AeOPS AGG

Airborne Geophysical Sensors

Here is the comprehensive, highly detailed technical breakdown of our STC (Supplemental Type Certificate) approvals for specific sensor configurations, written entirely in English from the perspective of our specialized airborne geophysical services company.

Como empresa de servicios aéreos de prospección geofísica bajo la normativa FAA, la instalación de sensores magnéticos y gravimétricos modifica el diseño original de la aeronave. Legalmente, estas modificaciones se clasifican como Alteraciones Mayores (Major Alterations).

Technical Dossier: Supplemental Type Certificate (STC) Approvals for Airborne Geophysical Sensors

Operating under FAA Part 91, any physical modification to our aircraft for mounting geophysical sensors is legally classified as a Major Alteration. To comply with airworthiness directives, each configuration requires Approved Data, which we satisfy via an STC and document on FAA Form 337 (Major Repair and Alteration).

Below are the engineering, structural, and aerodynamic certification details for our four primary sensor installations:

Para operar en cumplimiento absoluto con la FAA Parte 91, cada configuración requiere un paquete de Datos Aprobados (Approved Data), sustentado por un Certificado Tipo Suplementario (STC) y registrado formalmente mediante el Formulario FAA 337 (Major Repair and Alteration).

1. Tail/Nose Boom Configuration ("Stinger") for Magnetometers

This installation is designed to isolate highly sensitive optical pumping magnetometers from the aircraft’s residual magnetic field and engine-induced electrical noise.

Target Aircraft Platforms: Cessna 206, Cessna 208 Caravan, Piper PA-31 Navajo, and Airbus AS350 (AStar) helicopters.
Structural STC Requirements: The STC governs the modification of the aft fuselage or tail-cone. It mandates the installation of internal aluminum reinforcements (doublers) and bulkheads to distribute the static and dynamic loads of the extended fiberglass/carbon-fiber boom.
Aeroelastic and Control Stability (Flutter): Engineering data under the STC must prove that the weight and length of the stinger do not induce destructive aeroelastic vibrations (flutter) at any point within the aircraft's operational envelope. It must also verify that the aircraft remains well within its approved Center of Gravity (CG) envelope across all fuel burn weights.
Aircraft Flight Manual Supplement (AFMS): A mandatory AFMS is issued under the STC, defining new maximum structural speeds VNE or VNO and specific turbulence penetration limitations that the flight crew must strictly adhere to.

2. Wingtip Pod Configuration for Horizontal Magnetic Gradients

This configuration mounts dual magnetometers on the extreme ends of the wings to capture direct, real-time horizontal magnetic gradients.

Target Aircraft Platforms: Beechcraft King Air (90/100/200 series) and Piper PA-31 Cheyenne.
Aerodynamic STC Requirements: Mounting pods on the wingtips alters the airflow, directly affecting wing lift distribution and stall characteristics. The STC data includes wind-tunnel or computational fluid dynamics (CFD) modeling to guarantee that roll-control authority (aileron effectiveness) is maintained at low operational speeds and high angles of attack.
Electrical Load Analysis (ELA): Under FAA Part 21, the STC requires a comprehensive ELA. This ensures that powering the wingtip sensors, heating elements, and telemetry cables does not overload the aircraft's primary alternators. Furthermore, the routing of the cable shielding must be certified to prevent interference with avionics and to survive lightning strikes.

3. Internal Fuselage Integration for Gravimeters and Full Tensor Gradiometers (FTG)

Because relative gravimeters and FTG sensors are heavy and highly sensitive to external wind resistance, they must be mounted flat inside the aircraft cabin, looking through an engineered opening in the lower fuselage.

Target Aircraft Platforms: Cessna 208 Caravan, de Havilland DHC-6 Twin Otter, and King Air 200.
Fuselage Cut STC (Belly Hole / Camera Port): Cutting through the aircraft skin and floor beams requires a complex structural STC. For unpressurized aircraft, structural reinforcement frames must be riveted to restore the fuselage's original torsional rigidity. For pressurized aircraft, the STC must include a certified, pressure-sealed optical/sensor window system. All engineering drawings must be approved by an FAA Designated Engineering Representative (DER) via Form 8110-3.
Crashworthiness and Cabin Safety: To protect the flight crew, the gravimeter’s mounting cradle and vibration-isolation racks must be certified to withstand emergency landing impact loads (the FAA 9G forward inertia requirement). This prevents the heavy instrumentation from breaking free and becoming a cabin projectile.

4. Suspension Long-Line Systems ("Towed Bird") for Helicopter Geophysics

This setup suspends the magnetic, electromagnetic, or gamma-ray sensors on a 30 to 90-meter cable beneath a helicopter, removing the sensor entirely from the aircraft’s physical and electrical footprint.

Target Aircraft Platforms: Bell 206 JetRanger/LongRanger, Airbus AS350 B3, and Robinson R66.
External Cargo STC (FAA Part 133): The installation of the belly cargo hook, primary load-bearing structural beams, and electrical hookup requires an external load STC.
Emergency Release Systems: The STC legally mandates a dual-redundant emergency release mechanism. The pilot must have a mechanical release (cable cutter) and an electrical release switch integrated directly into the cyclic control stick. This allows immediate jettisoning of the towed sensor package in the event of an engine failure, severe low-level updrafts, or an unexpected ground snag.

1. Sistema de Magnetómetro en "Boom" o Aguijón (Stinger)

Esta configuración se utiliza para alejar el sensor del ruido magnético de los motores. Al alterar la aerodinámica externa y la estructura posterior o frontal, el proceso de certificación exige:

Aeronaves Comunes: Aviones de ala fija monomotores o bimotores ligeros como el Cessna 206, Cessna 208 Caravan, Piper Navajo, o helicópteros como el Eurocopter/Airbus AS350 (AStar).
Enfoque del STC Estructural: El STC debe aprobar la modificación del cono de cola (tail-cone) o fuselaje inferior para integrar la sección de transición del aguijón. Requiere análisis de fatiga del aluminio y refuerzos estructurales (doublers).
Aeroelasticidad y Control (Flutter): El STC exige ensayos en vuelo para demostrar que el peso extendido del "boom" no induce vibraciones aeroelásticas (flutter) destructivas ni altera los límites del centro de gravedad (CG) de la aeronave.
Suplemento del Manual de Vuelo (AFMS): El STC viene acompañado de un AFMS mandatorio que el piloto debe llevar a bordo, el cual define las nuevas velocidades estructurales máximas VNE o VNO con el aguijón instalado.

2. Cápsulas Alares ("Wingtip Pods") para Gradientes Magnéticos

Se instalan en los extremos de las alas para alojar múltiples magnetómetros en paralelo y medir gradientes horizontales directos.

Aeronaves Comunes: Aviones bimotores robustos como el Piper PA-31 Cheyenne o Beechcraft King Air (series 90, 100, 200).
Enfoque del STC Aerodinámico: Las cápsulas alteran el flujo de aire en las puntas de ala, afectando directamente la sustentación y las características de pérdida (stall). El STC evalúa el arrastre parásito (parasitic drag) y exige la instalación de kits de rendimiento si es necesario.
Certificación de Carga Eléctrica: El STC debe incluir un análisis de carga eléctrica (EAL - Electrical Load Analysis) bajo la Parte 21. Debe demostrar que la alimentación de los sensores en las alas no satura los alternadores originales y que el cableado posee protección contra descargas atmosféricas (rayos).

3. Gravímetros Relativos y Gradiómetros de Tensor Completo (FTG)

A diferencia de los magnetómetros, los pesados sensores de gravedad se instalan dentro del fuselaje (en la cabina de pasajeros o bahía de carga), apuntando hacia el suelo a través de un corte en la estructura inferior.

Aeronaves Comunes: Plataformas estables de gran tamaño como el Cessna 208 Caravan, de Havilland Twin Otter o King Air 200.
Enfoque del STC de Modificación de Fuselaje: Requiere un STC complejo de "Corte de Fuselaje" (Belly Hole / Camera Port STC). Cortar las cuadernas o la piel presurizada/no presurizada del avión exige marcos de refuerzo calculados por un Ingeniero de Estructuras Derivado de la FAA (DER - Designated Engineering Representative) mediante un Formulario 8110-3.
Rigidez y Atenuación de Vibraciones: Para los gravímetros, el STC aprueba el diseño de la montura amortiguada contra vibraciones (shock mounts). El instrumento debe soportar las cargas de impacto de emergencia de la FAA (típicamente hasta 9G en sentido de avance) para evitar que se suelte y lesione a la tripulación.

4. Sistemas de Línea Larga Suspendida ("Towed Bird") para Geofísica con Helicópteros

Esta configuración suspende los sensores magnéticos, electromagnéticos o de rayos gamma en un cable de 30 a 90 metros por debajo del helicóptero, alejando por completo al sensor de la huella física y eléctrica de la aeronave.

Plataformas de Aeronaves Objetivo: Bell 206 JetRanger/LongRanger, Airbus AS350 B3 y Robinson R66.
STC de Carga Externa (FAA Parte 133): La instalación del gancho de carga ventral, las vigas estructurales principales para el soporte de carga y la conexión eléctrica requieren un STC de carga externa.
Sistemas de Liberación de Emergencia: El STC exige legalmente un mecanismo de liberación de emergencia de doble redundancia. El piloto debe disponer de una liberación mecánica (corta-cables) y de un interruptor de liberación eléctrica integrado directamente en la palanca del paso cíclico. Esto permite el desenganche inmediato del paquete de sensores remolcado en caso de un fallo de motor, corrientes ascendentes severas a baja altura o un enganche inesperado con el terreno.

Regulatory Execution and Return to Service

Every single sensor modification performed on our fleet is executed by an FAA Part 145 Certified Repair Station or an A&P mechanic holding an Inspection Authorization (IA). By matching the physical installation with these specific, pre-approved STC data packages, we execute a seamless return to service, ensuring our mining operations are 100% compliant from day one of the contract.

Ejecución Regulatoria y Retorno al Servicio

Cada una de las modificaciones de sensores realizadas en nuestra flota es ejecutada por un Taller de Reparación Certificado por la FAA (Parte 145) o por un mecánico de células y motores (A&P) que posea una Autorización de Inspección (IA). Al asociar la instalación física con estos paquetes de datos STC específicos y aprobados previamente, ejecutamos un retorno al servicio impecable, garantizando que nuestras operaciones mineras cumplan al 100% con la normativa desde el primer día del contrato.

Summary of the Legalization Process (FAA Form 337)

For each specific installation performed on our fleet:

Purchase/Development of the STC: We acquire the usage rights of an existing STC (for example, from specialized developers such as Lake Central Air Services or New-Sense Geophysics) or develop our own in conjunction with an FAA DER (Designated Engineering Representative).
Execution of the Alteration: An FAA-Certified Repair Station (Part 145) or an A&P mechanic with an Inspection Authorization (IA) performs the physical modification in the hangars.
Sign-off of Form 337: The maintenance inspector documents the work on FAA Form 337, citing the specific STC number as the "Approved Data" used for the alteration.
Return to Service: One copy is filed in the aircraft's logbook, another is delivered to the owner, and the third is sent to the FAA Aircraft Registration Branch in Oklahoma City, making the aircraft 100% legal to fly mining contracts.

Resumen del Proceso de Legalización (FAA Form 337)

Para cada instalación específica que realizamos en nuestra flota:

Compra/Desarrollo del STC: Adquirimos los derechos de uso del STC existente (por ejemplo, de desarrolladores especializados como Lake Central Air Services o New-Sense Geophysics) o desarrollamos uno propio junto a un DER de la FAA.
Ejecución de la Alteración: Un Taller de Reparación Certificado por la FAA (Part 145 Repair Station) o un mecánico con Autorización de Inspección (IA) realiza la modificación física en los hangares.
Firma del Formulario 337: El inspector de mantenimiento documenta el trabajo en el Formulario FAA 337, citando el número de STC específico como los "Datos Aprobados" utilizados.
Retorno al Servicio: Una copia se archiva en la bitácora de la aeronave, otra se entrega al propietario y la tercera se envía a la División de Registro de Aeronaves de la FAA en Oklahoma City, haciendo que la aeronave sea 100% legal para volar contratos mineros.

To capture high-resolution magnetic and gravimetric data, aircraft must fly extremely low to the ground—often between 100 and 300 feet (30 to 90 meters) Above Ground Level (AGL). Under United States regulations, this requires a specialized regulatory instrument known as an FAA Low-Altitude Flight Waiver (Certificate of Waiver or Authorization - COA).

As an airborne geophysical services company, operating without this approved waiver is a direct violation of federal law. Below is the detailed operational and legal breakdown of our low-altitude waiver capabilities under 14 CFR Part 91:

1. The Regulatory Hurdle: 14 CFR § 91.119

The FAA strictly regulates minimum safe altitudes. Under 14 CFR § 91.119(c), aircraft operating over "other than congested areas" must not fly closer than 500 feet to any person, vessel, vehicle, or structure.

The Conflict: High-resolution mining exploration requires draping the terrain at 150–200 feet AGL to detect subtle magnetic or density anomalies.
The Solution: We secure an official Certificate of Waiver (FAA Form 7711-2) that specifically exempts our fleet from the 500-foot restriction of § 91.119(b) and (c), allowing legal, low-level data acquisition.

2. Anatomy of Our FAA Low-Altitude Waiver Package

Securing and executing a low-altitude waiver is not just a piece of paper; it involves a highly detailed operational safety package submitted to the local Flight Standards District Office (FSDO):

Congested vs. Sparsely Populated Areas: While most mining prospects are in remote areas, our waivers include strict provisions for transition corridors. If the flight path approaches rural dwellings, wind turbines, or local infrastructure, the waiver mandates specific lateral clearing distances.
The Congested Area Plan (CAP): If a survey line must cross a congested area (such as a mining town or an active open-pit operations hub), 14 CFR § 91.119(a) applies. We develop and submit a formal CAP under FAA Order 8900.1. This plan defines emergency block altitudes, dedicated engine-out glide paths, and coordinate-specific avoidance zones to ensure zero risk to ground populations.
Pre-Flight Ground Coordination: The waiver dictates that our operations team must notify local law enforcement, air traffic control (ATC), and power line/utility companies within the survey block at least 48 hours prior to the flight to prevent panic calls regarding a "low-flying aircraft."

3. Pilot Qualifications and Training Mandated by the Waiver

The FAA does not grant low-altitude privileges to standard commercial pilots. Our crew training program is baked directly into the waiver's special provisions:

Low-Level Flight Training Syllabus: Pilots must log specific initial and recurrent training in terrain-following tactics, mountain flying, and micro-meteorology (handling low-level wind shear and mechanical turbulence caused by topography).
Energy Management: Flying low with heavy gravimeters or external magnetic stingers reduces maneuver margins. Pilots are trained in precise energy management to maintain a safe margin above stall speed ($V_{S}$) while contouring ridges.
Crew Resource Management (CRM): Operations utilize a two-pilot cockpit or a pilot-and-operator system, where one individual focuses 100% on "eyes outside" terrain clearance while the other monitors sensor health and cross-track GPS deviations.

4. Special Provisions for Towed Systems (Helicopter "Bird" Operations)

If the project requires a helicopter towing a magnetic/electromagnetic "bird" on a long-line, the waiver integration becomes more complex:

14 CFR Part 133 Congruence: The low-altitude waiver must be married to our Class B/C external load authorizations.
Altimeter Cross-Checking: The waiver requires the helicopter to be equipped with a dual-pointer radar/laser altimeter. One sensor measures the helicopter's altitude, while a secondary telemetry link calculates the real-time height of the suspended "bird" above the canopy or terrain to prevent ground strikes.

Operational Integration Summary

By maintaining a current, nationwide, or region-specific FAA Low-Altitude Flight Waiver, our company eliminates the regulatory lead time for your mining project. We handle the FSDO interfaces, local airspace notifications, and risk mitigation profiles internally, ensuring your data is captured at the optimal scientific altitude without legal risk.

To finalize our operational readiness and complete the full technical dossier for your airborne survey, we must detail the two critical components that guarantee the safety, profitability, and legal compliance of low-altitude operations: Terrain-Following Performance (Climb/Descent Gradients) and Commercial Aviation Insurance Liability Requirements under FAA Part 91.

1. Aircraft Climb and Descent Gradients (Terrain-Following Capability)

High-resolution geophysics requires a "draped" flight profile—meaning the aircraft must maintain a constant height above the ground (e.g., 150 feet AGL), regardless of the topography. This is highly demanding on aircraft performance, especially with heavy gravimetric equipment.

The Problem of "Drape Deviation": If an aircraft cannot climb as fast as the terrain rises, it must deviate upward, increasing its AGL. This degrades the quality of the magnetic and gravimetric data, as geophysical signal strength decays exponentially with distance from the source.
Performance Metrics for Our Fleet:
- 1. Fixed-Wing (e.g., Cessna 208 Caravan / de Havilland Twin Otter): Modified with STC engine upgrades (such as Blackhawk PT6A conversions) to provide an immediate surplus of shaft horsepower. We calculate our flight lines based on a minimum sustainable climb gradient of 250 to 300 feet per nautical mile (NM) under high density-altitude conditions (high temperature + high altitude mining sites).
  2. Rotary-Wing (e.g., Airbus AS350 B3 / Eurocopter): Used for extremely rugged or mountainous terrain. They provide near-perfect drape capabilities due to their ability to slow down to maintain a constant AGL on steep vertical cliffs, though at the expense of a narrower daily coverage area.
The "Safety Box" Maneuver: If terrain contours exceed the aircraft's aerodynamic climb performance, our flight planning software automatically flags the area. The pilots are instructed to execute a pre-planned lateral exit or "turn-away" maneuver before entering a box canyon or valley where the climb gradient cannot match the topography.

2. Insurance and Liability Requirements for Low-Altitude Aerial Work

Operating a modified commercial aircraft at 150 feet AGL introduces a risk profile that standard aviation insurance policies strictly exclude. To protect both our flight operations and your mining assets, our insurance structure adheres to strict international mining standards and FAA risk profiles:

The Low-Altitude Waiver Endorsement: Standard aviation insurance contains a "hull and liability exclusion" for flights conducted below 500 feet AGL. Our corporate policy features a specific Low-Altitude Waiver Endorsement, meaning the underwriter explicitly approves and covers operations conducted down to 100 feet AGL, provided we maintain our valid FAA Form 7711-2 Waiver.
Chemical/Environmental Liability (For External Loads): For helicopter operations towing a "bird," the policy includes specific coverage for Inadvertent Sling Load Release. If the pilot must trigger the emergency hook release to drop the sensor due to an engine failure, the insurance covers both the hull loss of the expensive sensor and any third-party property damage on the ground.
Minimum Industry Liability Limits: For international mining clients, we maintain a comprehensive Aviation Hull & Combined Single Limit (CSL) Public Liability Insurance policy. While standard Part 91 general aviation requires minimal coverage, our specialized Aerial Work policy features a minimum of $20,000,000 to $50,000,000 USD CSL to meet the strict risk compliance standards of tier-one mining companies.

Comprehensive Summary of Your Airborne Survey Setup

With this final piece, your operational blueprint is complete:

Legal Framework: Operated legally under FAA Part 91 via the Aerial Survey exception of Part 119.1(e)(4)(iii).
Airworthiness: All sensors (Stingers, Pods, or Fuselaje Cuts) are fully documented using FAA Form 337 and backed by STCs / DER approvals.
Low-Altitude Execution: Protected by an FAA Certificate of Waiver (§ 91.119), complete with local FSDO coordination.
Risk Mitigation: Supported by high-performance aircraft capable of strict terrain draping and backed by specialized low-altitude aviation insurance.