SEATTLE, WA, USA
N3172A
Beech 1900C
The Beech 1900C cargo aircraft was loaded with more than 4,962 pounds of cargo during an approximate 20 minute period. No scale was available at the aircraft, forcing loaders to rely on tallying either waybill weights or estimates of total cargo weight and center of gravity (CG) during the brief loading period. Additionally, a strike had shut down a major cargo competitor at the time with substantial cargo overflow to the operator. Post-crash examination determined the cargo load was 656 pounds greater than that documented on the pilot's load manifest, and the CG was between 6.8 and 11.3 inches aft of the aft limit. The airplane behaved normally, according to the pilot, until he initiated full flaps for landing approaching the threshold of runway 34L at the Seattle-Tacoma International airport. At this time, the aircraft's airspeed began to decay rapidly and a high sink rate developed as the aircraft entered into a stall/mush condition. The aircraft then landed hard, overloading the nose and left-main landing gear which collapsed. A post-impact fuel system leak during the ground slide led to a post-crash fire.
HISTORY OF FLIGHT On August 13, 1997, at 1913 Pacific daylight time, a Beech 1900C, N3172A, registered to and operated by Ameriflight, Inc., and being flown by an airline transport pilot, was destroyed when the aircraft's left main and nose landing gear collapsed following a loss of control and subsequent in-flight collision with the runway on landing at the Seattle Tacoma (SEATAC) International airport, Seattle, Washington. A post-crash fire ensued, damaging the center structure of the aircraft and wing root areas. The pilot, who was the sole occupant, sustained serious injuries. Visual meteorological conditions existed at the time, and an instrument flight rules (IFR) flight plan was in effect. The flight, which had originated from Portland, Oregon, was an unscheduled cargo run which was to have been operated under 14CFR135. N3172A, call sign "AMFlight 262" (AMF262) departed Portland International airport at 1830 on the evening of August 13 en route to the SEATAC International airport. At 1859, the pilot of AMF262 contacted Seattle terminal radar approach control (TRACON) inbound, and advised he was at 10,000 feet. The aircraft was given vectors to SEATAC, a descent to 7,000 feet and, at 1904, was switched to Seattle approach (final) control on frequency 133.65 mHz (refer to ATTACHMENT T-I). At 1905:11, Seattle TRACON (final) contacted AMF262 and requested that the aircraft reduce speed to 210 knots and descend to and maintain 6,000 feet. Over the next four minutes the pilot of AMF262 verified SEATAC airport in sight, was cleared for a visual approach to runway 34L, was advised of traffic preceding him by five miles for the same runway, and was asked to "maintain that speed if you can until about five mile final." At 1909, AMF262 was asked to contact SEATAC air traffic control tower (ATCT) (refer to ATTACHMENT T-II). At 1909:50, the pilot of AMF262 contacted SEATAC ATCT reporting "over the mall for 34 left" (NOTE: "the mall" is located at the 7.5 nautical mile fix south of SEA VORTAC, which in turn, is located at the south end of the SEATAC airport runways). The local controller responded in part with "follow an airbus on a one mile final, caution wake turbulence, wind two seven zero at five, runway three four left cleared to land" and this was acknowledged by the pilot (refer to ATTACHMENTS T-III and RDR-I). Four of the controllers in the SEATAC ATCT facility observed the aircraft crash and two of these controllers reported seeing the aircraft in an "unusual descent" (refer to attached statements C-I through C-IV). Several other witnesses located on the SEATAC airport reported observing the accident. These witnesses reported seeing the aircraft "coming down at the wrong angle, too steep, like a helicopter," at "a high angle of attack and very low airspeed," "aircraft nose high, in approximately a 25 to 30 degree angle of descent, obviously stalled," and that "it looked like the aircraft stalled at about 300-400 ft. AGL (above ground level), and that the C.G. (center of gravity) appeared to be aft because the nose never dipped down after the stall, and the aircraft just pancaked in flat" (refer to attached statements S-I through S-IV). The pilot-in-command (PIC) was interviewed on August 19, 1997, at Harborview Hospital, Seattle, Washington. The PIC reported no mechanical nor communication malfunctions during the flight to Seattle. During the PIC's interview, he reported that the takeoff from Portland was uneventful, the aircraft accelerated normally, becoming airborne after a reasonable ground roll, and the climb performance was as expected. He also reported that the flight to SEATAC was uneventful, he was cleared to land on runway 34L and that although visual conditions existed, he utilized the ILS and normally flew one-half to a full dot above glide slope to avoid potential wake vortex conditions. The PIC reported that his intention was to touch down in the latter third of the touchdown area (the aircraft's destination was the cargo area in the northeast corner of the SEATAC airport - refer to DIAGRAM I). He further reported that his first indication of something out of the ordinary was somewhere between one quarter mile short of the threshold and the physical end of runway 34L. He stated that he had lowered full (landing) flaps and upon full extension noticed a decrease in airspeed below Vref (Vref is defined as any reference speed). Note: Vref speeds for flaps up and flaps landing at selected aircraft weights are provided to the pilot on the "Beech 1900 Normal Procedures Checklist" (refer to ATTACHMENT CL-I, page 2). He also reported that the pitch attitude of the aircraft did not change appreciably with flap extension, and the pitch change seemed to be normal for this event. The PIC reported remembering trying to counteract the airspeed decay by applying nose down elevator but did not remember events beyond that time until attempting to exit the aircraft. He also reported that he did not recall hearing the stall warning horn prior to the accident, and that he was able to trim the aircraft throughout the flight and experienced no pitch trim difficulties. The PIC reported that subsequent to the crash he recalled releasing his restraint system and unlatching and partially opening the cabin door. He observed AFFF (Aqueous Film Forming Foam, a fire fighting agent) entering the aircraft through the cabin door, and then reported that he allowed the door to rock back to a closed position. He also reported that there was smoke in the cockpit which prevented him from seeing the instrument panel. The SEATAC Aircraft Rescue and Fire Fighting (ARFF) Fire Run Report showed that the ARFF crew was dispatched at 1913:25, responded at 1914:46 and arrived at the site at 1915:36. The fire was knocked down using a turret and hand lines and the pilot was extricated from the cockpit by two ARFF responders. The report also indicated that the forward cabin door was partially open upon arrival of the ARFF team, and that the forward cabin area and door was partially blocked by cargo. OTHER DAMAGE Several runway lights along the west edge of runway 34L were knocked out during the aircraft's ground slide. Additionally, small abrasions and gouges of the runway's paved surface were noted. PERSONNEL INFORMATION The 34 year old PIC had logged approximately 6,370 hours of flight time at the time of the accident, including 4,225 hours of multi-engine flight time and 4,359 hours of PIC time. He had been issued an airline transport pilot certificate June 8, 1997, with a type rating in the BE-1900 aircraft. His most recent medical examination was conducted September 4, 1996, and he was issued a first class certificate with no limitations. The PIC had been hired by Horizon Air on October 2, 1995, and began flying as a first officer in the DeHavilland DHC-8, twin turboprop aircraft. He was subsequently issued a voluntary leave of absence on May 25, 1997, as Horizon Air faced potential reductions of pilots and requested volunteers for such absences. The leave of absence was projected to last six months. The PIC had been trained by Horizon Air in weight and balance procedures for the DHC-8 aircraft prior to his beginning line flights. The PIC was hired by Ameriflight in late May of 1997, underwent Beech 1900 and company training, and began line flights on June 9, 1997. He had logged a total of 106 hours of flight time in the cargo version BE-1900C (all PIC) at the time of the accident. Records maintained by Horizon Air showed the PIC as having logged a total of 1,230 hours of BE-1900 time (397 as pilot-in-command and 833 as second-in-command) as of June 26, 1995. This flight time was in scheduled FAR Part 135 passenger operations for GP Express in the 19 seat passenger version of the Be-1900. The PIC reported during his interview that he had an estimated 1,500 total hours of BE-1900 time (both passenger and cargo versions) and that he was familiar ("cognizant") of pitch and airspeed changes in tail heavy flights. AIRCRAFT INFORMATION N3172A, a Beech 1900C, serial number UB-47, was manufactured in 1985 as a 19-seat passenger aircraft, and issued a standard (normal) airworthiness certificate on December 12 of that year. The aircraft was subsequently converted to a cargo configuration in accordance with a Major Repair and Alteration, dated June 14, 1995 (FAA Form 337) by the operator, a certificated repair station (certificate number JIKR213F). This modification included an increase of the zero fuel weight from 14,000 pounds to 15,000 pounds (refer to ATTACHMENT MRA). The maximum gross takeoff weight (MGTOW) of 16,600 pounds was not affected. The aircraft's forward center of gravity limits varied from a minimum of 274.5 inches at 11,600 pounds increasing to a maximum of 282.8 inches at MGTOW. The aircraft's aft center of gravity limit was 299.9 inches at all weights (refer to ATTACHMENT CG-I). The aircraft's basic operating weight (BOW) for flight 262, which includes the weight of the aircraft (including all fluids exclusive of usable fuel), and the weight of the pilot, was 8,954 pounds (refer to ATTACHMENT LPS-I). The cargo configured BE-1900C (s/n UB-47): is divided into nine cargo zones (A through J) of equal size and load bearing capacity. Section K, directly aft of section J is larger and is directly opposite the aft cargo door. Section L is a stepped-up shelf-like area directly aft of section K. The maximum structural load capacity of sections A through J is 600 pounds per area. The maximum structural load capacity of section K is 700 pounds, and 630 pounds for section L (refer to ATTACHMENT APV-I). There are two additional areas of cargo storage available on the BE-1900C (s/n UB-47), the nose baggage compartment forward of the cockpit with a maximum structural load capacity of 150 pounds, and the forward cabin baggage compartment (jumpseat bay or ACM area) with a maximum structural load capacity of 250 pounds (refer to ATTACHMENT APV-II). WEIGHT AND BALANCE Cargo loading procedures to be used by the Operator's pilots were described in the Ameriflight Operations Manual, "Operations Procedures Section," pages 6.6 through 6.9, carried aboard the aircraft (refer to ATTACHMENT AOM-I). Specifically, the first page of this section of the Operations Manual states "Cargo weight may be determined by using the shipper's weight as shown on a bill of lading or manifest or by scale weighing prior to loading. Shipper's weights will be verified by periodically spot weighing cargo." According to DHL employees interviewed, standard DHL procedures at the time of the accident were to weigh each piece of cargo bound for a flight. The weight was documented on the associated waybill which was then affixed to the individual piece of cargo (refer to ATTACHMENT DHL-I which shows a representative waybill from AMF262). AMF262 would have been met by one large box truck and from two to four vans carrying cargo destined for dissemination at Seattle, or connecting to the DHL Boeing 727 departing Seattle shortly after AMF262's scheduled arrival time. It was not the responsibility of DHL employees to physically load the outbound flight. This task was accomplished by contract employees from Evergreen Eagle. No scale was available at the aircraft. Loading and distribution of cargo can only be accomplished through a knowledge of load limitations within the specific aircraft cargo compartments (refer to ATTACHMENTS LPS-I, APV-I and APV-II) along with an accurate tally of total cargo weights accrued in each compartment. The "PM Lead Courier" for DHL was interviewed and provided the following information: He oversaw the loading of AMF262 on the evening of August 13th, which spanned an approximate 20 minute time frame (1805 to 1825 local). Refer to photographs 1 through 3 which shows the majority of offloaded cargo onboard AMF262 subsequent to the accident. Photograph 4 shows the interior cargo compartment of the aircraft aft of the cockpit (ACM compartment aft to compartment "L"). He reported that the aircraft was "full with freight" (refer to ATTACHMENT IV-I). The driver of the DHL large box truck was interviewed and provided the following information: On August 13th he departed the DHL weighing facility with 2,457 pounds of freight and staged the truck after which the "Evergreen ground crew commenced to loading the aircraft." He also reported that "because of the limited time frame that we have I helped unload my truck-" and that "because we don't have a scale for accuracy I could only estimate what I felt was close to 900 lbs per zone." He reported that he received a total weight of 4,962 pounds to be enplaned (refer to ATTACHMENT LPS-I) by radio and ensured that the tail compartment ("L") was loaded with 250 pounds of freight and "added the remaining balance to zone "J-K" to be 700 lbs" (refer to ATTACHMENT IV-II). A courier for DHL was interviewed and provided the following information: On August 13th, having returned from his route, weighed his cargo, and loaded the cargo onto vans for the airport. He reported that "at 6:20 I called in the weight to airport operations and drove the last van to planeside. (The) van was unloaded and I placed the export paperwork bag into (the) front of the plane" (refer to ATTACHMENT IV-III). At the time of the accident United Parcel Service (UPS), a major air/surface freight company, was on strike. The strike had commenced at midnight on July 31st. Air freight normally carried by UPS was passing over to reliever carriers such as AmeriFlight and DHL. According to the BE-1900 Load Planning Sheet for flight AMF262 (ATTACHMENT LPS-I), the aircraft was dispatched from Portland with a total cargo load of 4,962 pounds and 1,700 pounds of fuel yielding (after taxi burn) an adjusted takeoff weight of 15,506 pounds (1,094 pounds below MGTOW). The Load Planning Sheet also showed, based upon the recorded distribution of weights, a total moment of 45,727/100 inch-pounds (center of gravity (CG) of 294.90 inches). A courier/ramp agent for DHL at Seattle reported in an interview that on the evening of August 13 she received a radio call from AMF262 indicating an estimated time of arrival of 1915. The pilot, according to the agent stated "he was "extremely heavy" and requested the tail stand be installed before he shut down the engines" and that "he also requested that loading personnel be advised to be careful when opening the cargo door because the compartment was full and freight could fall out" (refer to attached statement RI-I). Subsequent to the accident, the cargo was removed from the aircraft and stored at a secure location at SEATAC airport. The cargo was then examined, identified by personnel who were present during its offloading by ARFF responders following the accident, and weighed by a team of individuals under the guidance of FAA operations personnel (refer to attached statements WB-I, WB-II and WB-III). The examination and weighing of the cargo revealed that 59 pounds of cargo had been stowed in the nose compartment, a total of 984 pounds had been stowed in the ACM (Z net bay) area and compartment A/B, and 660 pounds had been stowed in compartment L (refer to ATTACHMENTS APV-I & II showing the locations of these compartments). The examination and weighing of the remainder of the cargo revealed that a total of approximately 3,915 pounds had been distributed between compartments C/D, E/F, G/H, and J/K although the precise distribution within and among these compartments was not known. The total cargo weight, which was adjusted conservatively for AFFF fluid containment, was measured as 5,618 pounds, or 656 pounds more than was reflected on the Load Planning Sheet (and less than the MGTOW allowable). Due to the inability to precisely establish cargo locations within compartments C/D, E/F, G/H, and J/K, a best-case, worst-case scenario was calculated with two intermediate cases. The results of these case evaluations were as follows: Total Moment CG Worst Case : 48,426.14/100 in-lb 311.2 inch Best Case : 47,733.85/100 in-lb 306.7 inch Intermediate Case(1): 47,976.57/100 in-lb 308.3 inch Intermedia
A stall/mush condition resulting from an aft center of gravity which was inaccurately provided to the pilot-in-command by contractual cargo-loading personnel. Additional causes were overloading of the aircraft's landing gear and fuel leakage resulting in a post-crash fire. Factors contributing to the accident were the pilot's improper lowering of flaps in an aft CG situation and the inadequate company procedures for cargo loading.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
