National Air Cargo B744 at Bagram on Apr 29th 2013, lost height shortly after takeoff following load shift and stall
Last Update: September 14, 2015 / 14:43:19 GMT/Zulu time
The National Transportation Safety Board determines that the probable cause of this accident was National Airlines’ inadequate procedures for restraining special cargo loads, which resulted in the loadmaster’s improper restraint of the cargo, which moved aft and damaged hydraulic systems Nos. 1 and 2 and horizontal stabilizer drive mechanism components, rendering the airplane uncontrollable.
Contributing to the accident was the Federal Aviation Administration’s inadequate oversight of National Airlines’ handling of special cargo loads.
The NTSB analysed:
The cargo that was loaded on board the accident airplane represented the first time that National Airlines had attempted to transport five MRAP vehicles. These vehicles, which were secured to pallets, were considered a special cargo load because they could not be restrained in the airplane using the locking capabilities of the airplane’s main deck cargo handling system. The airline’s safety department was not involved in the decision to begin carrying heavy vehicle special cargo loads. When interviewed by investigators, the National Airlines chief loadmaster described the operator’s role as “you call, we haul” and stated that approval of the cargo was up to NAC, the cargo handling vendor that gave National Airlines the freight.
Although the airplane could accommodate the weight of the proposed cargo within its weight and balance envelope, the MRAP vehicles were considered TRC and, therefore, were subject to specific restraint requirements designed to protect the upper deck passenger compartment in the event of an emergency landing. However, when personnel from the NAC load planning department contacted the chief loadmaster to inquire whether precautions should be taken before confirming the cargo load of two M-ATVs and three Cougars, the chief loadmaster’s response noted only weight and balance considerations. The National Airlines cargo operations manual, which was developed by the chief loadmaster, did not contain all of the required information from the Boeing and Telair weight and balance manuals and loading control documents. The NTSB concludes that, had the National Airlines chief loadmaster consulted the required manufacturers’ weight and balance manuals, he could have determined that the intended load of five vehicles could not be properly secured in the airplane in accordance with the TRC safety requirements; at most, only one M-ATV could be transported.
However, the cargo was accepted, and the loadmaster ensured that it was loaded within the weight and balance envelope for the airplane. Under the supervision of the loadmaster, NAC personnel secured and shored the vehicles onto centerline-loaded floating pallets and restrained the cargo in the airplane with tie-down straps. The airplane successfully completed one flight with the cargo from Camp Bastion to Bagram (the flight that preceded the accident flight); however, discussions between flight crewmembers and the loadmaster that the CVR captured indicated that at least some of the cargo had moved, one strap had broken, and other straps had become loose during that flight. The FDR data for that flight indicated that no unusually excessive G loads were encountered.
Before the airplane departed on the accident flight, the flight crew discussed that the loadmaster was taking action to re-secure the cargo. The first officer mentioned that the loadmaster was “cinching them all down,” and the captain said that he hoped that the loadmaster was adding more straps. Although some of the discussion was conducted in a joking manner, the comments indicated that the flight crewmembers were concerned that the cargo had moved and that they relied on the loadmaster to know how to correct the problem and ensure the safe restraint of the cargo. The NTSB concludes that, although the flight crewmembers and the loadmaster were aware that the cargo moved during the previous flight, they did not recognize that this indicated a serious problem with the cargo restraint methods.
The NTSB analysed that following liftoff only 3 seconds were recorded by the flight data recorder, although the accident flight lasted 30 seconds from liftoff to impact, at the time the FDR stopped recording the aircraft had reached 33 feet AGL and was already climbing more steeply than in all previous takeoffs available on the FDR. Video footage then showed the aircraft climbing more steeply at a high pitch attitude until reaching the highest point, rolling right and descending rapidly striking the ground in a nose down attitude with wings nearly level. The NTSB stated: "The airplane’s steep pitch attitude and subsequent departure from controlled flight were consistent with an aerodynamic stall."
The NTSB analysed: "Debris found on the runway starting near the airplane’s point of rotation included fragments of airplane skin, tubing from hydraulic system No. 2, fragments of the E8 rack, and part of a M-ATV antenna; all of the airplane debris came from structures that had been located aft of the loaded location of the rear M-ATV, and the installed location of the M-ATV’s antenna was its rear, upper left corner. This runway debris evidence strongly suggests that, about the time of the airplane’s rotation, the rear M-ATV moved aft, struck the E8 rack (which provides a shelf for the CVR and FDR), penetrated the APB, and damaged hydraulic system No. 2, the tubing for which passes through the APB on the airplane’s lower left side. Given that fragments of hydraulic system No. 2 were found on the runway (and the other evidence of hydraulic system damage described below), it is likely that the puffs of white “smoke” that one witness reported seeing was misting hydraulic fluid. ... Based on the wreckage evidence and evidence from the image study, scenarios that were considered the most plausible included aft movement of at least the rear M-ATV, failures of at least hydraulic systems Nos. 1 and 2, and the effects of a damaged horizontal stabilizer’s jackscrew actuator and surrounding structure (due to collision from the M-ATV).36 In one study scenario, when an aft movement of the rear M-ATV and the failure of hydraulic systems Nos. 1 and 2 (or Nos. 1, 2, and 3) were assumed, a shift of the horizontal stabilizer from the set takeoff position to a 5° leading-edge-down position resulted in an inability of the available flight control surfaces to counter the resulting nose-up pitching moment. Study calculations determined that, for a 5° deflection of the horizontal stabilizer’s leading edge, the corresponding displacement at the stabilizer’s root corresponded approximately with the displacement of the fractured stabilizer jackscrew and surrounding structure as found on the accident airplane. Therefore, the NTSB concludes that the airplane’s loss of pitch control was the result of the improper restraint of the rear M-ATV, which allowed it to move aft through the APB and damage hydraulic systems Nos. 1 and 2 and horizontal stabilizer drive mechanism components to the extent that it was not possible for the flight crew to regain pitch control of the airplane."
The NTSB analysed that there was no evidence of explosives being used against the aircraft.
The NTSB analysed with regards to cargo loading procedures: "Before takeoff from Camp Bastion (the flight that preceded the accident flight), the National Airlines loadmaster directed NAC personnel to use 24 straps to secure each of the two M-ATVs and 26 straps to secure each of the three Cougars. This configuration was not in compliance with National Airlines’ procedures (which would have indicated the use of 32 straps for each M-ATV and 46 for each Cougar); however, National Airlines’ procedures did not incorporate the required safety-critical cargo-securing information from the airplane and the cargo handling system manufacturers’ manuals."
With respect to oversight by the FAA the NTSB analysed: "As previously mentioned, National Airlines’ cargo operations manual not only omitted critical information from the Boeing and Telair manuals about properly restraining special cargo loads but also contained information that conflicted with the manufacturers’ FAA-approved information. Although the POI learned in early 2013 that National Airlines was carrying heavy loads on pallets, no FAA risk analysis was performed. The POI stated that “the manual seemed sufficient,” and “if they were following their manual, there should not be an issue.” However, as previously mentioned, the cargo operations manual was deficient. FAA Order 8900.1, volume 3, section 2, “Approval and Acceptance of Manuals and Checklists,” contains direction and guidance for POIs when approving or accepting an operator’s manuals and checklists and describes the POI’s role in the review process and for resolving any discrepancies in both approved and accepted manuals. The NTSB concludes that the FAA did not provide adequate oversight to ensure that the National Airlines cargo operations manual reflected the correct information and guidance from the airplane and cargo handling system manufacturers that specified how to safely secure the cargo."
This article is published under license from Avherald.com. © of text by Avherald.com.
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