H6E, EFI & Hydrone – Inspections

Fastener Inspection

There are over 900 individual pieces of hardware that fall under the fastener and hardware category in one Harris Aerial UAS. Keeping track of each of these before every flight not only ensures the most efficient performance of your aircraft, it also helps to certify the safety of your crew and civilians that may be in the immediate area.

The "Fastener and Torque Specifications" tables, Appendix A, should be used in conjunction with the procedures below to identify the location of each component and its associated hardware. Be sure to give extra attention to whether or not the fastener requires loctite and a specific torque specification when fixing or replacing hardware.

Lower Frame Inspection

The lower frame consists of two major assemblies: landing gear and payload support. Regular inspection of these areas prevents aircraft landing failure and potential damage to payloads like cameras and sensors.

• Landing Gear: Inspect SLS toes, carbon fiber leg tubes, and aluminum receivers for signs of fracturing. Ensure no parts exhibit free movement where fasteners are installed. Fully electric owners must test the lock-out capabilities of folding landing gear and its roll pin.
• Payload Support: Inspect aluminum clamps, carbon fiber payload rails, and the dampening plate. Replace any components showing fracturing or warping. Verify that polyurethane dampers are fully seated and free of dry-rot or tearing.

Upper Frame Inspection

This assembly includes the central airframe and the hinge and boom assembly, providing the rigid structure for propulsion.

• Hinge and Boom: Inspect for fracturing and ensure the boom arm is flush with the hinge base. The locking action is critical; a hinge must not budge unless the release pin is depressed. If movement in the z-plane exceeds ±2mm when locked, a new roll pin may be required.
• Central Airframe: Inspect the plunger assembly, which secures battery packs and fuel tanks. Ensure its movement is smooth. GPS stands must lock in place when upright to prevent failsafes during flight.

Propulsion Systems

Propulsion includes motors and propellers, which are responsible for lift and movement.

• Motor Inspection: Check motor bell-housing and coils. If rocking the motor reveals more than 0.5mm of play in the z-plane, it must be replaced. Inspect coils for oxidation or char patterns. Motors have a required replacement interval of 450 hours.
• Propeller Inspection: Visually check blades, tips, and the central hub for stress fractures or chipping. Ensure nuts under the hub are secure but do not attempt to adjust these bolts. Periodically verify the alignment of blade tips between propellers.

Energy Systems

The energy systems comprise battery storage, fuel, air, and spark systems that convert potential energy into kinetic energy. It is recommended to inspect battery integrity, cell health, fuel lines, tanks, and generator or fuel cell integrity. If any component fails, ordering a replacement is advised.

Battery Inspection

Trained personnel should inspect Tattu 125 batteries (Fully Electric users) or 6S Max Amp batteries (EFI and Hydrone users):

• Cell Health: Use a "Capacity Controller" or charging station to check cell health. No cell should be ±200mV (0.2V) from another.
• Pre-Flight Status: Batteries must have at least 80% charge before flight. Never fly with a battery exhibiting cell health depletion.
• Safety Warning: If a battery casing is damaged, swelling, or hot to the touch, cease use immediately and dispose of it according to local ordinances.

Pre-Flight Battery Checklist

Item	Note
Cell Health	Check for differences of ±0.2V between cell values; if present, the battery may be unhealthy.
Voltage Imbalances	Ensure no ±0.2V difference between batteries; do not operate if imbalanced.
Min. Voltage Rec.	EFI/Hydrone: Min 47.5V combined (23.75V each). Fully Electric: Failsafe occurs at 43.75V combined.
Max. Voltage	EFI/Hydrone: Avoid activating generator/fuel cell if combined voltage is above 49.5V.
Damaged/Swollen	Cease use and dispose of properly.

The lifetime of a battery is dependent on a number of factors which include but are not limited to: how often the battery is charged, how it is used, and how it is stored. Over time the performance, or rather the capacity, of a lithium-polymer battery will begin to deplete and it will fail to hold a charge or charge.

***To reduce the risk of failure during flights, the recommended replacement cycle for batteries used in HA-UAS is after every one-hundred and fifty hours of use or when a considerable drop in performance is observed.

Max Amp 4750mAh Battery Removal

To remove a Max Amp 4750mAh battery, known also as generator backup batteries, simply loosen the two velcro straps that hold each battery onto the lower frame plates located beneath frame arm 1 and 2.

Figure 14. 6S Battery for EFI Users

Tattu 16,000mAh 12S1P Battery Pack Removal and Disassembly

To remove Tattu 16,000mAh 12S1P battery pack, release each plunger on the top frame plate and lift the battery pack from the frame. A total of eight screws secure dovetails to the sides of the batteries, each requiring a 2.5mm hex driver to remove. Take note of each screw length and any spacers used as they will need to be replaced in the exact order for each replacement battery. Balance ports should face outward, if any one balance port faces the other battery the direction is incorrect and will need to be corrected.

Figure 15. 12S Battery Pack for Fully Electric Users

Fuel Tank and Fuel Line Inspection

In addition to the procedures listed in Section 1.1, trained personnel should inspect the fuel tank and all fuel lines. When inspecting the fuel tank verify that the fuel cap and vent plug are functional and look for signs of deformation, fuel permeation, or leaking each of which could indicate a faulty fuel tank and require a replacement. When inspecting the fuel lines start from inside the fuel tank working in the direction of the generator. Check the integrity of each fuel line, this could include but is not limited to:

• Connections: Strong connections at each brass L-pipe and at the generator.
• Condition: No line has any damage (kinking, pulling, or gouges) resulting in a loss of fuel flow.

Figure 4. Loweheiser EFI Generator Fuel Systems

Hydrogen Tank and Gas Line Inspection

In addition to the procedures listed in Section 1.1, trained personnel should inspect the fuel tank and all fuel lines. When inspecting the hydrogen tank and gas line make sure there are no leaks at the regulator or along the gas tubing, a hissing sound may be present if the tank is full and a leak has occurred. If a leak at the regulator or gas lines is suspected, a replacement will be required.

Figure 5. Intelligent Energy Fuel Systems
 

Generator Inspection

In addition to the procedures listed in Section 1.1, trained personnel should inspect the I/O wiring, telemetry cable, air filter, pulley, spark plug boot, and braided dampeners.

I/O Wiring

I/O wiring (input/output) installation should be verified before every flight if the generator or its wiring has been removed. Each I/O cable is labeled with a descriptive sleeve (e.g., "Battery 12S" or "Output PDB").

• Battery 12S: When looking from the rear, the XT90 Male connector should be inserted into the center right XT90 connector on the bottom frame plate. The opposite end (XT90 Female) should connect to the sunken connector on the generator.
• Output PDB: The XT90 Female connector should be inserted into the center left XT90 Male on the bottom frame plate. The opposite end (XT90 Male) should connect to the protruding connector on the generator.

Telemetry Cable

The telemetry cable has a five-pin connector on one end and a three-pin connector on the other. Ensure both are securely fastened to their respective ports:

• Five-pin: Governor board.
• Three-pin: Telemetry port at the rear of the Flight Control Box.

Component Inspection

• Air Filter: Verify it is free of excess debris or residue from fuel or oil. Ensure it is securely placed on the intake with the air temperature sensor snug between both.
• Crank Pulley: Verify ease of motion and ensure there is no seizure of the pulley system.
• Spark Plug Boot: Verify it is fully seated.
• Braided Dampers: Visually inspect each damper. When the generator is installed correctly onto the payload rails, dampers should be centered and not pulling in any direction, as pulling can damage them.

Over time, the integrity of the generator's cylinder, piston, and seals will degrade and when this occurs a lack of compression may occur. As a result, the Löweheiser EFI generator has a recommended replacement lifetime of three-hundred hours. This is to ensure that both the generator and aircraft function and operate at their optimal performance. Similarly, Intelligent Energy fuel cells are subject to a degradation in performance over many hours, and thus, replacement is required after three-hundred hours.

Generator Removal and Installation

To remove a Löweheiser EFI generator, first remove the large clear and large yellow fuel lines from the fuel inlet and fuel return, unplug the telemetry cable which is inserted into the flight control box, and remove the four M3x8 socket screws located on each rail clamp. Be sure to support the generator while removing these screws, otherwise the generator may fall during removal. Use the same process detailed here, but in reverse order for replacement generators. Refer to Appendix A for torque specifications.

Fuel Cell Removal and Installation

To remove an Intelligent Energy fuel cell, first make sure to remove any gas lines that may still be connected to a hydrogen tank, unplug the telemetry cable which is inserted into the flight control box, and remove the four M3x8 socket screws located on each rail clamp. Be sure to support the generator while removing these screws, otherwise the generator may fall during removal. Use the same process detailed here, but in reverse order for replacement generators. Refer to Appendix A for torque specifications.

Electrical & Communications Inspections

Connector and Antenna Inspection Guide

The electrical and communications systems include, but are not limited to, auxiliary and input power connections and telemetry connections. It is also necessary to verify that communication between the radio and flight controller is functioning correctly.

Connector Inspection

In addition to standard procedures, trained personnel using a multimeter should inspect the polarity and voltage output of various connections, especially after self-maintenance requiring their removal. All electrical testing should be performed by a technician familiar with multimeter equipment.

Connector	Location	Instructions
AS150U	Top Frame: Right Front, Left Rear	Continuity: Use a multimeter to check continuity between the black-tipped anti-spark brass connector and the positive PDB (right side). Repeat for the solid brass connector and the negative PDB (left side).
XT90 (EFI/Hydrone only)	Bottom Frame: Rear of Aircraft - Gen to PDB	Continuity: Use a multimeter to check continuity between the positive terminal of the male XT90 (second from left, under frame arm 6) and the positive PDB (right side). Repeat for the negative terminal and negative PDB (left side).
XT60	Flight Control Box: Auxiliary Power	Voltage: Use a multimeter to measure DC voltage with devices removed. Verify magnitude and polarity as labeled (e.g., 48V, 24V, 12V). Negative voltage indicates an internal short.
JST and JST-GH	Avionics Plate: Various	Visual: For JST, verify pin 1 is ground (black) and pin 2 is hot (red). For JST-GH, ensure they are seated in the Pixhawk or DC-DC converter and pins are secured in the housing.
Servo	Avionics Plate: Pixhawk Rail; Rear of Flight Control Box	Visual: Verify connectors are secure with the ground wire (black) facing up. On the Flight Control Box rear wall, incorrect polarity results in lost generator telemetry.

Coaxial Cable and Antenna Inspection

Trained personnel should inspect all applicable COAX connections, antennas, and related supports or housings.

Connection	Location	Notes
Coaxial Terminator	Various: Rear Legs, Booms 1 & 2, Booms 5 & 3, Flight Control Box	Check for damage (bent/crushed terminators) and remove debris. Verify each cable is secured with an 8mm lock and tooth washer.
Antenna	Various: Rear Legs, Booms 1 & 2, Booms 5 & 3, Flight Control Box	Verify the gender for each antenna is the opposite of its associated COAX terminator to avoid damage or loss of communication. Ensure the housing is not broken.

General Inspection Timetable (All H6 Carriers)

Description	Platform	Interval
Pre-Flight Checklist	All	Each Flight
Air Filter Replacement	H6-EFI	Every 25 hours
Battery Replacement	All	Every 150 hours
Generator Replacement	H6-EFI	Every 300 hours
Fuel Cell Replacement	Hydrone	Every 300 hours
Motor Replacement	All	Every 450 hours
ESC Replacement	All	Every 450 hours
Full Maintenance Inspection	All	Every 600 hours
Full Aircraft Review	All	Every 1000 hours

EFI Only: General Inspection Guidelines

To achieve the longest life from any engine, preventative maintenance is necessary to ensure the mechanical and electrical systems that it is composed of operate as efficiently as possible or are otherwise replaced. This section will provide detailed instructions for removal and replacement of the following Löweheiser components: air filter, fuel filter, fuel lines, spark plug, and braided wire dampers (if necessary).

Air Filter Replacement

Air Filters prevent any contaminants or environmental fallout from getting into the combustion chamber that would otherwise cause a poor ignition cycle. As a result, over time these filters will lose their ability to properly intake air, and should be replaced every 25 hours of flight. To replace, simply pull the air filter off the intake, and place another in its place while ensuring the air temperature sensor is placed between the filter and intake during installation.

Fuel Filter Replacement

Begin by removing the fuel line grommet located at the top of the fuel tank, and pull the fuel filter through the internal baffles. Firmly grasp the filter with one hand, while grasping the attached fuel line close to the nipple of the filter, and pull the fuel line off. If the fuel line is difficult to remove, cut the fuel line as close to the filter as possible, and use a razor knife to carefully score and remove the remaining fuel line. Before installing a new fuel filter, make sure the nipple is clear of any previous fuel line or material, and that the fuel line to be mated with the fuel filter has been trimmed flush.

Fuel Line Replacement

Begin by removing the fuel line grommet located at the top of the fuel tank, and pull the fuel filter through the internal baffles. Remove each fuel line from its respective brass-L pipe for both the internal and external fuel lines. Remove the large clear and large yellow fuel line from the generator taking note of which nipple they mate to. If any fuel line is difficult to remove, cut the fuel line as close to the nipple as possible, and use a razor knife to carefully score and remove the remaining fuel line. Lay out each fuel line and measure the length of each segment. Prepare fresh fuel lines using these measurements making sure the end of each line is trimmed flush. Insert each new fuel line in place of the pre-existing fuel line.

Spark Plug Replacement

Begin by removing the spark plug boot, located at the bottom of the generator. Using the spark plug removal wrench, loosen the spark plug and remove by hand being careful not to break the spark plug upon exit. Replace the spark plug with a new NGK-CMR7H, inserting the spark plug into the ignition chamber and tightening until snug. Be careful not to overtighten the new spark plug as this may result in fracturing and poor spark while running.

Braided Wire Damper Replacement

Inspect each braided damper around the generator mounting clamps. If any braided steel damper exhibits signs of wear or fraying, replacement is required. To remove a damper, loosen both the top and bottom retaining screws with a 2.5mm hex allen wrench and remove the faulty damper. Replace with a new braided damper, and insert two new screws with blue loctite. Repeat this procedure for all damaged braided steel dampers.

600 Hour General Inspection Guidelines (All H6 Carriers)

A T-Motor KV Electronic Speed Controller (ESC), is a linear control device that uses pulse-width modulation (PWM) inputs to determine how quickly a motor should spin in relation to the other motors. These ESCs play a crucial role in the aircraft's ability to hover and otherwise maneuver properly. The manufacturer recommends each ESC be replaced after 450 hours of use to prevent component or inefficient flight characteristics.

ESC Replacement

Removing ESCs on H6 requires extensive work due to the nature of the ESCs placement between the top and bottom frame plates. It is mandatory that all ESC replacements needed on H6E platforms be performed at our facility unless prior consent is given.

Any attempt by a client to replace ESCs themselves without prior consent will render the flight integrity of the airframe uncertifiable and will void warranty.

1000 Hour General Inspection Guidelines (All H6 Carriers)

Aircraft Analysis and Replacement

Congratulations on reaching 1000 hours of operation with your aircraft. Depending on how quickly this milestone has been reached, there should be a few things to consider.

1. The age of each component, specifically those manufactured in house at HA. Our product is always improving, and because of this, so are the specifications and designs of key components that your aircraft consists of, these usually include:

• a. Carbon Fiber
• b. Aluminum: Hinges, Landing Gear, Standoffs, etc.
• c. Frame Support Walls
• d. 3D Printed or SLS Parts
• e. Electronics: Avionics, Navigation, etc.

2. The condition of the aircraft. If an aircraft has experienced repeated use, transport, and exposure to varying environmental conditions, many components housed within each aircraft may experience degradation.

Therefore, it is highly recommended that an aircraft be assessed after being used for 1000 hours or more. Replacement of obsolete frame hardware guarantees that your experience with HA aircraft is up to date with our most recent standards, tolerances, electronics, and software which also allows us to provide the best support we can in regard to your aircraft.