Project 2 - Implement the Code for controlling the retraction and extension of Airplane’s landing gear

PROBLEM STATEMENT:-

Implement the code for controlling the retraction and extension of airplane's landing gear.

Landing Gear of an Airplane:-

• It is the undercarriage of an airplane, which is used for either take off or landing.
• It was also formerly called alighting gear by some manufacturers, such as the Glenn L. Martin company.
• An airplane has 3 gears for landing:- Nose gear, Left gear, Right gear.
• There is a hydraulic pump which is exerting pressure to the gears to bring it down or pull it up and that pump is electrically driven.
• Every leg of the gear has one limit switch.
• Nose gear has one extra squat switch to determine whether the airplane is in ground or not.

Main file.c:

#include "project.h"
int main()
{
Initiate_State_Machine();
while(1)
{
statetable[current_state]();
}
}

Source file.c:

/*
* aero.c
*
* Created on: 07-Aug-2022
* Author: IND
*/
#include "project.h"
void GearDown(void)
{
current_state=GEAR_DOWN;
printf("Enter the status of pilot's lever and squat switch");
fflush(stdout);
scanf("%d %d",&pl,&squat_switch);
if(pl==Raising && squat_switch==on)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("current state:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is :%s\n", State_Machine[current_state].light);
}
else
{
GearDown();
}
}
//CheckingBeforeTakeOFF
void CheckingBeforeTakeOFF(void)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("Enter the status of pilot's lever and squat switch and hydraulic mechanism:");
fflush(stdout);
scanf("%d %d %d",&pl,&squat_switch,&hm);
if(pl==falling&&squat_switch==off)
{
GearDown();
}
else if(pl==Raising && squat_switch==on && hm==working)
{
current_state=RAISING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
}
else if(pl==Raising && squat_switch==on && hm==not_working)
{
current_state=RAISING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
printf("Status of gas pressurised Spring System:%s\n",State_Machine[current_state].Gas_Pressurized_Spring_system_status);
}
}
//RaisingGear
void RaisingGear(void)
{
current_state=RAISING_GEAR;
printf("Enter the status of pilot's lever and limit switch:");
fflush(stdout);
scanf("%d%d",&pl,&limit_switch);
if(pl==falling && limit_switch==on)
{
current_state=CHECK_BEFORE_LANDING;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
fflush(stdout);
}
else if(pl==Raising && limit_switch==off)
{
current_state=GEAR_UP;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
fflush(stdout);
}
else
{
RaisingGear();
}
}
//GearUp
void GearUp(void)
{
current_state=GEAR_UP;
printf("Enter the status of pilot's lever:");
fflush(stdout);
scanf("%d",&pl);
if(pl==falling)
{
current_state=CHECK_BEFORE_LANDING;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
fflush(stdout);
}
else
{
GearUp();
}
}
//CheckBeforeLanding
void CheckBeforeLanding(void)
{
current_state=CHECK_BEFORE_LANDING;
printf("Enter the status of pilot's lever and hydraulic mechanism status:");
fflush(stdout);
scanf("%d %d",&pl,&hm);
if(pl==falling && hm==working)
{
current_state=LOWERING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
fflush(stdout);
}
else if(pl==falling && hm==not_working)
{
current_state=LOWERING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
printf("Status of gas pressurised Spring System:%s\n",State_Machine[current_state].Gas_Pressurized_Spring_system_status);
fflush(stdout);
}
else if(pl==(Raising))
{
CheckBeforeLanding();
}
}
//LoweringGear.
void LoweringGear(void)
{
current_state=LOWERING_GEAR;
printf("Enter the status of pilot's lever and limit switch:");
fflush(stdout);
scanf("%d %d",&pl,&limit_switch);
if(pl==Raising && limit_switch==on)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
fflush(stdout);
}
else if(pl==Raising && limit_switch==off)
{
current_state=GEAR_DOWN;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
fflush(stdout);
}
if(limit_switch==off)
{
LoweringGear();
}
}
void Initiate_State_Machine()
{
current_state==GEAR_DOWN;
printf("The Finite State Machine is Intialized and current the program is in"" GearDown State & Light is: %s\n",State_Machine[current_state].light);
}

Header file.h:

/*
* project.h
*
* Created on: 07-Aug-2022
* Author: IND
*/

#ifndef PROJECT_H_
#define PROJECT_H_
#include <stdio.h>
void Initiate_State_Machine();
void GearDown();
void CheckingBeforeTakeOFF();
void RaisingGear();
void GearUp();
void CheckBeforeLanding();
void LoweringGear();
static void(*statetable[])(void)={GearDown, CheckingBeforeTakeOFF, RaisingGear, GearUp, CheckBeforeLanding, LoweringGear};
typedef enum State
{
GEAR_DOWN,
CHECKING_BEFORE_TAKEOFF,
RAISING_GEAR,
GEAR_UP,
CHECK_BEFORE_LANDING,
LOWERING_GEAR,
}State_Type;
typedef enum Switch
{
on,
off//plane is on groung
}Switch_status;
typedef enum pilot_lever
{
Raising,
falling
}pilot_lever;
typedef enum hydraulic_mechanism
{
working,
not_working
}hydraulic_mechanism;
static volatile Switch_status squat_switch;
static volatile Switch_status limit_switch;
static volatile pilot_lever pl;
static volatile hydraulic_mechanism hm;

State_Type current_state;

typedef struct
{
char* current_state_indication;
char* light;
char* direction_valve_status;
char* landing_gear_hydraulic_control;
char* Gas_Pressurized_Spring_system_status[2];

}State_Table;
static State_Table State_Machine[6]={{"GearDown","Green","Down","Enabled",{NULL,NULL}},
{"CheckingBeforeTakeOFF","Green","Down","Enabled",{NULL,NULL}},
{"RaisingGear","Red","Up","Enabled",{"Disabled","Enabled"}},
{"GearUp","Off","NULL","Disbled",{NULL,NULL}},
{"CheckBeforeLanding","Red","Down","Enabled",{NULL,NULL}},
{"LoweringGear","Green","Down","Enabled",{"Disabled","Enabled"}}
};
#endif /* PROJECT_H_ */

Output:

OVERVIEW OF THE PROJECT:-

• The project is to know the knowledge of retraction and extensions of landing gear using a code.
• This can be achieved by using finite state machine which is used in the states header file.
• FSM (Finite state machine) is a mathematical model of computation.
• It is the most efficient algorithm which can be used.
• The creation of source file helps us easy to understand the program.

GOALS:-

• The main goals are to control the direction of valve and retraction and extension of landing gear.
• The control of direction valve is controlled by pilot lever which we can see in the program (reference given in attachment provided).
• The retraction and extension of landing gear is controlled by switch states in the program.
• Hence, all the goals are achieved.

KEY HIGHLIGHTS OF PROJECT:-

• We can observe that the direction valve helps us to raise or lower the landing gear.
• The direction valve is controlled by the software.
• With the help of this software we control the hydraulic mechanism.
• The hydraulic pump controls the raising or lowering of the landing gear.
• The hydraulic mechanism helps us to land and take off of the airplane.

DELIVERABLES OF THIS PROJECT:-

• The retraction and extension of landing gears is controlled by various switch and gear.
• The status of these switches and gears are shown below in various tables.

Table1:-

Switch State	State of Gears
Limit Switch CLOSED	Gear is UP
Limit Switch OPENED	Gear is DOWN
Switch State	State of Airplane
Squat Switch CLOSED	Airplane is grounded and Gears are locked
Squat Switch OPENED	Airplane is taking off / landing / airborne

A direction valve is controlled by the software to allow hydraulic pressure to either raise or lower the landing gear.

Table 2:-

Status of Direction Valve	States of landing gear
Direction valve = Down	(Gear Down)(Parked at bay or Landed)
Direction valve = Up	Raising Gear(Taking Off)
Control of hydraulic pump for the landing gear part is disabled	Gear Up(Airborne)
Direction valve = down	Lowering Gear(Landing)

INPUT FOR THE DIRECTION VALVE:-

Table 3:-

Pilot’s Lever State	Direction Valve State
Lever UP	Direction valve = Up
Lever Down	Direction valve = Down

Table 4:-

Pilot’s Lever State	Light Status
Lever Rising Edge	Red
Lever Falling Edge

Table 5:-

Every gear has one light. According to the state of the gear,color of light is changing.

Landing Gear State	Light Status
Gear is up	OFF
Gear is down	Green
Gear in transit(Raising or Lowering)	Red

EXPECTED OUTCOMES:-

• In this project we get a good knowledge about the finite state machine algorithm.
• This algorithm helps us to achieve the control over the retraction and extension of airplane's landing gear.
• The switch states and gear states of airplane plays a major role in control of retraction and extension.
• The project has a easy logics which is shown in flowchart diagram which makes it easy and interesting.
• All the .c files, .h file and screenshots of outputs are uploaded for the reference.