Senior Project

Mavrick20002

Hello.....this is my first post and I will introduce myself. My name is Mark Spangler from NW Indiana. I am graduating in May and need to write some quick code.....I am planning on using the BS2 as my micro to complete my project.

My project is as follows: I am monitoring the landing gear of an aircraft. When a certain altitude is achieved the LG will either retract or deploy based on the altitude of the aircraft and also based on whether it is in landing or takeoff configuration. The micro will also monitor·spark plug activity. No action takes place unless there is an active engine.·Under an engine "Flame Out" a manual procedure would take over.

I am using switches to monitor the position of the LG (Landing Gear), and the altimeter to indicate altitude. I will use a sensor (inductive pickup)·to indicate spark plug activity.

My plan is to simply "strobe" the switches to indicate either Down&Locked or Up&Locked landing gear. The reason for monitoring engine activity would be to insure no LG actions while the craft is sitting on the tarmack. The altimeter would be the device which would, based on initial settings prior to takeoff, and currrent altitude after takeoff,· initiate LG activity. All this activity would be reflected either thru an LCD display or LED's to indicate pertinent information to the pilot.

Any direction or assistance would be greatly appreciated as I have just found this forum.....thanks in advance....Mark

Rob311

What is the scale of the aircraft?

Franklin

I'd start by creating a flow chart of what happens and what you want the response to be. Once you understand the problem you can decide on what you need to monitor and control it. Good Luck.

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- Stephen

Mavrick20002

Franklin,
··········· I have already put together a flow chart but I will revise as needed.....but thank you for the thought and your input is appreciated....Mark


ROB311,
··········· I was initially looking at 1/4 scale R/C aircraft but with the use of an altimeter as a sensor·it would be anytype of aircraft that has retractable landing gear, upto and including commercial aircraft......hope this helps answer your question....and thanks for your input as well....much appreciated....Mark

Rob311

For my sr project i hooked up a hall effect sensor around the prop of a 1/8 (i think) scale piper cub. i found it to be much simpler then monitoring the spark plug.
i also monitored the signal going to my throttle servo, if it disappeared i know i was in trouble but i couldn't tell if the prop stopped by that.
my system was setup so that if the prop stopped spinning a parachute would pop out of the back and land the aircraft.

originally we wanted to monitor the electrical system, the gas level, prop speed, and tail pip temp. What we would have done with that information i have no clue.

Mavrick20002

ROB311,

··········· I appreciate your ideas and it sounds good.....but here is·a plan I am considering. I will be using switches to indicate LG up or down and locked. I will use the altimeter·as my altitude indicator and·a few additional sensors on the OLEO Struts for take off and landing. I was also considering using additional sensors on the flaps and wing leading edge movement as well as an inductive pickup for spark plug sensing.·A lot of sensors·I know but safety is also a major consideration....don't want·that landing gear activating improperly........thanks again....Mark·······

Unsoundcode

Hi Mark sounds like a good project. You need to decide exactly how many sensors/output devices·you need and what kind so you can begin to assign them to your I/O pins and write your code. If you run out of pins you may be able to interface some of them using external logic circuits.

I would say each set of LG needs a switch to indicate down and a switch to indicate up anywhere between would flag an alarm or indicate to the pilot that the LG was in motion, possibly with a timeout alarm if the gear did not extend/retract within a certain time, a couple of nand gates would reduce the 4·sensor inputs to 2 if you were short on I/O.

Is monitoring the engine a failsafe, the engine runs on the ground and in the air, I just wondered how useful that was and what your thinking behind it was. I know next to nothing about aircraft but my first thought was monitor the weight on the suspension (aircraft has suspension doesn't it? ) but that would depend on having enough travel/weight to measure.

Output via a serial LCD could communicate status to the pilot and also reduce on I/O

just a couple of ideas you might consider

Jeff T.

Mavrick20002

Unsoundcode,
thanks for the input....your right.....I have a timeout to disable any alarms during a normal travel time for the landing gear.......regarding the engine.....on takeoff your at max RPM, or lets hope so, so this would be an indicator of takeoff configuration......this input along with a few others would indicate a takeoff is near......for landing....the flaps are usually extended along with the leading edge of the wing extended, as well as the altimeter would indicate that at a specific altitude the LG would drop......but I will focus on the altimeter as my primary source as a sensor.....but thanks again for your input....much appreciated....Mark

Capt. Quirk

I would worry about your pressure sensor location.

You should be able to get a good density altitude reading before you take off to set your landing gear up & down altitude, but I really think your going to run into problems with that sensor as soon as it's airborne. Fuselages and wings internal air pressures are often greater than atmospheric pressure in flight and some times less than depending on the setup.

You might want to check into the parallax GPS sensor instead.

Mavrick20002

Capt. Quirk,
thank you for your input......but I am not relying on pressure's but more so on contact switches to sense the where the landing gear are and the output of an altimeter to determine height. Other sensors I would consider would also be contact sensors for placement of the flaps and compression of the OLEO struts of the landing gear......but I will consider what you have suggested....thank you...Mark

Capt. Quirk

Sorry I thought you were trying to automate the landing gear.

I thought of this after the post, http://www.parallax.com/detail.asp?product_id=605-00004 It·should be a good light weight flexible switch for the bay doors and your control surfaces.

LSB

My only comment would be to be sure that you consider fails carefully. Airplane landing gear is simple and developed enough that hydraulics are a viable answer when everything works—its when there’s a problem that the value of your system will manifest itself. For example: Do you simply monitor the current LG position, then “throw the switch”? Or do you also time the transition and report fluctuations? What happens if·the switches report contradicting positions? What if the altimeter has shown a steady drop in altitude for 8 minutes, does your system recognize that a gear up would be inappropriate?
·
What a system does do is every bit as important as what it doesn’t do and how you handle failure is sometimes more important than how you handle success. Be sure you've considered both.

Tim-M

You may have considered this situation already, but another thought regarding engine activity... While you DON'T want LG enabled while on the tarmack, you DO want to have LG capability while in the air and under an emergency condition such as an engine-out where engine activity would read zero or none to your system. Either that, or have a manual redundant backup in place or something.

Tim

Mavrick20002

Loosenut Fabricating,
I think I have addressed your question by disabling any alarms during the transition time from FULL UP to FULL DOWN....at which point I then rescan the landing gear positional switches and if they don't have the appropiate response then an alarm would be triggered. If there was a problem during the transition then the time required to fully deploy the gear would be extended and the alarms would activate. Regarding the altimeter my plan is to, based on the current settings of the LG, read the altimeter and set a flag. If the flag is set, then it means the system recognizes the fact that the altimeter has passed thru 100' AGL and sets the system to recognize that the next trip point would be to raise the LG once the altimeter passes back thru 100' AGL.

Tim-M,
The redundancy would be the manual system built into all LG systems. In the event that you have a malfunction in your LG system there is usually a method to manually lower the LG, assuming you have time to do so or the LG is currently down. Sometimes its better to land on your belly with the LG up.......

thankyou both for you input....Mark

Mavrick20002

To Anybody who can help:

I need to get some idea's on how to "Stobe" my positional switches. I know one way is to use a "For.....Next" loop and then if I get an irregular response then break out of the loop and perform the next required act, then return back to the "For....Next" loop to "strobe" my switches.......but I would like some input on that "strobing" concept??

Thanks in advance.....Mark

Unsoundcode

The INS statement (look under Memory and Variables in Pbasic help) is one way of looking at several inputs at one time. For example if you have 4 switches on pins 0 to 3 and the healthy condition was all switches NC then a fault condition would exist if INA < 15 therefore "IF INA<15 THEN alarm" .

Jeff T.

Mavrick20002

Here are some idea's I have for anyone's input:
upon startup of the aircraft the following settings would apply: Aircraft sitting on tarmac taxiing or idleing : LG Down Switches = 111......Alt. < 300' AGL = 1.......Eng. RPM < 1800 = 1
Aircraft during takeoff : LG Down Switches = 111........Alt. < 300' AGL = 1......Eng RPM >1800 = 1
LG UP Activation : LG Down Switches = 111......Alt. > 300' AGL = 0........Eng. RPM > 1800 = 1

During LG activation no readings of UP & Locked or DN & Locked would take place and all alarms suspended.
After a specified time frame....approx 30sec.....LG switches would be scanned for proper positioning. IF scanning indicated a landing gear out of position, then an alarm would be activated

The landing sequence would be as follows: LG UP switches = 000..........Alt. < 300' AGL = 1......Eng. RPM < 1800 = 0

These numbers for Engine RPM are based on SMALL AIRCRAFT.......NOT COMMERCIAL......

now I could monitor for Loss of engine activity and force the LG down should I lose engine activity for say more than 30 sec.???

Anyone have any thoughts on these parameters???

Thanks Mark

Capt. Quirk

In my experience, Select - Case, Lookup and Branch, were better for conditional programming, than IF-Then statements.
·
Use of the adc0834 http://www.parallax.com/detail.asp?product_id=604-00027·makes those conditional statements even easier. When combined with small light weight potentiometers, the ADC will return 0 to 255 units to·reference the position of each control surface, servo, etc. that's connected to a small potentiometer (Just like a throttle position sensor does in a car).
·
There are small 5K pots inside old servos and transmitters that you can easily use. 10K woks well too, either way be sure to add a 220 ohm resistor on the wiper.

Post Edited (Capt. Quirk) : 3/11/2007 11:49:51 PM GMT