GPS/Com Unit

We chose to purchase a Garmin 250-XL GPS/Com unit

For a number of reasons and maybe could have done better but with the small amount of knowledge and experience we have we gave it our best shot and went with it.

It has many features we wanted and a few we didn't know we wanted, and it doesn't have a few we found out we wanted later in our venture like a clock and the capability to scroll thru the Com channels via the cyclic stick for example.  It doe's have a clock with a counter capability but it takes more inputs to use it then its worth lol.  All in all we are very impressed with it even though we have no idea as of yet how to work it lol.  In comparison to the Bendix/King transponder we bought, it is far superior in the way it is built and the components it is made from.  It has a cooling tunnel which gives you an option to port air from a cooling fan into it.  On a summer day here in Tennessee (average of 97 degrees plus and usually around 95% humidity) inside that black instrument pod it has got to reach some tremendous temps.  For what we paid for this unit were gonna baby it all we can lol.

When you order it there's a home builders part number that is supposed to come with everything you need to mount it inside your aircraft. What we got was about 80 percent of what we needed and we had to go on a scavenger hunt for miscellaneous one of a kind parts.  We were lucky and our local Sheriff departments tech guy had everything we needed including a smile as he gave up the stuff from his goody box of left over parts from refitting several helicopters.  This guy was priceless in helping us with information to wire and install these things in our ship and we owe him big time.  He didn't do any hands on work but he answered many questions and gave up a lot of time for us going over our wiring schematics and providing us with sources for the things we needed from terminal ends to mil-spec wiring and gave us some hands on looks at a few Bell helis and even the king of the department a 63 completely restored and updated Huey helicopter which was a wow to get to touch much less sit in and get the tour lol.

My first Cross Country solo I spent two weeks playing with it on the kitchen table. I had to make a cabinet for it plus buy an AC adapter to run it. It allows you to set up simulated courses and such, everything but talk on the Com. When I got ready for my flight I dialed in everything and it took me right to every airport I without a hitch unlike my compass lol. During the southern course I took, my compass was off for some reason and if I had only had it to rely on, and didn't know where I was, I would have ended up about 9 miles southwest of my last airport. I accounted for the south west winds and temps at 3000 MSL  and it still wanted to steer me SSW for some reason.  There was a road called Hwy 411 that ran the whole length of the trip so I wasn't afraid of getting lost and I got to witness the hole navigation thing via both methods so I played with it a bit but never did figure out why the Compass was doing that.  When I was at RotorWay for training I explained to John O'neil about the anomaly I had encountered with the compass and his response was a quick smart ass answer "well why didn't you just follow the road Duh!"  Guess you can tell I wasn't to impressed huh!  Anyway I'm not positive but after pondering it for a long time the only thing that makes any sense is the windspeeds were less then what I was told so the ship didn't have the wind direction resistance to fight on its flight path thus taking me into the SSW direction.

We payed right around $2,590.00 for the unit and antenna plus

the miscellaneous parts and supplies needed to hook it all up. It was worth every dime of it and we are very pleased with it.  The only downside to it is it doesn't have a color display which would make things alot easier to see and navigate by.

The data chip updates for this thing is another unexpected and on going cost.

Just like new charts you can have a new chip every three months if you want to. I'm not sure at the moment and it's all depending on how up to date you want to keep yours but I think a chip upgrade is somewhere around $250.00 each time you do it.  The way it works is first you send them your money, then they send you a new chip and once you've received it and install it in your ship you send the old one back to them.

In January of 2004 we obtained a new chip

It was only $90 bucks plus shipping.  Seems they have a cheaper by the dozen kinda deal to for the folks that have to keep the date up to date.

With all the cell towers poping up all over the place I think keeping this thing up to date is pretty impotent but Donna and I just don't have that kind of moneys to keep throwing at this thing so well be doing ours about once a year at best.

Making the Avionics Tray

Where to Locate the GPS Antenna

This wasn't such a big deal once we figured out where we were going to put the thing.  I spoke to Tom Smith about it and he said most folks put them on the top of the tail boom just aft of the rear cowling.  That didn't set to well with me because I thought it was to close to the rotor disk and I didn't want to put holes that close to the end of the tailboom so I opted for another location.  After a bit of research I found out the best place for the antenna.

The idea here is to give it as much of a clear view of the sky as possible and if it's going to be under the rotor disk to place it as far below it as possible to avoid interference or blockage from the spinning blades.

The best place to mount it turned out to be on top of the vertical stabilizer fin.

A.   I didn't want to go through running the antenna wire all the way back there.

B.  We would have had to add 2 connectors which would be potential bad connections waiting to happen.

One at the base of the tailboom and a 2nd one where the vertical fin mounts to the tailboom.

C.   There would be a potential for the antenna wire to pick up interference from the strobe, nav and com antenna cable that it would have to run along side of.

Well that added up to at least 3 potential problems so again I opted to find another spot to mount it.

Keeping in mind the antenna needed to be low and as far out from the main rotor mast as possible and that only left one place to go which was the nose of the ship.

A.   The antenna can receive through both the fiberglass and the Plexiglass so that isn't a problem.

B.   The antenna cable would be extremely short making it much less susceptible to interference which is a good thing.

C.   Mounting the antenna itself in the nose of the pod would be about as simple as it gets.

D.   The Antenna doe's have a blind spot which is directly to the rear of the ship but to date it's never failed to receive a signal.

Making the mount for the GPS Antenna

Installing the Com Antenna

Fun Fun and more Fun! lol

This is the box we made for working with the Gps/Com unit at home.

This is a must have thing because it takes quite a bit of time to learn how the unit works.

It has a simulator mode that allows us to actually input true courses, airspeeds, winds and fuel burns into the unit and we're able to watch it just like we would if we were actually using the unit in flight.

About the only thing we can't simulate with it is using the Com. We can input Com channels but that's about it. Another thing we can do is input waypoints of places we plan on flying to in the future like friends houses, Homer's, Spurling's and the PRA Fly-Ins.

The power adapter is kinda pricey, about 60 or 90 bucks I think, but you gotta have one if your going to play at home or work with it out of the ship.  Having one direct from Garmin themselves made us feel better about it because of what we paid for the unit itself, we didn't want to take any chances of blowing it up lol.

The box is just something we threw together one afternoon at our shop. It has a 3 inch 110 volt electric fan installed in the back of it to help cool the unit while we're playing with it.

END