In-depth Study of CF188 Aircraft Landing Gear Upgrade: Analysis Report

This report presents a comprehensive study of the CF188 aircraft landing gear upgrade, focusing on the impact of proposed changes, static hold down force during rigging, bell crank gaps, pin head evaluation, and aircraft ground handling at various speeds. The study evaluates loads on planning and connecting links during different landing scenarios, including full stop, touchdown, arresting cable engagement, and cable overrun. The methodology involved interviews, questionnaires, experiments, and secondary sources, with a practical session testing components on the CF 188B aircraft. The testing process included evaluating maintenance rigging, ground handling quality at different taxi speeds, and various landing profiles. Safety and regulatory requirements were strictly observed, employing advanced technologies, improved analysis methods, high-quality materials, and improved production processes. The findings from fleet surveys of planning link spring length versus connecting link and connecting link length versus pinhead gap are presented, concluding with the need for landing gear systems with minimum volume, weight, reduced life cycle cost, and high performance, while adhering to all regulatory and safety requirements.

A STUDY OF THE CF188 AIRCRAFT
LANDING GEAR UPGRADE

 Project Aims and objectives
To research the impact of the proposed changes to the landing gear of the CF188.
To evaluate static hold down force during the landing gear rigging.
To confirm the increase of the bell crank gaps and the pin head.
To evaluate the aircraft ground handling at different ground speeds
To evaluate the loads on the planning and connecting links during many landings
which include full stop, touch down, arresting cable engagement and cable overrun.

 Purpose of the landing gear
To allow the aircraft to be controlled during landing, take-off and other ground
operations.
To support the aircraft on the ground while it keeps proper clearance between the
ground and the aircraft.
To provide sufficient support to the external stores such the fuel and weapons
tanks.

 Fixed and Retractable Landing Gears
1. Retractable landing gear 2. Fixed landing gear
 The landing gears are attached to the airframe and
they always remain exposed to the slipstream during
the aircraft flight.
 Retractable landing gear stow in the wing
compartment or fuselage when the aircraft is
in flight.

 Landing gear arrangement
i. Wheel type landing gear (convectional gear)
ii. Tandem landing gears
iii. Tricycle-type landing gear

 Tail Wheel-Type Landing Gear
The main gears are located at the forward centre of gravity
The tail is forced to get support from the third wheel assembly
Benefits
 Weight savings accompanying the light tail
wheel-type landing gears.
 Ability to operate in and out of the unpaved
runways.

 Tandem Landing Gear
 The tail gear and the main gear are aligned longitudinal to the axis of the aircraft.
Having the gear only under the fuselage facilitates the application of flexible
wings
• Flexible wings on a military
aircraft B-52
• VTOL Harrier with tandem gear

 Tricycle-Type Landing Gear
Made up of the nose gear and the main gear
Used on both small and large aircrafts
Benefits
 Permits more forceful application of brakes
without nosing over when braking. This enables
landing at high speed.
 Visibility from the flight deck is enhanced
especially during ground manoeuvring and
landing.
 Prevents ground-looping of the aircraft.

 Landing gear loads
During the operations of the landing gears on the ground it is subjected to:
1. horizontal
2. vertical
3. crush loads.
 The vertical loads are due to the aircraft weight and to the normal acceleration during the
touch down which is generated by descent rate and the impact of the weight of the air craft.

 Landing gear loads
 The horizontal loads which are also referred to as the drag loads are usually generated from the friction
between the landing surface and the tire.
 The crush loads happens when the aircraft runs over a sharp object for example the arresting cable.
Factors affects the landing gear loads
Weight of the aircraft.
Descent rate
Landing gear serving and maintenance.

 Main landing gear nomenclature

 Methodology
Various methods were used to obtain the data during the study such as:
 Interviews
 Use of questionnaires
 experiments
secondary sources

 Experiment
 A practical session was carried out regarding the
design of landing gears and various components were
tested on aircraft CF 188B (T/A-18B)
 The aircraft was designed with moderate swept mid-
mounted wings which had the twin vertical stabilizers
which was inclined at 20o outboard from the vertical.
 The aircraft was equipped with the a fly-by-wire
hydraulically which was actuated flight control system
Aircraft CF188907

 Test concept
The testing process was carried out in three phases.
• The first phase it involved evaluating the maintenance rigging and obtaining static measurement.
• During the second phase of testing it involved ground handling quality testing which was carried out
at different taxi speed.
• During the third phase of testing it consisted of different landing profiles including touch down and
cable overrun, full stop and the cable arresting landings.

 Rationale of choice of sample
The CF 188 aircraft which was under study was selected due to its landing gear
configuration which provided an opportunity to achieve all the aims and
objectives
The CF188 landing gear was a retractable tricycle type.
The landing gear was electronically controlled and hydraulically actuated.
The nose landing gear had two wheels in a dual arrangement.

 safety and regulatory requirements
To meet all the safety and regulatory requirements the following were to be observed during the
design process:
 Employing advanced technologies
 Using improved analysis methods,
 High quality and durable materials
 Improved production and process methods

 Landing gear configurations
• For the purpose of comparison, data was collected by use of two landing gear configurations.
• The first landing gear configuration which was used was the CF 188 which was the existing
main landing gear. This landing gear was used as the baseline.
• The other landing gear configuration which was used consisted of the parts which were
modified such as urethane connecting link, planning link urethane spring and the revised rigid
connecting link.

 Findings
Fleet Survey of Connecting Link Length vs Pinhead GapFleet Survey of Planning Link Spring Length vs Connecting
Link
 The figures above show that the connecting link had a direct influence on the pinhead gap and
the planning link.


 Conclusion
In conclusion, there is need to design a landing gear system with:
 the minimum volume
minimum weight
reduced life cycle cost
and high performance
 It is very important to reduce the landing development and design to meet all the
regulatory and safety requirements.

 REFERENCES
Graham, H., 2013. Landing gear design. 2nd ed. Auckland: Chapman & Hall.
Gudmundsson, S., 2013. General Aviation Aircraft Design: Applied Methods and Procedure. 5th ed. London: Butterworth-
Heinemann.
Hailiang, L., 2014. Assessment of Landing Gear Design Based on the Virtual Testing and Evaluation Methodology. 3rd ed. Berlin:
Elsevier Science.
Lixin, W., 2017. Aircraft Landing Gear Design: Principles and Practices. 4th ed. Los Agels: American Institute of Aeronautics
and Astronautics.
O'Massey, C., 2016. Introduction to Landing Gear Design. 4th ed. London: ASM.
Pazmany, L., 2015. Landing Gear Design for Light Aircraft. 1st ed. Paris: Pazmany Aircraft Corporation.