11.01.2012

St. Roger, the patron saint of wayward aircraft bits delivered unto me a windscreen and canopy last night!

 

As you can see, it’s pretty rough.  We figure it was either ejected or purposely damaged for whatever reason.  It CAN be salvaged however.

Finding a replacement glass section (lexan actually) is essentially impossible.  That is ok however, because since I don’t have the part of the fuselage where the hinge mounted, I really can’t make it an articulating canopy anyway.

What I’ll do is remove the broken lexan parts and then mount the canopy in the closed & locked position to the F-15.  Without the forward canopy glass there, you can just step over the rail to get into the cockpit.

The canopy is also bent a bit in the middle, but I’m sure I can straighten it out well enough to get it installed.  I’ll have to fabricate a replacement trim strip as the one on the left is broken where the canopy is bent.

The good news is that the mounts for the compass and lock/shoot lights are still in place.  The side handles are present as well.  I can’t wait to get this thing fixed and installed!  It’s gonna look kind of odd without the forward glass, but who cares!

Here’s a shot of the new windscreen:

The windscreen has a few gouges in it, but it’s actually in a lot better shape than the A model windscreen that came with the cockpit when I originally got it.  I’m going to test some Novus polish I have to see how well it works fixing some of the lighter scratches.  I think Novus also makes a fill that will handle the deeper gouges.

[Update: 20Nov12]

Thanks to Matt who sent me a link to a Craigslist ad for an F-15 canopy, it looks like I may get it.  I’m working on making arrangements with the seller right now.  How’s that for cool? 🙂

I also got the images resized thanks to a new plugin I found for WordPress called ImagePro.

 

05.02.2012

The TEWS panel (along with the rest) are known as a Type 5 edge-lit panel.  Here’s what the “inside” of that looks like.

 

As you can see, there’s a series of little pockets in the panel for lamps to fit into.  At the “bottom” of each of the holes is a tiny metal reflector.  This helps spread the light throughout the panel and also prevents a “hot-spot” from appearing on the panel face.

Here’s what the circuit board looks like:

As you can see, it’s REALLY simple.  The bulbs are very, very small.  They stand about 1/8″ above the surface of the board and are a bit less than that in diameter.  The metal part in the center of the board is the PCB side of the coaxial connector that provides +5V to the board.  This board will draw just under 1.5A at full illumination.  Incandescents are HUNGRY little beasties!

 

A couple of years ago I scored a nearly complete TEWS control panel from a gent in Cypress.  The panel was scuffed pretty badly and some nimrod tore out two of the three FAIL indicators.  However, there’s enough left for me to work with. 🙂

As you can see above, the panel itself isn’t in such bad shape except the FAIL indicators.

Last Saturday I started the artwork on the replacement edge lit panel for the TEWS control:

 

I go through an iterative process that involves measuring the original and transferring those dimensions to an AutoCAD drawing.  Periodically I’ll throw an 8.5×11 sheet of printer paper into the laser and cut a test to see how it matches to the original.  At the stage this picture was taken, the panel art is complete.  The next step will be to duplicate the pocketing on the back of the panel in order to reuse the original circuit board that carries all the grain-of-rice lamps that light up the panel.

After the edge-lit panel is complete, I still need to find two replacement FAIL indicators, otherwise I’ll need to fab three new ones in a similar fashion to what I did for the REPLY indicator on the IFF panel.

First, here’s the videos:


I’ve chosen to use an Arduino in conjunction with a pair of Centipede Shields to drive all the incandescent indicators in the cockpit.  Just between the BIT (Built In Test) and Master Caution Panels, there’s 74 channels of output required.  In order to drive those lamps, I needed to build an intermediary board that could handle both the high voltage (most of the lamps in the F-15 are 28VDC) and the high current draw.  While a LED can draw as little as 15 to 20mA, the typical lamps used in the F-15 can draw up to 150mA each!

The demo shows only 16 indicators being driven.  Each indicator has two lamps behind it.  The lamps installed are MS25237-387 and they draw 40mA@28VDC.   16 indicators eat up 1.28A – the whole panel can consume 3.12A if everything is lit at once.

The 16 channel output board was over-designed to make sure that I could drive high-current lamps as well as handle relays and the magnetically held toggle switches that are used in a few places in the cockpit.   In order to drive relays or other coil-oriented loads, “back-emf” diodes will be used in order to prevent the over-voltage created by the collapsing magnetic field in the relay or solenoid from destroying the driver circuit for that channel.

The good news is that I’ll be resuming work on the F-15 very soon – this project has been sitting on the bench awaiting final test out, which is something I _finally_ was able to accomplish while being stuck at home due to medical problems.

Work on the new collimated display designs (not for the F-15 unfortunately!) will be interwoven with new work on the F-15.  After planning, plotting, designing and re-designing, for the last 11+ years, things will advance quickly once work resumes!

 

03.22.2011

After having a discussion with a fellow simpits-tech list member, it was discovered that the Wikipedia link that discussed the loss of 80-0007 was a) lacking a citation and b) had a minor error.  The page can be found here.

Since I have a copy of the “releasable” portion of the accident report, I decided to scan a few pages in order to provide the Wikipedia article a citation.

Here’s the scan:

80-0007-accident-report

I’ve recently obtained a new set of boards for my 16 channel power driver board – this will allow me to drive the incandescent bulbs that are in the master caution and BIT panels without having to re-lamp them with VERY spendy LED equivalents.  I’ll get an update about that with more detail posted soon!

g.

This update is going to bounce around a bit – I’m presenting the pictures in the order in which they were taken…

Here are the two SFS box shells right off the ShopBot:

Each one as mentioned before is made from four layers of 1/2″ Baltic Birch plywood.

Space cut out for the Nose Wheel Steering and Auto Pilot disconnect paddle:

The “real” SFS box is a one piece casting that includes a 2″ mounting post that fits into the stick base in the cockpit.  For this version, I had to turn my own post:

The post blank is a 4″ long section of 1.5″ diameter Delrin.  Delrin is a very easy to machine material and is quite strong.

After turning it down to 1.4375″, it’s time to see if it fits…

Insert Happy Dance Here. 🙂

I then cut it down to the 2″ length needed and then drilled & tapped it for 3 #10-24 screws.

…and just one more test fit…

One word.  Muahahahahahahaha!

The box sides came next.  The sides are .062″ aluminum and I’m using #8-32 brass inserts to allow me to use machine screws with the plywood.

The box to the right is the one that will be in the ‘109F/X.

On a completely unrelated note…

For the poor girl in danger of loosing her Chick License:

Enjoy! *laughs*

BTW, I do need to find a left-hand pitot tube.  This one is for the right side only. 🙂

Thanks for reading!

I went to my local acrylic monger yesterday and was captivated by this huge block of gray UHMW.  It was _begging_ to become an SFS box.

The block was about 10 inches long, 8 inches wide and 2.5 inches thick.  I needed to pare it down to 1.75″ thick first…

You can see the UHMW chips flying away from the cutter.  I’m using a .50″ downshear cutter running at 12,000 RPM with a feed rate of 1.7in/sec.  That cutter is an _animal_ in this stuff.  I’ve never cut UHMW before and it was definately an experience I won’t soon forget.  I’ll be cleaning up little bits of gray plastic swarf for the rest of my life I think.

Now we get on to the interior of the SFS box…

All during the cutting process, I was trying to suck up as much of the swarf as I could with a narrow shop-vac hose.  The best I could do is keep the stuff from clogging the cutter…

All done!  What a f*cking mess. *sigh*  The block of material has been glued down to a sheet of scrap plywood with 3M 77 spray adhesive.  Worked great!

Here’s the end results:

I really don’t care for the finish the cutter left on the box so this will likely be just a fun paper weight.  Tomorrow I’ll get the .062″ aluminum cover plates made…

Yesterday (19Dec09) I had the privilege of working with an independent filmmaker.  The beginning scenes in the movie involve a couple of guys in dire straights after their F-15D suffers a catastrophic engine failure.  He was lucky enough to get access to an F-15D that he could use to film the actors, but he still needed to see the correct emergency lights going off and some shots of “switch magic” where the fire supression system is activated and the relevant warnings appear on the Master Caution panel.

Here’s a picture of the Master Caution panel in “test”:

This is the first time the MCP has been illuminated while installed in the cockpit.  There are 74 24v lamps in that panel and it got pretty hot for the 10 minutes or so I ran it so he could get static shots of it.  HD video was also taken.

On the SFS front, I managed to ruin two blanks when they moved while being machined. 🙁  I had to lay up two new blanks and wait another 24 hours.

Until next time!

Today I cut the first SFS box core on the ShopBot:

sfs box core

I went ahead and deleted the additional pocket operation that would have inset the aluminum box cover.  Now it will more accurately reflect the original part.

A little bit of finish work will be required to correct the bottom edge profiles where the AP/NWS disconnect lever is mounted.

Part 3, coming soon!

The F-15 uses a very interesting system for the roll and pitch control – it’s both Fly by Wire and mechanical interconnect.

If you were to pin the stick in place with your knees, you can fly the jet by pressure on the grip all by itself, just like an F-16.

The magic for this happens in the little box that the stick grip attaches to.  This box is known as a Stick Force Sensor:

Stick Force Sensor box

Stick Force Sensor box

This box holds a load cell beam, very similar to the one in the base that the flight grip of the F-16 plugs into.  This load cell is what translates the stick force into electrical signals that the on-board computer translates into control surface movement.

The lever in front of the grip base is the Auto Pilot/Nosewheel Steering disconnect.  If you’re on the ground, it disengages nose wheel steering – the red button in the picture next to the lever engages the nose wheel steering.  If you’re in the air, the lever will disengage the autopilot.

Because of how important this little box is to my project, I’ve probably got more dimension data than any other part in the whole cockpit.

This week I’ll be making one on the ShopBot.  The following images are renderings from the software that I use for creating tool paths for parts to be cut on the ShopBot.  The base material is a 10″ x 10″ laminated plywood block, 2″ thick.

First up, the drill holes:

drills

Six mounting holes and the hole for the hinge pin for the AP/NWS disconnect lever.

Now it gets machined down to 1.75″ thick:

machine to 175

Now it gets cut down a bit more to make room for the .062″ thick aluminum box cover:

machine to 16875

This will result in a different look to the SFS box and I may change it before I cut material.

Now we create the main interior pocket for the box:

machine interior

…and finally it’s time to cut the box shape out:

shell finished 2

The tabs hold the box into the base material so it won’t shift during cutting.  The box will be complete after the sides of the AP/NWS area are shaped to more closely resemble the original.

All the cutting will be done with a .50″ downshear end mill with a 1.75″ cutter length.  (The tool itself is 4″ long)

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