjusted on the fly while still maintaining the limitations on fuel, gross weight, and aircraft power margins (Tab V, 7.7, 17.1).
Preflight was uneventful. Auxiliary tank safety pins were removed during preflight (Tab V, 12.21-22; Tab DD, 35).
The mishap flight, Beatle 11 and 12, initially departed Bagram Air Base at 0653Z (1123L) for its first leg of the mission, according to the JOC logs. The routes the flight took were through mountainous terrain rising from the Bagram valley altitude of 4,900 feet MSL to 12,500 feet MSL ridgelines. They made two out-and-back trips between the base and tactical landing zones, each lasting approximately three hours. These legs of the mishap sortie were flown both in the valleys and across ridgelines, at altitudes varying from 200 feet AGL to 3000 feet AGL to climb over the ridgelines (Tab V, 7.1, 8.2-8.3, 8.6-8.7).
The mishap flight departed Bagram Air Base for its final leg of the day at approximately 12212 (1651L) from the approach end of runway 03 and began a climbing turn out to the east (Tab AA, 9). Takeoff weight for each aircraft was approximately 48,000 pounds with 7,500 pounds of fuel (Tab V, 5.2, 6.3, 7.7, 7.8, 8.5). The flight signed off with Bagram tower at approximately 12232 (1653L) and continued eastbound. Flight lead (Beatle 11) intended to climb up to 7000 feet MSL initially, then continue to climb across a 9500 feet MSL ridgeline approximately 17 miles east of Bagram once they got closer to the ridgeline (Tab V, 8.6, 16.1). According to witness testimony, the MA took off several seconds delayed from its flight lead aircraft due to a slight delay coming out of the FARP at Bagram (Tab V, 16.1, 8.6). The MA climbed and accelerated to catch up with the lead aircraft. During this time the flight lead aircraft had slowed its speed to allow Beatle 12 to catch up. After Beatle 12 caught up to a position of eight to ten rotor disks back and staggered slightly left, as reported by the Tail Scanner on Beatle 11, Beatle 11 resumed a normal acceleration (Tab V, 16.2).
MH-53M, 70-001625, 20031123
This was reported as approximately five minutes after takeoff (Tab V, 8.6). Tracking data showed the MA departing the FARP at Bagram and turning out to the east, while climbing and accelerating (Tab AA, 9).
At this time, with Beatle 12 in a loose staggered left formation with approximately mile separation, the Tail Scanner on Beatle 11 reported over intercom that Beatle 12 appeared to be dispensing flares. Almost immediately, he ·added that Beatle 12 was turning left and descending, and continuing to dispense flares (Tab V, 16.1, 16.2). Beatle 11 queried Beatle 12 on the interplane radio about their maneuver, but, at first, got no response. Beatle 11 then turned left to follow Beatle 12 (Tab V, 6.7).
Several personnel onboard the MA heard popping noises, accompanied by flames, sparks and what appeared to be sparkling flares. One distinctly heard a pop from the number two engine. Another saw flames out the right side passenger windows. A third saw sparks on the right hand side only. The MTS reported hearing several popping noises that he interpreted as flares being dispensed (Tab V, 1.1, 3.1, 4.2, 5.2, 9.8, 23.2, 10.1). At the time, he was adjusting something in the right rear of the cabin, and immediately turned to look out the rear (Tab V, 4.2, 5.8). He saw what appeared to be flares coming out the right side of the aircraft, but did not observe anything out the left. He did not hear the normal beeping tones that the Chaff and Flare Dispenser makes when flares are dispensed, nor did he hear any tones from the DIRCM. At that moment, the MTS and one passenger also felt a small shudder in the aircraft (Tab V, 4.2). Shortly thereafter, he heard the cockpit crew analyzing the situation and taking steps to remedy it. These included announcing that there was a compressor stall in the number two engine (Tab V, 5.2, 5.3); calling for the gear down; and verbalizing and attempting to jettison the aux fuel tanks.
SINGLE ENGINE PERFORMANCE DATA
|Pressure Altitude (feet MSL)||4,600||6,600||4,600||4,600|
|Temperature (degrees C)||+9||+5||+9||+9|
|Gross Weight (pounds)||48,000||47,600||46,000||42,700|
|Density Altitude (feet MSL)||5,000||7,000||5,000||5,000|
|Maximum Power Available (percent torque)||114||107||114||114|
|Dual Engine Service Ceiling (feet MSL)||12,000||12,200||13,000||13,000|
|Single Engine Weight (pounds)||42,700||39,700||42,700||42,700|
|Sink rate with aux tanks (FPM)||-380||-550||-240||N/A|
|Sink rate without aux tanks (FPM)||-50||-200||+90||0|
|Single engine capable without aux tanks?||No||No||Yes||Yes|
The MTS, realizing that they were going to make a precautionary landing, began to reduce weight by throwing his .50 caliber ammunition cans overboard. He considered throwing out the .50 caliber gun itself also, but was interrupted by the landing sequence (Tab V, 5.4).
During the descent after the initial compressor stall, Beatle 11 observed the MA dumping fuel (Tab V, 7.3, 6.8). No witnesses remember seeing the fuel dump stop prior to impact (Tab V, 6.8, 7.14-16). However, the post-crash analysis of the dump switches indicated that they were in the off position at impact (Tab DD, 9). Beatle 11 also descended and accelerated (approximately 1,500 feet per minute and 120 knots) to catch up with Beatle 12. From Beatle 11’s perspective, Beatle 12 was at the 12:30 position about 1 mile away (Tab V, 8.7, 6.8). Simulator recreation and analysis of the tracking data estimated that the MA descent rate averaged appr9ximately 3,000 FPM, which included a droop in the rotor RPM.
MH-53M, 70-001625, 20031123
One crewmember on Beatle 11 reported what appeared to be an orange flame from the right side of the MA, near the number two engine exhaust, just prior to impact. His perspective of the MA was to his 11:30, 1000 feet below and about 1 mile ahead (Tab V, 7.3-4). This corresponds with the timeframe when the number one engine made a popping sound. While it is uncertain whether this orange flame came from the number one or number two engine, it is possible that either the number one engine compressor stalled or the number two engine produced more flames due to its deteriorating condition. Nobody else, including the people on board the MA, reported any pre-impact fire.
Aircraft 70-1625, Beatle 12, impacted the terrain at approximately 1657L (1227Z) on 23 Nov 2003 at N 34 56.25 E 069 26.79 at approximately 4,500 feet MSL. Beatle 11 observed Beatle 12 impact the ground approximately 1.5 minutes after the initial turn, and reported it to the Joint Operations Center at Bagram at 1233Z (1703L) (Tab V, 7.3, 6.8). Photographs show initial impact scars near a riverbank extending towards a farmer’s field at a heading of 310 degrees (Tab Z). The entire crash site is a relatively flat area, approximately 630 feet long and 270 feet wide. Debris from the mishap aircraft is scattered as far as 360 feet from the main wreckage (Tab S, 3). There are no major obstacles such as trees, buildings or wires within 500 feet of the wreckage. The initial impact scars are on a flat surface covered with 6-inch diameter flat rocks, which appears to be the riverbed during the season in which the river would be wider and deeper (Tab Z). These scars lead up to the farmer’s field, which borders this rocky riverbed with a sloping berm of dirt, approximately 3 feet high and 6 feet wide. This berm wraps around the river bend near the crash site, forming a barrier and a riverbank separating the river from the farmer’s field. The field itself is made up of fertile soil with terraced sections separated by smaller berms (Tab Z).
Beatie 12 executed a normal, nose up, running landing into the crash site (Tab V, 5.3, 7.12), as the Flight Manual calls for (Tab BB, 21). Simulator recreations estimated that a touchdown speed of approximately 50 knots and descent rate of 500 feet per minute resulted from the flight path of the mishap aircraft from the initial point of engine failure to impact. · At approximately 100-200 feet above the ground, and 0.1 nautical miles (600 feet) from the impact site, the mishap pilot flared the aircraft, which brought the nose up and tail down (Tab V, 1.1, 5.3-5.4, 9.10, 22.4- 22.5). At this time, the MTS realized the landing was going to be rough, and dove forward off of the tail cargo ramp (Tab V, 5.4).
In order to maintain controlled flight with one engine operating, the: MP demanded a high power setting from the number one engine. As he increased power from an already high power setting to arrest the descent for landing, the number one engine strained even more and overheated (Tab V, 9.7, 9.14, Tab DD, 3-4). The number one engine made a loud pop (Tab V, 9.20). The MP continued to adjust the MA flare attitude and speed just prior to touchdown (Tab V, 9.7). When the MA touched down, scars indicated that the tail skid and the main landing gear touched down and began scraping on the flat rocky area approximately 180 feet prior to the berm (Tab S, 3). Witness testimony confirmed that the MA continued to slide on its belly until a significant bump that jarred the MA completely out of control (Tab V, 9.11, 10.7, 22.5). This bump was the berm, which acted as a ramp and caused the MA to pitch up slightly and become slightly airborne. As the nose pitched up, the tail section pitched down, causing the tail section to contact the ground at the intermediate gear box (IGB). The wreckage of the tail section shows significant damage to the IGB area but little damage to the tail rotors from rotating tail rotor blades digging into the ground (Tab Z). The tail skid assembly, mounted at the IGB, was also found on the berm near this impact point.
The force of the MA tail section impacting the berm caused it to separate just forward of the tail pylon hinge. Because the tail rotor blades were winding down after separation but still spinning, the thrust of them and the forward momentum of the aircraft carried the tail section forward and to the right of the berm approximately 50 feet (wreckage diagram). The effect of the tail section separation induced a right yawing motion in the MA due to the loss of tail rotor anti-torque. The nose then pitched down due to the shift in the center of gravity. The MA continued translating forward during this yaw, but did not make any scars
MH-53M, 70-001625, 20031123
on the ground between the berm and 60 feet down towards the main wreckage (Tab S, 3). The mishap flight engineer most likely shut off the number one engine throttle in response to this right yaw, as called for in the boldface emergency for tail rotor drive system failure in the Flight Manual (Tab BB, 19-20). Engine analysis indicated that the number one throttle was in the shutoff position, the number two throttle in the ground idle position (Tab DD, 37) and the number one engine’s inlet guide vanes were in the shutoff position (Tab DD, 3). The Flight Manual calls for the engine to be pulled to ground idle in the event of a compressor stall (Tab BB, 18). The ·1.:5 temperature from engine gauges analyzed indicated one engine at 700 degrees C and the other at 100 degrees C. This is consistent with the number one engine cooling off slightly (from over-temperature at 900 degrees C) between being shut off and losing electrical power as the generators went off line due to decayed rotor RPM; and with the number two engine cooling off after being placed in ground idle after the initial compressor stall and wind milling in cool air all the way down to the crash site.
As the MA lost its final lift, it impacted the ground on its left side while sliding left, ripping the left hand aux tank off, and causing it to roll over to the left once and come to rest on its top side, facing approximately 150 degrees right of its initial inbound course (Tab S, 3; Tab Z). A post crash fire consumed the aircraft rapidly due to ruptured fuel lines and fuel tanks (Tab V, 2.1, 5.4, 6.8, 17.2).
f. Life Support Equipment, Egress and Survival.
Upon boarding the MA the passengers received no safety or egress brief (as required IAW AFI 11-2 MH53 Vol. 3) and were provided with no means of securing themselves within the aircraft (Tab V, 4.1, 9.2). Upon impact the MA rolled to an inverted position and the body of the MA was divided by the post-crash fire into fore and aft sections (Tab S, 3). In the forward section the MCP, with a head injury, extricated himself from the cockpit and then reached into the rear section of the burning aircraft and found Specialist Aguilera attempting to locate an egress route. The MCP pulled Specialist Aguilera to safety (Tab V, 2.1). In the aft section of the MA, Specialist Craig, on his way out, attempted to extricate Sergeant Major Albert, who was pinned and unconscious. Unable to do that, he moved further back and saw Staff Sergeant Purser suspended from his personal safety line from the inverted floor and on fire. He paused, cut him free, and assisted him out of the MA into the nearby river, saving his life (Tab V, 9.12). The MTS and passengers Lieutenant Waggy, Specialist Gilliam, and Specialist Kincaid successfully egressed the aft portion of the MA after the crash and survived with injuries of varying levels.
Post-crash analysis indicates that position of the passengers within the aircraft, rather than the restraint method, was the significant factor in their post-crash condition and egress capability. The diagram included in Tab AA, which differs from the SIB Tab R, clearly shows that those passengers seated on the left of the MA sustained minimal injuries, while those on the right were either killed or severely injured (Tab AA, 1).
No deficiencies were noted in the life support and survival equipment. Inspection records of this equipment were reviewed and found to be appropriate and without discrepancy. Lack of a quick release on the HGU 56/P helmet may have delayed the egress of the MTS. The MTS’s communication cord became tangled during the post-crash sequence. One technique for untangling himself would have been removing his helmet, however, the chinstrap on this helmet requires two hands to unfasten. The MTS had sustained a shoulder separation, which rendered his left hand useless. He eventually pulled the cord loose and egressed (Tab V, 5.4).
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g. Search and Rescue.
Upon impact of the MA, Beatle 11 immediately assumed the CSAR role, landing approximately three to five minutes after the mishap (Tab V, 6.10). The crewmembers and passengers of Beatle 11 were unable to enter the MA to rescue any of the trapped members due to the post-crash fire and exploding ordinance. Passengers on Beatle 11 rapidly established site security and gathered casualties. Crewmembers on Beatle 11 helped the injured passengers and crew load onto their aircraft and then departed to Bagram AB about 20-25 minutes after the mishap, leaving a security detachment to secure the crash site (Tab V, 7.15, 16.3-4, 17.2). On approach to Bagram, Beatle 11 declared an emergency CASEYAC with the Bagram air traffic control tower, and stated their intentions to land at the Alpha taxiway, where they had coordinated with the JOC to meet SOF medical personnel. The tower controller misunderstood the term CASEVAC, and thus the needs of Beatle 11. The tower controller believed that Beatle 11 had an in-flight emergency and initiated a crash rescue response, but did not alert any ambulance or medical units (Tab V, 8.15; Tab AA, 11-12). No ambulances departed to meet Beatle 11 until four minutes and ten seconds after the aircraft landed on Alpha taxiway (Tab AA, 11-12). The reasons for this delay are three-fold: 1) Miscommunication with the tower controller, 2) Lack of a written mishap response plan in the Pavelow Operations Center (Tab V, 21.7), which meant that Pavelow crews did not have the MEDEVAC plans and frequencies to communicate with the Combat Support Hospital (CSH) (Tab V, 8.18), and 3). Lack of coordination between the JOC and the airfield MEDEVAC response system after the initial call from Beatle 11 (Tab V, 6.7). The CSH operated an independent MEDEVAC operations center and the standard procedure was for aircraft to land at the CSH, a location separate from Alpha taxiway. CSAR and MEDEVAC were not part of the mission profiles of the deployed Pavelow unit, although they routinely provide self-CSAR or can be called upon as CSAR aircraft of opportunity (Tab V, 21.4-21.6).
Additional aircraft on alert for CSAR were available but were not launched, since recovery of casualties was complete. Frustrated, Beatle 11 returned to the site with a team to continue site security and prepare for remains recovery (Tab V, 6.11-12, 8.17).
For summary, the initial medical response to Beatle 11 was delayed, but this did not contribute to the degradation in the medical condition of any of the casualties (Tab X, 1).
h. Recovery of Remains.
The 54th Quartermaster Company, a U.S. Army Mortuary Affairs detachment from Ft. Lee
Virginia deployed to Bagram Air Base, conducted remains recovery. A team of 8 mortuary affairs members searched and recovered all possible remains over a four-day period using standard recovery techniques. The remains departed Bagram Air Base on 30 Nov 2003 aboard a C-17 aircraft to the Dover AFB Port Mortuary, where positive identification of remains and autopsies (if possible) were conducted. The remains were then released to the families for burial at Arlington National Cemetery
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STATEMENT OF OPINION
MH-53M ACCIDENT, BAGRAM, AFGHANISTAN
23 NOVEMBER 2003
Under 10 U S.C. 2254(d), any opinion of the accident investigators as to the cause of, or the factors contributing to, the accident set forth in the accident investigation report may not be considered as evidence in any civil or criminal proceeding arising from an aircraft accident, nor may such information be considered an admission of liability by the United States or by any person referred to in those conclusions or statements.
CAUSE: I find by clear and convincing evidence that the cause of this fatal mishap was a sequence of events initiated by mechanical failure of the number two engine, followed by an electrical failure of the auxiliary fuel tanks to jettison, and concluded with the uneven terrain features of the landing area causing the aircraft to break apart, roll inverted and burst into flames after touchdown.
CONTRIBUTING FACTORS: I find sufficient evidence to conclude that high altitude, routine high gross weights, failure of the remaining engine just prior to a precautionary landing (when demand for power to arrest the descent rate exceeded the engine capability), inadequate Technical Order guidance, factored together, all contributed to this accident. Only excellent aircrew coordination and training allowed the remaining aircrew and passengers to survive. Timely rescue and recovery by flight lead, Beatle 11, ensured survivors were extricated to safety and medical facilities in minimum time. Awareness of self-Combat Rescue and Recovery procedures, miscommunication and coordination between multiple operations centers, medical facilities, aircraft and tower communications resulted in less than adequate medical response times at Bagram Field.
BACKGROUND: The board investigated the following areas and found them not to have contributed to this mishap: Hostile Action, Qualifications (both maintenance and operations), Operations Tempo, Crew Duty Day/Crew Rest, Supervision, Life Support, Weather or Medical. No evidence could be found to support any theory of hostile ground action against Beatle 11.
DISCUSSION: The Board discussed the mishap sequence in detail with surviving aircrew, passengers, Beatle 11 aircrew, supervision and technical experts from the depots, labs and other subject matter experts. The causes and contributing factors are detailed below.
The number two engine failure on Beatle 12 was caused by sustained high engine operating temperatures brought on by high engine speeds required at high altitudes and high gross weight. Excessive heat in the engine caused the compressor to rub against the engine casing. This compressor rub led to blade failure and engine compressor stall, which produced brief outbursts of flames and sparks. Additionally, prolonged anti-ice operations throughout the day could have contributed to the high engine temperatures. Analysis of recovered engine components determined that inlet guide vanes and engine performance indicators were the result of an engine not running or at ground idle at the time of impact, which is consistent with the emergency steps for engine compressor stall (Tab DD, 1-4). Due to the high engine power setting at the onset of the engine failure, a decay of rotor RPM occurred. As the MP accelerated and reduced power to regain this rotor RPM, the MA developed a high sink rate that demanded an immediate reduction in weight, one that fuel dumping alone would not meet, due to a limited time frame of about one minute until impact. There is evidence that the MA dispensed flares at the same time as the engine failure (Tab V, 5.2, 7.10, 16.2). This is likely the result of either an automatic dispense commanded by the Missile Warning System in response to engine flames, or a flare dispensed manually by a crewmember; however, no evidence supports any hostile ground fire.
The auxiliary fuel tank jettison system failure was causal such that failure of the jettison system to work resulted in the MA not having sufficient power remaining to overcome the high altitude and aircraft gross weight with only one operative engine. Had the aux tanks jettisoned, the MC could have maintained single engine flight back to Bagram. With the aux tanks still on, the MC was forced to land immediately. Extensive testing, including operational testing, was conducted on the fuel tanks release mechanism, electrical systems, and cartridges. Post-crash analysis on the jettison switches indicated they were in the up and on position. Release mechanisms indicate they were functioning at the time of the mishap (Tab DD, 5-117). Aircrew testimony indicated the MFE and MP discussed the failure of the tanks to jettison (Tab V, 5.3). It was determined that the cartridges did not ignite prior to impact. Engineers concluded the cartridges ignited during the post-impact fire (Tab DD, 45).
A review of Technical Order guidance on the electrical continuity check of the jettison system found it to be inadequate to assess whether the jettison circuit could deliver the current/amperage required to activate the cartridges (Tab BB, 1-8). I conclude that failure of the auxiliary fuel tanks to jettison was the result of an undetected electrical circuit failure and not a failure of the cartridges, the mechanical release systems, or the MC.
The terrain features of the landing zone were causal in the outcome of this mishap. The mishap time of 1657L was after sunset (during what is called “Pink” time by flyers) and visual cues of the surrounding terrain were diminished. Shadowing in the river valley caused by surrounding high mountains; and sparse, arid and almost featureless contrasts on the ground made the precautionary landing zone appear to be a flat area. The MP, committed to landing due to little or no output of his remaining number one engine, made a controlled, roll-on landing in a nose up attitude with a forward speed and sink rate of approximately 50 knots and 500 PPM. A three foot high river bank, 180 feet from his touchdown point, caused the helicopter to become airborne, break off the tail boom and tail rotor, yaw to the right and roll left coming to rest 150 degrees from his approach axis, inverted and on fire. I believe this crash sequence would have been survivable if the terrain had been flat.
d. The number one engine contributed to this accident when the demand on the engine for power (additional torque) to arrest the sink rate in the descent/landing phase caused the engine’s gas generator turbine to exceed maximum operating temperatures. Single engine capability did not exist at the weight and environmental conditions of the mishap. Analysis of the post-crash engine detem1ined the gas generator turbine blades tips had burned off 0.25 inches (Tab DD, 1-4). This likely caused a compressor stall, explaining the pop heard just prior to impact.