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Lab 04 - Ground Test Believer

15 points

Nathan Tyler Rose

Anestis Athanasios Tsagris

Last edited 28 days ago by Isabella Riley Avedician.

Overview

In this lab, teams will perform ground testing of their Believer aircraft to complete final setup prior to flight operations. At this stage of the project, the aircraft is assumed to be structurally complete and transitioning from build to operation.

The purpose of this lab is to verify that all control systems and propulsion components are configured correctly and behave predictably before any attempt at flight.

Objectives

By the end of this lab, teams will be able to:

Confirm correct servo centering and control surface neutral positions

Verify correct control direction at both the servo and control-surface level

Calibrate ESCs and verify propulsion system operation

Identify and correct discrepancies using the Ground Control Station (GCS)

Document aircraft readiness

Propellers must not be installed at any time during this lab.

Servos

When installing servos on the aircraft, they must be mechanically centered in order to operate correctly. Proper servo setup requires both physical alignment and software alignment/verification. These steps must be followed carefully and in order.

Part A – Servo Mechanical Installation and Centering

Before beginning this section, ensure that:

The servo is not installed in the aircraft and servo horn is disconnected

This prevents unintended movement of the control surface during centering.

Important:

If the servo gear is manually moved at any point after this process, the centering procedure must be repeated from the beginning.

Servo Centering Procedure

Obtain a GCS laptop

Power on the Cube

Ensure proper telemetry connection

Set the aircraft status to Manual mode

Plug in the servo

Allow the servo to self-center

Unplug the servo

Servo Horn Installation

Before fully securing the servo in its mounting location:

Install the servo horn so that it is as close as possible to perpendicular relative to the wing and control surface

Minor deviations are acceptable, but gross misalignment is not

Push-rod Adjustment

Adjust the push-rod length to make the associated control surface appear as level as possible when the servo is centered.

Do not connect the push-rod to the servo at this time

The goal is visual neutral, not final trim

Change the push-rod length to try to make control surface as level as possible. But do not install the rod to your servo

After completing these steps, the servo is mechanically centered.

Part B – GCS Trim and Control Adjustment

In previous labs, teams uploaded parameter sets based on a standard Believer configuration. While many parameters are universal, aircraft trim is unique and must be adjusted on a per-aircraft basis.

Teams must identify which control surfaces require trim and determine which direction the servo must move to achieve neutral control surfaces.

GCS Mechanical Trim Verification

Power on GCS Laptop, DATX and aircraft

Set the aircraft status to Manual mode

Observe the distance between the push rod and servo horn connection spot

If the distance is minimal

Power down aircraft and connect your push rods to the servo horn

You may continue to GCS Trim

If the distance is large and major control surface deflection is necessary to connect the push rod to servo

Repeat Part A and alert instructor

GCS Trim

Connect your GCS Laptop, DATX, and aircraft

Move all control surfaces and observe:

Which values change

Servo Outputs 1-7

How the servo responds to each input

Identify the parameter associated with the control surface requiring trim

Modify the parameter value based on observed servo movement to achieve a neutral control surface and fill out the table below

Ensure all control surface params are in the table even if no values are modified

Export your complete set of parameters and import them here:

Obtain instructor sign-off of trimmed aircraft:

Trim Parameters

Trim Parameters

Param Name

Corresponding Control Surface

Original Value

Modified Value

Servo Output 5 and 6

Rudder/VTail

Servo 1 and 2

Ailerons

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020326-G6.json

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02102026Group6Param.pdf

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ESC/Motor

Esc Calibration

Power on your GCS laptop, DATX, and Aircraft. Ensure that the aircraft is not armed. Following the instructions from

Lab 11 - Motors and Controls · AT 209⁠

calibrate both ESCs.

What was your method for calibrating the ESCs?

Applied power, full throttle, two beeps throttle all the way down.

Instructor sign-off: AT

Motor Direction

Observe the direction of your motor rotation under power. Take note of the initial direction.

Which direction should the motor be spinning?

Change the relevant parameter to make the motor spin in the correct direction.

Motor

Initial Direction

Correct Direction

Port

Starboard

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Weight and Balance

An important factor that we must consider before flying is the weight and balance of the aircraft. Each group has assembled their believer independently and there may be variation in the CG of each aircraft. Following the steps of this video complete a CG calculation for the aircraft.

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Loading youtu.be⁠

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CG Guiding Questions

What is a datum? Where is it?

Vertical reference plane or line established by manufacturer for which all horizontal measurements are taken, it serves as the center of gravity

If I state that a sensor is installed at -3 in and an additional battery is installed at +20 in, where are those components located relative to the datum?

The sensor would be -3 inches in front the datum and the battery would be +20 inches behind the datum.

What two configuration conditions must the aircraft be in during CG calculation?

Level attitude and everything neutral and everything on board

What are some ways to verify that the aircraft is in both of those configuration conditions?

lift it off the ground and level it on jacks

What is Tare? How is it depicted in a CG Table?

Tare is zeroing the scale while excluding whatever is actively on the scale, leading to a precise measurement.

What is a plumb bob? How is it used?

Used to establish vertical reference on a specific part of the aircraft.

Suspended on a string with a pointed edge

Used to align objects over a long vertical distance

Verify answers with instructor: AT

Calculating CG

Make sure that this portion is done on one singular table that is not finished to be able to draw on the table.

Discuss within your group and have consensus on your methodology of calculating the CG

Determine where the datum is located

Obtain CG jacks and scales

Weigh each jack individually and record the weight (grams) in the table below under Tare.

Decide where to place the two forward jacks on the aircraft and determine their distance from the datum.

Note: The forward jacks must be placed at the same longitudinal station on both sides of the aircraft.

Determine where to place the rear jack in order to satisfy the required configuration conditions.

Place each jack on a scale and carefully rest the aircraft on the three jacks.

Verify that the rear jack is in the correct location and adjust as needed

Record the weight depicted on each scale in the table below

Using a plumb bob, mark the exact longitudinal location of each jack stand on the physical table and the datum on your CG Table

Ensure that the measuring method used for each jack is consistent.

Determine the centerline between the two forward jacks.

Determine the centerline of the rear jack.

Determine the centerline of the datum.

Measure the horizontal distance from each jack location to the datum and record the value in inches.

CG Table

CG Table

Item

Location from datum(in)

Weight (grams)

Moment

Port Jack Tare

-2

Star Jack Tare

-2

Rear Jack Tare

23.68

Port Jack with aircraft

-2

1,957

-3,914

Star Jack with aircraft

-2

2,135

-4,270

Rear Jack with aircraft

23.68

325

7,696

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Total Weight 4,417 g

Total Moment -488

CG -0.11 in

Without Battery

Without Battery

Name

Location

Weight

Moment

starboard

-2

1,084

-2,168

port

-2

1,049

-2,098

rear

23.68

468

11,082.24

Battery

1,806 G

6,816.24

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Total Weight: 2601g

Total Moment: 6816.24

CG: 0.38 IN

We will use this when placing the battery into ensure our center of gravity is correct.

What ya should've done

What ya should've done

Item

Location from datum(in)

Weight (grams)

Moment

Port Jack with aircraft

-2

1,084

-2,168

Star Jack with aircraft

-2

1,049

-2,098

Rear Jack with aircraft

23.68

468

11,082.24

Batt

-3.75

1,816

-6,810

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Total Weight 4,417g

Total Moment 6.24

CG 0.00in

Evaluation of CG

What does

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in mean?

The center of gravity is 0.11 inches in front of the datum.

Do you think that this number is acceptable? How would you fix this if not?

We think this number is acceptable; however, we wanted to minimize the margin as much as possible. We removed the battery, placed the jacks and scales in the same positions, and reweighed the aircraft. Then using both of the weights to see how much we need to move the battery back.

Based on your CG Location, what flight characteristics would you expect during flight?

Nose heavy, having to use more elevator to keep the nose pitched up.

Deliverables

Fully completed document exported as a PDF to Brightspace

.json of exported parameters file name “MMDDYYYYGroup#Param” imported into this document

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