Repasando Aerodinámica de la Biblia Aeronáutica, Aerodinámica y actuaciones del avión de A. Isidoro Carmona en el capitulo referido a Limitaciones estructurales, diagrama de maniobras podemos comentar sobre este accidente:
11.14 DIAGRAMA BÁSICO DE RÁFAGAS
A mayor alargamiento del ala, envergadura/cuerda, mayor es el esfuerzo que se afectada una aeronave ante la misma ráfaga.
A mayor flecha del ala menor sera el factor de carga (n) que será afectada el ala.
11.17 CARGAS EN LAS ALAS. INFLUENCIA DE LA DISTRIBUCIÓN DE COMBUSTIBLE
En el encastre del ala se produce un esfuerzo que depende del peso del fuselaje, peso que tienen las alas y la sustentación que se está generando.
A menor peso en las alas mayor es el esfuerzo en el encastre y a su vez el consumo de combustible dentro del ala también hace que varíe dicho esfuerzo en cuanto a la distribución del mismo.
Por eso siempre se consumen primero el combustible de los tanques más cercanos a la raíz del ala y por último los de puntera. Esto es debido a que el Momento que produce este último es mayor que los más cercanos a la raíz del ala.
Recordemos que Momento es igual a la Fuerza (Peso del combustible en este caso) por la distancia al encastre.
Ese momento del combustible en las punteras ayuda a disminuir el esfuerzo en el encastre.
Por otra parte en el diseño de las aeronaves se calcula con el Maximum Zero Fuel Weight, o sea máximo peso del fuselaje sin combustible en las alas.
Así que en el caso de este C-130 seguramente debe haber sido una combinación de factores como son las fuertes ráfagas de viento que hay en un incendio forestal que quízas hiceron que el avión supere las limitaciones estructurales del diagrama de ráfaga de diseño.
A su vez el combustible, habría que ver como consumieron combustible. Si tuvieron algún problema en el trasbase de combustible durante el vuelo.
De todas formas por lo que se los Pilotos del Servicio Forestal de USA se encuentran entre los entrenados para estos menesteres, no cualquier "Rockee" se sienta a volar para dicho servicio.
Accident description
Last updated: 29 July 2016
Status: Final
Date: Monday 17 June 2002
Time: 14:45
Type:
Lockheed C-130A Hercules
Operator: Hawkins & Powers Aviation
Registration: N130HP
C/n / msn: 3146
First flight: 1957
Total airframe hrs: 21863
Engines: 4 Allison T56-A-9D
Crew: Fatalities: 3 / Occupants: 3
Passengers: Fatalities: 0 / Occupants: 0
Total: Fatalities: 3 / Occupants: 3
Airplane damage: Destroyed
Airplane fate: Written off (damaged beyond repair)
Location: Walker, CA (
Phase: Maneuvering (MNV)
Nature: Fire fighting
Departure airport: Minden-Tahoe Airport, NV (MEV/KMEV), United States of America
Destination airport: Minden-Tahoe Airport, NV (MEV/KMEV), United States of America
Narrative:
Hercules N130HP was hired to fight a 10,000-acre wildland blaze near Walker, CA. After dumping a red cloud of fire retardant, both wings separated in an upward motion. The right wing immediately separated from the fuselage at low altitude. The plane then lost control and rolled left. During this manoeuvre the left wing fell from the aircraft as well and the aircraft nose-dived into the ground. The whole event just took about 4 seconds and was captured on video a passer-by. In April 1998 two one-inch cracks were found on the bottom of a wing (the service difficulty report does not state which wing), at Outer Wing Station 33, which is 33 inch (83cm) from the wing joint. These cracks were repaired.
The investigations into the June 17, 2002 C-130A and July 18 PB-4Y crashes are closely looking at the fatigue cracks as well as other safety issues, such as inspection and maintenance procedures and operational factors. Preliminary results for both have indicated that widespread fatigue was not evident over the entire wing but that in some locations current crack detection techniques may have been unreliable.
PROBABLE CAUSE: "The inflight failure of the right wing due to fatigue cracking in the center wing lower skin and underlying structural members. A factor contributing to the accident was inadequate maintenance procedures to detect fatigue cracking."
Classification:
Wing failure
Loss of control
Following the June 17 C-130A and July 18 PB4Y-2 Privateer airtanker accidents the Blue Ribbon Panel on Aerial Firefighting was commissioned by the Forest Service and the Bureau of Land Management. The panel was chartered to identify key information for planning the safe and effective future of aerial firefighting.
The report was released December 6, 2002 and revealed eight findings. As a result the Forest Service and the Bureau of Land Management decided no longer to contract for the C-130A or PB4Y aircraft as airtankers and the Forest Service suspended fire missions of 19 P-58 Barons and 4 Shorts 330 aircraft pending evaluations of the issues identified in the Blue Ribbon panel’s report.
On September 26, 2002 the Federal Aviation Administration ordered wing inspections on all C-130A air tankers after NTSB investigators determined that cracks in the wings caused the C-130A crash. (AD-2002-19-14)
The NTSB's investigation of three air tanker accidents determined that the maintenance and inspection programs applicable to firefighting aircraft did not adequately account for the increased safety risks that the aircraft are exposed to as a result of the advanced age and the severe stresses of the firefighting environment. As a result the NTSB recommended that the Department of Agriculture and the Department of Interior develop maintenance and inspection programs for firefighting aircraft that include consideration of the airplane's original design, age, and operational stresses, as well as engineering evaluations to predict and prevent fatigue cracking. The Board also recommended that the Department of
Agriculture and Department of Interior hire personnel with aviation engineering and maintenance expertise to oversee the new maintenance programs. The NTSB recommended that the FAA require that these aircraft be maintained in accordance with such programs and that the FAA assume responsibility for collecting continuing airworthiness information about surplus military aircraft.
In a separate letter sent to the Department of Agriculture and the Department of Interior the Safety Board emphasized their position regarding the installation of video recorders on public use aircraft and.