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Ultra Stick Aircraft

Operations and Maintenance Plan

UAVLAB-OMP-001

Revision History

Date Description Changes

20130228 Baseline N/A

20131202 Rev 1. Updated to match COA applications

1 Purpose

Section 2 of this manual describes the aircraft, airframes, flight computer and 

software, ground control station, and airframe specific dimensions, airspeeds, and 

limits. Section 3 contains Standard Operating Procedures (SOPs) including crew 

roles, responsibilities, qualifications, and training. Section 4 describes the Safety of 

Flight/Safety of Test (SOF/SOT) limits for the aircraft. Section 5 describes the Ultra 

Stick maintenance and inspection plan. 

2 Systems Description

This section describes the Ultra Stick Uninhabited Aerial Vehicles and ground 

control stations used by the University of Minnesota Uninhabited Aerial Vehicle Lab. 

An overview of the airframes, flight control system, and ground control station is 

given in section 2.1. Section 2.2 and 2.3 discusses airworthiness of the airframes 

and certified equipment installations. Section 2.4 and 2.5 discuss the flight control 

system and ground control station in greater detail. Section 2.6 and 2.7 discuss the 

Ultra Stick 120 and Ultra Stick 25e airframes including physical dimensions, 

airspeeds, and limits.

2.1 System Overview

The University of Minnesota (UMN) Uninhabited Aerial Vehicle (UAV) Lab utilizes 

two commercially available, RC hobbyist airframes as platforms for aircraft 

research. The larger of these airframes is the Ultra Stick 120, designed and 

manufactured by Hanger 9. The second airframe is the Ultra Stick 25e, based on the 

Hanger 9 design, but at a smaller scale and manufactured by E-Flight RC. This 

approach was adopted after receiving an Ultra Stick 120 aircraft from NASA Langley 

Research Center (LaRC), which was used for wind-tunnel testing and as a low-cost 

UAV platform.

Both types of airframes at UMN are equipped with a commercial RC hobbyist control 

system for manual control as well as an in-house system for data collection and 

autonomous flight modes. A systems-level design has been implemented that allows 
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the pilot to take manual control of the aircraft at a hardware-level and defaults to a 

descending, power-off spiral to keep the aircraft contained within the test range in 

the event of lost link.

Figure 1 is a picture of an Ultra Stick 120 aircraft, which has been modified to 

include air data sensors, and two Ultra Stick 25e aircraft.

Figure 1: Ultra Stick 120 and Ultra Stick 25e aircraft

These airframes include standard RC hobbyist batteries, receiver, and servos for 

manual control. Additionally, an in-house system has been designed and integrated 

to record flight data and provide for autonomous flight. A functional diagram of this 

system is in figure 2.
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Figure 2: Avionics functional diagram

Commands are sent to the aircraft via a hobbyist RC transmitter and receiver. The 

receiver sends commands to both a manual/auto switch and a PWM reader. The 

receiver controls the manual/auto switch; in manual mode, commands from the 

receiver are sent directly to the servo actuators. In autonomous mode, commands 

from the flight computer are sent to the servo actuators. The flight computer 

receives flight data from sensors including GPS, Inertial Measurement Unit (IMU), 

and pressure transducers. Data from the flight computer is downlinked through a 

radio modem to a ground control station where researchers can monitor its 

operation.

At any time, the pilot can take manual control via the manual/auto switch. 

Additionally, failsafe commands are set in the RC receiver so that in the event of a 

lost link, the receiver switches the aircraft to manual control, cuts power to the 

motor, and puts the aircraft in a descending spiral.

2.2 Airworthiness

The Ultra Stick 25e aircraft is a commercially available, hobbyist aircraft of a conventional 

layout with many flight hours. This aircraft arrives in an Almost-Ready-to-Fly (ARF) 

condition, meaning that all major subassemblies are built at the factory and only minor 

work is needed to finish the aircraft. The chief maintainer at the University of Minnesota 

(UMN) Unmanned Aircraft System (UAS) Research Lab has 13 years of experience building 
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and flying remote control (RC) aircraft. He inspects the work done on each aircraft and 

performs the necessary maintenance and inspections.

Additionally, the UMN UAS Research Lab has several processes in place to minimize the risk 

of our operations. We utilize a Development and Flight Approval Process that is based on 

processes used in government and industry. This process standardizes our research and 

development efforts to ensure that the technical approach is sound and risk is minimized. 

Two peer reviews are included in this process including a risk assessment and hazard 

analysis/matrix. We also use Standard Operating Procedures (SOPs), Safety of Flight/Safety 

of Test (SOF/SOT) Limits, and an Aircraft Maintenance Plan to ensure our aircraft remain 

airworthy and are operated in manner that minimizes risk. Hardware-in-the-Loop (HIL) 

simulation is used to verify and validate software performance prior to flight and our flight 

control system is designed to allow the pilot to take over operation of the aircraft at any 

time. Our Test Range consists of University of Minnesota owned property that is not near a 

congested area and failsafes are in place to ensure the aircraft is kept on the test range in 

the event of lost link or lost communication. All of our pilots, observers, and maintainers 

are trained and have duty hour restrictions.

The maintenance plan includes three phases of inspection. Phase A checks are performed 

prior to every flight, Phase B checks every 50 flights, and Phase C checks every 100 flights. 

Phase A checks include visually inspecting all accessible components and checking their 

operation. Phase B check involves removing all hatches and panels, inspecting all interior 

components for wear, and replacing as necessary. The Phase B check is functionally similar 

to a general aviation annual inspection. A Phase C check involves removing all servos and 

checking for wear in the servo gears. The Phase C check is an intensive inspection, nearly 

disassembling and rebuilding the entire aircraft. Logbooks are maintained for all of our 

aircraft including squawk sheets for tracking and rectifying any problems with the aircraft.

The University has developed internal procedures using various methods to effectively 

demonstrate and assert that the UAS being considered is airworthy. The UAS meets the 

applicable airworthiness standards and requirements of our University, and is capable of 

operating in compliance with the applicable requirements in 14 CFR Part 91. The University 

assumes all risks and liabilities with the UAS and confirms there are no known limitations 

or nonstandard safety precautions with this airframe.

2.3 TSO Equipment

No FAA TSO equipment is installed in the Ultra Stick aircraft.

2.4 Flight Control Computer

An MPC5200 Tiny System on a Chip computer is used as a flight control computer 

for the Ultra Stick aircraft. Software is written for the computer using C code and a 

real-time operating system (eCos) is installed for executing the code. Subversion 

(SVN) is used for version and configuration control. Hardware-in-the-Loop (HIL) 

simulation is used to verify and validate software prior to flight in a high fidelity 

environment.
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2.5 Ground Control Station

The pilot issues commands to the Ultra Stick aircraft with a hobbyist RC transmitter. 

Additionally, a hobbyist RC telemetry module is used to monitor airspeed and 

aircraft battery voltages in real-time.

A laptop is used in conjunction with a radio modem to receive data from the flight 

control computer in real-time. Commands are not issued from the laptop; however, 

researchers use the laptop to monitor the aircraft airspeed and attitude as well as 

GPS signal strength and software modes. This capability allows researchers to 

monitor whether the aircraft autonomous modes are working as expected and have 

the pilot take manual control before any hazardous situations develop.

2.6 Ultra Stick 120

The Ultra Stick 120 aircraft is an almost ready to fly kit from Hanger 9. It is powered 

by an electric motor and has removable wings for transport. The Ultra Stick 120 has 

a conventional horizontal and vertical tail with rudder and elevator control surfaces. 

The aircraft has a symmetric airfoil wing with aileron and flap control surfaces. The 

rudder and elevator and actuated by Hitec HS5245MG servos while the flaps and 

ailerons use Hitec HS5625MG servos. The aircraft is propelled by a 1900W Actro 

40-4 brushless electric motor with a Graupner 14 x 9.5 folding propeller. Power for 

the motor comes from two 5000mAh 5-cell lithium polymer batteries connected in 

series. The servos are powered by a separate 1350 mAh 3-cell lithium polymer 

battery. The main internal payload bay is located directly under the wing in the 

fuselage and measures approximately 35cm L x 10cm H x 10cm W; additional 

payloads may be accommodated in the aft fuselage or externally. The Ultra Stick 

120 aircraft has space aft of the avionics bay for additional sensors or payloads and 

can carry approximately 5.5kg.

2.6.1 Aircraft Description

Wingspan: 1.92 m

Chord: 0.43 m

Length: 1.73 m

Weight: 7.07 kg

Payload capacity: 5.5 kg

Cruise speed: 23 m/s

Airspeed range: 6-41 m/s

2.6.2 Limits

Wind limits: 10 m/s total / no crosswind limit

2.7 Ultra Stick 25e

The Ultra Stick 25e is an approximately 65% scale model of the Ultra Stick 120, with 

the same basic configuration and is an almost ready to flight kit from E-Flight RC. 

All six control surfaces are actuated by Hitec HS-225BB servos. The aircraft is 

propelled by a 600W E-Flite Power 25 brushless electric motor with an APC 12 x 6 

propeller. Power for the motor and servos comes from a 4200mAh 3-cell lithium 
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polymer battery. The main internal payload bay is located directly under the wing 

in the fuselage and measures approximately 22cm L x 6cm H x 7.5cm W; additional 

payloads may be accommodated in the aft fuselage or externally. The Ultra Stick 

25e can carry approximately 2.25kg of payload.

2.7.1 Aircraft Description

Wingspan: 1.27 m

Chord: 0.25 m

Length: 1.09 m 

Weight: 1.96 kg

Payload capacity: 2.25 kg

Cruise speed: 17 m/s

Airspeed range: 5-26 m/s

2.7.2 Limits

Wind limits: 8 m/s total / no crosswind limit

3 Standard Operating Procedures (SOPs)

The Standard Operating Procedures cover the personnel required for operating the 

Ultra Stick aircraft as well as all procedures other than test specific cards.

3.1 Personnel Roles, Responsibilities, and Qualifications

Three personnel are required for operations; the Operations Lead, the Pilot who is 

also the Pilot-in-Command (PIC), and the Observer. All personnel must maintain 

logbooks of operations.

3.1.1 Operations Lead

The Operations Lead leads the operations team through the flight test process. 

Prior to the flight, the Operations Lead:

1. Ensures the aircraft and software is ready for flight

2. Plans the mission timeline

3. Ensures that crew currency and crew rest periods are met

4. Leads the T-1 and T-0 briefings

a. Checks the weather

b. Conducts a Test Card review

c. Conducts an Emergency Procedures review

d. Conducts a Test Range review

During the flight, the Operations Lead stands next to the pilot and coordinates the 

test. The Operations Lead:

1. Coordinates the launch and recovery of the aircraft

2. Ensures the Standard Operation Procedures are followed and the Safety of 

Flight / Safety of Test (SOF/SOT) limits are adhered to

3. Reads flight cards to the Pilot and Observer

4. Takes notes as test points are performed by the Pilot
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5. Observes the aircraft, test range boundaries, or other hazards to ensure a 

safe operation

Following recovery of the aircraft, the Operations Lead coordinates data retrieval 

and shutdown of the aircraft. 

3.1.2 Pilot (Pilot-in-Command, PIC)

The Pilot operates the aircraft according to direction from the Operations Lead, 

when it is safe to do so. In addition to operating the aircraft, the Pilot also:

1. Ensures the aircraft is kept within the test range and below 400 ft above 

ground level

2. Observes the aircraft and surrounding airspace to de-conflict with other 

aircraft traffic when necessary

3. Coordinates with FAA facilities

4. Is ultimately responsible for the safe conduct of a flight operation; the pilot 

takes whatever steps necessary to keep the aircraft in the test range and 

away for personnel and property

3.1.3 Observer

The Observer assists the Operations Lead and the Pilot by:

1. Ensuring that the aircraft is kept within the test range and below 400 ft 

above ground level

2. Observing the aircraft and surrounding airspace to alert the Pilot to the 

presence of other aircraft traffic

3. Observing the test range to alert the Pilot and Operations Lead if people not 

associated with the test enter the test range

3.2 Currency and Training Plan

All pilots will maintain currency according to FAR Part 61, though the currency 

requirement does not imply that manned aircraft licenses remain current. In 

addition each pilot will maintain currency on the UAS by performing at least 3 

launch and recovery operations with maneuvering within the preceding 90 days. If 

the 90 days elapses the pilot will gain currency by logging the 3 launch and recovery 

operations with a qualified instructor operator.

All observers will maintain currency according to FAR Part 61. If it has been more 

than 90 days since being involved with UAS operation the PIC/Operator will ensure 

the observer is thoroughly briefed on the standard operating procedures of the 

operation and any recent changes to operation protocol.

3.3 Qualifications

The Operations Lead, Pilot, and Observer must be current. In addition, they must 

meet duty requirements of at least an 8 hour rest period and less than 12 hours 

since being on duty. At least 8 hours must have passed since the last consumption 

of alcohol.
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The Pilot and Observer must have a current Class II medical. The Pilot must have 

passed an FAA Private Pilot Written Exam. The Operations Lead, Pilot, and Observer 

must be familiar with emergency procedures, the test range, weather, NOTAMs, and 

the nearest FAA facility including frequencies.

3.4 Operating Limitations

Operations are only conducted in day, Visual Flight Rules (VFR) conditions. 

Operational altitudes are restricted to 400 ft above ground level within 1 mile 

horizontal range from the pilot. All operations must be conducted within Class G 

airspace. Operations will not be conducted in precipitation, in the vicinity of 

thunderstorms, or at night. 

3.5 Communications Plan

The Operations Lead coordinates the operation by communicating with the Pilot 

and Observer. The Operations Lead stands next to the Pilot and has a handheld 

radio to facilitate communications with the Observer. All test cards and steps are 

called over the radio so the Observer will maintain situational awareness of the test 

being performed. The Pilot will have a handheld transceiver to communicate with 

the nearest FAA facility when necessary.

3.6 Checklists

1. See UAVLAB-SOP-001 for pre-flight and post-flight briefings and 

UAVLAB-SOP-002 for checklists and procedures involved with flight testing 

the Ultra Stick aircraft.

4 Safety of Flight/Safety of Test (SOF/SOT) Limits

4.1 Weather Conditions

The weather conditions should be adequate for VFR flight. This requires at least 1 

statute mile of visibility, and to remain clear of clouds.

4.2 Wind Conditions

Wind condition limits are dependent on the flight test at hand. However, there are 

maximum wind speeds for each airframe.

Ultra Stick 25e: 

Maximum steady wind: 8 m/s

Maximum crosswind component: None

Ultra Stick 120:

Maximum steady wind: 10 m/s

Maximum crosswind component: None

4.3 Temperature Conditions

The minimum outside air temperature with wind chill is 10 degrees Fahrenheit. 

Estimated battery charge time should be decreased to account for poor battery 
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performance in cold temperatures. Operations will cease if wet bulb globe 

temperatures (WBGT) rise to red or black flag conditions (WBGT values over 88 oF).

5 Maintenance Plan

5.1 Personnel Roles, Responsibilities, and Qualifications

Any person in the UAV Research Lab may perform aircraft maintenance. A 

Maintainer/Inspector must inspect any maintenance performed prior to the aircraft 

returning to flight. All maintenance must be logged in the aircraft logbook.

5.1.1 Maintainer/Inspector

In addition to performing maintenance, the Maintainer/Inspector inspects all 

maintenance performed within the UAV Research Lab and checks the airworthiness 

of the aircraft. A Maintainer/Inspector should have extensive experience with 

remote control aircraft and knowledge of the research flight control system. A 

Maintainer/Inspector can sign off on lab personnel becoming a 

Maintainer/Inspector provided they worked with that person through maintenance 

on the Ultra Stick aircraft and are confident in their work and ability to maintain 

these aircraft without supervision. 

The Maintainer/Inspector must meet duty requirements of at least an 8 hour rest 

period and less than 12 hours since being on duty. At least 8 hours must have 

passed since the last consumption of alcohol.

5.2 Ultra Stick Inspection Intervals

There are three inspection intervals for the Ultra Stick aircraft. A checks prior to 

every operation, B checks every 50 flights, and C checks every 100 flights. In the 

event that significant repairs are performed, mass properties testing must be 

performed and air data calibration and control surface calibration may be 

warranted.

5.2.1 A Check

1. Airframe structure, check:

a. Fuselage, wing, and hatches for signs of damage or cracking

b. For rips or tears in monocote, patch as necessary

c. Landing gear and motor bolts are tight

d. Wheels spin freely

2. RC Equipment, check:

a. RC equipment is plugged into receiver

b. Motor plugs are connected

3. Batteries

a. Charge motor and avionics batteries

b. Check for battery pack bloating or signs of damage

4. Flight Control Computer
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a. Check that component wiring harnesses are plugged in, no loose 

wires, and in good condition

5.2.2 B Check

1. Remove all hatches and panels

2. Motor and propeller

a. Check motor for excessive play

b. Check propeller condition

c. Check spinner condition and tightness

d. Runup and listen for loose or worn bearings

3. Structure

a. Check all screws, replace if heads are stripped or worn

b. Check landing gear condition and landing gear screws

c. Inspect tire condition and tire collets to ensure that wheels spin freely 

and are secure

d. Inspect rear landing gear condition and tire collets to ensure wheel 

spins freely and is secure

e. Check horizontal tail for excessive play and tighten screws as 

necessary

f. Check servo mounts, servo arms, and control horns

g. Check pushrods clear of obstructions

h. Check control surface hinges for excessive play

4. Flight Control Computer

a. Pull-test wiring harnesses, re-solder as necessary

5. Replace all hatches and panels

6. Perform Pre-Flight Inspection

5.2.3 C Check

1. Perform B Check

2. Remove servos and inspect servo gears

3. Check for cracked air pressure tubing

4. Balance Propeller

5. Test mass properties

a. Weight

b. Center of gravity

c. Moment of inertia

6. Perform air data calibration

7. Perform control surface calibration

5.3 Ultra Stick Overhaul and Life Limits

There are no overhaul or life limits for the Ultra Stick aircraft. Components are 

repaired or replaced as necessary according to the A, B, and C checks.